United States Department of Agriculture Keys to Soil Taxonomy

Eleventh Edition, 2010

Keys to Soil Taxonomy

By Soil Survey Staff

United States Department of Agriculture Natural Resources Conservation Service

Eleventh Edition, 2010 ii

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Cover: Profile of a Lamellic Quartzipsamment. Because of coatings of iron oxide, the part of the profile directly below the surface horizon is reddish. Lamellae of loamy sand, mostly less than 0.5 centimeter thick, are common in the lower part of the profile. The scale is in 15-centimeter increments. Photo by John Kelley, Soil Scientist (retired), Raleigh, North Carolina. iii

Table of Contents

Foreword...... v Chapter 1: The Soils That We Classify...... 1 Chapter 2: Differentiae for Mineral Soils and Organic Soils...... 3 Chapter 3: Horizons and Characteristics Diagnostic for the Higher Categories...... 5 Chapter 4: Identification of the Taxonomic Class of a Soil...... 31 Chapter 5: Alfisols...... 35 Chapter 6: Andisols...... 77 Chapter 7: Aridisols...... 97 Chapter 8: Entisols...... 123 Chapter 9: Gelisols...... 145 Chapter 10: Histosols...... 155 Chapter 11: Inceptisols...... 161 Chapter 12: Mollisols...... 197 Chapter 13: Oxisols...... 241 Chapter 14: Spodosols...... 257 Chapter 15: Ultisols...... 267 Chapter 16: Vertisols...... 287 Chapter 17: Family and Series Differentiae and Names...... 299 Chapter 18: Designations for Horizons and Layers...... 315 Appendix ...... 323 Index ...... 331



Foreword

The publication Keys to Soil Taxonomy serves two purposes. It provides the taxonomic keys necessary for the classification of soils in a form that can be used easily in the field. It also acquaints users of the taxonomic system with recent changes in the system. The eleventh edition of the Keys to Soil Taxonomy incorporates all changes approved since the publication of the second edition of Soil Taxonomy: A Basic System of Soil Classification for Making and Interpreting Soil Surveys (1999). One of the most significant changes in the eleventh edition is the addition of the suborders Wassents and Wassists for subaqueous Entisols and Histosols. We plan to continue issuing updated editions of the Keys to Soil Taxonomy as changes warrant new editions. Since it was first published 35 years ago,Soil Taxonomy: A Basic System of Soil Classification for Making and Interpreting Soil Surveyshas been used to support soil survey efforts in many countries around the world. It has been translated into several languages. Soil scientists from many nations have contributed significantly to the development of the taxonomic system. The authors encourage the continued use of soil taxonomy internationally and look forward to future collaborations with the international soil science community so we can continue to make improvements. Through continued communication and collaboration, we hope that our efforts will eventually result in a truly universal soil classification system. The authors of the Keys to Soil Taxonomy are identified as the “Soil Survey Staff.” This term is meant to include all of the soil classifiers in the National Cooperative Soil Survey program and in the international community who have made significant contributions to the improvement of the taxonomic system.

Micheal L. Golden Director, Soil Survey Division Natural Resources Conservation Service



S O I

CHAPTER 1 The Soils That We Classify

The word “soil,” like many common words, has several is arbitrarily set at 200 cm. In soils where either biological meanings. In its traditional meaning, soil is the natural medium activity or current pedogenic processes extend to depths greater for the growth of land plants, whether or not it has discernible than 200 cm, the lower limit of the soil for classification soil horizons. This meaning is still the common understanding purposes is still 200 cm. In some instances the more weakly of the word, and the greatest interest in soil is centered on this cemented bedrocks (paralithic materials, defined later) have meaning. People consider soil important because it supports been described and used to differentiate soil series (series plants that supply food, fibers, drugs, and other wants of control section, defined later), even though the paralithic humans and because it filters water and recycles wastes. Soil materials below a paralithic contact are not considered soil in covers the earth’s surface as a continuum, except on bare rock, the true sense. In areas where soil has thin cemented horizons in areas of perpetual frost, in deep water, or on the barren ice of that are impermeable to roots, the soil extends as deep as the glaciers. In this sense, soil has a thickness that is determined by deepest cemented horizon, but not below 200 cm. For certain the rooting depth of plants. management goals, layers deeper than the lower boundary of Soil in this text is a natural body comprised of solids the soil that is classified (200 cm) must also be described if (minerals and organic matter), liquid, and gases that occurs they affect the content and movement of water and air or other on the land surface, occupies space, and is characterized by interpretative concerns. one or both of the following: horizons, or layers, that are In the humid tropics, earthy materials may extend to a depth distinguishable from the initial material as a result of additions, of many meters with no obvious changes below the upper 1 or losses, transfers, and transformations of energy and matter or 2 m, except for an occasional stone line. In many wet soils, the ability to support rooted plants in a natural environment. gleyed soil material may begin a few centimeters below the This definition is expanded from the 1975 version of Soil surface and, in some areas, continue down for several meters Taxonomy to include soils in areas of Antarctica where apparently unchanged with increasing depth. The latter pedogenesis occurs but where the climate is too harsh to support condition can arise through the gradual filling of a wet basin the higher plant forms. in which the A horizon is gradually added to the surface and The upper limit of soil is the boundary between soil and becomes gleyed beneath. Finally, the A horizon rests on a thick air, shallow water, live plants, or plant materials that have not mass of gleyed material that may be relatively uniform. In both begun to decompose. Areas are not considered to have soil if of these situations, there is no alternative but to set the lower the surface is permanently covered by water too deep (typically limit of soil at the arbitrary limit of 200 cm. more than about 2.5 m) for the growth of rooted plants. The Soil, as defined in this text, does not need to have discernible horizontal boundaries of soil are areas where the soil grades horizons, although the presence or absence of horizons and their to deep water, barren areas, rock, or ice. In some places the nature are of extreme importance in soil classification. Plants separation between soil and nonsoil is so gradual that clear can be grown under glass in pots filled with earthy materials, distinctions cannot be made. such as peat or sand, or even in water. Under proper conditions The lower boundary that separates soil from the nonsoil all these media are productive for plants, but they are nonsoil underneath is most difficult to define. Soil consists of here in the sense that they cannot be classified in the same the horizons near the earth’s surface that, in contrast to system that is used for the soils of a survey area, county, or the underlying parent material, have been altered by the even nation. Plants even grow on trees, but trees are regarded as interactions of climate, relief, and living organisms over time. nonsoil. Commonly, soil grades at its lower boundary to hard rock or Soil has many properties that fluctuate with the seasons. It to earthy materials virtually devoid of animals, roots, or other may be alternately cold and warm or dry and moist. Biological marks of biological activity. The lowest depth of biological activity is slowed or stopped if the soil becomes too cold or too activity, however, is difficult to discern and is often gradual. dry. The soil receives flushes of organic matter when leaves fall For purposes of classification, the lower boundary of soil or grasses die. Soil is not static. The pH, soluble salts, amount 

of organic matter and carbon-nitrogen ratio, numbers of micro- establish a phase of the mantled soil or even another soil series organisms, soil fauna, temperature, and moisture all change if the mantle affects the use of the soil. with the seasons as well as with more extended periods of time. Any horizons or layers underlying a plaggen epipedon are Soil must be viewed from both the short-term and long-term considered to be buried. perspective. A surface mantle of new material, as defined here, is largely unaltered, at least in the lower part. It may have a diagnostic Buried Soils surface horizon (epipedon) and/or a cambic horizon, but it has no other diagnostic subsurface horizons, all defined later. A buried soil is covered with a surface mantle of new soil However, there remains a layer 7.5 cm or more thick that fails material that either is 50 cm or more thick or is 30 to 50 cm the requirements for all diagnostic horizons, as defined later, thick and has a thickness that equals at least half the total overlying a horizon sequence that can be clearly identified as thickness of the named diagnostic horizons that are preserved the solum of a buried soil in at least half of each pedon. The in the buried soil. A surface mantle of new material that does recognition of a surface mantle should not be based only on not have the required thickness for buried soils can be used to studies of associated soils. 

D I CHAPTER 2 F Differentiae for Mineral Soils1 and Organic Soils

Soil taxonomy differentiates between mineral soils and include what has been called litter or an O horizon. Material organic soils. To do this, first, it is necessary to distinguish that has more organic carbon than in item 2 has been called mineral soil material from organic soil material. Second, it peat or muck. Not all organic soil material accumulates in or is necessary to define the minimum part of a soil that should under water. Leaf litter may rest on a lithic contact and support be mineral if a soil is to be classified as a mineral soil and forest vegetation. The soil in this situation is organic only in the minimum part that should be organic if the soil is to be the sense that the mineral fraction is appreciably less than half classified as an organic soil. the weight and is only a small percentage of the volume of the Nearly all soils contain more than traces of both mineral soil. and organic components in some horizons, but most soils are dominantly one or the other. The horizons that are less Distinction Between Mineral Soils and Organic than about 20 to 35 percent organic matter, by weight, have Soils properties that are more nearly those of mineral than of organic soils. Even with this separation, the volume of organic matter at Most soils are dominantly mineral material, but many the upper limit exceeds that of the mineral material in the fine- mineral soils have horizons of organic material. For simplicity earth fraction. in writing definitions of taxa, a distinction between what is meant by a mineral soil and an organic soil is useful. To apply the definitions of many taxa, one must first decide whether the Mineral Soil Material soil is mineral or organic. An exception is the Andisols (defined Mineral soil material (less than 2.0 mm in diameter) either: later). These generally are considered to consist of mineral soils, but some may be organic if they meet other criteria for Andisols. 1. Is saturated with water for less than 30 days (cumulative) Those that exceed the organic carbon limit defined for mineral per year in normal years and contains less than 20 percent (by soils have a colloidal fraction dominated by short-range- weight) organic carbon; or order minerals or aluminum-humus complexes. The mineral 2. Is saturated with water for 30 days or more (cumulative) in fraction in these soils is believed to give more control to the normal years (or is artificially drained) and, excluding live roots, soil properties than the organic fraction. Therefore, the soils are has an organic carbon content (by weight) of: included with the Andisols rather than the organic soils defined later as Histosols and Histels. a. Less than 18 percent if the mineral fraction contains 60 If a soil has both organic and mineral horizons, the relative percent or more clay; or thickness of the organic and mineral soil materials must be b. Less than 12 percent if the mineral fraction contains no considered. At some point one must decide that the mineral clay; or horizons are more important. This point is arbitrary and depends in part on the nature of the materials. A thick layer of Sphagnum c. Less than 12 + (clay percentage multiplied by 0.1) has a very low bulk density and contains less organic matter percent if the mineral fraction contains less than 60 percent than a thinner layer of well-decomposed muck. It is much clay. easier to measure the thickness of layers in the field than it is to determine tons of organic matter per hectare. The definition of a Organic Soil Material mineral soil, therefore, is based on the thickness of the horizons, or layers, but the limits of thickness must vary with the kinds of Soil material that contains more than the amounts of organic materials. The definition that follows is intended to classify as carbon described above for mineral soil material is considered mineral soils those that have both thick mineral soil layers and organic soil material. no more organic material than the amount permitted in the histic In the definition of mineral soil material above, material epipedon, which is defined in chapter 3. that has more organic carbon than in item 1 is intended to In the determination of whether a soil is organic or mineral, the thickness of horizons is measured from the surface of 1 Mineral soils include all soils except the suborder Histels and the order Histosols. the soil whether that is the surface of a mineral or an organic 

horizon, unless the soil is buried as defined in chapter 1. a. Permafrost within 100 cm of the soil surface; or Thus, any O horizon at the surface is considered an organic horizon if it meets the requirements of organic soil material b. Gelic materials within 100 cm of the soil surface and as defined later, and its thickness is added to that of any other permafrost within 200 cm of the soil surface. organic horizons to determine the total thickness of organic soil materials. Plant materials at the soil surface must be at Definition of Organic Soils least slightly decomposed if they are to be considered part of Organic soils have organic soil materials that: an O horizon. Undecomposed plant litter is excluded from the concept of O horizons. 1. Do not have andic soil properties in 60 percent or more of the thickness between the soil surface and either a depth Definition of Mineral Soils of 60 cm or a densic, lithic, or paralithic contact or duripan if shallower; and Mineral soils are soils that have either: 2. Meet one or more of the following: 1. Mineral soil materials that meet one or more of the following: a. Overlie cindery, fragmental, or pumiceous materials and/or fill their interstices2 and directly below these materials a. Overlie cindery, fragmental, or pumiceous materials have a densic, lithic, or paralithic contact; or and/or have voids2 that are filled with 10 percent or less organic materials and directly below these materials have b. When added with the underlying cindery, fragmental, or either a densic, lithic, or paralithic contact; or pumiceous materials, total 40 cm or more between the soil surface and a depth of 50 cm; or b. When added with underlying cindery, fragmental, or pumiceous materials, total more than 10 cm between the soil c. Constitute two-thirds or more of the total thickness of surface and a depth of 50 cm; or the soil to a densic, lithic, or paralithic contact and have no mineral horizons or have mineral horizons with a total c. Constitute more than one-third of the total thickness of thickness of 10 cm or less; or the soil to a densic, lithic, or paralithic contact or have a total thickness of more than 10 cm; or d. Are saturated with water for 30 days or more per year in normal years (or are artificially drained), have an upper d. If they are saturated with water for 30 days or more per boundary within 40 cm of the soil surface, and have a total year in normal years (or are artificially drained) and have thickness of either: organic materials with an upper boundary within 40 cm of the soil surface, have a total thickness of either: (1) 60 cm or more if three-fourths or more of their volume consists of moss fibers or if their bulk density, (1) Less than 60 cm if three-fourths or more of their moist, is less than 0.1 g/cm3; or volume consists of moss fibers or if their bulk density, moist, is less than 0.1 g/cm3; or (2) 40 cm or more if they consist either of sapric or hemic materials, or of fibric materials with less than three- (2) Less than 40 cm if they consist either of sapric or fourths (by volume) moss fibers and a bulk density, moist, hemic materials, or of fibric materials with less than three- of 0.1 g/cm3 or more; or fourths (by volume) moss fibers and a bulk density, moist, of 0.1 g/cm3 or more; or e. Are 80 percent or more, by volume, from the soil surface to a depth of 50 cm or to a glacic layer or a densic, lithic, or 2. More than 20 percent, by volume, mineral soil materials paralithic contact, whichever is shallowest. from the soil surface to a depth of 50 cm or to a glacic layer or a densic, lithic, or paralithic contact, whichever is shallowest; and It is a general rule that a soil is classified as an organic soil (Histosol or Histel) if more than half of the upper 80 cm (32 in) of the soil is organic or if organic soil material of any thickness

2 Materials that meet the definition of the cindery, fragmental, or pumiceous substitute rests on rock or on fragmental material having interstices filled for particle-size class but have more than 10 percent, by volume, voids that are filled with with organic materials. organic soil materials are considered to be organic soil materials. 

CHAPTER 3 D I Horizons and Characteristics Diagnostic for the Higher Categories A

This chapter defines the horizons and characteristics indicate buried horizons, such as those in Thapto-Histic of both mineral and organic soils. It is divided into three subgroups. A soil with a mantle thick enough to have a buried parts—horizons and characteristics diagnostic for mineral soils, soil has no epipedon if the soil has rock structure to the surface characteristics diagnostic for organic soils, and horizons and or has an Ap horizon less than 25 cm thick that is underlain characteristics diagnostic for both mineral and organic soils. by soil material with rock structure. The melanic epipedon The horizons and characteristics defined below are not in (defined below) is unique among epipedons. It commonly a key format. The “required characteristics” for horizons or forms in deposits of tephra and can receive fresh deposits of features, however, are arranged as a key. Some diagnostic volcanic ash. Therefore, this horizon is permitted to have layers horizons are mutually exclusive, and some are not. An umbric within and above the epipedon that are not part of the melanic epipedon, for example, could not also be a mollic epipedon. A epipedon. kandic horizon with clay films, however, could also meet the A recent alluvial or eolian deposit that retains fine definition of an argillic horizon. stratifications (5 mm or less thick) or an Ap horizon directly underlain by such stratified material is not included in the concept of the epipedon because time has not been sufficient Horizons and Characteristics for soil-forming processes to erase these transient marks of Diagnostic for Mineral Soils deposition and for diagnostic and accessory properties to develop. The criteria for some of the following horizons and An epipedon is not the same as an A horizon. It may include characteristics, such as histic and folistic epipedons, can be part or all of an illuvial B horizon if the darkening by organic met in organic soils. They are diagnostic, however, only for the matter extends from the soil surface into or through the B mineral soils. horizon.

Diagnostic Surface Horizons: Anthropic Epipedon The Epipedon Required Characteristics The epipedon (Gr. epi, over, upon, and pedon, soil) is a The anthropic epipedon consists of mineral soil material that horizon that forms at or near the surface and in which most of shows some evidence of disturbance by human activity. After the rock structure has been destroyed. It is darkened by organic mixing of the upper 18 cm of the mineral soil, or of the whole matter or shows evidence of eluviation, or both. Rock structure mineral soil if its depth to a densic, lithic, or paralithic contact, a as used here and in other places in this taxonomy includes fine petrocalcic horizon, or a duripan (all defined below) is less than stratification (5 mm or less thick) in unconsolidated sediments 18 cm, the anthropic epipedon has the following properties: (eolian, alluvial, lacustrine, or marine) and saprolite derived from consolidated rocks in which the unweathered minerals 1. When dry, either or both: and pseudomorphs of weathered minerals retain their relative a. Structural units with a diameter of 30 cm or less or positions to each other. secondary structure with a diameter of 30 cm or less; or Any horizon may be at the surface of a truncated soil. The following section, however, is concerned with eight diagnostic b. A moderately hard or softer rupture-resistance class; and horizons that have formed at or near the soil surface. These 2. Rock structure, including fine stratifications (5 mm or less horizons can be covered by a surface mantle of new soil thick), in less than one-half of the volume of all parts; and material. If the surface mantle has rock structure, the top of the epipedon is considered the soil surface unless the mantle meets 3. One of the following: the definition of buried soils in chapter 1. If the soil includes a a. Both of the following: buried soil, the epipedon, if any, is at the soil surface and the epipedon of the buried soil is considered a buried epipedon and (1) Dominant colors with a value of 3 or less, moist, and is not considered in selecting taxa unless the keys specifically of 5 or less, dry; and  Keys to Soil Taxonomy

(2) Dominant colors with chroma of 3 or less, moist; or a. Has a phosphate content of 1,500 or more milligrams per kilogram by citric-acid extraction; and b. A fine-earth fraction that has a calcium carbonate equivalent of 15 to 40 percent and colors with value and (1) The phosphorus content decreases regularly with chroma of 3 or less, moist; or increasing depth below the epipedon; and c. A fine-earth fraction that has a calcium carbonate (2) Phosphorus is not in the form of nodules; or equivalent of 40 percent or more and a color value, moist, of b. All parts of the epipedon are moist for less than 90 days 5 or less; and (cumulative) in normal years during times when the soil 4. An organic-carbon content of: temperature at a depth of 50 cm is 5 oC or higher, if the soil is not irrigated; and a. 2.5 percent or more if the epipedon has a color value, moist, of 4 or 5; or 7. The n value (defined below) is less than 0.7. b. 0.6 percent more (absolute) than that of the C horizon (if one occurs) if the mollic epipedon has a color value less than Folistic Epipedon 1 unit lower or chroma less than 2 units lower (both moist Required Characteristics and dry) than the C horizon; or The folistic epipedon is defined as a layer (one or more c. 0.6 percent or more and the epipedon does not meet the horizons) that is saturated for less than 30 days (cumulative) in qualifications in 4-a or 4-b above;and normal years (and is not artificially drained) andeither : 5. The minimum thickness of the epipedon is as follows: 1. Consists of organic soil material that: a. 25 cm if: a. Is 20 cm or more thick and either contains 75 percent or more (by volume) Sphagnum fibers or has a bulk density, (1) The texture class of the epipedon is loamy fine sand moist, of less than 0.1; or or coarser throughout; or b. Is 15 cm or more thick; or (2) There are no underlying diagnostic horizons (defined below), and the organic-carbon content of the underlying 2. Is an Ap horizon that, when mixed to a depth of 25 cm, has materials decreases irregularly with increasing depth; or an organic-carbon content (by weight) of: (3) Any of the following, if present, are 75 cm or more a. 16 percent or more if the mineral fraction contains 60 below the mineral soil surface: percent or more clay; or (a) The upper boundary of the shallowest of any b. 8 percent or more if the mineral fraction contains no identifiable secondary carbonates or a calcic horizon, clay; or petrocalcic horizon, duripan, or fragipan (defined c. 8 + (clay percentage divided by 7.5) percent or more if below); and/or the mineral fraction contains less than 60 percent clay. (b) The lower boundary of the deepest of an argillic, Most folistic epipedons consist of organic soil material cambic, natric, oxic, or spodic horizon; or (defined in chapter 2). Item 2 provides for a folistic epipedon b. 10 cm if the epipedon has a texture class finer than that is an Ap horizon consisting of mineral soil material. loamy fine sand (when mixed) and it is directly above a densic, lithic, or paralithic contact, a petrocalcic horizon, or a Histic Epipedon duripan; or Required Characteristics c. 18 to 25 cm and the thickness is one-third or more of the total thickness between the mineral soil surface and: The histic epipedon is a layer (one or more horizons) that is characterized by saturation (for 30 days or more, cumulative) (1) The upper boundary of the shallowest of any and reduction for some time during normal years (or is identifiable secondary carbonates or a calcic horizon, artificially drained) andeither : petrocalcic horizon, duripan, or fragipan; and/or 1. Consists of organic soil material that: (2) The lower boundary of the deepest of an argillic, a. Is 20 to 60 cm thick and either contains 75 percent or cambic, natric, oxic, or spodic horizon; or more (by volume) Sphagnum fibers or has a bulk density, d. 18 cm if none of the above conditions apply. moist, of less than 0.1; or 6. One or both of the following: b. Is 20 to 40 cm thick; or Horizons and Characteristics Diagnostic for the Higher Categories 

2. Is an Ap horizon that, when mixed to a depth of 25 cm, has (1) Dominant colors with a value of 3 or less, moist, and an organic-carbon content (by weight) of: of 5 or less, dry; and a. 16 percent or more if the mineral fraction contains 60 (2) Dominant colors with chroma of 3 or less, moist; or percent or more clay; or b. A fine-earth fraction that has a calcium carbonate D I b. 8 percent or more if the mineral fraction contains no equivalent of 15 to 40 percent and colors with a value and A clay; or chroma of 3 or less, moist; or c. 8 + (clay percentage divided by 7.5) percent or more if c. A fine-earth fraction that has a calcium carbonate the mineral fraction contains less than 60 percent clay. equivalent of 40 percent or more and a color value, moist, of 5 or less; and Most histic epipedons consist of organic soil material

(defined in chapter 2). Item 2 provides for a histic epipedon that 4. A base saturation (by NH4OAc) of 50 percent or more is an Ap horizon consisting of mineral soil material. A histic throughout; and epipedon consisting of mineral soil material can also be part of 5. An organic-carbon content of: a mollic or umbric epipedon. a. 2.5 percent or more if the epipedon has a color value, Melanic Epipedon moist, of 4 or 5; or Required Characteristics b. 0.6 percent (absolute) more than that of the C horizon (if one occurs) if the mollic epipedon has a color value less than The melanic epipedon has both of the following: 1 unit lower or chroma less than 2 units lower (both moist 1. An upper boundary at, or within 30 cm of, either the and dry) than the C horizon; or mineral soil surface or the upper boundary of an organic c. 0.6 percent or more and the epipedon does not meet the layer with andic soil properties (defined below), whichever is qualifications in 5-a or 5-b above;and shallower; and 6. The minimum thickness of the epipedon is as follows: 2. In layers with a cumulative thickness of 30 cm or more within a total thickness of 40 cm, all of the following: a. 25 cm if: a. Andic soil properties throughout; and (1) The texture class of the epipedon is loamy fine sand or coarser throughout; or b. A color value, moist, and chroma of 2 or less throughout and a melanic index of 1.70 or less throughout; and (2) There are no underlying diagnostic horizons (defined below) and the organic-carbon content of the c. 6 percent or more organic carbon as a weighted average underlying materials decreases irregularly with increasing and 4 percent or more organic carbon in all layers. depth; or

Mollic Epipedon (3) Any of the following, if present, are 75 cm or more below the mineral soil surface: Required Characteristics (a) The upper boundary of the shallowest of any The mollic epipedon consists of mineral soil materials and, identifiable secondary carbonates or a calcic horizon, after mixing of the upper 18 cm of the mineral soil or of the petrocalcic horizon, duripan, or fragipan (defined whole mineral soil if its depth to a densic, lithic, or paralithic below); and/or contact, a petrocalcic horizon, or a duripan (all defined below) is (b) The lower boundary of the deepest of an argillic, less than 18 cm, has the following properties: cambic, natric, oxic, or spodic horizon; or 1. When dry, either or both: b. 10 cm if the epipedon has a texture class finer than a. Structural units with a diameter of 30 cm or less or loamy fine sand (when mixed) and it is directly above a secondary structure with a diameter of 30 cm or less; or densic, lithic, or paralithic contact, a petrocalcic horizon, or a duripan; or b. A moderately hard or softer rupture-resistance class; and c. 18 to 25 cm and the thickness is one-third or more of the 2. Rock structure, including fine stratifications (5 mm or less total thickness between the mineral soil surface and: thick), in less than one-half of the volume of all parts; and (1) The upper boundary of the shallowest of any 3. One of the following: identifiable secondary carbonates or a calcic horizon, a. Both of the following: petrocalcic horizon, duripan, or fragipan; and/or  Keys to Soil Taxonomy

(2) The lower boundary of the deepest of an argillic, A plaggen epipedon can be identified by several means. cambic, natric, oxic, or spodic horizon; or Commonly, it contains artifacts, such as bits of brick and pottery, throughout its depth. There may be chunks of diverse d. 18 cm if none of the above conditions apply; and materials, such as black sand and light gray sand, as large as 7. Phosphate: the size held by a spade. The plaggen epipedon normally shows spade marks throughout its depth and also remnants of thin a. Content less than 1,500 milligrams per kilogram by stratified beds of sand that were probably produced on the soil citric-acid extraction; or surface by beating rains and were later buried by spading. A b. Content decreasing irregularly with increasing depth map unit delineation of soils with plaggen epipedons would tend below the epipedon; or to have straight-sided rectangular bodies that are higher than the adjacent soils by as much as or more than the thickness of the c. Nodules are within the epipedon; and plaggen epipedon. 8. Some part of the epipedon is moist for 90 days or more Required Characteristics (cumulative) in normal years during times when the soil temperature at a depth of 50 cm is 5 oC or higher, if the soil is The plaggen epipedon consists of mineral soil materials and not irrigated; and has the following: 9. The n value (defined below) is less than 0.7. 1. Locally raised land surfaces; and one or both of the following: Ochric Epipedon a. Artifacts; or The ochric epipedon fails to meet the definitions for any of b. Spade marks below a depth of 30 cm; and the other seven epipedons because it is too thin or too dry, has too high a color value or chroma, contains too little organic 2. Colors with a value of 4 or less, moist, 5 or less, dry, and carbon, has too high an n value or melanic index, or is both chroma of 2 or less; and massive and hard or harder when dry. Many ochric epipedons 3. An organic-carbon content of 0.6 percent or more; and have either a color value of 4 or more, moist, and 6 or more, dry, or chroma of 4 or more, or they include an A or Ap horizon that 4. A thickness of 50 cm or more; and has both low color values and low chroma but is too thin to be 5. Some part of the epipedon that is moist for 90 days or recognized as a mollic or umbric epipedon (and has less than 15 more (cumulative) in normal years during times when the soil percent calcium carbonate equivalent in the fine-earth fraction). temperature at a depth of 50 cm is 5 oC or higher, if the soil is Ochric epipedons also include horizons of organic materials not irrigated. that are too thin to meet the requirements for a histic or folistic epipedon. Umbric Epipedon The ochric epipedon includes eluvial horizons that are at or near the soil surface, and it extends to the first underlying Required Characteristics diagnostic illuvial horizon (defined below as an argillic, The umbric epipedon consists of mineral soil materials and, kandic, natric, or spodic horizon). If the underlying horizon is after mixing of the upper 18 cm of the mineral soil or of the a B horizon of alteration (defined below as a cambic or oxic whole mineral soil if its depth to a densic, lithic, or paralithic horizon) and there is no surface horizon that is appreciably contact, a petrocalcic horizon, or a duripan (all defined below) is darkened by humus, the lower limit of the ochric epipedon is the less than 18 cm, has the following properties: lower boundary of the plow layer or an equivalent depth (18 cm) in a soil that has not been plowed. Actually, the same horizon 1. When dry, either or both: in an unplowed soil may be both part of the epipedon and part a. Structural units with a diameter of 30 cm or less or of the cambic horizon; the ochric epipedon and the subsurface secondary structure with a diameter of 30 cm or less; or diagnostic horizons are not all mutually exclusive. The ochric epipedon does not have rock structure and does not include b. A moderately hard or softer rupture-resistance class; and finely stratified fresh sediments, nor can it be an Ap horizon 2. Rock structure, including fine stratifications (5 mm or less directly overlying such deposits. thick), in less than one-half of the volume of all parts; and Plaggen Epipedon 3. Both of the following: The plaggen epipedon is a human-made surface layer 50 a. Dominant colors with a value of 3 or less, moist, and of cm or more thick that has been produced by long-continued 5 or less, dry; and manuring. b. Dominant colors with chroma of 3 or less, moist; and Horizons and Characteristics Diagnostic for the Higher Categories 

o 4. A base saturation (by NH4OAc) of less than 50 percent in temperature at a depth of 50 cm is 5 C or higher, if the soil is some or all parts; and not irrigated; and 5. An organic-carbon content of: 9. The n value (defined below) is less than 0.7;and a. 0.6 percent (absolute) more than that of the C horizon 10. The umbric epipedon does not have the artifacts, spade D I (if one occurs) if the umbric epipedon has a color value less marks, and raised surfaces that are characteristic of the plaggen A than 1 unit lower or chroma less than 2 units lower (both epipedon. moist and dry) than the C horizon; or b. 0.6 percent or more and the epipedon does not meet the Diagnostic Subsurface Horizons qualifications in 5-a above;and The horizons described in this section form below the 6. The minimum thickness of the epipedon is as follows: surface of the soil, although in some areas they form directly a. 25 cm if: below a layer of leaf litter. They may be exposed at the surface (1) The texture class of the epipedon is loamy fine sand by truncation of the soil. Some of these horizons are generally regarded as B horizons, some are considered B horizons by or coarser throughout; or many but not all pedologists, and others are generally regarded (2) There are no underlying diagnostic horizons as parts of the A horizon. (defined below) and the organic-carbon content of the underlying materials decreases irregularly with increasing Agric Horizon depth; or The agric horizon is an illuvial horizon that has formed (3) Any of the following, if present, are 75 cm or more under cultivation and contains significant amounts of illuvial below the mineral soil surface: silt, clay, and humus. (a) The upper boundary of the shallowest of any Required Characteristics identifiable secondary carbonates or a calcic horizon, petrocalcic horizon, duripan, or fragipan (defined The agric horizon is directly below an Ap horizon and has below); and/or the following properties: (b) The lower boundary of the deepest of an argillic, 1. A thickness of 10 cm or more and either: cambic, natric, oxic, or spodic horizon; or a. 5 percent or more (by volume) wormholes, including b. 10 cm if the epipedon has a texture class finer than coatings that are 2 mm or more thick and have a value, moist, loamy fine sand (when mixed) and it is directly above a of 4 or less and chroma of 2 or less; or densic, lithic, or paralithic contact, a petrocalcic horizon, or a b. 5 percent or more (by volume) lamellae that have a duripan; or thickness of 5 mm or more and have a value, moist, of 4 or c. 18 to 25 cm and the thickness is one-third or more of the less and chroma of 2 or less. total thickness between the mineral soil surface and: (1) The upper boundary of the shallowest of any Albic Horizon identifiable secondary carbonates or a calcic horizon, The albic horizon is an eluvial horizon, 1.0 cm or more petrocalcic horizon, duripan, or fragipan; and/or thick, that has 85 percent or more (by volume) albic materials (2) The lower boundary of the deepest of an argillic, (defined below). It generally occurs below an A horizon but cambic, natric, oxic, or spodic horizon; or may be at the mineral soil surface. Under the albic horizon there generally is an argillic, cambic, kandic, natric, or spodic d. 18 cm if none of the above conditions apply; and horizon or a fragipan (defined below). The albic horizon may 7. Phosphate: lie between a spodic horizon and either a fragipan or an argillic horizon, or it may be between an argillic or kandic horizon and a. Content less than 1,500 milligrams per kilogram by a fragipan. It may lie between a mollic epipedon and an argillic citric-acid extraction; or or natric horizon or between a cambic horizon and an argillic, b. Content decreasing irregularly with increasing depth kandic, or natric horizon or a fragipan. The albic horizon may below the epipedon; or separate horizons that, if they were together, would meet the requirements for a mollic epipedon. It may separate lamellae c. Nodules are within the epipedon; and that together meet the requirements for an argillic horizon. 8. Some part of the epipedon is moist for 90 days or more These lamellae are not considered to be part of the albic (cumulative) in normal years during times when the soil horizon. 10 Keys to Soil Taxonomy

Argillic Horizon 1.2 times more clay than the eluvial horizon; or An argillic horizon is normally a subsurface horizon with a c. If the eluvial horizon has 40 percent or more total clay significantly higher percentage of phyllosilicate clay than the in the fine-earth fraction, the argillic horizon must contain overlying soil material. It shows evidence of clay illuviation. at least 8 percent (absolute) more clay (42 percent versus 50 The argillic horizon forms below the soil surface, but it may be percent, for example). exposed at the surface later by erosion. Required Characteristics Calcic Horizon 1. All argillic horizons must meet both of the following The calcic horizon is an illuvial horizon in which secondary requirements: calcium carbonate or other carbonates have accumulated to a significant extent. a. One of the following: Required Characteristics (1) If the argillic horizon meets the particle-size class criteria for coarse-loamy, fine-loamy, coarse-silty, fine- The calcic horizon: silty, fine, or very-fine or is loamy or clayey, including 1. Is 15 cm or more thick; and skeletal counterparts, it must be at least 7.5 cm thick or at least one-tenth as thick as the sum of the thickness of all 2. Has one or more of the following: overlying horizons, whichever is greater; or a. 15 percent or more (by weight) CaCO3 equivalent (see below), and its CaCO equivalent is 5 percent or more (2) If the argillic horizon meets the sandy or sandy- 3 skeletal particle-size criteria, it must be at least 15 cm (absolute) higher than that of an underlying horizon; or thick; or b. 15 percent or more (by weight) CaCO3 equivalent (3) If the argillic horizon is composed entirely of and 5 percent or more (by volume) identifiable secondary lamellae, the combined thickness of the lamellae that are carbonates; or 0.5 cm or more thick must be 15 cm or more; and c. 5 percent or more (by weight) calcium carbonate b. Evidence of clay illuviation in at least one of the equivalent and: following forms: (1) Has less than 18 percent clay in the fine-earth (1) Oriented clay bridging the sand grains; or fraction; and (2) Clay films lining pores; or (2) Meets the criteria for a sandy, sandy-skeletal, coarse- loamy, or loamy-skeletal particle-size class; and (3) Clay films on both vertical and horizontal surfaces of peds; or (3) Has 5 percent or more (by volume) identifiable secondary carbonates or a calcium carbonate equivalent (4) Thin sections with oriented clay bodies that are more (by weight) that is 5 percent or more (absolute) higher than 1 percent of the section; or than that of an underlying horizon; and (5) If the coefficient of linear extensibility is 0.04 or 3. Is not cemented or indurated in any part by carbonates, with higher and the soil has distinct wet and dry seasons, then or without other cementing agents, or is cemented in some part the ratio of fine clay to total clay in the illuvial horizon is and the cemented part satisfiesone of the following: greater by 1.2 times or more than the ratio in the eluvial horizon; and a. It is characterized by so much lateral discontinuity that roots can penetrate through noncemented zones or along 2. If an eluvial horizon remains and there is no lithologic vertical fractures with a horizontal spacing of less than 10 discontinuity between it and the illuvial horizon and no plow cm; or layer directly above the illuvial layer, then the illuvial horizon must contain more total clay than the eluvial horizon within a b. The cemented layer is less than 1 cm thick and consists vertical distance of 30 cm or less, as follows: of a laminar cap underlain by a lithic or paralithic contact; or a. If any part of the eluvial horizon has less than 15 percent c. The cemented layer is less than 10 cm thick. total clay in the fine-earth fraction, the argillic horizon must contain at least 3 percent (absolute) more clay (10 percent Cambic Horizon versus 13 percent, for example); or A cambic horizon is the result of physical alterations, b. If the eluvial horizon has 15 to 40 percent total clay in chemical transformations, or removals or of a combination of the fine-earth fraction, the argillic horizon must have at least two or more of these processes. Horizons and Characteristics Diagnostic for the Higher Categories 11

Required Characteristics 1. The pan is cemented or indurated in more than 50 percent of the volume of some horizon; and The cambic horizon is an altered horizon 15 cm or more thick. If it is composed of lamellae, the combined thickness of 2. The pan shows evidence of the accumulation of opal or the lamellae must be 15 cm or more. In addition, the cambic other forms of silica, such as laminar caps, coatings, lenses, D horizon must meet all of the following: partly filled interstices, bridges between sand-sized grains, or I coatings on rock and pararock fragments; and A 1. Has a texture class of very fine sand, loamy very fine sand, or finer;and 3. Less than 50 percent of the volume of air-dry fragments slakes in 1N HCl even during prolonged soaking, but more 2. Shows evidence of alteration in one of the following forms: than 50 percent slakes in concentrated KOH or NaOH or in a. Aquic conditions within 50 cm of the soil surface or alternating acid and alkali; and artificial drainage andall of the following: 4. Because of lateral continuity, roots can penetrate the pan (1) Soil structure or the absence of rock structure, only along vertical fractures with a horizontal spacing of 10 cm including fine stratifications (5 mm or less thick), in more or more. than one-half of the volume; and (2) Colors that do not change on exposure to air; and Fragipan (3) Dominant color, moist, on faces of peds or in the Required Characteristics matrix as follows: To be identified as a fragipan, a layer must haveall of the (a) Value of 3 or less and chroma of 0; or following characteristics: (b) Value of 4 or more and chroma of 1 or less; or 1. The layer is 15 cm or more thick; and (c) Any value, chroma of 2 or less, and redox 2. The layer shows evidence of pedogenesis within the horizon concentrations; or or, at a minimum, on the faces of structural units; and b. Does not have the combination of aquic conditions 3. The layer has very coarse prismatic, columnar, or blocky within 50 cm of the soil surface or artificial drainage and structure of any grade, has weak structure of any size, or is colors, moist, as defined in item 2-a-(3) above, and has soil massive. Separations between structural units that allow roots structure or the absence of rock structure, including fine to enter have an average spacing of 10 cm or more on the stratifications (5 mm or less thick), in more than one-half of horizontal dimensions; and the volume and of the following properties: one or more 4. Air-dry fragments of the natural soil fabric, 5 to 10 cm in (1) Higher chroma, higher value, redder hue, or higher diameter, from more than 50 percent of the layer slake when clay content than the underlying horizon or an overlying they are submerged in water; and horizon; or 5. The layer has, in 60 percent or more of the volume, a firm (2) Evidence of the removal of carbonates or gypsum; or firmer rupture-resistance class, a brittle manner of failure at and or near field capacity, and virtually no roots;and 3. Has properties that do not meet the requirements for an 6. The layer is not effervescent (in dilute HCl). anthropic, histic, folistic, melanic, mollic, plaggen, or umbric epipedon, a duripan or fragipan, or an argillic, calcic, gypsic, Glossic Horizon natric, oxic, petrocalcic, petrogypsic, placic, or spodic horizon; and The glossic horizon (Gr. glossa, tongue) develops as a result of the degradation of an argillic, kandic, or natric horizon from 4. Is not part of an Ap horizon and does not have a brittle which clay and free iron oxides are removed. manner of failure in more than 60 percent of the matrix. Required Characteristics Duripan The glossic horizon is 5 cm or more thick and consists of: A duripan is a silica-cemented subsurface horizon with or 1. An eluvial part (albic materials, defined below), which without auxiliary cementing agents. It can occur in conjunction constitutes 15 to 85 percent (by volume) of the glossic horizon; with a petrocalcic horizon. and Required Characteristics 2. An illuvial part, i.e., remnants (pieces) of an argillic, A duripan must meet all of the following requirements: kandic, or natric horizon (defined below). 12 Keys to Soil Taxonomy

Gypsic Horizon (1) Between 100 cm and 200 cm from the mineral soil surface if the upper 100 cm meets the criteria for a sandy The gypsic horizon is a horizon in which gypsum has or sandy-skeletal particle-size class throughout; or accumulated or been transformed to a significant extent. It typically occurs as a subsurface horizon, but it may occur at the (2) Within 100 cm from the mineral soil surface if surface in some soils. the clay content in the fine-earth fraction of the surface horizon is 20 percent or more; or Required Characteristics (3) Within 125 cm from the mineral soil surface for all A gypsic horizon meets all of the following requirements: other soils; and 1. Is 15 cm or more thick; and 3. Has a thickness of either: 2. Is not cemented by gypsum, with or without other a. 30 cm or more; cementing agents; is cemented and the cemented parts are or less than 5 mm thick; or is cemented but, because of lateral b. 15 cm or more if there is a densic, lithic, paralithic, or discontinuity, roots can penetrate along vertical fractures with a petroferric contact within 50 cm of the mineral soil surface horizontal spacing of less than 10 cm; and and the kandic horizon constitutes 60 percent or more of the vertical distance between a depth of 18 cm and the contact; 3. Is 5 percent or more (by weight) gypsum and has 1 percent or more (by volume) visible secondary gypsum that has either and accumulated or been transformed; and 4. Has a texture class of loamy very fine sand or finer;and 4. Has a product of thickness, in cm, multiplied by the gypsum 5. Has an apparent CEC of 16 cmol(+) or less per kg clay (by content (percent by weight) of 150 or more. Thus, a horizon 30 1N NH4OAc pH 7) and an apparent ECEC of 12 cmol(+) or less cm thick that is 5 percent gypsum qualifies as a gypsic horizon per kg clay (sum of bases extracted with 1N NH4OAc pH 7 plus if it is 1 percent or more (by volume) visible gypsum and any 1N KCl-extractable Al) in 50 percent or more of its thickness cementation is as described in 2 above. between the point where the clay increase requirements are met and either a depth of 100 cm below that point or a densic, lithic, Kandic Horizon paralithic, or petroferric contact if shallower. (The percentage of clay is either measured by the pipette method or estimated to Required Characteristics be 2.5 times [percent water retained at 1500 kPa tension minus The kandic horizon: percent organic carbon], whichever is higher, but no more than 100); and 1. Is a vertically continuous subsurface horizon that underlies a coarser textured surface horizon. The minimum thickness of 6. Has a regular decrease in organic-carbon content with the surface horizon is 18 cm after mixing or 5 cm if the textural increasing depth, no fine stratification, and no overlying layers transition to the kandic horizon is abrupt and there is no densic, more than 30 cm thick that have fine stratification and/or lithic, paralithic, or petroferric contact (defined below) within an organic-carbon content that decreases irregularly with 50 cm of the mineral soil surface; and increasing depth. 2. Has its upper boundary: Natric Horizon a. At the point where the clay percentage in the fine-earth fraction, increasing with depth within a vertical distance of A natric horizon is an illuvial horizon that is normally 15 cm or less, is either: present in the subsurface and has a significantly higher percentage of silicate clay than the overlying horizons. It shows (1) 4 percent or more (absolute) higher than that in the evidence of clay illuviation that has been accelerated by the surface horizon if that horizon has less than 20 percent dispersive properties of sodium. total clay in the fine-earth fraction;or Required Characteristics (2) 20 percent or more (relative) higher than that in the surface horizon if that horizon has 20 to 40 percent total The natric horizon: clay in the fine-earth fraction; or 1. Meets one of the following thickness requirements: (3) 8 percent or more (absolute) higher than that in the a. If the horizon meets the particle-size class criteria surface horizon if that horizon has more than 40 percent for coarse-loamy, fine-loamy, coarse-silty, fine-silty, fine, total clay in the fine-earth fraction;and or very-fine or is loamy or clayey, including skeletal b. At a depth: counterparts, it must be at least 7.5 cm thick or at least one- Horizons and Characteristics Diagnostic for the Higher Categories 13

tenth as thick as the sum of the thickness of all overlying b. More exchangeable magnesium plus sodium than horizons, whichever is greater; or calcium plus exchange acidity (at pH 8.2) in one or more horizons within 40 cm of its upper boundary if the ESP is 15 b. If the horizon meets sandy or sandy-skeletal particle-size or more (or the SAR is 13 or more) in one or more horizons class criteria, it must be at least 15 cm thick; or within 200 cm of the mineral soil surface. D I c. If the horizon is composed entirely of lamellae, the A combined thickness of the lamellae that are 0.5 cm or more thick must be 15 cm or more; and Ortstein 2. Has evidence of clay illuviation in at least one of the Required Characteristics following forms: Ortstein has all of the following: a. Oriented clay bridging the sand grains; or 1. Consists of spodic materials; and b. Clay films lining pores; or 2. Is in a layer that is 50 percent or more cemented; and c. Clay films on both vertical and horizontal surfaces of 3. Is 25 mm or more thick. peds; or

d. Thin sections with oriented clay bodies that are more Oxic Horizon than 1 percent of the section; or e. If the coefficient of linear extensibility is 0.04 or higher Required Characteristics and the soil has distinct wet and dry seasons, then the ratio of The oxic horizon is a subsurface horizon that does not fine clay to total clay in the illuvial horizon is greater by 1.2 have andic soil properties (defined below) and hasall of the times or more than the ratio in the eluvial horizon; and following characteristics: 3. If an eluvial horizon remains and there is no lithologic 1. A thickness of 30 cm or more; and discontinuity between it and the illuvial horizon and no plow layer directly above the illuvial horizon, then the illuvial horizon 2. A texture class of sandy loam or finer in the fine-earth must contain more total clay than the eluvial horizon within a fraction; and vertical distance of 30 cm or less, as follows: 3. Less than 10 percent weatherable minerals in the 50- to a. If any part of the eluvial horizon has less than 15 percent 200-micron fraction; and total clay in the fine-earth fraction, the illuvial horizon must 4. Rock structure in less than 5 percent of its volume, unless contain at least 3 percent (absolute) more clay (10 percent the lithorelicts with weatherable minerals are coated with versus 13 percent, for example); or sesquioxides; and b. If the eluvial horizon has 15 to 40 percent total clay in the fine-earth fraction, the illuvial horizon must have at least 5. A diffuse upper boundary, i.e., within a vertical distance of 15 cm, a clay increase with increasing depth of: 1.2 times more clay than the eluvial horizon; or c. If the eluvial horizon has 40 percent or more total clay a. Less than 4 percent (absolute) in its fine-earth fraction in the fine-earth fraction, the illuvial horizon must contain if the fine-earth fraction of the surface horizon contains less at least 8 percent (absolute) more clay (42 percent versus 50 than 20 percent clay; or percent, for example); and b. Less than 20 percent (relative) in its fine-earth fraction if 4. Has either: the fine-earth fraction of the surface horizon contains 20 to 40 percent clay; or a. Columnar or prismatic structure in some part (generally the upper part), which may part to blocky structure; or c. Less than 8 percent (absolute) in its fine-earth fraction if the fine-earth fraction of the surface horizon contains 40 b. Both blocky structure and eluvial materials, which percent or more clay); and contain uncoated silt or sand grains and extend more than 2.5 cm into the horizon; and 6. An apparent CEC of 16 cmol(+) or less per kg clay (by 1N NH OAc pH 7) and an apparent ECEC of 12 cmol(+) or less per 5. Has either: 4 kg clay (sum of bases extracted with 1N NH4OAc pH 7 plus 1N a. An exchangeable sodium percentage (ESP) of 15 percent KCl-extractable Al). (The percentage of clay is either measured or more (or a sodium adsorption ratio [SAR] of 13 or more) by the pipette method or estimated to be 3 times [percent water in one or more horizons within 40 cm of its upper boundary; retained at 1500 kPa tension minus percent organic carbon], or whichever value is higher, but no more than 100.) 14 Keys to Soil Taxonomy

Petrocalcic Horizon manganese and organic matter, with or without other cementing agents; and The petrocalcic horizon is an illuvial horizon in which secondary calcium carbonate or other carbonates have 2. Because of lateral continuity, roots can penetrate only along accumulated to the extent that the horizon is cemented or vertical fractures with a horizontal spacing of 10 cm or more; indurated. and Required Characteristics 3. The horizon has a minimum thickness of 1 mm and, where associated with spodic materials, is less than 25 mm thick. A petrocalcic horizon must meet the following requirements: 1. The horizon is cemented or indurated by carbonates, with or Salic Horizon without silica or other cementing agents; and A salic horizon is a horizon of accumulation of salts that are 2. Because of lateral continuity, roots can penetrate only along more soluble than gypsum in cold water. vertical fractures with a horizontal spacing of 10 cm or more; and Required Characteristics 3. The horizon has a thickness of: A salic horizon is 15 cm or more thick and has, for 90 consecutive days or more in normal years: a. 10 cm or more; or 1. An electrical conductivity (EC) equal to or greater than 30 b. 1 cm or more if it consists of a laminar cap directly dS/m in the water extracted from a saturated paste; and underlain by bedrock. 2. A product of the EC, in dS/m, and thickness, in cm, equal to Petrogypsic Horizon 900 or more. The petrogypsic horizon is a horizon in which visible secondary gypsum has accumulated or has been transformed. Sombric Horizon The horizon is cemented (i.e., extremely weakly through A sombric horizon (F. sombre, dark) is a subsurface horizon indurated cementation classes), and the cementation is both in mineral soils that has formed under free drainage. It contains laterally continuous and root limiting, even when the soil is illuvial humus that is neither associated with aluminum, as is moist. The horizon typically occurs as a subsurface horizon, but the humus in the spodic horizon, nor dispersed by sodium, as it may occur at the surface in some soils. is common in the natric horizon. Consequently, the sombric Required Characteristics horizon does not have the high cation-exchange capacity in its clay that characterizes a spodic horizon and does not have the A petrogypsic horizon meets all of the following high base saturation of a natric horizon. It does not underlie an requirements: albic horizon. 1. Is cemented or indurated by gypsum, with or without other Sombric horizons are thought to be restricted to the cool, cementing agents; and moist soils of high plateaus and mountains in tropical or subtropical regions. Because of strong leaching, their base 2. Because of lateral continuity, can be penetrated by roots saturation is low (less than 50 percent by NH4OAc). only along vertical fractures with a horizontal spacing of 10 cm The sombric horizon has a lower color value or chroma, or more; and or both, than the overlying horizon and commonly contains 3. Is 5 mm or more thick; and more organic matter. It may have formed in an argillic, cambic, or oxic horizon. If peds are present, the dark colors are most 4. Is 40 percent or more (by weight) gypsum. pronounced on surfaces of peds. In the field a sombric horizon is easily mistaken for a buried Placic Horizon A horizon. It can be distinguished from some buried epipedons by lateral tracing. In thin sections the organic matter of a The placic horizon (Gr. base of plax, flat stone; meaning a sombric horizon appears more concentrated on peds and in thin cemented pan) is a thin, black to dark reddish pan that is pores than uniformly dispersed throughout the matrix. cemented by iron (or iron and manganese) and organic matter.

Required Characteristics Spodic Horizon A placic horizon must meet the following requirements: A spodic horizon is an illuvial layer with 85 percent or more 1. The horizon is cemented or indurated with iron or iron and spodic materials (defined below). Horizons and Characteristics Diagnostic for the Higher Categories 15

Required Characteristics 1. Chroma of 2 or less; and either A spodic horizon is normally a subsurface horizon a. A color value, moist, of 3 and a color value, dry, of 6 or underlying an O, A, Ap, or E horizon. It may, however, meet the more; or definition of an umbric epipedon. b. A color value, moist, of 4 or more and a color value, dry, D A spodic horizon must have 85 percent or more spodic I of 5 or more; or materials in a layer 2.5 cm or more thick that is not part of any A Ap horizon. 2. Chroma of 3 or less; and either a. A color value, moist, of 6 or more; or Diagnostic Soil Characteristics for Mineral b. A color value, dry, of 7 or more; or Soils 3. Chroma that is controlled by the color of uncoated grains of Diagnostic soil characteristics are features of the soil that silt or sand, hue of 5YR or redder, and the color values listed in are used in various places in the keys or in the definitions of item 1-a or 1-b above. diagnostic horizons. Relatively unaltered layers of light colored sand, volcanic ash, or other materials deposited by wind or water are not Abrupt Textural Change considered albic materials, although they may have the same An abrupt textural change is a specific kind of change that color and apparent morphology. These deposits are parent may occur between an ochric epipedon or an albic horizon materials that are not characterized by the removal of clay and an argillic horizon. It is characterized by a considerable and/or free iron and do not overlie an illuvial horizon or other increase in clay content within a very short vertical distance in soil horizon, except for a buried soil. Light colored krotovinas the zone of contact. If the clay content in the fine-earth fraction or filled root channels should be considered albic materials only of the ochric epipedon or albic horizon is less than 20 percent, if they have no fine stratifications or lamellae, if any sealing it doubles within a vertical distance of 7.5 cm or less. If the along the krotovina walls has been destroyed, and if these clay content in the fine-earth fraction of the ochric epipedon or intrusions have been leached of free iron oxides and/or clay the albic horizon is 20 percent or more, there is an increase of after deposition. 20 percent or more (absolute) within a vertical distance of 7.5 cm or less (e.g., an increase from 22 to 42 percent) and the clay Andic Soil Properties content in some part of the argillic horizon is 2 times or more the amount contained in the overlying horizon. Andic soil properties commonly form during weathering of Normally, there is no transitional horizon between an tephra or other parent materials containing a significant content ochric epipedon or an albic horizon and an argillic horizon, of volcanic glass. Soils that are in cool, humid climates and or the transitional horizon is too thin to be sampled. Some have abundant organic carbon, however, may develop andic soil soils, however, have a glossic horizon or interfingering of properties without the influence of volcanic glass. A suite of albic materials (defined below) in parts of the argillic horizon. glass and glass-coated minerals rich in silica is termed volcanic The upper boundary of such a horizon is irregular or even glass in this taxonomy. These minerals are relatively soluble and discontinuous. Sampling this mixture as a single horizon might undergo fairly rapid transformation when the soils are moist. create the impression of a relatively thick transitional horizon, Andic soil properties represent a stage in transition where whereas the thickness of the actual transition at the contact may weathering and transformation of primary alumino-silicates be no more than 1 mm. (e.g., volcanic glass) have proceeded only to the point of the formation of short-range-order materials, such as allophane, Albic Materials imogolite, and ferrihydrite, or of metal-humus complexes. The concept of andic soil properties includes moderately weathered Albic (L. albus, white) materials are soil materials with a soil material, rich in short-range-order materials or metal- color that is largely determined by the color of primary sand humus complexes, or both, with or without volcanic glass and silt particles rather than by the color of their coatings. (required characteristic 2) and weakly weathered soil, less rich This definition implies that clay and/or free iron oxides have in short-range-order materials with volcanic glass (required been removed from the materials or that the oxides have been characteristic 3). segregated to such an extent that the color of the materials is Relative amounts of allophane, imogolite, ferrihydrite, or largely determined by the color of the primary particles. metal-humus complexes in the colloidal fraction are inferred from laboratory analyses of aluminum, iron, and silica extracted Required Characteristics by ammonium oxalate, and from phosphate retention. Soil Albic materials have one of the following colors: scientists may use smeariness or pH in 1N sodium fluoride 16 Keys to Soil Taxonomy

3. All of the following: a. 30 percent or more of the fine-earth fraction is 0.02 to 2.0 mm in size; and b. Phosphate retention of 25 percent or more; and c. Al + ½ Fe content (by ammonium oxalate) equal to 0.4 percent or more; and d. Volcanic glass content of 5 percent or more; and e. [(Al + ½ Fe content, percent) times (15.625)] + [volcanic glass content, percent] = 36.25 or more. The shaded area in figure 1 illustrates criteria 3c, 3d, and 3e.

Anhydrous Conditions Anhydrous conditions (Gr. anydros, waterless) refer to the moisture condition of soils in very cold deserts and other areas with permafrost (often dry permafrost). These soils typically have low precipitation (usually less than 50 mm water equivalent per year) and a moisture content of less than 3 percent by weight. Anhydrous soil conditions are similar to the aridic (torric) soil moisture regimes (defined below), except that the soil temperature at 50 cm is less than 5 oC throughout the year in the soil layers with these conditions.

Required Characteristics

Figure 1.—Soils that are plotted in the shaded area meet the andic Soils with anhydrous conditions have a mean annual soil soil properties criteria c, d, and e under item 3 of the required temperature of 0 oC or colder. The layer from 10 to 70 cm characteristics. To qualify as soils with andic properties, the soils below the soil surface has a soil temperature of less than 5 oC must also meet the listed requirements for organic-carbon content, throughout the year and this layer: phosphate retention, and particle-size distribution. 1. Includes no ice-cemented permafrost; and

(NaF) as field indicators of andic soil properties.Volcanic 2. Is dry (water held at 1500 kPa or more) in one-half or more glass content is the percent volcanic glass (by grain count) in of the soil for one-half or more of the time the layer has a soil o the coarse silt and sand (0.02 to 2.0 mm) fraction. Most soil temperature above 0 C; or materials with andic soil properties consist of mineral soil 3. Has a rupture-resistance class of loose to slightly hard materials, but some are organic soil materials with less than 25 throughout when the soil temperature is 0 oC or colder, except percent organic carbon. where a cemented pedogenic horizon occurs. Required Characteristics Coefficient of Linear Extensibility (COLE) Soil materials with andic soil properties must have a fine- earth fraction that meets the following requirements: The coefficient of linear extensibility (COLE) is the ratio of the difference between the moist length and dry length of a 1. Less than 25 percent organic carbon (by weight) and one or clod to its dry length. It is (Lm - Ld)/Ld, where Lm is the length both of the following: at 33 kPa tension and Ld is the length when dry. COLE can be 2. All of the following: calculated from the differences in bulk density of the clod when moist and when dry. An estimate of COLE can be calculated in a. Bulk density, measured at 33 kPa water retention, of 0.90 the field by measuring the distance between two pins in a clod 3 g/cm or less; and of undisturbed soil at field capacity and again after the clod has b. Phosphate retention of 85 percent or more; and dried. COLE does not apply if the shrinkage is irreversible. c. Al + ½ Fe content (by ammonium oxalate) equal to 2.0 percent or more; or Horizons and Characteristics Diagnostic for the Higher Categories 17

Durinodes with cold, dilute HCl. The term “free carbonates” is nearly synonymous with the term “calcareous.” Soils that have free Durinodes (L. durus, hard, and nodus, knot) are weakly carbonates generally have calcium carbonate as a common cemented to indurated nodules or concretions with a diameter mineral, although sodium and magnesium carbonates are also of 1 cm or more. The cement is SiO , presumably opal and 2 included in this concept. Soils or horizons with free carbonates D microcrystalline forms of silica. Durinodes break down in I may have inherited the carbonate compounds from parent A hot concentrated KOH after treatment with HCl to remove materials without any translocation or transformation processes carbonates but do not break down with concentrated HCl alone. acting on them. There is no implication of pedogenesis in the Dry durinodes do not slake appreciably in water, but prolonged concept of free carbonates, as there is in identifiable secondary soaking can result in spalling of very thin platelets. Durinodes carbonates (defined below), although most forms of secondary are firm or firmer and brittle when wet, both before and after carbonates are freely effervescent. treatment with acid. Some durinodes are roughly concentric when viewed in cross section, and concentric stringers of opal are visible under a hand lens. Identifiable Secondary Carbonates The term “identifiable secondary carbonates” is used in Fragic Soil Properties the definitions of a number of taxa. It refers to translocated Fragic soil properties are the essential properties of a authigenic calcium carbonate that has been precipitated in place fragipan. They have neither the layer thickness nor volume from the soil solution rather than inherited from a soil parent requirements for the fragipan. Fragic soil properties are in material, such as calcareous loess or limestone residuum. subsurface horizons, although they can be at or near the surface Identifiable secondary carbonates either may disrupt the soil in truncated soils. Aggregates with fragic soil properties have structure or fabric, forming masses, nodules, concretions, or a firm or firmer rupture-resistance class and a brittle manner spheroidal aggregates (white eyes) that are soft and powdery of failure when soil water is at or near field capacity. Air-dry when dry, or may be present as coatings in pores, on structural fragments of the natural fabric, 5 to 10 cm in diameter, slake faces, or on the undersides of rock or pararock fragments. If when they are submerged in water. Aggregates with fragic soil present as coatings, the secondary carbonates cover a significant properties show evidence of pedogenesis, including one or more part of the surfaces. Commonly, they coat all of the surfaces of the following: oriented clay within the matrix or on faces of to a thickness of 1 mm or more. If little calcium carbonate is peds, redoximorphic features within the matrix or on faces of present in the soil, however, the surfaces may be only partially peds, strong or moderate soil structure, and coatings of albic coated. The coatings must be thick enough to be visible when materials or uncoated silt and sand grains on faces of peds or in moist. Some horizons are entirely engulfed by carbonates. The seams. Peds with these properties are considered to have fragic color of these horizons is largely determined by the carbonates. soil properties regardless of whether or not the density and The carbonates in these horizons are within the concept of brittleness are pedogenic. identifiable secondary carbonates. Soil aggregates with fragic soil properties must: The filaments commonly seen in a dry calcareous horizon are within the meaning of identifiable secondary carbonates if the 1. Show evidence of pedogenesis within the aggregates or, at a filaments are thick enough to be visible when the soil is moist. minimum, on the faces of the aggregates; and Filaments commonly branch on structural faces. 2. Slake when air-dry fragments of the natural fabric, 5 to 10 cm in diameter, are submerged in water; and Interfingering of Albic Materials 3. Have a firm or firmer rupture-resistance class and a brittle The term “interfingering of albic materials” refers to albic manner of failure when soil water is at or near field capacity; materials that penetrate 5 cm or more into an underlying and argillic, kandic, or natric horizon along vertical and, to a lesser 4. Restrict the entry of roots into the matrix when soil water is degree, horizontal faces of peds. There need not be a continuous at or near field capacity. overlying albic horizon. The albic materials constitute less than 15 percent of the layer that they penetrate, but they form continuous skeletans (ped coatings of clean silt or sand defined Free Carbonates by Brewer, 1976) 1 mm or more thick on the vertical faces of The term “free carbonates” is used in the definitions of a peds, which means a total width of 2 mm or more between number of taxa, is used as a criterion for the isotic mineralogy abutting peds. Because quartz is such a common constituent of class, and is mentioned in the discussion of chemical analyses silt and sand, these skeletans are usually light gray when moist in the Appendix. It refers to soil carbonates that are uncoated and nearly white when dry, but their color is determined in large or unbound and that effervesce visibly or audibly when treated part by the color of the sand or silt fraction. 18 Keys to Soil Taxonomy

Required Characteristics all soil horizons. Linear extensibility is a criterion for most Vertic subgroups in this taxonomy and is calculated as summed Interfingering of albic materials is recognized if albic products from the mineral soil surface to a depth of 100 cm or materials: to a root-limiting layer. 1. Penetrate 5 cm or more into an underlying argillic or natric horizon; and Lithologic Discontinuities 2. Are 2 mm or more thick between vertical faces of abutting Lithologic discontinuities are significant changes in particle- peds; and size distribution or mineralogy that represent differences in 3. Constitute less than 15 percent (by volume) of the layer that lithology within a soil. A lithologic discontinuity can also they penetrate. denote an age difference. For information on using horizon designations for lithologic discontinuities, see the Soil Survey Manual (USDA, SCS, 1993). Lamellae Not everyone agrees on the degree of change required for A lamella is an illuvial horizon less than 7.5 cm thick. Each a lithologic discontinuity. No attempt is made to quantify lamella contains an accumulation of oriented silicate clay on lithologic discontinuities. The discussion below is meant to or bridging sand and silt grains (and rock fragments if any are serve as a guideline. present). A lamella has more silicate clay than the overlying Several lines of field evidence can be used to evaluate eluvial horizon. lithologic discontinuities. In addition to mineralogical and textural differences that may require laboratory studies, certain Required Characteristics observations can be made in the field. These include but are not A lamella is an illuvial horizon less than 7.5 cm thick formed limited to the following: in unconsolidated regolith more than 50 cm thick. Each lamella 1. Abrupt textural contacts.—An abrupt change in contains an accumulation of oriented silicate clay on or bridging particle-size distribution, which is not solely a change in clay the sand and silt grains (and rock fragments if any are present). content resulting from pedogenesis, can often be observed. Each lamella is required to have more silicate clay than the 2. Contrasting sand sizes.—Significant changes in sand overlying eluvial horizon. size can be detected. For example, if material containing mostly Lamellae occur in a vertical series of two or more, and each medium sand or finer sand abruptly overlies material containing lamella must have an overlying eluvial horizon. (An eluvial mostly coarse sand and very coarse sand, one can assume that horizon is not required above the uppermost lamella if the soil is there are two different materials. Although the materials may be truncated.) of the same mineralogy, the contrasting sand sizes result from Lamellae may meet the requirements for either a cambic or differences in energy at the time of deposition by water and/or an argillic horizon. A combination of two or more lamellae 15 wind. cm or more thick is a cambic horizon if the texture class is 3. Bedrock lithology vs. rock fragment lithology in the very fine sand, loamy very fine sand, or finer. A combination soil.—If a soil with rock fragments overlies a lithic contact, one of two or more lamellae meets the requirements for an argillic would expect the rock fragments to have a lithology similar to horizon if there is 15 cm or more cumulative thickness of that of the material below the lithic contact. If many of the rock lamellae that are 0.5 cm or more thick and that have a clay fragments do not have the same lithology as the underlying content of either: bedrock, the soil is not derived completely from the underlying bedrock. 1. 3 percent or more (absolute) higher than in the overlying 4. Stone lines.—The occurrence of a horizontal line of eluvial horizon (e.g., 13 percent versus 10 percent) if any part of rock fragments in the vertical sequence of a soil indicates that the eluvial horizon has less than 15 percent clay in the fine-earth the soil may have developed in more than one kind of parent fraction; or material. The material above the stone line is most likely 2. 20 percent or more (relative) higher than in the overlying transported, and the material below may be of different origin. eluvial horizon (e.g., 24 percent versus 20 percent) if all parts of 5. Inverse distribution of rock fragments.—A lithologic the eluvial horizon have more than 15 percent clay in the fine- discontinuity is often indicated by an erratic distribution of rock earth fraction. fragments. The percentage of rock fragments decreases with increasing depth. This line of evidence is useful in areas of soils Linear Extensibility (LE) that have relatively unweathered rock fragments. 6. Rock fragment weathering rinds.—Horizons Linear extensibility (LE) helps to predict the potential of a containing rock fragments with no rinds that overlie horizons soil to shrink and swell. The LE of a soil layer is the product containing rocks with rinds suggest that the upper material is in of the thickness, in cm, multiplied by the COLE of the layer part depositional and not related to the lower part in time and in question. The LE of a soil is the sum of these products for perhaps in lithology. Horizons and Characteristics Diagnostic for the Higher Categories 19

7. Shape of rock fragments.—A soil with horizons n = (A - 0.2R)/(L + 3H) containing angular rock fragments overlying horizons In this formula, A is the percentage of water in the soil containing well rounded rock fragments may indicate a in field condition, calculated on a dry-soil basis; R is the discontinuity. This line of evidence represents different percentage of silt plus sand; L is the percentage of clay; and mechanisms of transport (colluvial vs. alluvial) or even different H is the percentage of organic matter (percent organic carbon D I transport distances. multiplied by 1.724). A 8. Soil color.—Abrupt changes in color that are not the Few data for calculations of the n value are available result of pedogenic processes can be used as indicators of in the United States, but the critical n value of 0.7 can be discontinuity. approximated closely in the field by a simple test of squeezing 9. Micromorphological features.—Marked differences in a soil sample in the palm of a hand. If the soil flows between the size and shape of resistant minerals in one horizon and not the fingers with difficulty, then value is between 0.7 and 1.0 in another are indicators of differences in materials. (slightly fluid manner of failure class); if the soil flows easily between the fingers, then value is 1 or more (moderately fluid Use of Laboratory Data or very fluid manner of failure class); and if no soil material Discontinuities are not always readily apparent in the field. In flows through the fingers during full compression, the sample these cases laboratory data are necessary. Even with laboratory has an n value less than 0.7 (nonfluid manner of failure class). data, detecting discontinuities may be difficult. The decision is a qualitative or perhaps a partly quantitative judgment. General Petroferric Contact concepts of lithology as a function of depth might include: 1. Laboratory data—visual scan.—The array of A petroferric (Gr. petra, rock, and L. ferrum, iron; implying laboratory data is assessed in an attempt to determine if a field- ironstone) contact is a boundary between soil and a continuous designated discontinuity is corroborated and if any data show layer of indurated material in which iron is an important cement evidence of a discontinuity not observed in the field. One must and organic matter is either absent or present only in traces. The sort changes in lithology from changes caused by pedogenic indurated layer must be continuous within the limits of each processes. In most cases the quantities of sand and coarser pedon, but it may be fractured if the average lateral distance fractions are not altered significantly by soil-forming processes. between fractures is 10 cm or more. The fact that this ironstone Therefore, an abrupt change in sand size or sand mineralogy layer contains little or no organic matter distinguishes it from a is a clue to lithologic change. Gross soil mineralogy and the placic horizon and an indurated spodic horizon (ortstein), both resistant mineral suite are other clues. of which contain organic matter. 2. Data on a clay-free basis.—A common manipulation Several features can aid in making the distinction between in assessing lithologic change is computation of sand and silt a lithic contact and a petroferric contact. First, a petroferric separates on a carbonate-free, clay-free basis (percent fraction, contact is roughly horizontal. Second, the material directly e.g., fine sand and very fine sand, divided by percent sand plus below a petroferric contact contains a high amount of iron silt, times 100). Clay distribution is subject to pedogenic change (normally 30 percent or more Fe2O3). Third, the ironstone sheets and may either mask inherited lithologic differences or produce below a petroferric contact are thin; their thickness ranges differences that are not inherited from lithology. The numerical from a few centimeters to very few meters. Sandstone, on the array computed on a clay-free basis can be inspected visually or other hand, may be thin or very thick, may be level-bedded or plotted as a function of depth. tilted, and may contain only a small percentage of Fe2O3. In the Another aid used to assess lithologic changes is computation Tropics, the ironstone is generally more or less vesicular. of the ratios of one sand separate to another. The ratios can be computed and examined as a numerical array, or they can Plinthite be plotted. The ratios work well if sufficient quantities of the two fractions are available. Low quantities magnify changes in Plinthite (Gr. plinthos, brick) is an iron-rich, humus-poor ratios, especially if the denominator is low. mixture of clay with quartz and other minerals. It commonly occurs as dark red redox concentrations that usually form platy, polygonal, or reticulate patterns. Plinthite changes irreversibly n Value to an ironstone hardpan or to irregular aggregates on exposure The n value (Pons and Zonneveld, 1965) characterizes the to repeated wetting and drying, especially if it is also exposed relation between the percentage of water in a soil under field to heat from the sun. The lower boundary of a zone in which conditions and its percentages of inorganic clay and humus. plinthite occurs generally is diffuse or gradual, but it may be The n value is helpful in predicting whether a soil can be grazed abrupt at a lithologic discontinuity. by livestock or can support other loads and in predicting what Plinthite may occur as a constituent of a number of horizons, degree of subsidence would occur after drainage. such as an epipedon, a cambic horizon, an argillic horizon, an For mineral soil materials that are not thixotropic, the n value oxic horizon, or a C horizon. It is one form of the material that can be calculated by the following formula: has been called laterite. It normally forms in a horizon below 20 Keys to Soil Taxonomy

the surface, but it may form at the surface in a seep area at the mm fraction. Examples are quartz, zircon, tourmaline, beryl, base of a slope. anatase, rutile, iron oxides and oxyhydroxides, 1:1 dioctahedral From a genetic viewpoint, plinthite forms by segregation phyllosilicates (kandites), gibbsite, and hydroxy-aluminum of iron. In many places iron probably has been added from interlayered 2:1 minerals (Burt, 2004). other horizons or from the higher adjacent soils. Generally, plinthite forms in a horizon that is saturated with water for Slickensides some time during the year. Initially, iron is normally segregated in the form of soft, more or less clayey, red or dark red redox Slickensides are polished and grooved surfaces and generally concentrations. These concentrations are not considered have dimensions exceeding 5 cm. They are produced when plinthite unless there has been enough segregation of iron to one soil mass slides past another. Some slickensides occur permit their irreversible hardening on exposure to repeated at the lower boundary of a slip surface where a mass of soil wetting and drying. moves downward on a relatively steep slope. Slickensides result Plinthite is firm or very firm when the soil moisture content directly from the swelling of clay minerals and shear failure. is near field capacity and hard when the moisture content is They are very common in swelling clays that undergo marked below the wilting point. Plinthite occurs as discrete bodies changes in moisture content. larger than 2 mm that can be separated from the matrix. A moist aggregate of plinthite will withstand moderate rolling between Spodic Materials thumb and forefinger and is less than strongly cemented. Moist Spodic materials form in an illuvial horizon that normally or air-dried plinthite will not slake when submerged in water underlies a histic, ochric, or umbric epipedon or an albic even with gentle agitation. Plinthite does not harden irreversibly horizon. In most undisturbed areas, spodic materials underlie an as a result of a single cycle of drying and rewetting. After a albic horizon. They may occur within an umbric epipedon or an single drying, it will remoisten and then can be dispersed in Ap horizon. large part if one shakes it in water with a dispersing agent. A horizon consisting of spodic materials normally has an In a moist soil, plinthite is soft enough to be cut with a spade. optical-density-of-oxalate-extract (ODOE) value of 0.25 or After irreversible hardening, it is no longer considered plinthite more, and that value is commonly at least 2 times as high as the but is called ironstone. Indurated ironstone materials can be ODOE value in an overlying eluvial horizon. This increase in broken or shattered with a spade but cannot be dispersed if one ODOE value indicates an accumulation of translocated organic shakes them in water with a dispersing agent. materials in an illuvial horizon. Soils with spodic materials A small amount of plinthite in the soil does not form a show evidence that organic materials and aluminum, with or continuous phase; that is, the individual redox concentrations without iron, have been moved from an eluvial horizon to an or aggregates are not connected with each other. If a large illuvial horizon. amount of plinthite is present, it may form a continuous phase. Individual aggregates of plinthite in a continuous phase are Definition of Spodic Materials interconnected, and the spacing of cracks or zones that roots can Spodic materials are mineral soil materials that do not enter is 10 cm or more. have all of the properties of an argillic or kandic horizon; are If a continuous layer becomes indurated, it is a massive dominated by active amorphous materials that are illuvial and ironstone layer that has irregular, somewhat tubular inclusions are composed of organic matter and aluminum, with or without of yellowish, grayish, or white, clayey material. If the layer iron; and have both of the following: is exposed, these inclusions may be washed out, leaving an ironstone that has many coarse, tubular pores. 1. A pH value in water (1:1) of 5.9 or less and an organic- Much that has been called laterite is included in the carbon content of 0.6 percent or more; and meaning of plinthite. Doughy and concretionary laterite that 2. One or both of the following: has not hardened is an example. Hardened laterite, whether it is vesicular or pisolitic, is not included in the definition of a. An overlying albic horizon that extends horizontally plinthite. through 50 percent or more of each pedon and, directly under the albic horizon, colors, moist (crushed and smoothed Resistant Minerals sample), as follows: (1) Hue of 5YR or redder; or Several references are made to resistant minerals in this taxonomy. Obviously, the stability of a mineral in the soil is a (2) Hue of 7.5YR, color value of 5 or less, and chroma partial function of the soil moisture regime. Where resistant of 4 or less; or minerals are referred to in the definitions of diagnostic horizons (3) Hue of 10YR or neutral and a color value and and of various taxa, a humid climate, past or present, is always chroma of 2 or less; or assumed. Resistant minerals are durable minerals in the 0.02 to 2.0 (4) A color of 10YR 3/1; or Horizons and Characteristics Diagnostic for the Higher Categories 21

b. With or without an albic horizon and one of the colors Obviously, this definition of the term “weatherable minerals” listed above or hue of 7.5YR, color value, moist, of 5 or less, is restrictive. The intent is to include, in the definitions of chroma of 5 or 6 (crushed and smoothed sample), and one or diagnostic horizons and various taxa, only those weatherable more of the following morphological or chemical properties: minerals that are unstable in a humid climate compared to other minerals, such as quartz and 1:1 lattice clays, but that are D (1) Cementation by organic matter and aluminum, with I more resistant to weathering than calcite. Calcite, carbonate or without iron, in 50 percent or more of each pedon A aggregates, gypsum, and halite are not considered weatherable and a very firm or firmer rupture-resistance class in the minerals because they are mobile in the soil. They appear to be cemented part; or recharged in some otherwise strongly weathered soils. (2) 10 percent or more cracked coatings on sand grains; or

1 Characteristics Diagnostic for (3) Al + /2 Fe percentages (by ammonium oxalate) totaling 0.50 or more, and half that amount or less in an Organic Soils overlying umbric (or subhorizon of an umbric) epipedon, Following is a description of the characteristics that are used ochric epipedon, or albic horizon; or only with organic soils. (4) An optical-density-of-oxalate-extract (ODOE) value of 0.25 or more, and a value half as high or lower in an Kinds of Organic Soil Materials overlying umbric (or subhorizon of an umbric) epipedon, ochric epipedon, or albic horizon. Three different kinds of organic soil materials are distinguished in this taxonomy, based on the degree of Volcanic Glass decomposition of the plant materials from which the organic materials are derived. The three kinds are (1) fibric, (2) hemic, Volcanic glass is defined herein as optically isotropic and (3) sapric. Because of the importance of fiber content in the translucent glass or pumice of any color. It includes glass, definitions of these materials, fibers are defined before the kinds pumice, glass-coated crystalline minerals, glass aggregates, and of organic soil materials. glassy materials. Volcanic glass is typically a dominant component in Fibers relatively unweathered tephra. Weathering and mineral transformation of volcanic glass can produce short-range-order Fibers are pieces of plant tissue in organic soil materials minerals, such as allophane, imogolite, and ferrihydrite. (excluding live roots) that: Volcanic glass content is the percent (by grain count) of 1. Are large enough to be retained on a 100-mesh sieve glass, glass-coated mineral grains, glass aggregates, and glassy (openings 0.15 mm across) when the materials are screened; materials in the 0.02 to 2.0 mm fraction. Typically, the content and is determined for one particle-size fraction (i.e., coarse silt, very fine sand, or fine sand) and used as an estimate of glass content 2. Show evidence of the cellular structure of the plants from in the 0.02 to 2.0 mm fraction. which they are derived; and Volcanic glass content is a criterion in classification of andic 3. Either are 2 cm or less in their smallest dimension or soil properties, subgroups with the formative element “vitr(i),” are decomposed enough to be crushed and shredded with the families with “ashy” substitutes for particle-size class, and the fingers. glassy mineralogy class. Pieces of wood that are larger than 2 cm in cross section and Weatherable Minerals are so undecomposed that they cannot be crushed and shredded with the fingers, such as large branches, logs, and stumps, Several references are made to weatherable minerals in this are not considered fibers but are considered coarse fragments taxonomy. Obviously, the stability of a mineral in a soil is a (comparable to gravel, stones, and boulders in mineral soils). partial function of the soil moisture regime. Where weatherable minerals are referred to in the definitions of diagnostic horizons Fibric Soil Materials and of various taxa in this taxonomy, a humid climate, either present or past, is always assumed. Examples of the minerals Fibric soil materials are organic soil materials that either: that are included in the meaning of weatherable minerals are all 1. Contain three-fourths or more (by volume) fibers after 2:1 phyllosilicates, chlorite, sepiolite, palygorskite, allophane, rubbing, excluding coarse fragments; or 1:1 trioctahedral phyllosilicates (serpentines), feldspars, feldspathoids, ferromagnesian minerals, volcanic glass, zeolites, 2. Contain two-fifths or more (by volume) fibers after rubbing, dolomite, and apatite in the 0.02 to 2.0 mm fraction. excluding coarse fragments, and yield color values and chromas 22 Keys to Soil Taxonomy

of 7/1, 7/2, 8/1, 8/2, or 8/3 (fig. 2) on white chromatographic and the lowest water content on a dry-weight basis at saturation. or filter paper that is inserted into a paste made of the soil Sapric soil materials are commonly very dark gray to black. materials in a saturated sodium-pyrophosphate solution. They are relatively stable; i.e., they change very little physically and chemically with time in comparison to other organic soil Hemic Soil Materials materials. Sapric materials have the following characteristics: Hemic soil materials (Gr. hemi, half; implying intermediate decomposition) are intermediate in their degree of 1. The fiber content, after rubbing, is less than one-sixth (by decomposition between the less decomposed fibric and more volume), excluding coarse fragments; and decomposed sapric materials. Their morphological features give 2. The color of the sodium-pyrophosphate extract on white intermediate values for fiber content, bulk density, and water chromatographic or filter paper is below or to the right of a content. Hemic soil materials are partly altered both physically line drawn to exclude blocks 5/1, 6/2, and 7/3 (fig. 2). If few and biochemically. or no fibers can be detected and the color of the pyrophosphate extract is to the left of or above this line, the possibility that the Sapric Soil Materials material is limnic must be considered. Sapric soil materials (Gr. sapros, rotten) are the most highly decomposed of the three kinds of organic soil materials. They Humilluvic Material have the smallest amount of plant fiber, the highest bulk density, Humilluvic material, i.e., illuvial humus, accumulates in the lower parts of some organic soils that are acid and have been drained and cultivated. The humilluvic material has a C14 age that is not older than the overlying organic materials. It has very high solubility in sodium pyrophosphate and rewets very slowly after drying. Most commonly, it accumulates near a contact with a sandy mineral horizon. To be recognized as a differentia in classification, the humilluvic material must constitute one-half or more (by volume) of a layer 2 cm or more thick.

Limnic Materials The presence or absence of limnic deposits is taken into account in the higher categories of Histosols but not Histels. The nature of such deposits is considered in the lower categories of Histosols. Limnic materials include both organic and inorganic materials that were either (1) deposited in water by precipitation or through the action of aquatic organisms, such as algae or diatoms, or (2) derived from underwater and floating aquatic plants and subsequently modified by aquatic animals. They include coprogenous earth (sedimentary peat), diatomaceous earth, and marl.

Coprogenous Earth A layer of coprogenous earth (sedimentary peat) is a limnic layer that: 1. Contains many fecal pellets with diameters between a few hundredths and a few tenths of a millimeter; and 2. Has a color value, moist, of 4 or less; and 3. Either forms a slightly viscous water suspension and is nonplastic or slightly plastic but not sticky, or shrinks upon drying, forming clods that are difficult to rewet and often tend to crack along horizontal planes; and Figure 2.—Value and chroma of pyrophosphate solution of fibric and sapric materials. 4. Either yields a saturated sodium-pyrophosphate extract Horizons and Characteristics Diagnostic for the Higher Categories 23

on white chromatographic or filter paper that has a color value substratum shallower than those limits does not change the of 7 or more and chroma of 2 or less (fig. 2) or has a cation- lower boundary of the control section. exchange capacity of less than 240 cmol(+) per kg organic The control section of Histosols and Histels is divided matter (measured by loss on ignition), or both. somewhat arbitrarily into three tiers—surface, subsurface, and bottom tiers. D Diatomaceous Earth I A A layer of diatomaceous earth is a limnic layer that: Surface Tier 1. If not previously dried, has a matrix color value of 3, 4, The surface tier of a Histosol or Histel extends from the soil or 5, which changes irreversibly on drying as a result of the surface to a depth of 60 cm if either (1) the materials within that irreversible shrinkage of organic-matter coatings on diatoms depth are fibric and three-fourths or more of the fiber volume (identifiable by microscopic, 440 X, examination of dry is derived from Sphagnum or other mosses or (2) the materials samples); and have a bulk density of less than 0.1. Otherwise, the surface tier extends from the soil surface to a depth of 30 cm. 2. Either yields a saturated sodium-pyrophosphate extract Some organic soils have a mineral surface layer less than 40 on white chromatographic or filter paper that has a color value cm thick as a result of flooding, volcanic eruptions, additions of of 8 or more and chroma of 2 or less or has a cation-exchange mineral materials to increase soil strength or reduce the hazard capacity of less than 240 cmol(+) per kg organic matter of frost, or other causes. If such a mineral layer is less than 30 (measured by loss on ignition), or both. cm thick, it constitutes the upper part of the surface tier; if it is Marl 30 to 40 cm thick, it constitutes the whole surface tier and part of the subsurface tier. A layer of marl is a limnic layer that: 1. Has a color value, moist, of 5 or more; and Subsurface Tier

2. Reacts with dilute HCl to evolve CO2. The subsurface tier is normally 60 cm thick. If the control section ends at a shallower depth (at a densic, lithic, or The color of marl usually does not change irreversibly on paralithic contact or a water layer or in permafrost), however, drying because a layer of marl contains too little organic matter, the subsurface tier extends from the lower boundary of the even before it has been shrunk by drying, to coat the carbonate surface tier to the lower boundary of the control section. It particles. includes any unconsolidated mineral layers that may be present within those depths. Thickness of Organic Soil Materials (Control Section of Histosols and Bottom Tier Histels) The bottom tier is 40 cm thick unless the control section has The thickness of organic materials over limnic materials, its lower boundary at a shallower depth (at a densic, lithic, or mineral materials, water, or permafrost is used to define the paralithic contact or a water layer or in permafrost). Histosols and Histels. Thus, if the organic materials are thick, there are two For practical reasons, an arbitrary control section has been possible thicknesses of the control section, depending on the established for the classification of Histosols and Histels. presence or absence and the thickness of a surface mantle of Depending on the kinds of soil material in the surface layers, fibric moss or other organic material that has a low bulk density the control section has a thickness of either 130 cm or 160 cm (less than 0.1). If the fibric moss extends to a depth of 60 cm from the soil surface if there is no densic, lithic, or paralithic and is the dominant material within this depth (three-fourths contact, thick layer of water, or permafrost within the respective or more of the volume), the control section is 160 cm thick. If limit. The thicker control section is used if the surface layers the fibric moss is thin or absent, the control section extends to a to a depth of 60 cm either contain three-fourths or more fibers depth of 130 cm. derived from Sphagnum, Hypnum, or other mosses or have a bulk density of less than 0.1. Layers of water, which may be between a few centimeters and many meters thick in these Horizons and Characteristics soils, are considered to be the lower boundary of the control Diagnostic for Both Mineral and section only if the water extends below a depth of 130 or 160 cm, respectively. A densic, lithic, or paralithic contact, if Organic Soils shallower than 130 or 160 cm, constitutes the lower boundary of Following are descriptions of the horizons and characteristics the control section. In some soils the lower boundary is 25 cm that are diagnostic for both mineral and organic soils. below the upper limit of permafrost. An unconsolidated mineral 24 Keys to Soil Taxonomy

Aquic Conditions c. Anthric saturation.—This term refers to a special kind of aquic conditions that occurs in soils that are cultivated and Soils with aquic (L. aqua, water) conditions are those irrigated (flood irrigation). Soils with anthraquic conditions that currently undergo continuous or periodic saturation and must meet the requirements for aquic conditions and in reduction. The presence of these conditions is indicated by addition have both of the following: redoximorphic features, except in Histosols and Histels, and can be verified by measuring saturation and reduction, except (1) A tilled surface layer and a directly underlying in artificially drained soils. Artificial drainage is defined here as slowly permeable layer that has, for 3 months or more in the removal of free water from soils having aquic conditions by normal years, both: surface mounding, ditches, or subsurface tiles or the prevention (a) Saturation and reduction; and of surface or ground water from reaching the soils by dams, levees, surface pumps, or other means. In these soils water (b) Chroma of 2 or less in the matrix; and table levels and/or their duration are changed significantly in (2) A subsurface horizon with one or more of the connection with specific types of land use. Upon removal of the following: drainage practices, aquic conditions would return. In the keys, artificially drained soils are included with soils that have aquic (a) Redox depletions with a color value, moist, of 4 conditions. or more and chroma of 2 or less in macropores; or Elements of aquic conditions are as follows: (b) Redox concentrations of iron; or 1. Saturation is characterized by zero or positive pressure in (c) 2 times or more the amount of iron (by dithionite the soil water and can generally be determined by observing citrate) contained in the tilled surface layer. free water in an unlined auger hole. Problems may arise, however, in clayey soils with peds, where an unlined auger 2. The degree of reduction in a soil can be characterized by the hole may fill with water flowing along faces of peds while the direct measurement of redox potentials. Direct measurements soil matrix is and remains unsaturated (bypass flow). Such free should take into account chemical equilibria as expressed by water may incorrectly suggest the presence of a water table, stability diagrams in standard soil textbooks. Reduction and while the actual water table occurs at greater depth. Use of well oxidation processes are also a function of soil pH. Obtaining sealed piezometers or tensiometers is therefore recommended accurate measurements of the degree of reduction in a soil is for measuring saturation. Problems may still occur, however, difficult. In the context of this taxonomy, however, only a degree if water runs into piezometer slits near the bottom of the of reduction that results in reduced iron is considered, because it piezometer hole or if tensiometers with slowly reacting produces the visible redoximorphic features that are identified in manometers are used. The first problem can be overcome by the keys. A simple field test is available to determine if reduced using piezometers with smaller slits and the second by using iron ions are present. A freshly broken surface of a field-wet transducer tensiometry, which reacts faster than manometers. soil sample is treated with alpha,alpha-dipyridyl in neutral, Soils are considered wet if they have pressure heads greater 1N ammonium-acetate solution. The appearance of a strong than -1 kPa. Only macropores, such as cracks between peds red color on the freshly broken surface indicates the presence or channels, are then filled with air, while the soil matrix is of reduced iron ions. A positive reaction to the alpha,alpha- usually still saturated. Obviously, exact measurements of the wet dipyridyl field test for ferrous iron (Childs, 1981) may be state can be obtained only with tensiometers. For operational used to confirm the existence of reducing conditions and is purposes, the use of piezometers is recommended as a standard especially useful in situations where, despite saturation, normal method. morphological indicators of such conditions are either absent The duration of saturation required for creating aquic or obscured (as by the dark colors characteristic of melanic conditions varies, depending on the soil environment, and is not great groups). A negative reaction, however, does not imply that specified. reducing conditions are always absent. It may only mean that the Three types of saturation are defined: level of free iron in the soil is below the sensitivity limit of the test or that the soil is in an oxidized phase at the time of testing. a. Endosaturation.—The soil is saturated with water in all Use of alpha,alpha-dipyridyl in a 10 percent acetic-acid solution layers from the upper boundary of saturation to a depth of is not recommended because the acid is likely to change soil 200 cm or more from the mineral soil surface. conditions, for example, by dissolving CaCO3. The duration of reduction required for creating aquic b. Episaturation.—The soil is saturated with water in one conditions is not specified. or more layers within 200 cm of the mineral soil surface and also has one or more unsaturated layers, with an upper 3. Redoximorphic features associated with wetness result boundary above a depth of 200 cm, below the saturated layer. from alternating periods of reduction and oxidation of iron and The zone of saturation, i.e., the water table, is perched on top manganese compounds in the soil. Reduction occurs during of a relatively impermeable layer. saturation with water, and oxidation occurs when the soil is not Horizons and Characteristics Diagnostic for the Higher Categories 25

saturated. The reduced iron and manganese ions are mobile Field experience indicates that it is not possible to define and may be transported by water as it moves through the soil. a specific set of redoximorphic features that is uniquely Certain redox patterns occur as a function of the patterns in characteristic of all of the taxa in one particular category. which the ion-carrying water moves through the soil and as Therefore, color patterns that are unique to specific taxa are a function of the location of aerated zones in the soil. Redox referenced in the keys. D I patterns are also affected by the fact that manganese is reduced Anthraquic conditions are a variant of episaturation and are A more rapidly than iron, while iron oxidizes more rapidly upon associated with controlled flooding (for such crops as wetland aeration. Characteristic color patterns are created by these rice and cranberries), which causes reduction processes in the processes. The reduced iron and manganese ions may be saturated, puddled surface soil and oxidation of reduced and removed from a soil if vertical or lateral fluxes of water occur, mobilized iron and manganese in the unsaturated subsoil. in which case there is no iron or manganese precipitation in that soil. Wherever the iron and manganese are oxidized and Cryoturbation precipitated, they form either soft masses or hard concretions or nodules. Movement of iron and manganese as a result of redox Cryoturbation (frost churning) is the mixing of the soil processes in a soil may result in redoximorphic features that are matrix within the pedon that results in irregular or broken defined as follows: horizons, involutions, accumulation of organic matter on the permafrost table, oriented rock fragments, and silt caps on rock a. Redox concentrations.—These are zones of apparent fragments. accumulation of Fe-Mn oxides, including: (1) Nodules and concretions, which are cemented Densic Contact bodies that can be removed from the soil intact. A densic contact (L. densus, thick) is a contact between soil Concretions are distinguished from nodules on the and densic materials (defined below). It has no cracks, or the basis of internal organization. A concretion typically spacing of cracks that roots can enter is 10 cm or more. has concentric layers that are visible to the naked eye. Nodules do not have visible organized internal structure. Densic Materials Boundaries commonly are diffuse if formed in situ and sharp after pedoturbation. Sharp boundaries may be relict Densic materials are relatively unaltered materials (do features in some soils; and not meet the requirements for any other named diagnostic horizons or any other diagnostic soil characteristic) that have (2) Masses, which are noncemented concentrations of a noncemented rupture-resistance class. The bulk density substances within the soil matrix; and or the organization is such that roots cannot enter, except in (3) Pore linings, i.e., zones of accumulation along cracks. These are mostly earthy materials, such as till, volcanic pores that may be either coatings on pore surfaces or mudflows, and some mechanically compacted materials, for impregnations from the matrix adjacent to the pores. example, mine spoils. Some noncemented rocks can be densic materials if they are dense or resistant enough to keep roots b. Redox depletions.—These are zones of low chroma from entering, except in cracks. (chromas less than those in the matrix) where either Fe- Densic materials are noncemented and thus differ from Mn oxides alone or both Fe-Mn oxides and clay have been paralithic materials and the material below a lithic contact, both stripped out, including: of which are cemented. (1) Iron depletions, i.e., zones that contain low amounts Densic materials have, at their upper boundary, a densic of Fe and Mn oxides but have a clay content similar to contact if they have no cracks or if the spacing of cracks that that of the adjacent matrix (often referred to as albans or roots can enter is 10 cm or more. These materials can be used neoalbans); and to differentiate soil series if the materials are within the series control section. (2) Clay depletions, i.e., zones that contain low amounts of Fe, Mn, and clay (often referred to as silt coatings or Gelic Materials skeletans). Gelic materials are mineral or organic soil materials that c. Reduced matrix.—This is a soil matrix that has low show evidence of cryoturbation (frost churning) and/or ice chroma in situ but undergoes a change in hue or chroma segregation in the active layer (seasonal thaw layer) and/or the within 30 minutes after the soil material has been exposed to upper part of the permafrost. Cryoturbation is manifested by air. irregular and broken horizons, involutions, accumulation of d. In soils that have no visible redoximorphic features, a organic matter on top of and within the permafrost, oriented reaction to an alpha,alpha-dipyridyl solution satisfies the rock fragments, and silt-enriched layers. The characteristic requirement for redoximorphic features. structures associated with gelic materials include platy, blocky, 26 Keys to Soil Taxonomy

or granular macrostructures; the structural results of sorting; they have no cracks or if the spacing of cracks that roots can and orbiculic, conglomeric, banded, or vesicular microfabrics. enter is 10 cm or more. Commonly, these materials are partially Ice segregation is manifested by ice lenses, vein ice, segregated weathered bedrock or weakly consolidated bedrock, such as ice crystals, and ice wedges. Cryopedogenic processes that lead sandstone, siltstone, or shale. Paralithic materials can be used to gelic materials are driven by the physical volume change of to differentiate soil series if the materials are within the series water to ice, moisture migration along a thermal gradient in the control section. Fragments of paralithic materials 2.0 mm or frozen system, or thermal contraction of the frozen material by more in diameter are referred to as pararock fragments. continued rapid cooling. Permafrost Glacic Layer Permafrost is defined as a thermal condition in which a A glacic layer is massive ice or ground ice in the form of ice material (including soil material) remains below 0 oC for 2 lenses or wedges. The layer is 30 cm or more thick and contains or more years in succession. Those gelic materials having 75 percent or more visible ice. permafrost contain the unfrozen soil solution that drives cryopedogenic processes. Permafrost may be cemented by ice Lithic Contact or, in the case of insufficient interstitial water, may be dry. The frozen layer has a variety of ice lenses, vein ice, segregated ice A lithic contact is the boundary between soil and a coherent crystals, and ice wedges. The permafrost table is in dynamic underlying material. Except in Ruptic-Lithic subgroups, the equilibrium with the environment. underlying material must be virtually continuous within the limits of a pedon. Cracks that can be penetrated by roots Soil Moisture Regimes are few, and their horizontal spacing is 10 cm or more. The underlying material must be sufficiently coherent when moist The term “soil moisture regime” refers to the presence or to make hand-digging with a spade impractical, although the absence either of ground water or of water held at a tension material may be chipped or scraped with a spade. The material of less than 1500 kPa in the soil or in specific horizons during below a lithic contact must be in a strongly cemented or more periods of the year. Water held at a tension of 1500 kPa or cemented rupture-resistance class. Commonly, the material more is not available to keep most mesophytic plants alive. The is indurated. The underlying material considered here does availability of water is also affected by dissolved salts. If a soil not include diagnostic soil horizons, such as a duripan or a is saturated with water that is too salty to be available to most petrocalcic horizon. plants, it is considered salty rather than dry. Consequently, a A lithic contact is diagnostic at the subgroup level if it is horizon is considered dry when the moisture tension is 1500 within 125 cm of the mineral soil surface in Oxisols and within kPa or more and is considered moist if water is held at a 50 cm of the mineral soil surface in all other mineral soils. In tension of less than 1500 kPa but more than zero. A soil may Gelisols composed mainly of organic soil materials, the lithic be continuously moist in some or all horizons either throughout contact is diagnostic at the subgroup level if it is within 50 the year or for some part of the year. It may be either moist cm of the soil surface in Folistels or within 100 cm of the soil in winter and dry in summer or the reverse. In the Northern surface in Fibristels, Hemistels, and Sapristels. In Histosols Hemisphere, summer refers to June, July, and August and winter the lithic contact must be at the lower boundary of the control refers to December, January, and February. section to be recognized at the subgroup level. Normal Years Paralithic Contact In the discussions that follow and throughout the keys, the term “normal years” is used. A normal year is defined as a year A paralithic (lithic-like) contact is a contact between soil that has: and paralithic materials (defined below) where the paralithic materials have no cracks or the spacing of cracks that roots can 1. Annual precipitation that is plus or minus one standard enter is 10 cm or more. deviation of the long-term (30 years or more) mean annual precipitation; and Paralithic Materials 2. Mean monthly precipitation that is plus or minus one standard deviation of the long-term monthly precipitation for 8 Paralithic materials are relatively unaltered materials (do of the 12 months. not meet the requirements for any other named diagnostic horizons or any other diagnostic soil characteristic) that have an For the most part, normal years can be calculated from the extremely weakly cemented to moderately cemented rupture- mean annual precipitation; however, when catastrophic events resistance class. Cementation, bulk density, and the organization occur during a year, the standard deviations of the monthly are such that roots cannot enter, except in cracks. Paralithic means should also be calculated. The term “normal years” materials have, at their upper boundary, a paralithic contact if replaces the terms “most years” and “6 out of 10 years,” which Horizons and Characteristics Diagnostic for the Higher Categories 27

were used in the 1975 edition of Soil Taxonomy (USDA, SCS, moisture is not being increased by irrigation or fallowing. These 1975). When precipitation data are evaluated to determine if the cultural practices affect the soil moisture conditions as long as criterion for the presence of aquic conditions, or number of days they are continued. that the moisture control section is moist, or number of days that Aquic soil moisture regime.—The aquic (L. aqua, water) some part of the soil is saturated has been met, it is permissible soil moisture regime is a reducing regime in a soil that is D I to include data from periods with below normal rainfall. virtually free of dissolved oxygen because it is saturated by A Similarly, when precipitation data are evaluated to determine water. Some soils are saturated with water at times while if the criterion for the number of days that the moisture control dissolved oxygen is present, either because the water is moving section is dry has been met, it is permissible to include data or because the environment is unfavorable for micro-organisms from periods with above normal rainfall. It is assumed that if (e.g., if the temperature is less than 1 oC); such a regime is not the criteria are met during these periods, they will also be met considered aquic. during normal years. It is not known how long a soil must be saturated before it is said to have an aquic soil moisture regime, but the duration Soil Moisture Control Section must be at least a few days, because it is implicit in the concept The intent in defining the soil moisture control section is to that dissolved oxygen is virtually absent. Because dissolved facilitate estimation of soil moisture regimes from climatic data. oxygen is removed from ground water by respiration of micro- The upper boundary of this control section is the depth to which organisms, roots, and soil fauna, it is also implicit in the concept a dry (tension of more than 1500 kPa, but not air-dry) soil will that the soil temperature is above biologic zero for some time be moistened by 2.5 cm of water within 24 hours. The lower while the soil is saturated. Biologic zero is defined as 5o C in boundary is the depth to which a dry soil will be moistened by this taxonomy. In some of the very cold regions of the world, 7.5 cm of water within 48 hours. These depths do not include however, biological activity occurs at temperatures below 5 oC. the depth of moistening along any cracks or animal burrows that Very commonly, the level of ground water fluctuates with are open to the surface. the seasons; it is highest in the rainy season or in fall, winter, or If 7.5 cm of water moistens the soil to a densic, lithic, spring if cold weather virtually stops evapotranspiration. There paralithic, or petroferric contact or to a petrocalcic or are soils, however, in which the ground water is always at or petrogypsic horizon or a duripan, the contact or the upper very close to the surface. Examples are soils in tidal marshes boundary of the cemented horizon constitutes the lower or in closed, landlocked depressions fed by perennial streams. boundary of the soil moisture control section. If a soil is Such soils are considered to have a peraquic soil moisture moistened to one of these contacts or horizons by 2.5 cm of regime. water, the soil moisture control section is the boundary of the Aridic and torric (L. aridus, dry, and L. torridus, hot contact itself. The control section of such a soil is considered and dry) soil moisture regimes.—These terms are used for moist if the contact or upper boundary of the cemented horizon the same moisture regime but in different categories of the has a thin film of water. If that upper boundary is dry, the taxonomy. control section is considered dry. In the aridic (torric) soil moisture regime, the moisture The moisture control section of a soil extends approximately control section is, in normal years: (1) from 10 to 30 cm below the soil surface if the particle-size class of the soil is fine-loamy, coarse-silty, fine-silty, or clayey; 1. Dry in all parts for more than half of the cumulative days (2) from 20 to 60 cm if the particle-size class is coarse-loamy; per year when the soil temperature at a depth of 50 cm below o and (3) from 30 to 90 cm if the particle-size class is sandy. If the soil surface is above 5 C; and the soil contains rock and pararock fragments that do not absorb 2. Moist in some or all parts for less than 90 consecutive days and release water, the limits of the moisture control section when the soil temperature at a depth of 50 cm below the soil are deeper. The limits of the soil moisture control section surface is above 8 oC. are affected not only by the particle-size class but also by differences in soil structure or pore-size distribution or by other Soils that have an aridic (torric) soil moisture regime factors that influence the movement and retention of water in normally occur in areas of arid climates. A few are in areas of the soil. semiarid climates and either have physical properties that keep them dry, such as a crusty surface that virtually precludes the Classes of Soil Moisture Regimes infiltration of water, or are on steep slopes where runoff is high. The soil moisture regimes are defined in terms of the level of There is little or no leaching in this soil moisture regime, and ground water and in terms of the seasonal presence or absence soluble salts accumulate in the soils if there is a source. of water held at a tension of less than 1500 kPa in the moisture The limits set for soil temperature exclude from these soil control section. It is assumed in the definitions that the soil moisture regimes soils in the very cold and dry polar regions supports whatever vegetation it is capable of supporting, i.e., and in areas at high elevations. Such soils are considered to have crops, grass, or native vegetation, and that the amount of stored anhydrous conditions (defined earlier). 28 Keys to Soil Taxonomy

Udic soil moisture regime.—The udic (L. udus, humid) control section is dry in all parts for less than 45 consecutive soil moisture regime is one in which the soil moisture control days in the 4 months following the summer solstice. section is not dry in any part for as long as 90 cumulative In tropical and subtropical regions that have a monsoon days in normal years. If the mean annual soil temperature is climate with either one or two dry seasons, summer and winter lower than 22 oC and if the mean winter and mean summer soil seasons have little meaning. In those regions the soil moisture temperatures at a depth of 50 cm below the soil surface differ regime is ustic if there is at least one rainy season of 3 months by 6 oC or more, the soil moisture control section, in normal or more. In temperate regions of subhumid or semiarid climates, years, is dry in all parts for less than 45 consecutive days in the the rainy seasons are usually spring and summer or spring and 4 months following the summer solstice. In addition, the udic fall, but never winter. Native plants are mostly annuals or plants soil moisture regime requires, except for short periods, a three- that have a dormant period while the soil is dry. phase system, solid-liquid-gas, in part or all of the soil moisture Xeric soil moisture regime.—The xeric (Gr. xeros, dry) control section when the soil temperature is above 5 oC. soil moisture regime is the typical moisture regime in areas of The udic soil moisture regime is common to the soils of Mediterranean climates, where winters are moist and cool and humid climates that have well distributed rainfall; have enough summers are warm and dry. The moisture, which falls during rain in summer so that the amount of stored moisture plus the winter, when potential evapotranspiration is at a minimum, rainfall is approximately equal to, or exceeds, the amount of is particularly effective for leaching. In areas of a xeric soil evapotranspiration; or have adequate winter rains to recharge the moisture regime, the soil moisture control section, in normal soils and cool, foggy summers, as in coastal areas. Water moves years, is dry in all parts for 45 or more consecutive days in the downward through the soils at some time in normal years. 4 months following the summer solstice and moist in all parts In climates where precipitation exceeds evapotranspiration in for 45 or more consecutive days in the 4 months following all months of normal years, the moisture tension rarely reaches the winter solstice. Also, in normal years, the moisture 100 kPa in the soil moisture control section, although there are control section is moist in some part for more than half of the occasional brief periods when some stored moisture is used. The cumulative days per year when the soil temperature at a depth water moves through the soil in all months when it is not frozen. of 50 cm below the soil surface is higher than 5 oC or for 90 or Such an extremely wet soil moisture regime is called perudic (L. more consecutive days when the soil temperature at a depth of per, throughout in time, and L. udus, humid). In the names of 50 cm is higher than 8 oC. The mean annual soil temperature is most taxa, the formative element “ud” is used to indicate either lower than 22 oC, and the mean summer and mean winter soil a udic or a perudic regime; the formative element “per” is used temperatures differ by 6 oC or more either at a depth of 50 cm in selected taxa. below the soil surface or at a densic, lithic, or paralithic contact Ustic soil moisture regime.—The ustic (L. ustus, burnt; if shallower. implying dryness) soil moisture regime is intermediate between the aridic regime and the udic regime. Its concept is one of Soil Temperature Regimes moisture that is limited but is present at a time when conditions Classes of Soil Temperature Regimes are suitable for plant growth. The concept of the ustic soil moisture regime is not applied to soils that have permafrost Following is a description of the soil temperature regimes (defined above). used in defining classes at various categorical levels in this If the mean annual soil temperature is 22 oC or higher or if taxonomy. the mean summer and winter soil temperatures differ by less Gelic (L. gelare, to freeze).— Soils in this temperature than 6 oC at a depth of 50 cm below the soil surface, the soil regime have a mean annual soil temperature at or below 0 oC moisture control section in areas of the ustic soil moisture (in Gelic suborders and Gelic great groups) or 1 oC or lower (in regime is dry in some or all parts for 90 or more cumulative Gelisols) either at a depth of 50 cm below the soil surface or at a days in normal years. It is moist, however, in some part either densic, lithic, or paralithic contact, whichever is shallower. for more than 180 cumulative days per year or for 90 or more Cryic (Gr. kryos, coldness; meaning very cold consecutive days. soils).—Soils in this temperature regime have a mean annual If the mean annual soil temperature is lower than 22 oC and temperature between 0 and 8 oC but do not have permafrost. if the mean summer and winter soil temperatures differ by 1. In mineral soils the mean summer soil temperature (June, 6 oC or more at a depth of 50 cm below the soil surface, the July, and August in the Northern Hemisphere and December, soil moisture control section in areas of the ustic soil moisture January, and February in the Southern Hemisphere) either at a regime is dry in some or all parts for 90 or more cumulative depth of 50 cm below the soil surface or at a densic, lithic, or days in normal years, but it is not dry in all parts for more than paralithic contact, whichever is shallower, is as follows: half of the cumulative days when the soil temperature at a depth of 50 cm is higher than 5 oC. If in normal years the moisture a. If the soil is not saturated with water during some part of control section is moist in all parts for 45 or more consecutive the summer and days in the 4 months following the winter solstice, the moisture Horizons and Characteristics Diagnostic for the Higher Categories 29

(1) If there is no O horizon: between 0 and 15 oC; or Sulfidic Materials (2) If there is an O horizon: between 0 and 8 oC; or Sulfidic materials contain oxidizable sulfur compounds b. If the soil is saturated with water during some part of the (elemental S or most commonly sulfide minerals, such as pyrite or iron monosulfides). They are mineral or organic soil summer and D materials that have a pH value of more than 3.5 and that become I A (1) If there is no O horizon: between 0 and 13 oC; or significantly more acid when oxidized. Sulfidic materials (2) If there is an O horizon or a histic epipedon: between accumulate as a soil or sediment that is permanently saturated, 0 and 6 oC. generally with brackish water. The sulfates in the water are biologically reduced to sulfides as the materials accumulate. 2. In organic soils the mean annual soil temperature is Sulfidic materials most commonly accumulate in coastal between 0 and 6 oC. marshes near the mouth of rivers that carry noncalcareous Cryic soils that have an aquic soil moisture regime sediments, but they may occur in freshwater marshes if there commonly are churned by frost. is sulfur in the water. Upland sulfidic materials may have Isofrigid soils could also have a cryic soil temperature accumulated in a similar manner in the geologic past. regime. A few with organic materials in the upper part are If a soil containing sulfidic materials is drained or if sulfidic exceptions. materials are otherwise exposed to aerobic conditions, the The concepts of the soil temperature regimes described sulfides oxidize and form sulfuric acid. The pH value, which below are used in defining classes of soils in the low categories. normally is near neutrality before drainage or exposure, may drop below 3. The acid may induce the formation of iron Frigid.—A soil with a frigid soil temperature regime is warmer in summer than a soil with a cryic regime, but its and aluminum sulfates. The iron hydroxysulfate mineral mean annual temperature is between 0 and 8 oC and the jarosite may segregate, forming the yellow redoximorphic difference between mean summer (June, July, and August) concentrations that commonly characterize a sulfuric horizon. and mean winter (December, January, and February) soil The transition from sulfidic materials to a sulfuric horizon temperatures is 6 oC or more either at a depth of 50 cm below normally requires only a few months and may occur within a the soil surface or at a densic, lithic, or paralithic contact, few weeks. A sample of sulfidic materials, if air-dried slowly whichever is shallower. in shade for about 2 months with occasional remoistening, becomes extremely acid. Mesic.—The mean annual soil temperature is 8 oC or higher but lower than 15 oC, and the difference between mean summer Required Characteristics and mean winter soil temperatures is 6 oC or more either at a depth of 50 cm below the soil surface or at a densic, lithic, or Sulfidic materials haveone or both of the following: paralithic contact, whichever is shallower. 1. A pH value (1:1 in water) of more than 3.5, and, when the o Thermic.—The mean annual soil temperature is 15 C or materials are incubated at room temperature as a layer 1 cm o higher but lower than 22 C, and the difference between mean thick under moist aerobic conditions (repeatedly moistened and o summer and mean winter soil temperatures is 6 C or more dried on a weekly basis), the pH decreases by 0.5 or more units either at a depth of 50 cm below the soil surface or at a densic, to a value of 4.0 or less (1:1 by weight in water or in a minimum lithic, or paralithic contact, whichever is shallower. of water to permit measurement) within 16 weeks or longer Hyperthermic.—The mean annual soil temperature is until the pH reaches a nearly constant value if the pH is still o 22 C or higher, and the difference between mean summer dropping after 16 weeks; or and mean winter soil temperatures is 6 oC or more either at a depth of 50 cm below the soil surface or at a densic, lithic, or 2. A pH value (1:1 in water) of more than 3.5 and 0.75 percent paralithic contact, whichever is shallower. or more S (dry mass), mostly in the form of sulfides, and less If the name of a soil temperature regime has the prefixiso , than three times as much calcium carbonate equivalent as S. the mean summer and mean winter soil temperatures differ o by less than 6 C at a depth of 50 cm or at a densic, lithic, or Sulfuric Horizon paralithic contact, whichever is shallower. Isofrigid.—The mean annual soil temperature is lower than Brackish water sediments frequently contain pyrite or other 8 oC. iron sulfide minerals or rarely elemental sulfur, which form Isomesic.—The mean annual soil temperature is 8 oC or sulfuric acid upon the oxidation of the sulfur forms they contain higher but lower than 15 oC. and/or upon the oxidation and hydrolysis of the iron in the Isothermic.—The mean annual soil temperature is 15 oC or iron sulfides. Pyrite is an iron sulfide mineral that forms as a higher but lower than 22 oC. result of the microbial decomposition of organic matter under Isohyperthermic.—The mean annual soil temperature is anaerobic conditions. Pyrite forms after iron oxide and sulfate 22 oC or higher. from sea water (or other sources) become reduced to ferrous 30

iron and sulfide, respectively, and then combine to form a very 1. The horizon has: insoluble compound (see description of the sulfidization process a. Concentrations of jarosite, schwertmannite, or other iron given by Fanning and Fanning, 1989, or Fanning et al., 2002). and/or aluminum sulfates or hydroxysulfate minerals; or Characteristically, the pyrite crystals occur as nests or framboids composed of bipyramidal crystals of pyrite. In an oxidizing b. 0.05 percent or more water-soluble sulfate; or environment, pyrite oxidizes and the products of oxidation 2. The layer directly underlying the horizon consists of sulfidic (and the hydrolysis of the ferric iron produced) are iron oxides materials (defined above). (and under sufficiently acidic and oxidizing conditions, jarosite and/or schwertmannite) and sulfuric acid. The jarosite has a straw-yellow color and frequently lines pores in the soil. Jarosite Literature Cited concentrations are among the indicators of a sulfuric horizon, Brewer, R. 1976. Fabric and Mineral Analysis of Soils. but jarosite is not present in all sulfuric horizons. Second edition. John Wiley and Sons, Inc. New York, New York. The low pH and high amount of soluble sulfates, and/or Burt, R., ed. 2004. Soil Survey Laboratory Methods Manual. underlying sulfidic materials, are other indicators of a sulfuric Soil Survey Investigations Report 42, Version 4.0. United States horizon. A quick test of sulfidic materials is a rapid fall in pH Department of Agriculture, Natural Resources Conservation on drying or after treatment with an oxidizing agent, such as Service, National Soil Survey Center. hydrogen peroxide. Childs, C.W. 1981. Field Test for Ferrous Iron and Ferric- A sulfuric horizon (L. sulfur) forms as a result of drainage Organic Complexes (on Exchange Sites or in Water-Soluble (most commonly artificial drainage) and oxidation of sulfide- Forms) in Soils. Austr. J. of Soil Res. 19: 175-180. rich mineral or organic soil materials. It can form in areas where Fanning, D.S., and M.C.B. Fanning. 1989. Soil: Morphology, sulfidic materials have been exposed as a result of surface Genesis, and Classification. John Wiley and Sons, New York. mining, dredging, or other earth-moving operations. A sulfuric Fanning, D.S., M.C. Rabenhorst, S.N. Burch, K.R. Islam, horizon is detrimental to most plants and, if sufficiently acid at and S.A. Tangren. 2002. Sulfides and Sulfates.In J.B. Dixon the soil surface, may prevent plant growth or limit it to certain and D.G. Schulze (eds.), Soil Mineralogy with Environmental plant species, such as Phragmites australis, that can tolerate the Applications, pp. 229-260. Soil Sci. Soc. Am., Madison, WI. acidity under certain conditions. Pons, L.J., and I.S. Zonneveld. 1965. Soil Ripening and Soil Classification. Initial Soil Formation in Alluvial Deposits and a Required Characteristics Classification of the Resulting Soils. Int. Inst. Land Reclam. and The sulfuric horizon is 15 cm or more thick and is composed Impr. Pub. 13. Wageningen, The Netherlands. of either mineral or organic soil material that has a pH value United States Department of Agriculture, Soil Conservation (1:1 by weight in water or in a minimum of water to permit Service. 1975. Soil Taxonomy: A Basic System of Soil measurement) of 3.5 or less or less than 4.0 if sulfide or other S- Classification for Making and Interpreting Soil Surveys. Soil bearing minerals that produce sulfuric acid upon their oxidation Surv. Staff. U.S. Dep. Agric. Handb. 436. are present. The horizon shows evidence that the low pH value United States Department of Agriculture, Soil Conservation is caused by sulfuric acid. Service. 1993. Soil Survey Manual. Soil Surv. Div. Staff. U.S. The evidence is one or both of the following: Dep. Agric. Handb. 18. 31

CHAPTER 4

Identification of the Taxonomic Class of a Soil

I D E The taxonomic class of a specific soil can be determined not included in this text. Definitions of the series and of the by using the keys that follow in this and other chapters. It control section are given in chapter 17. is assumed that the reader is familiar with the definitions of In the “Key to Soil Orders” and the other keys that follow, diagnostic horizons and properties that are given in chapters the diagnostic horizons and the properties mentioned do not 2 and 3 of this publication and with the meanings of the terms include those below any densic, lithic, paralithic, or petroferric used for describing soils given in the Soil Survey Manual. The contact. The properties of buried soils and the properties of a Index at the back of this publication indicates the pages on surface mantle are considered on the basis of whether or not which definitions of terms are given. the soil meets the meaning of the term “buried soil” given in Standard rounding conventions should be used to determine chapter 1. numerical values. If a soil has a surface mantle and is not a buried soil, the top Soil colors (hue, value, and chroma) are used in many of the of the original surface layer is considered the “soil surface” for criteria that follow. Soil colors typically change value and some determining depth to and thickness of diagnostic horizons and change hue and chroma, depending on the water state. In many most other diagnostic soil characteristics. The only properties of the criteria of the keys, the water state is specified. If no water of the surface mantle that are considered are soil temperature, state is specified, the soil is considered to meet the criterion if it soil moisture (including aquic conditions), and any andic or does so when moist or dry or both moist and dry. vitrandic properties and family criteria. All of the keys in this taxonomy are designed in such a way If a soil profile includes a buried soil, the present soil that the user can determine the correct classification of a soil surface is used to determine soil moisture and temperature as by going through the keys systematically. The user must start well as depth to and thickness of diagnostic horizons and other at the beginning of the “Key to Soil Orders” and eliminate, one diagnostic soil characteristics. Diagnostic horizons of the buried by one, all classes that include criteria that do not fit the soil in soil are not considered in selecting taxa unless the criteria in the question. The soil belongs to the first class listed for which it keys specifically indicate buried horizons, such as in Thapto- meets all the required criteria. Histic subgroups. Most other diagnostic soil characteristics In classifying a specific soil, the user of soil taxonomy begins of the buried soil are not considered, but organic carbon if of by checking through the “Key to Soil Orders” to determine Holocene age, andic soil properties, base saturation, and all the name of the first order that, according to the criteria listed, properties used to determine family and series placement are includes the soil in question. The next step is to go to the page considered. indicated to find the “Key to Suborders” of that particular order. If diagnostic horizons or characteristics are criteria that must Then the user systematically goes through the key to identify be “within” a specified depth measured from the soil surface, the suborder that includes the soil, i.e., the first in the list for then the upper boundary of the first subhorizon meeting the which it meets all the required criteria. The same procedure is requirements for the diagnostic horizon or characteristic must used to find the great group class of the soil in the “Key to Great be within the specified depth. Groups” of the identified suborder. Likewise, going through the “Key to Subgroups” of that great group, the user selects as the Key to Soil Orders correct subgroup name the name of the first taxon for which the soil meets all of the required criteria. A. Soils that have: The family level is determined, in a similar manner, after the subgroup has been determined. Chapter 17 can be used, 1. Permafrost within 100 cm of the soil surface; or as one would use other keys in this taxonomy, to determine 2. Gelic materials within 100 cm of the soil surface and which components are part of the family. The family, however, permafrost within 200 cm of the soil surface. typically has more than one component, and therefore the entire Gelisols, p. 145 chapter must be used. The keys to control sections for classes B. Other soils that: used as components of a family must be used to determine the control section before use of the keys to classes. 1. Do not have andic soil properties in 60 percent or more The descriptions and definitions of individual soil series are of the thickness between the soil surface and either a depth 32 Keys to Soil Taxonomy

of 60 cm or a densic, lithic, or paralithic contact or duripan if coarse-loamy, loamy-skeletal, or finer and a frigid shallower; and temperature regime in the soil; or 2. Have organic soil materials that meet one or more of the (5) A cryic or gelic temperature regime in the soil; following: and a. Overlie cindery, fragmental, or pumiceous materials b. An upper boundary within the following depths from and/or fill their interstices1 and directly below these the mineral soil surface: either materials, have a densic, lithic, or paralithic contact; or (1) Less than 50 cm; or b. When added with the underlying cindery, fragmental, or pumiceous materials, total 40 cm or more between the (2) Less than 200 cm if the soil meets the sandy soil surface and a depth of 50 cm; or particle-size class criteria in at least some part between the mineral soil surface and the spodic horizon; and c. Constitute two-thirds or more of the total thickness of the soil to a densic, lithic, or paralithic contact and have c. A lower boundary as follows: no mineral horizons or have mineral horizons with a total (1) Either at a depth of 25 cm or more below the thickness of 10 cm or less; or mineral soil surface or at the top of a duripan or d. Are saturated with water for 30 days or more per year fragipan or at a densic, lithic, paralithic, or petroferric in normal years (or are artificially drained), have an upper contact, whichever is shallowest; or boundary within 40 cm of the soil surface, and have a (2) At any depth, total thickness of either: (a) If the spodic horizon meets the criteria for a (1) 60 cm or more if three-fourths or more of their coarse-loamy, loamy-skeletal, or finer particle-size volume consists of moss fibers or if their bulk density, class and the soil has a frigid temperature regime; or moist, is less than 0.1 g/cm3; or (b) If the soil has a cryic or gelic temperature (2) 40 cm or more if they consist either of sapric regime; and or hemic materials, or of fibric materials with less than three-fourths (by volume) moss fibers and a bulk d. Either: 3 density, moist, of 0.1 g/cm or more. (1) A directly overlying albic horizon in 50 percent or Histosols, p. 155 more of each pedon; or C. Other soils that do not have a plaggen epipedon or an (2) No andic soil properties in 60 percent or more of argillic or kandic horizon above a spodic horizon, and have one the thickness either: or more of the following: (a) Within 60 cm either of the mineral soil surface 1. A spodic horizon, an albic horizon in 50 percent or or of the top of an organic layer with andic soil more of each pedon, and a cryic or gelic soil temperature properties, whichever is shallower, if there is no regime; or densic, lithic, or paralithic contact, duripan, or petrocalcic horizon within that depth; or 2. An Ap horizon containing 85 percent or more spodic materials; or (b) Between either the mineral soil surface or the top of an organic layer with andic soil properties, 3. A spodic horizon with all of the following whichever is shallower, and a densic, lithic, or characteristics: paralithic contact, a duripan, or a petrocalcic a. One or more of the following: horizon. Spodosols, p. 257 (1) A thickness of 10 cm or more; or (2) An overlying Ap horizon; or D. Other soils that have andic soil properties in 60 percent or more of the thickness either: (3) Cementation in 50 percent or more of each pedon; or 1. Within 60 cm either of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever (4) A particle-size class that meets the criteria for is shallower, if there is no densic, lithic, or paralithic contact, duripan, or petrocalcic horizon within that depth; or 1 Materials that meet the definition of cindery, fragmental, or pumiceous but have more than 10 percent, by volume, voids that are filled with organic soil materials are considered 2. Between either the mineral soil surface or the top to be organic soil materials. of an organic layer with andic soil properties, whichever Identification of the Taxonomic Class of a Soil 33

is shallower, and a densic, lithic, or paralithic contact, a b. A moisture control section that is dry in some or all duripan, or a petrocalcic horizon. parts at some time during normal years; and Andisols, p. 77 c. No sulfuric horizon within 150 cm of the mineral soil surface. E. Other soils that have either: Aridisols, p. 97 1. An oxic horizon within 150 cm of the mineral soil surface and no kandic horizon within that depth; or H. Other soils that have : either I D 2. 40 percent or more (by weight) clay in the fine-earth 1. An argillic or kandic horizon, but no fragipan, and a base E fraction between the mineral soil surface and a depth of saturation (by sum of cations) of less than 35 percent at one 18 cm (after mixing) and a kandic horizon that has the of the following depths: weatherable-mineral properties of an oxic horizon and has its upper boundary within 100 cm of the mineral soil surface. a. If the epipedon meets sandy or sandy-skeletal Oxisols, p. 241 particle-size class criteria throughout, either: (1) 125 cm below the upper boundary of the argillic F. Other soils that have: horizon (but no deeper than 200 cm below the mineral 1. A layer 25 cm or more thick, within 100 cm of the soil surface) or 180 cm below the mineral soil surface, mineral soil surface, that has either slickensides or wedge- whichever is deeper; or shaped peds that have their long axes tilted 10 to 60 degrees (2) At a densic, lithic, paralithic, or petroferric from the horizontal; and contact if shallower; or 2. A weighted average of 30 percent or more clay in the b. The shallowest of the following depths: fine-earth fraction either between the mineral soil surface and a depth of 18 cm or in an Ap horizon, whichever is thicker, (1) 125 cm below the upper boundary of the argillic and 30 percent or more clay in the fine-earth fraction of all or kandic horizon; or horizons between a depth of 18 cm and either a depth of 50 (2) 180 cm below the mineral soil surface; or cm or a densic, lithic, or paralithic contact, a duripan, or a petrocalcic horizon if shallower; and (3) At a densic, lithic, paralithic, or petroferric contact; or 3. Cracks2 that open and close periodically. Vertisols, p. 287 2. A fragipan and both of the following: a. Either an argillic or a kandic horizon above, within, or G. Other soils that: below it or clay films 1 mm or more thick in one or more 1. Have: of its subhorizons; and a. An aridic soil moisture regime; and b. A base saturation (by sum of cations) of less than 35 percent at the shallowest of the following depths: b. An ochric or anthropic epipedon; and (1) 75 cm below the upper boundary of the fragipan; c. One or more of the following within 100 cm of the or soil surface: a cambic horizon with a lower depth of 25 cm or more; a cryic soil temperature regime and a cambic (2) 200 cm below the mineral soil surface; or horizon; a calcic, gypsic, petrocalcic, petrogypsic, or salic (3) At a densic, lithic, paralithic, or petroferric horizon; or a duripan; or contact. d. An argillic or natric horizon; or Ultisols, p. 267 2. Have a salic horizon; and I. Other soils that have both of the following: a. Saturation with water in one or more layers within 1. Either: 100 cm of the soil surface for 1 month or more during a normal year; and a. A mollic epipedon; or b. Both a surface horizon that meets all the requirements 2 A crack is a separation between gross polyhedrons. If the surface is strongly self- for a mollic epipedon except thickness after the soil mulching, i.e., a mass of granules, or if the soil is cultivated while cracks are open, the has been mixed to a depth of 18 cm and a subhorizon cracks may be filled mainly by granular materials from the surface, but they are open in the sense that the polyhedrons are separated. A crack is regarded as open if it controls the more than 7.5 cm thick, within the upper part of an infiltration and percolation of water in a dry, clayey soil. argillic, kandic, or natric horizon, that meets the color, 34

organic-carbon content, base saturation, and structure d. A sulfuric horizon within 150 cm of the mineral soil requirements of a mollic epipedon but is separated from surface; or the surface horizon by an albic horizon; and e. A cryic or gelic soil temperature regime and a cambic

2. A base saturation of 50 percent or more (by NH4OAc) horizon; or in all horizons either between the upper boundary of any 2. No sulfidic materials within 50 cm of the mineral soil argillic, kandic, or natric horizon and a depth of 125 cm surface; and both: below that boundary, or between the mineral soil surface and a depth of 180 cm, or between the mineral soil surface a. In one or more horizons between 20 and 50 cm and a densic, lithic, or paralithic contact, whichever depth is below the mineral soil surface, either an n value of 0.7 or shallowest. less or less than 8 percent clay in the fine-earth fraction; Mollisols, p. 197 and b. One or both of the following: J. Other soils that do not have a plaggen epipedon and that have either: (1) A salic horizon or a histic, mollic, plaggen, or umbric epipedon; or 1. An argillic, kandic, or natric horizon; or (2) In 50 percent or more of the layers between 2. A fragipan that has clay films 1 mm or more thick in the mineral soil surface and a depth of 50 cm, an some part. exchangeable sodium percentage of 15 or more (or Alfisols, p. 35 a sodium adsorption ratio of 13 or more), which decreases with increasing depth below 50 cm, and also K. Other soils that have either: ground water within 100 cm of the mineral soil surface 1. One or more of the following: at some time during the year when the soil is not frozen in any part. a. A cambic horizon that is within 100 cm of the mineral Inceptisols, p. 161 soil surface and has a lower boundary at a depth of 25 cm or more below the mineral soil surface; or L. Other soils. b. A calcic, petrocalcic, gypsic, petrogypsic, or placic Entisols, p. 123 horizon or a duripan within a depth of 100 cm of the mineral soil surface; or c. A fragipan or an oxic, sombric, or spodic horizon within 200 cm of the mineral soil surface; or 35

CHAPTER 5 Alfisols

Key to Suborders JAB. Other Aqualfs that have one or more horizons, at a depth between 30 and 150 cm from the mineral soil surface, in which A L JA. Alfisols that have, in one or more horizons within 50 plinthite either forms a continuous phase or constitutes one-half F cm of the mineral soil surface, aquic conditions (other than or more of the volume. anthraquic conditions) for some time in normal years (or Plinthaqualfs, p. 43 artificial drainage)and have one or both of the following: 1. Redoximorphic features in all layers between either the JAC. Other Aqualfs that have a duripan. lower boundary of an Ap horizon or a depth of 25 cm below Duraqualfs, p. 37 the mineral soil surface, whichever is deeper, and a depth of 40 cm; and one of the following within the upper 12.5 cm of JAD. Other Aqualfs that have a natric horizon. the argillic, natric, glossic, or kandic horizon: Natraqualfs, p. 43

a. 50 percent or more redox depletions with chroma of JAE. Other Aqualfs that have a fragipan within 100 cm of the 2 or less on faces of peds and redox concentrations within mineral soil surface. peds; or Fragiaqualfs, p. 41 b. Redox concentrations and 50 percent or more redox depletions with chroma of 2 or less in the matrix; or JAF. Other Aqualfs that have a kandic horizon. Kandiaqualfs, p. 42 c. 50 percent or more redox depletions with chroma of 1 or less on faces of peds or in the matrix, or both; or JAG. Other Aqualfs that have one or more layers, at least 2. In the horizons that have aquic conditions, enough 25 cm thick (cumulative) within 100 cm of the mineral soil active ferrous iron to give a positive reaction to alpha,alpha- surface, that have 50 percent or more (by volume) recognizable dipyridyl at a time when the soil is not being irrigated. bioturbation, such as filled animal burrows, wormholes, or Aqualfs, p. 35 casts. Vermaqualfs, p. 43 JB. Other Alfisols that have a cryic or isofrigid soil temperature regime. JAH. Other Aqualfs that have an abrupt textural change Cryalfs, p. 44 between the ochric epipedon or albic horizon and the argillic horizon and have a saturated hydraulic conductivity of 0.4 JC. Other Alfisols that have an ustic soil moisture regime. cm/hr or slower (moderately low or lower Ksat class) in the Ustalfs, p. 59 argillic horizon. Albaqualfs, p. 36 JD. Other Alfisols that have a xeric soil moisture regime. Xeralfs, p. 71 JAI. Other Aqualfs that have a glossic horizon. Glossaqualfs, p. 41 JE. Other Alfisols. Udalfs, p. 47 JAJ. Other Aqualfs that have episaturation. Epiaqualfs, p. 39 Aqualfs JAK. Other Aqualfs. Key to Great Groups Endoaqualfs, p. 37 JAA. Aqualfs that have a cryic soil temperature regime. Cryaqualfs, p. 37 36 Keys to Soil Taxonomy

Albaqualfs 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or more Key to Subgroups for some time in normal years and slickensides or wedge- JAHA. Albaqualfs that meet sandy or sandy-skeletal particle- shaped peds in a layer 15 cm or more thick that has its upper size class criteria throughout a layer extending from the mineral boundary within 125 cm of the mineral soil surface; or soil surface to the top of an argillic horizon at a depth of 50 cm 2. A linear extensibility of 6.0 cm or more between the or more below the mineral soil surface. mineral soil surface and either a depth of 100 cm or a densic, Arenic Albaqualfs lithic, or paralithic contact, whichever is shallower. Vertic Albaqualfs JAHB. Other Albaqualfs that have both of the following: 1. One or both: JAHE. Other Albaqualfs that have both: a. Cracks within 125 cm of the mineral soil surface that 1. Chroma of 3 or more in 40 percent or more of the matrix are 5 mm or more wide through a thickness of 30 cm or between the lower boundary of the A or Ap horizon and a more for some time in normal years and slickensides or depth of 75 cm from the mineral soil surface; and wedge-shaped peds in a layer 15 cm or more thick that 2. A mollic epipedon, or the upper 18 cm of the mineral has its upper boundary within 125 cm of the mineral soil soil meets all of the requirements for a mollic epipedon, surface; or except for thickness, after mixing. b. A linear extensibility of 6.0 cm or more between Udollic Albaqualfs the mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is JAHF. Other Albaqualfs that have chroma of 3 or more in 40 shallower; and percent or more of the matrix between the lower boundary of the A or Ap horizon and a depth of 75 cm from the mineral soil 2. Chroma of 3 or more in 40 percent or more of the matrix surface. between the lower boundary of the A or Ap horizon and a depth of 75 cm from the mineral soil surface. Aeric Albaqualfs Aeric Vertic Albaqualfs JAHG. Other Albaqualfs that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm JAHC. Other Albaqualfs that have both of the following: of the mineral soil surface, one or more of the following: 1. One or both: 1. A fine-earth fraction with both a bulk density of 1.0 a. Cracks within 125 cm of the mineral soil surface that g/cm3 or less, measured at 33 kPa water retention, and Al 1 are 5 mm or more wide through a thickness of 30 cm or plus /2 Fe percentages (by ammonium oxalate) totaling more more for some time in normal years and slickensides or than 1.0; or wedge-shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil 2. More than 35 percent (by volume) fragments coarser surface; or than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm 3. A fine-earth fraction containing 30 percent or more or a densic, lithic, or paralithic contact, whichever is particles 0.02 to 2.0 mm in diameter; and shallower; and a. In the 0.02 to 2.0 mm fraction, 5 percent or more 2. An Ap horizon or materials between the mineral soil volcanic glass; and

surface and a depth of 18 cm that, after mixing, have one or 1 b. [(Al plus /2 Fe, percent extracted by ammonium more of the following: oxalate) times 60] plus the volcanic glass (percent) is a. A color value, moist, of 4 or more; or equal to 30 or more. Aquandic Albaqualfs b. A color value, dry, of 6 or more; or c. Chroma of 4 or more. Chromic Vertic Albaqualfs JAHH. Other Albaqualfs that have a mollic epipedon, or the upper 18 cm of the mineral soil meets all of the requirements JAHD. Other Albaqualfs that have one or both of the for a mollic epipedon, except for thickness, after mixing. following: Mollic Albaqualfs Alfisols 37

JAHI. Other Albaqualfs that have an umbric epipedon, or the has its upper boundary within 125 cm of the mineral soil upper 18 cm of the mineral soil meets all of the requirements surface; or for an umbric epipedon, except for thickness, after mixing. b. A linear extensibility of 6.0 cm or more between Umbric Albaqualfs the mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is JAHJ. Other Albaqualfs. shallower; and Typic Albaqualfs 2. An Ap horizon or materials between the mineral soil Cryaqualfs surface and a depth of 18 cm that, after mixing, have one or more of the following: Key to Subgroups a. A color value, moist, of 4 or more; or A L JAAA. All Cryaqualfs (provisionally). F Typic Cryaqualfs b. A color value, dry, of 6 or more; or c. Chroma of 4 or more. Duraqualfs Chromic Vertic Endoaqualfs Key to Subgroups JAKC. Other Endoaqualfs that have one or both of the JACA. All Duraqualfs (provisionally). following: Typic Duraqualfs 1. Cracks within 125 cm of the mineral soil surface that are Endoaqualfs 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge- Key to Subgroups shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil surface; or JAKA. Endoaqualfs that have, throughout one or more 2. A linear extensibility of 6.0 cm or more between the horizons with a total thickness of 18 cm or more within 75 cm mineral soil surface and either a depth of 100 cm or a densic, of the mineral soil surface, one or more of the following: lithic, or paralithic contact, whichever is shallower. 1. A fine-earth fraction with both a bulk density of 1.0 Vertic Endoaqualfs g/cm3 or less, measured at 33 kPa water retention, and Al 1 plus /2 Fe percentages (by ammonium oxalate) totaling more JAKD. Other Endoaqualfs that have both: than 1.0; or 1. Fragic soil properties: 2. More than 35 percent (by volume) fragments coarser a. In 30 percent or more of the volume of a layer 15 cm than 2.0 mm, of which more than 66 percent is cinders, or more thick that has its upper boundary within 100 cm pumice, and pumicelike fragments; or of the mineral soil surface; or 3. A fine-earth fraction containing 30 percent or more b. In 60 percent or more of the volume of a layer 15 cm particles 0.02 to 2.0 mm in diameter; and or more thick; and a. In the 0.02 to 2.0 mm fraction, 5 percent or more 2. In one or more horizons between the A or Ap horizon volcanic glass; and and a depth of 75 cm below the mineral soil surface, one or a 1 b. [(Al plus /2 Fe, percent extracted by ammonium combination of the following colors: oxalate) times 60] plus the volcanic glass (percent) is a. Hue of 7.5YR or redder in 50 percent or more of the equal to 30 or more. matrix; and Aquandic Endoaqualfs (1) If peds are present, chroma of 2 or more on 50 JAKB. Other Endoaqualfs that have both of the following: percent or more of ped exteriors or no redox depletions with chroma of 2 or less in ped interiors; or 1. One or both: (2) If peds are absent, chroma of 2 or more in 50 a. Cracks within 125 cm of the mineral soil surface that percent or more of the matrix; or are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or b. In 50 percent or more of the matrix, hue of 10YR or wedge-shaped peds in a layer 15 cm or more thick that yellower and either: 38 Keys to Soil Taxonomy

(1) Both a color value of 3 or more (moist) and JAKI. Other Endoaqualfs that have both: chroma of 3 or more (moist and dry); or 1. An umbric epipedon, or the upper 18 cm of the mineral (2) Chroma of 2 or more if there are no redox soil meets all of the requirements for an umbric epipedon, concentrations. except for thickness, after mixing; and Aeric Fragic Endoaqualfs 2. In one or more horizons between the A or Ap horizon JAKE. Other Endoaqualfs that have fragic soil properties: and a depth of 75 cm below the mineral soil surface, one or a combination of the following colors: 1. In 30 percent or more of the volume of a layer 15 cm or more thick that has its upper boundary within 100 cm of the a. Hue of 7.5YR or redder in 50 percent or more of the mineral soil surface; or matrix; and 2. In 60 percent or more of the volume of a layer 15 cm or (1) If peds are present, chroma of 2 or more on 50 more thick. percent or more of ped exteriors or no redox depletions Fragic Endoaqualfs with chroma of 2 or less in ped interiors; or

JAKF. Other Endoaqualfs that meet sandy or sandy-skeletal (2) If peds are absent, chroma of 2 or more in 50 particle-size class criteria throughout a layer extending from the percent or more of the matrix; or mineral soil surface to the top of an argillic horizon at a depth of b. In 50 percent or more of the matrix, hue of 10YR or 50 to 100 cm below the mineral soil surface. yellower and either: Arenic Endoaqualfs (1) Both a color value of 3 or more (moist) and JAKG. Other Endoaqualfs that meet sandy or sandy-skeletal chroma of 3 or more; or particle-size class criteria throughout a layer extending from the (2) Chroma of 2 or more if there are no redox mineral soil surface to the top of an argillic horizon at a depth of concentrations. 100 cm or more below the mineral soil surface. Aeric Umbric Endoaqualfs Grossarenic Endoaqualfs JAKJ. Other Endoaqualfs that have, in one or more horizons JAKH. Other Endoaqualfs that have both: between the A or Ap horizon and a depth of 75 cm below the 1. A mollic epipedon, or the upper 18 cm of the mineral mineral soil surface, in 50 percent or more of the matrix, one or soil meets all of the requirements for a mollic epipedon, a combination of the following colors: except for thickness, after mixing; and 1. Hue of 7.5YR or redder; and 2. In one or more horizons between the A or Ap horizon and a depth of 75 cm below the mineral soil surface, one or a a. If peds are present, chroma of 2 or more (both moist combination of the following colors: and dry) on 50 percent or more of ped exteriors or no redox depletions with chroma of 2 or less (both moist and a. Hue of 7.5YR or redder in 50 percent or more of the dry) in ped interiors; or matrix; and b. If peds are absent, chroma of 2 or more (both moist (1) If peds are present, chroma of 2 or more on 50 and dry); or percent or more of ped exteriors or no redox depletions with chroma of 2 or less in ped interiors; or 2. Hue of 10YR or yellower and either: (2) If peds are absent, chroma of 2 or more in 50 a. Both a color value of 3 or more (moist) and chroma percent or more of the matrix; or of 3 or more (moist and dry); or b. In 50 percent or more of the matrix, hue of 10YR or b. Chroma of 2 or more (both moist and dry) and no yellower and either: redox concentrations. Aeric Endoaqualfs (1) Both a color value of 3 or more (moist) and chroma of 3 or more; or JAKK. Other Endoaqualfs that have a mollic epipedon, or the (2) Chroma of 2 or more if there are no redox upper 18 cm of the mineral soil meets all of the requirements concentrations. for a mollic epipedon, except for thickness, after mixing. Udollic Endoaqualfs Mollic Endoaqualfs Alfisols 39

JAKL. Other Endoaqualfs that have an umbric epipedon, JAJB. Other Epiaqualfs that have both of the following: or the upper 18 cm of the mineral soil meets all of the 1. One or both: requirements for an umbric epipedon, except for thickness, after mixing. a. Cracks within 125 cm of the mineral soil surface that Umbric Endoaqualfs are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or JAKM. Other Endoaqualfs. wedge-shaped peds in a layer 15 cm or more thick that Typic Endoaqualfs has its upper boundary within 125 cm of the mineral soil surface; or Epiaqualfs b. A linear extensibility of 6.0 cm or more between Key to Subgroups the mineral soil surface and either a depth of 100 cm A L or a densic, lithic, or paralithic contact, whichever is F JAJA. Epiaqualfs that have all of the following: shallower; and 1. One or both: 2. In one or more horizons between the A or Ap horizon a. Cracks within 125 cm of the mineral soil surface that and a depth of 75 cm below the mineral soil surface, in 50 are 5 mm or more wide through a thickness of 30 cm or percent or more of the matrix, one or a combination of the more for some time in normal years and slickensides or following colors: wedge-shaped peds in a layer 15 cm or more thick that a. Hue of 7.5YR or redder; and has its upper boundary within 125 cm of the mineral soil surface; or (1) If peds are present, chroma of 2 or more (both moist and dry) on 50 percent or more of ped exteriors b. A linear extensibility of 6.0 cm or more between or no redox depletions with chroma of 2 or less (both the mineral soil surface and either a depth of 100 cm moist and dry) in ped interiors; or or a densic, lithic, or paralithic contact, whichever is shallower; and (2) If peds are absent, chroma of 2 or more (both 2. In one or more horizons between the A or Ap horizon moist and dry); or and a depth of 75 cm below the mineral soil surface, in 50 b. Hue of 10YR or yellower and either: percent or more of the matrix, one or a combination of the following colors: (1) Both a color value of 3 or more (moist) and chroma of 3 or more (moist and dry); or a. Hue of 7.5YR or redder; and (2) Chroma of 2 or more (both moist and dry) and no (1) If peds are present, chroma of 2 or more (both redox concentrations. moist and dry) on 50 percent or more of ped exteriors Aeric Vertic Epiaqualfs or no redox depletions with chroma of 2 or less (both moist and dry) in ped interiors; or JAJC. Other Epiaqualfs that have both of the following: (2) If peds are absent, chroma of 2 or more (both 1. One or both: moist and dry); or a. Cracks within 125 cm of the mineral soil surface that b. Hue of 10YR or yellower and either: are 5 mm or more wide through a thickness of 30 cm or (1) Both a color value of 3 or more (moist) and more for some time in normal years and slickensides or chroma of 3 or more (moist and dry); or wedge-shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil (2) Chroma of 2 or more (both moist and dry) and no surface; or redox concentrations; and b. A linear extensibility of 6.0 cm or more between 3. An Ap horizon or materials between the mineral soil the mineral soil surface and either a depth of 100 cm surface and a depth of 18 cm that, after mixing, have one or or a densic, lithic, or paralithic contact, whichever is more of the following: shallower; and a. A color value, moist, of 4 or more; or 2. An Ap horizon or materials between the mineral soil b. A color value, dry, of 6 or more; or surface and a depth of 18 cm that, after mixing, have one or more of the following: c. Chroma of 4 or more. Aeric Chromic Vertic Epiaqualfs a. A color value, moist, of 4 or more; or 40 Keys to Soil Taxonomy

b. A color value, dry, of 6 or more; or moist and dry) on 50 percent or more of ped exteriors or no redox depletions with chroma of 2 or less (both c. Chroma of 4 or more. moist and dry) in ped interiors; or Chromic Vertic Epiaqualfs (2) If peds are absent, chroma of 2 or more (both JAJD. Other Epiaqualfs that have one or both of the following: moist and dry); or 1. Cracks within 125 cm of the mineral soil surface that are b. Hue of 10YR or yellower and either: 5 mm or more wide through a thickness of 30 cm or more (1) Both a color value of 3 or more (moist) and for some time in normal years and slickensides or wedge- chroma of 3 or more (moist and dry); or shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil surface; or (2) Chroma of 2 or more (both moist and dry) and no redox concentrations. 2. A linear extensibility of 6.0 cm or more between the Aeric Fragic Epiaqualfs mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. JAJG. Other Epiaqualfs that have fragic soil properties: Vertic Epiaqualfs 1. In 30 percent or more of the volume of a layer 15 cm or JAJE. Other Epiaqualfs that have, throughout one or more more thick that has its upper boundary within 100 cm of the horizons with a total thickness of 18 cm or more within 75 cm mineral soil surface; or of the mineral soil surface, one or more of the following: 2. In 60 percent or more of the volume of a layer 15 cm or 1. A fine-earth fraction with both a bulk density of 1.0 more thick. g/cm3 or less, measured at 33 kPa water retention, and Al Fragic Epiaqualfs 1 plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0; or JAJH. Other Epiaqualfs that meet sandy or sandy-skeletal particle-size class criteria throughout a layer extending from the 2. More than 35 percent (by volume) fragments coarser mineral soil surface to the top of an argillic horizon at a depth of than 2.0 mm, of which more than 66 percent is cinders, 50 to 100 cm below the mineral soil surface. pumice, and pumicelike fragments; or Arenic Epiaqualfs 3. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and JAJI. Other Epiaqualfs that meet sandy or sandy-skeletal particle-size class criteria throughout a layer extending from the a. In the 0.02 to 2.0 mm fraction, 5 percent or more mineral soil surface to the top of an argillic horizon at a depth of volcanic glass; and 100 cm or more below the mineral soil surface. 1 b. [(Al plus /2 Fe, percent extracted by ammonium Grossarenic Epiaqualfs oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. JAJJ. Other Epiaqualfs that have both: Aquandic Epiaqualfs 1. An umbric epipedon, or the upper 18 cm of the mineral soil meets all of the requirements for an umbric epipedon, JAJF. Other Epiaqualfs that have both: except for thickness, after mixing; and 1. Fragic soil properties: 2. In one or more horizons between the A or Ap horizon a. In 30 percent or more of the volume of a layer 15 cm and a depth of 75 cm below the mineral soil surface, in 50 or more thick that has its upper boundary within 100 cm percent or more of the matrix, one or a combination of the of the mineral soil surface; or following colors: b. In 60 percent or more of the volume of a layer 15 cm a. Hue of 7.5YR or redder; and or more thick; and (1) If peds are present, chroma of 2 or more (both 2. In one or more horizons between the A or Ap horizon moist and dry) on 50 percent or more of ped exteriors and a depth of 75 cm below the mineral soil surface, in 50 or no redox depletions with chroma of 2 or less (both percent or more of the matrix, one or a combination of the moist and dry) in ped interiors; or following colors: (2) If peds are absent, chroma of 2 or more (both a. Hue of 7.5YR or redder; and moist and dry); or (1) If peds are present, chroma of 2 or more (both b. Hue of 10YR or yellower and either: Alfisols 41

(1) Both a color value of 3 or more (moist) and upper 18 cm of the mineral soil meets all of the requirements chroma of 3 or more (moist and dry); or for a mollic epipedon, except for thickness, after mixing. Mollic Epiaqualfs (2) Chroma of 2 or more (both moist and dry) and no redox concentrations. JAJN. Other Epiaqualfs that have an umbric epipedon, or the Aeric Umbric Epiaqualfs upper 18 cm of the mineral soil meets all of the requirements for an umbric epipedon, except for thickness, after mixing. JAJK. Other Epiaqualfs that have both: Umbric Epiaqualfs 1. A mollic epipedon, or the upper 18 cm of the mineral soil meets all of the requirements for a mollic epipedon, JAJO. Other Epiaqualfs. except for thickness, after mixing and Typic Epiaqualfs A L 2. In 50 percent or more of the matrix in one or more F horizons between the A or Ap horizon and a depth of 75 cm Fragiaqualfs below the mineral soil surface, one or a combination of the Key to Subgroups following colors: JAEA. Fragiaqualfs that have one or more layers, at least a. Hue of 7.5YR or redder; and 25 cm thick (cumulative) within 100 cm of the mineral soil (1) If peds are present, chroma of 2 or more on 50 surface, that have 25 percent or more (by volume) recognizable percent or more of ped exteriors or no redox depletions bioturbation, such as filled animal burrows, wormholes, or casts. with chroma of 2 or less in ped interiors; or Vermic Fragiaqualfs

(2) If peds are absent, chroma of 2 or more in 50 JAEB. Other Fragiaqualfs that have, between the A or Ap percent or more of the matrix; or horizon and a fragipan, a horizon with 50 percent or more b. Hue of 10YR or yellower and either: chroma of 3 or more if hue is 10YR or redder or of 4 or more if hue is 2.5Y or yellower. (1) Both a color value of 3 or more (moist) and Aeric Fragiaqualfs chroma of 3 or more; or (2) Chroma of 2 or more if there are no redox JAEC. Other Fragiaqualfs that have 5 percent or more (by concentrations. volume) plinthite in one or more horizons within 150 cm of the Udollic Epiaqualfs mineral soil surface. Plinthic Fragiaqualfs JAJL. Other Epiaqualfs that have, in one or more horizons between the A or Ap horizon and a depth of 75 cm below the JAED. Other Fragiaqualfs that have a color value, moist, mineral soil surface, in 50 percent or more of the matrix, one or of 3 or less and a color value, dry, of 5 or less (crushed and a combination of the following colors: smoothed sample) either throughout the upper 18 cm of the mineral soil (unmixed) or between the mineral soil surface and a 1. Hue of 7.5YR or redder; and depth of 18 cm after mixing. a. If peds are present, chroma of 2 or more (both moist Humic Fragiaqualfs and dry) on 50 percent or more of ped exteriors or no redox depletions with chroma of 2 or less (both moist and JAEE. Other Fragiaqualfs. dry) in ped interiors; or Typic Fragiaqualfs b. If peds are absent, chroma of 2 or more (both moist Glossaqualfs and dry); or Key to Subgroups 2. Hue of 10YR or yellower and either: JAIA. Glossaqualfs that have a histic epipedon. a. Both a color value of 3 or more (moist) and chroma Histic Glossaqualfs of 3 or more (moist and dry); or b. Chroma of 2 or more (both moist and dry) and no JAIB. Other Glossaqualfs that meet sandy or sandy-skeletal redox concentrations. particle-size class criteria throughout a layer extending from the Aeric Epiaqualfs mineral soil surface to the top of an argillic horizon at a depth of 50 cm or more below the mineral soil surface. JAJM. Other Epiaqualfs that have a mollic epipedon, or the Arenic Glossaqualfs 42 Keys to Soil Taxonomy

JAIC. Other Glossaqualfs that have both: a. Both a color value of 3 or more (moist) and chroma of 3 or more (moist and dry); or 1. Fragic soil properties: b. Chroma of 2 or more (both moist and dry) and no a. In 30 percent or more of the volume of a layer 15 cm redox concentrations. or more thick that has its upper boundary within 100 cm Aeric Glossaqualfs of the mineral soil surface; or b. In 60 percent or more of the volume of a layer 15 cm JAIF. Other Glossaqualfs that have a mollic epipedon, or the or more thick; and upper 18 cm of the mineral soil meets the requirements for a mollic epipedon after mixing. 2. In one or more horizons between the A or Ap horizon Mollic Glossaqualfs and a depth of 75 cm below the mineral soil surface, one or a combination of the following colors: JAIG. Other Glossaqualfs. a. Hue of 7.5YR or redder in 50 percent or more of the Typic Glossaqualfs matrix; and Kandiaqualfs (1) If peds are present, chroma of 2 or more on 50 percent or more of ped exteriors or no redox depletions Key to Subgroups with chroma of 2 or less in ped interiors; or JAFA. Kandiaqualfs that meet sandy or sandy-skeletal (2) If peds are absent, chroma of 2 or more in 50 particle-size class criteria throughout a layer extending from the percent or more of the matrix; or mineral soil surface to the top of a kandic horizon at a depth of 50 to 100 cm below the mineral soil surface. b. In 50 percent or more of the matrix, hue of 10YR or Arenic Kandiaqualfs yellower and either: (1) Both a color value of 3 or more (moist) and JAFB. Other Kandiaqualfs that meet sandy or sandy-skeletal chroma of 3 or more (moist and dry); or particle-size class criteria throughout a layer extending from the mineral soil surface to the top of a kandic horizon at a depth of (2) Chroma of 2 or more if there are no redox 100 cm or more below the mineral soil surface. concentrations. Grossarenic Kandiaqualfs Aeric Fragic Glossaqualfs JAFC. Other Kandiaqualfs that have 5 percent or more (by JAID. Other Glossaqualfs that have fragic soil properties: volume) plinthite in one or more horizons within 150 cm of the 1. In 30 percent or more of the volume of a layer 15 cm or mineral soil surface. more thick that has its upper boundary within 100 cm of the Plinthic Kandiaqualfs mineral soil surface; or JAFD. Other Kandiaqualfs that have both: 2. In 60 percent or more of the volume of a layer 15 cm or more thick. 1. A color value, moist, of 3 or less and a color value, dry, Fragic Glossaqualfs of 5 or less (crushed and smoothed sample) either throughout the upper 18 cm of the mineral soil (unmixed) or between the JAIE. Other Glossaqualfs that have, in one or more horizons mineral soil surface and a depth of 18 cm after mixing; and between the A or Ap horizon and a depth of 75 cm below the 2. In one or more horizons between the A or Ap horizon mineral soil surface, in 50 percent or more of the matrix, one or and a depth of 75 cm below the mineral soil surface, in 50 a combination of the following colors: percent or more of the matrix, one or a combination of the 1. Hue of 7.5YR or redder; and following colors: a. If peds are present, chroma of 2 or more (both moist a. Hue of 7.5YR or redder; and and dry) on 50 percent or more of ped exteriors or no (1) If peds are present, chroma of 2 or more (both redox depletions with chroma of 2 or less (both moist and moist and dry) on 50 percent or more of ped exteriors dry) in ped interiors; or or no redox depletions with chroma of 2 or less (both b. If peds are absent, chroma of 2 or more (both moist moist and dry) in ped interiors; or and dry); or (2) If peds are absent, chroma of 2 or more (both 2. Hue of 10YR or yellower and either: moist and dry); or Alfisols 43

b. Hue of 10YR or yellower and either: 25 cm thick (cumulative) within 100 cm of the mineral soil surface, that have 25 percent or more (by volume) recognizable (1) Both a color value of 3 or more (moist) and bioturbation, such as filled animal burrows, wormholes, or casts. chroma of 3 or more (moist and dry); or Vermic Natraqualfs (2) Chroma of 2 or more (both moist and dry) and no redox concentrations. JADC. Other Natraqualfs that have both: Aeric Umbric Kandiaqualfs 1. A glossic horizon or interfingering of albic materials into the natric horizon; and JAFE. Other Kandiaqualfs that have, in one or more horizons between the A or Ap horizon and a depth of 75 cm below the 2. An exchangeable sodium percentage of less than 15 and mineral soil surface, in 50 percent or more of the matrix, one or less magnesium plus sodium than calcium plus extractable A a combination of the following colors: acidity either throughout the upper 15 cm of the natric L F horizon or in all horizons within 40 cm of the mineral soil 1. Hue of 7.5YR or redder; and surface, whichever is deeper. a. If peds are present, chroma of 2 or more (both moist Albic Glossic Natraqualfs and dry) on 50 percent or more of ped exteriors or no redox depletions with chroma of 2 or less (both moist and JADD. Other Natraqualfs that have an exchangeable sodium dry) in ped interiors; or percentage of less than 15 and less magnesium plus sodium than b. If peds are absent, chroma of 2 or more (both moist calcium plus extractable acidity either throughout the upper 15 and dry); or cm of the natric horizon or in all horizons within 40 cm of the mineral soil surface, whichever is deeper. 2. Hue of 10YR or yellower and either: Albic Natraqualfs a. Both a color value of 3 or more (moist) and chroma of 3 or more (moist and dry); or JADE. Other Natraqualfs that have a glossic horizon or interfingering of albic materials into the natric horizon. b. Chroma of 2 or more (both moist and dry) and no Glossic Natraqualfs redox concentrations. Aeric Kandiaqualfs JADF. Other Natraqualfs that have a mollic epipedon, or the upper 18 cm of the mineral soil meets the color requirements for JAFF. Other Kandiaqualfs that have an umbric epipedon, a mollic epipedon after mixing. or the upper 18 cm of the mineral soil meets the color Mollic Natraqualfs requirements for an umbric epipedon after mixing. Umbric Kandiaqualfs JADG. Other Natraqualfs. Typic Natraqualfs JAFG. Other Kandiaqualfs. Typic Kandiaqualfs Plinthaqualfs Natraqualfs Key to Subgroups Key to Subgroups JABA. All Plinthaqualfs (provisionally). Typic Plinthaqualfs JADA. Natraqualfs that have one or both of the following: Vermaqualfs 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or more Key to Subgroups for some time in normal years and slickensides or wedge- JAGA. Vermaqualfs that have an exchangeable sodium shaped peds in a layer 15 cm or more thick that has its upper percentage of 7 or more (or a sodium adsorption ratio of 6 or boundary within 125 cm of the mineral soil surface; or more) either or both: 2. A linear extensibility of 6.0 cm or more between the 1. Throughout the upper 15 cm of the argillic horizon; mineral soil surface and either a depth of 100 cm or a densic, and/or lithic, or paralithic contact, whichever is shallower. Vertic Natraqualfs 2. Throughout all horizons within 40 cm of the mineral soil surface. JADB. Other Natraqualfs that have one or more layers, at least Natric Vermaqualfs 44 Keys to Soil Taxonomy

1 JAGB. Other Vermaqualfs. and Al plus /2 Fe percentages (by ammonium oxalate) totaling Typic Vermaqualfs more than 1.0. Andic Glossocryalfs Cryalfs JBBD. Other Glossocryalfs that have, throughout one or more Key to Great Groups horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: JBA. Cryalfs that have all of the following: 1. An argillic, kandic, or natric horizon that has its upper 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, boundary 60 cm or more below both: pumice, and pumicelike fragments; or a. The mineral soil surface; and 2. A fine-earth fraction containing 30 percent or more b. The lower boundary of any surface mantle containing particles 0.02 to 2.0 mm in diameter; and 30 percent or more vitric volcanic ash, cinders, or other vitric pyroclastic materials; and a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and 2. A texture class finer than loamy fine sand in one or more 1 horizons above the argillic, kandic, or natric horizon; and b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 3. Either a glossic horizon or interfingering of albic equal to 30 or more. materials into the argillic, kandic, or natric horizon. Vitrandic Glossocryalfs Palecryalfs, p. 47 JBBE. Other Glossocryalfs that have, in one or more JBB. Other Cryalfs that have a glossic horizon. subhorizons within the upper 25 cm of the argillic, kandic, or Glossocryalfs, p. 44 natric horizon, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial JBC. Other Cryalfs. drainage). Haplocryalfs, p. 45 Aquic Glossocryalfs

Glossocryalfs JBBF. Other Glossocryalfs that are saturated with water in one or more layers within 100 cm of the mineral soil surface in Key to Subgroups normal years for either or both: JBBA. Glossocryalfs that have a lithic contact within 50 cm of the mineral soil surface. 1. 20 or more consecutive days; or Lithic Glossocryalfs 2. 30 or more cumulative days. Oxyaquic Glossocryalfs JBBB. Other Glossocryalfs that have one or both of the following: JBBG. Other Glossocryalfs that have fragic soil properties: 1. Cracks within 125 cm of the mineral soil surface that are 1. In 30 percent or more of the volume of a layer 15 cm or 5 mm or more wide through a thickness of 30 cm or more more thick that has its upper boundary within 100 cm of the for some time in normal years and slickensides or wedge- mineral soil surface; or shaped peds in a layer 15 cm or more thick that has its upper 2. In 60 percent or more of the volume of a layer 15 cm or boundary within 125 cm of the mineral soil surface; or more thick. 2. A linear extensibility of 6.0 cm or more between the Fragic Glossocryalfs mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. JBBH. Other Glossocryalfs that have all of the following: Vertic Glossocryalfs 1. A xeric soil moisture regime; and JBBC. Other Glossocryalfs that have, throughout one or more 2. A color value, moist, of 3 or less and a color value, dry, horizons with a total thickness of 18 cm or more within 75 cm of 5 or less (crushed and smoothed sample) either throughout of the mineral soil surface, a fine-earth fraction with both a bulk the upper 18 cm of the mineral soil (unmixed) or between the density of 1.0 g/cm3 or less, measured at 33 kPa water retention, mineral soil surface and a depth of 18 cm after mixing; and Alfisols 45

3. A base saturation (by NH4OAc) of 50 percent or more smoothed sample) either throughout the upper 18 cm of the in all parts from the mineral soil surface to a depth of 180 mineral soil (unmixed) or between the mineral soil surface and a cm or to a densic, lithic, or paralithic contact, whichever is depth of 18 cm after mixing. shallower. Umbric Glossocryalfs Xerollic Glossocryalfs JBBO. Other Glossocryalfs that have a base saturation (by JBBI. Other Glossocryalfs that have both: NH4OAc) of 50 percent or more in all parts from the mineral soil surface to a depth of 180 cm or to a densic, lithic, or 1. A xeric soil moisture regime; and paralithic contact, whichever is shallower. 2. A color value, moist, of 3 or less and a color value, dry, Eutric Glossocryalfs of 5 or less (crushed and smoothed sample) either throughout A the upper 18 cm of the mineral soil (unmixed) or between the JBBP. Other Glossocryalfs. L F mineral soil surface and a depth of 18 cm after mixing. Typic Glossocryalfs Umbric Xeric Glossocryalfs Haplocryalfs JBBJ. Other Glossocryalfs that meet all of the following: Key to Subgroups 1. Are dry in some part of the moisture control section for 45 or more days (cumulative) in normal years; and JBCA. Haplocryalfs that have a lithic contact within 50 cm of the mineral soil surface. 2. Have a color value, moist, of 3 or less and a color value, Lithic Haplocryalfs dry, of 5 or less (crushed and smoothed sample) either throughout the upper 18 cm of the mineral soil (unmixed) or JBCB. Other Haplocryalfs that have one or both of the between the mineral soil surface and a depth of 18 cm after following: mixing; and 1. Cracks within 125 cm of the mineral soil surface that are 3. Have a base saturation (by NH OAc) of 50 percent or 4 5 mm or more wide through a thickness of 30 cm or more more in all parts from the mineral soil surface to a depth of for some time in normal years and slickensides or wedge- 180 cm or to a densic, lithic, or paralithic contact, whichever shaped peds in a layer 15 cm or more thick that has its upper is shallower. boundary within 125 cm of the mineral soil surface; or Ustollic Glossocryalfs 2. A linear extensibility of 6.0 cm or more between the JBBK. Other Glossocryalfs that have a xeric soil moisture mineral soil surface and either a depth of 100 cm or a densic, regime. lithic, or paralithic contact, whichever is shallower. Xeric Glossocryalfs Vertic Haplocryalfs

JBBL. Other Glossocryalfs that are dry in some part of the JBCC. Other Haplocryalfs that have, throughout one or more moisture control section for 45 or more days (cumulative) in horizons with a total thickness of 18 cm or more within 75 cm normal years. of the mineral soil surface, a fine-earth fraction with both a bulk Ustic Glossocryalfs density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling JBBM. Other Glossocryalfs that have both: more than 1.0. 1. A color value, moist, of 3 or less and a color value, dry, Andic Haplocryalfs of 5 or less (crushed and smoothed sample) either throughout the upper 18 cm of the mineral soil (unmixed) or between JBCD. Other Haplocryalfs that have, throughout one or more the mineral soil surface and a depth of 18 cm after mixing; horizons with a total thickness of 18 cm or more within 75 cm and of the mineral soil surface, one or both of the following: 1. More than 35 percent (by volume) fragments coarser 2. A base saturation (by NH4OAc) of 50 percent or more in all parts from the mineral soil surface to a depth of 180 than 2.0 mm, of which more than 66 percent is cinders, cm or to a densic, lithic, or paralithic contact, whichever is pumice, and pumicelike fragments; or shallower. 2. A fine-earth fraction containing 30 percent or more Mollic Glossocryalfs particles 0.02 to 2.0 mm in diameter; and JBBN. Other Glossocryalfs that have a color value, moist, a. In the 0.02 to 2.0 mm fraction, 5 percent or more of 3 or less and a color value, dry, of 5 or less (crushed and volcanic glass; and 46 Keys to Soil Taxonomy

1 b. [(Al plus /2 Fe, percent extracted by ammonium JBCJ. Other Haplocryalfs that have all of the following: oxalate) times 60] plus the volcanic glass (percent) is 1. A xeric soil moisture regime; and equal to 30 or more. Vitrandic Haplocryalfs 2. A color value, moist, of 3 or less and a color value, dry, of 5 or less (crushed and smoothed sample) either throughout JBCE. Other Haplocryalfs that have, in one or more horizons the upper 18 cm of the mineral soil (unmixed) or between the within 75 cm of the mineral soil surface, redox depletions with mineral soil surface and a depth of 18 cm after mixing; and chroma of 2 or less and also aquic conditions for some time in 3. A base saturation (by NH OAc) of 50 percent or more normal years (or artificial drainage). 4 in all parts from the mineral soil surface to a depth of 180 Aquic Haplocryalfs cm or to a densic, lithic, or paralithic contact, whichever is shallower. JBCF. Other Haplocryalfs that are saturated with water in Xerollic Haplocryalfs one or more layers within 100 cm of the mineral soil surface in normal years for either or both: JBCK. Other Haplocryalfs that have both: 1. 20 or more consecutive days; or 1. A xeric soil moisture regime; and 2. 30 or more cumulative days. 2. A color value, moist, of 3 or less and a color value, dry, Oxyaquic Haplocryalfs of 5 or less (crushed and smoothed sample) either throughout the upper 18 cm of the mineral soil (unmixed) or between the JBCG. Other Haplocryalfs that have an argillic horizon that mineral soil surface and a depth of 18 cm after mixing. meets one of the following: Umbric Xeric Haplocryalfs 1. Consists entirely of lamellae; or JBCL. Other Haplocryalfs that meet all of the following: 2. Is a combination of two or more lamellae and one or more subhorizons with a thickness of 7.5 to 20 cm, each 1. Are dry in some part of the moisture control section for layer with an overlying eluvial horizon; or 45 or more days (cumulative) in normal years; and 3. Consists of one or more subhorizons that are more than 2. Have a color value, moist, of 3 or less and a color value, 20 cm thick, each with an overlying eluvial horizon, and dry, of 5 or less (crushed and smoothed sample) either above these horizons there are either: throughout the upper 18 cm of the mineral soil (unmixed) or between the mineral soil surface and a depth of 18 cm after a. Two or more lamellae with a combined thickness of mixing; and 5 cm or more (that may or may not be part of the argillic

horizon); or 3. Have a base saturation (by NH4OAc) of 50 percent or more in all parts from the mineral soil surface to a depth of b. A combination of lamellae (that may or may not be 180 cm or to a densic, lithic, or paralithic contact, whichever part of the argillic horizon) and one or more parts of the is shallower. argillic horizon 7.5 to 20 cm thick, each with an overlying Ustollic Haplocryalfs eluvial horizon. Lamellic Haplocryalfs JBCM. Other Haplocryalfs that have a xeric soil moisture regime. JBCH. Other Haplocryalfs that have a sandy or sandy-skeletal Xeric Haplocryalfs particle-size class throughout the upper 75 cm of the argillic, kandic, or natric horizon or throughout the entire argillic, JBCN. Other Haplocryalfs that are dry in some part of the kandic, or natric horizon if it is less than 75 cm thick. moisture control section for 45 or more days (cumulative) in Psammentic Haplocryalfs normal years. Ustic Haplocryalfs JBCI. Other Haplocryalfs that: 1. Have an argillic, kandic, or natric horizon that is 35 cm JBCO. Other Haplocryalfs that have both: or less thick; and 1. A color value, moist, of 3 or less and a color value, dry, 2. Do not have a densic, lithic, or paralithic contact within of 5 or less (crushed and smoothed sample) either throughout 100 cm of the mineral soil surface. the upper 18 cm of the mineral soil (unmixed) or between the Inceptic Haplocryalfs mineral soil surface and a depth of 18 cm after mixing; and Alfisols 47

2. A base saturation (by NH4OAc) of 50 percent or more chroma of 2 or less and also aquic conditions for some time in in all parts from the mineral soil surface to a depth of 180 normal years (or artificial drainage). cm or to a densic, lithic, or paralithic contact, whichever is Aquic Palecryalfs shallower. Mollic Haplocryalfs JBAD. Other Palecryalfs that are saturated with water in one or more layers within 100 cm of the mineral soil surface in JBCP. Other Haplocryalfs that have a color value, moist, normal years for either or both: of 3 or less and a color value, dry, of 5 or less (crushed and 1. 20 or more consecutive days; or smoothed sample) either throughout the upper 18 cm of the mineral soil (unmixed) or between the mineral soil surface and a 2. 30 or more cumulative days. depth of 18 cm after mixing. Oxyaquic Palecryalfs A Umbric Haplocryalfs L F JBAE. Other Palecryalfs that have a xeric soil moisture JBCQ. Other Haplocryalfs that have a base saturation (by regime.

NH4OAc) of 50 percent or more in all parts from the mineral Xeric Palecryalfs soil surface to a depth of 180 cm or to a densic, lithic, or paralithic contact, whichever is shallower. JBAF. Other Palecryalfs that are dry in some part of the Eutric Haplocryalfs moisture control section for 45 or more days (cumulative) in normal years. JBCR. Other Haplocryalfs. Ustic Palecryalfs Typic Haplocryalfs JBAG. Other Palecryalfs that have both: Palecryalfs 1. A color value, moist, of 3 or less and a color value, dry, Key to Subgroups of 5 or less (crushed and smoothed sample) either throughout the upper 18 cm of the mineral soil (unmixed) or between the JBAA. Palecryalfs that have, throughout one or more horizons mineral soil surface and a depth of 18 cm after mixing; and with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction with both a bulk 2. A base saturation (by NH4OAc) of 50 percent or more density of 1.0 g/cm3 or less, measured at 33 kPa water retention, in all parts from the mineral soil surface to a depth of 180 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling cm or to a densic, lithic, or paralithic contact, whichever is more than 1.0. shallower. Andic Palecryalfs Mollic Palecryalfs

JBAB. Other Palecryalfs that have, throughout one or more JBAH. Other Palecryalfs that have a color value, moist, of 3 or horizons with a total thickness of 18 cm or more within 75 cm less and a color value, dry, of 5 or less (crushed and smoothed of the mineral soil surface, one or both of the following: sample) either throughout the upper 18 cm of the mineral soil (unmixed) or between the mineral soil surface and a depth of 18 1. More than 35 percent (by volume) fragments coarser cm after mixing. than 2.0 mm, of which more than 66 percent is cinders, Umbric Palecryalfs pumice, and pumicelike fragments; or 2. A fine-earth fraction containing 30 percent or more JBAI. Other Palecryalfs. particles 0.02 to 2.0 mm in diameter; and Typic Palecryalfs a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and Udalfs

1 b. [(Al plus /2 Fe, percent extracted by ammonium Key to Great Groups oxalate) times 60] plus the volcanic glass (percent) is JEA. Udalfs that have a natric horizon. equal to 30 or more. Natrudalfs, p. 56 Vitrandic Palecryalfs JEB. Other Udalfs that have both: JBAC. Other Palecryalfs that have, in one or more horizons within 100 cm of the mineral soil surface, redox depletions with 1. A glossic horizon; and 48 Keys to Soil Taxonomy

2. In the argillic or kandic horizon, discrete nodules, 2.5 to b. Have 5 percent or more (by volume) skeletans on 30 cm in diameter, that: faces of peds in the layer that has a 20 percent lower clay content and, below that layer, a clay increase of 3 percent a. Are enriched with iron and extremely weakly or more (absolute) in the fine-earth fraction;and cemented to indurated; and 3. Have an argillic horizon with one or more of the b. Have exteriors with either a redder hue or a higher following: chroma than the interiors. Ferrudalfs, p. 49 a. In 50 percent or more of the matrix of one or more subhorizons in its lower one-half, hue of 7.5YR or redder JEC. Other Udalfs that have both: and chroma of 5 or more; or 1. A glossic horizon; and b. In 50 percent or more of the matrix of horizons that total more than one-half the total thickness, hue of 2.5YR 2. A fragipan within 100 cm of the mineral soil surface. or redder, value, moist, of 3 or less, and value, dry, of 4 or Fraglossudalfs, p. 49 less; or JED. Other Udalfs that have a fragipan within 100 cm of the c. Many coarse redox concentrations with hue of 5YR mineral soil surface. or redder or chroma of 6 or more, or both, in one or more Fragiudalfs, p. 49 subhorizons; or 4. Have a frigid soil temperature regime and all of the JEE. Other Udalfs that meet all of the following: following: 1. Do not have a densic, lithic, paralithic, or petroferric a. An argillic horizon that has its upper boundary 60 cm contact within 150 cm of the mineral soil surface; and or more below both: 2. Have a kandic horizon; and (1) The mineral soil surface; and 3. Within 150 cm of the mineral soil surface, either: (2) The lower boundary of any surface mantle a. Do not have a clay decrease with increasing depth containing 30 percent or more vitric volcanic ash, of 20 percent or more (relative) from the maximum clay cinders, or other vitric pyroclastic materials; and content [Clay is measured noncarbonate clay or is based b. A texture class finer than loamy fine sand in one or on the following formula: Clay % = 2.5(% water retained more horizons above the argillic horizon; and at 1500 kPa tension - % organic carbon), whichever value is greater, but no more than 100]; or c. Either a glossic horizon or interfingering of albic materials into the argillic horizon. b. Have 5 percent or more (by volume) skeletans on Paleudalfs, p. 57 faces of peds in the layer that has a 20 percent lower clay content and, below that layer, a clay increase of 3 percent JEH. Other Udalfs that have, in all subhorizons in the upper or more (absolute) in the fine-earth fraction. 100 cm of the argillic horizon or throughout the entire argillic Kandiudalfs, p. 55 horizon if less than 100 cm thick, more than 50 percent colors that have all of the following: JEF. Other Udalfs that have a kandic horizon. Kanhapludalfs, p. 56 1. Hue of 2.5YR or redder; and 2. Value, moist, of 3 or less; and JEG. Other Udalfs that: 3. Dry value no more than 1 unit higher than the moist 1. Do not have a densic, lithic, or paralithic contact within value. 150 cm of the mineral soil surface; and Rhodudalfs, p. 59 2. Within 150 cm of the mineral soil surface, either: JEI. Other Udalfs that have a glossic horizon. a. Do not have a clay decrease with increasing depth Glossudalfs, p. 49 of 20 percent or more (relative) from the maximum clay content [Clay is measured noncarbonate clay or is based JEJ. Other Udalfs. on the following formula: Clay % = 2.5(% water retained Hapludalfs, p. 51 at 1500 kPa tension - % organic carbon), whichever value is greater, but no more than 100]; or Alfisols 49

Ferrudalfs JEDE. Other Fragiudalfs. Typic Fragiudalfs Key to Subgroups JEBA. Ferrudalfs that have, in one or more horizons within Fraglossudalfs 60 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal Key to Subgroups years (or artificial drainage). JECA. Fraglossudalfs that have, throughout one or more Aquic Ferrudalfs horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction with both a bulk JEBB. Other Ferrudalfs. density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 Typic Ferrudalfs and Al plus /2 Fe percentages (by ammonium oxalate) totaling A L more than 1.0. F Fragiudalfs Andic Fraglossudalfs

Key to Subgroups JECB. Other Fraglossudalfs that have, throughout one or more JEDA. Fragiudalfs that have, throughout one or more horizons horizons with a total thickness of 18 cm or more within 75 cm with a total thickness of 18 cm or more within 75 cm of the of the mineral soil surface, one or both of the following: mineral soil surface, a fine-earth fraction with both a bulk 1. More than 35 percent (by volume) fragments coarser 3 density of 1.0 g/cm or less, measured at 33 kPa water retention, than 2.0 mm, of which more than 66 percent is cinders, 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling pumice, and pumicelike fragments; or more than 1.0. Andic Fragiudalfs 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and JEDB. Other Fragiudalfs that have, throughout one or more a. In the 0.02 to 2.0 mm fraction, 5 percent or more horizons with a total thickness of 18 cm or more within 75 cm volcanic glass; and of the mineral soil surface, one or both of the following: 1 b. [(Al plus /2 Fe, percent extracted by ammonium 1. More than 35 percent (by volume) fragments coarser oxalate) times 60] plus the volcanic glass (percent) is than 2.0 mm, of which more than 66 percent is cinders, equal to 30 or more. pumice, and pumicelike fragments; or Vitrandic Fraglossudalfs 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and JECC. Other Fraglossudalfs that have, in one or more subhorizons within the upper 25 cm of the argillic or kandic a. In the 0.02 to 2.0 mm fraction, 5 percent or more horizon, redox depletions with chroma of 2 or less and also volcanic glass; and aquic conditions for some time in normal years (or artificial 1 b. [(Al plus /2 Fe, percent extracted by ammonium drainage). oxalate) times 60] plus the volcanic glass (percent) is Aquic Fraglossudalfs equal to 30 or more. Vitrandic Fragiudalfs JECD. Other Fraglossudalfs that are saturated with water in one or more layers above the fragipan in normal years for either JEDC. Other Fragiudalfs that have, in one or more horizons or both: within 40 cm of the mineral soil surface, redox depletions with 1. 20 or more consecutive days; or chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). 2. 30 or more cumulative days. Aquic Fragiudalfs Oxyaquic Fraglossudalfs

JEDD. Other Fragiudalfs that are saturated with water in one JECE. Other Fraglossudalfs. or more layers above the fragipan in normal years for either or Typic Fraglossudalfs both: 1. 20 or more consecutive days; or Glossudalfs 2. 30 or more cumulative days. Key to Subgroups Oxyaquic Fragiudalfs JEIA. Glossudalfs that have both: 50 Keys to Soil Taxonomy

1. One or both of the following: 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a densic, a. Cracks within 125 cm of the mineral soil surface that lithic, or paralithic contact, whichever is shallower. are 5 mm or more wide through a thickness of 30 cm or Vertic Glossudalfs more for some time in normal years and slickensides or wedge-shaped peds in a layer 15 cm or more thick that JEID. Other Glossudalfs that have both: has its upper boundary within 125 cm of the mineral soil surface; or 1. In one or more subhorizons within the upper 25 cm of the argillic horizon, redox depletions with chroma of 2 or b. A linear extensibility of 6.0 cm or more between less and also aquic conditions for some time in normal years the mineral soil surface and either a depth of 100 cm (or artificial drainage);and or a densic, lithic, or paralithic contact, whichever is shallower; and 2. Throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, 2. Redox depletions with chroma of 2 or less in layers one or more of the following: that also have aquic conditions in normal years (or artificial drainage) either: a. A fine-earth fraction with both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water retention, and Al a. Within the upper 25 cm of the argillic horizon if 1 plus /2 Fe percentages (by ammonium oxalate) totaling its upper boundary is within 50 cm of the mineral soil more than 1.0; or surface; or b. Within 75 cm of the mineral soil surface if the upper b. More than 35 percent (by volume) fragments coarser boundary of the argillic horizon is 50 cm or more below than 2.0 mm, of which more than 66 percent is cinders, the mineral soil surface. pumice, and pumicelike fragments; or Aquertic Glossudalfs c. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and JEIB. Other Glossudalfs that have both: (1) In the 0.02 to 2.0 mm fraction, 5 percent or more 1. Saturation with water in one or more layers within 100 volcanic glass; and

cm of the mineral soil surface in normal years for either or 1 (2) [(Al plus /2 Fe, percent extracted by ammonium both: oxalate) times 60] plus the volcanic glass (percent) is a. 20 or more consecutive days; or equal to 30 or more. b. 30 or more cumulative days; and Aquandic Glossudalfs 2. One or both of the following: JEIE. Other Glossudalfs that have, throughout one or more a. Cracks within 125 cm of the mineral soil surface that horizons with a total thickness of 18 cm or more within 75 cm are 5 mm or more wide through a thickness of 30 cm or of the mineral soil surface, a fine-earth fraction with both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water retention, more for some time in normal years and slickensides or 1 wedge-shaped peds in a layer 15 cm or more thick that and Al plus /2 Fe percentages (by ammonium oxalate) totaling has its upper boundary within 125 cm of the mineral soil more than 1.0. surface; or Andic Glossudalfs b. A linear extensibility of 6.0 cm or more between the JEIF. Other Glossudalfs that have, throughout one or more mineral soil surface and either a depth of 100 cm or a horizons with a total thickness of 18 cm or more within 75 cm densic, lithic, or paralithic contact, whichever is shallower. of the mineral soil surface, one or both of the following: Oxyaquic Vertic Glossudalfs 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, JEIC. Other Glossudalfs that have one or both of the following: pumice, and pumicelike fragments; or 1. Cracks within 125 cm of the mineral soil surface that are 2. A fine-earth fraction containing 30 percent or more 5 mm or more wide through a thickness of 30 cm or more particles 0.02 to 2.0 mm in diameter; and for some time in normal years and slickensides or wedge- a. In the 0.02 to 2.0 mm fraction, 5 percent or more shaped peds in a layer 15 cm or more thick that has its upper volcanic glass; and boundary within 125 cm of the mineral soil surface; or Alfisols 51

1 b. [(Al plus /2 Fe, percent extracted by ammonium to the top of the argillic horizon at a depth of 50 cm or more oxalate) times 60] plus the volcanic glass (percent) is below the mineral soil surface. equal to 30 or more. Arenic Oxyaquic Glossudalfs Vitrandic Glossudalfs JEIK. Other Glossudalfs that are saturated with water in one JEIG. Other Glossudalfs that have both: or more layers within 100 cm of the mineral soil surface in normal years for either or both: 1. Fragic soil properties: 1. 20 or more consecutive days; or a. In 30 percent or more of the volume of a layer 15 cm or more thick that has its upper boundary within 100 cm 2. 30 or more cumulative days. of the mineral soil surface; or Oxyaquic Glossudalfs A L b. In 60 percent or more of the volume of a layer 15 cm F JEIL. Other Glossudalfs that have fragic soil properties: or more thick; and 1. In 30 percent or more of the volume of a layer 15 cm or 2. Redox depletions with chroma of 2 or less in layers more thick that has its upper boundary within 100 cm of the that also have aquic conditions in normal years (or artificial mineral soil surface; or drainage) either: 2. In 60 percent or more of the volume of a layer 15 cm or a. Within the upper 25 cm of the argillic horizon if more thick. its upper boundary is within 50 cm of the mineral soil Fragic Glossudalfs surface; or b. Within 75 cm of the mineral soil surface if the upper JEIM. Other Glossudalfs that meet sandy or sandy-skeletal boundary of the argillic horizon is 50 cm or more below particle-size class criteria throughout a layer extending from the the mineral soil surface. mineral soil surface to the top of an argillic horizon at a depth of Fragiaquic Glossudalfs 50 cm or more below the mineral soil surface. Arenic Glossudalfs JEIH. Other Glossudalfs that: JEIN. Other Glossudalfs that have a glossic horizon less than 1. In one or more subhorizons within 75 cm of the mineral 50 cm in total thickness. soil surface, have redox depletions with chroma of 2 or less Haplic Glossudalfs and also aquic conditions for some time in normal years (or artificial drainage);and JEIO. Other Glossudalfs. 2. Meet sandy or sandy-skeletal particle-size class criteria Typic Glossudalfs throughout a layer extending from the mineral soil surface to the top of the argillic horizon at a depth of 50 cm or more Hapludalfs below the mineral soil surface. Key to Subgroups Aquic Arenic Glossudalfs JEJA. Hapludalfs that have a lithic contact within 50 cm of the JEII. Other Glossudalfs that have, in one or more subhorizons mineral soil surface. within the upper 25 cm of the argillic horizon, redox depletions Lithic Hapludalfs with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). JEJB. Other Hapludalfs that have all of the following: Aquic Glossudalfs 1. One or both of the following: JEIJ. Other Glossudalfs that: a. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or 1. Are saturated with water in one or more layers within more for some time in normal years and slickensides or 100 cm of the mineral soil surface in normal years for either wedge-shaped peds in a layer 15 cm or more thick that or both: has its upper boundary within 125 cm of the mineral soil surface; or a. 20 or more consecutive days; or b. A linear extensibility of 6.0 cm or more between b. 30 or more cumulative days; and the mineral soil surface and either a depth of 100 cm 2. Meet sandy or sandy-skeletal particle-size class criteria or a densic, lithic, or paralithic contact, whichever is throughout a layer extending from the mineral soil surface shallower; and 52 Keys to Soil Taxonomy

2. Redox depletions with chroma of 2 or less in layers b. 30 or more cumulative days; and that also have aquic conditions in normal years (or artificial 2. One or both of the following: drainage) either: a. Cracks within 125 cm of the mineral soil surface that a. Within the upper 25 cm of the argillic horizon if are 5 mm or more wide through a thickness of 30 cm or its upper boundary is within 50 cm of the mineral soil more for some time in normal years and slickensides or surface; or wedge-shaped peds in a layer 15 cm or more thick that b. Within 75 cm of the mineral soil surface if the upper has its upper boundary within 125 cm of the mineral soil boundary of the argillic horizon is 50 cm or more below surface; or the mineral soil surface; and b. A linear extensibility of 6.0 cm or more between the 3. An Ap horizon or materials between the mineral soil mineral soil surface and either a depth of 100 cm or a surface and a depth of 18 cm that, after mixing, have one or densic, lithic, or paralithic contact, whichever is shallower. more of the following: Oxyaquic Vertic Hapludalfs

a. A color value, moist, of 4 or more; or JEJE. Other Hapludalfs that have both: b. A color value, dry, of 6 or more; or 1. One or both of the following: c. Chroma of 4 or more. a. Cracks within 125 cm of the mineral soil surface that Aquertic Chromic Hapludalfs are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge-shaped peds in a layer 15 cm or more thick that JEJC. Other Hapludalfs that have both: has its upper boundary within 125 cm of the mineral soil 1. One or both of the following: surface; or a. Cracks within 125 cm of the mineral soil surface that b. A linear extensibility of 6.0 cm or more between are 5 mm or more wide through a thickness of 30 cm or the mineral soil surface and either a depth of 100 cm more for some time in normal years and slickensides or or a densic, lithic, or paralithic contact, whichever is wedge-shaped peds in a layer 15 cm or more thick that shallower; and has its upper boundary within 125 cm of the mineral soil 2. An Ap horizon or materials between the mineral soil surface; or surface and a depth of 18 cm that, after mixing, have one or b. A linear extensibility of 6.0 cm or more between more of the following: the mineral soil surface and either a depth of 100 cm a. A color value, moist, of 4 or more; or or a densic, lithic, or paralithic contact, whichever is shallower; and b. A color value, dry, of 6 or more; or 2. Redox depletions with chroma of 2 or less in layers c. Chroma of 4 or more. that also have aquic conditions in normal years (or artificial Chromic Vertic Hapludalfs drainage) either: JEJF. Other Hapludalfs that have one or both of the following: a. Within the upper 25 cm of the argillic horizon if its upper boundary is within 50 cm of the mineral soil 1. Cracks within 125 cm of the mineral soil surface that are surface; or 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge- b. Within 75 cm of the mineral soil surface if the upper shaped peds in a layer 15 cm or more thick that has its upper boundary of the argillic horizon is 50 cm or more below boundary within 125 cm of the mineral soil surface; or the mineral soil surface. Aquertic Hapludalfs 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a densic, JEJD. Other Hapludalfs that have both: lithic, or paralithic contact, whichever is shallower. Vertic Hapludalfs 1. Saturation with water in one or more layers within 100 cm of the mineral soil surface in normal years for either or JEJG. Other Hapludalfs that have, throughout one or more both: horizons with a total thickness of 18 cm or more within 75 cm a. 20 or more consecutive days; or of the mineral soil surface, a fine-earth fraction with both a bulk Alfisols 53

density of 1.0 g/cm3 or less, measured at 33 kPa water retention, a. 20 or more consecutive days; or 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling b. 30 or more cumulative days. more than 1.0. Fragic Oxyaquic Hapludalfs Andic Hapludalfs

JEJH. Other Hapludalfs that have, throughout one or more JEJK. Other Hapludalfs that: horizons with a total thickness of 18 cm or more within 75 cm 1. In one or more horizons within 75 cm of the mineral of the mineral soil surface, one or both of the following: soil surface, have redox depletions with chroma of 2 or less 1. More than 35 percent (by volume) fragments coarser and also aquic conditions for some time in normal years (or than 2.0 mm, of which more than 66 percent is cinders, artificial drainage);and pumice, and pumicelike fragments; or 2. Meet sandy or sandy-skeletal particle-size class criteria A L 2. A fine-earth fraction containing 30 percent or more throughout a layer extending from the mineral soil surface to F the top of an argillic horizon at a depth of 50 cm or more. particles 0.02 to 2.0 mm in diameter; and Aquic Arenic Hapludalfs a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and JEJL. Other Hapludalfs that:

1 b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 1. Are saturated with water in one or more layers within equal to 30 or more. 100 cm of the mineral soil surface in normal years for either Vitrandic Hapludalfs or both: a. 20 or more consecutive days; or JEJI. Other Hapludalfs that have both: b. 30 or more cumulative days; and 1. Fragic soil properties: 2. Meet sandy or sandy-skeletal particle-size class criteria a. In 30 percent or more of the volume of a layer 15 cm throughout a layer extending from the mineral soil surface or more thick that has its upper boundary within 100 cm to the top of the argillic horizon at a depth of 50 cm or more of the mineral soil surface; or below the mineral soil surface. b. In 60 percent or more of the volume of a layer 15 cm Arenic Oxyaquic Hapludalfs or more thick; and JEJM. Other Hapludalfs that have anthraquic conditions. 2. Redox depletions with chroma of 2 or less in layers Anthraquic Hapludalfs that also have aquic conditions in normal years (or artificial drainage) either: JEJN. Other Hapludalfs that have all of the following: a. Within the upper 25 cm of the argillic horizon if 1. An abrupt textural change; and its upper boundary is within 50 cm of the mineral soil surface; or 2. Redox depletions with chroma of 2 or less in layers that also have aquic conditions in normal years (or artificial b. Within 75 cm of the mineral soil surface if the upper drainage) either: boundary of the argillic horizon is 50 cm or more below the mineral soil surface. a. Within the upper 25 cm of the argillic horizon if Fragiaquic Hapludalfs its upper boundary is within 50 cm of the mineral soil surface; or JEJJ. Other Hapludalfs that have both: b. Within 75 cm of the mineral soil surface if the upper 1. Fragic soil properties: boundary of the argillic horizon is 50 cm or more below the mineral soil surface; and a. In 30 percent or more of the volume of a layer 15 cm or more thick that has its upper boundary within 100 cm 3. A base saturation (by sum of cations) of less than 60 of the mineral soil surface; or percent at a depth of 125 cm from the top of the argillic horizon, at a depth of 180 cm from the mineral soil surface, b. In 60 percent or more of the volume of a layer 15 cm or directly above a densic, lithic, or paralithic contact, or more thick; and whichever is shallowest. 2. Saturation with water in one or more layers within 100 Albaquultic Hapludalfs cm of the mineral soil surface in normal years for either or both: JEJO. Other Hapludalfs that have both: 54 Keys to Soil Taxonomy

1. An abrupt textural change; and the upper 18 cm of the mineral soil (unmixed) or between the mineral soil surface and a depth of 18 cm after mixing; and 2. Redox depletions with chroma of 2 or less in layers that also have aquic conditions in normal years (or artificial 2. Redox depletions with chroma of 2 or less in layers drainage) either: that also have aquic conditions in normal years (or artificial drainage) either: a. Within the upper 25 cm of the argillic horizon if its upper boundary is within 50 cm of the mineral soil a. Within the upper 25 cm of the argillic horizon if surface; or its upper boundary is within 50 cm of the mineral soil surface; or b. Within 75 cm of the mineral soil surface if the upper boundary of the argillic horizon is 50 cm or more below b. Within 75 cm of the mineral soil surface if the upper the mineral soil surface. boundary of the argillic horizon is 50 cm or more below Albaquic Hapludalfs the mineral soil surface. Aquollic Hapludalfs JEJP. Other Hapludalfs that have both: JEJS. Other Hapludalfs that have redox depletions with 1. Interfingering of albic materials in the upper part of the chroma of 2 or less in layers that also have aquic conditions in argillic horizon; and normal years (or artificial drainage)either : 2. Redox depletions with chroma of 2 or less in layers 1. Within the upper 25 cm of the argillic horizon if its that also have aquic conditions in normal years (or artificial upper boundary is within 50 cm of the mineral soil surface; drainage) either: or a. Within the upper 25 cm of the argillic horizon if 2. Within 75 cm of the mineral soil surface if the upper its upper boundary is within 50 cm of the mineral soil boundary of the argillic horizon is 50 cm or more below the surface; or mineral soil surface. b. Within 75 cm of the mineral soil surface if the upper Aquic Hapludalfs boundary of the argillic horizon is 50 cm or more below the mineral soil surface. JEJT. Other Hapludalfs that have both: Glossaquic Hapludalfs 1. A mollic epipedon, or the upper 18 cm of the mineral soil meets the color requirements for a mollic epipedon after JEJQ. Other Hapludalfs that have both: mixing; and 1. Redox depletions with chroma of 2 or less in layers 2. Saturation with water in 1 or more layers within 100 cm that also have aquic conditions in normal years (or artificial of the mineral soil surface in normal years for either or both: drainage) either: a. 20 or more consecutive days; or a. Within the upper 25 cm of the argillic horizon if its upper boundary is within 50 cm of the mineral soil b. 30 or more cumulative days. surface; or Mollic Oxyaquic Hapludalfs b. Within 75 cm of the mineral soil surface if the upper JEJU. Other Hapludalfs that are saturated with water in one or boundary of the argillic horizon is 50 cm or more below more layers within 100 cm of the mineral soil surface in normal the mineral soil surface; and years for either or both: 2. A base saturation (by sum of cations) of less than 60 1. 20 or more consecutive days; or percent at a depth of 125 cm from the top of the argillic horizon, at a depth of 180 cm from the mineral soil surface, 2. 30 or more cumulative days. or directly above a densic, lithic, or paralithic contact, Oxyaquic Hapludalfs whichever is shallowest. Aquultic Hapludalfs JEJV. Other Hapludalfs that have fragic soil properties: 1. In 30 percent or more of the volume of a layer 15 cm or JEJR. Other Hapludalfs that have both: more thick that has its upper boundary within 100 cm of the 1. A color value, moist, of 3 or less and a color value, dry, mineral soil surface; or of 5 or less (crushed and smoothed sample) either throughout Alfisols 55

2. In 60 percent or more of the volume of a layer 15 cm or upper 18 cm of the mineral soil meets all the color requirements more thick. for a mollic epipedon after mixing. Fragic Hapludalfs Mollic Hapludalfs

JEJW. Other Hapludalfs that have an argillic horizon that JEJZd. Other Hapludalfs. meets one of the following: Typic Hapludalfs 1. Consists entirely of lamellae; or Kandiudalfs 2. Is a combination of two or more lamellae and one or more subhorizons with a thickness of 7.5 to 20 cm, each Key to Subgroups layer with an overlying eluvial horizon; or JEEA. Kandiudalfs that have both: A L 3. Consists of one or more subhorizons that are more than 1. In one or more horizons within 75 cm of the mineral soil F 20 cm thick, each with an overlying eluvial horizon, and surface, redox depletions with chroma of 2 or less and also above these horizons there are either: aquic conditions for some time in normal years (or artificial a. Two or more lamellae with a combined thickness of drainage); and 5 cm or more (that may or may not be part of the argillic 2. 5 percent or more (by volume) plinthite in one or more horizon); or horizons within 150 cm of the mineral soil surface. b. A combination of lamellae (that may or may not be Plinthaquic Kandiudalfs part of the argillic horizon) and one or more parts of the argillic horizon 7.5 to 20 cm thick, each with an overlying JEEB. Other Kandiudalfs that have, in one or more horizons eluvial horizon. within 75 cm of the mineral soil surface, redox depletions with Lamellic Hapludalfs chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). JEJX. Other Hapludalfs that have a sandy particle-size class Aquic Kandiudalfs throughout the upper 75 cm of the argillic horizon or throughout the entire argillic horizon if it is less than 75 cm thick. JEEC. Other Kandiudalfs that are saturated with water in Psammentic Hapludalfs one or more layers within 100 cm of the mineral soil surface in normal years for either or both: JEJY. Other Hapludalfs that meet sandy or sandy-skeletal 1. 20 or more consecutive days; or particle-size class criteria throughout a layer extending from the mineral soil surface to the top of an argillic horizon at a depth of 2. 30 or more cumulative days. 50 cm or more. Oxyaquic Kandiudalfs Arenic Hapludalfs JEED. Other Kandiudalfs that: JEJZ. Other Hapludalfs that have interfingering of albic 1. Meet sandy or sandy-skeletal particle-size class criteria materials in one or more subhorizons of the argillic horizon. throughout a layer extending from the mineral soil surface to Glossic Hapludalfs the top of a kandic horizon at a depth of 50 to 100 cm; and

JEJZa. Other Hapludalfs that: 2. Have 5 percent or more (by volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. 1. Have an argillic horizon that is 35 cm or less thick; and Arenic Plinthic Kandiudalfs 2. Do not have a densic, lithic, or paralithic contact within 100 cm of the mineral soil surface. JEEE. Other Kandiudalfs that: Inceptic Hapludalfs 1. Meet sandy or sandy-skeletal particle-size class criteria throughout a layer extending from the mineral soil surface to JEJZb. Other Hapludalfs that have a base saturation (by sum the top of a kandic horizon at a depth of 100 cm or more; and of cations) of less than 60 percent at a depth of 125 cm below the top of the argillic horizon, at a depth of 180 cm below 2. Have 5 percent or more (by volume) plinthite in one or the mineral soil surface, or directly above a densic, lithic, or more horizons within 150 cm of the mineral soil surface. paralithic contact, whichever is shallowest. Grossarenic Plinthic Kandiudalfs Ultic Hapludalfs JEEF. Other Kandiudalfs that meet sandy or sandy-skeletal JEJZc. Other Hapludalfs that have a mollic epipedon, or the particle-size class criteria throughout a layer extending from the 56 Keys to Soil Taxonomy

mineral soil surface to the top of a kandic horizon at a depth of JEFD. Other Kanhapludalfs that have, in all subhorizons in 50 to 100 cm. the upper 100 cm of the kandic horizon or throughout the entire Arenic Kandiudalfs kandic horizon if less than 100 cm thick, more than 50 percent colors that have all of the following: JEEG. Other Kandiudalfs that meet sandy or sandy-skeletal particle-size class criteria throughout a layer extending from the 1. Hue of 2.5YR or redder; and mineral soil surface to the top of a kandic horizon at a depth of 2. Value, moist, of 3 or less; and 100 cm or more. Grossarenic Kandiudalfs 3. Dry value no more than 1 unit higher than the moist value. JEEH. Other Kandiudalfs that have 5 percent or more (by Rhodic Kanhapludalfs volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. JEFE. Other Kanhapludalfs. Plinthic Kandiudalfs Typic Kanhapludalfs

JEEI. Other Kandiudalfs that have, in all subhorizons in the Natrudalfs upper 100 cm of the kandic horizon or throughout the entire Key to Subgroups kandic horizon if less than 100 cm thick, more than 50 percent colors that have all of the following: JEAA. Natrudalfs that have one or both of the following: 1. Hue of 2.5YR or redder; and 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or more 2. Value, moist, of 3 or less; and for some time in normal years and slickensides or wedge- 3. Dry value no more than 1 unit higher than the moist shaped peds in a layer 15 cm or more thick that has its upper value. boundary within 125 cm of the mineral soil surface; or Rhodic Kandiudalfs 2. A linear extensibility of 6.0 cm or more between the JEEJ. Other Kandiudalfs that have a mollic epipedon, or the mineral soil surface and either a depth of 100 cm or a densic, upper 18 cm of the mineral soil meets the color requirements for lithic, or paralithic contact, whichever is shallower. a mollic epipedon after mixing. Vertic Natrudalfs Mollic Kandiudalfs JEAB. Other Natrudalfs that have both: JEEK. Other Kandiudalfs. 1. Either a glossic horizon or interfingering of albic Typic Kandiudalfs materials into the natric horizon; and

Kanhapludalfs 2. Redox depletions with chroma of 2 or less in layers that also have aquic conditions in normal years (or artificial Key to Subgroups drainage) either: JEFA. Kanhapludalfs that have a lithic contact within 50 cm a. Within the upper 25 cm of the natric horizon if of the mineral soil surface. its upper boundary is within 50 cm of the mineral soil Lithic Kanhapludalfs surface; or

JEFB. Other Kanhapludalfs that have, in one or more horizons b. Within 75 cm of the mineral soil surface if the upper within 75 cm of the mineral soil surface, redox depletions with boundary of the natric horizon is 50 cm or more below the chroma of 2 or less and also aquic conditions for some time in mineral soil surface. normal years (or artificial drainage). Glossaquic Natrudalfs Aquic Kanhapludalfs JEAC. Other Natrudalfs that have redox depletions with JEFC. Other Kanhapludalfs that are saturated with water in chroma of 2 or less in layers that also have aquic conditions in one or more layers within 100 cm of the mineral soil surface in normal years (or artificial drainage)either : normal years for either or both: 1. Within the upper 25 cm of the natric horizon if its upper 1. 20 or more consecutive days; or boundary is within 50 cm of the mineral soil surface; or 2. 30 or more cumulative days. 2. Within 75 cm of the mineral soil surface if the upper Oxyaquic Kanhapludalfs Alfisols 57

boundary of the natric horizon is 50 cm or more below the 1. Fragic soil properties: mineral soil surface. a. In 30 percent or more of the volume of a layer 15 cm Aquic Natrudalfs or more thick that has its upper boundary within 100 cm of the mineral soil surface; or JEAD. Other Natrudalfs. Typic Natrudalfs b. In 60 percent or more of the volume of a layer 15 cm or more thick; and Paleudalfs 2. Redox depletions with chroma of 2 or less in layers Key to Subgroups that also have aquic conditions in normal years (or artificial drainage) either: JEGA. Paleudalfs that have one or both of the following: A a. Within the upper 25 cm of the argillic horizon if L F 1. Cracks within 125 cm of the mineral soil surface that are its upper boundary is within 50 cm of the mineral soil 5 mm or more wide through a thickness of 30 cm or more surface; or for some time in normal years and slickensides or wedge- shaped peds in a layer 15 cm or more thick that has its upper b. Within 75 cm of the mineral soil surface if the upper boundary of the argillic horizon is 50 cm or more below boundary within 125 cm of the mineral soil surface; or the mineral soil surface. 2. A linear extensibility of 6.0 cm or more between the Fragiaquic Paleudalfs mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. JEGF. Other Paleudalfs that have both: Vertic Paleudalfs 1. In one or more horizons within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also JEGB. Other Paleudalfs that have, throughout one or more aquic conditions for some time in normal years (or artificial horizons with a total thickness of 18 cm or more within 75 cm drainage); and of the mineral soil surface, a fine-earth fraction with both a bulk 2. 5 percent or more (by volume) plinthite in one or more density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 horizons within 150 cm of the mineral soil surface. and Al plus /2 Fe percentages (by ammonium oxalate) totaling Plinthaquic Paleudalfs more than 1.0. Andic Paleudalfs JEGG. Other Paleudalfs that have both: JEGC. Other Paleudalfs that have, throughout one or more 1. In one or more horizons within 75 cm of the mineral soil horizons with a total thickness of 18 cm or more within 75 cm surface, redox depletions with chroma of 2 or less and also of the mineral soil surface, one or both of the following: aquic conditions for some time in normal years (or artificial drainage); and 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, 2. A glossic horizon or, in the upper part of the argillic pumice, and pumicelike fragments; or horizon, one or more subhorizons that have 5 percent or more (by volume) clay depletions with chroma of 2 or less. 2. A fine-earth fraction containing 30 percent or more Glossaquic Paleudalfs particles 0.02 to 2.0 mm in diameter; and a. In the 0.02 to 2.0 mm fraction, 5 percent or more JEGH. Other Paleudalfs that have both: volcanic glass; and 1. In one or more horizons within 75 cm of the mineral soil

1 surface, redox depletions with chroma of 2 or less and also b. [(Al plus /2 Fe, percent extracted by ammonium aquic conditions for some time in normal years (or artificial oxalate) times 60] plus the volcanic glass (percent) is drainage); and equal to 30 or more. Vitrandic Paleudalfs 2. A clay increase of 15 percent or more (absolute) in the fine-earth fraction within a vertical distance of 2.5 cm at the JEGD. Other Paleudalfs that have anthraquic conditions. upper boundary of the argillic horizon. Anthraquic Paleudalfs Albaquic Paleudalfs

JEGI. Other Paleudalfs that have, in one or more horizons JEGE. Other Paleudalfs that have both: within 75 cm of the mineral soil surface, redox depletions with 58 Keys to Soil Taxonomy

chroma of 2 or less and also aquic conditions for some time in b. A combination of lamellae (that may or may not be normal years (or artificial drainage). part of the argillic horizon) and one or more parts of the Aquic Paleudalfs argillic horizon 7.5 to 20 cm thick, each with an overlying eluvial horizon. JEGJ. Other Paleudalfs that are saturated with water in one or Lamellic Paleudalfs more layers within 100 cm of the mineral soil surface in normal years for either or both: JEGO. Other Paleudalfs that have a sandy particle-size class throughout the upper 75 cm of the argillic horizon or throughout 1. 20 or more consecutive days; or the entire argillic horizon if it is less than 75 cm thick. 2. 30 or more cumulative days. Psammentic Paleudalfs Oxyaquic Paleudalfs JEGP. Other Paleudalfs that meet sandy or sandy-skeletal JEGK. Other Paleudalfs that have fragic soil properties: particle-size class criteria throughout a layer extending from the mineral soil surface to the top of an argillic horizon at a depth of 1. In 30 percent or more of the volume of a layer 15 cm or 50 to 100 cm. more thick that has its upper boundary within 100 cm of the Arenic Paleudalfs mineral soil surface; or 2. In 60 percent or more of the volume of a layer 15 cm or JEGQ. Other Paleudalfs that meet sandy or sandy-skeletal more thick. particle-size class criteria throughout a layer extending from the Fragic Paleudalfs mineral soil surface to the top of an argillic horizon at a depth of 100 cm or more. JEGL. Other Paleudalfs that: Grossarenic Paleudalfs

1. Meet sandy or sandy-skeletal particle-size class criteria JEGR. Other Paleudalfs that have 5 percent or more (by throughout a layer extending from the mineral soil surface to volume) plinthite in one or more horizons within 150 cm of the the top of an argillic horizon at a depth of 50 to 100 cm; and mineral soil surface. Plinthic Paleudalfs 2. Have 5 percent or more (by volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. JEGS. Other Paleudalfs that have either: Arenic Plinthic Paleudalfs 1. A glossic horizon; or JEGM. Other Paleudalfs that: 2. In the upper part of the argillic horizon, one or more 1. Meet sandy or sandy-skeletal particle-size class criteria subhorizons that have 5 percent or more (by volume) throughout a layer extending from the mineral soil surface to skeletans with chroma of 2 or less; or the top of an argillic horizon at a depth of 100 cm or more; and 3. 5 percent or more (by volume) albic materials in some subhorizon of the argillic horizon. 2. Have 5 percent or more (by volume) plinthite in one or Glossic Paleudalfs more horizons within 150 cm of the mineral soil surface. Grossarenic Plinthic Paleudalfs JEGT. Other Paleudalfs that have, in all subhorizons in the upper 100 cm of the argillic horizon or throughout the entire JEGN. Other Paleudalfs that have an argillic horizon that argillic horizon if less than 100 cm thick, more than 50 percent meets one of the following: colors that have all of the following: 1. Consists entirely of lamellae; or 1. Hue of 2.5YR or redder; and 2. Is a combination of two or more lamellae and one or 2. Value, moist, of 3 or less; and more subhorizons with a thickness of 7.5 to 20 cm, each layer with an overlying eluvial horizon; or 3. Dry value no more than 1 unit higher than the moist value. 3. Consists of one or more subhorizons that are more than Rhodic Paleudalfs 20 cm thick, each with an overlying eluvial horizon, and above these horizons there are either: JEGU. Other Paleudalfs that have a mollic epipedon, or the a. Two or more lamellae with a combined thickness of upper 18 cm of the mineral soil meets the color requirements for 5 cm or more (that may or may not be part of the argillic a mollic epipedon after mixing. horizon); or Mollic Paleudalfs Alfisols 59

JEGV. Other Paleudalfs. a. Within 150 cm of the mineral soil surface, either: Typic Paleudalfs (1) With increasing depth, no clay decrease of 20 percent or more (relative) from the maximum clay Rhodudalfs content [Clay is measured noncarbonate clay or is Key to Subgroups based on the following formula: Clay % = 2.5(% water retained at 1500 kPa tension - % organic carbon), JEHA. All Rhodudalfs (provisionally). whichever value is greater, but no more than 100]; or Typic Rhodudalfs (2) 5 percent or more (by volume) skeletans on Ustalfs faces of peds in the layer that has a 20 percent lower clay content and, below that layer, a clay increase of 3 A percent or more (absolute) in the fine-earth fraction; L Key to Great Groups F and JCA. Ustalfs that have a duripan within 100 cm of the mineral soil surface. b. In the lower one-half of the argillic horizon, one or Durustalfs, p. 59 more subhorizons with either or both: (1) Hue of 7.5YR or redder and chroma of 5 or more JCB. Other Ustalfs that have one or more horizons within 150 in 50 percent or more of the matrix; or cm of the mineral soil surface in which plinthite either forms a continuous phase or constitutes one-half or more of the volume. (2) Common or many coarse redox concentrations Plinthustalfs, p. 70 with hue of 7.5YR or redder or chroma of 6 or more, or both; or JCC. Other Ustalfs that have a natric horizon. 3. No densic, lithic, or paralithic contact within 50 cm of Natrustalfs, p. 65 the mineral soil surface and an argillic horizon that has both: JCD. Other Ustalfs that meet all of the following: a. 35 percent or more noncarbonate clay throughout one or more subhorizons in its upper part; and 1. Have a kandic horizon; and b. At its upper boundary, a clay increase (in the fine- 2. Do not have a densic, lithic, paralithic, or petroferric earth fraction) of either 20 percent or more (absolute) contact within 150 cm of the mineral soil surface; and within a vertical distance of 7.5 cm or of 15 percent or 3. Within 150 cm of the mineral soil surface, either: more (absolute) within a vertical distance of 2.5 cm. Paleustalfs, p. 67 a. Do not have a clay decrease with increasing depth of 20 percent or more (relative) from the maximum clay content [Clay is measured noncarbonate clay or is based JCG. Other Ustalfs that have, in all subhorizons in the upper on the following formula: Clay % = 2.5(% water retained 100 cm of the argillic horizon or throughout the entire argillic at 1500 kPa tension - % organic carbon), whichever value horizon if less than 100 cm thick, more than 50 percent colors is greater, but no more than 100]; or that have all of the following: b. Have 5 percent or more (by volume) skeletans on 1. Hue of 2.5YR or redder; and faces of peds in the layer that has a 20 percent lower clay 2. Value, moist, of 3 or less; and content and, below that layer, a clay increase of 3 percent or more (absolute) in the fine-earth fraction. 3. Dry value no more than 1 unit higher than the moist Kandiustalfs, p. 63 value. Rhodustalfs, p. 70 JCE. Other Ustalfs that have a kandic horizon. Kanhaplustalfs, p. 64 JCH. Other Ustalfs. Haplustalfs, p. 60 JCF. Other Ustalfs that have one or more of the following: Durustalfs 1. A petrocalcic horizon within 150 cm of the mineral soil surface; or Key to Subgroups 2. No densic, lithic, or paralithic contact within 150 cm of JCAA. All Durustalfs (provisionally). the mineral soil surface and an argillic horizon that has both: Typic Durustalfs 60 Keys to Soil Taxonomy

Haplustalfs control section that in normal years is dry in all parts for four-tenths or more of the cumulative days per year when Key to Subgroups the soil temperature at a depth of 50 cm below the soil JCHA. Haplustalfs that have a lithic contact within 50 cm of surface is higher than 5 oC; or the mineral soil surface. b. A mesic or thermic soil temperature regime and a Lithic Haplustalfs moisture control section that in normal years is dry in some part for six-tenths or more of the cumulative days JCHB. Other Haplustalfs that have both: per year when the soil temperature at a depth of 50 cm 1. One or both of the following: below the soil surface is higher than 5 oC; or a. Cracks within 125 cm of the mineral soil surface that c. A hyperthermic, isomesic, or warmer iso soil are 5 mm or more wide through a thickness of 30 cm or temperature regime and a moisture control section that in more for some time in normal years and slickensides or normal years: wedge-shaped peds in a layer 15 cm or more thick that (1) Is moist in some or all parts for less than 90 has its upper boundary within 125 cm of the mineral soil consecutive days per year when the soil temperature at surface; or a depth of 50 cm below the soil surface is higher than b. A linear extensibility of 6.0 cm or more between 8 oC; and the mineral soil surface and either a depth of 100 cm (2) Is dry in some part for six-tenths or more of the or a densic, lithic, or paralithic contact, whichever is cumulative days per year when the soil temperature at shallower; and a depth of 50 cm below the soil surface is higher than 2. In one or more horizons within 75 cm of the mineral soil 5 oC; and surface, redox depletions with chroma of 2 or less and also 2. One or both of the following: aquic conditions for some time in normal years (or artificial drainage). a. Cracks within 125 cm of the soil surface that are 5 Aquertic Haplustalfs mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge- JCHC. Other Haplustalfs that have both: shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the soil surface; or 1. One or both of the following: b. A linear extensibility of 6.0 cm or more between the a. Cracks within 125 cm of the mineral soil surface that soil surface and either a depth of 100 cm or a densic, are 5 mm or more wide through a thickness of 30 cm or lithic, or paralithic contact, whichever is shallower. more for some time in normal years and slickensides or Torrertic Haplustalfs wedge-shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil JCHE. Other Haplustalfs that have both: surface; or 1. When neither irrigated nor fallowed to store moisture, b. A linear extensibility of 6.0 cm or more between either: the mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is a. A mesic or thermic soil temperature regime and a shallower; and moisture control section that in normal years is dry in some part for four-tenths or less of the cumulative days 2. Saturation with water in one or more layers within 100 per year when the soil temperature at a depth of 50 cm cm of the mineral soil surface in normal years for either or below the soil surface is higher than 5 oC; or both: b. A hyperthermic, isomesic, or warmer iso soil a. 20 or more consecutive days; or temperature regime and a moisture control section that in b. 30 or more cumulative days. normal years is dry in some or all parts for less than 120 Oxyaquic Vertic Haplustalfs cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 8 oC; JCHD. Other Haplustalfs that have both of the following: and 1. When neither irrigated nor fallowed to store moisture, 2. One or both of the following: one of the following: a. Cracks within 125 cm of the mineral soil surface that a. A frigid soil temperature regime and a moisture are 5 mm or more wide through a thickness of 30 cm or Alfisols 61

more for some time in normal years and slickensides or 2. 30 or more cumulative days. wedge-shaped peds in a layer 15 cm or more thick that Oxyaquic Haplustalfs has its upper boundary within 125 cm of the mineral soil surface; or JCHK. Other Haplustalfs that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm b. A linear extensibility of 6.0 cm or more between the of the mineral soil surface, one or both of the following: mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. 1. More than 35 percent (by volume) fragments coarser Udertic Haplustalfs than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or JCHF. Other Haplustalfs that have one or both of the 2. A fine-earth fraction containing 30 percent or more following: A particles 0.02 to 2.0 mm in diameter; and L F 1. Cracks within 125 cm of the mineral soil surface that are a. In the 0.02 to 2.0 mm fraction, 5 percent or more 5 mm or more wide through a thickness of 30 cm or more volcanic glass; and for some time in normal years and slickensides or wedge- 1 shaped peds in a layer 15 cm or more thick that has its upper b. [(Al plus /2 Fe, percent extracted by ammonium boundary within 125 cm of the mineral soil surface; or oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. 2. A linear extensibility of 6.0 cm or more between the Vitrandic Haplustalfs mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. JCHL. Other Haplustalfs that have an argillic horizon that Vertic Haplustalfs meets one of the following: JCHG. Other Haplustalfs that: 1. Consists entirely of lamellae; or 1. In one or more horizons within 75 cm of the mineral 2. Is a combination of two or more lamellae and one or soil surface, have redox depletions with chroma of 2 or less more subhorizons with a thickness of 7.5 to 20 cm, each and also aquic conditions for some time in normal years (or layer with an overlying eluvial horizon; or artificial drainage);and 3. Consists of one or more subhorizons that are more than 2. Meet sandy or sandy-skeletal particle-size class criteria 20 cm thick, each with an overlying eluvial horizon, and throughout a layer extending from the mineral soil surface to above these horizons there are either: the top of an argillic horizon at a depth of 50 to 100 cm. Aquic Arenic Haplustalfs a. Two or more lamellae with a combined thickness of 5 cm or more (that may or may not be part of the argillic JCHH. Other Haplustalfs that have both: horizon); or 1. In one or more horizons within 75 cm of the mineral soil b. A combination of lamellae (that may or may not be surface, redox depletions with chroma of 2 or less and also part of the argillic horizon) and one or more parts of the aquic conditions for some time in normal years (or artificial argillic horizon 7.5 to 20 cm thick, each with an overlying drainage); and eluvial horizon. Lamellic Haplustalfs 2. An argillic horizon that has a base saturation (by sum of cations) of less than 75 percent throughout. JCHM. Other Haplustalfs that have a sandy particle-size class Aquultic Haplustalfs throughout the upper 75 cm of the argillic horizon or throughout the entire argillic horizon if it is less than 75 cm thick. JCHI. Other Haplustalfs that have, in one or more horizons Psammentic Haplustalfs within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in JCHN. Other Haplustalfs that: normal years (or artificial drainage). Aquic Haplustalfs 1. Meet sandy or sandy-skeletal particle-size class criteria throughout a layer extending from the mineral soil surface JCHJ. Other Haplustalfs that are saturated with water in one or to the top of an argillic horizon at a depth of 50 cm or more; more layers within 100 cm of the mineral soil surface in normal and years for either or both: 2. When neither irrigated nor fallowed to store moisture, 1. 20 or more consecutive days; or have one of the following: 62 Keys to Soil Taxonomy

a. A frigid soil temperature regime and a moisture depth of 50 cm below the soil surface is higher than control section that in normal years is dry in all parts for 8 oC; and four-tenths or more of the cumulative days per year when (2) Is dry in some part for six-tenths or more of the the soil temperature at a depth of 50 cm below the soil cumulative days per year when the soil temperature at surface is higher than 5 oC; or a depth of 50 cm below the soil surface is higher than b. A mesic or thermic soil temperature regime and a 5 oC. moisture control section that in normal years is dry in Calcidic Haplustalfs some part for six-tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm JCHQ. Other Haplustalfs that, when neither irrigated nor below the soil surface is higher than 5 oC; or fallowed to store moisture, have one of the following: c. A hyperthermic, isomesic, or warmer iso soil 1. A frigid soil temperature regime and a moisture control temperature regime and a moisture control section that in section that in normal years is dry in all parts for four- normal years: tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is (1) Is moist in some or all parts for less than 90 higher than 5 oC; or consecutive days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 2. A mesic or thermic soil temperature regime and a 8 oC; and moisture control section that in normal years is dry in some part for six-tenths or more of the cumulative days per year (2) Is dry in some part for six-tenths or more of the when the soil temperature at a depth of 50 cm below the soil cumulative days per year when the soil temperature at a surface is higher than 5 oC; or depth of 50 cm below the soil surface is higher than 5 oC. 3. A hyperthermic, isomesic, or warmer iso soil Arenic Aridic Haplustalfs temperature regime and a moisture control section that in normal years: JCHO. Other Haplustalfs that meet sandy or sandy-skeletal a. Is moist in some or all parts for less than 90 particle-size class criteria throughout a layer extending from the consecutive days per year when the soil temperature at a mineral soil surface to the top of an argillic horizon at a depth of depth of 50 cm below the soil surface is higher than 8 oC; 50 cm or more. and Arenic Haplustalfs b. Is dry in some part for six-tenths or more of the JCHP. Other Haplustalfs that have both: cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC. 1. A calcic horizon within 100 cm of the mineral soil Aridic Haplustalfs surface; and 2. When neither irrigated nor fallowed to store moisture, JCHR. Other Haplustalfs that have a CEC of less than 24

one of the following: cmol(+)/kg clay (by 1N NH4OAc pH 7) in 50 percent or more either of the argillic horizon if less than 100 cm thick or of its a. A frigid soil temperature regime and a moisture upper 100 cm. control section that in normal years is dry in all parts for Kanhaplic Haplustalfs four-tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil JCHS. Other Haplustalfs that: surface is higher than 5 oC; or 1. Have an argillic horizon that is 35 cm or less thick; and b. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in 2. Do not have a densic, lithic, or paralithic contact within some part for six-tenths or more of the cumulative days 100 cm of the mineral soil surface. per year when the soil temperature at a depth of 50 cm Inceptic Haplustalfs below the soil surface is higher than 5 oC; or JCHT. Other Haplustalfs that have both: c. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in 1. A calcic horizon within 100 cm of the mineral soil normal years: surface; and (1) Is moist in some or all parts for less than 90 2. When neither irrigated nor fallowed to store moisture, consecutive days per year when the temperature at a one of the following: Alfisols 63

a. A frigid soil temperature regime and a moisture Kandiustalfs control section that in normal years is dry in some or all parts for less than 105 cumulative days per year when the Key to Subgroups soil temperature at a depth of 50 cm below the soil surface JCDA. Kandiustalfs that meet sandy or sandy-skeletal is higher than 5 oC; or particle-size class criteria throughout a layer extending from the mineral soil surface to the top of a kandic horizon at a depth of b. A mesic or thermic soil temperature regime and a 100 cm or more. moisture control section that in normal years is dry in Grossarenic Kandiustalfs some part for four-tenths or less of the cumulative days per year when the soil temperature at a depth of 50 cm JCDB. Other Kandiustalfs that: below the soil surface is higher than 5 oC; or 1. In one or more horizons within 75 cm of the mineral A L c. A hyperthermic, isomesic, or warmer iso soil soil surface, have redox depletions with chroma of 2 or less F temperature regime and a moisture control section that and also aquic conditions for some time in normal years (or in normal years is dry in some or all parts for less than artificial drainage);and 120 cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 2. Meet sandy or sandy-skeletal particle-size class criteria 8 oC. throughout a layer extending from the mineral soil surface to Calcic Udic Haplustalfs the top of a kandic horizon at a depth of 50 to 100 cm. Aquic Arenic Kandiustalfs JCHU. Other Haplustalfs that have an argillic horizon with a base saturation (by sum of cations) of less than 75 percent JCDC. Other Kandiustalfs that have 5 percent or more (by throughout. volume) plinthite in one or more horizons within 150 cm of the Ultic Haplustalfs mineral soil surface. Plinthic Kandiustalfs JCHV. Other Haplustalfs that have a calcic horizon within 100 JCDD. Other Kandiustalfs that have, in one or more horizons cm of the mineral soil surface. within 75 cm of the mineral soil surface, redox depletions with Calcic Haplustalfs chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). JCHW. Other Haplustalfs that, when neither irrigated nor Aquic Kandiustalfs fallowed to store moisture, have one of the following: 1. A frigid soil temperature regime and a moisture control JCDE. Other Kandiustalfs that: section that in normal years is dry in some or all parts 1. Meet sandy or sandy-skeletal particle-size class criteria for less than 105 cumulative days per year when the soil throughout a layer extending from the mineral soil surface to temperature at a depth of 50 cm below the soil surface is the top of a kandic horizon at a depth of 50 to 100 cm; and higher than 5 oC; or 2. When neither irrigated nor fallowed to store moisture, 2. A mesic or thermic soil temperature regime and a have either: moisture control section that in normal years is dry in some part for four-tenths or less of the cumulative days per year a. A mesic or thermic soil temperature regime and a when the soil temperature at a depth of 50 cm below the soil moisture control section that in normal years is dry in surface is higher than 5 oC; or some part for six-tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm 3. A hyperthermic, isomesic, or warmer iso soil below the soil surface is higher than 5 oC; or temperature regime and a moisture control section that in normal years is dry in some or all parts for less than 120 b. A hyperthermic, isomesic, or warmer iso soil cumulative days per year when the soil temperature at a temperature regime and a moisture control section that in depth of 50 cm below the soil surface is higher than 8 oC. normal years: Udic Haplustalfs (1) Is moist in some or all parts for less than 90 consecutive days per year when the soil temperature at JCHX. Other Haplustalfs. a depth of 50 cm below the soil surface is higher than Typic Haplustalfs 8 oC; and 64 Keys to Soil Taxonomy

(2) Is dry in some part for six-tenths or more of the 2. Value, moist, of 3 or less; and cumulative days per year when the soil temperature at 3. Dry value no more than 1 unit higher than the moist a depth of 50 cm below the soil surface is higher than value. 5 oC. Rhodic Kandiustalfs Arenic Aridic Kandiustalfs JCDJ. Other Kandiustalfs. JCDF. Other Kandiustalfs that meet sandy or sandy-skeletal Typic Kandiustalfs particle-size class criteria throughout a layer extending from the mineral soil surface to the top of a kandic horizon at a depth of 50 to 100 cm. Kanhaplustalfs Arenic Kandiustalfs Key to Subgroups

JCDG. Other Kandiustalfs that, when neither irrigated nor JCEA. Kanhaplustalfs that have a lithic contact within 50 cm fallowed to store moisture, have either: of the mineral soil surface. Lithic Kanhaplustalfs 1. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in some JCEB. Other Kanhaplustalfs that have, in one or more part for six-tenths or more of the cumulative days per year horizons within 75 cm of the mineral soil surface, redox when the soil temperature at a depth of 50 cm below the soil depletions with chroma of 2 or less and also aquic conditions surface is higher than 5 oC; or for some time in normal years (or artificial drainage). 2. A hyperthermic, isomesic, or warmer iso soil Aquic Kanhaplustalfs temperature regime and a moisture control section that in normal years: JCEC. Other Kanhaplustalfs that, when neither irrigated nor fallowed to store moisture, have either: a. Is moist in some or all parts for less than 90 1. A mesic or thermic soil temperature regime and a consecutive days per year when the soil temperature at a moisture control section that in normal years is dry in some depth of 50 cm below the soil surface is higher than 8 oC; part for six-tenths or more of the cumulative days per year and when the soil temperature at a depth of 50 cm below the soil b. Is dry in some part for six-tenths or more of the surface is higher than 5 oC; or cumulative days per year when the soil temperature at a 2. A hyperthermic, isomesic, or warmer iso soil depth of 50 cm below the soil surface is higher than 5 oC. temperature regime and a moisture control section that in Aridic Kandiustalfs normal years: JCDH. Other Kandiustalfs that, when neither irrigated nor a. Is moist in some or all parts for less than 90 fallowed to store moisture, have either: consecutive days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 8 oC; 1. A mesic or thermic soil temperature regime and a and moisture control section that in normal years is dry in some part for 135 cumulative days or less per year when the soil b. Is dry in some part for six-tenths or more of the temperature at a depth of 50 cm below the soil surface is cumulative days per year when the soil temperature at a higher than 5 oC; or depth of 50 cm below the soil surface is higher than 5 oC. Aridic Kanhaplustalfs 2. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in JCED. Other Kanhaplustalfs that, when neither irrigated nor normal years is dry in some or all parts for less than 120 fallowed to store moisture, have either: cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 8 oC. 1. A mesic or thermic soil temperature regime and a Udic Kandiustalfs moisture control section that in normal years is dry in some part for 135 cumulative days or less per year when the soil JCDI. Other Kandiustalfs that have, in all subhorizons in the temperature at a depth of 50 cm below the soil surface is upper 100 cm of the kandic horizon or throughout the entire higher than 5 oC; or kandic horizon if less than 100 cm thick, more than 50 percent 2. A hyperthermic, isomesic, or warmer iso soil colors that have all of the following: temperature regime and a moisture control section that in 1. Hue of 2.5YR or redder; and normal years is dry in some or all parts for less than 120 Alfisols 65

cumulative days per year when the soil temperature at a a depth of 50 cm below the soil surface is higher than depth of 50 cm below the soil surface is higher than 8 oC. 5 oC; and Udic Kanhaplustalfs 3. One or both of the following: JCEE. Other Kanhaplustalfs that have, in all subhorizons in a. Cracks within 125 cm of the mineral soil surface that the upper 100 cm of the kandic horizon or throughout the entire are 5 mm or more wide through a thickness of 30 cm or kandic horizon if less than 100 cm thick, more than 50 percent more for some time in normal years and slickensides or colors that have all of the following: wedge-shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil 1. Hue of 2.5YR or redder; and surface; or 2. Value, moist, of 3 or less; and b. A linear extensibility of 6.0 cm or more between A L 3. Dry value no more than 1 unit higher than the moist the mineral soil surface and either a depth of 100 cm F value. or a densic, lithic, or paralithic contact, whichever is Rhodic Kanhaplustalfs shallower. Leptic Torrertic Natrustalfs JCEF. Other Kanhaplustalfs. Typic Kanhaplustalfs JCCC. Other Natrustalfs that have both of the following: 1. When neither irrigated nor fallowed to store moisture, Natrustalfs one of the following: Key to Subgroups a. A frigid soil temperature regime and a moisture JCCA. Natrustalfs that have a salic horizon within 75 cm of control section that in normal years is dry in all parts for the mineral soil surface. four-tenths or more of the cumulative days per year when Salidic Natrustalfs the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or JCCB. Other Natrustalfs that have of the following: all b. A mesic or thermic soil temperature regime and a 1. Visible crystals of gypsum or other salts more soluble moisture control section that in normal years is dry in than gypsum, or both, within 40 cm of the soil surface; and some part for six-tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm 2. When neither irrigated nor fallowed to store moisture, below the soil surface is higher than 5 oC; or one of the following: c. A hyperthermic, isomesic, or warmer iso soil a. A frigid soil temperature regime and a moisture temperature regime and a moisture control section that in control section that in normal years is dry in all parts for normal years: four-tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil (1) Is moist in some or all parts for less than 90 surface is higher than 5 oC; or consecutive days per year when the temperature at a depth of 50 cm below the soil surface is higher than b. A mesic or thermic soil temperature regime and a 8 oC; and moisture control section that in normal years is dry in some part for six-tenths or more of the cumulative days (2) Is dry in some part for six-tenths or more of the per year when the soil temperature at a depth of 50 cm cumulative days per year when the soil temperature at below the soil surface is higher than 5 oC; or a depth of 50 cm below the soil surface is higher than 5 oC; and c. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in 2. One or both of the following: normal years: a. Cracks within 125 cm of the mineral soil surface that (1) Is moist in some or all parts for less than 90 are 5 mm or more wide through a thickness of 30 cm or consecutive days per year when the temperature at a more for some time in normal years and slickensides or depth of 50 cm below the soil surface is higher than wedge-shaped peds in a layer 15 cm or more thick that 8 oC; and has its upper boundary within 125 cm of the mineral soil surface; or (2) Is dry in some part for six-tenths or more of the cumulative days per year when the soil temperature at b. A linear extensibility of 6.0 cm or more between the 66 Keys to Soil Taxonomy

mineral soil surface and either a depth of 100 cm or a JCCF. Other Natrustalfs that have one or both of the densic, lithic, or paralithic contact, whichever is shallower. following: Torrertic Natrustalfs 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or more JCCD. Other Natrustalfs that have both: for some time in normal years and slickensides or wedge- 1. In one or more horizons within 75 cm of the mineral soil shaped peds in a layer 15 cm or more thick that has its upper surface, redox depletions with chroma of 2 or less and also boundary within 125 cm of the mineral soil surface; or aquic conditions for some time in normal years (or artificial 2. A linear extensibility of 6.0 cm or more between the drainage); and mineral soil surface and either a depth of 100 cm or a densic, 2. One or both of the following: lithic, or paralithic contact, whichever is shallower. Vertic Natrustalfs a. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or JCCG. Other Natrustalfs that: wedge-shaped peds in a layer 15 cm or more thick that 1. In one or more horizons within 75 cm of the mineral has its upper boundary within 125 cm of the mineral soil soil surface, have redox depletions with chroma of 2 or less surface; or and also aquic conditions for some time in normal years (or b. A linear extensibility of 6.0 cm or more between the artificial drainage);and mineral soil surface and either a depth of 100 cm or a 2. Meet sandy or sandy-skeletal particle-size class criteria densic, lithic, or paralithic contact, whichever is shallower. throughout a layer extending from the mineral soil surface to Aquertic Natrustalfs the top of an argillic horizon at a depth of 50 cm or more. Aquic Arenic Natrustalfs JCCE. Other Natrustalfs that have both of the following: 1. Visible crystals of gypsum or other salts more soluble JCCH. Other Natrustalfs that have, in one or more horizons than gypsum, or both, within 40 cm of the mineral soil within 75 cm of the mineral soil surface, redox depletions with surface; and chroma of 2 or less and also aquic conditions for some time in 2. When neither irrigated nor fallowed to store moisture, normal years (or artificial drainage). one of the following: Aquic Natrustalfs a. A frigid soil temperature regime and a moisture control section that in normal years is dry in all parts for JCCI. Other Natrustalfs that meet sandy or sandy-skeletal four-tenths or more of the cumulative days per year when particle-size class criteria throughout a layer extending from the the soil temperature at a depth of 50 cm below the soil mineral soil surface to the top of an argillic horizon at a depth of surface is higher than 5 oC; or 50 cm or more. Arenic Natrustalfs b. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in JCCJ. Other Natrustalfs that have a petrocalcic horizon within some part for six-tenths or more of the cumulative days 150 cm of the mineral soil surface. per year when the soil temperature at a depth of 50 cm Petrocalcic Natrustalfs below the soil surface is higher than 5 oC; or c. A hyperthermic, isomesic, or warmer iso soil JCCK. Other Natrustalfs that have visible crystals of gypsum temperature regime and a moisture control section that in or other salts more soluble than gypsum, or both, within 40 cm normal years: of the mineral soil surface. Leptic Natrustalfs (1) Is moist in some or all parts for less than 90 consecutive days per year when the temperature at a JCCL. Other Natrustalfs that have both of the following: depth of 50 cm below the soil surface is higher than 8 oC; and 1. An exchangeable sodium percentage of less than 15 (or a sodium adsorption ratio of less than 13) in 50 percent or (2) Is dry in some part for six-tenths or more of the more of the natric horizon; and cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 2. When neither irrigated nor fallowed to store moisture, 5 oC. one of the following: Aridic Leptic Natrustalfs Alfisols 67

a. A frigid soil temperature regime and a moisture 2. A glossic horizon or interfingering of albic materials into control section that in normal years is dry in all parts for the natric horizon. four-tenths or more of the cumulative days per year when Aridic Glossic Natrustalfs the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or JCCN. Other Natrustalfs that, when neither irrigated nor fallowed to store moisture, have one of the following: b. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in 1. A frigid soil temperature regime and a moisture control some part for six-tenths or more of the cumulative days section that in normal years is dry in all parts for four- per year when the soil temperature at a depth of 50 cm tenths or more of the cumulative days per year when the soil below the soil surface is higher than 5 oC; or temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or A c. A hyperthermic, isomesic, or warmer iso soil L F temperature regime and a moisture control section that in 2. A mesic or thermic soil temperature regime and a normal years: moisture control section that in normal years is dry in some part for six-tenths or more of the cumulative days per year (1) Is moist in some or all parts for less than 90 when the soil temperature at a depth of 50 cm below the soil consecutive days per year when the soil temperature at surface is higher than 5 oC; or a depth of 50 cm below the soil surface is higher than 8 oC; and 3. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in (2) Is dry in some part for six-tenths or more of the normal years: cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than a. Is moist in some or all parts for less than 90 5 oC. consecutive days per year when the soil temperature at a Haplargidic Natrustalfs depth of 50 cm below the soil surface is higher than 8 oC; and JCCM. Other Natrustalfs that have both: b. Is dry in some part for six-tenths or more of the 1. When neither irrigated nor fallowed to store moisture, one cumulative days per year when the soil temperature at a of the following: depth of 50 cm below the soil surface is higher than 5 oC. Aridic Natrustalfs a. A frigid soil temperature regime and a moisture control section that in normal years is dry in all parts for JCCO. Other Natrustalfs that have a mollic epipedon, or the four-tenths or more of the cumulative days per year when upper 18 cm of the mineral soil meets the color requirements for the soil temperature at a depth of 50 cm below the soil a mollic epipedon after mixing. surface is higher than 5 °C; or Mollic Natrustalfs b. A mesic or thermic soil temperature regime and a moisture control section that, in 6 normal years, is dry in JCCP. Other Natrustalfs. some part for six-tenths or more of the cumulative days Typic Natrustalfs per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 °C; or Paleustalfs c. A hyperthermic, isomesic, or warmer iso soil Key to Subgroups temperature regime and a moisture control section that, in JCFA. Paleustalfs that have normal years: both: (1) Is moist in some or all parts for less than 90 1. One or both of the following: consecutive days per year when the soil temperature at a. Cracks within 125 cm of the mineral soil surface that a depth of 50 cm below the soil surface is higher than are 5 mm or more wide through a thickness of 30 cm or 8 °C; and more for some time in normal years and slickensides or (2) Is dry in some part for six-tenths or more of the wedge-shaped peds in a layer 15 cm or more thick that cumulative days per year when the soil temperature at has its upper boundary within 125 cm of the mineral soil a depth of 50 cm below the soil surface is higher than surface; or 5 °C; and b. A linear extensibility of 6.0 cm or more between 68 Keys to Soil Taxonomy

the mineral soil surface and either a depth of 100 cm has its upper boundary within 125 cm of the mineral soil or a densic, lithic, or paralithic contact, whichever is surface; or shallower; and b. A linear extensibility of 6.0 cm or more between the 2. In one or more horizons within 75 cm of the mineral soil mineral soil surface and either a depth of 100 cm or a surface, redox depletions with chroma of 2 or less and also densic, lithic, or paralithic contact, whichever is shallower. aquic conditions for some time in normal years (or artificial Udertic Paleustalfs drainage). Aquertic Paleustalfs JCFD. Other Paleustalfs that have one or both of the following: JCFB. Other Paleustalfs that have both: 1. Cracks within 125 cm of the mineral soil surface that are 1. One or both of the following: 5 mm or more wide through a thickness of 30 cm or more a. Cracks within 125 cm of the mineral soil surface that for some time in normal years and slickensides or wedge- are 5 mm or more wide through a thickness of 30 cm or shaped peds in a layer 15 cm or more thick that has its upper more for some time in normal years and slickensides or boundary within 125 cm of the mineral soil surface; or wedge-shaped peds in a layer 15 cm or more thick that 2. A linear extensibility of 6.0 cm or more between the has its upper boundary within 125 cm of the mineral soil mineral soil surface and either a depth of 100 cm or a densic, surface; or lithic, or paralithic contact, whichever is shallower. b. A linear extensibility of 6.0 cm or more between Vertic Paleustalfs the mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is JCFE. Other Paleustalfs that: shallower; and 1. In one or more horizons within 75 cm of the mineral 2. Saturation with water in one or more layers within 100 soil surface, have redox depletions with chroma of 2 or less cm of the mineral soil surface in normal years for either or and also aquic conditions for some time in normal years (or both: artificial drainage);and a. 20 or more consecutive days; or 2. Meet sandy or sandy-skeletal particle-size class criteria throughout a layer extending from the mineral soil surface to b. 30 or more cumulative days. the top of an argillic horizon at a depth of 50 to 100 cm. Oxyaquic Vertic Paleustalfs Aquic Arenic Paleustalfs

JCFC. Other Paleustalfs that have both: JCFF. Other Paleustalfs that have, in one or more horizons 1. When neither irrigated nor fallowed to store moisture, within 75 cm of the mineral soil surface, redox depletions with either: chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). a. A mesic or thermic soil temperature regime a and Aquic Paleustalfs moisture control section that in normal years is dry in some part for four-tenths or less of the time (cumulative) JCFG. Other Paleustalfs that are saturated with water in one or per year when the soil temperature at a depth of 50 cm more layers within 100 cm of the mineral soil surface in normal below the soil surface is higher than 5 oC; or years for either or both: b. A hyperthermic, isomesic, or warmer soil iso 1. 20 or more consecutive days; or temperature regime and a moisture control section that in normal years is dry in some or all parts for less than 120 2. 30 or more cumulative days. cumulative days per year when the soil temperature at a Oxyaquic Paleustalfs depth of 50 cm below the soil surface is higher than 8 oC; and JCFH. Other Paleustalfs that have an argillic horizon that meets one of the following: 2. One or both of the following: 1. Consists entirely of lamellae; or a. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or 2. Is a combination of two or more lamellae and one or more for some time in normal years and slickensides or more subhorizons with a thickness of 7.5 to 20 cm, each wedge-shaped peds in a layer 15 cm or more thick that layer with an overlying eluvial horizon; or Alfisols 69

3. Consists of one or more subhorizons that are more than mineral soil surface to the top of an argillic horizon at a depth of 20 cm thick, each with an overlying eluvial horizon, and 100 cm or more. above these horizons there are either: Grossarenic Paleustalfs a. Two or more lamellae with a combined thickness of JCFL. Other Paleustalfs that meet sandy or sandy-skeletal 5 cm or more (that may or may not be part of the argillic particle-size class criteria throughout a layer extending from the horizon); or mineral soil surface to the top of an argillic horizon at a depth of b. A combination of lamellae (that may or may not be 50 to 100 cm. part of the argillic horizon) and one or more parts of the Arenic Paleustalfs argillic horizon 7.5 to 20 cm thick, each with an overlying eluvial horizon. JCFM. Other Paleustalfs that have 5 percent or more (by A Lamellic Paleustalfs volume) plinthite in one or more horizons within 150 cm of the L F mineral soil surface. JCFI. Other Paleustalfs that have a sandy particle-size class Plinthic Paleustalfs throughout the upper 75 cm of the argillic horizon or throughout the entire argillic horizon if it is less than 75 cm thick. JCFN. Other Paleustalfs that have a petrocalcic horizon within Psammentic Paleustalfs 150 cm of the mineral soil surface. Petrocalcic Paleustalfs JCFJ. Other Paleustalfs that: JCFO. Other Paleustalfs that have both: 1. Meet sandy or sandy-skeletal particle-size class criteria throughout a layer extending from the mineral soil surface to 1. When neither irrigated nor fallowed to store moisture, the top of an argillic horizon at a depth of 50 to 100 cm; and either: 2. When neither irrigated nor fallowed to store moisture, a. A frigid soil temperature regime and a moisture have one of the following: control section that in normal years is dry in all parts for four-tenths or more of the time (cumulative) per year a. A frigid soil temperature regime and a moisture when the soil temperature at a depth of 50 cm below the control section that in normal years is dry in all parts soil surface is higher than 5 oC; or for four-tenths or more of the time (cumulative) per year when the soil temperature at a depth of 50 cm below the b. A mesic or thermic soil temperature regime and a soil surface is higher than 5 oC; or moisture control section that in normal years is dry in some part for six-tenths or more of the time (cumulative) b. A mesic or thermic soil temperature regime and a per year when the soil temperature at a depth of 50 cm moisture control section that in normal years is dry in below the soil surface is higher than 5 oC; or some part for six-tenths or more of the time (cumulative) per year when the soil temperature at a depth of 50 cm c. A hyperthermic, isomesic, or warmer iso soil below the soil surface is higher than 5 oC; or temperature regime and a moisture control section that in normal years: c. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in (1) Is moist in some or all parts for less than 90 normal years: consecutive days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than (1) Is moist in some or all parts for less than 90 8 oC; and consecutive days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than (2) Is dry in some part for six-tenths or more of the 8 oC; and cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than (2) Is dry in some part for six-tenths or more of the 5 oC; and cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 2. A calcic horizon either within 100 cm of the mineral 5 oC. soil surface if the weighted average particle-size class of Arenic Aridic Paleustalfs the upper 50 cm of the argillic horizon is sandy, or within 60 cm if it is loamy, or within 50 cm if it is clayey, and free JCFK. Other Paleustalfs that meet sandy or sandy-skeletal carbonates in all horizons above the calcic horizon. particle-size class criteria throughout a layer extending from the Calcidic Paleustalfs 70 Keys to Soil Taxonomy

JCFP. Other Paleustalfs that, when neither irrigated nor 1. A mesic or thermic soil temperature regime and a fallowed to store moisture, have: moisture control section that in normal years is dry in some part for four-tenths or less of the time (cumulative) per year 1. A frigid soil temperature regime and a moisture control when the soil temperature at a depth of 50 cm below the soil section that in normal years is dry in all parts for four-tenths surface is higher than 5 oC; or or more of the time (cumulative) per year when the soil temperature at a depth of 50 cm below the soil surface is 2. A hyperthermic, isomesic, or warmer iso soil higher than 5 oC; or temperature regime and a moisture control section that in normal years is dry in some or all parts for less than 120 2. A mesic or thermic soil temperature regime and a cumulative days per year when the soil temperature at a moisture control section that in normal years is dry in some o part for six-tenths or more of the time (cumulative) per year depth of 50 cm below the soil surface is higher than 8 C. when the soil temperature at a depth of 50 cm below the soil Udic Paleustalfs surface is higher than 5 oC; or JCFU. Other Paleustalfs. 3. A hyperthermic, isomesic, or warmer iso soil Typic Paleustalfs temperature regime and a moisture control section that in normal years: Plinthustalfs a. Is moist in some or all parts for less than 90 Key to Subgroups consecutive days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 8 oC; JCBA. All Plinthustalfs (provisionally). and Typic Plinthustalfs b. Is dry in some part for six-tenths or more of the cumulative days per year when the soil temperature at Rhodustalfs a depth of 50 cm below the soil surface is higher than Key to Subgroups 5 oC. Aridic Paleustalfs JCGA. Rhodustalfs that have a lithic contact within 50 cm of the mineral soil surface. JCFQ. Other Paleustalfs that have a CEC of less than 24 Lithic Rhodustalfs cmol(+)/kg clay (by 1N NH4OAc pH 7) in 50 percent or more either of the argillic horizon if less than 100 cm thick or of its JCGB. Other Rhodustalfs that have a CEC of less than 24 upper 100 cm. cmol(+)/kg clay (by 1N NH4OAc pH 7) in 50 percent or more Kandic Paleustalfs either of the argillic horizon if less than 100 cm thick or of its upper 100 cm. JCFR. Other Paleustalfs that have, in all subhorizons in the Kanhaplic Rhodustalfs upper 100 cm of the argillic horizon or throughout the entire argillic horizon if less than 100 cm thick, more than 50 percent JCGC. Other Rhodustalfs that, when neither irrigated nor colors that have all of the following: fallowed to store moisture, have either: 1. Hue of 2.5YR or redder; and 1. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in some 2. Value, moist, of 3 or less; and part for four-tenths or less of the time (cumulative) per year 3. Dry value no more than 1 unit higher than the moist when the soil temperature at a depth of 50 cm below the soil value. surface is higher than 5 oC; or Rhodic Paleustalfs 2. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in JCFS. Other Paleustalfs that have an argillic horizon with normal years is dry in some or all parts for less than 120 a base saturation (by sum of cations) of less than 75 percent cumulative days per year when the soil temperature at a throughout. depth of 50 cm below the soil surface is higher than 8 oC. Ultic Paleustalfs Udic Rhodustalfs

JCFT. Other Paleustalfs that, when neither irrigated nor JCGD. Other Rhodustalfs. fallowed to store moisture, have either: Typic Rhodustalfs Alfisols 71

Xeralfs 3. No densic, lithic, or paralithic contact within 50 cm of the mineral soil surface and an argillic or kandic horizon that Key to Great Groups has within 15 cm of its upper boundary both: JDA. Xeralfs that have a duripan within 100 cm of the mineral a. 35 percent or more noncarbonate clay; and soil surface. b. A clay increase, in the fine-earth fraction, ofeither Durixeralfs, p. 71 20 percent or more (absolute) within a vertical distance of 7.5 cm or of 15 percent or more (absolute) within a JDB. Other Xeralfs that have a natric horizon. vertical distance of 2.5 cm. Natrixeralfs, p. 74 Palexeralfs, p. 74 A JDC. Other Xeralfs that have a fragipan within 100 cm of the JDG. Other Xeralfs. L F mineral soil surface. Haploxeralfs, p. 72 Fragixeralfs, p. 72 Durixeralfs JDD. Other Xeralfs that have one or more horizons within 150 cm of the mineral soil surface in which plinthite either forms a Key to Subgroups continuous phase or constitutes one-half or more of the volume. JDAA. Durixeralfs that have a natric horizon. Plinthoxeralfs, p. 76 Natric Durixeralfs

JDE. Other Xeralfs that have, in all subhorizons in the upper JDAB. Other Durixeralfs that have, above the duripan, one or 100 cm of the argillic or kandic horizon or throughout the entire both of the following: argillic or kandic horizon if less than 100 cm thick, more than 50 percent colors that have all of the following: 1. Cracks that are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and 1. Hue of 2.5YR or redder; and slickensides or wedge-shaped peds in a layer 15 cm or more 2. Value, moist, of 3 or less; and thick; or 3. Dry value no more than 1 unit higher than the moist 2. A linear extensibility of 6.0 cm or more. value. Vertic Durixeralfs Rhodoxeralfs, p. 76 JDAC. Other Durixeralfs that have, in one or more JDF. Other Xeralfs that have one or more of the following: subhorizons within the argillic horizon, redox depletions with chroma of 2 or less and also aquic conditions for some time in 1. A petrocalcic horizon within 150 cm of the mineral soil normal years (or artificial drainage). surface; or Aquic Durixeralfs 2. No densic, lithic, or paralithic contact within 150 cm of the mineral soil surface and an argillic or kandic horizon that JDAD. Other Durixeralfs that have both: has both: 1. An argillic horizon that has both: a. Within 150 cm of the mineral soil surface, either: a. A clayey particle-size class throughout some (1) With increasing depth, no clay decrease of 20 subhorizon 7.5 cm or more thick; and percent or more (relative) from the maximum clay content [Clay is measured noncarbonate clay or is b. At its upper boundary or within some part, a clay based on the following formula: Clay % = 2.5(% water increase either of 20 percent or more (absolute) within retained at 1500 kPa tension - % organic carbon), a vertical distance of 7.5 cm or of 15 percent or more whichever value is greater, but no more than 100]; or (absolute) within a vertical distance of 2.5 cm, in the fine- earth fraction; and (2) 5 percent or more (by volume) skeletans on 2. A duripan that is strongly cemented or less cemented in faces of peds in the layer that has a 20 percent lower all subhorizons. clay content and, below that layer, a clay increase of 3 Abruptic Haplic Durixeralfs percent or more (absolute) in the fine-earth fraction; and JDAE. Other Durixeralfs that have an argillic horizon that has b. A base at a depth of 150 cm or more; or both: 72 Keys to Soil Taxonomy

1. A clayey particle-size class throughout some subhorizon within 40 cm of the mineral soil surface, redox depletions with 7.5 cm or more thick; and chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). 2. At its upper boundary or within some part, a clay Aquic Fragixeralfs increase either of 20 percent or more (absolute) within a vertical distance of 7.5 cm or of 15 percent or more JDCE. Other Fragixeralfs that, above the fragipan, do not have (absolute) within a vertical distance of 2.5 cm, in the fine- an argillic or kandic horizon with clay films on both vertical and earth fraction. horizontal faces of any peds. Abruptic Durixeralfs Inceptic Fragixeralfs JDAF. Other Durixeralfs that have a duripan that is strongly JDCF. Other Fragixeralfs. cemented or less cemented in all subhorizons. Typic Fragixeralfs Haplic Durixeralfs

JDAG. Other Durixeralfs. Haploxeralfs Typic Durixeralfs Key to Subgroups

Fragixeralfs JDGA. Haploxeralfs that have both: 1. A lithic contact within 50 cm of the mineral soil surface; Key to Subgroups and JDCA. Fragixeralfs that have, throughout one or more 2. A color value, moist, of 3 or less and 0.7 percent or horizons with a total thickness of 18 cm or more within 75 cm more organic carbon either throughout an Ap horizon or of the mineral soil surface, a fine-earth fraction with both a bulk throughout the upper 10 cm of an A horizon. density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 Lithic Mollic Haploxeralfs and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. JDGB. Other Haploxeralfs that have both: Andic Fragixeralfs 1. A lithic contact within 50 cm of the mineral soil surface; JDCB. Other Fragixeralfs that have, throughout one or more and horizons with a total thickness of 18 cm or more within 75 cm 2. An argillic or kandic horizon that is discontinuous of the mineral soil surface, one or both of the following: horizontally in each pedon. 1. More than 35 percent (by volume) fragments coarser Lithic Ruptic-Inceptic Haploxeralfs than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or JDGC. Other Haploxeralfs that have a lithic contact within 50 cm of the mineral soil surface. 2. A fine-earth fraction containing 30 percent or more Lithic Haploxeralfs particles 0.02 to 2.0 mm in diameter; and a. In the 0.02 to 2.0 mm fraction, 5 percent or more JDGD. Other Haploxeralfs that have one or both of the volcanic glass; and following:

1 b. [(Al plus /2 Fe, percent extracted by ammonium 1. Cracks within 125 cm of the mineral soil surface that are oxalate) times 60] plus the volcanic glass (percent) is 5 mm or more wide through a thickness of 30 cm or more equal to 30 or more. for some time in normal years and slickensides or wedge- Vitrandic Fragixeralfs shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil surface; or JDCC. Other Fragixeralfs that have a color value, moist, 2. A linear extensibility of 6.0 cm or more between the of 3 or less and a color value, dry, of 5 or less (crushed and mineral soil surface and either a depth of 100 cm or a densic, smoothed sample) either throughout the upper 18 cm of the lithic, or paralithic contact, whichever is shallower. mineral soil (unmixed) or between the mineral soil surface and a Vertic Haploxeralfs depth of 18 cm after mixing. Mollic Fragixeralfs JDGE. Other Haploxeralfs that have both: JDCD. Other Fragixeralfs that have, in one or more horizons 1. In one or more horizons within 75 cm of the mineral soil Alfisols 73

surface, redox depletions with chroma of 2 or less and also or more thick that has its upper boundary within 100 cm aquic conditions for some time in normal years (or artificial of the mineral soil surface; or drainage); and b. In 60 percent or more of the volume of a layer 15 cm 2. Throughout one or more horizons with a total thickness or more thick; and of 18 cm or more within 75 cm of the mineral soil surface, 2. Redox depletions with chroma of 2 or less in layers one or more of the following: that also have aquic conditions in normal years (or artificial a. A fine-earth fraction with both a bulk density of 1.0 drainage) either: g/cm3 or less, measured at 33 kPa water retention, and Al 1 a. Within the upper 25 cm of the argillic or kandic plus /2 Fe percentages (by ammonium oxalate) totaling horizon if its upper boundary is within 50 cm of the more than 1.0; or A mineral soil surface; or L b. More than 35 percent (by volume) fragments coarser F than 2.0 mm, of which more than 66 percent is cinders, b. Within 75 cm of the mineral soil surface if the upper pumice, and pumicelike fragments; or boundary of the argillic or kandic horizon is 50 cm or more below the mineral soil surface. c. A fine-earth fraction containing 30 percent or more Fragiaquic Haploxeralfs particles 0.02 to 2.0 mm in diameter; and (1) In the 0.02 to 2.0 mm fraction, 5 percent or more JDGI. Other Haploxeralfs that have both: volcanic glass; and 1. In one or more horizons within 75 cm of the mineral soil 1 (2) [(Al plus /2 Fe, percent extracted by ammonium surface, redox depletions with chroma of 2 or less and also oxalate) times 60] plus the volcanic glass (percent) is aquic conditions for some time in normal years (or artificial equal to 30 or more. drainage); and Aquandic Haploxeralfs 2. An argillic or kandic horizon that has a base saturation (by sum of cations) of less than 75 percent in one or more JDGF. Other Haploxeralfs that have, throughout one or more subhorizons within its upper 75 cm or above a densic, lithic, horizons with a total thickness of 18 cm or more within 75 cm or paralithic contact, whichever is shallower. of the mineral soil surface, a fine-earth fraction with both a bulk Aquultic Haploxeralfs density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling JDGJ. Other Haploxeralfs that have, in one or more horizons more than 1.0. within 75 cm of the mineral soil surface, redox depletions with Andic Haploxeralfs chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). JDGG. Other Haploxeralfs that have, throughout one or more Aquic Haploxeralfs horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: JDGK. Other Haploxeralfs that have an exchangeable sodium 1. More than 35 percent (by volume) fragments coarser percentage of 15 or more (or a sodium adsorption ratio of 13 than 2.0 mm, of which more than 66 percent is cinders, or more) in one or more subhorizons of the argillic or kandic pumice, and pumicelike fragments; or horizon. Natric Haploxeralfs 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and JDGL. Other Haploxeralfs that have fragic soil properties: a. In the 0.02 to 2.0 mm fraction, 5 percent or more 1. In 30 percent or more of the volume of a layer 15 cm or volcanic glass; and more thick that has its upper boundary within 100 cm of the 1 b. [(Al plus /2 Fe, percent extracted by ammonium mineral soil surface; or oxalate) times 60] plus the volcanic glass (percent) is 2. In 60 percent or more of the volume of a layer 15 cm or equal to 30 or more. more thick. Vitrandic Haploxeralfs Fragic Haploxeralfs JDGH. Other Haploxeralfs that have both: JDGM. Other Haploxeralfs that have an argillic horizon that 1. Fragic soil properties: meets one of the following: a. In 30 percent or more of the volume of a layer 15 cm 1. Consists entirely of lamellae; or 74 Keys to Soil Taxonomy

2. Is a combination of two or more lamellae and one or Natrixeralfs more subhorizons with a thickness of 7.5 to 20 cm, each layer with an overlying eluvial horizon; or Key to Subgroups 3. Consists of one or more subhorizons that are more than JDBA. Natrixeralfs that have one or both of the following: 20 cm thick, each with an overlying eluvial horizon, and 1. Cracks within 125 cm of the mineral soil surface that are above these horizons there are either: 5 mm or more wide through a thickness of 30 cm or more a. Two or more lamellae with a combined thickness of for some time in normal years and slickensides or wedge- 5 cm or more (that may or may not be part of the argillic shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil surface; horizon); or or b. A combination of lamellae (that may or may not be 2. A linear extensibility of 6.0 cm or more between the part of the argillic horizon) and one or more parts of the mineral soil surface and either a depth of 100 cm or a densic, argillic horizon 7.5 to 20 cm thick, each with an overlying lithic, or paralithic contact, whichever is shallower. eluvial horizon. Vertic Natrixeralfs Lamellic Haploxeralfs JDBB. Other Natrixeralfs that have, in one or more horizons JDGN. Other Haploxeralfs that have a sandy particle-size within 75 cm of the mineral soil surface, redox depletions with class throughout the upper 75 cm of the argillic horizon or chroma of 2 or less and also aquic conditions for some time in throughout the entire argillic horizon if it is less than 75 cm normal years (or artificial drainage). thick. Aquic Natrixeralfs Psammentic Haploxeralfs JDBC. Other Natrixeralfs. JDGO. Other Haploxeralfs that have 5 percent or more (by Typic Natrixeralfs volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. Palexeralfs Plinthic Haploxeralfs Key to Subgroups

JDGP. Other Haploxeralfs that have a calcic horizon within JDFA. Palexeralfs that have one or both of the following: 100 cm of the mineral soil surface. 1. Cracks within 125 cm of the mineral soil surface that are Calcic Haploxeralfs 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge- JDGQ. Other Haploxeralfs that: shaped peds in a layer 15 cm or more thick that has its upper 1. Have an argillic or kandic horizon that is 35 cm or less boundary within 125 cm of the mineral soil surface; or thick; and 2. A linear extensibility of 6.0 cm or more between the 2. Do not have a densic, lithic, or paralithic contact within mineral soil surface and either a depth of 100 cm or a densic, 100 cm of the mineral soil surface. lithic, or paralithic contact, whichever is shallower. Inceptic Haploxeralfs Vertic Palexeralfs

JDGR. Other Haploxeralfs that have an argillic or kandic JDFB. Other Palexeralfs that have both: horizon that has a base saturation (by sum of cations) of less 1. In one or more horizons within 75 cm of the mineral soil than 75 percent in one or more subhorizons within its upper 75 surface, redox depletions with chroma of 2 or less and also cm or above a densic, lithic, or paralithic contact, whichever is aquic conditions for some time in normal years (or artificial shallower. drainage); and Ultic Haploxeralfs 2. Throughout one or more horizons with a total thickness JDGS. Other Haploxeralfs that have a color value, moist, of 3 of 18 cm or more within 75 cm of the mineral soil surface, or less and 0.7 percent or more organic carbon either throughout one or more of the following: the upper 10 cm of the mineral soil (unmixed) or throughout the a. A fine-earth fraction with both a bulk density of 1.0 upper 18 cm of the mineral soil after mixing. g/cm3 or less, measured at 33 kPa water retention, and Al Mollic Haploxeralfs 1 plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0; or JDGT. Other Haploxeralfs. Typic Haploxeralfs b. More than 35 percent (by volume) fragments coarser Alfisols 75

than 2.0 mm, of which more than 66 percent is cinders, b. Within 75 cm of the mineral soil surface if the upper pumice, and pumicelike fragments; or boundary of the argillic or kandic horizon is 50 cm or more below the mineral soil surface. c. A fine-earth fraction containing 30 percent or more Fragiaquic Palexeralfs particles 0.02 to 2.0 mm in diameter; and (1) In the 0.02 to 2.0 mm fraction, 5 percent or more JDFF. Other Palexeralfs that have, in one or more horizons volcanic glass; and within 75 cm of the mineral soil surface, redox depletions with

1 chroma of 2 or less and also aquic conditions for some time in (2) [(Al plus /2 Fe, percent extracted by ammonium normal years (or artificial drainage). oxalate) times 60] plus the volcanic glass (percent) is Aquic Palexeralfs equal to 30 or more. Aquandic Palexeralfs A JDFG. Other Palexeralfs that have a petrocalcic horizon L F within 150 cm of the mineral soil surface. JDFC. Other Palexeralfs that have, throughout one or more Petrocalcic Palexeralfs horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction with both a bulk JDFH. Other Palexeralfs that have an argillic horizon that density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 meets one of the following: and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. 1. Consists entirely of lamellae; or Andic Palexeralfs 2. Is a combination of two or more lamellae and one or more subhorizons with a thickness of 7.5 to 20 cm, each JDFD. Other Palexeralfs that have, throughout one or more layer with an overlying eluvial horizon; or horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: 3. Consists of one or more subhorizons that are more than 20 cm thick, each with an overlying eluvial horizon, and 1. More than 35 percent (by volume) fragments coarser above these horizons there are either: than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or a. Two or more lamellae with a combined thickness of 5 cm or more (that may or may not be part of the argillic 2. A fine-earth fraction containing 30 percent or more horizon); or particles 0.02 to 2.0 mm in diameter; and b. A combination of lamellae (that may or may not be a. In the 0.02 to 2.0 mm fraction, 5 percent or more part of the argillic horizon) and one or more parts of the volcanic glass; and argillic horizon 7.5 to 20 cm thick, each with an overlying 1 b. [(Al plus /2 Fe, percent extracted by ammonium eluvial horizon. oxalate) times 60] plus the volcanic glass (percent) is Lamellic Palexeralfs equal to 30 or more. Vitrandic Palexeralfs JDFI. Other Palexeralfs that have a sandy particle-size class throughout the upper 75 cm of the argillic horizon or throughout JDFE. Other Palexeralfs that have both: the entire argillic horizon if it is less than 75 cm thick. Psammentic Palexeralfs 1. Fragic soil properties: a. In 30 percent or more of the volume of a layer 15 cm JDFJ. Other Palexeralfs that meet sandy or sandy-skeletal or more thick that has its upper boundary within 100 cm particle-size class criteria throughout a layer extending from the of the mineral soil surface; or mineral soil surface to the top of an argillic or kandic horizon at a depth of 50 cm or more. b. In 60 percent or more of the volume of a layer 15 cm Arenic Palexeralfs or more thick; and 2. Redox depletions with chroma of 2 or less in layers JDFK. Other Palexeralfs that have an exchangeable sodium that also have aquic conditions in normal years (or artificial percentage of 15 or more (or a sodium adsorption ratio of 13 or drainage) either: more) in one or more horizons within 100 cm of the mineral soil a. Within the upper 25 cm of the argillic or kandic surface. horizon if its upper boundary is within 50 cm of the Natric Palexeralfs mineral soil surface; or 76

JDFL. Other Palexeralfs that have fragic soil properties: Plinthoxeralfs 1. In 30 percent or more of the volume of a layer 15 cm or Key to Subgroups more thick that has its upper boundary within 100 cm of the JDDA. All Plinthoxeralfs (provisionally). mineral soil surface; or Typic Plinthoxeralfs 2. In 60 percent or more of the volume of a layer 15 cm or more thick. Rhodoxeralfs Fragic Palexeralfs Key to Subgroups JDFM. Other Palexeralfs that have a calcic horizon within 150 JDEA. Rhodoxeralfs that have a lithic contact within 50 cm of cm of the mineral soil surface. the mineral soil surface. Calcic Palexeralfs Lithic Rhodoxeralfs

JDFN. Other Palexeralfs that have 5 percent or more (by JDEB. Other Rhodoxeralfs that have one or both of the volume) plinthite in one or more horizons within 150 cm of the following: mineral soil surface. Plinthic Palexeralfs 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or more JDFO. Other Palexeralfs that have an argillic or kandic for some time in normal years and slickensides or wedge- horizon that has a base saturation (by sum of cations) of less shaped peds in a layer 15 cm or more thick that has its upper than 75 percent throughout. boundary within 125 cm of the mineral soil surface; or Ultic Palexeralfs 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a densic, JDFP. Other Palexeralfs with an argillic or kandic horizon that lithic, or paralithic contact, whichever is shallower. has, in the fine-earth fraction,either or both: Vertic Rhodoxeralfs 1. Less than 35 percent clay throughout all subhorizons within 15 cm of its upper boundary; or JDEC. Other Rhodoxeralfs that have a petrocalcic horizon within 150 cm of the mineral soil surface. 2. At its upper boundary, a clay increase of less than 20 Petrocalcic Rhodoxeralfs percent (absolute) within a vertical distance of 7.5 cm and of less than 15 percent (absolute) within a vertical distance of JDED. Other Rhodoxeralfs that have a calcic horizon within 2.5 cm. 150 cm of the mineral soil surface. Haplic Palexeralfs Calcic Rhodoxeralfs

JDFQ. Other Palexeralfs that have a color value, moist, of 3 or JDEE. Other Rhodoxeralfs that have an argillic or kandic less and 0.7 percent or more organic carbon either throughout horizon that is either less than 35 cm thick or is discontinuous the upper 10 cm of the mineral soil (unmixed) or throughout the horizontally in each pedon. upper 18 cm of the mineral soil after mixing. Inceptic Rhodoxeralfs Mollic Palexeralfs JDEF. Other Rhodoxeralfs. JDFR. Other Palexeralfs. Typic Rhodoxeralfs Typic Palexeralfs 77

CHAPTER 6 Andisols

Key to Suborders layer with andic soil properties, whichever is shallower, and a densic, lithic, or paralithic contact, a duripan, or a petrocalcic DA. Andisols that have either: horizon. 1. A histic epipedon; or Vitrands, p. 93 A N 2. In a layer above a densic, lithic, or paralithic contact DG. Other Andisols that have an ustic soil moisture regime. D or in a layer at a depth between 40 and 50 cm either from Ustands, p. 92 the mineral soil surface or from the top of an organic layer with andic soil properties, whichever is shallowest, aquic DH. Other Andisols. conditions for some time in normal years (or artificial Udands, p. 85 drainage) and one or more of the following: a. 2 percent or more redox concentrations; or Aquands

b. A color value, moist, of 4 or more and 50 percent or Key to Great Groups more chroma of 2 or less either in redox depletions on faces of peds or in the matrix if peds are absent; or DAA. Aquands that have a gelic soil temperature regime. Gelaquands, p. 79 c. Enough active ferrous iron to give a positive reaction to alpha,alpha-dipyridyl at a time when the soil is not DAB. Other Aquands that have a cryic soil temperature being irrigated. regime. Aquands, p. 77 Cryaquands, p. 78

DB. Other Andisols that have a gelic soil temperature regime. DAC. Other Aquands that have, in half or more of each pedon, Gelands, p. 84 a placic horizon within 100 cm of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever DC. Other Andisols that have a cryic soil temperature regime. is shallower. Cryands, p. 80 Placaquands, p. 80

DD. Other Andisols that have an aridic soil moisture regime. DAD. Other Aquands that have, in 75 percent or more of Torrands, p. 84 each pedon, a cemented horizon within 100 cm of the mineral soil surface or of the top of an organic layer with andic soil DE. Other Andisols that have a xeric soil moisture regime. properties, whichever is shallower. Xerands, p. 94 Duraquands, p. 78

DF. Other Andisols that have a 1500 kPa water retention DAE. Other Aquands that have a 1500 kPa water retention of less than 15 percent on air-dried samples and less than 30 of less than 15 percent on air-dried samples and less than 30 percent on undried samples throughout 60 percent or more of percent on undried samples throughout 60 percent or more of the thickness either: the thickness either: 1. Within 60 cm of the mineral soil surface or of the top 1. Within 60 cm of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is of an organic layer with andic soil properties, whichever is shallower, if there is no densic, lithic, or paralithic contact, shallower, if there is no densic, lithic, or paralithic contact duripan, or petrocalcic horizon within that depth; or within that depth; or 2. Between the mineral soil surface or the top of an organic 2. Between the mineral soil surface or the top of an organic 78 Keys to Soil Taxonomy

layer with andic soil properties, whichever is shallower, and a DADC. Other Duraquands that have, at a depth between 25 densic, lithic, or paralithic contact. and 100 cm either from the mineral soil surface or from the Vitraquands, p. 80 top of an organic layer with andic soil properties, whichever is shallower, a layer 10 cm or more thick with more than 3.0 DAF. Other Aquands that have a melanic epipedon. percent organic carbon and the colors of a mollic epipedon Melanaquands, p. 79 throughout, underlying one or more horizons with a total thickness of 10 cm or more that have a color value, moist, 1 unit DAG. Other Aquands that have episaturation. or more higher and an organic-carbon content 1 percent or more Epiaquands, p. 79 (absolute) lower. Thaptic Duraquands DAH. Other Aquands. Endoaquands, p. 78 DADD. Other Duraquands. Typic Duraquands Cryaquands Endoaquands Key to Subgroups Key to Subgroups DABA. Cryaquands that have a lithic contact within 50 cm of the mineral soil surface or of the top of an organic layer with DAHA. Endoaquands that have a lithic contact within 50 cm andic soil properties, whichever is shallower. of the mineral soil surface or of the top of an organic layer with Lithic Cryaquands andic soil properties, whichever is shallower. Lithic Endoaquands DABB. Other Cryaquands that have a histic epipedon. Histic Cryaquands DAHB. Other Endoaquands that have a horizon 15 cm or more thick that has 20 percent or more (by volume) cemented DABC. Other Cryaquands that have, at a depth between 25 soil material within 100 cm of the mineral soil surface or of the and 100 cm either from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever is top of an organic layer with andic soil properties, whichever shallower. is shallower, a layer 10 cm or more thick with more than 3.0 Duric Endoaquands percent organic carbon and the colors of a mollic epipedon throughout, underlying one or more horizons with a total DAHC. Other Endoaquands that have a histic epipedon. thickness of 10 cm or more that have a color value, moist, 1 unit Histic Endoaquands or more higher and an organic-carbon content 1 percent or more (absolute) lower. DAHD. Other Endoaquands that have more than 2.0 Thaptic Cryaquands cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction of one or more horizons with a total thickness of 10 cm or more at a DABD. Other Cryaquands. depth between 25 and 50 cm either from the mineral soil surface Typic Cryaquands or from the top of an organic layer with andic soil properties, whichever is shallower. Duraquands Alic Endoaquands

Key to Subgroups DAHE. Other Endoaquands that have, on undried samples, DADA. Duraquands that have a histic epipedon. a 1500 kPa water retention of 70 percent or more throughout Histic Duraquands a layer 35 cm or more thick within 100 cm of the mineral soil surface or of the top of an organic layer with andic soil DADB. Other Duraquands that have a sum of extractable properties, whichever is shallower. 3+ Hydric Endoaquands bases (by NH4OAc) plus 1N KCl-extractable Al totaling less than 2.0 cmol(+)/kg in the fine-earth fraction of one or more horizons with a total thickness of 30 cm or more at a depth DAHF. Other Endoaquands that have, at a depth between 25 between 25 and 100 cm either from the mineral soil surface and 100 cm either from the mineral soil surface or from the or from the top of an organic layer with andic soil properties, top of an organic layer with andic soil properties, whichever whichever is shallower. is shallower, a layer 10 cm or more thick with more than 3.0 Acraquoxic Duraquands percent organic carbon and the colors of a mollic epipedon Andisols 79

throughout, underlying one or more horizons with a total DAAB. Other Gelaquands that have gelic materials within 200 thickness of 10 cm or more that have a color value, moist, 1 unit cm of the mineral soil surface. or more higher and an organic-carbon content 1 percent or more Turbic Gelaquands (absolute) lower. Thaptic Endoaquands DAAC. Other Gelaquands that have, at a depth between 25 and 100 cm either from the mineral soil surface or from the DAHG. Other Endoaquands. top of an organic layer with andic soil properties, whichever Typic Endoaquands is shallower, a layer 10 cm or more thick with more than 3.0 percent organic carbon and the colors of a mollic epipedon Epiaquands throughout, underlying one or more horizons with a total thickness of 10 cm or more that have a color value, moist, 1 unit Key to Subgroups or more higher and an organic-carbon content 1 percent or more DAGA. Epiaquands that have a horizon 15 cm or more thick (absolute) lower. that has 20 percent or more (by volume) cemented soil material Thaptic Gelaquands A within 100 cm of the mineral soil surface or of the top of an N organic layer with andic soil properties, whichever is shallower. DAAD. Other Gelaquands. D Duric Epiaquands Typic Gelaquands

DAGB. Other Epiaquands that have a histic epipedon. Melanaquands Histic Epiaquands Key to Subgroups DAGC. Other Epiaquands that have more than 2.0 DAFA. Melanaquands that have a lithic contact within 50 cm cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction of one of the mineral soil surface or of the top of an organic layer with or more horizons with a total thickness of 10 cm or more at a andic soil properties, whichever is shallower. depth between 25 and 50 cm either from the mineral soil surface Lithic Melanaquands or from the top of an organic layer with andic soil properties, whichever is shallower. DAFB. Other Melanaquands that have a sum of extractable Alic Epiaquands 3+ bases (by NH4OAc) plus 1N KCl-extractable Al totaling less than 2.0 cmol(+)/kg in the fine-earth fraction of one or more DAGD. Other Epiaquands that have, on undried samples, horizons with a total thickness of 30 cm or more at a depth a 1500 kPa water retention of 70 percent or more throughout between 25 and 100 cm either from the mineral soil surface a layer 35 cm or more thick within 100 cm of the mineral or from the top of an organic layer with andic soil properties, soil surface or of the top of an organic layer with andic soil whichever is shallower. properties, whichever is shallower. Acraquoxic Melanaquands Hydric Epiaquands DAFC. Other Melanaquands that have both: DAGE. Other Epiaquands that have, at a depth between 25 and 100 cm either from the mineral soil surface or from the 1. On undried samples, a 1500 kPa water retention of 70 top of an organic layer with andic soil properties, whichever percent or more throughout a layer 35 cm or more thick is shallower, a layer 10 cm or more thick with more than 3.0 within 100 cm of the mineral soil surface or of the top of percent organic carbon and the colors of a mollic epipedon an organic layer with andic soil properties, whichever is throughout, underlying one or more horizons with a total shallower; and thickness of 10 cm or more that have a color value, moist, 1 unit 2. More than 6.0 percent organic carbon and the colors of or more higher and an organic-carbon content 1 percent or more a mollic epipedon throughout a layer 50 cm or more thick (absolute) lower. within 60 cm of the mineral soil surface or of the top of Thaptic Epiaquands an organic layer with andic soil properties, whichever is shallower. DAGF. Other Epiaquands. Hydric Pachic Melanaquands Typic Epiaquands DAFD. Other Melanaquands that have, on undried samples, Gelaquands a 1500 kPa water retention of 70 percent or more throughout a layer 35 cm or more thick within 100 cm of the mineral Key to Subgroups soil surface or of the top of an organic layer with andic soil DAAA. Gelaquands that have a histic epipedon. properties, whichever is shallower. Histic Gelaquands Hydric Melanaquands 80 Keys to Soil Taxonomy

DAFE. Other Melanaquands that have more than 6.0 percent or more higher and an organic-carbon content 1 percent or more organic carbon and the colors of a mollic epipedon throughout (absolute) lower. a layer 50 cm or more thick within 60 cm of the mineral Thaptic Placaquands soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. DACF. Other Placaquands. Pachic Melanaquands Typic Placaquands

DAFF. Other Melanaquands that have, at a depth between Vitraquands 40 and 100 cm either from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever Key to Subgroups is shallower, a layer 10 cm or more thick with more than 3.0 DAEA. Vitraquands that have a lithic contact within 50 cm percent organic carbon and the colors of a mollic epipedon of the mineral soil surface or of the top of an organic layer with throughout, underlying one or more horizons with a total andic soil properties, whichever is shallower. thickness of 10 cm or more that have a color value, moist, 1 unit Lithic Vitraquands or more higher and an organic-carbon content 1 percent or more (absolute) lower. DAEB. Other Vitraquands that have a horizon 15 cm or more Thaptic Melanaquands thick that has 20 percent or more (by volume) cemented soil material within 100 cm of the mineral soil surface or of the DAFG. Other Melanaquands. top of an organic layer with andic soil properties, whichever is Typic Melanaquands shallower. Placaquands Duric Vitraquands

Key to Subgroups DAEC. Other Vitraquands that have a histic epipedon. DACA. Placaquands that have a lithic contact within 50 cm Histic Vitraquands of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. DAED. Other Vitraquands that have, at a depth between 25 Lithic Placaquands and 100 cm either from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever DACB. Other Placaquands that have both: is shallower, a layer 10 cm or more thick with more than 3.0 percent organic carbon and the colors of a mollic epipedon 1. A histic epipedon; and throughout, underlying one or more horizons with a total 2. A horizon 15 cm or more thick that has 20 percent or thickness of 10 cm or more that have a color value, moist, 1 unit more (by volume) cemented soil material within 100 cm of or more higher and an organic-carbon content 1 percent or more the mineral soil surface or of the top of an organic layer with (absolute) lower. andic soil properties, whichever is shallower. Thaptic Vitraquands Duric Histic Placaquands DAEE. Other Vitraquands. DACC. Other Placaquands that have a horizon 15 cm or more Typic Vitraquands thick that has 20 percent or more (by volume) cemented soil material within 100 cm of the mineral soil surface or of the Cryands top of an organic layer with andic soil properties, whichever is shallower. Key to Great Groups Duric Placaquands DCA. Cryands that have, in 75 percent or more of each pedon, a cemented horizon within 100 cm of the mineral soil surface DACD. Other Placaquands that have a histic epipedon. or of the top of an organic layer with andic soil properties, Histic Placaquands whichever is shallower. Duricryands, p. 81 DACE. Other Placaquands that have, at a depth between 25 and 100 cm either from the mineral soil surface or from the DCB. Other Cryands that have, on undried samples, a 1500 top of an organic layer with andic soil properties, whichever kPa water retention of 100 percent or more, by weighted is shallower, a layer 10 cm or more thick with more than 3.0 average, throughout either: percent organic carbon and the colors of a mollic epipedon throughout, underlying one or more horizons with a total 1. One or more layers with a total thickness of 35 cm thickness of 10 cm or more that have a color value, moist, 1 unit between the mineral soil surface or the top of an organic Andisols 81

layer with andic soil properties, whichever is shallower, to alpha,alpha-dipyridyl at a time when the soil is not being and 100 cm from the mineral soil surface or from the top irrigated. of an organic layer with andic soil properties, whichever is Aquic Duricryands shallower, if there is no densic, lithic, or paralithic contact, duripan, or petrocalcic horizon within that depth; or DCAB. Other Duricryands that have both: 2. 60 percent or more of the horizon thickness between the 1. No horizons with more than 2.0 cmol(+)/kg Al3+ (by 1N mineral soil surface or the top of an organic layer with andic KCl) in the fine-earth fraction and with a total thickness of soil properties, whichever is shallower, and a densic, lithic, or 10 cm or more at a depth between 25 and 50 cm either from paralithic contact, a duripan, or a petrocalcic horizon. the mineral soil surface or from the top of an organic layer Hydrocryands, p. 83 with andic properties, whichever is shallower; and

DCC. Other Cryands that have a melanic epipedon. 2. Saturation with water in one or more layers above the Melanocryands, p. 83 cemented horizon in normal years for either or both: A a. 20 or more consecutive days; or N DCD. Other Cryands that have a layer that meets the depth, D thickness, and organic-carbon requirements for a melanic b. 30 or more cumulative days. epipedon. Eutric Oxyaquic Duricryands Fulvicryands, p. 81 DCAC. Other Duricryands that are saturated with water in one DCE. Other Cryands that have a 1500 kPa water retention or more layers above the cemented horizon in normal years for of less than 15 percent on air-dried samples and less than 30 either or both: percent on undried samples throughout 60 percent or more of 1. 20 or more consecutive days; or the thickness either: 2. 30 or more cumulative days. 1. Within 60 cm of the mineral soil surface or of the top Oxyaquic Duricryands of an organic layer with andic soil properties, whichever is shallower, if there is no densic, lithic, or paralithic contact, DCAD. Other Duricryands that have no horizons with more duripan, or petrocalcic horizon within that depth; or than 2.0 cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction 2. Between the mineral soil surface or the top of an organic and with a total thickness of 10 cm or more at a depth between layer with andic soil properties, whichever is shallower, and a 25 and 50 cm either from the mineral soil surface or from the densic, lithic, or paralithic contact, a duripan, or a petrocalcic top of an organic layer with andic properties, whichever is horizon. shallower. Vitricryands, p. 83 Eutric Duricryands

DCF. Other Cryands. DCAE. Other Duricryands. Haplocryands, p. 82 Typic Duricryands

Duricryands Fulvicryands Key to Subgroups Key to Subgroups DCAA. Duricryands that have, in some subhorizon at a depth DCDA. Fulvicryands that have a lithic contact within 50 cm between 50 and 100 cm either from the mineral soil surface of the mineral soil surface or of the top of an organic layer with or from the top of an organic layer with andic soil properties, andic soil properties, whichever is shallower. whichever is shallower, aquic conditions for some time in Lithic Fulvicryands normal years (or artificial drainage) andone or more of the following: DCDB. Fulvicryands that have a folistic epipedon. Folistic Fulvicryands 1. 2 percent or more redox concentrations; or 2. A color value, moist, of 4 or more and 50 percent or DCDC. Other Fulvicryands that have both: more chroma of 2 or less either in redox depletions on faces 1. No horizons with more than 2.0 cmol(+)/kg Al3+ (by 1N of peds or in the matrix if peds are absent; or KCl) in the fine-earth fraction and with a total thickness of 3. Enough active ferrous iron to give a positive reaction 10 cm or more at a depth between 25 and 50 cm either from 82 Keys to Soil Taxonomy

the mineral soil surface or from the top of an organic layer soil surface or from the top of an organic layer with andic soil with andic properties, whichever is shallower; and properties, whichever is shallower, aquic conditions for some time in normal years (or artificial drainage) andone or more of 2. Throughout a layer 50 cm or more thick within 60 cm of the following: the mineral soil surface or of the top of an organic layer with andic properties, whichever is shallower: 1. 2 percent or more redox concentrations; or a. More than 6.0 percent organic carbon, by weighted 2. A color value, moist, of 4 or more and 50 percent or average; and more chroma of 2 or less either in redox depletions on faces of peds or in the matrix if peds are absent; or b. More than 4.0 percent organic carbon in all parts. Eutric Pachic Fulvicryands 3. Enough active ferrous iron to give a positive reaction to alpha,alpha-dipyridyl at a time when the soil is not being DCDD. Other Fulvicryands that have no horizons with more irrigated. than 2.0 cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction Aquic Haplocryands and with a total thickness of 10 cm or more at a depth between 25 and 50 cm either from the mineral soil surface or from the DCFD. Other Haplocryands that are saturated with water top of an organic layer with andic properties, whichever is within 100 cm of the mineral soil surface in normal years for shallower. either or both: Eutric Fulvicryands 1. 20 or more consecutive days; or DCDE. Other Fulvicryands that have, throughout a layer 50 2. 30 or more cumulative days. cm or more thick within 60 cm of the mineral soil surface or of Oxyaquic Haplocryands the top of an organic layer with andic soil properties, whichever is shallower: DCFE. Other Haplocryands that have more than 2.0 3+ 1. More than 6.0 percent organic carbon, by weighted cmol(+)/kg Al (by 1N KCl) in the fine-earth fraction of one or more horizons with a total thickness of 10 cm or more at a average; and depth between 25 and 50 cm either from the mineral soil surface 2. More than 4.0 percent organic carbon in all parts. or from the top of an organic layer with andic soil properties, Pachic Fulvicryands whichever is shallower. Alic Haplocryands DCDF. Other Fulvicryands that have a 1500 kPa water retention of less than 15 percent on air-dried samples and less DCFF. Other Haplocryands that have an albic horizon than 30 percent on undried samples throughout one or more overlying a cambic horizon in 50 percent or more of each pedon layers that have andic soil properties and have a total thickness or have a spodic horizon in 50 percent or more of each pedon. of 25 cm or more within 100 cm of the mineral soil surface Spodic Haplocryands or of the top of an organic layer with andic soil properties, whichever is shallower. DCFG. Other Haplocryands that have a sum of extractable Vitric Fulvicryands 3+ bases (by NH4OAc) plus 1N KCl-extractable Al totaling less than 2.0 cmol(+)/kg in the fine-earth fraction of one or more DCDG. Other Fulvicryands. horizons with a total thickness of 30 cm or more at a depth Typic Fulvicryands between 25 and 100 cm either from the mineral soil surface or from the top of an organic layer with andic soil properties, Haplocryands whichever is shallower. Acrudoxic Haplocryands Key to Subgroups DCFA. Haplocryands that have a lithic contact within 50 cm DCFH. Other Haplocryands that have a 1500 kPa water of the mineral soil surface or of the top of an organic layer with retention of less than 15 percent on air-dried samples and less andic soil properties, whichever is shallower. than 30 percent on undried samples throughout one or more Lithic Haplocryands layers that have andic soil properties and have a total thickness of 25 cm or more within 100 cm of the mineral soil surface DCFB. Other Haplocryands that have a folistic epipedon. or of the top of an organic layer with andic soil properties, Folistic Haplocryands whichever is shallower. Vitric Haplocryands DCFC. Other Haplocryands that have, in some subhorizon at a depth between 50 and 100 cm either from the mineral DCFI. Other Haplocryands that have, at a depth between 25 Andisols 83

and 100 cm either from the mineral soil surface or from the or more higher and an organic-carbon content 1 percent or more top of an organic layer with andic soil properties, whichever (absolute) lower. is shallower, a layer 10 cm or more thick with more than 3.0 Thaptic Hydrocryands percent organic carbon and the colors of a mollic epipedon throughout, underlying one or more horizons with a total DCBE. Other Hydrocryands. thickness of 10 cm or more that have a color value, moist, 1 unit Typic Hydrocryands or more higher and an organic-carbon content 1 percent or more (absolute) lower. Melanocryands Thaptic Haplocryands Key to Subgroups DCFJ. Other Haplocryands that have a xeric soil moisture DCCA. Melanocryands that have a lithic contact within 50 cm regime. of the mineral soil surface or of the top of an organic layer that Xeric Haplocryands has andic soil properties, whichever is shallower. Lithic Melanocryands A DCFK. Other Haplocryands. N D Typic Haplocryands DCCB. Other Melanocryands that have a 1500 kPa water retention of less than 15 percent on air-dried samples and less Hydrocryands than 30 percent on undried samples throughout one or more layers that have andic soil properties and have a total thickness Key to Subgroups of 25 cm or more within 100 cm of the mineral soil surface DCBA. Hydrocryands that have a lithic contact within 50 cm or of the top of an organic layer with andic soil properties, of the mineral soil surface or of the top of an organic layer with whichever is shallower. andic soil properties, whichever is shallower. Vitric Melanocryands Lithic Hydrocryands DCCC. Other Melanocryands. DCBB. Other Hydrocryands that have a placic horizon Typic Melanocryands within 100 cm of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. Vitricryands Placic Hydrocryands Key to Subgroups DCBC. Other Hydrocryands that have, in one or more DCEA. Vitricryands that have a lithic contact within 50 cm of horizons at a depth between 50 and 100 cm either from the the mineral soil surface or of the top of an organic layer that has mineral soil surface or from the top of an organic layer with andic soil properties, whichever is shallower. andic soil properties, whichever is shallower, aquic conditions Lithic Vitricryands for some time in normal years (or artificial drainage) andone or more of the following: DCEB. Other Vitricryands that have a folistic epipedon. 1. 2 percent or more redox concentrations; or Folistic Vitricryands 2. A color value, moist, of 4 or more and 50 percent DCEC. Other Vitricryands that have, in one or more horizons or more chroma of 2 or less either in redox depletions at a depth between 50 and 100 cm either from the mineral on faces of peds or in the matrix if peds are absent; or soil surface or from the top of an organic layer with andic soil 3. Enough active ferrous iron to give a positive reaction properties, whichever is shallower, aquic conditions for some to alpha,alpha-dipyridyl at a time when the soil is not being time in normal years (or artificial drainage) andone or more of irrigated. the following: Aquic Hydrocryands 1. 2 percent or more redox concentrations; or

DCBD. Other Hydrocryands that have, at a depth between 2. A color value, moist, of 4 or more and 50 percent or 25 and 100 cm either from the mineral soil surface or from the more chroma of 2 or less either in redox depletions on faces top of an organic layer with andic soil properties, whichever of peds or in the matrix if peds are absent; or is shallower, a layer 10 cm or more thick with more than 3.0 3. Enough active ferrous iron to give a positive reaction percent organic carbon and the colors of a mollic epipedon to alpha,alpha-dipyridyl at a time when the soil is not being throughout, underlying one or more horizons with a total irrigated. thickness of 10 cm or more that have a color value, moist, 1 unit Aquic Vitricryands 84 Keys to Soil Taxonomy

DCED. Other Vitricryands that are saturated with water in Gelands one or more layers within 100 cm of the mineral soil surface in normal years for either or both: Key to Great Groups 1. 20 or more consecutive days; or DBA. All Gelands are considered Vitrigelands. 2. 30 or more cumulative days. Vitrigelands, p. 84 Oxyaquic Vitricryands Key to Subgroups DCEE. Other Vitricryands that have an albic horizon DBAA. Vitrigelands that have a mollic or umbric epipedon. overlying a cambic horizon in 50 percent or more of each pedon Humic Vitrigelands or have a spodic horizon in 50 percent or more of each pedon. Spodic Vitricryands DBAB. Other Vitrigelands that have gelic materials within 200 cm of the mineral soil surface. DCEF. Other Vitricryands that have, at a depth between 25 Turbic Vitrigelands and 100 cm either from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever DBAC. Other Vitrigelands. is shallower, a layer 10 cm or more thick with more than 3.0 Typic Vitrigelands percent organic carbon and the colors of a mollic epipedon throughout, underlying one or more horizons with a total thickness of 10 cm or more that have a color value, moist, 1 unit Torrands or more higher and an organic-carbon content 1 percent or more Key to Great Groups (absolute) lower. Thaptic Vitricryands DDA. Torrands that have, in 75 percent or more of each pedon, a cemented horizon within 100 cm of the mineral DCEG. Other Vitricryands that have a xeric soil moisture soil surface or of the top of an organic layer with andic soil regime and a mollic or umbric epipedon. properties, whichever is shallower. Humic Xeric Vitricryands Duritorrands, p. 84

DCEH. Other Vitricryands that have a xeric soil moisture DDB. Other Torrands that have, on air-dried samples, a 1500 regime. kPa water retention of less than 15 percent throughout 60 Xeric Vitricryands percent or more of the thickness either:

DCEI. Other Vitricryands that have both: 1. Within 60 cm of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is 1. An argillic or kandic horizon within 125 cm of the shallower, if there is no densic, lithic, or paralithic contact, mineral soil surface or of the top of an organic layer with duripan, or petrocalcic horizon within that depth; or andic soil properties, whichever is shallower; and 2. Between the mineral soil surface or the top of an organic 2. A base saturation (by sum of cations) of less than 35 layer with andic soil properties, whichever is shallower, and a percent throughout the upper 50 cm or throughout the entire densic, lithic, or paralithic contact, a duripan, or a petrocalcic argillic or kandic horizon if it is less than 50 cm thick. horizon. Ultic Vitricryands Vitritorrands, p. 85 DCEJ. Other Vitricryands that have an argillic or kandic horizon within 125 cm of the mineral soil surface or of the DDC. Other Torrands. top of an organic layer with andic soil properties, whichever is Haplotorrands, p. 85 shallower. Alfic Vitricryands Duritorrands Key to Subgroups DCEK. Other Vitricryands that have a mollic or umbric epipedon. DDAA. Duritorrands that have a petrocalcic horizon within Humic Vitricryands 100 cm of the mineral soil surface. Petrocalcic Duritorrands DCEL. Other Vitricryands. Typic Vitricryands DDAB. Other Duritorrands that have, on air-dried samples, a Andisols 85

1500 kPa water retention of less than 15 percent throughout 60 more chroma of 2 or less either in redox depletions on faces percent or more of the thickness either: of peds or in the matrix if peds are absent; or 1. Between the mineral soil surface or the top of an organic 3. Enough active ferrous iron to give a positive reaction layer with andic soil properties, whichever is shallower, if to alpha,alpha-dipyridyl at a time when the soil is not being there is no paralithic contact or duripan within that depth, irrigated. and a point 60 cm below that depth; or Aquic Vitritorrands

2. Between the mineral soil surface or the top of an organic DDBD. Other Vitritorrands that have a calcic horizon within layer with andic soil properties, whichever is shallower, and a 125 cm of the mineral soil surface. paralithic contact or a duripan. Calcic Vitritorrands Vitric Duritorrands DDBE. Other Vitritorrands. DDAC. Other Duritorrands. Typic Vitritorrands Typic Duritorrands A N D Haplotorrands Udands Key to Subgroups Key to Great Groups DDCA. Haplotorrands that have a lithic contact within 50 cm DHA. Udands that have, in half or more of each pedon, a of the mineral soil surface. placic horizon within 100 cm of the mineral soil surface or of Lithic Haplotorrands the top of an organic layer with andic soil properties, whichever is shallower. DDCB. Other Haplotorrands that have a horizon 15 cm or Placudands, p. 91 more thick that has 20 percent or more (by volume) cemented soil material within 100 cm of the mineral soil surface. DHB. Other Udands that have, in 75 percent or more of each pedon, a cemented horizon within 100 cm of the mineral Duric Haplotorrands soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. DDCC. Other Haplotorrands that have a calcic horizon within Durudands, p. 86 125 cm of the mineral soil surface. Calcic Haplotorrands DHC. Other Udands that have a melanic epipedon. Melanudands, p. 90 DDCD. Other Haplotorrands. Typic Haplotorrands DHD. Other Udands that have, on undried samples, a 1500 kPa water retention of 100 percent or more, by weighted Vitritorrands average, throughout either: Key to Subgroups 1. One or more layers with a total thickness of 35 cm DDBA. Vitritorrands that have a lithic contact within 50 cm of between the mineral soil surface or the top of an organic the mineral soil surface. layer with andic soil properties, whichever is shallower, Lithic Vitritorrands and 100 cm from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever is DDBB. Other Vitritorrands that have a horizon 15 cm or more shallower, if there is no densic, lithic, or paralithic contact, thick that has 20 percent or more (by volume) cemented soil duripan, or petrocalcic horizon within that depth; or material within 100 cm of the mineral soil surface. 2. 60 percent or more of the horizon thickness between the Duric Vitritorrands mineral soil surface or the top of an organic layer with andic soil properties, whichever is shallower, and a densic, lithic, or DDBC. Other Vitritorrands that have, in one or more horizons paralithic contact, a duripan, or a petrocalcic horizon. at a depth between 50 and 100 cm from the mineral soil surface, Hydrudands, p. 89 aquic conditions for some time in normal years (or artificial drainage) and one or more of the following: DHE. Other Udands that have a layer that meets the depth, thickness, and organic-carbon requirements for a melanic 1. 2 percent or more redox concentrations; or epipedon. 2. A color value, moist, of 4 or more and 50 percent or Fulvudands, p. 86 86 Keys to Soil Taxonomy

DHF. Other Udands. Fulvudands Hapludands, p. 87 Key to Subgroups Durudands DHEA. Fulvudands that have both: 1. A lithic contact within 50 cm of the mineral soil surface Key to Subgroups or of the top of an organic layer with andic soil properties, DHBA. Durudands that have, in one or more horizons above whichever is shallower; and the cemented horizon, aquic conditions for some time in normal 2. No horizons with more than 2.0 cmol(+)/kg Al3+ (by 1N years (or artificial drainage) and of the following: one or more KCl) in the fine-earth fraction and with a total thickness of 1. 2 percent or more redox concentrations; or 10 cm or more at a depth between 25 cm from the mineral soil surface or from the top of an organic layer with andic 2. A color value, moist, of 4 or more and 50 percent or soil properties, whichever is shallower, and the lithic contact. more chroma of 2 or less either in redox depletions on faces Eutric Lithic Fulvudands of peds or in the matrix if peds are absent; or 3. Enough active ferrous iron to give a positive reaction DHEB. Other Fulvudands that have a lithic contact within 50 to alpha,alpha-dipyridyl at a time when the soil is not being cm of the mineral soil surface or of the top of an organic layer irrigated. with andic soil properties, whichever is shallower. Aquic Durudands Lithic Fulvudands DHEC. Other Fulvudands that have, in one or more horizons DHBB. Other Durudands that have no horizons with more at a depth between 50 and 100 cm either from the mineral than 2.0 cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction soil surface or from the top of an organic layer with andic soil and with a total thickness of 10 cm or more at a depth between properties, whichever is shallower, aquic conditions for some 25 and 50 cm either from the mineral soil surface or from the time in normal years (or artificial drainage) andone or more of top of an organic layer with andic properties, whichever is the following: shallower. Eutric Durudands 1. 2 percent or more redox concentrations; or 2. A color value, moist, of 4 or more and 50 percent or DHBC. Other Durudands that have a sum of extractable bases more chroma of 2 or less either in redox depletions on faces 3+ (by NH4OAc) plus 1N KCl-extractable Al totaling less than 2.0 of peds or in the matrix if peds are absent; or cmol(+)/kg in the fine-earth fraction of one or more horizons with a total thickness of 30 cm or more at a depth between 25 3. Enough active ferrous iron to give a positive reaction cm either from the mineral soil surface or from the top of an to alpha,alpha-dipyridyl at a time when the soil is not being organic layer with andic soil properties, whichever is shallower, irrigated. and the cemented horizon. Aquic Fulvudands Acrudoxic Durudands DHED. Other Fulvudands that are saturated with water within 100 cm of the mineral soil surface in normal years for either or DHBD. Other Durudands that have, on undried samples, a both: 1500 kPa water retention of 70 percent or more throughout a layer 35 cm or more thick above the cemented horizon. 1. 20 or more consecutive days; or Hydric Durudands 2. 30 or more cumulative days. Oxyaquic Fulvudands DHBE. Other Durudands that have more than 6.0 percent organic carbon and the colors of a mollic epipedon throughout DHEE. Other Fulvudands that have, on undried samples, a a layer 50 cm or more thick within 60 cm of the mineral 1500 kPa water retention of 70 percent or more throughout soil surface or of the top of an organic layer with andic soil a layer 35 cm or more thick within 100 cm of the mineral properties, whichever is shallower. soil surface or of the top of an organic layer with andic soil Pachic Durudands properties, whichever is shallower. Hydric Fulvudands DHBF. Other Durudands. Typic Durudands DHEF. Other Fulvudands that have a sum of extractable bases Andisols 87

3+ (by NH4OAc) plus 1N KCl-extractable Al totaling less than 2.0 top of an organic layer with andic soil properties, whichever cmol(+)/kg in the fine-earth fraction of one or more horizons is shallower, a layer 10 cm or more thick with more than 3.0 with a total thickness of 30 cm or more at a depth between 25 percent organic carbon and the colors of a mollic epipedon and 100 cm either from the mineral soil surface or from the throughout, underlying one or more horizons with a total top of an organic layer with andic soil properties, whichever is thickness of 10 cm or more that have a color value, moist, 1 unit shallower. or more higher and an organic-carbon content 1 percent or more Acrudoxic Fulvudands (absolute) lower. Thaptic Fulvudands DHEG. Other Fulvudands that have both: DHEL. Other Fulvudands. 1. An argillic or kandic horizon within 125 cm of the Typic Fulvudands mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower; and Hapludands 2. A base saturation (by sum of cations) of less than 35 A percent throughout the upper 50 cm of the argillic or kandic Key to Subgroups N D horizon. DHFA. Hapludands that have a lithic contact within 50 cm of Ultic Fulvudands the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. DHEH. Other Fulvudands that have : both Lithic Hapludands 1. No horizons with more than 2.0 cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction and with a total thickness of DHFB. Other Hapludands that have anthraquic conditions. 10 cm or more at a depth between 25 and 50 cm either from Anthraquic Hapludands the mineral soil surface or from the top of an organic layer with andic soil properties, whichever is shallower; and DHFC. Other Hapludands that have both: 2. Throughout a layer 50 cm or more thick within 60 cm of 1. A horizon 15 cm or more thick that has 20 percent or the mineral soil surface or of the top of an organic layer with more (by volume) cemented soil material within 100 cm of andic soil properties, whichever is shallower: the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower; and a. More than 6.0 percent organic carbon, by weighted average; and 2. In one or more horizons at a depth between 50 and 100 cm either from the mineral soil surface or from the top of b. More than 4.0 percent organic carbon in all parts. an organic layer with andic soil properties, whichever is Eutric Pachic Fulvudands shallower, aquic conditions for some time in normal years (or artificial drainage) andone or more of the following: DHEI. Other Fulvudands that have no horizons with more than 2.0 cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction a. 2 percent or more redox concentrations; or and with a total thickness of 10 cm or more at a depth between b. A color value, moist, of 4 or more and 50 percent or 25 and 50 cm either from the mineral soil surface or from the more chroma of 2 or less either in redox depletions on top of an organic layer with andic soil properties, whichever is faces of peds or in the matrix if peds are absent; or shallower. Eutric Fulvudands c. Enough active ferrous iron to give a positive reaction to alpha,alpha-dipyridyl at a time when the soil is not DHEJ. Other Fulvudands that have, throughout a layer 50 cm being irrigated. or more thick within 60 cm of the mineral soil surface or of the Aquic Duric Hapludands top of an organic layer with andic soil properties, whichever is shallower: DHFD. Other Hapludands that have a horizon 15 cm or more thick that has 20 percent or more (by volume) cemented soil 1. More than 6.0 percent organic carbon, by weighted material within 100 cm of the mineral soil surface or of the average; and top of an organic layer with andic soil properties, whichever is 2. More than 4.0 percent organic carbon in all parts. shallower. Pachic Fulvudands Duric Hapludands

DHEK. Other Fulvudands that have, at a depth between 40 DHFE. Other Hapludands that have, in one or more horizons and 100 cm either from the mineral soil surface or from the at a depth between 50 and 100 cm either from the mineral 88 Keys to Soil Taxonomy

soil surface or from the top of an organic layer with andic soil 2. A layer 10 cm or more thick with more than 3.0 properties, whichever is shallower, aquic conditions for some percent organic carbon and the colors of a mollic epipedon time in normal years (or artificial drainage) andone or more of throughout, underlying one or more horizons with a total the following: thickness of 10 cm or more that have a color value, moist, 1 unit or more higher and an organic-carbon content 1 percent 1. 2 percent or more redox concentrations; or or more (absolute) lower. 2. A color value, moist, of 4 or more and 50 percent or Acrudoxic Thaptic Hapludands more chroma of 2 or less either in redox depletions on faces of peds or in the matrix if peds are absent; or DHFJ. Other Hapludands that have both:

3. Enough active ferrous iron to give a positive reaction 1. A sum of extractable bases (by NH4OAc) plus 1N KCl- to alpha,alpha-dipyridyl at a time when the soil is not being extractable Al3+ totaling less than 2.0 cmol(+)/kg in the fine- irrigated. earth fraction of one or more horizons with a total thickness Aquic Hapludands of 30 cm or more at a depth between 25 and 100 cm either from the mineral soil surface or from the top of an organic DHFF. Other Hapludands that are saturated with water within layer with andic soil properties, whichever is shallower; and 100 cm of the mineral soil surface in normal years for either or 2. An argillic or kandic horizon that has both: both: a. An upper boundary within 125 cm of the mineral soil 1. 20 or more consecutive days; or surface or of the top of an organic layer with andic soil 2. 30 or more cumulative days. properties, whichever is shallower; and Oxyaquic Hapludands b. A base saturation (by sum of cations) of less than 35 percent throughout its upper 50 cm. DHFG. Other Hapludands that have more than 2.0 Acrudoxic Ultic Hapludands cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction of one or more horizons with a total thickness of 10 cm or more at a DHFK. Other Hapludands that have a sum of extractable bases depth between 25 and 50 cm either from the mineral soil surface (by NH OAc) plus 1N KCl-extractable Al3+ totaling less than 2.0 or from the top of an organic layer with andic soil properties, 4 cmol(+)/kg in the fine-earth fraction of one or more horizons whichever is shallower. with a total thickness of 30 cm or more at a depth between 25 Alic Hapludands and 100 cm either from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever is DHFH. Other Hapludands that have both: shallower.

1. A sum of extractable bases (by NH4OAc) plus 1N KCl- Acrudoxic Hapludands extractable Al3+ totaling less than 2.0 cmol(+)/kg in the fine- earth fraction of one or more horizons with a total thickness DHFL. Other Hapludands that have a 1500 kPa water of 30 cm or more at a depth between 25 and 100 cm either retention of less than 15 percent on air-dried samples and less from the mineral soil surface or from the top of an organic than 30 percent on undried samples throughout one or more layer with andic soil properties, whichever is shallower; and layers that have andic soil properties and have a total thickness of 25 cm or more within 100 cm of the mineral soil surface 2. On undried samples, a 1500 kPa water retention of 70 or of the top of an organic layer with andic soil properties, percent or more throughout a layer 35 cm or more thick whichever is shallower. within 100 cm of the mineral soil surface or of the top of Vitric Hapludands an organic layer with andic soil properties, whichever is shallower. DHFM. Other Hapludands that have both: Acrudoxic Hydric Hapludands 1. On undried samples, a 1500 kPa water retention of 70 DHFI. Other Hapludands that have, at a depth between 25 percent or more throughout a layer 35 cm or more thick and 100 cm either from the mineral soil surface or from the within 100 cm of the mineral soil surface or of the top of top of an organic layer with andic soil properties, whichever is an organic layer with andic soil properties, whichever is shallower, both: shallower; and

1. A sum of extractable bases (by NH4OAc) plus 1N KCl- 2. At a depth between 25 and 100 cm either from the extractable Al3+ totaling less than 2.0 cmol(+)/kg in the fine- mineral soil surface or from the top of an organic layer with earth fraction of one or more horizons with a total thickness andic soil properties, whichever is shallower, a layer 10 cm of 30 cm or more; and or more thick with more than 3.0 percent organic carbon and Andisols 89

the colors of a mollic epipedon throughout, underlying one DHFS. Other Hapludands that have both: or more horizons with a total thickness of 10 cm or more 1. An argillic or kandic horizon within 125 cm of the that have a color value, moist, 1 unit or more higher and an mineral soil surface or of the top of an organic layer with organic-carbon content 1 percent or more (absolute) lower. andic soil properties, whichever is shallower; and Hydric Thaptic Hapludands 2. A base saturation (by sum of cations) of less than 35 DHFN. Other Hapludands that have, on undried samples, percent throughout the upper 50 cm of the argillic or kandic a 1500 kPa water retention of 70 percent or more throughout horizon. a layer 35 cm or more thick within 100 cm of the mineral Ultic Hapludands soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. DHFT. Other Hapludands that have an argillic or kandic Hydric Hapludands horizon within 125 cm of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is DHFO. Other Hapludands that have both: shallower. A Alfic Hapludands N 1. A sum of extractable bases (by NH4OAc) of more than D 25.0 cmol(+)/kg in the fine-earth fraction throughout one DHFU. Other Hapludands. or more horizons with a total thickness of 15 cm or more at Typic Hapludands a depth between 25 and 75 cm either from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever is shallower; and Hydrudands 2. At a depth between 25 and 100 cm either from the Key to Subgroups mineral soil surface or from the top of an organic layer with DHDA. Hydrudands that have a lithic contact within 50 cm andic soil properties, whichever is shallower, a layer 10 cm of the mineral soil surface or of the top of an organic layer with or more thick with more than 3.0 percent organic carbon and andic soil properties, whichever is shallower. the colors of a mollic epipedon throughout, underlying one Lithic Hydrudands or more horizons with a total thickness of 10 cm or more that have a color value, moist, 1 unit or more higher and an DHDB. Other Hydrudands that have, in one or more horizons organic-carbon content 1 percent or more (absolute) lower. at a depth between 50 and 100 cm either from the mineral Eutric Thaptic Hapludands soil surface or from the top of an organic layer with andic soil properties, whichever is shallower, aquic conditions for some DHFP. Other Hapludands that have, at a depth between 25 time in normal years (or artificial drainage) andone or more of and 100 cm either from the mineral soil surface or from the the following: top of an organic layer with andic soil properties, whichever is shallower, a layer 10 cm or more thick with more than 3.0 1. 2 percent or more redox concentrations; or percent organic carbon and the colors of a mollic epipedon 2. A color value, moist, of 4 or more and 50 percent or throughout, underlying one or more horizons with a total more chroma of 2 or less either in redox depletions on faces thickness of 10 cm or more that have a color value, moist, 1 unit of peds or in the matrix if peds are absent; or or more higher and an organic-carbon content 1 percent or more (absolute) lower. 3. Enough active ferrous iron to give a positive reaction Thaptic Hapludands to alpha,alpha-dipyridyl at a time when the soil is not being irrigated. DHFQ. Other Hapludands that have a sum of extractable bases Aquic Hydrudands

(by NH4OAc) of more than 25.0 cmol(+)/kg in the fine-earth fraction throughout one or more horizons with a total thickness DHDC. Other Hydrudands that have, at a depth between 25 of 15 cm or more at a depth between 25 and 75 cm either from and 100 cm either from the mineral soil surface or from the the mineral soil surface or from the top of an organic layer with top of an organic layer with andic soil properties, whichever is andic soil properties, whichever is shallower. shallower, both: Eutric Hapludands 1. A sum of extractable bases (by NH4OAc) plus 1N KCl- extractable Al3+ totaling less than 2.0 cmol(+)/kg in the fine- DHFR. Other Hapludands that have an oxic horizon within earth fraction of one or more horizons with a total thickness 125 cm of the mineral soil surface or of the top of an organic of 30 cm or more; and layer with andic soil properties, whichever is shallower. Oxic Hapludands 2. A layer 10 cm or more thick with more than 3.0 90 Keys to Soil Taxonomy

percent organic carbon and the colors of a mollic epipedon DHCB. Other Melanudands that have anthraquic conditions. throughout, underlying one or more horizons with a total Anthraquic Melanudands thickness of 10 cm or more that have a color value, moist, 1 unit or more higher and an organic-carbon content 1 percent DHCC. Other Melanudands that have, in one or more or more (absolute) lower. horizons at a depth between 50 and 100 cm either from the Acrudoxic Thaptic Hydrudands mineral soil surface or from the top of an organic layer with andic soil properties, whichever is shallower, aquic conditions DHDD. Other Hydrudands that have a sum of extractable for some time in normal years (or artificial drainage) andone or 3+ bases (by NH4OAc) plus 1N KCl-extractable Al totaling less more of the following: than 2.0 cmol(+)/kg in the fine-earth fraction of one or more horizons with a total thickness of 30 cm or more at a depth 1. 2 percent or more redox concentrations; or between 25 and 100 cm either from the mineral soil surface 2. A color value, moist, of 4 or more and 50 percent or or from the top of an organic layer with andic soil properties, more chroma of 2 or less either in redox depletions on faces whichever is shallower. of peds or in the matrix if peds are absent; or Acrudoxic Hydrudands 3. Enough active ferrous iron to give a positive reaction DHDE. Other Hydrudands that have, at a depth between 25 to alpha,alpha-dipyridyl at a time when the soil is not being and 100 cm either from the mineral soil surface or from the irrigated. top of an organic layer with andic soil properties, whichever Aquic Melanudands is shallower, a layer 10 cm or more thick with more than 3.0 percent organic carbon and the colors of a mollic epipedon DHCD. Other Melanudands that have both: throughout, underlying one or more horizons with a total 1. A sum of extractable bases (by NH4OAc) plus 1N KCl- thickness of 10 cm or more that have a color value, moist, 1 unit extractable Al3+ totaling less than 2.0 cmol(+)/kg in the fine- or more higher and an organic-carbon content 1 percent or more earth fraction of one or more horizons with a total thickness (absolute) lower. of 30 cm or more at a depth between 25 and 100 cm either Thaptic Hydrudands from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever is shallower; and DHDF. Other Hydrudands that have a sum of extractable bases 2. A 1500 kPa water retention of less than 15 percent (by NH4OAc) of more than 25.0 cmol(+)/kg in the fine-earth fraction throughout one or more horizons with a total thickness on air-dried samples and less than 30 percent on undried of 15 cm or more at a depth between 25 and 75 cm either from samples throughout one or more layers that have andic soil the mineral soil surface or from the top of an organic layer with properties and have a total thickness of 25 cm or more within andic soil properties, whichever is shallower. 100 cm of the mineral soil surface or of the top of an organic Eutric Hydrudands layer with andic soil properties, whichever is shallower. Acrudoxic Vitric Melanudands DHDG. Other Hydrudands that have both: DHCE. Other Melanudands that have both: 1. An argillic or kandic horizon within 125 cm of the mineral soil surface or of the top of an organic layer with 1. A sum of extractable bases (by NH4OAc) plus 1N KCl- andic soil properties, whichever is shallower; and extractable Al3+ totaling less than 2.0 cmol(+)/kg in the fine- 2. A base saturation (by sum of cations) of less than 35 earth fraction of one or more horizons with a total thickness percent throughout the upper 50 cm of the argillic or kandic of 30 cm or more at a depth between 25 and 100 cm either horizon. from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever is shallower; Ultic Hydrudands and 2. On undried samples, a 1500 kPa water retention of 70 DHDH. Other Hydrudands. percent or more throughout a layer 35 cm or more thick Typic Hydrudands within 100 cm of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is Melanudands shallower. Acrudoxic Hydric Melanudands Key to Subgroups DHCA. Melanudands that have a lithic contact within 50 cm DHCF. Other Melanudands that have a sum of extractable 3+ of the mineral soil surface or of the top of an organic layer that bases (by NH4OAc) plus 1N KCl-extractable Al totaling less has andic soil properties, whichever is shallower. than 2.0 cmol(+)/kg in the fine-earth fraction of one or more Lithic Melanudands horizons with a total thickness of 30 cm or more at a depth Andisols 91

between 25 and 100 cm either from the mineral soil surface soil surface or of the top of an organic layer with andic soil or from the top of an organic layer with andic soil properties, properties, whichever is shallower. whichever is shallower. Hydric Melanudands Acrudoxic Melanudands DHCL. Other Melanudands that have, at a depth between 40 DHCG. Other Melanudands that have both: and 100 cm either from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever 1. More than 6.0 percent organic carbon and the colors of is shallower, a layer 10 cm or more thick with more than 3.0 a mollic epipedon throughout a layer 50 cm or more thick percent organic carbon and the colors of a mollic epipedon within 60 cm of the mineral soil surface or of the top of throughout, underlying one or more horizons with a total an organic layer with andic soil properties, whichever is thickness of 10 cm or more that have a color value, moist, 1 unit shallower; and or more higher and an organic-carbon content 1 percent or more 2. A 1500 kPa water retention of less than 15 percent (absolute) lower. on air-dried samples and less than 30 percent on undried Thaptic Melanudands A samples throughout one or more layers that have andic soil N properties and have a total thickness of 25 cm or more within DHCM. Other Melanudands that have both: D 100 cm of the mineral soil surface or of the top of an organic 1. An argillic or kandic horizon within 125 cm of the layer with andic soil properties, whichever is shallower. mineral soil surface or of the top of an organic layer with Pachic Vitric Melanudands andic soil properties, whichever is shallower; and DHCH. Other Melanudands that have a 1500 kPa water 2. A base saturation (by sum of cations) of less than 35 retention of less than 15 percent on air-dried samples and less percent throughout the upper 50 cm of the argillic or kandic than 30 percent on undried samples throughout one or more horizon. layers that have andic soil properties and have a total thickness Ultic Melanudands of 25 cm or more within 100 cm of the mineral soil surface or of the top of an organic layer with andic soil properties, DHCN. Other Melanudands that have a sum of extractable whichever is shallower. bases (by NH4OAc) of more than 25.0 cmol(+)/kg in the Vitric Melanudands fine-earth fraction throughout one or more horizons with a total thickness of 15 cm or more at a depth between 25 and 75 DHCI. Other Melanudands that have both: cm either from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever is shallower. 1. On undried samples, a 1500 kPa water retention of 70 Eutric Melanudands percent or more throughout a layer 35 cm or more thick within 100 cm of the mineral soil surface or of the top of DHCO. Other Melanudands. an organic layer with andic soil properties, whichever is Typic Melanudands shallower; and 2. More than 6.0 percent organic carbon and the colors of Placudands a mollic epipedon throughout a layer 50 cm or more thick Key to Subgroups within 60 cm of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is DHAA. Placudands that have a lithic contact within 50 cm of shallower. the mineral soil surface or of the top of an organic layer that has Hydric Pachic Melanudands andic soil properties, whichever is shallower. Lithic Placudands DHCJ. Other Melanudands that have more than 6.0 percent organic carbon and the colors of a mollic epipedon throughout DHAB. Other Placudands that have, in one or more horizons a layer 50 cm or more thick within 60 cm of the mineral at a depth between 50 cm either from the mineral soil surface soil surface or of the top of an organic layer with andic soil or from the top of an organic layer with andic soil properties, properties, whichever is shallower. whichever is shallower, and the placic horizon, aquic conditions Pachic Melanudands for some time in normal years (or artificial drainage) andone or more of the following: DHCK. Other Melanudands that have, on undried samples, 1. 2 percent or more redox concentrations; or a 1500 kPa water retention of 70 percent or more throughout a layer 35 cm or more thick within 100 cm of the mineral 2. A color value, moist, of 4 or more and 50 percent or 92 Keys to Soil Taxonomy

more chroma of 2 or less either in redox depletions on faces to alpha,alpha-dipyridyl at a time when the soil is not being of peds or in the matrix if peds are absent; or irrigated. Aquic Durustands 3. Enough active ferrous iron to give a positive reaction to alpha,alpha-dipyridyl at a time when the soil is not being irrigated. DGAB. Other Durustands that have, at a depth between 25 and 100 cm either from the mineral soil surface or from the Aquic Placudands top of an organic layer with andic soil properties, whichever DHAC. Other Placudands that have a sum of extractable bases is shallower, a layer 10 cm or more thick with more than 3.0 3+ percent organic carbon and the colors of a mollic epipedon (by NH4OAc) plus 1N KCl-extractable Al totaling less than 2.0 cmol(+)/kg in the fine-earth fraction of one or more horizons throughout, underlying one or more horizons with a total with a total thickness of 30 cm or more at a depth between 25 thickness of 10 cm or more that have a color value, moist, 1 unit cm either from the mineral soil surface or from the top of an or more higher and an organic-carbon content 1 percent or more organic layer with andic soil properties, whichever is shallower, (absolute) lower. and the placic horizon. Thaptic Durustands Acrudoxic Placudands DGAC. Other Durustands that have a melanic, mollic, or umbric epipedon. DHAD. Other Placudands that have, on undried samples, a 1500 kPa water retention of 70 percent or more throughout Humic Durustands a layer 35 cm or more thick within 100 cm of the mineral soil surface or of the top of an organic layer with andic soil DGAD. Other Durustands. properties, whichever is shallower. Typic Durustands Hydric Placudands Haplustands DHAE. Other Placudands. Key to Subgroups Typic Placudands DGBA. Haplustands that have a lithic contact within 50 cm of the mineral soil surface or of the top of an organic layer with Ustands andic soil properties, whichever is shallower. Key to Great Groups Lithic Haplustands

DGA. Ustands that have, in 75 percent or more of each DGBB. Other Haplustands that have, in one or more horizons pedon, a cemented horizon within 100 cm of the mineral at a depth between 50 and 100 cm either from the mineral soil surface or of the top of an organic layer with andic soil soil surface or from the top of an organic layer with andic soil properties, whichever is shallower. properties, whichever is shallower, aquic conditions for some Durustands, p. 92 time in normal years (or artificial drainage) andone or more of the following: DGB. Other Ustands. Haplustands, p. 92 1. 2 percent or more redox concentrations; or 2. A color value, moist, of 4 or more and 50 percent or Durustands more chroma of 2 or less either in redox depletions on faces Key to Subgroups of peds or in the matrix if peds are absent; or DGAA. Durustands that have, in one or more horizons at 3. Enough active ferrous iron to give a positive reaction a depth between 50 and 100 cm either from the mineral soil to alpha,alpha-dipyridyl at a time when the soil is not being surface or from the top of an organic layer with andic soil irrigated. properties, whichever is shallower, aquic conditions for some Aquic Haplustands time in normal years (or artificial drainage) andone or more of the following: DGBC. Other Haplustands that have both:

1. 2 percent or more redox concentrations; or 1. A sum of extractable bases (by NH4OAc) plus 1N KCl- extractable Al3+ totaling less than 15.0 cmol(+)/kg in the 2. A color value, moist, of 4 or more and 50 percent or fine-earth fraction throughout one or more horizons with a more chroma of 2 or less either in redox depletions on faces total thickness of 60 cm or more within 75 cm of the mineral of peds or in the matrix if peds are absent; or soil surface or of the top of an organic layer with andic soil 3. Enough active ferrous iron to give a positive reaction properties, whichever is shallower; and Andisols 93

2. A 1500 kPa water retention of less than 15 percent 1. An argillic or kandic horizon within 125 cm of the on air-dried samples and less than 30 percent on undried mineral soil surface or of the top of an organic layer with samples throughout one or more layers that have andic soil andic soil properties, whichever is shallower; and properties and have a total thickness of 25 cm or more within 2. A base saturation (by sum of cations) of less than 35 100 cm of the mineral soil surface or of the top of an organic percent throughout the upper 50 cm or throughout the entire layer with andic soil properties, whichever is shallower. argillic or kandic horizon if it is less than 50 cm thick. Dystric Vitric Haplustands Ultic Haplustands

DGBD. Other Haplustands that have a 1500 kPa water DGBK. Other Haplustands that have an argillic or kandic retention of less than 15 percent on air-dried samples and less horizon within 125 cm of the mineral soil surface or of the than 30 percent on undried samples throughout one or more top of an organic layer with andic soil properties, whichever is layers that have andic soil properties and have a total thickness shallower. of 25 cm or more within 100 cm of the mineral soil surface Alfic Haplustands or of the top of an organic layer with andic soil properties, A whichever is shallower. N DGBL. Other Haplustands that have a melanic, mollic, or D Vitric Haplustands umbric epipedon. Humic Haplustands DGBE. Other Haplustands that have more than 6.0 percent organic carbon and the colors of a mollic epipedon throughout DGBM. Other Haplustands. a layer 50 cm or more thick within 60 cm of the mineral Typic Haplustands soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. Pachic Haplustands Vitrands Key to Great Groups DGBF. Other Haplustands that have, at a depth between 25 and 100 cm either from the mineral soil surface or from the DFA. Vitrands that have an ustic soil moisture regime. top of an organic layer with andic soil properties, whichever Ustivitrands, p. 94 is shallower, a layer 10 cm or more thick with more than 3.0 percent organic carbon and the colors of a mollic epipedon DFB. Other Vitrands. throughout, underlying one or more horizons with a total Udivitrands, p. 93 thickness of 10 cm or more that have a color value, moist, 1 unit or more higher and an organic-carbon content 1 percent or more Udivitrands (absolute) lower. Key to Subgroups Thaptic Haplustands DFBA. Udivitrands that have a lithic contact within 50 cm of DGBG. Other Haplustands that have a calcic horizon within the mineral soil surface or of the top of an organic layer with 125 cm of the mineral soil surface or of the top of an organic andic soil properties, whichever is shallower. layer with andic soil properties, whichever is shallower. Lithic Udivitrands Calcic Haplustands DFBB. Other Udivitrands that have, in one or more horizons DGBH. Other Haplustands that have a sum of extractable at a depth between 50 and 100 cm either from the mineral 3+ soil surface or from the top of an organic layer with andic soil bases (by NH4OAc) plus 1N KCl-extractable Al totaling less than 15.0 cmol(+)/kg in the fine-earth fraction throughout one properties, whichever is shallower, aquic conditions for some or more horizons with a total thickness of 60 cm or more within time in normal years (or artificial drainage) andone or more of 75 cm either of the mineral soil surface or of the top of an the following: organic layer with andic soil properties, whichever is shallower. 1. 2 percent or more redox concentrations; or Dystric Haplustands 2. A color value, moist, of 4 or more and 50 percent or DGBI. Other Haplustands that have an oxic horizon within more chroma of 2 or less either in redox depletions on faces 125 cm of the mineral soil surface or of the top of an organic of peds or in the matrix if peds are absent; or layer with andic soil properties, whichever is shallower. 3. Enough active ferrous iron to give a positive reaction Oxic Haplustands to alpha,alpha-dipyridyl at a time when the soil is not being irrigated. DGBJ. Other Haplustands that have both: Aquic Udivitrands 94 Keys to Soil Taxonomy

DFBC. Other Udivitrands that are saturated with water within time in normal years (or artificial drainage) andone or more of 100 cm of the mineral soil surface in normal years for either or the following: both: 1. 2 percent or more redox concentrations; or 1. 20 or more consecutive days; or 2. A color value, moist, of 4 or more and 50 percent or 2. 30 or more cumulative days. more chroma of 2 or less either in redox depletions on faces Oxyaquic Udivitrands of peds or in the matrix if peds are absent; or 3. Enough active ferrous iron to give a positive reaction DFBD. Other Udivitrands that have, at a depth between 25 to alpha,alpha-dipyridyl at a time when the soil is not being and 100 cm either from the mineral soil surface or from the irrigated. top of an organic layer with andic soil properties, whichever Aquic Ustivitrands is shallower, a layer 10 cm or more thick with more than 3.0 percent organic carbon and the colors of a mollic epipedon DFAC. Other Ustivitrands that have, at a depth between 25 throughout, underlying one or more horizons with a total and 100 cm either from the mineral soil surface or from the thickness of 10 cm or more that have a color value, moist, 1 unit top of an organic layer with andic soil properties, whichever or more higher and an organic-carbon content 1 percent or more is shallower, a layer 10 cm or more thick with more than 3.0 (absolute) lower. percent organic carbon and the colors of a mollic epipedon Thaptic Udivitrands throughout, underlying one or more horizons with a total thickness of 10 cm or more that have a color value, moist, 1 unit DFBE. Other Udivitrands that have both: or more higher and an organic-carbon content 1 percent or more 1. An argillic or kandic horizon within 125 cm of the (absolute) lower. mineral soil surface or of the top of an organic layer with Thaptic Ustivitrands andic soil properties, whichever is shallower; and DFAD. Other Ustivitrands that have a calcic horizon within 2. A base saturation (by sum of cations) of less than 35 125 cm of the soil surface or of the top of an organic layer with percent throughout the upper 50 cm of the argillic or kandic andic soil properties, whichever is shallower. horizon. Calcic Ustivitrands Ultic Udivitrands DFAE. Other Ustivitrands that have a melanic, mollic, or DFBF. Other Udivitrands that have an argillic or kandic umbric epipedon. horizon within 125 cm of the mineral soil surface or of the Humic Ustivitrands top of an organic layer with andic soil properties, whichever is shallower. DFAF. Other Ustivitrands. Alfic Udivitrands Typic Ustivitrands DFBG. Other Udivitrands that have a melanic, mollic, or umbric epipedon. Xerands Humic Udivitrands Key to Great Groups DFBH. Other Udivitrands. DEA. Xerands that have a 1500 kPa water retention of less Typic Udivitrands than 15 percent on air-dried samples and less than 30 percent on undried samples throughout 60 percent or more of the thickness Ustivitrands either: Key to Subgroups 1. Within 60 cm of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is DFAA. Ustivitrands that have a lithic contact within 50 cm of shallower, if there is no densic, lithic, or paralithic contact, the mineral soil surface or of the top of an organic layer with duripan, or petrocalcic horizon within that depth; or andic soil properties, whichever is shallower. Lithic Ustivitrands 2. Between the mineral soil surface or the top of an organic layer with andic soil properties, whichever is shallower, and a DFAB. Other Ustivitrands that have, in one or more horizons densic, lithic, or paralithic contact, a duripan, or a petrocalcic at a depth between 50 and 100 cm either from the mineral horizon. soil surface or from the top of an organic layer with andic soil Vitrixerands, p. 95 properties, whichever is shallower, aquic conditions for some Andisols 95

DEB. Other Xerands that have a melanic epipedon. DECF. Other Haploxerands that have both: Melanoxerands, p. 95 1. A mollic or umbric epipedon; and DEC. Other Xerands. 2. An argillic or kandic horizon within 125 cm of the Haploxerands, p. 95 mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. Haploxerands Alfic Humic Haploxerands Key to Subgroups DECG. Other Haploxerands that have an argillic or kandic DECA. Haploxerands that have a lithic contact within 50 cm horizon within 125 cm of the mineral soil surface or of the of the mineral soil surface or of the top of an organic layer with top of an organic layer with andic soil properties, whichever is andic soil properties, whichever is shallower. shallower. Lithic Haploxerands Alfic Haploxerands A DECB. Other Haploxerands that have, in one or more horizons DECH. Other Haploxerands that have a mollic or umbric N D at a depth between 50 and 100 cm either from the mineral epipedon. soil surface or from the top of an organic layer with andic soil Humic Haploxerands properties, whichever is shallower, aquic conditions for some time in normal years (or artificial drainage) andone or more of DECI. Other Haploxerands. the following: Typic Haploxerands 1. 2 percent or more redox concentrations; or Melanoxerands 2. A color value, moist, of 4 or more and 50 percent or more chroma of 2 or less either in redox depletions on faces Key to Subgroups of peds or in the matrix if peds are absent; or DEBA. Melanoxerands that have more than 6.0 percent 3. Enough active ferrous iron to give a positive reaction organic carbon and the colors of a mollic epipedon throughout to alpha,alpha-dipyridyl at a time when the soil is not being a layer 50 cm or more thick within 60 cm of the mineral irrigated. soil surface or of the top of an organic layer with andic soil Aquic Haploxerands properties, whichever is shallower. Pachic Melanoxerands DECC. Other Haploxerands that have, at a depth between 25 and 100 cm from the mineral soil surface or from the top of an DEBB. Other Melanoxerands. organic layer with andic soil properties, whichever is shallower, Typic Melanoxerands a layer 10 cm or more thick with more than 3.0 percent organic carbon and the colors of a mollic epipedon throughout, Vitrixerands underlying one or more horizons with a total thickness of 10 cm Key to Subgroups or more that have a color value, moist, 1 unit or more higher and an organic-carbon content 1 percent or more (absolute) lower. DEAA. Vitrixerands that have a lithic contact within 50 cm Thaptic Haploxerands of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. DECD. Other Haploxerands that have a calcic horizon within Lithic Vitrixerands 125 cm of the mineral soil surface. Calcic Haploxerands DEAB. Other Vitrixerands that have, in one or more horizons at a depth between 50 and 100 cm either from the mineral DECE. Other Haploxerands that have both: soil surface or from the top of an organic layer with andic soil properties, whichever is shallower, aquic conditions for some 1. An argillic or kandic horizon within 125 cm of the time in normal years (or artificial drainage) andone or more of mineral soil surface or of the top of an organic layer with the following: andic soil properties, whichever is shallower; and 1. 2 percent or more redox concentrations; or 2. A base saturation (by sum of cations) of less than 35 percent throughout the upper 50 cm of the argillic or kandic 2. A color value, moist, of 4 or more and 50 percent or horizon. more chroma of 2 or less either in redox depletions on faces Ultic Haploxerands of peds or in the matrix if peds are absent; or 96

3. Enough active ferrous iron to give a positive reaction DEAE. Other Vitrixerands that have both: to alpha,alpha-dipyridyl at a time when the soil is not being 1. An argillic or kandic horizon within 125 cm of the irrigated. mineral soil surface or of the top of an organic layer with Aquic Vitrixerands andic soil properties, whichever is shallower; and DEAC. Other Vitrixerands that have, at a depth between 25 2. A base saturation (by sum of cations) of less than 35 and 100 cm from the mineral soil surface or from the top of an percent throughout the upper 50 cm or throughout the entire organic layer with andic soil properties, whichever is shallower, argillic or kandic horizon if it is less than 50 cm thick. a layer 10 cm or more thick with more than 3.0 percent Ultic Vitrixerands organic carbon and the colors of a mollic epipedon throughout, underlying one or more horizons with a total thickness of 10 cm DEAF. Other Vitrixerands that have an argillic or kandic or more that have a color value, moist, 1 unit or more higher and horizon within 125 cm of the mineral soil surface or of the an organic-carbon content 1 percent or more (absolute) lower. top of an organic layer with andic soil properties, whichever is Thaptic Vitrixerands shallower. Alfic Vitrixerands DEAD. Other Vitrixerands that have both: DEAG. Other Vitrixerands that have a melanic, mollic, or 1. A melanic, mollic, or umbric epipedon; and umbric epipedon. 2. An argillic or kandic horizon within 125 cm of the Humic Vitrixerands mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. DEAH. Other Vitrixerands. Alfic Humic Vitrixerands Typic Vitrixerands 97

CHAPTER 7 Aridisols

Key to Suborders 1. A clay increase of 15 percent or more (absolute) within a vertical distance of 2.5 cm either within the argillic horizon GA. Aridisols that have a cryic soil temperature regime. or at its upper boundary; or Cryids, p. 112 2. An argillic horizon that extends to 150 cm or more from GB. Other Aridisols that have a salic horizon within 100 cm of the soil surface, that does not have a clay decrease with the soil surface. increasing depth of 20 percent or more (relative) from the Salids, p. 122 maximum clay content, and that has, in 50 percent or more of A the matrix in some part between 100 and 150 cm, either: R I GC. Other Aridisols that have a duripan within 100 cm of the a. Hue of 7.5YR or redder and chroma of 5 or more; or soil surface. Durids, p. 115 b. Hue of 7.5YR or redder and value, moist, of 3 or less and value, dry, of 4 or less. GD. Other Aridisols that have a gypsic or petrogypsic Paleargids, p. 104 horizon within 100 cm of the soil surface and do not have a petrocalcic horizon overlying these horizons. GED. Other Argids that have a gypsic horizon within 150 cm Gypsids, p. 118 of the soil surface. Gypsiargids, p. 99 GE. Other Aridisols that have an argillic or natric horizon and do not have a petrocalcic horizon within 100 cm of the soil GEE. Other Argids that have a calcic horizon within 150 cm surface. of the soil surface. Argids, p. 97 Calciargids, p. 97

GF. Other Aridisols that have a calcic or petrocalcic horizon GEF. Other Argids. within 100 cm of the soil surface. Haplargids, p. 100 Calcids, p. 105 Calciargids Key to Subgroups GG. Other Aridisols. Cambids, p. 108 GEEA. Calciargids that have a lithic contact within 50 cm of the soil surface. Argids Lithic Calciargids GEEB. Other Calciargids that have both: Key to Great Groups 1. One or both of the following: GEA. Argids that have a duripan or a petrocalcic or petrogypsic horizon within 150 cm of the soil surface. a. Cracks within 125 cm of the soil surface that are 5 Petroargids, p. 105 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge- GEB. Other Argids that have a natric horizon. shaped peds in a layer 15 cm or more thick that has its Natrargids, p. 102 upper boundary within 125 cm of the soil surface; or b. A linear extensibility of 6.0 cm or more between the soil surface and either a depth of 100 cm or a densic, GEC. Other Argids that do not have a densic, lithic, or lithic, or paralithic contact if shallower; and paralithic contact within 50 cm of the soil surface and have either: 2. A moisture control section that, in normal years, is dry in 98 Keys to Soil Taxonomy

all parts for less than three-fourths of the time (cumulative) is dry in all parts for less than three-fourths of the time when the soil temperature at a depth of 50 cm below the (cumulative) when the soil temperature at a depth of 50 cm soil surface is 5 oC or higher and a soil moisture regime that below the soil surface is 5 oC or higher and a soil moisture borders on xeric. regime that borders on ustic. Xerertic Calciargids Arenic Ustic Calciargids

GEEC. Other Calciargids that have both: GEEG. Other Calciargids that meet sandy or sandy-skeletal particle-size class criteria throughout a layer extending from the 1. One or both of the following: soil surface to the top of an argillic horizon at a depth of 50 cm a. Cracks within 125 cm of the soil surface that are 5 or more. mm or more wide through a thickness of 30 cm or more Arenic Calciargids for some time in normal years and slickensides or wedge- shaped peds in a layer 15 cm or more thick that has its GEEH. Other Calciargids that have both: upper boundary within 125 cm of the soil surface; or 1. One or more horizons, within 100 cm of the soil surface b. A linear extensibility of 6.0 cm or more between the and with a combined thickness of 15 cm or more, that soil surface and either a depth of 100 cm or a densic, contain 20 percent or more (by volume) durinodes or are lithic, or paralithic contact if shallower; and brittle and have at least a firm rupture-resistance class when moist; and 2. A moisture control section that, in normal years, is dry in all parts for less than three-fourths of the time (cumulative) 2. A moisture control section that, in normal years, is dry in when the soil temperature at a depth of 50 cm below the all parts for less than three-fourths of the time (cumulative) soil surface is 5 oC or higher and a soil moisture regime that when the soil temperature at a depth of 50 cm below the borders on ustic. soil surface is 5 oC or higher and a soil moisture regime that Ustertic Calciargids borders on xeric. Durinodic Xeric Calciargids GEED. Other Calciargids that have one or both of the following: GEEI. Other Calciargids that have one or more horizons, within 100 cm of the soil surface and with a combined thickness 1. Cracks within 125 cm of the soil surface that are 5 mm of 15 cm or more, that contain 20 percent or more (by volume) or more wide through a thickness of 30 cm or more for some durinodes or are brittle and have at least a firm rupture- time in normal years and slickensides or wedge-shaped peds resistance class when moist. in a layer 15 cm or more thick that has its upper boundary Durinodic Calciargids within 125 cm of the soil surface; or 2. A linear extensibility of 6.0 cm or more between the soil GEEJ. Other Calciargids that have both: surface and either a depth of 100 cm or a densic, lithic, or 1. One or more horizons, within 100 cm of the soil paralithic contact if shallower. surface and with a combined thickness of 15 cm or more, Vertic Calciargids that contain 20 percent or more (by volume) nodules or concretions; and GEEE. Other Calciargids that are either: 2. A moisture control section that, in normal years, is dry in 1. Irrigated and have aquic conditions for some time in all parts for less than three-fourths of the time (cumulative) normal years in one or more layers within 100 cm of the soil when the soil temperature at a depth of 50 cm below the surface; or soil surface is 5 oC or higher and a soil moisture regime that 2. Saturated with water in one or more layers within 100 borders on xeric. cm of the soil surface for 1 month or more in normal years. Petronodic Xeric Calciargids Aquic Calciargids GEEK. Other Calciargids that have both: GEEF. Other Calciargids that: 1. One or more horizons, within 100 cm of the soil 1. Meet sandy or sandy-skeletal particle-size class criteria surface and with a combined thickness of 15 cm or more, throughout a layer extending from the soil surface to the top that contain 20 percent or more (by volume) nodules or of an argillic horizon at a depth of 50 cm or more; and concretions; and 2. Have a moisture control section that, in normal years, 2. A moisture control section that, in normal years, is dry in Aridisols 99

all parts for less than three-fourths of the time (cumulative) parts of the moisture control section for less than three-fourths when the soil temperature at a depth of 50 cm below the of the time (cumulative) when the soil temperature at a depth soil surface is 5 oC or higher and a soil moisture regime that of 50 cm below the soil surface is 5 oC or higher and have a soil borders on ustic moisture regime that borders on ustic. Petronodic Ustic Calciargids Ustic Calciargids

GEEL. Other Calciargids that have one or more horizons, GEEQ. Other Calciargids. within 100 cm of the soil surface and with a combined thickness Typic Calciargids of 15 cm or more, that contain 20 percent or more (by volume) nodules or concretions. Gypsiargids Petronodic Calciargids Key to Subgroups GEEM. Other Calciargids that have : both GEDA. Gypsiargids that are either: 1. A moisture control section that, in normal years, is dry in 1. Irrigated and have aquic conditions for some time in all parts for less than three-fourths of the time (cumulative) normal years in one or more layers within 100 cm of the soil when the soil temperature at a depth of 50 cm below the surface; or soil surface is 5 oC or higher and a soil moisture regime that A borders on xeric; and 2. Are saturated with water in one or more layers within R 100 cm of the soil surface for 1 month or more in normal I 2. Throughout one or more horizons with a total thickness years. of 18 cm or more within 75 cm of the soil surface, one or Aquic Gypsiargids both of the following: a. More than 35 percent (by volume) fragments coarser GEDB. Other Gypsiargids that have one or more horizons, than 2.0 mm, of which more than 66 percent is cinders, within 100 cm of the soil surface and with a combined thickness pumice, and pumicelike fragments; or of 15 cm or more, that either contain 20 percent or more (by volume) durinodes or are brittle and have at least a firm rupture- b. A fine-earth fraction containing 30 percent or more resistance class when moist. particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 Durinodic Gypsiargids or more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the GEDC. Other Gypsiargids that have both: volcanic glass (percent) is 30 or more. Vitrixerandic Calciargids 1. A moisture control section that, in normal years, is dry in all parts for less than three-fourths of the time (cumulative) GEEN. Other Calciargids that have, throughout one or more when the soil temperature at a depth of 50 cm below the horizons with a total thickness of 18 cm or more within 75 cm soil surface is 5 oC or higher and a soil moisture regime that of the soil surface, one or both of the following: borders on xeric; and 1. More than 35 percent (by volume) fragments coarser 2. Throughout one or more horizons with a total thickness than 2.0 mm, of which more than 66 percent is cinders, of 18 cm or more within 75 cm of the soil surface, one or pumice, and pumicelike fragments; or both of the following: 2. A fine-earth fraction containing 30 percent or more a. More than 35 percent (by volume) fragments coarser particles 0.02 to 2.0 mm in diameter, of which 5 percent or than 2.0 mm, of which more than 66 percent is cinders, 1 more is volcanic glass, and [(Al plus /2 Fe, percent extracted pumice, and pumicelike fragments; or by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. b. A fine-earth fraction containing 30 percent or more Vitrandic Calciargids particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 or more is volcanic glass, and [(Al plus /2 Fe, percent GEEO. Other Calciargids that, in normal years, are dry in all extracted by ammonium oxalate) times 60] plus the parts of the moisture control section for less than three-fourths volcanic glass (percent) is 30 or more. of the time (cumulative) when the soil temperature at a depth Vitrixerandic Gypsiargids of 50 cm below the soil surface is 5 oC or higher and have a soil moisture regime that borders on xeric. GEDD. Other Gypsiargids that have, throughout one or more Xeric Calciargids horizons with a total thickness of 18 cm or more within 75 cm of the soil surface, one or both of the following: GEEP. Other Calciargids that, in normal years, are dry in all 100 Keys to Soil Taxonomy

1. More than 35 percent (by volume) fragments coarser soil surface is 5 oC or higher and a soil moisture regime that than 2.0 mm, of which more than 66 percent is cinders, borders on ustic. pumice, and pumicelike fragments; or Lithic Ustic Haplargids 2. A fine-earth fraction containing 30 percent or more GEFD. Other Haplargids that have a lithic contact within 50 particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 cm of the soil surface. more is volcanic glass, and [(Al plus /2 Fe, percent extracted Lithic Haplargids by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. GEFE. Other Haplargids that have both: Vitrandic Gypsiargids 1. One or both of the following: GEDE. Other Gypsiargids that, in normal years, are dry in all parts of the moisture control section for less than three-fourths a. Cracks within 125 cm of the soil surface that are 5 of the time (cumulative) when the soil temperature at a depth mm or more wide through a thickness of 30 cm or more of 50 cm below the soil surface is 5 oC or higher and have a soil for some time in normal years and slickensides or wedge- moisture regime that borders on xeric. shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the soil surface; Xeric Gypsiargids or b. A linear extensibility of 6.0 cm or more between the GEDF. Other Gypsiargids that, in normal years, are dry in all soil surface and either a depth of 100 cm or a densic, parts of the moisture control section for less than three-fourths lithic, or paralithic contact if shallower; and of the time (cumulative) when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and have a soil 2. A moisture control section that, in normal years, is dry in moisture regime that borders on ustic. all parts for less than three-fourths of the time (cumulative) Ustic Gypsiargids when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and a soil moisture regime that GEDG. Other Gypsiargids. borders on xeric. Typic Gypsiargids Xerertic Haplargids

Haplargids GEFF. Other Haplargids that have both: 1. of the following: Key to Subgroups One or both GEFA. Haplargids that have both: a. Cracks within 125 cm of the soil surface that are 5 mm or more wide through a thickness of 30 cm or more 1. A lithic contact within 50 cm of the soil surface; and for some time in normal years and slickensides or wedge- 2. An argillic horizon that is discontinuous throughout each shaped peds in a layer 15 cm or more thick that has its pedon. upper boundary within 125 cm of the soil surface; or Lithic Ruptic-Entic Haplargids b. A linear extensibility of 6.0 cm or more between the soil surface and either a depth of 100 cm or a densic, GEFB. Other Haplargids that have both: lithic, or paralithic contact if shallower; and 1. A lithic contact within 50 cm of the soil surface; and 2. A moisture control section that, in normal years, is dry in 2. A moisture control section that, in normal years, is dry in all parts for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm below the all parts for less than three-fourths of the time (cumulative) o when the soil temperature at a depth of 50 cm below the soil surface is 5 C or higher and a soil moisture regime that soil surface is 5 oC or higher and a soil moisture regime that borders on ustic. borders on xeric. Ustertic Haplargids Lithic Xeric Haplargids GEFG. Other Haplargids that have one or both of the following: GEFC. Other Haplargids that have both: 1. Cracks within 125 cm of the soil surface that are 5 mm 1. A lithic contact within 50 cm of the soil surface; and or more wide through a thickness of 30 cm or more for some 2. A moisture control section that, in normal years, is dry in time in normal years and slickensides or wedge-shaped peds all parts for less than three-fourths of the time (cumulative) in a layer 15 cm or more thick that has its upper boundary when the soil temperature at a depth of 50 cm below the within 125 cm of the soil surface; or Aridisols 101

2. A linear extensibility of 6.0 cm or more between the soil 1. One or more horizons, within 100 cm of the soil surface and either a depth of 100 cm or a densic, lithic, or surface and with a combined thickness of 15 cm or more, paralithic contact if shallower. that contain 20 percent or more (by volume) nodules or Vertic Haplargids concretions; and 2. A moisture control section that, in normal years, is dry in GEFH. Other Haplargids that are either: all parts for less than three-fourths of the time (cumulative) 1. Irrigated and have aquic conditions for some time in when the soil temperature at a depth of 50 cm below the normal years in one or more layers within 100 cm of the soil soil surface is 5 oC or higher and a soil moisture regime that surface; or borders on ustic. Petronodic Ustic Haplargids 2. Saturated with water in one or more layers within 100 cm of the soil surface for 1 month or more in normal years. GEFN. Other Haplargids that have one or more horizons, Aquic Haplargids within 100 cm of the soil surface and with a combined thickness of 15 cm or more, that contain 20 percent or more (by volume) GEFI. Other Haplargids that: nodules or concretions. 1. Meet sandy or sandy-skeletal particle-size class criteria Petronodic Haplargids throughout a layer extending from the soil surface to the top A GEFO. Other Haplargids that have : R of an argillic horizon at a depth of 50 cm or more; and both I 2. Have a moisture control section that, in normal years, 1. A moisture control section that, in normal years, is dry in is dry in all parts for less than three-fourths of the time all parts for less than three-fourths of the time (cumulative) (cumulative) when the soil temperature at a depth of 50 cm when the soil temperature at a depth of 50 cm below the o below the soil surface is 5 oC or higher and a soil moisture soil surface is 5 C or higher and a soil moisture regime that regime that borders on ustic. borders on xeric; and Arenic Ustic Haplargids 2. Throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of the soil surface, one or GEFJ. Other Haplargids that meet sandy or sandy-skeletal both of the following: particle-size class criteria throughout a layer extending from the soil surface to the top of an argillic horizon at a depth of 50 cm a. More than 35 percent (by volume) fragments coarser or more. than 2.0 mm, of which more than 66 percent is cinders, Arenic Haplargids pumice, and pumicelike fragments; or b. A fine-earth fraction containing 30 percent or more GEFK. Other Haplargids that have both: particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 1. One or more horizons, within 100 cm of the soil surface or more is volcanic glass, and [(Al plus /2 Fe, percent and with a combined thickness of 15 cm or more, that extracted by ammonium oxalate) times 60] plus the contain 20 percent or more (by volume) durinodes or are volcanic glass (percent) is 30 or more. brittle and have at least a firm rupture-resistance class when Vitrixerandic Haplargids moist; and GEFP. Other Haplargids that have, throughout one or more 2. A moisture control section that, in normal years, is dry in horizons with a total thickness of 18 cm or more within 75 cm all parts for less than three-fourths of the time (cumulative) of the soil surface, one or both of the following: when the soil temperature at a depth of 50 cm below the 1. More than 35 percent (by volume) fragments coarser soil surface is 5 oC or higher and a soil moisture regime that than 2.0 mm, of which more than 66 percent is cinders, borders on xeric. pumice, and pumicelike fragments; or Durinodic Xeric Haplargids 2. A fine-earth fraction containing 30 percent or more GEFL. Other Haplargids that have one or more horizons, particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 within 100 cm of the soil surface and with a combined thickness more is volcanic glass, and [(Al plus /2 Fe, percent extracted of 15 cm or more, that contain 20 percent or more (by volume) by ammonium oxalate) times 60] plus the volcanic glass durinodes or are brittle and have at least a firm rupture- (percent) is 30 or more. resistance class when moist. Vitrandic Haplargids Durinodic Haplargids GEFQ. Other Haplargids that, in normal years, are dry in all GEFM. Other Haplargids that have both: parts of the moisture control section for less than three-fourths 102 Keys to Soil Taxonomy

of the time (cumulative) when the soil temperature at a depth shaped peds in a layer 15 cm or more thick that has its of 50 cm below the soil surface is 5 oC or higher and have a soil upper boundary within 125 cm of the soil surface; or moisture regime that borders on xeric. b. A linear extensibility of 6.0 cm or more between the Xeric Haplargids soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. GEFR. Other Haplargids that, in normal years, are dry in all Xerertic Natrargids parts of the moisture control section for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and have a soil GEBE. Other Natrargids that: moisture regime that borders on ustic. 1. In normal years, are dry in all parts of the moisture Ustic Haplargids control section for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 GEFS. Other Haplargids. cm below the soil surface is 5 oC or higher and have a soil Typic Haplargids moisture regime that borders on ustic; and

Natrargids 2. Have one or both of the following: Key to Subgroups a. Cracks within 125 cm of the soil surface that are 5 mm or more wide through a thickness of 30 cm or more GEBA. Natrargids that have both: for some time in most years and slickensides or wedge- 1. A lithic contact within 50 cm of the soil surface; and shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the soil surface; or 2. A moisture control section that, in normal years, is dry in all parts for less than three-fourths of the time (cumulative) b. A linear extensibility of 6.0 cm or more between the when the soil temperature at a depth of 50 cm below the soil surface and either a depth of 100 cm or a densic, soil surface is 5 oC or higher and a soil moisture regime that lithic, or paralithic contact, whichever is shallower. borders on xeric. Ustertic Natrargids Lithic Xeric Natrargids GEBF. Other Natrargids that have one or both of the GEBB. Other Natrargids that have both: following: 1. A lithic contact within 50 cm of the soil surface; and 1. Cracks within 125 cm of the soil surface that are 5 mm or more wide through a thickness of 30 cm or more for some 2. A moisture control section that, in normal years, is dry in time in normal years and slickensides or wedge-shaped peds all parts for less than three-fourths of the time (cumulative) in a layer 15 cm or more thick that has its upper boundary when the soil temperature at a depth of 50 cm below the within 125 cm of the soil surface; or soil surface is 5 oC or higher and a soil moisture regime that borders on ustic. 2. A linear extensibility of 6.0 cm or more between the soil Lithic Ustic Natrargids surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. GEBC. Other Natrargids that have a lithic contact within 50 Vertic Natrargids cm of the soil surface. Lithic Natrargids GEBG. Other Natrargids that are either: 1. Irrigated and have aquic conditions for some time in GEBD. Other Natrargids that: normal years in one or more layers within 100 cm of the soil 1. In normal years, are dry in all parts of the moisture surface; or control section for less than three-fourths of the time 2. Saturated with water in one or more layers within 100 (cumulative) when the soil temperature at a depth of 50 cm of the soil surface for 1 month or more in normal years. cm below the soil surface is 5 oC or higher and have a soil Aquic Natrargids moisture regime that borders on xeric; and 2. Have one or both of the following: GEBH. Other Natrargids that have both: a. Cracks within 125 cm of the soil surface that are 5 1. One or more horizons, within 100 cm of the soil surface mm or more wide through a thickness of 30 cm or more and with a combined thickness of 15 cm or more, that for some time in most years and slickensides or wedge- contain 20 percent or more (by volume) durinodes or are Aridisols 103

brittle and have at least a firm rupture-resistance class when soil surface is 5 oC or higher and a soil moisture regime that moist; and borders on xeric. Haploxeralfic Natrargids 2. A moisture control section that, in normal years, is dry in all parts for less than three-fourths of the time (cumulative) GEBN. Other Natrargids that have an exchangeable sodium when the soil temperature at a depth of 50 cm below the percentage of less than 15 (or an SAR of less than 13) in 50 soil surface is 5 oC or higher and a soil moisture regime that percent or more of the natric horizon. borders on xeric. Haplic Natrargids Durinodic Xeric Natrargids GEBO. Other Natrargids that have both: GEBI. Other Natrargids that have one or more horizons, within 100 cm of the soil surface and with a combined thickness 1. A moisture control section that, in normal years, is dry in of 15 cm or more, that contain 20 percent or more (by volume) all parts for less than three-fourths of the time (cumulative) durinodes or are brittle and have at least a firm rupture- when the soil temperature at a depth of 50 cm below the resistance class when moist. soil surface is 5 oC or higher and a soil moisture regime that Durinodic Natrargids borders on xeric; and 2. Throughout one or more horizons with a total thickness GEBJ. Other Natrargids that have one or more horizons, of 18 cm or more within 75 cm of the soil surface, one or A within 100 cm of the soil surface and with a combined thickness R both of the following: I of 15 cm or more, that contain 20 percent or more (by volume) nodules or concretions. a. More than 35 percent (by volume) fragments coarser Petronodic Natrargids than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or GEBK. Other Natrargids that have both: b. A fine-earth fraction containing 30 percent or more 1. Skeletans covering 10 percent or more of the surfaces of particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 peds at a depth of 2.5 cm or more below the upper boundary or more is volcanic glass, and [(Al plus /2 Fe, percent of the natric horizon; and extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. 2. A moisture control section that, in normal years, is dry in Vitrixerandic Natrargids all parts for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and a soil moisture regime that GEBP. Other Natrargids that have, throughout one or more borders on ustic. horizons with a total thickness of 18 cm or more within 75 cm of the soil surface, of the following: Glossic Ustic Natrargids one or both 1. More than 35 percent (by volume) fragments coarser GEBL. Other Natrargids that have both: than 2.0 mm, of which more than 66 percent is cinders, 1. An exchangeable sodium percentage of less than 15 (or pumice, and pumicelike fragments; or an SAR of less than 13) in 50 percent or more of the natric 2. A fine-earth fraction containing 30 percent or more horizon; and particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 2. A moisture control section that, in normal years, is dry in more is volcanic glass, and [(Al plus /2 Fe, percent extracted all parts for less than three-fourths of the time (cumulative) by ammonium oxalate) times 60] plus the volcanic glass when the soil temperature at a depth of 50 cm below the (percent) is 30 or more. soil surface is 5 oC or higher and a soil moisture regime that Vitrandic Natrargids borders on ustic. Haplic Ustic Natrargids GEBQ. Other Natrargids that, in normal years, are dry in all parts of the moisture control section for less than three-fourths GEBM. Other Natrargids that have both: of the time (cumulative) when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and have a soil 1. An exchangeable sodium percentage of less than 15 (or moisture regime that borders on xeric. an SAR of less than 13) in 50 percent or more of the natric Xeric Natrargids horizon; and 2. A moisture control section that, in normal years, is dry in GEBR. Other Natrargids that, in normal years, are dry in all all parts for less than three-fourths of the time (cumulative) parts of the moisture control section for less than three-fourths when the soil temperature at a depth of 50 cm below the of the time (cumulative) when the soil temperature at a depth 104 Keys to Soil Taxonomy

of 50 cm below the soil surface is 5 oC or higher and have a soil GECE. Other Paleargids that have a calcic horizon within 150 moisture regime that borders on ustic. cm of the soil surface. Ustic Natrargids Calcic Paleargids

GEBS. Other Natrargids that have skeletans covering 10 GECF. Other Paleargids that have both: percent or more of the surfaces of peds at a depth of 2.5 cm or 1. One or more horizons, within 100 cm of the soil surface more below the upper boundary of the natric horizon. and with a combined thickness of 15 cm or more, that Glossic Natrargids contain 20 percent or more (by volume) durinodes or are brittle and have at least a firm rupture-resistance class when GEBT. Other Natrargids. moist; and Typic Natrargids 2. A moisture control section that, in normal years, is dry in Paleargids all parts for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm below the Key to Subgroups soil surface is 5 oC or higher and a soil moisture regime that GECA. Paleargids that have one or both of the following: borders on xeric. Durinodic Xeric Paleargids 1. Cracks within 125 cm of the soil surface that are 5 mm or more wide through a thickness of 30 cm or more for some GECG. Other Paleargids that have one or more horizons, time in normal years and slickensides or wedge-shaped peds within 100 cm of the soil surface and with a combined thickness in a layer 15 cm or more thick that has its upper boundary of 15 cm or more, that contain 20 percent or more (by volume) within 125 cm of the soil surface; or durinodes or are brittle and have at least a firm rupture- 2. A linear extensibility of 6.0 cm or more between the soil resistance class when moist. surface and either a depth of 100 cm or a densic, lithic, or Durinodic Paleargids paralithic contact, whichever is shallower. Vertic Paleargids GECH. Other Paleargids that have both: 1. One or more horizons, within 100 cm of the soil GECB. Other Paleargids that are either: surface and with a combined thickness of 15 cm or more, 1. Irrigated and have aquic conditions for some time in that contain 20 percent or more (by volume) nodules or normal years in one or more layers within 100 cm of the soil concretions; and surface; or 2. A moisture control section that, in normal years, is dry in 2. Saturated with water in one or more layers within 100 all parts for less than three-fourths of the time (cumulative) cm of the soil surface for 1 month or more in normal years. when the soil temperature at a depth of 50 cm below the o Aquic Paleargids soil surface is 5 C or higher and a soil moisture regime that borders on ustic. GECC. Other Paleargids that: Petronodic Ustic Paleargids

1. Meet sandy or sandy-skeletal particle-size class criteria GECI. Other Paleargids that have one or more horizons, throughout a layer extending from the mineral soil surface within 100 cm of the soil surface and with a combined thickness to the top of an argillic horizon at a depth of 50 cm or more; of 15 cm or more, that contain 20 percent or more (by volume) and nodules or concretions. 2. Have a moisture control section that, in normal years, Petronodic Paleargids is dry in all parts for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm GECJ. Other Paleargids that have both: o below the soil surface is 5 C or higher and a soil moisture 1. A moisture control section that, in normal years, is dry in regime that borders on ustic. all parts for less than three-fourths of the time (cumulative) Arenic Ustic Paleargids when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and a soil moisture regime that GECD. Other Paleargids that meet sandy or sandy-skeletal borders on xeric; and particle-size class criteria throughout a layer extending from the mineral soil surface to the top of an argillic horizon at a depth of 2. Throughout one or more horizons with a total thickness 50 cm or more. of 18 cm or more within 75 cm of the soil surface, one or Arenic Paleargids both of the following: Aridisols 105

a. More than 35 percent (by volume) fragments coarser GEAB. Other Petroargids that have a petrogypsic horizon than 2.0 mm, of which more than 66 percent is cinders, within 150 cm of the soil surface. pumice, and pumicelike fragments; or Petrogypsic Petroargids b. A fine-earth fraction containing 30 percent or more GEAC. Other Petroargids that have both: particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 or more is volcanic glass, and [(Al plus /2 Fe, percent 1. A duripan within 150 cm of the soil surface; and extracted by ammonium oxalate) times 60] plus the 2. A moisture control section that, in normal years, is dry in volcanic glass (percent) is 30 or more. all parts for less than three-fourths of the time (cumulative) Vitrixerandic Paleargids when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and a soil moisture regime that GECK. Other Paleargids that have, throughout one or more borders on xeric. horizons with a total thickness of 18 cm or more within 75 cm Duric Xeric Petroargids of the soil surface, one or both of the following: 1. More than 35 percent (by volume) fragments coarser GEAD. Other Petroargids that have a duripan within 150 cm than 2.0 mm, of which more than 66 percent is cinders, of the soil surface. pumice, and pumicelike fragments; or Duric Petroargids A R 2. A fine-earth fraction containing 30 percent or more GEAE. Other Petroargids that have a natric horizon. I particles 0.02 to 2.0 mm in diameter, of which 5 percent or Natric Petroargids 1 more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass GEAF. Other Petroargids that, in normal years, are dry in all (percent) is 30 or more. parts of the moisture control section for less than three-fourths Vitrandic Paleargids of the time (cumulative) when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and have a soil GECL. Other Paleargids that, in normal years, are dry in all moisture regime that borders on xeric. parts of the moisture control section for less than three-fourths Xeric Petroargids of the time (cumulative) when the soil temperature at a depth of 50 cm below the surface is 5 oC or higher and have a soil GEAG. Other Petroargids that, in normal years, are dry in all moisture regime that borders on xeric. parts of the moisture control section for less than three-fourths Xeric Paleargids of the time (cumulative) when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and have a soil GECM. Other Paleargids that, in normal years, are dry in all moisture regime that borders on ustic. parts of the moisture control section for less than three-fourths Ustic Petroargids of the time (cumulative) when the soil temperature at a depth of 50 cm below the surface is 5 oC or higher and have a soil GEAH. Other Petroargids. moisture regime that borders on ustic. Typic Petroargids Ustic Paleargids

GECN. Other Paleargids. Calcids Typic Paleargids Key to Great Groups Petroargids GFA. Calcids that have a petrocalcic horizon within 100 cm of Key to Subgroups the soil surface. Petrocalcids, p. 107 GEAA. Petroargids that have both: 1. A petrogypsic horizon within 150 cm of the soil surface; GFB. Other Calcids. and Haplocalcids, p. 105 2. A moisture control section that, in normal years, is dry in Haplocalcids all parts for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm below the Key to Subgroups surface is 5 oC or higher and a soil moisture regime that GFBA. Haplocalcids that have both: borders on ustic. Petrogypsic Ustic Petroargids 1. A lithic contact within 50 cm of the soil surface; and 106 Keys to Soil Taxonomy

2. A moisture control section that, in normal years, is dry in normal years in one or more layers within 100 cm of the soil all parts for less than three-fourths of the time (cumulative) surface; or when the soil temperature at a depth of 50 cm below the 2. Saturated with water in one or more layers within 100 soil surface is 5 oC or higher and a soil moisture regime that cm of the soil surface for 1 month or more in normal years. borders on xeric. Aquic Haplocalcids Lithic Xeric Haplocalcids GFBG. Other Haplocalcids that have both: GFBB. Other Haplocalcids that have both: 1. A duripan within 150 cm of the soil surface; and 1. A lithic contact within 50 cm of the soil surface; and 2. A moisture control section that, in normal years, is dry in 2. A moisture control section that, in normal years, is dry in all parts for less than three-fourths of the time (cumulative) all parts for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm below the when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and a soil moisture regime that soil surface is 5 oC or higher and a soil moisture regime that borders on xeric. borders on ustic. Duric Xeric Haplocalcids Lithic Ustic Haplocalcids GFBH. Other Haplocalcids that have a duripan within 150 cm GFBC. Other Haplocalcids that have a lithic contact within 50 of the soil surface. cm of the soil surface. Duric Haplocalcids Lithic Haplocalcids GFBI. Other Haplocalcids that have both: GFBD. Other Haplocalcids that have one or both of the following: 1. One or more horizons, within 100 cm of the soil surface and with a combined thickness of 15 cm or more, that 1. Cracks within 125 cm of the soil surface that are 5 mm contain 20 percent or more (by volume) durinodes or are or more wide through a thickness of 30 cm or more for some brittle and have at least a firm rupture-resistance class when time in normal years and slickensides or wedge-shaped peds moist; and in a layer 15 cm or more thick that has its upper boundary within 125 cm of the soil surface; or 2. A moisture control section that, in normal years, is dry in all parts for less than three-fourths of the time (cumulative) 2. A linear extensibility of 6.0 cm or more between the soil when the soil temperature at a depth of 50 cm below the surface and either a depth of 100 cm or a densic, lithic, or soil surface is 5 oC or higher and a soil moisture regime that paralithic contact, whichever is shallower. borders on xeric. Vertic Haplocalcids Durinodic Xeric Haplocalcids GFBE. Other Haplocalcids that: GFBJ. Other Haplocalcids that have one or more horizons, 1. Are either: within 100 cm of the soil surface and with a combined thickness of 15 cm or more, that contain 20 percent or more (by volume) a. Irrigated and have aquic conditions for some time in durinodes or are brittle and have at least a firm rupture- normal years in one or more layers within 100 cm of the resistance class when moist. soil surface; or Durinodic Haplocalcids b. Saturated with water in one or more layers within 100 cm of the soil surface for 1 month or more in normal GFBK. Other Haplocalcids that have both: years; and 1. One or more horizons, within 100 cm of the soil 2. Have one or more horizons, within 100 cm of the soil surface and with a combined thickness of 15 cm or more, surface and with a combined thickness of 15 cm or more, that contain 20 percent or more (by volume) nodules or that contain 20 percent or more (by volume) durinodes or are concretions; and brittle and have at least a firm rupture-resistance class when 2. A moisture control section that, in normal years, is dry in moist. all parts for less than three-fourths of the time (cumulative) Aquic Durinodic Haplocalcids when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and a soil moisture regime that GFBF. Other Haplocalcids that are either: borders on xeric. 1. Irrigated and have aquic conditions for some time in Petronodic Xeric Haplocalcids Aridisols 107

GFBL. Other Haplocalcids that have both: when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and a soil moisture regime that 1. One or more horizons, within 100 cm of the soil borders on xeric; and surface and with a combined thickness of 15 cm or more, that contain 20 percent or more (by volume) nodules or 2. Throughout one or more horizons with a total thickness concretions; and of 18 cm or more within 75 cm of the soil surface, one or both of the following: 2. A moisture control section that, in normal years, is dry in all parts for less than three-fourths of the time (cumulative) a. More than 35 percent (by volume) fragments coarser when the soil temperature at a depth of 50 cm below the than 2.0 mm, of which more than 66 percent is cinders, soil surface is 5 oC or higher and a soil moisture regime that pumice, and pumicelike fragments; or borders on ustic. b. A fine-earth fraction containing 30 percent or more Petronodic Ustic Haplocalcids particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 GFBM. Other Haplocalcids that have one or more horizons, or more is volcanic glass, and [(Al plus /2 Fe, percent within 100 cm of the soil surface and with a combined thickness extracted by ammonium oxalate) times 60] plus the of 15 cm or more, that contain 20 percent or more (by volume) volcanic glass (percent) is 30 or more. nodules or concretions. Vitrixerandic Haplocalcids Petronodic Haplocalcids A GFBR. Other Haplocalcids that have, throughout one or more R I horizons with a total thickness of 18 cm or more within 75 cm GFBN. Other Haplocalcids that have both: of the soil surface, one or both of the following: 1. A horizon at least 25 cm thick within 100 cm of the soil surface that has an exchangeable sodium percentage of 15 or 1. More than 35 percent (by volume) fragments coarser more (or an SAR of 13 or more) during at least 1 month in than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; normal years; and or 2. A moisture control section that, in normal years, is dry in 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter, of which 5 percent or all parts for less than three-fourths of the time (cumulative) 1 when the soil temperature at a depth of 50 cm below the more is volcanic glass, and [(Al plus /2 Fe, percent extracted soil surface is 5 oC or higher and a soil moisture regime that by ammonium oxalate) times 60] plus the volcanic glass borders on xeric. (percent) is 30 or more. Sodic Xeric Haplocalcids Vitrandic Haplocalcids

GFBO. Other Haplocalcids that have both: GFBS. Other Haplocalcids that, in normal years, are dry in all parts of the moisture control section for less than three-fourths 1. A horizon at least 25 cm thick within 100 cm of the soil of the time (cumulative) when the soil temperature at a depth surface that has an exchangeable sodium percentage of 15 or of 50 cm below the soil surface is 5 oC or higher and have a soil more (or an SAR of 13 or more) during at least 1 month in moisture regime that borders on xeric. normal years; and Xeric Haplocalcids 2. A moisture control section that, in normal years, is dry in GFBT. Other Haplocalcids that, in normal years, are dry in all all parts for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm below the parts of the moisture control section for less than three-fourths o of the time (cumulative) when the soil temperature at a depth soil surface is 5 C or higher and a soil moisture regime that o borders on ustic. of 50 cm below the soil surface is 5 C or higher and have a soil moisture regime that borders on ustic. Sodic Ustic Haplocalcids Ustic Haplocalcids GFBP. Other Haplocalcids that have, in a horizon at least 25 cm thick within 100 cm of the mineral soil surface, an GFBU. Other Haplocalcids. exchangeable sodium percentage of 15 or more (or an SAR of Typic Haplocalcids 13 or more) during at least 1 month in normal years. Sodic Haplocalcids Petrocalcids Key to Subgroups GFBQ. Other Haplocalcids that have both: GFAA. Petrocalcids that are either: 1. A moisture control section that, in normal years, is dry in all parts for less than three-fourths of the time (cumulative) 1. Irrigated and have aquic conditions for some time in 108 Keys to Soil Taxonomy

normal years in one or more layers within 100 cm of the soil of the time (cumulative) when the soil temperature at a depth surface; or of 50 cm below the soil surface is 5 oC or higher and have a soil moisture regime that borders on ustic. 2. Saturated with water in one or more layers within 100 Ustic Petrocalcids cm of the soil surface for 1 month or more in normal years. Aquic Petrocalcids GFAJ. Other Petrocalcids. Typic Petrocalcids GFAB. Other Petrocalcids that have a natric horizon. Natric Petrocalcids Cambids GFAC. Other Petrocalcids that have both: Key to Great Groups 1. An argillic horizon within 100 cm of the soil surface; and GGA. Cambids that are either: 2. A moisture control section that, in normal years, is dry in 1. Irrigated and have aquic conditions for some time in all parts for less than three-fourths of the time (cumulative) normal years in one or more layers within 100 cm of the soil when the soil temperature at a depth of 50 cm below the surface; or soil surface is 5 oC or higher and a soil moisture regime that 2. Saturated with water in one or more layers within 100 borders on xeric. cm of the soil surface for 1 month or more in normal years. Xeralfic Petrocalcids Aquicambids, p. 108 GFAD. Other Petrocalcids that have both: GGB. Other Cambids that have a duripan or a petrocalcic or 1. An argillic horizon within 100 cm of the soil surface; petrogypsic horizon within 150 cm of the soil surface. and Petrocambids, p. 112 2. A moisture control section that, in normal years, is dry in GGC. Other Cambids that have an anthropic epipedon. all parts for less than three-fourths of the time (cumulative) Anthracambids, p. 108 when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and a soil moisture regime that GGD. Other Cambids. borders on ustic. Haplocambids, p. 109 Ustalfic Petrocalcids

GFAE. Other Petrocalcids that have an argillic horizon within Anthracambids 100 cm of the soil surface. Key to Subgroups Argic Petrocalcids GGCA. All Anthracambids. GFAF. Other Petrocalcids that have both: Typic Anthracambids 1. A calcic horizon overlying the petrocalcic horizon; and Aquicambids 2. A lithic contact within 50 cm of the soil surface. Key to Subgroups Calcic Lithic Petrocalcids GGAA. Aquicambids that have, in a horizon at least 25 cm GFAG. Other Petrocalcids that have a calcic horizon overlying thick within 100 cm of the soil surface, an exchangeable sodium the petrocalcic horizon. percentage of 15 or more (or an SAR of 13 or more) during at Calcic Petrocalcids least 1 month in normal years. Sodic Aquicambids GFAH. Other Petrocalcids that, in normal years, are dry in all parts of the moisture control section for less than three-fourths GGAB. Other Aquicambids that have both: of the time (cumulative) when the soil temperature at a depth o 1. One or more horizons, within 100 cm of the soil surface of 50 cm below the soil surface is 5 C or higher and have a soil and with a combined thickness of 15 cm or more, that moisture regime that borders on xeric. contain 20 percent or more (by volume) durinodes or are Xeric Petrocalcids brittle and have at least a firm rupture-resistance class when moist; and GFAI. Other Petrocalcids that, in normal years, are dry in all parts of the moisture control section for less than three-fourths 2. A moisture control section that, in normal years, is dry in Aridisols 109

all parts for less than three-fourths of the time (cumulative) GGAG. Other Aquicambids that have an irregular decrease in when the soil temperature at a depth of 50 cm below the organic-carbon content (Holocene age) between a depth of 25 soil surface is 5 oC or higher and a soil moisture regime that cm and either a depth of 125 cm below the mineral soil surface borders on xeric. or a densic, lithic, or paralithic contact, whichever is shallower. Durinodic Xeric Aquicambids Fluventic Aquicambids

GGAC. Other Aquicambids that have one or more horizons, GGAH. Other Aquicambids that, in normal years, are dry within 100 cm of the soil surface and with a combined thickness in all parts of the moisture control section for less than three- of 15 cm or more, that contain 20 percent or more (by volume) fourths of the time (cumulative) when the soil temperature at a durinodes or are brittle and have at least a firm rupture- depth of 50 cm below the soil surface is 5 oC or higher and have resistance class when moist. a soil moisture regime that borders on xeric. Durinodic Aquicambids Xeric Aquicambids

GGAD. Other Aquicambids that have one or more horizons, GGAI. Other Aquicambids that, in normal years, are dry in all within 100 cm of the soil surface and with a combined thickness parts of the moisture control section for less than three-fourths of 15 cm or more, that contain 20 percent or more (by volume) of the time (cumulative) when the soil temperature at a depth nodules or concretions. of 50 cm below the soil surface is 5 oC or higher and have a soil A Petronodic Aquicambids moisture regime that borders on ustic. R Ustic Aquicambids I GGAE. Other Aquicambids that have both: GGAJ. Other Aquicambids. 1. A moisture control section that, in normal years, is dry in Typic Aquicambids all parts for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and a soil moisture regime that Haplocambids borders on xeric; and Key to Subgroups 2. Throughout one or more horizons with a total thickness GGDA. Haplocambids that have both: of 18 cm or more within 75 cm of the soil surface, one or both of the following: 1. A lithic contact within 50 cm of the soil surface; and a. More than 35 percent (by volume) fragments coarser 2. A moisture control section that, in normal years, is dry in than 2.0 mm, of which more than 66 percent is cinders, all parts for less than three-fourths of the time (cumulative) pumice, and pumicelike fragments; or when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and a soil moisture regime that b. A fine-earth fraction containing 30 percent or more borders on xeric. particles 0.02 to 2.0 mm in diameter, of which 5 percent Lithic Xeric Haplocambids 1 or more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the GGDB. Other Haplocambids that have both: volcanic glass (percent) is 30 or more. Vitrixerandic Aquicambids 1. A lithic contact within 50 cm of the soil surface; and 2. A moisture control section that, in normal years, is dry in GGAF. Other Aquicambids that have, throughout one or more all parts for less than three-fourths of the time (cumulative) horizons with a total thickness of 18 cm or more within 75 cm when the soil temperature at a depth of 50 cm below the of the soil surface, one or both of the following: soil surface is 5 oC or higher and a soil moisture regime that 1. More than 35 percent (by volume) fragments coarser borders on ustic. than 2.0 mm, of which more than 66 percent is cinders, Lithic Ustic Haplocambids pumice, and pumicelike fragments; or GGDC. Other Haplocambids that have a lithic contact within 2. A fine-earth fraction containing 30 percent or more 50 cm of the soil surface. particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 Lithic Haplocambids more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass GGDD. Other Haplocambids that have both: (percent) is 30 or more. Vitrandic Aquicambids 1. One or both of the following: 110 Keys to Soil Taxonomy

a. Cracks within 125 cm of the soil surface that are 5 2. A moisture control section that, in normal years, is dry in mm or more wide through a thickness of 30 cm or more all parts for less than three-fourths of the time (cumulative) for some time in normal years and slickensides or wedge- when the soil temperature at a depth of 50 cm below the shaped peds in a layer 15 cm or more thick that has its soil surface is 5 oC or higher and a soil moisture regime that upper boundary within 125 cm of the soil surface; or borders on xeric. Durinodic Xeric Haplocambids b. A linear extensibility of 6.0 cm or more between the soil surface and either a depth of 100 cm or a densic, GGDH. Other Haplocambids that have one or more horizons, lithic, or paralithic contact if shallower; and within 100 cm of the soil surface and with a combined thickness 2. A moisture control section that, in normal years, is dry in of 15 cm or more, that contain 20 percent or more (by volume) all parts for less than three-fourths of the time (cumulative) durinodes or are brittle and have at least a firm rupture- when the soil temperature at a depth of 50 cm below the resistance class when moist. soil surface is 5 oC or higher and a soil moisture regime that Durinodic Haplocambids borders on xeric. Xerertic Haplocambids GGDI. Other Haplocambids that have both: 1. One or more horizons, within 100 cm of the soil GGDE. Other Haplocambids that have both: surface and with a combined thickness of 15 cm or more, 1. One or both of the following: that contain 20 percent or more (by volume) nodules or a. Cracks within 125 cm of the soil surface that are 5 concretions; and mm or more wide through a thickness of 30 cm or more 2. A moisture control section that, in normal years, is dry in for some time in normal years and slickensides or wedge- all parts for less than three-fourths of the time (cumulative) shaped peds in a layer 15 cm or more thick that has its when the soil temperature at a depth of 50 cm below the upper boundary within 125 cm of the soil surface; or soil surface is 5 oC or higher and a soil moisture regime that b. A linear extensibility of 6.0 cm or more between the borders on xeric. soil surface and either a depth of 100 cm or a densic, Petronodic Xeric Haplocambids lithic, or paralithic contact if shallower; and GGDJ. Other Haplocambids that have both: 2. A moisture control section that, in normal years, is dry in all parts for less than three-fourths of the time (cumulative) 1. One or more horizons, within 100 cm of the soil when the soil temperature at a depth of 50 cm below the surface and with a combined thickness of 15 cm or more, soil surface is 5 oC or higher and a soil moisture regime that that contain 20 percent or more (by volume) nodules or borders on ustic. concretions; and Ustertic Haplocambids 2. A moisture control section that, in normal years, is dry in all parts for less than three-fourths of the time (cumulative) GGDF. Other Haplocambids that have one or both of the when the soil temperature at a depth of 50 cm below the following: soil surface is 5 oC or higher and a soil moisture regime that 1. Cracks within 125 cm of the soil surface that are 5 mm borders on ustic. or more wide through a thickness of 30 cm or more for some Petronodic Ustic Haplocambids time in normal years and slickensides or wedge-shaped peds in a layer 15 cm or more thick that has its upper boundary GGDK. Other Haplocambids that have one or more horizons, within 125 cm of the soil surface; or within 100 cm of the soil surface and with a combined thickness of 15 cm or more, that contain 20 percent or more (by volume) 2. A linear extensibility of 6.0 cm or more between the soil nodules or concretions. surface and either a depth of 100 cm or a densic, lithic, or Petronodic Haplocambids paralithic contact, whichever is shallower. Vertic Haplocambids GGDL. Other Haplocambids that have both: GGDG. Other Haplocambids that have both: 1. A horizon at least 25 cm thick within 100 cm of the soil surface that has an exchangeable sodium percentage of 15 or 1. One or more horizons, within 100 cm of the soil surface more (or an SAR of 13 or more) during at least 1 month in and with a combined thickness of 15 cm or more, that normal years; and contain 20 percent or more (by volume) durinodes or are brittle and have at least a firm rupture-resistance class when 2. A moisture control section that, in normal years, is dry in moist; and all parts for less than three-fourths of the time (cumulative) Aridisols 111

1 when the soil temperature at a depth of 50 cm below the more is volcanic glass, and [(Al plus /2 Fe, percent extracted soil surface is 5 oC or higher and a soil moisture regime that by ammonium oxalate) times 60] plus the volcanic glass borders on xeric. (percent) is 30 or more. Sodic Xeric Haplocambids Vitrandic Haplocambids

GGDM. Other Haplocambids that have both: GGDQ. Other Haplocambids that: 1. A horizon at least 25 cm thick within 100 cm of the soil 1. In normal years, are dry in all parts of the moisture surface that has an exchangeable sodium percentage of 15 or control section for less than three-fourths of the time more (or an SAR of 13 or more) during at least 1 month in (cumulative) when the soil temperature at a depth of 50 normal years; and cm below the soil surface is 5 oC or higher and have a soil 2. A moisture control section that, in normal years, is dry in moisture regime that borders on xeric; and all parts for less than three-fourths of the time (cumulative) 2. Have an irregular decrease in organic-carbon content when the soil temperature at a depth of 50 cm below the (Holocene age) between a depth of 25 cm and either a depth soil surface is 5 oC or higher and a soil moisture regime that of 125 cm below the mineral soil surface or a densic, lithic, borders on ustic. or paralithic contact, whichever is shallower. Sodic Ustic Haplocambids Xerofluventic Haplocambids A R GGDN. Other Haplocambids that have, in a horizon at least GGDR. Other Haplocambids that: I 25 cm thick within 100 cm of the soil surface, an exchangeable sodium percentage of 15 or more (or an SAR of 13 or more) 1. In normal years, are dry in all parts of the moisture during at least 1 month in normal years. control section for less than three-fourths of the time Sodic Haplocambids (cumulative) when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and have a soil GGDO. Other Haplocambids that have both: moisture regime that borders on ustic; and 1. A moisture control section that, in normal years, is dry in 2. Have an irregular decrease in organic-carbon content all parts for less than three-fourths of the time (cumulative) (Holocene age) between a depth of 25 cm and either a depth when the soil temperature at a depth of 50 cm below the of 125 cm below the mineral soil surface or a densic, lithic, soil surface is 5 oC or higher and a soil moisture regime that or paralithic contact, whichever is shallower. borders on xeric; and Ustifluventic Haplocambids 2. Throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of the soil surface, one or GGDS. Other Haplocambids that have an irregular decrease both of the following: in organic-carbon content (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface a. More than 35 percent (by volume) fragments coarser or a densic, lithic, or paralithic contact, whichever is shallower. than 2.0 mm, of which more than 66 percent is cinders, Fluventic Haplocambids pumice, and pumicelike fragments; or b. A fine-earth fraction containing 30 percent or more GGDT. Other Haplocambids that, in normal years, are dry particles 0.02 to 2.0 mm in diameter, of which 5 percent in all parts of the moisture control section for less than three- 1 or more is volcanic glass, and [(Al plus /2 Fe, percent fourths of the time (cumulative) when the soil temperature at a extracted by ammonium oxalate) times 60] plus the depth of 50 cm below the soil surface is 5 oC or higher and have volcanic glass (percent) is 30 or more. a soil moisture regime that borders on xeric. Vitrixerandic Haplocambids Xeric Haplocambids

GGDP. Other Haplocambids that have, throughout one or GGDU. Other Haplocambids that, in normal years, are dry more horizons with a total thickness of 18 cm or more within 75 in all parts of the moisture control section for less than three- cm of the soil surface, one or both of the following: fourths of the time (cumulative) when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and have 1. More than 35 percent (by volume) fragments coarser a soil moisture regime that borders on ustic. than 2.0 mm, of which more than 66 percent is cinders, Ustic Haplocambids pumice, and pumicelike fragments; or 2. A fine-earth fraction containing 30 percent or more GGDV. Other Haplocambids. particles 0.02 to 2.0 mm in diameter, of which 5 percent or Typic Haplocambids 112 Keys to Soil Taxonomy

Petrocambids fourths of the time (cumulative) when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and have Key to Subgroups a soil moisture regime that borders on ustic. GGBA. Petrocambids that have, in a horizon at least 25 cm Ustic Petrocambids thick within 100 cm of the soil surface, an exchangeable sodium percentage of 15 or more (or an SAR of 13 or more) during at GGBF. Other Petrocambids. least 1 month in normal years. Typic Petrocambids Sodic Petrocambids

GGBB. Other Petrocambids that have both: Cryids 1. A moisture control section that, in normal years, is dry in Key to Great Groups all parts for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm below the GAA. Cryids that have a salic horizon within 100 cm of the soil surface is 5 oC or higher and a soil moisture regime that soil surface. borders on xeric; and Salicryids, p. 115

2. Throughout one or more horizons with a total thickness GAB. Other Cryids that have a duripan or a petrocalcic or of 18 cm or more within 75 cm of the soil surface, one or petrogypsic horizon within 100 cm of the soil surface. both of the following: Petrocryids, p. 115 a. More than 35 percent (by volume) fragments coarser GAC. Other Cryids that have a gypsic horizon within 100 cm than 2.0 mm, of which more than 66 percent is cinders, of the soil surface. pumice, and pumicelike fragments; or Gypsicryids, p. 114 b. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter, of which 5 percent GAD. Other Cryids that have an argillic or natric horizon. 1 or more is volcanic glass, and [(Al plus /2 Fe, percent Argicryids, p. 112 extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. GAE. Other Cryids that have a calcic horizon within 100 cm Vitrixerandic Petrocambids of the soil surface. Calcicryids, p. 113 GGBC. Other Petrocambids that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm GAF. Other Cryids. of the soil surface, one or both of the following: Haplocryids, p. 114 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, Argicryids pumice, and pumicelike fragments; or Key to Subgroups 2. A fine-earth fraction containing 30 percent or more GADA. Argicryids that have a lithic contact within 50 cm of particles 0.02 to 2.0 mm in diameter, of which 5 percent or the soil surface. 1 more is volcanic glass, and [(Al plus /2 Fe, percent extracted Lithic Argicryids by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. GADB. Other Argicryids that have one or both of the Vitrandic Petrocambids following: 1. Cracks within 125 cm of the soil surface that are 5 GGBD. Other Petrocambids that, in normal years, are dry mm or more wide throughout a thickness of 30 cm or more in all parts of the moisture control section for less than three- for some time in normal years and slickensides or wedge- fourths of the time (cumulative) when the soil temperature at a shaped peds in a layer 15 cm or more thick that has its upper depth of 50 cm below the soil surface is 5 oC or higher and have boundary within 125 cm of the mineral soil surface; a soil moisture regime that borders on xeric. or Xeric Petrocambids 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a densic, GGBE. Other Petrocambids that, in normal years, are dry lithic, or paralithic contact, whichever is shallower. in all parts of the moisture control section for less than three- Vertic Argicryids Aridisols 113

GADC. Other Argicryids that have a natric horizon within 100 Calcicryids cm of the soil surface. Natric Argicryids Key to Subgroups GAEA. Calcicryids that have a lithic contact within 50 cm of GADD. Other Argicryids that have both: the soil surface. 1. A moisture control section that, in normal years, is dry in Lithic Calcicryids all parts for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm below the GAEB. Other Calcicryids that have both: soil surface is 5 oC or higher and a soil moisture regime that 1. A moisture control section that, in normal years, is dry in borders on xeric; and all parts for less than three-fourths of the time (cumulative) 2. Throughout one or more horizons with a total thickness when the soil temperature at a depth of 50 cm below the o of 18 cm or more within 75 cm of the soil surface, one or soil surface is 5 C or higher and a soil moisture regime that both of the following: borders on xeric; and a. More than 35 percent (by volume) fragments coarser 2. Throughout one or more horizons with a total thickness than 2.0 mm, of which more than 66 percent is cinders, of 18 cm or more within 75 cm of the soil surface, one or pumice, and pumicelike fragments; both of the following: or A a. More than 35 percent (by volume) fragments coarser R b. A fine-earth fraction containing 30 percent or more than 2.0 mm, of which more than 66 percent is cinders, I particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 pumice, and pumicelike fragments; or or more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the b. A fine-earth fraction containing 30 percent or more volcanic glass (percent) is 30 or more. particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 Vitrixerandic Argicryids or more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the GADE. Other Argicryids that have, throughout one or more volcanic glass (percent) is 30 or more. horizons with a total thickness of 18 cm or more within 75 cm Vitrixerandic Calcicryids of the soil surface, one or both of the following: GAEC. Other Calcicryids that have, throughout one or more 1. More than 35 percent (by volume) fragments coarser horizons with a total thickness of 18 cm or more within 75 cm than 2.0 mm, of which more than 66 percent is cinders, of the soil surface, one or both of the following: pumice, and pumicelike fragments; or 1. More than 35 percent (by volume) fragments coarser 2. A fine-earth fraction containing 30 percent or more than 2.0 mm, of which more than 66 percent is cinders, particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 pumice, and pumicelike fragments; or more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass 2. A fine-earth fraction containing 30 percent or more (percent) is 30 or more. particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 Vitrandic Argicryids more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass GADF. Other Argicryids that, in normal years, are dry in all (percent) is 30 or more. parts of the moisture control section for less than three-fourths Vitrandic Calcicryids of the time (cumulative) when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and have a soil GAED. Other Calcicryids that, in normal years, are dry in all moisture regime that borders on xeric. parts of the moisture control section for less than three-fourths Xeric Argicryids of the time (cumulative) when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and have a soil GADG. Other Argicryids that, in normal years, are dry in all moisture regime that borders on xeric. parts of the moisture control section for less than three-fourths Xeric Calcicryids of the time (cumulative) when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and have a soil GAEE. Other Calcicryids that, in normal years, are dry in all moisture regime that borders on ustic. parts of the moisture control section for less than three-fourths Ustic Argicryids of the time (cumulative) when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and have a soil GADH. Other Argicryids. moisture regime that borders on ustic. Typic Argicryids Ustic Calcicryids 114 Keys to Soil Taxonomy

GAEF. Other Calcicryids. GAFB. Other Haplocryids that have one or both of the Typic Calcicryids following: Gypsicryids 1. Cracks within 125 cm of the soil surface that are 5 mm or more wide throughout a thickness of 30 cm or more Key to Subgroups for some time in normal years and slickensides or wedge- GACA. Gypsicryids that have a calcic horizon. shaped peds in a layer 15 cm or more thick that has its upper Calcic Gypsicryids boundary within 125 cm of the mineral soil surface; or 2. A linear extensibility of 6.0 cm or more between the GACB. Other Gypsicryids that have both: mineral soil surface and either a depth of 100 cm or a densic, 1. A moisture control section that, in normal years, is dry in lithic, or paralithic contact, whichever is shallower. all parts for less than three-fourths of the time (cumulative) Vertic Haplocryids when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and a soil moisture regime that GAFC. Other Haplocryids that have both: borders on xeric; and 1. A moisture control section that, in normal years, is dry in all parts for less than three-fourths of the time (cumulative) 2. Throughout one or more horizons with a total thickness when the soil temperature at a depth of 50 cm below the of 18 cm or more within 75 cm of the soil surface, one or soil surface is 5 oC or higher and a soil moisture regime that both of the following: borders on xeric; and a. More than 35 percent (by volume) fragments coarser 2. Throughout one or more horizons with a total thickness than 2.0 mm, of which more than 66 percent is cinders, of 18 cm or more within 75 cm of the soil surface, one or pumice, and pumicelike fragments; or both of the following: b. A fine-earth fraction containing 30 percent or more a. More than 35 percent (by volume) fragments coarser particles 0.02 to 2.0 mm in diameter, of which 5 percent than 2.0 mm, of which more than 66 percent is cinders, 1 or more is volcanic glass, and [(Al plus /2 Fe, percent pumice, and pumicelike fragments; or extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. b. A fine-earth fraction containing 30 percent or more Vitrixerandic Gypsicryids particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 or more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the GACC. Other Gypsicryids that have, throughout one or more volcanic glass (percent) is 30 or more. horizons with a total thickness of 18 cm or more within 75 cm Vitrixerandic Haplocryids of the soil surface, one or both of the following: 1. More than 35 percent (by volume) fragments coarser GAFD. Other Haplocryids that have, throughout one or more than 2.0 mm, of which more than 66 percent is cinders, horizons with a total thickness of 18 cm or more within 75 cm pumice, and pumicelike fragments; or of the soil surface, one or both of the following: 2. A fine-earth fraction containing 30 percent or more 1. More than 35 percent (by volume) fragments coarser particles 0.02 to 2.0 mm in diameter, of which 5 percent or than 2.0 mm, of which more than 66 percent is cinders, 1 pumice, and pumicelike fragments; more is volcanic glass, and [(Al plus /2 Fe, percent extracted or by ammonium oxalate) times 60] plus the volcanic glass 2. A fine-earth fraction containing 30 percent or more (percent) is 30 or more. particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 Vitrandic Gypsicryids more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass GACD. Other Gypsicryids. (percent) is 30 or more. Typic Gypsicryids Vitrandic Haplocryids

Haplocryids GAFE. Other Haplocryids that, in normal years, are dry in all parts of the moisture control section for less than three-fourths Key to Subgroups of the time (cumulative) when the soil temperature at a depth GAFA. Haplocryids that have a lithic contact within 50 cm of of 50 cm below the soil surface is 5 oC or higher and have a soil the soil surface. moisture regime that borders on xeric. Lithic Haplocryids Xeric Haplocryids Aridisols 115

GAFF. Other Haplocryids that, in normal years, are dry in all of 50 cm below the soil surface is 5 oC or higher and have a soil parts of the moisture control section for less than three-fourths moisture regime that borders on ustic. of the time (cumulative) when the soil temperature at a depth Ustic Petrocryids of 50 cm below the soil surface is 5 oC or higher and have a soil moisture regime that borders on ustic. GABG. Other Petrocryids. Ustic Haplocryids Typic Petrocryids

GAFG. Other Haplocryids. Salicryids Typic Haplocryids Key to Subgroups Petrocryids GAAA. Salicryids that are saturated with water in one or more layers within 100 cm of the soil surface for 1 month or more in Key to Subgroups normal years. GABA. Petrocryids that have both: Aquic Salicryids 1. A duripan that is strongly cemented or less cemented in GAAB. Other Salicryids. all subhorizons within 100 cm of the soil surface; and Typic Salicryids A 2. A moisture control section that, in normal years, is dry in R I all parts for less than three-fourths of the time (cumulative) Durids when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and a soil moisture regime that borders on xeric. Key to Great Groups Xereptic Petrocryids GCA. Durids that have a natric horizon above the duripan. Natridurids, p. 117 GABB. Other Petrocryids that have both: 1. A duripan within 100 cm of the soil surface; and GCB. Other Durids that have an argillic horizon above the duripan. 2. A moisture control section that, in normal years, is dry in Argidurids, p. 115 all parts for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm below the GCC. Other Durids. soil surface is 5 oC or higher and a soil moisture regime that Haplodurids, p. 116 borders on xeric. Duric Xeric Petrocryids Argidurids GABC. Other Petrocryids that have a duripan within 100 cm Key to Subgroups of the soil surface. GCBA. Argidurids that have one or both of the following: Duric Petrocryids 1. Cracks between the soil surface and the top of the GABD. Other Petrocryids that have a petrogypsic horizon duripan that are 5 mm or more wide through a thickness within 100 cm of the soil surface. of 30 cm or more for some time in normal years and Petrogypsic Petrocryids slickensides or wedge-shaped peds in a layer 15 cm or more thick that is above the duripan; or GABE. Other Petrocryids that, in normal years, are dry in all 2. A linear extensibility of 6.0 cm or more between the soil parts of the moisture control section for less than three-fourths surface and the top of the duripan. of the time (cumulative) when the soil temperature at a depth Vertic Argidurids of 50 cm below the soil surface is 5 oC or higher and have a soil moisture regime that borders on xeric. GCBB. Other Argidurids that are either: Xeric Petrocryids 1. Irrigated and have aquic conditions for some time in GABF. Other Petrocryids that, in normal years, are dry in all normal years in one or more layers within 100 cm of the soil parts of the moisture control section for less than three-fourths surface; or of the time (cumulative) when the soil temperature at a depth 116 Keys to Soil Taxonomy

2. Saturated with water in one or more layers within 100 when the soil temperature at a depth of 50 cm below the cm of the soil surface for 1 month or more in normal years. soil surface is 5 oC or higher and a soil moisture regime that Aquic Argidurids borders on xeric; and 2. Throughout one or more horizons with a total thickness GCBC. Other Argidurids that have : both of 18 cm or more within 75 cm of the soil surface, one or 1. An argillic horizon that has 35 percent or more clay in both of the following: the fine-earth fraction of some part;and either a. More than 35 percent (by volume) fragments coarser a. A clay increase of 15 percent or more (absolute) than 2.0 mm, of which more than 66 percent is cinders, within a vertical distance of 2.5 cm either within the pumice, and pumicelike fragments; or argillic horizon or at its upper boundary; or b. A fine-earth fraction containing 30 percent or more b. If there is an Ap horizon directly above the argillic particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 horizon, a clay increase of 10 percent or more (absolute) or more is volcanic glass, and [(Al plus /2 Fe, percent at the upper boundary of the argillic horizon; and extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. 2. A moisture control section that, in normal years, is dry in Vitrixerandic Argidurids all parts for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm below the o GCBH. Other Argidurids that have, throughout one or more soil surface is 5 C or higher and a soil moisture regime that horizons with a total thickness of 18 cm or more within 75 cm borders on xeric. of the soil surface, one or both of the following: Abruptic Xeric Argidurids 1. More than 35 percent (by volume) fragments coarser GCBD. Other Argidurids that have an argillic horizon that has than 2.0 mm, of which more than 66 percent is cinders, 35 percent or more clay in the fine-earth fraction of some part; pumice, and pumicelike fragments; or and either 2. A fine-earth fraction containing 30 percent or more 1. A clay increase of 15 percent or more (absolute) within a particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 vertical distance of 2.5 cm within the argillic horizon or at its more is volcanic glass, and [(Al plus /2 Fe, percent extracted upper boundary; or by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. 2. If there is an Ap horizon directly above the argillic Vitrandic Argidurids horizon, a clay increase of 10 percent or more (absolute) at the upper boundary of the argillic horizon. GCBI. Other Argidurids that, in normal years, are dry in all Abruptic Argidurids parts of the moisture control section for less than three-fourths of the time (cumulative) when the soil temperature at a depth GCBE. Other Argidurids that have both: of 50 cm below the soil surface is 5 oC or higher and have a soil 1. A duripan that is strongly cemented or less cemented in moisture regime that borders on xeric. all subhorizons; and Xeric Argidurids

2. A moisture control section that, in normal years, is dry in GCBJ. Other Argidurids that, in normal years, are dry in all all parts for less than three-fourths of the time (cumulative) parts of the moisture control section for less than three-fourths when the soil temperature at a depth of 50 cm below the of the time (cumulative) when the soil temperature at a depth o soil surface is 5 C or higher and a soil moisture regime that of 50 cm below the soil surface is 5 oC or higher and have a soil borders on xeric. moisture regime that borders on ustic. Haploxeralfic Argidurids Ustic Argidurids

GCBF. Other Argidurids that have a duripan that is strongly GCBK. Other Argidurids. cemented or less cemented in all subhorizons. Typic Argidurids Argidic Argidurids Haplodurids GCBG. Other Argidurids that have both: Key to Subgroups 1. A moisture control section that, in normal years, is dry in all parts for less than three-fourths of the time (cumulative) GCCA. Haplodurids that meet both of the following: Aridisols 117

1. Have a duripan that is strongly cemented or less extracted by ammonium oxalate) times 60] plus the cemented in all subhorizons; and volcanic glass (percent) is 30 or more. Vitrixerandic Haplodurids 2. Are either: a. Irrigated and have aquic conditions for some time in GCCF. Other Haplodurids that have, throughout one or more normal years in one or more layers within 100 cm of the horizons with a total thickness of 18 cm or more within 75 cm soil surface; or of the soil surface, one or both of the following: b. Saturated with water in one or more layers within 1. More than 35 percent (by volume) fragments coarser 100 cm of the soil surface for 1 month or more in normal than 2.0 mm, of which more than 66 percent is cinders, years. pumice, and pumicelike fragments; or Aquicambidic Haplodurids 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter, of which 5 percent or GCCB. Other Haplodurids that are either: 1 more is volcanic glass, and [(Al plus /2 Fe, percent extracted 1. Irrigated and have aquic conditions for some time in by ammonium oxalate) times 60] plus the volcanic glass normal years in one or more layers within 100 cm of the soil (percent) is 30 or more. surface; or Vitrandic Haplodurids A R 2. Saturated with water in one or more layers within 100 GCCG. Other Haplodurids that have a mean annual soil I cm of the soil surface for 1 month or more in normal years. temperature lower than 22 oC, a difference of 5 oC or more Aquic Haplodurids between mean summer and mean winter soil temperatures at a depth of 50 cm, and a soil moisture regime that borders on GCCC. Other Haplodurids that have both: xeric. 1. A duripan that is strongly cemented or less cemented in Xeric Haplodurids all subhorizons; and GCCH. Other Haplodurids that, in normal years, are dry in all o 2. A mean annual soil temperature lower than 22 C, a parts of the moisture control section for less than three-fourths o difference of 5 C or more between mean summer and mean of the time (cumulative) when the soil temperature at a depth winter soil temperatures at a depth of 50 cm, and a soil of 50 cm below the soil surface is 5 oC or higher and have a soil moisture regime that borders on xeric. moisture regime that borders on ustic. Xereptic Haplodurids Ustic Haplodurids

GCCD. Other Haplodurids that have a duripan that is strongly GCCI. Other Haplodurids. cemented or less cemented in all subhorizons. Typic Haplodurids Cambidic Haplodurids Natridurids GCCE. Other Haplodurids that have both: Key to Subgroups 1. A moisture control section that, in normal years, is dry in all parts for less than three-fourths of the time (cumulative) GCAA. Natridurids that have one or both of the following: when the soil temperature at a depth of 50 cm below the 1. Cracks between the soil surface and the top of the soil surface is 5 oC or higher and a soil moisture regime that duripan that are 5 mm or more wide through a thickness borders on xeric; and of 30 cm or more for some time in normal years and 2. Throughout one or more horizons with a total thickness slickensides or wedge-shaped peds in a layer 15 cm of 18 cm or more within 75 cm of the soil surface, one or or more thick that is above the duripan; or both of the following: 2. A linear extensibility of 6.0 cm or more between the soil a. More than 35 percent (by volume) fragments coarser surface and the top of the duripan. than 2.0 mm, of which more than 66 percent is cinders, Vertic Natridurids pumice, and pumicelike fragments; or GCAB. Other Natridurids that meet both of the following: b. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter, of which 5 percent 1. Have a duripan that is strongly cemented or less 1 or more is volcanic glass, and [(Al plus /2 Fe, percent cemented in all subhorizons; and 118 Keys to Soil Taxonomy

2. Are either: GCAG. Other Natridurids that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm a. Irrigated and have aquic conditions for some time in of the soil surface, one or both of the following: normal years in one or more layers within 100 cm of the soil surface; or 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, b. Saturated with water in one or more layers within pumice, and pumicelike fragments; or 100 cm of the soil surface for 1 month or more in normal years. 2. A fine-earth fraction containing 30 percent or more Aquic Natrargidic Natridurids particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 more is volcanic glass, and [(Al plus /2 Fe, percent extracted GCAC. Other Natridurids that are either: by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. 1. Irrigated and have aquic conditions for some time in Vitrandic Natridurids normal years in one or more layers within 100 cm of the soil surface; or GCAH. Other Natridurids that, in normal years, are dry in all 2. Saturated with water in one or more layers within 100 parts of the moisture control section for less than three-fourths cm of the soil surface for 1 month or more in normal years. of the time (cumulative) when the soil temperature at a depth Aquic Natridurids of 50 cm below the soil surface is 5 oC or higher and have a soil moisture regime that borders on xeric. GCAD. Other Natridurids that have both: Xeric Natridurids

1. A duripan that is strongly cemented or less cemented in GCAI. Other Natridurids. all subhorizons; and Typic Natridurids 2. A moisture control section that, in normal years, is dry in all parts for less than three-fourths of the time (cumulative) Gypsids when the soil temperature at a depth of 50 cm below the o soil surface is 5 C or higher and a soil moisture regime that Key to Great Groups borders on xeric. Natrixeralfic Natridurids GDA. Gypsids that have a petrogypsic or petrocalcic horizon within 100 cm of the soil surface. GCAE. Other Natridurids that have a duripan that is strongly Petrogypsids, p. 121 cemented or less cemented in all subhorizons. Natrargidic Natridurids GDB. Other Gypsids that have a natric horizon within 100 cm of the soil surface. GCAF. Other Natridurids that have both: Natrigypsids, p. 121

1. A moisture control section that, in normal years, is dry in GDC. Other Gypsids that have an argillic horizon within 100 all parts for less than three-fourths of the time (cumulative) cm of the soil surface. when the soil temperature at a depth of 50 cm below the Argigypsids, p. 118 soil surface is 5 oC or higher and a soil moisture regime that borders on xeric; and GDD. Other Gypsids that have a calcic horizon within 100 cm 2. Throughout one or more horizons with a total thickness of the soil surface. of 18 cm or more within 75 cm of the soil surface, one or Calcigypsids, p. 119 both of the following: GDE. Other Gypsids. a. More than 35 percent (by volume) fragments coarser Haplogypsids, p. 120 than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or Argigypsids b. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter, of which 5 percent Key to Subgroups 1 or more is volcanic glass, and [(Al plus /2 Fe, percent GDCA. Argigypsids that have a lithic contact within 50 cm of extracted by ammonium oxalate) times 60] plus the the soil surface. volcanic glass (percent) is 30 or more. Lithic Argigypsids Vitrixerandic Natridurids Aridisols 119

GDCB. Other Argigypsids that have one or both of the by ammonium oxalate) times 60] plus the volcanic glass following: (percent) is 30 percent or more. Vitrandic Argigypsids 1. Cracks within 125 cm of the soil surface that are 5 mm or more wide through a thickness of 30 cm or more for some GDCG. Other Argigypsids that, in normal years, are dry in all time in normal years and slickensides or wedge-shaped peds parts of the moisture control section for less than three-fourths in a layer 15 cm or more thick that has its upper boundary of the time (cumulative) when the soil temperature at a depth within 125 cm of the soil surface; or of 50 cm below the soil surface is 5 oC or higher and have a soil 2. A linear extensibility of 6.0 cm or more between the soil moisture regime that borders on xeric. surface and either a depth of 100 cm or a densic, lithic, or Xeric Argigypsids paralithic contact, whichever is shallower. Vertic Argigypsids GDCH. Other Argigypsids that, in normal years, are dry in all parts of the moisture control section for less than three-fourths GDCC. Other Argigypsids that have a calcic horizon overlying of the time (cumulative) when the soil temperature at a depth o the gypsic horizon. of 50 cm below the soil surface is 5 C or higher and have a soil Calcic Argigypsids moisture regime that borders on ustic. Ustic Argigypsids A GDCD. Other Argigypsids that have one or more horizons, R within 100 cm of the soil surface and with a combined thickness GDCI. Other Argigypsids. I of 15 cm or more, that contain 20 percent or more (by volume) Typic Argigypsids durinodes, nodules, or concretions. Calcigypsids Petronodic Argigypsids Key to Subgroups GDCE. Other Argigypsids that have both: GDDA. Calcigypsids that have a lithic contact within 50 cm 1. A moisture control section that, in normal years, is dry in of the soil surface. all parts for less than three-fourths of the time (cumulative) Lithic Calcigypsids when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher and a soil moisture regime that GDDB. Other Calcigypsids that have one or more horizons, within 100 cm of the soil surface and with a combined thickness borders on xeric; and of 15 cm or more, that contain 20 percent or more (by volume) 2. Throughout one or more horizons with a total thickness durinodes, nodules, or concretions. of 18 cm or more within 75 cm of the soil surface, one or Petronodic Calcigypsids both of the following: a. More than 35 percent (by volume) fragments coarser GDDC. Other Calcigypsids that have both: than 2.0 mm, of which more than 66 percent is cinders, 1. A moisture control section that, in normal years, is dry in pumice, and pumicelike fragments; or all parts for less than three-fourths of the time (cumulative) b. A fine-earth fraction containing 30 percent or more when the soil temperature at a depth of 50 cm below the o particles 0.02 to 2.0 mm in diameter, of which 5 percent soil surface is 5 C or higher and a soil moisture regime that 1 or more is volcanic glass, and [(Al plus /2 Fe, percent borders on xeric; and extracted by ammonium oxalate) times 60] plus the 2. Throughout one or more horizons with a total thickness volcanic glass (percent) is 30 or more. of 18 cm or more within 75 cm of the soil surface, one or Vitrixerandic Argigypsids both of the following: GDCF. Other Argigypsids that have, throughout one or more a. More than 35 percent (by volume) fragments coarser horizons with a total thickness of 18 cm or more within 75 cm than 2.0 mm, of which more than 66 percent is cinders, of the soil surface, one or both of the following: pumice, and pumicelike fragments; or 1. More than 35 percent (by volume) fragments coarser b. A fine-earth fraction containing 30 percent or more than 2.0 mm, of which more than 66 percent is cinders, particles 0.02 to 2.0 mm in diameter, of which 5 percent pumice, and pumicelike fragments; or 1 or more is volcanic glass, and [(Al plus /2 Fe, percent 2. A fine-earth fraction containing 30 percent or more extracted by ammonium oxalate) times 60] plus the particles 0.02 to 2.0 mm in diameter, of which 5 percent or volcanic glass (percent) is 30 or more. 1 more is volcanic glass, and [(Al plus /2 Fe, percent extracted Vitrixerandic Calcigypsids 120 Keys to Soil Taxonomy

GDDD. Other Calcigypsids that have, throughout one or more GDEE. Other Haplogypsids that have both: horizons with a total thickness of 18 cm or more within 75 cm 1. A moisture control section that, in normal years, is dry in of the soil surface, one or both of the following: all parts for less than three-fourths of the time (cumulative) 1. More than 35 percent (by volume) fragments coarser when the soil temperature at a depth of 50 cm below the than 2.0 mm, of which more than 66 percent is cinders, soil surface is 5 oC or higher and a soil moisture regime that pumice, and pumicelike fragments; or borders on xeric; and 2. A fine-earth fraction containing 30 percent or more 2. Throughout one or more horizons with a total thickness particles 0.02 to 2.0 mm in diameter, of which 5 percent or of 18 cm or more within 75 cm of the soil surface, one or 1 more is volcanic glass, and [(Al plus /2 Fe, percent extracted both of the following: by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. a. More than 35 percent (by volume) fragments coarser Vitrandic Calcigypsids than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or GDDE. Other Calcigypsids that, in normal years, are dry in all b. A fine-earth fraction containing 30 percent or more parts of the moisture control section for less than three-fourths particles 0.02 to 2.0 mm in diameter, of which 5 percent of the time (cumulative) when the soil temperature at a depth 1 or more is volcanic glass, and [(Al plus /2 Fe, percent of 50 cm below the soil surface is 5 oC or higher and have a soil extracted by ammonium oxalate) times 60] plus the moisture regime that borders on xeric. volcanic glass (percent) is 30 or more. Xeric Calcigypsids Vitrixerandic Haplogypsids GDDF. Other Calcigypsids that, in normal years, are dry in all parts of the moisture control section for less than three-fourths GDEF. Other Haplogypsids that have, throughout one or more of the time (cumulative) when the soil temperature at a depth horizons with a total thickness of 18 cm or more within 75 cm of 50 cm below the soil surface is 5 oC or higher and have a soil 0f the soil surface, one or both of the following: moisture regime that borders on ustic. 1. More than 35 percent (by volume) fragments coarser Ustic Calcigypsids than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or GDDG. Other Calcigypsids. Typic Calcigypsids 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 Haplogypsids more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass Key to Subgroups (percent) is 30 or more. GDEA. Haplogypsids that have a lithic contact within 50 cm Vitrandic Haplogypsids of the soil surface. Lithic Haplogypsids GDEG. Other Haplogypsids that, in normal years, are dry in all parts of the moisture control section for less than three- GDEB. Other Haplogypsids that have a gypsic horizon within fourths of the time (cumulative) when the soil temperature at a o 18 cm of the soil surface. depth of 50 cm below the soil surface is 5 C or higher and have Leptic Haplogypsids a soil moisture regime that borders on xeric. Xeric Haplogypsids GDEC. Other Haplogypsids that have, in a horizon at least 25 cm thick within 100 cm of the mineral soil surface, an GDEH. Other Haplogypsids that, in normal years, are dry exchangeable sodium percentage of 15 or more (or an SAR of in all parts of the moisture control section for less than three- 13 or more) during at least 1 month in normal years. fourths of the time (cumulative) when the soil temperature at a Sodic Haplogypsids depth of 50 cm below the soil surface is 5 oC or higher and have a soil moisture regime that borders on ustic. GDED. Other Haplogypsids that have one or more horizons, Ustic Haplogypsids within 100 cm of the soil surface and with a combined thickness of 15 cm or more, that contain 20 percent or more (by volume) GDEI. Other Haplogypsids. durinodes, nodules, or concretions. Typic Haplogypsids Petronodic Haplogypsids Aridisols 121

Natrigypsids 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter, of which 5 percent or Key to Subgroups 1 more is volcanic glass, and [(Al plus /2 Fe, percent extracted GDBA. Natrigypsids that have a lithic contact within 50 cm of by ammonium oxalate) times 60] plus the volcanic glass the soil surface. (percent) is 30 or more. Lithic Natrigypsids Vitrandic Natrigypsids

GDBB. Other Natrigypsids that have one or both of the GDBF. Other Natrigypsids that, in normal years, are dry in all following: parts of the moisture control section for less than three-fourths of the time (cumulative) when the soil temperature at a depth 1. Cracks within 125 cm of the soil surface that are 5 mm of 50 cm below the soil surface is 5 oC or higher and have a soil or more wide through a thickness of 30 cm or more for some moisture regime that borders on xeric. time in normal years and slickensides or wedge-shaped peds Xeric Natrigypsids in a layer 15 cm or more thick that has its upper boundary within 125 cm of the soil surface; or GDBG. Other Natrigypsids that, in normal years, are dry in all 2. A linear extensibility of 6.0 cm or more between the soil parts of the moisture control section for less than three-fourths surface and either a depth of 100 cm or a densic, lithic, or of the time (cumulative) when the soil temperature at a depth o A paralithic contact, whichever is shallower. of 50 cm below the soil surface is 5 C or higher and have a soil R Vertic Natrigypsids moisture regime that borders on ustic. I Ustic Natrigypsids GDBC. Other Natrigypsids that have one or more horizons, within 100 cm of the soil surface and with a combined thickness GDBH. Other Natrigypsids. of 15 cm or more, that contain 20 percent or more (by volume) Typic Natrigypsids durinodes, nodules, or concretions. Petronodic Natrigypsids Petrogypsids

GDBD. Other Natrigypsids that have both: Key to Subgroups 1. A moisture control section that, in normal years, is dry in GDAA. Petrogypsids that have a petrocalcic horizon within all parts for less than three-fourths of the time (cumulative) 100 cm of the soil surface. when the soil temperature at a depth of 50 cm below the Petrocalcic Petrogypsids soil surface is 5 oC or higher and a soil moisture regime that borders on xeric; and GDAB. Other Petrogypsids that have a calcic horizon overlying the petrogypsic horizon. 2. Throughout one or more horizons with a total thickness Calcic Petrogypsids of 18 cm or more within 75 cm of the soil surface, one or of the following: both GDAC. Other Petrogypsids that have both: a. More than 35 percent (by volume) fragments coarser 1. A moisture control section that, in normal years, is dry in than 2.0 mm, of which more than 66 percent is cinders, all parts for less than three-fourths of the time (cumulative) pumice, and pumicelike fragments; or when the soil temperature at a depth of 50 cm below the b. A fine-earth fraction containing 30 percent or more soil surface is 5 oC or higher and a soil moisture regime that particles 0.02 to 2.0 mm in diameter, of which 5 percent borders on xeric; and 1 or more is volcanic glass, and [(Al plus /2 Fe, percent 2. Throughout one or more horizons with a total thickness extracted by ammonium oxalate) times 60] plus the of 18 cm or more within 75 cm of the soil surface, one or volcanic glass (percent) is 30 or more. both of the following: Vitrixerandic Natrigypsids a. More than 35 percent (by volume) fragments coarser GDBE. Other Natrigypsids that have, throughout one or more than 2.0 mm, of which more than 66 percent is cinders, horizons with a total thickness of 18 cm or more within 75 cm pumice, and pumicelike fragments; or of the soil surface, one or both of the following: b. A fine-earth fraction containing 30 percent or more 1. More than 35 percent (by volume) fragments coarser particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 than 2.0 mm, of which more than 66 percent is cinders, or more is volcanic glass, and [(Al plus /2 Fe, percent pumice, and pumicelike fragments; or 122

extracted by ammonium oxalate) times 60] plus the GBB. Other Salids. volcanic glass (percent) is 30 or more. Haplosalids, p. 122 Vitrixerandic Petrogypsids Aquisalids GDAD. Other Petrogypsids that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm Key to Subgroups of the soil surface, one or both of the following: GBAA. Aquisalids that have a gypsic or petrogypsic horizon 1. More than 35 percent (by volume) fragments coarser within 100 cm of the soil surface. than 2.0 mm, of which more than 66 percent is cinders, Gypsic Aquisalids pumice, and pumicelike fragments; or GBAB. Other Aquisalids that have a calcic or petrocalcic 2. A fine-earth fraction containing 30 percent or more horizon within 100 cm of the soil surface. particles 0.02 to 2.0 mm in diameter, of which 5 percent or Calcic Aquisalids 1 more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass GBAC. Other Aquisalids. (percent) is 30 or more. Typic Aquisalids Vitrandic Petrogypsids Haplosalids GDAE. Other Petrogypsids that, in normal years, are dry in all parts of the moisture control section for less than three-fourths Key to Subgroups of the time (cumulative) when the soil temperature at a depth GBBA. Haplosalids that have a duripan within 100 cm of the o of 50 cm below the soil surface is 5 C or higher and have a soil soil surface. moisture regime that borders on xeric. Duric Haplosalids Xeric Petrogypsids GBBB. Other Haplosalids that have a petrogypsic horizon GDAF. Other Petrogypsids that, in normal years, are dry in all within 100 cm of the soil surface. parts of the moisture control section for less than three-fourths Petrogypsic Haplosalids of the time (cumulative) when the soil temperature at a depth o of 50 cm below the soil surface is 5 C or higher and have a soil GBBC. Other Haplosalids that have a gypsic horizon within moisture regime that borders on ustic. 100 cm of the soil surface. Ustic Petrogypsids Gypsic Haplosalids

GDAG. Other Petrogypsids. GBBD. Other Haplosalids that have a calcic horizon within Typic Petrogypsids 100 cm of the soil surface. Calcic Haplosalids Salids GBBE. Other Haplosalids. Key to Great Groups Typic Haplosalids GBA. Salids that are saturated with water in one or more layers within 100 cm of the mineral soil surface for 1 month or more in normal years. Aquisalids, p. 122 123

CHAPTER 8 Entisols

Key to Suborders c. Enough active ferrous iron to give a positive reaction to alpha,alpha-dipyridyl at a time when the soil is not LA. Entisols that have a positive water potential at the soil being irrigated. surface for more than 21 hours of each day in all years. Aquents, p. 124 Wassents, p. 142 LC. Other Entisols that have, in one or more layers at a depth LB. Other Entisols that have one or more of the following: between 25 and 100 cm below the mineral soil surface, 3 1. Aquic conditions and sulfidic materials within 50 cm of percent or more (by volume) fragments of diagnostic horizons the mineral soil surface; or that are not arranged in any discernible order. Arents, p. 127 2. Permanent saturation with water and a reduced matrix in all horizons below 25 cm from the mineral soil surface; or E LD. Other Entisols that have less than 35 percent (by volume) N 3. In a layer above a densic, lithic, or paralithic contact or rock fragments and a texture class of loamy fine sand or coarser T in a layer at a depth between 40 and 50 cm below the mineral in all layers (sandy loam lamellae are permitted) within the soil surface, whichever is shallower, aquic conditions for particle-size control section. some time in normal years (or artificial drainage) andone or Psamments, p. 138 more of the following: a. A texture class finer than loamy fine sand and, in LE. Other Entisols that do not have a densic, lithic, or 50 percent or more of the matrix, one or more of the paralithic contact within 25 cm of the mineral soil surface and following: have: (1) Chroma of 0; or 1. A slope of less than 25 percent; and (2) Chroma of 1 or less and a color value, moist, of 4 2. One or both of the following: or more; or a. An organic-carbon content (Holocene age) of 0.2 (3) Chroma of 2 or less and redox concentrations; or percent or more at a depth of 125 cm below the mineral soil surface; or b. A texture class of loamy fine sand or coarser and, in 50 percent or more of the matrix, one or more of the b. An irregular decrease in organic-carbon content following: (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or (1) Chroma of 0; or a densic, lithic, or paralithic contact, whichever is (2) Hue of 10YR or redder, a color value, moist, of 4 shallower; and or more, and chroma of 1; or 3. A soil temperature regime: (3) Hue of 10YR or redder, chroma of 2 or less, and a. That is warmer than cryic; or redox concentrations; or b. That is cryic and the soil has: (4) Hue of 2.5Y or yellower, chroma of 3 or less, and distinct or prominent redox concentrations; or (1) No gelic materials; and (5) Hue of 2.5Y or yellower and chroma of 1; or (2) Either a slope of less than 5 percent or less than 15 percent volcanic glass in the 0.02 to 2.0 mm (6) Hue of 5GY, 5G, 5BG, or 5B; or fraction in some part of the particle-size control (7) Any color if it results from uncoated sand grains; section. or Fluvents, p. 128 124 Keys to Soil Taxonomy

LF. Other Entisols. 1. A fine-earth fraction with both a bulk density of 1.0 Orthents, p. 133 g/cm3 or less, measured at 33 kPa water retention, and Al 1 plus /2 Fe percentages (by ammonium oxalate) totaling more Aquents than 1.0; or Key to Great Groups 2. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, LBA. Aquents that have sulfidic materials within 50 cm of the pumice, and pumicelike fragments; or mineral soil surface. 3. A fine-earth fraction containing 30 percent or more Sulfaquents, p. 127 particles 0.02 to 2.0 mm in diameter; and LBB. Other Aquents that have, in all horizons at a depth a. In the 0.02 to 2.0 mm fraction, 5 percent or more between 20 and 50 cm below the mineral soil surface, both an volcanic glass; and n value of more than 0.7 and 8 percent or more clay in the fine- 1 b. [(Al plus /2 Fe, percent extracted by ammonium earth fraction. oxalate) times 60] plus the volcanic glass (percent) is Hydraquents, p. 126 equal to 30 or more. Aquandic Cryaquents LBC. Other Aquents that have a gelic soil temperature regime. Gelaquents, p. 126 LBDB. Other Cryaquents. Typic Cryaquents LBD. Other Aquents that have a cryic soil temperature regime. Cryaquents, p. 124 Endoaquents LBE. Other Aquents that have less than 35 percent (by Key to Subgroups volume) rock fragments and a texture class of loamy fine sand or coarser in all layers (sandy loam lamellae are permitted) LBHA. Endoaquents that have, within 100 cm of the mineral within the particle-size control section. soil surface, one or both of the following: Psammaquents, p. 126 1. Sulfidic materials; or

LBF. Other Aquents that have both: 2. A horizon 15 cm or more thick that has all of the characteristics of a sulfuric horizon, except that it has a pH 1. A slope of less than 25 percent; and value between 3.5 and 4.0 and does not have sulfide or other 2. One or both of the following: sulfur-bearing minerals. Sulfic Endoaquents a. At a depth of 125 cm below the mineral soil surface, an organic-carbon content (Holocene age) of 0.2 percent LBHB. Other Endoaquents that have a lithic contact within 50 or more; or cm of the mineral soil surface. b. An irregular decrease in organic-carbon content Lithic Endoaquents (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a LBHC. Other Endoaquents that have, in one or more horizons densic, lithic, or paralithic contact, whichever is shallower. within 100 cm of the mineral soil surface, an exchangeable Fluvaquents, p. 125 sodium percentage of 15 or more (or a sodium adsorption ratio of 13 or more) for 6 or more months in normal years. LBG. Other Aquents that have episaturation. Sodic Endoaquents Epiaquents, p. 125 LBHD. Other Endoaquents that have, in one or more horizons LBH. Other Aquents. between either the Ap horizon or a depth of 25 cm from the Endoaquents, p. 124 mineral soil surface, whichever is deeper, and a depth of 75 cm, colors in 50 percent or more of the matrix as follows: Cryaquents 1. Hue of 2.5Y or redder, a color value, moist, of 6 or more, and chroma of 3 or more; or Key to Subgroups 2. Hue of 2.5Y or redder, a color value, moist, of 5 or less, LBDA. Cryaquents that have, throughout one or more and chroma of 2 or more; or horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or more of the following: 3. Hue of 5Y and chroma of 3 or more; or Entisols 125

4. Hue of 5Y or redder and chroma of 2 or more if there are mineral soil (unmixed) or between the mineral soil surface and a no redox concentrations. depth of 15 cm after mixing. Aeric Endoaquents Mollic Epiaquents

LBHE. Other Endoaquents that have both: LBGD. Other Epiaquents. Typic Epiaquents 1. A color value, moist, of 3 or less and a color value, dry, of 5 or less (crushed and smoothed sample) either throughout the upper 15 cm of the mineral soil (unmixed) or between the Fluvaquents mineral soil surface and a depth of 15 cm after mixing; and Key to Subgroups

2. A base saturation (by NH4OAc) of less than 50 percent LBFA. Fluvaquents that have, within 100 cm of the mineral in some part within 100 cm of the mineral soil surface. soil surface, one or both of the following: Humaqueptic Endoaquents 1. Sulfidic materials; or LBHF. Other Endoaquents that have a color value, moist, 2. A horizon 15 cm or more thick that has all of the of 3 or less and a color value, dry, of 5 or less (crushed and characteristics of a sulfuric horizon, except that it has a pH smoothed sample) either throughout the upper 15 cm of the value between 3.5 and 4.0 and does not have sulfide or other mineral soil (unmixed) or between the mineral soil surface and a sulfur-bearing minerals. depth of 15 cm after mixing. Sulfic Fluvaquents Mollic Endoaquents E LBFB. Other Fluvaquents that have one or both of the N LBHG. Other Endoaquents. following: T Typic Endoaquents 1. Cracks within 125 cm of the mineral soil surface that are Epiaquents 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge- Key to Subgroups shaped peds in a layer 15 cm or more thick that has its upper LBGA. Epiaquents that have, in one or more horizons boundary within 125 cm of the mineral soil surface; or between either the Ap horizon or a depth of 25 cm from the 2. A linear extensibility of 6.0 cm or more between the mineral soil surface, whichever is deeper, and a depth of 75 cm, mineral soil surface and either a depth of 100 cm or a densic, colors in 50 percent or more of the matrix as follows: lithic, or paralithic contact, whichever is shallower. 1. Hue of 2.5Y or redder, a color value, moist, of 6 or Vertic Fluvaquents more, and chroma of 3 or more; or LBFC. Other Fluvaquents that have a buried layer of organic 2. Hue of 2.5Y or redder, a color value, moist, of 5 or less, soil materials, 20 cm or more thick, within 100 cm of the and chroma of 2 or more; or mineral soil surface. 3. Hue of 5Y and chroma of 3 or more; or Thapto-Histic Fluvaquents 4. Chroma of 2 or more if there are no redox concentrations. LBFD. Other Fluvaquents that have, throughout one or more Aeric Epiaquents horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or more of the following: LBGB. Other Epiaquents that have both: 1. A fine-earth fraction with both a bulk density of 1.0 3 1. A color value, moist, of 3 or less and a color value, dry, g/cm or less, measured at 33 kPa water retention, and Al 1 of 5 or less (crushed and smoothed sample) either throughout plus /2 Fe percentages (by ammonium oxalate) totaling more the upper 15 cm of the mineral soil (unmixed) or between the than 1.0; or mineral soil surface and a depth of 15 cm after mixing; and 2. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, 2. A base saturation (by NH4OAc) of less than 50 percent in some part within 100 cm of the mineral soil surface. pumice, and pumicelike fragments; or Humaqueptic Epiaquents 3. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and LBGC. Other Epiaquents that have a color value, moist, of 3 or less and a color value, dry, of 5 or less (crushed and a. In the 0.02 to 2.0 mm fraction, 5 percent or more smoothed sample) either throughout the upper 15 cm of the volcanic glass; and 126 Keys to Soil Taxonomy

1 b. [(Al plus /2 Fe, percent extracted by ammonium 1. Sulfidic materials;or oxalate) times 60] plus the volcanic glass (percent) is 2. A horizon 15 cm or more thick that has all of the equal to 30 or more. characteristics of a sulfuric horizon, except that it has a pH Aquandic Fluvaquents value between 3.5 and 4.0 and does not have sulfide or other sulfur-bearing minerals. LBFE. Other Fluvaquents that have, in one or more horizons Sulfic Hydraquents between either the Ap horizon or a depth of 25 cm from the mineral soil surface, whichever is deeper, and a depth of 75 cm, LBBB. Other Hydraquents that have, in one or more horizons colors in 50 percent or more of the matrix as follows: within 100 cm of the mineral soil surface, an exchangeable 1. Hue of 2.5Y or redder, a color value, moist, of 6 or sodium percentage of 15 or more (or a sodium adsorption ratio more, and chroma of 3 or more; or of 13 or more) for 6 or more months in normal years. Sodic Hydraquents 2. Hue of 2.5Y or redder, a color value, moist, of 5 or less, and chroma of 2 or more; or LBBC. Other Hydraquents that have a buried layer of organic 3. Hue of 5Y and chroma of 3 or more; or soil materials, 20 cm or more thick, within 100 cm of the mineral soil surface. 4. Chroma of 2 or more if there are no redox Thapto-Histic Hydraquents concentrations. Aeric Fluvaquents LBBD. Other Hydraquents. Typic Hydraquents LBFF. Other Fluvaquents that have both: 1. A color value, moist, of 3 or less and a color value, Psammaquents dry, of 5 or less (crushed and smoothed sample) either Key to Subgroups throughout the upper 15 cm of the mineral soil (unmixed) or between the mineral soil surface and a depth of 15 cm after LBEA. Psammaquents that have a lithic contact within 50 cm mixing; and of the mineral soil surface. Lithic Psammaquents 2. A base saturation (by NH4OAc) of less than 50 percent in some part within 100 cm of the mineral soil surface. LBEB. Other Psammaquents that have, in one or more Humaqueptic Fluvaquents horizons within 100 cm of the mineral soil surface, an exchangeable sodium percentage of 15 or more (or a sodium LBFG. Other Fluvaquents that have a color value, moist, adsorption ratio of 13 or more) for 6 or more months in normal of 3 or less and a color value, dry, of 5 or less (crushed and years. smoothed sample) either throughout the upper 15 cm of the Sodic Psammaquents mineral soil (unmixed) or between the mineral soil surface and a depth of 15 cm after mixing. LBEC. Other Psammaquents that have a horizon, 5 cm or Mollic Fluvaquents more thick, either below an Ap horizon or at a depth of 18 cm or more from the mineral soil surface, whichever is deeper, that LBFH. Other Fluvaquents. has one or more of the following: Typic Fluvaquents 1. In 25 percent or more of each pedon, cementation by Gelaquents organic matter and aluminum, with or without iron; or 1 Key to Subgroups 2. Al plus /2 Fe percentages (by ammonium oxalate) totaling 0.25 or more, and half that amount or less in an LBCA. All Gelaquents. overlying horizon; or Typic Gelaquents 3. An ODOE value of 0.12 or more, and a value half as Hydraquents high or lower in an overlying horizon. Spodic Psammaquents Key to Subgroups LBED. Other Psammaquents that have both: LBBA. Hydraquents that have, within 100 cm of the mineral soil surface, one or both of the following: 1. A color value, moist, of 3 or less and a color value, dry, Entisols 127

of 5 or less (crushed and smoothed sample) either throughout Torriarents the upper 15 cm of the mineral soil (unmixed) or between the mineral soil surface and a depth of 15 cm after mixing; and Key to Subgroups LCCA. Torriarents that have, in one or more horizons within 2. A base saturation (by NH4OAc) of less than 50 percent in some part within 100 cm of the mineral soil surface. 100 cm of the mineral soil surface, 3 percent or more fragments Humaqueptic Psammaquents of a natric horizon. Sodic Torriarents LBEE. Other Psammaquents that have a color value, moist, of 3 or less and a color value, dry, of 5 or less (crushed and LCCB. Other Torriarents that have, within 100 cm of the smoothed sample) either throughout the upper 15 cm of the mineral soil surface, 3 percent or more fragments of a duripan mineral soil (unmixed) or between the mineral soil surface and a or a petrocalcic horizon. depth of 15 cm after mixing. Duric Torriarents Mollic Psammaquents LCCC. Other Torriarents. LBEF. Other Psammaquents. Haplic Torriarents Typic Psammaquents Udarents Sulfaquents Key to Subgroups Key to Subgroups LCDA. Udarents that have 3 percent or more fragments of an E LBAA. Sulfaquents that have, in some horizons at a depth argillic horizon in some horizon within 100 cm of the mineral N T between 20 and 50 cm below the mineral soil surface, either or soil surface and have a base saturation (by sum of cations) of 35 both: percent or more in all parts within 100 cm of the mineral soil surface. 1. An n value of 0.7 or less; or Alfic Udarents 2. Less than 8 percent clay in the fine-earth fraction. Haplic Sulfaquents LCDB. Other Udarents that have 3 percent or more fragments of an argillic horizon in some horizon within 100 cm of the LBAB. Other Sulfaquents that have a histic epipedon. mineral soil surface. Histic Sulfaquents Ultic Udarents

LBAC. Other Sulfaquents that have a buried layer of organic LCDC. Other Udarents that have 3 percent or more fragments soil materials, 20 cm or more thick, within 100 cm of the of a mollic epipedon in some horizon within 100 cm of the mineral soil surface. mineral soil surface and have a base saturation (by sum of Thapto-Histic Sulfaquents cations) of 35 percent or more in all parts within 100 cm of the mineral soil surface. LBAD. Other Sulfaquents. Mollic Udarents Typic Sulfaquents LCDD. Other Udarents. Arents Haplic Udarents Key to Great Groups Ustarents LCA. Arents that have an ustic soil moisture regime. Key to Subgroups Ustarents, p. 127 LCAA. All Ustarents. LCB. Other Arents that have a xeric soil moisture regime. Haplic Ustarents Xerarents, p. 127 Xerarents LCC. Other Arents that have an aridic (or torric) soil moisture Key to Subgroups regime. Torriarents, p. 127 LCBA. Xerarents that have, in one or more horizons within 100 cm of the mineral soil surface, 3 percent or more fragments LCD. Other Arents. of a natric horizon. Udarents, p. 127 Sodic Xerarents 128 Keys to Soil Taxonomy

LCBB. Other Xerarents that have, within 100 cm of the 2. A fine-earth fraction containing 30 percent or more mineral soil surface, 3 percent or more fragments of a duripan particles 0.02 to 2.0 mm in diameter; and or a petrocalcic horizon. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Duric Xerarents volcanic glass; and

1 LCBC. Other Xerarents that have fragments of an argillic b. [(Al plus /2 Fe, percent extracted by ammonium horizon with a base saturation (by sum of cations) of 35 percent oxalate) times 60] plus the volcanic glass (percent) is or more within 100 cm of the mineral soil surface. equal to 30 or more. Alfic Xerarents Vitrandic Cryofluvents

LCBD. Other Xerarents. LEBC. Other Cryofluvents that have, in one or more horizons Haplic Xerarents within 50 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in Fluvents normal years (or artificial drainage). Aquic Cryofluvents Key to Great Groups LEBD. Other Cryofluvents that are saturated with water in LEA. Fluvents that that have a gelic soil temperature regime. one or more layers within 100 cm of the mineral soil surface in Gelifluvents, p. 128 normal years for either or both: 1. 20 or more consecutive days; or LEB. Other Fluvents that have a cryic soil temperature regime. 2. 30 or more cumulative days. Cryofluvents, p. 128 Oxyaquic Cryofluvents

LEC. Other Fluvents that have a xeric soil moisture regime. LEBE. Other Cryofluvents that have a color value, moist, Xerofluvents, p. 132 of 3 or less and a color value, dry, of 5 or less (crushed and smoothed sample) either throughout the upper 15 cm of the LED. Other Fluvents that have an ustic soil moisture regime. mineral soil (unmixed) or between the mineral soil surface and a Ustifluvents, p. 131 depth of 15 cm after mixing. Mollic Cryofluvents LEE. Other Fluvents that have an aridic (or torric) soil moisture regime. LEBF. Other Cryofluvents. Torrifluvents, p. 128 Typic Cryofluvents

LEF. Other Fluvents. Gelifluvents Udifluvents, p. 130 Key to Subgroups Cryofluvents LEAA. Gelifluvents that have, in one or more horizons within 100 cm of the mineral soil surface, both redox depletions with Key to Subgroups chroma of 2 or less and aquic conditions for some time in LEBA. Cryofluvents that have, throughout one or more normal years (or artificial drainage). horizons with a total thickness of 18 cm or more within 75 Aquic Gelifluvents cm of the mineral soil surface, a fine-earth fraction with both LEAB. Other Gelifluvents. a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water Typic Gelifluvents 1 retention, and percent aluminum plus /2 the iron percentage (by ammonium oxalate) totaling more than 1.0. Torrifluvents Andic Cryofluvents Key to Subgroups LEBB. Other Cryofluvents that have, throughout one or more LEEA. Torrifluvents that have: horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: 1. One or both of the following: 1. More than 35 percent (by volume) fragments coarser a. Cracks within 125 cm of the mineral soil surface that than 2.0 mm, of which more than 66 percent is cinders, are 5 mm or more wide through a thickness of 30 cm or pumice, and pumicelike fragments; or more for some time in normal years and slickensides or Entisols 129

wedge-shaped peds in a layer 15 cm or more thick that LEED. Other Torrifluvents that have, throughout one or more has its upper boundary within 125 cm of the mineral soil horizons with a total thickness of 18 cm or more within 75 cm surface; or of the mineral soil surface, one or both of the following: b. A linear extensibility of 6.0 cm or more between 1. More than 35 percent (by volume) fragments coarser the mineral soil surface and either a depth of 100 cm than 2.0 mm, of which more than 66 percent is cinders, or a densic, lithic, or paralithic contact, whichever is pumice, and pumicelike fragments; or shallower; and 2. A fine-earth fraction containing 30 percent or more 2. A moisture control section that, in normal years, is dry in particles 0.02 to 2.0 mm in diameter; and all parts for less than three-fourths of the cumulative days per a. In the 0.02 to 2.0 mm fraction, 5 percent or more year when the soil temperature at a depth of 50 cm below the volcanic glass; and soil surface is 5 oC or higher; and 1 b. [(Al plus /2 Fe, percent extracted by ammonium 3. An aridic (or torric) soil moisture regime that borders on oxalate) times 60] plus the volcanic glass (percent) is ustic. equal to 30 or more. Ustertic Torrifluvents Vitrandic Torrifluvents LEEB. Other Torrifluvents that have one or both of the LEEE. Other Torrifluvents that have, in one or more horizons following: within 100 cm of the soil surface, both redox depletions with 1. Cracks within 125 cm of the soil surface that are 5 mm chroma of 2 or less and aquic conditions for some time in or more wide through a thickness of 30 cm or more for normal years (or artificial drainage). E N some time in most normal years and slickensides or wedge- Aquic Torrifluvents T shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the soil surface; or LEEF. Other Torrifluvents that are saturated with water in one or more layers within 150 cm of the soil surface in normal years 2. A linear extensibility of 6.0 cm or more between the soil for either or both: surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. 1. 20 or more consecutive days; or Vertic Torrifluvents 2. 30 or more cumulative days. Oxyaquic Torrifluvents LEEC. Other Torrifluvents that have: 1. A moisture control section that, in normal years, is dry in LEEG. Other Torrifluvents that have: all parts for less than three-fourths of the cumulative days per 1. A horizon within 100 cm of the mineral soil surface that year when the soil temperature at a depth of 50 cm below the is 15 cm or more thick and that either has 20 percent or more soil surface is 5 oC or higher; and (by volume) durinodes or is brittle and has at least a firm 2. A thermic, mesic, or frigid soil temperature regime and rupture-resistance class when moist; and an aridic (or torric) soil moisture regime that borders on xeric; and 2. A moisture control section that, in normal years, is dry in all parts for less than three-fourths of the cumulative days per 3. Throughout one or more horizons with a total thickness year when the soil temperature at a depth of 50 cm below the of 18 cm or more within 75 cm of the mineral soil surface, soil surface is 5 oC or higher; and one or both of the following: 3. A thermic, mesic, or frigid soil temperature regime and a. More than 35 percent (by volume) fragments coarser an aridic (or torric) soil moisture regime that borders on than 2.0 mm, of which more than 66 percent is cinders, xeric. pumice, and pumicelike fragments; or Duric Xeric Torrifluvents b. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and LEEH. Other Torrifluvents that have a horizon within 100 cm of the mineral soil surface that is 15 cm or more thick and that (1) In the 0.02 to 2.0 mm fraction, 5 percent or more either has 20 percent or more (by volume) durinodes or is brittle volcanic glass; and and has at least a firm rupture-resistance class when moist. 1 (2) [(Al plus /2 Fe, percent extracted by ammonium Duric Torrifluvents oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. LEEI. Other Torrifluvents that have both: Vitrixerandic Torrifluvents 130 Keys to Soil Taxonomy

1. A moisture control section that, in normal years, is dry in LEFB. Other Udifluvents that haveone or both of the all parts for less than three-fourths of the cumulative days per following: year when the soil temperature at a depth of 50 cm below the 1. Cracks within 125 cm of the mineral soil surface that are soil surface is 5 oC or higher; and 5 mm or more wide through a thickness of 30 cm or more 2. An aridic (or torric) soil moisture regime that borders on for some time in normal years and slickensides or wedge- ustic. shaped peds in a layer 15 cm or more thick that has its upper Ustic Torrifluvents boundary within 125 cm of the mineral soil surface; or

LEEJ. Other Torrifluvents that haveboth : 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a densic, 1. A moisture control section that, in normal years, is dry in lithic, or paralithic contact, whichever is shallower. all parts for less than three-fourths of the cumulative days per Vertic Udifluvents year when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher; and LEFC. Other Udifluvents that have, throughout one or more 2. A thermic, mesic, or frigid soil temperature regime and horizons with a total thickness of 18 cm or more within 75 cm an aridic (or torric) soil moisture regime that borders on of the mineral soil surface, a fine-earth fraction with both a bulk 3 xeric. density of 1.0 g/cm or less, measured at 33 kPa water retention, 1 Xeric Torrifluvents and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. LEEK. Other Torrifluvents that have an anthropic epipedon. Andic Udifluvents Anthropic Torrifluvents LEFD. Other Udifluvents that have, throughout one or more LEEL. Other Torrifluvents. horizons with a total thickness of 18 cm or more within 75 cm Typic Torrifluvents of the mineral soil surface, one or both of the following: 1. More than 35 percent (by volume) fragments coarser Udifluvents than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; Key to Subgroups or LEFA. Udifluvents that haveboth : 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and 1. One or both of the following: a. In the 0.02 to 2.0 mm fraction, 5 percent or more a. Cracks within 125 cm of the mineral soil surface that volcanic glass; and are 5 mm or more wide through a thickness of 30 cm or 1 more for some time in normal years and slickensides or b. [(Al plus /2 Fe, percent extracted by ammonium wedge-shaped peds in a layer 15 cm or more thick that oxalate) times 60] plus the volcanic glass (percent) is has its upper boundary within 125 cm of the mineral soil equal to 30 or more. surface; or Vitrandic Udifluvents

b. A linear extensibility of 6.0 cm or more between LEFE. Other Udifluvents that haveeither : the mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is 1. In one or more horizons within 50 cm of the mineral soil shallower; and surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial 2. of the following: Either or both drainage); or a. In one or more horizons within 50 cm of the mineral 2. In one or more horizons within 100 cm of the mineral soil surface, redox depletions with chroma of 2 or less and soil surface, a color value, moist, of 4 or more and either also aquic conditions for some time in normal years (or chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and also aquic artificial drainage);or conditions for some time in normal years (or artificial b. In one or more horizons within 100 cm of the mineral drainage). soil surface, a color value, moist, of 4 or more and Aquic Udifluvents either chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and also aquic conditions for some time in normal years (or LEFF. Other Udifluvents that are saturated with water in one artificial drainage). or more layers within 100 cm of the mineral soil surface in Aquertic Udifluvents normal years for either or both: Entisols 131

1. 20 or more consecutive days; or b. A mesic or thermic soil temperature regime and a moisture control section that, in normal years, is dry in 2. 30 or more cumulative days. some part for six-tenths or more of the cumulative days Oxyaquic Udifluvents per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or LEFG. Other Udifluvents that have a color value, moist, of 3 or less and a color value, dry, of 5 or less (crushed and c. A hyperthermic, isomesic, or warmer iso soil smoothed sample) either throughout the upper 15 cm of the temperature regime and a moisture control section that, mineral soil (unmixed) or between the mineral soil surface and a in normal years, remains moist in some or all parts for depth of 15 cm after mixing. less than 90 consecutive days per year when the soil Mollic Udifluvents temperature at a depth of 50 cm below the soil surface is higher than 8 oC; and LEFH. Other Udifluvents. 2. One or both of the following: Typic Udifluvents a. Cracks within 125 cm of the mineral soil surface that Ustifluvents are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or Key to Subgroups wedge-shaped peds in a layer 15 cm or more thick that LEDA. Ustifluvents that haveboth : has its upper boundary within 125 cm of the mineral soil surface; or 1. One or both of the following: b. A linear extensibility of 6.0 cm or more between the E a. Cracks within 125 cm of the mineral soil surface that N mineral soil surface and either a depth of 100 cm or a T are 5 mm or more wide through a thickness of 30 cm or densic, lithic, or paralithic contact, whichever is shallower. more for some time in normal years and slickensides or Torrertic Ustifluvents wedge-shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil LEDC. Other Ustifluvents that haveone or both of the surface; or following: b. A linear extensibility of 6.0 cm or more between 1. Cracks within 125 cm of the mineral soil surface that are the mineral soil surface and either a depth of 100 cm 5 mm or more wide through a thickness of 30 cm or more or a densic, lithic, or paralithic contact, whichever is for some time in normal years and slickensides or wedge- shallower; and shaped peds in a layer 15 cm or more thick that has its upper 2. Either or both of the following: boundary within 125 cm of the mineral soil surface; or a. In one or more horizons within 50 cm of the mineral 2. A linear extensibility of 6.0 cm or more between the soil surface, redox depletions with chroma of 2 or less and mineral soil surface and either a depth of 100 cm or a densic, also aquic conditions for some time in normal years (or lithic, or paralithic contact, whichever is shallower. artificial drainage);or Vertic Ustifluvents b. In one or more horizons within 150 cm of the mineral LEDD. Other Ustifluvents that have anthraquic conditions. soil surface, a color value, moist, of 4 or more and Anthraquic Ustifluvents either chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and also aquic conditions for some time in normal years (or LEDE. Other Ustifluvents that haveeither : artificial drainage). Aquertic Ustifluvents 1. In one or more horizons within 50 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also LEDB. Other Ustifluvents that haveboth of the following: aquic conditions for some time in normal years (or artificial 1. When neither irrigated nor fallowed to store moisture, drainage); or one of the following: 2. In one or more horizons within 150 cm of the mineral a. A frigid soil temperature regime and a moisture soil surface, a color value, moist, of 4 or more and either control section that, in normal years, is dry in all parts for chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and also aquic four-tenths or more of the cumulative days per year when conditions for some time in normal years (or artificial the soil temperature at a depth of 50 cm below the soil drainage). surface is higher than 5 oC; or Aquic Ustifluvents 132 Keys to Soil Taxonomy

LEDF. Other Ustifluvents that are saturated with water in mineral soil (unmixed) or between the mineral soil surface and a one or more layers within 150 cm of the mineral soil surface in depth of 15 cm after mixing. normal years for either or both: Mollic Ustifluvents 1. 20 or more consecutive days; or LEDJ. Other Ustifluvents. 2. 30 or more cumulative days. Typic Ustifluvents

Oxyaquic Ustifluvents Xerofluvents

LEDG. Other Ustifluvents that, when neither irrigated nor Key to Subgroups fallowed to store moisture, have one of the following: LECA. Xerofluvents that haveone or both of the following: 1. A frigid soil temperature regime and a moisture control 1. Cracks within 125 cm of the mineral soil surface that are section that, in normal years, is dry in all parts for four- 5 mm or more wide through a thickness of 30 cm or more tenths or more of the cumulative days per year when the soil for some time in normal years and slickensides or wedge- temperature at a depth of 50 cm below the soil surface is shaped peds in a layer 15 cm or more thick that has its upper higher than 5 oC; or boundary within 125 cm of the mineral soil surface; or 2. A mesic or thermic soil temperature regime and a 2. A linear extensibility of 6.0 cm or more between the moisture control section that, in normal years, is dry in some mineral soil surface and either a depth of 100 cm or a densic, part for six-tenths or more of the cumulative days per year lithic, or paralithic contact, whichever is shallower. when the soil temperature at a depth of 50 cm below the soil Vertic Xerofluvents surface is higher than 5 oC; or 3. A hyperthermic, isomesic, or warmer iso soil LECB. Other Xerofluvents that have: temperature regime and a moisture control section that, in 1. In one or more horizons within 50 cm of the mineral soil normal years, is moist in some or all parts for less than 180 surface, redox depletions with chroma of 2 or less and also cumulative days per year when the soil temperature at a aquic conditions for some time in normal years (or artificial depth of 50 cm below the soil surface is higher than 8 oC. drainage); or Aridic Ustifluvents 2. In one or more horizons within 150 cm of the mineral LEDH. Other Ustifluvents that, when neither irrigated nor soil surface, a color value, moist, of 4 or more and either chroma of 0 or hue bluer than 10Y and also aquic conditions fallowed to store moisture, have one of the following: for some time in normal years (or artificial drainage);and 1. A frigid soil temperature regime and a moisture control section that, in normal years, is dry in some or all parts 3. Throughout one or more horizons with a total thickness for less than 105 cumulative days per year when the soil of 18 cm or more within 75 cm of the mineral soil surface, temperature at a depth of 50 cm below the soil surface is one or more of the following: higher than 5 oC; or a. A fine-earth fraction with both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water retention, and Al 2. A mesic or thermic soil temperature regime and a 1 moisture control section that, in normal years, is dry in some plus /2 Fe percentages (by ammonium oxalate) totaling part for less than four-tenths of the cumulative days per year more than 1.0; or when the soil temperature at a depth of 50 cm below the soil b. More than 35 percent (by volume) fragments coarser surface is higher than 5 oC; or than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; 3. A hyperthermic, isomesic, or warmer iso soil or temperature regime and a moisture control section that, in c. A fine-earth fraction containing 30 percent or more normal years, is dry in some or all parts for less than 120 particles 0.02 to 2.0 mm in diameter; and cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 8 oC. (1) In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; Udic Ustifluvents and 1 (2) [(Al plus /2 Fe, percent extracted by ammonium LEDI. Other Ustifluvents that have a color value, moist, oxalate) times 60] plus the volcanic glass (percent) is of 3 or less and a color value, dry, of 5 or less (crushed and equal to 30 or more. smoothed sample) either throughout the upper 15 cm of the Aquandic Xerofluvents Entisols 133

LECC. Other Xerofluvents that have, throughout one or more mineral soil (unmixed) or between the mineral soil surface and a horizons with a total thickness of 18 cm or more within 75 cm depth of 15 cm after mixing. of the mineral soil surface, a fine-earth fraction with both a bulk Mollic Xerofluvents density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling LECI. Other Xerofluvents. more than 1.0. Typic Xerofluvents Andic Xerofluvents Orthents LECD. Other Xerofluvents that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm Key to Great Groups of the mineral soil surface, one or both of the following: LFA. Orthents that have a gelic soil temperature regime. 1. More than 35 percent (by volume) fragments coarser Gelorthents, p. 134 than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or LFB. Other Orthents that have a cryic soil temperature regime. Cryorthents, p. 133 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and LFC. Other Orthents that have an aridic (or torric) soil a. In the 0.02 to 2.0 mm fraction, 5 percent or more moisture regime. volcanic glass; and Torriorthents, p. 134

1 E b. [(Al plus /2 Fe, percent extracted by ammonium LFD. Other Orthents that have a xeric soil moisture regime. N oxalate) times 60] plus the volcanic glass (percent) is Xerorthents, p. 138 T equal to 30 or more. Vitrandic Xerofluvents LFE. Other Orthents that have an ustic soil moisture regime. Ustorthents, p. 136 LECE. Other Xerofluvents that haveeither : 1. In one or more horizons within 50 cm of the mineral soil LFF. Other Orthents. surface, redox depletions with chroma of 2 or less and also Udorthents, p. 135 aquic conditions for some time in normal years (or artificial drainage); or Cryorthents 2. In one or more horizons within 150 cm of the mineral Key to Subgroups soil surface, a color value, moist, of 4 or more and either LFBA. Cryorthents that have a lithic contact within 50 cm of chroma of 0 or hue of 5GY, 5G, 5BG, or 5B or aquic the mineral soil surface. conditions for some time in normal years. Lithic Cryorthents Aquic Xerofluvents LFBB. Other Cryorthents that have, throughout one or more LECF. Other Xerofluvents that are saturated with water in horizons with a total thickness of 18 cm or more within 75 cm one or more layers within 150 cm of the mineral soil surface in of the mineral soil surface, one or both of the following: normal years for either or both: 1. More than 35 percent (by volume) fragments coarser 1. 20 or more consecutive days; or than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or 2. 30 or more cumulative days. Oxyaquic Xerofluvents 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and LECG. Other Xerofluvents that have a horizon within 100 cm a. In the 0.02 to 2.0 mm fraction, 5 percent or more of the mineral soil surface that is 15 cm or more thick and that volcanic glass; and either has 20 percent or more (by volume) durinodes or is brittle 1 and has a firm rupture-resistance class when moist. b. [(Al plus /2 Fe, percent extracted by ammonium Durinodic Xerofluvents oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. LECH. Other Xerofluvents that have a color value, moist, Vitrandic Cryorthents of 3 or less and a color value, dry, of 5 or less (crushed and smoothed sample) either throughout the upper 15 cm of the LFBC. Other Cryorthents that have, in one or more horizons 134 Keys to Soil Taxonomy

within 50 cm of the mineral soil surface, redox depletions with LFCB. Other Torriorthents that have all of the following: chroma of 2 or less and also aquic conditions for some time in 1. A lithic contact within 50 cm of the soil surface; and normal years (or artificial drainage). Aquic Cryorthents 2. A moisture control section that, in normal years, is dry in all parts for less than three-fourths of the cumulative days per LFBD. Other Cryorthents that are saturated with water in year when the soil temperature at a depth of 50 cm below the one or more layers within 100 cm of the mineral soil surface in soil surface is 5 oC or higher; and normal years for either or both: 3. A thermic, mesic, or frigid soil temperature regime and 1. 20 or more consecutive days; or an aridic (or torric) soil moisture regime that borders on xeric. 2. 30 or more cumulative days. Lithic Xeric Torriorthents Oxyaquic Cryorthents LFCC. Other Torriorthents that have a lithic contact within 50 LFBE. Other Cryorthents that have lamellae within 200 cm of cm of the soil surface. the mineral soil surface. Lithic Torriorthents Lamellic Cryorthents LFCD. Other Torriorthents that have: LFBF. Other Cryorthents. Typic Cryorthents 1. One or both of the following: a. Cracks within 125 cm of the soil surface that are 5 Gelorthents mm or more wide through a thickness of 30 cm or more Key to Subgroups for some time in normal years and slickensides or wedge- shaped peds in a layer 15 cm or more thick that has its LFAA. Gelorthents that have, in one or more horizons within upper boundary within 125 cm of the soil surface; or 100 cm of the mineral soil surface, both redox depletions with chroma of 2 or less and aquic conditions for some time in b. A linear extensibility of 6.0 cm or more between the normal years (or artificial drainage). soil surface and either a depth of 100 cm or a densic, Aquic Gelorthents lithic, or paralithic contact, whichever is shallower; and 2. A moisture control section that, in normal years, is dry in LFAB. Other Gelorthents that are saturated with water in one all parts for less than three-fourths of the cumulative days per or more layers within 100 cm of the mineral soil surface in year when the soil temperature at a depth of 50 cm below the normal years for either or both: soil surface is 5 oC or higher; and 1. 20 or more consecutive days; or 3. A thermic, mesic, or frigid soil temperature regime and 2. 30 or more cumulative days. an aridic (or torric) soil moisture regime that borders on Oxyaquic Gelorthents xeric. Xerertic Torriorthents LFAC. Other Gelorthents. Typic Gelorthents LFCE. Other Torriorthents that have: 1. One or both of the following: Torriorthents a. Cracks within 125 cm of the soil surface that are 5 Key to Subgroups mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge- LFCA. Torriorthents that have all of the following: shaped peds in a layer 15 cm or more thick that has its 1. A lithic contact within 50 cm of the soil surface; and upper boundary within 125 cm of the soil surface; or 2. A moisture control section that, in normal years, is dry in b. A linear extensibility of 6.0 cm or more between the all parts for less than three-fourths of the cumulative days per soil surface and either a depth of 100 cm or a densic, year when the soil temperature at a depth of 50 cm below the lithic, or paralithic contact, whichever is shallower; and soil surface is 5 oC or higher; and 2. A moisture control section that, in normal years, is dry in 3. A hypertheric, thermic, mesic, frigid, or iso soil all parts for less than three-fourths of the cumulative days per temperature regime and an aridic (or torric) soil moisture year when the soil temperature at a depth of 50 cm below the regime that borders on ustic. soil surface is 5 oC or higher; and Lithic Ustic Torriorthents Entisols 135

3. An aridic (or torric) soil moisture regime that borders on 1. A moisture control section that, in normal years, is dry in ustic. all parts for less than three-fourths of the cumulative days per Ustertic Torriorthents year when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher; and LFCF. Other Torriorthents that have one or both of the 2. A hyperthermic, thermic, mesic, frigid, or iso soil following: temperature regime and an aridic (or torric) soil moisture 1. Cracks within 125 cm of the soil surface that are 5 mm regime that borders on ustic. or more wide through a thickness of 30 cm or more for some Ustic Torriorthents time in normal years and slickensides or wedge-shaped peds in a layer 15 cm or more thick that has its upper boundary LFCL. Other Torriorthents that have both: within 125 cm of the soil surface; or 1. A moisture control section that, in normal years, is dry in 2. A linear extensibility of 6.0 cm or more between the soil all parts for less than three-fourths of the cumulative days per surface and either a depth of 100 cm or a densic, lithic, or year when the soil temperature at a depth of 50 cm below the paralithic contact, whichever is shallower. soil surface is 5 oC or higher; and Vertic Torriorthents 2. A thermic, mesic, or frigid soil temperature regime LFCG. Other Torriorthents that have, throughout one or more and an aridic (or torric) soil moisture regime that borders on horizons with a total thickness of 18 cm or more within 75 cm xeric. of the soil surface, one or both of the following: Xeric Torriorthents E 1. More than 35 percent (by volume) fragments coarser LFCM. Other Torriorthents. N than 2.0 mm, of which more than 66 percent is cinders, Typic Torriorthents T pumice, and pumicelike fragments; or 2. A fine-earth fraction containing 30 percent or more Udorthents particles 0.02 to 2.0 mm in diameter; and Key to Subgroups a. In the 0.02 to 2.0 mm fraction, 5 percent or more LFFA. Udorthents that have a lithic contact within 50 cm of volcanic glass; and the mineral soil surface. 1 b. [(Al plus /2 Fe, percent extracted by ammonium Lithic Udorthents oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. LFFB. Other Udorthents that have, throughout one or more Vitrandic Torriorthents horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: LFCH. Other Torriorthents that have, in one or more horizons 1. More than 35 percent (by volume) fragments coarser within 100 cm of the soil surface, redox depletions with chroma than 2.0 mm, of which more than 66 percent is cinders, of 2 or less and also aquic conditions for some time in normal pumice, and pumicelike fragments; or years (or artificial drainage). Aquic Torriorthents 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and LFCI. Other Torriorthents that are saturated with water in one a. In the 0.02 to 2.0 mm fraction, 5 percent or more or more layers within 150 cm of the soil surface in normal years volcanic glass; and for either or both: 1 b. [(Al plus /2 Fe, percent extracted by ammonium 1. 20 or more consecutive days; or oxalate) times 60] plus the volcanic glass (percent) is 2. 30 or more cumulative days. equal to 30 or more. Oxyaquic Torriorthents Vitrandic Udorthents

LFCJ. Other Torriorthents that have a horizon within 100 cm LFFC. Other Udorthents that have, in one or more horizons of the soil surface that is 15 cm or more thick and that either has within 100 cm of the mineral soil surface, redox depletions with 20 percent or more (by volume) durinodes or is brittle and has at chroma of 2 or less and also aquic conditions for some time in least a firm rupture-resistance class when moist. normal years (or artificial drainage). Duric Torriorthents Aquic Udorthents

LFCK. Other Torriorthents that have both: LFFD. Other Udorthents that are saturated with water in one 136 Keys to Soil Taxonomy

or more layers within 150 cm of the mineral soil surface in are 5 mm or more wide through a thickness of 30 cm or normal years for either or both: more for some time in normal years and slickensides or wedge-shaped peds in a layer 15 cm or more thick that 1. 20 or more consecutive days; or has its upper boundary within 125 cm of the mineral soil 2. 30 or more cumulative days. surface; or Oxyaquic Udorthents b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm LFFE. Other Udorthents that have 50 percent or more (by or a densic, lithic, or paralithic contact, whichever is volume) wormholes, wormcasts, and filled animal burrows shallower; and between either the Ap horizon or a depth of 25 cm from the mineral soil surface, whichever is deeper, and either a depth 2. When neither irrigated nor fallowed to store moisture, of 100 cm or a densic, lithic, paralithic, or petroferric contact, one of the following: whichever is shallower. a. A frigid soil temperature regime and a moisture Vermic Udorthents control section that, in normal years, is dry in all parts for four-tenths or more of the cumulative days per year when LFFF. Other Udorthents. the soil temperature at a depth of 50 cm below the soil Typic Udorthents surface is higher than 5 oC; or Ustorthents b. A mesic or thermic soil temperature regime and a moisture control section that, in normal years, is dry in Key to Subgroups some part for six-tenths or more of the cumulative days LFEA. Ustorthents that have both: per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or 1. A lithic contact within 50 cm of the mineral soil surface; and c. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that, 2. When neither irrigated nor fallowed to store moisture, in normal years, remains moist in some or all parts for one of the following: less than 90 consecutive days per year when the soil a. A frigid soil temperature regime and a moisture temperature at a depth of 50 cm below the soil surface is control section that, in normal years, is dry in all parts for higher than 8 oC. four-tenths or more of the cumulative days per year when Torrertic Ustorthents the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or LFED. Other Ustorthents that have one or both of the following: b. A mesic or thermic soil temperature regime and a moisture control section that, in normal years, is dry in 1. Cracks within 125 cm of the mineral soil surface that are some part for six-tenths or more of the cumulative days 5 mm or more wide through a thickness of 30 cm or more per year when the soil temperature at a depth of 50 cm for some time in normal years and slickensides or wedge- below the soil surface is higher than 5 oC; or shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil surface; or c. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that, 2. A linear extensibility of 6.0 cm or more between the in normal years, remains moist in some or all parts for mineral soil surface and either a depth of 100 cm or a densic, less than 90 consecutive days per year when the soil lithic, or paralithic contact, whichever is shallower. temperature at a depth of 50 cm below the soil surface is Vertic Ustorthents higher than 8 oC. Aridic Lithic Ustorthents LFEE. Other Ustorthents that have anthraquic conditions. Anthraquic Ustorthents LFEB. Other Ustorthents that have a lithic contact within 50 cm of the mineral soil surface. LFEF. Other Ustorthents that have, in one or more horizons Lithic Ustorthents within 100 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in LFEC. Other Ustorthents that have both: normal years (or artificial drainage). Aquic Ustorthents 1. One or both of the following: a. Cracks within 125 cm of the mineral soil surface that LFEG. Other Ustorthents that are saturated with water in Entisols 137

one or more layers within 150 cm of the mineral soil surface in 1. More than 35 percent (by volume) fragments coarser normal years for either or both: than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or 1. 20 or more consecutive days; or 2. A fine-earth fraction containing 30 percent or more 2. 30 or more cumulative days. particles 0.02 to 2.0 mm in diameter; and Oxyaquic Ustorthents a. In the 0.02 to 2.0 mm fraction, 5 percent or more LFEH. Other Ustorthents that have a horizon within 100 cm volcanic glass; and of the mineral soil surface that is 15 cm or more thick and that 1 b. [(Al plus /2 Fe, percent extracted by ammonium either has 20 percent or more (by volume) durinodes or is brittle oxalate) times 60] plus the volcanic glass (percent) is and has at least a firm rupture-resistance class when moist. equal to 30 or more. Durinodic Ustorthents Vitrandic Ustorthents LFEI. Other Ustorthents that have both: LFEK. Other Ustorthents that, when neither irrigated nor 1. When neither irrigated nor fallowed to store moisture, fallowed to store moisture, have one of the following: one of the following: 1. A frigid soil temperature regime and a moisture control a. A frigid soil temperature regime and a moisture section that, in normal years, is dry in all parts for four- control section that, in normal years, is dry in all parts for tenths or more of the cumulative days per year when the soil four-tenths or more of the cumulative days per year when temperature at a depth of 50 cm below the soil surface is the soil temperature at a depth of 50 cm below the soil higher than 5 oC; or E N surface is higher than 5 oC; or 2. A mesic or thermic soil temperature regime and a T b. A mesic or thermic soil temperature regime and a moisture control section that, in normal years, is dry in some moisture control section that, in normal years, is dry in part for six-tenths or more of the cumulative days per year some part for six-tenths or more of the cumulative days when the soil temperature at a depth of 50 cm below the soil per year when the soil temperature at a depth of 50 cm surface is higher than 5 oC; or below the soil surface is higher than 5 oC; or 3. A hyperthermic, isomesic, or warmer iso soil c. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that, in temperature regime and a moisture control section that, normal years, is moist in some or all parts for less than 180 in normal years, remains moist in some or all parts for cumulative days per year when the soil temperature at a less than 90 consecutive days per year when the soil depth of 50 cm below the soil surface is higher than 8 oC. temperature at a depth of 50 cm below the soil surface is Aridic Ustorthents higher than 8 oC; and LFEL. Other Ustorthents that, when neither irrigated nor 2. Throughout one or more horizons with a total thickness fallowed to store moisture, have one of the following: of 18 cm or more within 75 cm of the soil surface, one or both of the following: 1. A frigid soil temperature regime and a moisture control section that, in normal years, is dry in some or all parts a. More than 35 percent (by volume) fragments coarser for less than 105 cumulative days per year when the soil than 2.0 mm, of which more than 66 percent is cinders, temperature at a depth of 50 cm below the soil surface is pumice, and pumicelike fragments; or higher than 5 oC; or b. A fine-earth fraction containing 30 percent or more 2. A mesic or thermic soil temperature regime and a particles 0.02 to 2.0 mm in diameter; and moisture control section that, in normal years, is dry in some (1) In the 0.02 to 2.0 mm fraction, 5 percent or more part for less than four-tenths of the cumulative days per year volcanic glass; and when the soil temperature at a depth of 50 cm below the soil o 1 surface is higher than 5 C; or (2) [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 3. A hyperthermic, isomesic, or warmer iso soil equal to 30 or more. temperature regime and a moisture control section that, in Vitritorrandic Ustorthents normal years, is dry in some or all parts for less than 120 cumulative days per year when the soil temperature at a LFEJ. Other Ustorthents that have, throughout one or more depth of 50 cm below the soil surface is higher than 8 oC. horizons with a total thickness of 18 cm or more within 75 cm Udic Ustorthents of the soil surface, one or both of the following: 138 Keys to Soil Taxonomy

LFEM. Other Ustorthents that have 50 percent or more (by LFDF. Other Xerorthents that have a base saturation (by volume) wormholes, wormcasts, and filled animal burrows NH4OAc) of less than 60 percent in all horizons at a depth between either the Ap horizon or a depth of 25 cm from the between 25 and 75 cm below the mineral soil surface or in the mineral soil surface, whichever is deeper, and either a depth horizon directly above a root-limiting layer that is at a shallower of 100 cm or a densic, lithic, paralithic, or petroferric contact, depth. whichever is shallower. Dystric Xerorthents Vermic Ustorthents LFDG. Other Xerorthents. LFEN. Other Ustorthents. Typic Xerorthents Typic Ustorthents Psamments Xerorthents Key to Great Groups Key to Subgroups LDA. Psamments that have a cryic soil temperature regime. LFDA. Xerorthents that have a lithic contact within 50 cm of Cryopsamments, p. 138 the mineral soil surface. Lithic Xerorthents LDB. Other Psamments that have an aridic (or torric) soil moisture regime. LFDB. Other Xerorthents that have, throughout one or more Torripsamments, p. 140 horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: LDC. Other Psamments that have, in the 0.02 to 2.0 mm 1. More than 35 percent (by volume) fragments coarser fraction within the particle-size control section, a total of more than 2.0 mm, of which more than 66 percent is cinders, than 90 percent (by weighted average) resistant minerals. pumice, and pumicelike fragments; or Quartzipsamments, p. 139 2. A fine-earth fraction containing 30 percent or more LDD. Other Psamments that have an ustic soil moisture particles 0.02 to 2.0 mm in diameter; and regime. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Ustipsamments, p. 141 volcanic glass; and

1 LDE. Other Psamments that have a xeric soil moisture regime. b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is Xeropsamments, p. 141 equal to 30 or more. Vitrandic Xerorthents LDF. Other Psamments. Udipsamments, p. 140 LFDC. Other Xerorthents that have, in one or more horizons within 100 cm of the mineral soil surface, redox depletions with Cryopsamments chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). Key to Subgroups Aquic Xerorthents LDAA. Cryopsamments that have a lithic contact within 50 cm of the mineral soil surface. LFDD. Other Xerorthents that are saturated with water in Lithic Cryopsamments one or more layers within 150 cm of the mineral soil surface in normal years for either or both: LDAB. Other Cryopsamments that have, in one or more 1. 20 or more consecutive days; or horizons within 50 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions 2. 30 or more cumulative days. for some time in normal years (or artificial drainage). Oxyaquic Xerorthents Aquic Cryopsamments LFDE. Other Xerorthents that have a horizon within 100 cm LDAC. Other Cryopsamments that are saturated with water in of the mineral soil surface that is 15 cm or more thick and that one or more layers within 100 cm of the mineral soil surface in either has 20 percent or more (by volume) durinodes or is brittle normal years for either or both: and has at least a firm rupture-resistance class when moist. Durinodic Xerorthents 1. 20 or more consecutive days; or Entisols 139

2. 30 or more cumulative days. c. An ODOE value of 0.12 or more, and a value half as Oxyaquic Cryopsamments high or lower in an overlying horizon. Aquodic Quartzipsamments LDAD. Other Cryopsamments that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 LDCC. Other Quartzipsamments that have, in one or more cm of the mineral soil surface, a fine-earth fraction containing horizons within 100 cm of the mineral soil surface, redox 1 5 percent or more volcanic glass, and [(Al plus /2 Fe, percent depletions with chroma of 2 or less and also aquic conditions extracted by ammonium oxalate) times 60] plus the volcanic for some time in normal years (or artificial drainage). glass (percent) is 30 or more. Aquic Quartzipsamments Vitrandic Cryopsamments LDCD. Other Quartzipsamments that are saturated with water LDAE. Other Cryopsamments that have a horizon 5 cm or in one or more layers within 100 cm of the mineral soil surface more thick that has one or more of the following: in normal years for either or both: 1. In 25 percent or more of each pedon, cementation by 1. 20 or more consecutive days; or organic matter and aluminum, with or without iron; or 2. 30 or more cumulative days. 1 2. Al plus /2 Fe percentages (by ammonium oxalate) Oxyaquic Quartzipsamments totaling 0.25 or more, and half that amount or less in an overlying horizon; or LDCE. Other Quartzipsamments that meet all of the 3. An ODOE value of 0.12 or more, and a value half as following: E high or lower in an overlying horizon. 1. Have an ustic soil moisture regime; and N Spodic Cryopsamments T 2. Have a clay fraction with a CEC of 16 cmol(+) or less

LDAF. Other Cryopsamments that have lamellae within 200 per kg clay (by 1N NH4OAc pH 7); and cm of the mineral soil surface. 3. The sum of the weighted average silt plus 2 times the Lamellic Cryopsamments weighted average clay (both by weight) is more than 5. Ustoxic Quartzipsamments LDAG. Other Cryopsamments. Typic Cryopsamments LDCF. Other Quartzipsamments that meet all of the following: Quartzipsamments 1. Have a udic soil moisture regime; and Key to Subgroups 2. Have a clay fraction with a CEC of 16 cmol(+) or less LDCA. Quartzipsamments that have a lithic contact within 50 per kg clay (by 1N NH OAc pH 7); and cm of the mineral soil surface. 4 Lithic Quartzipsamments 3. The sum of the weighted average silt plus 2 times the weighted average clay (both by weight) is more than 5. LDCB. Other Quartzipsamments that have both: Udoxic Quartzipsamments 1. In one or more horizons within 100 cm of the mineral LDCG. Other Quartzipsamments that have 5 percent or more soil surface, redox depletions with chroma of 2 or less and (by volume) plinthite in one or more horizons within 100 cm of also aquic conditions for some time in normal years (or the mineral soil surface. artificial drainage); and Plinthic Quartzipsamments 2. A horizon, 5 cm or more thick, either below an Ap horizon or at a depth of 18 cm or more from the mineral soil LDCH. Other Quartzipsamments that have both: surface, whichever is deeper, that has one or more of the 1. Lamellae within 200 cm of the mineral soil surface; and following: 2. An ustic soil moisture regime. a. In 25 percent or more of each pedon, cementation by Lamellic Ustic Quartzipsamments organic matter and aluminum, with or without iron; or

1 b. Al plus /2 Fe percentages (by ammonium oxalate) LDCI. Other Quartzipsamments that have lamellae within 200 totaling 0.25 or more, and half that amount or less in an cm of the mineral soil surface. overlying horizon; or Lamellic Quartzipsamments 140 Keys to Soil Taxonomy

LDCJ. Other Quartzipsamments that have an ustic soil LDBE. Other Torripsamments that have both: moisture regime. 1. A moisture control section that, in normal years, is dry in Ustic Quartzipsamments all parts for less than three-fourths of the cumulative days per year when the soil temperature at a depth of 50 cm below the LDCK. Other Quartzipsamments that have a xeric soil soil surface is 5 oC or higher; and moisture regime. Xeric Quartzipsamments 2. An aridic (or torric) soil moisture regime that borders on ustic. LDCL. Other Quartzipsamments that have a horizon, 5 cm or Ustic Torripsamments more thick, either below an Ap horizon or at a depth of 18 cm or more from the mineral soil surface, whichever is deeper, that LDBF. Other Torripsamments that have both: has one or more of the following: 1. A moisture control section that, in normal years, is dry in 1. In 25 percent or more of each pedon, cementation by all parts for less than three-fourths of the cumulative days per organic matter and aluminum, with or without iron; or year when the soil temperature at a depth of 50 cm below the soil surface is 5 oC or higher; and 1 2. Al plus /2 Fe percentages (by ammonium oxalate) totaling 0.25 or more, and half that amount or less in an 2. A thermic, mesic, or frigid soil temperature regime and overlying horizon; or an aridic (or torric) soil moisture regime that borders on xeric. 3. An ODOE value of 0.12 or more, and a value half as Xeric Torripsamments high or lower in an overlying horizon. Spodic Quartzipsamments LDBG. Other Torripsamments that have, in all horizons from a depth of 25 to 100 cm, more than 50 percent colors that have LDCM. Other Quartzipsamments. all of the following: Typic Quartzipsamments 1. Hue of 2.5YR or redder; and Torripsamments 2. A color value, moist, of 3 or less; and Key to Subgroups 3. A dry value no more than 1 unit higher than the moist value. LDBA. Torripsamments that have a lithic contact within 50 Rhodic Torripsamments cm of the soil surface. Lithic Torripsamments LDBH. Other Torripsamments. Typic Torripsamments LDBB. Other Torripsamments that are saturated with water in one or more layers within 150 cm of the mineral soil surface in Udipsamments normal years for either or both: Key to Subgroups 1. 20 or more consecutive days; or LDFA. Udipsamments that have a lithic contact within 50 cm 2. 30 or more cumulative days. of the mineral soil surface. Oxyaquic Torripsamments Lithic Udipsamments

LDBC. Other Torripsamments that have, throughout one or LDFB. Other Udipsamments that have, in one or more more horizons with a total thickness of 18 cm or more within 75 horizons within 100 cm of the mineral soil surface, redox cm of the mineral soil surface, a fine-earth fraction containing depletions with chroma of 2 or less and also aquic conditions 1 5 percent or more volcanic glass, and [(Al plus /2 Fe, percent for some time in normal years (or artificial drainage). extracted by ammonium oxalate) times 60] plus the volcanic Aquic Udipsamments glass (percent) is 30 or more. Vitrandic Torripsamments LDFC. Other Udipsamments that are saturated with water in one or more layers within 100 cm of the mineral soil surface in LDBD. Other Torripsamments that have a horizon within 100 normal years for either or both: cm of the soil surface that is 15 cm or more thick and that either 1. 20 or more consecutive days; or has 20 percent or more (by volume) durinodes or is brittle and has at least a firm rupture-resistance class when moist. 2. 30 or more cumulative days. Haploduridic Torripsamments Oxyaquic Udipsamments Entisols 141

LDFD. Other Udipsamments that have a horizon, 5 cm or 2. A mesic or thermic soil temperature regime and a more thick, either below an Ap horizon or at a depth of 18 cm moisture control section that, in normal years, is dry in some or more from the mineral soil surface, whichever is deeper, that part for six-tenths or more of the cumulative days per year has one or more of the following: when the soil temperature at a depth of 50 cm below the soil o 1. In 25 percent or more of each pedon, cementation by surface is higher than 5 C; or organic matter and aluminum, with or without iron; or 3. A hyperthermic, isomesic, or warmer iso soil 1 2. Al plus /2 Fe percentages (by ammonium oxalate) temperature regime and a moisture control section that, in totaling 0.25 or more, and half that amount or less in an normal years, is moist in some or all parts for less than 180 overlying horizon; or cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 8 oC. 3. An ODOE value of 0.12 or more, and a value half as Aridic Ustipsamments high or lower in an overlying horizon. Spodic Udipsamments LDDE. Other Ustipsamments that have lamellae within 200 cm of the mineral soil surface. LDFE. Other Udipsamments that have lamellae within 200 cm Lamellic Ustipsamments of the mineral soil surface. Lamellic Udipsamments LDDF. Other Ustipsamments that have, in all horizons from a depth of 25 to 100 cm, more than 50 percent colors that have all . Other Udipsamments that have a surface horizon LDFF of the following: between 25 and 50 cm thick that meets all of the requirements E for a plaggen epipedon except thickness. 1. Hue of 2.5YR or redder; and N Plagganthreptic Udipsamments T 2. A color value, moist, of 3 or less; and LDFG. Other Udipsamments. 3. A dry value no more than 1 unit higher than the moist Typic Udipsamments value. Rhodic Ustipsamments Ustipsamments LDDG. Other Ustipsamments. Key to Subgroups Typic Ustipsamments LDDA. Ustipsamments that have a lithic contact within 50 cm of the mineral soil surface. Xeropsamments Lithic Ustipsamments Key to Subgroups LDDB. Other Ustipsamments that have, in one or more LDEA. Xeropsamments that have a lithic contact within 50 horizons within 100 cm of the mineral soil surface, distinct or cm of the mineral soil surface. prominent redox concentrations and also aquic conditions for Lithic Xeropsamments some time in normal years (or artificial drainage). Aquic Ustipsamments LDEB. Other Xeropsamments that have both:

LDDC. Other Ustipsamments that are saturated with water in 1. In one or more horizons within 100 cm of the mineral one or more layers within 100 cm of the mineral soil surface in soil surface, distinct or prominent redox concentrations and normal years for either or both: also aquic conditions for some time in normal years (or artificial drainage); and 1. 20 or more consecutive days; or 2. A horizon within 100 cm of the mineral soil surface that 2. 30 or more cumulative days. is 15 cm or more thick and that either has 20 percent or more Oxyaquic Ustipsamments (by volume) durinodes or is brittle and has at least a firm rupture-resistance class when moist. LDDD. Other Ustipsamments that, when neither irrigated nor Aquic Durinodic Xeropsamments fallowed to store moisture, have one of the following: 1. A frigid soil temperature regime and a moisture control LDEC. Other Xeropsamments that have, in one or more section that, in normal years, is dry in all parts for four- horizons within 100 cm of the mineral soil surface, distinct or tenths or more of the cumulative days per year when the soil prominent redox concentrations and also aquic conditions for temperature at a depth of 50 cm below the soil surface is some time in normal years (or artificial drainage). higher than 5 oC; or Aquic Xeropsamments 142

LDED. Other Xeropsamments that are saturated with water in LAD. Other Wassents that have, in all horizons at a depth one or more layers within 100 cm of the mineral soil surface in between 20 and 50 cm below the mineral soil surface, both an normal years for either or both: n value of more than 0.7 and 8 percent or more clay in the fine- earth fraction. 1. 20 or more consecutive days; or Hydrowassents, p. 143 2. 30 or more cumulative days. Oxyaquic Xeropsamments LAE. Other Wassents that have one or both of the following:

LDEE. Other Xeropsamments that have, throughout one or 1. At a depth of 125 cm below the mineral soil surface, more horizons with a total thickness of 18 cm or more within 75 an organic-carbon content (Holocene age) of 0.2 percent or cm of the mineral soil surface, a fine-earth fraction containing more and no densic, lithic, or paralithic contact within that 1 depth; or 5 percent or more volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic 2. An irregular decrease in organic-carbon content glass (percent) is 30 or more. (Holocene age) between a depth of 25 cm and either a depth Vitrandic Xeropsamments of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is shallower. LDEF. Other Xeropsamments that have a horizon within 100 Fluviwassents, p. 142 cm of the mineral soil surface that is 15 cm or more thick and that either has 20 percent or more (by volume) durinodes or is LAF. Other Wassents. brittle and has at least a firm rupture-resistance class when moist. Haplowassents, p. 143 Durinodic Xeropsamments Fluviwassents LDEG. Other Xeropsamments that have lamellae within 200 cm of the mineral soil surface. Key to Subgroups Lamellic Xeropsamments LAEA. Fluviwassents that have a horizon or horizons with a combined thickness of at least 15 cm within 100 cm of the LDEH. Other Xeropsamments that have a base saturation mineral soil surface that contain sulfidic materials. (by NH OAc) of less than 60 percent in all horizons at a depth 4 Sulfic Fluviwassents between 25 and 75 cm below the mineral soil surface or in the horizon directly above a root-limiting layer that is at a shallower LAEB. Other Fluviwassents that have a lithic contact within depth. 100 cm of the mineral soil surface. Dystric Xeropsamments Lithic Fluviwassents

LDEI. Other Xeropsamments. LAEC. Other Fluviwassents that have a buried layer of Typic Xeropsamments organic soil materials, 20 cm or more thick, within 100 cm of the mineral soil surface. Wassents Thapto-Histic Fluviwassents

Key to Great Groups LAED. Other Fluviwassents that have a chroma of 3 or more LAA. Wassents that have, in all horizons within 100 cm of in 40 percent or more of the matrix of one or more horizons the mineral soil surface, an electrical conductivity of less than between a depth of 15 and 100 cm from the soil surface. 0.2 dS/m in a 5:1, by volume, mixture (not extract) of water and Aeric Fluviwassents soil. Frasiwassents, p. 142 LAEE. Other Fluviwassents. Typic Fluviwassents LAB. Other Wassents that have less than 35 percent (by volume) rock fragments and a texture class of loamy fine sand Frasiwassents or coarser in all layers within the particle-size control section. Key to Subgroups Psammowassents, p. 143 LAAA. Frasiwassents that have, in all horizons at a depth LAC. Other Wassents that have a horizon or horizons with between 20 and 50 cm below the mineral soil surface, both an a combined thickness of at least 15 cm within 50 cm of the n value of more than 0.7 and 8 percent or more clay in the fine- mineral soil surface that contain sulfidic materials. earth fraction. Sulfiwassents, p. 144 Hydric Frasiwassents Entisols 143

LAAB. Other Frasiwassents that have a lithic contact within Hydrowassents 100 cm of the mineral soil surface. Lithic Frasiwassents Key to Subgroups LADA. Hydrowassents that have a horizon or horizons with LAAC. Other Frasiwassents that have less than 35 percent (by a combined thickness of at least 15 cm within 100 cm of the volume) rock fragments and a texture class of loamy fine sand mineral soil surface that contain sulfidic materials. or coarser in all layers within the particle-size control section. Sulfic Hydrowassents Psammentic Frasiwassents LADB. Other Hydrowassents that have, in all horizons at a LAAD. Other Frasiwassents that have a buried layer of depth between 20 and 100 cm below the mineral soil surface, organic soil materials, 20 cm or more thick, within 100 cm of both an n value of more than 0.7 and 8 percent or more clay in the mineral soil surface. the fine-earth fraction. Thapto-Histic Frasiwassents Grossic Hydrowassents

LAAE. Other Frasiwassents that have one or both of the LADC. Other Hydrowassents that have a lithic contact within following: 100 cm of the mineral soil surface. 1. At a depth of 125 cm below the mineral soil surface, Lithic Hydrowassents an organic-carbon content (Holocene age) of 0.2 percent or more and no densic, lithic, or paralithic contact within that LADD. Other Hydrowassents that have a buried layer of organic soil materials, 20 cm or more thick, within 100 cm of depth; or the mineral soil surface. E N 2. An irregular decrease in organic-carbon content Thapto-Histic Hydrowassents T (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a densic, lithic, LADE. Other Hydrowassents. or paralithic contact, whichever is shallower. Typic Hydrowassents Fluventic Frasiwassents Psammowassents LAAF. Other Frasiwassents that have a chroma of 3 or more in 40 percent or more of the matrix of one or more horizons Key to Subgroups between a depth of 15 and 100 cm from the soil surface. LABA. Psammowassents that have a horizon or horizons with Aeric Frasiwassents a combined thickness of at least 15 cm within 100 cm of the mineral soil surface that contain sulfidic materials. LAAG. Other Frasiwassents. Sulfic Psammowassents Typic Frasiwassents LABB. Other Psammowassents that have a lithic contact Haplowassents within 100 cm of the mineral soil surface. Lithic Psammowassents Key to Subgroups LAFA. Haplowassents that have a horizon or horizons with LABC. Other Psammowassents that have one or both of the a combined thickness of at least 15 cm within 100 cm of the following: mineral soil surface that contain sulfidic materials. 1. At a depth of 125 cm below the mineral soil surface, Sulfic Haplowassents an organic-carbon content (Holocene age) of 0.2 percent or more and no densic, lithic, or paralithic contact within that LAFB. Other Haplowassents that have a lithic contact within depth; or 100 cm of the mineral soil surface. Lithic Haplowassents 2. An irregular decrease in organic-carbon content (Holocene age) between a depth of 25 cm and either a depth LAFC. Other Haplowassents that have a chroma of 3 or more of 125 cm below the mineral soil surface or a densic, lithic, in 40 percent or more of the matrix of one or more horizons or paralithic contact, whichever is shallower. between a depth of 15 and 100 cm from the soil surface. Fluventic Psammowassents Aeric Haplowassents LABD. Other Psammowassents that have a chroma of 3 LAFD. Other Haplowassents. or more in 40 percent or more of the matrix of one or more Typic Haplowassents 144

horizons between a depth of 15 and 100 cm from the soil LACD. Other Sulfiwassents that haveone or both of the surface. following: Aeric Psammowassents 1. At a depth of 125 cm below the mineral soil surface, an organic-carbon content (Holocene age) of 0.2 percent or LABE. Other Psammowassents. more and no densic, lithic, or paralithic contact within that Typic Psammowassents depth; or Sulfiwassents 2. An irregular decrease in organic-carbon content (Holocene age) between a depth of 25 cm and either a depth Key to Subgroups of 125 cm below the mineral soil surface or a densic, lithic, LACA. Sulfiwassents that have a lithic contact within 100 cm or paralithic contact, whichever is shallower. of the mineral soil surface. Fluventic Sulfiwassents Lithic Sulfiwassents LACE. Other Sulfiwassents that have a chroma of 3 or more LACB. Other Sulfiwassents that have, in some horizons at a in 40 percent or more of the matrix of one or more horizons depth between 20 and 50 cm below the mineral soil surface, between a depth of 15 and 100 cm from the soil surface. either or both: Aeric Sulfiwassents 1. An n value of 0.7 or less; or LACF. Other Sulfiwassents. Typic Sulfiwassents 2. Less than 8 percent clay in the fine-earth fraction. Haplic Sulfiwassents

LACC. Other Sulfiwassents that have a buried layer of organic soil materials, 20 cm or more thick, within 100 cm of the mineral soil surface. Thapto-Histic Sulfiwassents 145

CHAPTER 9 Gelisols

Key to Suborders of 50 cm or to a densic, lithic, or paralithic contact, whichever is shallower. AA. Gelisols that have organic soil materials that meet one or Fibristels, p. 145 more of the following: 1. Overlie cindery, fragmental, or pumiceous materials AAD. Other Histels that have more thickness of hemic soil and/or fill their intersticesand directly below these materials materials than any other kind of organic soil material to a depth have either a densic, lithic, or paralithic contact; or of 50 cm or to a densic, lithic, or paralithic contact, whichever is shallower. 2. When added with the underlying cindery, fragmental, or Hemistels, p. 146 pumiceous materials, total 40 cm or more between the soil surface and a depth of 50 cm; or AAE. Other Histels. 3. Comprise 80 percent or more, by volume, from the soil Sapristels, p. 146 surface to a depth of 50 cm or to a glacic layer or a densic, lithic, or paralithic contact, whichever is shallower. Fibristels G Histels, p. 145 E Key to Subgroups L AB. Other Gelisols that have one or more horizons showing AACA. Fibristels that have a lithic contact within 100 cm of cryoturbation in the form of irregular, broken, or distorted the soil surface. horizon boundaries, involutions, the accumulation of organic Lithic Fibristels matter on top of the permafrost, ice or sand wedges, and oriented rock fragments. AACB. Other Fibristels that have a layer of mineral soil Turbels, p. 150 material 30 cm or more thick within 100 cm of the soil surface. Terric Fibristels AC. Other Gelisols. Orthels, p. 146 AACC. Other Fibristels that have, within the organic soil materials, either one layer of mineral soil material 5 cm or more Histels thick or two or more layers of any thickness within 100 cm of the soil surface. Key to Great Groups Fluvaquentic Fibristels AAA. Histels that are saturated with water for less than 30 cumulative days during normal years (and are not artificially AACD. Other Fibristels in which three-fourths or more of the drained). fibric soil materials are derived fromSphagnum to a depth of Folistels, p. 145 50 cm or to a densic, lithic, or paralithic contact, whichever is shallower. AAB. Other Histels that are saturated with water for 30 or Sphagnic Fibristels more cumulative days during normal years and that have both: AACE. Other Fibristels. 1. A glacic layer within 100 cm of the soil surface; and Typic Fibristels 2. Less than three-fourths (by volume) Sphagnum fibers in the organic soil material to a depth of 50 cm or to a densic, Folistels lithic, or paralithic contact, whichever is shallower. Key to Subgroups Glacistels, p. 146 AAAA. Folistels that have a lithic contact within 50 cm of the AAC. Other Histels that have more thickness of fibric soil soil surface. materials than any other kind of organic soil material to a depth Lithic Folistels 146 Keys to Soil Taxonomy

AAAB. Other Folistels that have a glacic layer within 100 cm materials, either one layer of mineral soil material 5 cm or more of the soil surface. thick or two or more layers of any thickness within 100 cm of Glacic Folistels the soil surface. Fluvaquentic Sapristels AAAC. Other Folistels. Typic Folistels AAED. Other Sapristels. Typic Sapristels Glacistels Key to Subgroups Orthels AABA. Glacistels that have more thickness of hemic soil Key to Great Groups materials than any other kind of organic soil material in the upper 50 cm. ACA. Orthels that have, in 30 percent or more of the pedon, more than 40 percent, by volume, organic soil materials from Hemic Glacistels the soil surface to a depth of 50 cm. AABB. Other Glacistels that have more thickness of sapric Historthels, p. 148 soil materials than any other kind of organic soil material in the upper 50 cm. ACB. Other Orthels that have, within 50 cm of the mineral Sapric Glacistels soil surface, redox depletions with chroma of 2 or less and also aquic conditions during normal years (or artificial drainage). AABC. Other Glacistels. Aquorthels, p. 147 Typic Glacistels ACC. Other Orthels that have anhydrous conditions. Hemistels Anhyorthels, p. 146

Key to Subgroups ACD. Other Orthels that have a mollic epipedon. AADA. Hemistels that have a lithic contact within 100 cm of Mollorthels, p. 149 the soil surface. Lithic Hemistels ACE. Other Orthels that have an umbric epipedon. Umbrorthels, p. 150 AADB. Other Hemistels that have a layer of mineral soil material 30 cm or more thick within 100 cm of the soil surface. ACF. Other Orthels that have an argillic horizon within 100 Terric Hemistels cm of the mineral soil surface. Argiorthels, p. 147 AADC. Other Hemistels that have, within the organic soil materials, either one layer of mineral soil material 5 cm or more ACG. Other Orthels that have, below the Ap horizon or below thick or two or more layers of any thickness within 100 cm of a depth of 25 cm, whichever is deeper, less than 35 percent (by the soil surface. volume) rock fragments and a texture class of loamy fine sand Fluvaquentic Hemistels or coarser in all layers within the particle-size control section. Psammorthels, p. 149 AADD. Other Hemistels. Typic Hemistels ACH. Other Orthels. Haplorthels, p. 148 Sapristels Anhyorthels Key to Subgroups Key to Subgroups AAEA. Sapristels that have a lithic contact within 100 cm of the soil surface. ACCA. Anhyorthels that have a lithic contact within 50 cm of Lithic Sapristels the mineral soil surface. Lithic Anhyorthels AAEB. Other Sapristels that have a layer of mineral soil material 30 cm or more thick within 100 cm of the soil surface. ACCB. Other Anhyorthels that have a glacic layer within 100 Terric Sapristels cm of the mineral soil surface. Glacic Anhyorthels AAEC. Other Sapristels that have, within the organic soil Gelisols 147

1 ACCC. Other Anhyorthels that have a petrogypsic horizon and Al plus /2 Fe percentages (by ammonium oxalate) totaling within 100 cm of the mineral soil surface. more than 1.0. Petrogypsic Anhyorthels Andic Aquorthels

ACCD. Other Anhyorthels that have a gypsic horizon within ACBF. Other Aquorthels that have, throughout one or more 100 cm of the mineral soil surface. horizons with a total thickness of 18 cm or more within 75 cm Gypsic Anhyorthels of the mineral soil surface, one or both of the following: 1. More than 35 percent (by volume) fragments coarser ACCE. Other Anhyorthels that have a horizon 15 cm or more than 2.0 mm, of which more than 66 percent is cinders, thick that contains 12 cmol(-)/L nitrate in a 1:5 soil:water pumice, and pumicelike fragments; or extract and in which the product of its thickness (in cm) and its nitrate concentration is 3,500 or more. 2. A fine-earth fraction containing 30 percent or more Nitric Anhyorthels particles 0.02 to 2.0 mm in diameter; and a. In the 0.02 to 2.0 mm fraction, 5 percent or more ACCF. Other Anhyorthels that have a salic horizon within 100 volcanic glass; and cm of the mineral soil surface. 1 Salic Anhyorthels b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is ACCG. Other Anhyorthels that have a calcic horizon within equal to 30 or more. 100 cm of the mineral soil surface. Vitrandic Aquorthels Calcic Anhyorthels ACBG. Other Aquorthels that have a salic horizon within 100 ACCH. Other Anhyorthels. cm of the mineral soil surface. Salic Aquorthels G Typic Anhyorthels E L Aquorthels ACBH. Other Aquorthels that have less than 35 percent (by volume) rock fragments and a texture class of loamy fine sand Key to Subgroups or coarser in all layers within the particle-size control section. ACBA. Aquorthels that have a lithic contact within 50 cm of Psammentic Aquorthels the mineral soil surface. Lithic Aquorthels ACBI. Other Aquorthels that have a slope of less than 25 percent and one or both of the following: ACBB. Other Aquorthels that have a glacic layer within 100 1. At a depth of 125 cm below the mineral soil surface, cm of the mineral soil surface. an organic-carbon content (Holocene age) of 0.2 percent or Glacic Aquorthels more and no densic, lithic, or paralithic contact within that depth; or ACBC. Other Aquorthels that have a sulfuric horizon or sulfidic materials within 100 cm of the mineral soil surface. 2. An irregular decrease in organic-carbon content Sulfuric Aquorthels (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a densic, lithic, ACBD. Other Aquorthels that have either: or paralithic contact, whichever is shallower. Fluvaquentic Aquorthels 1. Organic soil materials that are discontinuous at the surface; or ACBJ. Other Aquorthels. 2. Organic soil materials at the surface that change in Typic Aquorthels thickness fourfold or more within a pedon. Ruptic-Histic Aquorthels Argiorthels Key to Subgroups ACBE. Other Aquorthels that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm ACFA. Argiorthels that have a lithic contact within 50 cm of of the mineral soil surface, a fine-earth fraction with both a bulk the mineral soil surface. density of 1.0 g/cm3 or less, measured at 33 kPa water retention, Lithic Argiorthels 148 Keys to Soil Taxonomy

ACFB. Other Argiorthels that have a glacic layer within 100 more and no densic, lithic, or paralithic contact within that cm of the mineral soil surface. depth; or Glacic Argiorthels 2. An irregular decrease in organic-carbon content (Holocene age) between a depth of 25 cm and either a depth ACFC. Other Argiorthels that have a natric horizon. of 125 cm below the mineral soil surface or a densic, lithic, Natric Argiorthels or paralithic contact, whichever is shallower. Fluventic Haplorthels ACFD. Other Argiorthels. Typic Argiorthels ACHG. Other Haplorthels. Typic Haplorthels Haplorthels Key to Subgroups Historthels ACHA. Haplorthels that have a lithic contact within 50 cm of Key to Subgroups the mineral soil surface. ACAA. Historthels that have a lithic contact within 50 cm of Lithic Haplorthels the soil surface. Lithic Historthels ACHB. Other Haplorthels that have a glacic layer within 100 cm of the mineral soil surface. ACAB. Other Historthels that have a glacic layer within 100 Glacic Haplorthels cm of the soil surface. Glacic Historthels ACHC. Other Haplorthels that have a slope of less than 25 percent; and ACAC. Other Historthels that have a slope of less than 25 1. In one or more horizons within 75 cm of the mineral soil percent; and surface, redox depletions with chroma of 2 or less and also 1. In one or more horizons within 75 cm of the mineral soil aquic conditions for some time in normal years (or artificial surface, redox depletions with chroma of 2 or less and also drainage); and aquic conditions for some time in normal years (or artificial 2. One or both of the following: drainage); and a. At a depth of 125 cm below the mineral soil surface, 2. One or both of the following: an organic-carbon content (Holocene age) of 0.2 percent a. At a depth of 125 cm below the mineral soil surface, or more and no densic, lithic, or paralithic contact within an organic-carbon content (Holocene age) of 0.2 percent that depth; or or more and no densic, lithic, or paralithic contact within b. An irregular decrease in organic-carbon content that depth; or (Holocene age) between a depth of 25 cm and either b. An irregular decrease in organic-carbon content a depth of 125 cm below the mineral soil surface or a (Holocene age) between a depth of 25 cm and either densic, lithic, or paralithic contact, whichever is shallower. a depth of 125 cm below the mineral soil surface or a Fluvaquentic Haplorthels densic, lithic, or paralithic contact, whichever is shallower. Fluvaquentic Historthels ACHD. Other Haplorthels that have a folistic epipedon. Folistic Haplorthels ACAD. Other Historthels that have a slope of less than 25 percent and one or both of the following: ACHE. Other Haplorthels that have, in one or more horizons within 75 cm of the mineral soil surface, redox depletions with 1. At a depth of 125 cm below the mineral soil surface, chroma of 2 or less and also aquic conditions for some time an organic-carbon content (Holocene age) of 0.2 percent or during normal years (or artificial drainage). more and no densic, lithic, or paralithic contact within that Aquic Haplorthels depth; or 2. An irregular decrease in organic-carbon content ACHF. Other Haplorthels that have a slope of less than 25 (Holocene age) between a depth of 25 cm and either a depth percent and one or both of the following: of 125 cm below the mineral soil surface or a densic, lithic, 1. At a depth of 125 cm below the mineral soil surface, or paralithic contact, whichever is shallower. an organic-carbon content (Holocene age) of 0.2 percent or Fluventic Historthels Gelisols 149

1 ACAE. Other Historthels that have more than 40 percent, by b. [(Al plus /2 Fe, percent extracted by ammonium volume, organic soil materials from the soil surface to a depth oxalate) times 60] plus the volcanic glass (percent) is of 50 cm in 75 percent or less of the pedon. equal to 30 or more. Ruptic Historthels Vitrandic Mollorthels

ACAF. Other Historthels. ACDF. Other Mollorthels that have a folistic epipedon. Typic Historthels Folistic Mollorthels

Mollorthels ACDG. Other Mollorthels that have both: Key to Subgroups 1. A mollic epipedon that is 40 cm or more thick with a ACDA. Mollorthels that have a lithic contact within 50 cm of texture class finer than loamy fine sand; and the mineral soil surface. 2. A slope of less than 25 percent. Lithic Mollorthels Cumulic Mollorthels ACDB. Other Mollorthels that have a glacic layer within 100 ACDH. Other Mollorthels that have, in one or more horizons cm of the mineral soil surface. within 100 cm of the mineral soil surface, distinct or prominent Glacic Mollorthels redox concentrations and also aquic conditions for some time during normal years (or artificial drainage). ACDC. Other Mollorthels that have one or both of the Aquic Mollorthels following: 1. Cracks within 125 cm of the mineral soil surface that are ACDI. Other Mollorthels. 5 mm or more wide through a thickness of 30 cm or more for Typic Mollorthels G some time during normal years and slickensides or wedge- E shaped peds in a layer 15 cm or more thick that has its upper Psammorthels L boundary within 125 cm of the mineral soil surface; or Key to Subgroups 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a densic, ACGA. Psammorthels that have a lithic contact within 50 cm lithic, or paralithic contact, whichever is shallower. of the mineral soil surface. Vertic Mollorthels Lithic Psammorthels

ACDD. Other Mollorthels that have, throughout one or more ACGB. Other Psammorthels that have a glacic layer within horizons with a total thickness of 18 cm or more within 75 cm 100 cm of the mineral soil surface. of the mineral soil surface, a fine-earth fraction with both a bulk Glacic Psammorthels density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling ACGC. Other Psammorthels that have a horizon 5 cm or more more than 1.0. thick that has one or more of the following: Andic Mollorthels 1. In 25 percent or more of each pedon, cementation by organic matter and aluminum, with or without iron; or

1 ACDE. Other Mollorthels that have, throughout one or more 2. Al plus /2 Fe percentages (by ammonium oxalate) horizons with a total thickness of 18 cm or more within 75 cm totaling 0.25 or more, and half that amount or less in an of the mineral soil surface, one or both of the following: overlying horizon; or 1. More than 35 percent (by volume) fragments coarser 3. An ODOE value of 0.12 or more, and a value half as than 2.0 mm, of which more than 66 percent is cinders, high or lower in an overlying horizon. pumice, and pumicelike fragments; or Spodic Psammorthels 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and ACGD. Other Psammorthels. Typic Psammorthels a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and 150 Keys to Soil Taxonomy

Umbrorthels 1. An umbric epipedon that is 40 cm or more thick with a texture class finer than loamy fine sand; and Key to Subgroups 2. A slope of less than 25 percent. ACEA. Umbrorthels that have a lithic contact within 50 cm of Cumulic Umbrorthels the mineral soil surface. Lithic Umbrorthels ACEH. Other Umbrorthels that have, in one or more horizons within 100 cm of the mineral soil surface, distinct or prominent ACEB. Other Umbrorthels that have a glacic layer within 100 redox concentrations and also aquic conditions for some time cm of the mineral soil surface. during normal years (or artificial drainage). Glacic Umbrorthels Aquic Umbrorthels

ACEC. Other Umbrorthels that have one or both of the ACEI. Other Umbrorthels. following: Typic Umbrorthels 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or more for Turbels some time during normal years and slickensides or wedge- shaped peds in a layer 15 cm or more thick that has its upper Key to Great Groups boundary within 125 cm of the mineral soil surface; or ABA. Turbels that have, in 30 percent or more of the pedon, 2. A linear extensibility of 6.0 cm or more between the more than 40 percent, by volume, organic soil materials from mineral soil surface and either a depth of 100 cm or a densic, the soil surface to a depth of 50 cm. lithic, or paralithic contact, whichever is shallower. Histoturbels, p. 151 Vertic Umbrorthels ABB. Other Turbels that have, within 50 cm of the mineral ACED. Other Umbrorthels that have, throughout one or more soil surface, redox depletions with chroma of 2 or less and also horizons with a total thickness of 18 cm or more within 75 cm aquic conditions during normal years (or artificial drainage). of the mineral soil surface, a fine-earth fraction with both a bulk Aquiturbels, p. 151 density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling ABC. Other Turbels that have anhydrous conditions. more than 1.0. Anhyturbels, p. 150 Andic Umbrorthels ABD. Other Turbels that have a mollic epipedon. ACEE. Other Umbrorthels that have, throughout one or more Molliturbels, p. 152 horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: ABE. Other Turbels that have an umbric epipedon. Umbriturbels, p. 152 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, ABF. Other Turbels that have less than 35 percent (by volume) pumice, and pumicelike fragments; or rock fragments and a texture class of loamy fine sand or coarser 2. A fine-earth fraction containing 30 percent or more in all layers within the particle-size control section. particles 0.02 to 2.0 mm in diameter; and Psammoturbels, p. 152

a. In the 0.02 to 2.0 mm fraction, 5 percent or more ABG. Other Turbels. volcanic glass; and Haploturbels, p. 151 1 b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is Anhyturbels equal to 30 or more. Key to Subgroups Vitrandic Umbrorthels ABCA. Anhyturbels that have a lithic contact within 50 cm of ACEF. Other Umbrorthels that have a folistic epipedon. the mineral soil surface. Folistic Umbrorthels Lithic Anhyturbels

ACEG. Other Umbrorthels that have both: Gelisols 151

ABCB. Other Anhyturbels that have a glacic layer within 100 ABBE. Other Aquiturbels that have less than 35 percent (by cm of the mineral soil surface. volume) rock fragments and a texture class of loamy fine sand Glacic Anhyturbels or coarser in all layers within the particle-size control section. Psammentic Aquiturbels ABCC. Other Anhyturbels that have a petrogypsic horizon within 100 cm of the mineral soil surface. ABBF. Other Aquiturbels. Petrogypsic Anhyturbels Typic Aquiturbels

ABCD. Other Anhyturbels that have a gypsic horizon within Haploturbels 100 cm of the mineral soil surface. Gypsic Anhyturbels Key to Subgroups ABGA. Haploturbels that have a lithic contact within 50 cm ABCE. Other Anhyturbels that have a horizon 15 cm or of the mineral soil surface. more thick that contains 12 cmol(-)/L nitrate in a 1:5 soil:water Lithic Haploturbels extract and in which the product of its thickness (in cm) and its nitrate concentration is 3,500 or more. ABGB. Other Haploturbels that have a glacic layer within 100 Nitric Anhyturbels cm of the mineral soil surface. Glacic Haploturbels ABCF. Other Anhyturbels that have a salic horizon within 100 cm of the mineral soil surface. ABGC. Other Haploturbels that have a folistic epipedon. Salic Anhyturbels Folistic Haploturbels ABCG. Other Anhyturbels that have a calcic horizon within 100 cm of the mineral soil surface. ABGD. Other Haploturbels that have, in one or more horizons within 100 cm of the mineral soil surface, distinct or prominent G Calcic Anhyturbels E redox concentrations and also aquic conditions for some time L ABCH. Other Anhyturbels. during normal years (or artificial drainage). Typic Anhyturbels Aquic Haploturbels

Aquiturbels ABGE. Other Haploturbels. Typic Haploturbels Key to Subgroups ABBA. Aquiturbels that have a lithic contact within 50 cm of Histoturbels the mineral soil surface. Key to Subgroups Lithic Aquiturbels ABAA. Histoturbels that have a lithic contact within 50 cm of ABBB. Other Aquiturbels that have a glacic layer within 100 the soil surface. cm of the mineral soil surface. Lithic Histoturbels Glacic Aquiturbels ABAB. Other Histoturbels that have a glacic layer within 100 ABBC. Other Aquiturbels that have a sulfuric horizon or cm of the soil surface. sulfidic materials within 100 cm of the mineral soil surface. Glacic Histoturbels Sulfuric Aquiturbels ABAC. Other Histoturbels that have more than 40 percent, by ABBD. Other Aquiturbels that have either: volume, organic soil materials from the soil surface to a depth of 50 cm in 75 percent or less of the pedon. 1. Organic soil materials that are discontinuous at the Ruptic Histoturbels surface; or 2. Organic soil materials at the surface that change in ABAD. Other Histoturbels. thickness fourfold or more within a pedon. Typic Histoturbels Ruptic-Histic Aquiturbels 152 Keys to Soil Taxonomy

Molliturbels 1. A mollic epipedon that is 40 cm or more thick with a texture class finer than loamy fine sand; and Key to Subgroups 2. A slope of less than 25 percent. ABDA. Molliturbels that have a lithic contact within 50 cm of Cumulic Molliturbels the mineral soil surface. Lithic Molliturbels ABDH. Other Molliturbels that have, in one or more horizons within 100 cm of the mineral soil surface, distinct or prominent ABDB. Other Molliturbels that have a glacic layer within 100 redox concentrations and also aquic conditions for some time cm of the mineral soil surface. during normal years (or artificial drainage). Glacic Molliturbels Aquic Molliturbels

ABDC. Other Molliturbels that have one or both of the ABDI. Other Molliturbels. following: Typic Molliturbels 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or more for Psammoturbels some time during normal years and slickensides or wedge- Key to Subgroups shaped peds in a layer 15 cm or more thick that has its upper ABFA. Psammoturbels that have a lithic contact within 50 cm boundary within 125 cm of the mineral soil surface; or of the mineral soil surface. 2. A linear extensibility of 6.0 cm or more between the Lithic Psammoturbels mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. ABFB. Other Psammoturbels that have a glacic layer within Vertic Molliturbels 100 cm of the mineral soil surface. Glacic Psammoturbels ABDD. Other Molliturbels that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm ABFC. Other Psammoturbels that have a horizon 5 cm or of the mineral soil surface, a fine-earth fraction with both a bulk more thick that has one or more of the following: 3 density of 1.0 g/cm or less, measured at 33 kPa water retention, 1. In 25 percent or more of each pedon, cementation by 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling organic matter and aluminum, with or without iron; or more than 1.0. 1 Andic Molliturbels 2. Al plus /2 Fe percentages (by ammonium oxalate) totaling 0.25 or more, and half that amount or less in an ABDE. Other Molliturbels that have, throughout one or more overlying horizon; or horizons with a total thickness of 18 cm or more within 75 cm 3. An ODOE value of 0.12 or more, and a value half as of the mineral soil surface, one or both of the following: high or lower in an overlying horizon. 1. More than 35 percent (by volume) fragments coarser Spodic Psammoturbels than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or ABFD. Other Psammoturbels. Typic Psammoturbels 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and Umbriturbels a. In the 0.02 to 2.0 mm fraction, 5 percent or more Key to Subgroups volcanic glass; and ABEA. Umbriturbels that have a lithic contact within 50 cm 1 b. [(Al plus /2 Fe, percent extracted by ammonium of the mineral soil surface. oxalate) times 60] plus the volcanic glass (percent) is Lithic Umbriturbels equal to 30 or more. Vitrandic Molliturbels ABEB. Other Umbriturbels that have a glacic layer within 100 cm of the mineral soil surface. ABDF. Other Molliturbels that have a folistic epipedon. Glacic Umbriturbels Folistic Molliturbels ABEC. Other Umbriturbels that have one or both of the ABDG. Other Molliturbels that have both: following: Gelisols 153

1. Cracks within 125 cm of the mineral soil surface that are a. In the 0.02 to 2.0 mm fraction, 5 percent or more 5 mm or more wide through a thickness of 30 cm or more for volcanic glass; and

some time during normal years and slickensides or wedge- 1 b. [(Al plus /2 Fe, percent extracted by ammonium shaped peds in a layer 15 cm or more thick that has its upper oxalate) times 60] plus the volcanic glass (percent) is boundary within 125 cm of the mineral soil surface; or equal to 30 or more. 2. A linear extensibility of 6.0 cm or more between the Vitrandic Umbriturbels mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. ABEF. Other Umbriturbels that have a folistic epipedon. Vertic Umbriturbels Folistic Umbriturbels ABED. Other Umbriturbels that have, throughout one or more ABEG. Other Umbriturbels that have both: horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction with both a bulk 1. An umbric epipedon that is 40 cm or more thick with a density of 1.0 g/cm3 or less, measured at 33 kPa water retention, texture class finer than loamy fine sand; and 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling 2. A slope of less than 25 percent. more than 1.0. Cumulic Umbriturbels Andic Umbriturbels ABEH. Other Umbriturbels that have, in one or more horizons ABEE. Other Umbriturbels that have, throughout one or more within 100 cm of the mineral soil surface, distinct or prominent horizons with a total thickness of 18 cm or more within 75 cm redox concentrations and also aquic conditions for some time of the mineral soil surface, one or both of the following: during normal years (or artificial drainage). 1. More than 35 percent (by volume) fragments coarser Aquic Umbriturbels than 2.0 mm, of which more than 66 percent is cinders, G E pumice, and pumicelike fragments; or ABEI. Other Umbriturbels. L Typic Umbriturbels 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and

155

CHAPTER 10 Histosols

Key to Suborders Fibrists BA. Histosols that are saturated with water for less than 30 Key to Great Groups cumulative days during normal years (and are not artificially drained). BCA. Fibrists that have a cryic soil temperature regime. Folists, p. 156 Cryofibrists, p. 155

BB. Other Histosols that have a positive water potential at the BCB. Other Fibrists in which fibricSphagnum constitutes soil surface for more than 21 hours of each day in all years. three-fourths or more of the volume to either a depth of 90 cm Wassists, p. 159 from the soil surface or to a densic, lithic, or paralithic contact, fragmental materials, or other mineral soil materials if at a depth BC. Other Histosols that: of less than 90 cm. Sphagnofibrists, p. 156 1. Have more thickness of fibric soil materials than any other kind of organic soil materials either: BCC. Other Fibrists. Haplofibrists, p. 156 a. In the organic parts of the subsurface tier if there is no continuous layer of mineral soil material 40 cm or more thick that has its upper boundary within the subsurface Cryofibrists H I tier; or Key to Subgroups S b. In the combined thickness of the organic parts of the BCAA. Cryofibrists that have a layer of water within the surface and subsurface tiers and there is a continuous control section, below the surface tier. layer of mineral soil material 40 cm or more thick that has Hydric Cryofibrists its upper boundary within the subsurface tier; and BCAB. Other Cryofibrists that have a lithic contact at the 2. Do not have a sulfuric horizon within 50 cm of the soil lower boundary of the control section. surface; and Lithic Cryofibrists 3. Do not have sulfidic materials within 100 cm of the soil surface. BCAC. Other Cryofibrists that have a layer of mineral soil Fibrists, p. 155 material 30 cm or more thick that has its upper boundary within the control section, below the surface tier. BD. Other Histosols that have more thickness of sapric soil Terric Cryofibrists materials than any other kind of organic soil materials either: BCAD. Other Cryofibrists that have, within the organic soil 1. In the organic parts of the subsurface tier if there is no materials, either one layer of mineral soil material 5 cm or continuous layer of mineral soil material 40 cm or more thick more thick or two or more layers of mineral soil material of any that has its upper boundary within the subsurface tier; or thickness in the control section, below the surface tier. 2. In the combined thickness of the organic parts of the Fluvaquentic Cryofibrists surface and subsurface tiers and there is a continuous layer of mineral soil material 40 cm or more thick that has its BCAE. Other Cryofibrists in which three-fourths or more of upper boundary within the subsurface tier. the fiber volume in the surface tier is derived fromSphagnum . Saprists, p. 158 Sphagnic Cryofibrists

BE. Other Histosols. BCAF. Other Cryofibrists. Hemists, p. 157 Typic Cryofibrists 156 Keys to Soil Taxonomy

Haplofibrists BCBE. Other Sphagnofibrists that have, within the organic soil materials, either one layer of mineral soil material 5 cm or Key to Subgroups more thick or two or more layers of mineral soil material of any BCCA. Haplofibrists that have a layer of water within the thickness in the control section, below the surface tier. control section, below the surface tier. Fluvaquentic Sphagnofibrists Hydric Haplofibrists BCBF. Other Sphagnofibrists that have one or more layers of BCCB. Other Haplofibrists that have a lithic contact at the hemic and sapric materials with a total thickness of 25 cm or lower boundary of the control section. more in the control section, below the surface tier. Lithic Haplofibrists Hemic Sphagnofibrists

BCCC. Other Haplofibrists that have one or more limnic BCBG. Other Sphagnofibrists. layers with a total thickness of 5 cm or more within the control Typic Sphagnofibrists section. Limnic Haplofibrists Folists BCCD. Other Haplofibrists that have a layer of mineral soil Key to Great Groups material 30 cm or more thick that has its upper boundary within the control section, below the surface tier. BAA. Folists that have a cryic soil temperature regime. Terric Haplofibrists Cryofolists, p. 156

BCCE. Other Haplofibrists that have, within the organic soil BAB. Other Folists that have an aridic (or torric) soil moisture materials, either one layer of mineral soil material 5 cm or regime. more thick or two or more layers of mineral soil material of any Torrifolists, p. 156 thickness in the control section, below the surface tier. Fluvaquentic Haplofibrists BAC. Other Folists that have an ustic or xeric soil moisture regime. BCCF. Other Haplofibrists that have one or more layers of Ustifolists, p. 157 hemic and sapric materials with a total thickness of 25 cm or more in the control section, below the surface tier. BAD. Other Folists. Hemic Haplofibrists Udifolists, p. 157

BCCG. Other Haplofibrists. Cryofolists Typic Haplofibrists Key to Subgroups Sphagnofibrists BAAA. Cryofolists that have a lithic contact within 50 cm of Key to Subgroups the soil surface. BCBA. Sphagnofibrists that have a layer of water within the Lithic Cryofolists control section, below the surface tier. Hydric Sphagnofibrists BAAB. Other Cryofolists. Typic Cryofolists BCBB. Other Sphagnofibrists that have a lithic contact at the lower boundary of the control section. Torrifolists Lithic Sphagnofibrists Key to Subgroups BCBC. Other Sphagnofibrists that have one or more limnic BABA. Torrifolists that have a lithic contact within 50 cm of layers with a total thickness of 5 cm or more within the control the soil surface. section. Lithic Torrifolists Limnic Sphagnofibrists BABB. Other Torrifolists. BCBD. Other Sphagnofibrists that have a layer of mineral soil Typic Torrifolists material 30 cm or more thick that has its upper boundary within the control section, below the surface tier. Terric Sphagnofibrists Histosols 157

Udifolists BEDC. Other Cryohemists that have a layer of mineral soil material 30 cm or more thick that has its upper boundary within Key to Subgroups the control section, below the surface tier. BADA. Udifolists that have a lithic contact within 50 cm of Terric Cryohemists the soil surface. Lithic Udifolists BEDD. Other Cryohemists that have, within the organic soil materials, either one layer of mineral soil material 5 cm or BADB. Other Udifolists. more thick or two or more layers of mineral soil material of any Typic Udifolists thickness in the control section, below the surface tier. Fluvaquentic Cryohemists Ustifolists BEDE. Other Cryohemists. Key to Subgroups Typic Cryohemists BACA. Ustifolists that have a lithic contact within 50 cm of the soil surface. Haplohemists Lithic Ustifolists Key to Subgroups BACB. Other Ustifolists. BEEA. Haplohemists that have a layer of water within the Typic Ustifolists control section, below the surface tier. Hydric Haplohemists Hemists BEEB. Other Haplohemists that have a lithic contact at the Key to Great Groups lower boundary of the control section. Lithic Haplohemists BEA. Hemists that have a sulfuric horizon within 50 cm of the soil surface. BEEC. Other Haplohemists that have one or more limnic Sulfohemists, p. 158 layers with a total thickness of 5 cm or more within the control H I section. S BEB. Other Hemists that have sulfidic materials within 100 Limnic Haplohemists cm of the soil surface. Sulfihemists, p. 158 BEED. Other Haplohemists that have a layer of mineral soil material 30 cm or more thick that has its upper boundary within BEC. Other Hemists that have a horizon 2 cm or more thick the control section, below the surface tier. in which humilluvic materials constitute one-half or more of the Terric Haplohemists volume. Luvihemists, p. 158 BEEE. Other Haplohemists that have, within the organic soil materials, either one layer of mineral soil material 5 cm or BED. Other Hemists that have a cryic soil temperature regime. more thick or two or more layers of mineral soil material of any Cryohemists, p. 157 thickness in the control section, below the surface tier. Fluvaquentic Haplohemists BEE. Other Hemists. Haplohemists, p. 157 BEEF. Other Haplohemists that have one or more layers of fibric materials with a total thickness of 25 cm or more in the Cryohemists control section, below the surface tier. Fibric Haplohemists Key to Subgroups BEDA. Cryohemists that have a layer of water within the BEEG. Other Haplohemists that have one or more layers of control section, below the surface tier. sapric materials with a total thickness of 25 cm or more below Hydric Cryohemists the surface tier. Sapric Haplohemists BEDB. Other Cryohemists that have a lithic contact at the lower boundary of the control section. BEEH. Other Haplohemists. Lithic Cryohemists Typic Haplohemists 158 Keys to Soil Taxonomy

Luvihemists material 30 cm or more thick that has its upper boundary within the control section, below the surface tier. Key to Subgroups Terric Cryosaprists BECA. All Luvihemists (provisionally). Typic Luvihemists BDCD. Other Cryosaprists that have, within the organic soil materials, either one layer of mineral soil material 5 cm or Sulfihemists more thick or two or more layers of mineral soil material of any thickness in the control section, below the surface tier. Key to Subgroups Fluvaquentic Cryosaprists BEBA. Sulfihemists that have a layer of mineral soil material 30 cm or more thick that has its upper boundary within the BDCE. Other Cryosaprists. control section, below the surface tier. Typic Cryosaprists Terric Sulfihemists Haplosaprists BEBB. Other Sulfihemists. Key to Subgroups Typic Sulfihemists BDDA. Haplosaprists that have a lithic contact at the lower Sulfohemists boundary of the control section. Lithic Haplosaprists Key to Subgroups BEAA. All Sulfohemists (provisionally). BDDB. Other Haplosaprists that have one or more limnic Typic Sulfohemists layers with a total thickness of 5 cm or more within the control section. Saprists Limnic Haplosaprists Key to Great Groups BDDC. Other Haplosaprists that have both: BDA. Saprists that have a sulfuric horizon within 50 cm of the 1. Throughout a layer 30 cm or thick that has its soil surface. upper boundary within the control section, an electrical Sulfosaprists, p. 159 conductivity of 30 dS/m or more (1:1 soil:water) for 6 months or more during normal years; and BDB. Other Saprists that have sulfidic materials within 100 2. A layer of mineral soil material 30 cm or more thick that cm of the soil surface. has its upper boundary within the control section, below the Sulfisaprists, p. 159 surface tier. Halic Terric Haplosaprists BDC. Other Saprists that have a cryic soil temperature regime. Cryosaprists, p. 158 BDDD. Other Haplosaprists that have, throughout a layer 30 cm or more thick that has its upper boundary within the BDD. Other Saprists. control section, an electrical conductivity of 30 dS/m or more Haplosaprists, p. 158 (1:1 soil:water) for 6 months or more during normal years. Halic Haplosaprists Cryosaprists BDDE. Other Haplosaprists that have a layer of mineral soil Key to Subgroups material 30 cm or more thick that has its upper boundary within BDCA. Cryosaprists that have a lithic contact at the lower the control section, below the surface tier. boundary of the control section. Terric Haplosaprists Lithic Cryosaprists BDDF. Other Haplosaprists that have, within the organic BDCB. Other Cryosaprists that have one or more limnic soil materials, either one layer of mineral soil material 5 cm or layers with a total thickness of 5 cm or more within the control more thick or two or more layers of mineral soil material of any section. thickness in the control section, below the surface tier. Limnic Cryosaprists Fluvaquentic Haplosaprists

BDCC. Other Cryosaprists that have a layer of mineral soil BDDG. Other Haplosaprists that have one or more layers of Histosols 159

fibric or hemic materials with a total thickness of 25 cm or more layer of mineral soil material 40 cm or more thick that has in the control section, below the surface tier. its upper boundary within the subsurface tier; and Hemic Haplosaprists 2. Do not have sulfidic materials within 100 cm of the soil surface. BDDH. Other Haplosaprists. Fibric Frasiwassists Typic Haplosaprists BBAB. Other Frasiwassists that have more thickness of sapric Sulfisaprists soil materials than any other kind of organic soil materials Key to Subgroups either: BDBA. Sulfisaprists that have a layer of mineral soil material 1. In the organic parts of the subsurface tier if there is no 30 cm or more thick that has its upper boundary within the continuous layer of mineral soil material 40 cm or more thick control section, below the surface tier. that has its upper boundary within the subsurface tier; or Terric Sulfisaprists 2. In the combined thickness of the organic parts of the surface and subsurface tiers and there is a continuous layer BDBB. Other Sulfisaprists. of mineral soil material 40 cm or more thick that has its Typic Sulfisaprists upper boundary within the subsurface tier. Sapric Frasiwassists Sulfosaprists Key to Subgroups BBAC. Other Frasiwassists. Typic Frasiwassists BDAA. All Sulfosaprists (provisionally). Typic Sulfosaprists Haplowassists Wassists Key to Subgroups BBCA. Haplowassists that have a horizon or horizons, with a Key to Great Groups H combined thickness of 15 cm within 100 cm of the soil surface, I BBA. Wassists that have, in all horizons within 100 cm of the that contain sulfidic materials. S soil surface, an electrical conductivity of less than 0.2 dS/m in a Sulfic Haplowassists 5:1, by volume, mixture (not extract) of water and soil. Frasiwassists, p. 159 BBCB. Other Haplowassists that have more thickness of fibric soil materials than any other kind of organic soil materials BBB. Other Wassists that have a horizon or horizons, with a either: combined thickness of at least 15 cm within 50 cm of the soil surface, that contain sulfidic materials. 1. In the organic parts of the subsurface tier if there is no Sulfiwassists, p. 160 continuous layer of mineral soil material 40 cm or more thick that has its upper boundary within the subsurface tier; or BBC. Other Wassists. 2. In the combined thickness of the organic parts of the Haplowassists, p. 159 surface and subsurface tiers and there is a continuous layer of mineral soil material 40 cm or more thick that has its Frasiwassists upper boundary within the subsurface tier. Key to Subgroups Fibric Haplowassists

BBAA. Frasiwassists that: BBCC. Other Haplowassists that have more thickness 1. Have more thickness of fibric soil materials than any of sapric soil materials than any other kind of organic soil other kind of organic soil materials either: materials either: a. In the organic parts of the subsurface tier if there is no 1. In the organic parts of the subsurface tier if there is no continuous layer of mineral soil material 40 cm or more continuous layer of mineral soil material 40 cm or more thick thick that has its upper boundary within the subsurface that has its upper boundary within the subsurface tier; or tier; or 2. In the combined thickness of the organic parts of the b. In the combined thickness of the organic parts of the surface and subsurface tiers and there is a continuous layer surface and subsurface tiers and there is a continuous 160

of mineral soil material 40 cm or more thick that has its BBBB. Other Sulfiwassists that have more thickness of sapric upper boundary within the subsurface tier. soil materials than any other kind of organic soil materials Sapric Haplowassists either:

BBCD. Other Haplowassists. 1. In the organic parts of the subsurface tier if there is no Typic Haplowassists continuous layer of mineral soil material 40 cm or more thick that has its upper boundary within the subsurface tier; or Sulfiwassists 2. In the combined thickness of the organic parts of the Key to Subgroups surface and subsurface tiers and there is a continuous layer of mineral soil material 40 cm or more thick that has its BBBA. Sulfiwassists that have more thickness of fibric soil upper boundary within the subsurface tier. materials than any other kind of organic soil materials : either Sapric Sulfiwassists 1. In the organic parts of the subsurface tier if there is no continuous layer of mineral soil material 40 cm or more thick BBBC. Other Sulfiwassists. that has its upper boundary within the subsurface tier; or Typic Sulfiwassists 2. In the combined thickness of the organic parts of the surface and subsurface tiers and there is a continuous layer of mineral soil material 40 cm or more thick that has its upper boundary within the subsurface tier. Fibric Sulfiwassists 161

CHAPTER 11

Inceptisols

Key to Suborders KF. Other Inceptisols that have a xeric soil moisture regime. Xerepts, p. 189 KA. Inceptisols that have one or more of the following: 1. In a layer above a densic, lithic, or paralithic contact or KG. Other Inceptisols. in a layer at a depth between 40 and 50 cm from the mineral Udepts, p. 174 soil surface, whichever is shallower, aquic conditions for some time in normal years (or artificial drainage) andone or Anthrepts more of the following: a. A histic epipedon; or Key to Great Groups b. A sulfuric horizon within 50 cm of the mineral soil KBA. Anthrepts that have a plaggen epipedon. surface; or Plagganthrepts, p. 161 c. A layer directly under the epipedon, or within 50 cm KBB. Other Anthrepts. of the mineral soil surface, that has, on faces of peds or in Haplanthrepts, p. 161 the matrix if peds are absent, 50 percent or more chroma of either: Haplanthrepts (1) 2 or less if there are redox concentrations; or Key to Subgroups (2) 1 or less; or KBBA. All Haplanthrepts (provisionally). d. Within 50 cm of the mineral soil surface, enough Typic Haplanthrepts I active ferrous iron to give a positive reaction to N C alpha,alpha-dipyridyl at a time when the soil is not being Plagganthrepts irrigated; or Key to Subgroups 2. An exchangeable sodium percentage (ESP) of 15 or more (or a sodium adsorption ratio [SAR] of 13 or more) KBAA. All Plagganthrepts (provisionally). in half or more of the soil volume within 50 cm of the Typic Plagganthrepts mineral soil surface, a decrease in ESP (or SAR) values with increasing depth below 50 cm, and ground water within 100 Aquepts cm of the mineral soil surface for some time during the year. Aquepts, p. 161 Key to Great Groups KAA. Aquepts that have a sulfuric horizon within 50 cm of KB. Other Inceptisols that have a plaggen or anthropic the mineral soil surface. epipedon. Sulfaquepts, p. 167 Anthrepts, p. 161 KAB. Other Aquepts that have, within 100 cm of the mineral KC. Other Inceptisols that have a gelic soil temperature regime. soil surface, one or more horizons in which plinthite or a , p. 173 Gelepts cemented diagnostic horizon either forms a continuous phase or constitutes one-half or more of the volume. KD. Other Inceptisols that have a cryic soil temperature Petraquepts, p. 167 regime. Cryepts, p. 167 KAC. Other Aquepts that have either: KE. Other Inceptisols that have an ustic soil moisture regime. 1. A salic horizon; or Ustepts, p. 182 162 Keys to Soil Taxonomy

2. In one or more horizons with a total thickness of 25 KAFD. Other Cryaquepts that have one or both of the cm or more within 50 cm of the mineral soil surface, an following: exchangeable sodium percentage (ESP) of 15 or more (or a 1. Cracks within 125 cm of the mineral soil surface that are sodium adsorption ratio [SAR] of 13 or more) and a decrease 5 mm or more wide through a thickness of 30 cm or more in ESP (or SAR) values with increasing depth below 50 cm. for some time in normal years and slickensides or wedge- Halaquepts, p. 166 shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil surface; or KAD. Other Aquepts that have a fragipan within 100 cm of the mineral soil surface. 2. A linear extensibility of 6.0 cm or more between the Fragiaquepts, p. 165 mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. KAE. Other Aquepts that have a gelic soil temperature regime. Vertic Cryaquepts Gelaquepts, p. 165 KAFE. Other Cryaquepts that have a histic epipedon. KAF. Other Aquepts that have a cryic soil temperature regime. Histic Cryaquepts Cryaquepts, p. 162 KAFF. Other Cryaquepts that have, throughout one or more KAG. Other Aquepts that have, in one or more layers at horizons with a total thickness of 18 cm or more within 75 cm least 25 cm thick (cumulative) within 100 cm of the mineral of the mineral soil surface, one or more of the following: soil surface, 25 percent or more (by volume) recognizable 1. A fine-earth fraction with both a bulk density of 1.0 bioturbation, such as filled animal burrows, wormholes, or casts. g/cm3 or less, measured at 33 kPa water retention, and Al Vermaquepts, p. 167 1 plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0; or KAH. Other Aquepts that have a histic, melanic, mollic, or umbric epipedon. 2. More than 35 percent (by volume) fragments coarser Humaquepts, p. 166 than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or KAI. Other Aquepts that have episaturation. 3. A fine-earth fraction containing 30 percent or more Epiaquepts, p. 164 particles 0.02 to 2.0 mm in diameter; and

KAJ. Other Aquepts. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Endoaquepts, p. 163 volcanic glass; and 1 b. [(Al plus /2 Fe, percent extracted by ammonium Cryaquepts oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. Key to Subgroups Aquandic Cryaquepts KAFA. Cryaquepts that have, within 150 cm of the mineral soil surface, one or more of the following: KAFG. Other Cryaquepts that have a slope of less than 25 percent and one or both of the following: 1. A sulfuric horizon; or 1. At a depth of 125 cm below the mineral soil surface, 2. A horizon 15 cm or more thick that has all of the an organic-carbon content (Holocene age) of 0.2 percent or characteristics of a sulfuric horizon, except that it has a pH more and no densic, lithic, or paralithic contact within that value between 3.5 and 4.0 and does not have sulfide or other depth; or sulfur-bearing minerals; or 2. An irregular decrease in organic-carbon content 3. Sulfidic materials. (Holocene age) between a depth of 25 cm and either a depth Sulfic Cryaquepts of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is shallower. KAFB. Other Cryaquepts that have both a histic epipedon and Fluvaquentic Cryaquepts a lithic contact within 50 cm of the mineral soil surface. Histic Lithic Cryaquepts KAFH. Other Cryaquepts that have both: KAFC. Other Cryaquepts that have a lithic contact within 50 1. Chroma of 3 or more in 40 percent or more of the matrix cm of the mineral soil surface. of one or more horizons at a depth between 15 and 50 cm Lithic Cryaquepts from the mineral soil surface; and Inceptisols 163

2. A mollic or umbric epipedon. 2. More than 35 percent (by volume) fragments coarser Aeric Humic Cryaquepts than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or KAFI. Other Cryaquepts that have chroma of 3 or more in 40 3. A fine-earth fraction containing 30 percent or more percent or more of the matrix of one or more horizons at a depth particles 0.02 to 2.0 mm in diameter; and between 15 and 50 cm from the mineral soil surface. Aeric Cryaquepts a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and

KAFJ. Other Cryaquepts that have a mollic or umbric 1 b. [(Al plus /2 Fe, percent extracted by ammonium epipedon. oxalate) times 60] plus the volcanic glass (percent) is Humic Cryaquepts equal to 30 or more. Aquandic Endoaquepts KAFK. Other Cryaquepts. Typic Cryaquepts KAJE. Other Endoaquepts that have, in one or more horizons between the A or Ap horizon and a depth of 75 cm below the Endoaquepts mineral soil surface, one of the following colors: Key to Subgroups 1. Hue of 7.5YR or redder in 50 percent or more of the KAJA. Endoaquepts that have, within 150 cm of the mineral matrix; and soil surface, one or more of the following: a. If peds are present, either chroma of 2 or more on 50 1. A sulfuric horizon; or percent or more of ped exteriors or no redox depletions with chroma of 2 or less in ped interiors; or 2. A horizon 15 cm or more thick that has all of the characteristics of a sulfuric horizon, except that it has a pH b. If peds are absent, a chroma of 2 or more in 50 value between 3.5 and 4.0 and does not have sulfide or other percent or more of the matrix; or sulfur-bearing minerals; or 2. In 50 percent or more of the matrix, hue of 10YR or 3. Sulfidic materials. yellower; and either Sulfic Endoaquepts a. Both a color value, moist, and chroma of 3 or more; or KAJB. Other Endoaquepts that have a lithic contact within 50 I N cm of the mineral soil surface. b. Chroma of 2 or more if there are no redox C Lithic Endoaquepts concentrations; and 3. A slope of less than 25 percent and one or both of the KAJC. Other Endoaquepts that have one or both of the following: following: a. At a depth of 125 cm below the mineral soil surface, 1. Cracks within 125 cm of the mineral soil surface that are an organic-carbon content (Holocene age) of 0.2 percent 5 mm or more wide through a thickness of 30 cm or more or more and no densic, lithic, or paralithic contact within for some time in normal years and slickensides or wedge- that depth; or shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil surface; or b. An irregular decrease in organic-carbon content (Holocene age) between a depth of 25 cm and either 2. A linear extensibility of 6.0 cm or more between the a depth of 125 cm below the mineral soil surface or a mineral soil surface and either a depth of 100 cm or a densic, densic, lithic, or paralithic contact, whichever is shallower. lithic, or paralithic contact, whichever is shallower. Fluventic Endoaquepts Vertic Endoaquepts KAJF. Other Endoaquepts that have a slope of less than 25 KAJD. Other Endoaquepts that have, throughout one or more percent and one or both of the following: horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or more of the following: 1. At a depth of 125 cm below the mineral soil surface, an organic-carbon content (Holocene age) of 0.2 percent or 1. A fine-earth fraction with both a bulk density of 1.0 more and no densic, lithic, or paralithic contact within that g/cm3 or less, measured at 33 kPa water retention, and Al 1 depth; or plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0; or 2. An irregular decrease in organic-carbon content 164 Keys to Soil Taxonomy

(Holocene age) between a depth of 25 cm and either a depth Epiaquepts of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is shallower. Key to Subgroups Fluvaquentic Endoaquepts KAIA. Epiaquepts that have one or both of the following:

KAJG. Other Endoaquepts that have fragic soil properties: 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or more 1. In 30 percent or more of the volume of a layer 15 cm or for some time in normal years and slickensides or wedge- more thick that has its upper boundary within 100 cm of the shaped peds in a layer 15 cm or more thick that has its upper mineral soil surface; or boundary within 125 cm of the mineral soil surface; or 2. In 60 percent or more of the volume of a layer 15 cm or 2. A linear extensibility of 6.0 cm or more between the more thick. mineral soil surface and either a depth of 100 cm or a densic, Fragic Endoaquepts lithic, or paralithic contact, whichever is shallower. Vertic Epiaquepts KAJH. Other Endoaquepts that have, in one or more horizons between the A or Ap horizon and a depth of 75 cm below the KAIB. Other Epiaquepts that have, throughout one or more mineral soil surface, one of the following colors: horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or more of the following: 1. Hue of 7.5YR or redder in 50 percent or more of the matrix; and 1. A fine-earth fraction with both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water retention, and Al 1 a. If peds are present, either chroma of 2 or more on 50 plus /2 Fe percentages (by ammonium oxalate) totaling more percent or more of ped exteriors or no redox depletions than 1.0; or with chroma of 2 or less in ped interiors; or 2. More than 35 percent (by volume) fragments coarser b. If peds are absent, chroma of 2 or more in 50 percent than 2.0 mm, of which more than 66 percent is cinders, or more of the matrix; or pumice, and pumicelike fragments; or 2. In 50 percent or more of the matrix, hue of 10YR or 3. A fine-earth fraction containing 30 percent or more yellower and either: particles 0.02 to 2.0 mm in diameter; and a. Both a color value, moist, and chroma of 3 or more; a. In the 0.02 to 2.0 mm fraction, 5 percent or more or volcanic glass; and 1 b. Chroma of 2 or more if there are no redox b. [(Al plus /2 Fe, percent extracted by ammonium concentrations. oxalate) times 60] plus the volcanic glass (percent) is Aeric Endoaquepts equal to 30 or more. Aquandic Epiaquepts KAJI. Other Endoaquepts that have both: KAIC. Other Epiaquepts that have a slope of less than 25 1. A color value, moist, of 3 or less and a color value, dry, percent and one or both of the following: of 5 or less (crushed and smoothed sample) either throughout the upper 15 cm of the mineral soil (unmixed) or between the 1. At a depth of 125 cm below the mineral soil surface, an organic-carbon content (Holocene age) of 0.2 percent or mineral soil surface and a depth of 15 cm after mixing; and more and no densic, lithic, or paralithic contact within that

2. A base saturation (by NH4OAc) of less than 50 percent depth; or in some part within 100 cm of the mineral soil surface. 2. An irregular decrease in organic-carbon content Humic Endoaquepts (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a densic, lithic, KAJJ. Other Endoaquepts that have a color value, moist, or paralithic contact, whichever is shallower. of 3 or less and a color value, dry, of 5 or less (crushed and Fluvaquentic Epiaquepts smoothed sample) either throughout the upper 15 cm of the mineral soil (unmixed) or between the mineral soil surface and a KAID. Other Epiaquepts that have fragic soil properties depth of 15 cm after mixing. either: Mollic Endoaquepts 1. In 30 percent or more of the volume of a layer 15 cm or KAJK. Other Endoaquepts. more thick that has its upper boundary within 100 cm of the Typic Endoaquepts mineral soil surface; or Inceptisols 165

2. In 60 percent or more of the volume of a layer 15 cm or 1. 3 or more; or more thick. 2. 2 or more if there are no redox concentrations. Fragic Epiaquepts Aeric Fragiaquepts KAIE. Other Epiaquepts that have, in one or more horizons KADB. Other Fragiaquepts that have a histic, mollic, or between the A or Ap horizon and a depth of 75 cm below the umbric epipedon. mineral soil surface, one of the following colors: Humic Fragiaquepts 1. Hue of 7.5YR or redder in 50 percent or more of the matrix; and KADC. Other Fragiaquepts. Typic Fragiaquepts a. If peds are present, either chroma of 2 or more on 50 percent or more of ped exteriors or no redox depletions Gelaquepts with chroma of 2 or less in ped interiors; or Key to Subgroups b. If peds are absent, chroma of 2 or more in 50 percent or more of the matrix; or KAEA. Gelaquepts that have a lithic contact within 50 cm of the mineral soil surface. 2. In 50 percent or more of the matrix, hue of 10YR or Lithic Gelaquepts yellower and either: a. Both a color value, moist, and chroma of 3 or more; KAEB. Other Gelaquepts that have a histic epipedon. or Histic Gelaquepts

b. Chroma of 2 or more if there are no redox KAEC. Other Gelaquepts that have, throughout one or more concentrations. horizons with a total thickness of 18 cm or more within 75 cm Aeric Epiaquepts of the mineral soil surface, one or more of the following: 1. A fine-earth fraction with both a bulk density of 1.0 KAIF. Other Epiaquepts that have both: g/cm3 or less, measured at 33 kPa water retention, and Al 1 1. A color value, moist, of 3 or less and a color value, dry, plus /2 Fe percentages (by ammonium oxalate) totaling more of 5 or less (crushed and smoothed sample) either throughout than 1.0; or the upper 15 cm of the mineral soil (unmixed) or between 2. More than 35 percent (by volume) fragments coarser I the mineral soil surface and a depth of 15 cm after mixing; N than 2.0 mm, of which more than 66 percent is cinders, C and pumice, and pumicelike fragments; or 2. A base saturation (by NH OAc) of less than 50 percent 4 3. A fine-earth fraction containing 30 percent or more in some part within 100 cm of the mineral soil surface. particles 0.02 to 2.0 mm in diameter; and Humic Epiaquepts a. In the 0.02 to 2.0 mm fraction, 5 percent or more KAIG. Other Epiaquepts that have a color value, moist, of 3 or volcanic glass; and 1 less and a color value, dry, of 5 or less (crushed and smoothed b. [(Al plus /2 Fe, percent extracted by ammonium sample) either throughout the upper 15 cm of the mineral soil oxalate) times 60] plus the volcanic glass (percent) is (unmixed) or between the mineral soil surface and a depth of 15 equal to 30 or more. cm after mixing. Aquandic Gelaquepts Mollic Epiaquepts KAED. Other Gelaquepts that have a slope of less than 25 KAIH. Other Epiaquepts. percent and one or both of the following: Typic Epiaquepts 1. At a depth of 125 cm below the mineral soil surface, Fragiaquepts an organic-carbon content (Holocene age) of 0.2 percent or more and no densic, lithic, or paralithic contact within that Key to Subgroups depth; or KADA. Fragiaquepts that have, in 50 percent or more of the 2. An irregular decrease in organic-carbon content matrix of one or more horizons either between the plow layer (Holocene age) between a depth of 25 cm and either a depth and a depth of 75 cm below the mineral soil surface or, if there of 125 cm below the mineral soil surface or a densic, lithic, is no plow layer, between depths of 15 and 75 cm, chroma of or paralithic contact, whichever is shallower. either: Fluvaquentic Gelaquepts 166 Keys to Soil Taxonomy

KAEE. Other Gelaquepts that have a mollic or umbric KACD. Other Halaquepts that have chroma of 3 or more in 40 epipedon. percent or more of the matrix of one or more horizons at a depth Humic Gelaquepts between 15 and 75 cm from the mineral soil surface. Aeric Halaquepts KAEF. Other Gelaquepts that have gelic materials within 200 cm of the mineral soil surface. KACE. Other Halaquepts. Turbic Gelaquepts Typic Halaquepts

KAEG. Other Gelaquepts. Humaquepts Typic Gelaquepts Key to Subgroups Halaquepts KAHA. Humaquepts that have an n value of either: Key to Subgroups 1. More than 0.7 (and less than 8 percent clay) in one or more layers at a depth between 20 and 50 cm from the KACA. Halaquepts that have one or both of the following: mineral soil surface; or 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or more 2. More than 0.9 in one or more layers at a depth between for some time in normal years and slickensides or wedge- 50 and 100 cm. shaped peds in a layer 15 cm or more thick that has its upper Hydraquentic Humaquepts boundary within 125 cm of the mineral soil surface; or KAHB. Other Humaquepts that have a histic epipedon. 2. A linear extensibility of 6.0 cm or more between the Histic Humaquepts mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. KAHC. Other Humaquepts that have, throughout one or more Vertic Halaquepts horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or more of the following: KACB. Other Halaquepts that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm 1. A fine-earth fraction with both a bulk density of 1.0 3 of the mineral soil surface, one or more of the following: g/cm or less, measured at 33 kPa water retention, and Al 1 plus /2 Fe percentages (by ammonium oxalate) totaling more 1. A fine-earth fraction with both a bulk density of 1.0 than 1.0; or g/cm3 or less, measured at 33 kPa water retention, and Al 1 plus /2 Fe percentages (by ammonium oxalate) totaling more 2. More than 35 percent (by volume) fragments coarser than 1.0; or than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or 2. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, 3. A fine-earth fraction containing 30 percent or more pumice, and pumicelike fragments; or particles 0.02 to 2.0 mm in diameter; and 3. A fine-earth fraction containing 30 percent or more a. In the 0.02 to 2.0 mm fraction, 5 percent or more particles 0.02 to 2.0 mm in diameter; and volcanic glass; and

1 a. In the 0.02 to 2.0 mm fraction, 5 percent or more b. [(Al plus /2 Fe, percent extracted by ammonium volcanic glass; and oxalate) times 60] plus the volcanic glass (percent) is

1 equal to 30 or more. b. [(Al plus /2 Fe, percent extracted by ammonium Aquandic Humaquepts oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. KAHD. Other Humaquepts that have a slope of less than 25 Aquandic Halaquepts percent; and KACC. Other Halaquepts that have one or more horizons, 1. An umbric or mollic epipedon that is 60 cm or more with a combined thickness of 15 cm or more, that contain 20 thick; and percent or more (by volume) cemented soil material and are 2. One or both of the following: within 100 cm of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. a. At a depth of 125 cm below the mineral soil surface, Duric Halaquepts an organic-carbon content (Holocene age) of 0.2 percent Inceptisols 167

or more and no densic, lithic, or paralithic contact within Sulfaquepts that depth; or Key to Subgroups b. An irregular decrease in organic-carbon content (Holocene age) between a depth of 25 cm and either KAAA. Sulfaquepts that have a salic horizon within 75 cm of a depth of 125 cm below the mineral soil surface or a the mineral soil surface. densic, lithic, or paralithic contact, whichever is shallower. Salidic Sulfaquepts Cumulic Humaquepts KAAB. Other Sulfaquepts that have an n value of either: KAHE. Other Humaquepts that have a slope of less than 25 1. More than 0.7 (and 8 or more percent clay) in one percent and one or both of the following: or more layers at a depth between 20 and 50 cm from the mineral soil surface; or 1. At a depth of 125 cm below the mineral soil surface, an organic-carbon content (Holocene age) of 0.2 percent or 2. More than 0.9 in one or more layers at a depth between more and no densic, lithic, or paralithic contact within that 50 and 100 cm from the mineral soil surface. depth; or Hydraquentic Sulfaquepts 2. An irregular decrease in organic-carbon content KAAC. Other Sulfaquepts. (Holocene age) between a depth of 25 cm and either a depth Typic Sulfaquepts of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is shallower. Fluvaquentic Humaquepts Vermaquepts Key to Subgroups KAHF. Other Humaquepts that have hue of 5Y or redder and chroma of 3 or more in more than 40 percent of the matrix of KAGA. Vermaquepts that have an exchangeable sodium one or more subhorizons at a depth between 15 and 75 cm from percentage of 7 or more (or a sodium adsorption ratio [SAR] the mineral soil surface. of 6 or more) in one or more subhorizons within 100 cm of the Aeric Humaquepts mineral soil surface. Sodic Vermaquepts KAHG. Other Humaquepts. Typic Humaquepts KAGB. Other Vermaquepts. Typic Vermaquepts I N Petraquepts C Cryepts Key to Subgroups Key to Great Groups KABA. Petraquepts that have both: KDA. Cryepts that have an umbric or mollic epipedon. 1. A histic epipedon; and Humicryepts, p. 171 2. A placic horizon. Histic Placic Petraquepts KDB. Other Cryepts that have a calcic or petrocalcic horizon within 100 cm of the mineral soil surface. KABB. Other Petraquepts that have a placic horizon. Calcicryepts, p. 168 Placic Petraquepts KDC. Other Cryepts that meet both of the following: KABC. Other Petraquepts that have one or more horizons 1. Do not have free carbonates within 200 cm of the within 125 cm of the mineral soil surface in which plinthite mineral soil surface; and either forms a continuous phase or constitutes one-half or more 2. Have a base saturation (by NH OAc) of less than 50 of the volume. 4 percent, either: Plinthic Petraquepts a. In one-half or more of the thickness between 25 KABD. Other Petraquepts. and 75 cm below the mineral soil surface and there is Typic Petraquepts no placic horizon, duripan, fragipan, or densic, lithic, 168 Keys to Soil Taxonomy

or paralithic contact within 50 cm of the mineral soil a. A fine-earth fraction with both a bulk density of 1.0 surface; or g/cm3 or less, measured at 33 kPa water retention, and Al plus ½ Fe (by ammonium oxalate) of 1.0 percent or more; b. In a layer, 10 cm or more thick, directly above a or placic horizon, duripan, fragipan, or densic, lithic, or paralithic contact within 50 cm of the mineral soil surface. b. More than 35 percent (by volume) fragments coarser Dystrocryepts, p. 168 than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or KDD. Other Cryepts. c. A fine-earth fraction containing 30 percent or more Haplocryepts, p. 169 particles 0.02 to 2.0 mm in diameter; and Calcicryepts (1) In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and Key to Subgroups (2) [(Al plus ½ Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is KDBA. Calcicryepts that have a lithic contact within 50 cm of equal to 30 or more. the mineral soil surface. Aquandic Dystrocryepts Lithic Calcicryepts KDCC. Other Dystrocryepts that have both: KDBB. Other Calcicryepts that in normal years are saturated with water in one or more layers within 100 cm of the mineral 1. A xeric soil moisture regime; and soil surface for either or both: 2. Throughout one or more horizons with a total thickness 1. 20 or more consecutive days; or of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction with both a bulk density of 1.0 g/cm3 or 2. 30 or more cumulative days. less, measured at 33 kPa water retention, and Al plus ½ Fe Oxyaquic Calcicryepts (by ammonium oxalate) of 1.0 percent or more. Haploxerandic Dystrocryepts KDBC. Other Calcicryepts that have a xeric soil moisture regime. KDCD. Other Dystrocryepts that have both: Xeric Calcicryepts 1. A xeric soil moisture regime; and KDBD. Other Calcicryepts that are dry in some part of the 2. Throughout one or more horizons with a total thickness moisture control section for 45 or more days (cumulative) in of 18 cm or more within 75 cm of the mineral soil surface, normal years. one or both of the following: Ustic Calcicryepts a. More than 35 percent (by volume) fragments coarser KDBE. Other Calcicryepts. than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; Typic Calcicryepts or b. A fine-earth fraction containing 30 percent or more Dystrocryepts particles 0.02 to 2.0 mm in diameter; and Key to Subgroups (1) In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and KDCA. Dystrocryepts that have a lithic contact within 50 cm of the mineral soil surface. (2) [(Al plus ½ Fe, percent extracted by ammonium Lithic Dystrocryepts oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. KDCB. Other Dystrocryepts that have both: Vitrixerandic Dystrocryepts 1. In one or more horizons within 75 cm of the mineral soil KDCE. Other Dystrocryepts that have, throughout one or surface, redox depletions with chroma of 2 or less and also more horizons with a total thickness of 18 cm or more within aquic conditions for some time in normal years (or artificial 75 cm of the mineral soil surface, a fine-earth fraction with drainage); and both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa 2. Throughout one or more horizons with a total thickness water retention, and Al plus ½ Fe (by ammonium oxalate) of 1.0 of 18 cm or more within 75 cm of the mineral soil surface, percent or more. one or more of the following: Andic Dystrocryepts Inceptisols 169

KDCF. Other Dystrocryepts that have, throughout one or more KDCK. Other Dystrocryepts that have lamellae (two or more) horizons with a total thickness of 18 cm or more within 75 cm within 200 cm of the mineral soil surface. of the mineral soil surface, one or both of the following: Lamellic Dystrocryepts

1. More than 35 percent (by volume) fragments coarser KDCL. Other Dystrocryepts that have a slope of less than 25 than 2.0 mm, of which more than 66 percent is cinders, percent and one or both of the following: pumice, and pumicelike fragments; or 1. At a depth of 125 cm below the mineral soil surface, 2. A fine-earth fraction containing 30 percent or more an organic-carbon content (Holocene age) of 0.2 percent or particles 0.02 to 2.0 mm in diameter; and more and no densic, lithic, or paralithic contact within that a. In the 0.02 to 2.0 mm fraction, 5 percent or more depth; or volcanic glass; and 2. An irregular decrease in organic-carbon content b. [(Al plus ½ Fe, percent extracted by ammonium (Holocene age) between a depth of 25 cm and either a depth oxalate) times 60] plus the volcanic glass (percent) is of 125 cm below the mineral soil surface or a densic, lithic, equal to 30 or more. or paralithic contact, whichever is shallower. Vitrandic Dystrocryepts Fluventic Dystrocryepts

KDCG. Other Dystrocryepts that have a slope of less than 25 KDCM. Other Dystrocryepts that have a horizon 5 cm or percent; and more thick that has one or more of the following: 1. In one or more horizons within 75 cm of the mineral soil 1. In 25 percent or more of each pedon, cementation by surface, redox depletions with chroma of 2 or less and also organic matter and aluminum, with or without iron; or aquic conditions for some time in normal years (or artificial 2. Al plus ½ Fe (by ammonium oxalate) of 0.25 percent or drainage); and more and half that amount or less in an overlying horizon; or 2. One or both of the following: 3. An ODOE value of 0.12 or more and a value half as high or lower in an overlying horizon. a. At a depth of 125 cm below the mineral soil surface, Spodic Dystrocryepts an organic-carbon content (Holocene age) of 0.2 percent or more and no densic, lithic, or paralithic contact within KDCN. Other Dystrocryepts that have a xeric soil moisture that depth; or regime. I N b. An irregular decrease in organic-carbon content Xeric Dystrocryepts C (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or KDCO. Other Dystrocryepts that are dry in some part of the a densic, lithic, or paralithic contact, whichever is moisture control section for 45 or more days (cumulative) in shallower. normal years. Fluvaquentic Dystrocryepts Ustic Dystrocryepts

KDCH. Other Dystrocryepts that have a folistic epipedon. KDCP. Other Dystrocryepts that have a base saturation

Folistic Dystrocryepts (by NH4OAc) of 50 percent or more in one or more horizons between 25 and 50 cm from the mineral soil surface. KDCI. Other Dystrocryepts that have, in one or more horizons Eutric Dystrocryepts within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in KDCQ. Other Dystrocryepts. normal years (or artificial drainage). Typic Dystrocryepts Aquic Dystrocryepts Haplocryepts KDCJ. Other Dystrocryepts that in normal years are saturated Key to Subgroups with water in one or more layers within 100 cm of the mineral soil surface for either or both: KDDA. Haplocryepts that have a lithic contact within 50 cm of the mineral soil surface. 1. 20 or more consecutive days; or Lithic Haplocryepts 2. 30 or more cumulative days. Oxyaquic Dystrocryepts KDDB. Other Haplocryepts that have both: 170 Keys to Soil Taxonomy

1. In one or more horizons within 75 cm of the mineral soil oxalate) times 60] plus the volcanic glass (percent) is surface, redox depletions with chroma of 2 or less and also equal to 30 or more. aquic conditions for some time in normal years (or artificial Vitrixerandic Haplocryepts drainage); and KDDE. Other Haplocryepts that have both: 2. Throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, 1. A moisture control section that is dry in some part for 45 one or more of the following: or more days (cumulative) in normal years; and a. A fine-earth fraction with both a bulk density of 1.0 2. Throughout one or more horizons with a total thickness g/cm3 or less, measured at 33 kPa water retention, and Al of 18 cm or more within 75 cm of the mineral soil surface, plus ½ Fe (by ammonium oxalate) of 1.0 percent or more; a fine-earth fraction with both a bulk density of 1.0 g/cm3 or or less, measured at 33 kPa water retention, and Al plus ½ Fe (by ammonium oxalate) of 1.0 percent or more. b. More than 35 percent (by volume) fragments coarser Haplustandic Haplocryepts than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or KDDF. Other Haplocryepts that have both: c. A fine-earth fraction containing 30 percent or more 1. A moisture control section that is dry in some part for 45 particles 0.02 to 2.0 mm in diameter; and or more days (cumulative) in normal years; and (1) In the 0.02 to 2.0 mm fraction, 5 percent or more 2. Throughout one or more horizons with a total thickness volcanic glass; and of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: (2) [(Al plus ½ Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is a. More than 35 percent (by volume) fragments coarser equal to 30 or more. than 2.0 mm, of which more than 66 percent is cinders, Aquandic Haplocryepts pumice, and pumicelike fragments; or b. A fine-earth fraction containing 30 percent or more KDDC. Other Haplocryepts that have both: particles 0.02 to 2.0 mm in diameter; and 1. A xeric soil moisture regime; and (1) In the 0.02 to 2.0 mm fraction, 5 percent or more 2. Throughout one or more horizons with a total thickness volcanic glass; and of 18 cm or more within 75 cm of the mineral soil surface, (2) [(Al plus ½ Fe, percent extracted by ammonium 3 a fine-earth fraction with both a bulk density of 1.0 g/cm or oxalate) times 60] plus the volcanic glass (percent) is less, measured at 33 kPa water retention, and Al plus ½ Fe equal to 30 or more. (by ammonium oxalate) of 1.0 percent or more. Ustivitrandic Haplocryepts Haploxerandic Haplocryepts KDDG. Other Haplocryepts that have, throughout one or more KDDD. Other Haplocryepts that have both: horizons with a total thickness of 18 cm or more within 75 cm 1. A xeric soil moisture regime; and of the mineral soil surface, a fine-earth fraction with both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 2. Throughout one or more horizons with a total thickness and Al plus ½ Fe (by ammonium oxalate) of 1.0 percent or of 18 cm or more within 75 cm of the mineral soil surface, more. one or both of the following: Andic Haplocryepts a. More than 35 percent (by volume) fragments coarser KDDH. Other Haplocryepts that have, throughout one or more than 2.0 mm, of which more than 66 percent is cinders, horizons with a total thickness of 18 cm or more within 75 cm pumice, and pumicelike fragments; or of the mineral soil surface, one or both of the following: b. A fine-earth fraction containing 30 percent or more 1. More than 35 percent (by volume) fragments coarser particles 0.02 to 2.0 mm in diameter; and than 2.0 mm, of which more than 66 percent is cinders, (1) In the 0.02 to 2.0 mm fraction, 5 percent or more pumice, and pumicelike fragments; or volcanic glass; and 2. A fine-earth fraction containing 30 percent or more (2) [(Al plus ½ Fe, percent extracted by ammonium particles 0.02 to 2.0 mm in diameter; and Inceptisols 171

a. In the 0.02 to 2.0 mm fraction, 5 percent or more of 125 cm below the mineral soil surface or a densic, lithic, volcanic glass; and or paralithic contact, whichever is shallower. Fluventic Haplocryepts b. [(Al plus ½ Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is KDDN. Other Haplocryepts that have identifiable secondary equal to 30 or more. carbonates within 100 cm of the mineral soil surface. Vitrandic Haplocryepts Calcic Haplocryepts KDDI. Other Haplocryepts that have a slope of less than 25 KDDO. Other Haplocryepts that have a xeric soil moisture percent; and regime. 1. In one or more horizons within 75 cm of the mineral soil Xeric Haplocryepts surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial KDDP. Other Haplocryepts that are dry in some part of the drainage); and moisture control section for 45 or more days (cumulative) in 2. One or both of the following: normal years. Ustic Haplocryepts a. At a depth of 125 cm below the mineral soil surface, an organic-carbon content (Holocene age) of 0.2 percent KDDQ. Other Haplocryepts. or more and no densic, lithic, or paralithic contact within Typic Haplocryepts that depth; or b. An irregular decrease in organic-carbon content Humicryepts (Holocene age) between a depth of 25 cm and either Key to Subgroups a depth of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is KDAA. Humicryepts that have a lithic contact within 50 cm shallower. of the mineral soil surface. Fluvaquentic Haplocryepts Lithic Humicryepts

KDDJ. Other Haplocryepts that have, in one or more horizons KDAB. Other Humicryepts that have both: within 75 cm of the mineral soil surface, redox depletions with 1. In one or more horizons within 75 cm of the mineral soil chroma of 2 or less and also aquic conditions for some time in surface, redox depletions with chroma of 2 or less and also I normal years (or artificial drainage). N aquic conditions for some time in normal years (or artificial C Aquic Haplocryepts drainage); and KDDK. Other Haplocryepts that in normal years are saturated 2. Throughout one or more horizons with a total thickness with water in one or more layers within 100 cm of the mineral of 18 cm or more within 75 cm of the mineral soil surface, soil surface for either or both: one or more of the following: 1. 20 or more consecutive days; or a. A fine-earth fraction with both a bulk density of 1.0 3 2. 30 or more cumulative days. g/cm or less, measured at 33 kPa water retention, and Al Oxyaquic Haplocryepts plus ½ Fe (by ammonium oxalate) of 1.0 percent or more; or KDDL. Other Haplocryepts that have lamellae (two or more) b. More than 35 percent (by volume) fragments coarser within 200 cm of the mineral soil surface. than 2.0 mm, of which more than 66 percent is cinders, Lamellic Haplocryepts pumice, and pumicelike fragments; or

KDDM. Other Haplocryepts that have a slope of less than 25 c. A fine-earth fraction containing 30 percent or more percent and one or both of the following: particles 0.02 to 2.0 mm in diameter; and 1. At a depth of 125 cm below the mineral soil surface, (1) In the 0.02 to 2.0 mm fraction, 5 percent or more an organic-carbon content (Holocene age) of 0.2 percent or volcanic glass; and more and no densic, lithic, or paralithic contact within that (2) [(Al plus ½ Fe, percent extracted by ammonium depth; or oxalate) times 60] plus the volcanic glass (percent) is 2. An irregular decrease in organic-carbon content equal to 30 or more. (Holocene age) between a depth of 25 cm and either a depth Aquandic Humicryepts 172 Keys to Soil Taxonomy

KDAC. Other Humicryepts that have both: KDAG. Other Humicryepts that have a slope of less than 25 percent; and 1. A xeric soil moisture regime; and 1. In one or more horizons within 75 cm of the mineral soil 2. Throughout one or more horizons with a total thickness surface, redox depletions with chroma of 2 or less and also of 18 cm or more within 75 cm of the mineral soil surface, aquic conditions for some time in normal years (or artificial a fine-earth fraction with both a bulk density of 1.0 g/cm3 or drainage); and less, measured at 33 kPa water retention, and Al plus ½ Fe (by ammonium oxalate) of 1.0 percent or more. 2. One or both of the following: Haploxerandic Humicryepts a. At a depth of 125 cm below the mineral soil surface, an organic-carbon content (Holocene age) of 0.2 percent KDAD. Other Humicryepts that have both: or more and no densic, lithic, or paralithic contact within 1. A xeric soil moisture regime; and that depth; or 2. Throughout one or more horizons with a total thickness b. An irregular decrease in organic-carbon content of 18 cm or more within 75 cm of the mineral soil surface, (Holocene age) between a depth of 25 cm and either one or both of the following: a depth of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is a. More than 35 percent (by volume) fragments coarser shallower. than 2.0 mm, of which more than 66 percent is cinders, Fluvaquentic Humicryepts pumice, and pumicelike fragments; or b. A fine-earth fraction containing 30 percent or more KDAH. Other Humicryepts that have, in one or more horizons particles 0.02 to 2.0 mm in diameter; and within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in (1) In the 0.02 to 2.0 mm fraction, 5 percent or more normal years (or artificial drainage). volcanic glass; and Aquic Humicryepts (2) [(Al plus ½ Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is KDAI. Other Humicryepts that in normal years are saturated equal to 30 or more. with water in one or more layers within 100 cm of the mineral Vitrixerandic Humicryepts soil surface for either or both: 1. 20 or more consecutive days; or KDAE. Other Humicryepts that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm 2. 30 or more cumulative days. of the mineral soil surface, a fine-earth fraction with both a bulk Oxyaquic Humicryepts density of 1.0 g/cm3 or less, measured at 33 kPa water retention, and Al plus ½ Fe (by ammonium oxalate) of 1.0 percent or KDAJ. Other Humicryepts that have lamellae (two or more) more. within 200 cm of the mineral soil surface. Andic Humicryepts Lamellic Humicryepts

KDAF. Other Humicryepts that have, throughout one or more KDAK. Other Humicryepts that have a slope of less than 25 horizons with a total thickness of 18 cm or more within 75 cm percent and one or both of the following: of the mineral soil surface, one or both of the following: 1. At a depth of 125 cm below the mineral soil surface, 1. More than 35 percent (by volume) fragments coarser an organic-carbon content (Holocene age) of 0.2 percent or than 2.0 mm, of which more than 66 percent is cinders, more and no densic, lithic, or paralithic contact within that pumice, and pumicelike fragments; or depth; or 2. A fine-earth fraction containing 30 percent or more 2. An irregular decrease in organic-carbon content particles 0.02 to 2.0 mm in diameter; and (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a densic, lithic, a. In the 0.02 to 2.0 mm fraction, 5 percent or more or paralithic contact, whichever is shallower. volcanic glass; and Fluventic Humicryepts b. [(Al plus ½ Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is KDAL. Other Humicryepts that have a horizon 5 cm or more equal to 30 or more. thick that has one or more of the following: Vitrandic Humicryepts Inceptisols 173

1. In 25 percent or more of each pedon, cementation by KCBB. Other Dystrogelepts that have, throughout one or more organic matter and aluminum, with or without iron; or horizons with a total thickness of 18 cm or more within 75 cm 2. Al plus ½ Fe (by ammonium oxalate) of 0.25 percent or of the mineral soil surface, a fine-earth fraction with both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water retention, more and half that amount or less in an overlying horizon; or 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling 3. An ODOE value of 0.12 or more and a value half as high more than 1.0. or lower in an overlying horizon. Andic Dystrogelepts Spodic Humicryepts KCBC. Other Dystrogelepts that have, in one or more KDAM. Other Humicryepts that have a xeric soil moisture horizons within 75 cm of the mineral soil surface, redox regime. depletions with chroma of 2 or less and also aquic conditions Xeric Humicryepts for some time in normal years (or artificial drainage). Aquic Dystrogelepts KDAN. Other Humicryepts that have a base saturation (by NH OAc) of 50 percent or more, either: 4 KCBD. Other Dystrogelepts that have a slope of less than 25 1. In one-half or more of the total thickness between 25 and percent, do not have irregular or broken horizon boundaries, and 75 cm from the mineral soil surface; or have one or both of the following: 2. In some part of the 10 cm thickness directly above a 1. At a depth of 125 cm below the mineral soil surface, densic, lithic, or paralithic contact that occurs less than 50 an organic-carbon content (Holocene age) of 0.2 percent or cm below the mineral soil surface. more and no densic, lithic, or paralithic contact within that Eutric Humicryepts depth; or KDAO. Other Humicryepts. 2. An irregular decrease in organic-carbon content Typic Humicryepts (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a densic, lithic, Gelepts or paralithic contact, whichever is shallower. Fluventic Dystrogelepts Key to Great Groups KCA. Gelepts that have an umbric or mollic epipedon. KCBE. Other Dystrogelepts that have gelic materials within , p. 174 200 cm of the mineral soil surface. I Humigelepts N Turbic Dystrogelepts C

KCB. Other Gelepts that have a base saturation (by NH4OAc) of less than 50 percent, either: KCBF. Other Dystrogelepts. Typic Dystrogelepts 1. In one or more horizons totaling 25 cm or more in thickness within 50 cm below the mineral soil surface and there is no placic horizon, duripan, fragipan, or densic, lithic, Haplogelepts or paralithic contact within 50 cm of the mineral soil surface; Key to Subgroups or KCCA. Haplogelepts that have a lithic contact within 50 cm 2. In one-half or more of the thickness between the of the mineral soil surface. mineral soil surface and the top of a placic horizon, duripan, Lithic Haplogelepts fragipan, or densic, lithic, or paralithic contact occurring within 50 cm of the mineral soil surface. KCCB. Other Haplogelepts that have, throughout one or more Dystrogelepts, p. 173 horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction with both a bulk KCC. Other Gelepts. density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 Haplogelepts, p. 173 and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. Dystrogelepts Andic Haplogelepts Key to Subgroups KCCC. Other Haplogelepts that have, in one or more horizons KCBA. Dystrogelepts that have a lithic contact within 50 cm within 75 cm of the mineral soil surface, redox depletions with of the mineral soil surface. Lithic Dystrogelepts 174 Keys to Soil Taxonomy

chroma of 2 or less and also aquic conditions for some time in KCAE. Other Humigelepts that have a slope of less than 25 normal years (or artificial drainage). percent, do not have irregular or broken horizon boundaries, and Aquic Haplogelepts have one or both of the following: 1. At a depth of 125 cm below the mineral soil surface, KCCD. Other Haplogelepts that have a slope of less than 25 an organic-carbon content (Holocene age) of 0.2 percent or percent, do not have irregular or broken horizon boundaries, and more and no densic, lithic, or paralithic contact within that have one or both of the following: depth; or 1. At a depth of 125 cm below the mineral soil surface, 2. An irregular decrease in organic-carbon content an organic-carbon content (Holocene age) of 0.2 percent or (Holocene age) between a depth of 25 cm and either a depth more and no densic, lithic, or paralithic contact within that of 125 cm below the mineral soil surface or a densic, lithic, depth; or or paralithic contact, whichever is shallower. 2. An irregular decrease in organic-carbon content Fluventic Humigelepts (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a densic, lithic, KCAF. Other Humigelepts that have gelic materials within or paralithic contact, whichever is shallower. 200 cm of the mineral soil surface. Fluventic Haplogelepts Turbic Humigelepts

KCCE. Other Haplogelepts that have gelic materials within KCAG. Other Humigelepts that have a base saturation (by

200 cm of the mineral soil surface. NH4OAc) of 50 percent or more, either: Turbic Haplogelepts 1. In one-half or more of the total thickness between 25 and 75 cm from the mineral soil surface; or KCCF. Other Haplogelepts. Typic Haplogelepts 2. In some part of the 10 cm thickness directly above a densic, lithic, or paralithic contact that occurs less than 50 Humigelepts cm below the mineral soil surface. Eutric Humigelepts Key to Subgroups KCAA. Humigelepts that have a lithic contact within 50 cm of KCAH. Other Humigelepts. the mineral soil surface. Typic Humigelepts Lithic Humigelepts Udepts KCAB. Other Humigelepts that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm Key to Great Groups of the mineral soil surface, a fine-earth fraction with both a bulk KGA. Udepts that have a sulfuric horizon within 50 cm of the density of 1.0 g/cm3 or less, measured at 33 kPa water retention, mineral soil surface. and Al plus ½ Fe (by ammonium oxalate) of 1.0 percent or Sulfudepts, p. 182 more. Andic Humigelepts KGB. Other Udepts that have a duripan or another cemented horizon within 100 cm of the mineral soil surface. KCAC. Other Humigelepts that have, in one or more horizons Durudepts, p. 175 within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in KGC. Other Udepts that have a fragipan within 100 cm of the normal years (or artificial drainage). mineral soil surface. Aquic Humigelepts Fragiudepts, p. 180

KCAD. Other Humigelepts that in normal years are saturated KGD. Other Udepts that have an umbric or mollic epipedon. with water in one or more layers within 100 cm of the mineral Humudepts, p. 180 soil surface for either or both: KGE. Other Udepts that have of the following: 1. 20 or more consecutive days; or one or both 1. Free carbonates within the soils; or 2. 30 or more cumulative days.

Oxyaquic Humigelepts 2. A base saturation (by NH4OAc) of 60 percent or more in Inceptisols 175

one or more horizons at a depth between 25 and 75 cm from 2. A fine-earth fraction containing 30 percent or more the mineral soil surface or directly above a root-limiting layer particles 0.02 to 2.0 mm in diameter; and if at a shallower depth. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Eutrudepts, p. 178 volcanic glass; and

1 KGF. Other Udepts. b. [(Al plus /2 Fe, percent extracted by ammonium Dystrudepts, p. 175 oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. Durudepts Vitrandic Durudepts

Key to Subgroups KGBD. Other Durudepts that have, in one or more horizons KGBA. Durudepts that have both: above the duripan and within 30 cm of the mineral soil surface, distinct or prominent redox concentrations and also aquic 1. In one or more horizons above the duripan and within 60 conditions for some time in normal years (or artificial drainage). cm of the mineral soil surface, distinct or prominent redox Aquic Durudepts concentrations and also aquic conditions for some time in normal years (or artificial drainage);and KGBE. Other Durudepts. 2. Throughout one or more horizons with a total thickness Typic Durudepts of 18 cm or more, above the duripan and within 75 cm of the mineral soil surface, one or more of the following: Dystrudepts a. A fine-earth fraction with both a bulk density of 1.0 Key to Subgroups 3 g/cm or less, measured at 33 kPa water retention, and Al KGFA. Dystrudepts that have both: 1 plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0; or 1. A lithic contact within 50 cm of the mineral soil surface; and b. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, 2. A color value, moist, of 3 or less and a color value, dry, pumice, and pumicelike fragments; or of 5 or less (crushed and smoothed sample) either throughout the upper 18 cm of the mineral soil (unmixed) or between the c. A fine-earth fraction containing 30 percent or more mineral soil surface and a depth of 18 cm after mixing. I particles 0.02 to 2.0 mm in diameter; and Humic Lithic Dystrudepts N C (1) In the 0.02 to 2.0 mm fraction, 5 percent or more KGFB. Other Dystrudepts that have a lithic contact within 50 volcanic glass; and cm of the mineral soil surface. 1 (2) [(Al plus /2 Fe, percent extracted by ammonium Lithic Dystrudepts oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. KGFC. Other Dystrudepts that have one or both of the Aquandic Durudepts following: 1. Cracks within 125 cm of the mineral soil surface that are KGBB. Other Durudepts that have, throughout one or 5 mm or more wide through a thickness of 30 cm or more more horizons with a total thickness of 18 cm or more, above for some time in normal years and slickensides or wedge- the duripan and within 75 cm of the mineral soil surface, a shaped peds in a layer 15 cm or more thick that has its upper fine-earth fraction with both a bulk density of 1.0 g/cm3 or 1 boundary within 125 cm of the mineral soil surface; or less, measured at 33 kPa water retention, and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. 2. A linear extensibility of 6.0 cm or more between the Andic Durudepts mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. KGBC. Other Durudepts that have, throughout one or more Vertic Dystrudepts horizons with a total thickness of 18 cm or more, above the duripan and within 75 cm of the mineral soil surface, one or KGFD. Other Dystrudepts that have both: both of the following: 1. In one or more horizons within 60 cm of the mineral soil 1. More than 35 percent (by volume) fragments coarser surface, redox depletions with chroma of 2 or less and also than 2.0 mm, of which more than 66 percent is cinders, aquic conditions for some time in normal years (or artificial pumice, and pumicelike fragments; or drainage); and 176 Keys to Soil Taxonomy

1 2. Throughout one or more horizons with a total thickness b. [(Al plus /2 Fe, percent extracted by ammonium of 18 cm or more within 75 cm of the mineral soil surface, oxalate) times 60] plus the volcanic glass (percent) is one or more of the following: equal to 30 or more. a. A fine-earth fraction with both a bulk density of 1.0 Vitrandic Dystrudepts g/cm3 or less, measured at 33 kPa water retention, and Al 1 KGFH. Other Dystrudepts that have both: plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0; or 1. Fragic soil properties either: b. More than 35 percent (by volume) fragments coarser a. In 30 percent or more of the volume of a layer 15 cm than 2.0 mm, of which more than 66 percent is cinders, or more thick that has its upper boundary within 100 cm pumice, and pumicelike fragments; or of the mineral soil surface; or c. A fine-earth fraction containing 30 percent or more b. In 60 percent or more of the volume of a layer 15 cm particles 0.02 to 2.0 mm in diameter; and or more thick; and (1) In the 0.02 to 2.0 mm fraction, 5 percent or more 2. In one or more horizons within 60 cm of the mineral volcanic glass; and soil surface, redox depletions with chroma of 2 or less 1 (2) [(Al plus /2 Fe, percent extracted by ammonium and also aquic conditions in normal years (or artificial oxalate) times 60] plus the volcanic glass (percent) is drainage). equal to 30 or more. Fragiaquic Dystrudepts Aquandic Dystrudepts KGFI. Other Dystrudepts that have a slope of less than 25 KGFE. Other Dystrudepts that have both: percent; and 1. In one or more horizons with a total thickness of 18 1. In one or more horizons within 60 cm of the mineral soil cm or more within 75 cm of the mineral soil surface, a surface, redox depletions with chroma of 2 or less and also fine-earth fraction with both a bulk density of 1.0 g/cm3 or aquic conditions for some time in normal years (or artificial 1 less, measured at 33 kPa water retention, and Al plus /2 Fe drainage); and percentages (by ammonium oxalate) totaling more than 1.0; and 2. One or both of the following: 2. Saturation with water within 100 cm of the mineral soil a. At a depth of 125 cm below the mineral soil surface, surface in normal years for either or both: an organic-carbon content (Holocene age) of 0.2 percent or more and no densic, lithic, or paralithic contact within a. 20 or more consecutive days; or that depth; or b. 30 or more cumulative days. Andic Oxyaquic Dystrudepts b. An irregular decrease in organic-carbon content (Holocene age) between a depth of 25 cm and either KGFF. Other Dystrudepts that have, throughout one or more a depth of 125 cm below the mineral soil surface or a horizons with a total thickness of 18 cm or more within 75 cm densic, lithic, or paralithic contact, whichever is shallower. of the mineral soil surface, a fine-earth fraction with both a bulk Fluvaquentic Dystrudepts density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling KGFJ. Other Dystrudepts that have both: more than 1.0. 1. A color value, moist, of 3 or less and a color value, dry, Andic Dystrudepts of 5 or less (crushed and smoothed sample) either throughout the upper 18 cm of the mineral soil (unmixed) or between the KGFG. Other Dystrudepts that have, throughout one or more mineral soil surface and a depth of 18 cm after mixing; and horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: 2. In one or more horizons within 60 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also 1. More than 35 percent (by volume) fragments coarser aquic conditions for some time in normal years (or artificial than 2.0 mm, of which more than 66 percent is cinders, drainage). pumice, and pumicelike fragments; or Aquic Humic Dystrudepts 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and KGFK. Other Dystrudepts that have, in one or more horizons within 60 cm of the mineral soil surface, redox depletions with a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and Inceptisols 177

chroma of 2 or less and also aquic conditions for some time in KGFQ. Other Dystrudepts that have a slope of less than 25 normal years (or artificial drainage). percent and one or both of the following: Aquic Dystrudepts 1. At a depth of 125 cm below the mineral soil surface, an organic-carbon content (Holocene age) of 0.2 percent or KGFL. Other Dystrudepts that in normal years are saturated more and no densic, lithic, or paralithic contact within that with water in one or more layers within 100 cm of the mineral depth; or soil surface for either or both: 2. An irregular decrease in organic-carbon content 1. 20 or more consecutive days; or (Holocene age) between a depth of 25 cm and either a depth 2. 30 or more cumulative days. of 125 cm below the mineral soil surface or a densic, lithic, Oxyaquic Dystrudepts or paralithic contact, whichever is shallower. Fluventic Dystrudepts KGFM. Other Dystrudepts that have fragic soil properties either: KGFR. Other Dystrudepts that have a horizon 5 cm or more thick that has one or more of the following: 1. In 30 percent or more of the volume of a layer 15 cm or more thick that has its upper boundary within 100 cm of the 1. In 25 percent or more of each pedon, cementation by mineral soil surface; or organic matter and aluminum, with or without iron; or

1 2. In 60 percent or more of the volume of a layer 15 cm or 2. Al plus /2 Fe percentages (by ammonium oxalate) more thick. totaling 0.25 or more, and half that amount or less in an Fragic Dystrudepts overlying horizon; or 3. An ODOE value of 0.12 or more, and a value half as KGFN. Other Dystrudepts that have lamellae (two or more) high or lower in an overlying horizon. within 200 cm of the mineral soil surface. Spodic Dystrudepts Lamellic Dystrudepts KGFS. Other Dystrudepts that have, in 50 percent or more KGFO. Other Dystrudepts that have both: of the soil volume between a depth of 25 cm from the mineral 1. A color value, moist, of 3 or less and a color value, dry, soil surface and either a depth of 100 cm or a densic, lithic, or of 5 or less (crushed and smoothed sample) either throughout paralithic contact if shallower: the upper 18 cm of the mineral soil (unmixed) or between the 1. A CEC (by 1N NH OAc pH 7) of less than 24 cmol(+) I mineral soil surface and a depth of 18 cm after mixing; 4 N and per kg clay; or C 2. A sandy particle-size class in all subhorizons throughout 2. Both a ratio of measured clay in the fine-earth fraction the particle-size control section. to percent water retained at 1500 kPa tension of 0.6 or more Humic Psammentic Dystrudepts and the following: the CEC (by 1N NH4OAc pH 7) divided by the product of three times [percent water retained at 1500 KGFP. Other Dystrudepts that have a slope of less than 25 kPa tension minus percent organic carbon (but no more than percent; and 1.00)] is less than 24. 1. A color value, moist, of 3 or less and a color value, dry, Oxic Dystrudepts of 5 or less (crushed and smoothed sample) either throughout the upper 18 cm of the mineral soil (unmixed) or between the KGFT. Other Dystrudepts that have both: mineral soil surface and a depth of 18 cm after mixing; and 1. In each pedon a cambic horizon that includes 10 to 50 2. One or both of the following: percent (by volume) illuvial parts that otherwise meet the requirements for an argillic, kandic, or natric horizon; and a. At a depth of 125 cm below the mineral soil surface, an organic-carbon content (Holocene age) of 0.2 percent 2. A base saturation (by sum of cations) of 35 percent or more either at a depth of 125 cm from the top of the cambic or more and no densic, lithic, or paralithic contact within horizon or directly above a densic, lithic, or paralithic contact that depth; or if shallower. b. An irregular decrease in organic-carbon content Ruptic-Alfic Dystrudepts (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a KGFU. Other Dystrudepts that have in each pedon a cambic densic, lithic, or paralithic contact, whichever is shallower. horizon that includes 10 to 50 percent (by volume) illuvial parts Fluventic Humic Dystrudepts 178 Keys to Soil Taxonomy

that otherwise meet the requirements for an argillic, kandic, or for some time in normal years and slickensides or wedge- natric horizon. shaped peds in a layer 15 cm or more thick that has its upper Ruptic-Ultic Dystrudepts boundary within 125 cm of the mineral soil surface; or 2. A linear extensibility of 6.0 cm or more between the KGFV. Other Dystrudepts that have a color value, moist, mineral soil surface and either a depth of 100 cm or a densic, of 3 or less and a color value, dry, of 5 or less (crushed and lithic, or paralithic contact, whichever is shallower. smoothed sample) either throughout the upper 18 cm of the Vertic Eutrudepts mineral soil (unmixed) or between the mineral soil surface and a depth of 18 cm after mixing. KGEE. Other Eutrudepts that have, throughout one or more Humic Dystrudepts horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction with both a bulk KGFW. Other Dystrudepts. density of 1.0 g/cm3 or less, measured at 33 kPa water retention, Typic Dystrudepts 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. Eutrudepts Andic Eutrudepts Key to Subgroups KGEF. Other Eutrudepts that have, throughout one or more KGEA. Eutrudepts that have both: horizons with a total thickness of 18 cm or more within 75 cm 1. A color value, moist, of 3 or less and a color value, dry, of the mineral soil surface, one or both of the following: of 5 or less (crushed and smoothed sample) either throughout 1. More than 35 percent (by volume) fragments coarser the upper 18 cm of the mineral soil (unmixed) or between the than 2.0 mm, of which more than 66 percent is cinders, mineral soil surface and a depth of 18 cm after mixing; and pumice, and pumicelike fragments; or 2. A lithic contact within 50 cm of the mineral soil surface. 2. A fine-earth fraction containing 30 percent or more Humic Lithic Eutrudepts particles 0.02 to 2.0 mm in diameter; and

KGEB. Other Eutrudepts that have a lithic contact within 50 a. In the 0.02 to 2.0 mm fraction, 5 percent or more cm of the mineral soil surface. volcanic glass; and 1 Lithic Eutrudepts b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is KGEC. Other Eutrudepts that have both: equal to 30 or more. 1. One or both of the following: Vitrandic Eutrudepts a. Cracks within 125 cm of the mineral soil surface that KGEG. Other Eutrudepts that have anthraquic conditions. are 5 mm or more wide through a thickness of 30 cm or Anthraquic Eutrudepts more for some time in normal years and slickensides or wedge-shaped peds in a layer 15 cm or more thick that KGEH. Other Eutrudepts that have both: has its upper boundary within 125 cm of the mineral soil 1. Fragic soil properties either: surface; or a. In 30 percent or more of the volume of a layer 15 cm b. A linear extensibility of 6.0 cm or more between or more thick that has its upper boundary within 100 cm the mineral soil surface and either a depth of 100 cm of the mineral soil surface; or or a densic, lithic, or paralithic contact, whichever is shallower; and b. In 60 percent or more of the volume of a layer 15 cm or more thick; and 2. In one or more horizons within 60 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also 2. In one or more horizons within 60 cm of the mineral soil aquic conditions for some time in normal years (or artificial surface, redox depletions with chroma of 2 or less and also drainage). aquic conditions in normal years (or artificial drainage). Aquertic Eutrudepts Fragiaquic Eutrudepts

KGED. Other Eutrudepts that have one or both of the KGEI. Other Eutrudepts that have a slope of less than 25 following: percent; and 1. Cracks within 125 cm of the mineral soil surface that are 1. In one or more horizons within 60 cm of the mineral soil 5 mm or more wide through a thickness of 30 cm or more surface, redox depletions with chroma of 2 or less and also Inceptisols 179

aquic conditions for some time in normal years (or artificial 1. Do not have free carbonates throughout any horizon drainage); and within 100 cm of the mineral soil surface; and 2. One or both of the following: 2. Have one or both of the following: a. At a depth of 125 cm below the mineral soil surface, a. At a depth of 125 cm below the mineral soil surface, an organic-carbon content (Holocene age) of 0.2 percent an organic-carbon content (Holocene age) of 0.2 percent or more and no densic, lithic, or paralithic contact within or more and no densic, lithic, or paralithic contact within that depth; or that depth; or b. An irregular decrease in organic-carbon content b. An irregular decrease in organic-carbon content (Holocene age) between a depth of 25 cm and either (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a a depth of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is shallower. densic, lithic, or paralithic contact, whichever is shallower. Fluvaquentic Eutrudepts Dystric Fluventic Eutrudepts

KGEJ. Other Eutrudepts that meet both of the following: KGEP. Other Eutrudepts that have a slope of less than 25 percent and one or both of the following: 1. In one or more horizons within 60 cm of the mineral soil surface, have redox depletions with chroma of 2 or less 1. At a depth of 125 cm below the mineral soil surface, and also aquic conditions for some time in normal years (or an organic-carbon content (Holocene age) of 0.2 percent or artificial drainage);and more and no densic, lithic, or paralithic contact within that depth; or 2. Do not have free carbonates throughout any horizon within 100 cm of the mineral soil surface. 2. An irregular decrease in organic-carbon content Aquic Dystric Eutrudepts (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a densic, lithic, KGEK. Other Eutrudepts that have, in one or more horizons or paralithic contact, whichever is shallower. within 60 cm of the mineral soil surface, redox depletions with Fluventic Eutrudepts chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). KGEQ. Other Eutrudepts that meet sandy or sandy-skeletal Aquic Eutrudepts particle-size class criteria in all horizons within 50 cm of the mineral soil surface. I N KGEL. Other Eutrudepts that in normal years are saturated Arenic Eutrudepts C with water in one or more layers within 100 cm of the mineral soil surface for either or both: KGER. Other Eutrudepts that do not have free carbonates throughout any horizon within 100 cm of the mineral soil 1. 20 or more consecutive days; or surface. 2. 30 or more cumulative days. Dystric Eutrudepts Oxyaquic Eutrudepts

KGES. Other Eutrudepts that have a CaCO3 equivalent of 40 KGEM. Other Eutrudepts that have fragic soil properties: percent or more, including fragments 2 to 75 mm in diameter, in all horizons between the top of the cambic horizon and either a 1. In 30 percent or more of the volume of a layer 15 cm or depth of 100 cm from the mineral soil surface or a densic, lithic, more thick that has its upper boundary within 100 cm of the or paralithic contact if shallower. mineral soil surface; or Rendollic Eutrudepts 2. In 60 percent or more of the volume of a layer 15 cm or more thick. KGET. Other Eutrudepts that have a cambic horizon that Fragic Eutrudepts includes 10 to 50 percent (by volume) illuvial parts that otherwise meet the requirements for an argillic, kandic, or natric KGEN. Other Eutrudepts that have lamellae (two or more) horizon. within 200 cm of the mineral soil surface. Ruptic-Alfic Eutrudepts Lamellic Eutrudepts KGEU. Other Eutrudepts that have a color value, moist, KGEO. Other Eutrudepts that have a slope of less than 25 of 3 or less and a color value, dry, of 5 or less (crushed and percent; and smoothed sample) either throughout the upper 18 cm of the 180 Keys to Soil Taxonomy

mineral soil (unmixed) or between the mineral soil surface and a Humudepts depth of 18 cm after mixing. Humic Eutrudepts Key to Subgroups KGDA. Humudepts that have a lithic contact within 50 cm of KGEV. Other Eutrudepts. the mineral soil surface. Typic Eutrudepts Lithic Humudepts

Fragiudepts KGDB. Other Humudepts that have one or both of the following: Key to Subgroups 1. Cracks within 125 cm of the mineral soil surface that are KGCA. Fragiudepts that have, throughout one or more 5 mm or more wide through a thickness of 30 cm or more horizons with a total thickness of 18 cm or more within 75 cm for some time in normal years and slickensides or wedge- of the mineral soil surface, a fine-earth fraction with both a bulk shaped peds in a layer 15 cm or more thick that has its upper density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 boundary within 125 cm of the mineral soil surface; or and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. 2. A linear extensibility of 6.0 cm or more between the Andic Fragiudepts mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. KGCB. Other Fragiudepts that have, throughout one or more Vertic Humudepts horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: KGDC. Other Humudepts that have both: 1. More than 35 percent (by volume) fragments coarser 1. In one or more horizons within 60 cm of the mineral soil than 2.0 mm, of which more than 66 percent is cinders, surface, redox depletions with chroma of 2 or less and also pumice, and pumicelike fragments; or aquic conditions for some time in normal years (or artificial drainage); and 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and 2. Throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a. In the 0.02 to 2.0 mm fraction, 5 percent or more one or more of the following: volcanic glass; and

1 a. A fine-earth fraction with both a bulk density of 1.0 b. [(Al plus /2 Fe, percent extracted by ammonium g/cm3 or less, measured at 33 kPa water retention, and Al oxalate) times 60] plus the volcanic glass (percent) is 1 plus /2 Fe percentages (by ammonium oxalate) totaling equal to 30 or more. more than 1.0; or Vitrandic Fragiudepts b. More than 35 percent (by volume) fragments coarser KGCC. Other Fragiudepts that have, in one or more horizons than 2.0 mm, of which more than 66 percent is cinders, within 30 cm of the mineral soil surface, distinct or prominent pumice, and pumicelike fragments; or redox concentrations and also aquic conditions for some time in c. A fine-earth fraction containing 30 percent or more normal years (or artificial drainage). particles 0.02 to 2.0 mm in diameter; and Aquic Fragiudepts (1) In the 0.02 to 2.0 mm fraction, 5 percent or more KGCD. Other Fragiudepts that have one or both of the volcanic glass; and following: 1 (2) [(Al plus /2 Fe, percent extracted by ammonium 1. An umbric or mollic epipedon; or oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. 2. A color value, moist, of 3 or less and a color value, dry, Aquandic Humudepts of 5 or less (crushed and smoothed sample) either throughout the upper 18 cm of the mineral soil (unmixed) or between the KGDD. Other Humudepts that have both: mineral soil surface and a depth of 18 cm after mixing. Humic Fragiudepts 1. In one or more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a KGCE. Other Fragiudepts. fine-earth fraction with both a bulk density of 1.0 g/cm3 or Typic Fragiudepts Inceptisols 181

1 less, measured at 33 kPa water retention, and Al plus /2 Fe KGDH. Other Humudepts that have, in one or more horizons percentages (by ammonium oxalate) totaling more than 1.0; within 60 cm of the mineral soil surface, redox depletions with and chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). 2. Saturation with water within 100 cm of the mineral soil Aquic Humudepts surface in normal years for either or both: a. 20 or more consecutive days; or KGDI. Other Humudepts that in normal years are saturated with water in one or more layers within 100 cm of the mineral b. 30 or more cumulative days. soil surface for either or both: Andic Oxyaquic Humudepts 1. 20 or more consecutive days; or KGDE. Other Humudepts that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm 2. 30 or more cumulative days. of the mineral soil surface, a fine-earth fraction with both a bulk Oxyaquic Humudepts density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 KGDJ. Other Humudepts that have a sandy particle-size class and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. in all subhorizons throughout the particle-size control section. Andic Humudepts Psammentic Humudepts

KGDF. Other Humudepts that have, throughout one or more KGDK. Other Humudepts that have, in 50 percent or more horizons with a total thickness of 18 cm or more within 75 cm of the soil volume between a depth of 25 cm from the mineral of the mineral soil surface, one or both of the following: soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact if shallower: 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, 1. A CEC (by 1N NH4OAc pH 7) of less than 24 cmol(+) pumice, and pumicelike fragments; or per kg clay; or 2. A fine-earth fraction containing 30 percent or more 2. Both a ratio of measured clay in the fine-earth fraction particles 0.02 to 2.0 mm in diameter; and to percent water retained at 1500 kPa tension of 0.6 or more

and the following: the CEC (by 1N NH4OAc pH 7) divided a. In the 0.02 to 2.0 mm fraction, 5 percent or more by the product of three times [percent water retained at 1500 volcanic glass; and kPa tension minus percent organic carbon (but no more than I 1 1.00)] is less than 24. N b. [(Al plus /2 Fe, percent extracted by ammonium C oxalate) times 60] plus the volcanic glass (percent) is Oxic Humudepts equal to 30 or more. Vitrandic Humudepts KGDL. Other Humudepts that have a slope of less than 25 percent; and KGDG. Other Humudepts that have a slope of less than 25 1. An umbric or mollic epipedon that is 50 cm or more percent; and thick; and 1. In one or more horizons within 60 cm of the mineral soil 2. One or both of the following: surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial a. At a depth of 125 cm below the mineral soil surface, drainage); and an organic-carbon content (Holocene age) of 0.2 percent or more and no densic, lithic, or paralithic contact within 2. of the following: One or both that depth; or a. At a depth of 125 cm below the mineral soil surface, b. An irregular decrease in organic-carbon content an organic-carbon content (Holocene age) of 0.2 percent (Holocene age) between a depth of 25 cm and either or more and no densic, lithic, or paralithic contact within a depth of 125 cm below the mineral soil surface or a that depth; or densic, lithic, or paralithic contact, whichever is shallower. b. An irregular decrease in organic-carbon content Cumulic Humudepts (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a KGDM. Other Humudepts that have a slope of less than 25 densic, lithic, or paralithic contact, whichever is shallower. percent and one or both of the following: Fluvaquentic Humudepts 182 Keys to Soil Taxonomy

1. At a depth of 125 cm below the mineral soil surface, horizon, after the soil between the mineral soil surface and a an organic-carbon content (Holocene age) of 0.2 percent or depth of 18 cm has been mixed. more and no densic, lithic, or paralithic contact within that Calciustepts, p. 182 depth; or KEC. Other Ustepts that have an umbric or mollic epipedon. 2. An irregular decrease in organic-carbon content Humustepts, p. 189 (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a densic, lithic, KED. Other Ustepts that meet both of the following: or paralithic contact, whichever is shallower. Fluventic Humudepts 1. No free carbonates within 200 cm of the mineral soil surface; and KGDN. Other Humudepts that have an umbric or mollic 2. A base saturation (by NH OAc) of less than 60 percent epipedon that is 50 cm or more thick. 4 in all horizons at a depth between 25 and 75 cm from the Pachic Humudepts mineral soil surface. Dystrustepts, p. 183 KGDO. Other Humudepts that have a base saturation (by NH OAc) of 60 percent or more either: 4 KEF. Other Ustepts. 1. In one-half or more of the total thickness between 25 and Haplustepts, p. 185 75 cm from the mineral soil surface; or 2. In some part of the 10 cm thickness directly above a Calciustepts densic, lithic, or paralithic contact that occurs less than 50 Key to Subgroups cm below the mineral soil surface. Eutric Humudepts KEBA. Calciustepts that have a petrocalcic horizon and a lithic contact within 50 cm of the mineral soil surface. KGDP. Other Humudepts that do not have a cambic horizon Lithic Petrocalcic Calciustepts and do not, in any part of the umbric or mollic epipedon, meet the requirements for a cambic horizon, except for the color KEBB. Other Calciustepts that have a lithic contact within 50 requirements. cm of the mineral soil surface. Entic Humudepts Lithic Calciustepts

KGDQ. Other Humudepts. KEBC. Other Calciustepts that have both: Typic Humudepts 1. One or both of the following:

Sulfudepts a. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or Key to Subgroups more for some time in normal years and slickensides or wedge-shaped peds in a layer 15 cm or more thick that KGAA. All Sulfudepts (provisionally). has its upper boundary within 125 cm of the mineral soil Typic Sulfudepts surface; or Ustepts b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm Key to Great Groups or a densic, lithic, or paralithic contact, whichever is shallower; and KEA. Ustepts that have a duripan within 100 cm of the mineral soil surface. 2. When neither irrigated nor fallowed to store moisture, Durustepts, p. 183 one of the following: a. A frigid soil temperature regime and a moisture KEB. Other Ustepts that have both: control section that in normal years is dry in all parts for 1. A calcic horizon within 100 cm of the mineral soil four-tenths or more of the cumulative days per year when surface or a petrocalcic horizon within 150 cm of the mineral the soil temperature at a depth of 50 cm below the soil soil surface; and surface is higher than 5 oC; or 2. Either free carbonates or a texture class of loamy fine b. A mesic or thermic soil temperature regime and a sand or coarser, in all parts above the calcic or petrocalcic moisture control section that in normal years is dry in Inceptisols 183

some or all parts for six-tenths or more of the cumulative or all parts for six-tenths or more of the cumulative days per days per year when the soil temperature at a depth of 50 year when the soil temperature at a depth of 50 cm below the cm below the soil surface is higher than 5 oC; or soil surface is higher than 5 oC; or c. A hyperthermic, isomesic, or warmer iso soil 3. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in temperature regime and a moisture control section that in normal years: normal years: (1) Is moist in some or all parts for fewer than 90 a. Is moist in some or all parts for fewer than 90 consecutive days per year when the soil temperature at consecutive days per year when the soil temperature at a a depth of 50 cm below the soil surface is higher than depth of 50 cm below the soil surface is higher than 8 oC; 8 oC; and and (2) Is dry in some or all parts for six-tenths or b. Is dry in some or all parts for six-tenths or more of more of the cumulative days per year when the soil the cumulative days per year when the soil temperature temperature at a depth of 50 cm below the soil surface at a depth of 50 cm below the soil surface is higher than o is higher than 5 oC. 5 C. Torrertic Calciustepts Aridic Calciustepts

KEBD. Other Calciustepts that have one or both of the KEBI. Other Calciustepts that have, when neither irrigated nor following: fallowed to store moisture, either: 1. Cracks within 125 cm of the mineral soil surface that are 1. A mesic or thermic soil temperature regime and a 5 mm or more wide through a thickness of 30 cm or more moisture control section that in normal years is dry in some for some time in normal years and slickensides or wedge- or all parts for four-tenths or less of the consecutive days per shaped peds in a layer 15 cm or more thick that has its upper year when the soil temperature at a depth of 50 cm below the o boundary within 125 cm of the mineral soil surface; or soil surface is higher than 5 C; or 2. A linear extensibility of 6.0 cm or more between the 2. A hyperthermic, isomesic, or warmer iso soil mineral soil surface and either a depth of 100 cm or a densic, temperature regime and a moisture control section that in lithic, or paralithic contact, whichever is shallower. normal years is dry in some or all parts for fewer than 120 Vertic Calciustepts cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 8 oC. I N KEBE. Other Calciustepts that have a petrocalcic horizon Udic Calciustepts C within 100 cm of the mineral soil surface. Petrocalcic Calciustepts KEBJ. Other Calciustepts. Typic Calciustepts KEBF. Other Calciustepts that have a gypsic horizon within 100 cm of the mineral soil surface. Durustepts Gypsic Calciustepts Key to Subgroups KEBG. Other Calciustepts that have, in one or more horizons KEAA. All Durustepts (provisionally). within 75 cm of the mineral soil surface, redox depletions with Typic Durustepts chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). Dystrustepts Aquic Calciustepts Key to Subgroups KEBH. Other Calciustepts that have, when neither irrigated KEDA. Dystrustepts that have a lithic contact within 50 cm of nor fallowed to store moisture, one of the following: the mineral soil surface. Lithic Dystrustepts 1. A frigid soil temperature regime and a moisture control section that in normal years is dry in all parts for four- KEDB. Other Dystrustepts that have both: tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is 1. When neither irrigated nor fallowed to store moisture, higher than 5 oC; or one of the following: 2. A mesic or thermic soil temperature regime and a a. A frigid soil temperature regime and a moisture moisture control section that in normal years is dry in some control section that in normal years is dry in all parts for 184 Keys to Soil Taxonomy

four-tenths or more of the cumulative days per year when KEDE. Other Dystrustepts that have, throughout one or more the soil temperature at a depth of 50 cm below the soil horizons with a total thickness of 18 cm or more within 75 cm surface is higher than 5 oC; or of the mineral soil surface, one or both of the following: b. A mesic or thermic soil temperature regime and a 1. More than 35 percent (by volume) fragments coarser moisture control section that, in 6 normal years, is dry in than 2.0 mm, of which more than 66 percent is cinders, some part for six-tenths or more of the cumulative days pumice, and pumicelike fragments; or per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and c. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in a. In the 0.02 to 2.0 mm fraction, 5 percent or more normal years: volcanic glass; and 1 (1) Is moist in some or all parts for fewer than 90 b. [(Al plus /2 Fe, percent extracted by ammonium consecutive days per year when the soil temperature at oxalate) times 60] plus the volcanic glass (percent) is a depth of 50 cm below the soil surface is higher than equal to 30 or more. 8 oC; and Vitrandic Dystrustepts (2) Is dry in some part for six-tenths or more of the KEDF. Other Dystrustepts that have, in one or more horizons cumulative days per year when the soil temperature at within 75 cm of the mineral soil surface, redox depletions with a depth of 50 cm below the soil surface is higher than chroma of 2 or less and also aquic conditions for some time in 5 oC; and normal years (or artificial drainage). 2. One or both of the following: Aquic Dystrustepts a. Cracks within 125 cm of the mineral soil surface that KEDG. Other Dystrustepts that have a slope of less than 25 are 5 mm or more wide through a thickness of 30 cm or percent and one or both of the following: more for some time in normal years and slickensides or wedge-shaped peds in a layer 15 cm or more thick that 1. At a depth of 125 cm below the mineral soil surface, has its upper boundary within 125 cm of the mineral soil an organic-carbon content (Holocene age) of 0.2 percent or surface; or more and no densic, lithic, or paralithic contact within that depth; or b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a 2. An irregular decrease in organic-carbon content densic, lithic, or paralithic contact, whichever is shallower. (Holocene age) between a depth of 25 cm and either a depth Torrertic Dystrustepts of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is shallower. KEDC. Other Dystrustepts that have one or both of the Fluventic Dystrustepts following: KEDH. Other Dystrustepts that, when neither irrigated nor 1. Cracks within 125 cm of the mineral soil surface that are fallowed to store moisture, have one of the following: 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge- 1. A frigid soil temperature regime and a moisture control shaped peds in a layer 15 cm or more thick that has its upper section that in normal years is dry in all parts for four- boundary within 125 cm of the mineral soil surface; or tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is 2. A linear extensibility of 6.0 cm or more between the higher than 5 oC; or mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. 2. A mesic or thermic soil temperature regime and a Vertic Dystrustepts moisture control section that in normal years is dry in some or all parts for six-tenths or more of the cumulative days per KEDD. Other Dystrustepts that have, throughout one or more year when the soil temperature at a depth of 50 cm below the horizons with a total thickness of 18 cm or more within 75 cm soil surface is higher than 5 oC; or of the mineral soil surface, a fine-earth fraction with both a bulk 3. A hyperthermic, isomesic, or warmer iso soil density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 temperature regime and a moisture control section that in and Al plus /2 Fe percentages (by ammonium oxalate) totaling normal years: more than 1.0. Andic Dystrustepts a. Is moist in some or all parts for fewer than 90 Inceptisols 185

consecutive days per year when the soil temperature at a c. A hyperthermic, isomesic, or warmer iso soil depth of 50 cm below the soil surface is higher than 8 oC; temperature regime and a moisture control section that in and normal years: b. Is dry in some part for six-tenths or more of the (1) Is moist in some or all parts for fewer than 90 cumulative days per year when the soil temperature at a consecutive days per year when the soil temperature at depth of 50 cm below the soil surface is higher than 5 oC. a depth of 50 cm below the soil surface is higher than Aridic Dystrustepts 8 oC; and (2) Is dry in some part for six-tenths or more of the KEDI. Other Dystrustepts that have, in 50 percent or more cumulative days per year when the soil temperature at of the soil volume between a depth of 25 cm from the mineral a depth of 50 cm below the soil surface is higher than soil surface and either a depth of 100 cm or a densic, lithic, or 5 oC. paralithic contact if shallower: Aridic Lithic Haplustepts

1. A CEC (by 1N NH4OAc pH 7) of less than 24 cmol(+) per kg clay; or KEEB. Other Haplustepts that have a lithic contact within 50 cm of the mineral soil surface. 2. Both a ratio of measured clay in the fine-earth fraction Lithic Haplustepts to percent water retained at 1500 kPa tension of 0.6 or more and the following: the CEC (by 1N NH OAc pH 7) divided 4 KEEC. Other Haplustepts that have both: by the product of three times [percent water retained at 1500 kPa tension minus percent organic carbon (but no more than 1. When neither irrigated nor fallowed to store moisture, 1.00)] is less than 24. one of the following: Oxic Dystrustepts a. A frigid soil temperature regime and a moisture KEDJ. Other Dystrustepts that have a color value, moist, control section that in normal years is dry in some or all of 3 or less and a color value, dry, of 5 or less (crushed and parts for fewer than 105 cumulative days per year when the soil temperature at a depth of 50 cm below the soil smoothed sample) either throughout the upper 18 cm of the o mineral soil (unmixed) or between the mineral soil surface and a surface is higher than 5 C; or depth of 18 cm after mixing. b. A mesic or thermic soil temperature regime and a Humic Dystrustepts moisture control section that in normal years is dry in some part for less than four-tenths of the cumulative days I N KEDK. Other Dystrustepts. per year when the soil temperature at a depth of 50 cm C Typic Dystrustepts below the soil surface is higher than 5 oC; or

Haplustepts c. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in Key to Subgroups normal years is dry in some or all parts for fewer than 120 KEEA. Haplustepts that have: cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 8 oC; 1. A lithic contact within 50 cm of the mineral soil surface; and and 2. One or both of the following: 2. When neither irrigated nor fallowed to store moisture, a. Cracks within 125 cm of the mineral soil surface that either: are 5 mm or more wide through a thickness of 30 cm or a. A frigid soil temperature regime and a moisture more for some time in normal years and slickensides or control section that in normal years is dry in all parts for wedge-shaped peds in a layer 15 cm or more thick that four-tenths or more of the cumulative days per year when has its upper boundary within 125 cm of the mineral soil the soil temperature at a depth of 50 cm below the soil surface; or surface is higher than 5 oC; or b. A linear extensibility of 6.0 cm or more between the b. A mesic or thermic soil temperature regime and a mineral soil surface and either a depth of 100 cm or a moisture control section that in normal years is dry in densic, lithic, or paralithic contact, whichever is shallower. some part for six-tenths or more of the cumulative days Udertic Haplustepts per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or KEED. Other Haplustepts that have both: 186 Keys to Soil Taxonomy

1. When neither irrigated nor fallowed to store moisture, of the mineral soil surface, a fine-earth fraction with both a bulk one of the following: density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling a. A frigid soil temperature regime and a moisture more than 1.0. control section that in normal years is dry in all parts for Andic Haplustepts four-tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil KEEG. Other Haplustepts that have, throughout one or more surface is higher than 5 oC; or horizons with a total thickness of 18 cm or more within 75 cm b. A mesic or thermic soil temperature regime and a of the mineral soil surface, one or both of the following: moisture control section that in normal years is dry in 1. More than 35 percent (by volume) fragments coarser some part for six-tenths or more of the cumulative days than 2.0 mm, of which more than 66 percent is cinders, per year when the soil temperature at a depth of 50 cm pumice, and pumicelike fragments; or below the soil surface is higher than 5 oC; or 2. A fine-earth fraction containing 30 percent or more c. A hyperthermic, isomesic, or warmer iso soil particles 0.02 to 2.0 mm in diameter; and temperature regime and a moisture control section that in normal years: a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and (1) Is moist in some or all parts for fewer than 90 1 consecutive days per year when the soil temperature at b. [(Al plus /2 Fe, percent extracted by ammonium a depth of 50 cm below the soil surface is higher than oxalate) times 60] plus the volcanic glass (percent) is 8 oC; and equal to 30 or more. Vitrandic Haplustepts (2) Is dry in some part for six-tenths or more of the cumulative days per year when the soil temperature at KEEH. Other Haplustepts that have anthraquic conditions. a depth of 50 cm below the soil surface is higher than Anthraquic Haplustepts 5 oC; and 2. One or both of the following: KEEI. Other Haplustepts that have, in one or more horizons within 75 cm of the mineral soil surface, redox depletions with a. Cracks within 125 cm of the mineral soil surface that chroma of 2 or less and also aquic conditions for some time in are 5 mm or more wide through a thickness of 30 cm or normal years (or artificial drainage). more for some time in normal years and slickensides or Aquic Haplustepts wedge-shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil KEEJ. Other Haplustepts that in normal years are saturated surface; or with water in one or more layers within 100 cm of the mineral b. A linear extensibility of 6.0 cm or more between the soil surface for either: mineral soil surface and either a depth of 100 cm or a 1. 20 or more consecutive days; or densic, lithic, or paralithic contact, whichever is shallower. Torrertic Haplustepts 2. 30 or more cumulative days. Oxyaquic Haplustepts KEEE. Other Haplustepts that have one or both of the following: KEEK. Other Haplustepts that have, in 50 percent or more of the soil volume between a depth of 25 cm from the mineral 1. Cracks within 125 cm of the mineral soil surface that are soil surface and either a depth of 100 cm or a densic, lithic, or 5 mm or more wide through a thickness of 30 cm or more paralithic contact if shallower: for some time in normal years and slickensides or wedge-

shaped peds in a layer 15 cm or more thick that has its upper 1. A CEC (by 1N NH4OAc pH 7) of less than 24 cmol(+) boundary within 125 cm of the mineral soil surface; or per kg clay; or 2. A linear extensibility of 6.0 cm or more between the 2. Both a ratio of measured clay in the fine-earth fraction mineral soil surface and either a depth of 100 cm or a densic, to percent water retained at 1500 kPa tension of 0.6 or more

lithic, or paralithic contact, whichever is shallower. and the following: the CEC (by 1N NH4OAc pH 7) divided Vertic Haplustepts by the product of three times [percent water retained at 1500 kPa tension minus percent organic carbon (but no more than KEEF. Other Haplustepts that have, throughout one or more 1.00)] is less than 24. horizons with a total thickness of 18 cm or more within 75 cm Oxic Haplustepts Inceptisols 187

KEEL. Other Haplustepts that have lamellae (two or more) b. A mesic or thermic soil temperature regime and a within 200 cm of the mineral soil surface. moisture control section that in normal years is dry in Lamellic Haplustepts some part for less than four-tenths of the cumulative days per year when the soil temperature at a depth of 50 cm KEEM. Other Haplustepts that have a slope of less than 25 below the soil surface is higher than 5 oC; or percent; and c. A hyperthermic, isomesic, or warmer iso soil 1. When neither irrigated nor fallowed to store moisture, temperature regime and a moisture control section that in one of the following: normal years is dry in some or all parts for fewer than 120 cumulative days per year when the soil temperature at a a. A frigid soil temperature regime and a moisture o control section that in normal years is dry in all parts for depth of 50 cm below the soil surface is higher than 8 C; four-tenths or more of the cumulative days per year when and the soil temperature at a depth of 50 cm below the soil 2. One or both of the following: surface is higher than 5 oC; or a. At a depth of 125 cm below the mineral soil surface, b. A mesic or thermic soil temperature regime and a an organic-carbon content (Holocene age) of 0.2 percent moisture control section that in normal years is dry in or more and no densic, lithic, or paralithic contact within some part for six-tenths or more of the cumulative days that depth; or per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or b. An irregular decrease in organic-carbon content (Holocene age) between a depth of 25 cm and either c. A hyperthermic, isomesic, or warmer iso soil a depth of 125 cm below the mineral soil surface or a temperature regime and a moisture control section that in densic, lithic, or paralithic contact, whichever is shallower. normal years: Udifluventic Haplustepts (1) Is moist in some or all parts for fewer than 90 consecutive days per year when the soil temperature at KEEO. Other Haplustepts that have a slope of less than 25 a depth of 50 cm below the soil surface is higher than percent and one or both of the following: o 8 C; and 1. At a depth of 125 cm below the mineral soil surface, (2) Is dry in some part for six-tenths or more of the an organic-carbon content (Holocene age) of 0.2 percent or cumulative days per year when the soil temperature at more and no densic, lithic, or paralithic contact within that I a depth of 50 cm below the soil surface is higher than depth; or N 5 oC; and C 2. An irregular decrease in organic-carbon content 2. One or both of the following: (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a densic, lithic, a. At a depth of 125 cm below the mineral soil surface, or paralithic contact, whichever is shallower. an organic-carbon content (Holocene age) of 0.2 percent Fluventic Haplustepts or more and no densic, lithic, or paralithic contact within that depth; or KEEP. Other Haplustepts that have a gypsic horizon within b. An irregular decrease in organic-carbon content 100 cm of the mineral soil surface. (Holocene age) between a depth of 25 cm and either Gypsic Haplustepts a depth of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is shallower. KEEQ. Other Haplustepts that have both: Torrifluventic Haplustepts 1. A calcic horizon within 100 cm of the mineral soil surface; and KEEN. Other Haplustepts that have a slope of less than 25 percent; and 2. When neither irrigated nor fallowed to store moisture, one of the following: 1. When neither irrigated nor fallowed to store moisture, one of the following: a. A frigid soil temperature regime and a moisture control section that in normal years is dry in all parts for a. A frigid soil temperature regime and a moisture four-tenths or more of the cumulative days per year when control section that in normal years is dry in some or all the soil temperature at a depth of 50 cm below the soil parts for fewer than 105 cumulative days per year when surface is higher than 5 oC; or the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or b. A mesic or thermic soil temperature regime and a 188 Keys to Soil Taxonomy

moisture control section that in normal years is dry in temperature at a depth of 50 cm below the soil surface is some part for six-tenths or more of the cumulative days higher than 5 oC; or per year when the soil temperature at a depth of 50 cm 2. A mesic or thermic soil temperature regime and a below the soil surface is higher than 5 oC; or moisture control section that in normal years is dry in some c. A hyperthermic, isomesic, or warmer iso soil part for six-tenths or more of the cumulative days per year temperature regime and a moisture control section that in when the soil temperature at a depth of 50 cm below the soil normal years: surface is higher than 5 oC; or (1) Is moist in some or all parts for fewer than 90 3. A hyperthermic, isomesic, or warmer iso soil consecutive days per year when the soil temperature at temperature regime and a moisture control section that in a depth of 50 cm below the soil surface is higher than normal years: 8 oC; and a. Is moist in some or all parts for fewer than 90 (2) Is dry in some part for six-tenths or more of the consecutive days per year when the soil temperature at a cumulative days per year when the soil temperature at depth of 50 cm below the soil surface is higher than 8 oC; a depth of 50 cm below the soil surface is higher than and 5 oC. b. Is dry in some part for six-tenths or more of the Haplocalcidic Haplustepts cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC. KEER. Other Haplustepts that have both: Aridic Haplustepts 1. A calcic horizon within 100 cm of the mineral soil surface; and KEEU. Other Haplustepts that have a base saturation (by sum of cations) of less than 60 percent in some horizon between 2. When neither irrigated nor fallowed to store moisture, either an Ap horizon or a depth of 25 cm from the mineral soil one of the following: surface, whichever is deeper, and either a depth of 75 cm below a. A frigid soil temperature regime and a moisture the mineral soil surface or a densic, lithic, or paralithic contact, control section that in normal years is dry in some or all whichever is shallower. parts for fewer than 105 cumulative days per year when Dystric Haplustepts the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or KEEV. Other Haplustepts that, when neither irrigated nor fallowed to store moisture, have one of the following: b. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in 1. A frigid soil temperature regime and a moisture control some part for less than four-tenths of the cumulative days section that in normal years is dry in some or all parts for per year when the soil temperature at a depth of 50 cm fewer than 105 cumulative days per year when the soil below the soil surface is higher than 5 oC; or temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or c. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in 2. A mesic or thermic soil temperature regime and a normal years is dry in some or all parts for fewer than 120 moisture control section that in normal years is dry in some cumulative days per year when the soil temperature at a part for less than four-tenths of the cumulative days per year depth of 50 cm below the soil surface is higher than 8 oC. when the soil temperature at a depth of 50 cm below the soil Calcic Udic Haplustepts surface is higher than 5 oC; or 3. A hyperthermic, isomesic, or warmer iso soil KEES. Other Haplustepts that have a calcic horizon within temperature regime and a moisture control section that in 100 cm of the mineral soil surface. normal years is dry in some or all parts for fewer than 120 Calcic Haplustepts cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 8 oC. KEET. Other Haplustepts that, when neither irrigated nor Udic Haplustepts fallowed to store moisture, have one of the following: 1. A frigid soil temperature regime and a moisture control KEEW. Other Haplustepts. section that in normal years is dry in all parts for four- Typic Haplustepts tenths or more of the cumulative days per year when the soil Inceptisols 189

Humustepts KECF. Other Humustepts that, when neither irrigated nor fallowed to store moisture, have one of the following: Key to Subgroups 1. A frigid soil temperature regime and a moisture control KECA. Humustepts that have a lithic contact within 50 cm of section that in normal years is dry in all parts for four- the mineral soil surface. tenths or more of the cumulative days per year when the soil Lithic Humustepts temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or KECB. Other Humustepts that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm 2. A mesic or thermic soil temperature regime and a of the mineral soil surface, a fine-earth fraction with both a bulk moisture control section that in normal years is dry in some density of 1.0 g/cm3 or less, measured at 33 kPa water retention, part for six-tenths or more of the cumulative days per year 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling when the soil temperature at a depth of 50 cm below the soil more than 1.0. surface is higher than 5 oC; or Andic Humustepts 3. A hyperthermic, isomesic, or warmer iso soil KECC. Other Humustepts that have, throughout one or more temperature regime and a moisture control section that in horizons with a total thickness of 18 cm or more within 75 cm normal years: of the mineral soil surface, one or both of the following: a. Is moist in some or all parts for fewer than 90 1. More than 35 percent (by volume) fragments coarser consecutive days per year when the soil temperature at a than 2.0 mm, of which more than 66 percent is cinders, depth of 50 cm below the soil surface is higher than 8 oC; pumice, and pumicelike fragments; or and 2. A fine-earth fraction containing 30 percent or more b. Is dry in some part for six-tenths or more of the particles 0.02 to 2.0 mm in diameter; and cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Aridic Humustepts volcanic glass; and

1 b. [(Al plus /2 Fe, percent extracted by ammonium KECG. Other Humustepts. oxalate) times 60] plus the volcanic glass (percent) is Typic Humustepts equal to 30 or more. I Vitrandic Humustepts N Xerepts C KECD. Other Humustepts that in normal years are saturated Key to Great Groups with water in one or more layers within 100 cm of the mineral soil surface for either or both: KFA. Xerepts that have a duripan within 100 cm of the mineral soil surface. 1. 20 or more consecutive days; or Durixerepts, p. 190 2. 30 or more cumulative days. Oxyaquic Humustepts KFB. Other Xerepts that have a fragipan within 100 cm of the mineral soil surface. KECE. Other Humustepts that have, in 50 percent or more Fragixerepts, p. 192 of the soil volume between a depth of 25 cm from the mineral soil surface and either a depth of 100 cm or a densic, lithic, or KFC. Other Xerepts that have an umbric or mollic epipedon. paralithic contact if shallower: Humixerepts, p. 194 1. A CEC (by 1N NH OAc pH 7) of less than 24 cmol(+) 4 KFD. Other Xerepts that have both: per kg clay; or 1. A calcic horizon within 100 cm of the mineral soil 2. Both a ratio of measured clay in the fine-earth fraction surface or a petrocalcic horizon within 150 cm of the mineral to percent water retained at 1500 kPa tension of 0.6 or more soil surface; and and the following: the CEC (by 1N NH4OAc pH 7) divided by the product of three times [percent water retained at 1500 2. Free carbonates in all parts above the calcic or kPa tension minus percent organic carbon (but no more than petrocalcic horizon, after the soil between the mineral soil 1.00)] is less than 24. surface and a depth of 18 cm has been mixed. Oxic Humustepts Calcixerepts, p. 190 190 Keys to Soil Taxonomy

1 KFE. Other Xerepts that have both of the following: b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 1. No free carbonates within 200 cm of the mineral soil equal to 30 or more. surface; and Vitrandic Calcixerepts

2. A base saturation (by NH4OAc) of less than 60 percent in all horizons at a depth between 25 and 75 cm from the KFDF. Other Calcixerepts that have, in one or more horizons mineral soil surface. within 75 cm of the mineral soil surface, redox depletions with Dystroxerepts, p. 191 chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). KFF. Other Xerepts. Aquic Calcixerepts Haploxerepts, p. 193 KFDG. Other Calcixerepts. Calcixerepts Typic Calcixerepts Key to Subgroups Durixerepts KFDA. Calcixerepts that have a lithic contact within 50 cm of Key to Subgroups the mineral soil surface. Lithic Calcixerepts KFAA. Durixerepts that have both: 1. In one or more horizons above the duripan and within 30 KFDB. Other Calcixerepts that have one or both of the cm of the mineral soil surface, distinct or prominent redox following: concentrations and also aquic conditions for some time in 1. Cracks within 125 cm of the mineral soil surface that are normal years (or artificial drainage);and 5 mm or more wide through a thickness of 30 cm or more 2. Throughout one or more horizons with a total thickness for some time in normal years and slickensides or wedge- of 18 cm or more, above the duripan and within 75 cm of the shaped peds in a layer 15 cm or more thick that has its upper mineral soil surface, one or more of the following: boundary within 125 cm of the mineral soil surface; or a. A fine-earth fraction with both a bulk density of 1.0 2. A linear extensibility of 6.0 cm or more between the g/cm3 or less, measured at 33 kPa water retention, and Al mineral soil surface and either a depth of 100 cm or a densic, 1 plus /2 Fe percentages (by ammonium oxalate) totaling lithic, or paralithic contact, whichever is shallower. more than 1.0; or Vertic Calcixerepts b. More than 35 percent (by volume) fragments coarser KFDC. Other Calcixerepts that have a petrocalcic horizon than 2.0 mm, of which more than 66 percent is cinders, within 100 cm of the mineral soil surface. pumice, and pumicelike fragments; or Petrocalcic Calcixerepts c. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and KFDD. Other Calcixerepts that have an exchangeable sodium percentage of 15 or more (or a sodium adsorption ratio [SAR] (1) In the 0.02 to 2.0 mm fraction, 5 percent or more of 13 or more) in one or more subhorizons within 100 cm of the volcanic glass; and mineral soil surface. 1 (2) [(Al plus /2 Fe, percent extracted by ammonium Sodic Calcixerepts oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. KFDE. Other Calcixerepts that have, throughout one or more Aquandic Durixerepts horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: KFAB. Other Durixerepts that have, throughout one or 1. More than 35 percent (by volume) fragments coarser more horizons with a total thickness of 18 cm or more, above than 2.0 mm, of which more than 66 percent is cinders, the duripan and within 75 cm of the mineral soil surface, a pumice, and pumicelike fragments; or fine-earth fraction with both a bulk density of 1.0 g/cm3 or 1 less, measured at 33 kPa water retention, and Al plus /2 Fe 2. A fine-earth fraction containing 30 percent or more percentages (by ammonium oxalate) totaling more than 1.0. particles 0.02 to 2.0 mm in diameter; and Andic Durixerepts a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and KFAC. Other Durixerepts that have, throughout one or more Inceptisols 191

horizons with a total thickness of 18 cm or more, above the of 18 cm or more within 75 cm of the mineral soil surface, duripan and within 75 cm of the mineral soil surface, one or one or more of the following: both of the following: a. A fine-earth fraction with both a bulk density of 1.0 1. More than 35 percent (by volume) fragments coarser g/cm3 or less, measured at 33 kPa water retention, and Al 1 than 2.0 mm, of which more than 66 percent is cinders, plus /2 Fe percentages (by ammonium oxalate) totaling pumice, and pumicelike fragments; or more than 1.0; or 2. A fine-earth fraction containing 30 percent or more b. More than 35 percent (by volume) fragments coarser particles 0.02 to 2.0 mm in diameter; and than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and c. A fine-earth fraction containing 30 percent or more

1 particles 0.02 to 2.0 mm in diameter; and b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is (1) In the 0.02 to 2.0 mm fraction, 5 percent or more equal to 30 or more. volcanic glass; and

Vitrandic Durixerepts 1 (2) [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is KFAD. Other Durixerepts that have, in one or more horizons equal to 30 or more. above the duripan and within 30 cm of the mineral soil surface, Aquandic Dystroxerepts distinct or prominent redox concentrations and also aquic conditions for some time in normal years (or artificial drainage). KFED. Other Dystroxerepts that have, throughout one or more Aquic Durixerepts horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction with both a bulk KFAE. Other Durixerepts that have a duripan that is strongly density of 1.0 g/cm3 or less, measured at 33 kPa water retention, cemented or less cemented in all subhorizons. 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling Entic Durixerepts more than 1.0. Andic Dystroxerepts KFAF. Other Durixerepts. Typic Durixerepts KFEE. Other Dystroxerepts that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm I Dystroxerepts N of the mineral soil surface, one or both of the following: C Key to Subgroups 1. More than 35 percent (by volume) fragments coarser KFEA. Dystroxerepts that have both: than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or 1. A lithic contact within 50 cm of the mineral soil surface; and 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and 2. A color value, moist, of 3 or less and a color value, dry, of 5 or less (crushed and smoothed sample) either throughout a. In the 0.02 to 2.0 mm fraction, 5 percent or more the upper 18 cm of the mineral soil (unmixed) or between the volcanic glass; and

mineral soil surface and a depth of 18 cm after mixing. 1 b. [(Al plus /2 Fe, percent extracted by ammonium Humic Lithic Dystroxerepts oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. KFEB. Other Dystroxerepts that have a lithic contact within Vitrandic Dystroxerepts 50 cm of the mineral soil surface. Lithic Dystroxerepts KFEF. Other Dystroxerepts that have both: KFEC. Other Dystroxerepts that have both: 1. Fragic soil properties either: 1. In one or more horizons within 75 cm of the mineral soil a. In 30 percent or more of the volume of a layer 15 cm surface, redox depletions with chroma of 2 or less and also or more thick that has its upper boundary within 100 cm aquic conditions for some time in normal years (or artificial of the mineral soil surface; or drainage); and b. In 60 percent or more of the volume of a layer 15 cm 2. Throughout one or more horizons with a total thickness or more thick; and 192 Keys to Soil Taxonomy

2. In one or more horizons within 75 cm of the mineral soil 2. One or both of the following: surface, redox depletions with chroma of 2 or less and also a. At a depth of 125 cm below the mineral soil surface, aquic conditions in normal years (or artificial drainage). an organic-carbon content (Holocene age) of 0.2 percent Fragiaquic Dystroxerepts or more and no densic, lithic, or paralithic contact within that depth; or KFEG. Other Dystroxerepts that have a slope of less than 25 percent; and b. An irregular decrease in organic-carbon content (Holocene age) between a depth of 25 cm and either 1. In one or more horizons within 75 cm of the mineral soil a depth of 125 cm below the mineral soil surface or a surface, redox depletions with chroma of 2 or less and also densic, lithic, or paralithic contact, whichever is shallower. aquic conditions for some time in normal years (or artificial Fluventic Humic Dystroxerepts drainage); and 2. One or both of the following: KFEL. Other Dystroxerepts that have a slope of less than 25 percent and one or both of the following: a. At a depth of 125 cm below the mineral soil surface, an organic-carbon content (Holocene age) of 0.2 percent 1. At a depth of 125 cm below the mineral soil surface, or more and no densic, lithic, or paralithic contact within an organic-carbon content (Holocene age) of 0.2 percent or that depth; or more and no densic, lithic, or paralithic contact within that depth; or b. An irregular decrease in organic-carbon content 2. An irregular decrease in organic-carbon content (Holocene age) between a depth of 25 cm and either (Holocene age) between a depth of 25 cm and either a depth a depth of 125 cm below the mineral soil surface or a of 125 cm below the mineral soil surface or a densic, lithic, densic, lithic, or paralithic contact, whichever is shallower. or paralithic contact, whichever is shallower. Fluvaquentic Dystroxerepts Fluventic Dystroxerepts KFEH. Other Dystroxerepts that have, in one or more horizons KFEM. Other Dystroxerepts that have a color value, moist, within 75 cm of the mineral soil surface, redox depletions with of 3 or less and a color value, dry, of 5 or less (crushed and chroma of 2 or less and also aquic conditions for some time in smoothed sample) either throughout the upper 18 cm of the normal years (or artificial drainage). mineral soil (unmixed) or between the mineral soil surface and a Aquic Dystroxerepts depth of 18 cm after mixing. Humic Dystroxerepts KFEI. Other Dystroxerepts that in normal years are saturated with water in one or more layers within 100 cm of the mineral KFEN. Other Dystroxerepts. soil surface for either or both: Typic Dystroxerepts 1. 20 or more consecutive days; or 2. 30 or more cumulative days. Fragixerepts Oxyaquic Dystroxerepts Key to Subgroups

KFEJ. Other Dystroxerepts that have fragic soil properties KFBA. Fragixerepts that have, throughout one or more either: horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction with both a bulk 1. In 30 percent or more of the volume of a layer 15 cm or density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 more thick that has its upper boundary within 100 cm of the and Al plus /2 Fe percentages (by ammonium oxalate) totaling mineral soil surface; or more than 1.0. 2. In 60 percent or more of the volume of a layer 15 cm or Andic Fragixerepts more thick. Fragic Dystroxerepts KFBB. Other Fragixerepts that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm KFEK. Other Dystroxerepts that have a slope of less than 25 of the mineral soil surface, one or both of the following: percent; and 1. More than 35 percent (by volume) fragments coarser 1. A color value, moist, of 3 or less and a color value, dry, than 2.0 mm, of which more than 66 percent is cinders, of 5 or less (crushed and smoothed sample) either throughout pumice, and pumicelike fragments; or the upper 18 cm of the mineral soil (unmixed) or between the 2. A fine-earth fraction containing 30 percent or more mineral soil surface and a depth of 18 cm after mixing; and particles 0.02 to 2.0 mm in diameter; and Inceptisols 193

a. In the 0.02 to 2.0 mm fraction, 5 percent or more KFFD. Other Haploxerepts that have both: volcanic glass; and 1. In one or more horizons within 75 cm of the mineral soil 1 b. [(Al plus /2 Fe, percent extracted by ammonium surface, redox depletions with chroma of 2 or less and also oxalate) times 60] plus the volcanic glass (percent) is aquic conditions for some time in normal years (or artificial equal to 30 or more. drainage); and Vitrandic Fragixerepts 2. Throughout one or more horizons with a total thickness KFBC. Other Fragixerepts that have, in one or more horizons of 18 cm or more within 75 cm of the mineral soil surface, within 30 cm of the mineral soil surface, distinct or prominent one or more of the following: redox concentrations and also aquic conditions for some time in a. A fine-earth fraction with both a bulk density of 1.0 normal years (or artificial drainage). g/cm3 or less, measured at 33 kPa water retention, and Al 1 Aquic Fragixerepts plus /2 Fe percentages (by ammonium oxalate) totaling KFBD. Other Fragixerepts that have one or both of the more than 1.0; or following: b. More than 35 percent (by volume) fragments coarser 1. An umbric or mollic epipedon; or than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or 2. A color value, moist, of 3 or less and a color value, dry, of 5 or less (crushed and smoothed sample) either throughout c. A fine-earth fraction containing 30 percent or more the upper 18 cm of the mineral soil (unmixed) or between the particles 0.02 to 2.0 mm in diameter; and mineral soil surface and a depth of 18 cm after mixing. (1) In the 0.02 to 2.0 mm fraction, 5 percent or more Humic Fragixerepts volcanic glass; and

1 KFBE. Other Fragixerepts. (2) [(Al plus /2 Fe, percent extracted by ammonium Typic Fragixerepts oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. Haploxerepts Aquandic Haploxerepts

Key to Subgroups KFFE. Other Haploxerepts that have both: KFFA. Haploxerepts that have both: 1. In one or more horizons with a total thickness of 18 I N 1. A lithic contact within 50 cm of the mineral soil surface; cm or more within 75 cm of the mineral soil surface, a C and fine-earth fraction with both a bulk density of 1.0 g/cm3 or 1 2. A color value, moist, of 3 or less and a color value, dry, less, measured at 33 kPa water retention, and Al plus /2 Fe of 5 or less (crushed and smoothed sample) either throughout percentages (by ammonium oxalate) totaling more than 1.0; the upper 18 cm of the mineral soil (unmixed) or between the and mineral soil surface and a depth of 18 cm after mixing. 2. Saturation with water within 100 cm of the mineral soil Humic Lithic Haploxerepts surface in normal years for either or both:

KFFB. Other Haploxerepts that have a lithic contact within 50 a. 20 or more consecutive days; or cm of the mineral soil surface. b. 30 or more cumulative days. Lithic Haploxerepts Andic Oxyaquic Haploxerepts

KFFC. Other Haploxerepts that have one or both of the KFFF. Other Haploxerepts that have, throughout one or more following: horizons with a total thickness of 18 cm or more within 75 cm 1. Cracks within 125 cm of the mineral soil surface that are of the mineral soil surface, a fine-earth fraction with both a bulk 5 mm or more wide through a thickness of 30 cm or more density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 for some time in normal years and slickensides or wedge- and Al plus /2 Fe percentages (by ammonium oxalate) totaling shaped peds in a layer 15 cm or more thick that has its upper more than 1.0. boundary within 125 cm of the mineral soil surface; or Andic Haploxerepts 2. A linear extensibility of 6.0 cm or more between the KFFG. Other Haploxerepts that have both: mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. 1. Saturation with water within 100 cm of the mineral soil Vertic Haploxerepts surface in normal years for either or both: 194 Keys to Soil Taxonomy

a. 20 or more consecutive days; or 1. In 30 percent or more of the volume of a layer 15 cm or more thick that has its upper boundary within 100 cm of the b. 30 or more cumulative days; and mineral soil surface; or 2. Throughout one or more horizons with a total thickness 2. In 60 percent or more of the volume of a layer 15 cm or of 18 cm or more within 75 cm of the mineral soil surface, more thick. one or more of the following: Fragic Haploxerepts a. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, KFFM. Other Haploxerepts that have a slope of less than 25 pumice, and pumicelike fragments; or percent and one or both of the following: b. A fine-earth fraction containing 30 percent or more 1. At a depth of 125 cm below the mineral soil surface, particles 0.02 to 2.0 mm in diameter; and an organic-carbon content (Holocene age) of 0.2 percent or more and no densic, lithic, or paralithic contact within that (1) In the 0.02 to 2.0 mm fraction, 5 percent or more depth; or volcanic glass; and

1 2. An irregular decrease in organic-carbon content (2) [(Al plus /2 Fe, percent extracted by ammonium (Holocene age) between a depth of 25 cm and either a depth oxalate) times 60] plus the volcanic glass (percent) is of 125 cm below the mineral soil surface or a densic, lithic, equal to 30 or more. or paralithic contact, whichever is shallower. Oxyaquic Vitrandic Haploxerepts Fluventic Haploxerepts KFFH. Other Haploxerepts that have, throughout one or more KFFN. Other Haploxerepts that have a calcic horizon or horizons with a total thickness of 18 cm or more within 75 cm identifiable secondary carbonates withinone of the following of the mineral soil surface, one or both of the following: particle-size class and depth combinations: 1. More than 35 percent (by volume) fragments coarser 1. A sandy or sandy-skeletal particle-size class and within than 2.0 mm, of which more than 66 percent is cinders, 150 cm of the mineral soil surface; or pumice, and pumicelike fragments; or 2. A clayey, clayey-skeletal, fine, or very-fine particle-size 2. A fine-earth fraction containing 30 percent or more class and within 90 cm of the mineral soil surface; or particles 0.02 to 2.0 mm in diameter; and 3. Any other particle-size class and within 110 cm of the a. In the 0.02 to 2.0 mm fraction, 5 percent or more mineral soil surface. volcanic glass; and Calcic Haploxerepts 1 b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is KFFO. Other Haploxerepts that have a color value, moist, equal to 30 or more. of 3 or less and a color value, dry, of 5 or less (crushed and Vitrandic Haploxerepts smoothed sample) either throughout the upper 18 cm of the mineral soil (unmixed) or between the mineral soil surface and a KFFI. Other Haploxerepts that have a gypsic horizon within depth of 18 cm after mixing. 100 cm of the mineral soil surface. Humic Haploxerepts Gypsic Haploxerepts KFFP. Other Haploxerepts. KFFJ. Other Haploxerepts that have, in one or more horizons Typic Haploxerepts within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in Humixerepts normal years (or artificial drainage). Aquic Haploxerepts Key to Subgroups KFCA. Humixerepts that have a lithic contact within 50 cm of KFFK. Other Haploxerepts that have lamellae (two or more) the mineral soil surface. within 200 cm of the mineral soil surface. Lithic Humixerepts Lamellic Haploxerepts KFCB. Other Humixerepts that have both: KFFL. Other Haploxerepts that have fragic soil properties either: 1. In one or more horizons within 75 cm of the mineral soil Inceptisols 195

surface, redox depletions with chroma of 2 or less and also KFCF. Other Humixerepts that in normal years are saturated aquic conditions for some time in normal years (or artificial with water in one or more layers within 100 cm of the mineral drainage); and soil surface for either or both: 2. Throughout one or more horizons with a total thickness 1. 20 or more consecutive days; or of 18 cm or more within 75 cm of the mineral soil surface, one or more of the following: 2. 30 or more cumulative days. Oxyaquic Humixerepts a. A fine-earth fraction with both a bulk density of 1.0 3 g/cm or less, measured at 33 kPa water retention, and Al KFCG. Other Humixerepts that have a slope of less than 25 1 plus /2 Fe percentages (by ammonium oxalate) totaling percent; and more than 1.0; or 1. An umbric or mollic epipedon that is 50 cm or more b. More than 35 percent (by volume) fragments coarser thick; and than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or 2. One or both of the following: c. A fine-earth fraction containing 30 percent or more a. At a depth of 125 cm below the mineral soil surface, particles 0.02 to 2.0 mm in diameter; and an organic-carbon content (Holocene age) of 0.2 percent or more and no densic, lithic, or paralithic contact within (1) In the 0.02 to 2.0 mm fraction, 5 percent or more that depth; or volcanic glass; and

1 b. An irregular decrease in organic-carbon content (2) [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is (Holocene age) between a depth of 25 cm and either equal to 30 or more. a depth of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is shallower. Aquandic Humixerepts Cumulic Humixerepts KFCC. Other Humixerepts that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm KFCH. Other Humixerepts that have a slope of less than 25 of the mineral soil surface, a fine-earth fraction with both a bulk percent and one or both of the following: 3 density of 1.0 g/cm or less, measured at 33 kPa water retention, 1. At a depth of 125 cm below the mineral soil surface, 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling an organic-carbon content (Holocene age) of 0.2 percent or I more than 1.0. more and no densic, lithic, or paralithic contact within that N C Andic Humixerepts depth; or

KFCD. Other Humixerepts that have, throughout one or more 2. An irregular decrease in organic-carbon content horizons with a total thickness of 18 cm or more within 75 cm (Holocene age) between a depth of 25 cm and either a depth of the mineral soil surface, one or both of the following: of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is shallower. 1. More than 35 percent (by volume) fragments coarser Fluventic Humixerepts than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or KFCI. Other Humixerepts that have an umbric or mollic 2. A fine-earth fraction containing 30 percent or more epipedon that is 50 cm or more thick. particles 0.02 to 2.0 mm in diameter; and Pachic Humixerepts a. In the 0.02 to 2.0 mm fraction, 5 percent or more KFCJ. Other Humixerepts that do not have a cambic horizon volcanic glass; and and do not, in any part of the umbric or mollic epipedon, meet 1 b. [(Al plus /2 Fe, percent extracted by ammonium the requirements for a cambic horizon, except for the color oxalate) times 60] plus the volcanic glass (percent) is requirements. equal to 30 or more. Entic Humixerepts Vitrandic Humixerepts KFCK. Other Humixerepts. KFCE. Other Humixerepts that have, in one or more horizons Typic Humixerepts within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). Aquic Humixerepts

197

CHAPTER 12 Mollisols

Key to Suborders (2) Either directly below the mollic epipedon or within 75 cm of the mineral soil surface if a calcic IA. Mollisols that have all of the following: horizon intervenes, a color value, moist, of 4 or more 1. An argillic or natric horizon; and and one of the following: 2. An albic horizon that has chroma of 2 or less and is 2.5 (a) 50 percent or more chroma of 1 on faces of cm or more thick, has its lower boundary 18 cm or more peds or in the matrix, hue of 10YR or redder, and below the mineral soil surface, and either lies directly below redox concentrations; or the mollic epipedon or separates horizons that together meet (b) 50 percent or more chroma of 2 or less on all of the requirements for a mollic epipedon; and faces of peds or in the matrix, hue of 2.5Y, and 3. In one or more subhorizons of the albic horizon and/or redox concentrations; or of the argillic or natric horizon and within 100 cm of the (c) 50 percent or more chroma of 1 on faces of mineral soil surface, redox concentrations in the form of peds or in the matrix and hue of 2.5Y or yellower; masses or concretions, or both, and also aquic conditions for or some time in normal years (or artificial drainage);and (d) 50 percent or more chroma of 3 or less on 4. A soil temperature regime that is warmer than cryic. faces of peds or in the matrix, hue of 5Y, and redox Albolls, p. 198 concentrations; or (e) 50 percent or more chroma of 0 on faces of IB. Other Mollisols that have, in a layer above a densic, lithic, peds or in the matrix; or or paralithic contact or in a layer at a depth between 40 and 50 cm from the mineral soil surface, whichever is shallower, aquic (f) Hue of 5GY, 5G, 5BG, or 5B; or conditions for some time in normal years (or artificial drainage) (g) Any color if it results from uncoated sand and one or more of the following: grains; or M O 1. A histic epipedon overlying the mollic epipedon; or b. Chroma of 2 in the lower part of the mollic epipedon; L 2. An exchangeable sodium percentage (ESP) of 15 or and either more (or a sodium adsorption ratio [SAR] of 13 or more) in (1) Distinct or prominent redox concentrations in the the upper part of the mollic epipedon and a decrease in ESP lower part of the mollic epipedon; or (or SAR) values with increasing depth below 50 cm from the (2) Directly below the mollic epipedon, one of the mineral soil surface; or following matrix colors: 3. A calcic or petrocalcic horizon within 40 cm of the (a) A color value, moist, of 4, chroma of 2, and mineral soil surface; or some redox depletions with a color value, moist, of 4. A mollic epipedon, with chroma of 1 or less, that extends 4 or more and chroma of 1 or less; or to a lithic contact within 30 cm of the mineral soil surface; or (b) A color value, moist, of 5 or more, chroma of 5. One of the following colors: 2 or less, and redox concentrations; or a. Chroma of 1 or less in the lower part of the mollic (c) A color value, moist, of 4 and chroma of 1 or epipedon;1 and either less; or (1) Distinct or prominent redox concentrations in the 6. At a depth between 40 and 50 cm from the mineral soil lower part of the mollic epipedon; or surface, enough active ferrous iron to give a positive reaction to alpha,alpha-dipyridyl at a time when the soil is not being 1 If the mollic epipedon extends to a lithic contact within 30 cm of the mineral soil irrigated. surface, the requirement for redoximorphic features is waived. Aquolls, p. 199 198 Keys to Soil Taxonomy

IC. Other Mollisols that: has its upper boundary within 125 cm of the mineral soil surface; or 1. Have a mollic epipedon that is less than 50 cm thick; and b. A linear extensibility of 6.0 cm or more between 2. Do not have an argillic or calcic horizon; and the mineral soil surface and either a depth of 100 cm 3. Have, either within or directly below the mollic or a densic, lithic, or paralithic contact, whichever is epipedon, mineral soil materials less than 75 mm in diameter shallower; and

that have a CaCO3 equivalent of 40 percent or more; and 2. If not irrigated, a moisture control section that in normal 4. Have either or both: years is dry in all parts for 45 or more consecutive days during the 120 days following the summer solstice. a. A udic soil moisture regime; or Xerertic Argialbolls b. A cryic soil temperature regime. IABB. Other Argialbolls that have one or both of the Rendolls, p. 207 following: ID. Other Mollisols that have a gelic soil temperature regime. 1. Cracks within 125 cm of the mineral soil surface that are Gelolls, p. 206 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge- IE. Other Mollisols that have a cryic soil temperature regime. shaped peds in a layer 15 cm or more thick that has its upper Cryolls, p. 203 boundary within 125 cm of the mineral soil surface; or 2. A linear extensibility of 6.0 cm or more between the IF. Other Mollisols that have either a xeric soil moisture mineral soil surface and either a depth of 100 cm or a densic, regime or an aridic soil moisture regime that borders on xeric. lithic, or paralithic contact, whichever is shallower. Xerolls, p. 230 Vertic Argialbolls

IG. Other Mollisols that have either an ustic soil moisture IABC. Other Argialbolls that: regime or an aridic soil moisture regime that borders on ustic. Ustolls, p. 215 1. Do not have an abrupt textural change from the albic to the argillic horizon; and IH. Other Mollisols. 2. If not irrigated, have a moisture control section that in Udolls, p. 207 normal years is dry in all parts for 45 or more consecutive days during the 120 days following the summer solstice. Albolls Argiaquic Xeric Argialbolls

Key to Great Groups IABD. Other Argialbolls that do not have an abrupt textural IAA. Albolls that have a natric horizon. change from the albic to the argillic horizon. Natralbolls, p. 199 Argiaquic Argialbolls

IAB. Other Albolls. IABE. Other Argialbolls that, if not irrigated, have a moisture Argialbolls, p. 198 control section that in normal years is dry in all parts for 45 or more consecutive days during the 120 days following the Argialbolls summer solstice. Xeric Argialbolls Key to Subgroups IABF. Other Argialbolls that have, throughout one or more IABA. Argialbolls that have both: horizons with a total thickness of 18 cm or more within 75 cm 1. One or both of the following: of the mineral soil surface, one or more of the following: a. Cracks within 125 cm of the mineral soil surface that 1. A fine-earth fraction with both a bulk density of 1.0 are 5 mm or more wide through a thickness of 30 cm or g/cm3 or less, measured at 33 kPa water retention, and Al 1 more for some time in normal years and slickensides or plus /2 Fe percentages (by ammonium oxalate) totaling more wedge-shaped peds in a layer 15 cm or more thick that than 1.0; or Mollisols 199

2. More than 35 percent (by volume) fragments coarser Argiaquolls than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or Key to Subgroups IBEA. Argiaquolls that meet sandy or sandy-skeletal particle- 3. A fine-earth fraction containing 30 percent or more size class criteria throughout a layer extending from the mineral particles 0.02 to 2.0 mm in diameter; and soil surface to the top of an argillic horizon at a depth of 50 to a. In the 0.02 to 2.0 mm fraction, 5 percent or more 100 cm. volcanic glass; and Arenic Argiaquolls

1 b. [(Al plus /2 Fe, percent extracted by ammonium IBEB. Other Argiaquolls that meet sandy or sandy-skeletal oxalate) times 60] plus the volcanic glass (percent) is particle-size class criteria throughout a layer extending from the equal to 30 or more. mineral soil surface to the top of an argillic horizon at a depth of Aquandic Argialbolls 100 cm or more. Grossarenic Argiaquolls IABG. Other Argialbolls. Typic Argialbolls IBEC. Other Argiaquolls that have one or both of the following: Natralbolls 1. Cracks within 125 cm of the mineral soil surface that are Key to Subgroups 5 mm or more wide through a thickness of 30 cm or more IAAA. Natralbolls that have visible crystals of gypsum and/or for some time in normal years and slickensides or wedge- more soluble salts within 40 cm of the mineral soil surface. shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil surface; Leptic Natralbolls or 2. A linear extensibility of 6.0 cm or more between the IAAB. Other Natralbolls. mineral soil surface and either a depth of 100 cm or a densic, Typic Natralbolls lithic, or paralithic contact, whichever is shallower. Vertic Argiaquolls Aquolls IBED. Other Argiaquolls that have an argillic horizon that, Key to Great Groups with increasing depth, has a clay increase of 20 percent or more (absolute, in the fine-earth fraction) within its upper 7.5 cm. IBA. Aquolls that have a cryic soil temperature regime. Abruptic Argiaquolls Cryaquolls, p. 200 IBEE. Other Argiaquolls. M IBB. Other Aquolls that have a duripan within 100 cm of the O Typic Argiaquolls L mineral soil surface. Duraquolls, p. 200 Calciaquolls IBC. Other Aquolls that have a natric horizon. Key to Subgroups Natraquolls, p. 202 IBDA. Calciaquolls that have a petrocalcic horizon within 100 cm of the mineral soil surface. IBD. Other Aquolls that have a calcic or gypsic horizon within Petrocalcic Calciaquolls 40 cm of the mineral soil surface but do not have an argillic horizon unless it is a buried horizon. IBDB. Other Calciaquolls that have 50 percent or more Calciaquolls, p. 199 chroma of 3 or more on faces of peds or in the matrix of one or more horizons within 75 cm of the mineral soil surface or that IBE. Other Aquolls that have an argillic horizon. have the following colors directly below the mollic epipedon: Argiaquolls, p. 199 1. Hue of 2.5Y or yellower and chroma of 3 or more; or IBF. Other Aquolls that have episaturation. 2. Hue of 10YR or redder and chroma of 2 or more; or Epiaquolls, p. 201 3. Hue of 2.5Y or yellower and chroma of 2 or more if IBG. Other Aquolls. there are no distinct or prominent redox concentrations. Endoaquolls, p. 200 Aeric Calciaquolls 200 Keys to Soil Taxonomy

IBDC. Other Calciaquolls. IBAG. Other Cryaquolls that have a mollic epipedon that is 50 Typic Calciaquolls cm or more thick. Cumulic Cryaquolls Cryaquolls IBAH. Other Cryaquolls. Key to Subgroups Typic Cryaquolls IBAA. Cryaquolls that have one or both of the following: Duraquolls 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or more Key to Subgroups for some time in normal years and slickensides or wedge- IBBA. Duraquolls that have a natric horizon. shaped peds in a layer 15 cm or more thick that has its upper Natric Duraquolls boundary within 125 cm of the mineral soil surface; or 2. A linear extensibility of 6.0 cm or more between the IBBB. Other Duraquolls that have one or both of the mineral soil surface and either a depth of 100 cm or a densic, following: lithic, or paralithic contact, whichever is shallower. 1. Cracks between the soil surface and the top of the Vertic Cryaquolls duripan that are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and IBAB. Other Cryaquolls that have a histic epipedon. slickensides or wedge-shaped peds in a layer 15 cm or more Histic Cryaquolls thick that is above the duripan; or IBAC. Other Cryaquolls that have a buried layer of organic 2. A linear extensibility of 6.0 cm or more between the soil soil materials, 20 cm or more thick, that has its upper boundary surface and the top of the duripan. within 100 cm of the mineral soil surface. Vertic Duraquolls Thapto-Histic Cryaquolls IBBC. Other Duraquolls that have an argillic horizon. IBAD. Other Cryaquolls that have, throughout one or more Argic Duraquolls horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or more of the following: IBBD. Other Duraquolls. Typic Duraquolls 1. A fine-earth fraction with both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water retention, and Al 1 Endoaquolls plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0; or Key to Subgroups 2. More than 35 percent (by volume) fragments coarser IBGA. Endoaquolls that have a lithic contact within 50 cm of than 2.0 mm, of which more than 66 percent is cinders, the mineral soil surface. pumice, and pumicelike fragments; or Lithic Endoaquolls

3. A fine-earth fraction containing 30 percent or more IBGB. Other Endoaquolls that have both: particles 0.02 to 2.0 mm in diameter; and 1. One or both of the following: a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and a. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or 1 b. [(Al plus /2 Fe, percent extracted by ammonium more for some time in normal years and slickensides or oxalate) times 60] plus the volcanic glass (percent) is wedge-shaped peds in a layer 15 cm or more thick that equal to 30 or more. has its upper boundary within 125 cm of the mineral soil Aquandic Cryaquolls surface; or

IBAE. Other Cryaquolls that have an argillic horizon. b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm Argic Cryaquolls or a densic, lithic, or paralithic contact, whichever is shallower; and IBAF. Other Cryaquolls that have a calcic horizon either within or directly below the mollic epipedon. 2. A mollic epipedon that is 60 cm or more thick. Calcic Cryaquolls Cumulic Vertic Endoaquolls Mollisols 201

1 IBGC. Other Endoaquolls that have both of the following: plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0; or 1. One or both of the following: 2. More than 35 percent (by volume) fragments coarser a. Cracks within 125 cm of the mineral soil surface that than 2.0 mm, of which more than 66 percent is cinders, are 5 mm or more wide through a thickness of 30 cm or pumice, and pumicelike fragments; or more for some time in normal years and slickensides or wedge-shaped peds in a layer 15 cm or more thick that 3. A fine-earth fraction containing 30 percent or more has its upper boundary within 125 cm of the mineral soil particles 0.02 to 2.0 mm in diameter; and surface; or a. In the 0.02 to 2.0 mm fraction, 5 percent or more b. A linear extensibility of 6.0 cm or more between volcanic glass; and

the mineral soil surface and either a depth of 100 cm 1 b. [(Al plus /2 Fe, percent extracted by ammonium or a densic, lithic, or paralithic contact, whichever is oxalate) times 60] plus the volcanic glass (percent) is shallower; and equal to 30 or more. 2. A slope of less than 25 percent and one or both of the Aquandic Endoaquolls following: IBGH. Other Endoaquolls that have a horizon, 15 cm or more a. An organic-carbon content (Holocene age) of 0.3 thick within 100 cm of the mineral soil surface, that either has percent or more in all horizons within 125 cm of the 20 percent or more (by volume) durinodes or is brittle and has at mineral soil surface; or least a firm rupture-resistance class when moist. b. An irregular decrease in organic-carbon content Duric Endoaquolls (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a IBGI. Other Endoaquolls that have a mollic epipedon that is densic, lithic, or paralithic contact, whichever is shallower. 60 cm or more thick. Fluvaquentic Vertic Endoaquolls Cumulic Endoaquolls

IBGD. Other Endoaquolls that have one or both of the IBGJ. Other Endoaquolls that have a slope of less than 25 following: percent and one or both of the following: 1. Cracks within 125 cm of the mineral soil surface that are 1. An organic-carbon content (Holocene age) of 0.3 percent 5 mm or more wide through a thickness of 30 cm or more or more in all horizons within 125 cm of the mineral soil for some time in normal years and slickensides or wedge- surface; or shaped peds in a layer 15 cm or more thick that has its upper 2. An irregular decrease in organic-carbon content boundary within 125 cm of the mineral soil surface; or M (Holocene age) between a depth of 25 cm and either a depth O 2. A linear extensibility of 6.0 cm or more between the of 125 cm below the mineral soil surface or a densic, lithic, L mineral soil surface and either a depth of 100 cm or a densic, or paralithic contact, whichever is shallower. lithic, or paralithic contact, whichever is shallower. Fluvaquentic Endoaquolls Vertic Endoaquolls IBGK. Other Endoaquolls. IBGE. Other Endoaquolls that have a histic epipedon. Typic Endoaquolls Histic Endoaquolls Epiaquolls IBGF. Other Endoaquolls that have a buried layer of organic Key to Subgroups soil materials, 20 cm or more thick, that has its upper boundary within 100 cm of the mineral soil surface. IBFA. Epiaquolls that have both of the following: Thapto-Histic Endoaquolls 1. One or both of the following: a. Cracks within 125 cm of the mineral soil surface that IBGG. Other Endoaquolls that have, throughout one or more are 5 mm or more wide through a thickness of 30 cm or horizons with a total thickness of 18 cm or more within 75 cm more for some time in normal years and slickensides or of the mineral soil surface, one or more of the following: wedge-shaped peds in a layer 15 cm or more thick that 1. A fine-earth fraction with both a bulk density of 1.0 has its upper boundary within 125 cm of the mineral soil g/cm3 or less, measured at 33 kPa water retention, and Al surface; or 202 Keys to Soil Taxonomy

b. A linear extensibility of 6.0 cm or more between IBFF. Other Epiaquolls that have, throughout one or more the mineral soil surface and either a depth of 100 cm horizons with a total thickness of 18 cm or more within 75 cm or a densic, lithic, or paralithic contact, whichever is of the mineral soil surface, one or more of the following: shallower; and 1. A fine-earth fraction with both a bulk density of 1.0 2. A mollic epipedon that is 60 cm or more thick. g/cm3 or less, measured at 33 kPa water retention, and Al 1 Cumulic Vertic Epiaquolls plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0; or IBFB. Other Epiaquolls that have both: 2. More than 35 percent (by volume) fragments coarser 1. One or both of the following: than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or a. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or 3. A fine-earth fraction containing 30 percent or more more for some time in normal years and slickensides or particles 0.02 to 2.0 mm in diameter; and wedge-shaped peds in a layer 15 cm or more thick that a. In the 0.02 to 2.0 mm fraction, 5 percent or more has its upper boundary within 125 cm of the mineral soil volcanic glass; and surface; or 1 b. [(Al plus /2 Fe, percent extracted by ammonium b. A linear extensibility of 6.0 cm or more between oxalate) times 60] plus the volcanic glass (percent) is the mineral soil surface and either a depth of 100 cm equal to 30 or more. or a densic, lithic, or paralithic contact, whichever is Aquandic Epiaquolls shallower; and 2. A slope of less than 25 percent and one or both of the IBFG. Other Epiaquolls that have a horizon, 15 cm or more following: thick within 100 cm of the mineral soil surface, that either has 20 percent or more (by volume) durinodes or is brittle and has at a. An organic-carbon content (Holocene age) of 0.3 least a firm rupture-resistance class when moist. percent or more in all horizons within 125 cm of the Duric Epiaquolls mineral soil surface; or IBFH. Other Epiaquolls that have a mollic epipedon that is 60 b. An irregular decrease in organic-carbon content cm or more thick. (Holocene age) between a depth of 25 cm and either Cumulic Epiaquolls a depth of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is shallower. IBFI. Other Epiaquolls that have a slope of less than 25 Fluvaquentic Vertic Epiaquolls percent and one or both of the following: IBFC. Other Epiaquolls that have one or both of the 1. An organic-carbon content (Holocene age) of 0.3 percent following: or more in all horizons within 125 cm of the mineral soil surface; or 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or more 2. An irregular decrease in organic-carbon content for some time in normal years and slickensides or wedge- (Holocene age) between a depth of 25 cm and either a depth shaped peds in a layer 15 cm or more thick that has its upper of 125 cm below the mineral soil surface or a densic, lithic, boundary within 125 cm of the mineral soil surface; or or paralithic contact, whichever is shallower. Fluvaquentic Epiaquolls 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a densic, IBFJ. Other Epiaquolls. lithic, or paralithic contact, whichever is shallower. Typic Epiaquolls Vertic Epiaquolls Natraquolls IBFD. Other Epiaquolls that have a histic epipedon. Histic Epiaquolls Key to Subgroups IBCA. Natraquolls that have one or both of the following: IBFE. Other Epiaquolls that have a buried layer of organic soil materials, 20 cm or more thick, that has its upper boundary 1. Cracks within 125 cm of the mineral soil surface that are within 100 cm of the mineral soil surface. 5 mm or more wide through a thickness of 30 cm or more Thapto-Histic Epiaquolls for some time in normal years and slickensides or wedge- Mollisols 203

shaped peds in a layer 15 cm or more thick that has its upper IEDB. Other Argicryolls that have one or both of the boundary within 125 cm of the mineral soil surface; or following: 2. A linear extensibility of 6.0 cm or more between the 1. Cracks within 125 cm of the mineral soil surface that are mineral soil surface and either a depth of 100 cm or a densic, 5 mm or more wide through a thickness of 30 cm or more lithic, or paralithic contact, whichever is shallower. for some time in normal years and slickensides or wedge- Vertic Natraquolls shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil surface; or IBCB. Other Natraquolls that have a glossic horizon or 2. A linear extensibility of 6.0 cm or more between the interfingering of albic materials into the natric horizon. mineral soil surface and either a depth of 100 cm or a densic, Glossic Natraquolls lithic, or paralithic contact, whichever is shallower. Vertic Argicryolls IBCC. Other Natraquolls. Typic Natraquolls IEDC. Other Argicryolls that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm Cryolls of the mineral soil surface, a fine-earth fraction with both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water retention, Key to Great Groups 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling IEA. Cryolls that have a duripan within 100 cm of the mineral more than 1.0. soil surface. Andic Argicryolls Duricryolls, p. 204 IEDD. Other Argicryolls that have, throughout one or more IEB. Other Cryolls that have a natric horizon. horizons with a total thickness of 18 cm or more within 75 cm Natricryolls, p. 206 of the soil surface, one or both of the following: 1. More than 35 percent (by volume) fragments coarser IEC. Other Cryolls that have both: than 2.0 mm, of which more than 66 percent is cinders, 1. An argillic horizon that has its upper boundary 60 cm or pumice, and pumicelike fragments; or more below the mineral soil surface; and 2. A fine-earth fraction containing 30 percent or more 2. A texture class finer than loamy fine sand in all horizons particles 0.02 to 2.0 mm in diameter; and above the argillic horizon. Palecryolls, p. 206 a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and

IED. Other Cryolls that have an argillic horizon. 1 M b. [(Al plus /2 Fe, percent extracted by ammonium O Argicryolls, p. 203 oxalate) times 60] plus the volcanic glass (percent) is L equal to 30 or more. IEE. Other Cryolls that have : both Vitrandic Argicryolls 1. A calcic or petrocalcic horizon within 100 cm of the mineral soil surface; and IEDE. Other Argicryolls that have an argillic horizon that, 2. In all parts above the calcic or petrocalcic horizon, after with increasing depth, has a clay increase of 20 percent or more the materials between the soil surface and a depth of 18 cm (absolute, in the fine-earth fraction) within its upper 7.5 cm. have been mixed, either free carbonates or a texture class of Abruptic Argicryolls loamy fine sand or coarser. IEDF. Other Argicryolls that have, in one or more horizons Calcicryolls, p. 204 within 100 cm of the mineral soil surface, redox depletions with IEF. Other Cryolls. chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). Haplocryolls, p. 204 Aquic Argicryolls

Argicryolls IEDG. Other Argicryolls that in normal years are saturated Key to Subgroups with water in one or more layers within 100 cm of the mineral soil surface for either or both: IEDA. Argicryolls that have a lithic contact within 50 cm of the mineral soil surface. 1. 20 or more consecutive days; or Lithic Argicryolls 204 Keys to Soil Taxonomy

than 2.0 mm, of which more than 66 percent is cinders, 2. 30 or more cumulative days. pumice, and pumicelike fragments; or Oxyaquic Argicryolls 2. A fine-earth fraction containing 30 percent or more IEDH. Other Argicryolls that have both: particles 0.02 to 2.0 mm in diameter; and 1. A mollic epipedon that is 40 cm or more thick and has a a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; texture class finer than loamy fine sand;and and 1 b. [(Al plus /2 Fe, percent extracted by ammonium 2. A calcic horizon within 100 cm of the mineral soil oxalate) times 60] plus the volcanic glass (percent) is surface. equal to 30 or more. Calcic Pachic Argicryolls Vitrandic Calcicryolls IEDI. Other Argicryolls that have a mollic epipedon that is 40 IEEC. Other Calcicryolls that have a petrocalcic horizon cm or more thick and has a texture class finer than loamy fine within 100 cm of the mineral soil surface. sand. Petrocalcic Calcicryolls Pachic Argicryolls IEED. Other Calcicryolls that have a mollic epipedon that is IEDJ. Other Argicryolls that have a calcic horizon within 100 40 cm or more thick and has a texture class finer than loamy fine cm of the mineral soil surface. sand. Calcic Argicryolls Pachic Calcicryolls IEDK. Other Argicryolls that have either: IEEE. Other Calcicryolls that have an ustic soil moisture 1. Above the argillic horizon, an albic horizon or a horizon regime. that has color values too high for a mollic epipedon and Ustic Calcicryolls chroma too high for an albic horizon; or IEEF. Other Calcicryolls that have a xeric soil moisture 2. A glossic horizon, or interfingering of albic materials regime. into the upper part of the argillic horizon, or skeletans of Xeric Calcicryolls clean silt and sand covering 50 percent or more of the faces of peds in the upper 5 cm of the argillic horizon. IEEG. Other Calcicryolls. Alfic Argicryolls Typic Calcicryolls

IEDL. Other Argicryolls that have an ustic soil moisture Duricryolls regime. Ustic Argicryolls Key to Subgroups IEAA. Duricryolls that have an argillic horizon. IEDM. Other Argicryolls that have a xeric soil moisture Argic Duricryolls regime. Xeric Argicryolls IEAB. Other Duricryolls that have a calcic horizon above the duripan. IEDN. Other Argicryolls. Calcic Duricryolls Typic Argicryolls IEAC. Other Duricryolls. Calcicryolls Typic Duricryolls Key to Subgroups Haplocryolls IEEA. Calcicryolls that have a lithic contact within 50 cm of the mineral soil surface. Key to Subgroups Lithic Calcicryolls IEFA. Haplocryolls that have a lithic contact within 50 cm of the mineral soil surface. IEEB. Other Calcicryolls that have, throughout one or more Lithic Haplocryolls horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: IEFB. Other Haplocryolls that have one or both of the 1. More than 35 percent (by volume) fragments coarser following: Mollisols 205

1. Cracks within 125 cm of the mineral soil surface that are 2. An irregular decrease in organic-carbon content 5 mm or more wide through a thickness of 30 cm or more (Holocene age) between a depth of 25 cm and either a depth for some time in normal years and slickensides or wedge- of 125 cm below the mineral soil surface or a densic, lithic, shaped peds in a layer 15 cm or more thick that has its upper or paralithic contact, whichever is shallower; and boundary within 125 cm of the mineral soil surface; or 3. A slope of less than 25 percent. 2. A linear extensibility of 6.0 cm or more between the Cumulic Haplocryolls mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. IEFG. Other Haplocryolls that have both: Vertic Haplocryolls 1. A slope of less than 25 percent and one or both of the IEFC. Other Haplocryolls that have, throughout one or more following: horizons with a total thickness of 18 cm or more within 75 cm a. An organic-carbon content (Holocene age) of 0.3 of the mineral soil surface, a fine-earth fraction with both a bulk percent or more at a depth of 125 cm below the mineral density of 1.0 g/cm3 or less, measured at 33 kPa water retention, soil surface; or 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. b. An irregular decrease in organic-carbon content Andic Haplocryolls (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or IEFD. Other Haplocryolls that have, throughout one or more a densic, lithic, or paralithic contact, whichever is horizons with a total thickness of 18 cm or more within 75 cm shallower; and of the mineral soil surface, one or both of the following: 2. In one or more horizons within 100 cm of the mineral 1. More than 35 percent (by volume) fragments coarser soil surface, distinct or prominent redox concentrations and than 2.0 mm, of which more than 66 percent is cinders, also aquic conditions for some time in normal years (or pumice, and pumicelike fragments; or artificial drainage). Fluvaquentic Haplocryolls 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and IEFH. Other Haplocryolls that have, in one or more horizons a. In the 0.02 to 2.0 mm fraction, 5 percent or more within 100 cm of the mineral soil surface, distinct or prominent volcanic glass; and redox concentrations and also aquic conditions for some time in 1 normal years (or artificial drainage). b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is Aquic Haplocryolls equal to 30 or more. IEFI. Other Haplocryolls that in normal years are saturated M Vitrandic Haplocryolls O with water in one or more layers within 100 cm of the mineral L IEFE. Other Haplocryolls that have: soil surface for either or both: 1. A mollic epipedon that is 40 cm or more thick and has a 1. 20 or more consecutive days; or texture class finer than loamy fine sand;and 2. 30 or more cumulative days. 2. An irregular decrease in organic-carbon content Oxyaquic Haplocryolls (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a densic, lithic, IEFJ. Other Haplocryolls that have both: or paralithic contact, whichever is shallower; and 1. A mollic epipedon that is 40 cm or more thick and has a 3. A slope of less than 25 percent; and texture class finer than loamy fine sand;and 4. In one or more horizons within 100 cm of the mineral 2. A calcic horizon within 100 cm of the mineral soil soil surface, distinct or prominent redox concentrations and surface. also aquic conditions for some time in normal years (or Calcic Pachic Haplocryolls artificial drainage). Aquic Cumulic Haplocryolls IEFK. Other Haplocryolls that have a mollic epipedon that is 40 cm or more thick and has a texture class finer than loamy fine IEFF. Other Haplocryolls that have: sand. 1. A mollic epipedon that is 40 cm or more thick and has a Pachic Haplocryolls texture class finer than loamy fine sand;and 206 Keys to Soil Taxonomy

IEFL. Other Haplocryolls that have a slope of less than 25 IECD. Other Palecryolls that have a mollic epipedon that is 40 percent and one or both of the following: cm or more thick and has a texture class finer than loamy fine sand. 1. An organic-carbon content (Holocene age) of 0.3 percent Pachic Palecryolls or more at a depth of 125 cm below the mineral soil surface; or IECE. Other Palecryolls that have an ustic soil moisture 2. An irregular decrease in organic-carbon content regime. (Holocene age) between a depth of 25 cm and either a depth Ustic Palecryolls of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is shallower. IECF. Other Palecryolls that have a xeric soil moisture regime. Fluventic Haplocryolls Xeric Palecryolls

IEFM. Other Haplocryolls that have a calcic horizon within IECG. Other Palecryolls. 100 cm of the mineral soil surface. Typic Palecryolls Calcic Haplocryolls Gelolls IEFN. Other Haplocryolls that have an ustic soil moisture regime. Key to Great Groups Ustic Haplocryolls IDA. All Gelolls. Haplogelolls, p. 206 IEFO. Other Haplocryolls that have a xeric soil moisture regime. Xeric Haplocryolls Haplogelolls Key to Subgroups IEFP. Other Haplocryolls. Typic Haplocryolls IDAA. Haplogelolls that have a lithic contact within 50 cm of the mineral soil surface. Natricryolls Lithic Haplogelolls

Key to Subgroups IDAB. Other Haplogelolls that have, throughout one or more IEBA. All Natricryolls. horizons with a total thickness of 18 cm or more within 75 cm Typic Natricryolls of the mineral soil surface, a fine-earth fraction with both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 Palecryolls and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. Key to Subgroups Andic Haplogelolls IECA. Palecryolls that have, in one or more horizons within 100 cm of the mineral soil surface, redox depletions with IDAC. Other Haplogelolls that have, in one or more horizons chroma of 2 or less and also aquic conditions for some time in within 100 cm of the mineral soil surface, distinct or prominent normal years (or artificial drainage). redox concentrations and also aquic conditions for some time in Aquic Palecryolls normal years (or artificial drainage). Aquic Haplogelolls IECB. Other Palecryolls that in normal years are saturated with water in one or more layers within 100 cm of the mineral IDAD. Other Haplogelolls that in normal years are saturated soil surface for either or both: with water in one or more layers within 100 cm of the mineral soil surface for either or both: 1. 20 or more consecutive days; or 1. 20 or more consecutive days; or 2. 30 or more cumulative days. Oxyaquic Palecryolls 2. 30 or more cumulative days. Oxyaquic Haplogelolls IECC. Other Palecryolls that have an argillic horizon that, with increasing depth, has a clay increase of 20 percent or more IDAE. Other Haplogelolls that have gelic materials within 200 (absolute, in the fine-earth fraction) within its upper 7.5 cm. cm of the mineral soil surface. Abruptic Palecryolls Turbic Haplogelolls Mollisols 207

IDAF. Other Haplogelolls that have both: ICBD. Other Haprendolls that have a color value, dry, of 6 or more either in the upper 18 cm of the mollic epipedon, after 1. A mollic epipedon that is 40 cm or more thick and has a mixing, or in an Ap horizon that is 18 cm or more thick. texture class finer than loamy fine sand; and Entic Haprendolls 2. An irregular decrease in organic-carbon content (Holocene age) between a depth of 25 cm and either a depth ICBE. Other Haprendolls. of 125 cm below the mineral soil surface or a densic, lithic, Typic Haprendolls or paralithic contact, whichever is shallower. Cumulic Haplogelolls Udolls IDAE. Other Haplogelolls. Key to Great Groups Typic Haplogelolls IHA. Udolls that have a natric horizon. Natrudolls, p. 213 Rendolls Key to Great Groups IHB. Other Udolls that: ICA. Rendolls that have a cryic soil temperature regime. 1. Have a calcic or petrocalcic horizon within 100 cm of the mineral soil surface; Cryrendolls, p. 207 and 2. Do not have an argillic horizon above the calcic or ICB. Other Rendolls. petrocalcic horizon; and Haprendolls, p. 207 3. In all parts above the calcic or petrocalcic horizon, after Cryrendolls the materials between the soil surface and a depth of 18 cm have been mixed, have either free carbonates or a texture Key to Subgroups class of loamy fine sand or coarser. Calciudolls, p. 210 ICAA. Cryrendolls that have a lithic contact within 50 cm of the mineral soil surface. IHC. Other Udolls that have one or more of the following: Lithic Cryrendolls 1. A petrocalcic horizon within 150 cm of the mineral soil ICAB. Other Cryrendolls. surface; or Typic Cryrendolls 2. All of the following: Haprendolls a. No densic, lithic, or paralithic contact within 150 cm M O of the mineral soil surface; and Key to Subgroups L b. Within 150 cm of the mineral soil surface, a clay ICBA. Haprendolls that have a lithic contact within 50 cm of decrease, with increasing depth, of less than 20 percent the mineral soil surface. (relative) from the maximum clay content (noncarbonate Lithic Haprendolls clay); and ICBB. Other Haprendolls that have one or both of the c. An argillic horizon with one or more of the following: following: (1) In 50 percent or more of the matrix of one or 1. Cracks within 125 cm of the mineral soil surface that are more subhorizons in its lower half, hue of 7.5YR or 5 mm or more wide through a thickness of 30 cm or more redder and chroma of 5 or more; or for some time in normal years and slickensides or wedge- (2) In 50 percent or more of the matrix of horizons shaped peds in a layer 15 cm or more thick that has its upper that total more than one-half the total thickness, hue boundary within 125 cm of the mineral soil surface; or of 2.5YR or redder, a value, moist, of 3 or less, and a 2. A linear extensibility of 6.0 cm or more between the value, dry, of 4 or less; or mineral soil surface and either a depth of 100 cm or a densic, (3) Many redox concentrations with hue of 5YR or lithic, or paralithic contact, whichever is shallower. redder or chroma of 6 or more, or both, in one or more Vertic Haprendolls subhorizons; or ICBC. Other Haprendolls that have a cambic horizon. 3. A frigid soil temperature regime; and Inceptic Haprendolls 208 Keys to Soil Taxonomy

a. An argillic horizon that has its upper boundary 60 cm wedge-shaped peds in a layer 15 cm or more thick that or more below the mineral soil surface; and has its upper boundary within 125 cm of the mineral soil surface; or b. A texture class finer than loamy fine sand in all horizons above the argillic horizon. b. A linear extensibility of 6.0 cm or more between the Paleudolls, p. 214 mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. IHD. Other Udolls that have an argillic horizon. Aquertic Argiudolls Argiudolls, p. 208 IHDC. Other Argiudolls that have both: IHE. Other Udolls that have a mollic epipedon that: 1. One or both of the following: 1. Either below an Ap horizon or below a depth of 18 cm from the mineral soil surface, contains 50 percent or a. Cracks within 125 cm of the mineral soil surface that more (by volume) wormholes, wormcasts, or filled animal are 5 mm or more wide through a thickness of 30 cm or burrows; and more for some time in normal years and slickensides or wedge-shaped peds in a layer 15 cm or more thick that 2. Either rests on a lithic contact or has a transition zone has its upper boundary within 125 cm of the mineral soil to the underlying horizon in which 25 percent or more of the surface; or soil volume consists of discrete wormholes, wormcasts, or animal burrows filled with material from the mollic epipedon b. A linear extensibility of 6.0 cm or more between and from the underlying horizon. the mineral soil surface and either a depth of 100 cm Vermudolls, p. 215 or a densic, lithic, or paralithic contact, whichever is shallower; and IHF. Other Udolls. 2. In normal years saturation with water in one or more Hapludolls, p. 211 layers within 100 cm of the mineral soil surface for either or both: Argiudolls a. 20 or more consecutive days; or Key to Subgroups b. 30 or more cumulative days. IHDA. Argiudolls that have a lithic contact within 50 cm of Oxyaquic Vertic Argiudolls the mineral soil surface. Lithic Argiudolls IHDD. Other Argiudolls that have:

IHDB. Other Argiudolls that have both: 1. A mollic epipedon that has a texture class finer than loamy fine sand and that is either: 1. Aquic conditions for some time in normal years (or artificial drainage)either : a. 40 cm or more thick in a frigid soil temperature regime; or a. Within 40 cm of the mineral soil surface, in horizons that also have redoximorphic features; or b. 50 cm or more thick; and b. Within 75 cm of the mineral soil surface, in one or 2. One or both of the following: more horizons with a total thickness of 15 cm or more that a. Cracks within 125 cm of the mineral soil surface that have one or more of the following: are 5 mm or more wide through a thickness of 30 cm or (1) A color value, moist, of 4 or more and redox more for some time in normal years and slickensides or depletions with chroma of 2 or less; or wedge-shaped peds in a layer 15 cm or more thick that (2) Hue of 10YR or redder and chroma of 2 or less; has its upper boundary within 125 cm of the mineral soil surface; or or (3) Hue of 2.5Y or yellower and chroma of 3 or less; b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a and densic, lithic, or paralithic contact, whichever is shallower. 2. One or both of the following: Pachic Vertic Argiudolls a. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or IHDE. Other Argiudolls that have: more for some time in normal years and slickensides or 1. Above the argillic horizon, an albic horizon or a horizon Mollisols 209

that has color values too high for a mollic epipedon and oxalate) times 60] plus the volcanic glass (percent) is chroma too high for an albic horizon; or equal to 30 or more. Vitrandic Argiudolls 2. A glossic horizon, or interfingering of albic materials into the upper part of the argillic horizon, skeletans of or IHDI. Other Argiudolls that have both: clean silt and sand covering 50 percent or more of the faces of peds in the upper 5 cm of the argillic horizon; and 1. Aquic conditions for some time in normal years (or artificial drainage)either : 3. One or both of the following: a. Within 40 cm of the mineral soil surface, in horizons a. Cracks within 125 cm of the mineral soil surface that that also have redoximorphic features; or are 5 mm or more wide through a thickness of 30 cm or b. Within 75 cm of the mineral soil surface, in one or more for some time in normal years and slickensides or more horizons with a total thickness of 15 cm or more that wedge-shaped peds in a layer 15 cm or more thick that have one or more of the following: has its upper boundary within 125 cm of the mineral soil surface; or (1) A color value, moist, of 4 or more and redox depletions with chroma of 2 or less; or b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a (2) Hue of 10YR or redder and chroma of 2 or less; densic, lithic, or paralithic contact, whichever is shallower. or Alfic Vertic Argiudolls (3) Hue of 2.5Y or yellower and chroma of 3 or less; and IHDF. Other Argiudolls that have one or both of the following: 2. A mollic epipedon that has a texture class finer than 1. Cracks within 125 cm of the mineral soil surface that are loamy fine sand and that is either: 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge- a. 40 cm or more thick in a frigid soil temperature shaped peds in a layer 15 cm or more thick that has its upper regime; or boundary within 125 cm of the mineral soil surface; or b. 50 cm or more thick. Aquic Pachic Argiudolls 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a densic, IHDJ. Other Argiudolls that have a mollic epipedon that has a lithic, or paralithic contact, whichever is shallower. texture class finer than loamy fine sand and that is either: Vertic Argiudolls 1. 40 cm or more thick in a frigid soil temperature regime; IHDG. Other Argiudolls that have, throughout one or more or M horizons with a total thickness of 18 cm or more within 75 cm O 2. 50 cm or more thick. L of the mineral soil surface, a fine-earth fraction with both a bulk Pachic Argiudolls density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling IHDK. Other Argiudolls that have aquic conditions for some more than 1.0. time in normal years (or artificial drainage)either : Andic Argiudolls 1. Within 40 cm of the mineral soil surface, in horizons that IHDH. Other Argiudolls that have, throughout one or more also have redoximorphic features; or horizons with a total thickness of 18 cm or more within 75 cm 2. Within 75 cm of the mineral soil surface, in one or more of the mineral soil surface, one or both of the following: horizons with a total thickness of 15 cm or more that have 1. More than 35 percent (by volume) fragments coarser one or more of the following: than 2.0 mm, of which more than 66 percent is cinders, a. A color value, moist, of 4 or more and redox pumice, and pumicelike fragments; or depletions with chroma of 2 or less; or 2. A fine-earth fraction containing 30 percent or more b. Hue of 10YR or redder and chroma of 2 or less; or particles 0.02 to 2.0 mm in diameter; and c. Hue of 2.5Y or yellower and chroma of 3 or less. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Aquic Argiudolls volcanic glass; and

1 b. [(Al plus /2 Fe, percent extracted by ammonium IHDL. Other Argiudolls that in normal years are saturated 210 Keys to Soil Taxonomy

with water in one or more layers within 100 cm of the mineral IHDR. Other Argiudolls that have a CEC of less than 24 soil surface for either or both: cmol(+)/kg clay (by 1N NH4OAc pH 7) in 50 percent or more either of the argillic horizon if less than 100 cm thick or of its 1. 20 or more consecutive days; or upper 100 cm. 2. 30 or more cumulative days. Oxic Argiudolls Oxyaquic Argiudolls IHDS. Other Argiudolls that have a calcic horizon within 100 IHDM. Other Argiudolls that have an argillic horizon that: cm of the mineral soil surface. Calcic Argiudolls 1. Consists entirely of lamellae; or 2. Is a combination of two or more lamellae and one or IHDT. Other Argiudolls. more subhorizons with a thickness of 7.5 to 20 cm, each Typic Argiudolls layer with an overlying eluvial horizon; or Calciudolls 3. Consists of one or more subhorizons that are more than 20 cm thick, each with an overlying eluvial horizon, and Key to Subgroups above these horizons there are either: IHBA. Calciudolls that have a lithic contact within 50 cm of a. Two or more lamellae with a combined thickness of the mineral soil surface. 5 cm or more (that may or may not be part of the argillic Lithic Calciudolls horizon); or IHBB. Other Calciudolls that have one or both of the b. A combination of lamellae (that may or may not be following: part of the argillic horizon) and one or more parts of the argillic horizon 7.5 to 20 cm thick, each with an overlying 1. Cracks within 125 cm of the mineral soil surface that are eluvial horizon. 5 mm or more wide through a thickness of 30 cm or more Lamellic Argiudolls for some time in normal years and slickensides or wedge- shaped peds in a layer 15 cm or more thick that has its upper IHDN. Other Argiudolls that have a sandy particle-size class boundary within 125 cm of the mineral soil surface; or throughout the upper 75 cm of the argillic horizon or throughout 2. A linear extensibility of 6.0 cm or more between the the entire argillic horizon if it is less than 75 cm thick. mineral soil surface and either a depth of 100 cm or a densic, Psammentic Argiudolls lithic, or paralithic contact, whichever is shallower. Vertic Calciudolls IHDO. Other Argiudolls that meet sandy or sandy-skeletal particle-size class criteria throughout a layer extending from the IHBC. Other Calciudolls that have, in one or more horizons mineral soil surface to the top of an argillic horizon at a depth of within 75 cm of the mineral soil surface, redox depletions with 50 cm or more. chroma of 2 or less and also aquic conditions for some time in Arenic Argiudolls normal years (or artificial drainage). Aquic Calciudolls IHDP. Other Argiudolls that have an argillic horizon that, with increasing depth, has a clay increase of 20 percent or more IHBD. Other Calciudolls that have a slope of less than 25 (absolute, in the fine-earth fraction) within its upper 7.5 cm. percent and one or both of the following: Abruptic Argiudolls 1. An organic-carbon content (Holocene age) of 0.3 percent IHDQ. Other Argiudolls that have: or more at a depth of 125 cm below the mineral soil surface; or 1. Above the argillic horizon, an albic horizon or a horizon that has color values too high for a mollic epipedon and 2. An irregular decrease in organic-carbon content chroma too high for an albic horizon; or (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a densic, lithic, 2. A glossic horizon, or interfingering of albic materials or paralithic contact, whichever is shallower. into the upper part of the argillic horizon, or skeletans of Fluventic Calciudolls clean silt and sand covering 50 percent or more of the faces of peds in the upper 5 cm of the argillic horizon. IHBE. Other Calciudolls. Alfic Argiudolls Typic Calciudolls Mollisols 211

Hapludolls a. 40 cm or more thick in a frigid soil temperature regime; or Key to Subgroups b. 50 cm or more thick. IHFA. Hapludolls that have a lithic contact within 50 cm of Pachic Vertic Hapludolls the mineral soil surface. Lithic Hapludolls IHFD. Other Hapludolls that have one or both of the following: IHFB. Other Hapludolls that have both: 1. Cracks within 125 cm of the mineral soil surface that are 1. Aquic conditions for some time in normal years (or 5 mm or more wide through a thickness of 30 cm or more artificial drainage)either : for some time in normal years and slickensides or wedge- a. Within 40 cm of the mineral soil surface, in horizons shaped peds in a layer 15 cm or more thick that has its upper that also have redoximorphic features; or boundary within 125 cm of the mineral soil surface; or b. Within 75 cm of the mineral soil surface, in one or 2. A linear extensibility of 6.0 cm or more between the more horizons with a total thickness of 15 cm or more that mineral soil surface and either a depth of 100 cm or a densic, have one or more of the following: lithic, or paralithic contact, whichever is shallower. Vertic Hapludolls (1) A color value, moist, of 4 or more and redox depletions with chroma of 2 or less; or IHFE. Other Hapludolls that have, throughout one or more (2) Hue of 10YR or redder and chroma of 2 or less; horizons with a total thickness of 18 cm or more within 75 cm or of the mineral soil surface, a fine-earth fraction with both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water retention, (3) Hue of 2.5Y or yellower and chroma of 3 or less; 1 and Al + /2 Fe percentages (by ammonium oxalate) totaling and more than 1.0. 2. One or both of the following: Andic Hapludolls

a. Cracks within 125 cm of the mineral soil surface that IHFF. Other Hapludolls that have, throughout one or more are 5 mm or more wide through a thickness of 30 cm or horizons with a total thickness of 18 cm or more within 75 cm more for some time in normal years and slickensides or of the mineral soil surface, one or both of the following: wedge-shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil 1. More than 35 percent (by volume) fragments coarser surface; or than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or b. A linear extensibility of 6.0 cm or more between the M 2. A fine-earth fraction containing 30 percent or more O mineral soil surface and either a depth of 100 cm or a L densic, lithic, or paralithic contact, whichever is shallower. particles 0.02 to 2.0 mm in diameter; and Aquertic Hapludolls a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and IHFC. Other Hapludolls that have both: 1 b. [(Al plus /2 Fe, percent extracted by ammonium 1. One or both of the following: oxalate) times 60] plus the volcanic glass (percent) is a. Cracks within 125 cm of the mineral soil surface that equal to 30 or more. are 5 mm or more wide through a thickness of 30 cm or Vitrandic Hapludolls more for some time in normal years and slickensides or wedge-shaped peds in a layer 15 cm or more thick that IHFG. Other Hapludolls that have: has its upper boundary within 125 cm of the mineral soil 1. Either: surface; or a. A frigid soil temperature regime and a mollic b. A linear extensibility of 6.0 cm or more between epipedon that is 40 cm or more thick, of which less than the mineral soil surface and either a depth of 100 cm 50 percent meets sandy or sandy-skeletal particle-size or a densic, lithic, or paralithic contact, whichever is class criteria, and there is no densic or paralithic contact shallower; and and no sandy or sandy-skeletal particle-size class at 2. A mollic epipedon that has a texture class finer than a depth between 40 and 50 cm from the mineral soil loamy fine sand and that is either: surface; or 212 Keys to Soil Taxonomy

b. A mollic epipedon that is 60 cm or more thick, of b. Within 75 cm of the mineral soil surface, in one or which 50 percent or more of the thickness has a texture more horizons with a total thickness of 15 cm or more that class finer than loamy fine sand; and have one or more of the following: 2. One or both of the following: (1) A color value, moist, of 4 or more and redox a. An organic-carbon content (Holocene age) of 0.3 depletions with chroma of 2 or less; or percent or more at a depth of 125 cm below the mineral (2) Hue of 10YR or redder and chroma of 2 or less; soil surface; or or b. An irregular decrease in organic-carbon content (3) Hue of 2.5Y or yellower and chroma of 3 or less; (Holocene age) between a depth of 25 cm and either and a depth of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is 2. A slope of less than 25 percent and one or both of the shallower; and following: 3. A slope of less than 25 percent; and a. An organic-carbon content (Holocene age) of 0.3 percent or more at a depth of 125 cm below the mineral 4. In one or more horizons within 75 cm of the mineral soil soil surface; or surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial b. An irregular decrease in organic-carbon content drainage). (Holocene age) between a depth of 25 cm and either Aquic Cumulic Hapludolls a depth of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is shallower. IHFH. Other Hapludolls that have: Fluvaquentic Hapludolls 1. Either: IHFJ. Other Hapludolls that have a slope of less than 25 a. A frigid soil temperature regime and a mollic percent and one or both of the following: epipedon that is 40 cm or more thick, of which less than 1. An organic-carbon content (Holocene age) of 0.3 percent 50 percent meets sandy or sandy-skeletal particle-size or more at a depth of 125 cm below the mineral soil surface; class criteria, and there is no densic or paralithic contact or and no sandy or sandy-skeletal particle-size class at a depth between 40 and 50 cm from the mineral soil 2. An irregular decrease in organic-carbon content surface; or (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a densic, lithic, b. A mollic epipedon that is 60 cm or more thick, of or paralithic contact, whichever is shallower. which 50 percent or more of the thickness has a texture Fluventic Hapludolls class finer than loamy fine sand; and 2. One or both of the following: IHFK. Other Hapludolls that have both: a. An organic-carbon content (Holocene age) of 0.3 1. Aquic conditions for some time in normal years (or percent or more at a depth of 125 cm below the mineral artificial drainage) either: soil surface; or a. Within 40 cm of the mineral soil surface, in horizons b. An irregular decrease in organic-carbon content that also have redoximorphic features; or (Holocene age) between a depth of 25 cm and either b. Within 75 cm of the mineral soil surface, in one or a depth of 125 cm below the mineral soil surface or more horizons with a total thickness of 15 cm or more that a densic, lithic, or paralithic contact, whichever is have one or more of the following: shallower; and (1) A color value, moist, of 4 or more and redox 3. A slope of less than 25 percent. depletions with chroma of 2 or less; or Cumulic Hapludolls (2) Hue of 10YR or redder and chroma of 2 or less; IHFI. Other Hapludolls that have both: or 1. Aquic conditions for some time in normal years (or (3) Hue of 2.5Y or yellower and chroma of 3 or less; artificial drainage) either: and a. Within 40 cm of the mineral soil surface, in horizons 2. A mollic epipedon that has a texture class finer than that also have redoximorphic features; or loamy fine sand and that is either: Mollisols 213

a. 40 cm or more thick in a frigid soil temperature IHFQ. Other Hapludolls that either: regime; or 1. Do not have a cambic horizon and do not, in any part b. 50 cm or more thick. of the mollic epipedon below 25 cm from the mineral soil Aquic Pachic Hapludolls surface, meet the requirements for a cambic horizon, except for the color requirements; or IHFL. Other Hapludolls that have a mollic epipedon that has a 2. Have free carbonates throughout the cambic horizon or texture class finer than loamy fine sand and that is either: in all parts of the mollic epipedon below a depth of 25 cm 1. 40 cm or more thick in a frigid soil temperature regime; from the mineral soil surface. or Entic Hapludolls 2. 50 cm or more thick. IHFR. Other Hapludolls. Pachic Hapludolls Typic Hapludolls IHFM. Other Hapludolls that have aquic conditions for some time in normal years (or artificial drainage)either : Natrudolls 1. Within 40 cm of the mineral soil surface, in horizons that Key to Subgroups also have redoximorphic features; or IHAA. Natrudolls that have a petrocalcic horizon within 100 2. Within 75 cm of the mineral soil surface, in one or more cm of the mineral soil surface. horizons with a total thickness of 15 cm or more that have Petrocalcic Natrudolls one or more of the following: IHAB. Other Natrudolls that have both: a. A color value, moist, of 4 or more and redox depletions with chroma of 2 or less; or 1. Visible crystals of gypsum and/or more soluble salts within 40 cm of the mineral soil surface; and b. Hue of 10YR or redder and chroma of 2 or less; or 2. One or both of the following: c. Hue of 2.5Y or yellower and chroma of 3 or less. Aquic Hapludolls a. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or IHFN. Other Hapludolls that in normal years are saturated more for some time in normal years and slickensides or with water in one or more layers within 100 cm of the mineral wedge-shaped peds in a layer 15 cm or more thick that soil surface for either or both: has its upper boundary within 125 cm of the mineral soil surface; or 1. 20 or more consecutive days; or M b. A linear extensibility of 6.0 cm or more between the O 2. 30 or more cumulative days. mineral soil surface and either a depth of 100 cm or a L Oxyaquic Hapludolls densic, lithic, or paralithic contact, whichever is shallower. Leptic Vertic Natrudolls IHFO. Other Hapludolls that have both: 1. A mollic epipedon that is 60 cm or more thick that has IHAC. Other Natrudolls that have: a texture class finer than loamy fine sand and contains 50 1. A glossic horizon or interfingering of albic materials into percent or more (by volume) wormholes, wormcasts, or filled the natric horizon; and animal burrows either below an Ap horizon or below a depth 2. One or both of the following: of 18 cm from the mineral soil surface; and a. Cracks within 125 cm of the mineral soil surface that 2. Either do not have a cambic horizon and do not, in the are 5 mm or more wide through a thickness of 30 cm or lower part of the mollic epipedon, meet the requirements for more for some time in normal years and slickensides or a cambic horizon, except for the color requirements, or have wedge-shaped peds in a layer 15 cm or more thick that free carbonates throughout either the cambic horizon or the has its upper boundary within 125 cm of the mineral soil lower part of the mollic epipedon. surface; or Vermic Hapludolls b. A linear extensibility of 6.0 cm or more between the IHFP. Other Hapludolls that have a calcic horizon within 100 mineral soil surface and either a depth of 100 cm or a cm of the mineral soil surface. densic, lithic, or paralithic contact, whichever is shallower. Calcic Hapludolls Glossic Vertic Natrudolls 214 Keys to Soil Taxonomy

IHAD. Other Natrudolls that have one or both of the b. Within 75 cm of the mineral soil surface, in one or following: more horizons with a total thickness of 15 cm or more that 1. Cracks within 125 cm of the mineral soil surface that are have one or more of the following: 5 mm or more wide through a thickness of 30 cm or more (1) A color value, moist, of 4 or more and redox for some time in normal years and slickensides or wedge- depletions with chroma of 2 or less; or shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil surface; or (2) Hue of 10YR or redder and chroma of 2 or less; or 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a densic, (3) Hue of 2.5Y or yellower and chroma of 3 or less; lithic, or paralithic contact, whichever is shallower. and Vertic Natrudolls 2. A mollic epipedon that has a texture class finer than loamy fine sand and that is either: IHAE. Other Natrudolls that have visible crystals of gypsum and/or more soluble salts within 40 cm of the mineral soil a. 40 cm or more thick in a frigid soil temperature surface. regime; or Leptic Natrudolls b. 50 cm or more thick. IHAF. Other Natrudolls that have a glossic horizon or Aquic Pachic Paleudolls interfingering of albic materials into the natric horizon. Glossic Natrudolls IHCD. Other Paleudolls that have a mollic epipedon that has a texture class finer than loamy fine sand and that is 50 cm or IHAG. Other Natrudolls that have a calcic horizon within 100 more thick. cm of the mineral soil surface. Pachic Paleudolls Calcic Natrudolls IHCE. Other Paleudolls that have, in one or more subhorizons IHAH. Other Natrudolls. within 75 cm of the mineral soil surface, redox depletions with Typic Natrudolls chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). Paleudolls Aquic Paleudolls

Key to Subgroups IHCF. Other Paleudolls that in normal years are saturated with IHCA. Paleudolls that have one or both of the following: water in one or more layers within 100 cm of the mineral soil surface for either or both: 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or more 1. 20 or more consecutive days; or for some time in normal years and slickensides or wedge- 2. 30 or more cumulative days. shaped peds in a layer 15 cm or more thick that has its upper Oxyaquic Paleudolls boundary within 125 cm of the mineral soil surface; or 2. A linear extensibility of 6.0 cm or more between the IHCG. Other Paleudolls that have both: mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. 1. A calcic horizon within 100 cm of the mineral soil Vertic Paleudolls surface; and 2. In all parts above the calcic horizon, after the materials IHCB. Other Paleudolls that have a petrocalcic horizon within between the soil surface and a depth of 18 cm have been 150 cm of the mineral soil surface. mixed, free carbonates or a texture class of loamy fine sand Petrocalcic Paleudolls or coarser. Calcic Paleudolls IHCC. Other Paleudolls that have both: 1. Aquic conditions for some time in normal years (or IHCH. Other Paleudolls. artificial drainage)either : Typic Paleudolls a. Within 40 cm of the mineral soil surface, in horizons that also have redoximorphic features; or Mollisols 215

Vermudolls b. 35 percent or more noncarbonate clay in its upper part and a clay increase either of 20 percent or more Key to Subgroups (absolute) within a vertical distance of 7.5 cm or of 15 IHEA. Vermudolls that have a lithic contact within 50 cm of percent or more (absolute) within a vertical distance of the mineral soil surface. 2.5 cm, in the fine-earth fraction (and there is no densic, Lithic Vermudolls lithic, or paralithic contact within 50 cm of the mineral soil surface). Paleustolls, p. 228 IHEB. Other Vermudolls that have a mollic epipedon that is less than 75 cm thick. IGE. Other Ustolls that have an argillic horizon. Haplic Vermudolls Argiustolls, p. 215

IHEC. Other Vermudolls. IGF. Other Ustolls that have a mollic epipedon that: Typic Vermudolls 1. Either below an Ap horizon or below a depth of 18 cm from the mineral soil surface, contains 50 percent or Ustolls more (by volume) wormholes, wormcasts, or filled animal Key to Great Groups burrows; and 2. Either rests on a lithic contact or has a transition zone IGA. Ustolls that have a duripan within 100 cm of the mineral to the underlying horizon in which 25 percent or more of the soil surface. soil volume consists of discrete wormholes, wormcasts, or Durustolls, p. 221 animal burrows filled with material from the mollic epipedon and from the underlying horizon. IGB. Other Ustolls that have a natric horizon. Vermustolls, p. 230 Natrustolls, p. 226 IGG. Other Ustolls. IGC. Other Ustolls that: Haplustolls, p. 221 1. Have either a calcic or gypsic horizon within 100 cm of the mineral soil surface or a petrocalcic horizon within 150 Argiustolls cm of the mineral soil surface; and Key to Subgroups 2. Do not have an argillic horizon above the calcic, gypsic, or petrocalcic horizon; and IGEA. Argiustolls that have both: 1. A lithic contact within 50 cm of the mineral soil surface; M 3. In all parts above the calcic, gypsic, or petrocalcic O horizon, after the materials between the soil surface and a and L depth of 18 cm have been mixed, have either free carbonates 2. When neither irrigated nor fallowed to store moisture, or a texture class of loamy fine sand or coarser. have one of the following: Calciustolls, p. 219 a. A frigid soil temperature regime and a moisture IGD. Other Ustolls that have either: control section that in normal years is dry in all parts for four-tenths or more of the cumulative days per year when 1. A petrocalcic horizon within 150 cm of the mineral soil the soil temperature at a depth of 50 cm below the soil surface; or surface is higher than 5 oC; or 2. An argillic horizon that has one or both of the following: b. A mesic or thermic soil temperature regime and a a. With increasing depth, no clay decrease of 20 percent moisture control section that in normal years is dry in or more (relative) from the maximum clay content some or all parts for six-tenths or more of the cumulative (noncarbonate clay) within 150 cm of the mineral soil days per year when the soil temperature at a depth of 50 surface (and there is no densic, lithic, or paralithic contact cm below the soil surface is higher than 5 oC; or within that depth); and either c. A hyperthermic, isomesic, or warmer iso soil (1) Hue of 7.5YR or redder and chroma of 5 or more temperature regime and a moisture control section that in in the matrix; or normal years: (2) Common redox concentrations with hue of 7.5YR (1) Is moist in some or all parts for fewer than 90 or redder or chroma of 6 or more, or both; or consecutive days per year when the soil temperature at 216 Keys to Soil Taxonomy

a depth of 50 cm below the soil surface is higher than 2. When neither irrigated nor fallowed to store moisture, 8 oC; and have one of the following: (2) Is dry in some or all parts for six-tenths or a. A frigid soil temperature regime and a moisture more of the cumulative days per year when the soil control section that in normal years is dry in all parts for temperature at a depth of 50 cm below the soil surface four-tenths or more of the cumulative days per year when is higher than 5 oC. the soil temperature at a depth of 50 cm below the soil Aridic Lithic Argiustolls surface is higher than 5 oC; or

IGEB. Other Argiustolls that have both: b. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in 1. A lithic contact within 50 cm of the mineral soil surface; some or all parts for six-tenths or more of the cumulative and days per year when the soil temperature at a depth of 50 o 2. Above the argillic horizon, either an albic horizon or a cm below the soil surface is higher than 5 C; or horizon that has color values too high for a mollic epipedon c. A hyperthermic, isomesic, or warmer iso soil and chroma too high for an albic horizon. temperature regime and a moisture control section that in Alfic Lithic Argiustolls normal years:

IGEC. Other Argiustolls that have a lithic contact within 50 (1) Is moist in some or all parts for fewer than 90 cm of the mineral soil surface. consecutive days per year when the soil temperature at Lithic Argiustolls a depth of 50 cm below the soil surface is higher than 8 oC; and IGED. Other Argiustolls that have both: (2) Is dry in some or all parts for six-tenths or 1. In one or more horizons within 100 cm of the mineral more of the cumulative days per year when the soil soil surface, redox depletions with chroma of 2 or less and temperature at a depth of 50 cm below the soil surface also aquic conditions for some time in normal years (or is higher than 5 oC. artificial drainage);and Torrertic Argiustolls 2. of the following: One or both IGEF. Other Argiustolls that have all of the following: a. Cracks within 125 cm of the mineral soil surface that 1. A mollic epipedon that has a texture class finer than are 5 mm or more wide through a thickness of 30 cm or loamy fine sand and that is either: more for some time in normal years and slickensides or wedge-shaped peds in a layer 15 cm or more thick that a. 40 cm or more thick in a frigid soil temperature has its upper boundary within 125 cm of the mineral soil regime; or surface; or b. 50 cm or more thick; and b. A linear extensibility of 6.0 cm or more between the 2. One or both of the following: mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. a. Cracks within 125 cm of the mineral soil surface that Aquertic Argiustolls are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or IGEE. Other Argiustolls that have both: wedge-shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil 1. One or both of the following: surface; or a. Cracks within 125 cm of the mineral soil surface that b. A linear extensibility of 6.0 cm or more between are 5 mm or more wide through a thickness of 30 cm or the mineral soil surface and either a depth of 100 cm more for some time in normal years and slickensides or or a densic, lithic, or paralithic contact, whichever is wedge-shaped peds in a layer 15 cm or more thick that shallower; and has its upper boundary within 125 cm of the mineral soil surface; or 3. When neither irrigated nor fallowed to store moisture, either: b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm a. A mesic or thermic soil temperature regime and a or a densic, lithic, or paralithic contact, whichever is moisture control section that in normal years is dry in shallower; and some part for four-tenths or less of the cumulative days Mollisols 217

per year when the soil temperature at a depth of 50 cm a. 40 cm or more thick in a frigid soil temperature below the soil surface is higher than 5 oC; or regime; or b. A hyperthermic, isomesic, or warmer iso soil b. 50 cm or more thick. temperature regime and a moisture control section that in Pachic Vertic Argiustolls normal years is dry in some or all parts for fewer than 120 cumulative days per year when the soil temperature at a IGEI. Other Argiustolls that have one or both of the following: depth of 50 cm below the soil surface is higher than 8 oC. 1. Cracks within 125 cm of the mineral soil surface that are Pachic Udertic Argiustolls 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge- IGEG. Other Argiustolls that have both: shaped peds in a layer 15 cm or more thick that has its upper 1. One or both of the following: boundary within 125 cm of the mineral soil surface; or a. Cracks within 125 cm of the mineral soil surface that 2. A linear extensibility of 6.0 cm or more between the are 5 mm or more wide through a thickness of 30 cm or mineral soil surface and either a depth of 100 cm or a densic, more for some time in normal years and slickensides or lithic, or paralithic contact, whichever is shallower. wedge-shaped peds in a layer 15 cm or more thick that Vertic Argiustolls has its upper boundary within 125 cm of the mineral soil surface; or IGEJ. Other Argiustolls that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm b. A linear extensibility of 6.0 cm or more between of the mineral soil surface, a fine-earth fraction with both a bulk the mineral soil surface and either a depth of 100 cm density of 1.0 g/cm3 or less, measured at 33 kPa water retention, or a densic, lithic, or paralithic contact, whichever is 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling shallower; and more than 1.0. 2. When neither irrigated nor fallowed to store moisture, Andic Argiustolls either: IGEK. Other Argiustolls that have both: a. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in 1. When neither irrigated nor fallowed to store moisture, some part for four-tenths or less of the cumulative days one of the following: per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or a. A frigid soil temperature regime and a moisture control section that in normal years is dry in all parts for b. A hyperthermic, isomesic, or warmer iso soil four-tenths or more of the cumulative days per year when temperature regime and a moisture control section that in the soil temperature at a depth of 50 cm below the soil M normal years is dry in some or all parts for fewer than 120 o O surface is higher than 5 C; or L cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 8 oC. b. A mesic or thermic soil temperature regime and a Udertic Argiustolls moisture control section that in normal years is dry in some or all parts for six-tenths or more of the cumulative IGEH. Other Argiustolls that have both: days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or 1. One or both of the following: c. A hyperthermic, isomesic, or warmer iso soil a. Cracks within 125 cm of the mineral soil surface that temperature regime and a moisture control section that in are 5 mm or more wide through a thickness of 30 cm or normal years: more for some time in normal years and slickensides or wedge-shaped peds in a layer 15 cm or more thick that (1) Is moist in some or all parts for fewer than 90 has its upper boundary within 125 cm of the mineral soil consecutive days per year when the soil temperature at surface; or a depth of 50 cm below the soil surface is higher than 8 oC; and b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm (2) Is dry in some or all parts for six-tenths or or a densic, lithic, or paralithic contact, whichever is more of the cumulative days per year when the soil shallower; and temperature at a depth of 50 cm below the soil surface is higher than 5 oC; and 2. A mollic epipedon that has a texture class finer than loamy fine sand and that is either: 2. Throughout one or more horizons with a total thickness 218 Keys to Soil Taxonomy

of 18 cm or more within 75 cm of the mineral soil surface, IGEP. Other Argiustolls that have either: one or both of the following: 1. Above the argillic horizon, an albic horizon or a horizon a. More than 35 percent (by volume) fragments coarser that has color values too high for a mollic epipedon and than 2.0 mm, of which more than 66 percent is cinders, chroma too high for an albic horizon; or pumice, and pumicelike fragments; or 2. A glossic horizon, or interfingering of albic materials b. A fine-earth fraction containing 30 percent or more into the upper part of the argillic horizon, or skeletans of particles 0.02 to 2.0 mm in diameter; and clean silt and sand covering 50 percent or more of the faces (1) In the 0.02 to 2.0 mm fraction, 5 percent or more of peds in the upper 5 cm of the argillic horizon. volcanic glass; and Alfic Argiustolls

1 (2) [(Al plus /2 Fe, percent extracted by ammonium IGEQ. Other Argiustolls that have both: oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. 1. A calcic horizon within 100 cm of the mineral soil Vitritorrandic Argiustolls surface; and 2. When neither irrigated nor fallowed to store moisture, IGEL. Other Argiustolls that have, throughout one or more one of the following: horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: a. A frigid soil temperature regime and a moisture control section that in normal years is dry in all parts for 1. More than 35 percent (by volume) fragments coarser four-tenths or more of the cumulative days per year when than 2.0 mm, of which more than 66 percent is cinders, the soil temperature at a depth of 50 cm below the soil pumice, and pumicelike fragments; or surface is higher than 5 oC; or 2. A fine-earth fraction containing 30 percent or more b. A mesic or thermic soil temperature regime and a particles 0.02 to 2.0 mm in diameter; and moisture control section that in normal years is dry in a. In the 0.02 to 2.0 mm fraction, 5 percent or more some part for six-tenths or more of the cumulative days volcanic glass; and per year when the soil temperature at a depth of 50 cm o 1 below the soil surface is higher than 5 C; or b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is c. A hyperthermic, isomesic, or warmer iso soil equal to 30 or more. temperature regime and a moisture control section that in Vitrandic Argiustolls normal years: (1) Is moist in some or all parts for fewer than 90 IGEM. Other Argiustolls that have, in one or more horizons consecutive days per year when the soil temperature at within 100 cm of the mineral soil surface, redox depletions with a depth of 50 cm below the soil surface is higher than chroma of 2 or less and also aquic conditions for some time in 8 oC; and normal years (or artificial drainage). Aquic Argiustolls (2) Is dry in some part for six-tenths or more of the cumulative days per year when the soil temperature at IGEN. Other Argiustolls that in normal years are saturated a depth of 50 cm below the soil surface is higher than with water in one or more layers within 100 cm of the mineral 5 oC. soil surface for either or both: Calcidic Argiustolls 1. 20 or more consecutive days; or IGER. Other Argiustolls that, when neither irrigated nor 2. 30 or more cumulative days. fallowed to store moisture, have one of the following: Oxyaquic Argiustolls 1. A frigid soil temperature regime and a moisture control section that in normal years is dry in all parts for four- IGEO. Other Argiustolls that have a mollic epipedon that has a tenths or more of the cumulative days per year when the soil texture class finer than loamy fine sand and that is either: temperature at a depth of 50 cm below the soil surface is 1. 40 cm or more thick in a frigid soil temperature regime; higher than 5 oC; or or 2. A mesic or thermic soil temperature regime and a 2. 50 cm or more thick. moisture control section that in normal years is dry in some Pachic Argiustolls or all parts for six-tenths or more of the cumulative days per Mollisols 219

year when the soil temperature at a depth of 50 cm below the IGCD. Other Calciustolls that have both: soil surface is higher than 5 oC; or 1. One or both of the following: 3. A hyperthermic, isomesic, or warmer iso soil a. Cracks within 125 cm of the mineral soil surface that temperature regime and a moisture control section that in are 5 mm or more wide through a thickness of 30 cm or normal years: more for some time in normal years and slickensides or a. Is moist in some or all parts for fewer than 90 wedge-shaped peds in a layer 15 cm or more thick that consecutive days per year when the soil temperature at a has its upper boundary within 125 cm of the mineral soil depth of 50 cm below the soil surface is higher than 8 oC; surface; or and b. A linear extensibility of 6.0 cm or more between b. Is dry in some or all parts for six-tenths or more of the mineral soil surface and either a depth of 100 cm the cumulative days per year when the soil temperature or a densic, lithic, or paralithic contact, whichever is at a depth of 50 cm below the soil surface is higher than shallower; and 5 oC. 2. When neither irrigated nor fallowed to store moisture, Aridic Argiustolls one of the following: IGES. Other Argiustolls that, when neither irrigated nor a. A frigid soil temperature regime and a moisture fallowed to store moisture, have either: control section that in normal years is dry in all parts for four-tenths or more of the cumulative days per year when 1. A mesic or thermic soil temperature regime and a the soil temperature at a depth of 50 cm below the soil moisture control section that in normal years is dry in some surface is higher than 5 oC; or part for four-tenths or less of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil b. A mesic or thermic soil temperature regime and a surface is higher than 5 oC; or moisture control section that in normal years is dry in some or all parts for six-tenths or more of the cumulative 2. A hyperthermic, isomesic, or warmer iso soil days per year when the soil temperature at a depth of 50 temperature regime and a moisture control section that in cm below the soil surface is higher than 5 oC; or normal years is dry in some or all parts for fewer than 120 cumulative days per year when the soil temperature at a c. A hyperthermic, isomesic, or warmer iso soil depth of 50 cm below the soil surface is higher than 8 oC. temperature regime and a moisture control section that in Udic Argiustolls normal years: (1) Is moist in some or all parts for fewer than 90 IGET. Other Argiustolls that have a horizon, 15 cm or more consecutive days per year when the soil temperature at thick within 100 cm of the mineral soil surface, that either is a depth of 50 cm below the soil surface is higher than M brittle and has some opal coats or has 20 percent or more (by O 8 oC; and L volume) durinodes. Duric Argiustolls (2) Is dry in some or all parts for six-tenths or more of the cumulative days per year when the soil IGEU. Other Argiustolls. temperature at a depth of 50 cm below the soil surface Typic Argiustolls is higher than 5 oC. Torrertic Calciustolls Calciustolls IGCE. Other Calciustolls that have both: Key to Subgroups 1. One or both of the following: IGCA. Calciustolls that have a salic horizon within 75 cm of the mineral soil surface. a. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or Salidic Calciustolls more for some time in normal years and slickensides or IGCB. Other Calciustolls that have a petrocalcic horizon and a wedge-shaped peds in a layer 15 cm or more thick that lithic contact within 50 cm of the mineral soil surface. has its upper boundary within 125 cm of the mineral soil surface; Lithic Petrocalcic Calciustolls or b. A linear extensibility of 6.0 cm or more between IGCC. Other Calciustolls that have a lithic contact within 50 the mineral soil surface and either a depth of 100 cm cm of the mineral soil surface. or a densic, lithic, or paralithic contact, whichever is Lithic Calciustolls shallower; and 220 Keys to Soil Taxonomy

2. When neither irrigated nor fallowed to store moisture, 1. 40 cm or more thick in a frigid soil temperature regime; either: or a. A mesic or thermic soil temperature regime and a 2. 50 cm or more thick. moisture control section that in normal years is dry in Pachic Calciustolls some part for four-tenths or less of the cumulative days per year when the soil temperature at a depth of 50 cm IGCL. Other Calciustolls that, when neither irrigated nor below the soil surface is higher than 5 oC; or fallowed to store moisture, have one of the following: b. A hyperthermic, isomesic, or warmer iso soil 1. A frigid soil temperature regime and a moisture control temperature regime and a moisture control section that in section that in normal years is dry in all parts for four- normal years is dry in some or all parts for fewer than 120 tenths or more of the cumulative days per year when the soil cumulative days per year when the soil temperature at a temperature at a depth of 50 cm below the soil surface is depth of 50 cm below the soil surface is higher than 8 oC. higher than 5 oC; or Udertic Calciustolls 2. A mesic or thermic soil temperature regime and a IGCF. Other Calciustolls that have one or both of the moisture control section that in normal years is dry in some following: or all parts for six-tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm below the 1. Cracks within 125 cm of the mineral soil surface that are soil surface is higher than 5 oC; or 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge- 3. A hyperthermic, isomesic, or warmer iso soil shaped peds in a layer 15 cm or more thick that has its upper temperature regime and a moisture control section that in boundary within 125 cm of the mineral soil surface; or normal years: 2. A linear extensibility of 6.0 cm or more between the a. Is moist in some or all parts for fewer than 90 mineral soil surface and either a depth of 100 cm or a densic, consecutive days per year when the soil temperature at a lithic, or paralithic contact, whichever is shallower. depth of 50 cm below the soil surface is higher than 8 oC; Vertic Calciustolls and b. Is dry in some or all parts for six-tenths or more of IGCG. Other Calciustolls that have a petrocalcic horizon the cumulative days per year when the soil temperature at within 100 cm of the mineral soil surface. a depth of 50 cm below the soil surface is higher than Petrocalcic Calciustolls 5 oC. Aridic Calciustolls IGCH. Other Calciustolls that have a gypsic horizon within 100 cm of the mineral soil surface. IGCM. Other Calciustolls that, when neither irrigated nor Gypsic Calciustolls fallowed to store moisture, have either: IGCI. Other Calciustolls that have, in one or more horizons 1. A mesic or thermic soil temperature regime and a within 75 cm of the mineral soil surface, redox concentrations moisture control section that in normal years is dry in some and also aquic conditions for some time in normal years (or or all parts for four-tenths or less of the consecutive days per artificial drainage). year when the soil temperature at a depth of 50 cm below the Aquic Calciustolls soil surface is higher than 5 oC; or 2. A hyperthermic, isomesic, or warmer iso soil IGCJ. Other Calciustolls that in normal years are saturated temperature regime and a moisture control section that in with water in one or more layers within 100 cm of the mineral normal years is dry in some or all parts for fewer than 120 soil surface for either or both: cumulative days per year when the soil temperature at a 1. 20 or more consecutive days; or depth of 50 cm below the soil surface is higher than 8 oC. Udic Calciustolls 2. 30 or more cumulative days. Oxyaquic Calciustolls IGCN. Other Calciustolls. IGCK. Other Calciustolls that have a mollic epipedon that has Typic Calciustolls a texture class finer than loamy fine sand and that is either: Mollisols 221

Durustolls c. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that, in Key to Subgroups normal years: IGAA. Durustolls that have a natric horizon above the (1) Is moist in some or all parts for fewer than 90 duripan. consecutive days per year when the soil temperature at Natric Durustolls a depth of 50 cm below the soil surface is higher than 8 oC; and IGAB. Other Durustolls that: (2) Is dry in some part for six-tenths or more of the 1. Do not have an argillic horizon above the duripan; and cumulative days per year when the soil temperature at 2. Have an aridic soil moisture regime that borders on ustic. a depth of 50 cm below the soil surface is higher than o Haploduridic Durustolls 5 C; and 2. A lithic contact within 50 cm of the mineral soil surface. IGAC. Other Durustolls that have an aridic soil moisture Aridic Lithic Haplustolls regime that borders on ustic. Argiduridic Durustolls IGGD. Other Haplustolls that have a lithic contact within 50 cm of the mineral soil surface. IGAD. Other Durustolls that do not have an argillic horizon Lithic Haplustolls above the duripan. Entic Durustolls IGGE. Other Haplustolls that have both:

IGAE. Other Durustolls that have a duripan that is strongly 1. In one or more horizons within 100 cm of the mineral cemented or less cemented in all subhorizons. soil surface, redox depletions with chroma of 2 or less and Haplic Durustolls also aquic conditions for some time in normal years (or artificial drainage);and IGAF. Other Durustolls. 2. One or both of the following: Typic Durustolls a. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or Haplustolls more for some time in normal years and slickensides or Key to Subgroups wedge-shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil IGGA. Haplustolls that have a salic horizon within 75 cm of surface; or the mineral soil surface. M Salidic Haplustolls b. A linear extensibility of 6.0 cm or more between the O mineral soil surface and either a depth of 100 cm or a L IGGB. Other Haplustolls that have, in part of each pedon, a densic, lithic, or paralithic contact, whichever is shallower. lithic contact within 50 cm of the mineral soil surface. Aquertic Haplustolls Ruptic-Lithic Haplustolls IGGF. Other Haplustolls that have both: IGGC. Other Haplustolls that have both: 1. One or both of the following: 1. When neither irrigated nor fallowed to store moisture, a. Cracks within 125 cm of the mineral soil surface that one of the following: are 5 mm or more wide through a thickness of 30 cm or a. A frigid soil temperature regime and a moisture more for some time in normal years and slickensides or control section that in normal years is dry in all parts for wedge-shaped peds in a layer 15 cm or more thick that four-tenths or more of the cumulative days per year when has its upper boundary within 125 cm of the mineral soil the soil temperature at a depth of 50 cm below the soil surface; or surface is higher than 5 oC; or b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm b. A mesic or thermic soil temperature regime and a or a densic, lithic, or paralithic contact, whichever is moisture control section that, in 6 normal years, is dry in shallower; some part for six-tenths or more of the cumulative days and per year when the soil temperature at a depth of 50 cm 2. When neither irrigated nor fallowed to store moisture, below the soil surface is higher than 5 oC; or one of the following: 222 Keys to Soil Taxonomy

temperature regime and a moisture control section that in a. A frigid soil temperature regime and a moisture normal years is dry in some or all parts for fewer than 120 control section that in normal years is dry in all parts for cumulative days per year when the soil temperature at a four-tenths or more of the cumulative days per year when depth of 50 cm below the soil surface is higher than 8 oC. the soil temperature at a depth of 50 cm below the soil Pachic Udertic Haplustolls surface is higher than 5 oC; or b. A mesic or thermic soil temperature regime and a IGGH. Other Haplustolls that have both: moisture control section that in normal years is dry in 1. One or both of the following: some or all parts for six-tenths or more of the cumulative days per year when the soil temperature at a depth of 50 a. Cracks within 125 cm of the mineral soil surface that cm below the soil surface is higher than 5 oC; or are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or c. A hyperthermic, isomesic, or warmer iso soil wedge-shaped peds in a layer 15 cm or more thick that temperature regime and a moisture control section that in has its upper boundary within 125 cm of the mineral soil normal years: surface; or (1) Is moist in some or all parts for fewer than 90 b. A linear extensibility of 6.0 cm or more between consecutive days per year when the soil temperature at the mineral soil surface and either a depth of 100 cm a depth of 50 cm below the soil surface is higher than or a densic, lithic, or paralithic contact, whichever is 8 oC; and shallower; and (2) Is dry in some or all parts for six-tenths or 2. When neither irrigated nor fallowed to store moisture, more of the cumulative days per year when the soil either: temperature at a depth of 50 cm below the soil surface is higher than 5 oC. a. A mesic or thermic soil temperature regime and a Torrertic Haplustolls moisture control section that in normal years is dry in some part for four-tenths or less of the cumulative days IGGG. Other Haplustolls that have all of the following: per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or 1. A mollic epipedon that has a texture class finer than loamy fine sand and that is either: b. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in a. 40 cm or more thick in a frigid soil temperature normal years is dry in some or all parts for fewer than 120 regime; or cumulative days per year when the soil temperature at a b. 50 cm or more thick; and depth of 50 cm below the soil surface is higher than 8 oC. Udertic Haplustolls 2. One or both of the following: a. Cracks within 125 cm of the mineral soil surface that IGGI. Other Haplustolls that have both: are 5 mm or more wide through a thickness of 30 cm or 1. A mollic epipedon that has a texture class finer than more for some time in normal years and slickensides or loamy fine sand and that is either: wedge-shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil a. 40 cm or more thick in a frigid soil temperature surface; or regime; or b. A linear extensibility of 6.0 cm or more between b. 50 cm or more thick; and the mineral soil surface and either a depth of 100 cm 2. One or both of the following: or a densic, lithic, or paralithic contact, whichever is shallower; and a. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or 3. When neither irrigated nor fallowed to store moisture, more for some time in normal years and slickensides or either: wedge-shaped peds in a layer 15 cm or more thick that a. A mesic or thermic soil temperature regime and a has its upper boundary within 125 cm of the mineral soil moisture control section that in normal years is dry in surface; or some part for four-tenths or less of the cumulative days b. A linear extensibility of 6.0 cm or more between the per year when the soil temperature at a depth of 50 cm mineral soil surface and either a depth of 100 cm or a below the soil surface is higher than 5 oC; or densic, lithic, or paralithic contact, whichever is shallower. b. A hyperthermic, isomesic, or warmer iso soil Pachic Vertic Haplustolls Mollisols 223

IGGJ. Other Haplustolls that have one or both of the more, then the percentage of clay is considered to equal either following: the measured percentage of clay or three times [percent water retained at 1500 kPa tension minus percent organic carbon], 1. Cracks within 125 cm of the mineral soil surface that are whichever value is higher, but no more than 100.) 5 mm or more wide through a thickness of 30 cm or more Oxic Haplustolls for some time in normal years and slickensides or wedge- shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil surface; or IGGM. Other Haplustolls that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm 2. A linear extensibility of 6.0 cm or more between the of the mineral soil surface, a fine-earth fraction with both a bulk mineral soil surface and either a depth of 100 cm or a densic, density of 1.0 g/cm3 or less, measured at 33 kPa water retention, lithic, or paralithic contact, whichever is shallower. 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling Vertic Haplustolls more than 1.0. Andic Haplustolls IGGK. Other Haplustolls that have both: 1. When neither irrigated nor fallowed to store moisture, IGGN. Other Haplustolls that have both: one of the following: 1. When neither irrigated nor fallowed to store moisture, a. A frigid soil temperature regime and a moisture one of the following: control section that in normal years is dry in all parts for a. A frigid soil temperature regime and a moisture four-tenths or more of the cumulative days per year when control section that in normal years is dry in all parts for the soil temperature at a depth of 50 cm below the soil four-tenths or more of the cumulative days per year when surface is higher than 5 oC; or the soil temperature at a depth of 50 cm below the soil b. A mesic or thermic soil temperature regime and a surface is higher than 5 oC; or moisture control section that in normal years is dry in b. A mesic or thermic soil temperature regime and a some part for six-tenths or more of the cumulative days moisture control section that in normal years is dry in per year when the soil temperature at a depth of 50 cm some part for six-tenths or more of the cumulative days below the soil surface is higher than 5 oC; or per year when the soil temperature at a depth of 50 cm c. A hyperthermic, isomesic, or warmer iso soil below the soil surface is higher than 5 oC; or temperature regime and a moisture control section that c. A hyperthermic, isomesic, or warmer iso soil in normal years remains moist in some or all parts for temperature regime and a moisture control section that in fewer than 90 consecutive days per year when the soil normal years: temperature at a depth of 50 cm below the soil surface is o M higher than 8 C; and (1) Is moist in some or all parts for fewer than 90 O consecutive days per year when the soil temperature at L 2. An apparent CEC (by 1N NH OAc pH 7) of less than 4 a depth of 50 cm below the soil surface is higher than 24 cmol(+)/kg clay in 50 percent or more of the soil volume 8 oC; and between a depth of 25 cm from the mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic (2) Is dry in some or all parts for six-tenths or contact, whichever is shallower. (If the ratio of [percent water more of the cumulative days per year when the soil retained at 1500 kPa tension minus percent organic carbon] temperature at a depth of 50 cm below the soil surface to the percentage of measured clay is 0.6 or more, then the is higher than 5 oC; and percentage of clay is considered to equal either the measured 2. Throughout one or more horizons with a total thickness percentage of clay or three times [percent water retained at of 18 cm or more within 75 cm of the mineral soil surface, 1500 kPa tension minus percent organic carbon], whichever one or both of the following: value is higher, but no more than 100.) Torroxic Haplustolls a. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, IGGL. Other Haplustolls that have an apparent CEC (by 1N pumice, and pumicelike fragments; or NH OAc pH 7) of less than 24 cmol(+)/kg clay in 50 percent 4 b. A fine-earth fraction containing 30 percent or more or more of the soil volume between a depth of 25 cm from the particles 0.02 to 2.0 mm in diameter; and mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. (If the ratio (1) In the 0.02 to 2.0 mm fraction, 5 percent or more of [percent water retained at 1500 kPa tension minus percent volcanic glass; and organic carbon] to the percentage of measured clay is 0.6 or 224 Keys to Soil Taxonomy

1 (2) [(Al plus /2 Fe, percent extracted by ammonium a. A frigid soil temperature regime and a mollic oxalate) times 60] plus the volcanic glass (percent) is epipedon that is 40 cm or more thick, of which less than equal to 30 or more. 50 percent meets sandy or sandy-skeletal particle-size Vitritorrandic Haplustolls class criteria, and there is no densic or paralithic contact and no sandy or sandy-skeletal particle-size class at IGGO. Other Haplustolls that have, throughout one or more a depth between 40 and 50 cm from the mineral soil horizons with a total thickness of 18 cm or more within 75 cm surface; or of the mineral soil surface, one or both of the following: b. A mollic epipedon that is 50 cm or more thick and has 1. More than 35 percent (by volume) fragments coarser a texture class finer than loamy fine sand;and than 2.0 mm, of which more than 66 percent is cinders, 2. One or both of the following: pumice, and pumicelike fragments; or a. An organic-carbon content (Holocene age) of 0.3 2. A fine-earth fraction containing 30 percent or more percent or more at a depth of 125 cm below the mineral particles 0.02 to 2.0 mm in diameter; and soil surface; or a. In the 0.02 to 2.0 mm fraction, 5 percent or more b. An irregular decrease in organic-carbon content volcanic glass; and (Holocene age) between a depth of 25 cm and either 1 b. [(Al plus /2 Fe, percent extracted by ammonium a depth of 125 cm below the mineral soil surface or oxalate) times 60] plus the volcanic glass (percent) is a densic, lithic, or paralithic contact, whichever is equal to 30 or more. shallower; and Vitrandic Haplustolls 3. A slope of less than 25 percent. Cumulic Haplustolls IGGP. Other Haplustolls that have: 1. Either: IGGR. Other Haplustolls that have anthraquic conditions. a. A frigid soil temperature regime and a mollic Anthraquic Haplustolls epipedon that is 40 cm or more thick, of which less than 50 percent meets sandy or sandy-skeletal particle-size IGGS. Other Haplustolls that have both: class criteria, and there is no densic or paralithic contact 1. In one or more horizons within 100 cm of the mineral and no sandy or sandy-skeletal particle-size class at soil surface, redox depletions with chroma of 2 or less and a depth between 40 and 50 cm from the mineral soil also aquic conditions for some time in normal years (or surface; or artificial drainage);and b. A mollic epipedon that is 50 cm or more thick and has 2. A slope of less than 25 percent and one or both of the a texture class finer than loamy fine sand;and following: 2. One or both of the following: a. An organic-carbon content (Holocene age) of 0.3 a. An organic-carbon content (Holocene age) of 0.3 percent or more at a depth of 125 cm below the mineral percent or more at a depth of 125 cm below the mineral soil surface; or soil surface; or b. An irregular decrease in organic-carbon content b. An irregular decrease in organic-carbon content (Holocene age) between a depth of 25 cm and either (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a a depth of 125 cm below the mineral soil surface or densic, lithic, or paralithic contact, whichever is shallower. a densic, lithic, or paralithic contact, whichever is Fluvaquentic Haplustolls shallower; and IGGT. Other Haplustolls that have, in one or more horizons 3. A slope of less than 25 percent; and within 100 cm of the mineral soil surface, redox depletions with 4. In one or more horizons within 100 cm of the mineral chroma of 2 or less and also aquic conditions for some time in soil surface, redox depletions with chroma of 2 or less and most years (or artificial drainage). also aquic conditions for some time in normal years (or Aquic Haplustolls artificial drainage). Aquic Cumulic Haplustolls IGGU. Other Haplustolls that have a mollic epipedon that has a texture class finer than loamy fine sand and that is either: IGGQ. Other Haplustolls that have: 1. 40 cm or more thick in a frigid soil temperature regime; 1. Either: or Mollisols 225

2. 50 cm or more thick. a. A frigid soil temperature regime and a moisture Pachic Haplustolls control section that in normal years is dry in all parts for four-tenths or more of the cumulative days per year when IGGV. Other Haplustolls that in normal years are saturated the soil temperature at a depth of 50 cm below the soil with water in one or more layers within 100 cm of the mineral surface is higher than 5 oC; or soil surface for either or both: b. A mesic or thermic soil temperature regime and a 1. 20 or more consecutive days; or moisture control section that in normal years is dry in some part for six-tenths or more of the cumulative days 2. 30 or more cumulative days. per year when the soil temperature at a depth of 50 cm Oxyaquic Haplustolls below the soil surface is higher than 5 oC; or IGGW. Other Haplustolls that have both: c. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in 1. When neither irrigated nor fallowed to store moisture, normal years: one of the following: (1) Is moist in some or all parts for fewer than 90 a. A frigid soil temperature regime and a moisture consecutive days per year when the soil temperature at control section that in normal years is dry in all parts for a depth of 50 cm below the soil surface is higher than four-tenths or more of the cumulative days per year when 8 oC; and the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or (2) Is dry in some or all parts for six-tenths or more of the cumulative days per year when the soil b. A mesic or thermic soil temperature regime and a temperature at a depth of 50 cm below the soil surface moisture control section that in normal years is dry in is higher than 5 oC; and some part for six-tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm 2. Either: below the soil surface is higher than 5 oC; or a. Do not have a cambic horizon and do not, in any part of the mollic epipedon below 25 cm from the mineral c. A hyperthermic, isomesic, or warmer iso soil soil surface, meet the requirements for a cambic horizon, temperature regime and a moisture control section that in except for the color requirements; or normal years: b. Have free carbonates throughout the cambic horizon (1) Is moist in some or all parts for fewer than 90 or in all parts of the mollic epipedon below a depth of 25 consecutive days per year when the soil temperature at cm from the mineral soil surface. a depth of 50 cm below the soil surface is higher than o Torriorthentic Haplustolls 8 C; and M O (2) Is dry in some or all parts for six-tenths or IGGY. Other Haplustolls that, when neither irrigated nor L more of the cumulative days per year when the soil fallowed to store moisture, have one of the following: temperature at a depth of 50 cm below the soil surface 1. A frigid soil temperature regime and a moisture control o is higher than 5 C; and section that in normal years is dry in all parts for four- 2. A slope of less than 25 percent and one or both of the tenths or more of the cumulative days per year when the soil following: temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or a. An organic-carbon content (Holocene age) of 0.3 percent or more at a depth of 125 cm below the mineral 2. A mesic or thermic soil temperature regime and a soil surface; or moisture control section that in normal years is dry in some part for six-tenths or more of the cumulative days per year b. An irregular decrease in organic-carbon content when the soil temperature at a depth of 50 cm below the soil (Holocene age) between a depth of 25 cm and either surface is higher than 5 oC; or a depth of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is shallower. 3. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in Torrifluventic Haplustolls normal years:

IGGX. Other Haplustolls that: a. Is moist in some or all parts for fewer than 90 consecutive days per year when the soil temperature at a 1. When neither irrigated nor fallowed to store moisture, depth of 50 cm below the soil surface is higher than 8 oC; have one of the following: and 226 Keys to Soil Taxonomy

b. Is dry in some or all parts for six-tenths or more of 2. A hyperthermic, isomesic, or warmer iso soil the cumulative days per year when the soil temperature temperature regime and a moisture control section that in at a depth of 50 cm below the soil surface is higher than normal years is dry in some or all parts for fewer than 120 5 oC. days per year when the soil temperature at a depth of 50 cm Aridic Haplustolls below the soil surface is higher than 8 oC. Udic Haplustolls IGGZ. Other Haplustolls that have a slope of less than 25 percent and one or both of the following: IGGZd. Other Haplustolls that either: 1. An organic-carbon content (Holocene age) of 0.3 percent 1. Do not have a cambic horizon and do not, in any part or more at a depth of 125 cm below the mineral soil surface; of the mollic epipedon below 25 cm from the mineral soil or surface, meet the requirements for a cambic horizon, except for the color requirements; or 2. An irregular decrease in organic-carbon content (Holocene age) between a depth of 25 cm and either a depth 2. Have free carbonates throughout the cambic horizon or of 125 cm below the mineral soil surface or a densic, lithic, in all parts of the mollic epipedon below a depth of 25 cm or paralithic contact, whichever is shallower. from the mineral soil surface. Fluventic Haplustolls Entic Haplustolls

IGGZa. Other Haplustolls that have a horizon, 15 cm or more IGGZe. Other Haplustolls. thick within 100 cm of the mineral soil surface, that either is Typic Haplustolls brittle and has some opal coats or has 20 percent or more (by volume) durinodes. Natrustolls Duric Haplustolls Key to Subgroups IGGZb. Other Haplustolls that: IGBA. Natrustolls that have all of the following: 1. When neither irrigated nor fallowed to store moisture, 1. Visible crystals of gypsum and/or more soluble salts have either: within 40 cm of the mineral soil surface; and a. A mesic or thermic soil temperature regime and a 2. One or both of the following: moisture control section that in normal years is dry in some part for four-tenths or less of the cumulative days a. Cracks within 125 cm of the mineral soil surface that per year when the soil temperature at a depth of 50 cm are 5 mm or more wide through a thickness of 30 cm or below the soil surface is higher than 5 oC; or more for some time in normal years and slickensides or wedge-shaped peds in a layer 15 cm or more thick that b. A hyperthermic, isomesic, or warmer iso soil has its upper boundary within 125 cm of the mineral soil temperature regime and a moisture control section that in surface; or normal years is dry in some or all parts for fewer than 120 days per year when the soil temperature at a depth of 50 b. A linear extensibility of 6.0 cm or more between cm below the soil surface is higher than 8 oC; and the mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is 2. Either do not have a cambic horizon and do not, in the shallower; and lower part of the mollic epipedon, meet the requirements for a cambic horizon, except for the color requirements, or have 3. When neither irrigated nor fallowed to store moisture, free carbonates throughout either the cambic horizon or the one of the following: lower part of the mollic epipedon. a. A frigid soil temperature regime and a moisture Udorthentic Haplustolls control section that in normal years is dry in all parts for four-tenths or more of the cumulative days per year when IGGZc. Other Haplustolls that, when neither irrigated nor the soil temperature at a depth of 50 cm below the soil fallowed to store moisture, have either: surface is higher than 5 oC; or 1. A mesic or thermic soil temperature regime and a b. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in some moisture control section that in normal years is dry in part for four-tenths or less of the cumulative days per year some or all parts for six-tenths or more of the cumulative when the soil temperature at a depth of 50 cm below the soil days per year when the soil temperature at a depth of 50 surface is higher than 5 oC; or cm below the soil surface is higher than 5 oC; or Mollisols 227

c. A hyperthermic, isomesic, or warmer iso soil IGBC. Other Natrustolls that have both of the following: temperature regime and a moisture control section that in 1. Visible crystals of gypsum and/or more soluble salts normal years: within 40 cm of the mineral soil surface; and (1) Is moist in some or all parts for fewer than 90 2. One or both of the following: consecutive days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than a. Cracks within 125 cm of the mineral soil surface that 8 oC; and are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or (2) Is dry in some or all parts for six-tenths or wedge-shaped peds in a layer 15 cm or more thick that more of the cumulative days per year when the soil has its upper boundary within 125 cm of the mineral soil temperature at a depth of 50 cm below the soil surface surface; or is higher than 5 oC. Leptic Torrertic Natrustolls b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a IGBB. Other Natrustolls that have both: densic, lithic, or paralithic contact, whichever is shallower. Leptic Vertic Natrustolls 1. One or both of the following: a. Cracks within 125 cm of the mineral soil surface that IGBD. Other Natrustolls that have both: are 5 mm or more wide through a thickness of 30 cm or 1. A glossic horizon or interfingering of albic materials into more for some time in normal years and slickensides or a natric horizon; and wedge-shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil 2. One or both of the following: surface; or a. Cracks within 125 cm of the mineral soil surface that b. A linear extensibility of 6.0 cm or more between are 5 mm or more wide through a thickness of 30 cm or the mineral soil surface and either a depth of 100 cm more for some time in normal years and slickensides or or a densic, lithic, or paralithic contact, whichever is wedge-shaped peds in a layer 15 cm or more thick that shallower; and has its upper boundary within 125 cm of the mineral soil surface; or 2. When neither irrigated nor fallowed to store moisture, one of the following: b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a a. A frigid soil temperature regime and a moisture densic, lithic, or paralithic contact, whichever is shallower. control section that in normal years is dry in all parts for Glossic Vertic Natrustolls four-tenths or more of the cumulative days per year when M the soil temperature at a depth of 50 cm below the soil O IGBE. Other Natrustolls that have one or both of the L surface is higher than 5 oC; or following: b. A mesic or thermic soil temperature regime and a 1. Cracks within 125 cm of the mineral soil surface that are moisture control section that in normal years is dry in 5 mm or more wide through a thickness of 30 cm or more some or all parts for six-tenths or more of the cumulative for some time in normal years and slickensides or wedge- days per year when the soil temperature at a depth of 50 shaped peds in a layer 15 cm or more thick that has its upper cm below the soil surface is higher than 5 oC; or boundary within 125 cm of the mineral soil surface; or c. A hyperthermic, isomesic, or warmer iso soil 2. A linear extensibility of 6.0 cm or more between the temperature regime and a moisture control section that in mineral soil surface and either a depth of 100 cm or a densic, normal years: lithic, or paralithic contact, whichever is shallower. (1) Is moist in some or all parts for fewer than 90 Vertic Natrustolls consecutive days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than IGBF. Other Natrustolls that have both: 8 oC; and 1. Visible crystals of gypsum or of more soluble salts, or (2) Is dry in some or all parts for six-tenths or both, within 40 cm of the mineral soil surface; and more of the cumulative days per year when the soil 2. When neither irrigated nor fallowed to store moisture, temperature at a depth of 50 cm below the soil surface one of the following: is higher than 5 oC. Torrertic Natrustolls a. A frigid soil temperature regime and a moisture 228 Keys to Soil Taxonomy

control section that in normal years is dry in all parts for part for six-tenths or more of the cumulative days per year four-tenths or more of the cumulative days per year when when the soil temperature at a depth of 50 cm below the soil the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or surface is higher than 5 oC; or 3. A hyperthermic, isomesic, or warmer iso soil b. A mesic or thermic soil temperature regime and a temperature regime and a moisture control section that in moisture control section that in normal years is dry in normal years: some or all parts for six-tenths or more of the cumulative a. Is moist in some or all parts for fewer than 90 days per year when the soil temperature at a depth of 50 consecutive days per year when the soil temperature at a o cm below the soil surface is higher than 5 C; or depth of 50 cm below the soil surface is higher than 8 oC; c. A hyperthermic, isomesic, or warmer iso soil and temperature regime and a moisture control section that in b. Is dry in some or all parts for six-tenths or more of normal years: the cumulative days per year when the soil temperature (1) Is moist in some or all parts for fewer than 90 at a depth of 50 cm below the soil surface is higher than o consecutive days per year when the soil temperature at 5 C. a depth of 50 cm below the soil surface is higher than Aridic Natrustolls 8 oC; and IGBJ. Other Natrustolls that have a horizon, 15 cm or more (2) Is dry in some or all parts for six-tenths or thick within 100 cm of the mineral soil surface, that either has more of the cumulative days per year when the soil 20 percent or more (by volume) durinodes or is brittle and has at temperature at a depth of 50 cm below the soil surface least a firm rupture-resistance class when moist. o is higher than 5 C. Duric Natrustolls Aridic Leptic Natrustolls IGBK. Other Natrustolls that have a glossic horizon or IGBG. Other Natrustolls that have visible crystals of gypsum interfingering of albic materials into a natric horizon. and/or more soluble salts within 40 cm of the mineral soil Glossic Natrustolls surface. Leptic Natrustolls IGBL. Other Natrustolls. Typic Natrustolls IGBH. Other Natrustolls that have, in one or more horizons at a depth between 50 and 100 cm from the mineral soil surface, Paleustolls aquic conditions for some time in normal years (or artificial drainage) and one of the following: Key to Subgroups 1. 50 percent or more chroma of 1 or less and hue of 2.5Y IGDA. Paleustolls that have both: or yellower; or 1. One or both of the following: 2. 50 percent or more chroma of 2 or less and redox a. Cracks within 125 cm of the mineral soil surface that concentrations; or are 5 mm or more wide through a thickness of 30 cm or 3. 50 percent or more chroma of 2 or less and also a higher more for some time in normal years and slickensides or exchangeable sodium percentage (or sodium adsorption wedge-shaped peds in a layer 15 cm or more thick that ratio) between the mineral soil surface and a depth of 25 cm has its upper boundary within 125 cm of the mineral soil than in the underlying horizon. surface; or Aquic Natrustolls b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm IGBI. Other Natrustolls that, when neither irrigated nor or a densic, lithic, or paralithic contact, whichever is fallowed to store moisture, have one of the following: shallower; and 1. A frigid soil temperature regime and a moisture control 2. When neither irrigated nor fallowed to store moisture, section that in normal years is dry in all parts for four- one of the following: tenths or more of the cumulative days per year when the soil a. A frigid soil temperature regime and a moisture temperature at a depth of 50 cm below the soil surface is control section that in normal years is dry in all parts for higher than 5 oC; or less than four-tenths of the cumulative days per year when 2. A mesic or thermic soil temperature regime and a the soil temperature at a depth of 50 cm below the soil moisture control section that in normal years is dry in some surface is higher than 5 oC; or Mollisols 229

b. A mesic or thermic soil temperature regime and a wedge-shaped peds in a layer 15 cm or more thick that moisture control section that in normal years is dry in has its upper boundary within 125 cm of the mineral soil some or all parts for six-tenths or more of the cumulative surface; or days per year when the soil temperature at a depth of 50 2. A linear extensibility of 6.0 cm or more between the cm below the soil surface is higher than 5 oC; or mineral soil surface and either a depth of 100 cm or a c. A hyperthermic, isomesic, or warmer iso soil densic, lithic, or paralithic contact, whichever is shallower. temperature regime and a moisture control section that in Vertic Paleustolls normal years: IGDD. Other Paleustolls that have, in one or more horizons (1) Is moist in some or all parts for fewer than 90 within 100 cm of the mineral soil surface, redox depletions with consecutive days per year when the soil temperature at chroma of 2 or less and also aquic conditions for some time in a depth of 50 cm below the soil surface is higher than normal years (or artificial drainage). 8 oC; and Aquic Paleustolls (2) Is dry in some or all parts for six-tenths or more of the cumulative days per year when the soil IGDE. Other Paleustolls that have a mollic epipedon that has temperature at a depth of 50 cm below the soil surface a texture class finer than loamy fine sand and that is 50 cm or is higher than 5 oC. more thick. Torrertic Paleustolls Pachic Paleustolls

IGDB. Other Paleustolls that have both: IGDF. Other Paleustolls that have a petrocalcic horizon within 150 cm of the mineral soil surface. 1. One or both of the following: Petrocalcic Paleustolls a. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or IGDG. Other Paleustolls that: more for some time in normal years and slickensides or 1. Have a calcic horizon within one of the following wedge-shaped peds in a layer 15 cm or more thick that particle-size class (by weighted average in the particle-size has its upper boundary within 125 cm of the mineral soil control section) and depth combinations: surface; or a. Sandy or sandy-skeletal and within 100 cm of the b. A linear extensibility of 6.0 cm or more between mineral soil surface; or the mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is b. Clayey, clayey-skeletal, fine, or very-fine and within shallower; and 50 cm of the mineral soil surface; or M 2. When neither irrigated nor fallowed to store moisture, c. Any other class and within 60 cm of the mineral soil O L either: surface; and a. A mesic or thermic soil temperature regime and a 2. When neither irrigated nor fallowed to store moisture, moisture control section that in normal years is dry in have one of the following: some part for four-tenths or less of the cumulative days a. A frigid soil temperature regime and a moisture per year when the soil temperature at a depth of 50 cm control section that in normal years is dry in all parts for below the soil surface is higher than 5 oC; or less than four-tenths of the cumulative days per year when b. A hyperthermic, isomesic, or warmer iso soil the soil temperature at a depth of 50 cm below the soil temperature regime and a moisture control section that in surface is higher than 5 oC; or normal years is dry in some or all parts for fewer than 120 b. A mesic or thermic soil temperature regime and a cumulative days per year when the soil temperature at a moisture control section that in normal years is dry in depth of 50 cm below the soil surface is higher than 8 oC. some part for six-tenths or more of the cumulative days Udertic Paleustolls per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or IGDC. Other Paleustolls that have one or both of the following: c. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in 1. Cracks within 125 cm of the mineral soil surface that normal years: are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or (1) Is moist in some or all parts for fewer than 90 230 Keys to Soil Taxonomy

consecutive days per year when the soil temperature at 1. Sandy or sandy-skeletal and within 100 cm of the a depth of 50 cm below the soil surface is higher than mineral soil surface; or 8 oC; and 2. Clayey, clayey-skeletal, fine, or very-fine and within 50 (2) Is dry in some or all parts for six-tenths or cm of the mineral soil surface; or more of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface 3. Any other class and within 60 cm of the mineral soil is higher than 5 oC. surface. Calcidic Paleustolls Calcic Paleustolls

IGDH. Other Paleustolls that, when neither irrigated nor IGDK. Other Paleustolls that have free carbonates throughout fallowed to store moisture, have one of the following: after the surface horizons have been mixed to a depth of 18 cm. Entic Paleustolls 1. A frigid soil temperature regime and a moisture control section that in normal years is dry in all parts for less than IGDL. Other Paleustolls. four-tenths of the cumulative days per year when the soil Typic Paleustolls temperature at a depth of 50 cm below the soil surface is o higher than 5 C; or Vermustolls 2. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in some Key to Subgroups part for six-tenths or more of the cumulative days per year IGFA. Vermustolls that have a lithic contact within 50 cm of when the soil temperature at a depth of 50 cm below the soil the mineral soil surface. surface is higher than 5 oC; or Lithic Vermustolls 3. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in IGFB. Other Vermustolls that have, in one or more horizons normal years: within 100 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in a. Is moist in some or all parts for fewer than 90 normal years (or artificial drainage). consecutive days per year when the soil temperature at a Aquic Vermustolls depth of 50 cm below the soil surface is higher than 8 oC; and IGFC. Other Vermustolls that have a mollic epipedon that is b. Is dry in some or all parts for six-tenths or more of 75 cm or more thick. the cumulative days per year when the soil temperature Pachic Vermustolls at a depth of 50 cm below the soil surface is higher than 5 oC. IGFD. Other Vermustolls that have a mollic epipedon that is Aridic Paleustolls less than 50 cm thick. Entic Vermustolls IGDI. Other Paleustolls that, when neither irrigated nor fallowed to store moisture, have either: IGFE. Other Vermustolls. Typic Vermustolls 1. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in some part for four-tenths or less of the cumulative days per year Xerolls when the soil temperature at a depth of 50 cm below the soil Key to Great Groups surface is higher than 5 oC; or IFA. Xerolls that have a duripan within 100 cm of the mineral 2. A hyperthermic, isomesic, or warmer iso soil soil surface. temperature regime and a moisture control section that in Durixerolls, p. 234 normal years is dry in some or all parts for fewer than 120 cumulative days per year when the soil temperature at a IFB. Other Xerolls that have a natric horizon. depth of 50 cm below the soil surface is higher than 8 oC. Natrixerolls, p. 239 Udic Paleustolls IFC. Other Xerolls that have either: IGDJ. Other Paleustolls have a calcic horizon within one of the following particle-size class (by weighted average in the 1. A petrocalcic horizon within 150 cm of the mineral soil particle-size control section) and depth combinations: surface; or Mollisols 231

2. An argillic horizon that has one or both of the following: IFEC. Other Argixerolls that have a lithic contact within 50 cm of the mineral soil surface. a. With increasing depth, no clay decrease of 20 percent Lithic Argixerolls or more (relative) from the maximum clay content (noncarbonate clay) within 150 cm of the mineral soil surface (and there is no densic, lithic, or paralithic contact IFED. Other Argixerolls that have both: within that depth); and either 1. An aridic soil moisture regime; and (1) Hue of 7.5YR or redder and chroma of 5 or more 2. One or both of the following: in the matrix; or a. Cracks within 125 cm of the mineral soil surface that (2) Common redox concentrations with hue of 7.5YR are 5 mm or more wide through a thickness of 30 cm or or redder or chroma of 6 or more, or both; or more for some time in normal years and slickensides or b. 35 percent or more noncarbonate clay in its upper wedge-shaped peds in a layer 15 cm or more thick that part and, at its upper boundary, a clay increase either of has its upper boundary within 125 cm of the mineral soil 20 percent or more (absolute) within a vertical distance surface; or of 7.5 cm or of 15 percent or more (absolute) within a b. A linear extensibility of 6.0 cm or more between the vertical distance of 2.5 cm, in the fine-earth fraction (and mineral soil surface and either a depth of 100 cm or a there is no densic, lithic, or paralithic contact within 50 densic, lithic, or paralithic contact, whichever is shallower. cm of the mineral soil surface). Torrertic Argixerolls Palexerolls, p. 239 IFEE. Other Argixerolls that have of the IFD. Other Xerolls that have both: one or both following: 1. A calcic or gypsic horizon within 150 cm of the mineral soil surface; and 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or more 2. In all parts above the calcic or gypsic horizon, after the for some time in normal years and slickensides or wedge- surface soil has been mixed to a depth of 18 cm, either free shaped peds in a layer 15 cm or more thick that has its upper carbonates or a texture class of loamy fine sand or coarser. boundary within 125 cm of the mineral soil surface; or Calcixerolls, p. 233 2. A linear extensibility of 6.0 cm or more between the IFE. Other Xerolls that have an argillic horizon. mineral soil surface and either a depth of 100 cm or a densic, Argixerolls, p. 231 lithic, or paralithic contact, whichever is shallower. Vertic Argixerolls M IFF. Other Xerolls. O Haploxerolls, p. 235 IFEF. Other Argixerolls that have, throughout one or more L horizons with a total thickness of 18 cm or more within 75 cm Argixerolls of the mineral soil surface, a fine-earth fraction with both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 Key to Subgroups and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. IFEA. Argixerolls that have both: Andic Argixerolls 1. An aridic soil moisture regime; and 2. A lithic contact within 50 cm of the mineral soil surface. IFEG. Other Argixerolls that have both: Aridic Lithic Argixerolls 1. An aridic soil moisture regime; and

IFEB. Other Argixerolls that have both: 2. Throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, 1. A lithic contact within 50 cm of the mineral soil surface; one or both of the following: and a. More than 35 percent (by volume) fragments coarser 2. A base saturation (by sum of cations) of 75 percent or than 2.0 mm, of which more than 66 percent is cinders, less in one or more horizons between either the mineral soil pumice, and pumicelike fragments; or surface or an Ap horizon, whichever is deeper, and the lithic contact. b. A fine-earth fraction containing 30 percent or more Lithic Ultic Argixerolls particles 0.02 to 2.0 mm in diameter; and 232 Keys to Soil Taxonomy

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more 1. Above the argillic horizon, an albic horizon or a horizon volcanic glass; and that has color values too high for a mollic epipedon and

1 chroma too high for an albic horizon; or (2) [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 2. A glossic horizon, or interfingering of albic materials equal to 30 or more. into the upper part of the argillic horizon, or skeletans of Vitritorrandic Argixerolls clean silt and sand covering 50 percent or more of the faces of peds in the upper 5 cm of the argillic horizon. IFEH. Other Argixerolls that have, throughout one or more Alfic Argixerolls horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: IFEM. Other Argixerolls that have both: 1. More than 35 percent (by volume) fragments coarser 1. A calcic horizon or identifiable secondary carbonates than 2.0 mm, of which more than 66 percent is cinders, within one of the following particle-size class (by weighted pumice, and pumicelike fragments; or average in the particle-size control section) and depth combinations: 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and a. Sandy or sandy-skeletal and within 150 cm of the mineral soil surface; or a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and b. Clayey, clayey-skeletal, fine, or very-fine and within 90 cm of the mineral soil surface; or 1 b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is c. Any other class and within 110 cm of the mineral soil equal to 30 or more. surface; and Vitrandic Argixerolls 2. A mollic epipedon that is 50 cm or more thick and has a texture class finer than loamy fine sand. IFEI. Other Argixerolls that have both: Calcic Pachic Argixerolls 1. In one or more horizons within 75 cm of the mineral soil IFEN. Other Argixerolls that have both: surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial 1. A mollic epipedon that is 50 cm or more thick and has a drainage); and texture class finer than loamy fine sand;and 2. A base saturation (by sum of cations) of 75 percent or 2. A base saturation (by sum of cations) of 75 percent or less in one or more horizons between either an Ap horizon less in one or more horizons between either an Ap horizon or a depth of 25 cm from the mineral soil surface, whichever or a depth of 25 cm from the mineral soil surface, whichever is deeper, and either a depth of 75 cm or a densic, lithic, or is deeper, and either a depth of 75 cm or a densic, lithic, or paralithic contact, whichever is shallower. paralithic contact, whichever is shallower. Aquultic Argixerolls Pachic Ultic Argixerolls

IFEJ. Other Argixerolls that have, in one or more horizons IFEO. Other Argixerolls that have a mollic epipedon that is 50 within 75 cm of the mineral soil surface, redox depletions with cm or more thick and has a texture class finer than loamy fine chroma of 2 or less and also aquic conditions for some time in sand. normal years (or artificial drainage). Pachic Argixerolls Aquic Argixerolls IFEP. Other Argixerolls that have both: IFEK. Other Argixerolls that in normal years are saturated 1. An aridic soil moisture regime; and with water in one or more layers within 100 cm of the mineral soil surface for either or both: 2. A horizon within 100 cm of the mineral soil surface that is 15 cm or more thick and either has 20 percent or more (by 1. 20 or more consecutive days; or volume) durinodes or is brittle and has at least a firm rupture- 2. 30 or more cumulative days. resistance class when moist. Oxyaquic Argixerolls Argiduridic Argixerolls

IFEL. Other Argixerolls that have either: IFEQ. Other Argixerolls that have a horizon within 100 cm of Mollisols 233

the mineral soil surface that is 15 cm or more thick and either 1. An aridic soil moisture regime; and has 20 percent or more (by volume) durinodes or is brittle and 2. A lithic contact within 50 cm of the mineral soil surface. has at least a firm rupture-resistance class when moist. Aridic Lithic Calcixerolls Duric Argixerolls IFDB. Other Calcixerolls that have a lithic contact within 50 IFER. Other Argixerolls that have both: cm of the mineral soil surface. 1. An aridic soil moisture regime; and Lithic Calcixerolls

2. A calcic horizon or identifiable secondary carbonates IFDC. Other Calcixerolls that have one or both of the within one of the following particle-size class (by weighted following: average in the particle-size control section) and depth combinations: 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or more a. Sandy or sandy-skeletal and within 150 cm of the for some time in normal years and slickensides or wedge- mineral soil surface; or shaped peds in a layer 15 cm or more thick that has its upper b. Clayey, clayey-skeletal, fine, or very-fine and within boundary within 125 cm of the mineral soil surface; or 90 cm of the mineral soil surface; or 2. A linear extensibility of 6.0 cm or more between the c. Any other class and within 110 cm of the mineral soil mineral soil surface and either a depth of 100 cm or a densic, surface. lithic, or paralithic contact, whichever is shallower. Calciargidic Argixerolls Vertic Calcixerolls

IFES. Other Argixerolls that have an aridic soil moisture IFDD. Other Calcixerolls that have, in one or more horizons regime. within 75 cm of the mineral soil surface, redox concentrations and also aquic conditions for some time in normal years (or Aridic Argixerolls artificial drainage). IFET. Other Argixerolls that have a calcic horizon or Aquic Calcixerolls identifiable secondary carbonates within one of the following particle-size class (by weighted average in the particle-size IFDE. Other Calcixerolls that in normal years are saturated control section) and depth combinations: with water in one or more layers within 100 cm of the mineral soil surface for either or both: 1. Sandy or sandy-skeletal and within 150 cm of the mineral soil surface; or 1. 20 or more consecutive days; or 2. 30 or more cumulative days. 2. Clayey, clayey-skeletal, fine, or very-fine and within 90 M Oxyaquic Calcixerolls O cm of the mineral soil surface; or L 3. Any other class and within 110 cm of the mineral soil IFDF. Other Calcixerolls that have a mollic epipedon that is 50 surface. cm or more thick and has a texture class finer than loamy fine Calcic Argixerolls sand. Pachic Calcixerolls IFEU. Other Argixerolls that have a base saturation (by sum of cations) of 75 percent or less in one or more horizons between IFDG. Other Calcixerolls that have, throughout one or more either an Ap horizon or a depth of 25 cm from the mineral soil horizons with a total thickness of 18 cm or more within 75 cm surface, whichever is deeper, and either a depth of 75 cm or a of the mineral soil surface, one or both of the following: densic, lithic, or paralithic contact, whichever is shallower. Ultic Argixerolls 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, IFEV. Other Argixerolls. pumice, and pumicelike fragments; or Typic Argixerolls 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 Calcixerolls more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass Key to Subgroups (percent) is equal to 30 or more. IFDA. Calcixerolls that have both: Vitrandic Calcixerolls 234 Keys to Soil Taxonomy

IFDH. Other Calcixerolls that have an aridic soil moisture 2. A fine-earth fraction containing 30 percent or more regime. particles 0.02 to 2.0 mm in diameter; and Aridic Calcixerolls a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and IFDI. Other Calcixerolls that have a mollic epipedon that 1 has, below any Ap horizon, 50 percent or more (by volume) b. [(Al plus /2 Fe, percent extracted by ammonium wormholes, wormcasts, or filled animal burrows. oxalate) times 60] plus the volcanic glass (percent) is Vermic Calcixerolls equal to 30 or more. Vitrandic Durixerolls IFDJ. Other Calcixerolls. Typic Calcixerolls IFAD. Other Durixerolls that have, in one or more horizons above the duripan, redox depletions with chroma of 2 or less Durixerolls and also aquic conditions for some time in normal years (or artificial drainage). Key to Subgroups Aquic Durixerolls IFAA. Durixerolls that have one or both of the following: IFAE. Other Durixerolls that have all of the following: 1. Cracks between the soil surface and the top of the duripan that are 5 mm or more wide through a thickness 1. An aridic soil moisture regime; and of 30 cm or more for some time in normal years and 2. An argillic horizon that, with increasing depth, has a slickensides or wedge-shaped peds in a layer 15 cm or more clay increase either of 20 percent or more (absolute) within thick that is above the duripan; or a vertical distance of 7.5 cm or of 15 percent or more 2. A linear extensibility of 6.0 cm or more between the soil (absolute) within a vertical distance of 2.5 cm; and surface and the top of the duripan. 3. A duripan that is neither very strongly cemented nor Vertic Durixerolls indurated in any subhorizon. Paleargidic Durixerolls IFAB. Other Durixerolls that have both: IFAF. Other Durixerolls that have : 1. An aridic soil moisture regime; and both 1. An aridic soil moisture regime; and 2. Throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, 2. An argillic horizon that, with increasing depth, has a one or both of the following: clay increase either of 20 percent or more (absolute) within a vertical distance of 7.5 cm or of 15 percent or more a. More than 35 percent (by volume) fragments coarser (absolute) within a vertical distance of 2.5 cm. than 2.0 mm, of which more than 66 percent is cinders, Abruptic Argiduridic Durixerolls pumice, and pumicelike fragments; or b. A fine-earth fraction containing 30 percent or more IFAG. Other Durixerolls that: particles 0.02 to 2.0 mm in diameter; and 1. Have an aridic soil moisture regime; and (1) In the 0.02 to 2.0 mm fraction, 5 percent or more 2. Do not have an argillic horizon above the duripan; and volcanic glass; and 3. Have a duripan that is neither very strongly cemented 1 (2) [(Al plus /2 Fe, percent extracted by ammonium nor indurated in any subhorizon. oxalate) times 60] plus the volcanic glass (percent) is Cambidic Durixerolls equal to 30 or more. Vitritorrandic Durixerolls IFAH. Other Durixerolls that:

IFAC. Other Durixerolls that have, throughout one or more 1. Have an aridic soil moisture regime; and horizons with a total thickness of 18 cm or more within 75 cm 2. Do not have an argillic horizon above the duripan. of the mineral soil surface, one or both of the following: Haploduridic Durixerolls 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, IFAI. Other Durixerolls that have both: pumice, and pumicelike fragments; or 1. An aridic soil moisture regime; and Mollisols 235

2. A duripan that is neither very strongly cemented nor 2. A base saturation (by sum of cations) of 75 percent or indurated in any subhorizon. less in one or more horizons between either the mineral soil Argidic Durixerolls surface or an Ap horizon, whichever is deeper, and the lithic contact. IFAJ. Other Durixerolls that have an aridic soil moisture Lithic Ultic Haploxerolls regime. Argiduridic Durixerolls IFFC. Other Haploxerolls that have a lithic contact within 50 cm of the mineral soil surface. IFAK. Other Durixerolls that have both: Lithic Haploxerolls 1. An argillic horizon that, with increasing depth, has a IFFD. Other Haploxerolls that have both: clay increase either of 20 percent or more (absolute) within a vertical distance of 7.5 cm or of 15 percent or more 1. An aridic soil moisture regime; and (absolute) within a vertical distance of 2.5 cm; and 2. One or both of the following: 2. A duripan that is neither very strongly cemented nor a. Cracks within 125 cm of the mineral soil surface that indurated in any subhorizon. are 5 mm or more wide through a thickness of 30 cm or Haplic Palexerollic Durixerolls more for some time in normal years and slickensides or wedge-shaped peds in a layer 15 cm or more thick that IFAL. Other Durixerolls that have an argillic horizon that, has its upper boundary within 125 cm of the mineral soil with increasing depth, has a clay increase either of 20 percent surface; or or more (absolute) within a vertical distance of 7.5 cm or of 15 percent or more (absolute) within a vertical distance of 2.5 cm. b. A linear extensibility of 6.0 cm or more between the Palexerollic Durixerolls mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. IFAM. Other Durixerolls that: Torrertic Haploxerolls 1. Have a duripan that is neither very strongly cemented IFFE. Other Haploxerolls that have one or both of the nor indurated in any subhorizon; and following: 2. Do not have an argillic horizon above the duripan. 1. Cracks within 125 cm of the mineral soil surface that are Haplic Haploxerollic Durixerolls 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge- IFAN. Other Durixerolls that do not have an argillic horizon shaped peds in a layer 15 cm or more thick that has its upper above the duripan. boundary within 125 cm of the mineral soil surface; or M Haploxerollic Durixerolls O 2. A linear extensibility of 6.0 cm or more between the L IFAO. Other Durixerolls that have a duripan that is neither mineral soil surface and either a depth of 100 cm or a densic, very strongly cemented nor indurated in any subhorizon. lithic, or paralithic contact, whichever is shallower. Haplic Durixerolls Vertic Haploxerolls

IFAP. Other Durixerolls. IFFF. Other Haploxerolls that have, throughout one or more Typic Durixerolls horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction with both a bulk Haploxerolls density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling Key to Subgroups more than 1.0. IFFA. Haploxerolls that have both: Andic Haploxerolls

1. An aridic soil moisture regime; and IFFG. Other Haploxerolls that have both: 2. A lithic contact within 50 cm of the mineral soil surface. 1. An aridic soil moisture regime; and Aridic Lithic Haploxerolls 2. Throughout one or more horizons with a total thickness IFFB. Other Haploxerolls that have both: of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: 1. A lithic contact within 50 cm of the mineral soil surface; and a. More than 35 percent (by volume) fragments coarser 236 Keys to Soil Taxonomy

than 2.0 mm, of which more than 66 percent is cinders, 2. One or both of the following: pumice, and pumicelike fragments; or a. An organic-carbon content (Holocene age) of 0.3 b. A fine-earth fraction containing 30 percent or more percent or more at a depth of 125 cm below the mineral particles 0.02 to 2.0 mm in diameter; and soil surface; or (1) In the 0.02 to 2.0 mm fraction, 5 percent or more b. An irregular decrease in organic-carbon content volcanic glass; and (Holocene age) between a depth of 25 cm and either

1 a depth of 125 cm below the mineral soil surface or (2) [(Al plus /2 Fe, percent extracted by ammonium a densic, lithic, or paralithic contact, whichever is oxalate) times 60] plus the volcanic glass (percent) is shallower; and equal to 30 or more. Vitritorrandic Haploxerolls 3. A slope of less than 25 percent; and 4. A base saturation (by sum of cations) of 75 percent or IFFH. Other Haploxerolls that have, throughout one or more less in one or more horizons between either an Ap horizon horizons with a total thickness of 18 cm or more within 75 cm or a depth of 25 cm from the mineral soil surface, whichever of the mineral soil surface, one or both of the following: is deeper, and either a depth of 75 cm or a densic, lithic, or 1. More than 35 percent (by volume) fragments coarser paralithic contact, whichever is shallower. than 2.0 mm, of which more than 66 percent is cinders, Cumulic Ultic Haploxerolls pumice, and pumicelike fragments; or IFFK. Other Haploxerolls that have all of the following: 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and 1. A mollic epipedon that is 50 cm or more thick and has a texture class finer than loamy fine sand;and a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and 2. One or both of the following:

1 b. [(Al plus /2 Fe, percent extracted by ammonium a. An organic-carbon content (Holocene age) of 0.3 oxalate) times 60] plus the volcanic glass (percent) is percent or more at a depth of 125 cm below the mineral equal to 30 or more. soil surface; or Vitrandic Haploxerolls b. An irregular decrease in organic-carbon content (Holocene age) between a depth of 25 cm and either IFFI. Other Haploxerolls that have all of the following: a depth of 125 cm below the mineral soil surface or 1. A mollic epipedon that is 50 cm or more thick and has a a densic, lithic, or paralithic contact, whichever is texture class finer than loamy fine sand;and shallower; and 2. One or both of the following: 3. A slope of less than 25 percent. a. An organic-carbon content (Holocene age) of 0.3 Cumulic Haploxerolls percent or more at a depth of 125 cm below the mineral soil surface; or IFFL. Other Haploxerolls that have both: b. An irregular decrease in organic-carbon content 1. In one or more horizons within 75 cm of the mineral soil (Holocene age) between a depth of 25 cm and either surface, redox depletions with chroma of 2 or less and also a depth of 125 cm below the mineral soil surface or aquic conditions for some time in normal years (or artificial a densic, lithic, or paralithic contact, whichever is drainage); and shallower; and 2. A slope of less than 25 percent and one or both of the 3. A slope of less than 25 percent; and following: 4. In one or more horizons within 75 cm of the mineral soil a. An organic-carbon content (Holocene age) of 0.3 surface, redox depletions with chroma of 2 or less and also percent or more in all horizons within 125 cm of the aquic conditions for some time in normal years (or artificial mineral soil surface; or drainage). b. An irregular decrease in organic-carbon content Aquic Cumulic Haploxerolls (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a IFFJ. Other Haploxerolls that have all of the following: densic, lithic, or paralithic contact, whichever is shallower. 1. A mollic epipedon that is 50 cm or more thick and has a Fluvaquentic Haploxerolls texture class finer than loamy fine sand;and Mollisols 237

IFFM. Other Haploxerolls that have both: IFFR. Other Haploxerolls that have both: 1. In one or more horizons within 75 cm of the mineral soil 1. A mollic epipedon that is 50 cm or more thick and has a surface, redox depletions with chroma of 2 or less and also texture class finer than loamy fine sand;and aquic conditions for some time in normal years (or artificial drainage); and 2. A base saturation (by sum of cations) of 75 percent or less in one or more horizons between either an Ap horizon 2. A horizon, 15 cm or more thick within 100 cm of the or a depth of 25 cm from the mineral soil surface, whichever mineral soil surface, that either has 20 percent or more (by is deeper, and either a depth of 75 cm or a densic, lithic, or volume) durinodes or is brittle and has at least a firm rupture- paralithic contact, whichever is shallower. resistance class when moist. Pachic Ultic Haploxerolls Aquic Duric Haploxerolls IFFS. Other Haploxerolls that have a mollic epipedon that is IFFN. Other Haploxerolls that have both: 50 cm or more thick and has a texture class finer than loamy fine 1. In one or more horizons within 75 cm of the mineral soil sand. surface, redox depletions with chroma of 2 or less and also Pachic Haploxerolls aquic conditions for some time in normal years (or artificial drainage); and IFFT. Other Haploxerolls that have all of the following: 2. A base saturation (by sum of cations) of 75 percent or 1. An aridic soil moisture regime; and less in one or more horizons between either an Ap horizon or a depth of 25 cm from the mineral soil surface, whichever 2. A slope of less than 25 percent; and is deeper, and either a depth of 75 cm or a densic, lithic, or 3. One or both of the following: paralithic contact, whichever is shallower. Aquultic Haploxerolls a. An organic-carbon content (Holocene age) of 0.3 percent or more in all horizons within 125 cm of the IFFO. Other Haploxerolls that have, in one or more horizons mineral soil surface; or within 75 cm of the mineral soil surface, redox depletions with b. An irregular decrease in organic-carbon content chroma of 2 or less and also aquic conditions for some time in (Holocene age) between a depth of 25 cm and either normal years (or artificial drainage). a depth of 125 cm below the mineral soil surface or a Aquic Haploxerolls densic, lithic, or paralithic contact, whichever is shallower. Torrifluventic Haploxerolls IFFP. Other Haploxerolls that in normal years are saturated with water in one or more layers within 100 cm of the mineral IFFU. Other Haploxerolls that have both: soil surface for either or both: M O 1. 20 or more consecutive days; or 1. An aridic soil moisture regime; and L 2. 30 or more cumulative days. 2. A horizon within 100 cm of the mineral soil surface that Oxyaquic Haploxerolls is 15 cm or more thick and either has 20 percent or more (by volume) durinodes or is brittle and has at least a firm rupture- IFFQ. Other Haploxerolls that have both: resistance class when moist. Duridic Haploxerolls 1. A mollic epipedon that is 50 cm or more thick and has a texture class finer than loamy fine sand;and IFFV. Other Haploxerolls that have both: 2. A calcic horizon or identifiable secondary carbonates within one of the following particle-size class (by weighted 1. An aridic soil moisture regime; and average in the particle-size control section) and depth 2. A calcic horizon or identifiable secondary carbonates combinations: within one of the following particle-size class (by weighted a. Sandy or sandy-skeletal and within 150 cm of the average in the particle-size control section) and depth mineral soil surface; or combinations: b. Clayey, clayey-skeletal, fine, or very-fine and within a. Sandy or sandy-skeletal and within 150 cm of the 90 cm of the mineral soil surface; or mineral soil surface; or c. Any other class and within 110 cm of the mineral soil b. Clayey, clayey-skeletal, fine, or very-fine and within surface. 90 cm of the mineral soil surface; or Calcic Pachic Haploxerolls 238 Keys to Soil Taxonomy

c. Any other class and within 110 cm of the mineral soil has granular structure and that has, below any Ap horizon, 50 surface. percent or more (by volume) wormholes, wormcasts, or filled Calcidic Haploxerolls animal burrows. Vermic Haploxerolls IFFW. Other Haploxerolls that have both: IFFZd. Other Haploxerolls that have a calcic horizon or 1. An aridic soil moisture regime; and identifiable secondary carbonates within one of the following 2. A sandy particle-size class in all horizons within 100 cm particle-size class (by weighted average in the particle-size of the mineral soil surface. control section) and depth combinations: Torripsammentic Haploxerolls 1. Sandy or sandy-skeletal and within 150 cm of the IFFX. Other Haploxerolls that: mineral soil surface; or 1. Have an aridic soil moisture regime; and 2. Clayey, clayey-skeletal, fine, or very-fine and within 90 cm of the mineral soil surface; or 2. Either: 3. Any other class and within 110 cm of the mineral soil a. Do not have a cambic horizon and do not, in any part surface. of the mollic epipedon below 25 cm from the mineral Calcic Haploxerolls soil surface, meet the requirements for a cambic horizon, except for the color requirements; or IFFZe. Other Haploxerolls that: b. Have free carbonates throughout the cambic horizon 1. Do not have a cambic horizon and do not, in the lower or in all parts of the mollic epipedon below a depth of 25 part of the mollic epipedon, meet the requirements for a cm from the mineral soil surface. cambic horizon, except for the color requirements; and Torriorthentic Haploxerolls 2. Have a base saturation (by sum of cations) of 75 percent IFFY. Other Haploxerolls that have an aridic soil moisture or less in one or more horizons between either an Ap horizon regime. or a depth of 25 cm from the mineral soil surface, whichever Aridic Haploxerolls is deeper, and either a depth of 75 cm or a densic, lithic, or paralithic contact, whichever is shallower. IFFZ. Other Haploxerolls that have a horizon within 100 cm Entic Ultic Haploxerolls of the mineral soil surface that is 15 cm or more thick and either has 20 percent or more (by volume) durinodes or is brittle and IFFZf. Other Haploxerolls that have a base saturation (by has at least a firm rupture-resistance class when moist. sum of cations) of 75 percent or less in one or more horizons Duric Haploxerolls between either an Ap horizon or a depth of 25 cm from the mineral soil surface, whichever is deeper, and either a depth IFFZa. Other Haploxerolls that have a sandy particle-size of 75 cm or a densic, lithic, or paralithic contact, whichever is class in all horizons within 100 cm of the mineral soil surface. shallower. Psammentic Haploxerolls Ultic Haploxerolls

IFFZb. Other Haploxerolls that have a slope of less than 25 IFFZg. Other Haploxerolls that either: percent and one or both of the following: 1. Do not have a cambic horizon and do not, in any part 1. An organic-carbon content (Holocene age) of 0.3 percent of the mollic epipedon below 25 cm from the mineral soil or more in all horizons within 125 cm of the mineral soil surface, meet the requirements for a cambic horizon, except surface; or for the color requirements; or 2. An irregular decrease in organic-carbon content 2. Have free carbonates throughout the cambic horizon or (Holocene age) between a depth of 25 cm and either a depth in all parts of the mollic epipedon below a depth of 25 cm of 125 cm below the mineral soil surface or a densic, lithic, from the mineral soil surface. or paralithic contact, whichever is shallower. Entic Haploxerolls Fluventic Haploxerolls IFFZh. Other Haploxerolls. IFFZc. Other Haploxerolls that have a mollic epipedon that Typic Haploxerolls Mollisols 239

Natrixerolls for some time in normal years and slickensides or wedge- shaped peds in a layer 15 cm or more thick that has its upper Key to Subgroups boundary within 125 cm of the mineral soil surface; or IFBA. Natrixerolls that have one or both of the following: 2. A linear extensibility of 6.0 cm or more between the 1. Cracks within 125 cm of the mineral soil surface that are mineral soil surface and either a depth of 100 cm or a densic, 5 mm or more wide through a thickness of 30 cm or more lithic, or paralithic contact, whichever is shallower. for some time in normal years and slickensides or wedge- Vertic Palexerolls shaped peds in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil surface; or IFCB. Other Palexerolls that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm 2. A linear extensibility of 6.0 cm or more between the of the mineral soil surface, one or both of the following: mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. 1. More than 35 percent (by volume) fragments coarser Vertic Natrixerolls than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or IFBB. Other Natrixerolls that have both: 2. A fine-earth fraction containing 30 percent or more 1. In one or more horizons within 75 cm of the mineral soil particles 0.02 to 2.0 mm in diameter; and surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial a. In the 0.02 to 2.0 mm fraction, 5 percent or more drainage); and volcanic glass; and 1 2. A horizon, 15 cm or more thick within 100 cm of the b. [(Al plus /2 Fe, percent extracted by ammonium mineral soil surface, that either has 20 percent or more (by oxalate) times 60] plus the volcanic glass (percent) is volume) durinodes or is brittle and has at least a firm rupture- equal to 30 or more. resistance class when moist. Vitrandic Palexerolls Aquic Duric Natrixerolls IFCC. Other Palexerolls that have, in one or more horizons IFBC. Other Natrixerolls that have, in one or more horizons within 75 cm of the mineral soil surface, redox depletions with within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). normal years (or artificial drainage). Aquic Palexerolls Aquic Natrixerolls IFCD. Other Palexerolls that have a mollic epipedon that is 50 cm or more thick and has a texture class finer than loamy fine M IFBD. Other Natrixerolls that have an aridic soil moisture O regime. sand. L Aridic Natrixerolls Pachic Palexerolls

IFBE. Other Natrixerolls that have a horizon within 100 cm of IFCE. Other Palexerolls that have both: the mineral soil surface that is 15 cm or more thick and either 1. An aridic soil moisture regime; and has 20 percent or more (by volume) durinodes or is brittle and has at least a firm rupture-resistance class when moist. 2. A petrocalcic horizon within 150 cm of the mineral soil Duric Natrixerolls surface. Petrocalcidic Palexerolls IFBF. Other Natrixerolls. Typic Natrixerolls IFCF. Other Palexerolls that have a horizon, 15 cm or more thick within 100 cm of the mineral soil surface, that either has 20 percent or more (by volume) durinodes or is brittle and has at Palexerolls least a firm rupture-resistance class when moist. Key to Subgroups Duric Palexerolls IFCA. Palexerolls that have one or both of the following: IFCG. Other Palexerolls that have an aridic soil moisture 1. Cracks within 125 cm of the mineral soil surface that are regime. 5 mm or more wide through a thickness of 30 cm or more Aridic Palexerolls 240

IFCH. Other Palexerolls that have a petrocalcic horizon within 1. Less than 35 percent clay in the upper part; or 150 cm of the mineral soil surface. 2. At its upper boundary, a clay increase that is both less Petrocalcic Palexerolls than 20 percent (absolute) within a vertical distance of 7.5 cm and less than 15 percent (absolute) within a vertical IFCI. Other Palexerolls that have a base saturation (by sum of distance of 2.5 cm, in the fine-earth fraction. cations) of 75 percent or less in one or more subhorizons either Haplic Palexerolls within the argillic horizon if more than 50 cm thick or within its upper 50 cm. IFCK. Other Palexerolls. Ultic Palexerolls Typic Palexerolls IFCJ. Other Palexerolls that have an argillic horizon that has either: 241

CHAPTER 13 Oxisols

Key to Suborders EAB. Other Aquox that have plinthite forming a continuous phase within 125 cm of the mineral soil surface. EA. Oxisols that have aquic conditions for some time in Plinthaquox, p. 242 normal years (or artificial drainage) in one or more horizons within 50 cm of the mineral soil surface and have one or more EAC. Other Aquox that have a base saturation (by NH4OAc) of the following: of 35 percent or more in all horizons within 125 cm of the 1. A histic epipedon; or mineral soil surface. Eutraquox, p. 241 2. An epipedon with a color value, moist, of 3 or less and, directly below it, a horizon with chroma of 2 or less; or EAD. Other Aquox. Haplaquox, p. 242 3. Distinct or prominent redox concentrations within 50 cm of the mineral soil surface, an epipedon, and, directly below it, a horizon with one or both of the following: Acraquox a. 50 percent or more hue of 2.5Y or yellower; or Key to Subgroups EAAA. Acraquox that have 5 percent or more (by volume) b. Chroma of 3 or less; or plinthite in one or more horizons within 125 cm of the mineral 4. Within 50 cm of the mineral soil surface, enough active soil surface. ferrous iron to give a positive reaction to alpha,alpha- Plinthic Acraquox dipyridyl at a time when the soil is not being irrigated. Aquox, p. 241 EAAB. Other Acraquox that have, directly below an epipedon, a horizon 10 cm or more thick that has 50 percent or more EB. Other Oxisols that have an aridic soil moisture regime. chroma of 3 or more. Torrox, p. 246 Aeric Acraquox

EC. Other Oxisols that have an ustic or xeric soil moisture EAAC. Other Acraquox. regime. Typic Acraquox O X Ustox, p. 251 I Eutraquox ED. Other Oxisols that have a perudic soil moisture regime. Key to Subgroups Perox, p. 242 EACA. Eutraquox that have a histic epipedon. EE. Other Oxisols. Histic Eutraquox Udox, p. 247 EACB. Other Eutraquox that have 5 percent or more (by Aquox volume) plinthite in one or more horizons within 125 cm of the mineral soil surface. Key to Great Groups Plinthic Eutraquox EAA. Aquox that have, in one or more subhorizons of an oxic or kandic horizon within 150 cm of the mineral soil surface, an EACC. Other Eutraquox that have, directly below an apparent ECEC of less than 1.50 cmol(+) per kg clay and a pH epipedon, a horizon 10 cm or more thick that has 50 percent or value (1N KCl) of 5.0 or more. more chroma of 3 or more. Acraquox, p. 241 Aeric Eutraquox 242 Keys to Soil Taxonomy

2 EACD. Other Eutraquox that have 16 kg/m or more organic EDC. Other Perox that have a base saturation (by NH4OAc) of carbon between the mineral soil surface and a depth of 100 cm. 35 percent or more in all horizons within 125 cm of the mineral Humic Eutraquox soil surface. Eutroperox, p. 243 EACE. Other Eutraquox. Typic Eutraquox EDD. Other Perox that have a kandic horizon within 150 cm of the mineral soil surface. Haplaquox Kandiperox, p. 245

Key to Subgroups EDE. Other Perox. EADA. Haplaquox that have a histic epipedon. Haploperox, p. 244 Histic Haplaquox Acroperox EADB. Other Haplaquox that have 5 percent or more (by Key to Subgroups volume) plinthite in one or more horizons within 125 cm of the mineral soil surface. EDBA. Acroperox that have, within 125 cm of the mineral soil Plinthic Haplaquox surface, both: 1. A petroferric contact; and EADC. Other Haplaquox that have, directly below an epipedon, a horizon 10 cm or more thick that has 50 percent or 2. Redox depletions with a color value, moist, of 4 or more more chroma of 3 or more. and chroma of 2 or less and also aquic conditions for some Aeric Haplaquox time in normal years (or artificial drainage). Aquic Petroferric Acroperox EADD. Other Haplaquox that have 16 kg/m2 or more organic carbon between the mineral soil surface and a depth of 100 cm. EDBB. Other Acroperox that have a petroferric contact within Humic Haplaquox 125 cm of the mineral soil surface. Petroferric Acroperox EADE. Other Haplaquox. Typic Haplaquox EDBC. Other Acroperox that have, within 125 cm of the mineral soil surface, both: Plinthaquox 1. A lithic contact; and Key to Subgroups 2. Redox depletions with a color value, moist, of 4 or more EABA. Plinthaquox that have, directly below an epipedon, and chroma of 2 or less and also aquic conditions for some a horizon 10 cm or more thick that has 50 percent or more time in normal years (or artificial drainage). chroma of 3 or more. Aquic Lithic Acroperox Aeric Plinthaquox EDBD. Other Acroperox that have a lithic contact within 125 EABB. Other Plinthaquox. cm of the mineral soil surface. Typic Plinthaquox Lithic Acroperox EDBE. Other Acroperox that have a delta pH (KCl pH minus Perox 1:1 water pH) with a 0 or net positive charge in a layer 18 cm or Key to Great Groups more thick within 125 cm of the mineral soil surface. Anionic Acroperox EDA. Perox that have a sombric horizon within 150 cm of the mineral soil surface. EDBF. Other Acroperox that have 5 percent or more (by Sombriperox, p. 246 volume) plinthite in one or more horizons within 125 cm of the mineral soil surface. EDB. Other Perox that have, in one or more subhorizons of Plinthic Acroperox an oxic or kandic horizon within 150 cm of the mineral soil surface, an apparent ECEC of less than 1.50 cmol(+) per kg clay EDBG. Other Acroperox that have, in one or more horizons and a pH value (1N KCl) of 5.0 or more. within 125 cm of the mineral soil surface, redox depletions with Acroperox, p. 242 a color value, moist, of 4 or more and chroma of 2 or less and Oxisols 243

also aquic conditions for some time in normal years (or artificial and chroma of 2 or less and also aquic conditions for some drainage). time in normal years (or artificial drainage). Aquic Acroperox Aquic Petroferric Eutroperox

EDBH. Other Acroperox that have both: EDCB. Other Eutroperox that have a petroferric contact within 125 cm of the mineral soil surface. 1. 16 kg/m2 or more organic carbon between the mineral Petroferric Eutroperox soil surface and a depth of 100 cm; and 2. In all horizons at a depth between 25 and 125 cm from EDCC. Other Eutroperox that have, within 125 cm of the the mineral soil surface, more than 50 percent colors that mineral soil surface, both: have both of the following: 1. A lithic contact; and a. Hue of 2.5YR or redder; and 2. Redox depletions with a color value, moist, of 4 or more b. A value, moist, of 3 or less. and chroma of 2 or less and also aquic conditions for some Humic Rhodic Acroperox time in normal years (or artificial drainage). Aquic Lithic Eutroperox EDBI. Other Acroperox that have both:

2 EDCD. Other Eutroperox that have a lithic contact within 125 1. 16 kg/m or more organic carbon between the mineral cm of the mineral soil surface. soil surface and a depth of 100 cm; and Lithic Eutroperox 2. 50 percent or more hue of 7.5YR or yellower and a color value, moist, of 6 or more at a depth between 25 and 125 cm EDCE. Other Eutroperox that have, in one or more horizons from the mineral soil surface. within 125 cm of the mineral soil surface, both: Humic Xanthic Acroperox 1. 5 percent or more (by volume) plinthite; and EDBJ. Other Acroperox that have 16 kg/m2 or more organic 2. Redox depletions with a color value, moist, of 4 or more carbon between the mineral soil surface and a depth of 100 cm. and chroma of 2 or less and also aquic conditions for some Humic Acroperox time in normal years (or artificial drainage). Plinthaquic Eutroperox EDBK. Other Acroperox that have, in all horizons at a depth between 25 and 125 cm from the mineral soil surface, more than EDCF. Other Eutroperox that have 5 percent or more (by 50 percent colors that have both of the following: volume) plinthite in one or more horizons within 125 cm of the mineral soil surface. 1. Hue of 2.5YR or redder; and Plinthic Eutroperox 2. A value, moist, of 3 or less. Rhodic Acroperox EDCG. Other Eutroperox that have, in one or more horizons within 125 cm of the mineral soil surface, redox depletions with O X EDBL. Other Acroperox that have 50 percent or more hue of a color value, moist, of 4 or more and chroma of 2 or less and I 7.5YR or yellower and a color value, moist, of 6 or more at a also aquic conditions for some time in normal years (or artificial depth between 25 and 125 cm from the mineral soil surface. drainage). Xanthic Acroperox Aquic Eutroperox

EDBM. Other Acroperox. EDCH. Other Eutroperox that have a kandic horizon within Typic Acroperox 150 cm of the mineral soil surface. Kandiudalfic Eutroperox Eutroperox EDCI. Other Eutroperox that have both: Key to Subgroups 1. 16 kg/m2 or more organic carbon between the mineral EDCA. Eutroperox that have, within 125 cm of the mineral soil surface and a depth of 100 cm; and soil surface, both: 2. An oxic horizon that has its lower boundary within 125 1. A petroferric contact; and cm of the mineral soil surface. 2. Redox depletions with a color value, moist, of 4 or more Humic Inceptic Eutroperox 244 Keys to Soil Taxonomy

EDCJ. Other Eutroperox that have an oxic horizon that has its and chroma of 2 or less and also aquic conditions for some lower boundary within 125 cm of the mineral soil surface. time in normal years (or artificial drainage). Inceptic Eutroperox Aquic Petroferric Haploperox

EDCK. Other Eutroperox that have both: EDEB. Other Haploperox that have a petroferric contact within 125 cm of the mineral soil surface. 2 1. 16 kg/m or more organic carbon between the mineral Petroferric Haploperox soil surface and a depth of 100 cm; and 2. In all horizons at a depth between 25 and 125 cm from EDEC. Other Haploperox that have, within 125 cm of the the mineral soil surface, more than 50 percent colors that mineral soil surface, both: have both of the following: 1. A lithic contact; and a. Hue of 2.5YR or redder; and 2. Redox depletions with a color value, moist, of 4 or more b. A value, moist, of 3 or less. and chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). Humic Rhodic Eutroperox Aquic Lithic Haploperox EDCL. Other Eutroperox that have both: EDED. Other Haploperox that have a lithic contact within 125 1. 16 kg/m2 or more organic carbon between the mineral cm of the mineral soil surface. soil surface and a depth of 100 cm; and Lithic Haploperox 2. 50 percent or more hue of 7.5YR or yellower and a color EDEE. Other Haploperox that have, in one or more horizons value, moist, of 6 or more at a depth between 25 and 125 cm within 125 cm of the mineral soil surface, both: from the mineral soil surface. Humic Xanthic Eutroperox 1. 5 percent or more (by volume) plinthite; and

2 2. Redox depletions with a color value, moist, of 4 or more EDCM. Other Eutroperox that have 16 kg/m or more organic and chroma of 2 or less and also aquic conditions for some carbon between the mineral soil surface and a depth of 100 cm. time in normal years (or artificial drainage). Humic Eutroperox Plinthaquic Haploperox

EDCN. Other Eutroperox that have, in all horizons at a depth EDEF. Other Haploperox that have 5 percent or more (by between 25 and 125 cm from the mineral soil surface, more than volume) plinthite in one or more horizons within 125 cm of the 50 percent colors that have both of the following: mineral soil surface. 1. Hue of 2.5YR or redder; and Plinthic Haploperox

2. A value, moist, of 3 or less. EDEG. Other Haploperox that have, in one or more horizons Rhodic Eutroperox within 125 cm of the mineral soil surface, redox depletions with a color value, moist, of 4 or more and chroma of 2 or less and EDCO. Other Eutroperox that have 50 percent or more hue of also aquic conditions for some time in normal years (or artificial 7.5YR or yellower and a color value, moist, of 6 or more at a drainage). depth between 25 and 125 cm from the mineral soil surface. Aquic Haploperox Xanthic Eutroperox EDEH. Other Haploperox that have, throughout one or more EDCP. Other Eutroperox. horizons with a total thickness of 18 cm or more within 75 cm Typic Eutroperox of the mineral soil surface, a fine-earth fraction with both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 Haploperox and Al plus /2 Fe percentages (by ammonium oxalate) totaling Key to Subgroups more than 1.0. Andic Haploperox EDEA. Haploperox that have, within 125 cm of the mineral soil surface, : both EDEI. Other Haploperox that have both: 1. A petroferric contact; and 1. 16 kg/m2 or more organic carbon between the mineral 2. Redox depletions with a color value, moist, of 4 or more soil surface and a depth of 100 cm; and Oxisols 245

2. In all horizons at a depth between 25 and 125 cm from EDDC. Other Kandiperox that have, within 125 cm of the the mineral soil surface, more than 50 percent colors that mineral soil surface, both: have both of the following: 1. A lithic contact; and a. Hue of 2.5YR or redder; and 2. Redox depletions with a color value, moist, of 4 or more b. A value, moist, of 3 or less. and chroma of 2 or less and also aquic conditions for some Humic Rhodic Haploperox time in normal years (or artificial drainage). Aquic Lithic Kandiperox EDEJ. Other Haploperox that have both: EDDD. Other Kandiperox that have a lithic contact within 125 2 1. 16 kg/m or more organic carbon between the mineral cm of the mineral soil surface. soil surface and a depth of 100 cm; and Lithic Kandiperox 2. 50 percent or more hue of 7.5YR or yellower and a color value, moist, of 6 or more at a depth between 25 and 125 cm EDDE. Other Kandiperox that have, in one or more horizons from the mineral soil surface. within 125 cm of the mineral soil surface, both: Humic Xanthic Haploperox 1. 5 percent or more (by volume) plinthite; and

EDEK. Other Haploperox that have 16 kg/m2 or more organic 2. Redox depletions with a color value, moist, of 4 or more carbon between the mineral soil surface and a depth of 100 cm. and chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). Humic Haploperox Plinthaquic Kandiperox EDEL. Other Haploperox that have, in all horizons at a depth between 25 and 125 cm from the mineral soil surface, more than EDDF. Other Kandiperox that have 5 percent or more (by volume) plinthite in one or more horizons within 125 cm of the 50 percent colors that have both of the following: mineral soil surface. 1. Hue of 2.5YR or redder; and Plinthic Kandiperox 2. A value, moist, of 3 or less. EDDG. Other Kandiperox that have, in one or more horizons Rhodic Haploperox within 125 cm of the mineral soil surface, redox depletions with EDEM. Other Haploperox that have 50 percent or more hue a color value, moist, of 4 or more and chroma of 2 or less and of 7.5YR or yellower and a color value, moist, of 6 or more at a also aquic conditions for some time in normal years (or artificial depth between 25 and 125 cm from the mineral soil surface. drainage). Xanthic Haploperox Aquic Kandiperox

EDEN. Other Haploperox. EDDH. Other Kandiperox that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm Typic Haploperox of the mineral soil surface, a fine-earth fraction with both a bulk O 3 X density of 1.0 g/cm or less, measured at 33 kPa water retention, I Kandiperox 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling Key to Subgroups more than 1.0. Andic Kandiperox EDDA. Kandiperox that have, within 125 cm of the mineral soil surface, : both EDDI. Other Kandiperox that have both: 1. A petroferric contact; and 1. 16 kg/m2 or more organic carbon between the mineral 2. Redox depletions with a color value, moist, of 4 or more soil surface and a depth of 100 cm; and and chroma of 2 or less and also aquic conditions for some 2. In all horizons at a depth between 25 and 125 cm from time in normal years (or artificial drainage). the mineral soil surface, more than 50 percent colors that Aquic Petroferric Kandiperox have both of the following:

EDDB. Other Kandiperox that have a petroferric contact a. Hue of 2.5YR or redder; and within 125 cm of the mineral soil surface. b. A value, moist, of 3 or less. Petroferric Kandiperox Humic Rhodic Kandiperox 246 Keys to Soil Taxonomy

EDDJ. Other Kandiperox that have both: apparent ECEC of less than 1.50 cmol(+) per kg clay and a pH 1. 16 kg/m2 or more organic carbon between the mineral value (1N KCl) of 5.0 or more. , p. 246 soil surface and a depth of 100 cm; and Acrotorrox 2. 50 percent or more hue of 7.5YR or yellower and a color EBB. Other Torrox that have a base saturation (by NH4OAc) value, moist, of 6 or more at a depth between 25 and 125 cm of 35 percent or more in all horizons within 125 cm of the from the mineral soil surface. mineral soil surface. Humic Xanthic Kandiperox Eutrotorrox, p. 246

EDDK. Other Kandiperox that have 16 kg/m2 or more organic EBC. Other Torrox. carbon between the mineral soil surface and a depth of 100 cm. Haplotorrox, p. 246 Humic Kandiperox Acrotorrox EDDL. Other Kandiperox that have, in all horizons at a depth between 25 and 125 cm from the mineral soil surface, more than Key to Subgroups 50 percent colors that have both of the following: EBAA. Acrotorrox that have a petroferric contact within 125 1. Hue of 2.5YR or redder; and cm of the mineral soil surface. Petroferric Acrotorrox 2. A value, moist, of 3 or less. Rhodic Kandiperox EBAB. Other Acrotorrox that have a lithic contact within 125 cm of the mineral soil surface. EDDM. Other Kandiperox that have 50 percent or more hue Lithic Acrotorrox of 7.5YR or yellower and a color value, moist, of 6 or more at a depth between 25 and 125 cm from the mineral soil surface. EBAC. Other Acrotorrox. Xanthic Kandiperox Typic Acrotorrox

EDDN. Other Kandiperox. Eutrotorrox Typic Kandiperox Key to Subgroups Sombriperox EBBA. Eutrotorrox that have a petroferric contact within 125 Key to Subgroups cm of the mineral soil surface. Petroferric Eutrotorrox EDAA. Sombriperox that have a petroferric contact within 125 cm of the mineral soil surface. EBBB. Other Eutrotorrox that have a lithic contact within 125 Petroferric Sombriperox cm of the mineral soil surface. Lithic Eutrotorrox EDAB. Other Sombriperox that have a lithic contact within 125 cm of the mineral soil surface. EBBC. Other Eutrotorrox. Lithic Sombriperox Typic Eutrotorrox

EDAC. Other Sombriperox that have 16 kg/m2 or more Haplotorrox organic carbon between the mineral soil surface and a depth of 100 cm. Key to Subgroups Humic Sombriperox EBCA. Haplotorrox that have a petroferric contact within 125 cm of the mineral soil surface. EDAD. Other Sombriperox. Petroferric Haplotorrox Typic Sombriperox EBCB. Other Haplotorrox that have a lithic contact within 125 Torrox cm of the mineral soil surface. Lithic Haplotorrox Key to Great Groups EBA. Torrox that have, in one or more subhorizons of an oxic EBCC. Other Haplotorrox. or kandic horizon within 150 cm of the mineral soil surface, an Typic Haplotorrox Oxisols 247

Udox EEBE. Other Acrudox that have, within 125 cm of the mineral soil surface, both: Key to Great Groups 1. A delta pH (KCl pH minus 1:1 water pH) with a 0 or net EEA. Udox that have a sombric horizon within 150 cm of the positive charge in a layer 18 cm or more thick; and mineral soil surface. Sombriudox, p. 251 2. Redox depletions with a color value, moist, of 4 or more and chroma of 2 or less and also aquic conditions for some EEB. Other Udox that have, in one or more subhorizons of time in normal years (or artificial drainage). an oxic or kandic horizon within 150 cm of the mineral soil Anionic Aquic Acrudox surface, an apparent ECEC of less than 1.50 cmol(+) per kg clay and a pH value (1N KCl) of 5.0 or more. EEBF. Other Acrudox that have a delta pH (KCl pH minus Acrudox, p. 247 1:1 water pH) with a 0 or net positive charge in a layer 18 cm or more thick within 125 cm of the mineral soil surface. Anionic Acrudox EEC. Other Udox that have a base saturation (by NH4OAc) of 35 percent or more in all horizons within 125 cm of the mineral soil surface. EEBG. Other Acrudox that have 5 percent or more (by Eutrudox, p. 248 volume) plinthite in one or more horizons within 125 cm of the mineral soil surface. EED. Other Udox that have a kandic horizon within 150 cm of Plinthic Acrudox the mineral soil surface. Kandiudox, p. 250 EEBH. Other Acrudox that have, in one or more horizons within 125 cm of the mineral soil surface, redox depletions with EEE. Other Udox. a color value, moist, of 4 or more and chroma of 2 or less and Hapludox, p. 249 also aquic conditions for some time in normal years (or artificial drainage). Aquic Acrudox Acrudox Key to Subgroups EEBI. Other Acrudox that have a base saturation (by NH OAc) of 35 percent or more in all horizons within 125 cm EEBA. Acrudox that have, within 125 cm of the mineral soil 4 of the mineral soil surface. surface, both: Eutric Acrudox 1. A petroferric contact; and EEBJ. Other Acrudox that have both: 2. Redox depletions with a color value, moist, of 4 or more and chroma of 2 or less and also aquic conditions for some 1. 16 kg/m2 or more organic carbon between the mineral time in normal years (or artificial drainage). soil surface and a depth of 100 cm; and

Aquic Petroferric Acrudox 2. In all horizons at a depth between 25 and 125 cm from O X the mineral soil surface, more than 50 percent colors that I EEBB. Other Acrudox that have a petroferric contact within have both of the following: 125 cm of the mineral soil surface. Petroferric Acrudox a. Hue of 2.5YR or redder; and b. A value, moist, of 3 or less. EEBC. Other Acrudox that have, within 125 cm of the mineral Humic Rhodic Acrudox soil surface, both: 1. A lithic contact; and EEBK. Other Acrudox that have both: 2. Redox depletions with a color value, moist, of 4 or more 1. 16 kg/m2 or more organic carbon between the mineral and chroma of 2 or less and also aquic conditions for some soil surface and a depth of 100 cm; and time in normal years (or artificial drainage). 2. 50 percent or more hue of 7.5YR or yellower and a color Aquic Lithic Acrudox value, moist, of 6 or more at a depth between 25 and 125 cm from the mineral soil surface. EEBD. Other Acrudox that have a lithic contact within 125 cm Humic Xanthic Acrudox of the mineral soil surface. Lithic Acrudox EEBL. Other Acrudox that have 16 kg/m2 or more organic 248 Keys to Soil Taxonomy

carbon between the mineral soil surface and a depth of 100 and chroma of 2 or less and also aquic conditions for some cm. time in normal years (or artificial drainage). Humic Acrudox Plinthaquic Eutrudox

EEBM. Other Acrudox that have, in all horizons at a depth EECF. Other Eutrudox that have 5 percent or more (by between 25 and 125 cm from the mineral soil surface, more than volume) plinthite in one or more horizons within 125 cm of the 50 percent colors that have both of the following: mineral soil surface. 1. Hue of 2.5YR or redder; and Plinthic Eutrudox

2. A value, moist, of 3 or less. EECG. Other Eutrudox that have, in one or more horizons Rhodic Acrudox within 125 cm of the mineral soil surface, redox depletions with a color value, moist, of 4 or more and chroma of 2 or less and EEBN. Other Acrudox that have 50 percent or more hue of also aquic conditions for some time in normal years (or artificial 7.5YR or yellower and a color value, moist, of 6 or more at a drainage). depth between 25 and 125 cm from the mineral soil surface. Aquic Eutrudox Xanthic Acrudox

EEBO. Other Acrudox. EECH. Other Eutrudox that have a kandic horizon within 150 cm of the mineral soil surface. Typic Acrudox Kandiudalfic Eutrudox Eutrudox EECI. Other Eutrudox that have both: Key to Subgroups 1. 16 kg/m2 or more organic carbon between the mineral EECA. Eutrudox that have, within 125 cm of the mineral soil soil surface and a depth of 100 cm; and surface, both: 2. An oxic horizon that has its lower boundary within 125 1. A petroferric contact; and cm of the mineral soil surface. 2. Redox depletions with a color value, moist, of 4 or more Humic Inceptic Eutrudox and chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). EECJ. Other Eutrudox that have an oxic horizon that has its Aquic Petroferric Eutrudox lower boundary within 125 cm of the mineral soil surface. Inceptic Eutrudox EECB. Other Eutrudox that have a petroferric contact within 125 cm of the mineral soil surface. EECK. Other Eutrudox that have both: Petroferric Eutrudox 1. 16 kg/m2 or more organic carbon between the mineral EECC. Other Eutrudox that have, within 125 cm of the soil surface and a depth of 100 cm; and mineral soil surface, both: 2. In all horizons at a depth between 25 and 125 cm from 1. A lithic contact; and the mineral soil surface, more than 50 percent colors that have both of the following: 2. Redox depletions with a color value, moist, of 4 or more and chroma of 2 or less and also aquic conditions for some a. Hue of 2.5YR or redder; and time in normal years (or artificial drainage). b. A value, moist, of 3 or less. Aquic Lithic Eutrudox Humic Rhodic Eutrudox EECD. Other Eutrudox that have a lithic contact within 125 EECL. Other Eutrudox that have both: cm of the mineral soil surface. Lithic Eutrudox 1. 16 kg/m2 or more organic carbon between the mineral soil surface and a depth of 100 cm; and EECE. Other Eutrudox that have, in one or more horizons 2. 50 percent or more hue of 7.5YR or yellower and a color within 125 cm of the mineral soil surface, both: value, moist, of 6 or more at a depth between 25 and 125 cm 1. 5 percent or more (by volume) plinthite; and from the mineral soil surface. Humic Xanthic Eutrudox 2. Redox depletions with a color value, moist, of 4 or more Oxisols 249

EECM. Other Eutrudox that have 16 kg/m2 or more organic 2. Redox depletions with a color value, moist, of 4 or more carbon between the mineral soil surface and a depth of 100 cm. and chroma of 2 or less and also aquic conditions for some Humic Eutrudox time in normal years (or artificial drainage). Plinthaquic Hapludox EECN. Other Eutrudox that have, in all horizons at a depth between 25 and 125 cm from the mineral soil surface, more than EEEF. Other Hapludox that have 5 percent or more (by 50 percent colors that have both of the following: volume) plinthite in one or more horizons within 125 cm of the mineral soil surface. 1. Hue of 2.5YR or redder; and Plinthic Hapludox 2. A value, moist, of 3 or less. Rhodic Eutrudox EEEG. Other Hapludox that have, in one or more horizons within 125 cm of the mineral soil surface, redox depletions with EECO. Other Eutrudox that have 50 percent or more hue of a color value, moist, of 4 or more and chroma of 2 or less and 7.5YR or yellower and a color value, moist, of 6 or more at a also aquic conditions for some time in normal years (or artificial depth between 25 and 125 cm from the mineral soil surface. drainage). Xanthic Eutrudox Aquic Hapludox

EECP. Other Eutrudox. EEEH. Other Hapludox that have an oxic horizon that has its Typic Eutrudox lower boundary within 125 cm of the mineral soil surface. Inceptic Hapludox Hapludox EEEI. Other Hapludox that have, throughout one or more Key to Subgroups horizons with a total thickness of 18 cm or more within 75 cm EEEA. Hapludox that have, within 125 cm of the mineral soil of the mineral soil surface, a fine-earth fraction with both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water retention, surface, both: 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling 1. A petroferric contact; and more than 1.0. 2. Redox depletions with a color value, moist, of 4 or more Andic Hapludox and chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). EEEJ. Other Hapludox that have both: Aquic Petroferric Hapludox 1. 16 kg/m2 or more organic carbon between the mineral soil surface and a depth of 100 cm; and EEEB. Other Hapludox that have a petroferric contact within 125 cm of the mineral soil surface. 2. In all horizons at a depth between 25 and 125 cm from Petroferric Hapludox the mineral soil surface, more than 50 percent colors that have both of the following: O EEEC. Other Hapludox that have, within 125 cm of the X a. Hue of 2.5YR or redder; and I mineral soil surface, both: b. A value, moist, of 3 or less. 1. A lithic contact; and Humic Rhodic Hapludox 2. Redox depletions with a color value, moist, of 4 or more and chroma of 2 or less and also aquic conditions for some EEEK. Other Hapludox that have both: time in normal years (or artificial drainage). 1. 16 kg/m2 or more organic carbon between the mineral Aquic Lithic Hapludox soil surface and a depth of 100 cm; and

EEED. Other Hapludox that have a lithic contact within 125 2. 50 percent or more hue of 7.5YR or yellower and a color cm of the mineral soil surface. value, moist, of 6 or more at a depth between 25 and 125 cm from the mineral soil surface. Lithic Hapludox Humic Xanthic Hapludox EEEE. Other Hapludox that have, in one or more horizons EEEL. Other Hapludox that have 16 kg/m2 or more organic within 125 cm of the mineral soil surface, both: carbon between the mineral soil surface and a depth of 100 cm. 1. 5 percent or more (by volume) plinthite; and Humic Hapludox 250 Keys to Soil Taxonomy

EEEM. Other Hapludox that have, in all horizons at a depth EEDF. Other Kandiudox hat have 5 percent or more (by between 25 and 125 cm from the mineral soil surface, more than volume) plinthite in one or more horizons within 125 cm of the 50 percent colors that have both of the following: mineral soil surface. Plinthic Kandiudox 1. Hue of 2.5YR or redder; and 2. A value, moist, of 3 or less. EEDG. Other Kandiudox that have, in one or more horizons Rhodic Hapludox within 125 cm of the mineral soil surface, redox depletions with a color value, moist, of 4 or more and chroma of 2 or less and EEEN. Other Hapludox that have 50 percent or more hue of also aquic conditions for some time in normal years (or artificial 7.5YR or yellower and a color value, moist, of 6 or more at a drainage). depth between 25 and 125 cm from the mineral soil surface. Aquic Kandiudox Xanthic Hapludox EEDH. Other Kandiudox that have, throughout one or more EEEO. Other Hapludox. horizons with a total thickness of 18 cm or more within 75 cm Typic Hapludox of the mineral soil surface, a fine-earth fraction with both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 Kandiudox and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. Key to Subgroups Andic Kandiudox EEDA. Kandiudox that have, within 125 cm of the mineral soil surface, both: EEDI. Other Kandiudox that have both: 1. A petroferric contact; and 1. 16 kg/m2 or more organic carbon between the mineral soil surface and a depth of 100 cm; and 2. Redox depletions with a color value, moist, of 4 or more and chroma of 2 or less and also aquic conditions for some 2. In all horizons at a depth between 25 and 125 cm from time in normal years (or artificial drainage). the mineral soil surface, more than 50 percent colors that Aquic Petroferric Kandiudox have both of the following: a. Hue of 2.5YR or redder; and EEDB. Other Kandiudox that have a petroferric contact within 125 cm of the mineral soil surface. b. A value, moist, of 3 or less. Petroferric Kandiudox Humic Rhodic Kandiudox

EEDC. Other Kandiudox that have, within 125 cm of the EEDJ. Other Kandiudox that have both: mineral soil surface, both: 1. 16 kg/m2 or more organic carbon between the mineral 1. A lithic contact; and soil surface and a depth of 100 cm; and 2. Redox depletions with a color value, moist, of 4 or more 2. 50 percent or more hue of 7.5YR or yellower and a color and chroma of 2 or less and also aquic conditions for some value, moist, of 6 or more at a depth between 25 and 125 cm time in normal years (or artificial drainage). from the mineral soil surface. Aquic Lithic Kandiudox Humic Xanthic Kandiudox

EEDD. Other Kandiudox that have a lithic contact within 125 EEDK. Other Kandiudox that have 16 kg/m2 or more organic cm of the mineral soil surface. carbon between the mineral soil surface and a depth of 100 cm. Lithic Kandiudox Humic Kandiudox

EEDE. Other Kandiudox that have, in one or more horizons EEDL. Other Kandiudox that have, in all horizons at a depth within 125 cm of the mineral soil surface, both: between 25 and 125 cm from the mineral soil surface, more than 50 percent colors that have both of the following: 1. 5 percent or more (by volume) plinthite; and 1. Hue of 2.5YR or redder; and 2. Redox depletions with a color value, moist, of 4 or more and chroma of 2 or less and also aquic conditions for some 2. A value, moist, of 3 or less. time in normal years (or artificial drainage). Rhodic Kandiudox Plinthaquic Kandiudox Oxisols 251

EEDM. Other Kandiudox that have 50 percent or more hue Acrustox of 7.5YR or yellower and a color value, moist, of 6 or more at a Key to Subgroups depth between 25 and 125 cm from the mineral soil surface. Xanthic Kandiudox ECBA. Acrustox that have, within 125 cm of the mineral soil surface, both: EEDN. Other Kandiudox. 1. A petroferric contact; and Typic Kandiudox 2. Redox depletions with a color value, moist, of 4 or more Sombriudox and chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). Key to Subgroups Aquic Petroferric Acrustox EEAA. Sombriudox that have a petroferric contact within 125 cm of the mineral soil surface. ECBB. Other Acrustox that have a petroferric contact within Petroferric Sombriudox 125 cm of the mineral soil surface. Petroferric Acrustox EEAB. Other Sombriudox that have a lithic contact within 125 cm of the mineral soil surface. ECBC. Other Acrustox that have, within 125 cm of the Lithic Sombriudox mineral soil surface, both: 1. A lithic contact; and EEAC. Other Sombriudox that have 16 kg/m2 or more organic carbon between the mineral soil surface and a depth of 2. Redox depletions with a color value, moist, of 4 or more 100 cm. and chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). Humic Sombriudox Aquic Lithic Acrustox EEAD. Other Sombriudox. ECBD. Other Acrustox that have a lithic contact within 125 Typic Sombriudox cm of the mineral soil surface. Lithic Acrustox Ustox Key to Great Groups ECBE. Other Acrustox that have, within 125 cm of the mineral soil surface, both: ECA. Ustox that have a sombric horizon within 150 cm of the 1. A delta pH (KCl pH minus 1:1 water pH) with a 0 or net mineral soil surface. positive charge in a layer 18 cm or more thick; and Sombriustox, p. 255 2. Redox depletions with a color value, moist, of 4 or more ECB. Other Ustox that have, in one or more subhorizons of and chroma of 2 or less and also aquic conditions for some an oxic or kandic horizon within 150 cm of the mineral soil time in normal years (or artificial drainage). O X surface, an apparent ECEC of less than 1.50 cmol(+) per kg clay Anionic Aquic Acrustox I and a pH value (1N KCl) of 5.0 or more. Acrustox, p. 251 ECBF. Other Acrustox that have a delta pH (KCl pH minus 1:1 water pH) with a 0 or net positive charge in a layer 18 cm or more thick within 125 cm of the mineral soil surface. ECC. Other Ustox that have a base saturation (by NH4OAc) of 35 percent or more in all horizons within 125 cm of the mineral Anionic Acrustox soil surface. Eutrustox, p. 252 ECBG. Other Acrustox that have 5 percent or more (by volume) plinthite in one or more horizons within 125 cm of the ECD. Other Ustox that have a kandic horizon within 150 cm mineral soil surface. of the mineral soil surface. Plinthic Acrustox Kandiustox, p. 254 ECBH. Other Acrustox that have, in one or more horizons ECE. Other Ustox. within 125 cm of the mineral soil surface, redox depletions with Haplustox, p. 253 a color value, moist, of 4 or more and chroma of 2 or less and 252 Keys to Soil Taxonomy

also aquic conditions for some time in normal years (or artificial Eutrustox drainage). Aquic Acrustox Key to Subgroups ECCA. Eutrustox that have, within 125 cm of the mineral ECBI. Other Acrustox that have a base saturation (by soil surface, both:

NH4OAc) of 35 percent or more in all horizons within 125 cm of the mineral soil surface. 1. A petroferric contact; and Eutric Acrustox 2. Redox depletions with a color value, moist, of 4 or more and chroma of 2 or less and also aquic conditions ECBJ. Other Acrustox that have both: for some time in normal years (or artificial drainage). Aquic Petroferric Eutrustox 1. 16 kg/m2 or more organic carbon between the mineral soil surface and a depth of 100 cm; and ECCB. Other Eutrustox that have a petroferric contact 2. In all horizons at a depth between 25 and 125 cm from within 125 cm of the mineral soil surface. the mineral soil surface, more than 50 percent colors that Petroferric Eutrustox have both of the following: ECCC. Other Eutrustox that have, within 125 cm of the a. Hue of 2.5YR or redder; and mineral soil surface, both: b. A value, moist, of 3 or less. 1. A lithic contact; and Humic Rhodic Acrustox 2. Redox depletions with a color value, moist, of 4 or ECBK. Other Acrustox that have both: more and chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). 1. 16 kg/m2 or more organic carbon between the mineral Aquic Lithic Eutrustox soil surface and a depth of 100 cm; and 2. 50 percent or more hue of 7.5YR or yellower and a color ECCD. Other Eutrustox that have a lithic contact within value, moist, of 6 or more at a depth between 25 and 125 cm 125 cm of the mineral soil surface. from the mineral soil surface. Lithic Eutrustox Humic Xanthic Acrustox ECCE. Other Eutrustox that have, in one or more horizons ECBL. Other Acrustox that have 16 kg/m2 or more organic within 125 cm of the mineral soil surface, both: carbon between the mineral soil surface and a depth of 100 1. 5 percent or more (by volume) plinthite; and cm. Humic Acrustox 2. Redox depletions with a color value, moist, of 4 or more and chroma of 2 or less and also aquic conditions ECBM. Other Acrustox that have, in all horizons at a depth for some time in normal years (or artificial drainage). between 25 and 125 cm from the mineral soil surface, more than Plinthaquic Eutrustox 50 percent colors that have both of the following: ECCF. Other Eutrustox that have 5 percent or more (by 1. Hue of 2.5YR or redder; and volume) plinthite in one or more horizons within 125 cm of 2. A value, moist, of 3 or less. the mineral soil surface. Rhodic Acrustox Plinthic Eutrustox

ECBN. Other Acrustox that have 50 percent or more hue of ECCG. Other Eutrustox that have, in one or more horizons 7.5YR or yellower and a color value, moist, of 6 or more at a within 125 cm of the mineral soil surface, redox depletions depth between 25 and 125 cm from the mineral soil surface. with a color value, moist, of 4 or more and chroma of 2 or Xanthic Acrustox less and also aquic conditions for some time in normal years (or artificial drainage). ECBO. Other Acrustox. Aquic Eutrustox Typic Acrustox Oxisols 253

ECCH. Other Eutrustox that have a kandic horizon within ECCP. Other Eutrustox. 150 cm of the mineral soil surface. Typic Eutrustox Kandiustalfic Eutrustox Haplustox ECCI. Other Eutrustox that have both: Key to Subgroups 1. 16 kg/m2 or more organic carbon between the mineral ECEA. Haplustox that have, within 125 cm of the mineral soil soil surface and a depth of 100 cm; and surface, both: 2. An oxic horizon that has its lower boundary within 125 1. A petroferric contact; and cm of the mineral soil surface. Humic Inceptic Eutrustox 2. Redox depletions with a color value, moist, of 4 or more and chroma of 2 or less and also aquic conditions for some ECCJ. Other Eutrustox that have an oxic horizon that has its time in normal years (or artificial drainage). lower boundary within 125 cm of the mineral soil surface. Aquic Petroferric Haplustox Inceptic Eutrustox ECEB. Other Haplustox that have a petroferric contact within ECCK. Other Eutrustox that have both: 125 cm of the mineral soil surface. Petroferric Haplustox 1. 16 kg/m2 or more organic carbon between the mineral soil surface and a depth of 100 cm; and ECEC. Other Haplustox that have, within 125 cm of the 2. In all horizons at a depth between 25 and 125 cm from mineral soil surface, both: the mineral soil surface, more than 50 percent colors that 1. A lithic contact; and have both of the following: 2. Redox depletions with a color value, moist, of 4 or more a. Hue of 2.5YR or redder; and and chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). b. A value, moist, of 3 or less. Aquic Lithic Haplustox Humic Rhodic Eutrustox ECED. Other Haplustox that have a lithic contact within 125 ECCL. Other Eutrustox that have both: cm of the mineral soil surface. 1. 16 kg/m2 or more organic carbon between the mineral Lithic Haplustox soil surface and a depth of 100 cm; and ECEE. Other Haplustox that have, in one or more horizons 2. 50 percent or more hue of 7.5YR or yellower and a color within 125 cm of the mineral soil surface, both: value, moist, of 6 or more at a depth between 25 and 125 cm from the mineral soil surface. 1. 5 percent or more (by volume) plinthite; and Humic Xanthic Eutrustox 2. Redox depletions with a color value, moist, of 4 or more O and chroma of 2 or less and also aquic conditions for some X 2 I ECCM. Other Eutrustox that have 16 kg/m or more organic time in normal years (or artificial drainage). carbon between the mineral soil surface and a depth of 100 cm. Plinthaquic Haplustox Humic Eutrustox ECEF. Other Haplustox that have 5 percent or more (by ECCN. Other Eutrustox that have, in all horizons at a depth volume) plinthite in one or more horizons within 125 cm of the between 25 and 125 cm from the mineral soil surface, more than mineral soil surface. 50 percent colors that have both of the following: Plinthic Haplustox 1. Hue of 2.5YR or redder; and ECEG. Other Haplustox that have, within 125 cm of the 2. A value, moist, of 3 or less. mineral soil surface, both: Rhodic Eutrustox 1. The lower boundary of the oxic horizon; and ECCO. Other Eutrustox that have 50 percent or more hue of 2. Redox depletions with a color value, moist, of 4 or more 7.5YR or yellower and a color value, moist, of 6 or more at a and chroma of 2 or less and also aquic conditions for some depth between 25 and 125 cm from the mineral soil surface. time in normal years (or artificial drainage). Xanthic Eutrustox Aqueptic Haplustox 254 Keys to Soil Taxonomy

ECEH. Other Haplustox that have, in one or more horizons 7.5YR or yellower and a color value, moist, of 6 or more at a within 125 cm of the mineral soil surface, redox depletions with depth between 25 and 125 cm from the mineral soil surface. a color value, moist, of 4 or more and chroma of 2 or less and Xanthic Haplustox also aquic conditions for some time in normal years (or artificial drainage). ECEP. Other Haplustox. Aquic Haplustox Typic Haplustox

ECEI. Other Haplustox that are saturated with water in one or Kandiustox more layers within 100 cm of the mineral soil surface in normal years for either or both: Key to Subgroups 1. 20 or more consecutive days; or ECDA. Kandiustox that have, within 125 cm of the mineral 2. 30 or more cumulative days. soil surface, both: Oxyaquic Haplustox 1. A petroferric contact; and

ECEJ. Other Haplustox that have an oxic horizon that has its 2. Redox depletions with a color value, moist, of 4 or more lower boundary within 125 cm of the mineral soil surface. and chroma of 2 or less and also aquic conditions for some Inceptic Haplustox time in normal years (or artificial drainage). Aquic Petroferric Kandiustox ECEK. Other Haplustox that have both: ECDB. Other Kandiustox that have a petroferric contact 2 1. 16 kg/m or more organic carbon between the mineral within 125 cm of the mineral soil surface. soil surface and a depth of 100 cm; and Petroferric Kandiustox 2. In all horizons at a depth between 25 and 125 cm from the mineral soil surface, more than 50 percent colors that ECDC. Other Kandiustox that have, within 125 cm of the have both of the following: mineral soil surface, both: a. Hue of 2.5YR or redder; and 1. A lithic contact; and b. A value, moist, of 3 or less. 2. Redox depletions with a color value, moist, of 4 or more Humic Rhodic Haplustox and chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). ECEL. Other Haplustox that have both: Aquic Lithic Kandiustox 1. 16 kg/m2 or more organic carbon between the mineral ECDD. Other Kandiustox that have a lithic contact within 125 soil surface and a depth of 100 cm; and cm of the mineral soil surface. 2. 50 percent or more hue of 7.5YR or yellower and a color Lithic Kandiustox value, moist, of 6 or more at a depth between 25 and 125 cm from the mineral soil surface. ECDE. Other Kandiustox that have, in one or more horizons Humic Xanthic Haplustox within 125 cm of the mineral soil surface, both:

ECEM. Other Haplustox that have 16 kg/m2 or more organic 1. 5 percent or more (by volume) plinthite; and carbon between the mineral soil surface and a depth of 100 cm. 2. Redox depletions with a color value, moist, of 4 or more Humic Haplustox and chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). ECEN. Other Haplustox that have, in all horizons at a depth Plinthaquic Kandiustox between 25 and 125 cm from the mineral soil surface, more than 50 percent colors that have both of the following: ECDF. Other Kandiustox that have 5 percent or more (by 1. Hue of 2.5YR or redder; and volume) plinthite in one or more horizons within 125 cm of the mineral soil surface. 2. A value, moist, of 3 or less. Plinthic Kandiustox Rhodic Haplustox ECDG. Other Kandiustox that have, in one or more horizons ECEO. Other Haplustox that have 50 percent or more hue of within 125 cm of the mineral soil surface, redox depletions with Oxisols 255

a color value, moist, of 4 or more and chroma of 2 or less and 1. Hue of 2.5YR or redder; and also aquic conditions for some time in normal years (or artificial drainage). 2. A value, moist, of 3 or less. Aquic Kandiustox Rhodic Kandiustox

ECDH. Other Kandiustox that have both: ECDL. Other Kandiustox that have 50 percent or more hue of 7.5YR or yellower and a color value, moist, of 6 or more at a 1. 16 kg/m2 or more organic carbon between the mineral depth between 25 and 125 cm from the mineral soil surface. soil surface and a depth of 100 cm; and Xanthic Kandiustox 2. In all horizons at a depth between 25 and 125 cm from the mineral soil surface, more than 50 percent colors that ECDM. Other Kandiustox. have both of the following: Typic Kandiustox a. Hue of 2.5YR or redder; and Sombriustox b. A value, moist, of 3 or less. Key to Subgroups Humic Rhodic Kandiustox ECAA. Sombriustox that have a petroferric contact within 125 ECDI. Other Kandiustox that have both: cm of the mineral soil surface. Petroferric Sombriustox 1. 16 kg/m2 or more organic carbon between the mineral soil surface and a depth of 100 cm; and ECAB. Other Sombriustox that have a lithic contact within 2. 50 percent or more hue of 7.5YR or yellower and a color 125 cm of the mineral soil surface. value, moist, of 6 or more at a depth between 25 and 125 cm Lithic Sombriustox from the mineral soil surface. Humic Xanthic Kandiustox ECAC. Other Sombriustox that have 16 kg/m2 or more organic carbon between the mineral soil surface and a depth of 100 cm. ECDJ. Other Kandiustox that have 16 kg/m2 or more organic Humic Sombriustox carbon between the mineral soil surface and a depth of 100 cm. ECAD. Other Sombriustox. Humic Kandiustox Typic Sombriustox

ECDK. Other Kandiustox that have, in all horizons at a depth between 25 and 125 cm from the mineral soil surface, more than 50 percent colors that have both of the following:

O X I

257

CHAPTER 14 Spodosols

Key to Suborders CAE. Other Aquods that have, in 90 percent or more of each pedon, a cemented horizon within 100 cm of the mineral soil CA. Spodosols that have aquic conditions for some time in surface. normal years (or artificial drainage) in one or more horizons Duraquods, p. 258 within 50 cm of the mineral soil surface and have one or both of the following: CAF. Other Aquods that have episaturation. 1. A histic epipedon; or Epiaquods, p. 259

2. Within 50 cm of the mineral soil surface, redoximorphic CAG. Other Aquods. features in an albic or a spodic horizon. Endoaquods, p. 258 Aquods, p. 257 Alaquods CB. Other Spodosols that have a gelic soil temperature regime. Key to Subgroups Gelods, p. 261 CABA. Alaquods that have a lithic contact within 50 cm of the mineral soil surface. CC. Other Spodosols that have a cryic soil temperature Lithic Alaquods regime. Cryods, p. 259 CABB. Other Alaquods that have, in 90 percent or more of each pedon, a cemented horizon within 100 cm of the mineral CD. Other Spodosols that have 6.0 percent or more organic soil surface. carbon in a layer 10 cm or more thick within the spodic horizon. Duric Alaquods Humods, p. 261 CABC. Other Alaquods that have a histic epipedon. CE. Other Spodosols. Histic Alaquods Orthods, p. 262 CABD. Other Alaquods that: Aquods 1. Within 200 cm of the mineral soil surface, have an Key to Great Groups argillic or kandic horizon that has a base saturation (by sum of cations) of 35 percent or more in some part; and S CAA. Aquods that have a cryic soil temperature regime. P O Cryaquods, p. 258 2. Meet sandy or sandy-skeletal particle-size class criteria throughout a layer extending from the mineral soil surface to CAB. Other Aquods that have less than 0.10 percent iron the top of a spodic horizon at a depth of 75 to 125 cm. (by ammonium oxalate) in 75 percent or more of the spodic Alfic Arenic Alaquods horizon. Alaquods, p. 257 CABE. Other Alaquods that: 1. Have an argillic or kandic horizon within 200 cm of the CAC. Other Aquods that have a fragipan within 100 cm of the mineral soil surface; and mineral soil surface. Fragiaquods, p. 259 2. Meet sandy or sandy-skeletal particle-size class criteria throughout a layer extending from the mineral soil surface to CAD. Other Aquods that have a placic horizon within 100 cm the top of a spodic horizon at a depth of 75 to 125 cm. of the mineral soil surface in 50 percent or more of each pedon. Arenic Ultic Alaquods Placaquods, p. 259 258 Keys to Soil Taxonomy

CABF. Other Alaquods that: throughout horizons that have a total thickness of 25 cm or more within 75 cm either of the mineral soil surface or of the 1. Have an umbric epipedon; and top of an organic layer with andic soil properties, whichever is 2. Meet sandy or sandy-skeletal particle-size class criteria shallower. throughout a layer extending from the mineral soil surface to Andic Cryaquods the top of a spodic horizon at a depth of 75 cm or more. Arenic Umbric Alaquods CAAE. Other Cryaquods that have a spodic horizon less than 10 cm thick in 50 percent or more of each pedon. CABG. Other Alaquods that meet sandy or sandy-skeletal Entic Cryaquods particle-size class criteria throughout a layer extending from the mineral soil surface to the top of a spodic horizon at a depth of CAAF. Other Cryaquods. 75 to 125 cm. Typic Cryaquods Arenic Alaquods Duraquods CABH. Other Alaquods that meet sandy or sandy-skeletal particle-size class criteria throughout a layer extending from the Key to Subgroups mineral soil surface to the top of a spodic horizon at a depth of CAEA. Duraquods that have a histic epipedon. 125 cm or more. Grossarenic Alaquods Histic Duraquods

CABI. Other Alaquods that have, within 200 cm of the CAEB. Other Duraquods that have andic soil properties mineral soil surface, an argillic or kandic horizon that has a base throughout horizons that have a total thickness of 25 cm or saturation (by sum of cations) of 35 percent or more in some more within 75 cm either of the mineral soil surface or of the part. top of an organic layer with andic soil properties, whichever is Alfic Alaquods shallower. Andic Duraquods CABJ. Other Alaquods that have an argillic or kandic horizon within 200 cm of the mineral soil surface. CAEC. Other Duraquods. Ultic Alaquods Typic Duraquods

CABK. Other Alaquods that have an ochric epipedon. Endoaquods Aeric Alaquods Key to Subgroups CABL. Other Alaquods. CAGA. Endoaquods that have a lithic contact within 50 cm of Typic Alaquods the mineral soil surface. Lithic Endoaquods Cryaquods CAGB. Other Endoaquods that have a histic epipedon. Key to Subgroups Histic Endoaquods CAAA. Cryaquods that have a lithic contact within 50 cm of the mineral soil surface. CAGC. Other Endoaquods that have andic soil properties Lithic Cryaquods throughout horizons that have a total thickness of 25 cm or more within 75 cm either of the mineral soil surface or of the CAAB. Other Cryaquods that have a placic horizon within top of an organic layer with andic soil properties, whichever is 100 cm of the mineral soil surface in 50 percent or more of each shallower. pedon. Andic Endoaquods Placic Cryaquods CAGD. Other Endoaquods that have an argillic or kandic CAAC. Other Cryaquods that have, in 90 percent or more of horizon within 200 cm of the mineral soil surface. each pedon, a cemented horizon within 100 cm of the mineral Argic Endoaquods soil surface. Duric Cryaquods CAGE. Other Endoaquods that have an umbric epipedon. Umbric Endoaquods CAAD. Other Cryaquods that have andic soil properties Spodosols 259

CAGF. Other Endoaquods. Placaquods Typic Endoaquods Key to Subgroups Epiaquods CADA. Placaquods that have andic soil properties throughout horizons that have a total thickness of 25 cm or Key to Subgroups more within 75 cm either of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is CAFA. Epiaquods that have a lithic contact within 50 cm of shallower. the mineral soil surface. Andic Placaquods Lithic Epiaquods CADB. Other Placaquods. CAFB. Other Epiaquods that have a histic epipedon. Typic Placaquods Histic Epiaquods

CAFC. Other Epiaquods that have andic soil properties Cryods throughout horizons that have a total thickness of 25 cm or Key to Great Groups more within 75 cm either of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is CCA. Cryods that have a placic horizon within 100 cm of the shallower. mineral soil surface in 50 percent or more of each pedon. Andic Epiaquods Placocryods, p. 261

CAFD. Other Epiaquods that have, within 200 cm of the CCB. Other Cryods that have, in 90 percent or more of each mineral soil surface, an argillic or kandic horizon that has a base pedon, a cemented horizon within 100 cm of the mineral soil saturation (by sum of cations) of 35 percent or more in some surface. part. Duricryods, p. 259 Alfic Epiaquods CCC. Other Cryods that have 6.0 percent or more organic CAFE. Other Epiaquods that have an argillic or kandic carbon throughout a layer 10 cm or more thick within the spodic horizon within 200 cm of the mineral soil surface. horizon. Ultic Epiaquods Humicryods, p. 260

CAFF. Other Epiaquods that have an umbric epipedon. CCD. Other Cryods. Umbric Epiaquods Haplocryods, p. 260 CAFG. Other Epiaquods. Duricryods Typic Epiaquods Key to Subgroups Fragiaquods CCBA. Duricryods that have both: Key to Subgroups 1. Redoximorphic features in one or more horizons within 75 cm of the mineral soil surface and also aquic conditions CACA. Fragiaquods that have a histic epipedon. S for some time in normal years (or artificial drainage);and P Histic Fragiaquods O 2. Andic soil properties throughout horizons that have a CACB. Other Fragiaquods that have a surface horizon 30 cm total thickness of 25 cm or more within 75 cm either of the or more thick that meets all of the requirements for a plaggen mineral soil surface or of the top of an organic layer with epipedon except thickness. andic soil properties, whichever is shallower. Plagganthreptic Fragiaquods Aquandic Duricryods

CACC. Other Fragiaquods that have an argillic or kandic CCBB. Other Duricryods that have andic soil properties horizon within 200 cm of the mineral soil surface. throughout horizons that have a total thickness of 25 cm or Argic Fragiaquods more within 75 cm either of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is CACD. Other Fragiaquods. shallower. Typic Fragiaquods Andic Duricryods 260 Keys to Soil Taxonomy

CCBC. Other Duricryods that have redoximorphic features in CCDF. Other Haplocryods that are saturated with water in one or more horizons within 75 cm of the mineral soil surface one or more layers within 100 cm of the mineral soil surface in and also aquic conditions for some time in normal years (or normal years for either or both: artificial drainage). 1. 20 or more consecutive days; or Aquic Duricryods 2. 30 or more cumulative days. CCBD. Other Duricryods that are saturated with water in Oxyaquic Haplocryods one or more layers within 100 cm of the mineral soil surface in normal years for either or both: CCDG. Other Haplocryods that have 1.1 percent or less organic carbon in the upper 10 cm of the spodic horizon. 1. 20 or more consecutive days; or Entic Haplocryods 2. 30 or more cumulative days. Oxyaquic Duricryods CCDH. Other Haplocryods. Typic Haplocryods CCBE. Other Duricryods that have 6.0 percent or more organic carbon throughout a layer 10 cm or more thick within Humicryods the spodic horizon. Humic Duricryods Key to Subgroups CCCA. Humicryods that have a lithic contact within 50 cm of CCBF. Other Duricryods. the mineral soil surface. Typic Duricryods Lithic Humicryods Haplocryods CCCB. Other Humicryods that have both: Key to Subgroups 1. Redoximorphic features in one or more horizons within CCDA. Haplocryods that have a lithic contact within 50 cm of 75 cm of the mineral soil surface and also aquic conditions the mineral soil surface. for some time in normal years (or artificial drainage);and Lithic Haplocryods 2. Andic soil properties throughout horizons that have a total thickness of 25 cm or more within 75 cm either of the CCDB. Other Haplocryods that have both: mineral soil surface or of the top of an organic layer with 1. Redoximorphic features in one or more horizons within andic soil properties, whichever is shallower. 75 cm of the mineral soil surface and also aquic conditions Aquandic Humicryods for some time in normal years (or artificial drainage);and CCCC. Other Humicryods that have andic soil properties 2. Andic soil properties throughout horizons that have a throughout horizons that have a total thickness of 25 cm or total thickness of 25 cm or more within 75 cm either of the more within 75 cm either of the mineral soil surface or of the mineral soil surface or of the top of an organic layer with top of an organic layer with andic soil properties, whichever is andic soil properties, whichever is shallower. shallower. Aquandic Haplocryods Andic Humicryods

CCDC. Other Haplocryods that have andic soil properties CCCD. Other Humicryods that have a folistic epipedon. throughout horizons that have a total thickness of 25 cm or Folistic Humicryods more within 75 cm either of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is CCCE. Other Humicryods that have redoximorphic features in shallower. one or more horizons within 75 cm of the mineral soil surface Andic Haplocryods and also aquic conditions for some time in normal years (or artificial drainage). CCDD. Other Haplocryods that have a folistic epipedon. Aquic Humicryods Folistic Haplocryods CCCF. Other Humicryods that are saturated with water in CCDE. Other Haplocryods that have redoximorphic features one or more layers within 100 cm of the mineral soil surface in in one or more horizons within 75 cm of the mineral soil surface normal years for either or both: and also aquic conditions for some time in normal years (or artificial drainage). 1. 20 or more consecutive days; or Aquic Haplocryods Spodosols 261

2. 30 or more cumulative days. CBBD. Other Haplogelods that have gelic materials within Oxyaquic Humicryods 200 cm of the mineral soil surface. Turbic Haplogelods CCCG. Other Humicryods. Typic Humicryods CBBE. Other Haplogelods. Typic Haplogelods Placocryods Humigelods Key to Subgroups Key to Subgroups CCAA. Placocryods that have andic soil properties throughout horizons that have a total thickness of 25 cm or more within 75 CBAA. Humigelods that have a lithic contact within 50 cm of cm either of the mineral soil surface or of the top of an organic the mineral soil surface. layer with andic soil properties, whichever is shallower. Lithic Humigelods Andic Placocryods CBAB. Other Humigelods that have andic soil properties CCAB. Other Placocryods that have 6.0 percent or more throughout horizons that have a total thickness of 25 cm or organic carbon in a layer 10 cm or more thick within the spodic more within 75 cm either of the mineral soil surface or of the horizon. top of an organic layer with andic soil properties, whichever is Humic Placocryods shallower. Andic Humigelods CCAC. Other Placocryods. Typic Placocryods CBAC. Other Humigelods that have redoximorphic features in one or more horizons within 75 cm of the mineral soil surface Gelods and also aquic conditions for some time in normal years (or artificial drainage). Key to Great Groups Aquic Humigelods CBA. Gelods that have 6.0 percent or more organic carbon throughout a layer 10 cm or more thick within the spodic CBAD. Other Humigelods that have gelic materials within horizon. 200 cm of the mineral soil surface. Humigelods, p. 261 Turbic Humigelods

CBB. Other Gelods. CBAE. Other Humigelods. Haplogelods, p. 261 Typic Humigelods

Haplogelods Humods Key to Subgroups Key to Great Groups CBBA. Haplogelods that have a lithic contact within 50 cm of CDA. Humods that have a placic horizon within 100 cm of the the mineral soil surface. mineral soil surface in 50 percent or more of each pedon. S P Lithic Haplogelods Placohumods, p. 262 O

CBBB. Other Haplogelods that have andic soil properties CDB. Other Humods that have, in 90 percent or more of each throughout horizons that have a total thickness of 25 cm or pedon, a cemented horizon within 100 cm of the mineral soil more within 75 cm either of the mineral soil surface or of the surface. top of an organic layer with andic soil properties, whichever is Durihumods, p. 262 shallower. Andic Haplogelods CDC. Other Humods that have a fragipan within 100 cm of the mineral soil surface. CBBC. Other Haplogelods that have redoximorphic features Fragihumods, p. 262 in one or more horizons within 75 cm of the mineral soil surface and also aquic conditions for some time in normal years (or CDD. Other Humods. artificial drainage). Haplohumods, p. 262 Aquic Haplogelods 262 Keys to Soil Taxonomy

Durihumods Orthods Key to Subgroups Key to Great Groups CDBA. Durihumods that have andic soil properties throughout CEA. Orthods that have, in 50 percent or more of each pedon, horizons that have a total thickness of 25 cm or more within 75 a placic horizon within 100 cm of the mineral soil surface. cm either of the mineral soil surface or of the top of an organic Placorthods, p. 265 layer with andic soil properties, whichever is shallower. Andic Durihumods CEB. Other Orthods that have, in 90 percent or more of each pedon, a cemented horizon within 100 cm of the mineral soil CDBB. Other Durihumods. surface. Typic Durihumods Durorthods, p. 263

Fragihumods CEC. Other Orthods that have a fragipan within 100 cm of the mineral soil surface. Key to Subgroups Fragiorthods, p. 263 CDCA. All Fragihumods (provisionally). Typic Fragihumods CED. Other Orthods that have less than 0.10 percent iron (by ammonium oxalate) in 75 percent or more of the spodic Haplohumods horizon. Alorthods, p. 262 Key to Subgroups CDDA. Haplohumods that have a lithic contact within 50 cm CEE. Other Orthods. of the mineral soil surface. Haplorthods, p. 264 Lithic Haplohumods Alorthods CDDB. Other Haplohumods that have andic soil properties Key to Subgroups throughout horizons that have a total thickness of 25 cm or more within 75 cm either of the mineral soil surface or of the CEDA. Alorthods that are saturated with water in one or more top of an organic layer with andic soil properties, whichever is layers within 100 cm of the mineral soil surface in normal years shallower. for either or both: Andic Haplohumods 1. 20 or more consecutive days; or CDDC. Other Haplohumods that have a surface horizon 2. 30 or more cumulative days. 30 cm or more thick that meets all of the requirements for a Oxyaquic Alorthods plaggen epipedon except thickness. Plagganthreptic Haplohumods CEDB. Other Alorthods that: 1. Meet sandy or sandy-skeletal particle-size class criteria CDDD. Other Haplohumods. throughout a layer extending from the mineral soil surface to Typic Haplohumods the top of a spodic horizon at a depth of 75 to 125 cm; and Placohumods 2. Have an argillic or kandic horizon below the spodic horizon. Key to Subgroups Arenic Ultic Alorthods CDAA. Placohumods that have andic soil properties CEDC. Other Alorthods that meet sandy or sandy-skeletal throughout horizons that have a total thickness of 25 cm or particle-size class criteria throughout a layer extending from the more within 75 cm either of the mineral soil surface or of the mineral soil surface to the top of a spodic horizon at a depth of top of an organic layer with andic soil properties, whichever is 75 to 125 cm. shallower. Arenic Alorthods Andic Placohumods CEDD. Other Alorthods that: CDAB. Other Placohumods. Typic Placohumods 1. Meet sandy or sandy-skeletal particle-size class criteria Spodosols 263

throughout a layer extending from the mineral soil surface to also aquic conditions for some time in normal years (or artificial the top of a spodic horizon at a depth of 125 cm or more; and drainage). Aquic Fragiorthods 2. Have, in 10 percent or more of each pedon, less than 3.0 percent organic carbon in the upper 2 cm of the spodic CECB. Other Fragiorthods that: horizon. Entic Grossarenic Alorthods 1. Are saturated with water in one or more layers within 100 cm of the mineral soil surface in normal years for either CEDE. Other Alorthods that have, in 10 percent or more of or both: each pedon, less than 3.0 percent organic carbon in the upper 2 a. 20 or more consecutive days; or cm of the spodic horizon. Entic Alorthods b. 30 or more cumulative days; and 2. Have, within 200 cm of the mineral soil surface, an CEDF. Other Alorthods that meet sandy or sandy-skeletal argillic or kandic horizon that has a base saturation (by sum particle-size class criteria throughout a layer extending from the of cations) of 35 percent or more in some part. mineral soil surface to the top of a spodic horizon at a depth of Alfic Oxyaquic Fragiorthods 125 cm or more. Grossarenic Alorthods CECC. Other Fragiorthods that are saturated with water in one or more layers within 100 cm of the mineral soil surface in CEDG. Other Alorthods that have a surface horizon 30 cm normal years for either or both: or more thick that meets all of the requirements for a plaggen epipedon except thickness. 1. 20 or more consecutive days; or Plagganthreptic Alorthods 2. 30 or more cumulative days. Oxyaquic Fragiorthods CEDH. Other Alorthods that have, within 200 cm of the mineral soil surface, an argillic or kandic horizon that has a base CECD. Other Fragiorthods that have a surface horizon 30 cm saturation (by sum of cations) of 35 percent or more in some or more thick that meets all of the requirements for a plaggen part. epipedon except thickness. Alfic Alorthods Plagganthreptic Fragiorthods

CEDI. Other Alorthods that have an argillic or kandic horizon CECE. Other Fragiorthods that have, within 200 cm of the within 200 cm of the mineral soil surface. mineral soil surface, an argillic or kandic horizon that has a base Ultic Alorthods saturation (by sum of cations) of 35 percent or more in some part. CEDJ. Other Alorthods. Alfic Fragiorthods Typic Alorthods CECF. Other Fragiorthods that have an argillic or kandic Durorthods horizon within 200 cm of the mineral soil surface. Ultic Fragiorthods Key to Subgroups S P CEBA. Durorthods that have andic soil properties throughout CECG. Other Fragiorthods that have a spodic horizon that has O horizons that have a total thickness of 25 cm or more within 75 one of the following: cm either of the mineral soil surface or of the top of an organic 1. A texture class of very fine sand, loamy very fine sand, layer with andic soil properties, whichever is shallower. or finer;and Andic Durorthods a. A thickness of 10 cm or less; and CEBB. Other Durorthods. b. A weighted average of less than 1.2 percent organic Typic Durorthods carbon; and c. Within the upper 7.5 cm, either or both a moist color Fragiorthods value or chroma of 4 or more (crushed and smoothed Key to Subgroups sample); or CECA. Fragiorthods that have redoximorphic features in one 2. A texture class of loamy fine sand, fine sand, or coarser or more horizons within 75 cm of the mineral soil surface and 264 Keys to Soil Taxonomy

and either or both a moist color value or chroma of 4 or more CEEE. Other Haplorthods that have redoximorphic features in (crushed and smoothed sample) in the upper 2.5 cm. one or more horizons within 75 cm of the mineral soil surface Entic Fragiorthods and also aquic conditions for some time in normal years (or artificial drainage) and either: CECH. Other Fragiorthods. Typic Fragiorthods 1. A spodic horizon with a texture class of very fine sand, loamy very fine sand, or finer;and Haplorthods a. A thickness of 10 cm or less; and Key to Subgroups b. A weighted average of less than 1.2 percent organic CEEA. Haplorthods that have a lithic contact within 50 cm of carbon; and the mineral soil surface and either: c. Within the upper 7.5 cm, either or both a moist color 1. A spodic horizon with a texture class of very fine sand, value or chroma of 4 or more (crushed and smoothed loamy very fine sand, or finer;and sample); or a. A thickness of 10 cm or less; and 2. A spodic horizon with a texture class of loamy fine sand, b. A weighted average of less than 1.2 percent organic fine sand, or coarser andeither or both a moist color value or chroma of 4 or more (crushed and smoothed sample) in the carbon; and upper 2.5 cm. c. Within the upper 7.5 cm, either or both a moist color Aquentic Haplorthods value or chroma of 4 or more (crushed and smoothed sample); or CEEF. Other Haplorthods that have redoximorphic features in 2. A spodic horizon with a texture class of loamy fine sand, one or more horizons within 75 cm of the mineral soil surface fine sand, or coarser andeither or both a moist color value or and also aquic conditions for some time in normal years (or chroma of 4 or more (crushed and smoothed sample) in the artificial drainage). upper 2.5 cm. Aquic Haplorthods Entic Lithic Haplorthods CEEG. Other Haplorthods that have: CEEB. Other Haplorthods that have a lithic contact within 50 1. Within 200 cm of the mineral soil surface, an argillic or cm of the mineral soil surface. kandic horizon that has a base saturation (by sum of cations) Lithic Haplorthods of 35 percent or more in some part; and CEEC. Other Haplorthods that have both: 2. Saturation with water in one or more layers within 100 cm of the mineral soil surface in normal years for either or 1. Fragic soil properties: both: a. In 30 percent or more of the volume of a layer 15 cm a. 20 or more consecutive days; or or more thick that has its upper boundary within 100 cm of the mineral soil surface; or b. 30 or more cumulative days. Alfic Oxyaquic Haplorthods b. In 60 percent or more of the volume of a layer 15 cm or more thick; and CEEH. Other Haplorthods that have: 2. Redoximorphic features in one or more horizons within 1. Within 200 cm of the mineral soil surface, an argillic or 75 cm of the mineral soil surface and also aquic conditions kandic horizon; and for some time in normal years (or artificial drainage). Fragiaquic Haplorthods 2. Saturation with water in one or more layers within 100 cm of the mineral soil surface in normal years for either or CEED. Other Haplorthods that have both: both: 1. Redoximorphic features in one or more horizons within a. 20 or more consecutive days; or 75 cm of the mineral soil surface and also aquic conditions b. 30 or more cumulative days. for some time in normal years (or artificial drainage);and Oxyaquic Ultic Haplorthods 2. Within 200 cm of the mineral soil surface, an argillic or CEEI. Other Haplorthods that have fragic soil properties kandic horizon that has a base saturation (by sum of cations) either: of 35 percent or more in some part. Aqualfic Haplorthods 1. In 30 percent or more of the volume of a layer 15 cm or Spodosols 265

more thick that has its upper boundary within 100 cm of the CEEN. Other Haplorthods that have, within 200 cm of the mineral soil surface; or mineral soil surface, an argillic or kandic horizon that has a base saturation (by sum of cations) of 35 percent or more in some 2. In 60 percent or more of the volume of a layer 15 cm or part. more thick. Alfic Haplorthods Fragic Haplorthods CEEO. Other Haplorthods that have an argillic or kandic CEEJ. Other Haplorthods that have both: horizon within 200 cm of the mineral soil surface. 1. Saturation with water in 1 or more layers within 100 cm Ultic Haplorthods of the mineral soil surface in normal years for either or both: CEEP. Other Haplorthods that have a spodic horizon that has a. 20 or more consecutive days; or one of the following: b. 30 or more cumulative days; and 1. A texture class of very fine sand, loamy very fine sand, 2. Below the spodic horizon but not below an argillic or finer;and horizon, lamellae (two or more) within 200 cm of the mineral a. A thickness of 10 cm or less; and soil surface. Lamellic Oxyaquic Haplorthods b. A weighted average of less than 1.2 percent organic carbon; and CEEK. Other Haplorthods that, below the spodic horizon c. Within the upper 7.5 cm, either or both a moist color but not below an argillic horizon, have lamellae (two or more) value or chroma of 4 or more (crushed and smoothed within 200 cm of the mineral soil surface. sample); or Lamellic Haplorthods 2. A texture class of loamy fine sand, fine sand, or coarser CEEL. Other Haplorthods that are saturated with water in and either or both a moist color value or chroma of 4 or more one or more layers within 100 cm of the mineral soil surface in (crushed and smoothed sample) in the upper 2.5 cm. normal years for either or both: Entic Haplorthods

1. 20 or more consecutive days; or CEEQ. Other Haplorthods. 2. 30 or more cumulative days. Typic Haplorthods Oxyaquic Haplorthods Placorthods CEEM. Other Haplorthods that have andic soil properties throughout horizons that have a total thickness of 25 cm or Key to Subgroups more within 75 cm either of the mineral soil surface or of the CEAA. All Placorthods (provisionally). top of an organic layer with andic soil properties, whichever is Typic Placorthods shallower. Andic Haplorthods

S P O

267

CHAPTER 15 Ultisols

Key to Suborders Aquults HA. Ultisols that have aquic conditions for some time in Key to Great Groups normal years (or artificial drainage) in one or more horizons within 50 cm of the mineral soil surface and one or both of the HAA. Aquults that have one or more horizons within 150 following: cm of the mineral soil surface in which plinthite either forms a continuous phase or constitutes one-half or more of the volume. 1. Redoximorphic features in all layers between either the Plinthaquults, p. 271 lower boundary of an Ap horizon or a depth of 25 cm from the mineral soil surface, whichever is deeper, and a depth of HAB. Other Aquults that have a fragipan within 100 cm of the 40 cm and one of the following within the upper 12.5 cm of mineral soil surface. the argillic or kandic horizon: Fragiaquults, p. 269 a. Redox concentrations and 50 percent or more redox depletions with chroma of 2 or less either on faces of peds HAC. Other Aquults that have an abrupt textural change or in the matrix; or between the ochric epipedon or albic horizon and the argillic or kandic horizon and have a saturated hydraulic conductivity of b. 50 percent or more redox depletions with chroma of 1 0.4 cm/hr or slower (moderately low or lower Ksat class) in the or less either on faces of peds or in the matrix; or argillic or kandic horizon. c. Distinct or prominent redox concentrations and 50 Albaquults, p. 268 percent or more hue of 2.5Y or 5Y in the matrix and also a thermic, isothermic, or warmer soil temperature regime; HAD. Other Aquults that: or 1. Do not have a densic, lithic, paralithic, or petroferric 2. Within 50 cm of the mineral soil surface, enough active contact within 150 cm of the mineral soil surface; and ferrous iron to give a positive reaction to alpha,alpha- 2. Have a kandic horizon; and dipyridyl at a time when the soil is not being irrigated. Aquults, p. 267 3. Within 150 cm of the mineral soil surface, either: a. With increasing depth, do not have a clay decrease HB. Other Ultisols that have one or both of the following: of 20 percent or more (relative) from the maximum clay 1. 0.9 percent (by weighted average) or more organic content; or carbon in the upper 15 cm of the argillic or kandic horizon; b. Have 5 percent or more (by volume) clay depletions or on faces of peds in the layer that has a 20 percent lower 2. 12 kg/m2 or more organic carbon between the mineral clay content and, below that layer, a clay increase of 3 U soil surface and a depth of 100 cm. percent or more (absolute) in the fine-earth fraction. L Humults, p. 271 Kandiaquults, p. 269 T

HC. Other Ultisols that have a udic soil moisture regime. HAE. Other Aquults that have a kandic horizon. Udults, p. 274 Kanhaplaquults, p. 269

HD. Other Ultisols that have an ustic soil moisture regime. HAF. Other Aquults that: Ustults, p. 281 1. Do not have a densic, lithic, paralithic, or petroferric HE. Other Ultisols. contact within 150 cm of the mineral soil surface; and Xerults, p. 285 2. Within 150 cm of the mineral soil surface, either: 268 Keys to Soil Taxonomy

a. With increasing depth, do not have a clay decrease HAIB. Other Endoaquults that meet sandy or sandy-skeletal of 20 percent or more (relative) from the maximum clay particle-size class criteria throughout a layer extending from the content; or mineral soil surface to the top of an argillic horizon at a depth of 100 cm or more. b. Have 5 percent or more (by volume) clay depletions Grossarenic Endoaquults on faces of peds in the layer that has a 20 percent lower clay content and, below that layer, a clay increase of 3 HAIC. Other Endoaquults that have 50 percent or more percent or more (absolute) in the fine-earth fraction. chroma of 3 or more in one or more horizons between either Paleaquults, p. 270 the A or Ap horizon or a depth of 25 cm from the mineral soil surface, whichever is deeper, and a depth of 75 cm. HAG. Other Aquults that have an umbric or mollic epipedon. Aeric Endoaquults Umbraquults, p. 271 HAID. Other Endoaquults. HAH. Other Aquults that have episaturation. Typic Endoaquults Epiaquults, p. 268

HAI. Other Aquults. Epiaquults Endoaquults, p. 268 Key to Subgroups

Albaquults HAHA. Epiaquults that have one or both of the following: 1. Cracks within 125 cm of the mineral soil surface that are Key to Subgroups 5 mm or more wide through a thickness of 30 cm or more HACA. Albaquults that have one or both of the following: for some time in normal years and slickensides or wedge- shaped peds in a layer 15 cm or more thick that has its upper 1. Cracks within 125 cm of the mineral soil surface that are boundary within 125 cm of the mineral soil surface; or 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge- 2. A linear extensibility of 6.0 cm or more between the shaped peds in a layer 15 cm or more thick that has its upper mineral soil surface and either a depth of 100 cm or a densic, boundary within 125 cm of the mineral soil surface; or lithic, or paralithic contact, whichever is shallower. Vertic Epiaquults 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a densic, HAHB. Other Epiaquults that have: lithic, or paralithic contact, whichever is shallower. Vertic Albaquults 1. Fragic soil properties either: a. In 30 percent or more of the volume of a layer 15 cm HACB. Other Albaquults that have a kandic horizon. or more thick that has its upper boundary within 100 cm Kandic Albaquults of the mineral soil surface; or

HACC. Other Albaquults that have 50 percent or more chroma b. In 60 percent or more of the volume of a layer 15 cm of 3 or more in one or more horizons between either the A or or more thick; and Ap horizon or a depth of 25 cm from the mineral soil surface, 2. 50 percent or more chroma of 3 or more in one or more whichever is deeper, and a depth of 75 cm. horizons between either the A or Ap horizon or a depth of 25 Aeric Albaquults cm from the mineral soil surface, whichever is deeper, and a depth of 75 cm. HACD. Other Albaquults. Aeric Fragic Epiaquults Typic Albaquults HAHC. Other Epiaquults that meet sandy or sandy-skeletal Endoaquults particle-size class criteria throughout a layer extending from the mineral soil surface to the top of an argillic horizon at a depth of Key to Subgroups 50 to 100 cm. HAIA. Endoaquults that meet sandy or sandy-skeletal Arenic Epiaquults particle-size class criteria throughout a layer extending from the mineral soil surface to the top of an argillic horizon at a depth of HAHD. Other Epiaquults that meet sandy or sandy-skeletal 50 to 100 cm. particle-size class criteria throughout a layer extending from the Arenic Endoaquults Ultisols 269

mineral soil surface to the top of an argillic horizon at a depth of HADB. Other Kandiaquults that: 100 cm or more. 1. Meet sandy or sandy-skeletal particle-size class criteria Grossarenic Epiaquults throughout a layer extending from the mineral soil surface to HAHE. Other Epiaquults that have fragic soil properties the top of a kandic horizon at a depth of 50 to 100 cm; and either: 2. Have 5 percent or more (by volume) plinthite in one or 1. In 30 percent or more of the volume of a layer 15 cm or more horizons within 150 cm of the mineral soil surface. more thick that has its upper boundary within 100 cm of the Arenic Plinthic Kandiaquults mineral soil surface; or HADC. Other Kandiaquults that: 2. In 60 percent or more of the volume of a layer 15 cm or more thick. 1. Have a mollic or umbric epipedon; and Fragic Epiaquults 2. Meet sandy or sandy-skeletal particle-size class criteria throughout a layer extending from the mineral soil surface to HAHF. Other Epiaquults that have 50 percent or more chroma the top of a kandic horizon at a depth of 50 to 100 cm. of 3 or more in one or more horizons between either the A or Arenic Umbric Kandiaquults Ap horizon or a depth of 25 cm from the mineral soil surface, whichever is deeper, and a depth of 75 cm. HADD. Other Kandiaquults that meet sandy or sandy-skeletal Aeric Epiaquults particle-size class criteria throughout a layer extending from the mineral soil surface to the top of a kandic horizon at a depth of HAHG. Other Epiaquults. 50 to 100 cm. Typic Epiaquults Arenic Kandiaquults

Fragiaquults HADE. Other Kandiaquults that meet sandy or sandy-skeletal particle-size class criteria throughout a layer extending from the Key to Subgroups mineral soil surface to the top of a kandic horizon at a depth of HABA. Fragiaquults that have 50 percent or more chroma 100 cm or more. of 3 or more in one or more horizons between either the A or Grossarenic Kandiaquults Ap horizon or a depth of 25 cm from the mineral soil surface, whichever is deeper, and the fragipan. HADF. Other Kandiaquults that have 5 percent or more (by Aeric Fragiaquults volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. HABB. Other Fragiaquults that have 5 percent or more (by Plinthic Kandiaquults volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. HADG. Other Kandiaquults that have 50 percent or more Plinthic Fragiaquults chroma of 3 or more in one or more horizons between either the A or Ap horizon or a depth of 25 cm from the mineral soil HABC. Other Fragiaquults that have a mollic or umbric surface, whichever is deeper, and a depth of 75 cm. epipedon. Aeric Kandiaquults Umbric Fragiaquults HADH. Other Kandiaquults that have a mollic or umbric HABD. Other Fragiaquults. epipedon. Typic Fragiaquults Umbric Kandiaquults U L T Kandiaquults HADI. Other Kandiaquults. Typic Kandiaquults Key to Subgroups HADA. Kandiaquults that have an ECEC of 1.5 cmol(+)/kg Kanhaplaquults clay or less (sum of bases extracted with 1N NH OAc pH 7, plus 4 Key to Subgroups 1N KCl-extractable Al) in one or more horizons within 150 cm of the mineral soil surface. HAEA. Kanhaplaquults that have, throughout one or Acraquoxic Kandiaquults more horizons with a total thickness of 18 cm or more 270 Keys to Soil Taxonomy

within 75 cm of the mineral soil surface, one or more of the shaped peds in a layer 15 cm or more thick that has its upper following: boundary within 125 cm of the mineral soil surface; or 1. A fine-earth fraction with both a bulk density of 1.0 2. A linear extensibility of 6.0 cm or more between the g/cm3 or less, measured at 33 kPa water retention, and Al mineral soil surface and either a depth of 100 cm or a densic, 1 plus /2 Fe percentages (by ammonium oxalate) totaling more lithic, or paralithic contact, whichever is shallower. than 1.0; or Vertic Paleaquults 2. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, HAFB. Other Paleaquults that: pumice, and pumicelike fragments; or 1. Meet sandy or sandy-skeletal particle-size class criteria 3. A fine-earth fraction containing 30 percent or more throughout a layer extending from the mineral soil surface to particles 0.02 to 2.0 mm in diameter; and the top of an argillic horizon at a depth of 50 to 100 cm; and a. In the 0.02 to 2.0 mm fraction, 5 percent or more 2. Have 5 percent or more (by volume) plinthite in one or volcanic glass; and more horizons within 150 cm of the mineral soil surface. 1 Arenic Plinthic Paleaquults b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. HAFC. Other Paleaquults that: Aquandic Kanhaplaquults 1. Have a mollic or umbric epipedon; and HAEB. Other Kanhaplaquults that have 5 percent or more (by 2. Meet sandy or sandy-skeletal particle-size class criteria volume) plinthite in one or more horizons within 150 cm of the throughout a layer extending from the mineral soil surface to mineral soil surface. the top of an argillic horizon at a depth of 50 to 100 cm. Plinthic Kanhaplaquults Arenic Umbric Paleaquults

HAEC. Other Kanhaplaquults that: HAFD. Other Paleaquults that meet sandy or sandy-skeletal particle-size class criteria throughout a layer extending from the 1. Have a mollic or umbric epipedon; and mineral soil surface to the top of an argillic horizon at a depth of 2. Have 50 percent or more chroma of 3 or more in one or 50 to 100 cm. more horizons between either the A or Ap horizon or a depth Arenic Paleaquults of 25 cm from the mineral soil surface, whichever is deeper, and a depth of 75 cm. HAFE. Other Paleaquults that meet sandy or sandy-skeletal Aeric Umbric Kanhaplaquults particle-size class criteria throughout a layer extending from the mineral soil surface to the top of an argillic horizon at a depth of HAED. Other Kanhaplaquults that have 50 percent or more 100 cm or more. chroma of 3 or more in one or more horizons between either Grossarenic Paleaquults the A or Ap horizon or a depth of 25 cm from the mineral soil surface, whichever is deeper, and a depth of 75 cm. HAFF. Other Paleaquults that have 5 percent or more (by Aeric Kanhaplaquults volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. HAEE. Other Kanhaplaquults that have a mollic or umbric Plinthic Paleaquults epipedon. Umbric Kanhaplaquults HAFG. Other Paleaquults that have 50 percent or more chroma of 3 or more in one or more horizons between either HAEF. Other Kanhaplaquults. the A or Ap horizon or a depth of 25 cm from the mineral soil Typic Kanhaplaquults surface, whichever is deeper, and a depth of 75 cm. Aeric Paleaquults Paleaquults Key to Subgroups HAFH. Other Paleaquults that have a mollic or umbric epipedon. HAFA. Paleaquults that have of the following: one or both Umbric Paleaquults 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or more HAFI. Other Paleaquults. for some time in normal years and slickensides or wedge- Typic Paleaquults Ultisols 271

Plinthaquults HBE. Other Humults that: Key to Subgroups 1. Do not have a densic, lithic, paralithic, or petroferric contact within 150 cm of the mineral soil surface; and HAAA. Plinthaquults that have a kandic horizon or a CEC (by

1N NH4OAc pH 7) of less than 24 cmol(+)/kg clay in 50 percent 2. Within 150 cm of the mineral soil surface, either: or more (by volume) of the argillic horizon if less than 100 cm thick or of its upper 100 cm. a. With increasing depth, do not have a clay decrease Kandic Plinthaquults of 20 percent or more (relative) from the maximum clay content; or HAAB. Other Plinthaquults. b. Have 5 percent or more (by volume) skeletans on Typic Plinthaquults faces of peds in the layer that has a 20 percent lower clay content and, below that layer, a clay increase of 3 percent Umbraquults or more (absolute) in the fine-earth fraction. Palehumults, p. 273 Key to Subgroups HAGA. Umbraquults that have 5 to 50 percent (by volume) HBF. Other Humults. plinthite in one or more horizons within 150 cm of the mineral Haplohumults, p. 271 soil surface. Plinthic Umbraquults Haplohumults HAGB. Other Umbraquults. Key to Subgroups Typic Umbraquults HBFA. Haplohumults that have a lithic contact within 50 cm of the mineral soil surface. Humults Lithic Haplohumults Key to Great Groups HBFB. Other Haplohumults that have both: HBA. Humults that have a sombric horizon within 100 cm of 1. In one or more subhorizons within the upper 25 cm of the mineral soil surface. the argillic horizon, redox depletions with a color value, Sombrihumults, p. 274 moist, of 4 or more and chroma of 2 or less, accompanied by redox concentrations and aquic conditions for some HBB. Other Humults that have one or more horizons within both time in normal years (or artificial drainage); 150 cm of the mineral soil surface in which plinthite either and forms a continuous phase or constitutes one-half or more of the 2. Throughout one or more horizons with a total thickness volume. of 18 cm or more within 75 cm of the mineral soil surface, Plinthohumults, p. 274 a fine-earth fraction with both a bulk density of 1.0 g/cm3 or 1 less, measured at 33 kPa water retention, and Al plus /2 Fe HBC. Other Humults that: percentages (by ammonium oxalate) totaling more than 1.0. 1. Do not have a densic, lithic, paralithic, or petroferric Aquandic Haplohumults contact within 150 cm of the mineral soil surface; and HBFC. Other Haplohumults that have, in one or more 2. Have a kandic horizon; and subhorizons within the upper 25 cm of the argillic horizon, redox depletions with a color value, moist, of 4 or more and 3. Within 150 cm of the mineral soil surface, either: U chroma of 2 or less, accompanied by redox concentrations L a. With increasing depth, do not have a clay decrease both and aquic conditions for some time in normal years (or artificial T of 20 percent or more (relative) from the maximum clay drainage). content; or Aquic Haplohumults b. Have 5 percent or more (by volume) skeletans on faces of peds in the layer that has a 20 percent lower clay HBFD. Other Haplohumults that have, throughout one or content and, below that layer, a clay increase of 3 percent more horizons with a total thickness of 18 cm or more within or more (absolute) in the fine-earth fraction. 75 cm of the mineral soil surface, a fine-earth fraction with both Kandihumults, p. 272 a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 retention, and Al plus /2 Fe percentages (by ammonium oxalate) HBD. Other Humults that have a kandic horizon. totaling more than 1.0. Kanhaplohumults, p. 273 Andic Haplohumults 272 Keys to Soil Taxonomy

HBFE. Other Haplohumults that have 5 percent or more (by percentages (by ammonium oxalate) totaling more than 1.0; volume) plinthite in one or more horizons within 150 cm of the and mineral soil surface. 2. An ustic soil moisture regime. Plinthic Haplohumults Ustandic Kandihumults HBFF. Other Haplohumults that in normal years are saturated HBCC. Other Kandihumults that have, throughout one or with water in one or more layers within 100 cm of the mineral more horizons with a total thickness of 18 cm or more within soil surface for either or both: 75 cm of the mineral soil surface, a fine-earth fraction with both 1. 20 or more consecutive days; or a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 retention, and Al plus /2 Fe percentages (by ammonium oxalate) 2. 30 or more cumulative days. totaling more than 1.0. Oxyaquic Haplohumults Andic Kandihumults HBFG. Other Haplohumults that have an ustic soil moisture HBCD. Other Kandihumults that have, in one or more regime. subhorizons within the upper 25 cm of the kandic horizon, Ustic Haplohumults redox depletions with a color value, moist, of 4 or more and chroma of 2 or less, accompanied by both redox concentrations HBFH. Other Haplohumults that have a xeric soil moisture and aquic conditions for some time in normal years (or artificial regime. drainage). Xeric Haplohumults Aquic Kandihumults HBFI. Other Haplohumults. HBCE. Other Kandihumults that: Typic Haplohumults 1. Have, in one or more horizons within 75 cm of the Kandihumults mineral soil surface, redox concentrations, a color value, moist, of 4 or more, and hue that is 10YR or yellower and Key to Subgroups becomes redder with increasing depth within 100 cm of the HBCA. Kandihumults that meet all of the following: mineral soil surface; and 1. Throughout one or more horizons with a total thickness 2. In normal years are saturated with water in one or more of 18 cm or more within 75 cm of the mineral soil surface, layers within 100 cm of the mineral soil surface for either or have a fine-earth fraction with both a bulk density of 1.0 both: 3 g/cm or less, measured at 33 kPa water retention, and Al a. 20 or more consecutive days; or 1 plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0; and b. 30 or more cumulative days. Ombroaquic Kandihumults 2. In one or more horizons within 75 cm of the mineral soil surface, have redox concentrations, a color value, moist, of HBCF. Other Kandihumults that have 5 percent or more (by 4 or more, and hue that is 10YR or yellower and becomes volume) plinthite in one or more horizons within 150 cm of the redder with increasing depth within 100 cm of the mineral mineral soil surface. soil surface; and Plinthic Kandihumults 3. In normal years are saturated with water in one or more HBCG. Other Kandihumults that have an ustic soil moisture layers within 100 cm of the mineral soil surface for either or regime. both: Ustic Kandihumults a. 20 or more consecutive days; or HBCH. Other Kandihumults that have a xeric soil moisture b. 30 or more cumulative days. regime. Andic Ombroaquic Kandihumults Xeric Kandihumults HBCB. Other Kandihumults that have both: HBCI. Other Kandihumults that have an anthropic epipedon. 1. Throughout one or more horizons with a total thickness Anthropic Kandihumults of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction with both a bulk density of 1.0 g/cm3 or HBCJ. Other Kandihumults. 1 less, measured at 33 kPa water retention, and Al plus /2 Fe Typic Kandihumults Ultisols 273

Kanhaplohumults HBDH. Other Kanhaplohumults that have an anthropic epipedon. Key to Subgroups Anthropic Kanhaplohumults HBDA. Kanhaplohumults that have a lithic contact within 50 cm of the mineral soil surface. HBDI. Other Kanhaplohumults. Lithic Kanhaplohumults Typic Kanhaplohumults

HBDB. Other Kanhaplohumults that have both: Palehumults 1. An ustic soil moisture regime; and Key to Subgroups 2. Throughout one or more horizons with a total thickness HBEA. Palehumults that have both: of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction with both a bulk density of 1.0 g/cm3 or 1. In one or more subhorizons within the upper 25 cm of 1 less, measured at 33 kPa water retention, and Al plus /2 Fe the argillic horizon, redox depletions with a color value, percentages (by ammonium oxalate) totaling more than 1.0. moist, of 4 or more and chroma of 2 or less, accompanied Ustandic Kanhaplohumults by both redox concentrations and aquic conditions for some time in normal years (or artificial drainage);and HBDC. Other Kanhaplohumults that have, throughout one or 2. Throughout one or more horizons with a total thickness more horizons with a total thickness of 18 cm or more within of 18 cm or more within 75 cm of the mineral soil surface, 75 cm of the mineral soil surface, a fine-earth fraction with both a fine-earth fraction with both a bulk density of 1.0 g/cm3 or 3 a bulk density of 1.0 g/cm or less, measured at 33 kPa water 1 less, measured at 33 kPa water retention, and Al plus /2 Fe 1 retention, and Al plus /2 Fe percentages (by ammonium oxalate) percentages (by ammonium oxalate) totaling more than 1.0. totaling more than 1.0. Aquandic Palehumults Andic Kanhaplohumults HBEB. Other Palehumults that have, throughout one or more HBDD. Other Kanhaplohumults that have, in one or more horizons with a total thickness of 18 cm or more within 75 cm subhorizons within the upper 25 cm of the kandic horizon, of the mineral soil surface, a fine-earth fraction with both a bulk redox depletions with a color value, moist, of 4 or more and density of 1.0 g/cm3 or less, measured at 33 kPa water retention, chroma of 2 or less, accompanied by both redox concentrations 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling and aquic conditions for some time in normal years (or artificial more than 1.0. drainage). Andic Palehumults Aquic Kanhaplohumults HBEC. Other Palehumults that have, in one or more HBDE. Other Kanhaplohumults that: subhorizons within the upper 25 cm of the argillic horizon, 1. Have, in one or more horizons within 75 cm of the redox depletions with a color value, moist, of 4 or more and mineral soil surface, redox concentrations, a color value, chroma of 2 or less, accompanied by both redox concentrations moist, of 4 or more, and hue that is 10YR or yellower and and aquic conditions for some time in normal years (or artificial becomes redder with increasing depth within 100 cm of the drainage). mineral soil surface; and Aquic Palehumults 2. In normal years are saturated with water in one or more layers within 100 cm of the mineral soil surface for either or HBED. Other Palehumults that have 5 percent or more (by both: volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. U L a. 20 or more consecutive days; or Plinthic Palehumults T b. 30 or more cumulative days. Ombroaquic Kanhaplohumults HBEE. Other Palehumults that in normal years are saturated with water in one or more layers within 100 cm of the mineral HBDF. Other Kanhaplohumults that have an ustic soil soil surface for either or both: moisture regime. 1. 20 or more consecutive days; or Ustic Kanhaplohumults 2. 30 or more cumulative days. HBDG. Other Kanhaplohumults that have a xeric soil Oxyaquic Palehumults moisture regime. Xeric Kanhaplohumults 274 Keys to Soil Taxonomy

HBEF. Other Palehumults that have an ustic soil moisture HCE. Other Udults that: regime. 1. Do not have a densic, lithic, paralithic, or petroferric Ustic Palehumults contact within 150 cm of the mineral soil surface; and HBEG. Other Palehumults that have a xeric soil moisture 2. Within 150 cm of the mineral soil surface, either: regime. a. With increasing depth, do not have a clay decrease Xeric Palehumults of 20 percent or more (relative) from the maximum clay content; or HBEH. Other Palehumults. Typic Palehumults b. Have 5 percent or more (by volume) skeletans on faces of peds in the layer that has a 20 percent lower clay Plinthohumults content and, below that layer, a clay increase of 3 percent or more (absolute) in the fine-earth fraction. Key to Subgroups Paleudults, p. 279 HBBA. All Plinthohumults. HCF. Other Udults that have both: Typic Plinthohumults 1. An epipedon that has a color value, moist, of 3 or less Sombrihumults throughout; and Key to Subgroups 2. In all subhorizons in the upper 100 cm of the argillic horizon or throughout the entire argillic horizon if it is less HBAA. All Sombrihumults. than 100 cm thick, more than 50 percent colors that have all Typic Sombrihumults of the following: a. Hue of 2.5YR or redder; and Udults b. A value, moist, of 3 or less; and Key to Great Groups c. A dry value no more than 1 unit higher than the moist HCA. Udults that have one or more horizons within 150 cm value. of the mineral soil surface in which plinthite either forms a Rhodudults, p. 281 continuous phase or constitutes one-half or more of the volume. Plinthudults, p. 281 HCG. Other Udults. Hapludults, p. 275 HCB. Other Udults that have a fragipan within 100 cm of the mineral soil surface. Fragiudults Fragiudults, p. 274 Key to Subgroups HCC. Other Udults that: HCBA. Fragiudults that meet sandy or sandy-skeletal particle- 1. Do not have a densic, lithic, paralithic, or petroferric size class criteria throughout a layer extending from the mineral soil surface to the top of an argillic or kandic horizon at a depth contact within 150 cm of the mineral soil surface; and of 50 to 100 cm. 2. Have a kandic horizon; and Arenic Fragiudults 3. Within 150 cm of the mineral soil surface, either: HCBB. Other Fragiudults that have both of the following: a. With increasing depth, do not have a clay decrease 1. In one or more horizons within 40 cm of the mineral soil of 20 percent or more (relative) from the maximum clay surface, redox depletions with chroma of 2 or less and also content; or aquic conditions for some time in normal years (or artificial b. Have 5 percent or more (by volume) skeletans on drainage); and faces of peds in the layer that has a 20 percent lower clay 2. 5 percent or more (by volume) plinthite in one or more content and, below that layer, a clay increase of 3 percent horizons within 150 cm of the mineral soil surface. or more (absolute) in the fine-earth fraction. Plinthaquic Fragiudults Kandiudults, p. 276 HCBC. Other Fragiudults that have both: HCD. Other Udults that have a kandic horizon. Kanhapludults, p. 278 1. One or more of the following: Ultisols 275

a. Have a glossic horizon above the fragipan; or Hapludults b. Do not have, above the fragipan, an argillic or kandic Key to Subgroups horizon that has clay films on both vertical and horizontal HCGA. Hapludults that have either or both: surfaces of any peds; or 1. In each pedon, a discontinuous lithic contact within 50 c. Between the argillic or kandic horizon and the cm of the mineral soil surface; and fragipan, have one or more horizons with 50 percent or more chroma of 3 or less and with a clay content 3 percent 2. In each pedon, a discontinuous argillic horizon that is or more (absolute, in the fine-earth fraction) lower than interrupted by ledges of bedrock. that in both the argillic or kandic horizon and the fragipan; Lithic-Ruptic-Entic Hapludults and HCGB. Other Hapludults that have a lithic contact within 50 2. In one or more horizons within 40 cm of the mineral soil cm of the mineral soil surface. surface, redox depletions with chroma of 2 or less and also Lithic Hapludults aquic conditions for some time in normal years (or artificial drainage). HCGC. Other Hapludults that have one or both of the Glossaquic Fragiudults following: HCBD. Other Fragiudults that have, in one or more 1. Cracks within 125 cm of the mineral soil surface that are subhorizons above the fragipan and within the upper 25 cm of 5 mm or more wide through a thickness of 30 cm or more the argillic or kandic horizon, redox depletions with chroma of 2 for some time in normal years and slickensides or wedge- or less and also aquic conditions for some time in normal years shaped peds in a layer 15 cm or more thick that has its upper (or artificial drainage). boundary within 125 cm of the mineral soil surface; or Aquic Fragiudults 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a densic, HCBE. Other Fragiudults that have 5 percent or more (by lithic, or paralithic contact, whichever is shallower. volume) plinthite in one or more horizons within 150 cm of the Vertic Hapludults mineral soil surface. Plinthic Fragiudults HCGD. Other Hapludults that have both: HCBF. Other Fragiudults that meet one or more of the 1. Fragic soil properties either: following: a. In 30 percent or more of the volume of a layer 15 cm 1. Have a glossic horizon above the fragipan; or or more thick that has its upper boundary within 100 cm of the mineral soil surface; or 2. Do not have, above the fragipan, an argillic or kandic horizon that has clay films on both vertical and horizontal b. In 60 percent or more of the volume of a layer 15 cm surfaces of any peds; or or more thick; and 3. Between the argillic or kandic horizon and the fragipan, 2. In one or more layers within 75 cm of the mineral soil have one or more horizons with 50 percent or more chroma surface, redox depletions with a color value, moist, of 4 or of 3 or less and with a clay content 3 percent or more more and chroma of 2 or less, accompanied by both redox (absolute, in the fine-earth fraction) lower than that in both concentrations and aquic conditions for some time in normal the argillic or kandic horizon and the fragipan. years (or artificial drainage). Glossic Fragiudults Fragiaquic Hapludults U L T HCBG. Other Fragiudults that have a color value, moist, HCGE. Other Hapludults that: of 3 or less and a color value, dry, of 5 or less (crushed and 1. Meet sandy or sandy-skeletal particle-size class criteria smoothed sample) in either: throughout a layer extending from the mineral soil surface to 1. An Ap horizon that is 18 cm or more thick; or the top of an argillic horizon at a depth of 50 to 100 cm; and 2. The surface layer after mixing of the upper 18 cm. 2. Have, in one or more subhorizons within the upper Humic Fragiudults 60 cm of the argillic horizon, redox depletions with a color value, moist, of 4 or more and chroma of 2 or less, HCBH. Other Fragiudults. accompanied by both redox concentrations and aquic Typic Fragiudults 276 Keys to Soil Taxonomy

conditions for some time in normal years (or artificial mineral soil surface to the top of an argillic horizon at a depth of drainage). 50 to 100 cm. Aquic Arenic Hapludults Arenic Hapludults

HCGF. Other Hapludults that have, in one or more subhorizons HCGL. Other Hapludults that meet sandy or sandy-skeletal within the upper 60 cm of the argillic horizon, redox depletions particle-size class criteria throughout a layer extending from the with a color value, moist, of 4 or more and chroma of 2 or less, mineral soil surface to the top of an argillic horizon at a depth of accompanied by both redox concentrations and aquic conditions 100 cm or more. for some time in normal years (or artificial drainage). Grossarenic Hapludults Aquic Hapludults HCGM. Other Hapludults that: HCGG. Other Hapludults that have fragic soil properties 1. Do not have a densic, lithic, or paralithic contact within either: 50 cm of the mineral soil surface; and 1. In 30 percent or more of the volume of a layer 15 cm or more thick that has its upper boundary within 100 cm of the 2. Have an argillic horizon that is 25 cm or less thick. mineral soil surface; or Inceptic Hapludults

2. In 60 percent or more of the volume of a layer 15 cm or HCGN. Other Hapludults that have a color value, moist, more thick. of 3 or less and a color value, dry, of 5 or less (crushed and Fragic Hapludults smoothed sample) in either: HCGH. Other Hapludults that in normal years are saturated 1. An Ap horizon that is 18 cm or more thick; or with water in one or more layers within 100 cm of the mineral 2. The surface layer after mixing of the upper 18 cm. soil surface for either or both: Humic Hapludults 1. 20 or more consecutive days; or 2. 30 or more cumulative days. HCGO. Other Hapludults. Oxyaquic Hapludults Typic Hapludults

HCGI. Other Hapludults that have an argillic horizon that: Kandiudults 1. Consists entirely of lamellae; or Key to Subgroups 2. Is a combination of two or more lamellae and one or HCCA. Kandiudults that: more subhorizons with a thickness of 7.5 to 20 cm, each 1. Meet sandy or sandy-skeletal particle-size class criteria layer with an overlying eluvial horizon; or throughout a layer extending from the mineral soil surface to 3. Consists of one or more subhorizons that are more than the top of a kandic horizon at a depth of 50 to 100 cm; and 20 cm thick, each with an overlying eluvial horizon, and above these horizons there are either: 2. Have 5 percent or more (by volume) plinthite in one or more horizons within 150 cm of the mineral soil surface; and a. Two or more lamellae with a combined thickness of 5 cm or more (that may or may not be part of the argillic 3. Have, in one or more layers either within 75 cm of horizon); or the mineral soil surface or, if the chroma throughout the upper 75 cm results from uncoated sand grains, within b. A combination of lamellae (that may or may not be the upper 12.5 cm of the kandic horizon, redox depletions part of the argillic horizon) and one or more parts of the with a color value, moist, of 4 or more and chroma of 2 or argillic horizon 7.5 to 20 cm thick, each with an overlying less, accompanied by both redox concentrations and aquic eluvial horizon. conditions for some time in normal years (or artificial Lamellic Hapludults drainage). Arenic Plinthaquic Kandiudults HCGJ. Other Hapludults that have a sandy particle-size class throughout the upper 75 cm of the argillic horizon or throughout HCCB. Other Kandiudults that: the entire argillic horizon if it is less than 75 cm thick. Psammentic Hapludults 1. Meet sandy or sandy-skeletal particle-size class criteria throughout a layer extending from the mineral soil surface to HCGK. Other Hapludults that meet sandy or sandy-skeletal the top of a kandic horizon at a depth of 50 to 100 cm; and particle-size class criteria throughout a layer extending from the Ultisols 277

2. Have, in one or more layers either within 75 cm of HCCH. Other Kandiudults that have both: the mineral soil surface or, if the chroma throughout the 1. An ECEC of 1.5 cmol(+)/kg clay or less (sum of bases upper 75 cm results from uncoated sand grains, within extracted with 1N NH OAc pH 7, plus 1N KCl-extractable the upper 12.5 cm of the kandic horizon, redox depletions 4 Al) in one or more horizons within 150 cm of the mineral with a color value, moist, of 4 or more and chroma of 2 or soil surface; and less, accompanied by both redox concentrations and aquic conditions for some time in normal years (or artificial 2. 5 percent or more (by volume) plinthite in one or more drainage). horizons within 150 cm of the mineral soil surface. Aquic Arenic Kandiudults Acrudoxic Plinthic Kandiudults

HCCC. Other Kandiudults that: HCCI. Other Kandiudults that have an ECEC of 1.5 1. Meet sandy or sandy-skeletal particle-size class criteria cmol(+)/kg clay or less (sum of bases extracted with 1N NH OAc pH 7, plus 1N KCl-extractable Al) in one or more throughout a layer extending from the mineral soil surface to 4 horizons within 150 cm of the mineral soil surface. the top of a kandic horizon at a depth of 50 to 100 cm; and Acrudoxic Kandiudults 2. Have 5 percent or more (by volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. HCCJ. Other Kandiudults that have both: Arenic Plinthic Kandiudults 1. 5 percent or more (by volume) plinthite in one or more HCCD. Other Kandiudults that: horizons within 150 cm of the mineral soil surface; and 1. Meet sandy or sandy-skeletal particle-size class criteria 2. In one or more layers within 75 cm of the mineral soil throughout a layer extending from the mineral soil surface to surface, redox depletions with a color value, moist, of 4 or the top of a kandic horizon at a depth of 50 to 100 cm; and more and chroma of 2 or less, accompanied by both redox concentrations and aquic conditions for some time in normal 2. Have, in all subhorizons in the upper 75 cm of the years (or artificial drainage). kandic horizon or throughout the entire kandic horizon if it is Plinthaquic Kandiudults less than 75 cm thick, more than 50 percent colors that have of the following: all HCCK. Other Kandiudults that have both: a. Hue of 2.5YR or redder; and 1. In one or more layers within 75 cm of the mineral soil b. A value, moist, of 3 or less; and surface, redox depletions with a color value, moist, of 4 or c. A dry value no more than 1 unit higher than the moist more and chroma of 2 or less, accompanied by both redox value. concentrations and aquic conditions for some time in normal Arenic Rhodic Kandiudults years (or artificial drainage);and 2. Throughout one or more horizons with a total thickness HCCE. Other Kandiudults that meet sandy or sandy-skeletal of 18 cm or more within 75 cm of the mineral soil surface, particle-size class criteria throughout a layer extending from the one or more of the following: mineral soil surface to the top of a kandic horizon at a depth of 50 to 100 cm. a. A fine-earth fraction with both a bulk density of 1.0 Arenic Kandiudults g/cm3 or less, measured at 33 kPa water retention, and Al 1 plus /2 Fe percentages (by ammonium oxalate) totaling HCCF. Other Kandiudults that: more than 1.0; or

1. Meet sandy or sandy-skeletal particle-size class criteria b. More than 35 percent (by volume) fragments coarser U L throughout a layer extending from the mineral soil surface to than 2.0 mm, of which more than 66 percent is cinders, T the top of a kandic horizon at a depth of 100 cm or more; and pumice, and pumicelike fragments; or 2. Have 5 percent or more (by volume) plinthite in one or c. A fine-earth fraction containing 30 percent or more more horizons within 150 cm of the mineral soil surface. particles 0.02 to 2.0 mm in diameter; and Grossarenic Plinthic Kandiudults (1) In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and HCCG. Other Kandiudults that meet sandy or sandy-skeletal 1 particle-size class criteria throughout a layer extending from the (2) [(Al plus /2 Fe, percent extracted by ammonium mineral soil surface to the top of a kandic horizon at a depth of oxalate) times 60] plus the volcanic glass (percent) is 100 cm or more. equal to 30 or more. Grossarenic Kandiudults Aquandic Kandiudults 278 Keys to Soil Taxonomy

HCCL. Other Kandiudults that have, throughout one or more 3. A dry value no more than 1 unit higher than the moist horizons with a total thickness of 18 cm or more within 75 cm value. of the mineral soil surface, a fine-earth fraction with both a bulk Rhodic Kandiudults density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling HCCS. Other Kandiudults. more than 1.0. Typic Kandiudults Andic Kandiudults Kanhapludults HCCM. Other Kandiudults that have, in one or more layers within 75 cm of the mineral soil surface, redox depletions with Key to Subgroups a color value, moist, of 4 or more and chroma of 2 or less, HCDA. Kanhapludults that have a lithic contact within 50 cm accompanied by both redox concentrations and aquic conditions of the mineral soil surface. for some time in normal years (or artificial drainage). Lithic Kanhapludults Aquic Kandiudults HCDB. Other Kanhapludults that have both: HCCN. Other Kandiudults that have 5 percent or more (by volume) plinthite in one or more horizons within 150 cm of the 1. 5 percent or more (by volume) plinthite in one or more mineral soil surface. horizons within 150 cm of the mineral soil surface; and Plinthic Kandiudults 2. In one or more layers within 75 cm of the mineral soil surface, redox depletions with a color value, moist, of 4 or HCCO. Other Kandiudults that: more and chroma of 2 or less, accompanied by both redox 1. Have, in one or more horizons within 75 cm of the concentrations and aquic conditions for some time in normal mineral soil surface, redox concentrations, a color value, years (or artificial drainage). moist, of 4 or more, and hue that is 10YR or yellower and Plinthaquic Kanhapludults becomes redder with increasing depth within 100 cm of the HCDC. Other Kanhapludults that: mineral soil surface; and 1. Meet sandy or sandy-skeletal particle-size class criteria 2. In normal years are saturated with water in one or more throughout a layer extending from the mineral soil surface to layers within 100 cm of the mineral soil surface for either or the top of a kandic horizon at a depth of 50 to 100 cm; and both: 2. Have 5 percent or more (by volume) plinthite in one or a. 20 or more consecutive days; or more horizons within 150 cm of the mineral soil surface. b. 30 or more cumulative days. Arenic Plinthic Kanhapludults Ombroaquic Kandiudults HCDD. Other Kanhapludults that meet sandy or sandy- HCCP. Other Kandiudults that in normal years are saturated skeletal particle-size class criteria throughout a layer extending with water in one or more layers within 100 cm of the mineral from the mineral soil surface to the top of a kandic horizon at a soil surface for either or both: depth of 50 to 100 cm. Arenic Kanhapludults 1. 20 or more consecutive days; or 2. 30 or more cumulative days. HCDE. Other Kanhapludults that have an ECEC of 1.5 Oxyaquic Kandiudults cmol(+)/kg clay or less (sum of bases extracted with 1N NH4OAc pH 7, plus 1N KCl-extractable Al) in one or more HCCQ. Other Kandiudults that have a sombric horizon within horizons within 150 cm of the mineral soil surface. 150 cm of the mineral soil surface. Acrudoxic Kanhapludults Sombric Kandiudults HCDF. Other Kanhapludults that have both: HCCR. Other Kandiudults that have, in all subhorizons in 1. Fragic soil properties either: the upper 75 cm of the kandic horizon or throughout the entire kandic horizon if it is less than 75 cm thick, more than 50 a. In 30 percent or more of the volume of a layer 15 cm percent colors that have all of the following: or more thick that has its upper boundary within 100 cm of the mineral soil surface; or 1. Hue of 2.5YR or redder; and b. In 60 percent or more of the volume of a layer 15 cm 2. A value, moist, of 3 or less; and or more thick; and Ultisols 279

2. In one or more layers within 75 cm of the mineral soil more thick that has its upper boundary within 100 cm of the surface, redox depletions with a color value, moist, of 4 or mineral soil surface; or more and chroma of 2 or less, accompanied by both redox 2. In 60 percent or more of the volume of a layer 15 cm or concentrations and aquic conditions for some time in normal more thick. years (or artificial drainage). Fragic Kanhapludults Fragiaquic Kanhapludults HCDM. Other Kanhapludults that have, in all subhorizons HCDG. Other Kanhapludults that have, throughout one or in the upper 50 cm of the kandic horizon or throughout the more horizons with a total thickness of 18 cm or more within entire kandic horizon if it is less than 50 cm thick, more than 50 75 cm of the mineral soil surface, a fine-earth fraction with both percent colors that have all of the following: a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 retention, and Al plus /2 Fe percentages (by ammonium oxalate) 1. Hue of 2.5YR or redder; and totaling more than 1.0. 2. A value, moist, of 3 or less; and Andic Kanhapludults 3. A dry value no more than 1 unit higher than the moist HCDH. Other Kanhapludults that have, in one or more layers value. within 75 cm of the mineral soil surface, redox depletions with Rhodic Kanhapludults a color value, moist, of 4 or more and chroma of 2 or less, accompanied by both redox concentrations and aquic conditions HCDN. Other Kanhapludults. for some time in normal years (or artificial drainage). Typic Kanhapludults Aquic Kanhapludults Paleudults HCDI. Other Kanhapludults that: Key to Subgroups 1. Have, in one or more horizons within 75 cm of the mineral soil surface, redox concentrations, a color value, HCEA. Paleudults that have one or both of the following: moist, of 4 or more, and hue that is 10YR or yellower and 1. Cracks within 125 cm of the mineral soil surface that are becomes redder with increasing depth within 100 cm of the 5 mm or more wide through a thickness of 30 cm or more mineral soil surface; and for some time in normal years and slickensides or wedge- 2. In normal years are saturated with water in one or more shaped peds in a layer 15 cm or more thick that has its upper layers within 100 cm of the mineral soil surface for either or boundary within 125 cm of the mineral soil surface; or both: 2. A linear extensibility of 6.0 cm or more between the a. 20 or more consecutive days; or mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. b. 30 or more cumulative days. Vertic Paleudults Ombroaquic Kanhapludults HCEB. Other Paleudults that have a horizon 5 cm or more HCDJ. Other Kanhapludults that in normal years are saturated thick, either below an Ap horizon or at a depth of 18 cm or more with water in one or more layers within 100 cm of the mineral from the mineral soil surface, whichever is deeper, that has one soil surface for either or both: or more of the following: 1. 20 or more consecutive days; or 1. In 25 percent or more of each pedon, cementation by 2. 30 or more cumulative days. organic matter and aluminum, with or without iron; or U Oxyaquic Kanhapludults 1 L 2. Al plus /2 Fe percentages (by ammonium oxalate) T totaling 0.25 or more, and half that amount or less in an HCDK. Other Kanhapludults that have 5 percent or more (by overlying horizon; or volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. 3. An ODOE value of 0.12 or more, and a value half as Plinthic Kanhapludults high or lower in an overlying horizon. Spodic Paleudults HCDL. Other Kanhapludults that have fragic soil properties either: HCEC. Other Paleudults that: 1. In 30 percent or more of the volume of a layer 15 cm or 1. Have, in one or more layers either within 75 cm of 280 Keys to Soil Taxonomy

the mineral soil surface or, if the chroma throughout the b. In 60 percent or more of the volume of a layer 15 cm upper 75 cm results from uncoated sand grains, within the or more thick; and upper 12.5 cm of the argillic horizon, redox depletions 2. In one or more layers within 75 cm of the mineral soil with a color value, moist, of 4 or more and chroma of 2 or surface, redox depletions with a color value, moist, of 4 or less, accompanied by both redox concentrations and aquic more and chroma of 2 or less, accompanied by both redox conditions for some time in normal years (or artificial concentrations and aquic conditions for some time in normal drainage); and years (or artificial drainage). 2. Meet sandy or sandy-skeletal particle-size class criteria Fragiaquic Paleudults throughout a layer extending from the mineral soil surface to the top of an argillic horizon at a depth of 50 cm or more; HCEH. Other Paleudults that have, in one or more layers and within 75 cm of the mineral soil surface, redox depletions with a color value, moist, of 4 or more and chroma of 2 or less, 3. Have 5 percent or more (by volume) plinthite in one or accompanied by both redox concentrations and aquic conditions more horizons within 150 cm of the mineral soil surface. for some time in normal years (or artificial drainage). Arenic Plinthaquic Paleudults Aquic Paleudults HCED. Other Paleudults that: HCEI. Other Paleudults that in normal years are saturated 1. Meet sandy or sandy-skeletal particle-size class criteria with water in one or more layers within 100 cm of the mineral throughout a layer extending from the mineral soil surface to soil surface for either or both: the top of an argillic horizon that is 50 cm or more below the 1. 20 or more consecutive days; or mineral soil surface; and 2. 30 or more cumulative days. 2. Have, in one or more layers either within 75 cm of Oxyaquic Paleudults the mineral soil surface or, if the chroma throughout the upper 75 cm results from uncoated sand grains, within the HCEJ. Other Paleudults that have an argillic horizon that: upper 12.5 cm of the argillic horizon, redox depletions with a color value, moist, of 4 or more and chroma of 2 or 1. Consists entirely of lamellae; or less, accompanied by both redox concentrations and aquic 2. Is a combination of two or more lamellae and one or conditions for some time in normal years (or artificial more subhorizons with a thickness of 7.5 to 20 cm, each drainage). layer with an overlying eluvial horizon; or Aquic Arenic Paleudults 3. Consists of one or more subhorizons that are more than HCEE. Other Paleudults that have anthraquic conditions. 20 cm thick, each with an overlying eluvial horizon, and Anthraquic Paleudults above these horizons there are either: a. Two or more lamellae with a combined thickness of HCEF. Other Paleudults that have both: 5 cm or more (that may or may not be part of the argillic 1. 5 percent or more (by volume) plinthite in one or more horizon); or horizons within 150 cm of the mineral soil surface; and b. A combination of lamellae (that may or may not be 2. In one or more layers either within 75 cm of the mineral part of the argillic horizon) and one or more parts of the soil surface or, if the chroma throughout the upper 75 cm argillic horizon 7.5 to 20 cm thick, each with an overlying results from uncoated sand grains, within the upper 12.5 cm eluvial horizon. of the argillic horizon, redox depletions with a color value, Lamellic Paleudults moist, of 4 or more and chroma of 2 or less, accompanied by both redox concentrations and aquic conditions for some HCEK. Other Paleudults that: time in normal years (or artificial drainage). 1. Meet sandy or sandy-skeletal particle-size class criteria Plinthaquic Paleudults throughout a layer extending from the mineral soil surface to the top of an argillic horizon at a depth of 50 to 100 cm; and HCEG. Other Paleudults that have both: 2. Have 5 percent or more (by volume) plinthite in one or 1. Fragic soil properties either: more horizons within 150 cm of the mineral soil surface. a. In 30 percent or more of the volume of a layer 15 cm Arenic Plinthic Paleudults or more thick that has its upper boundary within 100 cm of the mineral soil surface; or HCEL. Other Paleudults that have a sandy particle-size class Ultisols 281

throughout the upper 75 cm of the argillic horizon or throughout 2. In 60 percent or more of the volume of a layer 15 cm or the entire argillic horizon if it is less than 75 cm thick. more thick. Psammentic Paleudults Fragic Paleudults

HCEM. Other Paleudults that: HCES. Other Paleudults that have, in all subhorizons in the 1. Meet sandy or sandy-skeletal particle-size class criteria upper 75 cm of the argillic horizon or throughout the entire throughout a layer extending from the mineral soil surface to argillic horizon if it is less than 75 cm thick, more than 50 the top of an argillic horizon at a depth of 100 cm or more; percent colors that have all of the following: and 1. Hue of 2.5YR or redder; and 2. Have 5 percent or more (by volume) plinthite in one or 2. A value, moist, of 3 or less; and more horizons within 150 cm of the mineral soil surface. Grossarenic Plinthic Paleudults 3. A dry value no more than 1 unit higher than the moist value. HCEN. Other Paleudults that have 5 percent or more (by Rhodic Paleudults volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. HCET. Other Paleudults. Plinthic Paleudults Typic Paleudults

HCEO. Other Paleudults that: Plinthudults 1. Meet sandy or sandy-skeletal particle-size class criteria Key to Subgroups throughout a layer extending from the mineral soil surface to HCAA. All Plinthudults. the top of an argillic horizon at a depth of 50 to 100 cm; and Typic Plinthudults 2. Have, in all subhorizons in the upper 75 cm of the argillic horizon or throughout the entire argillic horizon if Rhodudults it is less than 75 cm thick, more than 50 percent colors that have all of the following: Key to Subgroups a. Hue of 2.5YR or redder; and HCFA. Rhodudults that have a lithic contact within 50 cm of the mineral soil surface. b. A value, moist, of 3 or less; and Lithic Rhodudults c. A dry value no more than 1 unit higher than the moist value. HCFB. Other Rhodudults that have a sandy particle-size class Arenic Rhodic Paleudults throughout the upper 75 cm of the argillic horizon or throughout the entire argillic horizon if it is less than 75 cm thick. HCEP. Other Paleudults that meet sandy or sandy-skeletal Psammentic Rhodudults particle-size class criteria throughout a layer extending from the mineral soil surface to the top of an argillic horizon at a depth of HCFC. Other Rhodudults. 50 to 100 cm. Typic Rhodudults Arenic Paleudults Ustults HCEQ. Other Paleudults that meet sandy or sandy-skeletal particle-size class criteria throughout a layer extending from the U Key to Great Groups L mineral soil surface to the top of an argillic horizon at a depth of T 100 cm or more. HDA. Ustults that have one or more horizons within 150 cm Grossarenic Paleudults of the mineral soil surface in which plinthite either forms a continuous phase or constitutes one-half or more of the volume. HCER. Other Paleudults that have fragic soil properties Plinthustults, p. 285 either: HDB. Other Ustults that: 1. In 30 percent or more of the volume of a layer 15 cm or more thick that has its upper boundary within 100 cm of the 1. Do not have a densic, lithic, paralithic, or petroferric mineral soil surface; or contact within 150 cm of the mineral soil surface; and 282 Keys to Soil Taxonomy

2. Have a kandic horizon; and HDFB. Other Haplustults that have a petroferric contact within 100 cm of the mineral soil surface. 3. Within 150 cm of the mineral soil surface, : either Petroferric Haplustults a. With increasing depth, do not have a clay decrease of 20 percent or more (relative) from the maximum clay HDFC. Other Haplustults that have, in one or more layers content; or both within the upper 12.5 cm of the argillic horizon and within b. Have 5 percent or more (by volume) skeletans on 75 cm of the mineral soil surface, redox depletions with a color faces of peds in the layer that has a 20 percent lower clay value, moist, of 4 or more and chroma of 2 or less, accompanied by redox concentrations and aquic conditions for some content and, below that layer, a clay increase of 3 percent both or more (absolute) in the fine-earth fraction. time in normal years (or artificial drainage). Kandiustults, p. 282 Aquic Haplustults

HDC. Other Ustults that have a kandic horizon. HDFD. Other Haplustults that meet sandy or sandy-skeletal Kanhaplustults, p. 284 particle-size class criteria throughout a layer extending from the mineral soil surface to the top of an argillic horizon at a depth of HDD. Other Ustults that: 50 cm or more below the mineral soil surface. Arenic Haplustults 1. Do not have a densic, lithic, paralithic, or petroferric contact within 150 cm of the mineral soil surface; and HDFE. Other Haplustults that: 2. Within 150 cm of the mineral soil surface, either: 1. Have, in one or more horizons within 75 cm of the a. With increasing depth, do not have a clay decrease mineral soil surface, redox concentrations, a color value, of 20 percent or more (relative) from the maximum clay moist, of 4 or more, and hue that is 10YR or yellower and content; or becomes redder with increasing depth within 100 cm of the b. Have 5 percent or more (by volume) skeletans on mineral soil surface; and faces of peds in the layer that has a 20 percent lower clay 2. In normal years are saturated with water in one or more content and, below that layer, a clay increase of 3 percent layers within 100 cm of the mineral soil surface for either or or more (absolute) in the fine-earth fraction. both: Paleustults, p. 285 a. 20 or more consecutive days; or HDE. Other Ustults that have both: b. 30 or more cumulative days. 1. An epipedon that has a color value, moist, of 3 or less Ombroaquic Haplustults throughout; and HDFF. Other Haplustults that have 5 percent or more (by 2. In all subhorizons in the upper 100 cm of the argillic volume) plinthite in one or more horizons within 150 cm of the horizon or throughout the entire argillic horizon if it is less mineral soil surface. than 100 cm thick, more than 50 percent colors that have all Plinthic Haplustults of the following:

a. Hue of 2.5YR or redder; and HDFG. Other Haplustults that have a CEC (by 1N NH4OAc pH 7) of less than 24 cmol(+)/kg clay in 50 percent or more b. A value, moist, of 3 or less; and of the entire argillic horizon if less than 100 cm thick or of its c. A dry value no more than 1 unit higher than the moist upper 100 cm. value. Kanhaplic Haplustults Rhodustults, p. 285 HDFH. Other Haplustults. HDF. Other Ustults. Typic Haplustults Haplustults, p. 282 Kandiustults Haplustults Key to Subgroups Key to Subgroups HDBA. Kandiustults that have an ECEC of 1.5 cmol(+)/kg

HDFA. Haplustults that have a lithic contact within 50 cm of clay or less (sum of bases extracted with 1N NH4OAc pH 7, plus the mineral soil surface. Lithic Haplustults Ultisols 283

1 1N KCl-extractable Al) in one or more horizons within 150 cm and Al plus /2 Fe percentages (by ammonium oxalate) totaling of the mineral soil surface. more than 1.0. Acrustoxic Kandiustults Andic Kandiustults

HDBB. Other Kandiustults that have, in one or more layers HDBG. Other Kandiustults that have 5 percent or more (by within 75 cm of the mineral soil surface, redox depletions with volume) plinthite in one or more horizons within 150 cm of the a color value, moist, of 4 or more and chroma of 2 or less, mineral soil surface. accompanied by both redox concentrations and aquic conditions Plinthic Kandiustults for some time in normal years (or artificial drainage). Aquic Kandiustults HDBH. Other Kandiustults that, when neither irrigated nor fallowed to store moisture, have either: HDBC. Other Kandiustults that: 1. A thermic, mesic, or colder soil temperature regime and 1. Meet sandy or sandy-skeletal particle-size class criteria a moisture control section that in normal years is dry in some throughout a layer extending from the mineral soil surface to part for more than four-tenths of the cumulative days per the top of a kandic horizon at a depth of 50 cm or more; and year when the soil temperature at a depth of 50 cm below the o 2. Have 5 percent or more (by volume) plinthite in one or soil surface is higher than 5 C; or more horizons within 150 cm of the mineral soil surface. 2. A hyperthermic, isomesic, or warmer iso soil Arenic Plinthic Kandiustults temperature regime and a moisture control section that in normal years: HDBD. Other Kandiustults that meet sandy or sandy-skeletal particle-size class criteria throughout a layer extending from the a. Is moist in some or all parts for fewer than 90 mineral soil surface to the top of a kandic horizon at a depth of consecutive days per year when the soil temperature at a 50 cm or more. depth of 50 cm below the soil surface is higher than 8 oC; Arenic Kandiustults and b. Is dry in some part for six-tenths or more of the HDBE. Other Kandiustults that have both: cumulative days per year when the soil temperature at a 1. Throughout one or more horizons with a total thickness depth of 50 cm below the soil surface is higher than 5 oC. of 18 cm or more within 75 cm of the mineral soil surface, Aridic Kandiustults a fine-earth fraction with both a bulk density of 1.0 g/cm3 or 1 less, measured at 33 kPa water retention, and Al plus /2 Fe HDBI. Other Kandiustults that, when neither irrigated nor percentages (by ammonium oxalate) totaling more than 1.0; fallowed to store moisture, have either: and 1. A mesic or thermic soil temperature regime and a 2. When neither irrigated nor fallowed to store moisture, moisture control section that in normal years is dry in some either: part for 135 or fewer of the cumulative days per year when a. A mesic or thermic soil temperature regime and a the soil temperature at a depth of 50 cm below the soil o moisture control section that is dry in some part for 135 surface is higher than 5 C; or or fewer of the cumulative days per year when the soil 2. A hyperthermic, isomesic, or warmer iso soil temperature at a depth of 50 cm below the soil surface is temperature regime and a moisture control section that in o higher than 5 C; or normal years is dry in some or all parts for fewer than 120 b. A hyperthermic, isomesic, or warmer iso soil cumulative days per year when the soil temperature at a o U temperature regime and a moisture control section that depth of 50 cm below the soil surface is higher than 8 C. L is dry in some or all parts for fewer than 120 cumulative Udic Kandiustults T days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 8 oC. HDBJ. Other Kandiustults that have, in all subhorizons in Udandic Kandiustults the upper 50 cm of the kandic horizon or throughout the entire kandic horizon if it is less than 50 cm thick, more than 50 HDBF. Other Kandiustults that have, throughout one or more percent colors that have all of the following: horizons with a total thickness of 18 cm or more within 75 cm 1. Hue of 2.5YR or redder; and of the mineral soil surface, a fine-earth fraction with both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 2. A value, moist, of 3 or less; and 284 Keys to Soil Taxonomy

3. A dry value no more than 1 unit higher than the moist cumulative days per year when the soil temperature at a value. depth of 50 cm below the soil surface is higher than 8 oC. Rhodic Kandiustults Udandic Kanhaplustults

HDBK. Other Kandiustults. HDCF. Other Kanhaplustults that have, throughout one or Typic Kandiustults more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction with both Kanhaplustults a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 retention, and Al plus /2 Fe percentages (by ammonium oxalate) Key to Subgroups totaling more than 1.0. HDCA. Kanhaplustults that have a lithic contact within 50 cm Andic Kanhaplustults of the mineral soil surface. Lithic Kanhaplustults HDCG. Other Kanhaplustults that have 5 percent or more (by volume) plinthite in one or more horizons within 150 cm of the HDCB. Other Kanhaplustults that have an ECEC of 1.5 mineral soil surface. cmol(+)/kg clay or less (sum of bases extracted with 1N Plinthic Kanhaplustults

NH4OAc pH 7, plus 1N KCl-extractable Al) in one or more horizons within 150 cm of the mineral soil surface. HDCH. Other Kanhaplustults that: Acrustoxic Kanhaplustults 1. Have, in one or more horizons within 75 cm of the mineral soil surface, redox concentrations, a color value, HDCC. Other Kanhaplustults that have, in one or more layers moist, of 4 or more, and hue that is 10YR or yellower and within 75 cm of the mineral soil surface, redox depletions with becomes redder with increasing depth within 100 cm of the a color value, moist, of 4 or more and chroma of 2 or less, mineral soil surface; and accompanied by both redox concentrations and aquic conditions for some time in normal years (or artificial drainage). 2. In normal years are saturated with water in one or more Aquic Kanhaplustults layers within 100 cm of the mineral soil surface for either or both: HDCD. Other Kanhaplustults that meet sandy or sandy- a. 20 or more consecutive days; or skeletal particle-size class criteria throughout a layer extending from the mineral soil surface to the top of a kandic horizon at a b. 30 or more cumulative days. depth of 50 to 100 cm. Ombroaquic Kanhaplustults Arenic Kanhaplustults HDCI. Other Kanhaplustults that, when neither irrigated nor HDCE. Other Kanhaplustults that have both: fallowed to store moisture, have either: 1. Throughout one or more horizons with a total thickness 1. A thermic, mesic, or colder soil temperature regime and of 18 cm or more within 75 cm of the mineral soil surface, a moisture control section that in normal years is dry in some a fine-earth fraction with both a bulk density of 1.0 g/cm3 or part for more than four-tenths of the cumulative days per 1 less, measured at 33 kPa water retention, and Al plus /2 Fe year when the soil temperature at a depth of 50 cm below the percentages (by ammonium oxalate) totaling more than 1.0; soil surface is higher than 5 oC; or and 2. A hyperthermic, isomesic, or warmer iso soil 2. When neither irrigated nor fallowed to store moisture, temperature regime and a moisture control section that in either: normal years: a. A mesic or thermic soil temperature regime and a a. Is moist in some or all parts for fewer than 90 moisture control section that in normal years is dry in consecutive days per year when the soil temperature at a some part for 135 or fewer of the cumulative days per year depth of 50 cm below the soil surface is higher than 8 oC; when the soil temperature at a depth of 50 cm below the and soil surface is higher than 5 oC; or b. Is dry in some part for six-tenths or more of the b. A hyperthermic, isomesic, or warmer iso soil cumulative days per year when the soil temperature at a temperature regime and a moisture control section that in depth of 50 cm below the soil surface is higher than 5 oC. normal years is dry in some or all parts for fewer than 120 Aridic Kanhaplustults Ultisols 285

HDCJ. Other Kanhaplustults that, when neither irrigated nor Rhodustults fallowed to store moisture, have either: Key to Subgroups 1. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in some HDEA. Rhodustults that have a lithic contact within 50 cm of part for 135 or fewer of the cumulative days per year when the mineral soil surface. the soil temperature at a depth of 50 cm below the soil Lithic Rhodustults surface is higher than 5 oC; or HDEB. Other Rhodustults that have a sandy particle-size class 2. A hyperthermic, isomesic, or warmer iso soil throughout the upper 75 cm of the argillic horizon or throughout temperature regime and a moisture control section that in the entire argillic horizon if it is less than 75 cm thick. normal years is dry in some or all parts for fewer than 120 Psammentic Rhodustults cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 8 oC. HDEC. Other Rhodustults. Udic Kanhaplustults Typic Rhodustults

HDCK. Other Kanhaplustults that have, in all subhorizons Xerults in the upper 50 cm of the kandic horizon or throughout the entire kandic horizon if it is less than 50 cm thick, more than 50 Key to Great Groups percent colors that have all of the following: HEA. Xerults that: 1. Hue of 2.5YR or redder; and 1. Do not have a densic, lithic, or paralithic contact within 2. A value, moist, of 3 or less; and 150 cm of the mineral soil surface; and 3. A dry value no more than 1 unit higher than the moist 2. Within 150 cm of the mineral soil surface, either: value. a. With increasing depth, do not have a clay decrease Rhodic Kanhaplustults of 20 percent or more (relative) from the maximum clay HDCL. Other Kanhaplustults. content; or Typic Kanhaplustults b. Have 5 percent or more (by volume) skeletans on faces of peds or 5 percent or more (by volume) plinthite, Paleustults or both, in the layer that has a 20 percent lower clay content and, below that layer, a clay increase of 3 percent Key to Subgroups or more (absolute) in the fine-earth fraction. HDDA. All Paleustults. Palexerults, p. 286 Typic Paleustults HEB. Other Xerults. Plinthustults Haploxerults, p. 285 Key to Subgroups Haploxerults HDAA. Plinthustults that have either: Key to Subgroups 1. A densic, lithic, paralithic, or petroferric contact within HEBA. Haploxerults that have both: 150 cm of the mineral soil surface; or 1. A lithic contact within 50 cm of the mineral soil surface; U 2. Within 150 cm of the mineral soil surface, both: L and T a. With increasing depth, a clay decrease of 20 percent 2. In each pedon, a discontinuous argillic or kandic horizon or more (relative) from the maximum clay content; and that is interrupted by ledges of bedrock. b. Less than 5 percent (by volume) skeletans on faces of Lithic Ruptic-Inceptic Haploxerults peds in the layer that has a 20 percent lower clay content or, below that layer, a clay increase of less than 3 percent HEBB. Other Haploxerults that have a lithic contact within 50 (absolute) in the fine-earth fraction. cm of the mineral soil surface. Haplic Plinthustults Lithic Haploxerults

HDAB. Other Plinthustults. HEBC. Other Haploxerults that have, in one or more Typic Plinthustults subhorizons within the upper 25 cm of the argillic or kandic 286

horizon, redox depletions with a color value, moist, of 4 or particle-size class criteria throughout a layer extending from the more and chroma of 2 or less, accompanied by both redox mineral soil surface to the top of an argillic or kandic horizon at concentrations and aquic conditions for some time in normal a depth of 100 cm or more. years (or artificial drainage). Grossarenic Haploxerults Aquic Haploxerults HEBI. Other Haploxerults. HEBD. Other Haploxerults that have, throughout one or more Typic Haploxerults horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction with both a bulk Palexerults density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 Key to Subgroups and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. HEAA. Palexerults that have both: Andic Haploxerults 1. In one or more subhorizons within the upper 25 cm HEBE. Other Haploxerults that have an argillic or kandic of the argillic or kandic horizon, redox depletions with a horizon that: color value, moist, of 4 or more and chroma of 2 or less, accompanied by both redox concentrations and aquic 1. Consists entirely of lamellae; or conditions for some time in normal years (or artificial 2. Is a combination of two or more lamellae and one or drainage); and more subhorizons with a thickness of 7.5 to 20 cm, each 2. Throughout one or more horizons with a total thickness layer with an overlying eluvial horizon; or of 18 cm or more within 75 cm of the mineral soil surface, 3. Consists of one or more subhorizons that are more a fine-earth fraction with both a bulk density of 1.0 g/cm3 or 1 than 20 cm thick, each with an overlying eluvial horizon, and less, measured at 33 kPa water retention, and Al plus /2 Fe above these horizons there are either: percentages (by ammonium oxalate) totaling more than 1.0. Aquandic Palexerults a. Two or more lamellae with a combined thickness of 5 cm or more (that may or may not be part of the argillic or HEAB. Other Palexerults that have, in one or more kandic horizon); or subhorizons within the upper 25 cm of the argillic or kandic b. A combination of lamellae (that may or may not be horizon, redox depletions with a color value, moist, of 4 or part of the argillic or kandic horizon) and one or more more and chroma of 2 or less, accompanied by both redox parts of the argillic or kandic horizon 7.5 to 20 cm thick, concentrations and aquic conditions for some time in normal each with an overlying eluvial horizon. years (or artificial drainage). Lamellic Haploxerults Aquic Palexerults

HEBF. Other Haploxerults that have a sandy particle-size class HEAC. Other Palexerults that have, throughout one or more throughout the upper 75 cm of the argillic or kandic horizon or horizons with a total thickness of 18 cm or more within 75 cm throughout the entire horizon if it is less than 75 cm thick. of the mineral soil surface, a fine-earth fraction with both a bulk Psammentic Haploxerults density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling HEBG. Other Haploxerults that meet sandy or sandy-skeletal more than 1.0. particle-size class criteria throughout a layer extending from the Andic Palexerults mineral soil surface to the top of an argillic or kandic horizon at a depth of 50 to 100 cm. HEAD. Other Palexerults. Arenic Haploxerults Typic Palexerults

HEBH. Other Haploxerults that meet sandy or sandy-skeletal 287

CHAPTER 16 Vertisols

Key to Suborders FF. Other Vertisols. Uderts, p. 292 FA. Vertisols that have, in one or more horizons within 50 cm of the mineral soil surface, aquic conditions for some time in normal years (or artificial drainage) andone or both of the Aquerts following: Key to Great Groups 1. In more than half of each pedon, either on faces of FAA. Aquerts that have within 100 cm of the mineral soil peds or in the matrix if peds are absent, 50 percent or more surface either: chroma of either: 1. A sulfuric horizon; or a. 2 or less if redox concentrations are present; or b. 1 or less; or 2. Sulfidic materials. Sulfaquerts, p. 291 2. Enough active ferrous iron (Fe2+) to give a positive reaction to alpha,alpha-dipyridyl at a time when the soil is FAB. Other Aquerts that have a salic horizon within 100 cm of not being irrigated. the mineral soil surface. Aquerts, p. 287 Salaquerts, p. 290 FB. Other Vertisols that have a cryic soil temperature regime. FAC. Other Aquerts that have a duripan within 100 cm of the , p. 291 Cryerts mineral soil surface. Duraquerts, p. 288 FC. Other Vertisols that in normal years have both: 1. A thermic, mesic, or frigid soil temperature regime; and FAD. Other Aquerts that have a natric horizon within 100 cm 2. If not irrigated during the year, cracks that remain both: of the mineral soil surface. Natraquerts, p. 290 a. 5 mm or more wide, through a thickness of 25 cm or more within 50 cm of the mineral soil surface, for 60 or FAE. Other Aquerts that have a calcic horizon within 100 cm more consecutive days during the 90 days following the of the mineral soil surface. summer solstice; and Calciaquerts, p. 288 b. Closed for 60 or more consecutive days during the 90 days following the winter solstice. FAF. Other Aquerts that have, throughout one or more Xererts, p. 297 horizons with a total thickness of 25 cm or more within 50 cm of the mineral soil surface, both: FD. Other Vertisols that, if not irrigated during the year, 1. An electrical conductivity in the saturation extract of less have cracks in normal years that remain closed for less than 60 than 4.0 dS/m at 25 oC; and consecutive days during a period when the soil temperature at a o 2. A pH value of 4.5 or less in 0.01 M CaCl (5.0 or less in depth of 50 cm from the soil surface is higher than 8 C. 2 V Torrerts, p. 291 1:1 water). E Dystraquerts, p. 288 R FE. Other Vertisols that, if not irrigated during the year, have cracks in normal years that are 5 mm or more wide, through a FAG. Other Aquerts that have episaturation. thickness of 25 cm or more within 50 cm of the mineral soil Epiaquerts, p. 289 surface, for 90 or more cumulative days per year. FAH. Other Aquerts. Usterts, p. 293 Endoaquerts, p. 289 288 Keys to Soil Taxonomy

Calciaquerts 1. Hue of 2.5Y or redder and either: Key to Subgroups a. A color value, moist, of 6 or more and chroma of 3 or more; or FAEA. Calciaquerts that have, in one or more horizons between either an Ap horizon or a depth of 25 cm from the b. A color value, moist, of 5 or less and chroma of 2 or mineral soil surface, whichever is deeper, and either a depth more; or of 75 cm or the upper boundary of a duripan if shallower, 50 2. Hue of 5Y and chroma of 3 or more; or percent or more colors as follows: 3. Chroma of 2 or more and no redox concentrations. 1. Hue of 2.5Y or redder and : either Aeric Duraquerts a. A color value, moist, of 6 or more and chroma of 3 or more; or FACE. Other Duraquerts that have, in one or more horizons within 30 cm of the mineral soil surface, one or both of the b. A color value, moist, of 5 or less and chroma of 2 or following in more than half of each pedon: more; or 1. A color value, moist, of 4 or more; or 2. Hue of 5Y and chroma of 3 or more; or 2. A color value, dry, of 6 or more. 3. Chroma of 2 or more and no redox concentrations. Chromic Duraquerts Aeric Calciaquerts

FAEB. Other Calciaquerts. FACF. Other Duraquerts. Typic Calciaquerts Typic Duraquerts

Duraquerts Dystraquerts Key to Subgroups Key to Subgroups FACA. Duraquerts that, if not irrigated during the year, have FAFA. Dystraquerts that have, in one or more horizons within cracks in normal years that are 5 mm or more wide, through a 100 cm of the mineral soil surface, jarosite concentrations and a thickness of 25 cm or more within 50 cm of the mineral soil pH value of 4.0 or less (1:1 water, air-dried slowly in shade). surface, for 210 or more cumulative days per year. Sulfaqueptic Dystraquerts Aridic Duraquerts FAFB. Other Dystraquerts that, if not irrigated during the FACB. Other Duraquerts that have a thermic, mesic, or frigid year, have cracks in normal years that are 5 mm or more wide, soil temperature regime and that, if not irrigated during the year, through a thickness of 25 cm or more within 50 cm of the have cracks in normal years that remain both: mineral soil surface, for 210 or more cumulative days per year. Aridic Dystraquerts 1. 5 mm or more wide, through a thickness of 25 cm or more within 50 cm of the mineral soil surface, for 60 or more FAFC. Other Dystraquerts that, if not irrigated during the consecutive days during the 90 days following the summer year, have cracks in normal years that are 5 mm or more wide, solstice; and through a thickness of 25 cm or more within 50 cm of the 2. Closed for 60 or more consecutive days during the 90 mineral soil surface, for 90 or more cumulative days per year. days following the winter solstice. Ustic Dystraquerts Xeric Duraquerts FAFD. Other Dystraquerts that have, in one or more horizons FACC. Other Duraquerts that, if not irrigated during the between either an Ap horizon or a depth of 25 cm from the year, have cracks in normal years that are 5 mm or more wide, mineral soil surface, whichever is deeper, and a depth of 75 cm, through a thickness of 25 cm or more within 50 cm of the 50 percent or more colors as follows: mineral soil surface, for 90 or more cumulative days per year. 1. Hue of 2.5Y or redder and either: Ustic Duraquerts a. A color value, moist, of 6 or more and chroma of 3 or FACD. Other Duraquerts that have, in one or more horizons more; or between either an Ap horizon or a depth of 25 cm from the b. A color value, moist, of 5 or less and chroma of 2 or mineral soil surface, whichever is deeper, and either a depth more; or of 75 cm or the upper boundary of the duripan if shallower, 50 percent or more colors as follows: 2. Hue of 5Y and chroma of 3 or more; or Vertisols 289

3. Chroma of 2 or more and no redox concentrations. 2. Closed for 60 or more consecutive days during the 90 Aeric Dystraquerts days following the winter solstice. Xeric Endoaquerts FAFE. Other Dystraquerts that have a densic, lithic, or paralithic contact within 100 cm of the mineral soil surface. FAHE. Other Endoaquerts that, if not irrigated during the Leptic Dystraquerts year, have cracks in normal years that are 5 mm or more wide, through a thickness of 25 cm or more within 50 cm of the FAFF. Other Dystraquerts that have a layer, 25 cm or more mineral soil surface, for 90 or more cumulative days per year. thick within 100 cm of the mineral soil surface, that contains Ustic Endoaquerts less than 27 percent clay in its fine-earth fraction. Entic Dystraquerts FAHF. Other Endoaquerts that have, in one or more horizons between either an Ap horizon or a depth of 25 cm from the FAFG. Other Dystraquerts that have, in one or more horizons mineral soil surface, whichever is deeper, and a depth of 75 cm, 50 percent or more colors as follows: within 30 cm of the mineral soil surface, one or both of the following in more than half of each pedon: 1. Hue of 2.5Y or redder and either: 1. A color value, moist, of 4 or more; or a. A color value, moist, of 6 or more and chroma of 3 or more; or 2. A color value, dry, of 6 or more. Chromic Dystraquerts b. A color value, moist, of 5 or less and chroma of 2 or more; or FAFH. Other Dystraquerts. 2. Hue of 5Y and chroma of 3 or more; or Typic Dystraquerts 3. Chroma of 2 or more and no redox concentrations. Endoaquerts Aeric Endoaquerts Key to Subgroups FAHG. Other Endoaquerts that have a densic, lithic, or paralithic contact within 100 cm of the mineral soil surface. FAHA. Endoaquerts that have, throughout a layer 15 cm Leptic Endoaquerts or more thick within 100 cm of the mineral soil surface, an electrical conductivity of 15 dS/m or more (saturated paste) for FAHH. Other Endoaquerts that have a layer, 25 cm or more 6 or more months in normal years. thick within 100 cm of the mineral soil surface, that contains Halic Endoaquerts less than 27 percent clay in its fine-earth fraction. Entic Endoaquerts FAHB. Other Endoaquerts that have, in one or more horizons within 100 cm of the mineral soil surface, an exchangeable FAHI. Other Endoaquerts that have, in one or more horizons sodium percentage of 15 or more (or a sodium adsorption ratio within 30 cm of the mineral soil surface, one or both of the of 13 or more) for 6 or more months in normal years. following in more than half of each pedon: Sodic Endoaquerts 1. A color value, moist, of 4 or more; or FAHC. Other Endoaquerts that, if not irrigated during the 2. A color value, dry, of 6 or more. year, have cracks in normal years that are 5 mm or more wide, Chromic Endoaquerts through a thickness of 25 cm or more within 50 cm of the mineral soil surface, for 210 or more cumulative days per year. FAHJ. Other Endoaquerts. Aridic Endoaquerts Typic Endoaquerts

FAHD. Other Endoaquerts that have a thermic, mesic, or Epiaquerts V frigid soil temperature regime and that, if not irrigated during Key to Subgroups E the year, have cracks in normal years that remain both: R FAGA. Epiaquerts that have, throughout a layer 15 cm or 1. 5 mm or more wide, through a thickness of 25 cm or more thick within 100 cm of the mineral soil surface, an more within 50 cm of the mineral soil surface, for 60 or more electrical conductivity of 15 dS/m or more (saturated paste) for consecutive days during the 90 days following the summer 6 or more months in normal years. solstice; and Halic Epiaquerts 290 Keys to Soil Taxonomy

FAGB. Other Epiaquerts that have, in one or more horizons FAGI. Other Epiaquerts that have, in one or more horizons within 100 cm of the mineral soil surface, an exchangeable within 30 cm of the mineral soil surface, one or both of the sodium percentage of 15 or more (or a sodium adsorption ratio following in more than half of each pedon: of 13 or more) for 6 or more months in normal years. 1. A color value, moist, of 4 or more; Sodic Epiaquerts or 2. A color value, dry, of 6 or more. FAGC. Other Epiaquerts that, if not irrigated during the Chromic Epiaquerts year, have cracks in normal years that are 5 mm or more wide, through a thickness of 25 cm or more within 50 cm of the FAGJ. Other Epiaquerts. mineral soil surface, for 210 or more cumulative days per year. Typic Epiaquerts Aridic Epiaquerts Natraquerts FAGD. Other Epiaquerts that have a thermic, mesic, or frigid soil temperature regime and that, if not irrigated during the year, Key to Subgroups have cracks in normal years that remain both: FADA. All Natraquerts. 1. 5 mm or more wide, through a thickness of 25 cm or Typic Natraquerts more within 50 cm of the mineral soil surface, for 60 or more consecutive days during the 90 days following the summer Salaquerts solstice; and Key to Subgroups 2. Closed for 60 or more consecutive days during the 90 days following the winter solstice. FABA. Salaquerts that, if not irrigated during the year, have Xeric Epiaquerts cracks in normal years that are 5 mm or more wide, through a thickness of 25 cm or more within 50 cm of the mineral soil FAGE. Other Epiaquerts that, if not irrigated during the surface, for 210 or more cumulative days per year. year, have cracks in normal years that are 5 mm or more wide, Aridic Salaquerts through a thickness of 25 cm or more within 50 cm of the mineral soil surface, for 90 or more cumulative days per year. FABB. Other Salaquerts that, if not irrigated during the Ustic Epiaquerts year, have cracks in normal years that are 5 mm or more wide, through a thickness of 25 cm or more within 50 cm of the FAGF. Other Epiaquerts that have, in one or more horizons mineral soil surface, for 90 or more cumulative days per year. between either an Ap horizon or a depth of 25 cm from the Ustic Salaquerts mineral soil surface, whichever is deeper, and a depth of 75 cm, 50 percent or more colors as follows: FABC. Other Salaquerts that have a densic, lithic, or paralithic contact within 100 cm of the mineral soil surface. 1. Hue of 2.5Y or redder and either: Leptic Salaquerts a. A color value, moist, of 6 or more and chroma of 3 or more; or FABD. Other Salaquerts that have a layer, 25 cm or more thick within 100 cm of the mineral soil surface, that contains less than b. A color value, moist, of 5 or less and chroma of 2 or 27 percent clay in its fine-earth fraction. more; or Entic Salaquerts 2. Hue of 5Y and chroma of 3 or more; or FABE. Other Salaquerts that have, in one or more horizons 3. Chroma of 2 or more and no redox concentrations. within 30 cm of the mineral soil surface, 50 percent or more Aeric Epiaquerts colors as follows: FAGG. Other Epiaquerts that have a densic, lithic, or 1. A color value, moist, of 4 or more; or paralithic contact within 100 cm of the mineral soil surface. 2. A color value, dry, of 6 or more; or Leptic Epiaquerts 3. Chroma of 3 or more. FAGH. Other Epiaquerts that have a layer, 25 cm or more Chromic Salaquerts thick within 100 cm of the mineral soil surface, that contains less than 27 percent clay in its fine-earth fraction. FABF. Other Salaquerts. Entic Epiaquerts Typic Salaquerts Vertisols 291

Sulfaquerts FBAB. Other Humicryerts. Typic Humicryerts Key to Subgroups FAAA. Sulfaquerts that have a salic horizon within 75 cm of the mineral soil surface. Torrerts Salic Sulfaquerts Key to Great Groups FAAB. Other Sulfaquerts that do not have a sulfuric horizon FDA. Torrerts that have a salic horizon within 100 cm of the within 100 cm of the mineral soil surface. soil surface. Sulfic Sulfaquerts Salitorrerts, p. 292

FAAC. Other Sulfaquerts. FDB. Other Torrerts that have a gypsic horizon within 100 cm Typic Sulfaquerts of the soil surface. Gypsitorrerts, p. 292 Cryerts Key to Great Groups FDC. Other Torrerts that have a calcic or petrocalcic horizon within 100 cm of the soil surface. FBA. Cryerts that have 10 kg/m2 or more organic carbon Calcitorrerts, p. 291 between the mineral soil surface and a depth of 50 cm. Humicryerts, p. 291 FDD. Other Torrerts. Haplotorrerts, p. 292 FBB. Other Cryerts. Haplocryerts, p. 291 Calcitorrerts Haplocryerts Key to Subgroups Key to Subgroups FDCA. Calcitorrerts that have a petrocalcic horizon within FBBA. Haplocryerts that have, in one or more horizons within 100 cm of the soil surface. 100 cm of the mineral soil surface, an exchangeable sodium Petrocalcic Calcitorrerts percentage of 15 or more (or a sodium adsorption ratio of 13 or more) for 6 or more months in normal years. FDCB. Other Calcitorrerts that have a densic, lithic, or Sodic Haplocryerts paralithic contact or a duripan within 100 cm of the soil surface. Leptic Calcitorrerts FBBB. Other Haplocryerts that have, in one or more horizons within 30 cm of the mineral soil surface, 50 percent or more FDCC. Other Calcitorrerts that have a layer, 25 cm or more colors as follows: thick within 100 cm of the soil surface, that contains less than 1. A color value, moist, of 4 or more; or 27 percent clay in its fine-earth fraction. Entic Calcitorrerts 2. A color value, dry, of 6 or more; or 3. Chroma of 3 or more. FDCD. Other Calcitorrerts that have, in one or more horizons Chromic Haplocryerts within 30 cm of the soil surface, 50 percent or more colors as follows: FBBC. Other Haplocryerts. Typic Haplocryerts 1. A color value, moist, of 4 or more; or 2. A color value, dry, of 6 or more; or Humicryerts 3. Chroma of 3 or more. V Key to Subgroups Chromic Calcitorrerts E R FBAA. Humicryerts that have, in one or more horizons within 100 cm of the mineral soil surface, an exchangeable sodium FDCE. Other Calcitorrerts. percentage of 15 or more (or a sodium adsorption ratio of 13 or Typic Calcitorrerts more) for 6 or more months in normal years. Sodic Humicryerts 292 Keys to Soil Taxonomy

Gypsitorrerts Salitorrerts Key to Subgroups Key to Subgroups FDBA. Gypsitorrerts that have, in one or more horizons FDAA. Salitorrerts that have, in one or more horizons within within 30 cm of the soil surface, 50 percent or more colors as 100 cm of the soil surface, aquic conditions for some time in follows: normal years (or artificial drainage) andeither : 1. A color value, moist, of 4 or more; or 1. Redoximorphic features; or 2. A color value, dry, of 6 or more; or 2. Enough active ferrous iron (Fe2+) to give a positive reaction to alpha,alpha-dipyridyl at a time when the soil is 3. Chroma of 3 or more. not being irrigated. Chromic Gypsitorrerts Aquic Salitorrerts FDBB. Other Gypsitorrerts. Typic Gypsitorrerts FDAB. Other Salitorrerts that have a densic, lithic, or paralithic contact, a duripan, or a petrocalcic horizon within 100 Haplotorrerts cm of the soil surface. Leptic Salitorrerts Key to Subgroups FDAC. Other Salitorrerts that have a layer, 25 cm or more FDDA. Haplotorrerts that have, throughout a layer 15 cm thick within 100 cm of the soil surface, that contains less than or more thick within 100 cm of the soil surface, an electrical 27 percent clay in its fine-earth fraction. conductivity of 15 dS/m or more (saturated paste) for 6 or more Entic Salitorrerts months in normal years. Halic Haplotorrerts FDAD. Other Salitorrerts that have, in one or more horizons within 30 cm of the soil surface, 50 percent or more colors as FDDB. Other Haplotorrerts that have, in one or more horizons follows: within 100 cm of the soil surface, an exchangeable sodium percentage of 15 or more (or a sodium adsorption ratio of 13 or 1. A color value, moist, of 4 or more; or more) for 6 or more months in normal years. 2. A color value, dry, of 6 or more; Sodic Haplotorrerts or 3. Chroma of 3 or more. FDDC. Other Haplotorrerts that have a densic, lithic, or Chromic Salitorrerts paralithic contact or a duripan within 100 cm of the soil surface. Leptic Haplotorrerts FDAE. Other Salitorrerts. Typic Salitorrerts FDDD. Other Haplotorrerts that have a layer, 25 cm or more thick within 100 cm of the soil surface, that contains less than 27 percent clay in its fine-earth fraction. Uderts Entic Haplotorrerts Key to Great Groups FDDE. Other Haplotorrerts that have, in one or more horizons FFA. Uderts that have, throughout one or more horizons with within 30 cm of the soil surface, 50 percent or more colors as a total thickness of 25 cm or more within 50 cm of the mineral follows: soil surface, both: 1. A color value, moist, of 4 or more; or 1. An electrical conductivity in the saturation extract of less than 4.0 dS/m at 25 oC; and 2. A color value, dry, of 6 or more; or 2. A pH value of 4.5 or less in 0.01 M CaCl2 (5.0 or less in 3. Chroma of 3 or more. saturated paste). Chromic Haplotorrerts Dystruderts, p. 293

FDDF. Other Haplotorrerts. FFB. Other Uderts. Typic Haplotorrerts Hapluderts, p. 293 Vertisols 293

Dystruderts 1. Redoximorphic features; or Key to Subgroups 2. Enough active ferrous iron (Fe2+) to give a positive reaction to alpha,alpha-dipyridyl at a time when the soil is FFAA. Dystruderts that have, in one or more horizons within not being irrigated. 100 cm of the mineral soil surface, aquic conditions for some Aquic Hapluderts time in normal years (or artificial drainage) andeither : 1. Redoximorphic features; or FFBC. Other Hapluderts that are saturated with water in one or more layers within 100 cm of the mineral soil surface in 2. Enough active ferrous iron (Fe2+) to give a positive normal years for either or both: reaction to alpha,alpha-dipyridyl at a time when the soil is not being irrigated. 1. 20 or more consecutive days; or Aquic Dystruderts 2. 30 or more cumulative days. Oxyaquic Hapluderts FFAB. Other Dystruderts that are saturated with water in one or more layers within 100 cm of the mineral soil surface in FFBD. Other Hapluderts that have a densic, lithic, or normal years for either or both: paralithic contact within 100 cm of the mineral soil surface. 1. 20 or more consecutive days; or Leptic Hapluderts 2. 30 or more cumulative days. FFBE. Other Hapluderts that have a layer, 25 cm or more Oxyaquic Dystruderts thick within 100 cm of the mineral soil surface, that contains less than 27 percent clay in its fine-earth fraction. FFAC. Other Dystruderts that have a densic, lithic, or Entic Hapluderts paralithic contact within 100 cm of the mineral soil surface. Leptic Dystruderts FFBF. Other Hapluderts that have, in one or more horizons within 30 cm of the mineral soil surface, 50 percent or more FFAD. Other Dystruderts that have a layer, 25 cm or more colors as follows: thick within 100 cm of the mineral soil surface, that contains less than 27 percent clay in its fine-earth fraction. 1. A color value, moist, of 4 or more; or Entic Dystruderts 2. A color value, dry, of 6 or more; or

FFAE. Other Dystruderts that have, in one or more horizons 3. Chroma of 3 or more. within 30 cm of the mineral soil surface, 50 percent or more Chromic Hapluderts colors as follows: FFBG. Other Hapluderts. 1. A color value, moist, of 4 or more; or Typic Hapluderts 2. A color value, dry, of 6 or more; or 3. Chroma of 3 or more. Usterts Chromic Dystruderts Key to Great Groups FFAF. Other Dystruderts. FEA. Usterts that have, throughout one or more horizons with Typic Dystruderts a total thickness of 25 cm or more within 50 cm of the mineral soil surface, both: Hapluderts 1. An electrical conductivity in the saturation extract of less Key to Subgroups than 4.0 dS/m at 25 oC; and FFBA. Hapluderts that have a lithic contact within 50 cm of V 2. A pH value of 4.5 or less in 0.01 M CaCl2 (5.0 or less in E the mineral soil surface. saturated paste). R Lithic Hapluderts Dystrusterts, p. 294

FFBB. Other Hapluderts that have, in one or more horizons FEB. Other Usterts that have a salic horizon within 100 cm of within 100 cm of the mineral soil surface, aquic conditions for the mineral soil surface. some time in normal years (or artificial drainage) andeither : Salusterts, p. 296 294 Keys to Soil Taxonomy

FEC. Other Usterts that have a gypsic horizon within 100 cm FEDH. Other Calciusterts that have a layer, 25 cm or more of the mineral soil surface. thick within 100 cm of the mineral soil surface, that contains Gypsiusterts, p. 295 less than 27 percent clay in its fine-earth fraction. Entic Calciusterts FED. Other Usterts that have a calcic or petrocalcic horizon within 100 cm of the mineral soil surface. FEDI. Other Calciusterts that have, in one or more horizons Calciusterts, p. 294 within 30 cm of the mineral soil surface, 50 percent or more colors as follows: FEE. Other Usterts. 1. A color value, moist, of 4 or more; or Haplusterts, p. 295 2. A color value, dry, of 6 or more; or Calciusterts 3. Chroma of 3 or more. Key to Subgroups Chromic Calciusterts

FEDA. Calciusterts that have a lithic contact within 50 cm of FEDJ. Other Calciusterts. the mineral soil surface. Typic Calciusterts Lithic Calciusterts Dystrusterts FEDB. Other Calciusterts that have, throughout a layer 15 cm or more thick within 100 cm of the mineral soil surface, an Key to Subgroups electrical conductivity of 15 dS/m or more (saturated paste) for FEAA. Dystrusterts that have a lithic contact within 50 cm of 6 or more months in normal years. the mineral soil surface. Halic Calciusterts Lithic Dystrusterts

FEDC. Other Calciusterts that have, in one or more horizons FEAB. Other Dystrusterts that have, in one or more horizons within 100 cm of the mineral soil surface, an exchangeable within 100 cm of the mineral soil surface, aquic conditions for sodium percentage of 15 or more (or a sodium adsorption ratio some time in normal years (or artificial drainage) andeither : of 13 or more) for 6 or more months in normal years. Sodic Calciusterts 1. Redoximorphic features; or 2. Enough active ferrous iron (Fe2+) to give a positive FEDD. Other Calciusterts that have a petrocalcic horizon reaction to alpha,alpha-dipyridyl at a time when the soil is within 100 cm of the mineral soil surface. not being irrigated. Petrocalcic Calciusterts Aquic Dystrusterts

FEDE. Other Calciusterts that, if not irrigated during the FEAC. Other Dystrusterts that, if not irrigated during the year, have cracks in normal years that are 5 mm or more wide, year, have cracks in normal years that are 5 mm or more wide, through a thickness of 25 cm or more within 50 cm of the through a thickness of 25 cm or more within 50 cm of the mineral soil surface, for 210 or more cumulative days per year. mineral soil surface, for 210 or more cumulative days per year. Aridic Calciusterts Aridic Dystrusterts

FEDF. Other Calciusterts that, if not irrigated during the FEAD. Other Dystrusterts that, if not irrigated during the year, have cracks in normal years that are 5 mm or more wide, year, have cracks in normal years that are 5 mm or more wide, through a thickness of 25 cm or more within 50 cm of the through a thickness of 25 cm or more within 50 cm of the mineral soil surface, for less than 150 cumulative days per year. mineral soil surface, for less than 150 cumulative days. Udic Calciusterts Udic Dystrusterts

FEDG. Other Calciusterts that have a densic, lithic, or FEAE. Other Dystrusterts that have a densic, lithic, or paralithic contact or a duripan within 100 cm of the mineral soil paralithic contact or a duripan within 100 cm of the mineral soil surface. surface. Leptic Calciusterts Leptic Dystrusterts Vertisols 295

FEAF. Other Dystrusterts that have a layer, 25 cm or more FECG. Other Gypsiusterts that have a layer, 25 cm or more thick within 100 cm of the mineral soil surface, that contains thick within 100 cm of the mineral soil surface, that contains less than 27 percent clay in its fine-earth fraction. less than 27 percent clay in its fine-earth fraction. Entic Dystrusterts Entic Gypsiusterts

FEAG. Other Dystrusterts that have, in one or more horizons FECH. Other Gypsiusterts that have, in one or more horizons within 30 cm of the mineral soil surface, 50 percent or more within 30 cm of the mineral soil surface, 50 percent or more colors as follows: colors as follows: 1. A color value, moist, of 4 or more; or 1. A color value, moist, of 4 or more; or 2. A color value, dry, of 6 or more; or 2. A color value, dry, of 6 or more; or 3. Chroma of 3 or more. 3. Chroma of 3 or more. Chromic Dystrusterts Chromic Gypsiusterts

FEAH. Other Dystrusterts. FECI. Other Gypsiusterts. Typic Dystrusterts Typic Gypsiusterts

Gypsiusterts Haplusterts Key to Subgroups Key to Subgroups FECA. Gypsiusterts that have a lithic contact within 50 cm of FEEA. Haplusterts that have a lithic contact within 50 cm of the mineral soil surface. the mineral soil surface. Lithic Gypsiusterts Lithic Haplusterts

FECB. Other Gypsiusterts that have, throughout a layer 15 FEEB. Other Haplusterts that have, throughout a layer 15 cm or more thick within 100 cm of the mineral soil surface, an cm or more thick within 100 cm of the mineral soil surface, an electrical conductivity of 15 dS/m or more (saturated paste) for electrical conductivity of 15 dS/m or more (saturated paste) for 6 or more months in normal years. 6 or more months in normal years. Halic Gypsiusterts Halic Haplusterts FEEC. Other Haplusterts that have, in one or more horizons FECC. Other Gypsiusterts that have, in one or more horizons within 100 cm of the mineral soil surface, an exchangeable within 100 cm of the mineral soil surface, an exchangeable sodium percentage of 15 or more (or a sodium adsorption ratio sodium percentage of 15 or more (or a sodium adsorption ratio of 13 or more) for 6 or more months in normal years. of 13 or more) for 6 or more months in normal years. Sodic Haplusterts Sodic Gypsiusterts FEED. Other Haplusterts that have a petrocalcic horizon FECD. Other Gypsiusterts that, if not irrigated during the within 150 cm of the mineral soil surface. year, have cracks in normal years that are 5 mm or more Petrocalcic Haplusterts wide, through a thickness of 25 cm or more within 50 cm of the mineral soil surface, for 210 or more cumulative days per year. FEEE. Other Haplusterts that have a gypsic horizon within Aridic Gypsiusterts 150 cm of the mineral soil surface. Gypsic Haplusterts FECE. Other Gypsiusterts that, if not irrigated during the year, have cracks in normal years that are 5 mm or more wide, FEEF. Other Haplusterts that have a calcic horizon within 150 through a thickness of 25 cm or more within 50 cm of the cm of the mineral soil surface. mineral soil surface, for less than 150 cumulative days per year. V Calcic Haplusterts E Udic Gypsiusterts R FEEG. Other Haplusterts that have both: FECF. Other Gypsiusterts that have a densic, lithic, or paralithic contact, a duripan, or a petrocalcic horizon within 100 1. A densic, lithic, or paralithic contact within 100 cm of cm of the mineral soil surface. the mineral soil surface; and Leptic Gypsiusterts 296 Keys to Soil Taxonomy

2. If not irrigated during the year, cracks in normal years FEEM. Other Haplusterts that have a densic, lithic, or that are 5 mm or more wide, through a thickness of 25 cm paralithic contact or a duripan within 100 cm of the mineral soil or more within 50 cm of the mineral soil surface, for 210 or surface. more cumulative days per year. Leptic Haplusterts Aridic Leptic Haplusterts FEEN. Other Haplusterts that have a layer, 25 cm or more FEEH. Other Haplusterts that, if not irrigated during the thick within 100 cm of the mineral soil surface, that contains year, have cracks in normal years that are 5 mm or more wide, less than 27 percent clay in its fine-earth fraction. through a thickness of 25 cm or more within 50 cm of the Entic Haplusterts mineral soil surface, for 210 or more cumulative days per year. Aridic Haplusterts FEEO. Other Haplusterts that have, in one or more horizons within 30 cm of the mineral soil surface, 50 percent or more FEEI. Other Haplusterts that have both: colors as follows: 1. A densic, lithic, or paralithic contact within 100 cm of 1. A color value, moist, of 4 or more; or the mineral soil surface; and 2. A color value, dry, of 6 or more; or 2. If not irrigated during the year, cracks in normal years that are 5 mm or more wide, through a thickness of 25 cm or 3. Chroma of 3 or more. more within 50 cm of the mineral soil surface, for less than Chromic Haplusterts 150 cumulative days per year. Leptic Udic Haplusterts FEEP. Other Haplusterts. Typic Haplusterts FEEJ. Other Haplusterts that have both: 1. A layer, 25 cm or more thick within 100 cm of the Salusterts mineral soil surface, that contains less than 27 percent clay in Key to Subgroups its fine-earth fraction;and FEBA. Salusterts that have a lithic contact within 50 cm of the 2. If not irrigated during the year, cracks in normal years mineral soil surface. that are 5 mm or more wide, through a thickness of 25 cm or Lithic Salusterts more within 50 cm of the mineral soil surface, for less than 150 cumulative days per year. FEBB. Other Salusterts that have, in one or more horizons Entic Udic Haplusterts within 100 cm of the mineral soil surface, an exchangeable sodium percentage of 15 or more (or a sodium adsorption ratio FEEK. Other Haplusterts that have both: of 13 or more) for 6 or more months in normal years. 1. In one or more horizons within 30 cm of the mineral soil Sodic Salusterts surface, 50 percent or more colors as follows: FEBC. Other Salusterts that have, in one or more horizons a. A color value, moist, of 4 or more; or within 100 cm of the mineral soil surface, aquic conditions for b. A color value, dry, of 6 or more; or some time in normal years (or artificial drainage) andeither : c. Chroma of 3 or more; and 1. Redoximorphic features; or 2. If not irrigated during the year, cracks in normal years 2. Enough active ferrous iron (Fe2+) to give a positive that are 5 mm or more wide, through a thickness of 25 cm or reaction to alpha,alpha-dipyridyl at a time when the soil is more within 50 cm of the mineral soil surface, for less than not being irrigated. 150 cumulative days per year. Aquic Salusterts Chromic Udic Haplusterts FEBD. Other Salusterts that, if not irrigated during the year, FEEL. Other Haplusterts that, if not irrigated during the have cracks in normal years that are 5 mm or more wide, year, have cracks in normal years that are 5 mm or more wide, through a thickness of 25 cm or more within 50 cm of the through a thickness of 25 cm or more within 50 cm of the mineral soil surface, for 210 or more cumulative days per year. mineral soil surface, for less than 150 cumulative days per year. Aridic Salusterts Udic Haplusterts Vertisols 297

FEBE. Other Salusterts that have a densic, lithic, or paralithic FCBD. Other Calcixererts that have a densic, lithic, or contact, a duripan, or a petrocalcic horizon within 100 cm of the paralithic contact within 100 cm of the mineral soil surface. mineral soil surface. Leptic Calcixererts Leptic Salusterts FCBE. Other Calcixererts that have a layer, 25 cm or more FEBF. Other Salusterts that have a layer, 25 cm or more thick thick within 100 cm of the mineral soil surface, that contains within 100 cm of the mineral soil surface, that contains less than less than 27 percent clay in its fine-earth fraction. 27 percent clay in its fine-earth fraction. Entic Calcixererts Entic Salusterts FCBF. Other Calcixererts that have, in one or more horizons FEBG. Other Salusterts that have, in one or more horizons within 30 cm of the mineral soil surface, 50 percent or more within 30 cm of the mineral soil surface, 50 percent or more colors as follows: colors as follows: 1. A color value, moist, of 4 or more; or 1. A color value, moist, of 4 or more; or 2. A color value, dry, of 6 or more; or 2. A color value, dry, of 6 or more; or 3. Chroma of 3 or more. 3. Chroma of 3 or more. Chromic Calcixererts Chromic Salusterts FCBG. Other Calcixererts. FEBH. Other Salusterts. Typic Calcixererts Typic Salusterts Durixererts Xererts Key to Subgroups Key to Great Groups FCAA. Durixererts that have, throughout a layer 15 cm or FCA. Xererts that have a duripan within 100 cm of the more thick above the duripan, an electrical conductivity of 15 mineral soil surface. dS/m or more (saturated paste) for 6 or more months in normal Durixererts, p. 297 years. Halic Durixererts FCB. Other Xererts that have a calcic or petrocalcic horizon within 100 cm of the mineral soil surface. FCAB. Other Durixererts that have, in one or more horizons Calcixererts, p. 297 above the duripan, an exchangeable sodium percentage of 15 or more (or a sodium adsorption ratio of 13 or more) for 6 or more FCC. Other Xererts. months in normal years. Haploxererts, p. 298 Sodic Durixererts

Calcixererts FCAC. Other Durixererts that have, in one or more horizons above the duripan, aquic conditions for some time in normal Key to Subgroups years (or artificial drainage) andeither : FCBA. Calcixererts that have a lithic contact within 50 cm of 1. Redoximorphic features; or the mineral soil surface. Lithic Calcixererts 2. Enough active ferrous iron (Fe2+) to give a positive reaction to alpha,alpha-dipyridyl at a time when the soil is FCBB. Other Calcixererts that have a petrocalcic horizon not being irrigated. within 100 cm of the mineral soil surface. Aquic Durixererts V Petrocalcic Calcixererts E FCAD. Other Durixererts that, if not irrigated during the year, R FCBC. Other Calcixererts that, if not irrigated during the have cracks in normal years that remain 5 mm or more wide, year, have cracks in normal years that remain 5 mm or more through a thickness of 25 cm or more above the duripan, for 180 wide, through a thickness of 25 cm or more within 50 cm of the or more consecutive days. mineral soil surface, for 180 or more consecutive days. Aridic Durixererts Aridic Calcixererts 298

FCAE. Other Durixererts that, if not irrigated during the year, year, have cracks in normal years that remain 5 mm or more have cracks in normal years that remain 5 mm or more wide, wide, through a thickness of 25 cm or more within 50 cm of the through a thickness of 25 cm or more above the duripan, for less mineral soil surface, for 180 or more consecutive days. than 90 consecutive days. Aridic Haploxererts Udic Durixererts FCCE. Other Haploxererts that have, in one or more horizons FCAF. Other Durixererts that have a duripan that is not within 100 cm of the mineral soil surface, aquic conditions for indurated in any subhorizon. some time in normal years (or artificial drainage) andeither : Haplic Durixererts 1. Redoximorphic features; or FCAG. Other Durixererts that have, in one or more horizons 2. Enough active ferrous iron (Fe2+) to give a positive within 30 cm of the mineral soil surface, 50 percent or more reaction to alpha,alpha-dipyridyl at a time when the soil is colors as follows: not being irrigated. Aquic Haploxererts 1. A color value, moist, of 4 or more; or 2. A color value, dry, of 6 or more; or FCCF. Other Haploxererts that, if not irrigated during the year, have cracks in normal years that remain 5 mm or more 3. Chroma of 3 or more. wide, through a thickness of 25 cm or more within 50 cm of the Chromic Durixererts mineral soil surface, for less than 90 consecutive days. Udic Haploxererts FCAH. Other Durixererts. Typic Durixererts FCCG. Other Haploxererts that have a densic, lithic, or paralithic contact within 100 cm of the mineral soil surface. Haploxererts Leptic Haploxererts Key to Subgroups FCCH. Other Haploxererts that have a layer, 25 cm or more FCCA. Haploxererts that have a lithic contact within 50 cm of thick within 100 cm of the mineral soil surface, that contains the mineral soil surface. less than 27 percent clay in its fine-earth fraction. Lithic Haploxererts Entic Haploxererts

FCCB. Other Haploxererts that have, throughout a layer 15 FCCI. Other Haploxererts that have, in one or more horizons cm or more thick within 100 cm of the mineral soil surface, an within 30 cm of the mineral soil surface, 50 percent or more electrical conductivity of 15 dS/m or more (saturated paste) for colors as follows: 6 or more months in normal years. Halic Haploxererts 1. A color value, moist, of 4 or more; or 2. A color value, dry, of 6 or more; or FCCC. Other Haploxererts that have, in one or more horizons within 100 cm of the mineral soil surface, an exchangeable 3. Chroma of 3 or more. sodium percentage of 15 or more (or a sodium adsorption ratio Chromic Haploxererts of 13 or more) for 6 or more months in normal years. Sodic Haploxererts FCCJ. Other Haploxererts. Typic Haploxererts FCCD. Other Haploxererts that, if not irrigated during the 299

CHAPTER 17 Family and Series Differentiae and Names

Families and series serve purposes that are largely pragmatic; microns. Engineering classifications have been based on grain- the series name is abstract, and the technical family name is size percentages, by weight, in the soil fraction less than 74 mm descriptive. In this chapter the descriptive terms used in the in diameter, while texture classes in pedologic classifications names of families are defined, the control sections to which the have been based on percentages, by weight, in the fraction less terms apply are given, and the criteria, including the taxa in than 2.0 mm in diameter. In engineering classifications, the which they are used, are indicated. separate very fine sand (diameter between 50 and 100 microns or 0.05 and 0.1 mm) has been subdivided at 74 microns. In Family Differentiae for Mineral Soils and defining the particle-size classes for this taxonomy, a similar division has been made, but in a different way. Soil materials Mineral Layers of Some Organic Soils that have a texture class of fine sand or loamy fine sand The following differentiae are used to distinguish families of normally have an appreciable amount of very fine sand, most mineral soils and the mineral layers of some organic soils within of which is coarser than 74 microns. A silty sediment, such as a subgroup. The class names of these components are used to loess, may also contain an appreciable amount of very fine sand, form the family name. The components are listed and defined most of which is finer than 74 microns. Thus, in the design of in the same sequence in which the components appear in the particle-size classes for this taxonomy, the very fine sand has family names. been allowed to “float.” It is included with the sand if the texture class (fine-earth fraction) of a soil is sand, loamy fine sand, or Particle-size classes and their substitutes coarser. It is treated as silt, however, if the texture class is very Mineralogy classes fine sand, loamy very fine sand, sandy loam, silt loam, or finer. Cation-exchange activity classes No single set of particle-size classes seems adequate to Calcareous and reaction classes serve as family differentiae for all of the different kinds of Soil temperature classes soil. Thus, this taxonomy provides 2 generalized and 11 Soil depth classes more narrowly defined classes, which permit relatively fine Rupture-resistance classes distinctions between families of soils for which particle size Classes of coatings on sands is important, while providing broader groupings for soils in Classes of permanent cracks which narrowly defined particle-size classes would produce undesirable separations. Thus, the term “clayey” is used for Particle-Size Classes and Their Substitutes some soil families to indicate a clay content of 35 percent (30 percent in Vertisols) or more in specific horizons, while in other Definition of Particle-Size Classes and Their Substitutes for families the more narrowly defined terms “fine” and “very-fine” Mineral Soils indicate that these horizons have a clay content either of 35 (30 The first part of the family name is the name of either a percent in Vertisols) to 60 percent or of 60 percent or more in particle-size class or a substitute for a particle-size class. The their fine-earth fraction. Fine earth refers to particles smaller term particle-size class is used to characterize the grain-size than 2.0 mm in diameter. Rock fragments are particles 2.0 mm composition of the whole soil, including both the fine earth and or more in diameter that are strongly cemented or more resistant the rock and pararock fragments up to the size of a pedon, but to rupture and include all particles with horizontal dimensions it excludes organic matter and salts more soluble than gypsum. smaller than the size of a pedon. Cemented fragments 2.0 mm Substitutes for particle-size classes are used for soils that have or more in diameter that are in a rupture-resistance class that is andic soil properties or a high content of volcanic glass, pumice, less cemented than the strongly cemented class are referred to cinders, rock fragments, or gypsum. as pararock fragments. Pararock fragments, like rock fragments, F The particle-size classes of this taxonomy represent a include all particles between 2.0 mm and a horizontal dimension A M compromise between conventional divisions in pedologic and smaller than the size of a pedon. Most pararock fragments engineering classifications. Engineering classifications have are broken into fragments 2.0 mm or less in diameter during set the limit between sand and silt at a diameter of 74 microns, the preparation of samples for particle-size analysis in the while pedologic classifications have set it at either 50 or 20 laboratory. Therefore, pararock fragments are generally included 300 Keys to Soil Taxonomy

with the fine earth in the particle-size classes, although cinders, name applies to one or more parts of the particle-size control pumice, and pumicelike fragments are treated as fragments in section and the parts are not strongly contrasting classes, the the substitutes for classes, regardless of their rupture-resistance name of the thickest part (cumulative) is used as the soil family class. name. Substitutes for particle-size classes are used for soils Aniso Class that have andic soil properties or a high content of volcanic glass, pumice, cinders, rock fragments, or gypsum. These If the particle-size control section includes more than one materials cannot be readily dispersed and have variable results pair of the strongly contrasting classes, listed below, then the of dispersion. The substitute classes dominated by rock and soil is assigned to an aniso class named for the pair of adjacent pararock fragments have too little fine-earth component for classes that contrast most strongly. The aniso class is considered valid data, and soil properties are dominated by the fragments. a modifier of the particle-size class name and is set off by Consequently, normal particle-size classes do not adequately commas after the particle-size name. An example is a sandy characterize these soils. Substitutes for particle-size class names over clayey, aniso, mixed, active, mesic Aridic Haplustoll. are used for those parts of soils that have andic soil properties Generalized Particle-Size Classes or a high content of volcanic glass, pumice, or cinders, as is the case with Andisols and many Andic and Vitrandic subgroups Two generalized particle-size classes, loamy and clayey, are of other soil orders. The “gypseous” substitutes for particle- used for shallow classes (defined below) and for soils in Arenic, size class are used for mineral soils (e.g., Aridisols) that have Grossarenic, and Lithic subgroups. The clayey class is used a high content of gypsum. Some Spodosols, whether identified for all strongly contrasting particle-size classes with more than in Andic subgroups or not, have andic soil properties in some 35 percent clay (30 percent in Vertisols). The loamy particle- horizons within the particle-size control section, and particle- size class is used for contrasting classes, where appropriate, to size substitute class names are used for these horizons. characterize the lower part of the particle-size control section. Neither a particle-size class nor a substitute for a The generalized classes, where appropriate, are also used for particle-size class is used for Psamments, Psammaquents, all strongly contrasting particle-size classes that include a Psammowassents, Psammoturbels, Psammorthels, and substitute class. For example, loamy over pumiceous or cindery Psammentic subgroups that meet sandy particle-size class (not fine-loamy over pumiceous or cindery) is used. criteria. These taxa, by definition, meet sandy particle-size class Six generalized classes, defined later in this chapter, are used criteria (i.e., have a texture class of sand or loamy sand), so the for Terric subgroups of Histosols and Histels. sandy particle-size class is considered redundant in the family Control Section for Particle-Size Classes and Their name. The ashy substitute class, however, is used, if appropriate Substitutes in Mineral Soils in these taxa (e.g., high content of volcanic glass). Particle-size classes are applied, although with reservations, The particle-size and substitute class names listed below to spodic horizons and other horizons that do not have andic are applied to certain horizons, or to the soil materials within soil properties but contain significant amounts of allophane, specific depth limits, that have been designated as the control imogolite, ferrihydrite, or aluminum-humus complexes. The section for particle-size classes and their substitutes. The lower isotic mineralogy class (defined below) is helpful in identifying boundary of the control section may be at a specified depth (in these particle-size classes. centimeters) below the mineral soil surface or below the upper In general, the weighted average particle-size class of the boundary of an organic layer with andic soil properties, or it whole particle-size control section (defined below) determines may coincide with the upper boundary of a root-limiting layer what particle-size class name is used as a component of the (defined below). family name. Root-Limiting Layers Strongly Contrasting Particle-Size Classes The concept of root-limiting layers as used in this taxonomy If the particle-size control section consists of two parts with defines the base of the soil horizons considered for most (but strongly contrasting particle-size or substitute classes (listed not all) differentiae at the family level. The properties of soil below), if both parts are 12.5 cm or more thick (including parts materials above the base and within the control section are not in the control section), and if the transition zone between used for assignment of classes, such as particle-size classes and them is less than 12.5 cm thick, both class names are used. For their substitutes. One notable exception to the concept of root- example, the family particle-size class is sandy over clayey if limiting layers is in assignment of soil depth classes (defined all of the following criteria are met: the soil meets criterion D below) to soils with fragipans. Unless otherwise indicated, the (listed below) under the control section for particle-size classes following are considered root-limiting layers in this chapter: or their substitutes; any Ap horizon is less than 30 cm thick; the a duripan; a fragipan; petrocalcic, petrogypsic, and placic weighted average particle-size class of the upper 30 cm of the horizons; continuous ortstein; and densic, lithic, paralithic, and soil is sandy; the weighted average of the lower part is clayey; petroferric contacts. and the transition zone is less than 12.5 cm thick. If a substitute Family and Series Differentiae and Names 301

Key to the Control Section for Particle-Size Classes and argillic, kandic, or natric horizon if 50 cm or less thick or the Their Substitutes in Mineral Soils upper 50 cm of the horizon if more than 50 cm thick. The following list of particle-size control sections for D. For those Alfisols, Ultisols, and great groups of Aridisols particular kinds of mineral soils is arranged as a key. This key, and Mollisols that are in a Lamellic subgroup or have an like other keys in this taxonomy, is designed in such a way that argillic, kandic, or natric horizon that has its upper boundary the reader makes the correct classification by going through the at a depth of 100 cm or more from the mineral surface and that key systematically, starting at the beginning and eliminating one are not in a Grossarenic or Arenic subgroup: Between the lower by one all classes that include criteria that do not fit the soil in boundary of an Ap horizon or a depth of 25 cm from the mineral question. The soil belongs to the first class for which it meets all soil surface, whichever is deeper, and 100 cm below the mineral of the criteria listed. The upper boundary of an argillic, natric, soil surface or a root-limiting layer, whichever is shallower; or or kandic horizon is used in the following key. This boundary E. For other soils that have an argillic or natric horizon that is not always obvious. If one of these horizons is present but has its lower boundary at a depth of less than 25 cm from the the upper boundary is irregular or broken, as in an A/B or B/A mineral soil surface: Between the upper boundary of the argillic horizon, the depth at which half or more of the volume has or natric horizon and a depth of 100 cm below the mineral soil the fabric of an argillic, natric, or kandic horizon should be surface or a root-limiting layer, whichever is shallower; or considered the upper boundary. F. All other mineral soils: Between the lower boundary of an A. For mineral soils that have a root-limiting layer (listed Ap horizon or a depth of 25 cm below the mineral soil surface, above) within 36 cm of the mineral soil surface or below whichever is deeper, and the shallower of the following: (a) a the upper boundary of organic soil materials with andic soil depth of 100 cm below the mineral soil surface or (b) a root- properties, whichever is shallower: From the mineral soil limiting layer. surface or the upper boundary of the organic soil materials with andic soil properties, whichever is shallower, to the root-limiting Key to the Particle-Size and Substitute Classes of Mineral layer; or Soils B. For Andisols: Between either the mineral soil surface or the This key, like other keys in this taxonomy, is designed in upper boundary of an organic layer with andic soil properties, such a way that the reader makes the correct classification by whichever is shallower, and the shallower of the following: (a) going through the key systematically, starting at the beginning a depth 100 cm below the starting point or (b) a root-limiting and eliminating one by one all classes that include criteria that layer; or do not fit the soil or layer in question. The class or substitute C. For those Alfisols, Ultisols, and great groups of Aridisols name for each layer within the control section must be and Mollisols, excluding soils in Lamellic subgroups, that determined from the key. If any two layers meet the criteria for have an argillic, kandic, or natric horizon that has its upper strongly contrasting particle-size classes (listed below), the soil boundary within 100 cm of the mineral soil surface and its is named for that strongly contrasting class. If more than one lower boundary at a depth of 25 cm or more below the mineral pair meets the criteria for strongly contrasting classes, the soil soil surface or that are in a Grossarenic or Arenic subgroup, use is also in an aniso class named for the pair of adjacent classes items 1 through 4 below. For other soils, go to section D below. that contrast most strongly. If the soil has none of the strongly contrasting classes, the weighted average soil materials within 1. Strongly contrasting particle-size classes (defined and the particle-size control section generally determine the class. listed later) within or below the argillic, kandic, or natric Exceptions are soils that are not strongly contrasting and that horizon and within 100 cm of the mineral soil surface: The have a substitute class name for one or more parts of the control upper 50 cm of the argillic, kandic, or natric horizon or to section. In these soils the class or substitute name of the thickest a depth of 100 cm, whichever is deeper, but not below the (cumulative) part within the control section is used to determine upper boundary of a root-limiting layer; or the family name. 2. All parts of the argillic, kandic, or natric horizon in or A. Mineral soils that have, in the thickest part of the control below a fragipan: Between a depth of 25 cm from the mineral section (if the control section is not in one of the strongly soil surface and the top of the fragipan; or contrasting particle-size classes listed below), or in a part of the control section that qualifies as an element in one of the strongly 3. A fragipan at a depth of less than 50 cm below the top contrasting particle-size classes listed below, or throughout the of the argillic, kandic, or natric horizon: Between the upper F control section, a fine-earth component (including associated boundary of the argillic, kandic, or natric horizon and the top A medium and finer pores) of less than 10 percent of the total M the fragipan; or volume and that meet one of the following sets of substitute 4. Other soils that meet section C above: Either the whole class criteria: 302 Keys to Soil Taxonomy

1. Have, in the whole soil, more than 60 percent (2) 35 percent or more (by volume) rock fragments. (by weight) volcanic ash, cinders, lapilli, pumice, and Ashy-skeletal pumicelike1 fragments and, in the fraction more than 2.0 mm or in diameter, two-thirds or more (by volume) pumice and/or pumicelike fragments. (3) Less than 35 percent (by volume) rock fragments. Pumiceous Ashy or or

2. Have, in the whole soil, more than 60 percent (by 2. Have a fine-earth fraction that has andic soil properties weight) volcanic ash, cinders, lapilli, pumice, and pumicelike and that has a water content at 1500 kPa tension of less than fragments and, in the fraction more than 2.0 mm in diameter, 100 percent on undried samples; and less than two-thirds (by volume) pumice and/or pumicelike a. Have a total of 35 percent or more (by volume) rock fragments. and pararock fragments, of which two-thirds or more (by Cindery volume) is pumice or pumicelike fragments. or Medial-pumiceous or 3. Other mineral soils that have a fine-earth component of less than 10 percent (including associated medium and finer b. Have 35 percent or more (by volume) rock fragments. pores) of the total volume. Medial-skeletal Fragmental or or c. Have less than 35 percent (by volume) rock fragments. B. Other mineral soils that have a fine-earth component of 10 Medial percent or more (including associated medium and finer pores) or of the total volume and meet, in the thickest part of the control section (if the control section is not in one of the strongly 3. Have a fine-earth fraction that has andic soil properties contrasting particle-size classes listed below), or in a part of the and that has a water content at 1500 kPa tension of 100 control section that qualifies as an element in one of the strongly percent or more on undried samples; and contrasting particle-size classes listed below, or throughout a. Have a total of 35 percent or more (by volume) rock the control section, one of the following sets of substitute class and pararock fragments, of which two-thirds or more (by criteria: volume) is pumice or pumicelike fragments. 1. They: Hydrous-pumiceous or a. Have andic soil properties and have a water content at 1500 kPa tension of less than 30 percent b. Have 35 percent or more (by volume) rock fragments. on undried samples and less than 12 percent on dried Hydrous-skeletal samples; or or b. Do not have andic soil properties, have 30 percent c. Have less than 35 percent (by volume) rock fragments. or more of the fine-earth fraction in the 0.02 to 2.0 mm Hydrous fraction, and have a volcanic glass content (by grain or count) of 30 percent or more in the 0.02 to 2.0 mm fraction; and 4. Have, in the fraction less than 20 mm in diameter, 40 percent of more (by weight) gypsum one of the c. Have one of the following; and following: (1) A total of 35 percent or more (by volume) rock and pararock fragments, of which two-thirds or more a. A total of 35 percent or more (by volume) rock fragments. (by volume) is pumice or pumicelike fragments. Gypseous-skeletal Ashy-pumiceous or or b. Less than 35 percent (by volume) rock fragments and 50 percent or more (by weight) particles with diameters of 0.1 to 2.0 mm. 1 Pumicelike—vesicular pyroclastic materials other than pumice that have an apparent Coarse-gypseous specific gravity (including vesicles) of less than 1.0 g/cm3. or Family and Series Differentiae and Names 303

c. Less than 35 percent (by volume) rock fragments. 6. Have, in the fraction less than 75 mm in diameter, 15 Fine-gypseous percent or more (by weight) particles with diameters of 0.1 to 75 mm (fine sand or coarser, including gravel)and , in the or fine-earth fraction, less than 18 percent (by weight) clay. Coarse-loamy Note: In the following classes, “clay” excludes clay-size or carbonates. Carbonates of clay size are treated as silt. If the ratio of percent water retained at 1500 kPa tension to the 7. Have, in the fraction less than 75 mm in diameter, 15 percentage of measured clay is 0.25 or less or 0.6 or more in percent or more (by weight) particles with diameters of 0.1 half or more of the particle-size control section or part of the to 75 mm (fine sand or coarser, including gravel)and , in particle-size control section in strongly contrasting classes, then the fine-earth fraction, 18 to 35 percent (by weight) clay the percentage of clay is estimated by the following formula: (Vertisols are excluded). Clay % = 2.5(% water retained at 1500 kPa tension - % organic Fine-loamy carbon). or C. Other mineral soils that, in the thickest part of the control 8. Have, in the fraction less than 75 mm in diameter, less section (if part of the control section has a substitute for than 15 percent (by weight) particles with diameters of 0.1 particle-size class and is not in one of the strongly contrasting to 75 mm (fine sand or coarser, including gravel)and , in the particle-size classes listed below), or in a part of the control fine-earth fraction, less than 18 percent (by weight) clay. section that qualifies as an element in one of the strongly Coarse-silty contrasting particle-size classes listed below, or throughout the or control section, meet one of the following sets of particle-size class criteria: 9. Have, in the fraction less than 75 mm in diameter, less 1. Have 35 percent or more (by volume) rock fragments than 15 percent (by weight) particles with diameters of 0.1 and a fine-earth fraction with a texture class of sand or loamy to 75 mm (fine sand or coarser, including gravel)and , in sand, including less than 50 percent (by weight) very fine the fine-earth fraction, 18 to 35 percent (by weight) clay sand. (Vertisols are excluded). Sandy-skeletal Fine-silty or or

2. Have 35 percent or more (by volume) rock fragments 10. Have 35 percent or more (by weight) clay (more than and less than 35 percent (by weight) clay. 30 percent in Vertisols) and are in a shallow family (defined Loamy-skeletal below) or in a Lithic, Arenic, or Grossarenic subgroup, or or the layer is an element in a strongly contrasting particle-size class (listed below). 3. Have 35 percent or more (by volume) rock fragments. Clayey Clayey-skeletal or or 11. Have (by weighted average) less than 60 percent (by 4. Have a texture class of sand or loamy sand, including weight) clay in the fine-earth fraction. less than 50 percent (by weight) very fine sand particles in Fine the fine-earth fraction. or Sandy or 12. Have 60 percent or more (by weight) clay. Very-fine 5. Have a texture class of loamy very fine sand, very fine Strongly Contrasting Particle-Size Classes sand, or finer, including less than 35 percent (by weight) clay in the fine-earth fraction (excluding Vertisols), and are in The purpose of strongly contrasting particle-size classes is a shallow family (defined below) or in a Lithic, Arenic, or to identify changes in pore-size distribution or composition that F Grossarenic subgroup, or the layer is an element in a strongly are not identified in higher soil categories and that seriously A contrasting particle-size class (listed below). affect the movement and retention of water and/or nutrients. M Loamy The particle-size or substitute classes listed below are or considered strongly contrasting if both parts are 12.5 cm or 304 Keys to Soil Taxonomy

more thick (including the thickness of these parts not entirely of the fine-earth fraction in the two parts of the control within the particle-size control section; however, substitute class section) names are used only if the soil materials to which they apply 22. Clayey over sandy or sandy-skeletal extend 10 cm or more into the upper part of the particle-size control section) and if the transition zone between the two parts 23. Clayey-skeletal over sandy or sandy-skeletal of the particle-size control section is less than 12.5 cm thick. 24. Coarse-loamy over clayey Some classes, such as sandy and sandy-skeletal, have been combined in the following list. In those cases the combined 25. Coarse-loamy over fragmental name is used as the family class if part of the control section 26. Coarse-loamy over sandy or sandy-skeletal (if the coarse- meets the criteria for either class. The following classes are loamy material contains less than 50 percent, by weight, listed alphabetically and are not presented in a key format. fine sand or coarser sand) 1. Ashy over clayey 27. Coarse-silty over clayey 2. Ashy over clayey-skeletal 28. Coarse-silty over sandy or sandy-skeletal 3. Ashy over loamy 29. Fine-loamy over clayey (if there is an absolute difference 4. Ashy over loamy-skeletal of 25 percent or more between clay percentages of the fine-earth fraction in the two parts of the control section) 5. Ashy over medial (if the water content at 1500 kPa tension in dried samples of the fine-earth fraction is 10 percent 30. Fine-loamy over fragmental or less for the ashy part and 15 percent or more for the 31. Fine-loamy over sandy or sandy-skeletal medial part) 32. Fine-silty over clayey (if there is an absolute difference of 6. Ashy over medial-skeletal 25 percent or more between clay percentages of the fine- 7. Ashy over pumiceous or cindery earth fraction in the two parts of the control section) 8. Ashy over sandy or sandy-skeletal 33. Fine-silty over fragmental 9. Ashy-skeletal over clayey 34. Fine-silty over sandy or sandy-skeletal 10. Ashy-skeletal over fragmental or cindery (if the volume 35. Hydrous over clayey of the fine-earth fraction is 35 percent or more [absolute] 36. Hydrous over clayey-skeletal greater in the ashy-skeletal part than in the fragmental or cindery part) 37. Hydrous over fragmental 11. Ashy-skeletal over loamy-skeletal 38. Hydrous over loamy 12. Ashy-skeletal over sandy or sandy-skeletal 39. Hydrous over loamy-skeletal 13. Cindery over loamy 40. Hydrous over sandy or sandy-skeletal 14. Cindery over medial 41. Loamy over ashy or ashy-pumiceous 15. Cindery over medial-skeletal 42. Loamy over coarse-gypseous (if there is an absolute difference of 15 percent or more gypsum between the two 16. Clayey over coarse-gypseous parts of the control section) 17. Clayey over fine-gypseous (if there is an absolute 43. Loamy over fine-gypseous (if there is an absolute difference of 15 percent or more gypsum between the two difference of 15 percent or more gypsum between the two parts of the control section) parts of the control section) 18. Clayey over fragmental 44. Loamy over pumiceous or cindery 19. Clayey over gypseous-skeletal 45. Loamy over sandy or sandy-skeletal (if the loamy material 20. Clayey over loamy (if there is an absolute difference of 25 contains less than 50 percent, by weight, fine sand or percent or more between clay percentages of the fine-earth coarser sand) fraction in the two parts of the control section) 46. Loamy-skeletal over cindery (if the volume of the fine- 21. Clayey over loamy-skeletal (if there is an absolute earth fraction is 35 percent or more [absolute] greater in difference of 25 percent or more between clay percentages the loamy-skeletal part than in the cindery part) Family and Series Differentiae and Names 305

47. Loamy-skeletal over clayey (if there is an absolute 70. Sandy over loamy (if the loamy material contains less than difference of 25 percent or more between clay percentages 50 percent, by weight, fine sand or coarser sand) of the fine-earth fraction in the two parts of the control 71. Sandy-skeletal over loamy (if the loamy material contains section) less than 50 percent, by weight, fine sand or coarser sand) 48. Loamy-skeletal over fragmental (if the volume of the fine- earth fraction is 35 percent or more [absolute] greater in Mineralogy Classes the loamy-skeletal part than in the fragmental part) The mineralogy of soils is known to be useful in making 49. Loamy-skeletal over gypseous-skeletal (if there is an predictions about soil behavior and responses to management. absolute difference of 15 percent or more gypsum between Some mineralogy classes occur or are important only in certain the two parts of the control section) taxa or particle-size classes, and others are important in all 50. Loamy-skeletal over sandy or sandy-skeletal (if the loamy particle-size classes. A mineralogy class is assigned to all material contains less than 50 percent, by weight, fine mineral soils, except for Quartzipsamments. sand or coarser sand) Control Section for Mineralogy Classes 51. Medial over ashy (if the water content at 1500 kPa tension The control section for mineralogy classes is the same as that in dried samples of the fine-earth fraction is 15 percent defined for the particle-size classes and their substitutes. or more for the medial part and 10 percent or less for the ashy part) Key to Mineralogy Classes 52. Medial over ashy-pumiceous or ashy-skeletal (if the water This key, like other keys in this taxonomy, is designed in content at 1500 kPa tension in dried samples of the fine- such a way that the reader makes the correct classification by earth fraction is 15 percent or more for the medial part and going through the key systematically, starting at the beginning 10 percent or less for the ashy part) and eliminating one by one any classes that include criteria that do not fit the soil in question. The soil belongs to the first class 53. Medial over clayey for which it meets all of the required criteria. The user should 54. Medial over clayey-skeletal first check the criteria in section A and, if the soil in question does not meet the criteria listed there, proceed on to sections B, 55. Medial over fragmental C, D, and E, until the soil meets the criteria listed. All criteria 56. Medial over hydrous (if the water content at 1500 kPa are based on a weighted average. tension in undried samples of the fine-earth fraction is 75 For soils with strongly contrasting particle-size classes, percent or less for the medial part) mineralogy classes are used for both of the named parts of particle-size classes or substitute classes, unless they are the 57. Medial over loamy same. The same mineralogy class name cannot be used for 58. Medial over loamy-skeletal both parts of the control section (e.g., “mixed over mixed”). Examples of soils that require assignment of two different 59. Medial over pumiceous or cindery mineralogy classes are a clayey over sandy or sandy-skeletal, 60. Medial over sandy or sandy-skeletal smectitic over mixed, thermic Vertic Haplustept and an ashy- skeletal over loamy-skeletal, glassy over mixed (if the ashy- 61. Medial-skeletal over fragmental or cindery (if the volume skeletal part has 30 percent or more volcanic glass), superactive of the fine-earth fraction is 35 percent or more [absolute] Vitrandic Argicryoll. Examples of soils that are not assigned greater in the medial-skeletal part than in the fragmental two mineralogy classes are an ashy over clayey, mixed (if both or cindery part) the ashy part with andic soil properties and the clayey part 62. Medial-skeletal over loamy-skeletal without andic soil properties are mixed), superactive, mesic Typic Vitraquand and a fine-loamy over sandy or sandy-skeletal, 63. Medial-skeletal over sandy or sandy-skeletal mixed (if both the fine-loamy and sandy or sandy-skeletal parts 64. Pumiceous or ashy-pumiceous over loamy are mixed), active, frigid Pachic Argiudoll. 65. Pumiceous or ashy-pumiceous over loamy-skeletal A. Oxisols and “kandi” and “kanhap” great groups of Alfisols 66. Pumiceous or ashy-pumiceous over medial and Ultisols that in the mineralogy control section have: F A 67. Pumiceous or ashy-pumiceous over medial-skeletal 1. More than 40 percent (by weight) iron oxide as Fe2O3 M (more than 28 percent Fe), by dithionite citrate, in the fine- 68. Pumiceous or ashy-pumiceous over sandy or sandy- earth fraction. skeletal Ferritic 69. Sandy over clayey or 306 Keys to Soil Taxonomy

2. More than 40 percent (by weight) gibbsite in the fine- extracted by ammonium oxalate from the fine-earth earth fraction. fraction) plus 2 times the Fe (percent by weight extracted by Gibbsitic ammonium oxalate from the fine-earth fraction) of 5 or more, or and 8 times the Si is more than 2 times the Fe. Amorphic 3. Both: or a. 18 to 40 percent (by weight) iron oxide as Fe O (12.6 2 3 3. Other soils that have a sum of 8 times the Si (percent by to 28 percent Fe), by dithionite citrate, in the fine-earth weight extracted by ammonium oxalate from the fine-earth fraction; and fraction) plus 2 times the Fe (percent by weight extracted by b. 18 to 40 percent (by weight) gibbsite in the fine-earth ammonium oxalate from the fine-earth fraction) of 5 or more. fraction. Ferrihydritic Sesquic or or 4. Other soils that have 30 percent or more (by grain count)

4. 18 to 40 percent (by weight) iron oxide as Fe2O3 (12.6 to volcanic glass in the 0.02 to 2.0 mm fraction. 28 percent Fe), by dithionite citrate, in the fine-earth fraction. Glassy Ferruginous or or 5. All other soils in section B. 5. 18 to 40 percent (by weight) gibbsite in the fine-earth Mixed fraction. or Allitic or C. Other mineral soil layers or horizons, in the mineralogy control section, in all other mineral soil orders and in Terric 6. More than 50 percent (by weight) kaolinite plus subgroups of Histosols and Histels that have: halloysite, dickite, nacrite, and other 1:1 or nonexpanding 2:1 layer minerals and gibbsite and less than 10 percent (by 1. Any particle-size class and 15 percent or more (by weight) smectite in the fraction less than 0.002 mm in size; weight) gypsum, either in the fine-earth fraction or in the and more kaolinite than halloysite. fraction less than 20 mm in size, whichever has a higher Kaolinitic percentage of gypsum. or Gypsic or 7. More than 50 percent (by weight) halloysite plus kaolinite and allophane and less than 10 percent (by weight) 2. Any particle-size class and more than 40 percent (by

smectite in the fraction less than 0.002 mm in size. weight) carbonates (expressed as CaCO3) plus gypsum, Halloysitic either in the fine-earth fraction or in the fraction less than 20 or mm in size, whichever has a higher percentage of carbonates plus gypsum. 8. All other soils in section A. Carbonatic Mixed or or 3. Any particle-size class, except for fragmental, and more

B. Other soil layers or horizons, in the mineralogy control than 40 percent (by weight) iron oxide as Fe2O3 (more than section, that have a substitute class that replaces the particle-size 28 percent Fe) extractable by dithionite citrate, in the fine- class, other than fragmental, and that: earth fraction. Ferritic 1. Have 40 percent or more (by weight) gypsum either in or the fine-earth fraction or in the fraction less than 20 mm in size, whichever has a higher percentage of gypsum. 4. Any particle-size class, except for fragmental, and more Hypergypsic than 40 percent (by weight) gibbsite and boehmite in the or fine-earth fraction. Gibbsitic 2. Have a sum of 8 times the Si (percent by weight or Family and Series Differentiae and Names 307

5. Any particle-size class, except for fragmental, and more f. In more than 50 percent of the thickness, meet all of than 40 percent (by weight) magnesium-silicate minerals, the following: such as the serpentine minerals (antigorite, chrysotile, and (1) Have no free carbonates; and lizardite) plus talc, olivines, Mg-rich pyroxenes, and Mg-rich amphiboles, in the fine-earth fraction. (2) The pH of a suspension of 1 g soil in 50 ml 1 M Magnesic NaF is more than 8.4 after 2 minutes; and or (3) The ratio of 1500 kPa water to measured clay is 0.6 or more. 6. Any particle-size class, except for fragmental, and more Isotic than 20 percent (by weight) glauconitic pellets in the fine- or earth fraction. Glauconitic g. All other soils in section D. or Mixed or D. Other mineral soil layers or horizons, in the mineralogy control section, of soils in all other mineral orders and in Terric E. All other mineral soil layers or horizons (except for those subgroups of Histosols and Histels, in a clayey, clayey-skeletal, in Quartzipsamments), in the mineralogy control section, that fine, or very-fine particle-size class, that: have: 1. In the fine-earth fraction, have a total percent (by weight) 1. More than 45 percent (by grain count) mica and stable iron oxide as Fe O (percent Fe by dithionate citrate times 2 3 mica pseudomorphs in the 0.02 to 0.25 mm fraction. 1.43) plus the percent ( by weight) gibbsite of more than 10. Micaceous Parasesquic or or 2. A total percent (by weight) iron oxide as Fe O (percent 2. In the fraction less than 0.002 mm in size: 2 3 Fe by dithionate citrate times 1.43) plus the percent (by a. Have more than 50 percent (by weight) halloysite plus weight) gibbsite of more than 10 in the fine-earth fraction. kaolinite and allophane and more halloysite than any other Parasesquic single kind of clay mineral. or Halloysitic or 3. In more than one-half of the thickness, all of the following: b. Have more than 50 percent (by weight) kaolinite plus a. No free carbonates; and halloysite, dickite, nacrite, and other 1:1 or nonexpanding 2:1 layer minerals and gibbsite and less than 10 percent b. NaF pH of 8.4 or more; and (by weight) smectite. c. A ratio of 1500 kPa water to measured clay of 0.6 or Kaolinitic more. or Isotic or c. Have more smectite minerals (montmorillonite, beidellite, and nontronite), by weight, than any other 4. More than 90 percent (by weight or grain count) silica single kind of clay mineral. minerals (quartz, chalcedony, or opal) and other resistant Smectitic minerals in the 0.02 to 2.0 mm fraction. or Siliceous or d. Have more than 50 percent (by weight) illite (hydrous mica) and commonly more than 4 percent K O. 2 5. All other soils. Illitic Mixed or F A Cation-Exchange Activity Classes M e. Have more vermiculite than any other single kind of clay mineral. The cation-exchange activity classes help in making Vermiculitic interpretations of mineral assemblages and of the nutrient- or holding capacity of soils in mixed and siliceous mineralogy 308 Keys to Soil Taxonomy

classes of clayey, clayey-skeletal, coarse-loamy, coarse-silty, a. 0.60 or more. fine, fine-loamy, fine-silty, loamy, loamy-skeletal, and very-fine Superactive particle-size classes. Cation-exchange activity classes are not b. 0.40 to 0.60. assigned to Histosols and Histels, and they are not assigned to Active Oxisols and “kandi” and “kanhap” great groups and subgroups of Alfisols and Ultisols because assigning such classes to them c. 0.24 to 0.40. would be redundant. Cation-exchange activity classes are not Semiactive assigned to Psamments, “psamm” great groups of Entisols and d. Less than 0.24. Gelisols, Psammentic subgroups, or other soils with sandy or Subactive sandy-skeletal particle-size classes or the fragmental substitute or class because the low clay content causes cation-exchange activity classes to be less useful and less reliable. Soils with B. All other soils: No cation-exchange activity classes used. other substitutes for particle-size class (e.g., ashy) or with such mineralogy classes as smectitic also are not assigned cation- exchange activity classes since cation-exchange capacity Calcareous and Reaction Classes of Mineral Soils (CEC) is high in such soils or the clay mineralogy dictates soil The presence or absence of carbonates, soil reaction, and the properties. presence of high concentrations of aluminum in mineral soils

The cation-exchange capacity is determined by NH4OAc at are treated together because they are so intimately related. There pH 7 on the fine-earth fraction. The CEC of the organic matter, are four classes—calcareous, acid, nonacid, and allic. These are sand, silt, and clay is included in the determination. The criteria defined later, in the key to calcareous and reaction classes. The for the classes use ratios of CEC to the percent, by weight, of classes are not used in all taxa, nor is more than one used in the silicate clay, both by weighted average in the control section. same taxa. In the following classes “clay” excludes clay-size carbonates. If the ratio of percent water retained at 1500 kPa tension to Use of the Calcareous and Reaction Classes the percentage of measured clay is 0.25 or less or 0.6 or more The calcareous, acid, and nonacid classes are used in the in half or more of the particle-size control section (or part in names of the families of Entisols, Gelisols, Aquands, Aquepts, contrasting families), then the percentage of clay is estimated by and all Gelic suborders and Gelic great groups, except they are the following formula: Clay % = 2.5(% water retained at 1500 not used in any of the following: kPa tension - % organic carbon). 1. Duraquands and Placaquands Control Section for Cation-Exchange Activity Classes 2. Sulfaquepts, Fragiaquepts, and Petraquepts The control section for cation-exchange activity classes is the 3. The Psamments, Psammaquents, Psammowassents, same as that used to determine the particle-size and mineralogy Psammoturbels, Psammorthels, and Psammentic subgroups that classes. For soils with strongly contrasting particle-size classes, have no particle-size class where both named parts of the control section use a cation- exchange activity class, the class associated with the particle- 4. Sandy, sandy-skeletal, cindery, pumiceous, or fragmental size class that has the most clay is named. For example, in a families pedon with a classification of loamy over clayey, mixed, active, 5. Families with carbonatic, gypsic, or hypergypsic calcareous, thermic Typic Udorthent, the cation-exchange mineralogy activity class “active” is associated with the clayey part of the control section. 6. Histels

Key to Cation-Exchange Activity Classes The calcareous class is used not only in the names of the taxa listed above but also in the names of the families of Aquolls, A. Soils that are not Histosols, Histels, Oxisols, or except that it is not used with any of the following: Psamments, that are not in “psamm” great groups of Entisols or Gelisols, that are not in Psammentic subgroups, that are not 1. Calciaquolls, Natraquolls, and Argiaquolls in “kandi” or “kanhap” great groups or subgroups of Alfisols 2. Cryaquolls and Duraquolls that have an argillic or natric or Ultisols, that are not in a sandy or sandy-skeletal particle- horizon size class or any substitute for a particle-size class (including fragmental), and that have: 3. Families with carbonatic, gypsic, or hypergypsic mineralogy 1. A mixed or siliceous mineralogy class; and

2. A ratio of cation-exchange capacity (by IN NH4OAc The allic class is used only in families of Oxisols. pH 7) to percent clay (by weight) of: Family and Series Differentiae and Names 309

Control Section for Calcareous and Reaction Classes The calcareous, acid, nonacid, and allic classes are listed in the family name, when appropriate, following the mineralogy The control section for the calcareous class is one of the and cation-exchange activity classes. following: 1. All Gelisols (except for Histels) and all Gelic suborders Soil Temperature Classes and Gelic great groups: The layer from the mineral soil surface to a depth of 25 cm or to a root-limiting layer, whichever is Soil temperature classes, as named and defined here, are used shallower. as part of the family name in both mineral and organic soils. Temperature class names are used as part of the family name 2. Soils with a root-limiting layer that is 25 cm or less below unless the criteria for a higher taxon carry the same limitation. the mineral soil surface: A 2.5-cm-thick layer directly above the Thus, frigid is implied in all cryic suborders, great groups, root-limiting layer. and subgroups and would be redundant if used in the names of 3. Soils with a root-limiting layer that is 26 to 50 cm below the families within these classes. mineral soil surface: The layer between a depth of 25 cm below The Celsius (centigrade) scale is the standard. It is assumed the mineral soil surface and the root-limiting layer. that the temperature is that of a soil that is not being irrigated. 4. All other listed soils: Between a depth of 25 and 50 cm Control Section for Soil Temperature below the mineral soil surface. The control section for soil temperature is either at a depth of 50 cm below the soil surface or at the upper boundary of a The control section for the acid and nonacid classes is one of root-limiting layer, whichever is shallower. The soil temperature the following: classes, defined in terms of the mean annual soil temperature 1. All Gelisols (except for Histels) and all Gelic suborders and the difference between mean summer and mean winter and Gelic great groups: The layer from the mineral soil surface temperatures, are determined by the following key. to a depth of 25 cm or to a root-limiting layer, whichever is Key to Soil Temperature Classes shallower. A. Gelisols and Gelic suborders and great groups that have a 2. All other listed soils: The same control section depths as mean annual soil temperature as follows: those for particle-size classes. 1. -10 oC or lower. The control section for the allic class in Oxisols is the same Hypergelic as that for particle-size classes. or

Key to Calcareous and Reaction Classes 2. -4 oC to -10 oC. Pergelic A. Oxisols that have a layer, 30 cm or more thick within the or control section, that contains more than 2 cmol(+) of KCl- extractable Al per kg soil in the fine-earth fraction. 3. +1 oC to -4 oC. Allic Subgelic B. Other listed soils that, in the fine-earth fraction, effervesce or (in cold dilute HCl) in all parts of the control section. Calcareous B. Other soils that have a difference in soil temperature of 6 oC or more between mean summer (June, July, and August C. Other listed soils with a pH of less than 5.0 in 0.01 M in the Northern Hemisphere) and mean winter (December, CaCl (1:2) (about pH 5.5 in H O, 1:1) throughout the control 2 2 January, and February in the Northern Hemisphere) and a mean section. annual soil temperature of: Acid 1. Lower than 8 oC (47 oF). D. Other listed soils with a pH of 5.0 or more in 0.01 M CaCl 2 Frigid (1:2) in some or all layers in the control section. or Nonacid It should be noted that a soil containing dolomite is o o o o F 2. 8 C (47 F) to 15 C (59 F). A calcareous and that effervescence of dolomite, when treated Mesic M with cold dilute HCl, is slow. or 310 Keys to Soil Taxonomy

3. 15 oC (59 oF) to 22 oC (72 oF). C. Other Histels that are less than 50 cm deep to a root- Thermic limiting layer. or Shallow or 4. 22 oC (72 oF) or higher. Hyperthermic D. All other Histels and mineral soils: No soil depth class or used.

C. All other soils that have a mean annual soil temperature as Rupture-Resistance Classes follows: In this taxonomy, some partially cemented soil materials, 1. Lower than 8 oC (47 oF). such as durinodes, serve as differentiae in categories above Isofrigid the family, while others, such as partially cemented spodic or materials (ortstein), do not. No single family, however, should include soils both with and without partially cemented horizons. 2. 8 oC (47 oF) to 15 oC (59 oF). In Spodosols, a partially cemented spodic horizon is used as Isomesic a family differentia. The following rupture-resistance class is or defined for families of Spodosols:

3. 15 oC (59 oF) to 22 oC (72 oF). A. Spodosols that have an ortstein horizon. Isothermic Ortstein or or

4. 22 oC (72 oF) or higher. B. All other soils: No rupture-resistance class used. Isohyperthermic Classes of Coatings on Sands Soil Depth Classes Despite the emphasis given to particle-size classes in this Soil depth classes are used in all families of mineral soils taxonomy, variability remains in the sandy particle-size class, and Histels that have a root-limiting layer at a specified depth which includes sands and loamy sands. Some sands are very from the mineral soil surface, except for those families in Lithic clean, i.e., almost completely free of silt and clay, while others subgroups (defined below) and those with a fragipan. The are mixed with appreciable amounts of finer grains. Clay is root-limiting layers included in soil depth classes are duripans; more efficient at coating sand than is silt. A weighted average petrocalcic, petrogypsic, and placic horizons; continuous silt plus 2 times the weighted average clay of more than 5 ortstein (90 percent or more); and densic, lithic, paralithic, and makes a reasonable division of the sands at the family level. petroferric contacts. Soil depth classes for Histosols are given Two classes of Quartzipsamments are defined in terms of their later in this chapter. One soil depth class name, “shallow,” is content of silt plus 2 times their content of clay. used to characterize certain soil families that have one of the Control Section for Classes of Coatings on Sands depths indicated in the following key. The control section for classes of coatings is the same as that Key to Soil Depth Classes for Mineral Soils and Histels for particle-size classes or their substitutes and for mineralogy A. Oxisols that are less than 100 cm deep (from the mineral classes. soil surface) to a root-limiting layer and are not in a Lithic Key to Classes of Coatings on Sands subgroup. Shallow A. Quartzipsamments that have a sum of the weighted average or silt (by weight) plus 2 times the weighted average clay (by weight) of more than 5. B. Other mineral soils and Folistels that are less than 50 cm Coated deep (from the mineral soil surface) to a root-limiting layer and or are not in a Lithic subgroup. Shallow B. Other Quartzipsamments. or Uncoated Family and Series Differentiae and Names 311

Classes of Permanent Cracks Particle-Size Classes Some Hydraquents consolidate or shrink after drainage and Particle-size classes are used only for the family names become Fluvaquents or Humaquepts. In the process they can of Terric subgroups of Histosols and Histels. The classes are form polyhedrons roughly 12 to 50 cm in diameter, depending determined from the properties of the mineral soil materials on their n value and texture. These polyhedrons are separated by in the control section through use of the key to particle-size cracks that range in width from 2 mm to more than 1 cm. The classes. The classes are more generalized than those for soils in polyhedrons may shrink and swell with changes in the moisture other orders. content of the soils, but the cracks are permanent and can persist Control Section for Particle-Size Classes for several hundreds of years, even if the soils are cultivated. The cracks permit rapid movement of water through the soils, The particle-size control section is the upper 30 cm of the either vertically or laterally. Such soils may have the same mineral layer or of that part of the mineral layer that is within texture, mineralogy, and other family properties as soils that do the control section for Histosols and Histels (given in chapter not form cracks or that have cracks that open and close with the 3), whichever is thicker. seasons. Soils with permanent cracks are very rare in the United Key to Particle-Size Classes of Histosols and Histels States. A. Terric subgroups of Histosols and Histels that have (by Control Section for Classes of Permanent Cracks weighted average) in the particle-size control section: The control section for classes of permanent cracks is from the base of any plow layer or 25 cm from the soil surface, 1. A fine-earth component of less than 10 percent whichever is deeper, to 100 cm below the soil surface. (including associated medium and finer pores) of the total volume. Key to Classes of Permanent Cracks Fragmental A. Fluvaquents or Humaquepts that have, throughout a layer or 50 cm or more thick, continuous, permanent, lateral and vertical cracks 2 mm or more wide, spaced at average lateral intervals of 2. A texture class (of the fine-earth material) of sand or less than 50 cm. loamy sand, including less than 50 percent (by weight) very Cracked fine sand in the fine-earth fraction. or Sandy or sandy-skeletal or B. All other Fluvaquents and Humaquepts: No class of permanent cracks used. 3. Less than 35 percent (by weight) clay in the fine-earth fraction and a content of rock fragments of 35 percent or more of the total volume. Family Differentiae for Histosols and Loamy-skeletal Histels or Most of the differentiae that are used to distinguish families 4. A content of rock fragments of 35 percent or more of the of Histosols and Histels have already been defined, either total volume. because they are used as differentiae in mineral soils as well as Clayey-skeletal Histosols and Histels or because their definitions are used for or the classification of some Histosols and Histels in categories higher than the family. In the following descriptions, differentiae 5. A clay content of 35 percent or more (by weight) in the not previously mentioned are defined and the classes in which fine-earth fraction. they are used are enumerated. Clayey The order in which family classes, if appropriate for a or particular family, are placed in the technical family names of Histosols and Histels is as follows: 6. All other Terric subgroups of Histosols and Histels. Particle-size classes Loamy Mineralogy classes, including the nature of limnic deposits or F in Histosols A Reaction classes B. All other Histosols and Histels: No particle-size class used. M Soil temperature classes Soil depth classes (used only in Histosols) 312 Keys to Soil Taxonomy

Mineralogy Classes Control Section for Mineralogy Classes Applied Only to Terric Subgroups There are three different kinds of mineralogy classes recognized for families in certain great groups and subgroups For Terric subgroups of Histosols and Histels, use the same of Histosols. The first kind is the ferrihumic soil material control section for mineralogy classes as that used for the defined below. The second is three types of limnic materials— particle-size classes. coprogenous earth, diatomaceous earth, and marl, defined in Key to Mineralogy Classes chapter 3. The third is mineral layers of Terric subgroups. The key to mineralogy classes for these mineral layers is the same as A. Histosols (except for Folists, Sphagnofibrists, and Sphagnic that for mineral soils. Terric subgroups of Histels also have the subgroups of other great groups) that have ferrihumic soil same mineralogy classes as those for mineral soils. material within the control section for Histosols. Ferrihumic Ferrihumic Mineralogy Class or

Ferrihumic soil material, i.e., bog iron, is an authigenic B. Other Histosols that have, within the control section for (formed in place) deposit consisting of hydrated iron oxide Histosols, limnic materials, 5 cm or more thick, that consist of: mixed with organic matter, either dispersed and soft or cemented into large aggregates, in a mineral or organic layer 1. Coprogenous earth. that has all of the following characteristics: Coprogenous or 1. Saturation with water for more than 6 months per year (or artificial drainage); 2. Diatomaceous earth. 2. 2 percent or more (by weight) iron concretions having Diatomaceous lateral dimensions ranging from less than 5 to more than 100 or mm and containing 10 percent or more (by weight) free iron oxide (7 percent or more Fe) and 1 percent or more (by weight) 3. Marl. organic matter; and Marly or 3. A dark reddish or brownish color that changes little on drying. C. Histels and other Histosols in Terric subgroups: Use the The ferrihumic mineralogy class is used for families of key to mineralogy classes for mineral soils. Fibrists, Hemists, and Saprists, but it is not used for Folists, Sphagnofibrists, or Sphagnic subgroups of other great groups. or If the ferrihumic class is used in the family name of a Histosol, no other mineralogy classes are used in that family because the D. All other Histels and Histosols: No mineralogy class used. presence of iron is considered to be by far the most important mineralogical characteristic. Reaction Classes Reaction classes are used in all families of Histosols and Mineralogy Classes Applied Only to Limnic Subgroups Histels. The two classes recognized are defined in the following Limnic materials (defined in chapter 3) with a thickness of 5 key: cm or more are mineralogy class criteria if the soil does not also A. Histosols and Histels that have a pH value, on undried have ferrihumic mineralogy. The following family classes are samples, of 4.5 or more (in 0.01 M CaCl ) in one or more layers used: coprogenous, diatomaceous, and marly. 2 of organic soil materials within the control section for Histosols. Euic Control Section for the Ferrihumic Mineralogy Class and or Mineralogy Classes Applied to Limnic Subgroups The control section for the ferrihumic mineralogy class B. All other Histosols and Histels. and the classes applied to Limnic subgroups is the same as the Dysic control section for Histosols. Soil Temperature Classes Mineralogy Classes Applied Only to Terric Subgroups The soil temperature classes of Histosols are determined For Histosols and Histels in Terric subgroups, use the same through use of the same key and definitions as those used for key to mineralogy classes as that used for mineral soils unless a mineral soils. Histels have the same temperature classes as other Histosol also has ferrihumic mineralogy. Gelisols. Family and Series Differentiae and Names 313

Soil Depth Classes and also the first 25 cm below a densic or paralithic contact if its upper boundary is less than 125 cm below the mineral soil Soil depth classes refer to the depth to a root-limiting layer surface. Properties of horizons and layers below the particle-size or to a pumiceous, cindery, or fragmental substitute class. The control section, a depth between 100 and 150 cm (or to 200 cm root-limiting layers included in soil depth classes of Histosols if in a diagnostic horizon) from the mineral soil surface, also are are duripans; petrocalcic, petrogypsic, and placic horizons; considered. continuous ortstein; and densic, lithic, paralithic, and petroferric contacts. The following key is used for families in all subgroups Key to the Control Section for the Differentiation of Series of Histosols. The shallow class is not used in the suborder Folists. The part of a soil to be considered in differentiating series within a family is as follows: Key to Soil Depth Classes for Histosols A. Mineral soils that have permafrost within 150 cm of the A. Histosols that are less than 18 cm deep to a root-limiting soil surface: From the soil surface to the shallowest of the layer or to a pumiceous, cindery, or fragmental substitute class. following: Micro or 1. A lithic or petroferric contact; or B. Other Histosols, excluding Folists, that have a root-limiting 2. A depth of 100 cm if the depth to permafrost is less than layer or a pumiceous, cindery, or fragmental substitute class at a 75 cm; or depth between 18 and 50 cm from the soil surface. 3. 25 cm below the upper boundary of permafrost if that Shallow boundary is 75 cm or more below the soil surface; or or 4. 25 cm below a densic or paralithic contact; or C. All other Histosols: No soil depth class used. 5. A depth of 150 cm; or Series Differentiae Within a Family B. Other mineral soils: From the soil surface to the shallowest of the following: The function of the series is pragmatic, and differences within a family that affect the use of a soil should be considered 1. A lithic or petroferric contact; or in classifying soil series. The separation of soils at the series 2. A depth of either 25 cm below a densic or paralithic level of this taxonomy can be based on any property that is contact or 150 cm below the soil surface, whichever is used as criteria at higher levels in the system. The criteria most shallower, if there is a densic or paralithic contact within 150 commonly used include presence of, depth to, thickness of, and cm; expression of horizons and properties diagnostic for the higher or categories and differences in texture, mineralogy, soil moisture, 3. A depth of 150 cm if the bottom of the deepest soil temperature, and amounts of organic matter. The limits diagnostic horizon is less than 150 cm from the soil surface; of the properties used as differentiae must be more narrowly or defined than the limits for the family. The properties used, 4. The lower boundary of the deepest diagnostic horizon however, must be reliably observable or be inferable from other or a depth of 200 cm, whichever is shallower, if the lower soil properties or from the setting or vegetation. boundary of the deepest diagnostic horizon is 150 cm or The differentiae used must be within the series control more below the soil surface; section. Differences in soil or regolith that are outside the series or control section and that have not been recognized as series C. Organic soils (Histosols and Histels): From the soil surface differentiae but are relevant to potential uses of certain soils are to the shallowest of the following: considered as a basis for phase distinctions. 1. A lithic or petroferric contact; or Control Section for the Differentiation of Series 2. A depth of 25 cm below a densic or paralithic contact; or The control section for the soil series is similar to that for the 3. A depth of 100 cm if the depth to permafrost is less than family, but it differs in a few important respects. The particle- 75 cm; or size and mineralogy control sections for families end at the 4. 25 cm below the upper boundary of permafrost if that upper boundary of a fragipan, duripan, or petrocalcic horizon F boundary is between a depth of 75 and 125 cm below the soil A because these horizons have few roots. In contrast to the control M surface; or section for the series, the thickness of such horizons is not taken into account in the control sections for the family. The series 5. The base of the bottom tier. control section includes materials starting at the soil surface

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CHAPTER 18 Designations for Horizons and Layers

This chapter describes soil layers and genetic soil horizons. L horizons or layers include coprogenous earth (sedimentary The genetic horizons are not the equivalent of the diagnostic peat), diatomaceous earth, and marl. They are used only horizons of Soil Taxonomy. While designations of genetic in Histosols. They have only the following subordinate horizons express a qualitative judgment about the kinds distinctions: co, di, or ma. They do not have the subordinate of changes that are believed to have taken place in a soil, distinctions of the other master horizons and layers. diagnostic horizons are quantitatively defined features that are A horizons: Mineral horizons that have formed at the used to differentiate between taxa. A diagnostic horizon may surface or below an O horizon. They exhibit obliteration of all encompass several genetic horizons, and the changes implied by or much of the original rock structure1 and show one or both of genetic horizon designations may not be large enough to justify the following: (1) an accumulation of humified organic matter recognition of different diagnostic horizons. closely mixed with the mineral fraction and not dominated by properties characteristic of E or B horizons (defined below) or (2) properties resulting from cultivation, pasturing, or similar Master Horizons and Layers kinds of disturbance. The capital letters O, L, A, E, B, C, R, M, and W represent If a surface horizon has properties of both A and E horizons the master horizons and layers of soils. These letters are the but the feature emphasized is an accumulation of humified base symbols to which other characters are added to complete organic matter, it is designated as an A horizon. In some areas, the designations. Most horizons and layers are given a single such as areas of warm, arid climates, the undisturbed surface capital-letter symbol; some require two. horizon is less dark than the adjacent underlying horizon O horizons or layers: Horizons or layers dominated by and contains only small amounts of organic matter. It has a organic soil materials. Some are saturated with water for long morphology distinct from the C layer, although the mineral periods or were once saturated but are now artificially drained; fraction is unaltered or only slightly altered by weathering. others have never been saturated. Such a horizon is designated as an A horizon because it is Some O layers consist of undecomposed or partially at the surface. Recent alluvial or eolian deposits that retain decomposed litter (such as leaves, needles, twigs, moss, and fine stratification are not considered to be A horizons unless lichens) that has been deposited on the surface. They may be on cultivated. top of either mineral or organic soils. Other O layers consist of E horizons: Mineral horizons in which the main feature is organic material that was deposited under saturated conditions the loss of silicate clay, iron, aluminum, or some combination of and has decomposed to varying stages. The mineral fraction these, leaving a concentration of sand and silt particles. These of such material constitutes only a small percentage of the horizons exhibit obliteration of all or much of the original rock volume of the material and generally much less than half of its structure. weight. Some soils consist entirely of materials designated as O An E horizon is most commonly differentiated from an horizons or layers. underlying B horizon in the same sequum by a color of higher An O layer may be on the surface of a mineral soil, or it value or lower chroma, or both, by coarser texture, or by a may be at any depth below the surface if it is buried. A horizon combination of these properties. In some soils the color of the formed by the illuviation of organic material into a mineral E horizon is that of the sand and silt particles, but in many subsoil is not an O horizon, although some horizons that have soils coatings of iron oxides or other compounds mask the formed in this manner contain considerable amounts of organic color of the primary particles. An E horizon is most commonly matter. differentiated from an overlying A horizon by its lighter color. It L horizons or layers: Limnic horizons or layers include generally contains less organic matter than the A horizon. An E both organic and mineral limnic materials that were either (1) horizon is commonly near the surface, below an O or A horizon deposited in water by precipitation or through the actions of aquatic organisms, such as algae and diatoms, or (2) derived 1 Rock structure includes fine stratification in unconsolidated soil materials as well as from underwater and floating aquatic plants and subsequently pseudomorphs of weathered minerals that retain their positions relative to each other and to H O modified by aquatic animals. unweathered minerals in saprolite. R 316 Keys to Soil Taxonomy

and above a B horizon, but eluvial horizons that are within or or B horizons, it is designated by the letter C. Changes that are between parts of the B horizon or extend to depths greater than not considered pedogenic are those not related to the overlying those of normal observation can be assigned the letter E if they horizons. Some layers that have accumulations of silica, are pedogenic. carbonates, gypsum, or more soluble salts are included in C B horizons: Horizons that have formed below an A, E, or horizons, even if cemented. If a cemented layer formed through O horizon. They are dominated by the obliteration of all or pedogenic processes, however, it is considered a B horizon. much of the original rock structure and show one or more of the R layers: Strongly cemented to indurated bedrock. following: Granite, basalt, quartzite, limestone, and sandstone are examples of bedrock designated by the letter R. The excavation 1. Illuvial concentration of silicate clay, iron, aluminum, difficulty commonly exceeds high. The R layer is sufficiently humus, carbonates, gypsum, or silica, alone or in coherent when moist to make hand-digging with a spade combination; impractical, although the layer may be chipped or scraped. 2. Evidence of the removal, addition, or transformation of Some R layers can be ripped with heavy power equipment. The carbonates and/or gypsum; bedrock may have cracks, but these are generally too few and too small to allow root penetration. The cracks may be coated or 3. Residual concentration of oxides; filled with clay or other material. 4. Coatings of sesquioxides that make the horizon M layers: Root-limiting subsoil layers consisting of nearly conspicuously lower in color value, higher in chroma, or continuous, horizontally oriented, human-manufactured redder in hue, without apparent illuviation of iron; materials. Examples of materials designated by the letter M are 5. Alteration that forms silicate clay or liberates oxides, or geotextile liners, asphalt, concrete, rubber, and plastic. both, and that forms a granular, blocky, or prismatic structure W layers: Water if volume changes accompany changes in moisture content; This symbol indicates water layers within or beneath the 6. Brittleness; or soil. The water layer is designated as Wf if it is permanently frozen and as W if it is not permanently frozen. The W (or Wf) 7. Strong gleying. designation is not used for shallow water, ice, or snow above the All of the different kinds of B horizons are, or were soil surface. originally, subsurface horizons. Some examples included as B horizons, where contiguous to other genetic horizons, are layers of illuvial concentration of carbonates, gypsum, or silica Transitional and Combination Horizons that are the result of pedogenic processes (and may or may not Horizons dominated by properties of one master horizon be cemented) and brittle layers that show other evidence of but having subordinate properties of another.—Two capital- alteration, such as prismatic structure or illuvial accumulation letter symbols are used for such transitional horizons, e.g., AB, of clay. EB, BE, or BC. The first of these symbols indicates that the Examples of layers that are not B horizons are layers in properties of the horizon so designated dominate the transitional which clay films either coat rock fragments or cover finely horizon. An AB horizon, for example, has characteristics of both stratified unconsolidated sediments, regardless of whether the an overlying A horizon and an underlying B horizon, but it is films were formed in place or by illuviation; layers into which more like the A horizon than the B horizon. carbonates have been illuviated but that are not contiguous to an In some cases a horizon can be designated as transitional overlying genetic horizon; and layers with gleying but no other even if one of the master horizons to which it presumably forms pedogenic changes. a transition is not present. A BE horizon may be recognized C horizons or layers: Horizons or layers, excluding in a truncated soil if its properties are similar to those of a BE strongly cemented and harder bedrock, that are little affected horizon in a soil from which the overlying E horizon has not by pedogenic processes and lack the properties of O, A, E, or B been removed by erosion. A BC horizon may be recognized horizons. Most are mineral layers. The material of C horizons even if no underlying C horizon is present; it is transitional to or layers may be either like or unlike the material from which assumed parent materials. the solum has presumably formed. The C horizon may have Horizons with two distinct parts that have recognizable been modified, even if there is no evidence of pedogenesis. properties of the two kinds of master horizons indicated by Included as C layers (typically designated Cr) are sediment, the capital letters.—The two capital letters designating such saprolite, bedrock, and other geologic materials that are combination horizons are separated by a virgule (/), e.g., moderately cemented or less cemented. The excavation E/B, B/E, or B/C. Most of the individual parts of one horizon difficulty in these materials commonly is low or moderate. component are surrounded by the other. The designation Some soils form in material that is already highly weathered, may be used even when horizons similar to one or both of and if such material does not meet the requirements for A, E, the components are not present, provided that the separate Designations for Horizons and Layers 317

components can be recognized in the combination horizon. The di Diatomaceous earth first symbol is that of the horizon with the greater volume. This symbol, used only with L, indicates a limnic layer Single sets of horizon designators do not cover all situations; of diatomaceous earth. therefore, some improvising is needed. For example, Lamellic Udipsamments have lamellae that are separated from each e Organic material of intermediate decomposition other by eluvial layers. Because it is generally not practical to This symbol is used with O to indicate organic describe each lamella and eluvial layer as a separate horizon, materials of intermediate decomposition. The fiber the horizons can be combined but the components described content of these materials is 17 to 40 percent (by volume) separately. One horizon then has several lamellae and eluvial after rubbing. layers and can be designated an “E and Bt” horizon. The complete horizon sequence for these soils could be: Ap-Bw-E f Frozen soil or water and Bt1-E and Bt2-C. This symbol indicates that a horizon or layer contains permanent ice. The symbol is not used for seasonally Suffix Symbols frozen layers or for dry permafrost. Lowercase letters are used as suffixes to designate specific ff Dry permafrost kinds of master horizons and layers. The term “accumulation” is This symbol indicates a horizon or layer that is used in many of the definitions of such horizons to indicate that continually colder than 0 oC and does not contain enough these horizons must contain more of the material in question ice to be cemented by ice. This suffix is not used for than is presumed to have been present in the parent material. horizons or layers that have a temperature warmer than The suffix symbols and their meanings are as follows: 0 oC at some time of the year. a Highly decomposed organic material g Strong gleying This symbol is used with O to indicate the most highly This symbol indicates either that iron has been reduced decomposed organic materials, which have a fiber content and removed during soil formation or that saturation with of less than 17 percent (by volume) after rubbing. stagnant water has preserved it in a reduced state. Most of the affected layers have chroma of 2 or less, and many b Buried genetic horizon have redox concentrations. The low chroma can represent This symbol is used in mineral soils to indicate either the color of reduced iron or the color of uncoated identifiable buried horizons with major genetic features sand and silt particles from which iron has been removed. that were developed before burial. Genetic horizons may The symbol g is not used for materials of low chroma or may not have formed in the overlying material, which that have no history of wetness, such as some shales may be either like or unlike the assumed parent material or E horizons. If g is used with B, pedogenic change of the buried soil. This symbol is not used in organic soils, in addition to gleying is implied. If no other pedogenic nor is it used to separate an organic layer from a mineral change besides gleying has taken place, the horizon is layer. designated Cg. c Concretions or nodules h Illuvial accumulation of organic matter This symbol indicates a significant accumulation This symbol is used with B to indicate the of concretions or nodules. Cementation is required. accumulation of illuvial, amorphous, dispersible The cementing agent commonly is iron, aluminum, complexes of organic matter and sesquioxides if the manganese, or titanium. It cannot be silica, dolomite, sesquioxide component is dominated by aluminum but calcite, or more soluble salts. is present only in very small quantities. The organo- sesquioxide material coats sand and silt particles. In co Coprogenous earth some horizons these coatings have coalesced, filled This symbol, used only with L, indicates a limnic layer pores, and cemented the horizon. The symbol h is also of coprogenous earth (or sedimentary peat). used in combination with s as “Bhs” if the amount of the sesquioxide component is significant but the color value d Physical root restriction and chroma, moist, of the horizon are 3 or less. This symbol indicates noncemented, root-restricting i Slightly decomposed organic material layers in naturally occurring or human-made sediments or materials. Examples are dense basal till, plowpans, and This symbol is used with O to indicate the least H other mechanically compacted zones. decomposed of the organic materials. The fiber content O R 318 Keys to Soil Taxonomy

of these materials is 40 percent or more (by volume) after n Accumulation of sodium rubbing. This symbol indicates an accumulation of j Accumulation of jarosite exchangeable sodium. Jarosite is a potassium (ferric) iron hydroxy sulfate o Residual accumulation of sesquioxides

mineral, KFe3(SO4)2(OH)6, that is commonly an alteration product of pyrite that has been exposed to an oxidizing This symbol indicates a residual accumulation of environment. Jarosite has hue of 2.5Y or yellower and sesquioxides. normally has chroma of 6 or more, although chromas as p Tillage or other disturbance low as 3 or 4 have been reported. It forms in preference to iron (hydr)oxides in active acid sulfate soils at pH of 3.5 This symbol indicates a disturbance of the surface or less and can be stable in post-active acid sulfate soils layer by mechanical means, pasturing, or similar uses. A for long periods of time at higher pH. disturbed organic horizon is designated Op. A disturbed mineral horizon is designated Ap even though it is clearly jj Evidence of cryoturbation a former E, B, or C horizon. Evidence of cryoturbation includes irregular and q Accumulation of silica broken horizon boundaries, sorted rock fragments, and organic soil materials occurring as bodies and broken This symbol indicates an accumulation of secondary layers within and/or between mineral soil layers. The silica. organic bodies and layers are most commonly at the r Weathered or soft bedrock contact between the active layer and the permafrost. This symbol is used with C to indicate layers of k Accumulation of secondary carbonates bedrock that are moderately cemented or less cemented. This symbol indicates an accumulation of visible Examples are weathered igneous rock and partly pedogenic calcium carbonate (less than 50 percent, by consolidated sandstone, siltstone, or shale. The excavation volume). Carbonate accumulations occur as carbonate difficulty is low to high. filaments, coatings, masses, nodules, disseminated s Illuvial accumulation of sesquioxides and organic matter carbonate, or other forms. This symbol is used with B to indicate an accumulation kk Engulfment of horizon by secondary carbonates of illuvial, amorphous, dispersible complexes of organic This symbol indicates major accumulations of matter and sesquioxides if both the organic matter and pedogenic calcium carbonate. The suffix kk is used when sesquioxide components are significant and if either the the soil fabric is plugged with fine grained pedogenic color value or chroma, moist, of the horizon is 4 or more. carbonate (50 percent or more, by volume) that occurs as The symbol is also used in combination with h as “Bhs” if an essentially continuous medium. The suffix corresponds both the organic matter and sesquioxide components are to the stage III plugged horizon or higher of the carbonate significant and if the color value and chroma, moist, are 3 morphogenetic stages (Gile et al., 1966). or less. m Cementation or induration ss Presence of slickensides This symbol indicates continuous or nearly continuous This symbol indicates the presence of slickensides. cementation. It is used only for horizons that are more Slickensides result directly from the swelling of clay than 90 percent cemented, although they may be fractured. minerals and shear failure, commonly at angles of 20 to The cemented layer is physically root-restrictive. The 60 degrees above horizontal. They are indicators that other predominant cementing agent (or the two dominant vertic characteristics, such as wedge-shaped peds and ones) may be indicated by adding defined letter suffixes, surface cracks, may be present. singly or in pairs. The horizon suffix kkm (and less t Accumulation of silicate clay commonly km) indicates cementation by carbonates; qm, cementation by silica; sm, cementation by iron; yym, This symbol indicates an accumulation of silicate clay cementation by gypsum; kqm, cementation by carbonates that either has formed within a horizon and subsequently and silica; and zm, cementation by salts more soluble than has been translocated within the horizon or has been gypsum. moved into the horizon by illuviation, or both. At least some part of the horizon should show evidence of clay ma Marl accumulation either as coatings on surfaces of peds or in This symbol, used only with L, indicates a limnic layer pores, as lamellae, or as bridges between mineral grains. of marl. Designations for Horizons and Layers 319

u Presence of human-manufactured materials (artifacts) Conventions for Using Letter Suffixes This symbol indicates the presence of manufactured Many master horizons and layers that are symbolized by a artifacts that have been created or modified by single capital letter have one or more lowercase letter suffixes. humans, usually for a practical purpose in habitation, The following rules apply: manufacturing, excavation, or construction activities. Examples of artifacts are processed wood products, liquid 1. Letter suffixes should directly follow the capital letter. petroleum products, coal combustion by-products, asphalt, 2. More than three suffixes are rarely used. fibers and fabrics, bricks, cinder blocks, concrete, plastic, glass, rubber, paper, cardboard, iron and steel, altered 3. If more than one suffix is needed, the following letters, metals and minerals, sanitary and medical waste, garbage, if used, are written first: a, d, e, h, i, r, s, t, and w. Except in 2 and landfill waste. the Bhs or Crt horizon designations, none of these letters are used in combination in a single horizon. v Plinthite 4. If more than one suffix is needed and the horizon is not This symbol indicates the presence of iron-rich, buried, the following symbols, if used, are written last: c, f, g, humus-poor, reddish material that is firm or very firm m, v, and x. Some examples: Btc, Bkm, and Bsv. when moist and is less than strongly cemented. It hardens irreversibly when exposed to the atmosphere and to 5. If a horizon is buried, the suffix b is written last. It is repeated wetting and drying. used only for buried mineral soils. w Development of color or structure 6. If the above rules do not apply to certain suffixes, such as k, kk, q, or y, the suffixes may be listed together in order This symbol is used only with B horizons to indicate of assumed dominance or they are listed alphabetically if the development of color or structure, or both, with little dominance is not a concern. or no apparent illuvial accumulation of material. It should not be used to indicate a transitional horizon. A B horizon that has a significant accumulation of clay and also shows evidence of a development of color or structure, or x Fragipan character both, is designated Bt (t has precedence over w, s, and h). A This symbol indicates a genetically developed layer B horizon that is gleyed or has accumulations of carbonates, that has a combination of firmness and brittleness and sodium, silica, gypsum, or salts more soluble than gypsum or commonly a higher bulk density than the adjacent layers. residual accumulations of sesquioxides carries the appropriate Some part of the layer is physically root-restrictive. symbol: g, k, n, q, y, z, or o. If illuvial clay also is present, t precedes the other symbol: Bto. y Accumulation of gypsum Unless needed for explanatory purposes, the suffixes h, s, This symbol indicates an accumulation of gypsum. and w are not used with g, k, n, q, y, z, or o. The suffix y is used when the horizon fabric is dominated by soil particles or minerals other than gypsum. Gypsum Vertical Subdivision is present in amounts that do not significantly obscure or Commonly, a horizon or layer identified by a single letter disrupt other features of the horizon. or a combination of letters has to be subdivided. For this yy Dominance of horizon by gypsum purpose, Arabic numerals are added to the letters of the horizon designation. These numerals follow all the letters. Within a C This symbol indicates a horizon that is dominated horizon, for example, successive layers may be designated C1, by the presence of gypsum. The gypsum content may C2, C3, etc. If the lower part is gleyed and the upper part is be due to an accumulation of secondary gypsum, the not gleyed, the layers may be designated C1-C2-Cg1-Cg2 or transformation of primary gypsum inherited from parent C-Cg1-Cg2-R. material, or other processes. Suffix yy is used when These conventions apply whatever the purpose of the the horizon fabric has such an abundance of gypsum subdivision. In many soils a horizon that could be identified (generally 50 percent or more, by volume) that pedogenic by a single set of letters is subdivided because of the need and/or lithologic features are obscured or disrupted to recognize differences in morphological features, such as by growth of gypsum crystals. Colors associated with structure, color, or texture. These divisions are numbered horizons that have suffix yy typically are highly whitened consecutively with Arabic numerals, but the numbering starts with value of 7 through 9.5 and chroma of 2 or less. again with 1 wherever in the profile any letter of the horizon z Accumulation of salts more soluble than gypsum symbol changes, e.g., Bt1-Bt2-Btk1-Btk2 (not Bt1-Bt2- H This symbol indicates an accumulation of salts that are O R more soluble than gypsum. 2 Indicates weathered bedrock or saprolite in which clay films are present. 320 Keys to Soil Taxonomy

Btk3-Btk4). The numbering of vertical subdivisions within suffix numbers designating vertical subdivisions of the Bt consecutive horizons is not interrupted at a discontinuity horizon continue in consecutive order across the discontinuity. (indicated by a numerical prefix) if the same letter combination However, vertical subdivisions do not continue across lithologic is used in both materials, e.g., Bs1-Bs2-2Bs3-2Bs4 (not Bs1- discontinuities if the horizons are not consecutive or contiguous Bs2-2Bs1-2Bs2). to each other. If other horizons intervene, another vertical During sampling for laboratory analyses, thick soil numbering sequence begins for the lower horizons: A-C1-C2- horizons are sometimes subdivided even though differences in 2Bw1-2Bw2-2C1-2C2. morphology are not evident in the field. These subdivisions are If an R layer is present below a soil that has formed in identified by Arabic numerals that follow the respective horizon residuum and if the material of the R layer is judged to be like designations. For example, four layers of a Bt horizon sampled the material from which the soil has developed, the Arabic- by 10-cm increments are designated Bt1, Bt2, Bt3, and Bt4. If number prefix is not used. The prefix is used, however, if it is the horizon has already been subdivided because of differences thought that the R layer would produce material unlike that in in morphological features, the set of Arabic numerals that the solum, e.g., A-Bt-C-2R or A-Bt-2R. If part of the solum identifies the additional sampling subdivisions follows the first has formed in residuum, the symbol R is given the appropriate numeral. For example, three layers of a Bt2 horizon sampled prefix: Ap-Bt1-2Bt2-2Bt3-2C1-2C2-2R. by 10-cm increments are designated Bt21, Bt22, and Bt23. The A buried horizon (designated by the letter b) presents descriptions for each of these sampling subdivisions can be special problems. It is obviously not in the same deposit as the same, and a statement indicating that the horizon has been the overlying horizons. Some buried horizons, however, have subdivided only for sampling purposes can be added. formed in material that is lithologically like the overlying deposit. A prefix is not used to distinguish material of such a Discontinuities buried horizon. If the material in which a horizon of a buried soil has formed is lithologically unlike the overlying material, Arabic numerals are used as prefixes to horizon designations however, the discontinuity is indicated by a number prefix and (preceding the letters A, E, B, C, and R) to indicate the symbol for the buried horizon also is used, e.g., Ap-Bt1-Bt2- discontinuities in mineral soils. These prefixes are distinct from BC-C-2ABb-2Btb1-2Btb2-2C. the Arabic numerals that are used as suffixes denoting vertical Discontinuities between different kinds of layers in organic subdivisions. soils are not identified. In most cases such differences are A discontinuity that can be identified by a number prefix is identified either by letter-suffix designations if the different a significant change in particle-size distribution or mineralogy layers are organic or by the master symbol if the different layers that indicates a difference in the material from which the are mineral. horizons have formed and/or a significant difference in age, unless that difference in age is indicated by the suffix b. Symbols that identify discontinuities are used only when Use of the Prime Symbol they can contribute substantially to an understanding of the If two or more horizons with identical Arabic-numeral relationships among horizons. The stratification common prefixes and letter combinations are separated by one or more to soils that formed in alluvium is not designated as a horizons with a different horizon designation in a pedon, discontinuity, unless particle-size distribution differs markedly identical letter and number symbols can be used for those from layer to layer (i.e., particle-size classes are strongly horizons that have the same characteristics. For example, contrasting), even though genetic horizons may have formed in the sequence A-E-Bt-E-Btx-C identifies a soil that has two E the contrasting layers. horizons. To emphasize this characteristic, the prime symbol (´) Where a soil has formed entirely in one kind of material, is added after the master-horizon symbol of the lower of the two the whole profile is understood to be material 1 and the number horizons that have identical designations, e.g., A-E-Bt-E´-Btx- prefix is omitted from the symbol. Similarly, the uppermost C. The prime symbol, where appropriate, is placed after the material in a profile consisting of two or more contrasting capital-letter horizon designation and before the lowercase materials is understood to be material 1, but the number is suffix letter symbols that follow it: B´t. omitted. Numbering starts with the second layer of contrasting The prime symbol is not used unless all letters and Arabic- material, which is designated 2. Underlying contrasting layers numeral prefixes are completely identical. The sequence A-Bt1- are numbered consecutively. Even when the material of a layer Bt2-2E-2Bt1-2Bt2 is an example. It has two Bt master horizons below material 2 is similar to material 1, it is designated 3 in of different lithologies; thus, the Bt horizons are not identical the sequence; the numbers indicate a change in materials, not and the prime symbol is not needed. The prime symbol is used types of material. Where two or more consecutive horizons have for soils with lithologic discontinuities when horizons have formed in the same kind of material, the same prefix number identical designations: A-C-2Bw-2Bc-2B´w-3Bc. This soil has indicating the discontinuity is applied to all the designations two identical 2Bw horizons but has two different Bc horizons (a of horizons in that material: Ap-E-Bt1-2Bt2-2Bt3-2BC. The 2Bc and a 3Bc), so the prime symbol is used only with the lower Designations for Horizons and Layers 321

2Bw horizon (2B´w). In the rare cases where three layers have transported material. This material has been moved horizontally identical letter symbols, double prime symbols can be used for onto a pedon from a source area outside of that pedon by the lowest of these horizons: E´´. directed human activity, usually with the aid of machinery. Vertical subdivisions of horizons or layers (Arabic-numeral All horizons and layers formed in human-transported material suffixes) are not taken into account when the prime symbol are indicated by a “caret” prefix (e.g., ^A-^C-Ab-Btb). When is assigned. The sequence A-E-Bt-E-B´t1-B´t2-B´t3-C is an they can contribute substantially to an understanding of the example. relationship of the horizons or layers, Arabic-numeral prefixes These same principles apply in designating layers of organic may be used before the caret symbol to indicate the presence soils. The prime symbol is used only to distinguish two or more of discontinuities within the human-transported material or horizons that have identical symbols, e.g., Oi-C-O´i-C´ (when between the human-transported material and underlying layers the soil has two identical Oi and C layers) and Oi-C-Oe-C´ (e.g., ^A-^C1-2^C2-3Bwb). (when the soil has two identical C layers). The prime symbol is added to the lower layers to differentiate them from the upper. Literature Cited Use of the Caret Symbol Gile, L.H., F.F. Peterson, and R.B. Grossman. 1966. The “caret” symbol (^) is used as a prefix to master horizon Morphological and Genetic Sequences of Carbonate designations to indicate mineral or organic layers of human- Accumulation in Desert Soils. Soil Sci. 101: 347–360.

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323

Appendix

Laboratory Methods for Soil Taxonomy method is listed by code on the data sheet at the beginning of the chapters describing soil orders in the second edition of Soil The standard laboratory methods upon which the operational Taxonomy. On the data sheets presented with each order, the definitions of the second edition of Soil Taxonomy are based method code (e.g., 3A1 for Particles <2mm) is shown for each are described in the Soil Survey Laboratory Methods Manual determination made. These data sheets should be consulted (Burt, 2004). Copies of standard laboratory data sheets are for reference to the Soil Survey Laboratory Methods Manual. included with the typifying pedons in the chapters on soil This manual specifies method codes for pedon sampling, orders in the second edition of Soil Taxonomy. For specific sample handling, site selection, sample collection, and sample information about an analytical procedure, these data sheets preparation. should be checked and reference should be made to the Soil The units of measure reported on the data sheets in the Survey Laboratory Methods Manual. Much of the information second edition of Soil Taxonomy are not SI units. Following are included in this appendix is derived from “Soil Survey SI conversions: Laboratory Methods for Characterizing Physical and Chemical Properties and Mineralogy of Soils” (Kimble et al., 1993). Also, 1 meq/100 g = 1 cmol(+)/kg the information is summarized in the Soil Survey Laboratory 1 meq/liter = 1 mmol (±)/L Information Manual (USDA, NRCS, 1995). 1 mmho/cm = 1 dS/m Pedon characterization data, or any soil survey data, are 15 bar = 1500 kPa 1 most useful when the operations for collecting the data are well /3 bar = 33 kPa 1 understood. The mental pictures and conceptual definitions that /10 bar = 10 kPa aid in visualizing properties and processes often differ from In this taxonomy the terms (1) particle-size analysis (size the information supplied by an analysis. Also, results differ by separates), (2) texture, and (3) particle-size classes are all method, even though two methods may carry the same name used. Particle-size analysis is needed to determine texture and or the same concept. There is uncertainty in comparing one bit particle-size classes. Texture differs from particle-size class in of data with another without knowledge of how both bits were that texture includes only the fine-earth fraction (less than 2 gathered. Operational definitions, definitions tied to a specific mm), while particle size includes both the fraction less than 2 method, are needed. This soil taxonomy has many class limits mm in size and the fraction equal to or more than 2 mm. (at all levels) that are based on chemical or physical properties determined in the laboratory. One can question a given limit, Physical Analyses but that is not the purpose of this appendix. This appendix is written to show what procedures are used for given class limits. Atterberg limits are determined on the fraction less than By using specific class limits, everyone will come to the same 0.4 mm in size. Plasticity index is the difference in water classification if they follow the same procedures. content between liquid limit and plastic limit. It is the range This taxonomy is based almost entirely on criteria that are of water content over which a soil paste can be deformed defined operationally. One example is the definition of particle- without breaking, but it does not include flow as a liquid under size classes. There is no one definition of clay that works well operationally defined conditions. Liquid limit is the minimum for all soils. Hence, an operation for testing the validity of a water content at which the paste begins to flow as a liquid. clay measurement and a default operation for those situations Samples that do not deform without breaking at any water where the clay measurement is not valid are defined. The default content are reported as NP, nonplastic. Operational definitions method is based on a water content at 1500 kPa and on content are in the Annual Book of ASTM Standards (ASTM, 1998). of organic carbon. Bulk density is obtained typically by equilibration of Saran- coated natural fabric clods at designated pressure differentials. Data Elements Used in Classifying Soils Bulk densities are determined at two or more water contents. For coarse textured and moderately coarse textured soils, Detailed explanations of laboratory methods are given in the they are determined when the sample is at 10 kPa suction and Soil Survey Laboratory Methods Manual (Burt, 2004). Each when ovendry. For soils of medium and finer texture, the bulk 324 Keys to Soil Taxonomy

acetate is equal to the sum of the bases extracted by ammonium densities are determined when the sample is at 33 kPa suction acetate, divided by the CEC (by ammonium acetate), and and when ovendry. multiplied by 100. If extractable calcium is not reported on the Bulk density determined at 33 kPa suction is used to convert data sheet because of free carbonates or salts in the sample, then other analytical results to a volumetric basis (for example, kg of the base saturation is assumed to be 100 percent. organic carbon per m3). Base saturation percentage by sum of cations is equal to the Coefficient of linear extensibility (COLE) is a derived value. sum of bases extracted by ammonium acetate, divided by the It is computed from the difference in bulk density between a CEC (by sum of cations), and multiplied by 100. This value is moist clod and an ovendry clod. It is based on the shrinkage of a not reported if either extractable calcium or extractable acidity natural soil clod between a water content of 33 kPa (10 kPa for is omitted. sandier soils) and ovendry. Differences between the two methods of determining base Linear extensibility (LE) of a soil layer is the product of saturation reflect the amount of the pH-dependent CEC. Class the thickness, in centimeters, multiplied by the COLE of the definitions in this taxonomy specify which method is used. layer in question. The LE of a soil is the sum of these products The sum of exchangeable cations is considered equal to the for all soil horizons. COLE multiplied by 100 is called linear sum of bases extracted by ammonium acetate unless carbonates, extensibility percent (LEP). gypsum, or other salts are present. When these salts are present, Water retention difference (WRD) is computed from the sum of the bases extracted by ammonium acetate typically gravimetric water retentions at 33 kPa (10 kPa for sandier exceeds 100 percent of the CEC. Therefore, a base saturation of soils) and 1500 kPa suction. It is converted to cm of water per 100 percent is assumed. The amount of calcium from carbonates cm of soil through use of the bulk density. The 33 or 10 kPa is usually much larger than the amount of magnesium from water contents are determined by desorption of the natural the carbonates. Extractable calcium is not shown on the data fabric clods, and the 1500 kPa water content is determined by sheet if more than a trace (more than 0.4 percent) of carbonates desorption of crushed and sieved fine-earth (<2 mm) soil. (reported as calcium carbonate) is present or if calculated base saturation exceeds 110 percent, based on CEC by ammonium Chemical Analyses acetate at pH 7. Aluminum saturation is the amount of KCl-extractable Al Calcium carbonate equivalent is the amount of carbonates divided by extractable bases (extracted by ammonium acetate) in the soil as measured by treating the sample with HCl. The plus the KCl-extractable Al. It is expressed as percent. A evolved carbon dioxide is measured manometrically. The general rule of thumb is that if there is more than 50 percent amount of carbonate is then calculated as a calcium carbonate Al saturation, Al problems in the soil are likely. The problems equivalent regardless of the form of carbonates (dolomite, may not be related to Al toxicity but to a deficiency of calcium sodium carbonate, magnesium carbonate, etc.) in the sample. and/or magnesium. Calcium carbonate equivalent is reported as a percentage of the Ammonium oxalate-extractable aluminum, iron, and total dry weight of the sample. It can be reported on material silicon are determined by a single extraction made in the that is less than 2 mm or less than 20 mm in size. dark with 0.2 molar ammonium oxalate at a pH of 3.5. The Calcium sulfate as gypsum is determined by extraction in amount of aluminum, iron, and silicon is measured by atomic water and precipitation in acetone. The amount of gypsum is absorption and reported as a percentage of the total dry weight reported as a percentage of the total dry weight of the fraction of the fine-earth fraction. These values are used as criteria in less than 2 mm in size and the fraction less than 20 mm in size. identifying soils in the Andisol and Spodosol orders and in Drying soils to oven-dryness, the standard base for reporting the the andic and spodic subgroups in other orders. They also are data, removes part of the water of hydration from the gypsum. used to determine amorhic and ferrihydric mineralogy classes. Many measured values, particularly water retention values, must The procedure extracts iron, aluminum, and silicon from be recalculated to compensate for the weight of the water of organic matter and from amorphous mineral material. It is hydration lost during drying. used in conjunction with dithionite-citrate and pyrophosphate Cation-exchange capacity (CEC) by ammonium acetate (1N extractions to identify the sources of iron and aluminum in the NH4OAc pH 7), by sum of cations (at pH 8.2), and by bases soil. Pyrophosphate extracts iron and aluminum from organic plus aluminum is given on the data sheets in the chapters on matter. Dithionite-citrate extracts iron from iron oxides and soil orders. The CEC depends on the method of analysis as oxyhydroxides as well as from organic matter. A field test using well as the nature of the exchange complex. CEC by sum of potassium hydroxide (KOH) can be used to estimate the amount cations at pH 8.2 is calculated by adding the sum of bases and of aluminum that is extractable by ammonium oxalate. the extractable acidity. CEC by ammonium acetate is measured Base saturation is reported on the data sheets as percent of at pH 7. CEC by bases plus aluminum, or effective cation- the CEC. It is reported as CEC by sum of cations at pH 8.2 and exchange capacity (ECEC), is derived by adding the sum of by ammonium acetate at pH 7. Base saturation by ammonium bases and KCl-extractable Al. Aluminum extracted by 1N KCl Appendix 325

is negligible if the extractant pH rises toward 5.5. ECEC then is soluble sodium is converted to cmol(+)/kg-1 soil. This value is equal to extractable bases. CEC and ECEC are reported on the subtracted from extractable sodium, divided by the CEC (by data sheets as cmol(+)/kg-1 soil. ammonium acetate), and multiplied by 100. An ESP of more The reported CEC may differ from the CEC of the soil at its than 15 percent is used in this taxonomy as a criterion for the natural pH. The standard methods allow the comparison of one natric horizon. soil with another even though the pH of the extractant differs Extractable acidity is the acidity released from the soil by from the pH of the natural soil. Cation-exchange capacity a barium chloride-triethanolamine solution buffered at pH by ammonium acetate and by sum of cations applies to all 8.2. It includes all the acidity generated by replacement of the soils. CEC at pH 8.2 is not reported if the soil contains free hydrogen and aluminum from permanent and pH-dependent carbonates because bases are extracted from the carbonates. exchange sites. It is reported as cmol(+)/kg-1 soil. Extractable The effective CEC (ECEC) is reported only for acid soils. acidity data are reported on some data sheets as exchangeable ECEC is not reported for soils having soluble salts, although it acidity and on others as exchangeable H+. can be calculated by subtracting the soluble components from Extractable aluminum is exchangeable aluminum extracted the extractable components. ECEC also may be defined as by 1N KCl. It is a major constituent only in strongly acid bases plus aluminum plus hydrogen. That is the more common soils (pH of less than 5.0). Aluminum will precipitate if the definition for agronomic interpretations. This taxonomy pH rises above 4.5 to 5.0 during analysis. The extractant specifies bases plus aluminum. KCl usually affects the soil pH 1 unit or less. Extractable Generally, the ECEC is less than the CEC at pH 7, which in aluminum is measured at the Soil Survey Laboratory (SSL), turn is less than the CEC at pH 8.2. If the soil is dominated by National Soil Survey Center, by atomic absorption. Many positively charged colloids (e.g., iron oxides), however, the trend laboratories measure the aluminum by titration with a base to is reversed. Most soils have negatively charged colloids, which the phenopthalein end point. Titration measures exchangeable cause the CEC to increase with increasing pH. This difference acidity as well as extractable aluminum. Soils with a pH below in CEC is commonly called the pH-dependent or variable 4.0 or 4.5 are likely to have values determined by atomic charge. The CEC at the soil pH can be estimated by plotting absorption similar to values determined by titration because the CEC of the soil vs. the pH of the extractant on a graph and very little hydrogen is typically on the exchange complex. If reading the CEC at the soil pH. there is a large percentage of organic matter, however, some CEC measurements at pH levels other than those described hydrogen may be present. For some soils it is important to know in the paragraphs above and CEC derived by use of other which procedure was used. Extractable aluminum is reported as cations will yield somewhat different results. It is important to cmol(+)/kg-1 soil. know the procedure, pH, and extracting cation used before CEC Extractable bases (calcium, magnesium, sodium, and data are evaluated or data from different sources are compared. potassium) are extracted with ammonium acetate buffered Citric-acid-extractable phosphorus (acid-soluble phosphate) at pH 7. They are equilibrated, filtered in an auto-extractor, is used to separate the mollic epipedon (less than 1,500 mg/kg and measured by atomic absorption. They are reported as -1 P2O5) from the anthropic epipedon (equal to or more than 1,500 cmol(+)/kg soil. The bases are extracted from the cation- mg/kg). exchange complex by displacement with ammonium ions. Color of sodium-pyrophosphate extract is used as a criterion The term “extractable bases” is used instead of “exchangeable in the separation of different types of organic materials. bases” because soluble salts and some bases from carbonates A saturated solution is made by adding 1 g of sodium can be included in the extract. pyrophosphate to 4 ml of distilled water, and a moist organic Sum of bases is the sum of the calcium, magnesium, sodium, matter sample is added to the solution. The sample is mixed and and potassium described in the previous paragraph. allowed to stand overnight, chromatographic paper is dipped in Iron and aluminum extracted by citrate are removed in a the solution, and the color of the paper is ascertained through single extraction. They are measured by atomic absorption use of a Munsell color chart. and reported as a percentage of the total dry weight. The iron Electrical conductivity (EC) is the conductivity of the water is primarily from ferric oxides (hematite, magnetite) and iron extracted from saturated paste. The EC is used to determine the oxyhydroxides (goethite). Aluminum substituted into these total content of salts. It is reported as dS/m. minerals is extracted simultaneously. The dithionite reduces Exchangeable magnesium and calcium plus exchangeable the ferric iron, and the citrate stabilizes the iron by chelation. acidity (at pH 8.2) is used as a criterion for the natric Iron and aluminum bound in organic matter are extracted if horizon. The exchangeable acidity is measured at pH 8.2, the citrate is a stronger chelator than the organic molecules. and the magnesium and calcium are extracted at pH 7.0 with Manganese extracted by this procedure also is recorded. The ammonium acetate. See the paragraphs about extractable acidity iron extracted is commonly related to the clay distribution and exchangeable bases. within a pedon. Exchangeable sodium percentage (ESP) is reported as a Melanic index is used in the identification of the melanic percentage of the CEC by ammonium acetate at pH 7. Water- epipedon. The index is related to the ratio of the humic and 326 Keys to Soil Taxonomy

fulvic acids in the organic fraction of the soil (Honna et al., also have high NaF pH values. NaF is poisonous with ingestion 1988). About 0.50 gram of air-dried soil material that is and eye contact and moderately hazardous with skin contact. less than 2 mm in size is shaken with 25 ml of 0.5 percent Phosphate retention (P ret.) refers to the percent phosphorus NaOH solution in a 50-ml centrifuge tube for 1 hour at room retained by soil after equilibration with 1,000 mg/kg phosphorus temperature. One drop of a flocculating agent is added, and the solution for 24 hours. This procedure is used in the detection mixture is centrifuged at 4,000 rpm for 10 minutes. The melanic of andic soil properties. It identifies soils in which phosphorus index is the ratio of the absorbance at 450 nm over that at 520 fixation may be a problem affecting agronomic uses. nm. Sodium adsorption ratio (SAR) was developed as a measure Nitrogen in the SSL database is reported as a percentage of irrigation water quality. Water-soluble sodium is divided by of the total dry weight. A soil sample is combusted at high water-soluble calcium and magnesium. The formula is SAR 0.5 temperature with oxygen, and atmospheric nitrogen (N2) is = Na/[(Ca+Mg)/2] . An SAR of 13 or more is used as an measured by thermal conductivity detection. alternate to the ESP criterion for the natric horizon. Optical density of the ammonium oxalate extract (ODOE) Sodium-pyrophosphate-extractable iron and aluminum are is determined with a spectrophotometer using a 430 nm determined by a single extraction and measured by atomic wavelength. An increase in the ODOE value in an illuvial absorption. Results are reported as a percentage of the total dry horizon, relative to an overlying eluvial horizon, indicates an weight. This procedure has been used widely to extract iron and accumulation of translocated organic materials. aluminum from organic matter. It successfully removes much of Organic carbon data in the SSL database have been the organo-metal accumulations in spodic horizons but extracts determined mostly by wet digestion (Walkley, 1935). Because little of the inorganically bound iron and aluminum. of environmental concerns about waste products, however, Total salts is calculated from the electrical conductivity of that procedure is no longer in use. The only procedure that is the saturation extract. It is reported as a weight percentage of currently used to determine organic carbon is a dry combustion the total water-soluble salts in the soil. procedure that determines the percent of total carbon. In Water-soluble cations and anions are determined in water calcareous horizons the content of organic carbon is determined extracted from a saturated paste. The cations include calcium, by subtracting the amount of carbon contributed by carbonates magnesium, sodium, and potassium, and the anions include from the total carbon data (percent organic carbon = percent carbonate, bicarbonate, sulfate, chloride, nitrite, nitrate, fluoride, total carbon – [% <2 mm CaCO3 x 0.12]). The content of phosphate, silicate, and borate. The cations and anions are organic carbon determined by this computation is very close to reported as mmol(±) L-1. the content determined by the wet digestion procedure. Water-soluble sulfate is used as a criterion for the sulfuric pH is measured in water and in salts. The pH measured in horizon. The sulfate is determined in the saturation extract and water is determined in distilled water typically mixed 1:1 with is reported as one of the anions. dry soil. The pH measured in potassium chloride is determined in 1N KCl solution mixed 1:1 with soil. The pH measured in Mineral Analyses calcium chloride is determined in 0.01M CaCl2 solution mixed 2:1 with soil. Mineralogy of the clay, silt, and sand fractions is needed for The pH is measured by a pH meter in a soil-water or soil-salt classification in some taxa. X-ray diffraction (XRD) and thermal solution. The extent of the dilution is shown in the heading on and petrographic analyses are classically viewed as mineralogy the data sheets. A ratio of 1:1 means one part dry soil and one techniques, although some mineralogy classes (e.g., ferritic, part water, by weight. amorphic, gypsic, carbonatic, and isotic) are determined by Measurement of pH in a dilute salt solution is common chemical and/or physical analyses. because it tends to mask seasonal variations in pH. Readings in Halloysite, illite, kaolinite, smectite, vermiculite, and other

0.01M CaCl2 tend to be uniform regardless of the time of year. minerals in the clay fraction (less than 0.002 mm) may be Readings in 1N KCl also tend to be uniform. The former are identified by XRD analysis. Relative peak positions identify clay more popular in regions with less acid soils. The latter are more minerals, and peak intensities are the basis for semi-quantitative popular in regions with more acid soils. If KCl is used to extract estimates of mineral percent by weight in the clay fraction. exchangeable aluminum, the pH reading (in KCl) shows the pH The SSL reports relative peak intensities of clay minerals at which the aluminum was extracted. from XRD in a five-class system that generally corresponds to pH in sodium fluoride (NaF pH) is measured in a suspension percent by weight of a mineral (class 1 = 0 to 2 percent, class of 1 gram of soil in 50 ml 1M NaF after stirring for 2 minutes. 2 = 3 to 9 percent, class 3 = 10 to 29 percent, class 4 = 30 to A NaF pH of 9.4 or more is a strong indicator that short-range- 50 percent, and class 5 = more than 50 percent). There are order minerals dominate the soil exchange complex. A NaF pH multiple potential interferences in the analysis of a clay sample of 8.4 or more is a criterion for the isotic mineralogy class. It (Burt, 2004). Peak intensities may be attenuated by one or indicates a significant component of short-range-order minerals more interferences, and the reported class may underestimate in the exchange complex. Soil materials with free carbonates the actual amount of mineral present. Thus, these assigned Appendix 327

percentages are given for informational use only and should not Two general types of petrographic analysis are conducted be used to quantify minerals in a clay fraction. Clay minerals are in the SSL: (a) complete mineral grain count, in which all listed in the order of decreasing quantity on the data sheet. XRD minerals in the sample are identified and counted, or (b) a glass is used to determine smectitic, vermiculitic, illitic, kaolinitic, or count, in which glass, glass aggregates, glass-coated minerals, halloysitic mineralogy classes in Soil Taxonomy. Some family and glassy materials are identified and quantified and all other classes require a clay mineral to be more than one-half (by minerals are counted as “other.” Other isotropic materials, such weight) of the clay fraction, corresponding to XRD class 5. as plant opal, sponge spicules, and diatoms, also are identified Other mineralogy classes require more of the specified mineral and quantified in the glass count grain studies. “Glass-coated than any other single mineral, corresponding to the clay mineral grains” are crystalline mineral grains (e.g., quartz and feldspar) being listed first on the SSL data sheet. in which more than 50 percent of the grain is covered in glass. Kaolinite and gibbsite may be determined by thermal “Glassy materials” is a general category for grains that have analysis. Results from this analysis are reported as percent optical properties of glass but lack definitive characteristics of by weight in the clay fraction and are more quantitative than glass, glass-coated grains, or glass aggregates. Percent of total the results of XRD for these minerals. Thermal analysis is a resistant minerals is reported on the SSL data sheet. (Calcite technique in which the dried sample (typically the clay fraction) and more soluble minerals are included in determinations of the is heated in a controlled environment. Certain minerals undergo percentage of resistant minerals reported on the laboratory data decomposition at specific temperature ranges, and the mineral sheet but are not included in the values used in this taxonomy.) can be quantified when compared to standard clays. Results may Total percent volcanic glass, weatherable minerals, or other be used to determine kaolinitic and gibbsitic family mineralogy groups of minerals used in classification may be calculated by classes, complementary to or in lieu of XRD data. summing the percent of individual minerals included in the Resistant minerals, weatherable minerals, volcanic glass, group. A complete list of minerals in each category is in the Soil magnesium-silicate minerals, glauconitic pellets, mica, and Survey Laboratory Methods Manual (Burt, 2004). stable mica pseudomorphs may be determined by petrographic analysis. Magnesium-silicate minerals (e.g., serpentine Other Information Useful in Classifying Soils minerals) and glauconitic pellets are reported as percent by weight in the fine-earth fraction (less than 2.0 mm). Resistant Volumetric amounts of organic carbon are used in some minerals, weatherable minerals, and volcanic glass are taxonomic criteria. The following calculation is used: (Datum determined as percent of total grains counted in the coarse silt [percent] times bulk density [at 33 or 10 kPa] times thickness through very coarse sand (0.02 to 2.0 mm) fractions, while mica [cm]) divided by 10. This calculation is normally used for and stable mica pseudomorphs are determined in the 0.02 to organic carbon, but it can be used for some other measurements. 0.25 mm fractions (coarse silt, very fine sand, and fine sand). Each horizon is calculated separately, and the product of the Individual mineral grains in a specific particle-size fraction calculations can be summed to any desired depth, commonly are mounted on a glass slide, identified, and counted (at least 100 cm. 300 grains) under a polarizing light microscope. Data are Ratios that can be developed from the data are useful in reported as percent of grains counted for a specific size fraction. making internal checks of the data, in making management- This percentage is generally regarded as equivalent to weight related interpretations, and in answering taxonomic questions. percent for spherical minerals. Alternative techniques are Some of the ratios are used as criteria in determining argillic, available for determining weight percent micas and other platy kandic, or oxic horizons. grains in a soil separate. The usual SSL protocol is to count The ratio of 1500 kPa water to clay is used to indicate the mineral grains in either the coarse silt (0.02-0.05 mm), very relevancy of the particle-size determination. If the ratio is fine sand (0.05-0.10 mm), or fine sand (0.10-0.25 mm) fraction, 0.6 or more and the soil does not have andic soil properties, whichever one has the highest weight percent based on particle- incomplete dispersion of the clay is assumed and clay is size analysis. Mineral or glass content in the analyzed fraction estimated by the following formula: Clay % = 2.5(% water is assumed to be representative of the content in the whole 0.02 retained at 1500 kPa tension - % organic carbon). For a typical to 2.0 mm or fine-earth fraction. It may be necessary to count soil with well dispersed clays, the ratio is 0.4. Some soil-related additional fractions to obtain a reliable estimate of volcanic factors that can cause deviation from the 0.4 value are: (1) low- glass content in soil materials with a non-uniform distribution activity clays (kaolinites, chlorites, and some micas), which tend of glass in dominant particle-size fractions. If more than to have a ratio of 0.35 or below; (2) iron oxides and clay-size one fraction is counted, the weighted average of the counted carbonates, which tend to decrease the ratio; (3) organic matter, fractions may be calculated to represent glass content in the which increases the ratio because it increases the water content 0.02 to 2.0 mm fraction. For soils expected to have significant at 1500 kPa; (4) andic and spodic materials and materials with amounts of glass in dominant fractions of medium, coarse, or an isotic mineralogy class, which increase the ratio because they very coarse sand, a request is made to count grains in the larger do not disperse well; (5) large amounts of gypsum; and (6) clay fractions. minerals within grains of sand and silt. These clay minerals hold 328 Keys to Soil Taxonomy

water at 1500 kPa and thus increase the ratio. They are most Literature Cited common in shale and in pseudomorphs of primary minerals in saprolite. American Society for Testing and Materials (ASTM). 1998. The ratio of CEC by ammonium acetate at pH 7 to Annual Book of ASTM Standards. Vol. 4.08, D 4318-95a. percent clay can be used to estimate clay mineralogy and Burt, R., ed. 2004. Soil Survey Laboratory Methods Manual. clay dispersion. If the ratio is multiplied by 100, the product Soil Survey Investigations Report 42, Version 4.0. United States is cmol(+)/kg clay. The following ratios are typical for the Department of Agriculture, Natural Resources Conservation following classes of clay mineralogy: less than 0.2, kaolinitic; Service, National Soil Survey Center. 0.2-0.3, kaolinitic or mixed; 0.3-0.5, mixed or illitic; 0.5- Honna,T., S. Yamamoto, and K. Matsui. 1988. A Simple 0.7, mixed or smectitic; and more than 0.7, smectitic. These Procedure to Determine Melanic Index That Is Useful for ratios are most valid when some detailed mineralogy data are Differentiating Melanic from Fulvic Andisols. Pedol. 32: 69-78. available. If the ratio of 1500 kPa water to clay is 0.25 or less Kimble, J.M, E.G. Knox, and C.S. Holzhey. 1993. Soil or 0.6 or more, the ratio of CEC by ammonium acetate to clay Survey Laboratory Methods for Characterizing Physical and is not valid. Ratios of 1500 kPa water to clay of 0.6 or more are Chemical Properties and Mineralogy of Soils. In Applications typical of poorly dispersed clays, andic and spodic materials, of Agriculture Analysis in Environmental Studies, ASTM Spec. and materials with an isotic mineralogy class, and ratios of less Pub. 1162, K.B. Hoddinott and T.A. O’Shay, eds. than 0.3 are common in some soils that contain large amounts United States Department of Agriculture, Natural Resources of gypsum. Conservation Service. 1995. Soil Survey Laboratory A ratio of CEC at pH 8.2 to 1500 kPa water of more than 1.5 Information Manual. National Soil Survey Center, Soil Survey and more exchange acidity than the sum of bases plus KCl- Laboratory, Soil Survey Investigations Report 45. extractable Al imply a soil with a high pH-dependent charge. Walkley, A. 1935. An Examination of Methods for Along with bulk density data, they help to distinguish soils that Determining Organic Carbon and Nitrogen in Soils. J. Agr. Sci. have andic and spodic materials or soils that have materials 25: 598-609. with an isotic mineralogy class from soils with minerals that are more crystalline. Appendix 329

Percentages of clay (less than 0.002 mm), silt (0.002 to 0.05 mm), and sand (0.05 to 2.0 mm) in the basic soil texture classes

331

Index

A Aquiturbels...... 151 Aquods...... 257 A horizons. See Horizons and layers. Aquolls...... 199 Abrupt textural change...... 15 Aquorthels...... 147 Acraquox...... 241 Aquox...... 241 Acroperox...... 242 Aquults...... 267 Acrotorrox...... 246 Arents...... 127 Acrudox...... 247 Argialbolls...... 198 Acrustox...... 251 Argiaquolls...... 199 Agric horizon...... 9 Argicryids...... 112 Alaquods...... 257 Argicryolls...... 203 Albaqualfs...... 36 Argids...... 97 Albaquults...... 268 Argidurids...... 115 Albic horizon...... 9 Argigypsids...... 118 Albic materials...... 15 Argillic horizon...... 10 Albolls...... 198 Argiorthels...... 147 Alfisols...... 35 Argiudolls...... 208 Alorthods...... 262 Argiustolls...... 215 Andic soil properties...... 15 Argixerolls...... 231 Andisols...... 77 Aridic moisture regime. See Soil moisture regimes. Anhydrous conditions...... 16 Aridisols...... 97 Anhyorthels...... 146 Artificial drainage. See Aquic conditions. Anhyturbels...... 150 Aniso class...... 300 B Anthracambids...... 108 Anthrepts...... 161 B horizons. See Horizons and layers. Anthropic epipedon...... 5 Bottom tier...... 23 Aqualfs...... 35 Buried soils...... 2 Aquands...... 77 C Aquents...... 124 Aquepts...... 161 C horizons or layers. See Horizons and layers. Aquerts...... 287 Calcareous and reaction classes of mineral soils...... 308 Aquic conditions...... 24 Calciaquerts...... 288 Redoximorphic features...... 24 Calciaquolls...... 199 Reduced matrix...... 25 Calciargids...... 97 Redox concentrations...... 25 Calcic horizon...... 10 Redox depletions...... 25 Calcicryepts...... 168 Reduction...... 24 Calcicryids...... 113 Saturation...... 24 Calcicryolls...... 204 Anthric saturation (anthraquic conditions)...... 24 Calcids...... 105 Endosaturation...... 24 Calcigypsids...... 119 Episaturation...... 24 Calcitorrerts...... 291 Aquic moisture regime. See Soil moisture regimes. Calciudolls...... 210 Aquicambids...... 108 Calciustepts...... 182 Aquisalids...... 122 Calciusterts...... 294 332 Keys to Soil Taxonomy

Calciustolls...... 219 Durihumods...... 262 Calcixerepts...... 190 Durinodes...... 17 Calcixererts...... 297 Duripan...... 11 Calcixerolls...... 233 Duritorrands...... 84 Cambic horizon...... 10 Durixeralfs...... 71 Cambids...... 108 Durixerepts...... 190 Caret symbol in horizon designations...... 321 Durixererts...... 297 Cation-exchange activity classes for mineral soils...... 307 Durixerolls...... 234 Chemical analyses...... 324 Durorthods...... 263 Coatings (classes) on sands...... 310 Durudands...... 86 Coefficient of linear extensibility (COLE)...... 16 Durudepts...... 175 Control section of Histosols and Histels...... 23 Durustalfs...... 59 Coprogenous earth. See Organic soil materials. Durustands...... 92 Cryalfs...... 44 Durustepts...... 183 Cryands...... 80 Durustolls...... 221 Cryaqualfs...... 37 Dystraquerts...... 288 Cryaquands...... 78 Dystrocryepts...... 168 Cryaquents...... 124 Dystrogelepts...... 173 Cryaquepts...... 162 Dystroxerepts...... 191 Cryaquods...... 258 Dystrudepts...... 175 Cryaquolls...... 200 Dystruderts...... 293 Cryepts...... 167 Dystrustepts...... 183 Cryerts...... 291 Dystrusterts...... 294 Cryic temperature regime. See Soil temperature regimes. Cryids...... 112 E Cryods...... 259 E horizons. See Horizons and layers. Cryofibrists...... 155 Endoaqualfs...... 37 Cryofluvents...... 128 Endoaquands...... 78 Cryofolists...... 156 Endoaquents...... 124 Cryohemists...... 157 Endoaquepts...... 163 Cryolls...... 203 Endoaquerts...... 289 Cryopsamments...... 138 Endoaquods...... 258 Cryorthents...... 133 Endoaquolls...... 200 Cryosaprists...... 158 Endoaquults...... 268 Cryoturbation...... 25 Endosaturation. See Aquic conditions. Cryrendolls...... 207 Entisols...... 123 D Epiaqualfs...... 39 Epiaquands...... 79 Densic contact...... 25 Epiaquents...... 125 Densic materials...... 25 Epiaquepts...... 164 Diagnostic subsurface horizons...... 9 Epiaquerts...... 289 Diagnostic surface horizons...... 5 Epiaquods...... 259 Diatomaceous earth. See Organic soil materials. Epiaquolls...... 201 Discontinuities in horizon designations...... 320 Epiaquults...... 268 Duraqualfs...... 37 Epipedon...... 5 Duraquands...... 78 Episaturation. See Aquic conditions. Duraquerts...... 288 Eutraquox...... 241 Duraquods...... 258 Eutroperox...... 243 Duraquolls...... 200 Eutrotorrox...... 246 Duricryands...... 81 Eutrudepts...... 178 Duricryods...... 259 Eutrudox...... 248 Duricryolls...... 204 Eutrustox...... 252 Durids...... 115 Index 333

F Glossudalfs...... 49 Gypsiargids...... 99 Family differentiae for Histosols and Histels...... 311 Gypsic horizon...... 12 Family differentiae for mineral soils...... 299 Gypsicryids...... 114 Ferrudalfs...... 49 Gypsids...... 118 Fibers. See Organic soil materials. Gypsitorrerts...... 292 Fibric soil materials. See Organic soil materials. Gypsiusterts...... 295 Fibristels...... 145 Fibrists...... 155 H Fluvaquents...... 125 Fluvents...... 128 Halaquepts...... 166 Fluviwassents...... 142 Haplanthrepts...... 161 Folistels...... 145 Haplaquox...... 242 Folistic epipedon...... 6 Haplargids...... 100 Folists...... 156 Haplocalcids...... 105 Fragiaqualfs...... 41 Haplocambids...... 109 Fragiaquepts...... 165 Haplocryalfs...... 45 Fragiaquods...... 259 Haplocryands...... 82 Fragiaquults...... 269 Haplocryepts...... 169 Fragic soil properties...... 17 Haplocryerts...... 291 Fragihumods...... 262 Haplocryids...... 114 Fragiorthods...... 263 Haplocryods...... 260 Fragipan...... 11 Haplocryolls...... 204 Fragiudalfs...... 49 Haplodurids...... 116 Fragiudepts...... 180 Haplofibrists...... 156 Fragiudults...... 274 Haplogelepts...... 173 Fragixeralfs...... 72 Haplogelods...... 261 Fragixerepts...... 192 Haplogelolls...... 206 Fraglossudalfs...... 49 Haplogypsids...... 120 Frasiwassents...... 142 Haplohemists...... 157 Frasiwassists...... 159 Haplohumods...... 262 Free carbonates...... 17 Haplohumults...... 271 Frigid temperature regime. See Soil temperature regimes. Haploperox...... 244 Fulvicryands...... 81 Haplorthels...... 148 Fulvudands...... 86 Haplorthods...... 264 Haplosalids...... 122 G Haplosaprists...... 158 Haplotorrands...... 85 Gelands...... 84 Haplotorrerts...... 292 Gelaquands...... 79 Haplotorrox...... 246 Gelaquents...... 126 Haploturbels...... 151 Gelaquepts...... 165 Haplowassents...... 143 Gelepts...... 173 Haplowassists...... 159 Gelic materials...... 25 Haploxeralfs...... 72 Gelic temperature regime. See Soil temperature regimes. Haploxerands...... 95 Gelifluvents...... 128 Haploxerepts...... 193 Gelisols...... 145 Haploxererts...... 298 Gelods...... 261 Haploxerolls...... 235 Gelolls...... 206 Haploxerults...... 285 Gelorthents...... 134 Hapludalfs...... 51 Glacic layer...... 26 Hapludands...... 87 Glacistels...... 146 Hapluderts...... 293 Glossaqualfs...... 41 Hapludolls...... 211 Glossic horizon...... 11 Hapludox...... 249 Glossocryalfs...... 44 Hapludults...... 275 334 Keys to Soil Taxonomy

Haplustalfs...... 60 Isomesic temperature regime. See Soil temperature Haplustands...... 92 regimes. Haplustepts...... 185 Isothermic temperature regime. See Soil temperature Haplusterts...... 295 regimes. Haplustolls...... 221 Haplustox...... 253 K Haplustults...... 282 Kandiaqualfs...... 42 Haprendolls...... 207 Kandiaquults...... 269 Hemic soil materials. See Organic soil materials. Kandic horizon...... 12 Hemistels...... 146 Kandihumults...... 272 Hemists...... 157 Kandiperox...... 245 Histels...... 145 Kandiudalfs...... 55 Histic epipedon...... 6 Kandiudox...... 250 Historthels...... 148 Kandiudults...... 276 Histosols...... 155 Kandiustalfs...... 63 Histoturbels...... 151 Kandiustox...... 254 Horizons and layers...... 315 Kandiustults...... 282 A horizons...... 315 Kanhaplaquults...... 269 B horizons...... 316 Kanhaplohumults...... 273 C horizons or layers...... 316 Kanhapludalfs...... 56 E horizons...... 315 Kanhapludults...... 278 L horizons or layers...... 315 Kanhaplustalfs...... 64 M layers...... 316 Kanhaplustults...... 284 O horizons or layers...... 315 Key to soil orders...... 31 R layers...... 316 W layers...... 316 L Humaquepts...... 166 Humicryepts...... 171 L horizons or layers. See Horizons and layers. Humicryerts...... 291 Lamellae...... 18 Humicryods...... 260 Limnic materials. See Organic soil materials. Humigelepts...... 174 Linear extensibility (LE)...... 18 Humigelods...... 261 Lithic contact...... 26 Humilluvic material. See Organic soil materials. Lithologic discontinuities...... 18 Humixerepts...... 194 Luvihemists...... 158 Humods...... 261 Humudepts...... 180 M Humults...... 271 M layers. See Horizons and layers. Humustepts...... 189 Marl. See Organic soil materials. Hydraquents...... 126 Melanaquands...... 79 Hydrocryands...... 83 Melanic epipedon...... 7 Hydrowassents...... 143 Melanocryands...... 83 Hydrudands...... 89 Melanoxerands...... 95 Hyperthermic temperature regime. See Soil temperature Melanudands...... 90 regimes. Mesic temperature regime. See Soil temperature regimes. I Mineral analyses...... 326 Mineral soil material...... 3 Identifiable secondary carbonates...... 17 Mineral soils...... 4 Inceptisols...... 161 Mineralogy classes for Histosols and Histels...... 312 Interfingering of albic materials...... 17 Mineralogy classes for mineral soils...... 305 Isofrigid temperature regime. See Soil temperature Mollic epipedon...... 7 regimes. Mollisols...... 197 Isohyperthermic temperature regime. See Soil temperature Molliturbels...... 152 regimes. Mollorthels...... 149 Index 335

N Palexerolls...... 239 Palexerults...... 286 n value...... 19 Paralithic contact...... 26 Natralbolls...... 199 Paralithic materials...... 26 Natraqualfs...... 43 Pararock fragments...... 299 Natraquerts...... 290 Particle-size classes for Histosols and Histels...... 311 Natraquolls...... 202 Particle-size classes and their substitutes for mineral soils.....299 Natrargids...... 102 Permafrost...... 26 Natric horizon...... 12 Permanent cracks (classes) in mineral soils...... 311 Natricryolls...... 206 Perox...... 242 Natridurids...... 117 Perudic moisture regime. See Soil moisture regimes. Natrigypsids...... 121 Petraquepts...... 167 Natrixeralfs...... 74 Petroargids...... 105 Natrixerolls...... 239 Petrocalcic horizon...... 14 Natrudalfs...... 56 Petrocalcids...... 107 Natrudolls...... 213 Petrocambids...... 112 Natrustalfs...... 65 Petrocryids...... 115 Natrustolls...... 226 Petroferric contact...... 19 Normal years...... 26 Petrogypsic horizon...... 14 O Petrogypsids...... 121 Physical analyses...... 323 O horizons or layers. See Horizons and layers. Placaquands...... 80 Ochric epipedon...... 8 Placaquods...... 259 Organic soil materials...... 3 Placic horizon...... 14 Fibers...... 21 Placocryods...... 261 Fibric soil materials...... 21 Placohumods...... 262 Hemic soil materials...... 22 Placorthods...... 265 Humilluvic material...... 22 Placudands...... 91 Limnic materials...... 22 Plagganthrepts...... 161 Coprogenous earth...... 22 Plaggen epipedon...... 8 Diatomaceous earth...... 23 Plinthaqualfs...... 43 Marl...... 23 Plinthaquox...... 242 Sapric soil materials...... 22 Plinthaquults...... 271 Organic soils...... 4 Plinthite...... 19 Orthels...... 146 Plinthohumults...... 274 Orthents...... 133 Plinthoxeralfs...... 76 Orthods...... 262 Plinthudults...... 281 Ortstein...... 13 Plinthustalfs...... 70 Oxic horizon...... 13 Plinthustults...... 285 Oxisols...... 241 Prime symbol in horizon designations...... 320 Psammaquents...... 126 P Psamments...... 138 Psammorthels...... 149 Paleaquults...... 270 Psammoturbels...... 152 Paleargids...... 104 Psammowassents...... 143 Palecryalfs...... 47 Palecryolls...... 206 Q Palehumults...... 273 Quartzipsamments...... 139 Paleudalfs...... 57 Paleudolls...... 214 R Paleudults...... 279 Paleustalfs...... 67 R layers. See Horizons and layers. Paleustolls...... 228 Ratio, 1500 kPa water to clay...... 303 Paleustults...... 285 Ratio, CEC to clay...... 308 Palexeralfs...... 74 Reaction classes for Histosols and Histels...... 312 336 Keys to Soil Taxonomy

Redoximorphic features. See Aquic conditions. Sombrihumults...... 274 Reduction. See Aquic conditions. Sombriperox...... 246 Rendolls...... 207 Sombriudox...... 251 Resistant minerals...... 20 Sombriustox...... 255 Rhodoxeralfs...... 76 Sphagnofibrists...... 156 Rhodudalfs...... 59 Spodic horizon...... 14 Rhodudults...... 281 Spodic materials...... 20 Rhodustalfs...... 70 Spodosols...... 257 Rhodustults...... 285 Strongly contrasting particle-size classes...... 303 Rock fragments...... 299 Subsurface tier...... 23 Rock structure...... 5 Suffix symbols in horizon designations...... 317 Root-limiting layers...... 300 Conventions for using letter suffixes...... 319 Rounding...... 31 Sulfaquents...... 127 Rupture-resistance classes for mineral soils...... 310 Sulfaquepts...... 167 Sulfaquerts...... 291 S Sulfidic materials...... 29 Salaquerts...... 286 Sulfihemists...... 158 Salic horizon...... 14 Sulfisaprists...... 159 Salicryids...... 115 Sulfiwassents...... 144 Salids...... 122 Sulfiwassists...... 160 Salitorrerts...... 292 Sulfohemists...... 158 Salusterts...... 296 Sulfosaprists...... 159 Sulfudepts...... 182 Sapric soil materials. See Organic soil materials. Sapristels...... 146 Sulfuric horizon...... 29 Saprists...... 158 Surface tier...... 23 Saturation. See Aquic conditions. T Series control section...... 313 Series differentiae within a family...... 313 Thermic temperature regime. See Soil temperature Slickensides...... 20 regimes. Soil ...... 1 Torrands...... 84 Soil color, water state criteria...... 31 Torrerts...... 291 Soil depth classes for Histosols...... 313 Torriarents...... 127 Soil depth classes for mineral soils and Histels...... 310 Torric moisture regime. See Soil moisture regimes. Soil moisture regimes...... 26 Torrifluvents...... 128 Aquic...... 27 Torrifolists...... 156 Aridic and torric...... 27 Torriorthents...... 134 Perudic...... 28 Torripsamments...... 140 Udic...... 28 Torrox...... 246 Ustic...... 28 Transitional and combination horizons...... 316 Xeric...... 28 Turbels...... 150 Soil temperature classes for Histosols and Histels...... 312 Soil temperature classes for mineral soils...... 309 U Soil temperature regimes...... 28 Cryic...... 28 Udalfs...... 47 Frigid...... 29 Udands...... 85 Gelic...... 28 Udarents...... 127 Hyperthermic...... 29 Udepts...... 174 Isofrigid...... 29 Uderts...... 292 Isohyperthermic...... 29 Udic moisture regime. See Soil moisture regimes. Isomesic...... 29 Udifluvents...... 130 Isothermic...... 29 Udifolists...... 157 Mesic...... 29 Udipsamments...... 140 Thermic...... 29 Udivitrands...... 93 Sombric horizon...... 14 Udolls...... 207 Index 337

Udorthents...... 135 Vertical subdivision in horizon designations...... 319 Udox...... 247 Vertisols...... 287 Udults...... 274 Vitrands...... 93 Ultisols...... 267 Vitraquands...... 80 Umbraquults...... 271 Vitricryands...... 83 Umbric epipedon...... 8 Vitrigelands...... 84 Umbriturbels...... 152 Vitritorrands...... 85 Umbrorthels...... 150 Vitrixerands...... 95 Ustalfs...... 59 Volcanic glass...... 21 Ustands...... 92 Ustarents...... 127 W Ustepts...... 182 W layers. See Horizons and layers. Usterts...... 293 Wassents...... 142 Ustic moisture regime. See Soil moisture regimes. Wassists...... 159 Ustifluvents...... 131 Weatherable minerals...... 21 Ustifolists...... 157 Ustipsamments...... 141 X Ustivitrands...... 94 Ustolls...... 215 Xeralfs...... 71 Ustorthents...... 136 Xerands...... 94 Ustox...... 251 Xerarents...... 127 Ustults...... 281 Xerepts...... 189 Xererts...... 297 V Xeric moisture regime. See Soil moisture regimes. Xerofluvents...... 132 Vermaqualfs...... 43 Xerolls...... 230 Vermaquepts...... 167 Xeropsamments...... 141 Vermudolls...... 215 Xerorthents...... 138 Vermustolls...... 230 Xerults...... 285 338 S O The Soils That We Classify I

D I Differentiae for Mineral Soils and Organic Soils F

D I Horizons and Characteristics Diagnostic for the Higher Categories A

I D Identification of the Taxonomic Class of a Soil E

A L Alfisols F

A N Andisols D

A R Aridisols I

E N Entisols T

G E Gelisols L

H I Histosols S

I N Inceptisols C

M O Mollisols L

O X Oxisols I

S P Spodosols O

U L Ultisols T

V E Vertisols R

F A Family and Series Differentiae and Names M

H O Designations for Horizons and Layers R