United States Department of Agriculture Keys to Taxonomy

Ninth Edition, 2003

Keys to Soil Taxonomy

By Soil Survey Staff

United States Department of Agriculture Natural Resources Conservation Service

Ninth Edition, 2003 The United States Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, gender, religion, age, disability, political beliefs, sexual orientation, and marital or family status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Center at 202-720-2600 (voice and TDD). To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326W, Whitten Building, 14th and Independence Avenue, SW, Washington, DC 20250-9410, or call 202-720-5964 (voice and TDD). USDA is an equal opportunity provider and employer.

Cover: A natric horizon with columnar structure in a Natrudoll from Argentina. 5

Table of Contents

Foreword ...... 7 Chapter 1: The That We Classify...... 9 Chapter 2: Differentiae for Mineral Soils and Organic Soils ...... 11 Chapter 3: Horizons and Characteristics Diagnostic for the Higher Categories ...... 13 Chapter 4: Identification of the Taxonomic Class of a Soil ...... 37 Chapter 5: ...... 41 Chapter 6: ...... 83 Chapter 7: ...... 103 Chapter 8: ...... 129 Chapter 9: ...... 149 Chapter 10: ...... 159 Chapter 11: ...... 165 Chapter 12: ...... 193 Chapter 13: ...... 237 Chapter 14: Spodosols ...... 253 Chapter 15: ...... 263 Chapter 16: ...... 285 Chapter 17: Family and Series Differentiae and Names ...... 297 Chapter 18: Designations for Horizons and Layers ...... 313 Appendix ...... 319 Index ...... 325

7

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 previous eight editions of the Keys to Soil Taxonomy included all revisions of the original keys in Soil Taxonomy: A Basic System of for Making and Interpreting Soil Surveys (1975). The ninth edition of the of the Keys to Soil Taxonomy incorporates all changes approved since the publication of the second edition of Soil Taxonomy (1999). We plan to continue issuing updated editions of the Keys to Soil Taxonomy as changes warrant new editions. 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

9 S O I

CHAPTER 1 The Soils That We Classify

The word “soil,” like many common words, has several arbitrarily set at 200 cm. In soils where either biological activity meanings. In its traditional meaning, soil is the natural medium or current pedogenic processes extend to depths for the growth of land plants, whether or not it has discernible greater than 200 cm, the lower limit of the soil for classification soil horizons. This meaning is still the common understanding of purposes is still 200 cm. In some instances the more weakly 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 humans control section, defined later), even though the paralithic and because it filters water and recycles wastes. Soil covers the materials below a paralithic contact are not considered soil in earth’s surface as a continuum, except on bare rock, in areas of the true sense. In areas where soil has thin cemented horizons perpetual frost or deep water, or on the bare ice of glaciers. In that are impermeable to roots, the soil extends as deep as the this sense, soil has a thickness that is determined by the rooting deepest cemented horizon, but not below 200 cm. For certain depth of plants. management goals, layers deeper than the lower boundary of the Soil in this text is a natural body comprised of solids soil that is classified (200 cm) must also be described if they (minerals and organic matter), liquid, and gases that occurs on affect the content and movement of water and air or other the land surface, occupies space, and is characterized by one or interpretative concerns. 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 2 losses, transfers, and transformations of energy and matter or the m, except for an occasional stone line. In many wet soils, gleyed ability to support rooted plants in a natural environment. This soil material may begin a few centimeters below the surface and, definition is expanded from the 1975 version of Soil Taxonomy in some areas, continue down for several meters apparently to include soils in areas of Antarctica where occurs unchanged with increasing depth. The latter condition can arise but where the climate is too harsh to support the higher plant through the gradual filling of a wet basin in which the A horizon forms. is gradually added to the surface and becomes gleyed beneath. The upper limit of soil is the boundary between soil and air, Finally, the A horizon rests on a thick mass of gleyed material shallow water, live plants, or plant materials that have not begun that may be relatively uniform. In both of these situations, there to decompose. Areas are not considered to have soil if the is no alternative but to set the lower limit of soil at the arbitrary surface is permanently covered by water too deep (typically limit of 200 cm. more than 2.5 m) for the growth of rooted plants. The horizontal Soil, as defined in this text, does not need to have discernible boundaries of soil are areas where the soil grades to deep water, horizons, although the presence or absence of horizons and their barren areas, rock, or ice. In some places the separation between nature are of extreme importance in soil classification. Plants soil and nonsoil is so gradual that clear distinctions cannot be can be grown under glass in pots filled with earthy materials, made. such as or , 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 the here in the sense that they cannot be classified in the same horizons near the earth’s surface that, in contrast to the system that is used for the soils of a survey area, county, or even underlying parent material, have been altered by the interactions nation. Plants even grow on trees, but trees are regarded as of climate, relief, and living organisms over time. Commonly, nonsoil. soil grades at its lower boundary to hard rock or to earthy Soil has many properties that fluctuate with the seasons. It materials virtually devoid of animals, roots, or other marks of may be alternately cold and warm or dry and moist. Biological biological activity. The lowest depth of biological activity, activity is slowed or stopped if the soil becomes too cold or too however, is difficult to discern and is often gradual. For dry. The soil receives flushes of organic matter when leaves fall purposes of classification, the lower boundary of soil is or grasses die. Soil is not static. The pH, soluble salts, amount of 10

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 with if the mantle affects the use of the soil. the seasons as well as with more extended periods of time. Soil Any horizons or layers underlying a plaggen epipedon are 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 the thickness of the named diagnostic horizons that are preserved in solum of a buried soil in at least half of each pedon. The the buried soil. A surface mantle of new material that does not recognition of a surface mantle should not be based only on have the required thickness for buried soils can be used to studies of associated soils. 11

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

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

any O horizon at the surface is considered an organic horizon if b. Gelic materials within 100 cm of the soil surface and it meets the requirements of organic soil material as defined permafrost within 200 cm of the soil surface. later, and its thickness is added to that of any other organic horizons to determine the total thickness of organic soil Definition of Organic Soils materials. Organic soils have organic soil materials that: Definition of Mineral Soils 1. Do not have andic soil properties in 60 percent or more of the thickness between the soil surface and either a depth of 60 Mineral soils are soils that have either of the following: cm or a densic, lithic, or paralithic contact or duripan if shallower; and 1. Mineral soil materials that meet one or more of the following: 2. Meet one or more of the following: a. Overlie cindery, fragmental, or pumiceous materials and/ a. Overlie cindery, fragmental, or pumiceous materials and/ or have voids2 that are filled with 10 percent or less organic or fill their interstices2 and directly below these materials materials and directly below these materials have either a have a densic, lithic, or paralithic contact; or densic, lithic, or paralithic contact; or b. When added with the underlying cindery, fragmental, or b. When added with underlying cindery, fragmental, or pumiceous materials, total 40 cm or more between the soil pumiceous materials, total more than 10 cm between the soil surface and a depth of 50 cm; or surface and a depth of 50 cm; or c. Constitute two-thirds or more of the total thickness of the c. Constitute more than one-third of the total thickness of soil to a densic, lithic, or paralithic contact and have no the soil to a densic, lithic, or paralithic contact or have a total mineral horizons or have mineral horizons with a total thickness of more than 10 cm; or thickness of 10 cm or less; or d. If they are saturated with water for 30 days or more per d. Are saturated with water for 30 days or more per year in year in normal years (or are artificially drained) and have normal years (or are artificially drained), have an upper organic materials with an upper boundary within boundary within 40 cm of the soil surface, and have a total 40 cm of the soil surface, have a total thickness of either: thickness of either: (1) Less than 60 cm if three-fourths or more of their (1) 60 cm or more if three-fourths or more of their volume consists of moss fibers or if their bulk density, volume consists of moss fibers or if their bulk density, moist, is less than 0.1 g/cm3; or moist, is less than 0.1 g/cm3; or (2) Less than 40 cm if they consist either of sapric or (2) 40 cm or more if they consist either of sapric or hemic materials, or of fibric materials with less than three- hemic materials, or of fibric materials with less than three- fourths (by volume) moss fibers and a bulk density, moist, fourths (by volume) moss fibers and a bulk density, moist, of 0.1 g/cm3 or more; or of 0.1 g/cm3 or more; or 2. More than 20 percent, by volume, mineral soil materials e. Are 80 percent or more, by volume, from the soil surface from the soil surface to a depth of 50 cm or to a glacic layer or a to a depth of 50 cm or to a glacic layer or a densic, lithic, or densic, lithic, or paralithic contact, whichever is shallowest; and paralithic contact, whichever is shallowest. a. Permafrost within 100 cm of the soil surface; or It is a general rule that a soil is classified as an organic soil () if more than half of the upper 80 cm (32 in) of the soil is organic or if organic soil material of any thickness rests 2 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 to on rock or on fragmental material having interstices filled with be organic soil materials. organic materials. 13

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

This chapter defines the horizons and characteristics of soil has no epipedon if the soil has rock structure to the surface both mineral and organic soils. It is divided into three parts— or has an Ap horizon less than 25 cm thick that is underlain by horizons and characteristics diagnostic for mineral soils, soil material with rock structure. The melanic epipedon (defined characteristics diagnostic for organic soils, and horizons and below) is unique among epipedons. It forms commonly in characteristics diagnostic for both mineral and organic soils. volcanic deposits and can receive fresh deposits of ash. The horizons and characteristics defined below are not in a Therefore, this horizon is permitted to have layers within and key format. Some diagnostic horizons are mutually exclusive, above the epipedon that are not part of the melanic epipedon. and some are not. An umbric epipedon, for example, could A recent alluvial or eolian deposit that retains stratifications not also be a mollic epipedon. A kandic horizon with clay films, (5 mm or less thick) or an Ap horizon directly underlain by such however, could also meet the definition of an argillic horizon. stratified material is not included in the concept of the epipedon because time has not been sufficient for soil-forming processes to erase these transient marks of deposition and for diagnostic Horizons and Characteristics and accessory properties to develop. Diagnostic for Mineral Soils An epipedon is not the same as an A horizon. It may include part or all of an illuvial B horizon if the darkening by organic The criteria for some of the following horizons and matter extends from the soil surface into or through the B characteristics, such as histic and folistic epipedons, can be met horizon. in organic soils. They are diagnostic, however, only for the mineral soils. Anthropic Epipedon Diagnostic Surface Horizons: The Epipedon Required Characteristics The anthropic epipedon shows some evidence of disturbance The epipedon (Gr. epi, over, upon, and pedon, soil) is a by human activity and meets all of the requirements for a mollic horizon that forms at or near the surface and in which most of epipedon, except for one or both of the following: the rock structure has been destroyed. It is darkened by organic 1. 1,500 milligrams per kilogram or more P O soluble in 1 matter or shows evidence of eluviation, or both. Rock structure 2 5 percent citric acid and a regular decrease in P O to a depth of as used here and in other places in this taxonomy includes fine 2 5 125 cm; or stratification (less than 5 mm) in unconsolidated sediments (eolian, alluvial, lacustrine, or marine) and saprolite derived 2. If the soil is not irrigated, all parts of the epipedon are dry from consolidated rocks in which the unweathered minerals and for 9 months or more in normal years. pseudomorphs of weathered minerals retain their relative positions to each other. Folistic Epipedon Any horizon may be at the surface of a truncated soil. The following section, however, is concerned with eight diagnostic Required Characteristics horizons that have formed at or near the soil surface. These The folistic epipedon is defined as a layer (one or more horizons can be covered by a surface mantle of new soil horizons) that is saturated for less than 30 days (cumulative) in material. If the surface mantle has rock structure, the top of the normal years (and is not artificially drained) and either: epipedon is considered the soil surface unless the mantle meets the definition of buried soils in chapter 1. If the soil includes a 1. Consists of organic soil material that: buried soil, the epipedon, if any, is at the soil surface and the a. Is 20 cm or more thick and either contains 75 percent or epipedon of the buried soil is considered a buried epipedon and more (by volume) Sphagnum fibers or has a bulk density, is not considered in selecting taxa unless the keys specifically moist, of less than 0.1; or indicate buried horizons, such as those in Thapto-Histic subgroups. A soil with a mantle thick enough to have a buried b. Is 15 cm or more thick; or 14 Keys to Soil Taxonomy

2. Is an Ap horizon that, when mixed to a depth of 25 cm, has 2. In layers with a cumulative thickness of 30 cm or more an organic-carbon content (by weight) of: within a total thickness of 40 cm, all of the following: a. 16 percent or more if the mineral fraction contains 60 a. Andic soil properties throughout; and percent or more clay; or b. A color value, moist, and chroma (Munsell designations) b. 8 percent or more if the mineral fraction contains no of 2 or less throughout and a melanic index of 1.70 or less clay; or throughout; and c. 8 + (clay percentage divided by 7.5) percent or more if c. 6 percent or more organic carbon as a weighted average the mineral fraction contains less than 60 percent clay. and 4 percent or more organic carbon in all layers. Most folistic epipedons consist of organic soil material (defined in chapter 2). Item 2 provides for a folistic epipedon Mollic Epipedon that is an Ap horizon consisting of mineral soil material. Required Characteristics Histic Epipedon The mollic epipedon consists of mineral soil materials and has the following properties: Required Characteristics 1. When dry, either or both: The histic epipedon is a layer (one or more horizons) that is a. Structural units with a diameter of 30 cm or less characterized by saturation (for 30 days or more, cumulative) or secondary structure with a diameter of 30 cm or less; or and reduction for some time during normal years (or is artificially drained) and either: b. A moderately hard or softer rupture-resistance class; and 1. Consists of organic soil material that: 2. Rock structure, including fine (less than 5 mm) a. Is 20 to 60 cm thick and either contains 75 percent or stratifications, in less than one-half of the volume of all parts; more (by volume) Sphagnum fibers or has a bulk density, and moist, of less than 0.1; or 3. One of the following: b. Is 20 to 40 cm thick; or a. All of the following: 2. Is an Ap horizon that, when mixed to a depth of 25 cm, has an organic-carbon content (by weight) of: (1) Colors with a value of 3 or less, moist, and of 5 or less, dry; and a. 16 percent or more if the mineral fraction contains 60 percent or more clay; or (2) Colors with chroma of 3 or less, moist; and b. 8 percent or more if the mineral fraction contains no (3) If the soil has a C horizon, the mollic epipedon has a clay; or color value at least 1 Munsell unit lower or chroma at least 2 units lower (both moist and dry) than that of the C c. 8 + (clay percentage divided by 7.5) percent or more if horizon or the epipedon has at least 0.6 percent more the mineral fraction contains less than 60 percent clay. organic carbon than the C horizon; or Most histic epipedons consist of organic soil material b. A fine-earth fraction that has a calcium carbonate (defined in chapter 2). Item 2 provides for a histic epipedon that equivalent of 15 to 40 percent and colors with a value and is an Ap horizon consisting of mineral soil material. A histic chroma of 3 or less, moist; or epipedon consisting of mineral soil material can also be part of a mollic or umbric epipedon. c. A fine-earth fraction that has a calcium carbonate equivalent of 40 percent or more and a color value, moist, of Melanic Epipedon 5 or less; and 4. A base saturation (by NH OAc) of 50 percent or more; Required Characteristics 4 and The melanic epipedon has both of the following: 5. An organic-carbon content of: 1. An upper boundary at, or within 30 cm of, either the a. 2.5 percent or more if the epipedon has a color value, mineral soil surface or the upper boundary of an organic layer moist, of 4 or 5; or with andic soil properties (defined below), whichever is shallower; and b. 0.6 percent more than that of the C horizon (if one Horizons and Characteristics Diagnostic for the Higher Categories 15

occurs) if the mollic epipedon has a color value less than 1 Ochric Epipedon Munsell unit lower or chroma less than 2 units lower (both moist and dry) than the C horizon; or The ochric epipedon fails to meet the definitions for any of the other seven epipedons because it is too thin or too dry, has c. 0.6 percent or more; and D too high a color value or chroma, contains too little organic I 6. After mixing of the upper 18 cm of the mineral soil or of the carbon, has too high an n value or melanic index, or is both A whole mineral soil if its depth to a densic, lithic, or paralithic massive and hard or harder when dry . Many ochric epipedons contact, petrocalcic horizon, or duripan (all defined below) is have either a Munsell color value of 4 or more, moist, and 6 or less than 18 cm, the minimum thickness of the epipedon is as more, dry, or chroma of 4 or more, or they include an A or Ap follows: horizon that has both low color values and low chroma but is too thin to be recognized as a mollic or umbric epipedon (and has a. 25 cm if: less than 15 percent calcium carbonate equivalent in the fine- (1) The texture of the epipedon is loamy fine sand or earth fraction). Ochric epipedons also include horizons of coarser throughout; or organic materials that are too thin to meet the requirements for a histic or folistic epipedon. (2) There are no underlying diagnostic horizons The ochric epipedon includes eluvial horizons that are at or (defined below) and the organic-carbon content of the near the soil surface, and it extends to the first underlying underlying materials decreases irregularly with increasing diagnostic illuvial horizon (defined below as an argillic, kandic, depth; or natric, or spodic horizon). If the underlying horizon is a B (3) All of the following are 75 cm or more below the horizon of alteration (defined below as a cambic or oxic mineral soil surface: horizon) and there is no surface horizon that is appreciably darkened by humus, the lower limit of the ochric epipedon is the (a) The lower boundary of any argillic, cambic, lower boundary of the plow layer or an equivalent depth (18 cm) natric, oxic, or spodic horizon (defined below); and in a soil that has not been plowed. Actually, the same horizon in (b) The upper boundary of any petrocalcic horizon, an unplowed soil may be both part of the epipedon and part of duripan, fragipan, or identifiable secondary carbonates; the cambic horizon; the ochric epipedon and the subsurface or diagnostic horizons are not all mutually exclusive. The ochric epipedon does not have rock structure and does not include b. 10 cm if the epipedon is finer than loamy fine sand finely stratified fresh sediments, nor can it be an Ap horizon (when mixed) and it is directly above a densic, lithic, or directly overlying such deposits. paralithic contact, a petrocalcic horizon, or a duripan; or c. 18 to 25 cm and one-third or more of the total thickness Plaggen Epipedon between the mineral soil surface and: The plaggen epipedon is a human-made surface layer 50 cm (1) The upper boundary of any identifiable secondary or more thick that has been produced by long-continued carbonates, petrocalcic horizon, duripan, or fragipan; manuring. or A plaggen epipedon can be identified by several means. (2) The lower boundary of any argillic, cambic, natric, Commonly, it contains artifacts, such as bits of brick and oxic, or spodic horizon; or pottery, throughout its depth. There may be chunks of diverse materials, such as black sand and light gray sand, as large as the d. 18 cm if none of the above conditions apply; and size held by a spade. The plaggen epipedon normally shows 7. Phosphate: spade marks throughout its depth and also remnants of thin stratified beds of sand that were probably produced on the soil a. Content less than 1,500 milligrams per kilogram soluble surface by beating rains and were later buried by spading. A map in 1 percent citric acid; or unit delineation of soils with plaggen epipedons would tend to b. Content decreasing irregularly with increasing depth have straight-sided rectangular bodies that are higher than the below the epipedon; or adjacent soils by as much as or more than the thickness of the plaggen epipedon. c. Nodules are within the epipedon; and 8. Some part of the epipedon is moist for 90 days or more Umbric Epipedon (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 Required Characteristics not irrigated; and The umbric epipedon consists of mineral soil materials and 9. The n value (defined below) is less than 0.7. has the following properties: 16 Keys to Soil Taxonomy

1. When dry, either or both: (1) The upper boundary of any identifiable secondary carbonates, petrocalcic horizon, duripan, or fragipan; a. Structural units with a diameter of 30 cm or less or or secondary structure with a diameter of 30 cm or less; or (2) The lower boundary of any argillic, cambic, natric, b. A moderately hard or softer rupture-resistance class; and oxic, or spodic horizon; or 2. All of the following: c. 18 cm if none of the above conditions apply; and a. Colors with a value of 3 or less, moist, and of 5 or less, 6. Phosphate: dry; and a. Content less than 1,500 milligrams per kilogram soluble b. Colors with chroma of 3 or less moist; and in 1 percent citric acid; or c. If the soil has a C horizon, the umbric epipedon has a b. Content decreasing irregularly with increasing depth color value at least 1 Munsell unit lower or chroma at least 2 below the epipedon; or units lower (both moist and dry) than that of the C horizon or the epipedon has at least 0.6 percent more organic carbon c. Nodules are within the epipedon; and than that of the C horizon; and 7. Some part of the epipedon is moist for 90 days or more

3. A base saturation (by NH4OAc) of less than 50 percent in (cumulative) in normal years during times when the soil some or all parts; and temperature at a depth of 50 cm is 5 oC or higher, if the soil is not irrigated; and 4. An organic-carbon content of: 8. The n value (defined below) is less than 0.7; and a. 0.6 percent more than that of the C horizon (if one occurs) if the umbric epipedon has a color value less than 1 9. The umbric epipedon does not have the artifacts, spade Munsell unit lower or chroma less than 2 units lower (both marks, and raised surfaces that are characteristic of the plaggen moist and dry) than the C horizon; or epipedon. b. 0.6 percent or more; and 5. After mixing of the upper 18 cm of the mineral soil or Diagnostic Subsurface Horizons of the whole mineral soil if its depth to a densic, lithic, or The horizons described in this section form below the surface paralithic contact, petrocalcic horizon, or a duripan (all defined of the soil, although in some areas they form directly below a below) is less than 18 cm, the minimum thickness of the layer of leaf litter. They may be exposed at the surface by epipedon is as follows: truncation of the soil. Some of these horizons are generally a. 25 cm if: regarded as B horizons, some are considered B horizons by many but not all pedologists, and others are generally regarded (1) The texture of the epipedon is loamy fine sand or as parts of the A horizon. coarser throughout; or (2) There are no underlying diagnostic horizons (defined Agric Horizon below) and the organic-carbon content of the underlying materials decreases irregularly with increasing depth; or The agric horizon is an illuvial horizon that has formed under cultivation and contains significant amounts of illuvial , clay, (3) All of the following are 75 cm or more below the and humus. mineral soil surface: Required Characteristics (a) The lower boundary of any argillic, cambic, natric, oxic, or spodic horizon (defined below); and The agric horizon is directly below an Ap horizon and has the following properties: (b) The upper boundary of any petrocalcic horizon, duripan, fragipan, or identifiable secondary carbonates; 1. A thickness of 10 cm or more and either: or a. 5 percent or more (by volume) wormholes, including b. 10 cm if the epipedon is finer than loamy fine sand coatings that are 2 mm or more thick and have a value, moist, (when mixed) and it is directly above a densic, lithic, or of 4 or less and chroma of 2 or less; or paralithic contact, a petrocalcic horizon, or a duripan; or b. 5 percent or more (by volume) lamellae that have a c. 18 to 25 cm and one-third or more of the total thickness thickness of 5 mm or more and have a value, moist, of 4 or between the mineral soil surface and: less and chroma of 2 or less. Horizons and Characteristics Diagnostic for the Higher Categories 17

Albic Horizon (4) Thin sections with oriented clay bodies that are more than 1 percent of the section; or The albic horizon is an eluvial horizon, 1.0 cm or more thick, (5) If the coefficient of linear extensibility is 0.04 or that has 85 percent or more (by volume) albic materials (defined higher and the soil has distinct wet and dry seasons, then D below). It generally occurs below an A horizon but may be at the the ratio of fine clay to total clay in the illuvial horizon is I mineral soil surface. Under the albic horizon there generally is greater by 1.2 times or more than the ratio in the eluvial A an argillic, cambic, kandic, natric, or spodic horizon or a horizon; and fragipan (defined below). The albic horizon may lie between a spodic horizon and either a fragipan or an argillic horizon, or it 2. If an eluvial horizon remains and there is no lithologic may be between an argillic or kandic horizon and a fragipan. It discontinuity between it and the illuvial horizon and no plow may lie between a mollic epipedon and an argillic or natric layer directly above the illuvial layer, then the illuvial horizon horizon or between a cambic horizon and an argillic, kandic, or must contain more total clay than the eluvial horizon within a natric horizon or a fragipan. The albic horizon may separate vertical distance of 30 cm or less, as follows: horizons that, if they were together, would meet the a. If any part of the eluvial horizon has less than 15 percent requirements for a mollic epipedon. It may separate lamellae total clay in the fine-earth fraction, the argillic horizon must that together meet the requirements for an argillic horizon. contain at least 3 percent (absolute) more clay (10 percent These lamellae are not considered to be part of the albic versus 13 percent, for example); or horizon. b. If the eluvial horizon has 15 to 40 percent total clay in Argillic Horizon the fine-earth fraction, the argillic horizon must have at least 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 in significantly higher percentage of phyllosilicate clay than the the fine-earth fraction, the argillic horizon must contain at overlying soil material. It shows evidence of clay illuviation. 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 requirements: The calcic horizon is an illuvial horizon in which secondary calcium carbonate or other carbonates have accumulated to a a. One of the following: significant extent. (1) If the argillic horizon is coarse-loamy, fine-loamy, Required Characteristics coarse-silty, fine-silty, fine, or very-fine or is loamy or clayey, including skeletal counterparts, it must be at least The calcic horizon has all of the following properties: 7.5 cm thick or at least one-tenth as thick as the sum of the 1. Is 15 cm or more thick; and thickness of all overlying horizons, whichever is greater; or 2. Is not indurated or cemented to such a degree that it meets the requirements for a petrocalcic horizon; and (2) If the argillic horizon is sandy or sandy-skeletal, it must be at least 15 cm thick; or 3. Has one or more of the following:

(3) If the argillic horizon is composed entirely of a. 15 percent or more CaCO3 equivalent (see below), and

lamellae, the combined thickness of the lamellae that are its CaCO3 equivalent is 5 percent or more (absolute) higher 0.5 cm or more thick must be 15 cm or more; and than that of an underlying horizon; or

b. Evidence of clay illuviation in at least one of the b. 15 percent or more CaCO3 equivalent and 5 percent or following forms: more (by volume) identifiable secondary carbonates; or (1) Oriented clay bridging the sand grains; or c. 5 percent or more calcium carbonate equivalent and has: (2) Clay films lining pores; or (1) Less than 18 percent clay in the fine-earth fraction; and (3) Clay films on both vertical and horizontal surfaces of (2) A sandy, sandy-skeletal, coarse-loamy, or loamy- peds; or skeletal particle-size class; and 18 Keys to Soil Taxonomy

(3) 5 percent or more (by volume) identifiable natric, oxic, petrocalcic, petrogypsic, placic, or spodic horizon; secondary carbonates or a calcium carbonate equivalent and (by weight) that is 5 percent or more (absolute) higher 4. Is not part of an Ap horizon and does not have a brittle than that of an underlying horizon. manner of failure in more than 60 percent of the matrix.

Cambic Horizon Duripan A cambic horizon is the result of physical alterations, Required Characteristics chemical transformations, or removals or of a combination of two or more of these processes. A duripan is a silica-cemented subsurface horizon with or without auxiliary cementing agents. It can occur in conjunction Required Characteristics with a petrocalcic horizon. The cambic horizon is an altered horizon 15 cm or more A duripan must meet all of the following requirements: thick. If it is composed of lamellae, the combined thickness of 1. The pan is cemented or indurated in more than 50 percent the lamellae must be 15 cm or more. In addition, the cambic of the volume of some horizon; and horizon must meet all of the following: 2. The pan shows evidence of the accumulation of opal or 1. Has a texture of very fine sand, loamy very fine sand, or other forms of silica, such as laminar caps, coatings, lenses, finer; and partly filled interstices, bridges between sand-sized grains, or 2. Shows evidence of alteration in one of the following coatings on rock and pararock fragments; and forms: 3. Less than 50 percent of the volume of air-dry fragments a. Aquic conditions within 50 cm of the soil surface or slakes in 1N HCl even during prolonged soaking, but more than artificial drainage and all of the following: 50 percent slakes in concentrated KOH or NaOH or in alternating acid and alkali; and (1) or the absence of rock structure in more than one-half of the volume; and 4. Because of lateral continuity, roots can penetrate the pan only along vertical fractures with a horizontal spacing of 10 cm (2) Colors that do not change on exposure to air; or more. and (3) Dominant color, moist, on faces of peds or in the Fragipan matrix as follows: Required Characteristics (a) Value of 3 or less and chroma of 0; or To be identified as a fragipan, a layer must have all of the (b) Value of 4 or more and chroma of 1 or less; or following characteristics: (c) Any value, chroma of 2 or less, and redox 1. The layer is 15 cm or more thick; and concentrations; or 2. The layer shows evidence of pedogenesis within the horizon b. Does not have the combination of aquic conditions or, at a minimum, on the faces of structural units; and within 50 cm of the soil surface or artificial drainage and colors, moist, as defined in item 2-a-(3) above, and has soil 3. The layer has very coarse prismatic, columnar, or blocky structure or the absence of rock structure in more than one- structure of any grade, has weak structure of any size, or is half of the volume and one or more of the following massive. Separations between structural units that allow roots to properties: enter have an average spacing of 10 cm or more on the horizontal dimensions; and (1) Higher chroma, higher value, redder hue, or higher clay content than the underlying horizon or an overlying 4. Air-dry fragments of the natural soil fabric, 5 to 10 cm in horizon; or diameter, from more than 50 percent of the layer slake when they are submerged in water; and (2) Evidence of the removal of carbonates or gypsum; and 5. The layer has, in 60 percent or more of the volume, a firm or firmer rupture-resistance class, a brittle manner of failure at 3. Has properties that do not meet the requirements for an or near field capacity, and virtually no roots; and anthropic, histic, folistic, melanic, mollic, plaggen, or umbric epipedon, a duripan or fragipan, or an argillic, calcic, gypsic, 6. The layer is not effervescent (in dilute HCl). Horizons and Characteristics Diagnostic for the Higher Categories 19

Glossic Horizon 2. Has its upper boundary: a. At the point where the clay percentage in the fine-earth The glossic horizon (Gr. glossa, tongue) develops as a result fraction, increasing with depth within a vertical distance of of the degradation of an argillic, kandic, or natric horizon from 15 cm or less, is either: D which clay and free iron oxides are removed. I (1) 4 percent or more (absolute) higher than that in the Required Characteristics A surface horizon if that horizon has less than 20 percent The glossic horizon is 5 cm or more thick and consists of: total clay in the fine-earth fraction; or 1. An eluvial part, i.e., albic materials (defined below), which (2) 20 percent or more (relative) higher than that in the constitute 15 to 85 percent (by volume) of the glossic horizon; surface horizon if that horizon has 20 to 40 percent total and clay in the fine-earth fraction; or 2. An illuvial part, i.e., remnants (pieces) of an argillic, kandic, (3) 8 percent or more (absolute) higher than that in the or natric horizon (defined below). surface horizon if that horizon has more than 40 percent total clay in the fine-earth fraction; and Gypsic Horizon b. At a depth: The gypsic horizon is an illuvial horizon in which secondary (1) Between 100 cm and 200 cm from the mineral soil gypsum has accumulated to a significant extent. surface if the particle-size class is sandy or sandy-skeletal throughout the upper 100 cm; or Required Characteristics (2) Within 100 cm from the mineral soil surface if the A gypsic horizon has all of the following properties: clay content in the fine-earth fraction of the surface 1. Is 15 cm or more thick; and horizon is 20 percent or more; or 2. Is not cemented or indurated to such a degree that it meets (3) Within 125 cm from the mineral soil surface for all the requirements for a petrogypsic horizon; and other soils; and 3. Is 5 percent or more gypsum and 1 percent or more (by 3. Has a thickness of either: volume) secondary visible gypsum; and a. 30 cm or more; or 4. Has a product of thickness, in cm, multiplied by the gypsum b. 15 cm or more if there is a densic, lithic, paralithic, or content percentage of 150 or more. petroferric contact within 50 cm of the mineral soil surface Thus, a horizon 30 cm thick that is 5 percent gypsum and the kandic horizon constitutes 60 percent or more of the qualifies as a gypsic horizon if it is 1 percent or more (by vertical distance between a depth of 18 cm and the contact; and volume) visible gypsum and is not cemented or indurated to 4. Has a texture of loamy very fine sand or finer; and such a degree that it meets the requirements for a petrogypsic horizon. 5. Has an apparent CEC of 16 cmol(+) or less per kg clay (by

The gypsum percentage can be calculated by multiplying 1N NH4OAc pH 7) and an apparent ECEC of 12 cmol(+) or less the milliequivalents of gypsum per 100 g soil by the per kg clay (sum of bases extracted with 1N NH OAc pH 7 plus . 4 milliequivalent weight of CaSO4 2H2O, which is 0.086. 1N KCl-extractable Al) in 50 percent or more of its thickness 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 be Required Characteristics 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 an lithic, paralithic, or petroferric contact (defined below) within organic-carbon content that decreases irregularly with increasing 50 cm of the mineral soil surface; and depth. 20 Keys to Soil Taxonomy

Natric Horizon a. Less than 4 percent (absolute) in its fine-earth fraction if the fine-earth fraction of the surface horizon contains less Required Characteristics than 20 percent clay; or The natric horizon has, in addition to the properties of the b. Less than 20 percent (relative) in its fine-earth fraction if argillic horizon: the fine-earth fraction of the surface horizon contains 20 to 40 percent clay; or 1. Either: c. Less than 8 percent (absolute) in its fine-earth fraction if a. Columns or prisms in some part (generally the upper the fine-earth fraction of the surface horizon contains 40 part), which may break to blocks; or percent or more clay); and b. Both blocky structure and eluvial materials, which 6. An apparent CEC of 16 cmol(+) or less per kg clay (by 1N contain uncoated silt or sand grains and extend more than 2.5 NH OAc pH 7) and an apparent ECEC of 12 cmol(+) or less per cm into the horizon; and 4 kg clay (sum of bases extracted with 1N NH4OAc pH 7 plus 1N 2. Either: KCl-extractable Al). (The percentage of clay is either measured by the pipette method or estimated to be 3 times [percent water a. An exchangeable sodium percentage (ESP) of 15 percent retained at 1500 kPa tension minus percent organic carbon], or more (or a sodium adsorption ratio [SAR] of 13 or more) whichever value is higher, but no more than 100). in one or more horizons within 40 cm of its upper boundary; or b. More exchangeable magnesium plus sodium than Petrocalcic Horizon calcium plus exchange acidity (at pH 8.2) in one or more The petrocalcic horizon is an illuvial horizon in which horizons within 40 cm of its upper boundary if the ESP is 15 secondary calcium carbonate or other carbonates have or more (or the SAR is 13 or more) in one or more horizons accumulated to the extent that the horizon is cemented or within 200 cm of the mineral soil surface. indurated. Ortstein Required Characteristics A petrocalcic horizon must meet the following requirements: Required Characteristics 1. The horizon is cemented or indurated by carbonates, with or Ortstein has all of the following: without silica or other cementing agents; and 1. Consists of spodic materials; and 2. Because of lateral continuity, roots can penetrate only along 2. Is in a layer that is 50 percent or more cemented; and vertical fractures with a horizontal spacing of 10 cm or more; and 3. Is 25 mm or more thick. 3. The horizon has a thickness of: Oxic Horizon a. 10 cm or more; or Required Characteristics b. 1 cm or more if it consists of a laminar cap directly underlain by bedrock. The oxic horizon is a subsurface horizon that does not have andic soil properties (defined below) and has all of the following characteristics: Petrogypsic Horizon 1. A thickness of 30 cm or more; and The petrogypsic horizon is an illuvial horizon, 10 cm or more thick, in which secondary gypsum has accumulated to the extent 2. A texture of sandy or finer in the fine-earth fraction; that the horizon is cemented or indurated. and Required Characteristics 3. Less than 10 percent weatherable minerals in the 50- to 200-micron fraction; and A petrogypsic horizon must meet the following requirements: 4. Rock structure in less than 5 percent of its volume, unless 1. The horizon is cemented or indurated by gypsum, with or the lithorelicts with weatherable minerals are coated with without other cementing agents; and sesquioxides; and 2. Because of lateral continuity, roots can penetrate only along 5. A diffuse upper boundary, i.e., within a vertical distance vertical fractures with a horizontal spacing of 10 cm or more; of 15 cm, a clay increase with increasing depth of: and Horizons and Characteristics Diagnostic for the Higher Categories 21

3. The horizon is 10 cm or more thick; and both, than the overlying horizon and commonly contains more organic matter. It may have formed in an argillic, cambic, or 4. The horizon is 5 percent or more gypsum, and the product oxic horizon. If peds are present, the dark colors are most of its thickness, in cm, multiplied by the gypsum content pronounced on surfaces of peds. percentage is 150 or more. D In the field a sombric horizon is easily mistaken for a I buried A horizon. It can be distinguished from some buried A Placic Horizon epipedons by lateral tracing. In thin sections the organic matter of a sombric horizon appears more concentrated on The placic horizon (Gr. base of plax, flat stone; meaning a peds and in pores than uniformly dispersed throughout the thin cemented pan) is a thin, black to dark reddish pan that is 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). manganese and organic matter, with or without other cementing Required Characteristics agents; and A spodic horizon is normally a subsurface horizon underlying 2. Because of lateral continuity, roots can penetrate only along an O, A, Ap, or E horizon. It may, however, meet the definition vertical fractures with a horizontal spacing of 10 cm or more; of an umbric epipedon. and A spodic horizon must have 85 percent or more spodic 3. The horizon has a minimum thickness of 1 mm and, where materials in a layer 2.5 cm or more thick that is not part of any associated with spodic materials, is less than 25 mm thick. Ap horizon.

Salic Horizon Other Diagnostic Soil Characteristics A salic horizon is a horizon of accumulation of salts that are (Mineral Soils) more soluble than gypsum in cold water. Diagnostic soil characteristics are features of the soil that are Required Characteristics used in various places in the keys or in definitions of diagnostic horizons. A salic horizon is 15 cm or more thick and has, for 90 consecutive days or more in normal years: Abrupt Textural Change 1. An electrical conductivity (EC) equal to or greater than 30 dS/m in the water extracted from a saturated paste; and An abrupt textural change is a specific kind of change that may occur between an ochric epipedon or an albic horizon and 2. A product of the EC, in dS/m, and thickness, in cm, an argillic horizon. It is characterized by a considerable increase equal to 900 or more. in clay content within a very short vertical distance in the zone of contact. If the clay content in the fine-earth fraction of the Sombric Horizon ochric epipedon or albic horizon is less than 20 percent, it doubles within a vertical distance of 7.5 cm or less. If the clay A sombric horizon (F. sombre, dark) is a subsurface horizon content in the fine-earth fraction of the ochric epipedon or the in mineral soils that has formed under free drainage. It contains albic horizon is 20 percent or more, there is an increase of 20 illuvial humus that is neither associated with aluminum, as is the percent or more (absolute) within a vertical distance of 7.5 cm humus in the spodic horizon, nor dispersed by sodium, as is or less (e.g., an increase from 22 to 42 percent) and the clay common in the natric horizon. Consequently, the sombric content in some part of the argillic horizon is 2 times or more horizon does not have the high cation-exchange capacity in its the amount contained in the overlying horizon. clay that characterizes a spodic horizon and does not have the Normally, there is no transitional horizon between an ochric high base saturation of a natric horizon. It does not underlie an epipedon or an albic horizon and an argillic horizon, or the albic horizon. transitional horizon is too thin to be sampled. Some soils, Sombric horizons are thought to be restricted to the cool, however, have a glossic horizon or interfingering of albic moist soils of high plateaus and mountains in tropical or materials (defined below) in parts of the argillic horizon. The subtropical regions. Because of strong leaching, their base upper boundary of such a horizon is irregular or even saturation is low (less than 50 percent by NH4OAc). discontinuous. Sampling this mixture as a single horizon might The sombric horizon has a lower color value or chroma, or create the impression of a relatively thick transitional horizon, 22 Keys to Soil Taxonomy

whereas the thickness of the actual transition at the contact may Required Characteristics be no more than 1 mm. To be recognized as having andic soil properties, soil materials must contain less than 25 percent (by weight) organic Albic Materials carbon and meet one or both of the following requirements: Albic (L. albus, white) materials are soil materials with a 1. In the fine-earth fraction, all of the following: color that is largely determined by the color of primary sand and 1 a. Al + /2 Fe percentages (by ammonium oxalate) totaling silt particles rather than by the color of their coatings. This 2.0 percent or more; and definition implies that clay and/or free iron oxides have been removed from the materials or that the oxides have been b. A bulk density, measured at 33 kPa water retention, of segregated to such an extent that the color of the materials is 0.90 g/cm3 or less; and largely determined by the color of the primary particles. c. A phosphate retention of 85 percent or more; or Required Characteristics 2. In the fine-earth fraction, a phosphate retention of 25 Albic materials have one of the following colors: percent or more, 30 percent or more particles 0.02 to 2.0 mm in size, and all of the following: 1. Chroma of 2 or less; and either 1 a. Al + /2 Fe percentages (by ammonium oxalate) totaling a. A color value, moist, of 3 and a color value, dry, of 6 or 0.4 or more in the fine-earth fraction; and more; or b. A volcanic glass content of 5 percent or more in the .02 b. A color value, moist, of 4 or more and a color value, dry, to 2.0 mm fraction; and of 5 or more; or 1 c. [(Al + /2 Fe, percent by ammonium oxalate) times 2. Chroma of 3 or less; and either (15.625)] + [glass content, percent] = 36.25 or more. a. A color value, moist, of 6 or more; or The shaded area in figure 1 illustrates criteria 2a, 2b, and 2c. b. A color value, dry, of 7 or more; or 3. Chroma that is controlled by the color of uncoated grains of Anhydrous Conditions silt or sand, hue of 5YR or redder, and the color values listed in Anhydrous conditions (Gr. anydros, waterless) refer to the item 1-a or 1-b above. active layer in soils of cold deserts and other areas with Relatively unaltered layers of light colored sand, volcanic permafrost (often dry permafrost) and low precipitation (usually ash, or other materials deposited by wind or water are not less than 50 mm water equivalent). Anhydrous soil conditions considered albic materials, although they may have the same are similar to the aridic (torric) regimes, except color and apparent morphology. These deposits are parent that the soil temperature is less than 0 oC. materials that are not characterized by the removal of clay and/or free iron and do not overlie an illuvial horizon or other Coefficient of Linear Extensibility (COLE) , except for a buried soil. Light colored krotovinas or filled root channels should be considered albic materials only The coefficient of linear extensibility (COLE) is the ratio of if they have no fine stratifications or lamellae, if any sealing the difference between the moist length and dry length of a clod along the krotovina walls has been destroyed, and if these to its dry length. It is (Lm - Ld)/Ld, where Lm is the length at 33 intrusions have been leached of free iron oxides and/or clay kPa tension and Ld is the length when dry. COLE can be after deposition. calculated from the differences in bulk density of the clod when moist and when dry. An estimate of COLE can be calculated in Andic Soil Properties the field by measuring the distance between two pins in a clod of undisturbed soil at field capacity and again after the clod has Andic soil properties result mainly from the presence of dried. COLE does not apply if the shrinkage is irreversible. significant amounts of allophane, imogolite, ferrihydrite, or aluminum-humus complexes in soils. These materials, originally Durinodes termed “amorphous” (but understood to contain allophane) in the 1975 edition of Soil Taxonomy (USDA, SCS, 1975), are Durinodes (L. durus, hard, and nodus, knot) are weakly commonly formed during the weathering of tephra and other cemented to indurated nodules with a diameter of 1 cm or more. parent materials with a significant content of volcanic glass. The cement is SiO , presumably opal and microcrystalline forms 2 Although volcanic glass is or was a common component in of silica. Durinodes break down in hot concentrated KOH after many Andisols, it is not a requirement of the order. treatment with HCl to remove carbonates but do not break down Horizons and Characteristics Diagnostic for the Higher Categories 23

peds, redoximorphic features within the matrix or on faces of peds, strong or moderate soil structure, and coatings of albic materials or uncoated silt and sand grains on faces of peds or in seams. Peds with these properties are considered to have fragic D soil properties regardless of whether or not the density and I brittleness are pedogenic. A Soil aggregates with fragic soil properties must: 1. Show evidence of pedogenesis within the aggregates or, at a minimum, on the faces of the aggregates; and 2. Slake when air-dry fragments of the natural fabric, 5 to 10 cm in diameter, are submerged in water; and 3. Have a firm or firmer rupture-resistance class and a brittle manner of failure when soil water is at or near field capacity; and 4. Restrict the entry of roots into the matrix when soil water is at or near field capacity.

Identifiable Secondary Carbonates

The term “identifiable secondary carbonates” is used in the definitions of a number of taxa. It refers to translocated authigenic calcium carbonate that has been precipitated in place from the soil solution rather than inherited from a soil parent material, such as a calcareous or till. Identifiable secondary carbonates either may disrupt the soil structure or fabric, forming masses, nodules, , or Figure 1.—Soils that are plotted in the shaded area meet the andic soil spheroidal aggregates (white eyes) that are soft and powdery properties criteria a, b, and c under item 2 of the required when dry, or may be present as coatings in pores, on structural characteristics. To qualify as soils with andic properties, the soils faces, or on the undersides of rock or pararock fragments. If must also meet the listed requirements for organic-carbon content, present as coatings, the secondary carbonates cover a significant phosphate retention, and particle-size distribution. part of the surfaces. Commonly, they coat all of the surfaces to a thickness of 1 mm or more. If little calcium carbonate is present with concentrated HCl alone. Dry durinodes do not slake in the soil, however, the surfaces may be only partially coated. appreciably in water, but prolonged soaking can result in The coatings must be thick enough to be visible when moist. spalling of very thin platelets. Durinodes are firm or firmer and Some horizons are entirely engulfed by carbonates. The color of brittle when wet, both before and after treatment with acid. Most these horizons is largely determined by the carbonates. The durinodes are roughly concentric when viewed in cross section, carbonates in these horizons are within the concept of and concentric stringers of opal are visible under a hand lens. identifiable secondary carbonates. The filaments commonly seen in a dry calcareous horizon are Fragic Soil Properties within the meaning of identifiable secondary carbonates if the filaments are thick enough to be visible when the soil is moist. Fragic soil properties are the essential properties of a Filaments commonly branch on structural faces. fragipan. They have neither the layer thickness nor volume requirements for the fragipan. Fragic soil properties are in Interfingering of Albic Materials subsurface horizons, although they can be at or near the surface in truncated soils. Aggregates with fragic soil properties have a The term “interfingering of albic materials” refers to albic firm or firmer rupture-resistance class and a brittle manner of materials that penetrate 5 cm or more into an underlying argillic, failure when soil water is at or near field capacity. Air-dry kandic, or natric horizon along vertical and, to a lesser degree, fragments of the natural fabric, 5 to 10 cm in diameter, slake horizontal faces of peds. There need not be a continuous when they are submerged in water. Aggregates with fragic soil overlying albic horizon. The albic materials constitute less than properties show evidence of pedogenesis, including one or more 15 percent of the layer that they penetrate, but they form of the following: oriented clay within the matrix or on faces of continuous skeletans (ped coatings of clean silt or sand defined 24 Keys to Soil Taxonomy

by Brewer, 1976) 1 mm or more thick on the vertical faces of Linear Extensibility (LE) peds, which means a total width of 2 mm or more between abutting peds. Because quartz is such a common constituent of Linear extensibility (LE) helps to predict the potential of a silt and sand, these skeletans are usually light gray when moist soil to shrink and swell. The LE of a soil layer is the product of and nearly white when dry, but their color is determined in large the thickness, in cm, multiplied by the COLE of the layer in part by the color of the sand or silt fraction. question. The LE of a soil is the sum of these products for all soil horizons. Required Characteristics Interfingering of albic materials is recognized if albic Lithologic Discontinuities materials: Lithologic discontinuities are significant changes in particle- 1. Penetrate 5 cm or more into an underlying argillic or natric size distribution or mineralogy that represent differences in horizon; and lithology within a soil. A lithologic discontinuity can also denote 2. Are 2 mm or more thick between vertical faces of abutting an age difference. For information on using horizon designations peds; and for lithologic discontinuities, see the Soil Survey Manual (USDA, SCS, 1993). 3. Constitute less than 15 percent (by volume) of the layer that Not everyone agrees on the degree of change required for a they penetrate. lithologic discontinuity. No attempt is made to quantify lithologic discontinuities. The discussion below is meant to Lamellae serve as a guideline. Several lines of field evidence can be used to evaluate A lamella is an illuvial horizon less than 7.5 cm thick. Each lithologic discontinuities. In addition to mineralogical and lamella contains an accumulation of oriented silicate clay on or textural differences that may require laboratory studies, certain bridging sand and silt grains (and rock fragments if any are observations can be made in the field. These include but are not present). A lamella has more silicate clay than the overlying limited to the following: eluvial horizon. 1. Abrupt textural contacts.—An abrupt change in particle-size distribution, which is not solely a change in clay Required Characteristics content resulting from pedogenesis, can often be observed. A lamella is an illuvial horizon less than 7.5 cm thick formed 2. Contrasting sand sizes.—Significant changes in sand in unconsolidated regolith more than 50 cm thick. Each lamella size can be detected. For example, if material containing mostly contains an accumulation of oriented silicate clay on or bridging medium sand or finer sand abruptly overlies material containing the sand and silt grains (and coarse fragments if any are mostly coarse sand and very coarse sand, one can assume that present). Each lamella is required to have more silicate clay than there are two different materials. Although the materials may be the overlying eluvial horizon. of the same mineralogy, the contrasting sand sizes result from Lamellae occur in a vertical series of two or more, and each differences in energy at the time of deposition by water and/or lamella must have an overlying eluvial horizon. (An eluvial wind. horizon is not required above the uppermost lamella if the soil is 3. Bedrock lithology vs. rock fragment lithology in the truncated.) soil.—If a soil with rock fragments overlies a lithic contact, one Lamellae may meet the requirements for either a cambic or would expect the rock fragments to have a lithology similar to an argillic horizon. A combination of two or more lamellae 15 that of the material below the lithic contact. If many of the rock cm or more thick is a cambic horizon if the texture is very fine fragments do not have the same lithology as the underlying sand, loamy very fine sand, or finer. A combination of two or bedrock, the soil is not derived completely from the underlying more lamellae meets the requirements for an argillic horizon if bedrock. there is 15 cm or more cumulative thickness of lamellae that are 4. Stone lines.—The occurrence of a horizontal line of 0.5 cm or more thick and that have a clay content of either: rock fragments in the vertical sequence of a soil indicates that the soil may have developed in more than one kind of parent 1. 3 percent or more (absolute) higher than in the overlying material. The material above the stone line is most likely eluvial horizon (e.g., 13 percent versus 10 percent) if any part of transported, and the material below may be of different origin. the eluvial horizon has less than 15 percent clay in the fine-earth 5. Inverse distribution of rock fragments.—A lithologic fraction; or discontinuity is often indicated by an erratic distribution of rock 2. 20 percent or more (relative) higher than in the overlying fragments. The percentage of rock fragments decreases with eluvial horizon (e.g., 24 percent versus 20 percent) if all parts of increasing depth. This line of evidence is useful in areas of soils the eluvial horizon have more than 15 percent clay in the fine- that have relatively unweathered rock fragments. earth fraction. 6. Rock fragment weathering rinds.—Horizons Horizons and Characteristics Diagnostic for the Higher Categories 25

containing rock fragments with no rinds that overlie horizons livestock or can support other loads and in predicting what containing rocks with rinds suggest that the upper material is in degree of subsidence would occur after drainage. part depositional and not related to the lower part in time and For mineral soil materials that are not thixotropic, the n value perhaps in lithology. can be calculated by the following formula: D 7. Shape of rock fragments.—A soil with horizons n = (A - 0.2R)/(L + 3H) I containing angular rock fragments overlying horizons containing In this formula, A is the percentage of water in the soil in A well rounded rock fragments may indicate a discontinuity. This field condition, calculated on a dry-soil basis; R is the line of evidence represents different mechanisms of transport percentage of silt plus sand; L is the percentage of clay; and H is (colluvial vs. alluvial) or even different transport distances. the percentage of organic matter (percent organic carbon 8. Soil color.—Abrupt changes in color that are not the multiplied by 1.724). result of pedogenic processes can be used as indicators of Few data for calculations of the n value are available in the discontinuity. United States, but the critical n value of 0.7 can be 9. Micromorphological features.—Marked differences in approximated closely in the field by a simple test of squeezing a the size and shape of resistant minerals in one horizon and not in soil sample in the hand. If the soil flows between the fingers another are indicators of differences in materials. with difficulty, the n value is between 0.7 and 1.0 (slightly fluid manner of failure class); if the soil flows easily between the Use of Laboratory Data fingers, the n value is 1 or more (moderately fluid or very fluid Discontinuities are not always readily apparent in the field. In manner of failure class). these cases laboratory data are necessary. Even with laboratory data, detecting discontinuities may be difficult. The decision is a Petroferric Contact qualitative or perhaps a partly quantitative judgment. General concepts of lithology as a function of depth might include: A petroferric (Gr. petra, rock, and L. ferrum, iron; implying 1. Laboratory data—visual scan.—The array of ironstone) contact is a boundary between soil and a continuous laboratory data is assessed in an attempt to determine if a field- layer of indurated material in which iron is an important cement designated discontinuity is corroborated and if any data show and organic matter is either absent or present only in traces. The evidence of a discontinuity not observed in the field. One must indurated layer must be continuous within the limits of each sort changes in lithology from changes caused by pedogenic pedon, but it may be fractured if the average lateral distance processes. In most cases the quantities of sand and coarser between fractures is 10 cm or more. The fact that this ironstone fractions are not altered significantly by soil-forming processes. layer contains little or no organic matter distinguishes it from a Therefore, an abrupt change in sand size or sand mineralogy is a placic horizon and an indurated spodic horizon (ortstein), both clue to lithologic change. Gross soil mineralogy and the resistant of which contain organic matter. mineral suite are other clues. Several features can aid in making the distinction between a 2. Data on a clay-free basis.—A common manipulation in lithic contact and a petroferric contact. First, a petroferric assessing lithologic change is computation of sand and silt contact is roughly horizontal. Second, the material directly separates on a carbonate-free, clay-free basis (percent fraction, below a petroferric contact contains a high amount of iron e.g., fine sand and very fine sand, divided by percent sand plus (normally 30 percent or more Fe2O3). Third, the ironstone sheets silt, times 100). Clay distribution is subject to pedogenic change below a petroferric contact are thin; their thickness ranges from and may either mask inherited lithologic differences or produce a few centimeters to very few meters. Sandstone, on the other differences that are not inherited from lithology. The numerical hand, may be thin or very thick, may be level-bedded or tilted, array computed on a clay-free basis can be inspected visually or and may contain only a small percentage of Fe2O3. In the plotted as a function of depth. Tropics, the ironstone is generally more or less vesicular. Another aid used to assess lithologic changes is computation of the ratios of one sand separate to another. The ratios can be Plinthite computed and examined as a numerical array, or they can be plotted. The ratios work well if sufficient quantities of the two Plinthite (Gr. plinthos, brick) is an iron-rich, humus-poor fractions are available. Low quantities magnify changes in mixture of clay with quartz and other minerals. It commonly ratios, especially if the denominator is low. occurs as dark red redox concentrations that usually form platy, polygonal, or reticulate patterns. Plinthite changes irreversibly n Value to an ironstone or to irregular aggregates on exposure to repeated wetting and drying, especially if it is also exposed to The n value (Pons and Zonneveld, 1965) characterizes the heat from the sun. The lower boundary of a zone in which relation between the percentage of water in a soil under field plinthite occurs generally is diffuse or gradual, but it may be conditions and its percentages of inorganic clay and humus. The abrupt at a lithologic discontinuity. n value is helpful in predicting whether a soil can be grazed by Generally, plinthite forms in a horizon that is saturated with 26 Keys to Soil Taxonomy

water for some time during the year. Initially, iron is normally ODOE value indicates an accumulation of translocated organic segregated in the form of soft, more or less clayey, red or dark materials in an illuvial horizon. Soils with spodic materials show red redox concentrations. These concentrations are not evidence that organic materials and aluminum, with or without considered plinthite unless there has been enough segregation of iron, have been moved from an eluvial horizon to an illuvial iron to permit their irreversible hardening on exposure to horizon. repeated wetting and drying. Plinthite is firm or very firm when Definition of Spodic Materials the soil moisture content is near field capacity and hard when the moisture content is below the wilting point. Plinthite does Spodic materials are mineral soil materials that do not have not harden irreversibly as a result of a single cycle of drying and all of the properties of an argillic or kandic horizon; are rewetting. After a single drying, it will remoisten and then can dominated by active amorphous materials that are illuvial and be dispersed in large part if one shakes it in water with a are composed of organic matter and aluminum, with or without dispersing agent. iron; and have both of the following: In a moist soil, plinthite is soft enough to be cut with a spade. 1. A pH value in water (1:1) of 5.9 or less and an organic- After irreversible hardening, it is no longer considered plinthite carbon content of 0.6 percent or more; and but is called ironstone. Indurated ironstone materials can be broken or shattered with a spade but cannot be dispersed if one 2. One or both of the following: shakes tham in water with a dispersing agent. a. An overlying albic horizon that extends horizontally through 50 percent or more of each pedon and, directly under Resistant Minerals the albic horizon, colors, moist (crushed and smoothed sample), as follows: Several references are made to resistant minerals in this taxonomy. Obviously, the stability of a mineral in the soil is a (1) Hue of 5YR or redder; or partial function of the soil moisture regime. Where resistant (2) Hue of 7.5YR, color value of 5 or less, and chroma minerals are referred to in the definitions of diagnostic horizons of 4 or less; or and of various taxa, a humid climate, past or present, is always assumed. (3) Hue of 10YR or neutral and a color value and Resistant minerals are durable minerals in the 0.02 to 2.0 mm chroma of 2 or less; or fraction. Examples are quartz, zircon, tourmaline, beryl, (4) A color of 10YR 3/1; or anatase, rutile, iron oxides and oxyhydroxides, 1:1 dioctahedral phyllosilicates (kandites), gibbsite, and hydroxy-alluminum b. With or without an albic horizon and one of the colors interlayered 2:1 minerals (USDA, in press). listed above or hue of 7.5YR, color value, moist, of 5 or less, chroma of 5 or 6 (crushed and smoothed sample), and one or Slickensides more of the following morphological or chemical properties: (1) Cementation by organic matter and aluminum, with Slickensides are polished and grooved surfaces and generally or without iron, in 50 percent or more of each pedon and a have dimensions exceeding 5 cm. They are produced when one very firm or firmer rupture-resistance class in the soil mass slides past another. Some slickensides occur at the cemented part; or lower boundary of a slip surface where a mass of soil moves downward on a relatively steep slope. Slickensides result (2) 10 percent or more cracked coatings on sand grains; directly from the swelling of clay minerals and shear failure. or

They are very common in swelling clays that undergo marked 1 (3) Al + /2 Fe percentages (by ammonium oxalate) changes in moisture content. totaling 0.50 or more, and half that amount or less in an overlying umbric (or subhorizon of an umbric) epipedon, Spodic Materials ochric epipedon, or albic horizon; or Spodic materials form in an illuvial horizon that normally (4) An optical-density-of-oxalate-extract (ODOE) value underlies a histic, ochric, or umbric epipedon or an albic of 0.25 or more, and a value half as high or lower in an horizon. In most undisturbed areas, spodic materials underlie an overlying umbric (or subhorizon of an umbric) epipedon, albic horizon. They may occur within an umbric epipedon or an ochric epipedon, or albic horizon. Ap horizon. A horizon consisting of spodic materials normally has an Weatherable Minerals optical-density-of-oxalate-extract (ODOE) value of 0.25 or more, and that value is commonly at least 2 times as high as the Several references are made to weatherable minerals in this ODOE value in an overlying eluvial horizon. This increase in taxonomy. Obviously, the stability of a mineral in a soil is a Horizons and Characteristics Diagnostic for the Higher Categories 27

partial function of the soil moisture regime. Where weatherable stumps, are not considered fibers but are considered coarse minerals are referred to in the definitions of diagnostic horizons fragments (comparable to gravel, stones, and boulders in and of various taxa in this taxonomy, a humid climate, either mineral soils). present or past, is always assumed. Examples of the minerals D that are included in the meaning of weatherable minerals are all Fibric Soil Materials I 2:1 phyllosilicates, chlorite, sepiolite, palygorskite, allophane, A 1:1 trioctahedral phyllosilicates (serpentines), feldspars, Fibric soil materials are organic soil materials that either: feldspathoids, ferromagnesian minerals, glass, zeolites, 1. Contain three-fourths or more (by volume) fibers after dolomite, and apatite in the 0.02 to 2.0 mm fraction. rubbing, excluding coarse fragments; or Obviously, this definition of the term “weatherable minerals” is restrictive. The intent is to include, in the definitions of 2. Contain two-fifths or more (by volume) fibers after rubbing, diagnostic horizons and various taxa, only excluding coarse fragments, and yield color values and chromas those weatherable minerals that are unstable in a humid climate of 7/1, 7/2, 8/1, 8/2, or 8/3 (fig. 2) on white chromatographic or compared to other minerals, such as quartz and 1:1 lattice clays, filter paper that is inserted into a paste made of the soil materials but that are more resistant to weathering than calcite. Calcite, in a saturated sodium-pyrophosphate solution. carbonate aggregates, gypsum, and halite are not considered weatherable minerals because they are mobile in the soil. They Hemic Soil Materials appear to be recharged in some otherwise strongly weathered soils. Hemic soil materials (Gr. hemi, half; implying intermediate decomposition) are intermediate in their degree of decomposition between the less decomposed fibric and more Characteristics Diagnostic for decomposed sapric materials. Their morphological features give Organic Soils intermediate values for fiber content, bulk density, and water content. Hemic soil materials are partly altered both physically Following is a description of the characteristics that are used and biochemically. only with organic soils. Sapric Soil Materials Kinds of Organic Soil Materials Sapric soil materials (Gr. sapros, rotten) are the most highly Three different kinds of organic soil materials are decomposed of the three kinds of organic soil materials. They distinguished in this taxonomy, based on the degree of have the smallest amount of plant fiber, the highest bulk density, decomposition of the plant materials from which the organic and the lowest water content on a dry-weight basis at saturation. materials are derived. The three kinds are (1) fibric, (2) hemic, Sapric soil materials are commonly very dark gray to black. and (3) sapric. Because of the importance of fiber content in the They are relatively stable; i.e., they change very little physically definitions of these materials, fibers are defined before the kinds and chemically with time in comparison to other organic soil of organic soil materials. materials. Sapric materials have the following characteristics: Fibers 1. The fiber content, after rubbing, is less than one-sixth (by volume), excluding coarse fragments; and Fibers are pieces of plant tissue in organic soil materials (excluding live roots) that: 2. The color of the sodium-pyrophosphate extract on white chromatographic or filter paper is below or to the right of a line 1. Are large enough to be retained on a 100-mesh sieve drawn to exclude blocks 5/1, 6/2, and 7/3 (Munsell designations, (openings 0.15 mm across) when the materials are screened; and fig. 2). If few or no fibers can be detected and the color of the 2. Show evidence of the cellular structure of the plants from pyrophosphate extract is to the left of or above this line, the which they are derived; and possibility that the material is limnic must be considered. 3. Either are 2 cm or less in their smallest dimension or are decomposed enough to be crushed and shredded with the Humilluvic Material fingers. Humilluvic material, i.e., illuvial humus, accumulates in the Pieces of wood that are larger than 2 cm in cross section lower parts of some organic soils that are acid and have been and are so undecomposed that they cannot be crushed and drained and cultivated. The humilluvic material has a C14 age shredded with the fingers, such as large branches, logs, and that is not older than the overlying organic materials. It has very 28 Keys to Soil Taxonomy

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

4. Either yields a saturated sodium-pyrophosphate extract on Figure 2.—Value and chroma of pyrophosphate solution of fibric and white chromatographic or filter paper that has a color value of 7 sapric materials. or more and chroma of 2 or less (fig. 2) or has a cation- exchange capacity of less than 240 cmol(+) per kg organic matter (measured by loss on ignition), or both. capacity of less than 240 cmol(+) per kg organic matter (by loss on ignition), or both. Diatomaceous Earth

A layer of diatomaceous earth is a limnic layer that: Marl 1. If not previously dried, has a matrix color value of 3, 4, A layer of marl is a limnic layer that: or 5, which changes irreversibly on drying as a result of the 1. Has a color value, moist, of 5 or more; and irreversible shrinkage of organic-matter coatings on diatoms

(identifiable by microscopic, 440 X, examination of dry 2. Reacts with dilute HCl to evolve CO2. samples); and The color of marl usually does not change irreversibly on 2. Either yields a saturated sodium-pyrophosphate extract on drying because a layer of marl contains too little organic matter, white chromatographic or filter paper that has a color value of 8 even before it has been shrunk by drying, to coat the carbonate or more and chroma of 2 or less or has a cation-exchange particles. Horizons and Characteristics Diagnostic for the Higher Categories 29

Thickness of Organic Soil Materials includes any unconsolidated mineral layers that may be present (Control Section of Histosols and Histels) within those depths.

The thickness of organic materials over limnic materials, Bottom Tier D mineral materials, water, or permafrost is used to define the I The bottom tier is 40 cm thick unless the control section has Histosols and Histels. A its lower boundary at a shallower depth (at a densic, lithic, or For practical reasons, an arbitrary control section has been paralithic contact or a water layer or in permafrost). established for the classification of Histosols and Histels. Thus, if the organic materials are thick, there are two possible Depending on the kinds of soil material in the surface layer, the thicknesses of the control section, depending on the presence or control section has a thickness of either 130 cm or 160 cm from absence and the thickness of a surface mantle of fibric moss or the soil surface if there is no densic, lithic, or paralithic contact, other organic material that has a low bulk density (less than 0.1). thick layer of water, or permafrost within the respective limit. If the fibric moss extends to a depth of 60 cm and is the The thicker control section is used if the surface layer to a depth dominant material within this depth (three-fourths or more of the of 60 cm either contains three-fourths or more fibers derived volume), the control section is 160 cm thick. If the fibric moss is from Sphagnum, Hypnum, or other mosses or has a bulk density thin or absent, the control section extends to a depth of 130 cm. of less than 0.1. Layers of water, which may be between a few centimeters and many meters thick in these soils, are considered to be the lower boundary of the control section only if the water Horizons and Characteristics extends below a depth of 130 or 160 cm, respectively. A densic, lithic, or paralithic contact, if shallower than 130 or 160 cm, Diagnostic for Both Mineral and constitutes the lower boundary of the control section. In some Organic Soils soils the lower boundary is 25 cm below the upper limit of Following are descriptions of the horizons and characteristics permafrost. An unconsolidated mineral substratum shallower that are diagnostic for both mineral and organic soils. than those limits does not change the lower boundary of the control section. Aquic Conditions The control section of Histosols and Histels is divided Soils with aquic (L. aqua, water) conditions are those that somewhat arbitrarily into three tiers—surface, subsurface, and currently undergo continuous or periodic saturation and bottom tiers. reduction. The presence of these conditions is indicated by redoximorphic features, except in Histosols and Histels, and can Surface Tier be verified by measuring saturation and reduction, except in artificially drained soils. Artificial drainage is defined here as The surface tier of a Histosol or Histel extends from the soil the removal of free water from soils having aquic conditions by surface to a depth of 60 cm if either (1) the materials within that surface mounding, ditches, or subsurface tiles to the extent that depth are fibric and three-fourths or more of the fiber volume is water table levels are changed significantly in connection with derived from Sphagnum or other mosses or (2) the materials specific types of land use. In the keys, artificially drained soils have a bulk density of less than 0.1. Otherwise, the surface tier are included with soils that have aquic conditions. extends from the soil surface to a depth of 30 cm. Elements of aquic conditions are as follows: Some organic soils have a mineral surface layer less than 40 cm thick as a result of flooding, volcanic eruptions, additions of 1. Saturation is characterized by zero or positive pressure in mineral materials to increase soil strength or reduce the hazard the soil water and can generally be determined by observing free of frost, or other causes. If such a mineral layer is less than 30 water in an unlined auger hole. Problems may arise, however, in cm thick, it constitutes the upper part of the surface tier; if it is clayey soils with peds, where an unlined auger hole may fill with 30 to 40 cm thick, it constitutes the whole surface tier and part water flowing along faces of peds while the soil matrix is and of the subsurface tier. remains unsaturated (bypass flow). Such free water may incorrectly suggest the presence of a water table, while the actual water table occurs at greater depth. Use of well sealed Subsurface Tier piezometers or tensiometers is therefore recommended for measuring saturation. Problems may still occur, however, if The subsurface tier is normally 60 cm thick. If the control water runs into piezometer slits near the bottom of the section ends at a shallower depth (at a densic, lithic, or piezometer hole or if tensiometers with slowly reacting paralithic contact or a water layer or in permafrost), however, manometers are used. The first problem can be overcome by the subsurface tier extends from the lower boundary of the using piezometers with smaller slits and the second by using surface tier to the lower boundary of the control section. It transducer tensiometry, which reacts faster than manometers. 30 Keys to Soil Taxonomy

Soils are considered wet if they have pressure heads greater than alpha,alpha-dipyridyl in neutral, 1-normal ammonium-acetate -1 kPa. Only macropores, such as cracks between peds or solution. The appearance of a strong red color on the freshly channels, are then filled with air, while the soil matrix is usually broken surface indicates the presence of reduced iron ions. A still saturated. Obviously, exact measurements of the wet state positive reaction to the alpha,alpha-dipyridyl field test for can be obtained only with tensiometers. For operational ferrous iron (Childs, 1981) may be used to confirm the existence purposes, the use of piezometers is recommended as a standard of reducing conditions and is especially useful in situations method. where, despite saturation, normal morphological indicators of The duration of saturation required for creating aquic such conditions are either absent or obscured (as by the dark conditions varies, depending on the soil environment, and is not colors characteristic of melanic great groups). A negative specified. reaction, however, does not imply that reducing conditions are Three types of saturation are defined: always absent. It may only mean that the level of free iron in the soil is below the sensitivity limit of the test or that the soil is in a. Endosaturation.—The soil is saturated with water in all an oxidized phase at the time of testing. Use of alpha,alpha- layers from the upper boundary of saturation to a depth of dipyridyl in a 10 percent acetic-acid solution is not 200 cm or more from the mineral soil surface. recommended because the acid is likely to change soil

b. Episaturation.—The soil is saturated with water in one conditions, for example, by dissolving CaCO3. or more layers within 200 cm of the mineral soil surface and The duration of reduction required for creating aquic also has one or more unsaturated layers, with an upper conditions is not specified. boundary above a depth of 200 cm, below the saturated layer. 3. Redoximorphic features associated with wetness result from The zone of saturation, i.e., the water table, is perched on top alternating periods of reduction and oxidation of iron and of a relatively impermeable layer. manganese compounds in the soil. Reduction occurs during c. Anthric saturation.—This term refers to a special kind of saturation with water, and oxidation occurs when the soil is not aquic conditions that occur in soils that are cultivated and saturated. The reduced iron and manganese ions are mobile and irrigated (flood irrigation). Soils with anthraquic conditions may be transported by water as it moves through the soil. must meet the requirements for aquic conditions and in Certain redox patterns occur as a function of the patterns in addition have both of the following: which the ion-carrying water moves through the soil and as a function of the location of aerated zones in the soil. Redox (1) A tilled surface layer and a directly underlying patterns are also affected by the fact that manganese is reduced slowly permeable layer that has, for 3 months or more in more rapidly than iron, while iron oxidizes more rapidly upon normal years, both: aeration. Characteristic color patterns are created by these (a) Saturation and reduction; and processes. The reduced iron and manganese ions may be removed from a soil if vertical or lateral fluxes of water occur, (b) Chroma of 2 or less in the matrix; and in which case there is no iron or manganese precipitation in that (2) A subsurface horizon with one or more of the soil. Wherever the iron and manganese are oxidized and following: precipitated, they form either soft masses or hard concretions or nodules. Movement of iron and manganese as a result of redox (a) Redox depletions with a color value, moist, of 4 processes in a soil may result in redoximorphic features that are or more and chroma of 2 or less in macropores; or defined as follows: (b) Redox concentrations of iron; or a. Redox concentrations.—These are zones of apparent (c) 2 times or more the amount of iron (by dithionite accumulation of Fe-Mn oxides, including: citrate) contained in the tilled surface layer. (1) Nodules and concretions, which are cemented 2. The degree of reduction in a soil can be characterized by bodies that can be removed from the soil intact. the direct measurement of redox potentials. Direct Concretions are distinguished from nodules on the basis of measurements should take into account chemical equilibria as internal organization. A typically has expressed by stability diagrams in standard soil textbooks. concentric layers that are visible to the naked eye. Reduction and oxidation processes are also a function of soil Nodules do not have visible organized internal structure. pH. Obtaining accurate measurements of the degree of reduction Boundaries commonly are diffuse if formed in situ and in a soil is difficult. In the context of this taxonomy, however, sharp after pedoturbation. Sharp boundaries may be relict only a degree of reduction that results in reduced iron is features in some soils; and considered, because it produces the visible redoximorphic (2) Masses, which are noncemented concentrations of features that are identified in the keys. A simple field test is substances within the soil matrix; and available to determine if reduced iron ions are present. A freshly broken surface of a field-wet soil sample is treated with (3) Pore linings, i.e., zones of accumulation along pores Horizons and Characteristics Diagnostic for the Higher Categories 31

that may be either coatings on pore surfaces or noncemented rupture-resistance class. The bulk density or the impregnations from the matrix adjacent to the pores. organization is such that roots cannot enter, except in cracks. These are mostly earthy materials, such as till, volcanic b. Redox depletions.—These are zones of low chroma mudflows, and some mechanically compacted materials, for D (chromas less than those in the matrix) where either Fe-Mn example, mine spoils. Some noncemented rocks can be densic I oxides alone or both Fe-Mn oxides and clay have been materials if they are dense or resistant enough to keep roots A stripped out, including: from entering, except in cracks. Densic materials are noncemented and thus differ from (1) Iron depletions, i.e., zones that contain low amounts paralithic materials and the material below a lithic contact, both of Fe and Mn oxides but have a clay content similar to of which are cemented. that of the adjacent matrix (often referred to as albans or Densic materials have, at their upper boundary, a densic neoalbans); and contact if they have no cracks or if the spacing of cracks that (2) Clay depletions, i.e., zones that contain low amounts roots can enter is 10 cm or more. These materials can be used to of Fe, Mn, and clay (often referred to as silt coatings or differentiate soil series if the materials are within the series skeletans). control section. c. Reduced matrix.—This is a soil matrix that has low chroma in situ but undergoes a change in hue or chroma Gelic Materials within 30 minutes after the soil material has been exposed to Gelic materials are mineral or organic soil materials that air. show evidence of cryoturbation (frost churning) and/or ice d. In soils that have no visible redoximorphic features, a segregation in the active layer (seasonal thaw layer) and/or the reaction to an alpha,alpha-dipyridyl solution satisfies the upper part of the permafrost. Cryoturbation is manifested by requirement for redoximorphic features. irregular and broken horizons, involutions, accumulation of organic matter on top of and within the permafrost, oriented Field experience indicates that it is not possible to define a rock fragments, and silt-enriched layers. The characteristic specific set of redoximorphic features that is uniquely structures associated with gelic materials include platy, blocky, characteristic of all of the taxa in one particular category. or granular macrostructures; the structural results of sorting; and Therefore, color patterns that are unique to specific taxa are orbiculic, conglomeric, banded, or vesicular microfabrics. Ice referenced in the keys. segregation is manifested by ice lenses, vein ice, segregated ice Anthraquic conditions are a variant of episaturation and are crystals, and ice wedges. Cryopedogenic processes that lead to associated with controlled flooding (for such crops as wetland gelic materials are driven by the physical volume change of rice and cranberries), which causes reduction processes in the water to ice, moisture migration along a thermal gradient in the saturated, puddled surface soil and oxidation of reduced and frozen system, or thermal contraction of the frozen material by mobilized iron and manganese in the unsaturated . continued rapid cooling.

Cryoturbation Glacic Layer

Cryoturbation (frost churning) is the mixing of the soil matrix A glacic layer is massive ice or ground ice in the form of ice within the pedon that results in irregular or broken horizons, lenses or wedges. The layer is 30 cm or more thick and contains involutions, accumulation of organic matter on the permafrost 75 percent or more visible ice. table, oriented rock fragments, and silt caps on rock fragments. Lithic Contact Densic Contact A lithic contact is the boundary between soil and a coherent A densic contact (L. densus, thick) is a contact between underlying material. Except in Ruptic-Lithic subgroups, the soil and densic materials (defined below). It has no cracks, underlying material must be virtually continuous within the or the spacing of cracks that roots can enter is 10 cm or limits of a pedon. Cracks that can be penetrated by roots are more. few, and their horizontal spacing is 10 cm or more. The underlying material must be sufficiently coherent when moist to Densic Materials make hand-digging with a spade impractical, although the material may be chipped or scraped with a spade. The material Densic materials are relatively unaltered materials (do not below a lithic contact must be in a strongly cemented or more meet the requirements for any other named diagnostic horizons cemented rupture-resistance class. Commonly, the material is or any other diagnostic soil characteristic) that have a indurated. The underlying material considered here does not 32 Keys to Soil Taxonomy

include diagnostic soil horizons, such as a duripan or a horizon is considered dry when the moisture tension is 1500 kPa petrocalcic horizon. or more and is considered moist if water is held at a tension of A lithic contact is diagnostic at the subgroup level if it less than 1500 kPa but more than zero. A soil may be is within 125 cm of the mineral soil surface in Oxisols and continuously moist in some or all horizons either throughout the within 50 cm of the mineral soil surface in all other mineral year or for some part of the year. It may be either moist in winter soils. In organic soils the lithic contact must be within the and dry in summer or the reverse. In the Northern Hemisphere, control section to be recognized at the subgroup level. summer refers to June, July, and August and winter refers to December, January, and February. Paralithic Contact Normal Years A paralithic (lithiclike) contact is a contact between soil and In the discussions that follow and throughout the keys, the paralithic materials (defined below) where the paralithic term “normal years” is used. A normal year is defined as a year materials have no cracks or the spacing of cracks that roots can that has plus or minus one standard deviation of the long-term enter is 10 cm or more. mean annual precipitation. (Long-term refers to 30 years or more.) Also, the mean monthly precipitation during a normal Paralithic Materials year must be plus or minus one standard deviation of the long- term monthly precipitation for 8 of the 12 months. For the most Paralithic materials are relatively unaltered materials (do not part, normal years can be calculated from the mean annual meet the requirements for any other named diagnostic horizons precipitation. When catastrophic events occur during a year, or any other diagnostic soil characteristic) that have an however, the standard deviations of the monthly means should extremely weakly cemented to moderately cemented rupture- also be calculated. The term “normal years” replaces the terms resistance class. Cementation, bulk density, and the organization “most years” and “6 out of 10 years,” which were used in the are such that roots cannot enter, except in cracks. Paralithic 1975 edition of Soil Taxonomy (USDA, SCS, 1975). materials have, at their upper boundary, a paralithic contact if Soil Moisture Control Section they have no cracks or if the spacing of cracks that roots can enter is 10 cm or more. Commonly, these materials are partially The intent in defining the soil moisture control section is to weathered bedrock or weakly consolidated bedrock, such as facilitate estimation of soil moisture regimes from climatic data. sandstone, siltstone, or shale. Paralithic materials can be used to The upper boundary of this control section is the depth to which differentiate soil series if the materials are within the series a dry (tension of more than 1500 kPa, but not air-dry) soil will control section. Fragments of paralithic materials 2.0 mm or be moistened by 2.5 cm of water within 24 hours. The lower more in diameter are referred to as pararock fragments. boundary is the depth to which a dry soil will be moistened by 7.5 cm of water within 48 hours. These depths do not include Permafrost the depth of moistening along any cracks or animal burrows that are open to the surface. Permafrost is defined as a thermal condition in which a If 7.5 cm of water moistens the soil to a densic, lithic, material (including soil material) remains below 0 oC for 2 or paralithic, or petroferric contact or to a petrocalcic or more years in succession. Those gelic materials having petrogypsic horizon or a duripan, the contact or the upper permafrost contain the unfrozen soil solution that drives boundary of the cemented horizon constitutes the lower cryopedogenic processes. Permafrost may be cemented by ice boundary of the soil moisture control section. If a soil is or, in the case of insufficient interstitial water, may be dry. The moistened to one of these contacts or horizons by 2.5 cm of frozen layer has a variety of ice lenses, vein ice, segregated ice water, the soil moisture control section is the boundary or the crystals, and ice wedges. The permafrost table is in dynamic contact itself. The control section of such a soil is considered equilibrium with the environment. moist if the contact or upper boundary of the cemented horizon has a thin film of water. If that upper boundary is dry, the control Soil Moisture Regimes section is considered dry. The moisture control section of a soil extends approximately The term “soil moisture regime” refers to the presence or (1) from 10 to 30 cm below the soil surface if the particle-size absence either of ground water or of water held at a tension of class of the soil is fine-loamy, coarse-silty, fine-silty, or clayey; less than 1500 kPa in the soil or in specific horizons during (2) from 20 to 60 cm if the particle-size class is coarse-loamy; periods of the year. Water held at a tension of 1500 kPa or more and (3) from 30 to 90 cm if the particle-size class is sandy. If the is not available to keep most mesophytic plants alive. The soil contains rock and pararock fragments that do not absorb and availability of water is also affected by dissolved salts. If a soil release water, the limits of the moisture control section are is saturated with water that is too salty to be available to most deeper. The limits of the soil moisture control section are plants, it is considered salty rather than dry. Consequently, a affected not only by the particle-size class but also by Horizons and Characteristics Diagnostic for the Higher Categories 33

differences in soil structure or pore-size distribution or by other such as a crusty surface that virtually precludes the infiltration of factors that influence the movement and retention of water in the water, or are on steep slopes where runoff is high. There is little soil. or no leaching in this moisture regime, and soluble salts accumulate in the soils if there is a source. Classes of Soil Moisture Regimes D The limits set for soil temperature exclude from these I The soil moisture regimes are defined in terms of the level of moisture regimes soils in the very cold and dry polar regions A ground water and in terms of the seasonal presence or absence and in areas at high elevations. Such soils are considered to have of water held at a tension of less than 1500 kPa in the moisture anhydrous conditions (defined earlier). control section. It is assumed in the definitions that the soil Udic moisture regime.—The udic (L. udus, humid) moisture supports whatever vegetation it is capable of supporting, i.e., regime is one in which the soil moisture control section is not crops, grass, or native vegetation, and that the amount of stored dry in any part for as long as 90 cumulative days in normal moisture is not being increased by irrigation or fallowing. These years. If the mean annual soil temperature is lower than 22 oC cultural practices affect the soil moisture conditions as long as and if the mean winter and mean summer soil temperatures at a they are continued. depth of 50 cm from the soil surface differ by 6 oC or more, the Aquic moisture regime.—The aquic (L. aqua, water) soil moisture control section, in normal years, is dry in all parts moisture regime is a reducing regime in a soil that is virtually for less than 45 consecutive days in the 4 months following the free of dissolved oxygen because it is saturated by water. Some summer solstice. In addition, the udic moisture regime requires, soils are saturated with water at times while dissolved oxygen is except for short periods, a three-phase system, solid-liquid-gas, present, either because the water is moving or because the in part or all of the soil moisture control section when the soil environment is unfavorable for micro-organisms (e.g., if the temperature is above temperature is less than 1 oC); such a regime is not considered 5 oC. aquic. The udic moisture regime is common to the soils of humid It is not known how long a soil must be saturated before it is climates that have well distributed rainfall; have enough rain in said to have an aquic moisture regime, but the duration must be summer so that the amount of stored moisture plus rainfall is at least a few days, because it is implicit in the concept that approximately equal to, or exceeds, the amount of dissolved oxygen is virtually absent. Because dissolved oxygen evapotranspiration; or have adequate winter rains to recharge is removed from ground water by respiration of micro- the soils and cool, foggy summers, as in coastal areas. Water organisms, roots, and soil fauna, it is also implicit in the concept moves downward through the soils at some time in normal that the soil temperature is above biologic zero for some time years. while the soil is saturated. Biologic zero is defined as 5 oC in In climates where precipitation exceeds evapotranspiration in this taxonomy. In some of the very cold regions of the world, all months of normal years, the moisture tension rarely reaches however, biological activity occurs at temperatures below 5 oC. 100 kPa in the soil moisture control section, although there are Very commonly, the level of ground water fluctuates with the occasional brief periods when some stored moisture is used. The seasons; it is highest in the rainy season or in fall, winter, or water moves through the soil in all months when it is not frozen. spring if cold weather virtually stops evapotranspiration. There Such an extremely wet moisture regime is called perudic (L. per, are soils, however, in which the ground water is always at or throughout in time, and L. udus, humid). In the names of most very close to the surface. Examples are soils in tidal marshes or taxa, the formative element “ud” is used to indicate either a udic in closed, landlocked depressions fed by perennial streams. or a perudic regime; the formative element “per” is used in Such soils are considered to have a peraquic moisture regime. selected taxa. Aridic and torric (L. aridus, dry, and L. torridus, hot and moisture regime.—The ustic (L. ustus, burnt; dry) moisture regimes.—These terms are used for the same implying dryness) moisture regime is intermediate between the moisture regime but in different categories of the taxonomy. aridic regime and the udic regime. Its concept is one of moisture In the aridic (torric) moisture regime, the moisture control that is limited but is present at a time when conditions are section is, in normal years: suitable for plant growth. The concept of the ustic moisture regime is not applied to soils that have permafrost or a cryic soil 1. Dry in all parts for more than half of the cumulative days temperature regime (defined below). per year when the soil temperature at a depth of 50 cm from the If the mean annual soil temperature is 22 oC or higher or if o soil surface is above 5 C; and the mean summer and winter soil temperatures differ by less o 2. Moist in some or all parts for less than 90 consecutive days than 6 C at a depth of 50 cm below the soil surface, the soil when the soil temperature at a depth of 50 cm is above 8 oC. moisture control section in areas of the ustic moisture regime is dry in some or all parts for 90 or more cumulative days in Soils that have an aridic (torric) moisture regime normally normal years. It is moist, however, in some part either for more occur in areas of arid climates. A few are in areas of semiarid than 180 cumulative days per year or for 90 or more consecutive climates and either have physical properties that keep them dry, days. 34 Keys to Soil Taxonomy

If the mean annual soil temperature is lower than 22 oC and if January, and February in the Southern Hemisphere) either at a the mean summer and winter soil temperatures differ by 6 oC or depth of 50 cm from the soil surface or at a densic, lithic, or more at a depth of 50 cm from the soil surface, the soil moisture paralithic contact, whichever is shallower, is as follows: control section in areas of the ustic moisture regime is dry in a. If the soil is not saturated with water during some part of some or all parts for 90 or more cumulative days in normal the summer and years, but it is not dry in all parts for more than half of the cumulative days when the soil temperature at a depth of 50 cm (1) If there is no O horizon: lower than 15 oC; or is higher than 5 oC. If in normal years the moisture control (2) If there is an O horizon: lower than 8 oC; or section is moist in all parts for 45 or more consecutive days in the 4 months following the winter solstice, the moisture control b. If the soil is saturated with water during some part of the section is dry in all parts for less than 45 consecutive days in the summer and 4 months following the summer solstice. (1) If there is no O horizon: lower than 13 oC; or In tropical and subtropical regions that have a monsoon climate with either one or two dry seasons, summer and winter (2) If there is an O horizon or a histic epipedon: lower seasons have little meaning. In those regions the moisture than 6 oC. regime is ustic if there is at least one rainy season of 3 months or 2. In organic soils the mean annual soil temperature is lower more. In temperate regions of subhumid or semiarid climates, than 6 oC. the rainy seasons are usually spring and summer or spring and fall, but never winter. Native plants are mostly annuals or plants Cryic soils that have an aquic moisture regime commonly are that have a dormant period while the soil is dry. churned by frost. Xeric moisture regime.—The xeric (Gr. xeros, dry) moisture Isofrigid soils could also have a cryic temperature regime. A regime is the typical moisture regime in areas of Mediterranean few with organic materials in the upper part are exceptions. climates, where winters are moist and cool and summers are The concepts of the soil temperature regimes described warm and dry. The moisture, which falls during the winter, when below are used in defining classes of soils in the low categories. potential evapotranspiration is at a minimum, is particularly Frigid.—A soil with a frigid temperature regime is effective for leaching. In areas of a xeric moisture regime, the warmer in summer than a soil with a cryic regime, but its soil moisture control section, in normal years, is dry in all parts mean annual temperature is lower than 8 oC and the difference for 45 or more consecutive days in the 4 months following the between mean summer (June, July, and August) and mean winter summer solstice and moist in all parts for 45 or more (December, January, and February) soil temperatures is more consecutive days in the 4 months following the winter solstice. than 6 oC either at a depth of 50 cm from the soil surface or at a Also, in normal years, the moisture control section is moist in densic, lithic, or paralithic contact, whichever is shallower. some part for more than half of the cumulative days per year Mesic.—The mean annual soil temperature is 8 oC or higher when the soil temperature at a depth of 50 cm from the soil but lower than 15 oC, and the difference between mean summer surface is higher than 6 oC or for 90 or more consecutive days and mean winter soil temperatures is more than 6 oC either at a when the soil temperature at a depth of 50 cm is higher than 8 depth of 50 cm from the soil surface or at a densic, lithic, or oC. The mean annual soil temperature is lower than 22 oC, and paralithic contact, whichever is shallower. the mean summer and mean winter soil temperatures differ by 6 Thermic.—The mean annual soil temperature is 15 oC or oC or more either at a depth of 50 cm from the soil surface or at higher but lower than 22 oC, and the difference between mean a densic, lithic, or paralithic contact if shallower. summer and mean winter soil temperatures is more than 6 oC either at a depth of 50 cm from the soil surface or at a densic, Soil Temperature Regimes lithic, or paralithic contact, whichever is shallower. Hyperthermic.—The mean annual soil temperature is Classes of Soil Temperature Regimes 22 oC or higher, and the difference between mean summer and mean winter soil temperatures is more than 6 oC either at a depth Following is a description of the soil temperature regimes of 50 cm from the soil surface or at a densic, lithic, or paralithic used in defining classes at various categoric levels in this contact, whichever is shallower. taxonomy. If the name of a soil temperature regime has the prefix iso, Cryic (Gr. kryos, coldness; meaning very cold soils).— the mean summer and mean winter soil temperatures differ by Soils in this temperature regime have a mean annual temperature less than 6 oC at a depth of 50 cm or at a densic, lithic, or lower than 8 oC but do not have permafrost. paralithic contact, whichever is shallower. 1. In mineral soils the mean summer soil temperature (June, Isofrigid.—The mean annual soil temperature is lower than July, and August in the Northern Hemisphere and December, 8 oC. Horizons and Characteristics Diagnostic for the Higher Categories 35

Isomesic.—The mean annual soil temperature is 8 oC or Sulfuric Horizon higher but lower than 15 oC. Isothermic.—The mean annual soil temperature is 15 oC or Required Characteristics higher but lower than 22 oC. The sulfuric (L. sulfur) horizon is 15 cm or more thick and is D Isohyperthermic.—The mean annual soil temperature is composed of either mineral or organic soil material that has a I 22 oC or higher. pH value of 3.5 or less (1:1 by weight in water or in a minimum A of water to permit measurement) and shows evidence that the Sulfidic Materials low pH value is caused by sulfuric acid. The evidence is one or more of the following: Sulfidic materials contain oxidizable sulfur compounds. They are mineral or organic soil materials that have a pH value of 1. Jarosite concentrations; or more than 3.5 and that, if incubated as a layer 1 cm thick under 2. Directly underlying sulfidic materials (defined above); or moist aerobic conditions (field capacity) at room temperature, show a drop in pH of 0.5 or more units to a pH value of 4.0 or 3. 0.05 percent or more water-soluble sulfate. less (1:1 by weight in water or in a minimum of water to permit measurement) within 8 weeks. Sulfidic materials accumulate as a soil or sediment that is Literature Cited permanently saturated, generally with brackish water. The Brewer, R. 1976. Fabric and Mineral Analysis of Soils. sulfates in the water are biologically reduced to sulfides as the Second edition. John Wiley and Sons, Inc. New York, New materials accumulate. Sulfidic materials most commonly York. accumulate in coastal marshes near the mouth of rivers that Childs, C.W. 1981. Field Test for Ferrous Iron and Ferric- carry noncalcareous sediments, but they may occur in Organic Complexes (on Exchange Sites or in Water-Soluble freshwater marshes if there is sulfur in the water. Upland sulfidic Forms) in Soils. Austr. J. of Soil Res. 19: 175-180. materials may have accumulated in a similar manner in the Pons, L.J., and I.S. Zonneveld. 1965. Soil Ripening geologic past. and Soil Classification. Initial Soil Formation in Alluvial If a soil containing sulfidic materials is drained or if sulfidic Deposits and a Classification of the Resulting Soils. Int. Inst. materials are otherwise exposed to aerobic conditions, the Land Reclam. and Impr. Pub. 13. Wageningen, The Netherlands. sulfides oxidize and form sulfuric acid. The pH value, which United States Department of Agriculture, Natural Resources normally is near neutrality before drainage or exposure, may Conservation Service, National Soil Survey Center. (In press.) drop below 3. The acid may induce the formation of iron and Soil Survey Laboratory Methods Manual. Soil Survey aluminum sulfates. The iron sulfate, jarosite, may segregate, Investigations Report 42, Version 4.0. forming the yellow redoximorphic concentrations that United States Department of Agriculture, Soil Conservation commonly characterize a sulfuric horizon. The transition from Service. 1975. Soil Taxonomy: A Basic System of Soil sulfidic materials to a sulfuric horizon normally requires very Classification for Making and Interpreting Soil Surveys. Soil few years and may occur within a few weeks. A sample of Surv. Staff. U.S. Dep. Agric. Handb. 436. sulfidic materials, if air-dried slowly in shade for about 2 United States Department of Agriculture, Soil Conservation months with occasional remoistening, becomes extremely Service. 1993. Soil Survey Manual. Soil Surv. Div. Staff. U.S. acid. Dep. Agric. Handb. 18.

37

CHAPTER 4 Identification of the Taxonomic Class of a Soil I D E The taxonomic class of a specific soil can be determined used to determine the control section before use of the keys to by using the keys that follow in this and other chapters. It is classes. assumed that the reader is familiar with the definitions of The descriptions and definitions of individual soil series are diagnostic horizons and properties that are given in chapters 2 not included in this text. Definitions of the series and of the and 3 of this publication and with the meanings of the terms control section are given in chapter 17. used for describing soils given in the Soil Survey Manual. The In the “Key to Soil Orders” and the other keys that follow, Index at the back of this publication indicates the pages on the diagnostic horizons and the properties mentioned do not which definitions of terms are given. include those below any densic, lithic, paralithic, or petroferric Standard rounding conventions should be used to determine contact. The properties of buried soils and the properties of a numerical values. surface mantle are considered on the basis of whether or not the Soil colors (hue, value, and chroma) are used in many of soil meets the meaning of the term “buried soil” given in chapter 1. the criteria that follow. Soil colors typically change value and If a soil has a surface mantle and is not a buried soil, the top some change hue and chroma, depending on the water state. of the original surface layer is considered the “soil surface” for In many of the criteria of the keys, the water state is specified. If determining depth to and thickness of diagnostic horizons and no water state is specified, the soil is considered to meet most other diagnostic soil characteristics. The only properties of the criterion if it does so when moist or dry or both moist and the surface mantle that are considered are soil temperature, soil dry. moisture (including aquic conditions), and any andic or All of the keys in this taxonomy are designed in such a way vitrandic properties and family criteria. that the user can determine the correct classification of a soil by If a soil profile includes a buried soil, the present soil surface going through the keys systematically. The user must start at the is used to determine soil moisture and temperature as well as beginning of the “Key to Soil Orders” and eliminate, one by depth to and thickness of diagnostic horizons and other one, all classes that include criteria that do not fit the soil in diagnostic soil characteristics. Diagnostic horizons of the buried question. The soil belongs to the first class listed for which it soil are not considered in selecting taxa unless the criteria in the meets all the required criteria. keys specifically indicate buried horizons, such as in Thapto- In classifying a specific soil, the user of soil taxonomy begins Histic subgroups. Most other diagnostic soil characteristics of by checking through the “Key to Soil Orders” to determine the the buried soil are not considered, but organic carbon if of name of the first order that, according to the criteria listed, Holocene age, andic soil properties, base saturation, and all includes the soil in question. The next step is properties used to determine family and series placement are to go to the page indicated to find the “Key to Suborders” of considered. that particular order. Then the user systematically goes through the key to identify the suborder that includes the soil, i.e., the first in the list for which it meets all the required criteria. The Key to Soil Orders same procedure is used to find the great group class of the soil A. Soils that have: in the “Key to Great Groups” of the identified suborder. Likewise, going through the “Key to Subgroups” of that great 1. Permafrost within 100 cm of the soil surface; or group, the user selects as the correct subgroup name the name of 2. Gelic materials within 100 cm of the soil surface and the first taxon for which the soil meets all of the required permafrost within 200 cm of the soil surface. criteria. Gelisols, p. 149 The family level is determined, in a similar manner, after the subgroup has been determined. Chapter 17 can be used, B. Other soils that: as one would use other keys in this taxonomy, to determine which components are part of the family. The family, 1. Do not have andic soil properties in 60 percent or more however, typically has more than one component, and of the thickness between the soil surface and either a depth of therefore the entire chapter must be used. The keys to control 60 cm or a densic, lithic, or paralithic contact or duripan if sections for classes used as components of a family must be shallower; and 38 Keys to Soil Taxonomy

2. Have organic soil materials that meet one or more of the (5) A cryic temperature regime in the soil; and following: b. An upper boundary within the following depths from a. Overlie cindery, fragmental, or pumiceous materials the mineral soil surface: either and/or fill their interstices1 and directly below these (1) Less than 50 cm; or materials, have a densic, lithic, or paralithic contact; or (2) Less than 200 cm if the soil has a sandy particle- size class in at least some part between the mineral soil b. When added with the underlying cindery, fragmental, surface and the spodic horizon; and or pumiceous materials, total 40 cm or more between the soil surface and a depth of 50 cm; or c. A lower boundary as follows: c. Constitute two-thirds or more of the total thickness of (1) Either at a depth of 25 cm or more below the the soil to a densic, lithic, or paralithic contact and have mineral soil surface or at the top of a duripan or no mineral horizons or have mineral horizons with a total fragipan or at a densic, lithic, paralithic, or petroferric thickness of 10 cm or less; or contact, whichever is shallowest; or d. Are saturated with water for 30 days or more per year (2) At any depth, in normal years (or are artificially drained), have an upper (a) If the spodic horizon has a coarse-loamy, boundary within 40 cm of the soil surface, and have a total loamy-skeletal, or finer particle-size class and the thickness of either: soil has a frigid temperature regime; or (1) 60 cm or more if three-fourths or more of their (b) If the soil has a cryic temperature regime; and volume consists of moss fibers or if their bulk density, moist, is less than 0.1 g/cm3; or d. Either: (2) 40 cm or more if they consist either of sapric or (1) A directly overlying albic horizon in 50 percent or hemic materials, or of fibric materials with less than more of each pedon; or three-fourths (by volume) moss fibers and a bulk (2) No andic soil properties in 60 percent or more of density, moist, of 0.1 g/cm3 or more. the thickness either: Histosols, p. 159 (a) Within 60 cm either of the mineral soil surface C. Other soils that do not have a plaggen epipedon or an or of the top of an organic layer with andic soil argillic or kandic horizon above a spodic horizon, and have one properties, whichever is shallower, if there is no or more of the following: densic, lithic, or paralithic contact, duripan, or petrocalcic horizon within that depth; or 1. A spodic horizon, an albic horizon in 50 percent or more of each pedon, and a cryic soil temperature regime; (b) Between either the mineral soil surface or the or top of an organic layer with andic soil properties, whichever is shallower, and a densic, lithic, or 2. An Ap horizon containing 85 percent or more spodic paralithic contact, a duripan, or a petrocalcic materials; or horizon. 3. A spodic horizon with all of the following Spodosols, p. 253 characteristics: D. Other soils that have andic soil properties in 60 percent or a. One or more of the following: more of the thickness either: (1) A thickness of 10 cm or more; or 1. Within 60 cm either of the mineral soil surface or of the (2) An overlying Ap horizon; or top of an organic layer with andic soil properties, whichever is shallower, if there is no densic, lithic, or paralithic contact, (3) Cementation in 50 percent or more of each duripan, or petrocalcic horizon within that depth; or pedon; or 2. Between either the mineral soil surface or the top of an (4) A coarse-loamy, loamy-skeletal, or finer particle- organic layer with andic soil properties, whichever is size class and a frigid temperature regime in the soil; or shallower, and a densic, lithic, or paralithic contact, a duripan, or a petrocalcic horizon. Andisols, p. 83 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 to be organic soil materials. E. Other soils that have either: Identification of the Taxonomic Class of a Soil 39

1. An oxic horizon that has its upper boundary within 150 c. No sulfuric horizon that has its upper boundary within cm of the mineral soil surface and no kandic horizon that has 150 cm of the mineral soil surface. its upper boundary within that depth; or Aridisols, p. 103 2. 40 percent or more (by weight) clay in the fine-earth H. Other soils that have either: fraction between the mineral soil surface and a depth of 18 cm (after mixing) and a kandic horizon that has the 1. An argillic or kandic horizon, but no fragipan, and a base weatherable-mineral properties of an oxic horizon and has its saturation (by sum of cations) of less than 35 percent at one I upper boundary within 100 cm of the mineral soil surface. of the following depths: D Oxisols, p. 237 E a. If the epipedon has a sandy or sandy-skeletal particle- size class throughout, either: F. Other soils that have: (1) 125 cm below the upper boundary of the argillic 1. A layer 25 cm or more thick, with an upper boundary horizon (but no deeper than 200 cm below the mineral within 100 cm of the mineral soil surface, that has either soil surface) or 180 cm below the mineral soil surface, slickensides or wedge-shaped peds that have their long axes whichever is deeper; or tilted 10 to 60 degrees from the horizontal; and (2) At a densic, lithic, paralithic, or petroferric 2. A weighted average of 30 percent or more clay in the contact if shallower; or fine-earth fraction either between the mineral soil surface and b. The shallowest of the following depths: a depth of 18 cm or in an Ap horizon, whichever is thicker, and 30 percent or more clay in the fine-earth fraction of all (1) 125 cm below the upper boundary of the argillic horizons between a depth of 18 cm and either a depth of 50 or kandic horizon; or cm or a densic, lithic, or paralithic contact, a duripan, or a (2) 180 cm below the mineral soil surface; or petrocalcic horizon if shallower; and (3) At a densic, lithic, paralithic, or petroferric 3. Cracks2 that open and close periodically. contact; or Vertisols, p. 285 2. A fragipan and both of the following: G. Other soils that: a. Either an argillic or a kandic horizon above, within, or 1. Have: below it or clay films 1 mm or more thick in one or more of its subhorizons; and a. An aridic soil moisture regime; and b. A base saturation (by sum of cations) of less than b. An ochric or anthropic epipedon; and 35 percent at the shallowest of the following depths: c. One or more of the following with the upper boundary (1) 75 cm below the upper boundary of the fragipan; within 100 cm of the soil surface: a cambic horizon with a or lower depth of 25 cm or more; a cryic temperature regime and a cambic horizon; a calcic, gypsic, petrocalcic, (2) 200 cm below the mineral soil surface; or petrogypsic, or salic horizon; or a duripan; or (3) At a densic, lithic, paralithic, or petroferric d. An argillic or natric horizon; or contact. Ultisols, p. 263 2. Have a salic horizon; and a. Saturation with water in one or more layers within I. Other soils that have both of the following: 100 cm of the soil surface for 1 month or more during a 1. Either: normal year; and a. A mollic epipedon; or b. A moisture control section that is dry in some or all parts at some time during normal years; and b. Both a surface horizon that meets all the requirements for a mollic epipedon except thickness after the soil has been mixed to a depth of 18 cm and a subhorizon more than 7.5 cm thick, within the upper part of an argillic, 2 A crack is a separation between gross polyhedrons. If the surface is strongly self- kandic, or natric horizon, that meets the color, organic- mulching, i.e., a mass of granules, or if the soil is cultivated while cracks are open, the cracks carbon content, base saturation, and structure 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 infiltration requirements of a mollic epipedon but is separated from and percolation of water in a dry, clayey soil. the surface horizon by an albic horizon; and 40

2. A base saturation of 50 percent or more (by NH4OAc) in an upper boundary within 200 cm of the mineral soil all horizons either between the upper boundary of any surface; or argillic, kandic, or natric horizon and a depth of 125 cm d. A sulfuric horizon that has its upper boundary within below that boundary, or between the mineral soil surface and 150 cm of the mineral soil surface; or a depth of 180 cm, or between the mineral soil surface and a densic, lithic, or paralithic contact, whichever depth is e. A cryic temperature regime and a cambic horizon; or shallowest. 2. No sulfidic materials within 50 cm of the mineral soil Mollisols, p. 193 surface; and both: a. In one or more horizons between 20 and 50 cm below J. Other soils that do not have a plaggen epipedon and that the mineral soil surface, either an n value of 0.7 or less or have either: less than 8 percent clay in the fine-earth fraction; and 1. An argillic, kandic, or natric horizon; or b. One or both of the following: 2. A fragipan that has clay films 1 mm or more thick in (1) A salic horizon or a histic, mollic, plaggen, or some part. umbric epipedon; or Alfisols, p. 41 (2) In 50 percent or more of the layers between the K. Other soils that have either: mineral soil surface and a depth of 50 cm, an exchangeable sodium percentage of 15 or more (or a 1. One or more of the following: sodium adsorption ratio of 13 or more), which a. A cambic horizon with its upper boundary within 100 decreases with increasing depth below 50 cm, and also cm of the mineral soil surface and its lower boundary at a ground water within 100 cm of the mineral soil surface depth of 25 cm or more below the mineral soil surface; or at some time during the year when the soil is not frozen in any part. b. A calcic, petrocalcic, gypsic, petrogypsic, or Inceptisols, p. 165 placic horizon or a duripan with an upper boundary within a depth of 100 cm of the mineral soil surface; or L. Other soils. c. A fragipan or an oxic, sombric, or spodic horizon with Entisols, p. 129 41

CHAPTER 5 Alfisols

Key to Suborders JAB. Other Aqualfs that have one or more horizons, at a A depth between 30 and 150 cm from the mineral soil surface, in L JA. Alfisols that have, in one or more horizons within 50 cm which plinthite either forms a continuous phase or constitutes F of the mineral soil surface, aquic conditions (other than one-half or more of the volume. anthraquic conditions) for some time in normal years (or Plinthaqualfs, p. 50 artificial drainage) and have one or both of the following: JAC. Other Aqualfs that have a duripan. 1. Redoximorphic features in all layers between either the Duraqualfs, p. 43 lower boundary of an Ap horizon or a depth of 25 cm below the mineral soil surface, whichever is deeper, and a depth of JAD. Other Aqualfs that have a natric horizon. 40 cm; and one of the following within the upper 12.5 cm of Natraqualfs, p. 49 the argillic, natric, glossic, or kandic horizon: a. 50 percent or more redox depletions with chroma of 2 JAE. Other Aqualfs that have a fragipan with an upper or less on faces of peds and redox concentrations within boundary within 100 cm of the mineral soil surface. peds; or Fragiaqualfs, p. 47 b. Redox concentrations and 50 percent or more JAF. Other Aqualfs that have a kandic horizon. redox depletions with chroma of 2 or less in the matrix; or Kandiaqualfs, p. 48 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 25 cm thick (cumulative) within 100 cm of the mineral soil surface, 2. In the horizons that have aquic conditions, enough active that have 50 percent or more (by volume) recognizable ferrous iron to give a positive reaction to alpha,alpha- bioturbation, such as filled animal burrows, wormholes, or casts. dipyridyl at a time when the soil is not being irrigated. Vermaqualfs, p. 50 Aqualfs, p. 41 JAH. Other Aqualfs that have an abrupt textural change JB. Other Alfisols that have a cryic or isofrigid temperature between the ochric epipedon or the albic horizon and the regime. argillic horizon and have a moderately low or lower saturated Cryalfs, p. 50 hydraulic conductivity in the argillic horizon. Albaqualfs, p. 41 JC. Other Alfisols that have an ustic moisture regime. Ustalfs, p. 65 JAI. Other Aqualfs that have a glossic horizon. Glossaqualfs, p. 48 JD. Other Alfisols that have a xeric moisture regime. Xeralfs, p. 77 JAJ. Other Aqualfs that have episaturation. Epiaqualfs, p. 45 JE. Other Alfisols. Udalfs, p. 54 JAK. Other Aqualfs. Endoaqualfs, p. 43 Aqualfs Albaqualfs

Key to Great Groups Key to Subgroups JAA. Aqualfs that have a cryic temperature regime. JAHA. Albaqualfs that have a sandy or sandy-skeletal Cryaqualfs, p. 43 particle-size class throughout a layer extending from the 42 Keys to Soil Taxonomy

mineral soil surface to the top of an argillic horizon at a depth of 2. A linear extensibility of 6.0 cm or more between the 50 cm 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: JAHE. Other Albaqualfs that have both: 1. One or both: 1. Chroma of 3 or more in 40 percent or more of the matrix a. Cracks within 125 cm of the mineral soil surface that between the lower boundary of the A or Ap horizon and a are 5 mm or more wide through a thickness of 30 cm or depth of 75 cm from the mineral soil surface; and more for some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick 2. A mollic epipedon, an Ap horizon that meets all of the that has its upper boundary within 125 cm of the mineral requirements for a mollic epipedon except thickness, or soil surface; or materials between the soil surface and a depth of 18 cm that meet these requirements after mixing. b. A linear extensibility of 6.0 cm or more between the Udollic Albaqualfs 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 2. Chroma of 3 or more in 40 percent or more of the matrix A or Ap horizon and a depth of 75 cm from the mineral soil between the lower boundary of the A or Ap horizon and a surface. depth of 75 cm from the mineral soil surface. Aeric Albaqualfs Aeric Vertic Albaqualfs JAHG. Other Albaqualfs that have, throughout one or more JAHC. Other Albaqualfs that have 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. 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 are 5 mm or more wide through a thickness of 30 cm or 1 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 aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral 2. More than 35 percent (by volume) fragments coarser soil 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 or a 3. A fine-earth fraction containing 30 percent or more 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. JAHH. Other Albaqualfs that have a mollic epipedon, an Ap Chromic Vertic Albaqualfs horizon that meets all of the requirements for a mollic epipedon except thickness, or materials between the soil surface and a depth of 18 cm that meet these requirements after mixing. JAHD. Other Albaqualfs that have one or both of the Mollic Albaqualfs following: 1. Cracks within 125 cm of the mineral soil surface that are JAHI. Other Albaqualfs that have an umbric epipedon, an Ap 5 mm or more wide through a thickness of 30 cm or more for horizon that meets all of the requirements for an umbric some time in normal years and slickensides or wedge-shaped epipedon except thickness, or materials between the soil surface aggregates in a layer 15 cm or more thick that has its upper and a depth of 18 cm that meet these requirements after mixing. boundary within 125 cm of the mineral soil surface; or Umbric Albaqualfs Alfisols 43

JAHJ. Other Albaqualfs. mineral soil surface and either a depth of 100 cm or a Typic Albaqualfs densic, lithic, or paralithic contact, whichever is shallower; and Cryaqualfs 2. An Ap horizon or materials between the mineral soil surface and a depth of 18 cm that, after mixing, have one or Key to Subgroups more of the following: JAAA. All Cryaqualfs (provisionally). a. A color value, moist, of 4 or more; or Typic Cryaqualfs b. A color value, dry, of 6 or more; or Duraqualfs c. Chroma of 4 or more. A Chromic Vertic Endoaqualfs L Key to Subgroups F JACA. All Duraqualfs (provisionally). JAKC. Other Endoaqualfs that have one or both of the Typic Duraqualfs following: 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-shaped Key to Subgroups aggregates 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 horizons with a total thickness of 18 cm or more within 2. A linear extensibility of 6.0 cm or more between 75 cm of the mineral soil surface, one or more of the the mineral soil surface and either a depth of 100 cm following: or a densic, 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 than 1.0; or JAKD. Other Endoaqualfs that have: 2. More than 35 percent (by volume) fragments coarser 1. Fragic soil properties: than 2.0 mm, of which more than 66 percent is cinders, a. In 30 percent or more of the volume of a layer 15 cm pumice, and pumicelike fragments; or or more thick that has its upper boundary within 100 cm 3. A fine-earth fraction containing 30 percent or more of the mineral soil surface; or particles 0.02 to 2.0 mm in diameter; and b. In 60 percent or more of the volume of a layer 15 cm a. In the 0.02 to 2.0 mm fraction, 5 percent or more or more thick; and volcanic glass; and 2. In one or more horizons between the A or Ap horizon 1 b. [(Al plus /2 Fe, percent extracted by ammonium and a depth of 75 cm below the mineral soil surface, one or a oxalate) times 60] plus the volcanic glass (percent) is combination of the following colors: equal to 30 or more. a. Hue of 7.5YR or redder in 50 percent or more of the Aquandic Endoaqualfs matrix; and JAKB. Other Endoaqualfs that have both of the following: (1) If peds are present, chroma of 2 or more on 50 percent or more of ped exteriors or no redox depletions 1. One or both: with chroma of 2 or less in ped interiors; or a. Cracks within 125 cm of the mineral soil surface that (2) If peds are absent, chroma of 2 or more in 50 are 5 mm or more wide through a thickness of 30 cm or percent or more of the matrix; or more for some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick b. In 50 percent or more of the matrix, hue of 10YR or that has its upper boundary within 125 cm of the mineral yellower and either: soil surface; or (1) Both a color value of 3 or more (moist) and b. A linear extensibility of 6.0 cm or more between the chroma of 3 or more (moist and dry); or 44 Keys to Soil Taxonomy

(2) Chroma of 2 or more if there are no redox 1. An umbric epipedon, an Ap horizon that meets all of the concentrations. requirements for an umbric epipedon except thickness, or Aeric Fragic Endoaqualfs materials between the soil surface and a depth of 18 cm that meet these requirements after mixing; and JAKE. Other Endoaqualfs that have fragic soil properties: 2. In one or more horizons between the A or Ap horizon 1. In 30 percent or more of the volume of a layer 15 cm or and a depth of 75 cm below the mineral soil surface, one or a more thick that has its upper boundary within 100 cm of the combination of the following colors: mineral soil surface; or a. Hue of 7.5YR or redder in 50 percent or more of the 2. In 60 percent or more of the volume of a layer 15 cm or matrix; and more thick. (1) If peds are present, chroma of 2 or more on 50 Fragic Endoaqualfs percent or more of ped exteriors or no redox depletions with chroma of 2 or less in ped interiors; or JAKF. Other Endoaqualfs that have a sandy or sandy-skeletal particle-size class throughout a layer extending from the mineral (2) If peds are absent, chroma of 2 or more in 50 soil surface to the top of an argillic horizon at a depth of 50 to percent or more of the matrix; or 100 cm below the mineral soil surface. b. In 50 percent or more of the matrix, hue of 10YR or Arenic Endoaqualfs yellower and either: JAKG. Other Endoaqualfs that have a sandy or sandy-skeletal (1) Both a color value of 3 or more (moist) and particle-size class throughout a layer extending chroma of 3 or more; or from the mineral soil surface to the top of an argillic (2) Chroma of 2 or more if there are no redox horizon at a depth of 100 cm or more below the mineral soil concentrations. 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 mineral soil surface, in 50 percent or more of the matrix, one or 1. A mollic epipedon, an Ap horizon that meets all of the a combination of the following colors: requirements for a mollic epipedon except thickness, or materials between the soil surface and a depth of 18 cm that 1. Hue of 7.5YR or redder; and meet these requirements after mixing; and a. If peds are present, chroma of 2 or more (both moist 2. In one or more horizons between the A or Ap horizon and dry) on 50 percent or more of ped exteriors or no and a depth of 75 cm below the mineral soil surface, one or a redox depletions with chroma of 2 or less (both moist and combination of the following colors: dry) in ped interiors; or a. Hue of 7.5YR or redder in 50 percent or more of the b. If peds are absent, chroma of 2 or more (both moist matrix; and and dry); or (1) If peds are present, chroma of 2 or more on 50 2. Hue of 10YR or yellower and either: percent or more of ped exteriors or no redox depletions a. Both a color value of 3 or more (moist) and chroma of with chroma of 2 or less in ped interiors; or 3 or more (moist and dry); or (2) If peds are absent, chroma of 2 or more in 50 b. Chroma of 2 or more (both moist and dry) and no percent or more of the matrix; or redox concentrations. b. In 50 percent or more of the matrix, hue of 10YR or Aeric Endoaqualfs yellower and either: JAKK. Other Endoaqualfs that have a mollic epipedon, an Ap (1) Both a color value of 3 or more (moist) and horizon that meets all of the requirements for a mollic epipedon chroma of 3 or more; or except thickness, or materials between the soil surface and a (2) Chroma of 2 or more if there are no redox depth of 18 cm that meet these requirements after mixing. concentrations. Mollic Endoaqualfs Udollic Endoaqualfs JAKL. Other Endoaqualfs that have an umbric epipedon, an JAKI. Other Endoaqualfs that have both: Ap horizon that meets all of the requirements for an umbric Alfisols 45

epipedon except thickness, or materials between the soil surface JAJB. Other Epiaqualfs that have both of the following: and a depth of 18 cm that meet these requirements after mixing. 1. One or both: Umbric Endoaqualfs a. Cracks within 125 cm of the mineral soil surface that JAKM. Other Endoaqualfs. are 5 mm or more wide through a thickness of 30 cm or Typic Endoaqualfs more for some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick Epiaqualfs that has its upper boundary within 125 cm of the mineral soil surface; or Key to Subgroups b. A linear extensibility of 6.0 cm or more between the A JAJA. Epiaqualfs that have all of the following: mineral soil surface and either a depth of 100 cm or a L densic, lithic, or paralithic contact, whichever is 1. One or both: F shallower; and a. Cracks within 125 cm of the mineral soil surface that 2. In one or more horizons between the A or Ap horizon are 5 mm or more wide through a thickness of 30 cm or and a depth of 75 cm below the mineral soil surface, in 50 more for some time in normal years and slickensides or percent or more of the matrix, one or a combination of the wedge-shaped aggregates in a layer 15 cm or more thick following colors: that has its upper boundary within 125 cm of the mineral soil surface; or a. Hue of 7.5YR or redder; and b. A linear extensibility of 6.0 cm or more between the (1) If peds are present, chroma of 2 or more (both mineral soil surface and either a depth of 100 cm or a moist and dry) on 50 percent or more of ped exteriors densic, lithic, or paralithic contact, whichever is or no redox depletions with chroma of 2 or less (both shallower; and moist and dry) in ped interiors; or 2. In one or more horizons between the A or Ap horizon (2) If peds are absent, chroma of 2 or more (both and a depth of 75 cm below the mineral soil surface, in 50 moist and dry); or percent or more of the matrix, one or a combination of the b. Hue of 10YR or yellower and either: following colors: (1) Both a color value of 3 or more (moist) and a. Hue of 7.5YR or redder; and chroma of 3 or more (moist and dry); or (1) If peds are present, chroma of 2 or more (both (2) Chroma of 2 or more (both moist and dry) and no moist and dry) on 50 percent or more of ped exteriors redox concentrations. or no redox depletions with chroma of 2 or less (both Aeric Vertic Epiaqualfs moist and dry) in ped interiors; or (2) If peds are absent, chroma of 2 or more (both JAJC. Other Epiaqualfs that have both of the following: moist and dry); or 1. One or both: b. Hue of 10YR or yellower and either: a. Cracks within 125 cm of the mineral soil surface that (1) Both a color value of 3 or more (moist) are 5 mm or more wide through a thickness of 30 cm or and chroma of 3 or more (moist and dry); or more for some time in normal years and slickensides or (2) Chroma of 2 or more (both moist and dry) and no wedge-shaped aggregates in a layer 15 cm or more thick redox concentrations; and that has its upper boundary within 125 cm of the mineral soil surface; or 3. An Ap horizon or materials between the mineral soil surface and a depth of 18 cm that, after mixing, have one or b. A linear extensibility of 6.0 cm or more between the more of the following: mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is a. A color value, moist, of 4 or more; or shallower; and b. A color value, dry, of 6 or more; or 2. An Ap horizon or materials between the mineral soil c. Chroma of 4 or more. surface and a depth of 18 cm that, after mixing, have one or Aeric Chromic Vertic Epiaqualfs more of the following: 46 Keys to Soil Taxonomy

a. A color value, moist, of 4 or more; or percent or more of the matrix, one or a combination of the following colors: b. A color value, dry, of 6 or more; or a. Hue of 7.5YR or redder; and c. Chroma of 4 or more. Chromic Vertic Epiaqualfs (1) If peds are present, chroma of 2 or more (both moist and dry) on 50 percent or more of ped exteriors or no redox depletions with chroma of 2 or less (both JAJD. Other Epiaqualfs that have one or both of the moist and dry) in ped interiors; or following: (2) If peds are absent, chroma of 2 or more (both 1. Cracks within 125 cm of the mineral soil surface that are moist and dry); or 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge-shaped b. Hue of 10YR or yellower and either: aggregates in a layer 15 cm or more thick that has its upper (1) Both a color value of 3 or more (moist) and boundary within 125 cm of the mineral soil surface; or chroma of 3 or more (moist and dry); or 2. A linear extensibility of 6.0 cm or more between the (2) Chroma of 2 or more (both moist and dry) and no mineral soil surface and either a depth of 100 cm or a densic, redox concentrations. lithic, or paralithic contact, whichever is shallower. Aeric Fragic Epiaqualfs Vertic Epiaqualfs JAJG. Other Epiaqualfs that have fragic soil properties: JAJE. Other Epiaqualfs that have, throughout one or more horizons with a total thickness of 18 cm or more within 1. In 30 percent or more of the volume of a layer 15 cm or 75 cm of the mineral soil surface, one or more of the more thick that has its upper boundary within 100 cm of the following: mineral soil surface; or 1. A fine-earth fraction with both a bulk density of 1.0 2. In 60 percent or more of the volume of a layer 15 cm or g/cm3 or less, measured at 33 kPa water retention, and Al more thick. 1 plus /2 Fe percentages (by ammonium oxalate) totaling more Fragic Epiaqualfs than 1.0; or JAJH. Other Epiaqualfs that have a sandy or sandy-skeletal 2. More than 35 percent (by volume) fragments coarser particle-size class throughout a layer extending from the mineral than 2.0 mm, of which more than 66 percent is cinders, soil surface to the top of an argillic horizon at a depth of 50 to pumice, and pumicelike fragments; or 100 cm below the mineral soil surface. 3. A fine-earth fraction containing 30 percent or more Arenic Epiaqualfs particles 0.02 to 2.0 mm in diameter; and JAJI. Other Epiaqualfs that have a sandy or sandy-skeletal a. In the 0.02 to 2.0 mm fraction, 5 percent or more particle-size class throughout a layer extending from the mineral volcanic glass; and soil surface to the top of an argillic horizon at a depth of 100 cm 1 b. [(Al plus /2 Fe, percent extracted by ammonium or more below the mineral soil surface. oxalate) times 60] plus the volcanic glass (percent) is Grossarenic Epiaqualfs equal to 30 or more. Aquandic Epiaqualfs JAJJ. Other Epiaqualfs that have: 1. An umbric epipedon, an Ap horizon that meets all of the JAJF. Other Epiaqualfs that have: requirements for an umbric epipedon except thickness, or 1. Fragic soil properties: materials between the soil surface and a depth of 18 cm that meet these requirements after mixing; 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 2. In one or more horizons between the A or Ap horizon of the mineral soil surface; or and a depth of 75 cm below the mineral soil surface, in 50 percent or more of the matrix, one or a combination of the b. In 60 percent or more of the volume of a layer 15 cm following colors: or more thick; and a. 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, in 50 (1) If peds are present, chroma of 2 or more (both Alfisols 47

moist and dry) on 50 percent or more of ped exteriors 2. Hue of 10YR or yellower and either: or no redox depletions with chroma of 2 or less (both a. Both a color value of 3 or more (moist) and chroma of moist and dry) in ped interiors; or 3 or more (moist and dry); or (2) If peds are absent, chroma of 2 or more (both b. Chroma of 2 or more (both moist and dry) and no moist and dry); or redox concentrations. b. Hue of 10YR or yellower and either: Aeric Epiaqualfs (1) Both a color value of 3 or more (moist) and JAJM. Other Epiaqualfs that have a mollic epipedon, an Ap chroma of 3 or more (moist and dry); or horizon that meets all of the requirements for a mollic epipedon (2) Chroma of 2 or more (both moist and dry) and no except thickness, or materials between the soil surface and a A redox concentrations. depth of 18 cm that meet these requirements after mixing. L Aeric Umbric Epiaqualfs Mollic Epiaqualfs F

JAJK. Other Epiaqualfs that have both: JAJN. Other Epiaqualfs that have an umbric epipedon, an Ap horizon that meets all of the requirements for an umbric 1. A mollic epipedon, an Ap horizon that meets all of the epipedon except thickness, or materials between the soil surface requirements for a mollic epipedon except thickness, or and a depth of 18 cm that meet these requirements after mixing. materials between the soil surface and a depth of 18 cm that Umbric Epiaqualfs meet these requirements after mixing; and 2. In 50 percent or more of the matrix in one or more JAJO. Other Epiaqualfs. horizons between the A or Ap horizon and a depth of 75 cm Typic Epiaqualfs below the mineral soil surface, one or a combination of the following colors: Fragiaqualfs a. Hue of 7.5YR or redder; and Key to Subgroups (1) If peds are present, chroma of 2 or more on 50 JAEA. Fragiaqualfs that have one or more layers, at least 25 percent or more of ped exteriors or no redox depletions cm thick (cumulative) within 100 cm of the mineral soil surface, with chroma of 2 or less in ped interiors; or that have 25 percent or more (by volume) recognizable (2) If peds are absent, chroma of 2 or more in 50 bioturbation, such as filled animal burrows, wormholes, or casts. percent or more of the matrix; or Vermic Fragiaqualfs b. Hue of 10YR or yellower and either: JAEB. Other Fragiaqualfs that have, between the A or Ap (1) Both a color value of 3 or more (moist) and horizon and a fragipan, a horizon with 50 percent or more chroma of 3 or more; or chroma of 3 or more if hue is 10YR or redder or of 4 or more if hue is 2.5Y or yellower. (2) Chroma of 2 or more if there are no redox Aeric Fragiaqualfs concentrations. Udollic Epiaqualfs JAEC. Other Fragiaqualfs that have 5 percent or more (by volume) plinthite in one or more horizons within 150 cm of the JAJL. Other Epiaqualfs that have, in one or more horizons mineral soil surface. between the A or Ap horizon and a depth of 75 cm below the Plinthic Fragiaqualfs mineral soil surface, in 50 percent or more of the matrix, one or a combination of the following colors: JAED. Other Fragiaqualfs that have an Ap horizon with a 1. Hue of 7.5YR or redder; and color value, moist, of 3 or less and a color value, dry, of 5 or less (crushed and smoothed sample) or materials between the a. If peds are present, chroma of 2 or more (both moist soil surface and a depth of 18 cm that have these color values and dry) on 50 percent or more of ped exteriors or no after mixing. redox depletions with chroma of 2 or less (both moist and Humic Fragiaqualfs dry) in ped interiors; or b. If peds are absent, chroma of 2 or more (both moist JAEE. Other Fragiaqualfs. and dry); or Typic Fragiaqualfs 48 Keys to Soil Taxonomy

Glossaqualfs mineral soil surface, in 50 percent or more of the matrix, one or a combination of the following colors: Key to Subgroups 1. Hue of 7.5YR or redder; and JAIA. Glossaqualfs that have a histic epipedon. a. If peds are present, chroma of 2 or more (both moist Histic Glossaqualfs and dry) on 50 percent or more of ped exteriors or no redox depletions with chroma of 2 or less (both moist and JAIB. Other Glossaqualfs that have a sandy or sandy-skeletal dry) in ped interiors; or particle-size class throughout a layer extending from the mineral soil surface to the top of an argillic horizon at a depth of 50 cm b. If peds are absent, chroma of 2 or more (both moist or more below the mineral soil surface. and dry); or Arenic Glossaqualfs 2. Hue of 10YR or yellower and either: JAIC. Other Glossaqualfs that have: 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, an Ap or more thick; and horizon that meets all of the requirements for a mollic epipedon except thickness, or materials between the soil surface and a 2. In one or more horizons between the A or Ap horizon depth of 18 cm that meet these requirements after mixing. and a depth of 75 cm below the mineral soil surface, one or a Mollic Glossaqualfs combination of the following colors: a. Hue of 7.5YR or redder in 50 percent or more of the JAIG. Other Glossaqualfs. matrix; and Typic Glossaqualfs (1) If peds are present, chroma of 2 or more on 50 percent or more of ped exteriors or no redox depletions Kandiaqualfs with chroma of 2 or less in ped interiors; or Key to Subgroups (2) If peds are absent, chroma of 2 or more in 50 JAFA. Kandiaqualfs that have a sandy or sandy-skeletal percent or more of the matrix; or particle-size class throughout a layer extending from the mineral b. In 50 percent or more of the matrix, hue of 10YR or soil surface to the top of a kandic horizon at a depth of 50 to yellower and either: 100 cm below the mineral soil surface. Arenic Kandiaqualfs (1) Both a color value of 3 or more (moist) and chroma of 3 or more (moist and dry); or JAFB. Other Kandiaqualfs that have a sandy or sandy-skeletal (2) Chroma of 2 or more if there are no redox particle-size class throughout a layer extending from the mineral concentrations. soil surface to the top of a kandic horizon at a depth of 100 cm Aeric Fragic Glossaqualfs or more below the mineral soil surface. Grossarenic Kandiaqualfs JAID. Other Glossaqualfs that have fragic soil properties: JAFC. Other Kandiaqualfs that have 5 percent or more (by 1. In 30 percent or more of the volume of a layer 15 cm or volume) plinthite in one or more horizons within 150 cm of the more thick that has its upper boundary within 100 cm of the mineral soil surface. mineral soil surface; or Plinthic Kandiaqualfs 2. In 60 percent or more of the volume of a layer 15 cm or JAFD. Other Kandiaqualfs that have both: more thick. Fragic Glossaqualfs 1. An Ap horizon with a color value, moist, of 3 or less and a color value, dry, of 5 or less (crushed and smoothed JAIE. Other Glossaqualfs that have, in one or more horizons sample) or materials between the soil surface and a depth of between the A or Ap horizon and a depth of 75 cm below the 18 cm that have these color values after mixing; and Alfisols 49

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

JAFG. Other Kandiaqualfs. JADG. Other Natraqualfs. Typic Kandiaqualfs Typic Natraqualfs 50 Keys to Soil Taxonomy

Plinthaqualfs Glossocryalfs

Key to Subgroups Key to Subgroups JABA. All Plinthaqualfs (provisionally). JBBA. Glossocryalfs that have a lithic contact within 50 cm of Typic Plinthaqualfs the mineral soil surface. Lithic Glossocryalfs Vermaqualfs JBBB. Other Glossocryalfs that have one or both of the Key to Subgroups following: JAGA. Vermaqualfs that have an exchangeable sodium 1. Cracks within 125 cm of the mineral soil surface that are percentage of 7 or more (or a sodium adsorption ratio of 6 or 5 mm or more wide through a thickness of 30 cm or more for more) either or both: some time in normal years and slickensides or wedge-shaped 1. Throughout the upper 15 cm of the argillic horizon; aggregates in a layer 15 cm or more thick that has its upper and/or boundary within 125 cm of the mineral soil surface; or 2. Throughout all horizons within 40 cm of the mineral soil 2. A linear extensibility of 6.0 cm or more between surface. the mineral soil surface and either a depth of 100 cm Natric Vermaqualfs or a densic, lithic, or paralithic contact, whichever is shallower. JAGB. Other Vermaqualfs. Vertic Glossocryalfs Typic Vermaqualfs JBBC. Other Glossocryalfs that have, throughout one or more Cryalfs 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 Key to Great Groups 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 JBA. Cryalfs that have all of the following: more than 1.0. Andic Glossocryalfs 1. An argillic, kandic, or natric horizon that has its upper boundary 60 cm or more below both: JBBD. Other Glossocryalfs that have, throughout one or more a. The mineral soil surface; and horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the b. The lower boundary of any surface mantle containing following: 30 percent or more vitric volcanic ash, cinders, or other vitric pyroclastic materials; and 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, 2. A texture (in the fine-earth fraction) finer than loamy fine pumice, and pumicelike fragments; or sand in one or more horizons above the argillic, kandic, or natric horizon; and 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and 3. Either a glossic horizon or interfingering of albic materials into the argillic, kandic, or natric horizon. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Palecryalfs, p. 53 volcanic glass; and

1 b. [(Al plus /2 Fe, percent extracted by ammonium JBB. Other Cryalfs that have a glossic horizon. oxalate) times 60] plus the volcanic glass (percent) is Glossocryalfs, p. 50 equal to 30 or more. Vitrandic Glossocryalfs JBC. Other Cryalfs. Haplocryalfs, p. 51 JBBE. Other Glossocryalfs that have, in one or more Alfisols 51

subhorizons within the upper 25 cm of the argillic, kandic, or smoothed sample) or materials between the soil surface and a natric horizon, redox depletions with chroma of 2 or less depth of 18 cm that have these color values after mixing; and and also aquic conditions for some time in normal years 3. Have a base saturation of 50 percent or more (by (or artificial drainage). NH OAc) in all parts from the mineral soil surface to a depth Aquic Glossocryalfs 4 of 180 cm or to a densic, lithic, or paralithic contact, whichever is shallower. JBBF. Other Glossocryalfs that are saturated with water in one Ustollic Glossocryalfs or more layers within 100 cm of the mineral soil surface in normal years for either or both: JBBK. Other Glossocryalfs that have a xeric moisture regime. 1. 20 or more consecutive days; or Xeric Glossocryalfs A 2. 30 or more cumulative days. L JBBL. Other Glossocryalfs that are dry in some part of the Oxyaquic Glossocryalfs F moisture control section for 45 or more days (cumulative) in normal years. JBBG. Other Glossocryalfs that have fragic soil properties: Ustic Glossocryalfs 1. In 30 percent or more of the volume of a layer 15 cm or JBBM. Other Glossocryalfs that: more thick that has its upper boundary within 100 cm of the mineral soil surface; or 1. Have an Ap horizon with a color value, moist, of 3 or less and a color value, dry, of 5 or less (crushed and 2. In 60 percent or more of the volume of a layer 15 cm or smoothed sample) or materials between the soil surface and a more thick. depth of 18 cm that have these color values after mixing; and Fragic Glossocryalfs 2. Have a base saturation of 50 percent or more (by

JBBH. Other Glossocryalfs that have: NH4OAc) in all parts from the mineral soil surface to a depth of 180 cm or to a densic, lithic, or paralithic contact, 1. A xeric moisture regime; and whichever is shallower. 2. An Ap horizon with a color value, moist, of 3 or Mollic Glossocryalfs less and a color value, dry, of 5 or less (crushed and smoothed sample) or materials between the soil surface JBBN. Other Glossocryalfs that have an Ap horizon with a and a depth of 18 cm that have these color values after color value, moist, of 3 or less and a color value, dry, of 5 or mixing; and less (crushed and smoothed sample) or materials between the soil surface and a depth of 18 cm that have these color values 3. A base saturation of 50 percent or more (by NH OAc) in 4 after mixing. all parts from the mineral soil surface to a depth of 180 cm or Umbric Glossocryalfs to a densic, lithic, or paralithic contact, whichever is shallower. JBBO. Other Glossocryalfs that have a base saturation of 50 Xerollic Glossocryalfs percent or more (by NH4OAc) in all parts from the mineral soil surface to a depth of 180 cm or to a densic, lithic, or paralithic JBBI. Other Glossocryalfs that have: contact, whichever is shallower. 1. A xeric moisture regime; and Eutric Glossocryalfs 2. An Ap horizon with a color value, moist, of 3 or JBBP. Other Glossocryalfs. less and a color value, dry, of 5 or less (crushed and Typic Glossocryalfs smoothed sample) or materials between the soil surface and a depth of 18 cm that have these color values after mixing. Haplocryalfs Umbric Xeric Glossocryalfs Key to Subgroups JBBJ. Other Glossocryalfs that: JBCA. Haplocryalfs that have a lithic contact within 50 cm of the mineral soil surface. 1. Are dry in some part of the moisture control section for Lithic Haplocryalfs 45 or more days (cumulative) in normal years; and 2. Have an Ap horizon with a color value, moist, of 3 or JBCB. Other Haplocryalfs that have one or both of the less and a color value, dry, of 5 or less (crushed and following: 52 Keys to Soil Taxonomy

1. Cracks within 125 cm of the mineral soil surface that are 2. Is a combination of two or more lamellae and one or 5 mm or more wide through a thickness of 30 cm or more for more subhorizons with a thickness of 7.5 to 20 cm, each layer some time in normal years and slickensides or wedge-shaped with an overlying eluvial horizon; or aggregates in a layer 15 cm or more thick that has its upper 3. Consists of one or more subhorizons that are more than boundary within 125 cm of the mineral soil surface; or 20 cm thick, each with an overlying eluvial horizon, and 2. A linear extensibility of 6.0 cm or more between above these horizons there are either: the mineral soil surface and either a depth of 100 cm a. Two or more lamellae with a combined thickness of 5 or a densic, lithic, or paralithic contact, whichever is cm or more (that may or may not be part of the argillic shallower. horizon); or Vertic Haplocryalfs b. A combination of lamellae (that may or may not be JBCC. Other Haplocryalfs that have, throughout one or more part of the argillic horizon) and one or more parts of the horizons with a total thickness of 18 cm or more within 75 cm of argillic horizon 7.5 to 20 cm thick, each with an overlying the mineral soil surface, a fine-earth fraction with both a bulk eluvial horizon. density of 1.0 g/cm3 or less, measured at 33 kPa water retention, Lamellic Haplocryalfs 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. JBCH. Other Haplocryalfs that have a sandy or sandy-skeletal Andic Haplocryalfs particle-size class throughout the upper 75 cm of the argillic, kandic, or natric horizon or throughout the entire argillic, JBCD. Other Haplocryalfs that have, throughout one or kandic, or natric horizon if it is less than 75 cm thick. more horizons with a total thickness of 18 cm or more Psammentic Haplocryalfs within 75 cm of the mineral soil surface, one or both of the following: JBCI. Other Haplocryalfs that have: 1. More than 35 percent (by volume) fragments 1. An argillic, kandic, or natric horizon that is 35 cm or less coarser than 2.0 mm, of which more than 66 percent thick; and is cinders, pumice, and pumicelike fragments; or 2. No densic, lithic, or paralithic contact within 100 cm of 2. A fine-earth fraction containing 30 percent or more the mineral soil surface. particles 0.02 to 2.0 mm in diameter; and Inceptic Haplocryalfs a. In the 0.02 to 2.0 mm fraction, 5 percent or more JBCJ. Other Haplocryalfs that have: volcanic glass; and

1 1. A xeric moisture regime; and b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 2. An Ap horizon with a color value, moist, of 3 or less and equal to 30 or more. a color value, dry, of 5 or less (crushed and smoothed Vitrandic Haplocryalfs sample) or materials between the soil surface and a depth of 18 cm that have these color values after mixing; and JBCE. Other Haplocryalfs that have, in one or more horizons 3. A base saturation of 50 percent or more (by NH OAc) in within 75 cm of the mineral soil surface, redox depletions with 4 all parts from the mineral soil surface to a depth of 180 cm or chroma of 2 or less and also aquic conditions for some time in to a densic, lithic, or paralithic contact, whichever is normal years (or artificial drainage). shallower. Aquic Haplocryalfs Xerollic Haplocryalfs JBCF. Other Haplocryalfs that are saturated with water in one JBCK. Other Haplocryalfs that have: or more layers within 100 cm of the mineral soil surface in normal years for either or both: 1. A xeric moisture regime; and 1. 20 or more consecutive days; or 2. An Ap horizon with a color value, moist, of 3 or less and a color value, dry, of 5 or less (crushed and smoothed 2. 30 or more cumulative days. sample) or materials between the soil surface and a depth of Oxyaquic Haplocryalfs 18 cm that have these color values after mixing. Umbric Xeric Haplocryalfs JBCG. Other Haplocryalfs that have an argillic horizon that: 1. Consists entirely of lamellae; or JBCL. Other Haplocryalfs that: Alfisols 53

1. Are dry in some part of the moisture control section for mineral soil surface, a fine-earth fraction with both a bulk 45 or more days (cumulative) in normal years; and 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 2. Have an Ap horizon with a color value, moist, of 3 or more than 1.0. less and a color value, dry, of 5 or less (crushed and Andic Palecryalfs smoothed sample) or materials between the soil surface and a depth of 18 cm that have these color values after mixing; and JBAB. Other Palecryalfs that have, throughout one or 3. Have a base saturation of 50 percent or more (by more horizons with a total thickness of 18 cm or more within 75

NH4OAc) in all parts from the mineral soil surface to a depth cm of the mineral soil surface, one or both of the of 180 cm or to a densic, lithic, or paralithic contact, following: whichever is shallower. A 1. More than 35 percent (by volume) fragments coarser Ustollic Haplocryalfs L than 2.0 mm, of which more than 66 percent is cinders, F pumice, and pumicelike fragments; or JBCM. Other Haplocryalfs that have a xeric moisture regime. Xeric Haplocryalfs 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and JBCN. Other Haplocryalfs that are dry in some part of the a. In the 0.02 to 2.0 mm fraction, 5 percent or more moisture control section for 45 or more days (cumulative) in volcanic glass; and normal years. 1 Ustic Haplocryalfs b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is JBCO. Other Haplocryalfs that: equal to 30 or more. Vitrandic Palecryalfs 1. Have an Ap horizon with a color value, moist, of 3 or less and a color value, dry, of 5 or less (crushed and JBAC. Other Palecryalfs that have, in one or more horizons smoothed sample) or materials between the soil surface and a within 100 cm of the mineral soil surface, redox depletions with depth of 18 cm that have these color values after mixing; and chroma of 2 or less and also aquic conditions for some time in 2. Have a base saturation of 50 percent or more (by normal years (or artificial drainage).

NH4OAc) in all parts from the mineral soil surface to a depth Aquic Palecryalfs of 180 cm or to a densic, lithic, or paralithic contact, whichever is shallower. JBAD. Other Palecryalfs that are saturated with water in one Mollic Haplocryalfs or more layers within 100 cm of the mineral soil surface in normal years for either or both: JBCP. Other Haplocryalfs that have an Ap horizon with a 1. 20 or more consecutive days; or color value, moist, of 3 or less and a color value, dry, of 5 or less (crushed and smoothed sample) or materials between the 2. 30 or more cumulative days. soil surface and a depth of 18 cm that have these color values Oxyaquic Palecryalfs after mixing. Umbric Haplocryalfs JBAE. Other Palecryalfs that have a xeric moisture regime. Xeric Palecryalfs JBCQ. Other Haplocryalfs that have a base saturation of 50 percent or more (by NH OAc) in all parts from the mineral soil 4 JBAF. Other Palecryalfs that are dry in some part of the surface to a depth of 180 cm or to a densic, lithic, or paralithic moisture control section for 45 or more days (cumulative) in contact, whichever is shallower. normal years. Eutric Haplocryalfs Ustic Palecryalfs JBCR. Other Haplocryalfs. JBAG. Other Palecryalfs that: Typic Haplocryalfs 1. Have an Ap horizon with a color value, moist, of 3 or Palecryalfs less and a color value, dry, of 5 or less (crushed and smoothed sample) or materials between the soil surface and a Key to Subgroups depth of 18 cm that have these color values after mixing; and JBAA. Palecryalfs that have, throughout one or more horizons 2. Have a base saturation of 50 percent or more (by with a total thickness of 18 cm or more within 75 cm of the NH4OAc) in all parts from the mineral soil surface to a depth 54 Keys to Soil Taxonomy

of 180 cm or to a densic, lithic, or paralithic contact, the following formula: Clay % = 2.5(% water retained at whichever is shallower. 1500 kPa tension - % organic carbon), whichever value is Mollic Palecryalfs greater, but no more than 100]; or b. Have 5 percent or more (by volume) skeletans on JBAH. Other Palecryalfs that have an Ap horizon with a color faces of peds in the layer that has a 20 percent lower clay value, moist, of 3 or less and a color value, dry, of 5 or less content and, below that layer, a clay increase of 3 percent (crushed and smoothed sample) or materials between the soil or more (absolute) in the fine-earth fraction. surface and a depth of 18 cm that have these color values after Kandiudalfs, p. 61 mixing. Umbric Palecryalfs JEF. Other Udalfs that have a kandic horizon. JBAI. Other Palecryalfs. Kanhapludalfs, p. 62 Typic Palecryalfs JEG. Other Udalfs that: Udalfs 1. Do not have a densic, lithic, or paralithic contact within Key to Great Groups 150 cm of the mineral soil surface; and 2. Within 150 cm of the mineral soil surface, either: JEA. Udalfs that have a natric horizon. Natrudalfs, p. 62 a. Do not have a clay decrease with increasing depth of 20 percent or more (relative) from the maximum clay JEB. Other Udalfs that have: content [Clay is measured noncarbonate clay or based on the following formula: Clay % = 2.5(% water retained at 1. A glossic horizon; and 1500 kPa tension - % organic carbon), whichever value is 2. In the argillic or kandic horizon, discrete nodules, 2.5 to greater, but no more than 100]; or 30 cm in diameter, that: b. Have 5 percent or more (by volume) skeletans on a. Are enriched with iron and extremely weakly faces of peds in the layer that has a 20 percent lower clay cemented to indurated; and content and, below that layer, a clay increase of 3 percent or more (absolute) in the fine-earth fraction; and b. Have exteriors with either a redder hue or a higher chroma than the interiors. 3. Have an argillic horizon with one or more of the Ferrudalfs, p. 55 following: JEC. Other Udalfs that have both: 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 1. A glossic horizon; and and chroma of 5 or more; or 2. A fragipan with an upper boundary within 100 cm of the b. In 50 percent or more of the matrix of horizons that mineral soil surface. total more than one-half the total thickness, hue of 2.5YR Fraglossudalfs, p. 55 or redder, value, moist, of 3 or less, and value, dry, of 4 or less; or JED. Other Udalfs that have a fragipan with an upper boundary within 100 cm of the mineral soil surface. c. Many coarse redox concentrations with hue of 5YR or Fragiudalfs, p. 55 redder or chroma of 6 or more, or both, in one or more subhorizons; or JEE. Other Udalfs that: 4. Have a frigid temperature regime and all of the 1. Do not have a densic, lithic, paralithic, or petroferric following: contact within 150 cm of the mineral soil surface; and a. An argillic horizon that has its upper boundary 60 cm 2. Have a kandic horizon; and or more below both: 3. Within 150 cm of the mineral soil surface, either: (1) The mineral soil surface; and a. Do not have a clay decrease with increasing depth of (2) The lower boundary of any surface mantle 20 percent or more (relative) from the maximum clay containing 30 percent or more vitric volcanic ash, content [Clay is measured noncarbonate clay or based on cinders, or other vitric pyroclastic materials; and Alfisols 55

b. A texture (in the fine-earth fraction) finer than loamy than 2.0 mm, of which more than 66 percent is cinders, fine sand in one or more horizons above the argillic pumice, and pumicelike fragments; or horizon; and 2. A fine-earth fraction containing 30 percent or more c. Either a glossic horizon or interfingering of albic particles 0.02 to 2.0 mm in diameter; and materials into the argillic horizon. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Paleudalfs, p. 63 volcanic glass; and

1 JEH. Other Udalfs that have, in all subhorizons in the upper b. [(Al plus /2 Fe, percent extracted by ammonium 100 cm of the argillic horizon or throughout the entire argillic oxalate) times 60] plus the volcanic glass (percent) is horizon if less than 100 cm thick, more than 50 percent colors equal to 30 or more. A that have all of the following: Vitrandic Fragiudalfs L 1. Hue of 2.5YR or redder; and F JEDC. Other Fragiudalfs that have, in one or more horizons 2. Value, moist, of 3 or less; and within 40 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in 3. Dry value no more than 1 unit higher than the moist normal years (or artificial drainage). value. Aquic Fragiudalfs Rhodudalfs, p. 65 JEDD. Other Fragiudalfs that are saturated with water in one JEI. Other Udalfs that have a glossic horizon. or more layers above the fragipan in normal years for either or Glossudalfs, p. 56 both: JEJ. Other Udalfs. 1. 20 or more consecutive days; or Hapludalfs, p. 58 2. 30 or more cumulative days. Oxyaquic Fragiudalfs Ferrudalfs JEDE. Other Fragiudalfs. Key to Subgroups Typic Fragiudalfs JEBA. Ferrudalfs that have, in one or more horizons within 60 cm of the mineral soil surface, redox depletions with chroma of Fraglossudalfs 2 or less and also aquic conditions for some time in normal Key to Subgroups years (or artificial drainage). Aquic Ferrudalfs JECA. Fraglossudalfs that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of JEBB. Other Ferrudalfs. the mineral soil surface, a fine-earth fraction with both a bulk Typic Ferrudalfs 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 Fragiudalfs more than 1.0. 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 of with a total thickness of 18 cm or more within 75 cm of the the mineral soil surface, one or both of the following: 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. More than 35 percent (by volume) fragments coarser 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling than 2.0 mm, of which more than 66 percent is cinders, more than 1.0. pumice, and pumicelike fragments; or 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 horizons with a total thickness of 18 cm or more within 75 cm of a. In the 0.02 to 2.0 mm fraction, 5 percent or more the mineral soil surface, one or both of the following: volcanic glass; and

1 1. More than 35 percent (by volume) fragments coarser b. [(Al plus /2 Fe, percent extracted by ammonium 56 Keys to Soil Taxonomy

oxalate) times 60] plus the volcanic glass (percent) is cm of the mineral soil surface in normal years for either or equal to 30 or more. both: Vitrandic Fraglossudalfs a. 20 or more consecutive days; or JECC. Other Fraglossudalfs that have, in one or more b. 30 or more cumulative days; and subhorizons within the upper 25 cm of the argillic or kandic 2. One or both of the following: horizon, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial a. Cracks within 125 cm of the mineral soil surface that drainage). are 5 mm or more wide through a thickness of 30 cm or Aquic Fraglossudalfs more for some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick JECD. Other Fraglossudalfs that are saturated with water in that has its upper boundary within 125 cm of the mineral one or more layers above the fragipan in normal years for either soil surface; or or both: b. A linear extensibility of 6.0 cm or more between the 1. 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. 2. 30 or more cumulative days. Oxyaquic Vertic Glossudalfs Oxyaquic Fraglossudalfs

JECE. Other Fraglossudalfs. JEIC. Other Glossudalfs that have one or both of the Typic Fraglossudalfs following: 1. Cracks within 125 cm of the mineral soil surface that are Glossudalfs 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge-shaped Key to Subgroups aggregates in a layer 15 cm or more thick that has its upper JEIA. Glossudalfs that have both: boundary within 125 cm of the mineral soil surface; or 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 aggregates in a layer 15 cm or more thick JEID. Other Glossudalfs that have both: that 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 less b. A linear extensibility of 6.0 cm or more between the and also aquic conditions for some time in normal years (or mineral soil surface and either a depth of 100 cm or a artificial drainage); and 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 that one or more of the following: 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 its 1 plus /2 Fe percentages (by ammonium oxalate) totaling upper boundary is within 50 cm of the mineral soil more than 1.0; or surface; or b. More than 35 percent (by volume) fragments coarser b. Within 75 cm of the mineral soil surface if the upper than 2.0 mm, of which more than 66 percent is cinders, boundary of the argillic horizon is 50 cm or more below pumice, and pumicelike fragments; or the mineral soil surface. 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 Alfisols 57

1 (2) [(Al plus /2 Fe, percent extracted by ammonium also aquic conditions for some time in normal years (or oxalate) times 60] plus the volcanic glass (percent) is artificial drainage); and equal to 30 or more. 2. A sandy or sandy-skeletal particle-size class throughout a Aquandic Glossudalfs layer extending from the mineral soil surface to the top of the argillic horizon at a depth of 50 cm or more below the JEIE. Other Glossudalfs that have, throughout one or more mineral soil surface. horizons with a total thickness of 18 cm or more within 75 cm of Aquic Arenic Glossudalfs 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 JEII. Other Glossudalfs that have, in one or more subhorizons and Al plus /2 Fe percentages (by ammonium oxalate) totaling within the upper 25 cm of the argillic horizon, redox depletions more than 1.0. A with chroma of 2 or less and also aquic conditions for some time Andic Glossudalfs L in normal years (or artificial drainage). F Aquic Glossudalfs JEIF. Other Glossudalfs that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of JEIJ. Other Glossudalfs that have both: the mineral soil surface, one or both of the following: 1. Saturation with water in one or more layers within 100 1. More than 35 percent (by volume) fragments coarser cm of the mineral soil surface in normal years for either or than 2.0 mm, of which more than 66 percent is cinders, both: pumice, and pumicelike fragments; or a. 20 or more consecutive days; or 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and b. 30 or more cumulative days; and a. In the 0.02 to 2.0 mm fraction, 5 percent or more 2. A sandy or sandy-skeletal particle-size class throughout a volcanic glass; and layer extending from the mineral soil surface to the top of the

1 argillic horizon at a depth of 50 cm or more below the b. [(Al plus /2 Fe, percent extracted by ammonium mineral soil surface. oxalate) times 60] plus the volcanic glass (percent) is Arenic Oxyaquic Glossudalfs equal to 30 or more. Vitrandic Glossudalfs JEIK. Other Glossudalfs that are saturated with water in one or more layers within 100 cm of the mineral soil surface in JEIG. Other Glossudalfs that have both: 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 2. 30 or more cumulative days. or more thick that has its upper boundary within 100 cm Oxyaquic Glossudalfs of the mineral soil surface; or b. In 60 percent or more of the volume of a layer 15 cm 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 that more thick that has its upper boundary within 100 cm of the 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 its more thick. upper boundary is within 50 cm of the mineral soil Fragic Glossudalfs surface; or JEIM. Other Glossudalfs that have a sandy or sandy-skeletal b. Within 75 cm of the mineral soil surface if the upper particle-size class throughout a layer extending from the mineral boundary of the argillic horizon is 50 cm or more below soil surface to the top of an argillic horizon at a depth of 50 cm the mineral soil surface. or more below the mineral soil surface. Fragiaquic Glossudalfs Arenic Glossudalfs JEIH. Other Glossudalfs that have both: 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, redox depletions with chroma of 2 or less and Haplic Glossudalfs 58 Keys to Soil Taxonomy

JEIO. Other Glossudalfs. b. A linear extensibility of 6.0 cm or more between the Typic Glossudalfs mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower; and Hapludalfs 2. Redox depletions with chroma of 2 or less in layers that Key to Subgroups also have aquic conditions in normal years (or artificial drainage) either: JEJA. Hapludalfs that have a lithic contact within 50 cm of the mineral soil surface. a. Within the upper 25 cm of the argillic horizon if its Lithic Hapludalfs upper boundary is within 50 cm of the mineral soil surface; or JEJB. Other Hapludalfs that have all of the following: b. Within 75 cm of the mineral soil surface if the upper 1. One or both of the following: boundary of the argillic horizon is 50 cm or more below the mineral soil surface. a. Cracks within 125 cm of the mineral soil surface that Aquertic Hapludalfs are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or JEJD. Other Hapludalfs that have both: wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral 1. Saturation with water in one or more layers within 100 soil surface; or cm of the mineral soil surface in normal years for either or both: 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. 20 or more consecutive days; or densic, lithic, or paralithic contact, whichever is b. 30 or more cumulative days; and shallower; and 2. One or both of the following: 2. Redox depletions with chroma of 2 or less in layers that also have aquic conditions in normal years (or artificial a. Cracks within 125 cm of the mineral soil surface that drainage) either: are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or a. Within the upper 25 cm of the argillic horizon if its wedge-shaped aggregates in a layer 15 cm or more thick upper boundary is within 50 cm of the mineral soil that has its upper boundary within 125 cm of the mineral surface; or soil surface; or b. Within 75 cm of the mineral soil surface if the upper b. A linear extensibility of 6.0 cm or more between the boundary of the argillic horizon is 50 cm or more below mineral soil surface and either a depth of 100 cm or a the mineral soil surface; and densic, lithic, or paralithic contact, whichever is shallower. 3. An Ap horizon or materials between the mineral soil Oxyaquic Vertic Hapludalfs surface and a depth of 18 cm that, after mixing, have one or more of the following: JEJE. Other Hapludalfs that have both: a. A color value, moist, of 4 or more; or 1. One or both of the following: b. A color value, dry, of 6 or more; 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 c. Chroma of 4 or more. more for some time in normal years and slickensides or Aquertic Chromic Hapludalfs wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral JEJC. Other Hapludalfs that have both: soil surface; or 1. One or both 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. Cracks within 125 cm of the mineral soil surface that densic, lithic, or paralithic contact, whichever is are 5 mm or more wide through a thickness of 30 cm or shallower; and more for some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick 2. An Ap horizon or materials between the mineral soil that has its upper boundary within 125 cm of the mineral surface and a depth of 18 cm that, after mixing, have one or soil surface; or more of the following: Alfisols 59

a. A color value, moist, of 4 or more; or also have aquic conditions in normal years (or artificial drainage) either: b. A color value, dry, of 6 or more; or a. Within the upper 25 cm of the argillic horizon if its c. Chroma of 4 or more. upper boundary is within 50 cm of the mineral soil Chromic Vertic Hapludalfs surface; or JEJF. Other Hapludalfs that have one or both of the following: b. Within 75 cm of the mineral soil surface if the upper boundary of the argillic horizon is 50 cm or more below 1. Cracks within 125 cm of the mineral soil surface that are the mineral soil surface. 5 mm or more wide through a thickness of 30 cm or more for Fragiaquic Hapludalfs some time in normal years and slickensides or wedge-shaped A aggregates in a layer 15 cm or more thick that has its upper JEJJ. Other Hapludalfs that have both: L boundary within 125 cm of the mineral soil surface; or F 1. Fragic soil properties: 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a. In 30 percent or more of the volume of a layer 15 cm a densic, lithic, or paralithic contact, whichever is shallower. or more thick that has its upper boundary within 100 cm Vertic Hapludalfs of the mineral soil surface; or b. In 60 percent or more of the volume of a layer 15 cm JEJG. Other Hapludalfs that have, throughout one or more or more thick; and horizons with a total thickness of 18 cm or more within 75 cm of 2. Saturation with water in one or more layers within 100 the mineral soil surface, a fine-earth fraction with both a bulk cm of the mineral soil surface in normal years for either or density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 both: and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. a. 20 or more consecutive days; or Andic Hapludalfs b. 30 or more cumulative days. Fragic Oxyaquic Hapludalfs JEJH. Other Hapludalfs that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of JEJK. Other Hapludalfs that have both: the mineral soil surface, one or both of the following: 1. In one or more horizons within 75 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 2. A fine-earth fraction containing 30 percent or more 2. A sandy or sandy-skeletal particle-size class particles 0.02 to 2.0 mm in diameter; and throughout a layer extending from the mineral soil surface to a. In the 0.02 to 2.0 mm fraction, 5 percent or more the top of an argillic horizon at a depth of 50 cm or volcanic glass; and more.

1 Aquic Arenic Hapludalfs b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. JEJL. Other Hapludalfs that have both: Vitrandic Hapludalfs 1. Saturation with water in one or more layers within 100 cm of the mineral soil surface in normal years for either or JEJI. Other Hapludalfs that have both: both: 1. Fragic soil properties: a. 20 or more consecutive days; or a. In 30 percent or more of the volume of a layer 15 cm b. 30 or more cumulative days; and or more thick that has its upper boundary within 100 cm of the mineral soil surface; or 2. A sandy or sandy-skeletal particle-size class throughout a layer extending from the mineral soil surface to the top of the b. In 60 percent or more of the volume of a layer 15 cm argillic horizon at a depth of 50 cm or more below the or more thick; and mineral soil surface. 2. Redox depletions with chroma of 2 or less in layers that Arenic Oxyaquic Hapludalfs 60 Keys to Soil Taxonomy

JEJM. Other Hapludalfs that have anthraquic conditions. JEJQ. Other Hapludalfs that have both: Anthraquic Hapludalfs 1. Redox depletions with chroma of 2 or less in layers that also have aquic conditions in normal years (or artificial JEJN. Other Hapludalfs that have: drainage) either: 1. An abrupt textural change; and a. Within the upper 25 cm of the argillic horizon if its 2. Redox depletions with chroma of 2 or less in layers that upper boundary is within 50 cm of the mineral soil also have aquic conditions in normal years (or artificial surface; or drainage) either: b. Within 75 cm of the mineral soil surface if the upper a. Within the upper 25 cm of the argillic horizon if its boundary of the argillic horizon is 50 cm or more below upper boundary is within 50 cm of the mineral soil the mineral soil surface; and surface; or 2. A base saturation (by sum of cations) of less than 60 b. Within 75 cm of the mineral soil surface if the upper percent at a depth of 125 cm from the top of the argillic boundary of the argillic horizon is 50 cm or more below horizon, at a depth of 180 cm from the mineral soil surface, the mineral soil surface; and or directly above a densic, lithic, or paralithic contact, whichever is shallowest. 3. A base saturation (by sum of cations) of less than 60 Aquultic Hapludalfs 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, JEJR. Other Hapludalfs that have both: or directly above a densic, lithic, or paralithic contact, whichever is shallowest. 1. An Ap horizon that has a color value, moist, of 3 or less Albaquultic Hapludalfs and a color value, dry, of 5 or less (crushed and smoothed sample) or materials between the soil surface and a depth of JEJO. Other Hapludalfs that have both: 18 cm that have these color values after mixing; and 1. An abrupt textural change; 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 that drainage) either: 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 its surface; or 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 Aquollic Hapludalfs the mineral soil surface. Albaquic Hapludalfs JEJS. Other Hapludalfs that have redox depletions with chroma of 2 or less in layers that also have aquic conditions in JEJP. Other Hapludalfs that have both: normal years (or artificial drainage) either: 1. Interfingering of albic materials in the upper part of the 1. Within the upper 25 cm of the argillic horizon if its upper argillic horizon; and boundary is within 50 cm of the mineral soil surface; or 2. Redox depletions with chroma of 2 or less in layers that 2. Within 75 cm of the mineral soil surface if the upper also have aquic conditions in normal years (or artificial boundary of the argillic horizon is 50 cm or more below the drainage) either: mineral soil surface. a. Within the upper 25 cm of the argillic horizon if its Aquic Hapludalfs upper boundary is within 50 cm of the mineral soil surface; or JEJT. Other Hapludalfs that have both: b. Within 75 cm of the mineral soil surface if the upper 1. A mollic epipedon, an Ap horizon that meets all of the boundary of the argillic horizon is 50 cm or more below requirements for a mollic epipedon except thickness, or the mineral soil surface. materials between the soil surface and a depth of 18 cm that Glossaquic Hapludalfs meet these requirements after mixing; and Alfisols 61

2. Saturation with water in 1 or more layers within 100 JEJZ. Other Hapludalfs that have interfingering of albic cm of the mineral soil surface in normal years for either or materials in one or more subhorizons of the argillic horizon. both: Glossic Hapludalfs a. 20 or more consecutive days; or JEJZa. Other Hapludalfs that have: b. 30 or more cumulative days. 1. An argillic, kandic, or natric horizon that is 35 cm or less Mollic Oxyaquic Hapludalfs thick; and JEJU. Other Hapludalfs that are saturated with water in one or 2. No densic, lithic, or paralithic contact within 100 cm of more layers within 100 cm of the mineral soil surface in normal the mineral soil surface. years for either or both: Inceptic Hapludalfs A L 1. 20 or more consecutive days; or JEJZb. Other Hapludalfs that have a base saturation (by sum F 2. 30 or more cumulative days. of cations) of less than 60 percent at a depth of 125 cm below Oxyaquic Hapludalfs the top of the argillic horizon, at a depth of 180 cm below the mineral soil surface, or directly above a densic, lithic, or JEJV. Other Hapludalfs that have fragic soil properties: paralithic contact, whichever is shallowest. Ultic Hapludalfs 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 JEJZc. Other Hapludalfs that have a mollic epipedon, an Ap mineral soil surface; or horizon that meets all of the requirements for a mollic epipedon 2. In 60 percent or more of the volume of a layer 15 cm or except thickness, or materials between the soil surface and a more thick. depth of 18 cm that meet these requirements after mixing. Fragic Hapludalfs Mollic Hapludalfs

JEJW. Other Hapludalfs that have an argillic horizon that: JEJZd. Other Hapludalfs. Typic Hapludalfs 1. Consists entirely of lamellae; or 2. Is a combination of two or more lamellae and one or Kandiudalfs 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 JEEA. Kandiudalfs that have both: 20 cm thick, each with an overlying eluvial horizon, and 1. In one or more horizons within 75 cm of the mineral soil above these horizons there are either: surface, redox depletions with chroma of 2 or less and also a. Two or more lamellae with a combined thickness of 5 aquic conditions for some time in normal years (or artificial cm or more (that may or may not be part of the argillic drainage); and horizon); or 2. 5 percent or more (by volume) plinthite in one or more b. A combination of lamellae (that may or may not be horizons within 150 cm of the mineral soil surface. part of the argillic horizon) and one or more parts of the Plinthaquic Kandiudalfs argillic horizon 7.5 to 20 cm thick, each with an overlying eluvial horizon. JEEB. Other Kandiudalfs that have, in one or more horizons Lamellic Hapludalfs within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in JEJX. Other Hapludalfs that have a sandy particle-size class normal years (or artificial drainage). throughout the upper 75 cm of the argillic horizon or throughout Aquic Kandiudalfs the entire argillic horizon if it is less than 75 cm thick. Psammentic Hapludalfs JEEC. Other Kandiudalfs that are saturated with water in one or more layers within 100 cm of the mineral soil surface in JEJX. Other Hapludalfs that have a sandy or sandy-skeletal normal years for either or both: particle-size class throughout a layer extending from the mineral 1. 20 or more consecutive days; or soil surface to the top of an argillic horizon at a depth of 50 cm or more. 2. 30 or more cumulative days. Arenic Hapludalfs Oxyaquic Kandiudalfs 62 Keys to Soil Taxonomy

JEED. Other Kandiudalfs that have both: Kanhapludalfs 1. A sandy or sandy-skeletal particle-size class throughout a Key to Subgroups layer extending from the mineral soil surface to the top of a kandic horizon at a depth of 50 to 100 cm; and JEFA. Kanhapludalfs that have a lithic contact within 50 cm of the mineral soil surface. 2. 5 percent or more (by volume) plinthite in one or more Lithic Kanhapludalfs horizons within 150 cm of the mineral soil surface. Arenic Plinthic Kandiudalfs JEFB. Other Kanhapludalfs that have, in one or more horizons within 75 cm of the mineral soil surface, JEEE. Other Kandiudalfs that have both: redox depletions with chroma of 2 or less and also aquic 1. A sandy or sandy-skeletal particle-size class throughout a conditions for some time in normal years (or artificial layer extending from the mineral soil surface to the top of a drainage). kandic horizon at a depth of 100 cm or more; and Aquic Kanhapludalfs 2. 5 percent or more (by volume) plinthite in one or more JEFC. Other Kanhapludalfs that are saturated with water in horizons within 150 cm of the mineral soil surface. one or more layers within 100 cm of the mineral soil surface in Grossarenic Plinthic Kandiudalfs normal years for either or both: JEEF. Other Kandiudalfs that have a sandy or sandy-skeletal 1. 20 or more consecutive days; or particle-size class throughout a layer extending from the mineral 2. 30 or more cumulative days. soil surface to the top of a kandic horizon at a depth of 50 to Oxyaquic Kanhapludalfs 100 cm. Arenic Kandiudalfs JEFD. Other Kanhapludalfs that have, in all subhorizons in the upper 100 cm of the kandic horizon or throughout the entire JEEG. Other Kandiudalfs that have a sandy or sandy-skeletal kandic horizon if less than 100 cm thick, more than 50 percent particle-size class throughout a layer extending from the mineral colors that have all of the following: soil surface to the top of a kandic horizon at a depth of 100 cm or more. 1. Hue of 2.5YR or redder; and Grossarenic Kandiudalfs 2. Value, moist, of 3 or less; and JEEH. Other Kandiudalfs that have 5 percent or more (by 3. Dry value no more than 1 unit higher than the moist volume) plinthite in one or more horizons within 150 cm of the value. mineral soil surface. Rhodic Kanhapludalfs Plinthic Kandiudalfs JEFE. Other Kanhapludalfs. JEEI. Other Kandiudalfs that have, in all subhorizons in the Typic Kanhapludalfs upper 100 cm of the kandic horizon or throughout the entire kandic horizon if less than 100 cm thick, more than 50 percent Natrudalfs colors that have all of the following: Key to Subgroups 1. Hue of 2.5YR or redder; and JEAA. Natrudalfs that have one or both of the following: 2. Value, moist, of 3 or less; and 1. Cracks within 125 cm of the mineral soil surface that 3. Dry value no more than 1 unit higher than the moist are 5 mm or more wide through a thickness of 30 cm or value. more for some time in normal years and slickensides or Rhodic Kandiudalfs wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral JEEJ. Other Kandiudalfs that have a mollic epipedon, an Ap soil surface; or horizon that meets all of the requirements for a mollic epipedon except thickness, or materials between the soil surface and a 2. A linear extensibility of 6.0 cm or more between the depth of 18 cm that meet these requirements after mixing. mineral soil surface and either a depth of 100 cm or a densic, Mollic Kandiudalfs lithic, or paralithic contact, whichever is shallower. Vertic Natrudalfs JEEK. Other Kandiudalfs. Typic Kandiudalfs JEAB. Other Natrudalfs that have: Alfisols 63

1. Either a glossic horizon or interfingering of albic 1. More than 35 percent (by volume) fragments coarser materials into the natric horizon; and than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or 2. Redox depletions with chroma of 2 or less in layers that also have aquic conditions in normal years (or artificial 2. A fine-earth fraction containing 30 percent or more drainage) either: particles 0.02 to 2.0 mm in diameter; and a. Within the upper 25 cm of the natric horizon if its a. In the 0.02 to 2.0 mm fraction, 5 percent or more upper boundary is within 50 cm of the mineral soil volcanic glass; and

surface; or 1 b. [(Al plus /2 Fe, percent extracted by ammonium b. Within 75 cm of the mineral soil surface if the upper oxalate) times 60] plus the volcanic glass (percent) is A boundary of the natric horizon is 50 cm or more below the equal to 30 or more. L mineral soil surface. Vitrandic Paleudalfs F Glossaquic Natrudalfs JEGD. Other Paleudalfs that have anthraquic conditions. JEAC. Other Natrudalfs that have redox depletions with Anthraquic Paleudalfs chroma of 2 or less in layers that also have aquic conditions in normal years (or artificial drainage) either: JEGE. Other Paleudalfs that have both: 1. Within the upper 25 cm of the natric horizon if its upper 1. Fragic soil properties: boundary is within 50 cm of the mineral soil surface; or a. In 30 percent or more of the volume of a layer 15 cm 2. Within 75 cm of the mineral soil surface if the upper or more thick that has its upper boundary within 100 cm boundary of the natric horizon is 50 cm or more below the of the mineral soil surface; or mineral soil surface. b. In 60 percent or more of the volume of a layer 15 cm Aquic Natrudalfs or more thick; and JEAD. Other Natrudalfs. 2. Redox depletions with chroma of 2 or less in layers that Typic Natrudalfs also have aquic conditions in normal years (or artificial drainage) either: Paleudalfs a. Within the upper 25 cm of the argillic horizon if its upper boundary is within 50 cm of the mineral soil Key to Subgroups surface; or JEGA. Paleudalfs that have one or both of the following: b. Within 75 cm of the mineral soil surface if the upper 1. Cracks within 125 cm of the mineral soil surface that are boundary of the argillic horizon is 50 cm or more below 5 mm or more wide through a thickness of 30 cm or more for the mineral soil surface. some time in normal years and slickensides or wedge-shaped Fragiaquic Paleudalfs aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil surface; or JEGF. Other Paleudalfs that have both: 2. A linear extensibility of 6.0 cm or more between the 1. In one or more horizons within 75 cm of the mineral soil mineral soil surface and either a depth of 100 cm or a densic, surface, redox depletions with chroma of 2 or less and also lithic, or paralithic contact, whichever is shallower. aquic conditions for some time in normal years (or artificial Vertic Paleudalfs drainage); and JEGB. Other Paleudalfs that have, throughout one or more 2. 5 percent or more (by volume) plinthite in one or more horizons with a total thickness of 18 cm or more within 75 cm of horizons within 150 cm of the mineral soil surface. the mineral soil surface, a fine-earth fraction with both a bulk Plinthaquic Paleudalfs 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 JEGG. Other Paleudalfs that have both: more than 1.0. 1. In one or more horizons within 75 cm of the mineral soil Andic Paleudalfs surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial JEGC. Other Paleudalfs that have, throughout one or more drainage); 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. A glossic horizon or, in the upper part of the argillic 64 Keys to Soil Taxonomy

horizon, one or more subhorizons that have 5 percent 2. 5 percent or more (by volume) plinthite in one or more or more (by volume) clay depletions with chroma of 2 horizons within 150 cm of the mineral soil surface. or less. Grossarenic Plinthic Paleudalfs Glossaquic Paleudalfs JEGN. Other Paleudalfs that have an argillic horizon that: JEGH. Other Paleudalfs that have both: 1. Consists entirely of lamellae; or 1. In one or more horizons within 75 cm of the mineral soil 2. Is a combination of two or more lamellae and one or surface, redox depletions with chroma of 2 or less and also more subhorizons with a thickness of 7.5 to 20 cm, each layer aquic conditions for some time in normal years (or artificial with an overlying eluvial horizon; or drainage); and 3. Consists of one or more subhorizons that are more than 2. A clay increase of 15 percent or more (absolute) in the 20 cm thick, each with an overlying eluvial horizon, and fine-earth fraction within a vertical distance of 2.5 cm at the above these horizons there are either: upper boundary of the argillic horizon. Albaquic Paleudalfs a. Two or more lamellae with a combined thickness of 5 cm or more (that may or may not be part of the argillic JEGI. Other Paleudalfs that have, in one or more horizons horizon); or within 75 cm of the mineral soil surface, redox depletions with b. A combination of lamellae (that may or may not be chroma of 2 or less and also aquic conditions for some time in part of the argillic horizon) and one or more parts of the normal years (or artificial drainage). argillic horizon 7.5 to 20 cm thick, each with an overlying Aquic Paleudalfs eluvial horizon. Lamellic Paleudalfs JEGJ. Other Paleudalfs that are saturated with water in one or more layers within 100 cm of the mineral soil surface in normal JEGO. Other Paleudalfs that have a sandy particle-size years for either or both: class throughout the upper 75 cm of the argillic horizon or 1. 20 or more consecutive days; or throughout 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 have a sandy or sandy-skeletal JEGK. Other Paleudalfs that have fragic soil properties: particle-size class throughout a layer extending from the mineral 1. In 30 percent or more of the volume of a layer 15 cm or soil surface to the top of an argillic horizon at a depth of 50 to more thick that has its upper boundary within 100 cm of the 100 cm. mineral soil surface; or Arenic Paleudalfs 2. In 60 percent or more of the volume of a layer 15 cm or JEGQ. Other Paleudalfs that have a sandy or sandy-skeletal more thick. particle-size class throughout a layer extending from the mineral Fragic Paleudalfs soil surface to the top of an argillic horizon at a depth of 100 cm or more. JEGL. Other Paleudalfs that have both: Grossarenic Paleudalfs 1. A sandy or sandy-skeletal particle-size class throughout a layer extending from the mineral soil surface to the top of an JEGR. Other Paleudalfs that have 5 percent or more (by argillic horizon at a depth of 50 to 100 cm; and volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. 2. 5 percent or more (by volume) plinthite in one or more Plinthic Paleudalfs horizons within 150 cm of the mineral soil surface. Arenic Plinthic Paleudalfs JEGS. Other Paleudalfs that have either: JEGM. Other Paleudalfs that have both: 1. A glossic horizon; or 1. A sandy or sandy-skeletal particle-size class throughout a 2. In the upper part of the argillic horizon, one or more layer extending from the mineral soil surface to the top of an subhorizons that have 5 percent or more (by volume) argillic horizon at a depth of 100 cm or more; and skeletans with chroma of 2 or less; or Alfisols 65

3. 5 percent or more (by volume) albic materials in some a. Do not have a clay decrease with increasing depth of subhorizon of the argillic horizon. 20 percent or more (relative) from the maximum clay Glossic Paleudalfs content [Clay is measured noncarbonate clay or based on the following formula: Clay % = 2.5(% water retained at JEGT. Other Paleudalfs that have, in all subhorizons in the 1500 kPa tension - % organic carbon), whichever value is upper 100 cm of the argillic horizon or throughout the entire greater, but no more than 100]; or argillic horizon if less than 100 cm thick, more than 50 percent b. Have 5 percent or more (by volume) skeletans on colors that have all of the following: faces of peds in the layer that has a 20 percent lower clay 1. Hue of 2.5YR or redder; and content and, below that layer, a clay increase of 3 percent or more (absolute) in the fine-earth fraction. 2. Value, moist, of 3 or less; and A Kandiustalfs, p. 69 L 3. Dry value no more than 1 unit higher than the moist F value. JCE. Other Ustalfs that have a kandic horizon. Rhodic Paleudalfs Kanhaplustalfs, p. 70

JEGU. Other Paleudalfs that have a mollic epipedon, an Ap JCF. Other Ustalfs that have one or more of the following: horizon that meets all of the requirements for a mollic epipedon 1. A petrocalcic horizon that has its upper boundary within except thickness, or materials between the soil surface and a 150 cm of the mineral soil surface; or depth of 18 cm that meet these requirements after mixing. Mollic Paleudalfs 2. No densic, lithic, or paralithic contact within 150 cm of the mineral soil surface and an argillic horizon that has both: JEGV. Other Paleudalfs. a. Within 150 cm of the mineral soil surface, either: Typic Paleudalfs (1) With increasing depth, no clay decrease of 20 Rhodudalfs percent or more (relative) from the maximum clay content [Clay is measured noncarbonate clay or based Key to Subgroups 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 faces of peds in the layer that has a 20 percent lower clay Ustalfs content and, below that layer, a clay increase of 3 percent or more (absolute) in the fine-earth fraction; Key to Great Groups and JCA. Ustalfs that have a duripan that has its upper boundary b. In the lower one-half of the argillic horizon, one or within 100 cm of the mineral soil surface. more subhorizons with either or both: Durustalfs, p. 66 (1) Hue of 7.5YR or redder and chroma of 5 or more in 50 percent or more of the matrix; or JCB. Other Ustalfs that have one or more horizons within 150 cm of the mineral soil surface in which plinthite either forms a (2) Common or many coarse redox concentrations continuous phase or constitutes one-half or more of the volume. with hue of 7.5YR or redder or chroma of 6 or more, or Plinthustalfs, p. 76 both; or 3. No densic, lithic, or paralithic contact within 50 cm of JCC. Other Ustalfs that have a natric horizon. the mineral soil surface and an argillic horizon that has both: Natrustalfs, p. 71 a. A clayey or clayey-skeletal particle-size class JCD. Other Ustalfs that: 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- earth fraction) of either 20 percent or more (absolute) 2. Do not have a densic, lithic, paralithic, or petroferric within a vertical distance of 7.5 cm or of 15 percent or contact within 150 cm of the mineral soil surface; and more (absolute) within a vertical distance of 2.5 cm. 3. Within 150 cm of the mineral soil surface, either: Paleustalfs, p. 73 66 Keys to Soil Taxonomy

JCG. Other Ustalfs that have, in all subhorizons in the upper wedge-shaped aggregates in a layer 15 cm or more thick 100 cm of the argillic horizon or throughout the entire argillic that has its upper boundary within 125 cm of the mineral horizon if less than 100 cm thick, more than 50 percent colors soil surface; or that have all of the following: b. A linear extensibility of 6.0 cm or more between the 1. Hue of 2.5YR or redder; and mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is 2. Value, moist, of 3 or less; and shallower; and 3. Dry value no more than 1 unit higher than the moist 2. Saturation with water in one or more layers within 100 value. cm of the mineral soil surface in normal years for either or Rhodustalfs, p. 76 both: JCH. Other Ustalfs. a. 20 or more consecutive days; or Haplustalfs, p. 66 b. 30 or more cumulative days. Oxyaquic Vertic Haplustalfs Durustalfs JCHD. Other Haplustalfs that have both of the following: Key to Subgroups 1. When neither irrigated nor fallowed to store moisture, JCAA. All Durustalfs (provisionally). one of the following: Typic Durustalfs a. A frigid temperature regime and a moisture control Haplustalfs section that in normal years is dry in all parts for four- tenths or more of the cumulative days per year when the Key to Subgroups soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or JCHA. Haplustalfs that have a lithic contact within 50 cm of 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 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 aggregates in a layer 15 cm or more thick (1) Is moist in some or all parts for less than 90 that has its upper boundary within 125 cm of the mineral consecutive days per year when the temperature at a soil surface; or 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 or a (2) Is dry in some part for six-tenths or more of the 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 5 oC; 2. In one or more horizons within 75 cm of the mineral soil 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 a. Cracks within 125 cm of the soil surface that are 5 drainage). mm or more wide through a thickness of 30 cm or more Aquertic Haplustalfs for some time in normal years and slickensides or wedge- shaped aggregates in a layer 15 cm or more thick that has JCHC. Other Haplustalfs that have both: 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 Alfisols 67

JCHE. Other Haplustalfs 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. When neither irrigated nor fallowed to store moisture, drainage); and either: 2. An argillic horizon that has a base saturation (by sum of a. A mesic or thermic soil temperature regime and a cations) of less than 75 percent throughout. moisture control section that in normal years is dry in Aquultic Haplustalfs some part for four-tenths or less of the cumulative days per year when the temperature at a depth of 50 cm below JCHI. Other Haplustalfs that have, in one or more horizons the soil surface is higher than 5 oC; or within 75 cm of the mineral soil surface, redox depletions with b. A hyperthermic, isomesic, or warmer iso soil chroma of 2 or less and also aquic conditions for some time in A temperature regime and a moisture control section that in normal years (or artificial drainage). L normal years is dry in some or all parts for less than 120 Aquic Haplustalfs F cumulative days per year when the temperature at a depth of 50 cm below the soil surface is higher than 8 oC; and JCHJ. Other Haplustalfs that are saturated with water in one or more layers within 100 cm of the mineral soil surface in normal 2. One or both of the following: years for either or both: a. Cracks within 125 cm of the mineral soil surface that 1. 20 or more consecutive days; or are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or 2. 30 or more cumulative days. wedge-shaped aggregates in a layer 15 cm or more thick Oxyaquic Haplustalfs that 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 of b. A linear extensibility of 6.0 cm or more between the 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: particles 0.02 to 2.0 mm in diameter; and 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 in normal years and slickensides or wedge-shaped 1 aggregates 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. Vertic Haplustalfs JCHL. Other Haplustalfs that have an argillic horizon that: 1. Consists entirely of lamellae; or JCHG. Other Haplustalfs that have both: 2. Is a combination of two or more lamellae and one or 1. In one or more horizons within 75 cm of the mineral soil more subhorizons with a thickness of 7.5 to 20 cm, each layer surface, redox depletions with chroma of 2 or less and also with an overlying eluvial horizon; or aquic conditions for some time in normal years (or artificial drainage); and 3. Consists of one or more subhorizons that are more than 20 cm thick, each with an overlying eluvial horizon, and 2. A sandy or sandy-skeletal particle-size class throughout a above these horizons there are either: layer extending from the mineral soil surface to the top of an argillic horizon at a depth of 50 to 100 cm. a. Two or more lamellae with a combined thickness of 5 Aquic Arenic Haplustalfs cm or more (that may or may not be part of the argillic horizon); or JCHH. Other Haplustalfs that have both: b. A combination of lamellae (that may or may not be 1. In one or more horizons within 75 cm of the mineral soil part of the argillic horizon) and one or more parts of the 68 Keys to Soil Taxonomy

argillic horizon 7.5 to 20 cm thick, each with an overlying 2. When neither irrigated nor fallowed to store moisture, eluvial horizon. one of the following: Lamellic Haplustalfs a. A frigid temperature regime and a moisture control section that in normal years is dry in all parts for four- JCHM. Other Haplustalfs that have a sandy particle-size class tenths or more of the cumulative days per year when the throughout the upper 75 cm of the argillic horizon or throughout soil temperature at a depth of 50 cm below the soil surface the entire argillic horizon if it is less than 75 cm thick. is higher than 5 oC; or Psammentic Haplustalfs b. A mesic or thermic soil temperature regime and a JCHN. Other Haplustalfs that have both: moisture control section that in normal years is dry in some part for six-tenths or more of the cumulative days 1. A sandy or sandy-skeletal particle-size class throughout a per year when the soil temperature at a depth of 50 cm layer extending from the mineral soil surface to the top of an below the soil surface is higher than 5 oC; or argillic horizon at a depth of 50 cm or more; and c. 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 one of the following: normal years: a. A frigid temperature regime and a moisture control (1) Is moist in some or all parts for less than 90 section that in normal years is dry in all parts for four- consecutive days per year when the temperature at a tenths or more of the cumulative days per year when the depth of 50 cm below the soil surface is higher than soil temperature at a depth of 50 cm below the soil surface 8 oC; and is higher than 5 oC; or (2) Is dry in some part for six-tenths or more of the b. A mesic or thermic soil temperature regime cumulative days per year when the soil temperature at a and a moisture control section that in normal years depth of 50 cm below the soil surface is higher than 5 is dry in some part for six-tenths or more of the oC. cumulative days per year when the soil temperature Calcidic Haplustalfs at a depth of 50 cm below the soil surface is higher than 5 oC; or JCHQ. Other Haplustalfs that, when neither irrigated nor c. A hyperthermic, isomesic, or warmer iso soil fallowed to store moisture, have one of the following: temperature regime and a moisture control section that in normal years: 1. A frigid temperature regime and a moisture control section that in normal years is dry in all parts for four-tenths (1) Is moist in some or all parts for less than 90 or more of the cumulative days per year when the soil consecutive days per year when the 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 higher than 5 oC; or 8 oC; and 2. A mesic or thermic soil temperature regime and a (2) Is dry in some part for six-tenths or more of the moisture control section that in normal years is dry in some cumulative days per year when the soil temperature at a part for six-tenths or more of the cumulative days per year depth of 50 cm below the soil surface is higher than when the soil temperature at a depth of 50 cm below the soil 5 oC. surface is higher than 5 oC; or Arenic Aridic Haplustalfs 3. A hyperthermic, isomesic, or warmer iso soil JCHO. Other Haplustalfs that have a sandy or sandy-skeletal temperature regime and a moisture control section that in particle-size class throughout a layer extending from the mineral normal years: soil surface to the top of an argillic horizon at a depth of 50 cm a. Is moist in some or all parts for less than 90 or more. consecutive days per year when the temperature at a depth Arenic Haplustalfs of 50 cm below the soil surface is higher than 8 oC; and 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 1. A calcic horizon with its upper boundary within 100 cm depth of 50 cm below the soil surface is higher than 5 oC. of the mineral soil surface; and Aridic Haplustalfs Alfisols 69

JCHR. Other Haplustalfs that have a CEC of less than 24 2. A mesic or thermic soil temperature regime and a cmol(+)/kg clay (by 1N NH4OAc pH 7) in 50 percent or more moisture control section that in normal years is dry in some either of the argillic horizon if less than 100 cm thick or of its part for four-tenths or less of the cumulative days per year upper 100 cm. when the temperature at a depth of 50 cm below the soil Kanhaplic Haplustalfs surface is higher than 5 oC; or JCHS. Other Haplustalfs that have: 3. A hyperthermic, isomesic, or warmer iso soil 1. An argillic, kandic, or natric horizon that is 35 cm or less temperature regime and a moisture control section that in thick; and normal years is dry in some or all parts for less than 120 cumulative days per year when the temperature at a depth of 2. No densic, lithic, or paralithic contact within 100 cm of 50 cm below the soil surface is higher than 8 oC. the mineral soil surface. A Udic Haplustalfs Inceptic Haplustalfs L F JCHX. Other Haplustalfs. JCHT. Other Haplustalfs that have both: Typic Haplustalfs 1. A calcic horizon with its upper boundary within 100 cm of the mineral soil surface; and Kandiustalfs 2. When neither irrigated nor fallowed to store moisture, Key to Subgroups one of the following: JCDA. Kandiustalfs that have a sandy or sandy-skeletal a. A frigid temperature regime and a moisture control particle-size class throughout a layer extending from the mineral section that in normal years is dry in some or all parts for soil surface to the top of a kandic horizon at a depth of 100 cm less than 105 cumulative days per year when the or more. temperature at a depth of 50 cm below the soil surface is Grossarenic Kandiustalfs higher than 5 oC; or b. A mesic or thermic soil temperature regime and a JCDB. Other Kandiustalfs that have both: moisture control section that in normal years is dry in 1. In one or more horizons within 75 cm of the mineral soil some part for four-tenths or less of the cumulative days surface, redox depletions with chroma of 2 or less and also per year when the temperature at a depth of 50 cm below aquic conditions for some time in normal years (or artificial the soil surface is higher than 5 oC; or drainage); and c. A hyperthermic, isomesic, or warmer iso soil 2. A sandy or sandy-skeletal particle-size class throughout a temperature regime and a moisture control section that in layer extending from the mineral soil surface to the top of a normal years is dry in some or all parts for less than 120 kandic horizon at a depth of 50 to 100 cm. cumulative days per year when the temperature at a depth Aquic Arenic Kandiustalfs of 50 cm below the soil surface is higher than 8 oC. Calcic Udic Haplustalfs JCDC. Other Kandiustalfs that have 5 percent or more (by volume) plinthite in one or more horizons within 150 cm of the JCHU. Other Haplustalfs that have an argillic horizon with a mineral soil surface. base saturation (by sum of cations) of less than 75 percent Plinthic Kandiustalfs throughout. Ultic Haplustalfs JCDD. Other Kandiustalfs that have, in one or more horizons within 75 cm of the mineral soil surface, redox depletions with JCHV. Other Haplustalfs that have a calcic horizon with its chroma of 2 or less and also aquic conditions for some time in upper boundary within 100 cm of the mineral soil surface. normal years (or artificial drainage). Calcic Haplustalfs Aquic Kandiustalfs JCHW. Other Haplustalfs that, when neither irrigated nor JCDE. Other Kandiustalfs that have both: fallowed to store moisture, have one of the following: 1. A sandy or sandy-skeletal particle-size class throughout a 1. A frigid temperature regime and a moisture control layer extending from the mineral soil surface to the top of a section that in normal years is dry in some or all parts for kandic horizon at a depth of 50 to 100 cm; and less than 105 cumulative days per year when the temperature at a depth of 50 cm below the soil surface is higher than 5 oC; 2. When neither irrigated nor fallowed to store moisture, or either: 70 Keys to Soil Taxonomy

a. A mesic or thermic soil temperature regime and a 2. A hyperthermic, isomesic, or warmer iso soil moisture control section that in normal years is dry in temperature regime and a moisture control section that in some part for six-tenths or more of the cumulative days normal years is dry in some or all parts for less than 120 per year when the soil temperature at a depth of 50 cm cumulative days per year when the temperature at a depth of below the soil surface is higher than 5 oC; or 50 cm below the soil surface is higher than 8 oC. Udic Kandiustalfs b. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in JCDI. Other Kandiustalfs that have, in all subhorizons in the normal years: upper 100 cm of the kandic horizon or throughout the entire (1) Is moist in some or all parts for less than 90 kandic horizon if less than 100 cm thick, more than 50 percent consecutive days per year when the temperature at a colors that have all of the following: depth of 50 cm below the soil surface is higher than 1. Hue of 2.5YR or redder; and 8 oC; and 2. Value, moist, of 3 or less; and (2) Is dry in some part for six-tenths or more of the cumulative days per year when the soil temperature at a 3. Dry value no more than 1 unit higher than the moist depth of 50 cm below the soil surface is higher than 5 value. oC. Rhodic Kandiustalfs Arenic Aridic Kandiustalfs JCDJ. Other Kandiustalfs. JCDF. Other Kandiustalfs that have a sandy or sandy-skeletal Typic Kandiustalfs particle-size class throughout a layer extending from the mineral soil surface to the top of a kandic horizon at a depth of 50 to Kanhaplustalfs 100 cm. Arenic Kandiustalfs Key to Subgroups JCEA. Kanhaplustalfs that have a lithic contact within 50 cm JCDG. Other Kandiustalfs that, when neither irrigated nor of the mineral soil surface. fallowed to store moisture, have either: 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 for surface is higher than 5 oC; or some time in normal years (or artificial drainage). Aquic Kanhaplustalfs 2. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in JCEC. Other Kanhaplustalfs that, when neither irrigated nor normal years: 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 temperature at a depth moisture control section that in normal years is dry in some of 50 cm below the soil surface is higher than 8 oC; and part for six-tenths or more of the cumulative days per year b. 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 2. A hyperthermic, isomesic, or warmer iso soil 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 temperature at a depth of 50 cm below the soil surface is higher than 8 oC; and 1. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in some b. Is dry in some part for six-tenths or more of the part for 135 cumulative days or less per year when the 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 than5 oC. higher than 5 oC; or Aridic Kanhaplustalfs Alfisols 71

JCED. Other Kanhaplustalfs that, when neither irrigated nor c. A hyperthermic, isomesic, or warmer iso soil fallowed to store moisture, have either: temperature regime and a moisture control section that in normal years: 1. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in some (1) Is moist in some or all parts for less than 90 part for 135 cumulative days or less per year when the consecutive days per year when the 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 higher than 5 oC; or 8 oC; and 2. A hyperthermic, isomesic, or warmer iso soil (2) Is dry in some part for six-tenths or more of the temperature regime and a moisture control section that in cumulative days per year when the soil temperature at a normal years is dry in some or all parts for less than 120 depth of 50 cm below the soil surface is higher than 5 A cumulative days per year when the temperature at a depth of oC; and L 50 cm below the soil surface is higher than 8 oC. F 3. One or both of the following: Udic Kanhaplustalfs a. Cracks within 125 cm of the mineral soil surface that JCEE. Other Kanhaplustalfs that have, in all subhorizons in are 5 mm or more wide through a thickness of 30 cm or the upper 100 cm of the kandic horizon or throughout the entire more for some time in normal years and slickensides or kandic horizon if less than 100 cm thick, more than 50 percent wedge-shaped aggregates in a layer 15 cm or more thick colors that have all of the following: that has its upper boundary within 125 cm of the mineral soil surface; or 1. Hue of 2.5YR or redder; and b. A linear extensibility of 6.0 cm or more between the 2. Value, moist, of 3 or less; and mineral soil surface and either a depth of 100 cm or a 3. Dry value no more than 1 unit higher than the moist densic, lithic, or paralithic contact, whichever is shallower. value. Leptic Torrertic Natrustalfs Rhodic Kanhaplustalfs JCCC. Other Natrustalfs that have both of the following: JCEF. Other Kanhaplustalfs. 1. When neither irrigated nor fallowed to store moisture, Typic Kanhaplustalfs one of the following: Natrustalfs a. A frigid temperature regime and a moisture control section that in normal years is dry in all parts for four- Key to Subgroups tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface JCCA. Natrustalfs that have a salic horizon that has its upper is higher than 5 oC; or boundary within 75 cm of the mineral soil surface. Salidic Natrustalfs b. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in JCCB. Other Natrustalfs that have all of the following: some part for six-tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm 1. Visible crystals of gypsum or other salts more soluble below the soil surface is higher than 5 oC; or than gypsum, or both, within 40 cm of the soil surface; and c. 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 one of the following: normal years: a. A frigid temperature regime and a moisture control (1) Is moist in some or all parts for less than 90 section that in normal years is dry in all parts for four- consecutive days per year when the temperature at a tenths or more of the cumulative days per year when the depth of 50 cm below the soil surface is higher than soil temperature at a depth of 50 cm below the soil surface 8 oC; and is higher than 5 oC; or (2) Is dry in some part for six-tenths or more of the 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 5 some part for six-tenths or more of the cumulative days oC; and per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or 2. One or both of the following: 72 Keys to Soil Taxonomy

a. Cracks within 125 cm of the mineral soil surface that consecutive days per year when the temperature at a are 5 mm or more wide through a thickness of 30 cm or depth of 50 cm below the soil surface is higher than more for some time in normal years and slickensides or 8 oC; and wedge-shaped aggregates in a layer 15 cm or more thick (2) Is dry in some part for six-tenths or more of the that has its upper boundary within 125 cm of the mineral cumulative days per year when the soil temperature at soil 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 the 5 oC. mineral soil surface and either a depth of 100 cm or a Aridic Leptic Natrustalfs densic, lithic, or paralithic contact, whichever is shallower. Torrertic Natrustalfs JCCF. Other Natrustalfs that have one or both of the following: JCCD. Other Natrustalfs that have both: 1. Cracks within 125 cm of the mineral soil surface that are 1. In one or more horizons within 75 cm of the mineral soil 5 mm or more wide through a thickness of 30 cm or more for surface, redox depletions with chroma of 2 or less and also some time in normal years and slickensides or wedge-shaped aquic conditions for some time in normal years (or artificial aggregates in a layer 15 cm or more thick that has its upper drainage); and boundary within 125 cm of the mineral soil surface; or 2. 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. Cracks within 125 cm of the mineral soil surface that a densic, lithic, or paralithic contact, whichever is shallower. are 5 mm or more wide through a thickness of 30 cm or Vertic Natrustalfs more for some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral JCCG. Other Natrustalfs that have both: soil surface; or 1. In one or more horizons within 75 cm of the mineral soil b. A linear extensibility of 6.0 cm or more between the surface, redox depletions with chroma of 2 or less and also mineral soil surface and either a depth of 100 cm or a aquic conditions for some time in normal years (or artificial densic, lithic, or paralithic contact, whichever is shallower. drainage); and Aquertic Natrustalfs 2. A sandy or sandy-skeletal particle-size class throughout a JCCE. Other Natrustalfs that have both of the following: layer extending from the mineral soil surface to the top of an argillic horizon at a depth of 50 cm or more. 1. Visible crystals of gypsum or other salts more soluble Aquic Arenic Natrustalfs than gypsum, or both, within 40 cm of the mineral soil surface; and JCCH. Other Natrustalfs that have, in one or more horizons 2. When neither irrigated nor fallowed to store moisture, within 75 cm of the mineral soil surface, redox depletions with one of the following: chroma of 2 or less and also aquic conditions for some time in a. A frigid temperature regime and a moisture control normal years (or artificial drainage). section that in normal years is dry in all parts for four- Aquic Natrustalfs tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface JCCI. Other Natrustalfs that have a sandy or sandy-skeletal is higher than 5 oC; or particle-size class throughout a layer extending from the mineral b. A mesic or thermic soil temperature regime and a soil surface to the top of an argillic horizon at a depth of 50 cm moisture control section that in normal years is dry in or more. some part for six-tenths or more of the cumulative days Arenic Natrustalfs per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or JCCJ. Other Natrustalfs that have a petrocalcic horizon that has its upper boundary within 150 cm of the mineral soil c. A hyperthermic, isomesic, or warmer iso soil surface. temperature regime and a moisture control section that in Petrocalcic Natrustalfs normal years: (1) Is moist in some or all parts for less than 90 JCCK. Other Natrustalfs that have visible crystals of gypsum Alfisols 73

or other salts more soluble than gypsum, or both, within 40 cm (1) Is moist in some or all parts for fewer than 90 of the mineral soil surface. consecutive days per year when the temperature at a depth Leptic Natrustalfs of 50 cm below the soil surface is higher than 8 °C; and (2) Is dry in some part for six-tenths or more of the JCCL. Other Natrustalfs that have both of the following: cumulative days per year when the temperature at a depth 1. An exchangeable sodium percentage of less than 15 (or a of 50 cm below the soil surface is higher than 5 °C; and sodium adsorption ratio of less than 13) in 50 percent or 2. A glossic horizon or interfingering of albic materials into more of the natric horizon; and the natric horizon. 2. When neither irrigated nor fallowed to store moisture, Aridic Glossic Natrustalfs one of the following: A JCCN. Other Natrustalfs that, when neither irrigated nor L a. A frigid temperature regime and a moisture control fallowed to store moisture, have one of the following: F section that in normal years is dry in all parts for four- tenths or more of the cumulative days per year when the 1. A frigid temperature regime and a moisture control soil temperature at a depth of 50 cm below the soil surface section that in normal years is dry in all parts for four-tenths is higher than 5 oC; or or more of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is b. A mesic or thermic soil temperature regime and a higher than 5 oC; or moisture control section that in normal years is dry in some part for six-tenths or more of the cumulative days 2. 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 some below the soil surface is higher than 5 oC; or part for six-tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil c. A hyperthermic, isomesic, or warmer iso soil surface is higher than 5 oC; or temperature regime and a moisture control section that in normal years: 3. 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 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 8 oC; and consecutive days per year when the temperature at a depth of 50 cm below the soil surface is higher than 8 oC; and (2) Is dry in some part for six-tenths or more of the cumulative days per year when the soil temperature at a b. Is dry in some part for six-tenths or more of the depth of 50 cm below the soil surface is higher than 5 cumulative days per year when the soil temperature at a oC. depth of 50 cm below the soil surface is higher than 5 oC. Haplargidic Natrustalfs Aridic Natrustalfs JCCM. Other Natrustalfs that have both: JCCO. Other Natrustalfs that have an Ap horizon with a color 1. When neither irrigated nor fallowed to store moisture, one value, moist, of 3 or less and a color value, dry, of 5 or less of the following: (crushed and smoothed sample) or materials between the soil surface and a depth of 18 cm that have these color values after a. A frigid soil temperature regime and a moisture mixing. control section that in normal years is dry in all parts for Mollic Natrustalfs four-tenths or more of the cumulative days per year when the temperature at a depth of 50 cm below the soil surface JCCP. Other Natrustalfs. is higher than 5 °C; or Typic Natrustalfs b. A mesic or thermic soil temperature regime and a moisture control section that, in 6 normal years, is dry in Paleustalfs some part for six-tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm Key to Subgroups below the soil surface is higher than 5 °C; or JCFA. Paleustalfs that have both: c. A hyperthermic, an isomesic, or a warmer iso soil 1. One or both of the following: temperature regime and a moisture control section that, in normal years: a. Cracks within 125 cm of the mineral soil surface that 74 Keys to Soil Taxonomy

are 5 mm or more wide through a thickness of 30 cm or a. Cracks within 125 cm of the mineral soil surface that more for some time in normal years and slickensides or are 5 mm or more wide through a thickness of 30 cm or wedge-shaped aggregates in a layer 15 cm or more thick more for some time in normal years and slickensides or that has its upper boundary within 125 cm of the mineral wedge-shaped aggregates in a layer 15 cm or more thick soil surface; or that has its upper boundary within 125 cm of the mineral soil surface; 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 b. A linear extensibility of 6.0 cm or more between the densic, lithic, or paralithic contact, whichever is mineral soil surface and either a depth of 100 cm or a shallower; and densic, lithic, or paralithic contact, whichever is shallower. Udertic Paleustalfs 2. In one or more horizons within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also JCFD. Other Paleustalfs that have one or both of the aquic conditions for some time in normal years (or artificial following: drainage). Aquertic Paleustalfs 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 JCFB. Other Paleustalfs that have both: some time in normal years and slickensides or wedge-shaped aggregates 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 aggregates in a layer 15 cm or more thick Vertic Paleustalfs that has its upper boundary within 125 cm of the mineral soil surface; or JCFE. Other Paleustalfs that have both: b. A linear extensibility of 6.0 cm or more between the 1. 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 aquic conditions for some time in normal years (or artificial shallower; and drainage); and 2. Saturation with water in one or more layers within 100 2. A sandy or sandy-skeletal particle-size class throughout a cm of the mineral soil surface in normal years for either or layer extending from the mineral soil surface to the top of an both: argillic horizon at a depth of 50 to 100 cm. a. 20 or more consecutive days; or Aquic Arenic Paleustalfs b. 30 or more cumulative days. JCFF. Other Paleustalfs that have, in one or more horizons Oxyaquic Vertic Paleustalfs within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in JCFC. Other Paleustalfs that have both: normal years (or artificial drainage). 1. When neither irrigated nor fallowed to store moisture, Aquic Paleustalfs either: a. A mesic or thermic soil temperature regime and a JCFG. Other Paleustalfs that are saturated with water in one or moisture control section that in normal years is dry in more layers within 100 cm of the mineral soil surface in normal some part for four-tenths or less of the time (cumulative) years for either or both: per year when the temperature at a depth of 50 cm below 1. 20 or more consecutive days; or the soil surface is higher than 5 oC; or 2. 30 or more cumulative days. b. A hyperthermic, isomesic, or warmer iso soil Oxyaquic Paleustalfs temperature regime and a moisture control section that in normal years is dry in some or all parts for less than 120 JCFH. Other Paleustalfs that have an argillic horizon that: cumulative days per year when the temperature at a depth of 50 cm below the soil surface is higher than 8 oC; and 1. Consists entirely of lamellae; or 2. One or both of the following: 2. Is a combination of two or more lamellae and one or Alfisols 75

more subhorizons with a thickness of 7.5 to 20 cm, each layer particle-size class throughout a layer extending from the mineral with an overlying eluvial horizon; or soil surface to the top of an argillic horizon at a depth of 100 cm or more. 3. Consists of one or more subhorizons that are more than Grossarenic Paleustalfs 20 cm thick, each with an overlying eluvial horizon, and above these horizons there are either: JCFL. Other Paleustalfs that have a sandy or sandy-skeletal a. Two or more lamellae with a combined thickness of 5 particle-size class throughout a layer extending from the mineral cm or more (that may or may not be part of the argillic soil surface to the top of an argillic horizon at a depth of 50 to horizon); or 100 cm. Arenic Paleustalfs b. A combination of lamellae (that may or may not be A part of the argillic horizon) and one or more parts of the JCFM. Other Paleustalfs that have 5 percent or more (by L argillic horizon 7.5 to 20 cm thick, each with an overlying volume) plinthite in one or more horizons within 150 cm of the F eluvial horizon. mineral soil surface. Lamellic Paleustalfs Plinthic Paleustalfs JCFI. Other Paleustalfs that have a sandy particle-size class JCFN. Other Paleustalfs that have a petrocalcic horizon that throughout the upper 75 cm of the argillic horizon or throughout has its upper boundary within 150 cm of the mineral soil the entire argillic horizon if it is less than 75 cm thick. surface. Psammentic Paleustalfs Petrocalcic Paleustalfs

JCFJ. Other Paleustalfs that have both: JCFO. Other Paleustalfs that have both: 1. A sandy or sandy-skeletal particle-size class throughout a 1. When neither irrigated nor fallowed to store moisture, layer extending from the mineral soil surface to the top of an either: argillic horizon at a depth of 50 to 100 cm; and a. A frigid 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 time (cumulative) per year when the soil temperature at a depth of 50 cm below the soil surface a. A frigid temperature regime and a moisture control is higher than 5 oC; or section that in normal years is dry in all parts for four- tenths or more of the time (cumulative) per year when the b. A mesic or thermic soil temperature regime and a soil 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; or some part for six-tenths or more of the time (cumulative) per year when the soil temperature at a depth of 50 cm b. 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 part for six-tenths or more of the time (cumulative) c. A hyperthermic, isomesic, or warmer iso soil per year when the soil temperature at a depth of 50 cm temperature regime and a moisture control section that in below the soil surface is higher than 5 oC; or normal years: c. A hyperthermic, isomesic, or warmer iso soil (1) Is moist in some or all parts for less than 90 temperature regime and a moisture control section that in consecutive days per year when the temperature at a normal years: depth of 50 cm below the soil surface is higher than 8 oC; and (1) Is moist in some or all parts for less than 90 consecutive days per year when the temperature at a (2) Is dry in some part for six-tenths or more of the depth of 50 cm below the soil surface is higher than cumulative days per year when the soil temperature at 8 oC; and a depth of 50 cm below the soil surface is higher than 5 oC; and (2) Is dry in some part for six-tenths or more of the cumulative days per year when the soil temperature at 2. A calcic horizon either within 100 cm of the mineral soil a depth of 50 cm below the soil surface is higher than surface if the weighted average particle-size class of the 5 oC. upper 50 cm of the argillic horizon is sandy, or within 60 cm Arenic Aridic Paleustalfs if it is loamy, or within 50 cm if it is clayey, and carbonates in all horizons above the calcic horizon. JCFK. Other Paleustalfs that have a sandy or sandy-skeletal Calcidic Paleustalfs 76 Keys to Soil Taxonomy

JCFP. Other Paleustalfs that, when neither irrigated nor moisture control section that in normal years is dry in some fallowed to store moisture, have: part for four-tenths or less of the time (cumulative) per year when the temperature at a depth of 50 cm below the soil 1. A frigid temperature regime and a moisture control surface is higher than 5 oC; or section that in normal years is dry in all parts for four-tenths or more of the time (cumulative) 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 higher than 5 oC; or normal years is dry in some or all parts for less than 120 cumulative days per year when the temperature at a depth of 2. A mesic or thermic soil temperature regime and a 50 cm below the soil surface is higher than 8 oC. moisture control section that in normal years is dry in some Udic Paleustalfs part for six-tenths or more of the time (cumulative) per year when the soil temperature at a depth of 50 cm below the soil JCFU. Other Paleustalfs. surface is higher than 5 oC; or Typic Paleustalfs 3. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in Plinthustalfs normal years: Key to Subgroups a. Is moist in some or all parts for less than 90 consecutive days per year when the temperature at a depth JCBA. All Plinthustalfs (provisionally). of 50 cm below the soil surface is higher than 8 oC; 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 a Rhodustalfs depth of 50 cm below the soil surface is higher than 5 oC. Aridic Paleustalfs Key to Subgroups JCGA. Rhodustalfs that have a lithic contact within 50 cm of JCFQ. Other Paleustalfs that have a CEC of less than 24 the mineral soil surface. cmol(+)/kg clay (by 1N NH OAc pH 7) in 50 percent or more 4 Lithic Rhodustalfs either of the argillic horizon if less than 100 cm thick or of its upper 100 cm. JCGB. Other Rhodustalfs that have a CEC of less than 24 Kandic Paleustalfs 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 JCFR. Other Paleustalfs that have, in all subhorizons in the upper 100 cm. upper 100 cm of the argillic horizon or throughout the entire Kanhaplic Rhodustalfs argillic horizon if less than 100 cm thick, more than 50 percent colors that have all of the following: JCGC. Other Rhodustalfs that, when neither irrigated nor 1. Hue of 2.5YR or redder; and fallowed to store moisture, have either: 2. Value, moist, of 3 or less; and 1. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in some 3. Dry value no more than 1 unit higher than the moist part for four-tenths or less of the time (cumulative) per year value. when the temperature at a depth of 50 cm below the soil Rhodic Paleustalfs surface is higher than 5 oC; or JCFS. Other Paleustalfs that have an argillic horizon with a 2. A hyperthermic, isomesic, or warmer iso soil base saturation (by sum of cations) of less than 75 percent temperature regime and a moisture control section that in throughout. normal years is dry in some or all parts for less than 120 Ultic Paleustalfs cumulative days per year when the temperature at a depth of 50 cm below the soil surface is higher than 8 oC. Udic Rhodustalfs JCFT. Other Paleustalfs that, when neither irrigated nor fallowed to store moisture, have either: JCGD. Other Rhodustalfs. 1. A mesic or thermic soil temperature regime and a Typic Rhodustalfs Alfisols 77

Xeralfs b. A base at a depth of 150 cm or mre; or 3. No densic, lithic, or paralithic contact within 50 cm of Key to Great Groups the mineral soil surface and an argillic or kandic horizon that has within 15 cm of its upper boundary both: JDA. Xeralfs that have a duripan that has its upper boundary a. A clayey, clayey-skeletal, fine, or very-fine particle- within 100 cm of the mineral soil surface. size class; and Durixeralfs, p. 77 b. A clay increase, in the fine-earth fraction, of either 20 JDB. Other Xeralfs that have a natric horizon. percent or more (absolute) within a vertical distance of 7.5 Natrixeralfs, p. 80 cm or of 15 percent or more (absolute) within a vertical A distance of 2.5 cm. L JDC. Other Xeralfs that have a fragipan with an upper Palexeralfs, p. 80 F boundary within 100 cm of the mineral soil surface. Fragixeralfs, p. 78 JDG. Other Xeralfs. Haploxeralfs, p. 78 JDD. Other Xeralfs that have one or more horizons within 150 cm of the mineral soil surface in which plinthite either forms a Durixeralfs continuous phase or constitutes one-half or more of the volume. Plinthoxeralfs, p. 82 Key to Subgroups JDAA. Durixeralfs that have a natric horizon. JDE. Other Xeralfs that have, in all subhorizons in the upper Natric Durixeralfs 100 cm of the argillic or kandic horizon or throughout the entire argillic or kandic horizon if less than 100 cm thick, more than JDAB. Other Durixeralfs that have, above the duripan, one or 50 percent colors that have all of the following: both of the following: 1. Hue of 2.5YR or redder; and 1. Cracks that are 5 mm or more wide through a thickness 2. Value, moist, of 3 or less; and of 30 cm or more for some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or 3. Dry value no more than 1 unit higher than the moist more thick; or value. Rhodoxeralfs, p. 82 2. A linear extensibility of 6.0 cm or more. Vertic Durixeralfs JDF. Other Xeralfs that have one or more of the following: JDAC. Other Durixeralfs that have, in one or more 1. A petrocalcic horizon that has its upper boundary within subhorizons within the argillic horizon, redox depletions with 150 cm of the mineral soil surface; or croma of 2 or less and also aquic conditions for some time in 2. No densic, lithic, or paralithic contact within 150 cm of normal years (or artificial drainage). the mineral soil surface and an argillic or kandic horizon that Aquic Durixeralfs has both: a. Within 150 cm of the mineral soil surface, either: JDAD. Other Durixeralfs that have both: (1) With increasing depth, no clay decrease of 20 1. An argillic horizon that has both: percent or more (relative) from the maximum clay a. A clayey particle-size class throughout some content [Clay is measured noncarbonate clay or based subhorizon 7.5 cm or more thick; and on the following formula: Clay % = 2.5(% water retained at 1500 kPa tension - % organic carbon), b. At its upper boundary or within some part, a clay whichever value is greater, but no more than 100]; increase either of 20 percent or more (absolute) within a or vertical distance of 7.5 cm or of 15 percent or more (absolute) within a vertical distance of 2.5 cm, in the fine- (2) 5 percent or more (by volume) skeletans on faces earth fraction; and of peds in the layer that has a 20 percent lower clay content and, below that layer, a clay increase of 3 2. A duripan that is strongly cemented or less cemented in percent or more (absolute) in the fine-earth fraction; all subhorizons. and Abruptic Haplic Durixeralfs 78 Keys to Soil Taxonomy

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

JDAG. Other Durixeralfs. Key to Subgroups Typic Durixeralfs JDGA. Haploxeralfs that have both: Fragixeralfs 1. A lithic contact within 50 cm of the mineral soil surface; and Key to Subgroups 2. A color value, moist, of 3 or less and 0.7 percent or more JDCA. Fragixeralfs that have, throughout one or more organic carbon either throughout an Ap horizon or horizons with a total thickness of 18 cm or more within 75 cm of throughout the upper 10 cm of an A horizon. the mineral soil surface, a fine-earth fraction with both a bulk Lithic Mollic 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 JDGB. Other Haploxeralfs that have both: more than 1.0. 1. A lithic contact within 50 cm of the mineral soil surface; Andic Fragixeralfs and JDCB. Other Fragixeralfs that have, throughout one or 2. An argillic or kandic horizon that is discontinuous more horizons with a total thickness of 18 cm or more horizontally in each pedon. within 75 cm of the mineral soil surface, one or both of the Lithic Ruptic-Inceptic Haploxeralfs following: JDGC. Other Haploxeralfs that have a lithic contact within 50 1. More than 35 percent (by volume) fragments coarser cm of the mineral soil surface. than 2.0 mm, of which more than 66 percent is cinders, Lithic Haploxeralfs pumice, and pumicelike fragments; or 2. A fine-earth fraction containing 30 percent or more JDGD. Other Haploxeralfs that have one or both of the particles 0.02 to 2.0 mm in diameter; and following: a. In the 0.02 to 2.0 mm fraction, 5 percent or more 1. Cracks within 125 cm of the mineral soil surface that are volcanic glass; and 5 mm or more wide through a thickness of 30 cm or more for

1 some time in normal years and slickensides or wedge-shaped b. [(Al plus /2 Fe, percent extracted by ammonium aggregates 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. Vitrandic Fragixeralfs 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, JDCC. Other Fragixeralfs that have an Ap horizon with a color lithic, or paralithic contact, whichever is shallower. value, moist, of 3 or less and a color value, dry, of 5 or ess Vertic Haploxeralfs (crushed and smoothed sample) or materials between the soil JDGE. Other Haploxeralfs that have both: surface and a depth of 18 cm that have these color values after mixing. 1. In one or more horizons within 75 cm of the mineral soil Mollic Fragixeralfs surface, redox depletions with chroma of 2 or less and also Alfisols 79

aquic conditions for some time in normal years (or artificial or more thick that has its upper boundary within 100 cm drainage); and of the mineral soil surface; or 2. Throughout one or more horizons with a total thickness b. In 60 percent or more of the volume of a layer 15 cm of 18 cm or more within 75 cm of the mineral soil surface, or more thick; and one or more of the following: 2. Redox depletions with chroma of 2 or less in layers that a. A fine-earth fraction with both a bulk density of 1.0 also have aquic conditions in normal years (or artificial g/cm3 or less, measured at 33 kPa water retention, and Al drainage) either: 1 plus /2 Fe percentages (by ammonium oxalate) totaling a. Within the upper 25 cm of the argillic or kandic more than 1.0; or horizon if its upper boundary is within 50 cm of the A b. More than 35 percent (by volume) fragments coarser mineral soil surface; or L than 2.0 mm, of which more than 66 percent is cinders, b. Within 75 cm of the mineral soil surface if the upper F pumice, and pumicelike fragments; or boundary of the argillic or kandic horizon is 50 cm or c. A fine-earth fraction containing 30 percent or more more below the mineral soil surface. particles 0.02 to 2.0 mm in diameter; and Fragiaquic Haploxeralfs (1) In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and JDGI. Other Haploxeralfs that have both:

1 (2) [(Al plus /2 Fe, percent extracted by ammonium 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 Aquandic Haploxeralfs drainage); and 2. An argillic or kandic horizon that has a base saturation JDGF. Other Haploxeralfs that have, throughout one or more (by sum of cations) of less than 75 percent in one or more horizons with a total thickness of 18 cm or more within 75 cm of subhorizons within its upper 75 cm or above a densic, lithic, the mineral soil surface, a fine-earth fraction with both a bulk or paralithic contact, whichever is shallower. density of 1.0 g/cm3 or less, measured at 33 kPa water retention, Aquultic Haploxeralfs 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. JDGJ. Other Haploxeralfs that have, in one or more horizons Andic Haploxeralfs within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in JDGG. Other Haploxeralfs that have, throughout one or more normal years (or artificial drainage). horizons with a total thickness of 18 cm or more within 75 cm of Aquic Haploxeralfs 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 or than 2.0 mm, of which more than 66 percent is cinders, more) in one or more subhorizons of the argillic or kandic pumice, and pumicelike fragments; or horizon. 2. A fine-earth fraction containing 30 percent or more Natric Haploxeralfs 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 volcanic glass; and 1. In 30 percent or more of the volume of a layer 15 cm or

1 more thick that has its upper boundary within 100 cm of the b. [(Al plus /2 Fe, percent extracted by ammonium mineral soil surface; or oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. 2. In 60 percent or more of the volume of a layer 15 cm or Vitrandic Haploxeralfs more thick. Fragic Haploxeralfs JDGH. Other Haploxeralfs that have both: 1. Fragic soil properties: JDGM. Other Haploxeralfs that have an argillic horizon that: a. In 30 percent or more of the volume of a layer 15 cm 1. Consists entirely of lamellae; or 80 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 above these horizons there are either: are 5 mm or more wide through a thickness of 30 cm or a. Two or more lamellae with a combined thickness of 5 more for some time in normal years and slickensides or cm or more (that may or may not be part of the argillic wedge-shaped aggregates in a layer 15 cm or more thick that horizon); or has its upper boundary within 125 cm of the mineral soil surface; or b. A combination of lamellae (that may or may not be part of the argillic horizon) and one or more parts of the 2. A linear extensibility of 6.0 cm or more between the argillic horizon 7.5 to 20 cm thick, each with an overlying mineral soil surface and either a depth of 100 cm or a densic, eluvial horizon. lithic, or paralithic contact, whichever is shallower. Lamellic Haploxeralfs Vertic Natrixeralfs

JDGN. Other Haploxeralfs that have a sandy particle-size JDBB. Other Natrixeralfs that have, in one or more horizons class throughout the upper 75 cm of the argillic horizon or within 75 cm of the mineral soil surface, redox depletions with throughout the entire argillic horizon if it is less than 75 cm chroma of 2 or less and also aquic conditions for some time in thick. normal years (or artificial drainage). Psammentic Haploxeralfs Aquic Natrixeralfs

JDGO. Other Haploxeralfs that have 5 percent or more (by JDBC. Other Natrixeralfs. volume) plinthite in one or more horizons within 150 cm of the Typic Natrixeralfs mineral soil surface. Plinthic Haploxeralfs Palexeralfs

JDGP. Other Haploxeralfs that have a calcic horizon that has Key to Subgroups its upper boundary within 100 cm of the mineral soil surface. JDFA. Palexeralfs that have one or both of the following: Calcic Haploxeralfs 1. Cracks within 125 cm of the mineral soil surface that are JDGQ. Other Haploxeralfs that have: 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge-shaped 1. An argillic, kandic, or natric horizon that is 35 cm or less aggregates in a layer 15 cm or more thick that has its upper thick; and boundary within 125 cm of the mineral soil surface; or 2. No densic, lithic, or paralithic contact within 100 cm of 2. A linear extensibility of 6.0 cm or more between the the mineral soil surface. mineral soil surface and either a depth of 100 cm or a densic, Inceptic Haploxeralfs lithic, or paralithic contact, whichever is shallower. Vertic Palexeralfs JDGR. Other Haploxeralfs that have an argillic or kandic horizon that has a base saturation (by sum of cations) of less JDFB. Other Palexeralfs that have both: than 75 percent in one or more subhorizons within its upper 75 cm or above a densic, lithic, or paralithic contact, whichever is 1. In one or more horizons within 75 cm of the mineral soil shallower. surface, redox depletions with chroma of 2 or less and also Ultic Haploxeralfs aquic conditions for some time in normal years (or artificial drainage); and JDGS. Other Haploxeralfs that have a color value, moist, of 2. Throughout one or more horizons with a total thickness 3 or less and 0.7 percent or more organic carbon either of 18 cm or more within 75 cm of the mineral soil surface, throughout an Ap horizon or throughout the upper 10 cm of an A one or more of the following: horizon. Mollic Haploxeralfs 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 1 JDGT. Other Haploxeralfs. plus /2 Fe percentages (by ammonium oxalate) totaling Typic Haploxeralfs more than 1.0; or Alfisols 81

b. More than 35 percent (by volume) fragments coarser a. Within the upper 25 cm of the argillic or kandic than 2.0 mm, of which more than 66 percent is cinders, horizon if its upper boundary is within 50 cm of the pumice, and pumicelike fragments; or mineral soil surface; or c. A fine-earth fraction containing 30 percent or more b. Within 75 cm of the mineral soil surface if the upper particles 0.02 to 2.0 mm in diameter; and boundary of the argillic or kandic horizon is 50 cm or more below the mineral soil surface. (1) In the 0.02 to 2.0 mm fraction, 5 percent or more Fragiaquic Palexeralfs volcanic glass; and

1 (2) [(Al plus /2 Fe, percent extracted by ammonium JDFF. Other Palexeralfs that have, in one or more horizons oxalate) times 60] plus the volcanic glass (percent) is within 75 cm of the mineral soil surface, redox depletions with A equal to 30 or more. chroma of 2 or less and also aquic conditions for some time in L Aquandic Palexeralfs normal years (or artificial drainage). F Aquic Palexeralfs JDFC. Other Palexeralfs that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of JDFG. Other Palexeralfs that have a petrocalcic horizon that the mineral soil surface, a fine-earth fraction with both a bulk has its upper boundary within 150 cm of the mineral soil density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 surface. and Al plus /2 Fe percentages (by ammonium oxalate) totaling Petrocalcic Palexeralfs more than 1.0. Andic Palexeralfs JDFH. Other Palexeralfs that have an argillic horizon that: 1. Consists entirely of lamellae; or JDFD. Other Palexeralfs that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of 2. Is a combination of two or more lamellae and one or the mineral soil surface, one or both of the following: more subhorizons with a thickness of 7.5 to 20 cm, each layer with an overlying eluvial horizon; or 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, 3. Consists of one or more subhorizons that are more than pumice, and pumicelike fragments; or 20 cm thick, each with an overlying eluvial horizon, and above these horizons there are either: 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; 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 a. In the 0.02 to 2.0 mm fraction, 5 percent or more horizon); or volcanic glass; and

1 b. A combination of lamellae (that may or may not be b. [(Al plus /2 Fe, percent extracted by ammonium part of the argillic horizon) and one or more parts of the oxalate) times 60] plus the volcanic glass (percent) is argillic horizon 7.5 to 20 cm thick, each with an overlying equal to 30 or more. eluvial horizon. Vitrandic Palexeralfs Lamellic Palexeralfs JDFE. Other Palexeralfs that have both: JDFI. Other Palexeralfs that have a sandy particle-size class 1. Fragic soil properties: throughout the upper 75 cm of the argillic horizon or throughout the entire argillic horizon if it is less than 75 cm thick. a. In 30 percent or more of the volume of a layer 15 cm Psammentic Palexeralfs or more thick that has its upper boundary within 100 cm of the mineral soil surface; or JDFJ. Other Palexeralfs that have a sandy or sandy-skeletal b. In 60 percent or more of the volume of a layer 15 cm particle-size class throughout a layer extending from the mineral or more thick; and soil surface to the top of an argillic or kandic horizon at a depth of 50 cm or more. 2. Redox depletions with chroma of 2 or less in layers that Arenic Palexeralfs also have aquic conditions in normal years (or artificial drainage) either: JDFK. Other Palexeralfs that have an exchangeable sodium 82

percentage of 15 or more (or a sodium adsorption ratio of 13 or Plinthoxeralfs more) in one or more horizons within 100 cm of the mineral soil surface. Key to Subgroups Natric Palexeralfs JDDA. All Plinthoxeralfs (provisionally). Typic Plinthoxeralfs JDFL. Other Palexeralfs that have fragic soil properties: 1. In 30 percent or more of the volume of a layer 15 cm or Rhodoxeralfs more thick that has its upper boundary within 100 cm of the mineral soil surface; or Key to Subgroups 2. In 60 percent or more of the volume of a layer 15 cm or JDEA. Rhodoxeralfs that have a lithic contact within 50 cm of more thick. the mineral soil surface. Fragic Palexeralfs Lithic Rhodoxeralfs

JDFM. Other Palexeralfs that have a calcic horizon within 150 JDEB. Other Rhodoxeralfs that have one or both of the cm of the mineral soil surface. following: Calcic 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 JDFN. Other Palexeralfs that have 5 percent or more (by more for some time in normal years and slickensides or volume) plinthite in one or more horizons within 150 cm of the wedge-shaped aggregates in a layer 15 cm or more thick mineral soil surface. that has its upper boundary within 125 cm of the mineral Plinthic Palexeralfs soil surface; or JDFO. Other Palexeralfs that have an argillic or kandic 2. A linear extensibility of 6.0 cm or more between horizon that has a base saturation (by sum of cations) of less the mineral soil surface and either a depth of 100 cm than 75 percent throughout. or a densic, lithic, or paralithic contact, whichever is Ultic Palexeralfs shallower. Vertic Rhodoxeralfs JDFP. Other Palexeralfs with an argillic or kandic horizon that has, in the fine-earth fraction, either or both: JDEC. Other Rhodoxeralfs that have a petrocalcic horizon that has its upper boundary within 150 cm of the mineral soil 1. Less than 35 percent clay throughout all subhorizons surface. within 15 cm of its upper boundary; or Petrocalcic Rhodoxeralfs 2. At its upper boundary, a clay increase of less than 20 percent (absolute) within a vertical distance of 7.5 cm and of JDED. Other Rhodoxeralfs that have a calcic horizon that less than 15 percent (absolute) within a vertical distance of has its upper boundary within 150 cm of the mineral soil 2.5 cm. 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 an horizon that is either less than 35 cm thick or is discontinuous Ap horizon or throughout the upper 10 cm of an A horizon. horizontally in each pedon. Mollic Palexeralfs Inceptic Rhodoxeralfs

JDFR. Other Palexeralfs. JDEF. Other Rhodoxeralfs. Typic Palexeralfs Typic Rhodoxeralfs 83

CHAPTER 6 Andisols

Key to Suborders is shallower, if there is no densic, lithic, or paralithic contact, duripan, or petrocalcic horizon within that depth; or DA. Andisols that have either: 2. Between either the mineral soil surface or the top of an 1. A histic epipedon; or organic layer with andic soil properties, whichever is A shallower, and a densic, lithic, or paralithic contact, a N 2. In a layer above a densic, lithic, or paralithic contact or duripan, or a petrocalcic horizon. D in a layer at a depth between 40 and 50 cm either from the Vitrands, p. 99 mineral soil surface or from the top of an organic layer with andic soil properties, whichever is shallowest, aquic DG. Other Andisols that have an ustic moisture regime. conditions for some time in normal years (or artificial Ustands, p. 98 drainage) and one or more of the following: a. 2 percent or more redox concentrations; or DH. Other Andisols. Udands, p. 91 b. A color value, moist, of 4 or more and 50 percent or more chroma of 2 or less either in redox depletions on faces of peds or in the matrix if peds are absent; or Aquands c. Enough active ferrous iron to give a positive reaction to alpha,alpha-dipyridyl at a time when the soil is not Key to Great Groups being irrigated. Aquands, p. 83 DAA. Aquands that have, in normal years, a mean annual soil temperature of 0 oC or colder and a mean summer soil DB. Other Andisols that have, in normal years, a mean annual temperature that: soil temperature of 0 oC or colder and a mean summer soil 1. Is 8 oC or colder if there is no O horizon; or temperature that: 2. Is 5 oC or colder if there is an O horizon. 1. Is 8 oC or colder if there is no O horizon; or Gelaquands, p. 85 2. Is 5 oC or colder if there is an O horizon. Gelands, p.90 DAB. Other Aquands that have a cryic soil temperature regime. DC. Other Andisols that have a cryic soil temperature regime. Cryaquands, p. 84 Cryands, p. 87 DAC. Other Aquands that have, in half or more of each pedon, DD. Other Andisols that have an aridic moisture regime. a placic horizon within 100 cm either of the mineral soil surface Torrands, p. 90 or of the top of an organic layer with andic soil properties, whichever is shallower. DE. Other Andisols that have a xeric moisture regime. Placaquands, p. 86 Xerands, p. 101 DAD. Other Aquands that have, in 75 percent or more of each DF. Other Andisols that have a 1500 kPa water retention of pedon, a cemented horizon that has its upper boundary within less than 15 percent on air-dried samples and less than 30 100 cm either of the mineral soil surface or of the top of an percent on undried samples throughout 60 percent or more of organic layer with andic soil properties, whichever is shallower. the thickness either: Duraquands, p. 84 1. Within 60 cm either of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever DAE. Other Aquands that have a 1500 kPa water retention of 84 Keys to Soil Taxonomy

less than 15 percent on air-dried samples and less than 30 DADB. Other Duraquands that have extractable bases (by 3+ percent on undried samples throughout 60 percent or more of NH4OAc) plus 1N KCl-extractable Al totaling less than 2.0 the thickness either: 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 1. Within 60 cm either of the mineral soil surface or of the and 100 cm either from the mineral soil surface or from the top top of an organic layer with andic soil properties, whichever of an organic layer with andic soil properties, whichever is is shallower, if there is no densic, lithic, or paralithic contact shallower. within that depth; or Acraquoxic Duraquands 2. Between either the mineral soil surface or the top of an organic layer with andic soil properties, DADC. Other Duraquands that have, at a depth between 25 whichever is shallower, and a densic, lithic, or paralithic and 100 cm either from the mineral soil surface or from the top contact. of an organic layer with andic soil properties, whichever is Vitraquands, p. 86 shallower, a layer 10 cm or more thick with more than 3.0 percent organic carbon and the colors of a mollic epipedon DAF. Other Aquands that have a melanic epipedon. throughout, underlying one or more horizons with a total Melanaquands, p. 85 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 DAG. Other Aquands that have episaturation. (absolute) lower. Epiaquands, p. 85 Thaptic Duraquands

DAH. Other Aquands. DADD. Other Duraquands. Endoaquands, p. 84 Typic Duraquands

Cryaquands Endoaquands Key to Subgroups Key to Subgroups DABA. Cryaquands that have a lithic contact within 50 cm DAHA. Endoaquands that have a lithic contact within 50 cm either of the mineral soil surface or of the top of an organic layer either of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. with andic soil properties, whichever is shallower. Lithic Cryaquands Lithic Endoaquands DABB. Other Cryaquands that have a histic epipedon. DAHB. Other Endoaquands that have a horizon 15 cm or Histic Cryaquands more thick that has 20 percent or more (by volume) cemented soil material and has its upper boundary within 100 cm either of DABC. Other Cryaquands that have, at a depth between 25 the mineral soil surface or of the top of an organic layer with and 100 cm either from the mineral soil surface or from the top of andic soil properties, whichever is shallower. an organic layer with andic soil properties, whichever is shallower, Duric Endoaquands a layer 10 cm or more thick with more than 3.0 percent organic carbon and the colors of a mollic epipedon throughout, DAHC. Other Endoaquands that have a histic epipedon. underlying one or more horizons with a total thickness of 10 cm Histic Endoaquands or more that have a color value, moist, 1 unit 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 Typic Cryaquands surface 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, a DADA. Duraquands that have a histic epipedon. 1500 kPa water retention of 70 percent or more throughout a Histic Duraquands layer 35 cm or more thick within 100 cm either of the mineral Andisols 85

soil surface or of the top of an organic layer with andic soil or more higher and an organic-carbon content 1 percent or more properties, whichever is shallower. (absolute) lower. Hydric Endoaquands Thaptic Epiaquands

DAHF. Other Endoaquands that have, at a depth between 25 DAGF. Other Epiaquands. and 100 cm either from the mineral soil surface or from the top Typic Epiaquands of an organic layer with andic soil properties, whichever is shallower, a layer 10 cm or more thick with more than 3.0 Gelaquands percent organic carbon and the colors of a mollic epipedon throughout, underlying one or more horizons with a total Key to Subgroups thickness of 10 cm or more that have a color value, moist, 1 unit DAAA. Gelaquands that have a histic epipedon. or more higher and an organic-carbon content 1 percent or more Histic Gelaquands (absolute) lower. Thaptic Endoaquands A DAAB. Other Gelaquands that have, at a depth between 25 N DAHG. Other Endoaquands. and 100 cm either from the mineral soil surface or from the top D Typic Endoaquands of an organic layer with andic soil properties, whichever is shallower, a layer 10 cm or more thick with more than 3.0 Epiaquands percent organic carbon and the colors of a mollic epipedon throughout, underlying one or more horizons with a total Key to Subgroups 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 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 and has its upper boundary within 100 cm either of the mineral soil surface or of the top of an organic layer with andic soil DAAC. Other Gelaquands. properties, whichever is shallower. Typic Gelaquands Duric Epiaquands

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 cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction of one or 50 cm either of the mineral soil surface or of the top of an more horizons with a total thickness of 10 cm or more at a depth organic layer with andic soil properties, whichever is shallower. between 25 and 50 cm either from the mineral soil surface or Lithic Melanaquands from the top of an organic layer with andic soil properties, whichever is shallower. DAFB. Other Melanaquands that have extractable bases (by 3+ Alic Epiaquands NH4OAc) plus 1N KCl-extractable Al totaling less than 2.0 cmol(+)/kg in the fine-earth fraction of one or more horizons DAGD. Other Epiaquands that have, on undried samples, a with a total thickness of 30 cm or more at a depth between 25 1500 kPa water retention of 70 percent or more throughout a and 100 cm either from the mineral soil surface or from the top layer 35 cm or more thick within 100 cm either of the mineral of an organic layer with andic soil properties, whichever is soil surface or of the top of an organic layer with andic soil 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 1. On undried samples, a 1500 kPa water retention of 70 and 100 cm either from the mineral soil surface or from the top percent or more throughout a layer 35 cm or more thick of an organic layer with andic soil properties, whichever is within 100 cm either of the mineral soil surface or of the top shallower, a layer 10 cm or more thick with more than 3.0 of an organic layer with andic soil properties, whichever is percent organic carbon and the colors of a mollic epipedon shallower; and throughout, underlying one or more horizons with a total 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 a 86 Keys to Soil Taxonomy

mollic epipedon throughout a layer 50 cm or more thick material and has its upper boundary within 100 cm either of the within 60 cm either of the mineral soil surface or of the top of mineral soil surface or of the top of an organic layer with andic an organic layer with andic soil properties, whichever is soil properties, whichever is shallower. shallower. Duric Placaquands Hydric Pachic Melanaquands DACD. Other Placaquands that have a histic epipedon. DAFD. Other Melanaquands that have, on undried samples, a Histic Placaquands 1500 kPa water retention of 70 percent or more throughout a layer 35 cm or more thick within 100 cm either of the mineral DACE. Other Placaquands that have, at a depth between 25 soil surface or of the top of an organic layer with andic soil and 100 cm either from the mineral soil surface or from the top properties, whichever is shallower. of an organic layer with andic soil properties, whichever is Hydric Melanaquands shallower, a layer 10 cm or more thick with more than 3.0 percent organic carbon and the colors of a mollic epipedon DAFE. Other Melanaquands that have more than 6.0 percent throughout, underlying one or more horizons with a total organic carbon and the colors of a mollic epipedon throughout a thickness of 10 cm or more that have a color value, moist, 1 unit layer 50 cm or more thick within 60 cm either of the mineral soil or more higher and an organic-carbon content 1 percent or more surface or of the top of an organic layer with andic soil (absolute) lower. properties, whichever is shallower. Thaptic Placaquands Pachic Melanaquands DAFF. Other Placaquands. DAFF. Other Melanaquands that have, at a depth between 40 Typic Placaquands and 100 cm either from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever is Vitraquands shallower, a layer 10 cm or more thick with more than 3.0 percent organic carbon and the colors of a mollic epipedon Key to Subgroups throughout, underlying one or more horizons with a total DAEA. Vitraquands that have a lithic contact within thickness of 10 cm or more that have a color value, moist, 1 unit 50 cm either of the mineral soil surface or of the top of or more higher and an organic-carbon content 1 percent or more an organic layer with andic soil properties, whichever is (absolute) lower. shallower. Thaptic Melanaquands Lithic Vitraquands DAFG. Other Melanaquands. DAEB. Other Vitraquands that have a horizon 15 cm or more Typic Melanaquands thick that has 20 percent or more (by volume) cemented soil material and has its upper boundary within 100 cm either of the Placaquands mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. Key to Subgroups Duric Vitraquands DACA. Placaquands that have a lithic contact within 50 cm either of the mineral soil surface or of the top of an DAEC. Other Vitraquands that have a histic epipedon. organic layer with andic soil properties, whichever is shallower. Histic Vitraquands Lithic Placaquands DAED. Other Vitraquands that have, at a depth between 25 DACB. Other Placaquands 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 is 1. A histic epipedon; and shallower, a layer 10 cm or more thick with more than 3.0 2. A horizon 15 cm or more thick that has 20 percent or percent organic carbon and the colors of a mollic epipedon more (by volume) cemented soil material and has its upper throughout, underlying one or more horizons with a total boundary within 100 cm either of the mineral soil surface or thickness of 10 cm or more that have a color value, moist, 1 unit of the top of an organic layer with andic soil properties, or more higher and an organic-carbon content 1 percent or more whichever is shallower. (absolute) lower. Duric Histic Placaquands Thaptic Vitraquands

DACC. Other Placaquands that have a horizon 15 cm or more DAEE. Other Vitraquands. thick that has 20 percent or more (by volume) cemented soil Typic Vitraquands Andisols 87

Cryands Duricryands Key to Great Groups Key to Subgroups DCAA. Duricryands that have, in some subhorizon at a depth DCA. Cryands that have, in 75 percent or more of each pedon, between 50 and 100 cm either from the mineral soil surface or a cemented horizon that has its upper boundary within 100 cm from the top of an organic layer with andic soil properties, either of the mineral soil surface or of the top of an organic layer whichever is shallower, aquic conditions for some time in normal with andic soil properties, whichever is shallower. years (or artificial drainage) and one or more of the following: Duricryands, p. 87 1. 2 percent or more redox concentrations; or DCB. Other Cryands that have, on undried samples, a 1500 2. A color value, moist, of 4 or more and 50 percent or kPa water retention of 100 percent or more, by weighted more chroma of 2 or less either in redox depletions on faces average, throughout either: of peds or in the matrix if peds are absent; or A 1. One or more layers with a total thickness of 35 cm 3. Enough active ferrous iron to give a positive reaction to N between the mineral soil surface or the top of an organic alpha,alpha-dipyridyl at a time when the soil is not being D layer with andic soil properties, whichever is shallower, irrigated. and 100 cm from the mineral soil surface or from the top Aquic Duricryands of an organic layer with andic soil properties, whichever is shallower, if there is no densic, lithic, or paralithic contact, DCAB. 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. 60 percent or more of the horizon thickness between and with a total thickness of 10 cm or more at a depth between either the mineral soil surface or the top of an organic layer 25 and 50 cm either from the mineral soil surface or from the with andic soil properties, whichever is shallower, and a top of an organic layer with andic properties, whichever is densic, lithic, or paralithic contact, a duripan, or a petrocalcic shallower. horizon. Eutric Duricryands Hydrocryands, p. 89 DCAC. Other Duricryands. DCC. Other Cryands that have a melanic epipedon. Typic Duricryands Melanocryands, p. 89

DCD. Other Cryands that have a layer that meets the depth, Fulvicryands thickness, and organic-carbon requirements for a melanic Key to Subgroups epipedon. Fulvicryands, p. 87 DCDA. Fulvicryands that have a lithic contact within 50 cm either of the mineral soil surface or of the top of an organic layer DCE. Other Cryands that have a 1500 kPa water retention of with andic soil properties, whichever is shallower. less than 15 percent on air-dried samples and less than 30 Lithic Fulvicryands percent on undried samples throughout 60 percent or more of the thickness either: DCDB. Other Fulvicryands that have both: 1. Within 60 cm either of the mineral soil surface or of 1. No horizons with more than 2.0 cmol(+)/kg Al3+ (by 1N the top of an organic layer with andic soil properties, KCl) in the fine-earth fraction and with a total thickness of 10 whichever is shallower, if there is no densic, lithic, or cm or more at a depth between 25 and 50 cm either from the paralithic contact, duripan, or petrocalcic horizon within mineral soil surface or from the top of an organic layer with that depth; or andic properties, whichever is shallower; and 2. Between either the mineral soil surface or the top of an 2. Throughout a layer 50 cm or more thick within 60 cm organic layer with andic soil properties, whichever is either of the mineral soil surface or of the top of an organic shallower, and a densic, lithic, or paralithic contact, a layer with andic properties, whichever is shallower: duripan, or a petrocalcic horizon. a. More than 6.0 percent organic carbon, by weighted Vitricryands, p. 89 average; and DCF. Other Cryands. b. More than 4.0 percent organic carbon in all parts. Haplocryands, p. 88 Eutric Pachic Fulvicryands 88 Keys to Soil Taxonomy

DCDC. Other Fulvicryands that have no horizons with more DCFC. Other Haplocryands that are saturated with water than 2.0 cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction within 100 cm of the mineral soil surface in normal years for and with a total thickness of 10 cm or more at a depth between either or both: 25 and 50 cm either from the mineral soil surface or from the 1. 20 or more consecutive days; or top of an organic layer with andic properties, whichever is shallower. 2. 30 or more cumulative days. Eutric Fulvicryands Oxyaquic Haplocryands

DCDD. Other Fulvicryands that have, throughout a layer 50 DCFD. Other Haplocryands that have more than 2.0 cm or more thick within 60 cm either of the mineral soil surface cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction of one or or of the top of an organic layer with andic soil properties, more horizons with a total thickness of 10 cm or more at a depth whichever is shallower: between 25 and 50 cm either from the mineral soil surface or from the top of an organic layer with andic soil properties, 1. More than 6.0 percent organic carbon, by weighted whichever is shallower. average; and Alic Haplocryands 2. More than 4.0 percent organic carbon in all parts. Pachic Fulvicryands DCFE. Other Haplocryands that have an ablic horizon overlying a cambic horizon in 50 percent or more in each pedon DCDE. Other Fulvicryands that have a 1500 kPa water or have a spodic horizon in 50 percent or more of each pedon. retention of less than 15 percent on air-dried samples and less Spodic Haplocryands than 30 percent on undried samples throughout one or more layers that have andic soil properties and have a total thickness DCFF. Other Haplocryands that have extractable bases (by 3+ of 25 cm or more within 100 cm either of the mineral soil NH4OAc) plus 1N KCl-extractable Al totaling less than 2.0 surface or of the top of an organic layer with andic soil cmol(+)/kg in the fine-earth fraction of one or more horizons properties, whichever is shallower. with a total thickness of 30 cm or more at a depth between 25 and Vitric Fulvicryands 100 cm either from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever is shallower. DCDF. Other Fulvicryands. Acrudoxic Haplocryands Typic Fulvicryands DCFG. Other Haplocryands that have a 1500 kPa water Haplocryands retention of less than 15 percent on air-dried samples and less than 30 percent on undried samples throughout one or more Key to Subgroups layers that have andic soil properties and have a total thickness of 25 cm or more within 100 cm either of the mineral soil DCFA. Haplocryands that have a lithic contact within 50 cm surface or of the top of an organic layer with andic soil either of the mineral soil surface or of the top of an organic layer properties, whichever is shallower. with andic soil properties, whichever is shallower. Vitric Haplocryands Lithic Haplocryands DCFH. Other Haplocryands that have, at a depth between 25 DCFB. Other Haplocryands that have, in some subhorizon at a and 100 cm either from the mineral soil surface or from the top depth between 50 and 100 cm either from the mineral soil of an organic layer with andic soil properties, whichever is surface or from the top of an organic layer with andic soil shallower, 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) and one 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 1. 2 percent or more redox concentrations; or or more higher and an organic-carbon content 1 percent or more (absolute) lower. 2. A color value, moist, of 4 or more and 50 percent or Thaptic Haplocryands more chroma of 2 or less either in redox depletions on faces of peds or in the matrix if peds are absent; or DCFI. Other Haplocryands that have a xeric moisture regime. 3. Enough active ferrous iron to give a positive reaction to Xeric Haplocryands alpha,alpha-dipyridyl at a time when the soil is not being irrigated. DCFJ. Other Haplocryands. Aquic Haplocryands Typic Haplocryands Andisols 89

Hydrocryands DCCB. Other Melanocryands that have a 1500 kPa water retention of less than 15 percent on air-dried samples and less Key to Subgroups than 30 percent on undried samples throughout one or more layers that have andic soil properties and have a total thickness DCBA. Hydrocryands that have a lithic contact within 50 cm of 25 cm or more within 100 cm either of the mineral soil either of the mineral soil surface or of the top of an organic layer surface or of the top of an organic layer with andic soil with andic soil properties, whichever is shallower. properties, whichever is shallower. Lithic Hydrocryands Vitric Melanocryands DCBB. Other Hydrocryands that have a placic horizon within DCCC. Other Melanocryands. 100 cm either of the mineral soil surface or of the top of an Typic Melanocryands organic layer with andic soil properties, whichever is shallower. Placic Hydrocryands

Vitricryands A DCBC. Other Hydrocryands that have, in one or more N horizons at a depth between 50 and 100 cm either from the Key to Subgroups D mineral soil surface or from the top of an organic layer with DCEA. Vitricryands that have a lithic contact within andic soil properties, whichever is shallower, aquic conditions 50 cm either of the mineral soil surface or of the top of an for some time in normal years (or artificial drainage) and one or organic layer that has andic soil properties, whichever is more of the following: shallower. 1. 2 percent or more redox concentrations; or Lithic Vitricryands 2. A color value, moist, of 4 or more and 50 percent DCEB. 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 soil on faces of peds or in the matrix if peds are absent; or surface or from the top of an organic layer with andic soil 3. Enough active ferrous iron to give a positive reaction to properties, whichever is shallower, aquic conditions for some alpha,alpha-dipyridyl at a time when the soil is not being time in normal years (or artificial drainage) and one 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 25 2. A color value, moist, of 4 or more and 50 percent or and 100 cm either from the mineral soil surface or from the top more chroma of 2 or less either in redox depletions on faces of an organic layer with andic soil properties, whichever is of peds or in the matrix if peds are absent; or shallower, a layer 10 cm or more thick with more than 3.0 3. Enough active ferrous iron to give a positive reaction to percent organic carbon and the colors of a mollic epipedon 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 or more higher and an organic-carbon content 1 percent or more (absolute) lower. DCEC. Other Vitricryands that are saturated with water in one Thaptic Hydrocryands or more layers within 100 cm of the mineral soil surface in normal years for either or both: DCBE. Other Hydrocryands. Typic Hydrocryands 1. 20 or more consecutive days; or 2. 30 or more cumulative days. Melanocryands Oxyaquic Vitricryands Key to Subgroups DCED. Other Vitricryands that have an albic horizon DCCA. Melanocryands that have a lithic contact within overlying a cambic horizon in 50 percent or more in each pedon 50 cm either of the mineral soil surface or of the top of an or have a spodic horizon in 50 percent or more of each pedon. organic layer that has andic soil properties, whichever is Spodic Vitricryands shallower. Lithic Melanocryands DCEE. Other Vitricryands that have, at a depth between 25 90 Keys to Soil Taxonomy

and 100 cm either from the mineral soil surface or from the top DBAB. Other Vitrigelands. of an organic layer with andic soil properties, whichever is Typic Vitrigelands shallower, a layer 10 cm or more thick with more than 3.0 percent organic carbon and the colors of a mollic epipedon Torrands 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 Great Groups or more higher and an organic-carbon content 1 percent or more (absolute) lower. DDA. Torrands that have, in 75 percent or more of each Thaptic Vitricryands pedon, a cemented horizon that has its upper boundary within 100 cm either of the mineral soil surface or of the top of an DCEF. Other Vitricryands that have a xeric moisture regime organic layer with andic soil properties, whichever is and a mollic or umbric epipedon. shallower. Humic Xeric Vitricryands Duritorrands, p. 90

DCEG. Other Vitricryands that have a xeric moisture regime. DDB. Other Torrands that have, on air-dried samples, a 1500 Xeric Vitricryands kPa water retention of less than 15 percent throughout 60 percent or more of the thickness either: DCEH. Other Vitricryands that have an argillic or kandic 1. Within 60 cm either of the mineral soil surface or of the horizon that has both: top of an organic layer with andic soil properties, whichever 1. An upper boundary within 125 cm either of the mineral is shallower, if there is no densic, lithic, or paralithic contact, soil surface or of the top of an organic layer with andic soil duripan, or petrocalcic horizon within that depth; or properties, whichever is shallower; and 2. Between either the mineral soil surface or the top of an 2. A base saturation (by sum of cations) of less than 35 organic layer with andic soil properties, whichever is percent throughout the upper 50 cm or throughout the entire shallower, and a densic, lithic, or paralithic contact, a argillic or kandic horizon if it is less than 50 cm thick. duripan, or a petrocalcic horizon. Ultic Vitricryands Vitritorrands, p. 91

DCEI. Other Vitricryands that have an argillic or kandic DDC. Other Torrands. horizon that has its upper boundary within 125 cm either of the Haplotorrands, p. 91 mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. Duritorrands Alfic Vitricryands Key to Subgroups DCEJ. Other Vitricryands that have a mollic or umbric DDAA. Duritorrands that have a petrocalcic horizon that has epipedon. its upper boundary within 100 cm of the mineral soil surface. Humic Vitricryands Petrocalcic Duritorrands DCEK. Other Vitricryands. DDAB. Other Duritorrands that have, on air-dried samples, a Typic Vitricryands 1500 kPa water retention of less than 15 percent throughout 60 percent or more of the thickness either: Gelands 1. Between either the mineral soil surface or the top of an Key to Great Groups organic layer with andic soil properties, whichever is shallower, if there is no paralithic contact or duripan within DBA. All Gelands are considered Vitrigelands. that depth, and a point 60 cm below that depth; or Vitrigelands, p. 90 2. Between either the mineral soil surface or the top of an organic layer with andic soil properties, whichever is Vitrigelands shallower, and a paralithic contact or a duripan. Vitric Duritorrands Key to Subgroups DBAA. Vitrigelands that have a mollic or umbric epipedon. DDAC. Other Duritorrands. Humic Vitrigelands Typic Duritorrands Andisols 91

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 either of the mineral soil surface Lithic Haplotorrands or of 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. 97 more thick that has 20 percent or more (by volume) cemented soil material and has its upper boundary within 100 cm of the DHB. Other Udands that have, in 75 percent or more of each mineral soil surface. pedon, a cemented horizon that has its upper boundary within Duric Haplotorrands 100 cm either of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. A DDCC. Other Haplotorrands that have a calcic horizon that has Durudands, p. 91 N its upper boundary within 125 cm of the mineral soil surface. D Calcic Haplotorrands DHC. Other Udands that have a melanic epipedon. Melanudands, p. 96 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 between the mineral soil surface or the top of an organic DDBA. Vitritorrands that have a lithic contact within 50 cm of layer with andic soil properties, whichever is shallower, the mineral soil surface. and 100 cm from the mineral soil surface or from the Lithic Vitritorrands top of an organic layer with andic soil properties, whichever is shallower, if there is no densic, lithic, or DDBB. Other Vitritorrands that have a horizon 15 cm or more paralithic contact, duripan, or petrocalcic horizon within that thick that has 20 percent or more (by volume) cemented soil depth; or material and has its upper boundary within 100 cm of the mineral soil surface. 2. 60 percent or more of the horizon thickness between Duric Vitritorrands either the mineral soil surface or the top of an organic layer with andic soil properties, whichever is shallower, and a DDBC. Other Vitritorrands 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 from the mineral soil surface, horizon. aquic conditions for some time in normal years (or artificial Hydrudands, p. 95 drainage) and one or more of the following: DHE. Other Udands that have a layer that meets the depth, 1. 2 percent or more redox concentrations; or thickness, and organic-carbon requirements for a melanic 2. A color value, moist, of 4 or more and 50 percent or epipedon. more chroma of 2 or less either in redox depletions on faces Fulvudands, p. 92 of peds or in the matrix if peds are absent; or DHF. Other Udands. 3. Enough active ferrous iron to give a positive reaction to Hapludands, p. 93 alpha,alpha-dipyridyl at a time when the soil is not being irrigated. Aquic Vitritorrands Durudands

DDBD. Other Vitritorrands that have a calcic horizon that has Key to Subgroups its upper boundary within 125 cm of the mineral soil surface. DHBA. Durudands that have, in one or more horizons above Calcic Vitritorrands the cemented horizon, aquic conditions for some time in normal years (or artificial drainage) and one or more of the following: DDBE. Other Vitritorrands. Typic Vitritorrands 1. 2 percent or more redox concentrations; or 92 Keys to Soil Taxonomy

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

Fulvudands DHEF. Other Fulvudands that have extractable bases (by NH OAc) plus 1N KCl-extractable Al3+ totaling less than 2.0 Key to Subgroups 4 cmol(+)/kg in the fine-earth fraction of one or more horizons DHEA. Fulvudands that have both: with a total thickness of 30 cm or more at a depth between 25 and 100 cm either from the mineral soil surface or from the top 1. A lithic contact within 50 cm either of the mineral soil of an organic layer with andic soil properties, whichever is surface or of the top of an organic layer with andic soil shallower. properties, whichever is shallower; and Acrudoxic Fulvudands 2. No horizons with more than 2.0 cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction and with a total thickness of 10 DHEG. Other Fulvudands that have an argillic or kandic cm or more at a depth between 25 cm from the mineral soil horizon that has both: Andisols 93

1. An upper boundary within 125 cm either of the mineral DHEL. Other Fulvudands. soil surface or of the top of an organic layer with andic soil Typic Fulvudands properties, whichever is shallower; and 2. A base saturation (by sum of cations) of less than 35 Hapludands percent throughout its upper 50 cm. Ultic Fulvudands Key to Subgroups DHFA. Hapludands that have a lithic contact within 50 cm DHEH. Other Fulvudands that have both: either of the mineral soil surface or of the top of an organic layer 1. No horizons with more than 2.0 cmol(+)/kg Al3+ (by 1N with andic soil properties, whichever is shallower. KCl) in the fine-earth fraction and with a total thickness of 10 Lithic Hapludands cm or more at a depth between 25 and 50 cm either from the mineral soil surface or from the top of an organic layer with DHFB. Other Hapludands that have anthraquic conditions. andic soil properties, whichever is shallower; and Anthraquic Hapludands A N 2. Throughout a layer 50 cm or more thick within 60 cm DHFC. Other Hapludands that have both: D either of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower: 1. A horizon 15 cm or more thick that has 20 percent or more (by volume) cemented soil material and has its upper a. More than 6.0 percent organic carbon, by weighted boundary within 100 cm either of the mineral soil surface or average; and of the top of an organic layer with andic soil properties, b. More than 4.0 percent organic carbon in all parts. whichever is shallower; and Eutric Pachic Fulvudands 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 an DHEI. Other Fulvudands that have no horizons with more than organic layer with andic soil properties, whichever is 2.0 cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction and shallower, aquic conditions for some time in normal years (or with a total thickness of 10 cm or more at a depth between 25 artificial drainage) and one or more of the following: and 50 cm either from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever is a. 2 percent or more redox concentrations; or shallower. b. A color value, moist, of 4 or more and 50 percent or Eutric Fulvudands more chroma of 2 or less either in redox depletions on faces of peds or in the matrix if peds are absent; or DHEJ. Other Fulvudands that have, throughout a layer 50 cm or more thick within 60 cm either of the mineral soil surface or c. Enough active ferrous iron to give a positive reaction of the top of an organic layer with andic soil properties, to alpha,alpha-dipyridyl at a time when the soil is not whichever is shallower: being irrigated. Aquic Duric Hapludands 1. More than 6.0 percent organic carbon, by weighted average; and DHFD. Other Hapludands that have a horizon 15 cm or more 2. More than 4.0 percent organic carbon in all parts. thick that has 20 percent or more (by volume) cemented soil Pachic Fulvudands material and has its upper boundary within 100 cm either of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. DHEK. Other Fulvudands that have, at a depth between 40 Duric Hapludands and 100 cm either from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever is DHFE. Other Hapludands that have, in one or more horizons shallower, a layer 10 cm or more thick with more than 3.0 at a depth between 50 and 100 cm either from the mineral soil percent organic carbon and the colors of a mollic epipedon surface or from the top of an organic layer with andic soil throughout, underlying one or more horizons with a total properties, whichever is shallower, aquic conditions for some thickness of 10 cm or more that have a color value, moist, 1 unit time in normal years (or artificial drainage) and one or more of or more higher and an organic-carbon content 1 percent or more the following: (absolute) lower. Thaptic Fulvudands 1. 2 percent or more redox concentrations; or 94 Keys to Soil Taxonomy

2. A color value, moist, of 4 or more and 50 percent or unit or more higher and an organic-carbon content 1 percent more chroma of 2 or less either in redox depletions on faces or more (absolute) lower. of peds or in the matrix if peds are absent; or Acrudoxic Thaptic Hapludands 3. Enough active ferrous iron to give a positive reaction to DHFJ. Other Hapludands that have both: alpha,alpha-dipyridyl at a time when the soil is not being

irrigated. 1. Extractable bases (by NH4OAc) plus 1N KCl-extractable Aquic Hapludands Al3+ totaling less than 2.0 cmol(+)/kg in the fine-earth fraction of one or more horizons with a total thickness of 30 DHFF. Other Hapludands that are saturated with water within cm or more at a depth between 25 and 100 cm either from the 100 cm of the mineral soil surface in normal years for either or mineral soil surface or from the top of an organic layer with both: andic soil properties, whichever is shallower; and 1. 20 or more consecutive days; or 2. An argillic or kandic horizon that has both: 2. 30 or more cumulative days a. An upper boundary within 125 cm either of the Oxyaquic Hapludands mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower; and DHFG. Other Hapludands that have more than 2.0 b. A base saturation (by sum of cations) of less than 35 cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction of one or percent throughout its upper 50 cm. more horizons with a total thickness of 10 cm or more at a depth Acrudoxic Ultic Hapludands between 25 and 50 cm either from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever is shallower. DHFK. Other Hapludands that have extractable bases (by 3+ Alic Hapludands NH4OAc) plus 1N KCl-extractable Al totaling less than 2.0 cmol(+)/kg in the fine-earth fraction of one or more horizons DHFH. Other Hapludands that have both: with a total thickness of 30 cm or more at a depth between 25 and 100 cm either from the mineral soil surface or from the top 1. Extractable bases (by NH OAc) plus 1N KCl-extractable 4 of an organic layer with andic soil properties, whichever is Al3+ totaling less than 2.0 cmol(+)/kg in the fine-earth shallower. fraction of one or more horizons with a total thickness of 30 Acrudoxic Hapludands cm or more at a depth between 25 and 100 cm either from the mineral soil surface or from the top of an organic layer with DHFL. Other Hapludands that have a 1500 kPa water andic soil properties, whichever is shallower; and retention of less than 15 percent on air-dried samples and less 2. On undried samples, a 1500 kPa water retention of 70 than 30 percent on undried samples throughout one or more percent or more throughout a layer 35 cm or more thick layers that have andic soil properties and have a total thickness within 100 cm either of the mineral soil surface or of the top of 25 cm or more within 100 cm either of the mineral soil of an organic layer with andic soil properties, whichever is surface or of the top of an organic layer with andic soil shallower. properties, whichever is shallower. Acrudoxic Hydric Hapludands Vitric Hapludands

DHFI. Other Hapludands that have, at a depth between 25 and DHFM. Other Hapludands that have both: 100 cm either from the mineral soil surface or from the top of an 1. On undried samples, a 1500 kPa water retention of 70 organic layer with andic soil properties, whichever is shallower, percent or more throughout a layer 35 cm or more thick both: within 100 cm either of the mineral soil surface or of the top

1. Extractable bases (by NH4OAc) plus 1N KCl-extractable of an organic layer with andic soil properties, whichever is Al3+ totaling less than 2.0 cmol(+)/kg in the fine-earth shallower; and fraction of one or more horizons with a total thickness of 30 2. At a depth between 25 and 100 cm either from the cm or more; and mineral soil surface or from the top of an organic layer with 2. A layer 10 cm or more thick with more than 3.0 percent andic soil properties, whichever is shallower, a layer 10 cm organic carbon and the colors of a mollic epipedon or more thick with more than 3.0 percent organic carbon and throughout, underlying one or more horizons with a total the colors of a mollic epipedon throughout, underlying one or thickness of 10 cm or more that have a color value, moist, 1 more horizons with a total thickness of 10 cm or more that Andisols 95

have a color value, moist, 1 unit or more higher and an DHFS. Other Hapludands that have an argillic or kandic organic-carbon content 1 percent or more (absolute) lower. horizon that has both: Hydric Thaptic Hapludands 1. An upper boundary within 125 cm either of the mineral soil surface or of the top of an organic layer with andic soil DHFN. Other Hapludands that have, on undried samples, a properties, whichever is shallower; and 1500 kPa water retention of 70 percent or more throughout a layer 35 cm or more thick within 100 cm either of the mineral 2. A base saturation (by sum of cations) of less than 35 soil surface or of the top of an organic layer with andic soil percent throughout its upper 50 cm. properties, whichever is shallower. Ultic Hapludands Hydric Hapludands DHFT. Other Hapludands that have an argillic or kandic DHFO. Other Hapludands that have both: horizon that has its upper boundary within 125 cm either of the mineral soil surface or of the top of an organic layer with andic 1. A sum of extractable bases of more than 25.0 soil properties, whichever is shallower. A cmol(+)/kg in the fine-earth fraction throughout one or more Alfic Hapludands N horizons with a total thickness of 15 cm or more at a depth D between 25 and 75 cm either from the mineral soil surface or DHFU. Other Hapludands. from the top of an organic layer with andic soil properties, Typic Hapludands whichever is shallower; and 2. At a depth between 25 and 100 cm either from the mineral soil surface or from the top of an organic layer with Hydrudands andic soil properties, whichever is shallower, a layer 10 cm Key to Subgroups or more thick with more than 3.0 percent organic carbon and the colors of a mollic epipedon throughout, underlying one or DHDA. Hydrudands that have a lithic contact within 50 cm more horizons with a total thickness of 10 cm or more that either of the mineral soil surface or of the top of an organic layer have a color value, moist, 1 unit or more higher and an with andic soil properties, whichever is shallower. organic-carbon content 1 percent or more (absolute) lower. Lithic Hydrudands Eutric Thaptic Hapludands DHDB. Other Hydrudands that have, in one or more horizons DHFP. Other Hapludands that have, at a depth between 25 at a depth between 50 and 100 cm either from the mineral soil and 100 cm either from the mineral soil surface or from the top surface or from the top of an organic layer with andic soil of an organic layer with andic soil properties, whichever is properties, whichever is shallower, aquic conditions for some shallower, a layer 10 cm or more thick with more than 3.0 time in normal years (or artificial drainage) and one or more of percent organic carbon and the colors of a mollic epipedon the following: throughout, underlying one or more horizons with a total 1. 2 percent or more redox concentrations; or 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 2. A color value, moist, of 4 or more and 50 percent or (absolute) lower. more chroma of 2 or less either in redox depletions on faces Thaptic Hapludands of peds or in the matrix if peds are absent; or 3. Enough active ferrous iron to give a positive reaction to DHFQ. Other Hapludands that have a sum of extractable bases alpha,alpha-dipyridyl at a time when the soil is not being of more than 25.0 cmol(+)/kg in the fine-earth fraction irrigated. throughout one or more horizons with a total thickness of 15 cm Aquic Hydrudands or more at a depth between 25 and 75 cm either from the mineral soil surface or from the top of an organic layer with DHDC. Other Hydrudands that have, at a depth between 25 andic soil properties, whichever is shallower. and 100 cm either from the mineral soil surface or from the top Eutric Hapludands of an organic layer with andic soil properties, whichever is shallower, both: DHFR. Other Hapludands that have an oxic horizon that has its upper boundary within 125 cm either of the mineral soil 1. Extractable bases (by NH4OAc) plus 1N KCl-extractable surface or of the top of an organic layer with andic soil Al3+ totaling less than 2.0 cmol(+)/kg in the fine-earth properties, whichever is shallower. fraction of one or more horizons with a total thickness of 30 Oxic Hapludands cm or more; and 96 Keys to Soil Taxonomy

2. A layer 10 cm or more thick with more than 3.0 percent DHCB. Other Melanudands that have anthraquic conditions. organic carbon and the colors of a mollic epipedon Anthraquic Melanudands throughout, underlying one or more horizons with a total thickness of 10 cm or more that have a color value, moist, 1 DHCC. Other Melanudands that have, in one or more horizons unit or more higher and an organic-carbon content 1 percent at a depth between 50 and 100 cm either from the mineral soil or more (absolute) lower. surface or from the top of an organic layer with andic soil Acrudoxic Thaptic Hydrudands properties, whichever is shallower, aquic conditions for some time in normal years (or artificial drainage) and one or more of DHDD. Other Hydrudands that have extractable bases (by the following: NH OAc) plus 1N KCl-extractable Al3+ totaling less than 2.0 4 1. 2 percent or more redox concentrations; 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 and 2. A color value, moist, of 4 or more and 50 percent or 100 cm either from the mineral soil surface or from the top of an more chroma of 2 or less either in redox depletions on faces organic layer with andic soil properties, 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 to alpha,alpha-dipyridyl at a time when the soil is not being DHDE. Other Hydrudands that have, at a depth between 25 and irrigated. 100 cm either from the mineral soil surface or from the top of an Aquic Melanudands organic layer with andic soil properties, whichever is shallower, a layer 10 cm or more thick with more than 3.0 percent organic DHCD. Other Melanudands that have both: carbon and the colors of a mollic epipedon throughout, underlying one or more horizons with a total thickness of 10 cm 1. Extractable bases (by NH4OAc) plus 1N KCl-extractable or more that have a color value, moist, 1 unit or more higher and Al3+ totaling less than 2.0 cmol(+)/kg in the fine-earth an organic-carbon content 1 percent or more (absolute) lower. fraction of one or more horizons with a total thickness of 30 Thaptic Hydrudands cm or more at a depth between 25 and 100 cm either from the mineral soil surface or from the top of an organic layer with DHDF. Other Hydrudands that have a sum of extractable andic soil properties, whichever is shallower; and bases of more than 25.0 cmol(+)/kg in the fine-earth fraction 2. A 1500 kPa water retention of less than 15 percent on throughout one or more horizons with a total thickness of 15 cm air-dried samples and less than 30 percent on undried or more at a depth between 25 and 75 cm either from the samples throughout one or more layers that have andic soil 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 either of the mineral soil surface or of the top of an Eutric Hydrudands organic layer with andic soil properties, whichever is shallower. DHDG. Other Hydrudands that have an argillic or kandic Acrudoxic Vitric Melanudands horizon that has both: 1. An upper boundary within 125 cm either of the mineral DHCE. Other Melanudands that have both: soil surface or of the top of an organic layer with andic soil 1. Extractable bases (by NH OAc) plus 1N KCl-extractable properties, whichever is shallower; and 4 Al3+ totaling less than 2.0 cmol(+)/kg in the fine-earth 2. A base saturation (by sum of cations) of less than 35 fraction of one or more horizons with a total thickness of 30 percent throughout its upper 50 cm. cm or more at a depth between 25 and 100 cm either from the Ultic Hydrudands mineral soil surface or from the top of an organic layer with andic soil properties, whichever is shallower; and DHDH. Other Hydrudands. 2. On undried samples, a 1500 kPa water retention of 70 Typic Hydrudands percent or more throughout a layer 35 cm or more thick within 100 cm either of the mineral soil surface or of the top Melanudands of an organic layer with andic soil properties, whichever is shallower. Key to Subgroups Acrudoxic Hydric Melanudands DHCA. Melanudands that have a lithic contact within 50 cm either of the mineral soil surface or of the top of an organic layer DHCF. Other Melanudands that have extractable bases (by 3+ that has andic soil properties, whichever is shallower. NH4OAc) plus 1N KCl-extractable Al totaling less than 2.0 Lithic Melanudands cmol(+)/kg in the fine-earth fraction of one or more horizons Andisols 97

with a total thickness of 30 cm or more at a depth between 25 layer 35 cm or more thick within 100 cm either of the mineral and 100 cm either from the mineral soil surface or from the top soil surface or of the top of an organic layer with andic soil of an organic layer with andic soil properties, whichever is properties, whichever is shallower. 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 is 1. More than 6.0 percent organic carbon and the colors of a shallower, a layer 10 cm or more thick with more than 3.0 mollic epipedon throughout a layer 50 cm or more thick percent organic carbon and the colors of a mollic epipedon within 60 cm either 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 on (absolute) lower. A air-dried samples and less than 30 percent on undried Thaptic Melanudands N samples throughout one or more layers that have andic soil D properties and have a total thickness of 25 cm or more within DHCM. Other Melanudands that have an argillic or kandic 100 cm either of the mineral soil surface or of the top of an horizon that has both: organic layer with andic soil properties, whichever is 1. An upper boundary within 125 cm either of the mineral shallower. soil surface or of the top of an organic layer with andic soil Pachic Vitric Melanudands properties, whichever is shallower; and DGCH. 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 its upper 50 cm. than 30 percent on undried samples throughout one or more Ultic Melanudands layers that have andic soil properties and have a total thickness of 25 cm or more within 100 cm either of the mineral soil DHCN. Other Melanudands that have a sum of extractable surface or of the top of an organic layer with andic soil bases of more than 25.0 cmol(+)/kg in the fine-earth fraction properties, whichever is shallower. throughout one or more horizons with a total thickness of 15 cm Vitric Melanudands or more at a depth between 25 and 75 cm either from the mineral soil surface or from the top of an organic layer with DHCI. Other Melanudands that have both: andic soil properties, whichever is shallower. Eutric Melanudands 1. On undried samples, a 1500 kPa water retention of 70 percent or more throughout a layer 35 cm or more thick DHCO. Other Melanudands. within 100 cm either of the mineral soil surface or of the top Typic Melanudands of an organic layer with andic soil properties, whichever is shallower; and Placudands 2. More than 6.0 percent organic carbon and the colors of a mollic epipedon throughout a layer 50 cm or more thick Key to Subgroups within 60 cm either of the mineral soil surface or of the top of DHAA. Placudands that have a lithic contact within an organic layer with andic soil properties, whichever is 50 cm either of the mineral soil surface or of the top of an shallower. organic layer that has andic soil properties, whichever is Hydric Pachic Melanudands shallower. Lithic Placudands DHCJ. Other Melanudands that have more than 6.0 percent organic carbon and the colors of a mollic epipedon throughout a DHAB. Other Placudands that have, in one or more horizons layer 50 cm or more thick within 60 cm either of the mineral soil at a depth between 50 cm either from the mineral soil surface or surface or of the top of an organic layer with andic soil 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) and one or more of the following: DHCK. Other Melanudands that have, on undried samples, a 1500 kPa water retention of 70 percent or more throughout a 1. 2 percent or more redox concentrations; or 98 Keys to Soil Taxonomy

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 more chroma of 2 or less either in redox depletions on faces of peds or in the matrix if peds are absent; or of peds or in the matrix if peds are absent; or 3. Enough active ferrous iron to give a positive reaction to 3. Enough active ferrous iron to give a positive reaction to alpha,alpha-dipyridyl at a time when the soil is not being alpha,alpha-dipyridyl at a time when the soil is not being irrigated. irrigated. Aquic Durustands Aquic Placudands DGAB. Other Durustands that have, at a depth between 25 DHAC. Other Placudands that have extractable bases (by and 100 cm either from the mineral soil surface or from the top 3+ NH4OAc) plus 1N KCl-extractable Al totaling less than 2.0 of an organic layer with andic soil properties, whichever is cmol(+)/kg in the fine-earth fraction of one or more horizons 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 cm either from the mineral soil surface or from the top of an throughout, underlying one or more horizons with a total organic layer with andic soil properties, whichever is shallower, thickness of 10 cm or more that have a color value, moist, 1 unit and the placic horizon. or more higher and an organic-carbon content 1 percent or more Acrudoxic Placudands (absolute) lower. Thaptic Durustands DHAD. Other Placudands that have, on undried samples, a 1500 kPa water retention of 70 percent or more throughout a DGAC. Other Durustands that have a melanic, mollic, or layer 35 cm or more thick within 100 cm either of the mineral umbric epipedon. soil surface or of the top of an organic layer with andic soil Humic Durustands properties, whichever is shallower. Hydric Placudands DGAD. Other Durustands. Typic Durustands DHAE. Other Placudands. Typic Placudands Haplustands Ustands Key to Subgroups DGBA. Haplustands that have a lithic contact within 50 cm Key to Great Groups either of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. DGA. Ustands that have, in 75 percent or more of each pedon, Lithic Haplustands a cemented horizon that has its upper boundary within 100 cm either of the mineral soil surface or of the top of an organic layer DGBB. Other Haplustands that have, in one or more horizons with andic soil properties, whichever is shallower. at a depth between 50 and 100 cm either from the mineral soil Durustands, p. 98 surface or from the top of an organic layer with andic soil properties, whichever is shallower, aquic conditions for some DGB. Other Ustands. time in normal years (or artificial drainage) and one or more of Haplustands, p. 98 the following: Durustands 1. 2 percent or more redox concentrations; or 2. A color value, moist, of 4 or more and 50 percent or Key to Subgroups more chroma of 2 or less either in redox depletions on faces DGAA. Durustands that have, in one or more horizons at a of peds or in the matrix if peds are absent; or depth between 50 and 100 cm either from the mineral soil 3. Enough active ferrous iron to give a positive reaction to surface or from the top of an organic layer with andic soil alpha,alpha-dipyridyl at a time when the soil is not being properties, whichever is shallower, aquic conditions for some irrigated. time in normal years (or artificial drainage) and one or more of Aquic Haplustands the following: 1. 2 percent or more redox concentrations; or DGBC. Other Haplustands that have both:

2. A color value, moist, of 4 or more and 50 percent or 1. Extractable bases (by NH4OAc) plus 1N KCl-extractable Andisols 99

Al3+ totaling less than 15.0 cmol(+)/kg in the fine-earth DGBI. Other Haplustands that have an oxic horizon that has fraction throughout one or more horizons with a total its upper boundary within 125 cm either of the mineral soil thickness of 60 cm or more within 75 cm either of the surface or of the top of an organic layer with andic soil mineral soil surface or of the top of an organic layer with properties, whichever is shallower. andic soil properties, whichever is shallower; and Oxic Haplustands 2. A 1500 kPa water retention of less than 15 percent on DGBJ. Other Haplustands that have an argillic or kandic air-dried samples and less than 30 percent on undried horizon that has both: samples throughout one or more layers that have andic soil properties and have a total thickness of 25 cm or more within 1. An upper boundary within 125 cm either of the mineral 100 cm either of the mineral soil surface or of the top of an soil surface or of the top of an organic layer with andic soil organic layer with andic soil properties, whichever is properties, whichever is shallower; and shallower. 2. A base saturation (by sum of cations) of less than 35 Dystric Vitric Haplustands percent throughout the upper 50 cm or throughout the entire A argillic or kandic horizon if it is less than 50 cm thick. N DGBD. Other Haplustands that have a 1500 kPa water Ultic Haplustands D retention of less than 15 percent on air-dried samples and less than 30 percent on undried samples throughout one or more DGBK. Other Haplustands that have an argillic or kandic layers that have andic soil properties and have a total thickness horizon that has its upper boundary within 125 cm either of the of 25 cm or more within 100 cm either of the mineral soil mineral soil surface or of the top of an organic layer with andic surface or of the top of an organic layer with andic soil soil properties, whichever is shallower. properties, whichever is shallower. Alfic Haplustands Vitric Haplustands DGBL. Other Haplustands that have a melanic, mollic, or DGBE. Other Haplustands that have more than 6.0 percent umbric epipedon. organic carbon and the colors of a mollic epipedon throughout a Humic Haplustands layer 50 cm or more thick within 60 cm either of the mineral soil surface or of the top of an organic layer with andic soil DGBM. Other Haplustands. properties, whichever is shallower. Typic Haplustands Pachic Haplustands

DGBF. Other Haplustands that have, at a depth between 25 Vitrands and 100 cm either from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever is Key to Great Groups shallower, a layer 10 cm or more thick with more than 3.0 DFA. Vitrands that have an ustic moisture regime. percent organic carbon and the colors of a mollic epipedon Ustivitrands, p. 100 throughout, underlying one or more horizons with a total thickness of 10 cm or more that have a color value, moist, 1 unit DFB. Other Vitrands. or more higher and an organic-carbon content 1 percent or more Udivitrands, p. 99 (absolute) lower. Thaptic Haplustands Udivitrands DGBG. Other Haplustands that have a calcic horizon that has Key to Subgroups its upper boundary within 125 cm either of the mineral soil surface or of the top of an organic layer with andic soil DFBA. Udivitrands that have a lithic contact within 50 cm properties, whichever is shallower. either of the mineral soil surface or of the top of an organic layer Calcic Haplustands with andic soil properties, whichever is shallower. Lithic Udivitrands DGBH. Other Haplustands that have extractable bases (by 3+ NH4OAc) plus 1N KCl-extractable Al totaling less than 15.0 DFBB. Other Udivitrands that have, in one or more horizons cmol(+)/kg in the fine-earth fraction throughout one or more at a depth between 50 and 100 cm either from the mineral soil horizons with a total thickness of 60 cm or more within 75 cm surface or from the top of an organic layer with andic soil either of the mineral soil surface or of the top of an organic layer properties, whichever is shallower, aquic conditions for some with andic soil properties, whichever is shallower. time in normal years (or artificial drainage) and one or more of Dystric Haplustands the following: 100 Keys to Soil Taxonomy

1. 2 percent or more redox concentrations; or DFBH. Other Udivitrands. Typic Udivitrands 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 of peds or in the matrix if peds are absent; or Ustivitrands 3. Enough active ferrous iron to give a positive reaction to Key to Subgroups alpha,alpha-dipyridyl at a time when the soil is not being DFAA. Ustivitrands that have a lithic contact within 50 cm irrigated. either of the mineral soil surface or of the top of an organic layer Aquic Udivitrands with andic soil properties, whichever is shallower. Lithic Ustivitrands DFBC. Other Udivitrands that are saturated with water within 100 cm of the mineral soil surface in normal years for either or DFAB. Other Ustivitrands that have, in one or more horizons both: at a depth between 50 and 100 cm either from the mineral soil 1. 20 or more consecutive days; or surface or from the top of an organic layer with andic soil properties, whichever is shallower, aquic conditions for some 2. 30 or more cumulative days time in normal years (or artificial drainage) and one or more of Oxyaquic Udivitrands the following: 1. 2 percent or more redox concentrations; or DFBD. Other Udivitrands that have, at a depth between 25 and 100 cm either from the mineral soil surface or from the top 2. A color value, moist, of 4 or more and 50 percent or of an organic layer with andic soil properties, whichever is more chroma of 2 or less either in redox depletions on faces shallower, a layer 10 cm or more thick with more than 3.0 of peds or in the matrix if peds are absent; or percent organic carbon and the colors of a mollic epipedon 3. Enough active ferrous iron to give a positive reaction to throughout, underlying one or more horizons with a total alpha,alpha-dipyridyl at a time when the soil is not being thickness of 10 cm or more that have a color value, moist, 1 unit irrigated. or more higher and an organic-carbon content 1 percent or more Aquic Ustivitrands (absolute) lower. Thaptic Udivitrands DFAC. Other Ustivitrands that have, at a depth between 25 and 100 cm either from the mineral soil surface or from the top of DFBE. Other Udivitrands that have both: an organic layer with andic soil properties, whichever is shallower, a layer 10 cm or more thick with more than 3.0 percent organic 1. An argillic or kandic horizon that has its upper boundary carbon and the colors of a mollic epipedon throughout, within 125 cm of the mineral soil surface or of the upper underlying one or more horizons with a total thickness of 10 cm boundary of an organic layer with andic soil properties, or more that have a color value, moist, 1 unit or more higher and whichever is shallower; and an organic-carbon content 1 percent or more (absolute) lower. 2. A base saturation (by sum of cations) of less than 35 Thaptic Ustivitrands percent throughout the upper 50 cm of the argillic or kandic horizon. DFAD. Other Ustivitrands that have a calcic horizon that has Ultic Udivitrands its upper boundary within 125 cm either of the mineral soil surface or of the top of an organic layer with andic soil DFBF. Other Udivitrands that have an argillic or kandic properties, whichever is shallower. horizon that has its upper boundary within 125 cm of the Calcic Ustivitrands mineral soil surface or of the upper boundary of an organic layer with andic soil properties, whichever is shallower. DFAE. Other Ustivitrands that have a melanic, mollic, or Alfic Udivitrands umbric epipedon. Humic Ustivitrands DFBG. Other Udivitrands that have a melanic, mollic, or umbric epipedon. DFAF. Other Ustivitrands. Humic Udivitrands Typic Ustivitrands Andisols 101

Xerands shallower, a layer 10 cm or more thick with more than 3.0 percent organic carbon and the colors of a mollic epipedon Key to Great Groups throughout, underlying one or more horizons with a total thickness of 10 cm or more that have a color value, moist, 1 unit DEA. Xerands that have a 1500 kPa water retention of less or more higher and an organic-carbon content 1 percent or more than 15 percent on air-dried samples and less than 30 percent on (absolute) lower. undried samples throughout 60 percent or more of the thickness Thaptic Haploxerands either: DECD. Other Haploxerands that have a calcic horizon that has 1. Within 60 cm either of the mineral soil surface or of the its upper boundary within 125 cm of the mineral soil surface. top of an organic layer with andic soil properties, whichever Calcic Haploxerands is shallower, if there is no densic, lithic, or paralithic contact, duripan, or petrocalcic horizon within that depth; or DECE. Other Haploxerands that have an argillic or kandic 2. Between either the mineral soil surface or the top of an horizon that has both: A organic layer with andic soil properties, whichever is N 1. An upper boundary within 125 cm of the mineral soil shallower, and a densic, lithic, or paralithic contact, a D surface or of the top of an organic layer with andic soil duripan, or a petrocalcic horizon. properties, whichever is shallower; and Vitrixerands, p. 102 2. A base saturation (by sum of cations) of less than 35 DEB. Other Xerands that have a melanic epipedon. percent throughout its upper 50 cm. Melanoxerands, p. 101 Ultic Haploxerands

DEC. Other Xerands. DECF. Other Haploxerands that have both: Haploxerands, p. 101 1. A mollic or umbric epipedon; and Haploxerands 2. An argillic or kandic horizon that has its upper boundary within 125 cm of the mineral soil surface or of the top of an Key to Subgroups organic layer with andic soil properties, whichever is shallower. DECA. Haploxerands that have a lithic contact within 50 cm Alfic Humic Haploxerands of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. DECG. Other Haploxerands that have an argillic or kandic Lithic Haploxerands horizon that has its upper boundary within 125 cm of the mineral soil surface or of the top of an organic layer with andic DECB. Other Haploxerands that have, in one or more soil properties, whichever is shallower. horizons at a depth between 50 and 100 cm either from the Alfic Haploxerands mineral soil surface or from the top of an organic layer with andic soil properties, whichever is shallower, aquic conditions DECH. Other Haploxerands that have a mollic or umbric for some time in normal years (or artificial drainage) and one or epipedon. more of the following: Humic Haploxerands 1. 2 percent or more redox concentrations; or DECI. Other Haploxerands. 2. A color value, moist, of 4 or more and 50 percent or Typic Haploxerands more chroma of 2 or less either in redox depletions on faces of peds or in the matrix if peds are absent; or Melanoxerands 3. Enough active ferrous iron to give a positive reaction to alpha,alpha-dipyridyl at a time when the soil is not being Key to Subgroups irrigated. DEBA. Melanoxerands that have more than 6.0 percent Aquic Haploxerands organic carbon and the colors of a mollic epipedon throughout a layer 50 cm or more thick within 60 cm either of the mineral soil DECC. Other Haploxerands that have, at a depth between surface or of the top of an organic layer with andic soil 25 and 100 cm from the mineral soil surface or from the top of properties, whichever is shallower. an organic layer with andic soil properties, whichever is Pachic Melanoxerands 102 Keys to Soil Taxonomy

DEBB. Other Melanoxerands. or more higher and an organic-carbon content 1 percent or more Typic Melanoxerands (absolute) lower. Thaptic Vitrixerands Vitrixerands DEAD. Other Vitrixerands that have both: Key to Subgroups 1. A melanic, mollic, or umbric epipedon; and DEAA. Vitrixerands that have a lithic contact within 50 cm of 2. An argillic or kandic horizon that has its upper boundary the mineral soil surface or of the top of an organic layer with within 125 cm of the mineral soil surface or of the top of an andic soil properties, whichever is shallower. organic layer with andic soil properties, whichever is shallower. Lithic Vitrixerands Alfic Humic Vitrixerands DEAB. Other Vitrixerands that have, in one or more horizons DEAE. Other Vitrixerands that have an argillic or kandic at a depth between 50 and 100 cm either from the mineral soil horizon that has both: surface or from the top of an organic layer with andic soil properties, whichever is shallower, aquic conditions for some 1. An upper boundary within 125 cm either of the mineral time in normal years (or artificial drainage) and one or more of soil surface or of the top of an organic layer with andic soil the following: 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 or throughout the 2. A color value, moist, of 4 or more and 50 percent or entire argillic or kandic horizon if it is less than 50 cm thick. more chroma of 2 or less either in redox depletions on faces Ultic Vitrixerands of peds or in the matrix if peds are absent; or 3. Enough active ferrous iron to give a positive reaction to DEAF. Other Vitrixerands that have an argillic or kandic alpha,alpha-dipyridyl at a time when the soil is not being horizon that has its upper boundary within 125 cm of the irrigated. mineral soil surface or of the top of an organic layer with andic Aquic Vitrixerands soil properties, whichever is shallower. Alfic Vitrixerands DEAC. Other Vitrixerands that have, at a depth between 25 and 100 cm from the mineral soil surface or from the top of DEAG. Other Vitrixerands that have a melanic, mollic, or an organic layer with andic soil properties, whichever is umbric epipedon. shallower, a layer 10 cm or more thick with more than 3.0 Humic Vitrixerands percent organic carbon and the colors of a mollic epipedon throughout, underlying one or more horizons with a total DEAH. Other Vitrixerands. thickness of 10 cm or more that have a color value, moist, 1 unit Typic Vitrixerands 103

CHAPTER 7 Aridisols

Key to Suborders paralithic contact within 50 cm of the soil surface and have either: GA. Aridisols that have a cryic soil temperature regime. 1. A clay increase of 15 percent or more (absolute) within a Cryids, p. 118 vertical distance of 2.5 cm either within the argillic horizon or at its upper boundary; or GB. Other Aridisols that have a salic horizon that has its upper boundary within 100 cm of the soil surface. 2. An argillic horizon that extends to 150 cm or more from Salids, p. 127 the soil surface, that does not have a clay decrease with A increasing depth of 20 percent or more (relative) from the R GC. Other Aridisols that have a duripan that has its upper maximum clay content, and that has, in 50 percent or more of I boundary within 100 cm of the soil surface. the matrix in some part between 100 and 150 cm, either: Durids, p. 121 a. Hue of 7.5YR or redder and chroma of 5 or more; or GD. Other Aridisols that have a gypsic or petrogypsic horizon that has its upper boundary within 100 cm of the soil b. Hue of 7.5YR or redder and value, moist, of 3 or less surface and do not have a petrocalcic horizon overlying these and value, dry, of 4 or less. horizons. Paleargids, p. 110 Gypsids, p. 124 GED. Other Argids that have a gypsic horizon that has its GE. Other Aridisols that have an argillic or natric horizon and upper boundary within 150 cm of the soil surface. do not have a petrocalcic horizon that has an upper boundary Gypsiargids, p. 105 within 100 cm of the soil surface. Argids, p. 103 GEE. Other Argids that have a calcic horizon that has its upper boundary within 150 cm of the soil surface. GF. Other Aridisols that have a calcic or petrocalcic horizon Calciargids, p. 103 that has its upper boundary within 100 cm of the soil surface. Calcids, p. 111 GEF. Other Argids. Haplargids, p. 106 GG. Other Aridisols. Calciargids Cambids, p. 114 Key to Subgroups Argids GEEA. Calciargids that have a lithic contact within 50 cm of the soil surface. Key to Great Groups Lithic Calciargids

GEA. Argids that have a duripan or a petrocalcic or GEEB. Other Calciargids that have both: petrogypsic horizon that has its upper boundary within 150 cm 1. One or both of the following: of the soil surface. Petroargids, p. 111 a. Cracks within 125 cm of the soil surface that are 5 mm or more wide through a thickness of 30 cm or more GEB. Other Argids that have a natric horizon. for some time in normal years and slickensides or wedge- Natrargids, p. 108 shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the soil surface; or GEC. Other Argids that do not have a densic, lithic, or b. A linear extensibility of 6.0 cm or more between the 104 Keys to Soil Taxonomy

soil surface and either a depth of 100 cm or a densic, 2. A moisture control section that is dry in all parts for less lithic, or paralithic contact if shallower; and than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm is 5 oC or higher and a soil 2. A moisture control section that is dry in all parts for less moisture regime that borders on ustic. than three-fourths of the time (cumulative) when the soil Arenic Ustic Calciargids temperature is 5 oC or higher at a depth of 50 cm and a soil moisture regime that borders on xeric. GEEG. Other Calciargids that have a sandy or sandy-skeletal Xerertic Calciargids particle-size class throughout a layer extending from the soil surface to the top of an argillic horizon at a depth of 50 cm or GEEC. Other Calciargids that have both: more. 1. One or both of the following: Arenic Calciargids a. Cracks within 125 cm of the soil surface that are 5 GEEH. Other Calciargids that have the following combination mm or more wide through a thickness of 30 cm or more of characteristics: for some time in normal years and slickensides or wedge- shaped aggregates in a layer 15 cm or more thick that has 1. Have one or more horizons, within 100 cm of the soil its upper boundary within 125 cm of the soil surface; or surface and with a combined thickness of 15 cm or more, that contain 20 percent or more (by volume) durinodes or are b. A linear extensibility of 6.0 cm or more between the brittle and have at least a firm rupture-resistance class when soil surface and either a depth of 100 cm or a densic, moist; and lithic, or paralithic contact if shallower; and 2. Are dry in all parts of the moisture control section for 2. A moisture control section that is dry in all parts for less less than three-fourths of the time (cumulative) when the soil than three-fourths of the time (cumulative) when the soil temperature is 5 oC or higher at a depth of 50 cm and have a temperature is 5 oC or higher at a depth of 50 cm and a soil soil moisture regime that borders on xeric. moisture regime that borders on ustic. Durinodic Xeric Calciargids Ustertic Calciargids GEEI. Other Calciargids that have one or more horizons, GEED. Other Calciargids that have one or both of the within 100 cm of the soil surface and with a combined thickness following: of 15 cm or more, that contain 20 percent or more (by volume) 1. Cracks within 125 cm of the soil surface that are 5 mm durinodes or are brittle and have at least a firm rupture- or more wide through a thickness of 30 cm or more for some resistance class when moist. time in normal years and slickensides or wedge-shaped Durinodic Calciargids aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the soil surface; or GEEJ. Other Calciargids that: 2. A linear extensibility of 6.0 cm or more between the soil 1. Are dry in all parts of the moisture control section surface and either a depth of 100 cm or a densic, lithic, or for less than three-fourths of the time (cumulative) when paralithic contact if shallower. the soil temperature at a depth of 50 cm is 5 oC or higher and Vertic Calciargids have a soil moisture regime that borders on xeric; and GEEE. Other Calciargids that are either: 2. Have one or more horizons, within 100 cm of the soil 1. Irrigated and have aquic conditions for some time in surface and with a combined thickness of 15 cm or more, that normal years in one or more layers within 100 cm of the soil contain 20 percent or more (by volume) nodules or surface; or concretions. Petronodic Xeric Calciargids 2. Saturated with water in one or more layers within 100 cm of the soil surface for 1 month or more in normal GEEK. Other Calciargids that: years. Aquic Calciargids 1. Are dry in all parts of the moisture control section for less than three-fourths of the time (cumulative) when GEEF. Other Calciargids that have: the soil temperature at a depth of 50 cm is 5 oC or higher and have a soil moisture regime that borders on ustic; 1. A sandy or sandy-skeletal particle-size class throughout a and layer extending from the soil surface to the top of an argillic horizon at a depth of 50 cm or more; and 2. Have one or more horizons, within 100 cm of the soil Aridisols 105

surface and with a combined thickness of 15 cm or more, that moisture control section for less than three-fourths of the time contain 20 percent or more (by volume) nodules or (cumulative) when the soil temperature at a depth of 50 cm is concretions. 5 oC or higher and have a soil moisture regime that borders on Petronodic Ustic Calciargids ustic. Ustic Calciargids GEEL. Other Calciargids that have one or more horizons, within 100 cm of the soil surface and with a combined thickness GEEQ. Other Calciargids. of 15 cm or more, that contain 20 percent or more (by volume) Typic Calciargid nodules or concretions. Petronodic Calciargids Gypsiargids GEEM. Other Calciargids that have both: Key to Subgroups 1. A moisture control section that is dry in all parts for less GEDA. Gypsiargids that are either: than three-fourths of the time (cumulative) when the soil temperature is 5 oC or higher at a depth of 50 cm and a soil 1. Irrigated and have aquic conditions for some time in moisture regime that borders on xeric; and normal years in one or more layers within 100 cm of the soil surface; or A 2. Throughout one or more horizons with a total thickness R of 18 cm or more within 75 cm of the soil surface, one or 2. Are saturated with water in one or more layers within I both of the following: 100 cm of the soil surface for 1 month or more in normal years. a. More than 35 percent (by volume) fragments coarser Aquic Gypsiargids than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or GEDB. Other Gypsiargids that have one or more horizons, b. A fine-earth fraction containing 30 percent or more within 100 cm of the soil surface and with a combined thickness particles 0.02 to 2.0 mm in diameter, of which 5 percent of 15 cm or more, that either contain 20 percent or more (by 1 or more is volcanic glass, and [(Al plus /2 Fe, percent volume) durinodes or are brittle and have at least a firm rupture- extracted by ammonium oxalate) times 60] plus the resistance class when moist. volcanic glass (percent) is 30 or more. Durinodic Gypsiargids Vitrixerandic Calciargids GEDC. Other Gypsiargids that have both: GEEN. Other Calciargids that have, throughout one or more 1. A moisture control section that is dry in all parts for less horizons with a total thickness of 18 cm or more within 75 cm of than three-fourths of the time (cumulative) when the soil the soil surface, one or both of the following: temperature is 5 oC or higher at a depth of 50 cm and a soil 1. More than 35 percent (by volume) fragments coarser moisture regime that borders on xeric; and than 2.0 mm, of which more than 66 percent is cinders, 2. Throughout one or more horizons with a total thickness pumice, and pumicelike fragments; or of 18 cm or more within 75 cm of the soil surface, one or 2. A fine-earth fraction containing 30 percent or more both of the following: particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 a. More than 35 percent (by volume) fragments coarser more is volcanic glass, and [(Al plus /2 Fe, percent extracted than 2.0 mm, of which more than 66 percent is cinders, by ammonium oxalate) times 60] plus the volcanic glass pumice, and pumicelike fragments; or (percent) is 30 or more. Vitrandic Calciargids b. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 GEEO. Other Calciargids that are dry in all parts of the or more is volcanic glass, and [(Al plus /2 Fe, percent moisture control section for less than three-fourths of the time extracted by ammonium oxalate) times 60] plus the (cumulative) when the soil temperature at a depth of 50 cm is volcanic glass (percent) is 30 or more. 5 oC or higher and have a soil moisture regime that borders on Vitrixerandic Gypsiargids xeric. Xeric Calciargids GEDD. Other Gypsiargids that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of GEEP. Other Calciargids that are dry in all parts of the the soil surface, one or both of the following: 106 Keys to Soil Taxonomy

1. More than 35 percent (by volume) fragments coarser temperature is 5 oC or higher at a depth of 50 cm and a soil than 2.0 mm, of which more than 66 percent is cinders, moisture regime that 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 are dry in all parts of the a. Cracks within 125 cm of the soil surface that are 5 moisture control section for less than three-fourths of the time mm or more wide through a thickness of 30 cm or more (cumulative) when the soil temperature at a depth of 50 cm is for some time in normal years and slickensides or wedge- 5 oC or higher and have a soil moisture regime that borders on shaped aggregates in a layer 15 cm or more thick that xeric. has its upper boundary within 125 cm of the soil surface; Xeric Gypsiargids or GEDF. Other Gypsiargids that are dry in all parts of the b. A linear extensibility of 6.0 cm or more between the moisture control section for less than three-fourths of the time soil surface and either a depth of 100 cm or a densic, (cumulative) when the soil temperature is 5 oC or higher at a lithic, or paralithic contact if shallower; and depth of 50 cm and have a soil moisture regime that borders on 2. A moisture control section that is dry in all parts for less ustic. than three-fourths of the time (cumulative) when the soil Ustic Gypsiargids temperature is 5 oC or higher at a depth of 50 cm and a soil moisture regime that borders on xeric. GEDG. Other Gypsiargids. Xerertic Haplargids Typic Gypsiargids GEFF. Other Haplargids that have both: Haplargids 1. One or both of the following: 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 GEFA. Haplargids that have: for some time in normal years and slickensides or wedge- shaped aggregates in a layer 15 cm or more thick that has 1. A lithic contact within 50 cm of the soil surface; and its upper boundary within 125 cm of the soil surface; or 2. An argillic horizon that is discontinuous throughout each b. A linear extensibility of 6.0 cm or more between the pedon. soil surface and either a depth of 100 cm or a densic, Lithic Ruptic-Entic Haplargids lithic, or paralithic contact if shallower; and GEFB. Other Haplargids that have: 2. A moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) when the soil 1. A lithic contact within 50 cm of the soil surface; temperature is 5 oC or higher at a depth of 50 cm and a soil and moisture regime that borders on ustic. 2. A moisture control section that is dry in all parts for less Ustertic Haplargids than three-fourths of the time (cumulative) when the soil temperature is 5 oC or higher at a depth of 50 cm and a soil GEFG. Other Haplargids that have one or both of the moisture regime that borders on xeric. following: Lithic Xeric Haplargids 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 GEFC. Other Haplargids that have: time in normal years and slickensides or wedge-shaped 1. A lithic contact within 50 cm of the soil surface; and aggregates 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 is dry in all parts for less than three-fourths of the time (cumulative) when the soil 2. A linear extensibility of 6.0 cm or more between the soil Aridisols 107

surface and either a depth of 100 cm or a densic, lithic, or 2. Are dry in all parts of the moisture control section for paralithic contact if shallower. less than three-fourths of the time (cumulative) when the soil Vertic Haplargids temperature at a depth of 50 cm is 5 oC or higher and have a soil moisture regime that borders on ustic. GEFH. Other Haplargids that are either: Petronodic Ustic Haplargids 1. Irrigated and have aquic conditions for some time in GEFN. Other Haplargids that have one or more horizons, normal years in one or more layers within 100 cm of the soil within 100 cm of the soil surface and with a combined thickness surface; or of 15 cm or more, that contain 20 percent or more (by volume) 2. Saturated with water in one or more layers within 100 nodules or concretions. cm of the soil surface for 1 month or more in normal years. Petronodic Haplargids Aquic Haplargids GEFO. Other Haplargids that have both: GEFI. Other Haplargids that have: 1. A moisture control section that is dry in all parts for less 1. A sandy or sandy-skeletal particle-size class throughout a than three-fourths of the time (cumulative) when the soil layer extending from the soil surface to the top of an argillic temperature is 5 oC or higher at a depth of 50 cm and a soil horizon at a depth of 50 cm or more; and moisture regime that borders on xeric; and A R 2. A moisture control section that is dry in all parts for less 2. Throughout one or more horizons with a total thickness I than three-fourths of the time (cumulative) when the soil of 18 cm or more within 75 cm of the soil surface, one or temperature at a depth of 50 cm is 5 oC or higher and a soil both of the following: moisture regime that borders on ustic. a. More than 35 percent (by volume) fragments coarser Arenic Ustic Haplargids than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or GEFJ. Other Haplargids that have a sandy or sandy-skeletal particle-size class throughout a layer extending from the soil b. A fine-earth fraction containing 30 percent or more surface to the top of an argillic horizon at a depth of 50 cm or particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 more. or more is volcanic glass, and [(Al plus /2 Fe, percent Arenic Haplargids extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. GEFK. Other Haplargids that have: Vitrixerandic Haplargids 1. One or more horizons, within 100 cm of the soil surface and with a combined thickness of 15 cm or more, that contain GEFP. Other Haplargids that have, throughout one or more 20 percent or more (by volume) durinodes or are brittle and horizons with a total thickness of 18 cm or more within 75 cm of have at least a firm rupture-resistance class when moist; and the soil surface, one or both of the following: 2. A moisture control section that is dry in all parts for less 1. More than 35 percent (by volume) fragments coarser than three-fourths of the time (cumulative) when the soil than 2.0 mm, of which more than 66 percent is cinders, temperature is 5 oC or higher at a depth of 50 cm and a soil pumice, and pumicelike fragments; or moisture regime that borders on xeric. 2. A fine-earth fraction containing 30 percent or more Durinodic Xeric Haplargids 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 GEFL. Other Haplargids that have one or more horizons, by ammonium oxalate) times 60] plus the volcanic glass within 100 cm of the soil surface and with a combined thickness (percent) is 30 or more. of 15 cm or more, that contain 20 percent or more (by volume) Vitrandic Haplargids durinodes or are brittle and have at least a firm rupture- resistance class when moist. GEFQ. Other Haplargids that are dry in all parts of the Durinodic Haplargids moisture control section for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm is GEFM. Other Haplargids that: 5 oC or higher and have a soil moisture regime that borders on 1. Have one or more horizons, within 100 cm of the soil xeric. surface and with a combined thickness of 15 cm or more, that Xeric Haplargids contain 20 percent or more (by volume) nodules or concretions; and GEFR. Other Haplargids that are dry in all parts of the 108 Keys to Soil Taxonomy

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

GEBE. Other Natrargids that: GEBI. Other Natrargids that have one or more horizons, Aridisols 109

within 100 cm of the soil surface and with a combined thickness than three-fourths of the time (cumulative) when the soil of 15 cm or more, that contain 20 percent or more (by volume) temperature is 5 oC or higher at a depth of 50 cm and a soil durinodes or are brittle and have at least a firm rupture- moisture regime that borders on xeric; and resistance class when moist. 2. Throughout one or more horizons with a total thickness Durinodic Natrargids of 18 cm or more within 75 cm of the soil surface, one or both of the following: GEBJ. Other Natrargids that have one or more horizons, within 100 cm of the soil surface and with a combined thickness a. More than 35 percent (by volume) fragments coarser of 15 cm or more, that contain 20 percent or more (by volume) than 2.0 mm, of which more than 66 percent is cinders, nodules or concretions. pumice, and pumicelike fragments; or Petronodic Natrargids b. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter, of which 5 percent GEBK. Other Natrargids that have: 1 or more is volcanic glass, and [(Al plus /2 Fe, percent 1. Skeletans covering 10 percent or more of the surfaces of extracted by ammonium oxalate) times 60] plus the peds at a depth 2.5 cm or more below the upper boundary of volcanic glass (percent) is 30 or more. the natric horizon; and Vitrixerandic Natrargids A 2. A moisture control section that is dry in all parts for less GEBP. Other Natrargids that have, throughout one or more R than three-fourths of the time (cumulative) when the soil horizons with a total thickness of 18 cm or more within 75 cm of I temperature is 5 oC or higher at a depth of 50 cm and a soil the soil surface, one or both of the following: moisture regime that borders on ustic. Glossic Ustic Natrargids 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, GEBL. Other Natrargids that have: pumice, and pumicelike fragments; or 1. An exchangeable sodium percentage of less than 15 (or 2. A fine-earth fraction containing 30 percent or more an SAR of less than 13) in 50 percent or more of the natric particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 horizon; and more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass 2. A moisture control section that is dry in all parts for less (percent) is 30 or more. than three-fourths of the time (cumulative) when the soil Vitrandic Natrargids temperature is 5 oC or higher at a depth of 50 cm and a soil moisture regime that borders on ustic. GEBQ. Other Natrargids that are dry in all parts of the Haplic Ustic Natrargids moisture control section for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm is GEBM. Other Natrargids that have: 5 oC or higher and have a soil moisture regime that borders on 1. An exchangeable sodium percentage of less than 15 xeric. (or an SAR of less than 13) in 50 percent or more of the Xeric Natrargids natric horizon; and GEBR. Other Natrargids that are dry in all parts of the 2. A moisture control section that is dry in all parts for less moisture control section for less than three-fourths of the time than three-fourths of the time (cumulative) when the soil (cumulative) when the soil temperature at a depth of 50 cm is temperature is 5 oC or higher at a depth of 50 cm and a soil 5 oC or higher and have a soil moisture regime that borders on moisture regime that borders on xeric. ustic. Haploxeralfic Natrargids Ustic Natrargids GEBN. Other Natrargids that have an exchangeable sodium GEBS. Other Natrargids that have skeletans covering 10 percentage of less than 15 (or an SAR of less than 13) in 50 percent or more of the surfaces of peds at a depth 2.5 cm or percent or more of the natric horizon. more below the upper boundary of the natric horizon. Haplic Natrargids Glossic Natrargids GEBO. Other Natrargids that have both: GEBT. Other Natrargids. 1. A moisture control section that is dry in all parts for less Typic Natrargids 110 Keys to Soil Taxonomy

Paleargids temperature is 5 oC or higher at a depth of 50 cm and a soil moisture regime that borders on xeric. Key to Subgroups Durinodic Xeric Paleargids GECA. Paleargids that have one or both of the following: GECG. Other Paleargids that have one or more horizons, 1. Cracks within 125 cm of the soil surface that are within 100 cm of the soil surface and with a combined thickness 5 mm or more wide through a thickness of 30 cm or of 15 cm or more, that contain 20 percent or more (by volume) more for some time in normal years and slickensides or durinodes or are brittle and have at least a firm rupture- wedge-shaped aggregates in a layer 15 cm or more thick that resistance class when moist. has its upper boundary within 125 cm of the soil surface; or Durinodic Paleargids 2. A linear extensibility of 6.0 cm or more between the soil GECH. Other Paleargids that: surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. 1. Have one or more horizons, within 100 cm of the soil Vertic Paleargids surface and with a combined thickness of 15 cm or more, that contain 20 percent or more (by volume) nodules or GECB. Other Paleargids that are either: concretions; and 1. Irrigated and have aquic conditions for some time in 2. Are dry in all parts of the moisture control section for normal years in one or more layers within 100 cm of the soil less than three-fourths of the time (cumulative) when the soil surface; or temperature at a depth of 50 cm 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 Petronodic Ustic Paleargids cm of the soil surface for 1 month or more in normal years. Aquic Paleargids GECI. Other Paleargids that have one or more horizons, within 100 cm of the soil surface and with a combined thickness GECC. Other Paleargids that have: of 15 cm or more, that contain 20 percent or more (by volume) 1. A sandy or sandy-skeletal particle-size class throughout a nodules or concretions. layer extending from the mineral soil surface to the top of an Petronodic Paleargids argillic horizon at a depth of 50 cm or more; and GECJ. Other Paleargids that have both: 2. A moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) when the soil 1. A moisture control section that is dry in all parts for less temperature is 5 oC or higher at a depth of 50 cm and a soil than three-fourths of the time (cumulative) when the soil moisture regime that borders on ustic. temperature is 5 oC or higher at a depth of 50 cm and a soil Arenic Ustic Paleargids moisture regime that borders on xeric; and 2. Throughout one or more horizons with a total thickness GECD. Other Paleargids that have a sandy or sandy-skeletal of 18 cm or more within 75 cm of the soil surface, one or particle-size class throughout a layer extending from the mineral both of the following: soil surface to the top of an argillic horizon at a depth of 50 cm or more. a. More than 35 percent (by volume) fragments coarser Arenic Paleargids than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or GECE. Other Paleargids that have a calcic horizon that has its b. A fine-earth fraction containing 30 percent or more upper boundary within 150 cm of the soil surface. particles 0.02 to 2.0 mm in diameter, of which 5 percent Calcic Paleargids 1 or more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the GECF. Other Paleargids that have: volcanic glass (percent) is 30 or more. 1. One or more horizons, within 100 cm of the soil surface Vitrixerandic Paleargids and with a combined thickness of 15 cm or more, that contain 20 percent or more (by volume) durinodes or are brittle and GECK. Other Paleargids that have, throughout one or more have at least a firm rupture-resistance class when moist; and horizons with a total thickness of 18 cm or more within 75 cm of the soil surface, one or both of the following: 2. A moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) when the soil 1. More than 35 percent (by volume) fragments coarser Aridisols 111

than 2.0 mm, of which more than 66 percent is cinders, GEAD. Other Petroargids that have a duripan that has its pumice, and pumicelike fragments; or upper boundary within 150 cm of the soil surface. Duric Petroargids 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 GEAE. Other Petroargids that have a natric horizon. more is volcanic glass, and [(Al plus /2 Fe, percent extracted Natric Petroargids by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. GEAF. Other Petroargids that have a moisture control section Vitrandic Paleargids that is dry in all parts for less than three-fourths of the time (cumulative) when the soil temperature is 5 oC or higher at a GECL. Other Paleargids that are dry in all parts of the depth of 50 cm and have a soil moisture regime that borders on moisture control section for less than three-fourths of the time xeric. (cumulative) when the soil temperature is 5 oC or higher at a Xeric Petroargids depth of 50 cm and have a soil moisture regime that borders on xeric. GEAG. Other Petroargids that have a moisture control section Xeric Paleargids that is dry in all parts for less than three-fourths of the time (cumulative) when the soil temperature is 5 oC or higher at a GECM. Other Paleargids that are dry in all parts of the A depth of 50 cm and have a soil moisture regime that borders on moisture control section for less than three-fourths of the time R ustic. (cumulative) when the soil temperature is 5 oC or higher at a I Ustic Petroargids depth of 50 cm and have a soil moisture regime that borders on ustic. GEAH. Other Petroargids. Ustic Paleargids Typic Petroargids GECN. Other Paleargids. Typic Paleargids Calcids Petroargids Key to Great Groups

Key to Subgroups GFA. Calcids that have a petrocalcic horizon that has its upper boundary within 100 cm of the soil surface. GEAA. Petroargids that meet both of the following: Petrocalcids, p. 113 1. Have a petrogypsic horizon that has its upper boundary within 150 cm of the soil surface; and GFB. Other Calcids. Haplocalcids, p. 111 2. Are dry in all parts of the moisture control section for less than three-fourths of the time (cumulative) when the soil temperature is 5 oC or higher at a depth of 50 cm and have a Haplocalcids soil moisture regime that borders on ustic. Key to Subgroups Petrogypsic Ustic Petroargids GFBA. Haplocalcids that have: GEAB. Other Petroargids that have a petrogypsic horizon that 1. A lithic contact within 50 cm of the soil surface; and has its upper boundary within 150 cm of the soil surface. Petrogypsic Petroargids 2. A moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) when the soil GEAC. Other Petroargids that have: temperature is 5 oC or higher at a depth of 50 cm and a soil moisture regime that borders on xeric. 1. A duripan that has its upper boundary within 150 cm of Lithic Xeric Haplocalcids the soil surface; and 2. A moisture control section that is dry in all parts for less GFBB. Other Haplocalcids that have: than three-fourths of the time (cumulative) when the soil 1. A lithic contact within 50 cm of the soil surface; and temperature is 5 oC or higher at a depth of 50 cm and a soil moisture regime that borders on xeric. 2. A moisture control section that is dry in all parts for less Duric Xeric Petroargids than three-fourths of the time (cumulative) when the soil 112 Keys to Soil Taxonomy

temperature is 5 oC or higher at a depth of 50 cm and a soil temperature is 5 oC or higher at a depth of 50 cm and a soil moisture regime that borders on ustic. moisture regime that borders on xeric. Lithic Ustic Haplocalcids Duric Xeric Haplocalcids

GFBC. Other Haplocalcids that have a lithic contact within 50 GFBH. Other Haplocalcids that have a duripan that has its cm of the soil surface. upper boundary within 150 cm of the surface. Lithic Haplocalcids Duric Haplocalcids

GFBD. Other Haplocalcids that have: GFBI. Other Haplocalcids that have: 1. Cracks within 125 cm of the soil surface that are 5 mm 1. One or more horizons, within 100 cm of the soil surface or more wide through a thickness of 30 cm or more for some and with a combined thickness of 15 cm or more, that contain time in normal years and slickensides or wedge-shaped 20 percent or more (by volume) durinodes or are brittle and aggregates in a layer 15 cm or more thick that has its upper have at least a firm rupture-resistance class when moist; and boundary within 125 cm of the soil surface; or 2. A moisture control section that is dry in all parts for less 2. A linear extensibility of 6.0 cm or more between the soil than three-fourths of the time (cumulative) when the soil surface and either a depth of 100 cm or a densic, lithic, or temperature is 5 oC or higher at a depth of 50 cm and a soil paralithic contact, whichever is shallower. moisture regime that borders on xeric. Vertic Haplocalcids Durinodic Xeric Haplocalcids

GFBE. Other Haplocalcids that: GFBJ. Other Haplocalcids that have one or more horizons, within 100 cm of the soil surface and with a combined thickness 1. Are either: 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 GFBK. Other Haplocalcids that have: cm of the soil surface for 1 month or more in normal years; and 1. One or more horizons, within 100 cm of the soil surface and with a combined thickness of 15 cm or more, that contain 2. Have one or more horizons, within 100 cm of the soil 20 percent or more (by volume) nodules or concretions; and surface and with a combined thickness of 15 cm or more, that contain 20 percent or more (by volume) durinodes or are 2. A moisture control section that is dry in all parts for less brittle and have at least a firm rupture-resistance class when than three-fourths of the time (cumulative) when the soil moist. temperature is 5 oC or higher at a depth of 50 cm and a soil Aquic Durinodic Haplocalcids moisture regime that borders on xeric. Petronodic Xeric Haplocalcids GFBF. Other Haplocalcids that are either: GFBL. Other Haplocalids that: 1. Irrigated and have aquic conditions for some time in normal years in one or more layers within 100 cm of the soil 1. Have one or more horizons, within 100 cm of the soil surface; or surface and with a combined thickness of 15 cm or more, that contain 20 percent or more (by volume) nodules or 2. Saturated with water in one or more layers within 100 concretions; and cm of the soil surface for 1 month or more in normal years. Aquic Haplocalcids 2. Are dry in all parts of the moisture control section for less than three-fourths of the time (cumulative) GFBG. Other Haplocalcids that have: when the soil temperature at a depth of 50 cm is 5 oC or higher and have a soil moisture regime that borders on ustic. 1. A duripan that has its upper boundary within 150 cm of Petronodic Ustic Haplocalcids the surface; and 2. A moisture control section that is dry in all parts for less GFBM. Other Haplocalcids that have one or more horizons, than three-fourths of the time (cumulative) when the soil within 100 cm of the soil surface and with a combined thickness Aridisols 113

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

GFBP. Other Haplocalcids that have, in a horizon at least 25 GFBU. Other Haplocalcids. cm thick within 100 cm of the mineral soil surface, an Typic Haplocalcids exchangeable sodium percentage of 15 or more (or an SAR of 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 is dry in all parts for less than three-fourths of the time (cumulative) when the soil 1. Irrigated and have aquic conditions for some time in temperature is 5 oC or higher at a depth of 50 cm and a soil normal years in one or more layers within 100 cm of the soil moisture regime that borders on xeric; and surface; or 2. Throughout one or more horizons with a total thickness 2. Saturated with water in one or more layers within 100 of 18 cm or more within 75 cm of the soil surface, one or cm of the soil surface for 1 month or more in normal years. both of the following: Aquic Petrocalcids a. More than 35 percent (by volume) fragments coarser GFAB. Other Petrocalcids that have a natric horizon. than 2.0 mm, of which more than 66 percent is cinders, Natric Petrocalcids pumice, and pumicelike fragments; or b. A fine-earth fraction containing 30 percent or more GFAC. Other Petrocalcids that have both of the following: particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 1. An argillic horizon that has its upper boundary within or more is volcanic glass, and [(Al plus /2 Fe, percent 100 cm of the soil surface; and extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. 2. A moisture control section that is dry in all parts for less Vitrixerandic Haplocalcids than three-fourths of the time (cumulative) when the soil 114 Keys to Soil Taxonomy

temperature is 5 oC or higher at a depth of 50 cm and a soil 2. Saturated with water in one or more layers within moisture regime that borders on xeric. 100 cm of the soil surface for 1 month or more in normal Xeralfic Petrocalcids years. Aquicambids, p. 114 GFAD. Other Petrocalcids that have both of the following: GGB. Other Cambids that have a duripan or a petrocalcic or 1. An argillic horizon that has its upper boundary within petrogypsic horizon that has its upper boundary within 150 cm 100 cm of the soil surface; and of the soil surface. 2. A moisture control section that is dry in all parts for less Petrocambids, p. 117 than three-fourths of the time (cumulative) when the soil temperature is 5 oC or higher at a depth of 50 cm and a soil GGC. Other Cambids that have an anthropic epipedon. moisture regime that borders on ustic. Anthracambids, p. 114 Ustalfic Petrocalcids GGD. Other Cambids. GFAE. Other Petrocalcids that have an argillic horizon that Haplocambids, p. 115 has its upper boundary within 100 cm of the soil surface. Argic Petrocalcids Anthracambids

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

GGAC. Other Aquicambids that have one or more horizons, Cambids 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) Key to Great Groups durinodes or are brittle and have at least a firm rupture- resistance class when moist. GGA. Cambids that are either: Durinodic Aquicambids 1. Irrigated and have aquic conditions for some time in normal years in one or more layers within 100 cm of the soil GGAD. Other Aquicambids that have one or more horizons, surface; or within 100 cm of the soil surface and with a combined thickness Aridisols 115

of 15 cm or more, that contain 20 percent or more (by volume) depth of 50 cm and have a soil moisture regime that borders on nodules or concretions. ustic. Petronodic Aquicambids Ustic Aquicambids

GGAE. Other Aquicambids that have both: GGAJ. Other Aquicambids. Typic Aquicambids 1. A moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) when the soil temperature is 5 oC or higher at a depth of 50 cm and a soil Haplocambids moisture regime that borders on xeric; and Key to Subgroups 2. Throughout one or more horizons with a total thickness GGDA. Haplocambids that have: 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 is dry in all parts for less than 2.0 mm, of which more than 66 percent is cinders, than three-fourths of the time (cumulative) when the soil pumice, and pumicelike fragments; or temperature is 5 oC or higher at a depth of 50 cm and a soil moisture regime that borders on xeric. A b. A fine-earth fraction containing 30 percent or more Lithic Xeric Haplocambids R particles 0.02 to 2.0 mm in diameter, of which 5 percent I 1 or more is volcanic glass, and [(Al plus /2 Fe, percent GGDB. Other Haplocambids that have: extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. 1. A lithic contact within 50 cm of the soil surface; and Vitrixerandic Aquicambids 2. A moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) when the soil GGAF. Other Aquicambids that have, throughout one or more temperature is 5 oC or higher at a depth of 50 cm and a soil horizons with a total thickness of 18 cm or more within 75 cm of moisture regime that borders on ustic. the soil surface, one or both of the following: Lithic Ustic Haplocambids 1. More than 35 percent (by volume) fragments coarser GGDC. Other Haplocambids that have a lithic contact within than 2.0 mm, of which more than 66 percent is cinders, 50 cm of the soil surface. pumice, and pumicelike fragments; or Lithic Haplocambids 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter, of which 5 percent or GGDD. Other Haplocambids that have: 1 more is volcanic glass, and [(Al plus /2 Fe, percent extracted 1. One or both of the following: by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. a. Cracks within 125 cm of the soil surface that are 5 Vitrandic Aquicambids mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge- GGAG. Other Aquicambids that have an irregular decrease in shaped aggregates in a layer 15 cm or more thick that has content of organic carbon from a depth of 25 cm either to a its upper boundary within 125 cm of the soil surface; or depth of 125 cm or to a densic, lithic, or paralithic contact if b. A linear extensibility of 6.0 cm or more between the shallower. soil surface and either a depth of 100 cm or a densic, Fluventic Aquicambids lithic, or paralithic contact if shallower; and GGAH. Other Aquicambids that are dry in all parts of the 2. A moisture control section that is dry in all parts for less moisture control section for less than three-fourths of the time than three-fourths of the time (cumulative) when the soil (cumulative) when the soil temperature is 5 oC or higher at a temperature is 5 oC or higher at a depth of 50 cm and a soil depth of 50 cm and have a soil moisture regime that borders on moisture regime that borders on xeric. xeric. Xerertic Haplocambids Xeric Aquicambids GGDE. Other Haplocambids that have: GGAI. Other Aquicambids that are dry in all parts of the 1. One or both of the following: moisture control section for less than three-fourths of the time (cumulative) when the soil temperature is 5 oC or higher at a a. Cracks within 125 cm of the soil surface that are 5 116 Keys to Soil Taxonomy

mm or more wide through a thickness of 30 cm or more temperature at a depth of 50 cm is 5 oC or higher and a soil for some time in normal years and slickensides or wedge- moisture regime that borders on xeric. shaped aggregates in a layer 15 cm or more thick that has Petronodic Xeric Haplocambids its upper boundary within 125 cm of the soil surface; or GGDJ. Other Haplocambids that: b. A linear extensibility of 6.0 cm or more between the soil surface and either a depth of 100 cm or a densic, 1. Have one or more horizons, within 100 cm of the soil lithic, or paralithic contact if shallower; and surface and with a combined thickness of 15 cm or more, that contain 20 percent or more (by volume) nodules or 2. A moisture control section that is dry in all parts for less concretions; and than three-fourths of the time (cumulative) when the soil temperature is 5 oC or higher at a depth of 50 cm and a soil 2. Are dry in all parts of the moisture control section for moisture regime that borders on ustic. less than three-fourths of the time (cumulative) when the soil Ustertic Haplocambids temperature at a depth of 50 cm is 5 oC or higher and have a soil moisture regime that borders on ustic. GGDF. Other Haplocambids that have at least one of the Petronodic Ustic Haplocambids following: GGDK. Other Haplocambids that have one or more horizons, 1. Cracks within 125 cm of the soil surface that are 5 mm within 100 cm of the soil surface and with a combined thickness or more wide through a thickness of 30 cm or more for some of 15 cm or more, that contain 20 percent or more (by volume) time in normal years and slickensides or wedge-shaped nodules or concretions. aggregates in a layer 15 cm or more thick that has its upper Petronodic Haplocambids boundary within 125 cm of the soil surface; or 2. A linear extensibility of 6.0 cm or more between the soil GGDL. Other Haplocambids that have both: surface and either a depth of 100 cm or a densic, lithic, or 1. A horizon at least 25 cm thick within 100 cm of the soil paralithic contact, whichever is shallower. surface that has an exchangeable sodium percentage of 15 or Vertic Haplocambids more (or an SAR of 13 or more) during at least 1 month in normal years; and GGDG. Other Haplocambids that have both of the following: 2. A moisture control section that is dry in all parts for less 1. One or more horizons, within 100 cm of the soil surface than three-fourths of the time (cumulative) when the soil and with a combined thickness of 15 cm or more, that temperature at a depth of 50 cm is 5 oC or higher and a soil contain 20 percent or more (by volume) durinodes or are moisture regime that borders on xeric. brittle and have at least a firm rupture-resistance class when Sodic Xeric Haplocambids moist; and GGDM. Other Haplocambids that meet both of the following: 2. A moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) when the soil 1. Have, in a horizon at least 25 cm thick within 100 cm of temperature at a depth of 50 cm is 5 oC or higher and a soil the soil surface, an exchangeable sodium percentage of 15 or moisture regime that borders on xeric. more (or an SAR of 13 or more) during at least 1 month in Durinodic Xeric Haplocambids normal years; and 2. Are dry in all parts of the moisture control section for GGDH. Other Haplocambids that have one or more horizons, less than three-fourths of the time (cumulative) when the soil within 100 cm of the soil surface and with a combined thickness temperature at a depth of 50 cm is 5 oC or higher and have a of 15 cm or more, that contain 20 percent or more (by volume) soil moisture regime that borders on ustic. durinodes or are brittle and have at least a firm rupture- Sodic Ustic Haplocambids resistance class when moist. Durinodic Haplocambids GGDN. Other Haplocambids that have, in a horizon at least 25 cm thick within 100 cm of the soil surface, an exchangeable GGDI. Other Haplocambids that have: sodium percentage of 15 or more (or an SAR of 13 or more) 1. One or more horizons, within 100 cm of the soil surface during at least 1 month in normal years. and with a combined thickness of 15 cm or more, that contain Sodic Haplocambids 20 percent or more (by volume) nodules or concretions; and GGDO. Other Haplocambids that have both: 2. A moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) when the soil 1. A moisture control section that is dry in all parts Aridisols 117

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

GGDQ. Other Haplocambids that: GGBB. Other Petrocambids that have both: 1. Are dry in all parts of the moisture control section for 1. A moisture control section that is dry in all parts for less less than three-fourths of the time (cumulative) when the soil than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm is 5 oC or higher and have a temperature is 5 oC or higher at a depth of 50 cm and a soil soil moisture regime that borders on xeric; and moisture regime that borders on xeric; and 2. Have an irregular decrease in content of organic carbon 2. Throughout one or more horizons with a total thickness from a depth of 25 cm either to a depth of 125 cm or to a of 18 cm or more within 75 cm of the soil surface, one or densic, lithic, or paralithic contact if shallower. both of the following: Xerofluventic Haplocambids a. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, GGDR. Other Haplocambids that: pumice, and pumicelike fragments; or 1. Are dry in all parts of the moisture control section for b. A fine-earth fraction containing 30 percent or more less than three-fourths of the time (cumulative) when the soil o particles 0.02 to 2.0 mm in diameter, of which 5 percent temperature at a depth of 50 cm is 5 C or higher and have a 1 or more is volcanic glass, and [(Al plus /2 Fe, percent soil moisture regime that borders on ustic; and extracted by ammonium oxalate) times 60] plus the 2. Have an irregular decrease in content of organic carbon volcanic glass (percent) is 30 or more. from a depth of 25 cm either to a depth of 125 cm or to a Vitrixerandic Petrocambids densic, lithic, or paralithic contact if shallower. Ustifluventic Haplocambids GGBC. Other Petrocambids that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of GGDS. Other Haplocambids that have an irregular decrease in the soil surface, one or both of the following: 118 Keys to Soil Taxonomy

1. More than 35 percent (by volume) fragments coarser Argicryids than 2.0 mm, of which more than 66 percent is cinders, 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 mm GGBD. Other Petrocambids that are dry in all parts of the or more wide throughout a thickness of 30 cm or more for moisture control section for less than three-fourths of the time some time in normal years and slickensides or wedge-shaped (cumulative) when the soil temperature at a depth of 50 cm is aggregates in a layer 15 cm or more thick that has its upper 5 oC or higher and have a soil moisture regime that borders on boundary within 125 cm of the mineral soil surface; or xeric. 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 are dry in all parts of the lithic, or paralithic contact, whichever is shallower. moisture control section for less than three-fourths of the time Vertic Argicryids (cumulative) when the soil temperature at a depth of 50 cm is 5 oC or higher and have a soil moisture regime that borders on GADC. Other Argicryids that have a natric horizon that has its ustic. upper boundary within 100 cm of the soil surface. Ustic Petrocambids Natric Argicryids

GGBF. Other Petrocambids. GADD. Other Argicryids that have both: Typic Petrocambids 1. A moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) when the soil Cryids temperature is 5 oC or higher at a depth of 50 cm and a soil moisture regime that borders on xeric; and Key to Great Groups 2. Throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of the soil surface, one or GAA. Cryids that have a salic horizon that has its upper both of the following: boundary within 100 cm of the soil surface. a. More than 35 percent (by volume) fragments coarser Salicryids, p. 121 than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or GAB. Other Cryids that have a duripan or a petrocalcic or petrogypsic horizon that has its upper boundary within 100 cm b. A fine-earth fraction containing 30 percent or more of the soil surface. particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 Petrocryids, p. 120 or more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the GAC. Other Cryids that have a gypsic horizon that has its volcanic glass (percent) is 30 or more. upper boundary within 100 cm of the soil surface. Vitrixerandic Argicryids Gypsicryids, p. 119 GADE. Other Argicryids that have, throughout one or more GAD. Other Cryids that have an argillic or natric horizon. horizons with a total thickness of 18 cm or more within 75 cm of Argicryids, p. 118 the soil surface, one or both of the following: 1. More than 35 percent (by volume) fragments coarser GAE. Other Cryids that have a calcic horizon that has its than 2.0 mm, of which more than 66 percent is cinders, upper boundary within 100 cm of the soil surface. pumice, and pumicelike fragments; or Calcicryids, p. 119 2. A fine-earth fraction containing 30 percent or more GAF. Other Cryids. particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 Haplocryids, p. 120 more is volcanic glass, and [(Al plus /2 Fe, percent extracted Aridisols 119

by ammonium oxalate) times 60] plus the volcanic glass than 2.0 mm, of which more than 66 percent is cinders, (percent) is 30 or more. pumice, and pumicelike fragments; or Vitrandic Argicryids 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter, of which 5 percent or GADF. Other Argicryids that are dry in all parts of the 1 more is volcanic glass, and [(Al plus /2 Fe, percent extracted moisture control section for less than three-fourths of the time by ammonium oxalate) times 60] plus the volcanic glass (cumulative) when the soil temperature is 5 oC or higher at a (percent) is 30 or more. depth of 50 cm and have a soil moisture regime that borders on Vitrandic Calcicryids xeric. Xeric Argicryids GAED. Other Calcicryids that are dry in all parts of the moisture control section for less than three-fourths of the time GADG. Other Argicryids that are dry in all parts of the (cumulative) when the soil temperature is 5 oC or higher at a moisture control section for less than three-fourths of the time depth of 50 cm and have a soil moisture regime that borders on (cumulative) when the soil temperature is 5 oC or higher at a xeric. depth of 50 cm and have a soil moisture regime that borders on Xeric Calcicryids ustic. Ustic Argicryids GAEE. Other Calcicryids that are dry in all parts of the A moisture control section for less than three-fourths of the time R GADH. Other Argicryids. (cumulative) when the soil temperature is 5 oC or higher at a I Typic Argicryids depth of 50 cm and have a soil moisture regime that borders on ustic. Calcicryids Ustic Calcicryids Key to Subgroups GAEF. Other Calcicryids. GAEA. Calcicryids that have a lithic contact within 50 cm of Typic Calcicryids the soil surface. Lithic Calcicryids Gypsicryids

GAEB. Other Calcicryids that have both: Key to Subgroups 1. A moisture control section that is dry in all parts for less GACA. Gypsicryids that have a calcic horizon. than three-fourths of the time (cumulative) when the soil Calcic Gypsicryids temperature is 5 oC or higher at a depth of 50 cm and a soil moisture regime that borders on xeric; and GACB. Other Gypsicryids that have both: 2. Throughout one or more horizons with a total thickness 1. A moisture control section that is dry in all parts of 18 cm or more within 75 cm of the soil surface, one or for less than three-fourths of the time (cumulative) both of the following: when the soil temperature is 5 oC or higher at a depth of 50 cm and a soil moisture regime that borders on xeric; a. More than 35 percent (by volume) fragments coarser and than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or 2. Throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of the soil surface, one or b. A fine-earth fraction containing 30 percent or more both of the following: 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 a. More than 35 percent (by volume) fragments coarser extracted by ammonium oxalate) times 60] plus the than 2.0 mm, of which more than 66 percent is cinders, volcanic glass (percent) is 30 or more. pumice, and pumicelike fragments; or Vitrixerandic Calcicryids b. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter, of which 5 percent GAEC. Other Calcicryids that have, throughout one or more 1 or more is volcanic glass, and [(Al plus /2 Fe, percent horizons with a total thickness of 18 cm or more within 75 cm of extracted by ammonium oxalate) times 60] plus the the soil surface, one or both of the following: volcanic glass (percent) is 30 or more. 1. More than 35 percent (by volume) fragments coarser Vitrixerandic Gypsicryids 120 Keys to Soil Taxonomy

GACC. Other Gypsicryids that have, throughout one or more extracted by ammonium oxalate) times 60] plus the horizons with a total thickness of 18 cm or more within 75 cm of volcanic glass (percent) is 30 or more. the soil surface, one or both of the following: Vitrixerandic Haplocryids 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 of pumice, and pumicelike fragments; or 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 1 than 2.0 mm, of which more than 66 percent is cinders, 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. 2. A fine-earth fraction containing 30 percent or more Vitrandic Gypsicryids 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 GACD. Other Gypsicryids. by ammonium oxalate) times 60] plus the volcanic glass Typic Gypsicryids (percent) is 30 or more. Vitrandic Haplocryids Haplocryids GAFE. Other Haplocryids that are dry in all parts of the Key to Subgroups moisture control section for less than three-fourths of the time (cumulative) when the soil temperature is 5 oC or higher at a GAFA. Haplocryids that have a lithic contact within 50 cm of depth of 50 cm and have a soil moisture regime that borders on the soil surface. xeric. Lithic Haplocryids Xeric Haplocryids GAFB. Other Haplocryids that have one or both of the GAFF. Other Haplocryids that are dry in all parts of the following: moisture control section for less than three-fourths of the time 1. Cracks within 125 cm of the soil surface that are 5 mm (cumulative) when the soil temperature is 5 oC or higher at a or more wide throughout a thickness of 30 cm or more for depth of 50 cm and have a soil moisture regime that borders on some time in normal years and slickensides or wedge- ustic. shaped aggregates in a layer 15 cm or more thick that has Ustic Haplocryids its upper boundary within 125 cm of the mineral soil surface; or GAFG. Other Haplocryids. Typic Haplocryids 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, lithic, or paralithic contact, whichever is shallower. Petrocryids Vertic Haplocryids Key to Subgroups GAFC. Other Haplocryids that have both: GABA. Petrocryids that: 1. A moisture control section that is dry in all parts for less 1. Have a duripan that is strongly cemented or less than three-fourths of the time (cumulative) when the soil cemented in all subhorizons and has its upper boundary temperature is 5 oC or higher at a depth of 50 cm and a soil within 100 cm of the soil surface; and moisture regime that borders on xeric; and 2. Are dry in all parts of the moisture control section for 2. Throughout one or more horizons with a total thickness less than three-fourths of the time (cumulative) when the soil of 18 cm or more within 75 cm of the soil surface, one or temperature is 5 oC or higher at a depth of 50 cm and have a both of the following: soil moisture regime that borders on xeric. Xereptic Petrocryids a. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, GABB. Other Petrocryids that: pumice, and pumicelike fragments; or 1. Have a duripan that has its upper boundary within 100 b. A fine-earth fraction containing 30 percent or more cm of the soil surface; and 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 2. Are dry in all parts of the moisture control section for Aridisols 121

less than three-fourths of the time (cumulative) when the soil GCC. Other Durids. temperature is 5 oC or higher at a depth of 50 cm and have a Haplodurids, p. 122 soil moisture regime that borders on xeric. Duric Xeric Petrocryids Argidurids

GABC. Other Petrocryids that have a duripan that has its Key to Subgroups upper boundary within 100 cm of the soil surface. GCBA. Argidurids that have, above the duripan, one or both Duric Petrocryids of the following: GABD. Other Petrocryids that have a petrogypsic horizon 1. Cracks between the soil surface and the top of the that has its upper boundary within 100 cm of the soil duripan that are 5 mm or more wide through a thickness of surface. 30 cm or more for some time in normal years and Petrogypsic Petrocryids slickensides or wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary above the duripan; or GABE. Other Petrocryids that are dry in all parts of the 2. A linear extensibility of 6.0 cm or more between the soil moisture control section for less than three-fourths of the time surface and the top of the duripan. (cumulative) when the soil temperature is 5 oC or higher at a Vertic Argidurids A depth of 50 cm and have a soil moisture regime that borders on R xeric. GCBB. Other Argidurids that are either: I Xeric Petrocryids 1. Irrigated and have aquic conditions for some time in GABF. Other Petrocryids that are dry in all parts of the normal years in one or more layers within 100 cm of the soil moisture control section for less than three-fourths of the time surface; or (cumulative) when the soil temperature is 5 oC or higher at a 2. Saturated with water in one or more layers within depth of 50 cm and have a soil moisture regime that borders on 100 cm of the soil surface for 1 month or more in normal ustic. years. Ustic Petrocryids Aquic Argidurids GABG. Other Petrocryids. GCBC. Other Argidurids that have the following combination Typic Petrocryids of characteristics: Salicryids 1. An argillic horizon that has 35 percent or more clay in the fine-earth fraction of some part; and either Key to Subgroups a. A clay increase of 15 percent or more (absolute) GAAA. Salicryids that are saturated with water in one or more within a vertical distance of 2.5 cm either within the layers within 100 cm of the soil surface for 1 month or more in argillic horizon or at its upper boundary; or normal years. b. If there is an Ap horizon directly above the argillic Aquic Salicryids horizon, a clay increase of 10 percent or more (absolute) at the upper boundary of the argillic horizon; and GAAB. Other Salicryids. Typic Salicryids 2. A moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) when the soil temperature is 5 oC or higher at a depth of 50 cm and a soil Durids moisture regime that borders on xeric. Abruptic Xeric Argidurids Key to Great Groups GCBD. Other Argidurids that have an argillic horizon that has GCA. Durids that have a natric horizon above the 35 percent or more clay in the fine-earth fraction of some part; duripan. and either Natridurids, p. 123 1. A clay increase of 15 percent or more (absolute) within a vertical distance of 2.5 cm within the argillic horizon or at its GCB. Other Durids that have an argillic horizon above the upper boundary; or duripan. Argidurids, p. 121 2. If there is an Ap horizon directly above the argillic 122 Keys to Soil Taxonomy

horizon, a clay increase of 10 percent or more (absolute) at that is dry in all parts for less than three-fourths of the time the upper boundary of the argillic horizon. (cumulative) when the soil temperature is 5 oC or higher at a Abruptic Argidurids depth of 50 cm and have a soil moisture regime that borders on xeric. GCBE. Other Argidurids that have: Xeric Argidurids 1. A duripan that is strongly cemented or less cemented in GCBJ. Other Argidurids that have a moisture control section all subhorizons; and that is dry in all parts for less than three-fourths of the time 2. A moisture control section that is dry in all parts for less (cumulative) when the soil temperature at a depth of 50 cm is than three-fourths of the time (cumulative) when the soil 5 oC or higher and have a soil moisture regime that borders on temperature is 5 oC or higher at a depth of 50 cm and a soil ustic. moisture regime that borders on xeric. Ustic Argidurids Haploxeralfic Argidurids GCBK. Other Argidurids. GCBF. Other Argidurids that have a duripan that is strongly Typic Argidurids cemented or less cemented in all subhorizons. Argidic Argidurids Haplodurids GCBG. Other Argidurids that have both: Key to Subgroups 1. A moisture control section that is dry in all parts for less GCCA. Haplodurids that: than three-fourths of the time (cumulative) when the soil temperature is 5 oC or higher at a depth of 50 cm and a soil 1. Have a duripan that is strongly cemented or less moisture regime that borders on xeric; and cemented in all subhorizons; and 2. Throughout one or more horizons with a total thickness 2. Are either: of 18 cm or more within 75 cm of the soil surface, one or a. Irrigated and have aquic conditions for some time in both of the following: normal years in one or more layers within 100 cm of the a. More than 35 percent (by volume) fragments coarser soil surface; or than 2.0 mm, of which more than 66 percent is cinders, b. Saturated with water in one or more layers within 100 pumice, and pumicelike fragments; or cm of the soil surface for 1 month or more in normal b. A fine-earth fraction containing 30 percent or more years. particles 0.02 to 2.0 mm in diameter, of which 5 percent Aquicambidic Haplodurids 1 or more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the GCCB. Other Haplodurids that are either: volcanic glass (percent) is 30 or more. 1. Irrigated and have aquic conditions for some time in Vitrixerandic Argidurids normal years in one or more layers within 100 cm of the soil surface; or GCBH. Other Argidurids that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of 2. Saturated with water in one or more layers within the soil surface, one or both of the following: 100 cm of the soil surface for 1 month or more in normal years. 1. More than 35 percent (by volume) fragments coarser Aquic Haplodurids than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or GCCC. Other Haplodurids that have: 2. A fine-earth fraction containing 30 percent or more 1. A duripan that is strongly cemented or less cemented in particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 all subhorizons; and more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass 2. A mean annual soil temperature lower than 22 oC, a (percent) is 30 or more. difference of 5 oC or more between mean summer and mean Vitrandic Argidurids winter soil temperatures at a depth of 50 cm, and a soil moisture regime that borders on xeric. GCBI. Other Argidurids that have a moisture control section Xereptic Haplodurids Aridisols 123

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: Key to Subgroups 1. A moisture control section that is dry in all parts for GCAA. Natridurids that have, above the duripan, one or both three-fourths of the time (cumulative) or less when the soil of the following: temperature at a depth of 50 cm is 5 oC or higher and a soil moisture regime that borders on xeric; and 1. Cracks between the soil surface and the top of the duripan that are 5 mm or more wide through a thickness of 2. Throughout one or more horizons with a total thickness 30 cm or more for some time in normal years and of 18 cm or more within 75 cm of the soil surface, one or slickensides or wedge-shaped aggregates in a layer 15 cm both of the following: or more thick that has its upper boundary above the duripan; a. More than 35 percent (by volume) fragments coarser or than 2.0 mm, of which more than 66 percent is cinders, 2. A linear extensibility of 6.0 cm or more between the soil pumice, and pumicelike fragments; or surface and the top of the duripan. A b. A fine-earth fraction containing 30 percent or more Vertic Natridurids R particles 0.02 to 2.0 mm in diameter, of which 5 percent I 1 or more is volcanic glass, and [(Al plus /2 Fe, percent GCAB. Other Natridurids that meet both of the following: extracted by ammonium oxalate) times 60] plus the 1. Have a duripan that is strongly cemented or less volcanic glass (percent) is 30 or more. cemented in all subhorizons; and Vitrixerandic Haplodurids 2. Are either: GCCF. Other Haplodurids that have, throughout one or more a. Irrigated and have aquic conditions for some time in horizons with a total thickness of 18 cm or more within 75 cm of normal years in one or more layers within 100 cm of the the soil surface, one or both of the following: soil surface; or 1. More than 35 percent (by volume) fragments coarser b. Saturated with water in one or more layers within than 2.0 mm, of which more than 66 percent is cinders, 100 cm of the soil surface for 1 month or more in normal pumice, and pumicelike fragments; or years. Aquic Natrargidic Natridurids 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 GCAC. Other Natridurids that are either: more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass 1. Irrigated and have aquic conditions for some time in (percent) is 30 or more. normal years in one or more layers within 100 cm of the soil Vitrandic Haplodurids surface; or 2. Saturated with water in one or more layers within 100 GCCG. Other Haplodurids that have a mean annual soil 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 Natridurids between mean summer and mean winter soil temperatures at a depth of 50 cm, and a soil moisture regime that borders on GCAD. Other Natridurids that have the following combination xeric. of characteristics: Xeric Haplodurids 1. A duripan that is strongly cemented or less cemented in all subhorizons; and GCCH. Other Haplodurids that have a moisture control section that is dry in all parts for less than three-fourths of the 2. A moisture control section that is dry in all parts for less time (cumulative) when the soil temperature at a depth of 50 cm than three-fourths of the time (cumulative) when the soil is 5 oC or higher and have a soil moisture regime that borders on temperature is 5 oC or higher at a depth of 50 cm and a soil ustic. moisture regime that borders on xeric. Ustic Haplodurids Natrixeralfic Natridurids 124 Keys to Soil Taxonomy

GCAE. Other Natridurids that have a duripan that is strongly GDB. Other Gypsids that have a natric horizon that has its cemented or less cemented in all subhorizons. upper boundary within 100 cm of the soil surface. Natrargidic Natridurids Natrigypsids, p. 126

GCAF. Other Natridurids that have both: GDC. Other Gypsids that have an argillic horizon that has its upper boundary within 100 cm of the soil surface. 1. A moisture control section that is dry in all parts for less Argigypsids, p. 124 than three-fourths of the time (cumulative) when the soil temperature is 5 oC or higher at a depth of 50 cm and a soil GDD. Other Gypsids that have a calcic horizon that has its moisture regime that borders on xeric; and upper boundary within 100 cm of the soil surface. 2. Throughout one or more horizons with a total thickness Calcigypsids, p. 125 of 18 cm or more within 75 cm of the soil surface, one or both of the following: GDE. Other Gypsids. Haplogypsids, p. 125 a. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, Argigypsids pumice, and pumicelike fragments; or Key to Subgroups b. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter, of which 5 percent GDCA. Argigypsids that have a lithic contact within 50 cm of 1 or more is volcanic glass, and [(Al plus /2 Fe, percent the soil surface. extracted by ammonium oxalate) times 60] plus the Lithic Argigypsids volcanic glass (percent) is 30 or more. Vitrixerandic Natridurids GDCB. Other Argigypsids that have: 1. Cracks within 125 cm of the soil surface that are 5 mm GCAG. Other Natridurids that have, throughout one or more wide through a thickness of 30 cm or more for some or more horizons with a total thickness of 18 cm or more within time in normal years and slickensides or wedge-shaped 75 cm of the soil surface, one or both of the following: aggregates in a layer 15 cm or more thick that has its upper 1. More than 35 percent (by volume) fragments coarser boundary within 125 cm of the soil surface; or than 2.0 mm, of which more than 66 percent is cinders, 2. A linear extensibility of 6.0 cm or more between the soil pumice, and pumicelike fragments; or surface and either a depth of 100 cm or a densic, lithic, or 2. A fine-earth fraction containing 30 percent or more paralithic contact, whichever is shallower. particles 0.02 to 2.0 mm in diameter, of which 5 percent or Vertic Argigypsids 1 more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass GDCC. Other Argigypsids that have a calcic horizon overlying (percent) is 30 or more. the gypsic horizon. Vitrandic Natridurids Calcic Argigypsids

GCAH. Other Natridurids that have a moisture control section GDCD. Other Argigypsids that have one or more horizons, that is dry in all parts for less than three-fourths of the time within 100 cm of the soil surface and with a combined thickness (cumulative) when the soil temperature is 5 oC or higher at a depth of 15 cm or more, that contain 20 percent or more (by volume) of 50 cm and have a soil moisture regime that borders on xeric. durinodes, nodules, or concretions. Xeric Natridurids Petronodic Argigypsids

GCAI. Other Natridurids. GDCE. Other Argigypsids that have both: Typic Natridurids 1. A moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) when the soil Gypsids temperature is 5 oC or higher at a depth of 50 cm and a soil moisture regime that borders on xeric; and Key to Great Groups 2. Throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of the soil surface, one or GDA. Gypsids that have a petrogypsic or petrocalcic horizon both of the following: that has its upper boundary within 100 cm of the soil surface. Petrogypsids, p. 127 a. More than 35 percent (by volume) fragments coarser Aridisols 125

than 2.0 mm, of which more than 66 percent is cinders, than three-fourths of the time (cumulative) when the soil pumice, and pumicelike fragments; or temperature is 5 oC or higher at a depth of 50 cm and a soil moisture regime that borders on xeric; and b. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter, of which 5 percent 2. Throughout one or more horizons with a total thickness 1 or more is volcanic glass, and [(Al plus /2 Fe, percent of 18 cm or more within 75 cm of the soil surface, one or extracted by ammonium oxalate) times 60] plus the both of the following: volcanic glass (percent) is 30 or more. a. More than 35 percent (by volume) fragments coarser Vitrixerandic Argigypsids than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or GDCF. Other Argigypsids that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of b. A fine-earth fraction containing 30 percent or more the soil surface, one or both of the following: 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. More than 35 percent (by volume) fragments coarser extracted by ammonium oxalate) times 60] plus the than 2.0 mm, of which more than 66 percent is cinders, volcanic glass (percent) is 30 or more. pumice, and pumicelike fragments; or Vitrixerandic Calcigypsids 2. A fine-earth fraction containing 30 percent or more A particles 0.02 to 2.0 mm in diameter, of which 5 percent or GDDD. Other Calcigypsids that have, throughout one or more R 1 I more is volcanic glass, and [(Al plus /2 Fe, percent extracted horizons with a total thickness of 18 cm or more within 75 cm of by ammonium oxalate) times 60] plus the volcanic glass the soil surface, one or both of the following: (percent) is 30 percent or more. 1. More than 35 percent (by volume) fragments coarser Vitrandic Argigypsids than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or GDCG. Other Argigypsids that have a moisture control section that is dry in all parts for less than three-fourths of the time 2. A fine-earth fraction containing 30 percent or more (cumulative) when the soil temperature at a depth of 50 cm is 5 oC particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 or higher and have a soil moisture regime that borders on xeric. more is volcanic glass, and [(Al plus /2 Fe, percent extracted Xeric Argigypsids by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. GDCH. Other Argigypsids that have a moisture control section Vitrandic Calcigypsids that is dry in all parts for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm is 5 oC GDDE. Other Calcigypsids that have a moisture control or higher and have a soil moisture regime that borders on ustic. section that is dry in all parts for less than three-fourths of the Ustic Argigypsids time (cumulative) when the soil temperature at a depth of 50 cm is 5 oC or higher and have a soil moisture regime that borders on GDCI. Other Argigypsids. xeric. Typic Argigypsids Xeric Calcigypsids

Calcigypsids GDDF. Other Calcigypsids that have a moisture control section that is dry in all parts for less than three-fourths of the time Key to Subgroups (cumulative) when the soil temperature at a depth of 50 cm is 5 oC or higher and have a soil moisture regime that borders on ustic. GDDA. Calcigypsids that have a lithic contact within 50 cm of Ustic Calcigypsids the soil surface. Lithic Calcigypsids GDDG. Other Calcigypsids. Typic Calcigypsids GDDB. Other Calcigypsids that have one or more horizons, 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) Haplogypsids durinodes, nodules, or concretions. Petronodic Calcigypsids Key to Subgroups GDEA. Haplogypsids that have a lithic contact within 50 cm GDDC. Other Calcigypsids that have both: of the soil surface. 1. A moisture control section that is dry in all parts for less Lithic Haplogypsids 126 Keys to Soil Taxonomy

GDEB. Other Haplogypsids that have a gypsic horizon section that is dry in all parts for less than three-fourths of the time that has its upper boundary within 18 cm of the soil (cumulative) when the soil temperature at a depth of 50 cm is 5 oC surface. or higher and have a soil moisture regime that borders on xeric. Leptic Haplogypsids Xeric Haplogypsids

GDEC. Other Haplogypsids that have, in a horizon at least GDEH. Other Haplogypsids that have a moisture control 25 cm thick within 100 cm of the mineral soil surface, an section that is dry in all parts for less than three-fourths of the exchangeable sodium percentage of 15 or more (or an SAR of time (cumulative) when the soil temperature at a depth of 50 cm 13 or more) during at least 1 month in normal years. is 5 oC or higher and have a soil moisture regime that borders on Sodic Haplogypsids ustic. Ustic Haplogypsids GDED. Other Haplogypsids that have one or more horizons, within 100 cm of the soil surface and with a combined thickness GDEI. Other Haplogypsids. of 15 cm or more, that contain 20 percent or more (by volume) Typic Haplogypsids durinodes, nodules, or concretions. Petronodic Haplogypsids Natrigypsids

GDEE. Other Haplogypsids that have both: Key to Subgroups 1. A moisture control section that is dry in all parts for less GDBA. Natrigypsids that have a lithic contact within 50 cm of than three-fourths of the time (cumulative) when the soil the soil surface. temperature is 5 oC or higher at a depth of 50 cm and a soil Lithic Natrigypsids moisture regime that borders on xeric; and GDBB. Other Natrigypsids that have: 2. Throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of the soil surface, one or 1. Cracks within 125 cm of the soil surface that are 5 mm both of the following: or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge-shaped a. More than 35 percent (by volume) fragments coarser aggregates in a layer 15 cm or more thick that has its upper than 2.0 mm, of which more than 66 percent is cinders, boundary within 125 cm of the soil surface; or pumice, and pumicelike fragments; or 2. A linear extensibility of 6.0 cm or more between the soil b. A fine-earth fraction containing 30 percent or more surface and either a depth of 100 cm or a densic, lithic, or particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 paralithic contact, whichever is shallower. or more is volcanic glass, and [(Al plus /2 Fe, percent Vertic Natrigypsids extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. GDBC. Other Natrigypsids that have one or more horizons, Vitrixerandic 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) GDEF. Other Haplogypsids that have, throughout one durinodes, nodules, or concretions. or more horizons with a total thickness of 18 cm or more within Petronodic Natrigypsids 75 cm of the soil surface, one or both of the following: GDBD. Other Natrigypsids that have both: 1. More than 35 percent (by volume) fragments coarser 1. A moisture control section that is dry in all parts for less than 2.0 mm, of which more than 66 percent is cinders, than three-fourths of the time (cumulative) when the soil pumice, and pumicelike fragments; or temperature is 5 oC or higher at a depth of 50 cm and a soil 2. A fine-earth fraction containing 30 percent or more moisture regime that borders on xeric; and particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 2. Throughout one or more horizons with a total thickness more is volcanic glass, and [(Al plus /2 Fe, percent extracted of 18 cm or more within 75 cm of the soil surface, one or by ammonium oxalate) times 60] plus the volcanic glass both of the following: (percent) is 30 or more. Vitrandic Haplogypsids a. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, GDEG. Other Haplogypsids that have a moisture control pumice, and pumicelike fragments; or Aridisols 127

b. A fine-earth fraction containing 30 percent or more temperature is 5 oC or higher at a depth of 50 cm and a soil particles 0.02 to 2.0 mm in diameter, of which 5 percent moisture regime that 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 of pumice, and pumicelike fragments; or 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 extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. 2. A fine-earth fraction containing 30 percent or more Vitrixerandic Petrogypsids 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 GDAD. Other Petrogypsids that have, throughout one A by ammonium oxalate) times 60] plus the volcanic glass or more horizons with a total thickness of 18 cm or more within R (percent) is 30 or more. 75 cm of the soil surface, one or both of the I Vitrandic Natrigypsids following: GDBF. Other Natrigypsids that have a moisture control 1. More than 35 percent (by volume) fragments coarser section that is dry in all parts for less than three-fourths of the than 2.0 mm, of which more than 66 percent is cinders, time (cumulative) when the soil temperature at a depth of 50 cm pumice, and pumicelike fragments; or is 5 oC or higher and have a soil moisture regime that borders on 2. A fine-earth fraction containing 30 percent or more xeric. particles 0.02 to 2.0 mm in diameter, of which 5 percent or Xeric Natrigypsids 1 more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass GDBG. Other Natrigypsids that have a moisture control (percent) is 30 or more. section that is dry in all parts for less than three-fourths of the Vitrandic Petrogypsids time (cumulative) when the soil temperature at a depth of 50 cm is 5 oC or higher and have a soil moisture regime that borders on GDAE. Other Petrogypsids that have a moisture control ustic. section that is dry in all parts for less than three-fourths of the Ustic Natrigypsids time (cumulative) when the soil temperature at a depth of 50 cm is 5 oC or higher and have a soil moisture regime that borders on GDBH. Other Natrigypsids. xeric. Typic Natrigypsids Xeric Petrogypsids

Petrogypsids GDAF. Other Petrogypsids that have a moisture control section that is dry in all parts for less than three-fourths of the Key to Subgroups time (cumulative) when the soil temperature at a depth of 50 cm GDAA. Petrogypsids that have a petrocalcic horizon that has is 5 oC or higher and have a soil moisture regime that borders on its upper boundary within 100 cm of the soil surface. ustic. Petrocalcic Petrogypsids Ustic Petrogypsids GDAG. Other Petrogypsids. GDAB. Other Petrogypsids that have a calcic horizon Typic Petrogypsids overlying the petrogypsic horizon. Calcic Petrogypsids Salids GDAC. Other Petrogypsids that have both: Key to Great Groups 1. A moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) when the soil GBA. Salids that are saturated with water in one or more 128

layers within 100 cm of the mineral soil surface for 1 month or Haplosalids more in normal years. Aquisalids, p. 128 Key to Subgroups GBBA. Haplosalids that have a duripan that has its upper GBB. Other Salids. boundary within 100 cm of the soil surface. Haplosalids, p. 128 Duric Haplosalids

Aquisalids GBBB. Other Haplosalids that have a petrogypsic horizon that has its upper boundary within 100 cm of the soil surface. Key to Subgroups Petrogypsic Haplosalids GBAA. Aquisalids that have a gypsic or petrogypsic horizon that has its upper boundary within 100 cm of the soil GBBC. Other Haplosalids that have a gypsic horizon that has surface. its upper boundary within 100 cm of the soil surface. Gypsic Aquisalids Gypsic Haplosalids

GBAB. Other Aquisalids that have a calcic or petrocalcic GBBD. Other Haplosalids that have a calcic horizon that has horizon that has an upper boundary within 100 cm of the soil its upper boundary within 100 cm of the soil surface. surface. Calcic Haplosalids Calcic Aquisalids GBAC. Other Aquisalids. GBBE. Other Haplosalids. Typic Aquisalids Typic Haplosalids 129

CHAPTER 8 Entisols

Key to Suborders LB. Other Entisols that have, in one or more layers at a depth between 25 and 100 cm below the mineral soil surface, 3 LA. Entisols that have one or more of the following: percent or more (by volume) fragments of diagnostic horizons that are not arranged in any discernible order. 1. Aquic conditions and sulfidic materials within 50 cm of Arents, p. 133 the mineral soil surface; or 2. Permanent saturation with water and a reduced matrix LC. Other Entisols that have less than 35 percent (by volume) in all horizons below 25 cm from the mineral soil surface; rock fragments and a texture of loamy fine sand or coarser in all or layers (sandy loam lamellae are permitted) within the particle- size control section. 3. In a layer above a densic, lithic, or paralithic contact or , p. 144 E in a layer at a depth between 40 and 50 cm below the mineral N soil surface, whichever is shallower, aquic conditions for LD. Other Entisols that do not have a densic, lithic, or paralithic T some time in normal years (or artificial drainage) and one or contact within 25 cm of the mineral soil surface and have: more of the following: 1. A slope of less than 25 percent; and a. A texture finer than loamy fine sand and, in 50 percent or more of the matrix, one or more of the following: 2. Either 0.2 percent or more organic carbon of Holocene age at a depth of 125 cm below the mineral soil surface or an (1) Chroma of 0; or irregular decrease in content of organic carbon from a depth (2) Chroma of 1 or less and a color value, moist, of 4 of 25 cm to a depth of 125 cm or to a densic, lithic, or or more; or paralithic contact if shallower; and (3) Chroma of 2 or less and redox concentrations; or 3. A soil temperature regime: b. A texture of loamy fine sand or coarser and, in 50 a. That is warmer than cryic; or percent or more of the matrix, one or more of the b. That is cryic and the soil has: following: (1) No gelic material; and (1) Chroma of 0; or (2) Either a slope of less than 5 percent or less than (2) Hue of 10YR or redder, a color value, moist, of 4 15 percent volcanic glass in the 0.02 to 2.0 mm fraction or more, and chroma of 1; or in some part of the particle-size control section. (3) Hue of 10YR or redder, chroma of 2 or less, and Fluvents, p. 134 redox concentrations; or LE. Other Entisols. (4) Hue of 2.5Y or yellower, chroma of 3 or less, and Orthents, p. 139 distinct or prominent redox concentrations; or (5) Hue of 2.5Y or yellower and chroma of 1; or Aquents (6) Hue of 5GY, 5G, 5BG, or 5B; or (7) Any color if it results from uncoated sand grains; Key to Great Groups or LAA. Aquents that have sulfidic materials within 50 cm of the c. Enough active ferrous iron to give a positive reaction mineral soil surface. to alpha,alpha-dipyridyl at a time when the soil is not Sulfaquents, p. 133 being irrigated. Aquents, p. 129 LAB. Other Aquents that have, in all horizons at a depth 130 Keys to Soil Taxonomy

1 between 20 and 50 cm below the mineral soil surface, both an n b. [(Al plus /2 Fe, percent extracted by ammonium value of more than 0.7 and 8 percent or more clay in the fine- oxalate) times 60] plus the volcanic glass (percent) is earth fraction. equal to 30 or more. Hydraquents, p. 132 Aquandic Cryaquents

LAC. Other Aquents that have, in normal years, a mean annual LADB. Other Cryaquents. soil temperature of 0 oC or colder and a mean summer soil Typic Cryaquents temperature that: 1. Is 8 oC or colder if there is no O horizon; or Endoaquents 2. Is 5 oC or colder if there is an O horizon. Key to Subgroups Gelaquents, p. 132 LAHA. Endoaquents that have, within 100 cm of the mineral soil surface, one or both of the following: LAD. Other Aquents that have a cryic soil temperature regime. Cryaquents, p. 130 1. Sulfidic materials; or 2. A horizon 15 cm or more thick that has all of the LAE. Other Aquents that have less than 35 percent (by characteristics of a sulfuric horizon, except that it has a pH volume) rock fragments and a texture of loamy fine sand or value between 3.5 and 4.0. coarser in all layers (sandy loam lamellae are permitted) within Sulfic Endoaquents the particle-size control section. Psammaquents, p. 132 LAHB. Other Endoaquents that have a lithic contact within 50 cm of the mineral soil surface. LAF. Other Aquents that have either 0.2 percent or more Lithic Endoaquents organic carbon of Holocene age at a depth of 125 cm below the mineral soil surface or an irregular decrease in content of LAHC. Other Endoaquents that have, in one or more horizons organic carbon from a depth of 25 cm to a depth of 125 cm or to within 100 cm of the mineral soil surface, an exchangeable a densic, lithic, or paralithic contact if shallower. sodium percentage of 15 or more (or a sodium adsorption ratio Fluvaquents, p. 131 of 13 or more) for 6 or more months in normal years. Sodic Endoaquents LAG. Other Aquents that have episaturation. Epiaquents, p. 131 LAHD. Other Endoaquents that have, in one or more horizons between either the Ap horizon or a depth of 25 cm from the LAH. Other Aquents. mineral soil surface, whichever is deeper, and a depth of 75 cm, Endoaquents, p. 130 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, LADA. 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 3. Hue of 5Y and chroma of 3 or more; or the mineral soil surface, one or more of the following: 4. Hue of 5Y or redder and chroma of 2 or more if there are 1. A fine-earth fraction with both a bulk density of 1.0 no redox concentrations. g/cm3 or less, measured at 33 kPa water retention, and Al 1 Aeric Endoaquents plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0; or LAHE. Other Endoaquents that have both: 2. More than 35 percent (by volume) fragments coarser 1. An Ap horizon that has a color value, moist, of 3 or less than 2.0 mm, of which more than 66 percent is cinders, and a color value, dry, of 5 or less (crushed and smoothed) or pumice, and pumicelike fragments; or materials in the upper 15 cm that have these colors after 3. A fine-earth fraction containing 30 percent or more mixing; and particles 0.02 to 2.0 mm in diameter; and 2. A base saturation (by NH4OAc) of less than 50 percent a. In the 0.02 to 2.0 mm fraction, 5 percent or more in some part within 100 cm of the mineral soil surface. volcanic glass; and Humaqueptic Endoaquents Entisols 131

LAHF. Other Endoaquents that have either an Ap horizon that 2. A horizon 15 cm or more thick that has all of the has a color value, moist, of 3 or less and a color value, dry, of 5 characteristics of a sulfuric horizon, except that it has a pH or less (crushed and smoothed) or materials in the upper 15 cm value between 3.5 and 4.0. that have these colors after mixing. Sulfic Fluvaquents Mollic Endoaquents LAFB. Other Fluvaquents that have one or both of the LAHG. Other Endoaquents. following: Typic Endoaquents 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or Epiaquents more for some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick Key to Subgroups that has its upper boundary within 125 cm of the mineral LAGA. Epiaquents that have, in one or more horizons 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 LAFC. Other Fluvaquents that have a buried layer of organic 2. Hue of 2.5Y or redder, a color value, moist, of 5 or less, E soil materials, 20 cm or more thick, that has its upper boundary and chroma of 2 or more; or N within 100 cm of the mineral soil surface. T 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 LAFD. Other Fluvaquents that have, throughout one or more concentrations. horizons with a total thickness of 18 cm or more within 75 cm of Aeric Epiaquents the mineral soil surface, one or more of the following: LAGB. Other Epiaquents that have both: 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. An Ap horizon that has a color value, moist, of 3 or less 1 plus /2 Fe percentages (by ammonium oxalate) totaling more and a color value, dry, of 5 or less (crushed and smoothed) or than 1.0; or materials in the upper 15 cm that have these colors 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 NH OAc) of less than 4 pumice, and pumicelike fragments; or 50 percent in some part within 100 cm of the mineral soil surface. 3. A fine-earth fraction containing 30 percent or more Humaqueptic Epiaquents particles 0.02 to 2.0 mm in diameter; and a. In the 0.02 to 2.0 mm fraction, 5 percent or more LAGC. Other Epiaquents that have either an Ap horizon that volcanic glass; and has a color value, moist, of 3 or less and a color value, dry, of 5 1 or less (crushed and smoothed) or materials in the upper 15 cm b. [(Al plus /2 Fe, percent extracted by ammonium that have these colors after mixing. oxalate) times 60] plus the volcanic glass (percent) is Mollic Epiaquents equal to 30 or more. Aquandic Fluvaquents LAGD. Other Epiaquents. Typic Epiaquents LAFE. Other Fluvaquents that have, in one or more horizons between either the Ap horizon or a depth of 25 cm from the Fluvaquents mineral soil surface, whichever is deeper, and a depth of 75 cm, colors in 50 percent or more of the matrix as follows: Key to Subgroups 1. Hue of 2.5Y or redder, a color value, moist, of 6 or LAFA. Fluvaquents that have, within 100 cm of the mineral more, and chroma of 3 or more; or soil surface, one or both of the following: 2. Hue of 2.5Y or redder, a color value, moist, of 5 or less, 1. Sulfidic materials; or and chroma of 2 or more; or 132 Keys to Soil Taxonomy

3. Hue of 5Y and chroma of 3 or more; or soil materials, 20 cm or more thick, that has its upper boundary 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 LABD. Other Hydraquents. Typic Hydraquents LAFF. Other Fluvaquents that have both: 1. An Ap horizon that has a color value, moist, of 3 or less Psammaquents and a color value, dry, of 5 or less (crushed and smoothed) or materials in the upper 15 cm that have these colors after Key to Subgroups mixing; and LAEA. Psammaquents that have a lithic contact within 50 cm

2. A base saturation (by NH4OAc) of less than 50 percent of the mineral soil surface. in some part within 100 cm of the mineral soil surface. Lithic Psammaquents Humaqueptic Fluvaquents LAEB. Other Psammaquents that have, in one or more LAFG. Other Fluvaquents that have either an Ap horizon that horizons within 100 cm of the mineral soil surface, an has a color value, moist, of 3 or less and a color value, dry, of 5 exchangeable sodium percentage of 15 or more (or a sodium or less (crushed and smoothed) or materials in the upper 15 cm adsorption ratio of 13 or more) for 6 or more months in normal that have these colors after mixing. years. Mollic Fluvaquents Sodic Psammaquents

LAFH. Other Fluvaquents. LAEC. Other Psammaquents that have a horizon, 5 cm or Typic 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 has one or more of the following: Gelaquents 1. In 25 percent or more of each pedon, cementation by Key to Subgroups organic matter and aluminum, with or without iron; or

1 LACA. All Gelaquents. 2. Al plus /2 Fe percentages (by ammonium oxalate) Typic Gelaquents totaling 0.25 or more, and half that amount or less in an overlying horizon; or Hydraquents 3. An ODOE value of 0.12 or more, and a value half as high or lower in an overlying horizon. Key to Subgroups Spodic Psammaquents LABA. Hydraquents that have, within 100 cm of the mineral soil surface, one or both of the following: LAED. Other Psammaquents that have both: 1. Sulfidic materials; or 1. An Ap horizon that has a color value, moist, of 3 or less and a color value, dry, of 5 or less (crushed and smoothed) or 2. A horizon 15 cm or more thick that has all of the materials in the upper 15 cm that have these colors after characteristics of a sulfuric horizon, except that it has a pH mixing; and value between 3.5 and 4.0.

Sulfic Hydraquents 2. A base saturation (by NH4OAc) of less than 50 percent in some part within 100 cm of the mineral soil surface. LABB. Other Hydraquents that have, in one or more horizons Humaqueptic Psammaquents within 100 cm of the mineral soil surface, an exchangeable sodium percentage of 15 or more (or a sodium adsorption ratio LAEE. Other Psammaquents that have either an Ap horizon of 13 or more) for 6 or more months in normal years. that has a color value, moist, of 3 or less and a color value, dry, Sodic Hydraquents of 5 or less (crushed and smoothed) or materials in the upper 15 cm that have these colors after mixing. LABC. Other Hydraquents that have a buried layer of organic Mollic Psammaquents Entisols 133

LAEF. Other Psammaquents. mineral soil surface, 3 percent or more fragments of a duripan or Typic Psammaquents a petrocalcic horizon; Duric Torriarents

Sulfaquents LBCC. Other Torriarents. Haplic Torriarents Key to Subgroups LAAA. Sulfaquents that have, in some horizons at a depth Udarents between 20 and 50 cm below the mineral soil surface, either or both: Key to Subgroups 1. An n value of 0.7 or less; or LBDA. Udarents that have 3 percent or more fragments of an argillic horizon in some horizon within 100 cm of the mineral 2. Less than 8 percent clay in the fine-earth fraction. soil surface and have a base saturation (by sum of cations) of 35 Haplic Sulfaquents percent or more in all parts within 100 cm of the mineral soil surface. LAAB. Other Sulfaquents that have a histic epipedon. Alfic Udarents Histic Sulfaquents LBDB. Other Udarents that have 3 percent or more fragments LAAC. Other Sulfaquents that have a buried layer of organic of an argillic horizon in some horizon within 100 cm of the soil materials, 20 cm or more thick, that has its upper boundary mineral soil surface. E within 100 cm of the mineral soil surface. Ultic Udarents N Thapto-Histic Sulfaquents T LBDC. Other Udarents that have 3 percent or more fragments LAAD. Other Sulfaquents. of a mollic epipedon in some horizon within 100 cm of the Typic Sulfaquents mineral soil surface and have a base saturation (by sum of cations) of 35 percent or more in all parts within 100 cm of the mineral soil surface. Arents Mollic Udarents

Key to Great Groups LBDD. Other Udarents. Haplic Udarents LBA. Arents that have an ustic moisture regime. Ustarents, p. 133 Ustarents LBB. Other Arents that have a xeric moisture regime. Key to Subgroups Xerarents, p. 133 LBAA. All Ustarents. LBC. Other Arents that have an aridic (or torric) moisture Haplic Ustarents regime. Torriarents, p. 133 Xerarents

LBD. Other Arents. Key to Subgroups Udarents, p. 133 LBBA. Xerarents that have, in one or more horizons within 100 cm of the mineral soil surface, 3 percent or more fragments Torriarents of a natric horizon. Sodic Xerarents Key to Subgroups LBCA. Torriarents that have, in one or more horizons within LBBB. Other Xerarents that have, within 100 cm of the 100 cm of the mineral soil surface, 3 percent or more fragments mineral soil surface, 3 percent or more fragments of a duripan or of a natric horizon. a petrocalcic horizon. Sodic Torriarents Duric Xerarents

LBCB. Other Torriarents that have, within 100 cm of the LBBC. Other Xerarents that have fragments of an argillic 134 Keys to Soil Taxonomy

horizon with a base saturation (by sum of cations) of 35 percent 2. A fine-earth fraction containing 30 percent or more or more within 100 cm of the mineral soil surface. particles 0.02 to 2.0 mm in diameter; and Alfic Xerarents a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and LBBD. Other Xerarents. 1 Haplic Xerarents b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is Fluvents equal to 30 or more. Vitrandic Cryofluvents

Key to Great Groups LDBC. Other Cryofluvents that have, in one or more horizons within 50 cm of the mineral soil surface, redox depletions with LDA. Fluvents that that have, in normal years, a mean annual chroma of 2 or less and also aquic conditions for some time in soil temperature of 0 oC or colder and a mean summer soil normal years (or artificial drainage). temperature that: Aquic Cryofluvents 1. Is 8 oC or colder if there is no O horizon; or LDBD. Other Cryofluvents that are saturated with water in 2. Is 5 oC or colder if there is an O horizon. one or more layers within 100 cm of the mineral soil surface in Gelifluvents, p. 134 normal years for either or both: LDB. Other Fluvents that have a cryic soil temperature 1. 20 or more consecutive days; or regime. 2. 30 or more cumulative days. Cryofluvents, p. 134 Oxyaquic Cryofluvents LDC. Other Fluvents that have a xeric moisture regime. LDBE. Other Cryofluvents that have either an Ap horizon that Xerofluvents, p. 138 has a color value, moist, of 3 or less and a color value, dry, of 5 or less (crushed and smoothed) or materials in the upper 15 cm LDD. Other Fluvents that have an ustic moisture regime. that have these colors after mixing. Ustifluvents, p. 137 Mollic Cryofluvents LDE. Other Fluvents that have an aridic (or torric) moisture LDBF. Other Cryofluvents. regime. Typic Cryofluvents Torrifluvents, p. 134

LDF. Other Fluvents. Gelifluvents Udifluvents, p. 136 Key to Subgroups Cryofluvents LDAA. 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 LDBA. Cryofluvents that have, throughout one or more normal years (or artificial drainage). horizons with a total thickness of 18 cm or more within 75 cm of Aquic Gelifluvents 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, LDAB. Other Gelifluvents. 1 and percent aluminum plus /2 the iron percentage (by Typic Gelifluvents ammonium oxalate) totaling more than 1.0. Andic Cryofluvents Torrifluvents

LDDB. Other Cryofluvents that have, throughout one or more Key to Subgroups horizons with a total thickness of 18 cm or more within 75 cm of LDEA. Torrifluvents that have: 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 than 2.0 mm, of which more than 66 percent is cinders, a. Cracks within 125 cm of the mineral soil surface that pumice, and pumicelike fragments; or are 5 mm or more wide through a thickness of 30 cm or Entisols 135

more for some time in normal years and slickensides or oxalate) times 60] plus the volcanic glass (percent) is wedge-shaped aggregates in a layer 15 cm or more thick equal to 30 or more. that has its upper boundary within 125 cm of the mineral Vitrixerandic Torrifluvents soil surface; or LDED. Other Torrifluvents that have, throughout one or more b. A linear extensibility of 6.0 cm or more between the horizons with a total thickness of 18 cm or more within 75 cm of mineral soil surface and either a depth of 100 cm or a the mineral soil surface, one or both of the following: densic, lithic, or paralithic contact, whichever is shallower; and 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, 2. A moisture control section that, in normal years, is dry in pumice, and pumicelike fragments; or all its parts for less than three-fourths of the cumulative days per year when the soil temperature at a depth of 50 cm from 2. A fine-earth fraction containing 30 percent or more the soil surface is 5 oC or higher; and particles 0.02 to 2.0 mm in diameter; and 3. An aridic (or torric) moisture regime that borders on a. In the 0.02 to 2.0 mm fraction, 5 percent or more ustic. volcanic glass; and

Ustertic Torrifluvents 1 b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is LDEB. Other Torrifluvents that have one or both of the equal to 30 or more. following: Vitrandic Torrifluvents E 1. Cracks within 125 cm of the soil surface that are N 5 mm or more wide through a thickness of 30 cm or more for LDEE. Other Torrifluvents that have, in one or more horizons T some time in most normal years and slickensides or wedge- within 100 cm of the soil surface, both redox depletions with shaped aggregates in a layer 15 cm or more thick that has its chroma of 2 or less and aquic conditions for some time in upper boundary within 125 cm of the soil surface; or normal years (or artificial drainage). 2. A linear extensibility of 6.0 cm or more between the soil Aquic Torrifluvents surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. LDEF. Other Torrifluvents that are saturated with water in one Vertic Torrifluvents or more layers within 150 cm of the soil surface in normal years for either or both: LDEC. Other Torrifluvents that have: 1. 20 or more consecutive days; or 1. A moisture control section that, in normal years, is dry in 2. 30 or more cumulative days. all its parts for less than three-fourths of the cumulative days Oxyaquic Torrifluvents per year when the soil temperature at a depth of 50 cm from the soil surface is 5 oC or higher; and LDEG. Other Torrifluvents that have: 2. A thermic, mesic, or frigid soil temperature regime and 1. A horizon within 100 cm of the mineral soil surface that an aridic (or torric) moisture regime that borders on xeric; is 15 cm or more thick and that either has 20 percent or more and (by volume) durinodes or is brittle and has a firm rupture- 3. Throughout one or more horizons with a total thickness resistance class when moist; and of 18 cm or more within 75 cm of the mineral soil surface, 2. A moisture control section that, in normal years, is dry in one or both of the following: all its parts for less than three-fourths of the cumulative days a. More than 35 percent (by volume) fragments coarser per year when the soil temperature at a depth of 50 cm from than 2.0 mm, of which more than 66 percent is cinders, the soil surface is 5 oC or higher; and pumice, and pumicelike fragments; or 3. A thermic, mesic, or frigid soil temperature regime b. A fine-earth fraction containing 30 percent or more and an aridic (or torric) moisture regime that borders on particles 0.02 to 2.0 mm in diameter; and xeric. Duric Xeric Torrifluvents (1) In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and LDEH. Other Torrifluvents that have a horizon within 100 cm 1 (2) [(Al plus /2 Fe, percent extracted by ammonium of the mineral soil surface that is 15 cm or more thick and that 136 Keys to Soil Taxonomy

either has 20 percent or more (by volume) durinodes or is brittle b. In one or more horizons within 100 cm of the mineral and has a firm rupture-resistance class when moist. soil surface, a color value, moist, of 4 or more and either Duric Torrifluvents chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and also aquic conditions for some time in normal years (or artificial LDEI. Other Torrifluvents that have both: drainage). Aquertic Udifluvents 1. A moisture control section that, in normal years, is dry in all its parts for less than three-fourths of the cumulative days LDFB. Other Udifluvents that have one or both of the per year when the soil temperature at a depth of 50 cm from following: the soil surface is 5 oC or higher; and 1. Cracks within 125 cm of the mineral soil surface that are 2. An aridic (or torric) moisture regime that borders on 5 mm or more wide through a thickness of 30 cm or more for ustic. some time in normal years and slickensides or wedge-shaped Ustic Torrifluvents aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil surface; or LDEJ. Other Torrifluvents that have both: 2. A linear extensibility of 6.0 cm or more between the 1. A moisture control section that, in normal years, is dry in mineral soil surface and either a depth of 100 cm or a densic, all its parts for less than three-fourths of the cumulative days lithic, or paralithic contact, whichever is shallower. per year when the soil temperature at a depth of 50 cm from Vertic Udifluvents the soil surface is 5 oC or higher; and 2. A thermic, mesic, or frigid soil temperature regime and LDFC. Other Udifluvents that have, throughout one or more an aridic (or torric) moisture regime that borders on xeric. horizons with a total thickness of 18 cm or more within 75 cm of Xeric Torrifluvents 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 LDEK. Other Torrifluvents that have an anthropic epipedon. and Al plus /2 Fe percentages (by ammonium oxalate) totaling Anthropic Torrifluvents more than 1.0. Andic Udifluvents LDEL. Other Torrifluvents. Typic Torrifluvents LDFD. Other Udifluvents that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of Udifluvents the mineral soil surface, one or both of the following: 1. More than 35 percent (by volume) fragments coarser Key to Subgroups than 2.0 mm, of which more than 66 percent is cinders, LDFA. Udifluvents that have both: pumice, and pumicelike fragments; or 1. One or both of the following: 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; 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 a. In the 0.02 to 2.0 mm fraction, 5 percent or more more for some time in normal years and slickensides or volcanic glass; and

wedge-shaped aggregates in a layer 15 cm or more thick 1 b. [(Al plus /2 Fe, percent extracted by ammonium that has its upper boundary within 125 cm of the mineral oxalate) times 60] plus the volcanic glass (percent) is soil surface; or equal to 30 or more. b. A linear extensibility of 6.0 cm or more between the Vitrandic Udifluvents mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is LDFE. Other Udifluvents that have either: shallower; and 1. In one or more horizons within 50 cm of the mineral soil 2. Either 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. In one or more horizons within 50 cm of the mineral drainage); or soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or 2. In one or more horizons within 100 cm of the mineral artificial drainage); or soil surface, a color value, moist, of 4 or more and either Entisols 137

chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and also aquic LDDB. Other Ustifluvents that have both of the following: conditions for some time in normal years (or artificial 1. When neither irrigated nor fallowed to store moisture, drainage). one of the following: Aquic Udifluvents a. A frigid temperature regime and a moisture control LDFF. Other Udifluvents that are saturated with water in one section that, in normal years, is dry in all parts for four- or more layers within 100 cm of the mineral soil surface in tenths or more of the cumulative days per year when the normal years for either or both: soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or 1. 20 or more consecutive days; or b. A mesic or thermic soil temperature regime and a 2. 30 or more cumulative days. moisture control section that, in normal years, is dry in Oxyaquic Udifluvents some part for six-tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm LDFG. Other Udifluvents that have either an Ap horizon that below the soil surface is higher than 5 oC; or has a color value, moist, of 3 or less and a color value, dry, of 5 or less (crushed and smoothed) or materials in the upper 15 cm c. A hyperthermic, isomesic, or warmer iso soil that have these colors after mixing. temperature regime and a moisture control section that, Mollic Udifluvents in normal years, remains moist in some or all parts for less than 90 consecutive days per year when the LDFH. Other Udifluvents. temperature at a depth of 50 cm below the soil surface is E Typic Udifluvents higher than 8 oC; and N 2. One or both of the following: T Ustifluvents a. Cracks within 125 cm of the mineral soil surface that Key to Subgroups are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or LDDA. Ustifluvents that have both: wedge-shaped aggregates in a layer 15 cm or more thick 1. One or both of the following: that has its upper boundary within 125 cm of the mineral soil surface; 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 b. A linear extensibility of 6.0 cm or more between more for some time in normal years and slickensides or the mineral soil surface and either a depth of 100 cm or wedge-shaped aggregates in a layer 15 cm or more thick a densic, lithic, or paralithic contact, whichever is that has its upper boundary within 125 cm of the mineral shallower. soil surface; or Torrertic Ustifluvents b. A linear extensibility of 6.0 cm or more between the LDDC. Other Ustifluvents that have one or both of the mineral soil surface and either a depth of 100 cm or a following: densic, lithic, or paralithic contact, whichever is shallower; 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 2. Either or both of the following: more for some time in normal years and slickensides or a. In one or more horizons within 50 cm of the mineral wedge-shaped aggregates in a layer 15 cm or more thick that soil surface, redox depletions with chroma of 2 or less and has its upper boundary within 125 cm of the mineral soil also aquic conditions for some time in normal years (or surface; or artificial drainage); or 2. A linear extensibility of 6.0 cm or more between the b. In one or more horizons within 150 cm of the mineral mineral soil surface and either a depth of 100 cm or a densic, soil surface, a color value, moist, of 4 or more and either lithic, or paralithic contact, whichever is shallower. chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and also aquic Vertic Ustifluvents conditions for some time in normal years (or artificial drainage). LDDD. Other Ustifluvents that have anthraquic conditions. Aquertic Ustifluvents Anthraquic Ustifluvents 138 Keys to Soil Taxonomy

LDDE. Other Ustifluvents that have either: 3. A hyperthermic, isomesic, or warmer iso soil 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 dry in some or all parts for less than 120 surface, redox depletions with chroma of 2 or less and also cumulative days per year when the temperature at a depth of aquic conditions for some time in normal years (or artificial 50 cm below the soil surface is higher than 8 oC. drainage); or Udic Ustifluvents 2. In one or more horizons within 150 cm of the mineral soil surface, a color value, moist, of 4 or more and either LDDI. Other Ustifluvents that have either an Ap horizon that chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and also aquic has a color value, moist, of 3 or less and a color value, dry, of 5 conditions for some time in normal years (or artificial or less (crushed and smoothed) or materials in the upper 15 cm drainage). that have these colors after mixing. Aquic Ustifluvents Mollic Ustifluvents

LDDF. Other Ustifluvents that are saturated with water in one LDDJ. Other Ustifluvents. or more layers within 150 cm of the mineral soil surface in Typic Ustifluvents normal years for either or both: 1. 20 or more consecutive days; or Xerofluvents 2. 30 or more cumulative days. Key to Subgroups Oxyaquic Ustifluvents LDCA. Xerofluvents that have one or both of the following: LDDG. Other Ustifluvents 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-shaped 1. A frigid soil temperature regime and a moisture control aggregates in a layer 15 cm or more thick that has its upper section that, in normal years, is dry in all parts for four-tenths boundary within 125 cm of the mineral soil surface; or 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 higher than 5 oC; or the mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is 2. A mesic or thermic soil temperature regime and a shallower. moisture control section that, in normal years, is dry in some Vertic Xerofluvents part for six-tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil LDCB. Other Xerofluvents that have: surface is higher than 5 oC; or 1. In one or more horizons within 50 cm of the mineral soil 3. A hyperthermic, isomesic, or warmer iso soil surface, redox depletions with chroma of 2 or less and also temperature regime and a moisture control section that, in aquic conditions for some time in normal years (or artificial normal years, is moist in some or all parts for less than 180 drainage); or cumulative days per year when the temperature at a depth of 50 cm below the soil surface is higher than 8 oC. 2. In one or more horizons within 150 cm of the mineral Aridic Ustifluvents soil surface, a color value, moist, of 4 or more and either chroma of 0 or hue bluer than 10Y and also aquic conditions LDDH. Other Ustifluvents that, when neither irrigated nor for some time in normal years (or artificial drainage); and fallowed to store moisture, have one of the following: 3. Throughout one or more horizons with a total thickness 1. A frigid soil temperature regime and a moisture control of 18 cm or more within 75 cm of the mineral soil surface, section that, in normal years, is dry in some or all parts for one or more of the following: less than 105 cumulative days per year when the soil a. A fine-earth fraction with both a bulk density of 1.0 temperature at a depth of 50 cm below the soil surface is 3 o g/cm or less, measured at 33 kPa water retention, and Al higher than 5 C; or 1 plus /2 Fe percentages (by ammonium oxalate) totaling 2. A mesic or thermic soil temperature regime and a more than 1.0; or moisture control section that, in normal years, is dry in some b. More than 35 percent (by volume) fragments coarser part for less than four-tenths of the cumulative days per year than 2.0 mm, of which more than 66 percent is cinders, when the temperature at a depth of 50 cm below the soil pumice, and pumicelike fragments; or surface is higher than 5 oC; or Entisols 139

c. A fine-earth fraction containing 30 percent or more LDCG. Other Xerofluvents that have a horizon within 100 cm particles 0.02 to 2.0 mm in diameter; and 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 brittle (1) In the 0.02 to 2.0 mm fraction, 5 percent or more and has a firm rupture-resistance class when moist. volcanic glass; and Durinodic Xerofluvents 1 (2) [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is LDCH. Other Xerofluvents that have either an Ap horizon that equal to 30 or more. has a color value, moist, of 3 or less and a color value, dry, of 5 Aquandic Xerofluvents or less (crushed and smoothed) or materials in the upper 15 cm that have these colors after mixing. LDCC. Other Xerofluvents that have, throughout one or more Mollic Xerofluvents 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 LDCI. Other Xerofluvents. density of 1.0 g/cm3 or less, measured at 33 kPa water retention, Typic Xerofluvents 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. Orthents Andic Xerofluvents Key to Great Groups LDCD. Other Xerofluvents that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of LEA. Orthents that have, in normal years, a mean annual soil E the mineral soil surface, one or both of the following: temperature of 0 oC or colder and a mean summer soil N temperature that: 1. More than 35 percent (by volume) fragments coarser T than 2.0 mm, of which more than 66 percent is cinders, 1. Is 8 oC or colder if there is no O horizon; or pumice, and pumicelike fragments; or 2. Is 5 oC or colder if there is an O horizon. 2. A fine-earth fraction containing 30 percent or more Gelorthents, p. 140 particles 0.02 to 2.0 mm in diameter; and LEB. Other Orthents that have a cryic soil temperature regime. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Cryorthents, p. 139 volcanic glass; and

1 b. [(Al plus /2 Fe, percent extracted by ammonium LEC. Other Orthents that have an aridic (or torric) moisture oxalate) times 60] plus the volcanic glass (percent) is regime. equal to 30 or more. Torriorthents, p. 140 Vitrandic Xerofluvents LEC. Other Orthents that have a xeric moisture regime. LDCE. Other Xerofluvents that have either: Xerorthents, p. 144 1. In one or more horizons within 50 cm of the mineral soil LED. Other Orthents that have an ustic moisture regime. surface, redox depletions with chroma of 2 or less and also Ustorthents, p. 142 aquic conditions for some time in normal years (or artificial drainage); or LEF. Other Orthents. 2. In one or more horizons within 150 cm of the mineral Udorthents, p. 141 soil surface, a color value, moist, of 4 or more and either chroma of 0 or hue of 5GY, 5G, 5BG, or 5B or aquic conditions for some time in normal years. Cryorthents Aquic Xerofluvents Key to Subgroups LDCF. Other Xerofluvents that are saturated with water in one LEBA. Cryorthents that have a lithic contact within 50 cm of or more layers within 150 cm of the mineral soil surface in the mineral soil surface. normal years for either or both: Lithic Cryorthents 1. 20 or more consecutive days; or LEBB. Other Cryorthents that have, throughout one 2. 30 or more cumulative days. or more horizons with a total thickness of 18 cm or more within Oxyaquic Xerofluvents 75 cm of the mineral soil surface, one or both of the following: 140 Keys to Soil Taxonomy

1. 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 its parts for less than three-fourths of the cumulative days pumice, and pumicelike fragments; or per year when the soil temperature at a depth of 50 cm from the soil surface is 5 oC or higher; and 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and 3. A hyperthermic, thermic, mesic, frigid, or iso soil temperature regime and an aridic (or torric) moisture regime a. In the 0.02 to 2.0 mm fraction, 5 percent or more that borders on ustic. volcanic glass; and Lithic Ustic Torriorthents 1 b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is LECB. Other Torriorthents that have: equal to 30 or more. 1. A lithic contact within 50 cm of the soil surface; and Vitrandic Cryorthents 2. A moisture control section that, in normal years, is dry in all its parts for less than three-fourths of the cumulative days LEBC. Other Cryorthents that have, in one or more horizons per year when the soil temperature at a depth of 50 cm from within 50 cm of the mineral soil surface, redox depletions with the soil surface is 5 oC or higher; and chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). 3. A thermic, mesic, or frigid soil temperature regime and Aquic Cryorthents an aridic (or torric) moisture regime that borders on xeric. Lithic Xeric Torriorthents LEDD. Other Cryorthents that are saturated with water in one or more layers within 100 cm of the mineral soil surface in LECC. Other Torriorthents that have a lithic contact within 50 normal years for either or both: cm of the soil surface. Lithic Torriorthents 1. 20 or more consecutive days; or 2. 30 or more cumulative days. LECD. Other Torriorthents that have: Oxyaquic Cryorthents 1. One or both of the following: LEBE. Other Cryorthents that have lamellae within 200 cm of a. Cracks within 125 cm of the soil surface that are 5 the mineral soil surface. mm or more wide through a thickness of 30 cm or more Lamellic Cryorthents for some time in normal years and slickensides or wedge- shaped aggregates in a layer 15 cm or more thick that has LEBF. Other Cryorthents. its upper boundary within 125 cm of the soil surface; or Typic Cryorthents b. A linear extensibility of 6.0 cm or more between the soil surface and either a depth of 100 cm or a densic, Gelorthents lithic, or paralithic contact, whichever is shallower; and Key to Subgroups 2. A moisture control section that, in normal years, is dry in all its parts for less than three-fourths of the cumulative days LEAA. Gelorthents that are saturated with water in one or per year when the soil temperature at a depth of 50 cm from more layers within 100 cm of the mineral soil surface in normal the soil surface is 5 oC or higher; and 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) moisture regime that borders on xeric. 2. 30 or more cumulative days. Xerertic Torriorthents Oxyaquic Gelorthents LEAB. Other Gelorthents. LECE. Other Torriorthents that have: Typic Gelorthents 1. One or both of the following: Torriorthents a. Cracks within 125 cm of the 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- shaped aggregates in a layer 15 cm or more thick that LECA. Torriorthents that have: has its upper boundary within 125 cm of the soil surface; 1. A lithic contact within 50 cm of the soil surface; and or Entisols 141

b. A linear extensibility of 6.0 cm or more between the 1. 20 or more consecutive days; or soil surface and either a depth of 100 cm or a densic, 2. 30 or more cumulative days. lithic, or paralithic contact, whichever is shallower; and Oxyaquic Torriorthents 2. A moisture control section that, in normal years, is dry in all its parts for less than three-fourths of the cumulative days LECJ. Other Torriorthents that have a horizon within 100 cm per year when the soil temperature at a depth of 50 cm from of the soil surface that is 15 cm or more thick and that either has the soil surface is 5 oC or higher; and 20 percent or more (by volume) durinodes or is brittle and has a firm rupture-resistance class when moist. 3. An aridic (or torric) moisture regime that borders on Duric Torriorthents ustic. Ustertic Torriorthents LEBC. Other Torriorthents that have both: LECF. Other Torriorthents that have one or both of the 1. A moisture control section that, in normal years, is dry in following: all its parts for less than three-fourths of the cumulative days per year when the soil temperature at a depth of 50 cm from 1. Cracks within 125 cm of the soil surface that are 5 mm the soil surface is 5 oC or higher; and or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge-shaped 2. A hyperthermic, thermic, mesic, frigid, or iso soil aggregates in a layer 15 cm or more thick that has its upper temperature regime and an aridic (or torric) moisture regime boundary within 125 cm of the soil surface; or that borders on ustic. Ustic Torriorthents E 2. A linear extensibility of 6.0 cm or more between the soil N surface and either a depth of 100 cm or a densic, lithic, or LECL. Other Torriorthents that have both: T paralithic contact, whichever is shallower. Vertic Torriorthents 1. A moisture control section that, in normal years, is dry in all its parts for less than three-fourths of the cumulative days LECG. Other Torriorthents that have, throughout one or more per year when the soil temperature at a depth of 50 cm from horizons with a total thickness of 18 cm or more within 75 cm of the soil surface is 5 oC or higher; and the soil surface, one or both of the following: 2. A thermic, mesic, or frigid soil temperature regime 1. More than 35 percent (by volume) fragments coarser and an aridic (or torric) moisture regime that borders on than 2.0 mm, of which more than 66 percent is cinders, xeric. pumice, and pumicelike fragments; or Xeric Torriorthents 2. A fine-earth fraction containing 30 percent or more LECM. Other Torriorthents. particles 0.02 to 2.0 mm in diameter; and Typic Torriorthents a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and Udorthents

1 b. [(Al plus /2 Fe, percent extracted by ammonium Key to Subgroups oxalate) times 60] plus the volcanic glass (percent) is LEFA. Udorthents that have a lithic contact within 50 cm of equal to 30 or more. the mineral soil surface. Vitrandic Torriorthents Lithic Udorthents LECH. Other Torriorthents that have, in one or more horizons LEFB. Other Udorthents that have, throughout one or more within 100 cm of the soil surface, redox depletions with chroma horizons with a total thickness of 18 cm or more within 75 cm of of 2 or less and also aquic conditions for some time in normal the mineral soil surface, one or both of the following: years (or artificial drainage). Aquic Torriorthents 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, LECI. Other Torriorthents that are saturated with water in one pumice, and pumicelike fragments; or or more layers within 150 cm of the soil surface in normal years 2. A fine-earth fraction containing 30 percent or more for either or both: particles 0.02 to 2.0 mm in diameter; and 142 Keys to Soil Taxonomy

a. In the 0.02 to 2.0 mm fraction, 5 percent or more c. A hyperthermic, isomesic, or warmer iso soil volcanic glass; and temperature regime and a moisture control section that, in

1 normal years, remains moist in some or all parts for less b. [(Al plus /2 Fe, percent extracted by ammonium than 90 consecutive days per year when the temperature oxalate) times 60] plus the volcanic glass (percent) is at a depth of 50 cm below the soil surface is higher than equal to 30 or more. 8 oC. Vitrandic Udorthents Aridic Lithic Ustorthents LEFC. Other Udorthents that have, in one or more horizons LEEB. Other Ustorthents that have a lithic contact within 50 within 100 cm of the mineral soil surface, redox depletions with cm of the mineral soil surface. chroma of 2 or less and also aquic conditions for some time in Lithic Ustorthents normal years (or artificial drainage). Aquic Udorthents LEEC. Other Ustorthents that have both: LEFD. Other Udorthents that are saturated with water in one 1. One or both of the following: or more layers within 150 cm of the mineral soil surface in a. Cracks within 125 cm of the mineral soil surface that normal years for either or both: are 5 mm or more wide through a thickness of 30 cm or 1. 20 or more consecutive days; or more for some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick 2. 30 or more cumulative days. that has its upper boundary within 125 cm of the mineral Oxyaquic Udorthents soil surface; or LEFE. Other Udorthents that have 50 percent or more (by b. A linear extensibility of 6.0 cm or more between the volume) wormholes, wormcasts, and filled animal burrows mineral soil surface and either a depth of 100 cm or a between either the Ap horizon or a depth of 25 cm from the densic, lithic, or paralithic contact, whichever is mineral soil surface, whichever is deeper, and either a depth of shallower; and 100 cm or a densic, lithic, paralithic, or petroferric contact, 2. When neither irrigated nor fallowed to store moisture, whichever is shallower. one of the following: Vermic Udorthents a. A frigid temperature regime and a moisture control LEFF. Other Udorthents. section that, in normal years, is dry in all parts for four- Typic Udorthents tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface Ustorthents is higher than 5 oC; or b. A mesic or thermic soil temperature regime and a Key to Subgroups moisture control section that, in normal years, is dry in LEEA. Ustorthents that have: some part for six-tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm 1. A lithic contact within 50 cm of the mineral soil surface; below the soil surface is higher than 5 oC; or and c. 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 one of the following: normal years, remains moist in some or all parts for less a. A frigid temperature regime and a moisture than 90 consecutive days per year when the temperature control section that, in normal years, is dry in all parts for at 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. the soil temperature at a depth of 50 cm below the soil Torrertic Ustorthents surface is higher than 5 oC; or LEED. Other Ustorthents that have one or both of the b. A mesic or thermic soil temperature regime and a following: moisture control section that, in normal years, is dry in some part for six-tenths or more of the cumulative days 1. Cracks within 125 cm of the mineral soil surface that are per year when the soil temperature at a depth of 50 cm 5 mm or more wide through a thickness of 30 cm or more for below the soil surface is higher than 5 oC; or some time in normal years and slickensides or wedge-shaped Entisols 143

aggregates in a layer 15 cm or more thick that has its upper of 18 cm or more within 75 cm of the soil surface, one or boundary within 125 cm of the mineral soil surface; or both of the following: 2. A linear extensibility of 6.0 cm or more between the a. More than 35 percent (by volume) fragments coarser mineral soil surface and either a depth of 100 cm or a densic, than 2.0 mm, of which more than 66 percent is cinders, lithic, or paralithic contact, whichever is shallower. pumice, and pumicelike fragments; or Vertic Ustorthents b. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and LEEE. Other Ustorthents that have anthraquic conditions. Anthraquic Ustorthents (1) In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and

LEEF. Other Ustorthents that have, in one or more horizons 1 (2) [(Al plus /2 Fe, percent extracted by ammonium within 100 cm of the mineral soil surface, redox depletions with oxalate) times 60] plus the volcanic glass (percent) is chroma of 2 or less and also aquic conditions for some time in equal to 30 or more. normal years (or artificial drainage). Vitritorrandic Ustorthents Aquic Ustorthents

LEEG. Other Ustorthents that are saturated with water in one LEEJ. Other Ustorthents that have, throughout one or more or more layers within 150 cm of the mineral soil surface in horizons with a total thickness of 18 cm or more within 75 cm of normal years for either or both: the soil surface, one or both of the following: E 1. 20 or more consecutive days; or 1. More than 35 percent (by volume) fragments coarser N than 2.0 mm, of which more than 66 percent is cinders, 2. 30 or more cumulative days. T pumice, and pumicelike fragments; or Oxyaquic Ustorthents 2. A fine-earth fraction containing 30 percent or more LEEH. Other Ustorthents that have a horizon within 100 particles 0.02 to 2.0 mm in diameter; and cm of the mineral soil surface that is 15 cm or more thick a. In the 0.02 to 2.0 mm fraction, 5 percent or more and that either has 20 percent or more (by volume) durinodes or volcanic glass; and is brittle and has a firm rupture-resistance class when moist. 1 Durinodic Ustorthents b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is LEEI. Other Ustorthents that have both: equal to 30 or more. Vitrandic Ustorthents 1. When neither irrigated nor fallowed to store moisture, one of the following: LEEK. Other Ustorthents that, when neither irrigated nor a. A frigid temperature regime and a moisture control fallowed to store moisture, have one of the following: section that, in normal years, is dry in all parts for four- 1. A frigid soil temperature regime and a moisture control tenths or more of the cumulative days per year when the section that, in normal years, is dry in all parts for four-tenths soil temperature at a depth of 50 cm below the soil surface or more of the cumulative days per year when the soil is higher than 5 oC; or temperature at a depth of 50 cm below the soil surface is b. A mesic or thermic soil temperature regime and a higher than 5 oC; or moisture control section that, in normal years, is dry in 2. 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 some per year when the soil temperature at a depth of 50 cm part for six-tenths or more of the cumulative days per year below the soil surface is higher than 5 oC; or when the soil temperature at a depth of 50 cm below the soil c. A hyperthermic, isomesic, or warmer iso soil surface is higher than 5 oC; or temperature regime and a moisture control section that, in 3. A hyperthermic, isomesic, or warmer iso soil normal years, remains moist in some or all parts for less temperature regime and a moisture control section that, in than 90 consecutive days per year when the temperature normal years, is moist in some or all parts for less than 180 at a depth of 50 cm below the soil surface is higher than cumulative days per year when the temperature at a depth of 8 oC; and 50 cm below the soil surface is higher than 8 oC. 2. Throughout one or more horizons with a total thickness Aridic Ustorthents 144 Keys to Soil Taxonomy

LEEL. Other Ustorthents that, when neither irrigated nor LEDC. Other Xerorthents that have, in one or more horizons fallowed to store moisture, have one of the following: within 100 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in 1. A frigid soil temperature regime and a moisture control normal years (or artificial drainage). section that, in normal years, is dry in some or all parts for Aquic Xerorthents less than 105 cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is LEDD. Other Xerorthents that are saturated with water in one higher than 5 oC; or or more layers within 150 cm of the mineral soil surface in 2. A mesic or thermic soil temperature regime and a normal years for either or both: moisture control section that, in normal years, is dry in some 1. 20 or more consecutive days; or part for less than four-tenths of the cumulative days per year when the temperature at a depth of 50 cm below the soil 2. 30 or more cumulative days. surface is higher than 5 oC; or Oxyaquic Xerorthents 3. A hyperthermic, isomesic, or warmer iso soil LEDE. Other Xerorthents that have a horizon within 100 cm temperature regime and a moisture control section that, in of the mineral soil surface that is 15 cm or more thick and that normal years, is dry in some or all parts for less than 120 either has 20 percent or more (by volume) durinodes or is brittle cumulative days per year when the temperature at a depth of and has a firm rupture-resistance class when moist. 50 cm below the soil surface is higher than 8 oC. Durinodic Xerorthents Udic Ustorthents LEDF. Other Xerorthents that have a base saturation (by LEEM. Other Ustorthents that have 50 percent or more (by NH OAc) of less than 60 percent in all horizons at a depth volume) wormholes, wormcasts, and filled animal burrows 4 between 25 and 75 cm below the mineral soil surface surface or between either the Ap horizon or a depth of 25 cm from the in the horizon directly above a root-limiting layer that is at a mineral soil surface, whichever is deeper, and either a depth of shallower depth. 100 cm or a densic, lithic, paralithic, or petroferric contact, Dystric Xerorthents whichever is shallower. Vermic Ustorthents LEDG. Other Xerorthents. Typic Xerorthents LEEN. Other Ustorthents. Typic Ustorthents Xerorthents Psamments

Key to Subgroups Key to Great Groups LEDA. Xerorthents that have a lithic contact within 50 cm of LCA. Psamments that have a cryic soil temperature regime. the mineral soil surface. Cryopsamments, p. 145 Lithic Xerorthents LCB. Other Psamments that have an aridic (or torric) moisture LEDB. Other Xerorthents that have, throughout one or more regime. horizons with a total thickness of 18 cm or more within 75 cm of Torripsamments, p. 146 the mineral soil surface, one or both of the following: LCC. 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. 145 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and LCD. Other Psamments that have an ustic moisture regime. Ustipsamments, p. 147 a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and LCE. Other Psamments that have a xeric moisture regime. 1 b. [(Al plus /2 Fe, percent extracted by ammonium Xeropsamments, p. 148 oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. LCF. Other Psamments. Vitrandic Xerorthents Udipsamments, p. 147 Entisols 145

Cryopsamments Quartzipsamments

Key to Subgroups Key to Subgroups LCAA. Cryopsamments that have a lithic contact within 50 cm LCCA. Quartzipsamments that have a lithic contact within 50 of the mineral soil surface. cm of the mineral soil surface. Lithic Cryopsamments Lithic Quartzipsamments

LCAB. Other Cryopsamments that have, in one or more LCCB. Other Quartzipsamments that have both: horizons within 50 cm of the mineral soil surface, redox 1. In one or more horizons within 100 cm of the mineral depletions with chroma of 2 or less and also aquic conditions for soil surface, redox depletions with chroma of 2 or less and some time in normal years (or artificial drainage). also aquic conditions for some time in normal years (or Aquic Cryopsamments artificial drainage); and LCAC. Other Cryopsamments that are saturated with water in 2. A horizon, 5 cm or more thick, either below an Ap one or more layers within 100 cm of the mineral soil surface in horizon or at a depth of 18 cm or more from the mineral soil normal years for either or both: surface, whichever is deeper, that has one or more of the following: 1. 20 or more consecutive days; or a. In 25 percent or more of each pedon, cementation 2. 30 or more cumulative days. by organic matter and aluminum, with or without iron; or Oxyaquic Cryopsamments E 1 b. Al plus /2 Fe percentages (by ammonium oxalate) N LCAD. Other Cryopsamments that have, throughout one or totaling 0.25 or more, and half that amount or less in an T more horizons with a total thickness of 18 cm or more within 75 overlying horizon; or cm of the mineral soil surface, a fine-earth fraction containing 5 1 c. An ODOE value of 0.12 or more, and a value half as percent or more volcanic glass, and [(Al plus /2 Fe, percent high or lower in an overlying horizon. extracted by ammonium oxalate) times 60] plus the volcanic Aquodic Quartzipsamments glass (percent) is 30 or more. Vitrandic Cryopsamments LCCC. Other Quartzipsamments that have, in one or more horizons within 100 cm of the mineral soil surface, LCAE. Other Cryopsamments that have a horizon 5 cm or redox depletions with chroma of 2 or less and also aquic more thick that has one or more of the following: conditions for some time in normal years (or artificial drainage). 1. In 25 percent or more of each pedon, cementation by Aquic Quartzipsamments organic matter and aluminum, with or without iron; or

1 LCCD. Other Quartzipsamments that are saturated with water 2. Al plus /2 Fe percentages (by ammonium oxalate) in one or more layers within 100 cm of the mineral soil surface totaling 0.25 or more, and half that amount or less in an in normal years for either or both: overlying horizon; or 1. 20 or more consecutive days; or 3. An ODOE value of 0.12 or more, and a value half as high or lower in an overlying horizon. 2. 30 or more cumulative days. Spodic Cryopsamments Oxyaquic Quartzipsamments

LCAF. Other Cryopsamments that have lamellae within 200 LCCE. Other Quartzipsamments that meet all of the cm of the mineral soil surface. following: Lamellic Cryopsamments 1. Have an ustic moisture regime; and LCAG. Other Cryopsamments. 2. Have a clay fraction with a CEC of 16 cmol(+) or less

Typic Cryopsamments per kg clay (by NH4OAc pH 7); and 146 Keys to Soil Taxonomy

3. The sum of the weighted average silt plus 2 times Torripsamments the weighted average clay (both by weight) is more than 5. Ustoxic Quartzipsamments Key to Subgroups LCBA. Torripsamments that have a lithic contact within 50 cm LCCF. Other Quartzipsamments that meet all of the following: of the soil surface. 1. Have a udic moisture regime; and Lithic Torripsamments 2. Have a clay fraction with a CEC of 16 cmol(+) or less LCBB. Other Torripsamments that are saturated with water in per kg clay (by NH OAc pH 7); and 4 one or more layers within 150 cm of the mineral soil surface in 3. The sum of the weighted average silt plus 2 times the normal years for either or both: weighted average clay (both by weight) is more than 5. 1. 20 or more consecutive days; or Udoxic Quartzipsamments 2. 30 or more cumulative days LCCG. Other Quartzipsamments that have 5 percent or more Oxyaquic Torripsamments (by volume) plinthite in one or more horizons within 100 cm of the mineral soil surface. LCBC. Other Torripsamments that have, throughout one or Plinthic Quartzipsamments more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction containing 5 1 LCCH. Other Quartzipsamments that have both: percent or more volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic 1. Lamellae within 200 cm of the mineral soil surface; and glass (percent) is 30 or more. 2. An ustic moisture regime. Vitrandic Torripsamments Lamellic Ustic Quartzipsamments LCBD. Other Torripsamments that have a horizon within 100 LCCI. Other Quartzipsamments that have lamellae within 200 cm of the soil surface that is 15 cm or more thick and that either cm of the mineral soil surface. has 20 percent or more (by volume) durinodes or is brittle and Lamellic Quartzipsamments has a firm rupture-resistance class when moist. Haploduridic Torripsamments LCCJ. Other Quartzipsamments that have an ustic moisture regime. LCBE. Other Torripsamments that have both: Ustic Quartzipsamments 1. A moisture control section that, in normal years, is dry in all its parts for less than three-fourths of the cumulative days LCCK. Other Quartzipsamments that have a xeric moisture per year when the soil temperature at a depth of 50 cm from regime. the soil surface is 5 oC or higher; and Xeric Quartzipsamments 2. An aridic (or torric) moisture regime that borders on LCCL. Other Quartzipsamments that have a horizon, 5 cm or ustic. more thick, either below an Ap horizon or at a depth of 18 cm or Ustic Torripsamments more from the mineral soil surface, whichever is deeper, that has one or more of the following: LCBF. Other Torripsamments that have both: 1. In 25 percent or more of each pedon, cementation 1. A moisture control section that, in normal years, is dry in by organic matter and aluminum, with or without iron; all its parts for less than three-fourths of the cumulative days or per year when the soil temperature at a depth of 50 cm from o 1 the soil surface is 5 C or higher; and 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) moisture regime that borders on xeric. Xeric Torripsamments 3. An ODOE value of 0.12 or more, and a value half as high or lower in an overlying horizon. LCBG. Other Torripsamments that have, in all horizons from a Spodic Quartzipsamments depth of 25 to 100 cm, more than 50 percent colors that have all of the following: LCCM. Other Quartzipsamments. Typic Quartzipsamments 1. Hue of 2.5YR or redder; and Entisols 147

2. A color value, moist, of 3 or less; and LCFG. Other Udipsamments. Typic Udipsamments 3. A dry value no more than 1 unit higher than the moist value. Rhodic Torripsamments Ustipsamments

LCBH. Other Torripsamments. Key to Subgroups Typic Torripsamments LCDA. Ustipsamments that have a lithic contact within 50 cm of the mineral soil surface. Udipsamments Lithic Ustipsamments Key to Subgroups LCDB. Other Ustipsamments that have, in one or LCFA. Udipsamments that have a lithic contact within 50 cm more horizons within 100 cm of the mineral soil surface, distinct of the mineral soil surface. or prominent redox concentrations and also aquic conditions for Lithic Udipsamments some time in normal years (or artificial drainage). Aquic Ustipsamments LCFB. Other Udipsamments that have, in one or more horizons within 100 cm of the mineral soil surface, redox LCDC. Other Ustipsamments that are saturated with water in depletions with chroma of 2 or less and also aquic conditions for one or more layers within 100 cm of the mineral soil surface in some time in normal years (or artificial drainage). normal years for either or both: E Aquic Udipsamments 1. 20 or more consecutive days; or N T LCFC. Other Udipsamments that are saturated with water in 2. 30 or more cumulative days. one or more layers within 100 cm of the mineral soil surface in Oxyaquic Ustipsamments normal years for either or both: LCDD. Other Ustipsamments that, when neither irrigated nor 1. 20 or more consecutive days; or fallowed to store moisture, have one of the following: 2. 30 or more cumulative days. 1. A frigid soil temperature regime and a moisture control Oxyaquic Udipsamments section that, in normal years, is dry in all parts for four-tenths or more of the cumulative days per year when the soil LCFD. Other Udipsamments that have a horizon, 5 cm or temperature at a depth of 50 cm below the soil surface is more thick, either below an Ap horizon or at a depth of 18 cm or higher than 5 oC; or more from the mineral soil surface, whichever is deeper, that has one or more of the following: 2. A mesic or thermic soil temperature regime and a moisture control section that, in normal years, is dry in some 1. In 25 percent or more of each pedon, cementation by part for six-tenths or more of the cumulative days per year organic matter and aluminum, with or without iron; or when the soil temperature at a depth of 50 cm below the soil 1 o 2. Al plus /2 Fe percentages (by ammonium oxalate) surface is higher than 5 C; or totaling 0.25 or more, and half that amount or less in an 3. A hyperthermic, isomesic, or warmer iso soil overlying horizon; or temperature regime and a moisture control section that, in 3. An ODOE value of 0.12 or more, and a value half as normal years, is moist in some or all parts for less than 180 high or lower in an overlying horizon. cumulative days per year when the temperature at a depth of Spodic Udipsamments 50 cm below the soil surface is higher than 8 oC. Aridic Ustipsamments LCFE. Other Udipsamments that have lamellae within 200 cm of the mineral soil surface. LCDE. Other Ustipsamments that have lamellae within 200 Lamellic Udipsamments cm of the mineral soil surface. Lamellic Ustipsamments LCFF. Other Udipsamments that have a surface horizon between 25 and 50 cm thick that meets all of the requirements LCDF. Other Ustipsamments that have, in all horizons from a for a plaggen epipedon except thickness. depth of 25 to 100 cm, more than 50 percent colors that have all Plagganthreptic Udipsamments of the following: 148

1. Hue of 2.5YR or redder; and LCED. Other Xeropsamments that are saturated with water in one or more layers within 100 cm of the mineral soil surface in 2. A color value, moist, of 3 or less; and normal years for either or both: 3. A dry value no more than 1 unit higher than the moist 1. 20 or more consecutive days; or value. Rhodic Ustipsamments 2. 30 or more cumulative days. Oxyaquic Xeropsamments LCDG. Other Ustipsamments. Typic Ustipsamments LCEE. Other Xeropsamments that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction containing 5 Xeropsamments 1 percent or more volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic Key to Subgroups glass (percent) is 30 or more. LCEA. Xeropsamments have a lithic contact within 50 cm of Vitrandic Xeropsamments the mineral soil surface. Lithic Xeropsamments LCEF. Other Xeropsamments that have a horizon within 100 cm of the mineral soil surface that is 15 cm or more thick LCEB. Other Xeropsamments that have both: and that either has 20 percent or more (by volume) durinodes or is brittle and has a firm rupture-resistance class when moist. 1. In one or more horizons within 100 cm of the mineral Durinodic Xeropsamments soil surface, distinct or prominent redox concentrations and also aquic conditions for some time in normal years (or LCEG. Other Xeropsamments that have lamellae within 200 artificial drainage); and cm of the mineral soil surface. 2. A horizon within 100 cm of the mineral soil surface that Lamellic Xeropsamments is 15 cm or more thick and that either has 20 percent or more (by volume) durinodes or is brittle and has a firm rupture- LCEH. Other Xeropsamments that have a base saturation

resistance class when moist. (by NH4OAc) of less than 60 percent in all horizons at a depth Aquic Durinodic Xeropsamments between 25 and 75 cm below the mineral soil surface or in the horizon directly above a root-limiting layer that is at a LCEC. Other Xeropsamments that have, in one or more shallower depth. horizons within 100 cm of the mineral soil surface, distinct or Dystric Xeropsamments prominent redox concentrations and also aquic conditions for some time in normal years (or artificial drainage). LCEI. Other Xeropsamments. Aquic Xeropsamments Typic Xeropsamments 149

CHAPTER 9 Gelisols

Key to Suborders the organic soil materials to a depth 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 Glacistels, p. 150 more of the following: AAC. Other Histels that have more thickness of fibric soil 1. Overlie cindery, fragmental, or pumiceous materials materials than any other kind of organic soil material to a depth and/or fill their interstices and directly below these materials of 50 cm or to a densic, lithic, or paralithic contact, whichever is have either a densic, lithic, or paralithic contact; or shallowest. 2. When added with the underlying cindery, fragmental, or Fibristels, p. 149 pumiceous materials, total 40 cm or more between the soil surface and a depth of 50 cm; or AAD. Other Histels that have more thickness of hemic soil materials than any other kind of organic soil material to a depth 3. Are saturated with water for 30 or more cumulative days of 50 cm or to a densic, lithic, or paralithic contact, whichever is during normal years (or are artificially drained) and have 80 shallowest. percent or more, by volume, organic soil materials from the G Hemistels, p. 150 soil surface to a depth of 50 cm or to a glacic layer or a E densic, lithic, or paralithic contact, whichever is shallowest. L AAE. Other Histels. Histels, p. 149 Sapristels, p. 150 AB. Other Gelisols that have one or more horizons showing cryoturbation in the form of irregular, broken, or distorted Fibristels horizon boundaries, involutions, the accumulation of organic Key to Subgroups matter on top of the permafrost, ice or sand wedges, and oriented rock fragments. AACA. Fibristels that have a lithic contact within 100 cm of Turbels, p. 154 the soil surface. Lithic Fibristels AC. Other Gelisols. Orthels, p. 150 AACB. Other Fibristels that have a mineral layer 30 cm or more thick within 100 cm of the soil surface. Histels Terric Fibristels Key to Great Groups AACC. Other Fibristels that have, within the organic materials, either one mineral layer 5 cm or more thick or two or AAA. Histels that are saturated with water for less than 30 more layers of any thickness within 100 cm of the soil surface. cumulative days during normal years (and are not artificially Fluvaquentic Fibristels drained). Folistels, p. 150 AACD. Other Fibristels in which three-fourths or more of . the fibric material is derived from Sphagnum to a depth of 50 AAB. Other Histels that are saturated with water for 30 or cm or to a densic, lithic, or paralithic contact, whichever is more cumulative days during normal years and that have both: shallowest. Sphagnic Fibristels 1. A glacic layer with its upper boundary within 100 cm of the soil surface; and AACE. Other Fibristels. 2. Less than three-fourths (by volume) Sphagnum fibers in Typic Fibristels 150 Keys to Soil Taxonomy

Folistels Sapristels

Key to Subgroups Key to Subgroups AAAA. Folistels that have a lithic contact within 50 cm of the AAEA. Sapristels that have a lithic contact within 100 cm of soil surface. the soil surface. Lithic Folistels Lithic Sapristels

AAAB. Other Folistels that have a glacic layer with its upper AAEB. Other Sapristels that have a mineral layer 30 cm or boundary within 100 cm of the soil surface. more thick within 100 cm of the soil surface. Glacic Folistels Terric Sapristels

AAAC. Other Folistels. AAEC. Other Sapristels that have, within the organic Typic Folistels materials, either one mineral layer 5 cm or more thick or two or more layers of any thickness within 100 cm of the soil surface. Fluvaquentic Sapristels Glacistels AAED. Other Sapristels. Key to Subgroups Typic Sapristels AABA. Glacistels that have more thickness of hemic materials than any other kind of organic soil material in the Orthels upper 50 cm. Hemic Glacistels Key to Great Groups

AABB. Other Glacistels that have more thickness of sapric ACA. Orthels that have in 30 percent or more of the pedon materials than any other kind of organic soil material in the more than 40 percent, by volume, organic materials from the upper 50 cm. soil surface to a depth of 50 cm. Sapric Glacistels Historthels, p. 152

AABC. Other Glacistels ACB. Other Orthels that have, within 50 cm of the mineral soil Typic Glacistels surface, redox depletions with chroma of 2 or less and also aquic conditions during normal years (or artificial drainage). Aquorthels, p. 151 Hemistels ACC. Other Orthels that have anhydrous conditions. Key to Subgroups Anhyorthels, p. 151 AADA. Hemistels that have a lithic contact within 100 cm of the soil surface. ACD. Other Orthels that have a mollic epipedon. Lithic Hemistels Mollorthels, p. 153

AADB. Other Hemistels that have a mineral layer 30 cm or ACE. Other Orthels that have an umbric epipedon. more thick within 100 cm of the soil surface. Umbrorthels, p. 154 Terric Hemistels ACF. Other Orthels that have an argillic horizon that has its AADC. Other Hemistels that have, within the organic upper boundary within 100 cm of the mineral soil surface. materials, either one mineral layer 5 cm or more thick or two Argiorthels, p. 152 or more layers of any thickness within 100 cm of the soil surface. ACG. Other Orthels that have, below the Ap horizon or below Fluvaquentic Hemistels a depth of 25 cm, whichever is deeper, less than 35 percent (by volume) rock fragments and have a texture of loamy fine sand or AADD. Other Hemistels. coarser in the particle-size control section. Typic Hemistels Psammorthels, p. 153 Gelisols 151

ACH. Other Orthels. sulfidic materials with an upper boundary within 100 cm of the Haplorthels, p. 152 mineral soil surface. Sulfuric Aquorthels

Anhyorthels ACBD. Other Aquorthels that have either: Key to Subgroups 1. Organic soil materials that are discontinuous at the surface; or ACCA. Anhyorthels that have a lithic contact within 50 cm of the mineral soil surface. 2. Organic soil materials at the surface that change in Lithic Anhyorthels thickness fourfold or more within a pedon. Ruptic-Histic Aquorthels ACCB. Other Anhyorthels that have a glacic layer that has its upper boundary within 100 cm of the mineral soil surface. ACBE. Other Aquorthels that have, throughout one or more Glacic Anhyorthels 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 ACCC. Other Anhyorthels that have a petrogypsic horizon that density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 has its upper boundary within 100 cm of the mineral soil and Al plus /2 Fe percentages (by ammonium oxalate) totaling surface. more than 1.0. Petrogypsic Anhyorthels Andic Aquorthels

ACCD. Other Anhyorthels that have a gypsic horizon that has ACBF. Other Aquorthels that have, throughout one or more its upper boundary within 100 cm of the mineral soil surface. horizons with a total thickness of 18 cm or more within 75 cm of Gypsic Anhyorthels the mineral soil surface, one or both of the following: G 1. More than 35 percent (by volume) fragments coarser ACCE. Other Anhyorthels that have a horizon 15 cm or more E than 2.0 mm, of which more than 66 percent is cinders, thick that contains 12 cmol(-)/L in 1:5 soil:water nitrate and in L pumice, and pumicelike fragments; or 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 that has its volcanic glass; and upper boundary within 100 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 with its equal to 30 or more. upper boundary within 100 cm of the mineral soil surface. Vitrandic Aquorthels Calcic Anhyorthels ACBG. Other Aquorthels that have a salic horizon that ACCH. Other Anhyorthels. has its upper boundary within 100 cm of the mineral soil Typic Anhyorthels surface. Salic Aquorthels Aquorthels ACBH. Other Aquorthels that have less than 35 percent (by Key to Subgroups volume) rock fragments and a texture of loamy fine sand 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 either ACBB. Other Aquorthels that have a glacic layer that has its upper boundary within 100 cm of the mineral soil surface. 1. At a depth of 125 cm below the mineral soil surface, an Glacic Aquorthels organic-carbon content (Holocene age) of 0.2 percent or more and no densic, lithic, or paralithic contact within that ACBC. Other Aquorthels that have a sulfuric horizon or depth; or 152 Keys to Soil Taxonomy

2. An irregular decrease in organic-carbon content depth of 125 cm or a densic, lithic, or paralithic contact, (Holocene age) between a depth of 25 cm and either a depth whichever is shallower. of 125 cm or a densic, lithic, or paralithic contact, whichever Fluvaquentic Haplorthels is shallower. Fluvaquentic Aquorthels ACHD. Other Haplorthels that have, in one or more horizons within 75 cm of the mineral soil surface, redox depletions with ACBJ. Other Aquorthels. chroma of 2 or less and also aquic conditions for some time Typic Aquorthels during normal years (or artificial drainage). Aquic Haplorthels Argiorthels ACHE. Other Haplorthels that have a slope of less than 25 Key to Subgroups percent; and either ACFA. Argiorthels that have a lithic contact within 50 cm of 1. At a depth of 125 cm below the mineral soil surface, an the mineral soil surface. organic-carbon content (Holocene age) of 0.2 percent or Lithic Argiorthels more and no densic, lithic, or paralithic contact within that depth; or ACFB. Other Argiorthels that have a glacic layer that has its 2. An irregular decrease in organic-carbon content upper boundary within 100 cm of the mineral soil surface. (Holocene age) between a depth of 25 cm and either a depth Glacic Argiorthels of 125 cm or a densic, lithic, or paralithic contact, whichever is shallower. ACFC. Other Argiorthels that have a natric horizon. Fluventic Haplorthels Natric Argiorthels ACHF. Other Haplorthels. ACFD. Other Argiorthels. Typic Haplorthels Typic Argiorthels

Haplorthels Historthels

Key to Subgroups Key to Subgroups ACHA. Haplorthels that have a lithic contact within 50 cm of ACAA. Historthels that have a lithic contact within 50 cm of the mineral soil surface. the soil surface. Lithic Haplorthels Lithic Historthels

ACHB. Other Haplorthels that have a glacic layer that has its ACAB. Other Historthels that have a glacic layer that has its upper boundary within 100 cm of the mineral soil surface. upper boundary within 100 cm of the soil surface. Glacic Haplorthels Glacic Historthels

ACHC. Other Haplorthels that have a slope of less than 25 ACAC. Other Historthels that have a slope of less than 25 percent; and percent; and 1. In one or more horizons within 75 cm of the mineral soil 1. In one or more horizons within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or artifical aquic conditions for some time in normal years (or artifical drainage); and drainage); and 2. Either: 2. Either: 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 a (Holocene age) between a depth of 25 cm and either a Gelisols 153

depth of 125 cm or a densic, lithic or paralithic contact, the mineral soil surface, a fine-earth fraction with both a bulk which ever is shallower. density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 Fluvaquentic Historthels and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. ACAD. Other Historthels that have a slope of less than 25 Andic Mollorthels percent; and either ACDE. Other Mollorthels that have, throughout one or more 1. At a depth of 125 cm below the mineral soil surface, an horizons with a total thickness of 18 cm or more within 75 cm of organic-carbon content (Holocene age) of 0.2 percent or the mineral soil surface, one or both of the following: more and no densic, lithic, or paralithic contact within that depth; or 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, 2. An irregular decrease in organic-carbon content pumice, and pumicelike fragments; or (Holocene age) between a depth of 25 cm and either a depth of 125 cm or a densic, lithic or paralithic contact, which ever 2. A fine-earth fraction containing 30 percent or more is shallower. particles 0.02 to 2.0 mm in diameter; and Fluventic Historthels a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and ACAE. Other Historthels that have more than 40 percent, by 1 volume, organic soil materials from the soil surface to a depth of b. [(Al plus /2 Fe, percent extracted by ammonium 50 cm in 75 percent or less of the pedon. oxalate) times 60] plus the volcanic glass (percent) is Ruptic Historthels equal to 30 or more. Vitrandic Mollorthels ACAF. Other Historthels. Typic Historthels ACDF. Other Mollorthels that have: G E 1. A mollic epipedon 40 cm or more thick with a texture L Mollorthels finer than loamy fine sand; and Key to Subgroups 2. A slope of less than 25 percent. Cumulic Mollorthels ACDA. Mollorthels that have a lithic contact within 50 cm of the mineral soil surface. ACDG. Other Mollorthels that have, in one or more horizons Lithic Mollorthels within 100 cm of the mineral soil surface, distinct or prominent redox concentrations and also aquic conditions for some time ACDB. Other Mollorthels that have a glacic layer that during normal years (or artificial drainage). has its upper boundary within 100 cm of the mineral soil Aquic Mollorthels surface. Glacic Mollorthels ACDH. Other Mollorthels. Typic Mollorthels ACDC. Other Mollorthels that have one or both of the following: Psammorthels 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 Key to Subgroups some time during normal years and slickensides or wedge- ACGA. Psammorthels that have a lithic contact within 50 cm shaped aggregates in a layer 15 cm or more thick that has its of the mineral soil surface. upper boundary within 125 cm of the mineral soil surface; or Lithic Psammorthels 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm ACGB. Other Psammorthels that have a glacic layer that or a densic, lithic, or paralithic contact, whichever is has its upper boundary within 100 cm of the mineral soil shallowest. surface. Vertic Mollorthels Glacic Psammorthels

ACDD. Other Mollorthels that have, throughout one or more ACGC. Other Psammorthels that have a horizon 5 cm or more horizons with a total thickness of 18 cm or more within 75 cm of thick that has one or more of the following: 154 Keys to Soil Taxonomy

1. In 25 percent or more of each pedon, cementation by 2. A fine-earth fraction containing 30 percent or more organic matter and aluminum, with or without iron; or particles 0.02 to 2.0 mm in diameter; and

1 2. Al plus /2 Fe percentages (by ammonium oxalate) a. In the 0.02 to 2.0 mm fraction, 5 percent or more totaling 0.25 or more, and half that amount or less in an volcanic glass; and

overlying horizon; or 1 b. [(Al plus /2 Fe, percent extracted by ammonium 3. An ODOE value of 0.12 or more, and a value half as oxalate) times 60] plus the volcanic glass (percent) is high or lower in an overlying horizon. equal to 30 or more. Spodic Psammorthels Vitrandic Umbrorthels

ACGD. Other Psammorthels. ACEF. Other Umbrorthels that have: Typic Psammorthels 1. An umbric epipedon 40 cm or more thick with a texture finer than loamy fine sand; and Umbrorthels 2. A slope of less than 25 percent. Key to Subgroups Cumulic Umbrorthels ACEA. Umbrorthels that have a lithic contact within 50 cm of ACEG. Other Umbrorthels that have, in one or more horizons the mineral soil surface. within 100 cm of the mineral soil surface, distinct or prominent Lithic Umbrorthels redox concentrations and also aquic conditions for some time during normal years (or artificial drainage). ACEB. Other Umbrorthels that have a glacic layer that has its Aquic Umbrorthels upper boundary within 100 cm of the mineral soil surface. Glacic Umbrorthels ACEH. Other Umbrorthels. Typic Umbrorthels ACEC. Other Umbrorthels that have one or both of the following: Turbels 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 Great Groups for some time during normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick that ABA. Turbels that have in 30 percent or more of the pedon has its upper boundary within 125 cm of the mineral soil more than 40 percent, by volume, organic materials from the surface; or soil surface to a depth of 50 cm. Histoturbels, p. 155 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, ABB. Other Turbels that have, within 50 cm of the mineral lithic, or paralithic contact, whichever is shallowest. soil surface, redox depletions with chroma of 2 or less and also Vertic Umbrorthels aquic conditions during normal years (or artificial drainage). Aquiturbels, p. 155 ACED. Other Umbrorthels that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of ABC. Other Turbels that have anhydrous conditions. the mineral soil surface, a fine-earth fraction with both a bulk Anhyturbels, p. 155 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 ABD. Other Turbels that have a mollic epipedon. more than 1.0. Molliturbels, p. 156 Andic Umbrorthels ABE. Other Turbels that have an umbric epipedon. ACEE. Other Umbrorthels that have, throughout one or more Umbriturbels, p. 156 horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: ABF. Other Turbels that have less than 35 percent (by volume) 1. More than 35 percent (by volume) fragments coarser rock fragments and a texture of loamy fine sand or coarser in all than 2.0 mm, of which more than 66 percent is cinders, layers within the particle-size control section. pumice, and pumicelike fragments; or Psammoturbels, p. 156 Gelisols 155

ABG. Other Turbels. ABBC. Other Aquiturbels that have a sulfuric horizon or Haploturbels, p. 155 sulfidic materials with an upper boundary within 100 cm of the mineral soil surface. Anhyturbels Sulfuric Aquiturbels

Key to Subgroups ABBD. Other Aquiturbels that have either: ABCA. Anhyturbels that have a lithic contact within 50 cm of 1. Organic soil materials that are discontinous at the the mineral soil surface. surface; or Lithic Anhyturbels 2. Organic soil materials at the surface that change in thickness fourfold or more within a pedon. ABCB. Other Anhyturbels that have a glacic layer with its Ruptic-Histic Aquiturbels upper boundary within 100 cm of the mineral soil surface. Glacic Anhyturbels ABBE. Other Aquiturbels that have less than 35 percent (by volume) rock fragments and a texture of loamy fine sand or ABCC. Other Anhyturbels that have a petrogypsic horizon coarser in all layers within the particle-size control section. with its upper boundary within 100 cm of the mineral soil Psammentic Aquiturbels surface. Petrogypsic Anhyturbels ABBF. Other Aquiturbels. Typic Aquiturbels ABCD. Other Anhyturbels that have a gypsic horizon with its upper boundary within 100 cm of the mineral soil surface. Haploturbels Gypsic Anhyturbels G Key to Subgroups E ABCE. Other Anhyturbels that have a horizon 15 cm or more ABGA. Haploturbels that have a lithic contact within 50 cm of L thick that contains 12 cmol(-)/L nitrate in 1:5 soil:water extract the mineral soil surface. and in which the product of its thickness (in cm) and its nitrate Lithic Haploturbels concentration is 3,500 or more. Nitric Anhyturbels ABGB. Other Haploturbels that have a glacic layer that has an upper boundary within 100 cm of the mineral soil surface. ABCF. Other Anhyturbels that have a salic horizon Glacic Haploturbels that has its upper boundary within 100 cm of the mineral soil surface. ABGC. Other Haploturbels that have, in one or more horizons Salic Anhyturbels within 100 cm of the mineral soil surface, distinct or prominent redox concentrations and also aquic conditions for some time ABCG. Other Anhyturbels that have a calcic horizon during normal years (or artificial drainage). that has its upper boundary within 100 cm of the mineral soil Aquic Haploturbels surface. Calcic Anhyturbels ABGD. Other Haploturbels. Typic Haploturbels ABCH. Other Anhyturbels. Typic Anhyturbels Histoturbels Aquiturbels Key to Subgroups ABAA. Histoturbels that have a lithic contact within 50 cm of Key to Subgroups the soil surface. ABBA. Aquiturbels that have a lithic contact within 50 cm of Lithic Histoturbels the mineral soil surface. Lithic Aquiturbels ABAB. Other Histoturbels that have a glacic layer with its upper boundary within 100 cm of the soil surface. ABBB. Other Aquiturbels that have a glacic layer with its Glacic Histoturbels upper boundary within 100 cm of the mineral soil surface. Glacic Aquiturbels ABAC. Other Histoturbels that have more than 40 percent, by 156 Keys to Soil Taxonomy

volume, organic soil materials from the soil surface to a depth of oxalate) times 60] plus the volcanic glass (percent) is 50 cm in 75 percent or less of the pedon. equal to 30 or more. Ruptic Histoturbels Vitrandic Molliturbels

ABAD. Other Histoturbels. ABDF. Other Molliturbels that have: Typic Histoturbels 1. A mollic epipedon 40 cm or more thick with a texture finer than loamy fine sand; and Molliturbels 2. A slope of less than 25 percent. Cumulic Molliturbels Key to Subgroups ABDA. Molliturbels that have a lithic contact within 50 cm of ABDG. Other Molliturbels that have, in one or more horizons the mineral soil surface. within 100 cm of the mineral soil surface, distinct or prominent Lithic Molliturbels redox concentrations and also aquic conditions for some time during normal years (or artificial drainage). ABDB. Other Molliturbels that have a glacic layer that has its Aquic Molliturbels upper boundary within 100 cm of the mineral soil surface. Glacic Molliturbels ABDH. Other Molliturbels. Typic Molliturbels ABDC. Other Molliturbels that have one or both of the following: Psammoturbels 1. Cracks within 125 cm of the mineral soil surface that Key to Subgroups are 5 mm or more wide through a thickness of 30 cm or more for some time during normal years and slickensides or ABFA. Psammoturbels that have a lithic contact within 50 cm wedge-shaped aggregates in a layer 15 cm or more thick that of the mineral soil surface. has its upper boundary within 125 cm of the mineral soil Lithic Psammoturbels surface; or ABFB. Other Psammoturbels that have a glacic layer that has 2. A linear extensibility of 6.0 cm or more between the its upper boundary within 100 cm of the mineral soil surface. mineral soil surface and either a depth of 100 cm or a densic, Glacic Psammoturbels lithic, or paralithic contact, whichever is shallowest. Vertic Molliturbels ABFC. Other Psammoturbels that have a horizon 5 cm or more thick that has one or more of the following: ABDD. Other Molliturbels that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of 1. In 25 percent or more of each pedon, cementation the mineral soil surface, a fine-earth fraction with both a bulk by organic matter and aluminum, with or without iron; density of 1.0 g/cm3 or less, measured at 33 kPa water retention, or 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling 1 2. Al plus /2 Fe percentages (by ammonium oxalate) more than 1.0. totaling 0.25 or more, and half that amount or less in an Andic Molliturbels overlying horizon; or ABDE. Other Molliturbels that have, throughout one or more 3. An ODOE value of 0.12 or more, and a value half as horizons with a total thickness of 18 cm or more within 75 cm of high or lower in an overlying horizon. the mineral soil surface, one or both of the following: Spodic Psammoturbels 1. More than 35 percent (by volume) fragments coarser ABFD. Other Psammoturbels. than 2.0 mm, of which more than 66 percent is cinders, Typic Psammoturbels pumice, and pumicelike fragments; or 2. A fine-earth fraction containing 30 percent or more Umbriturbels 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 ABEA. Umbriturbels 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 Umbriturbels Gelisols 157

ABEB. Other Umbriturbels that have a glacic layer that has its 1. More than 35 percent (by volume) fragments coarser upper boundary within 100 cm of the mineral soil surface. than 2.0 mm, of which more than 66 percent is cinders, Glacic Umbriturbels pumice, and pumicelike fragments; or 2. A fine-earth fraction containing 30 percent or more ABEC. Other Umbriturbels that have one or both of the particles 0.02 to 2.0 mm in diameter; and following: a. In the 0.02 to 2.0 mm fraction, 5 percent or more 1. Cracks within 125 cm of the mineral soil surface that are volcanic glass; and 5 mm or more wide through a thickness of 30 cm or more for 1 some time during normal years and slickensides or wedge- b. [(Al plus /2 Fe, percent extracted by ammonium shaped aggregates in a layer 15 cm or more thick that has its oxalate) times 60] plus the volcanic glass (percent) is upper boundary within 125 cm of the mineral soil surface; or equal to 30 or more. Vitrandic Umbriturbels 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or ABEF. Other Umbriturbels that have: a densic, lithic, or paralithic contact, whichever is shallowest. 1. An umbric epipedon 40 cm or more thick with a texture Vertic Umbriturbels finer than loamy fine sand; and ABED. Other Umbriturbels that have, throughout one or more 2. A slope of less than 25 percent. horizons with a total thickness of 18 cm or more within 75 cm of Cumulic Umbriturbels 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, ABEG. Other Umbriturbels that have, in one or more horizons 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling within 100 cm of the mineral soil surface, distinct or prominent more than 1.0. redox concentrations and also aquic conditions for some time Andic Umbriturbels during normal years (or artificial drainage). G Aquic Umbriturbels E ABEE. Other Umbriturbels that have, throughout one or more L horizons with a total thickness of 18 cm or more within 75 cm of ABEH. Other Umbriturbels. the mineral soil surface, one or both of the following: Typic Umbriturbels

159

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). BBA. Fibrists that have a cryic soil temperature regime. Folists, p. 160 Cryofibrists, p. 159

BB. Other Histosols that: BBB. Other Fibrists in which fibric Sphagnum constitutes three-fourths or more of the volume to either a depth of 90 cm 1. Have more thickness of fibric soil materials than any from the soil surface or to a densic, lithic, or paralithic contact, other kind of organic soil material either: fragmental materials, or other mineral soil materials if at a depth a. In the organic parts of the subsurface tier if there is no of less than 90 cm. continuous mineral layer 40 cm or more thick that has its Sphagnofibrists, p. 160 upper boundary within the subsurface tier; or b. In the combined thickness of the organic parts BBC. Other Fibrists. of the surface and subsurface tiers if there is a continuous Haplofibrists, p. 160 mineral layer 40 cm or more thick that has its upper H boundary within the subsurface tier; and I Cryofibrists S 2. Do not have a sulfuric horizon that has its upper boundary within 50 cm of the soil surface; and Key to Subgroups 3. Do not have sulfidic materials within 100 cm of the BBAA. Cryofibrists that have a layer of water within the soil surface. control section, below the surface tier. Fibrists, p. 159 Hydric Cryofibrists

BC. Other Histosols that have more thickness of sapric soil BBAB. Other Cryofibrists that have a lithic contact within the materials than any other kind of organic soil materials either: control section. Lithic Cryofibrists 1. In the organic parts of the subsurface tier if there is no continuous mineral layer 40 cm or more thick that has its BBAC. Other Cryofibrists that have a mineral layer 30 cm or upper boundary within the subsurface tier; or more thick that has its upper boundary within the control 2. In the combined thickness of the organic parts of the section, below the surface tier. surface and subsurface tiers if there is a continuous mineral Terric Cryofibrists layer 40 cm or more thick that has its upper boundary within the subsurface tier. BBAD. Other Cryofibrists that have, within the organic Saprists, p. 162 materials, either one mineral layer 5 cm or more thick or two or more mineral layers of any thickness in the control section, BD. Other Histosols. below the surface tier. Hemists, p. 161 Fluvaquentic Cryofibrists 160 Keys to Soil Taxonomy

BBAE. Other Cryofibrists in which three-fourths or more of BBBC. Other Sphagnofibrists that have one or more limnic the fiber volume in the surface tier is derived from Sphagnum. layers with a total thickness of 5 cm or more within the control Sphagnic Cryofibrists section. Limnic Sphagnofibrists BBAF. Other Cryofibrists. Typic Cryofibrists BBBD. Other Sphagnofibrists that have a mineral layer 30 cm or more thick that has its upper boundary within the control Haplofibrists section, below the surface tier. Terric Sphagnofibrists Key to Subgroups BBBE. Other Sphagnofibrists that have, within the organic BBCA. Haplofibrists that have a layer of water within the materials, either one mineral layer 5 cm or more thick or two or control section, below the surface tier. more mineral layers of any thickness in the control section, Hydric Haplofibrists below the surface tier. Fluvaquentic Sphagnofibrists BBCB. Other Haplofibrists that have a lithic contact within the control section. BBBF. Other Sphagnofibrists that have one or more layers of Lithic Haplofibrists hemic and sapric materials with a total thickness of 25 cm or more in the control section, below the surface tier. BBCC. Other Haplofibrists that have one or more limnic layers Hemic Sphagnofibrists with a total thickness of 5 cm or more within the control section. Limnic Haplofibrists BBBG. Other Sphagnofibrists. Typic Sphagnofibrists BBCD. Other Haplofibrists that have a mineral layer 30 cm or more thick that has its upper boundary within the control section, below the surface tier. Folists Terric Haplofibrists Key to Great Groups BBCE. Other Haplofibrists that have, within the organic materials, either one mineral layer 5 cm or more thick or two or BAA. Folists that have a cryic soil temperature regime. more mineral layers of any thickness in the control section, Cryofolists, p. 160 below the surface tier. Fluvaquentic Haplofibrists BAB. Other Folists that have an aridic (or torric) soil moisture regime. BBCF. Other Haplofibrists that have one or more layers of Torrifolists, p. 161 hemic and sapric materials with a total thickness of 25 cm or more in the control section, below the surface tier. BAC. Other Folists that have an ustic or xeric soil moisture Hemic Haplofibrists regime. Ustifolists, p. 161 BBCG. Other Haplofibrists. Typic Haplofibrists BAD. Other Folists. Udifolists, p. 161 Sphagnofibrists Cryofolists Key to Subgroups Key to Subgroups BBBA. Sphagnofibrists that have a layer of water within the control section, below the surface tier. BAAA. Cryofolists that have a lithic contact within 50 cm of Hydric Sphagnofibrists the soil surface. Lithic Cryofolists BBBB. Other Sphagnofibrists that have a lithic contact within the control section. BAAB. Other Cryofolists. Lithic Sphagnofibrists Typic Cryofolists Histosols 161

Torrifolists Cryohemists

Key to Subgroups Key to Subgroups BABA. Torrifolists that have a lithic contact within 50 cm of BDDA. Cryohemists that have a layer of water within the the soil surface. control section, below the surface tier. Lithic Torrifolists Hydric Cryohemists

BABB. Other Torrifolists. BDDB. Other Cryohemists that have a lithic contact within the Typic Torrifolists control section. Lithic Cryohemists Udifolists BDDC. Other Cryohemists that have a mineral layer 30 cm or Key to Subgroups more thick that has its upper boundary within 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 BDDD. Other Cryohemists that have, within the organic materials, either one mineral layer 5 cm or more thick or two or BADB. Other Udifolists. more mineral layers of any thickness in the control section, Typic Udifolists below the surface tier. Fluvaquentic Cryohemists Ustifolists BDDE. Other Cryohemists. Key to Subgroups Typic Cryohemists BACA. Ustifolists that have a lithic contact within 50 cm of the soil surface. H Lithic Ustifolists Haplohemists I Key to Subgroups S BACB. Other Ustifolists. Typic Ustifolists BDEA. Haplohemists that have a layer of water within the control section, below the surface tier. Hemists Hydric Haplohemists Key to Great Groups BDEB. Other Haplohemists that have a lithic contact within the control section. BDA. Hemists that have a sulfuric horizon that has its upper Lithic Haplohemists boundary within 50 cm of the soil surface. Sulfohemists, p. 162 BDEC. Other Haplohemists that have one or more limnic layers with a total thickness of 5 cm or more within the control BDB. Other Hemists that have sulfidic materials within 100 section. cm of the soil surface. Limnic Haplohemists Sulfihemists, p. 162 BDED. Other Haplohemists that have a mineral layer 30 cm or BDC. Other Hemists that have a horizon 2 cm or more thick in more thick that has its upper boundary within the control which humilluvic materials constitute one-half or more of the section, below the surface tier. volume. Terric Haplohemists Luvihemists, p. 162 BDEE. Other Haplohemists that have, within the organic BDD. Other Hemists that have a cryic temperature materials, either one mineral layer 5 cm or more thick or two or regime. more mineral layers of any thickness in the control section, Cryohemists, p. 161 below the surface tier. Fluvaquentic Haplohemists BDE. Other Hemists. Haplohemists, p. 161 BDEF. Other Haplohemists that have one or more layers of 162 Keys to Soil Taxonomy

fibric materials with a total thickness of 25 cm or more in the Cryosaprists control section, below the surface tier. Fibric Haplohemists Key to Subgroups BCCA. Cryosaprists that have a lithic contact within the BDEG. Other Haplohemists that have one or more layers of control section. sapric materials with a total thickness of 25 cm or more below Lithic Cryosaprists the surface tier. Sapric Haplohemists BCCB. Other Cryosaprists that have a mineral layer 30 cm or more thick that has its upper boundary within the control BDEH. Other Haplohemists. section, below the surface tier. Typic Haplohemists Terric Cryosaprists

Luvihemists BCCC. Other Cryosaprists that have, within the organic materials, either one mineral layer 5 cm or more thick or two or Key to Subgroups more mineral layers of any thickness in the control section, BDCA. All Luvihemists (provisionally). below the surface tier. Typic Luvihemists Fluvaquentic Cryosaprists

Sulfihemists BCCD. Other Cryosaprists. Typic Cryosaprists Key to Subgroups BDBA. Sulfihemists that have a mineral layer 30 cm or more Haplosaprists thick that has its upper boundary within the control section, below the surface tier. Key to Subgroups Terric Sulfihemists BCDA. Haplosaprists that have a lithic contact within the control section. BDBB. Other Sulfihemists. Lithic Haplosaprists Typic Sulfihemists BCDB. Other Haplosaprists that have one or more limnic Sulfohemists layers with a total thickness of 5 cm or more within the control section. Key to Subgroups Limnic Haplosaprists BDAA. All Sulfohemists (provisionally). BCDC. Other Haplosaprists that have both: Typic Sulfohemists 1. Throughout a layer 30 cm or thick that has its upper Saprists boundary within the control section, an electrical conductivity of 30 dS/m or more (1:1 soil:water) for 6 Key to Great Groups months or more during normal years; and 2. A mineral layer 30 cm or more thick that has its BCA. Saprists that have a sulfuric horizon that has its upper upper boundary within the control section, below the surface boundary within 50 cm of the soil surface. tier. Sulfosaprists, p. 163 Halic Terric Haplosaprists BCB. Other Saprists that have sulfidic materials within 100 cm of the soil surface. BCDD. Other Haplosaprists that have throughout a layer 30 Sulfisaprists, p. 163 cm or more thick within the control section, an electrical conductivity of 30 dS/m or more (1:1 soil:water) for 6 months or BCC. Other Saprists that have a cryic temperature regime. more during normal years. Cryosaprists, p. 162 Halic Haplosaprists BCD. Other Saprists. Haplosaprists, p. 162 BCDE. Other Haplosaprists that have a mineral layer 30 cm or Histosols 163

more thick that has its upper boundary within the control Sulfisaprists section, below the surface tier. Terric Haplosaprists Key to Subgroups BCBA. Sulfisaprists that have a mineral layer 30 cm or more BCDF. Other Haplosaprists that have, within the organic thick that has its upper boundary within the control section, materials, either one mineral layer 5 cm or more thick or two or below the surface tier. more mineral layers of any thickness in the control section, Terric Sulfisaprists below the surface tier. Fluvaquentic Haplosaprists BCBB. Other Sulfisaprists. Typic Sulfisaprists BCDG. Other Haplosaprists that have one or more layers of fibric or hemic materials with a total thickness of 25 cm or more in the control section, below the surface tier. Sulfosaprists Hemic Haplosaprists Key to Subgroups BCDH. Other Haplosaprists. BCAA. All Sulfosaprists (provisionally). Typic Haplosaprists Typic Sulfosaprists

H I S

165

CHAPTER 11 Inceptisols

Key to Suborders KD. Other Inceptisols that have a cryic soil temperature regime. KA. Inceptisols that have one or more of the following: Cryepts, p. 171 1. In a layer above a densic, lithic, or paralithic contact or KE. Other Inceptisols that have an ustic soil moisture regime. in a layer at a depth between 40 and 50 cm from the mineral Ustepts, p. 179 soil surface, whichever is shallower, aquic conditions for some time in normal years (or artificial drainage) and one or KF. Other Inceptisols that have a xeric soil moisture regime. more of the following: Xerepts, p. 186 a. A histic epipedon; or KG. Other Inceptisols that have a udic soil moisture regime. b. A sulfuric horizon that has its upper boundary within Udepts, p. 174 50 cm of the mineral soil surface; or c. A layer directly under the epipedon, or within 50 cm of the mineral soil surface, that has, on faces of peds or in Anthrepts the matrix if peds are absent, 50 percent or more chroma of either: Key to Great Groups (1) 2 or less if there are redox concentrations; or KBA. Anthrepts that have a plaggen epipedon. (2) 1 or less; or Plagganthrepts, p. 165 I d. Within 50 cm of the mineral soil surface, enough KBB. Other Anthrepts. N active ferrous iron to give a positive reaction to Haplanthrepts, p. 165 C alpha,alpha-dipyridyl at a time when the soil is not being irrigated; or Haplanthrepts 2. An exchangeable sodium percentage (ESP) of 15 or more (or a sodium adsorption ratio [SAR] of 13 or more) in Key to Subgroups half or more of the soil volume within 50 cm of the mineral KBBA. All Haplanthrepts (provisionally). soil surface, a decrease in ESP (or SAR) values with Typic Haplanthrepts increasing depth below 50 cm, and ground water within 100 cm of the mineral soil surface for some time during the year. Aquepts, p. 165 Plagganthrepts Key to Subgroups KB. Other Inceptisols that have a plaggen or anthropic epipedon. KBAA. All Plagganthrepts (provisionally). Anthrepts, p. 165 Typic Plagganthrepts

KC. Other Inceptisols that have, in normal years, a mean Aquepts annual soil temperature of 0 oC or colder and a mean summer soil temperature that: Key to Great Groups 1. Is 8 oC or colder if there is no O horizon; or KAA. Aquepts that have a sulfuric horizon that has its upper 2. Is 5 oC or colder if there is an O horizon. boundary within 50 cm of the mineral soil surface. Gelepts, p. 173 Sulfaquepts, p. 171 166 Keys to Soil Taxonomy

KAB. Other Aquepts that have, within 100 cm of the mineral 1. A sulfuric horizon; or soil surface, one or more horizons in which plinthite or a 2. A horizon 15 cm or more thick that has all of the cemented or indurated diagnostic horizon either forms a characteristics of a sulfuric horizon, except that it has a pH continuous phase or constitutes one-half or more of the volume. between 3.5 and 4.0; or Petraquepts, p. 171 3. Sulfidic materials. KAC. Other Aquepts that have either: Sulfic Cryaquepts 1. A salic horizon; or KAFB. Other Cryaquepts that have both a histic epipedon and 2. In one or more horizons with a total thickness of 25 cm a lithic contact within 50 cm of the mineral soil surface. or more within 50 cm of the mineral soil surface, an Histic Lithic Cryaquepts exchangeable sodium percentage (ESP) of 15 or more (or a sodium adsorption ratio [SAR] of 13 or more) and a KAFC. Other Cryaquepts that have a lithic contact within 50 decrease in ESP (or SAR) values with increasing depth below cm of the mineral soil surface. 50 cm. Lithic Cryaquepts Halaquepts, p. 170 KAFD. Other Cryaquepts that have one or both of the KAD. Other Aquepts that have a fragipan with its upper following: boundary within 100 cm of the mineral soil surface. 1. Cracks within 125 cm of the mineral soil surface that Fragiaquepts, p. 169 are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or KAE. Other Aquepts that have, in normal years, a mean annual wedge-shaped aggregates in a layer 15 cm or more thick that soil temperature of 0 oC or colder and a mean summer soil has its upper boundary within 125 cm of the mineral soil temperature that: surface; or 1. Is 8 oC or colder if there is no O horizon; or 2. A linear extensibility of 6.0 cm or more between the 2. Is 5 oC or colder if there is an O horizon. mineral soil surface and either a depth of 100 cm or a densic, Gelaquepts, p. 169 lithic, or paralithic contact, whichever is shallower. Vertic Cryaquepts KAF. Other Aquepts that have a cryic soil temperature regime. Cryaquepts, p. 166 KAFE. Other Cryaquepts that have a histic epipedon. Histic Cryaquepts KAG. Other Aquepts that have, in one or more layers at least 25 cm thick (cumulative) within 100 cm of the mineral soil KAFF. Other Cryaquepts that have, throughout one or more surface, 25 percent or more (by volume) recognizable horizons with a total thickness of 18 cm or more within 75 cm of bioturbation, such as filled animal burrows, wormholes, or casts. the mineral soil surface, one or more of the following: Vermaquepts, p. 171 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 KAH. Other Aquepts that have a histic, melanic, mollic, or 1 plus /2 Fe percentages (by ammonium oxalate) totaling more umbric epipedon. than 1.0; or Humaquepts, p. 170 2. More than 35 percent (by volume) fragments coarser KAI. Other Aquepts that have episaturation. than 2.0 mm, of which more than 66 percent is cinders, Epiaquepts, p. 168 pumice, and pumicelike fragments; or 3. A fine-earth fraction containing 30 percent or more KAJ. Other Aquepts. particles 0.02 to 2.0 mm in diameter; and Endoaquepts, p. 167 a. In the 0.02 to 2.0 mm fraction, 5 percent or more Cryaquepts volcanic glass; and 1 b. [(Al plus /2 Fe, percent extracted by ammonium Key to Subgroups oxalate) times 60] plus the volcanic glass (percent) is KAFA. Cryaquepts that have, within 150 cm of the mineral equal to 30 or more. soil surface, one or more of the following: Aquandic Cryaquepts Inceptisols 167

KAFG. Other Cryaquepts that have a slope of less than 25 5 mm or more wide through a thickness of 30 cm or more for percent; and some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick that has its upper 1. At a depth of 125 cm below the mineral soil surface, an boundary within 125 cm of the mineral soil surface; or organic-carbon content (Holocene age) of 0.2 percent or more and no densic, lithic, or paralithic contact within that 2. A linear extensibility of 6.0 cm or more between the depth; or mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. 2. An irregular decrease in organic-carbon content Vertic 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, KAJD. Other Endoaquepts that have, throughout one or more or paralithic contact, whichever is shallower. horizons with a total thickness of 18 cm or more within 75 cm of Fluvaquentic Cryaquepts the mineral soil surface, one or more of the following: KAFH. Other Cryaquepts that have both: 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. Chroma of 3 or more in 40 percent or more of the matrix 1 plus /2 Fe percentages (by ammonium oxalate) totaling more of one or more horizons at a depth between 15 and 50 cm than 1.0; or from the mineral soil surface; and 2. More than 35 percent (by volume) fragments coarser 2. A mollic or umbric epipedon. than 2.0 mm, of which more than 66 percent is cinders, Aeric Humic Cryaquepts 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. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Aeric Cryaquepts volcanic glass; and

1 KAFJ. Other Cryaquepts that have a mollic or umbric 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 I KAFK. Other Cryaquepts. N Typic Cryaquepts KAJE. Other Endoaquepts that have, in one or more horizons C 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 matrix; and KAJA. Endoaquepts that have, within 150 cm of the mineral soil surface, one or more of the following: a. If peds are present, either chroma of 2 or more on 50 percent or more of ped exteriors or no redox depletions 1. A sulfuric horizon; or with chroma of 2 or less in ped interiors; or 2. A horizon 15 cm or more thick that has all of the b. If peds are absent, a chroma of 2 or more in 50 characteristics of a sulfuric horizon, except that it has a pH percent or more of the matrix; or between 3.5 and 4.0; 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; KAJB. Other Endoaquepts that have a lithic contact within 50 or cm of the mineral soil surface. b. Chroma of 2 or more if there are no redox Lithic Endoaquepts concentrations; and KAJC. Other Endoaquepts that have one or both of the 3. A slope of less than 25 percent; and 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 168 Keys to Soil Taxonomy

or more and no densic, lithic, or paralithic contact within of 5 or less (crushed and smoothed) in the Ap horizon or in that depth; or the upper 15 cm after mixing; and

b. An irregular decrease in organic-carbon content 2. A base saturation (by NH4OAc) of less than 50 percent (Holocene age) between a depth of 25 cm and either a in some part within 100 cm of the mineral soil surface. depth of 125 cm below the mineral soil surface or a Humic Endoaquepts densic, lithic, or paralithic contact, whichever is shallower. Fluventic Endoaquepts KAJJ. Other Endoaquepts that have a color value, moist, of 3 or less and a color value, dry, of 5 or less (crushed and KAJF. Other Endoaquepts that have a slope of less than 25 smoothed) either in the Ap horizon or in the upper 15 cm after percent; and mixing. Mollic Endoaquepts 1. At a depth of 125 cm below the mineral soil surface, an organic-carbon content (Holocene age) of 0.2 percent or KAJK. Other Endoaquepts. more and no densic, lithic, or paralithic contact within that Typic Endoaquepts depth; or 2. An irregular decrease in organic-carbon content Epiaquepts (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a densic, lithic, Key to Subgroups or paralithic contact, whichever is shallower. KAIA. Epiaquepts that have one or both of the following: Fluvaquentic Endoaquepts 1. Cracks within 125 cm of the mineral soil surface that are KAJG. Other Endoaquepts that have fragic soil properties: 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge-shaped 1. In 30 percent or more of the volume of a layer 15 cm or aggregates in a layer 15 cm or more thick that has its upper more thick that has its upper boundary within 100 cm of the boundary within 125 cm of the mineral soil surface; or mineral soil surface; or 2. A linear extensibility of 6.0 cm or more between the 2. In 60 percent or more of the volume of a layer 15 cm or mineral soil surface and either a depth of 100 cm or a densic, more thick. lithic, or paralithic contact, whichever is shallower. Fragic Endoaquepts Vertic Epiaquepts

KAJH. Other Endoaquepts that have, in one or more horizons KAIB. Other Epiaquepts that have, throughout one or more between the A or Ap horizon and a depth of 75 cm below the horizons with a total thickness of 18 cm or more within 75 cm of mineral soil surface, one of the following colors: the mineral soil surface, one or more of the following: 1. Hue of 7.5YR or redder in 50 percent or more of the 1. A fine-earth fraction with both a bulk density of 1.0 matrix; and g/cm3 or less, measured at 33 kPa water retention, and Al 1 plus /2 Fe percentages (by ammonium oxalate) totaling more a. If peds are present, either chroma of 2 or more on 50 than 1.0; or percent or more of ped exteriors or no redox depletions with chroma of 2 or less in ped interiors; or 2. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, b. If peds are absent, chroma of 2 or more in 50 percent pumice, and pumicelike fragments; or or more of the matrix; or 3. A fine-earth fraction containing 30 percent or more 2. In 50 percent or more of the matrix, hue of 10YR or particles 0.02 to 2.0 mm in diameter; and yellower and either: a. In the 0.02 to 2.0 mm fraction, 5 percent or more a. Both a color value, moist, and chroma of 3 or more; volcanic glass; and or 1 b. [(Al plus /2 Fe, percent extracted by ammonium b. Chroma of 2 or more if there are no redox oxalate) times 60] plus the volcanic glass (percent) is concentrations. equal to 30 or more. Aeric Endoaquepts Aquandic Epiaquepts KAJI. Other Endoaquepts that have: 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 Inceptisols 169

1. At a depth of 125 cm below the mineral soil surface, an KAIH. Other Epiaquepts. organic-carbon content (Holocene age) of 0.2 percent or Typic Epiaquepts more and no densic, lithic, or paralithic contact within that depth; or Fragiaquepts 2. An irregular decrease in organic-carbon content Key to Subgroups (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a densic, lithic, KADA. Fragiaquepts that have, in 50 percent or more of the or paralithic contact, whichever is shallower. matrix of one or more horizons either between the plow layer and Fluvaquentic Epiaquepts a depth of 75 cm below the mineral soil surface or, if there is no plow layer, between depths of 15 and 75 cm, chroma of either: KAID. Other Epiaquepts that have fragic soil properties: 1. 3 or more; or 1. In 30 percent or more of the volume of a layer 15 cm or 2. 2 or more if there are no redox concentrations. more thick that has its upper boundary within 100 cm of the Aeric Fragiaquepts mineral soil surface; or 2. In 60 percent or more of the volume of a layer 15 cm or KADB. Other Fragiaquepts that have a histic, mollic, or more thick. umbric epipedon. Fragic Epiaquepts Humic Fragiaquepts

KAIE. Other Epiaquepts that have, in one or more horizons KADC. Other Fragiaquepts. between the A or Ap horizon and a depth of 75 cm below the Typic Fragiaquepts mineral soil surface, one of the following colors: 1. Hue of 7.5YR or redder in 50 percent or more of the Gelaquepts matrix; and Key to Subgroups a. If peds are present, either chroma of 2 or more on 50 KAEA. Gelaquepts that have a lithic contact within 50 cm of percent or more of ped exteriors or no redox depletions the mineral soil surface. with chroma of 2 or less in ped interiors; or Lithic Gelaquepts b. If peds are absent, chroma of 2 or more in 50 percent I or more of the matrix; or KAEB. Other Gelaquepts that have a histic epipedon. N 2. In 50 percent or more of the matrix, hue of 10YR or Histic Gelaquepts C yellower and either: a. Both a color value, moist, and chroma of 3 or more; KAEC. Other Gelaquepts that have, throughout one 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: b. Chroma of 2 or more if there are no redox concentrations. 1. A fine-earth fraction with both a bulk density of 1.0 Aeric Epiaquepts g/cm3 or less, measured at 33 kPa water retention, and Al plus 1 /2 Fe percentages (by ammonium oxalate) totaling more than KAIF. Other Epiaquepts that have both: 1.0; or 1. A color value, moist, of 3 or less and a color value, dry, 2. More than 35 percent (by volume) fragments coarser of 5 or less (crushed and smoothed) in the Ap horizon or in than 2.0 mm, of which more than 66 percent is cinders, the upper 15 cm after mixing; and pumice, and pumicelike fragments; or

2. A base saturation (by NH4OAc) of less than 3. A fine-earth fraction containing 30 percent or more 50 percent in some part within 100 cm of the mineral particles 0.02 to 2.0 mm in diameter; and soil surface. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Humic Epiaquepts volcanic glass; and

1 KAIG. Other Epiaquepts that have a color value, moist, of 3 or b. [(Al plus /2 Fe, percent extracted by ammonium less and a color value, dry, of 5 or less (crushed and smoothed) oxalate) times 60] plus the volcanic glass (percent) is either in the Ap horizon or in the upper 15 cm after mixing. equal to 30 or more. Mollic Epiaquepts Aquandic Gelaquepts 170 Keys to Soil Taxonomy

1 KAED. Other Gelaquepts that have a slope of less than 25 b. [(Al plus /2 Fe, percent extracted by ammonium percent; and oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. 1. At a depth of 125 cm below the mineral soil surface, an Aquandic Halaquepts organic-carbon content (Holocene age) of 0.2 percent or more and no densic, lithic, or paralithic contact within that KACC. Other Halaquepts that have a horizon 15 cm or more depth; or thick that has 20 percent or more (by volume) cemented or 2. An irregular decrease in organic-carbon content indurated soil material and has its upper boundary within 100 (Holocene age) between a depth of 25 cm and either a depth cm either of the mineral soil surface or of the top of an organic of 125 cm below the mineral soil surface or a densic, lithic, layer with andic soil properties, whichever is shallower. or paralithic contact, whichever is shallower. Duric Halaquepts Fluvaquentic Gelaquepts KACD. Other Halaquepts that have chroma of 3 or more in 40 percent or more of the matrix of one or more horizons at a depth KAEE. Other Gelaquepts that have a mollic or umbric between 15 and 75 cm from the mineral soil surface. epipedon. Aeric Halaquepts Humic Gelaquepts KACE. Other Halaquepts. KAEF. Other Gelaquepts. Typic Halaquepts Typic Gelaquepts Humaquepts

Halaquepts Key to Subgroups Key to Subgroups KAHA. Humaquepts that have an n value of either: KACA. Halaquepts that have one or both of the following: 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 1. Cracks within 125 cm of the mineral soil surface that are 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-shaped 2. More than 0.9 in one or more layers at a depth aggregates in a layer 15 cm or more thick that has its upper between 50 and 100 cm. boundary within 125 cm of the mineral soil surface; or Hydraquentic Humaquepts 2. A linear extensibility of 6.0 cm or more between the KAHB. Other Humaquepts that have a histic epipedon. mineral soil surface and either a depth of 100 cm or a densic, Histic Humaquepts lithic, or paralithic contact, whichever is shallower. Vertic Halaquepts KAHC. Other Humaquepts that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of KACB. Other Halaquepts that have, throughout one or more the mineral soil surface, one or more 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. 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 fine-earth fraction with both a bulk density of 1.0 1 plus /2 Fe percentages (by ammonium oxalate) totaling more g/cm3 or less, measured at 33 kPa water retention, and Al 1 than 1.0; or plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0; or 2. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, 2. More than 35 percent (by volume) fragments coarser pumice, and pumicelike fragments; or than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or 3. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and 3. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and a. In the 0.02 to 2.0 mm fraction, 5 percent or more 1 volcanic glass; and b. [(Al plus /2 Fe, percent extracted by ammonium Inceptisols 171

oxalate) times 60] plus the volcanic glass (percent) is KABC. Other Petraquepts that have one or more horizons equal to 30 or more. within 125 cm of the mineral soil surface in which plinthite Aquandic Humaquepts either forms a continuous phase or constitutes one-half or more of the volume. KAHD. Other Humaquepts that have a slope of less than 25 Plinthic Petraquepts percent; and KABD. Other Petraquepts. 1. An umbric or mollic epipedon 60 cm or more thick; and Typic Petraquepts either 2. At a depth of 125 cm below the mineral soil surface, an organic-carbon content (Holocene age) of 0.2 percent or Sulfaquepts more and no densic, lithic, or paralithic contact within that Key to Subgroups depth; or KAAA. Sulfaquepts that have a salic horizon within 75 cm of 3. An irregular decrease in organic-carbon content the mineral soil surface. (Holocene age) between a depth of 25 cm and either a depth Salidic Sulfaquepts of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is shallower. KAAB. Other Sulfaquepts that have an n value of either: Cumulic Humaquepts 1. More than 0.7 (and less than 8 percent clay) in one or KAHE. Other Humaquepts that have a slope of less than 25 more layers at a depth between 20 and 50 cm from the percent; and mineral soil surface; or 1. At a depth of 125 cm below the mineral soil surface, an 2. More than 0.9 in one or more layers at a depth organic-carbon content (Holocene age) of 0.2 percent or between 50 and 100 cm from the mineral soil surface. more and no densic, lithic, or paralithic contact within that Hydraquentic Sulfaquepts depth; or KAAC. Other Sulfaquepts. 2. An irregular decrease in organic-carbon content Typic Sulfaquepts (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is shallower. Vermaquepts I Fluvaquentic Humaquepts N Key to Subgroups C KAHF. Other Humaquepts that have hue of 5Y or redder and KAGA. Vermaquepts that have an exchangeable sodium chroma of 3 or more in more than 40 percent of the matrix of percentage of 7 or more (or a sodium adsorption ratio [SAR] of one or more subhorizons at a depth between 15 and 75 cm from 6 or more) in one or more subhorizons within 100 cm of the the mineral soil surface. mineral soil surface. Aeric Humaquepts Sodic Vermaquepts

KAHG. Other Humaquepts. KAGB. Other Vermaquepts. Typic Humaquepts Typic Vermaquepts

Petraquepts Cryepts

Key to Subgroups Key to Great Groups KABA. Petraquepts that have both: KDA. Cryepts that have one or both of the following: 1. A histic epipedon; and 1. Free carbonates within the soils; or

2. A placic horizon. 2. A base saturation (by NH4OAc) of 60 percent or more in Histic Placic Petraquepts one or more horizons at a depth between 25 and 75 cm from the mineral soil surface or directly above a root-limiting layer KABB. Other Petraquepts that have a placic horizon. if at a shallower depth. Placic Petraquepts Eutrocryepts, p. 172 172 Keys to Soil Taxonomy

KDB. Other Cryepts. KDBG. Other Dystrocryepts that have lamellae (two or more) Dystrocryepts, p. 172 within 200 cm of the mineral soil surface. Lamellic Dystrocryepts Dystrocryepts KDBH. Other Dystrocryepts that have a horizon 5 cm or more Key to Subgroups thick that has one or more of the following: KDBA. Dystrocryepts that have both: 1. In 25 percent or more of each pedon, cementation by organic matter and aluminum, with or without iron; or 1. An umbric or mollic epipedon; and 1 2. Al plus /2 Fe percentages (by ammonium oxalate) 2. A lithic contact within 50 cm of the mineral soil surface. totaling 0.25 or more, and half that amount or less in an Humic Lithic Dystrocryepts overlying horizon; or KDBB. Other Dystrocryepts that have a lithic contact within 3. An ODOE value of 0.12 or more, and a value half as 50 cm of the mineral soil surface. high or lower in an overlying horizon. Lithic Dystrocryepts Spodic Dystrocryepts

KDBC. Other Dystrocryepts that have, throughout one or KDBI. Other Dystrocryepts that have a xeric moisture regime. more horizons with a total thickness of 18 cm or more within 75 Xeric Dystrocryepts cm 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 KDBJ. Other Dystrocryepts that are dry in some part of the 1 retention, and Al plus /2 Fe percentages (by ammonium oxalate) moisture control section for 45 or more days (cumulative) in totaling more than 1.0. normal years. Andic Dystrocryepts Ustic Dystrocryepts

KDBD. Other Dystrocryepts that have, throughout one or KDBK. Other Dystrocryepts that have an umbric or mollic more horizons with a total thickness of 18 cm or more within 75 epipedon. cm of the mineral soil surface, one or both of the following: Humic Dystrocryepts 1. More than 35 percent (by volume) fragments coarser KDBL. Other Dystrocryepts. than 2.0 mm, of which more than 66 percent is cinders, Typic Dystrocryepts pumice, and pumicelike fragments; or 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and Eutrocryepts a. In the 0.02 to 2.0 mm fraction, 5 percent or more Key to Subgroups volcanic glass; and KDAA. Eutrocryepts that have both: 1 b. [(Al plus /2 Fe, percent extracted by ammonium 1. An umbric or mollic epipedon; and oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. 2. A lithic contact within 50 cm of the mineral soil surface. Vitrandic Dystrocryepts Humic Lithic Eutrocryepts

KDBE. Other Dystrocryepts that have, in one or more KDAB. Other Eutrocryepts that have a lithic contact within 50 horizons within 75 cm of the mineral soil surface, redox cm of the mineral soil surface. depletions with chroma of 2 or less and also aquic conditions for Lithic Eutrocryepts some time in normal years (or artificial drainage). Aquic Dystrocryepts KDAC. Other Eutrocryepts that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of KDBF. Other Dystrocryepts that in normal years are saturated the mineral soil surface, a fine-earth fraction with both a bulk with water in one or more layers within 100 cm of the mineral density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 soil surface for either or both: and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. 1. 20 or more consecutive days; or Andic Eutrocryepts 2. 30 or more cumulative days. Oxyaquic Dystrocryepts KDAD. Other Eutrocryepts that have, throughout one or more Inceptisols 173

horizons with a total thickness of 18 cm or more within 75 cm of 1. Free carbonates within the soils; or the mineral soil surface, one or both of the following: 2. A base saturation (by NH4OAc) of 60 percent or more in 1. More than 35 percent (by volume) fragments coarser one or more horizons at a depth between 25 and 75 cm from than 2.0 mm, of which more than 66 percent is cinders, the mineral soil surface or directly above a root-limiting layer pumice, and pumicelike fragments; or if at a shallower depth. Eutrogelepts, p. 173 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and KCB. Other Gelepts. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Dystrogelepts, p. 173 volcanic glass; and

1 b. [(Al plus /2 Fe, percent extracted by ammonium Dystrogelepts oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. Key to Subgroups Vitrandic Eutrocryepts KCBA. Dystrogelepts that have a lithic contact within 50 cm of the mineral soil surface. KDAE. Other Eutrocryepts that have, in one or more horizons Lithic Dystrogelepts within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in KCBB. Other Dystrogelepts that have, throughout one or more normal years (or artificial drainage). horizons with a total thickness of 18 cm or more within 75 cm of Aquic Eutrocryepts 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, KDAF. Other Eutrocryepts that in normal years are saturated 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling with water in one or more layers within 100 cm of the mineral more than 1.0. soil surface for either or both: Andic Dystrogelepts 1. 20 or more consecutive days; or KCBC. Other Dystrogelepts that have, in one or more 2. 30 or more cumulative days. horizons within 75 cm of the mineral soil surface, redox Oxyaquic Eutrocryepts depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). I KDAG. Other Eutrocryepts that have lamellae (two or more) Aquic Dystrogelepts N within 200 cm of the mineral soil surface. C Lamellic Eutrocryepts KCBD. Other Dystrogelepts that have a mollic or umbric epipedon. KDAH. Other Eutrocryepts that have a xeric moisture regime. Humic Dystrogelepts Xeric Eutrocryepts KCBE. Other Dystrogelepts. KDAI. Other Eutrocryepts that are dry in some part of the Typic Dystrogelepts moisture control section for 45 or more days (cumulative) in normal years. Ustic Eutrocryepts Eutrogelepts Key to Subgroups KDAJ. Other Eutrocryepts that have an umbric or mollic epipedon. KCAA. Eutrogelepts that have a lithic contact within 50 cm of Humic Eutrocryepts the mineral soil surface. Lithic Eutrogelepts KDAK. Other Eutrocryepts. Typic Eutrocryepts KCAB. Other Eutrogelepts that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of Gelepts 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 Great Groups and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. KCA. Gelepts that have one or both of the following: Andic Eutrogelepts 174 Keys to Soil Taxonomy

KCAC. Other Eutrogelepts that have, in one or more horizons of 18 cm or more, above the duripan and within 75 cm of the within 75 cm of the mineral soil surface, redox depletions with mineral soil surface, one or more of the following: chroma of 2 or less 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 Aquic Eutrogelepts 1 plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0; or KCAD. Other Eutrogelepts that have a mollic or umbric epipedon. b. More than 35 percent (by volume) fragments coarser Humic Eutrogelepts than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or KCAE. Other Eutrogelepts. c. A fine-earth fraction containing 30 percent or more Typic Eutrogelepts particles 0.02 to 2.0 mm in diameter; and Udepts (1) In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and

Key to Great Groups 1 (2) [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is KGA. Udepts that have a sulfuric horizon within 50 cm of the equal to 30 or more. mineral soil surface. Aquandic Durudepts Sulfudepts, p. 179 KGBB. Other Durudepts that have, throughout one or more KGB. Other Udepts that have a duripan that has its upper horizons with a total thickness of 18 cm or more, above the boundary within 100 cm of the mineral soil surface. duripan and within 75 cm of the mineral soil surface, a fine- Durudepts, p. 174 earth fraction with both a bulk density of 1.0 g/cm3 or less, 1 measured at 33 kPa water retention, and Al plus /2 Fe KGC. Other Udepts that have a fragipan with its upper percentages (by ammonium oxalate) totaling more than 1.0. boundary within 100 cm of the mineral soil surface. Andic Durudepts Fragiudepts, p. 179 KGBC. Other Durudepts that have, throughout one or more KGD. Other Udepts that have one or both of the following: horizons with a total thickness of 18 cm or more, above the 1. Free carbonates within the soils; or duripan and within 75 cm of the mineral soil surface, one or both of the following: 2. A base saturation (by NH4OAc) of 60 percent or more in one or more horizons at a depth between 25 and 75 cm from 1. More than 35 percent (by volume) fragments coarser the mineral soil surface or directly above a root-limiting layer than 2.0 mm, of which more than 66 percent is cinders, if at a shallower depth. pumice, and pumicelike fragments; or Eutrudepts, p. 177 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and KGE. Other Udepts. Dystrudepts, p. 175 a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and

Durudepts 1 b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is Key to Subgroups equal to 30 or more. KGBA. Durudepts that have both: Vitrandic Durudepts 1. In one or more horizons above the duripan and within 60 KGBD. Other Durudepts that have, in one or more horizons cm of the mineral soil surface, distinct or prominent redox above the duripan and within 30 cm of the mineral soil surface, concentrations and also aquic conditions for some time in distinct or prominent redox concentrations and also aquic normal years (or artificial drainage); and conditions for some time in normal years (or artificial drainage). 2. Throughout one or more horizons with a total thickness Aquic Durudepts Inceptisols 175

1 KGBE. Other Durudepts. (2) [(Al plus /2 Fe, percent extracted by ammonium Typic Durudepts oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. Aquandic Dystrudepts Dystrudepts KGEE. Other Dystrudepts that have both: Key to Subgroups 1. In one or more horizons with a total thickness of 18 cm KGEA. Dystrudepts that have both: or more within 75 cm of the mineral soil surface, a fine-earth 1. A lithic contact within 50 cm of the mineral soil surface; with both a bulk density of 1.0 g/cm3 or less, measured at 1 and 33 kPa water retention, and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0; and 2. An umbric or mollic epipedon. Humic Lithic Dystrudepts 2. Saturation with water within 100 cm of the mineral soil surface in normal years for either or both: KGEB. Other Dystrudepts that have a lithic contact within 50 a. 20 or more consecutive days; or cm of the mineral soil surface. Lithic Dystrudepts b. 30 or more cumulative days. Andic Oxyaquic Dystrudepts KGEC. Other Dystrudepts that have one or both of the following: KGEF. Other Dystrudepts that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of 1. Cracks within 125 cm of the mineral soil surface that are 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 for density of 1.0 g/cm3 or less, measured at 33 kPa water retention, some time in normal years and slickensides or wedge-shaped 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling aggregates 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 Dystrudepts 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm KGEG. Other Dystrudepts that have, throughout one or more or a densic, lithic, or paralithic contact, whichever is horizons with a total thickness of 18 cm or more within 75 cm of shallower. the mineral soil surface, one or both of the following: I Vertic Dystrudepts 1. More than 35 percent (by volume) fragments coarser N than 2.0 mm, of which more than 66 percent is cinders, C KGED. Other Dystrudepts that have both: pumice, and pumicelike fragments; or 1. In one or more horizons within 60 cm of the mineral soil 2. A fine-earth fraction containing 30 percent or more surface, redox depletions with chroma of 2 or less and also particles 0.02 to 2.0 mm in diameter; and aquic conditions for some time in normal years (or artificial drainage); and a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and 2. Throughout one or more horizons with a total thickness 1 of 18 cm or more within 75 cm of the mineral soil surface, b. [(Al plus /2 Fe, percent extracted by ammonium one or more of the following: oxalate) times 60] plus the volcanic glass (percent) is 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 plus /2 Fe percentages (by ammonium oxalate) totaling KGEH. Other Dystrudepts that have both: more than 1.0; or 1. Fragic soil properties: b. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, a. In 30 percent or more of the volume of a layer 15 cm pumice, and pumicelike fragments; or or more thick that has its upper boundary within 100 cm of the mineral soil surface; or c. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and b. In 60 percent or more of the volume of a layer 15 cm or more thick; and (1) In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and 2. In one or more horizons within 60 cm of the mineral soil 176 Keys to Soil Taxonomy

surface, redox depletions with chroma of 2 or less and also KGEN. Other Dystrudepts that have lamellae (two or more) aquic conditions in normal years (or artificial drainage). within 200 cm of the mineral soil surface. Fragiaquic Dystrudepts Lamellic Dystrudepts

KGEI. Other Dystrudepts that have a slope of less than 25 KGEO. Other Dystrudepts that have both: percent; and 1. An umbric or mollic epipedon; and 1. In one or more horizons within 60 cm of the mineral soil 2. A sandy particle-size class throughout the particle-size surface, redox depletions with chroma of 2 or less and also control section. aquic conditions for some time in normal years (or artificial Humic Psammentic Dystrudepts drainage); and 2. Either: KGEP. Other Dystrudepts that have a slope of less than 25 percent; and a. At a depth of 125 cm below the mineral soil surface, an organic-carbon content (Holocene age) of 0.2 percent 1. An umbric or mollic epipedon; and or more and no densic, lithic, or paralithic contact within 2. Either: 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 a or more and no densic, lithic, or paralithic contact within depth of 125 cm below the mineral soil surface or a that depth; or densic, lithic, or paralithic contact, whichever is shallower. Fluvaquentic Dystrudepts b. An irregular decrease in organic-carbon content (Holocene age) between a depth of 25 cm and either a KGEJ. Other Dystrudepts that have both: depth of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is shallower. 1. An umbric or mollic epipedon; and Fluventic Humic Dystrudepts 2. In one or more horizons within 60 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also KGEQ. Other Dystrudepts that have a slope of less than 25 aquic conditions for some time in normal years (or artificial percent; and either drainage). 1. At a depth of 125 cm below the mineral soil surface, an Aquic Humic Dystrudepts organic-carbon content (Holocene age) of 0.2 percent or more and no densic, lithic, or paralithic contact within that KGEK. Other Dystrudepts that have, in one or more horizons depth; or within 60 cm of the mineral soil surface, redox depletions with 2. 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 a depth normal years (or artificial drainage). of 125 cm below the mineral soil surface or a densic, lithic, Aquic Dystrudepts or paralithic contact, whichever is shallower. Fluventic Dystrudepts KGEL. Other Dystrudepts that in normal years are saturated with water in one or more layers within 100 cm of the mineral KGER. Other Dystrudepts that have a horizon 5 cm or more soil surface for either or both: thick that has one 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

Oxyaquic Dystrudepts 1 2. Al plus /2 Fe percentages (by ammonium oxalate) totaling 0.25 or more, and half that amount or less in an KGEM. Other Dystrudepts that have fragic soil properties: overlying horizon; or 1. In 30 percent or more of the volume of a layer 15 cm or 3. An ODOE value of 0.12 or more, and a value half as more thick that has its upper boundary within 100 cm of the high or lower in an overlying horizon. mineral soil surface; or Spodic Dystrudepts 2. In 60 percent or more of the volume of a layer 15 cm or more thick. KGES. Other Dystrudepts that have in 50 percent or more of Fragic Dystrudepts the soil volume between a depth of 25 cm from the mineral soil Inceptisols 177

surface and either a depth of 100 cm or a densic, lithic, or KGDC. Other Eutrudepts that have both: paralithic contact if shallower: 1. One or both of the following: 1. A CEC (by 1N NH OAc pH 7) of less than 24 cmol(+) 4 a. Cracks within 125 cm of the mineral soil surface that per kg clay; or are 5 mm or more wide through a thickness of 30 cm or 2. Both a ratio of measured clay in the fine-earth fraction to more for some time in normal years and slickensides or percent water retained at 1500 kPa tension of 0.6 or more wedge-shaped aggregates in a layer 15 cm or more thick

and the following: the CEC (by 1N NH4OAc pH 7) divided that has its upper boundary within 125 cm of the mineral by the product of three times [percent water retained at 1500 soil surface; or kPa tension minus percent organic carbon (but no more than b. A linear extensibility of 6.0 cm or more between the 1.00)] is less than 24. mineral soil surface and either a depth of 100 cm or a Oxic Dystrudepts densic, lithic, or paralithic contact, whichever is shallower; and KGET. Other Dystrudepts that have an umbric or mollic epipedon that is 50 cm or more thick. 2. In one or more horizons within 60 cm of the mineral soil Humic Pachic Dystrudepts surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial KGEU. Other Dystrudepts that have an umbric or mollic drainage). epipedon. Aquertic Eutrudepts Humic Dystrudepts KGDD. Other Eutrudepts that have one or both of the KGEV. Other Dystrudepts that have both: following: 1. In each pedon a cambic horizon that includes 10 to 50 1. Cracks within 125 cm of the mineral soil surface that are percent (by volume) illuvial parts that otherwise meet the 5 mm or more wide through a thickness of 30 cm or more for requirements for an argillic, kandic, or natric horizon; and some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick that has its upper 2. A base saturation (by sum of cations) of 35 percent or boundary within 125 cm of the mineral soil surface; or more either at a depth of 125 cm from the top of the cambic horizon or directly above a densic, lithic, or paralithic contact 2. A linear extensibility of 6.0 cm or more between the if shallower. mineral soil surface and either a depth of 100 cm or a densic, I Ruptic-Alfic Dystrudepts lithic, or paralithic contact, whichever is shallower. N Vertic Eutrudepts C KGEW. Other Dystrudepts that have in each pedon a cambic horizon that includes 10 to 50 percent (by volume) illuvial parts KGDE. Other Eutrudepts that have, throughout one or more that otherwise meet the requirements for an argillic, kandic, or horizons with a total thickness of 18 cm or more within 75 cm of natric horizon. the mineral soil surface, a fine-earth fraction with both a bulk Ruptic-Ultic 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 KGEX. Other Dystrudepts. more than 1.0. Typic Dystrudepts Andic Eutrudepts

Eutrudepts KGDF. Other Eutrudepts that have, throughout one or more horizons with a total thickness of 18 cm or more Key to Subgroups within 75 cm of the mineral soil surface, one or both of the following: KGDA. Eutrudepts that have both: 1. More than 35 percent (by volume) fragments coarser 1. An umbric or mollic epipedon; and than 2.0 mm, of which more than 66 percent is cinders, 2. A lithic contact within 50 cm of the mineral soil surface. pumice, and pumicelike fragments; or Humic Lithic Eutrudepts 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and KGDB. Other Eutrudepts that have a lithic contact within 50 cm of the mineral soil surface. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Lithic Eutrudepts volcanic glass; and 178 Keys to Soil Taxonomy

1 b. [(Al plus /2 Fe, percent extracted by ammonium chroma of 2 or less and also aquic conditions for some time in oxalate) times 60] plus the volcanic glass (percent) is normal years (or artificial drainage). equal to 30 or more. Aquic Eutrudepts Vitrandic Eutrudepts KGDL. Other Eutrudepts that in normal years are saturated KGDG. Other Eutrudepts that have anthraquic conditions. with water in one or more layers within 100 cm of the mineral Anthraquic Eutrudepts soil surface for either or both: 1. 20 or more consecutive days; or KGDH. Other Eutrudepts that have both: 2. 30 or more cumulative days. 1. Fragic soil properties: Oxyaquic Eutrudepts 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 KGDM. Other Eutrudepts that have fragic soil properties: of the mineral soil surface; or 1. In 30 percent or more of the volume of a layer 15 cm or b. In 60 percent or more of the volume of a layer 15 cm more thick that has its upper boundary within 100 cm of the or more thick; and mineral soil surface; or 2. In one or more horizons within 60 cm of the mineral soil 2. In 60 percent or more of the volume of a layer 15 cm or surface, redox depletions with chroma of 2 or less and also more thick. aquic conditions in normal years (or artificial drainage). Fragic Eutrudepts Fragiaquic Eutrudepts KGDN. Other Eutrudepts that have lamellae (two or more) within 200 cm of the mineral soil surface. KGDI. Other Eutrudepts that have a slope of less than 25 Lamellic Eutrudepts percent; and 1. In one or more horizons within 60 cm of the mineral soil KGDO. Other Eutrudepts that have a slope of less than 25 surface, redox depletions with chroma of 2 or less and also percent; and aquic conditions for some time in normal years (or artificial 1. Do not have free carbonates throughout any drainage); and horizon within 100 cm of the mineral soil surface; and either 2. Either: 2. Have, at a depth of 125 cm below the mineral soil a. At a depth of 125 cm below the mineral soil surface, surface, an organic-carbon content (Holocene age) of 0.2 an organic-carbon content (Holocene age) of 0.2 percent percent or more and no densic, lithic, or paralithic contact or more and no densic, lithic, or paralithic contact within within that depth; or that depth; or 3. Have 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 a depth (Holocene age) between a depth of 25 cm and either of 125 cm below the mineral soil surface or a densic, lithic, a depth of 125 cm below the mineral soil surface or or paralithic contact, whichever is shallower. a densic, lithic, or paralithic contact, whichever is Dystric Fluventic Eutrudepts shallower. Fluvaquentic Eutrudepts KGDP. Other Eutrudepts that have a slope of less than 25 percent; and either KGDJ. Other Eutrudepts that: 1. At a depth of 125 cm below the mineral soil surface, an 1. Have, in one or more horizons within 60 cm of the organic-carbon content (Holocene age) of 0.2 percent or mineral soil surface, redox depletions with chroma of 2 or more and no densic, lithic, or paralithic contact within that less and also aquic conditions for some time in normal years depth; or (or artificial drainage); and 2. An irregular decrease in organic-carbon content 2. Do not have free carbonates throughout any horizon (Holocene Age) between a depth of 25 cm and either a depth within 100 cm of the mineral soil surface. of 125 cm below the mineral soil surface or a densic, lithic, Aquic Dystric Eutrudepts or paralithic contact, whichever is shallower. Fluventic Eutrudepts KGDK. Other Eutrudepts that have, in one or more horizons within 60 cm of the mineral soil surface, redox depletions with KGDQ. Other Eutrudepts that have a sandy or sandy-skeletal Inceptisols 179

1 particle-size class in all horizons within 50 cm of the mineral b. [(Al plus /2 Fe, percent extracted by ammonium soil surface. oxalate) times 60] plus the volcanic glass (percent) is Arenic Eutrudepts equal to 30 or more. Vitrandic Fragiudepts KGDR. Other Eutrudepts that do not have free carbonates throughout any horizon within 100 cm of the mineral soil KGCC. Other Fragiudepts that have, in one or more horizons surface. within 30 cm of the mineral soil surface, distinct or prominent Dystric Eutrudepts redox concentrations and also aquic conditions for some time in normal years (or artificial drainage). KGDS. Other Eutrudepts that have 40 percent or more free Aquic Fragiudepts carbonates, including coarse fragments as much as 75 mm in diameter, in all horizons between the top of the cambic horizon KGCD. Other Fragiudepts that have an umbric or mollic and either a depth of 100 cm from the mineral soil surface or a epipedon. densic, lithic, or paralithic contact if shallower. Humic Fragiudepts Rendollic Eutrudepts KGCE. Other Fragiudepts. KGDT. Other Eutrudepts that have an umbric or mollic Typic Fragiudepts epipedon. Humic Eutrudepts Sulfudepts

KGDU. Other Eutrudepts that have a cambic horizon that Key to Subgroups includes 10 to 50 percent (by volume) illuvial parts that KGAA. All Sulfudepts (provisionally). otherwise meet the requirements for an argillic, kandic, or natric Typic Sulfudepts horizon. Ruptic-Alfic Eutrudepts Ustepts KGDV. Other Eutrudepts. Typic Eutrudepts Key to Great Groups KEA. Ustepts that have a duripan that has its upper boundary Fragiudepts within 100 cm of the mineral soil surface. I Durustepts, p. 181 N Key to Subgroups C KEB. Other Ustepts that both: KGCA. Fragiudepts that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of 1. Have a calcic horizon with its upper boundary the mineral soil surface, a fine-earth fraction with both a bulk within 100 cm of the mineral soil surface or a petrocalcic density of 1.0 g/cm3 or less, measured at 33 kPa water retention, horizon that has its upper boundary within 150 cm of the 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling mineral soil surface; and more than 1.0. 2. Are either calcareous or have a texture of loamy fine Andic Fragiudepts sand or coarser in all parts above the calcic or petrocalcic horizon, after the soil between the mineral soil surface and a KGCB. Other Fragiudepts that have, throughout one or more depth of 18 cm has been mixed. horizons with a total thickness of 18 cm or more within 75 cm of Calciustepts, p. 180 the mineral soil surface, one or both of the following: 1. More than 35 percent (by volume) fragments coarser KEC. Other Ustepts that have both of the following: than 2.0 mm, of which more than 66 percent is cinders, 1. No free carbonates within 200 cm of the mineral soil pumice, and pumicelike fragments; or surface; and 2. A fine-earth fraction containing 30 percent or more 2. A base saturation (by NH OAc) of less than 60 percent particles 0.02 to 2.0 mm in diameter; and 4 in all horizons at a depth between 25 and 75 cm from the a. In the 0.02 to 2.0 mm fraction, 5 percent or more mineral soil surface. volcanic glass; and Dystrustepts, p. 181 180 Keys to Soil Taxonomy

KED. Other Ustepts. at a depth of 50 cm below the soil surface is higher Haplustepts, p. 182 than 5 oC. Torrertic Calciustepts Calciustepts KEBD. Other Calciustepts that have one or both of the Key to Subgroups following: KEBA. Calciustepts that have a petrocalcic horizon and a 1. Cracks within 125 cm of the mineral soil surface that are lithic contact within 50 cm of the mineral soil surface. 5 mm or more wide through a thickness of 30 cm or more for Lithic Petrocalcic Calciustepts some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick that has its upper KEBB. Other Calciustepts that have a lithic contact within 50 boundary within 125 cm of the mineral soil surface; or cm of the mineral soil surface. 2. A linear extensibility of 6.0 cm or more between the Lithic Calciustepts mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. KEBC. Other Calciustepts that have both: Vertic Calciustepts 1. One or both of the following: KEBE. Other Calciustepts that have a petrocalcic horizon that a. Cracks within 125 cm of the mineral soil surface that has its upper boundary within 100 cm of the mineral soil are 5 mm or more wide through a thickness of 30 cm or surface. more for some time in normal years and slickensides or Petrocalcic Calciustepts wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral KEBF. Other Calciustepts that have a gypsic horizon that has soil surface; or its upper boundary within 100 cm of the mineral soil surface. b. A linear extensibility of 6.0 cm or more between the Gypsic Calciustepts mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is KEBG. Other Calciustepts that have, in one or more horizons shallower; 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 2. When neither irrigated nor fallowed to store moisture, normal years (or artificial drainage). one of the following: Aquic Calciustepts a. A frigid temperature regime and a moisture control section that in normal years is dry in all parts for four- KEBH. Other Calciustepts that have, when neither irrigated tenths or more of the cumulative days per year when the nor fallowed to store moisture, one of the following: temperature at a depth of 50 cm below the soil surface is 1. A frigid temperature regime and a moisture control higher than 5 oC; or section that in normal years is dry in all parts for four-tenths b. A mesic or thermic soil temperature regime and a or more of the cumulative days per year when the moisture control section that in normal years is dry in temperature at a depth of 50 cm below the soil surface is some or all parts for six-tenths or more of the cumulative higher than 5 oC; or days per year when the 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 or all parts for six-tenths or more of the cumulative days per temperature regime and a moisture control section that in year when the 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 temperature at a temperature regime and a moisture control section that in 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 or all parts for six-tenths or more consecutive days per year when the temperature at a depth of the cumulative days per year when the temperature of 50 cm below the soil surface is higher than 8 oC; and Inceptisols 181

b. Is dry in some or all parts for six-tenths or more c. A hyperthermic, isomesic, or warmer iso soil of the cumulative days per year when the 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: 5 oC. (1) Is moist in some or all parts for fewer than 90 Aridic Calciustepts consecutive days per year when the temperature at a depth of 50 cm below the soil surface is higher than KEBI. Other Calciustepts that have, when neither irrigated nor 8 oC; and fallowed to store moisture, either: (2) Is dry in some part for six-tenths or more of the 1. A mesic or thermic soil temperature regime and a cumulative days per year when the 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 or all parts for four-tenths or less of the consecutive days per 5 oC; and year when the temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or 2. One or both of the following: 2. 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 are 5 mm or more wide through a thickness of 30 cm or in normal years is dry in some or all parts for fewer more for some time in normal years and slickensides or than 120 cumulative days per year when the temperature wedge-shaped aggregates in a layer 15 cm or more thick at a depth of 50 cm below the soil surface is higher than that has its upper boundary within 125 cm of the mineral 8 oC. soil surface; or Udic Calciustepts b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a KEBJ. Other Calciustepts. densic, lithic, or paralithic contact, whichever is shallower. Typic Calciustepts Torrertic Dystrustepts Durustepts KECC. Other Dystrustepts that have one or both of the Key to Subgroups following: KEAA. All Durustepts (provisionally). 1. Cracks within 125 cm of the mineral soil surface that are Typic Durustepts 5 mm or more wide through a thickness of 30 cm or more for I some time in normal years and slickensides or wedge-shaped N Dystrustepts aggregates in a layer 15 cm or more thick that has its upper C 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 KECA. Dystrustepts that have a lithic contact within 50 cm of mineral soil surface and either a depth of 100 cm or a densic, the mineral soil surface. lithic, or paralithic contact, whichever is shallower. Lithic Dystrustepts Vertic Dystrustepts

KECB. Other Dystrustepts that have both: KECD. Other Dystrustepts that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of 1. When neither irrigated nor fallowed to store moisture, 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 a. A frigid soil temperature regime and a moisture and Al plus /2 Fe percentages (by ammonium oxalate) totaling control section that in normal years is dry in all parts for more than 1.0. four-tenths or more of the cumulative days per year when Andic Dystrustepts the temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or KECE. Other Dystrustepts that have, throughout one or more horizons with a total thickness of 18 cm or more within b. A mesic or thermic soil temperature regime and a 75 cm of the mineral soil surface, one or both of the following: moisture control section that, in 6 normal years, is dry in some part for six-tenths or more of the cumulative days 1. More than 35 percent (by volume) fragments coarser per year when the soil temperature at a depth of 50 cm than 2.0 mm, of which more than 66 percent is cinders, below the soil surface is higher than 5 oC; or pumice, and pumicelike fragments; or 182 Keys to Soil Taxonomy

2. A fine-earth fraction containing 30 percent or more KECI. Other Dystrustepts that have in 50 percent or more of particles 0.02 to 2.0 mm in diameter; and 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 a. In the 0.02 to 2.0 mm fraction, 5 percent or more paralithic contact if shallower: volcanic glass; and

1 1. A CEC (by 1N NH OAc pH 7) of less than 24 cmol(+) b. [(Al plus /2 Fe, percent extracted by ammonium 4 per kg clay; or oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. 2. Both a ratio of measured clay in the fine-earth fraction to Vitrandic Dystrustepts percent water retained at 1500 kPa tension of 0.6 or more

and the following: the CEC (by 1N NH4OAc pH 7) divided KECF. Other Dystrustepts that have, in one or more horizons by the product of three times [percent water retained at 1500 within 75 cm of the mineral soil surface, redox depletions with kPa tension minus percent organic carbon (but no more than chroma of 2 or less and also aquic conditions for some time in 1.00)] is less than 24. normal years (or artificial drainage). Oxic Dystrustepts Aquic Dystrustepts KECJ. Other Dystrustepts that have an umbric or mollic KECG. Other Dystrustepts that have a slope of less than 25 epipedon. percent; and either Humic Dystrustepts 1. At a depth of 125 cm below the mineral soil surface, an KECK. Other Dystrustepts. organic-carbon content (Holocene age) of 0.2 percent or Typic Dystrustepts more and no densic, lithic, or paralithic contact within that depth; or 2. An irregular decrease in organic-carbon content Haplustepts (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, or paralithic contact, whichever is shallower. KEDA. Haplustepts that have: Fluventic Dystrustepts 1. A lithic contact within 50 cm of the mineral soil surface; and KECH. Other Dystrustepts that, when neither irrigated nor fallowed to store moisture, have one of the following;: 2. When neither irrigated nor fallowed to store moisture, either: 1. A frigid soil temperature regime and a moisture control section that in normal years is dry in all parts for four-tenths a. A frigid temperature regime and a moisture control or more of the cumulative days per year when the section that in normal years is dry in all parts for four- temperature at a depth of 50 cm below the soil surface is tenths or more of the cumulative days per year when the higher than 5 oC; or temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or 2. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in some b. A mesic or thermic soil temperature regime and a or all parts for six-tenths or more of the cumulative days per moisture control section that in normal years is dry in year when the soil temperature at a depth of 50 cm below the some part for six-tenths or more of the cumulative days soil surface is higher than 5 oC; or per year when the temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or 3. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in c. A hyperthermic, isomesic, or warmer iso soil normal years: temperature regime and a moisture control section that in normal years: a. Is moist in some or all parts for fewer than 90 consecutive days per year when the temperature at a depth (1) Is moist in some or all parts for fewer than 90 of 50 cm below the soil surface is higher than 8 oC; and consecutive days per year when the temperature at a depth of 50 cm below the soil surface is higher than b. Is dry in some part for six-tenths or more of the 8 oC; and cumulative days per year when the temperature at a depth of 50 cm below the soil surface is higher than 5 oC. (2) Is dry in some part for six-tenths or more of the Aridic Dystrustepts cumulative days per year when the temperature at a Inceptisols 183

depth of 50 cm below the soil surface is higher than per year when the temperature at a depth of 50 cm below 5 oC. the soil surface is higher than 5 oC; or Aridic Lithic Haplustepts c. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in KEDB. Other Haplustepts that have a lithic contact within 50 normal years: cm of the mineral soil surface. Lithic Haplustepts (1) Is moist in some or all parts for fewer than 90 consecutive days per year when the temperature at a KEDC. Other Haplustepts that have both: depth of 50 cm below the soil surface is higher than 8 oC; and 1. When neither irrigated nor fallowed to store moisture, one of the following: (2) Is dry in some part for six-tenths or more of the cumulative days per year when the temperature at a 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 some or all 5 oC; and parts for fewer than 105 cumulative days per year when the temperature at a depth of 50 cm below the soil surface 2. One or both of the following: is higher than 5 oC; or a. Cracks within 125 cm of the mineral soil surface that b. A mesic or thermic soil temperature regime and a are 5 mm or more wide through a thickness of 30 cm or moisture control section that in normal years is dry in more for some time in normal years and slickensides or some part for less than four-tenths of the cumulative days wedge-shaped aggregates in a layer 15 cm or more thick per year when the temperature at a depth of 50 cm below that has its upper boundary within 125 cm of the mineral the soil surface is higher than 5 oC; or soil surface; or c. A hyperthermic, isomesic, or warmer iso soil b. 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 normal years is dry in some or all parts for fewer than 120 densic, lithic, or paralithic contact, whichever is shallower. cumulative days per year when the temperature at a depth Torrertic Haplustepts of 50 cm below the soil surface is higher than 8 oC; and KEDE. Other Haplustepts that have one or both of the 2. One or both of the following: following: I a. Cracks within 125 cm of the mineral soil surface that 1. Cracks within 125 cm of the mineral soil surface that are N are 5 mm or more wide through a thickness of 30 cm or 5 mm or more wide through a thickness of 30 cm or more for C more for some time in normal years and slickensides or some time in normal years and slickensides or wedge-shaped wedge-shaped aggregates in a layer 15 cm or more thick aggregates in a layer 15 cm or more thick that has its upper that has its upper boundary within 125 cm of the mineral boundary within 125 cm of the mineral soil surface; or soil surface; or 2. A linear extensibility of 6.0 cm or more between the b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a densic, mineral soil surface and either a depth of 100 cm or a lithic, or paralithic contact, whichever is shallower. densic, lithic, or paralithic contact, whichever is shallower. Vertic Haplustepts Udertic Haplustepts

KEDD. Other Haplustepts that have both: KEDF. Other Haplustepts that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of 1. When neither irrigated nor fallowed to store moisture, 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 a. A frigid soil temperature regime and a moisture and Al plus /2 Fe percentages (by ammonium oxalate) totaling control section that in normal years is dry in all parts for more than 1.0. four-tenths or more of the cumulative days per year when Andic Haplustepts the temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or KEDG. Other Haplustepts that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of b. A mesic or thermic soil temperature regime and a the mineral soil surface, one or both of the following: moisture control section that in normal years is dry in some part for six-tenths or more of the cumulative days 1. More than 35 percent (by volume) fragments coarser 184 Keys to Soil Taxonomy

than 2.0 mm, of which more than 66 percent is cinders, control section that in normal years is dry in all parts for pumice, and pumicelike fragments; or four-tenths or more of the cumulative days per year when the temperature at a depth of 50 cm below the soil surface 2. A fine-earth fraction containing 30 percent or more is higher than 5 oC; or particles 0.02 to 2.0 mm in diameter; and b. A mesic or thermic soil temperature regime and a a. In the 0.02 to 2.0 mm fraction, 5 percent or more moisture control section that in normal years is dry in volcanic glass; and some part for six-tenths or more of the cumulative days 1 b. [(Al plus /2 Fe, percent extracted by ammonium per year when the temperature at a depth of 50 cm below oxalate) times 60] plus the volcanic glass (percent) is the soil surface is higher than 5 oC; or equal to 30 or more. c. A hyperthermic, isomesic, or warmer iso soil Vitrandic Haplustepts temperature regime and a moisture control section that in normal years: KEDH. Other Haplustepts that have anthraquic conditions. Anthraquic Haplustepts (1) Is moist in some or all parts for fewer than 90 consecutive days per year when the temperature at a KEDI. Other Haplustepts that have, in one or more horizons depth of 50 cm below the soil surface is higher than within 75 cm of the mineral soil surface, redox depletions with 8 oC; and chroma of 2 or less and also aquic conditions for some time in (2) Is dry in some part for six-tenths or more of the normal years (or artificial drainage). cumulative days per year when the temperature at a Aquic Haplustepts depth of 50 cm below the soil surface is higher than 5 oC; and KEDJ. Other Haplustepts that in normal years are saturated with water in one or more layers within 100 cm of the mineral 2. Either: soil surface for either: a. At a depth of 125 cm below the mineral soil surface, 1. 20 or more consecutive days; or an organic-carbon content (Holocene age) of 0.2 percent or more and no densic, lithic, or paralithic contact within 2. 30 or more cumulative days. that depth; or Oxyaquic Haplustepts b. An irregular decrease in organic-carbon content KEDK. Other Haplustepts that have in 50 percent or more of (Holocene age) between a depth of 25 cm and either the soil volume between a depth of 25 cm from the mineral soil a depth of 125 cm below the mineral soil surface or surface and either a depth of 100 cm or a densic, lithic, or a densic, lithic, or paralithic contact, whichever is paralithic contact if shallower: shallower. Torrifluventic Haplustepts 1. A CEC (by 1N NH4OAc pH 7) of less than 24 cmol(+) per kg clay; or KEDN. Other Haplustepts that have a slope of less than 25 2. Both a ratio of measured clay in the fine-earth fraction to percent; and percent water retained at 1500 kPa tension of 0.6 or more 1. When neither irrigated nor fallowed to store moisture, and the following: the CEC (by 1N NH OAc pH 7) divided 4 one of the following: by the product of three times [percent water retained at 1500 kPa tension minus percent organic carbon (but no more than a. A frigid soil temperature regime and a moisture 1.00)] is less than 24. control section that in normal years is dry in some or all Oxic Haplustepts parts for fewer than 105 cumulative days per year when the temperature at a depth of 50 cm below the soil surface KEDL. Other Haplustepts that have lamellae (two or more) is higher than 5 oC; or within 200 cm of the mineral soil surface. b. A mesic or thermic soil temperature regime and a Lamellic Haplustepts moisture control section that in normal years is dry in some part for less than four-tenths of the cumulative days KEDM. Other Haplustepts that have a slope of less than 25 per year when the temperature at a depth of 50 cm below percent; and the soil surface is higher than 5 oC; or 1. When neither irrigated nor fallowed to store moisture, c. A hyperthermic, isomesic, or warmer iso soil one of the following: 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 Inceptisols 185

cumulative days per year when the temperature at a depth consecutive days per year when the temperature at a of 50 cm below the soil surface is higher than 8 oC; and depth of 50 cm below the soil surface is higher than 8 oC; and 2. Either: (2) Is dry in some part for six-tenths or more of the a. At a depth of 125 cm below the mineral soil surface, cumulative days per year when the temperature at a an organic-carbon content (Holocene age) of 0.2 percent depth of 50 cm below the soil surface is higher than or more and no densic, lithic, or paralithic contact within 5 oC. that depth; or Haplocalcidic Haplustepts b. An irregular decrease in organic-carbon content (Holocene age) between a depth of 25 cm and either a KEDR. Other Haplustepts that have both: depth of 125 cm below the mineral soil surface or a 1. A calcic horizon that has its upper boundary within 100 densic, lithic, or paralithic contact, whichever is shallower. cm of the mineral soil surface; and Udifluventic Haplustepts 2. When neither irrigated nor fallowed to store moisture, KEDO. Other Haplustepts that have a slope of less than 25 one of the following: percent; and either a. A frigid soil temperature regime and a moisture 1. At a depth of 125 cm below the mineral soil surface, an control section that in normal years is dry in some or all organic-carbon content (Holocene age) of 0.2 percent or parts for fewer than 105 cumulative days per year when more and no densic, lithic, or paralithic contact within that the temperature at a depth of 50 cm below the soil surface depth; or is higher than 5 oC; or 2. An irregular decrease in organic-carbon content b. A mesic or thermic soil temperature regime and a (Holocene age) between a depth of 25 cm and either a depth moisture control section that in normal years is dry in of 125 cm below the mineral soil surface or a densic, lithic, some part for less than four-tenths of the cumulative days or paralithic contact, whichever is shallower. per year when the temperature at a depth of 50 cm below Fluventic Haplustepts the soil surface is higher than 5 oC; or c. A hyperthermic, isomesic, or warmer iso soil KEDP. Other Haplustepts that have a gypsic horizon that temperature regime and a moisture control section that in has its upper boundary within 100 cm of the mineral soil normal years is dry in some or all parts for fewer than 120 surface. I cumulative days per year when the temperature at a depth N Gypsic Haplustepts o of 50 cm below the soil surface is higher than 8 C. C Calcic Udic Haplustepts KEDQ. Other Haplustepts that have both: 1. A calcic horizon that has its upper boundary within 100 KEDS. Other Haplustepts that have a calcic horizon that has cm of the mineral soil surface; and its upper boundary within 100 cm of the mineral soil surface. Calcic Haplustepts 2. When neither irrigated nor fallowed to store moisture, one of the following: KEDT. Other Haplustepts that, when neither irrigated nor a. A frigid soil temperature regime and a moisture fallowed to store moisture, have one of the following: control section that in normal years is dry in all parts for 1. A frigid soil temperature regime and a moisture control four-tenths or more of the cumulative days per year when section that in normal years is dry in all parts for four-tenths the temperature at a depth of 50 cm below the soil surface or more of the cumulative days per year when the is higher than 5 oC; or temperature at a depth of 50 cm below the soil surface is b. A mesic or thermic soil temperature regime and a higher than 5 oC; or moisture control section that in normal years is dry in 2. 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 some per year when the temperature at a depth of 50 cm below part for six-tenths or more of the cumulative days per year the soil surface is higher than 5 oC; or when the temperature at a depth of 50 cm below the soil c. A hyperthermic, isomesic, or warmer iso soil surface is higher than 5 oC; or temperature regime and a moisture control section that in 3. A hyperthermic, isomesic, or warmer iso soil normal years: temperature regime and a moisture control section that in (1) Is moist in some or all parts for fewer than 90 normal years: 186 Keys to Soil Taxonomy

a. Is moist in some or all parts for fewer than 90 2. Are calcareous in all parts above the calcic or petrocalcic consecutive days per year when the temperature at a depth horizon, after the soil between the mineral soil surface and a of 50 cm below the soil surface is higher than 8 oC; and depth of 18 cm has been mixed. Calcixerepts, p. 186 b. Is dry in some part for six-tenths or more of the cumulative days per year when the temperature at a KFC. Other Xerepts that have a fragipan that has its upper depth of 50 cm below the soil surface is higher than boundary within 100 cm of the mineral soil surface. 5 oC. Fragixerepts, p. 189 Aridic Haplustepts KFD. Other Xerepts that have both of the following: KEDU. Other Haplustepts that have a base saturation (by sum of cations) of less than 60 percent in some horizon between 1. No free carbonates within 200 cm of the mineral soil either an Ap horizon or a depth of 25 cm from the mineral soil surface; and surface, whichever is deeper, and either a depth of 75 cm below 2. A base saturation (by NH OAc) of less than 60 percent the mineral soil surface or a densic, lithic, or paralithic contact, 4 in all horizons at a depth between 25 and 75 cm from the whichever is shallower. mineral soil surface. Dystric Haplustepts Dystroxerepts, p. 187 KEDV. Other Haplustepts that, when neither irrigated nor KFE. Other Xerepts. fallowed to store moisture, have one of the following: Haploxerepts, p. 189 1. A frigid soil temperature regime and a moisture control section that in normal years is dry in some or all parts for Calcixerepts fewer than 105 cumulative days per year when the temperature at a depth of 50 cm below the soil surface is Key to Subgroups higher than 5 oC; or KFBA. Calcixerepts that have a lithic contact within 50 cm of 2. A mesic or thermic soil temperature regime and a the mineral soil surface. moisture control section that in normal years is dry in some Lithic Calcixerepts part for less than four-tenths of the cumulative days per year when the temperature at a depth of 50 cm below the soil KFBB. Other Calcixerepts that have one or both of the surface is higher than 5 oC; or following: 3. A hyperthermic, isomesic, or warmer iso soil 1. 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 is dry in some or all parts for fewer than 120 more for some time in normal years and slickensides or cumulative days per year when the temperature at a depth of wedge-shaped aggregates in a layer 15 cm or more thick that 50 cm below the soil surface is higher than 8 oC. has its upper boundary within 125 cm of the mineral soil Udic Haplustepts surface; or 2. A linear extensibility of 6.0 cm or more between the KEDW. Other Haplustepts. mineral soil surface and either a depth of 100 cm or a densic, Typic Haplustepts lithic, or paralithic contact, whichever is shallower. Vertic Calcixerepts Xerepts KFBC. Other Calcixerepts that have a petrocalcic horizon that Key to Great Groups has its upper boundary within 100 cm of the mineral soil surface. KFA. Xerepts that have a duripan that has its upper boundary Petrocalcic Calcixerepts within 100 cm of the mineral soil surface. Durixerepts, p. 187 KFBD. Other Calcixerepts that have an exchangeable sodium percentage of 15 or more (or a sodium adsorption ratio [SAR] KFB. Other Xerepts that both: of 13 or more) in one or more subhorizons within 100 cm of the 1. Have a calcic horizon with its upper boundary mineral soil surface. within 100 cm of the mineral soil surface or a petrocalcic Sodic Calcixerepts horizon with its upper boundary within 150 cm of the mineral soil surface; and KFBE. Other Calcixerepts that have, throughout one or more Inceptisols 187

horizons with a total thickness of 18 cm or more within 75 cm of oxalate) times 60] plus the volcanic glass (percent) is the mineral soil surface, one or both of the following: equal to 30 or more. Aquandic Durixerepts 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, KFAB. Other Durixerepts that have, throughout one or more pumice, and pumicelike fragments; or horizons with a total thickness of 18 cm or more, above the 2. A fine-earth fraction containing 30 percent or more duripan and within 75 cm of the mineral soil surface, a fine- particles 0.02 to 2.0 mm in diameter; and earth fraction with both a bulk density of 1.0 g/cm3 or less, 1 measured at 33 kPa water retention, and Al plus /2 Fe a. In the 0.02 to 2.0 mm fraction, 5 percent or more percentages (by ammonium oxalate) totaling more than 1.0. volcanic glass; and Andic Durixerepts 1 b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is KFAC. Other Durixerepts that have, throughout one or more equal to 30 or more. horizons with a total thickness of 18 cm or more, above the Vitrandic Calcixerepts duripan and within 75 cm of the mineral soil surface, one or both of the following: KFBF. Other Calcixerepts that have, in one or more horizons 1. More than 35 percent (by volume) fragments coarser within 75 cm of the mineral soil surface, redox depletions with than 2.0 mm, of which more than 66 percent is cinders, chroma of 2 or less and also aquic conditions for some time in pumice, and pumicelike fragments; or normal years (or artificial drainage). Aquic Calcixerepts 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and KFBG. Other Calcixerepts. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Typic Calcixerepts volcanic glass; and

1 b. [(Al plus /2 Fe, percent extracted by ammonium Durixerepts oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. Key to Subgroups Vitrandic Durixerepts KFAA. Durixerepts that have both: I KFAD. Other Durixerepts that have, in one or more horizons 1. In one or more horizons above the duripan and N above the duripan and within 30 cm of the mineral soil surface, within 30 cm of the mineral soil surface, distinct or C distinct or prominent redox concentrations and also aquic prominent redox concentrations and also aquic conditions for conditions for some time in normal years (or artificial drainage). some time in normal years (or artificial drainage); and Aquic Durixerepts 2. Throughout one or more horizons with a total thickness of 18 cm or more, above the duripan and within 75 cm of the KFAE. Other Durixerepts that have a duripan that is strongly mineral soil surface, one or more of the following: cemented or less cemented in all subhorizons. Entic Durixerepts 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 1 KFAF. Other Durixerepts. plus /2 Fe percentages (by ammonium oxalate) totaling Typic Durixerepts more than 1.0; or b. More than 35 percent (by volume) fragments coarser Dystroxerepts than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or Key to Subgroups c. A fine-earth fraction containing 30 percent or more KFDA. Dystroxerepts that have both: particles 0.02 to 2.0 mm in diameter; and 1. A lithic contact within 50 cm of the mineral soil surface; (1) In the 0.02 to 2.0 mm fraction, 5 percent or more and volcanic glass; and 2. An umbric or mollic epipedon. 1 (2) [(Al plus /2 Fe, percent extracted by ammonium Humic Lithic Dystroxerepts 188 Keys to Soil Taxonomy

KFDB. Other Dystroxerepts that have a lithic contact within oxalate) times 60] plus the volcanic glass (percent) is 50 cm of the mineral soil surface. equal to 30 or more. Lithic Dystroxerepts Vitrandic Dystroxerepts

KFDC. Other Dystroxerepts that have both: KFDF. Other Dystroxerepts that have both: 1. In one or more horizons within 75 cm of the mineral soil 1. Fragic soil properties: surface, redox depletions with chroma of 2 or less and also a. In 30 percent or more of the volume of a layer 15 cm aquic conditions for some time in normal years (or artificial or more thick that has its upper boundary within 100 cm drainage); and of the mineral soil surface; or 2. Throughout one or more horizons with a total thickness b. In 60 percent or more of the volume of a layer 15 cm of 18 cm or more within 75 cm of the mineral soil surface, or more thick; and one or more of the following: 2. In one or more horizons within 75 cm of the mineral soil a. A fine-earth fraction with both a bulk density of 1.0 surface, redox depletions with chroma of 2 or less and also g/cm3 or less, measured at 33 kPa water retention, and Al 1 aquic conditions in normal years (or artificial drainage). plus /2 Fe percentages (by ammonium oxalate) totaling Fragiaquic Dystroxerepts more than 1.0; or b. More than 35 percent (by volume) fragments coarser KFDG. Other Dystroxerepts that have a slope of less than 25 than 2.0 mm, of which more than 66 percent is cinders, percent; and pumice, and pumicelike fragments; or 1. In one or more horizons within 75 cm of the mineral soil c. A fine-earth fraction containing 30 percent or more surface, redox depletions with chroma of 2 or less and also particles 0.02 to 2.0 mm in diameter; and aquic conditions for some time in normal years (or artificial drainage); and (1) In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and 2. Either:

1 (2) [(Al plus /2 Fe, percent extracted by ammonium a. At a depth of 125 cm below the mineral soil surface, oxalate) times 60] plus the volcanic glass (percent) is an organic-carbon content (Holocene age) of 0.2 percent equal to 30 or more. or more and no densic, lithic, or paralithic contact within Aquandic Dystroxerepts that depth; or b. An irregular decrease in organic-carbon content KFDD. Other Dystroxerepts that have, throughout one or (Holocene age) between a depth of 25 cm and either a more horizons with a total thickness of 18 cm or more within 75 depth of 125 cm below the mineral soil surface or a cm of the mineral soil surface, a fine-earth fraction with both a densic, lithic, or paralithic contact, whichever is shallower. bulk density of 1.0 g/cm3 or less, measured at 33 kPa water Fluvaquentic Dystroxerepts 1 retention, and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. KFDH. Other Dystroxerepts that have, in one or more Andic Dystroxerepts horizons 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). KFDE. Other Dystroxerepts that have, throughout one or more Aquic Dystroxerepts horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: KFDI. Other Dystroxerepts that in normal years are saturated 1. More than 35 percent (by volume) fragments coarser with water in one or more layers within 100 cm of the mineral than 2.0 mm, of which more than 66 percent is cinders, soil surface for either or both: pumice, and pumicelik 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 Dystroxerepts a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and KFDJ. Other Dystroxerepts that have fragic soil properties:

1 b. [(Al plus /2 Fe, percent extracted by ammonium 1. In 30 percent or more of the volume of a layer 15 cm or Inceptisols 189

more thick that has its upper boundary within 100 cm of the KFCB. Other Fragixerepts that have, throughout one or more mineral soil surface; 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: 2. In 60 percent or more of the volume of a layer 15 cm or more thick. 1. More than 35 percent (by volume) fragments coarser Fragic Dystroxerepts than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or KFDK. Other Dystroxerepts that have a slope of less than 25 2. A fine-earth fraction containing 30 percent or more percent; and particles 0.02 to 2.0 mm in diameter; and 1. An umbric or mollic epipedon; and a. In the 0.02 to 2.0 mm fraction, 5 percent or more 2. Either: volcanic glass; and

1 a. At a depth of 125 cm below the mineral soil surface, b. [(Al plus /2 Fe, percent extracted by ammonium an organic-carbon content (Holocene age) of 0.2 percent oxalate) times 60] plus the volcanic glass (percent) is or more and no densc, lithic, or paralithic contact within equal to 30 or more. that depth; or Vitrandic Fragixerepts b. An irregular decrease in organic-carbon content KFCC. Other Fragixerepts that have, in one or more horizons (Holocene age) between a depth of 25 cm and either within 30 cm of the mineral soil surface, distinct or prominent a depth of 125 cm below the mineral soil surface or redox concentrations and also aquic conditions for some time in a densic, lithic, or paralithic contact, whichever is normal years (or artificial drainage). shallower. Aquic Fragixerepts Fluventic Humic Dystroxerepts KFCD. Other Fragixerepts that have an umbric or mollic KFDL. Other Dystroxerepts that have a slope of less than 25 epipedon. percent; and either Humic Fragixerepts 1. At a depth of 125 cm below the mineral soil surface, an organic-carbon content (Holocene age) of 0.2 percent or KFCE. Other Fragixerepts. more and no densic, lithic, or paralithic contact within that Typic Fragixerepts depth; or I 2. An irregular decrease in organic-carbon content Haploxerepts N (Holocene age) between a depth of 25 cm and either a depth C Key to Subgroups of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is shallower. KFEA. Haploxerepts that have both: Fluventic Dystroxerepts 1. A lithic contact within 50 cm of the mineral soil surface; and KFDM. Other Dystroxerepts that have an umbric or mollic epipedon. 2. An umbric or mollic epipedon. Humic Dystroxerepts Humic Lithic Haploxerepts

KFDN. Other Dystroxerepts. KFEB. Other Haploxerepts that have a lithic contact within 50 Typic Dystroxerepts cm of the mineral soil surface. Lithic Haploxerepts

Fragixerepts KFEC. Other Haploxerepts that have one or both of the following: Key to Subgroups 1. Cracks within 125 cm of the mineral soil surface that are KFCA. Fragixerepts that have, throughout one or more 5 mm or more wide through a thickness of 30 cm or more for horizons with a total thickness of 18 cm or more within 75 cm of some time in normal years and slickensides or wedge-shaped the mineral soil surface, a fine-earth fraction with both a bulk aggregates 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 Andic Fragixerepts the mineral soil surface and either a depth of 100 cm 190 Keys to Soil Taxonomy

or a densic, lithic, or paralithic contact, whichever is 1. Saturation with water within 100 cm of the mineral soil shallower. surface in normal years for either or both: Vertic Haploxerepts a. 20 or more consecutive days; or KFED. Other Haploxerepts that have both: b. 30 or more cumulative days; 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 one or more of the following: drainage); 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 mineral soil surface, pumice, and pumicelike fragments; or one or more of the following: b. A fine-earth fraction containing 30 percent or more a. A fine-earth fraction with both a bulk density of 1.0 particles 0.02 to 2.0 mm in diameter; and g/cm3 or less, measured at 33 kPa water retention, and Al 1 (1) In the 0.02 to 2.0 mm fraction, 5 percent or more plus /2 Fe percentages (by ammonium oxalate) totaling volcanic glass; and more than 1.0; or 1 (2) [(Al plus /2 Fe percentages extracted by b. More than 35 percent (by volume) fragments coarser ammonium oxalate) times 60] plus the volcanic glass than 2.0 mm, of which more than 66 percent is cinders, (percent) is equal to 30 or more. pumice, and pumicelike fragments; or Oxyaquic Vitrandic Haploxerepts c. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and KFEH. Other Haploxerepts that have, throughout one or more (1) 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 of volcanic glass; and the mineral soil surface, one or both of the following: 1 (2) [(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 Aquandic Haploxerepts 2. A fine-earth fraction containing 30 percent or more KFEE. Other Haploxerepts that have both: particles 0.02 to 2.0 mm in diameter; and 1. In one or more horizons with a total thickness of 18 cm a. In the 0.02 to 2.0 mm fraction, 5 percent or more or more within 75 cm of the mineral soil surface, a fine-earth volcanic glass; and 3 fraction with both a bulk density of 1.0 g/cm or less, 1 1 b. [(Al plus /2 Fe, percent extracted by ammonium measured at 33 kPa water retention, and Al plus /2 Fe oxalate) times 60] plus the volcanic glass (percent) is percentages (by ammonium oxalate) totaling more than 1.0. equal to 30 or more. 2. Saturation with water within 100 cm of the mineral soil Vitrandic Haploxerepts surface in normal years for either or both: KFEI. Other Haploxerepts that have a gypsic horizon within a. 20 or more consecutive days; or 100 cm of the mineral soil surface. b. 30 or more cumulative days. Gypsic Haploxerepts Andic Oxyaquic Haploxerepts KFEJ. Other Haploxerepts that have, in one or more horizons KFEF. Other Haploxerepts that have, throughout one or more within 75 cm of the mineral soil surface, redox depletions with horizons with a total thickness of 18 cm or more within 75 cm of chroma of 2 or less and also aquic conditions for some time in the mineral soil surface, a fine-earth fraction with both a bulk normal years (or artificial drainage). density of 1.0 g/cm3 or less, measured at 33 kPa water retention, Aquic Haploxerepts 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. KFEK. Other Haploxerepts that have lamellae (two or more) Andic Haploxerepts within 200 cm of the mineral soil surface. Lamellic Haploxerepts KFEG. Other Haploxerepts that have both: Inceptisols 191

KFEL. Other Haploxerepts that have fragic soil properties: KFEN. Other Haploxerepts that have a calcic horizon or identifiable secondary carbonates within one of the following 1. In 30 percent or more of the volume of a layer 15 cm or particle-size class and depth combinations: more thick that has its upper boundary within 100 cm of the mineral soil surface; or 1. A sandy or sandy-skeletal particle-size class and within 150 cm of the mineral soil surface; or 2. In 60 percent or more of the volume of a layer 15 cm or more thick. 2. A clayey, clayey-skeletal, fine, or very-fine Fragic Haploxerepts particle-size class and within 90 cm of the mineral soil surface; or KFEM. Other Haploxerepts that have a slope of less than 25 3. Any other particle-size class and within 110 cm of the percent; and either mineral soil surface. 1. At a depth of 125 cm below the mineral soil surface, an Calcic Haploxerepts organic-carbon content (Holocene age) of 0.2 percent or more and no densic, lithic, or paralithic contact within that depth; or KFEO. Other Haploxerepts that have an umbric or mollic epipedon. 2. An irregular decrease in organic-carbon content Humic Haploxerepts (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is shallower. KFEP. Other Haploxerepts. Fluventic Haploxerepts Typic Haploxerepts

I N C

193

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: horizon intervenes, a color value, moist, of 4 or more and one of the following: 1. An argillic or natric horizon; and (a) 50 percent or more chroma of 1 on faces of 2. An albic horizon that has chroma of 2 or less and is 2.5 peds or in the matrix, hue of 10YR or redder, and cm or more thick, has its lower boundary 18 cm or more redox concentrations; or below the mineral soil surface, and either lies directly below 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 redox concentrations; or 3. In one or more subhorizons of the albic horizon and/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; or masses or concretions, or both, and also aquic conditions for (d) 50 percent or more chroma of 3 or less on some time in normal years (or artificial drainage). faces of peds or in the matrix, hue of 5Y, and redox Albolls, p. 194 concentrations; or IB. Other Mollisols that have, in a layer above a densic, lithic, (e) 50 percent or more chroma of 0 on faces of or paralithic contact or in a layer at a depth between 40 and 50 peds or in the matrix; or 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) and one or more of the following: (g) Any color if it results from uncoated sand grains; or 1. A histic epipedon overlying the mollic epipedon; or M b. Chroma of 2 in the lower part of the mollic epipedon; O 2. An exchangeable sodium percentage (ESP) of 15 or and either L more (or a sodium adsorption ratio [SAR] of 13 or more) in the upper part of the mollic epipedon and a decrease in ESP (1) Distinct or prominent redox concentrations in the (or SAR) values with increasing depth below 50 cm from the lower part of the mollic epipedon; or mineral soil surface; or (2) Directly below the mollic epipedon, one of the 3. A calcic or petrocalcic horizon that has its upper following matrix colors: boundary within 40 cm of the mineral soil surface; or (a) A color value, moist, of 4, chroma of 2, and 4. A mollic epipedon, with chroma of 1 or less, that extends some redox depletions with a color value, moist, of to a lithic contact within 30 cm of the mineral soil surface; or 4 or more and chroma of 1 or less; or 5. One of the following colors: (b) A color value, moist, of 5 or more, chroma of 2 or less, and redox concentrations; or a. Chroma of 1 or less in the lower part of the mollic epipedon;1 and either (c) A color value, moist, of 4 and chroma of 1 or less; or (1) Distinct or prominent redox concentrations in the lower part of the mollic epipedon; or 6. At a depth between 40 and 50 cm from the mineral soil 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. 195 194 Keys to Soil Taxonomy

IC. Other Mollisols that: wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral 1. Have a mollic epipedon less than 50 cm thick; soil surface; or and b. A linear extensibility of 6.0 cm or more between the 2. Do not have an argillic or calcic horizon; and mineral soil surface and either a depth of 100 cm or a 3. Have, either within or directly below the mollic densic, lithic, or paralithic contact, whichever is epipedon, mineral soil materials less than 7.5 cm in diameter shallower; and that have a CaCO equivalent of 40 percent or more; and 3 2. If not irrigated, a moisture control section that in normal 4. Have either or both a udic moisture regime or a cryic soil years is dry in all parts for 45 or more consecutive days temperature regime. during the 120 days following the summer solstice. Rendolls, p. 203 Xerertic Argialbolls

ID. Other Mollisols that have, in normal years, a mean annual IABB. Other Argialbolls that have one or both of the soil temperature of 0 oC or colder and a mean summer soil following: temperature that: 1. Cracks within 125 cm of the mineral soil surface that 1. Is 8 oC or colder if there is no O horizon; or 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 5 oC or colder if there is an O horizon. wedge-shaped aggregates in a layer 15 cm or more thick that Gelolls, p. 202 has its upper boundary within 125 cm of the mineral soil surface; or IE. Other Mollisols that have a cryic soil temperature regime. Cryolls, p. 199 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm IF. Other Mollisols that have either a xeric moisture regime or or a densic, lithic, or paralithic contact, whichever is an aridic moisture regime that borders on xeric. shallower. Xerolls, p. 226 Vertic Argialbolls

IG. Other Mollisols that have either an ustic moisture regime IABC. Other Argialbolls that: or an aridic moisture regime that borders on ustic. 1. Do not have an abrupt textural change from the albic to Ustolls, p. 211 the argillic horizon; and IH. Other Mollisols. 2. If not irrigated, have a moisture control section that in Udolls, p. 203 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 change from the albic to the argillic horizon. IAA. Albolls that have a natric horizon. Argiaquic Argialbolls Natralbolls, p. 195 IABE. Other Argialbolls that, if not irrigated, have a moisture IAB. Other Albolls. control section that in normal years is dry in all parts for 45 or Argialbolls, p. 194 more consecutive days during the 120 days following the summer solstice. Argialbolls Xeric Argialbolls

Key to Subgroups IABF. Other Argialbolls that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of IABA. Argialbolls that have both: the mineral soil surface, one or more of the following: 1. One or both of the following: 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 Mollisols 195

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 3. A fine-earth fraction containing 30 percent or more IBEA. Argiaquolls that have a sandy or sandy-skeletal particles 0.02 to 2.0 mm in diameter; and particle-size class throughout a layer extending from the mineral 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 oxalate) times 60] plus the volcanic glass (percent) is IBEB. Other Argiaquolls that have a sandy or sandy-skeletal equal to 30 or more. particle-size class throughout a layer extending from the mineral Aquandic Argialbolls soil surface to the top of an argillic horizon at a depth of 100 cm or more. IABG. Other Argialbolls. Grossarenic Argiaquolls Typic Argialbolls IBEC. Other Argiaquolls that have one or both of the Natralbolls following: Key to Subgroups 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 IAAA. Natralbolls that have visible crystals of gypsum some time in normal years and slickensides or wedge-shaped and/or more soluble salts within 40 cm of the mineral soil aggregates in a layer 15 cm or more thick that has its upper surface. boundary within 125 cm of the mineral soil surface; or Leptic Natralbolls 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. 196 M IBEE. Other Argiaquolls. O IBB. Other Aquolls that have a duripan that has its upper Typic Argiaquolls L boundary within 100 cm of the mineral soil surface. Duraquolls, p. 196 Calciaquolls

IBC. Other Aquolls that have a natric horizon. Key to Subgroups Natraquolls, p. 198 IBDA. Calciaquolls that have a petrocalcic horizon that has its upper boundary within 100 cm of the mineral soil surface. IBD. Other Aquolls that have a calcic or gypsic horizon that Petrocalcic Calciaquolls has its upper boundary within 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. 195 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. 195 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. 197 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. 196 Aeric Calciaquolls 196 Keys to Soil Taxonomy

IBDC. Other Calciaquolls. IBAF. Other Cryaquolls that have a calcic horizon either Typic Calciaquolls within or directly below the mollic epipedon. Calcic Cryaquolls Cryaquolls IBAG. Other Cryaquolls that have a mollic epipedon 50 cm or Key to Subgroups more thick. Cumulic Cryaquolls IBAA. Cryaquolls that have one or both of the following: 1. Cracks within 125 cm of the mineral soil surface that IBAH. Other Cryaquolls. are 5 mm or more wide through a thickness of 30 cm or Typic Cryaquolls more for some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick that Duraquolls has its upper boundary within 125 cm of the mineral soil surface; or Key to Subgroups 2. A linear extensibility of 6.0 cm or more between IBBA. Duraquolls that have a natric horizon. the mineral soil surface and either a depth of 100 cm Natric Duraquolls or a densic, lithic, or paralithic contact, whichever is shallower. IBBB. Other Duraquolls that have, above the duripan, one or Vertic Cryaquolls both of the following: 1. Cracks that are 5 mm or more wide through a thickness IBAB. Other Cryaquolls that have a histic epipedon. of 30 cm or more for some time in normal years and Histic Cryaquolls slickensides or wedge-shaped aggregates in a layer 15 cm or more thick; or IBAC. Other Cryaquolls that have a buried layer of organic soil materials, 20 cm or more thick, that has its upper boundary 2. A linear extensibility of 6.0 cm or more. 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 plus /2 Fe percentages (by ammonium oxalate) totaling more Endoaquolls than 1.0; or Key to Subgroups 2. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, IBGA. Endoaquolls that have a lithic contact within 50 cm of pumice, and pumicelike fragments; or the mineral soil surface. Lithic Endoaquolls 3. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and IBGB. Other Endoaquolls that have both: a. In the 0.02 to 2.0 mm fraction, 5 percent or more 1. One or both of the following: volcanic glass; and

1 a. Cracks within 125 cm of the mineral soil surface that b. [(Al plus /2 Fe, percent extracted by ammonium are 5 mm or more wide through a thickness of 30 cm or oxalate) times 60] plus the volcanic glass (percent) is more for some time in normal years and slickensides or equal to 30 or more. wedge-shaped aggregates in a layer 15 cm or more thick Aquandic Cryaquolls that has its upper boundary within 125 cm of the mineral soil surface; or IBAE. Other Cryaquolls that have an argillic horizon. Argic Cryaquolls b. A linear extensibility of 6.0 cm or more between the Mollisols 197

mineral soil surface and either a depth of 100 cm or a 1. A fine-earth fraction with both a bulk density of 1.0 densic, lithic, or paralithic contact, whichever is g/cm3 or less, measured at 33 kPa water retention, and Al 1 shallower; and plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0; or 2. A mollic epipedon 60 cm or more thick. Cumulic Vertic Endoaquolls 2. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, IBGC. Other Endoaquolls that have both of the following: pumice, and pumicelike fragments; or 1. One or both of the following: 3. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; 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 a. In the 0.02 to 2.0 mm fraction, 5 percent or more more for some time in normal years and slickensides or volcanic glass; and

wedge-shaped aggregates in a layer 15 cm or more thick 1 b. [(Al plus /2 Fe, percent extracted by ammonium that has its upper boundary within 125 cm of the mineral oxalate) times 60] plus the volcanic glass (percent) is soil surface; or equal to 30 or more. b. A linear extensibility of 6.0 cm or more between the Aquandic Endoaquolls mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is IBGH. Other Endoaquolls that have a horizon, 15 cm or more shallower; and thick within 100 cm of the mineral soil surface, that either has 20 percent or more (by volume) durinodes or is brittle and has a 2. A slope of less than 25 percent; and either firm rupture-resistance class when moist. a. An organic-carbon content of 0.3 percent or more in Duric Endoaquolls all horizons within 125 cm of the mineral soil surface; or IBGI. Other Endoaquolls that have a mollic epipedon 60 cm b. An irregular decrease in organic-carbon content from or more thick. a depth of 25 cm to a depth of 125 cm or to a densic, Cumulic Endoaquolls lithic, or paralithic contact if shallower. Fluvaquentic Vertic Endoaquolls IBGJ. Other Endoaquolls that have a slope of less than 25 percent; and either IBGD. Other Endoaquolls that have one or both of the following: 1. An organic-carbon content of 0.3 percent 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 M 5 mm or more wide through a thickness of 30 cm or more for 2. An irregular decrease in organic-carbon content from a O some time in normal years and slickensides or wedge-shaped depth of 25 cm to a depth of 125 cm or to a densic, lithic, or L aggregates in a layer 15 cm or more thick that has its upper paralithic contact if shallower. boundary within 125 cm of the mineral soil surface; or Fluvaquentic Endoaquolls 2. A linear extensibility of 6.0 cm or more between the IBGK. Other Endoaquolls. mineral soil surface and either a depth of 100 cm or a densic, Typic Endoaquolls lithic, or paralithic contact, whichever is shallower. Vertic Endoaquolls Epiaquolls IBGE. Other Endoaquolls that have a histic epipedon. Histic Endoaquolls Key to Subgroups IBFA. Epiaquolls that have both of the following: IBGF. Other Endoaquolls that have a buried layer of organic soil materials, 20 cm or more thick, that has its upper boundary 1. One or both of the following: within 100 cm of the mineral soil surface. a. Cracks within 125 cm of the mineral soil surface that Thapto-Histic Endoaquolls are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or IBGG. Other Endoaquolls that have, throughout one or more wedge-shaped aggregates in a layer 15 cm or more thick horizons with a total thickness of 18 cm or more within 75 cm of that has its upper boundary within 125 cm of the mineral the mineral soil surface, one or more of the following: soil surface; or 198 Keys to Soil Taxonomy

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

IBFC. Other Epiaquolls that have one or both of the IBFI. Other Epiaquolls that have a slope of less than 25 following: percent; and either 1. Cracks within 125 cm of the mineral soil surface that are 1. An organic-carbon content of 0.3 percent or more in all 5 mm or more wide through a thickness of 30 cm or more for horizons within 125 cm of the mineral soil surface; or some time in normal years and slickensides or wedge-shaped 2. An irregular decrease in organic-carbon content from a aggregates in a layer 15 cm or more thick that has its upper depth of 25 cm to a depth of 125 cm or to a densic, lithic, or boundary within 125 cm of the mineral soil surface; or paralithic contact if shallower. 2. A linear extensibility of 6.0 cm or more between the Fluvaquentic Epiaquolls mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. IBFJ. Other Epiaquolls. Vertic Epiaquolls Typic Epiaquolls

IBFD. Other Epiaquolls that have a histic epipedon. Natraquolls Histic Epiaquolls Key to Subgroups IBFE. Other Epiaquolls that have a buried layer of organic soil IBCA. Natraquolls that have one or both of the following: materials, 20 cm or more thick, that has its upper boundary within 100 cm of the mineral soil surface. 1. Cracks within 125 cm of the mineral soil surface that Thapto-Histic Epiaquolls are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or IBFF. Other Epiaquolls that have, throughout one or more wedge-shaped aggregates in a layer 15 cm or more thick that Mollisols 199

has its upper boundary within 125 cm of the mineral soil Argicryolls 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, IEDA. Argicryolls that have a lithic contact within 50 cm of lithic, or paralithic contact, whichever is shallower. the mineral soil surface. Vertic Natraquolls Lithic Argicryolls

IBCB. Other Natraqolls that have a glossic horizon or IEDB. Other Argicryolls that have one or both of the following: interfingering of albic materials into the natric horizon. 1. Cracks within 125 cm of the mineral soil surface that are Glossic Natraquolls 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge-shaped IBCC. Other Natraquolls. aggregates in a layer 15 cm or more thick that has its upper Typic Natraquolls boundary within 125 cm of the mineral soil surface; or 2. A linear extensibility of 6.0 cm or more between the Cryolls mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. Key to Great Groups Vertic Argicryolls

IEA. Cryolls that have a duripan that has its upper boundary IEDC. Other Argicryolls that have, throughout one or more within 100 cm of the mineral soil surface. horizons with a total thickness of 18 cm or more within 75 cm of Duricryolls, p. 200 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 IEB. Other Cryolls that have a natric horizon. and Al plus /2 Fe percentages (by ammonium oxalate) totaling Natricryolls, p. 202 more than 1.0. Andic Argicryolls IEC. Other Cryolls that have both: IEDD. Other Argicryolls that have, throughout one or more 1. An argillic horizon that has its upper boundary 60 cm or horizons with a total thickness of 18 cm or more within 75 cm of more below the mineral soil surface; and the soil surface, one or both of the following: 2. A texture finer than loamy fine sand in all horizons 1. More than 35 percent (by volume) fragments coarser above the argillic horizon. than 2.0 mm, of which more than 66 percent is cinders, Palecryolls, p. 202 M pumice, and pumicelike fragments; or O IED. Other Cryolls that have an argillic horizon. 2. A fine-earth fraction containing 30 percent or more L Argicryolls, p. 199 particles 0.02 to 2.0 mm in diameter; and a. In the 0.02 to 2.0 mm fraction, 5 percent or more IEE. Other Cryolls that: volcanic glass; and

1. Have a calcic or petrocalcic horizon that has its 1 b. [(Al plus /2 Fe, percent extracted by ammonium upper boundary within 100 cm of the mineral soil surface; oxalate) times 60] plus the volcanic glass (percent) is and equal to 30 or more. 2. In all parts above the calcic or petrocalcic horizon, after Vitrandic Argicryolls the materials between the soil surface and a depth of 18 cm have been mixed, either are calcareous or have a texture of IEDE. Other Argicryolls that have an argillic horizon that, loamy fine sand or coarser. with increasing depth, has a clay increase of 20 percent or more Calcicryolls, p. 200 (absolute, in the fine-earth fraction) within its upper 7.5 cm. Abruptic Argicryolls IEF. Other Cryolls. Haplocryolls, p. 201 IEDF. Other Argicryolls that have, in one or more horizons 200 Keys to Soil Taxonomy

within 100 cm of the mineral soil surface, redox depletions with Calcicryolls chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). Key to Subgroups Aquic Argicryolls IEEA. Calcicryolls that have a lithic contact within 50 cm of the mineral soil surface. IEDG. Other Argicryolls that in normal years are saturated Lithic Calcicryolls with water in one or more layers within 100 cm of the mineral soil surface for either or both: IEEB. Other Calcicryolls that have, throughout one or more 1. 20 or more consecutive days; 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: 2. 30 or more cumulative days. Oxyaquic Argicryolls 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, IEDH. Other Argicryolls that have both: pumiceous, and pumicelike fragments; or 1. A mollic epipedon that is 40 cm or more thick and has a 2. A fine-earth fraction containing 30 percent or more texture finer than loamy fine sand; and particles 0.02 to 2.0 mm in diameter; and 2. A calcic horizon within 100 cm of the mineral soil a. In the 0.02 to 2.0 mm fraction, 5 percent or more surface. volcanic glass; and

Calcic Pachic Argicryolls 1 b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is IEDI. Other Argicryolls that have a mollic epipedon that is equal to 30 or more. 40 cm or more thick and has a texture finer than loamy fine Vitrandic Calcicryolls sand. Pachic Argicryolls IEEC. Other Calcicryolls that have a petrocalcic horizon that has its upper boundary within 100 cm of the mineral soil surface. IEDJ. Other Argicryolls that have a calcic horizon within 100 Petrocalcic Calcicryolls cm of the mineral soil surface. Calcic Argicryolls IEED. Other Calcicryolls that have a mollic epipedon that is 40 cm or more thick and has a texture finer than loamy fine sand. IEDK. Other Argicryolls that have either: Pachic Calcicryolls 1. Above the argillic horizon, an albic horizon or a horizon that has color values too high for a mollic epipedon and IEEE. Other Calcicryolls that have an ustic moisture regime. chroma too high for an albic horizon; or Ustic Calcicryolls 2. A glossic horizon, or interfingering of albic materials IEEF. Other Calcicryolls that have a xeric moisture 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 moisture regime. Duricryolls Ustic Argicryolls Key to Subgroups IEDM. Other Argicryolls that have a xeric moisture IEAA. Duricryolls that have an argillic horizon. regime. Argic Duricryolls Xeric Argicryolls IEAB. Other Duricryolls that have a calcic horizon above the IEDN. Other Argicryolls. duripan. Typic Argicryolls Calcic Duricryolls Mollisols 201

IEAC. Other Duricryolls. 125 cm or to a densic, lithic, or paralithic contact if Typic Duricryolls shallower; and 3. A slope of less than 25 percent; and Haplocryolls 4. In one or more horizons within 100 cm of the mineral Key to Subgroups soil surface, distinct or prominent redox concentrations and also aquic conditions for some time in normal years (or IEFA. Haplocryolls that have a lithic contact within 50 cm of artificial drainage). the mineral soil surface. Aquic Cumulic Haplocryolls Lithic Haplocryolls IEFF. Other Haplocryolls that have: IEFB. Other Haplocryolls that have one or both of the following: 1. A mollic epipedon that is 40 cm or more thick and has a texture finer than loamy fine sand; 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 for 2. An irregular decrease in organic-carbon content from a some time in normal years and slickensides or wedge-shaped depth of 25 cm below the mineral soil surface to a depth of aggregates in a layer 15 cm or more thick that has its upper 125 cm or to a densic, lithic, or paralithic contact if boundary within 125 cm of the mineral soil surface; or shallower; and 2. A linear extensibility of 6.0 cm or more between the 3. A slope of less than 25 percent. mineral soil surface and either a depth of 100 cm or a densic, Cumulic Haplocryolls lithic, or paralithic contact, whichever is shallower. Vertic Haplocryolls IEFG. Other Haplocryolls that have both: 1. A slope of less than 25 percent; and either IEFC. Other Haplocryolls that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of a. An organic-carbon content of 0.3 percent or more at a the mineral soil surface, a fine-earth fraction with both a bulk depth of 125 cm below the mineral soil surface; or density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 b. An irregular decrease in organic-carbon content from and Al plus /2 Fe percentages (by ammonium oxalate) totaling a depth of 25 cm to a depth of 125 cm or to a densic, more than 1.0. lithic, or paralithic contact if shallower; and Andic Haplocryolls 2. In one or more horizons within 100 cm of the mineral IEFD. Other Haplocryolls that have, throughout one or more soil surface, distinct or prominent redox concentrations and horizons with a total thickness of 18 cm or more within 75 cm of also aquic conditions for some time in normal years (or M the mineral soil surface, one or both of the following: artificial drainage). O Fluvaquentic Haplocryolls L 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or IEFH. Other Haplocryolls that have, in one or more horizons within 100 cm of the mineral soil surface, distinct or prominent 2. A fine-earth fraction containing 30 percent or more redox concentrations and also aquic conditions for some time in particles 0.02 to 2.0 mm in diameter; and normal years (or artificial drainage). a. In the 0.02 to 2.0 mm fraction, 5 percent or more Aquic Haplocryolls volcanic glass; and

1 IEFI. Other Haplocryolls that in normal years are saturated b. [(Al plus /2 Fe, percent extracted by ammonium with water in one or more layers within 100 cm of the mineral oxalate) times 60] plus the volcanic glass (percent) is soil surface for either or both: equal to 30 or more. Vitrandic Haplocryolls 1. 20 or more consecutive days; or 2. 30 or more cumulative days. IEFE. Other Haplocryolls that have: Oxyaquic Haplocryolls 1. A mollic epipedon that is 40 cm or more thick and has a texture finer than loamy fine sand; and IEFJ. Other Haplocryolls that have both: 2. An irregular decrease in organic-carbon content from a 1. A mollic epipedon that is 40 cm or more thick and has a depth of 25 cm below the mineral soil surface to a depth of texture finer than loamy fine sand; and 202 Keys to Soil Taxonomy

2. A calcic horizon within 100 cm of the mineral soil IECC. Other Palecryolls that have an argillic horizon that, surface. with increasing depth, has a clay increase of 20 percent or more Calcic Pachic Haplocryolls (absolute, in the fine-earth fraction) within its upper 7.5 cm. Abruptic Palecryolls IEFK. Other Haplocryolls that have a mollic epipedon that is 40 cm or more thick and has a texture finer than loamy fine sand. IECD. Other Palecryolls that have a mollic epipedon that is Pachic Haplocryolls 40 cm or more thick and has a texture finer than loamy fine sand. IEFL. Other Haplocryolls that have a slope of less than 25 Pachic Palecryolls percent; and either IECE. Other Palecryolls that have an ustic moisture regime. 1. An organic-carbon content of 0.3 percent or more at a Ustic Palecryolls depth of 125 cm below the mineral soil surface; or 2. An irregular decrease in organic-carbon content from a IECF. Other Palecryolls that have a xeric moisture regime. depth of 25 cm to a depth of 125 cm or to a densic, lithic, or Xeric Palecryolls paralithic contact if shallower. Fluventic Haplocryolls IECG. Other Palecryolls. Typic Palecryolls IEFM. Other Haplocryolls that have a calcic horizon within 100 cm of the mineral soil surface. Calcic Haplocryolls Gelolls IEFN. Other Haplocryolls that have an ustic moisture regime. Key to Great Groups Ustic Haplocryolls IDA. All Gelolls. IEFO. Other Haplocryolls that have a xeric moisture regime. Haplogelolls, p. 202 Xeric Haplocryolls Haplogelolls IEFP. Other Haplocryolls. Typic Haplocryolls Key to Subgroups

Natricryolls IDAA. Haplogelolls that have a lithic contact within 50 cm of the mineral soil surface. Key to Subgroups Lithic Haplogelolls IEBA. All Natricryolls. Typic Natricryolls IDAB. Other Haplogelolls that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of Palecryolls 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. IECA. Palecryolls that have, in one or more horizons within Andic Haplogelolls 100 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). IDAC. Other Haplogelolls that have, in one or more horizons Aquic Palecryolls within 100 cm of the mineral soil surface, distinct or prominent redox concentrations and also aquic conditions for some time in IECB. Other Palecryolls that in normal years are saturated normal years (or artificial drainage). with water in one or more layers within 100 cm of the mineral Aquic Haplogelolls soil surface for either or both: IDAD. Other Haplogelolls that have: 1. 20 or more consecutive days; or 1. A mollic epipedon that is 40 cm or more thick and has a texture finer than loamy fine sand; and 2. 30 or more cumulative days. Oxyaquic Palecryolls 2. An irregular decrease in organic-carbon content from a Mollisols 203

depth of 25 cm below the mineral soil surface to a depth of 125 more either in the upper 18 cm of the mollic epipedon, after cm or a densic, lithic, or paralithic contact if shallower. mixing, or in an Ap horizon 18 cm or more thick. Cumulic Haplogelolls Entic Haprendolls

ICBE. Other Haprendolls. IDAE. Other Haplogelolls. Typic Haprendolls Typic Haplogelolls

Udolls Rendolls Key to Great Groups Key to Great Groups IHA. Udolls that have a natric horizon. ICA. Rendolls that have a cryic soil temperature regime. Natrudolls, p. 209 Cryrendolls, p. 203 IHB. Other Udolls that: ICB. Other Rendolls. 1. Have a calcic or petrocalcic horizon that has its upper Haprendolls, p. 203 boundary within 100 cm of the mineral soil surface; and Cryrendolls 2. Do not have an argillic horizon above the calcic or petrocalcic horizon; and Key to Subgroups 3. In all parts above the calcic or petrocalcic horizon, after ICAA. Cryrendolls that have a lithic contact within 50 cm of the materials between the soil surface and a depth of 18 cm the mineral soil surface. have been mixed, either are calcareous or have a texture of Lithic Cryrendolls loamy fine sand or coarser. Calciudolls, p. 206 ICAB. Other Cryrendolls. Typic Cryrendolls IHC. Other Udolls that have one or more of the following: 1. A petrocalcic horizon that has its upper boundary within Haprendolls 150 cm of the mineral soil surface; or Key to Subgroups 2. All of the following: ICBA. Haprendolls that have a lithic contact within 50 cm of a. No densic, lithic, or paralithic contact within 150 cm M the mineral soil surface. of the mineral soil surface; and O Lithic Haprendolls L b. Within 150 cm of the mineral soil surface, a clay decrease, with increasing depth, of less than 20 percent ICBB. Other Haprendolls that have one or both of the (relative) from the maximum clay content (noncarbonate following: clay); and 1. Cracks within 125 cm of the mineral soil surface that are c. An argillic horizon with one or more 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-shaped (1) In 50 percent or more of the matrix of one or aggregates in a layer 15 cm or more thick that has its upper more subhorizons in its lower half, hue of 7.5YR or boundary within 125 cm of the mineral soil surface; or redder and chroma of 5 or more; or 2. A linear extensibility of 6.0 cm or more between the (2) In 50 percent or more of the matrix of horizons mineral soil surface and either a depth of 100 cm or a densic, that total more than one-half the total thickness, hue of lithic, or paralithic contact, whichever is shallower. 2.5YR or redder, a value, moist, of 3 or less, and a Vertic Haprendolls value, dry, of 4 or less; or (3) Many redox concentrations with hue of 5YR or ICBC. Other Haprendolls that have a cambic horizon. redder or chroma of 6 or more, or both, in one or more Inceptic Haprendolls subhorizons; or ICBD. Other Haprendolls that have a color value, dry, of 6 or 3. A frigid temperature regime; and both 204 Keys to Soil Taxonomy

a. An argillic horizon that has its upper boundary 60 cm more for some time in normal years and slickensides or or more below the mineral soil surface; and wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral b. A texture finer than loamy fine sand in all horizons soil surface; or above the argillic horizon. Paleudolls, p. 210 b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a IHD. Other Udolls that have an argillic horizon. densic, lithic, or paralithic contact, whichever is shallower. Argiudolls, p. 204 Aquertic Argiudolls

IHE. Other Udolls that have a mollic epipedon that: IHDC. Other Argiudolls that have both: 1. Either below an Ap horizon or below a depth of 18 cm 1. One or both of the following: from the mineral soil surface, contains 50 percent or more a. Cracks within 125 cm of the mineral soil surface that (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 2. Either rests on a lithic contact or has a transition zone to wedge-shaped aggregates in a layer 15 cm or more thick the underlying horizon in which 25 percent or more of the that has its upper boundary within 125 cm of the mineral soil volume consists of discrete wormholes, wormcasts, or soil surface; or animal burrows filled with material from the mollic epipedon b. A linear extensibility of 6.0 cm or more between the and from the underlying horizon. mineral soil surface and either a depth of 100 cm or a Vermudolls, p. 210 densic, lithic, or paralithic contact, whichever is shallower; and IHF. Other Udolls. Hapludolls, p. 207 2. In normal years saturation with water in one or more layers within 100 cm of the mineral soil surface for either or Argiudolls both: 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 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 temperature regime; or a. Within 40 cm of the mineral soil surface, in horizons b. 50 cm or more thick; and that also have redoximorphic features; or 2. One or both of the following: b. Within 75 cm of the mineral soil surface, in one or a. Cracks within 125 cm of the mineral soil surface that more horizons with a total thickness of 15 cm or more that are 5 mm or more wide through a thickness of 30 cm or have one or more of the following: more for some time in normal years and slickensides or (1) A color value, moist, of 4 or more and redox wedge-shaped aggregates in a layer 15 cm or more thick depletions with chroma of 2 or less; or 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 b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a (3) Hue of 2.5Y or yellower and chroma of 3 or less; densic, lithic, or paralithic contact, whichever is shallower. and Pachic Vertic Argiudolls 2. One or both of the following: IHDE. Other Argiudolls that have: 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. Above the argillic horizon, an albic horizon or a horizon Mollisols 205

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, or skeletans of clean silt and sand covering 50 percent or more of the faces IHDI. Other Agriudolls that have both: of peds in the upper 5 cm of the argillic horizon; and 1. Aquic conditions for some time normal years (or 3. Either: artificial drainage) either: a. Cracks within 125 cm of the mineral soil surface that a. Within 40 cm of the mineral soil surface, in horizons are 5 mm or more wide through a thickness of 30 cm or that also have redoximorphic features; or more for some time in normal years and slickensides or b. Within 75 cm of the mineral soil surface, in one or wedge-shaped aggregates in a layer 15 cm or more thick more horizons with a total thickness of 15 cm or more that that has its upper boundary within 125 cm of the mineral have one or more of the following: soil surface; or (1) A color value, moist, of 4 or more and redox b. A linear extensibility of 6.0 cm or more between the depletions with chroma of 2 or less; or mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. (2) Hue of 10YR or redder and chroma of 2 or less; Alfic Vertic Argiudolls or (3) Hue of 2.5Y or yellower and chroma of 3 or less; IHDF. Other Argiudolls that have one or both of the and following: 2. A mollic epipedon that has a texture finer than loamy 1. Cracks within 125 cm of the mineral soil surface that are 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-shaped a. 40 cm or more thick in a frigid temperature regime; or aggregates in a layer 15 cm or more thick that has its upper b. 50 cm or more thick. boundary within 125 cm of the mineral soil surface; or Aquic Pachic Agriudolls 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 finer than loamy fine sand and that is either: Vertic Argiudolls 1. 40 cm or more thick in a frigid temperature regime; or 2. 50 cm or more thick. M IHDG. Other Argiudolls that have, throughout one or more Pachic Argiudolls O horizons with a total thickness of 18 cm or more within 75 cm of L the mineral soil surface, a fine-earth fraction with both a bulk IHDK. Other Argiudolls that have aquic conditions for some density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 time in normal years (or artificial drainage) either: and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. 1. Within 40 cm of the mineral soil surface, in horizons that Andic Argiudolls also have redoximorphic features; or 2. Within 75 cm of the mineral soil surface, in one or more IHDH. Other Argiudolls that have, throughout one or more horizons with a total thickness of 15 cm or more that have horizons with a total thickness of 18 cm or more within 75 cm of one or more of the following: the mineral soil surface, one or both of the following: a. A color value, moist, of 4 or more and redox 1. More than 35 percent (by volume) fragments coarser depletions with chroma of 2 or less; or than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or b. Hue of 10YR or redder and chroma of 2 or less; or 2. A fine-earth fraction containing 30 percent or more c. Hue of 2.5Y or yellower and chroma of 3 or less. particles 0.02 to 2.0 mm in diameter; and Aquic Argiudolls a. In the 0.02 to 2.0 mm fraction, 5 percent or more IHDL. Other Argiudolls that in normal years are saturated with volcanic glass; and water in one or more layers within 100 cm of the mineral soil 1 b. [(Al plus /2 Fe, percent extracted by ammonium surface for either or both: 206 Keys to Soil Taxonomy

1. 20 or more consecutive days; or than 24 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 2. 30 or more cumulative days. its upper 100 cm. Oxyaquic Argiudolls Oxic Argiudolls IHDM. Other Argiudolls that have an argillic horizon that: IHDS. Other Argiudolls that have a calcic horizon within 100 1. Consists entirely of lamellae; or cm of the mineral soil surface. Calcic Argiudolls 2. Is a combination of two or more lamellae and one or more subhorizons with a thickness of 7.5 to 20 cm, each layer IHDT. Other Argiudolls. with an overlying eluvial horizon; or Typic Argiudolls 3. Consists of one or more subhorizons that are more than 20 cm thick, each with an overlying eluvial horizon, and above these horizons there are either: Calciudolls a. Two or more lamellae with a combined thickness of 5 Key to Subgroups cm or more (that may or may not be part of the argillic IHBA. Calciudolls that have a lithic contact within 50 cm of horizon); or the mineral soil surface. b. A combination of lamellae (that may or may not be Lithic Calciudolls part of the argillic horizon) and one or more parts of the argillic horizon 7.5 to 20 cm thick, each with an overlying IHBB. Other Calciudolls that have one or both of the eluvial horizon. following: Lamellic Argiudolls 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or IHDN. Other Argiudolls that have a sandy particle-size class more for some time in normal years and slickensides or throughout the upper 75 cm of the argillic horizon or throughout wedge-shaped aggregates in a layer 15 cm or more thick that the entire argillic horizon if it is less than 75 cm thick. has its upper boundary within 125 cm of the mineral soil Psammentic Argiudolls surface; or IHDO. Other Argiudolls that have a sandy or sandy-skeletal 2. A linear extensibility of 6.0 cm or more between the particle-size class throughout a layer extending from the mineral mineral soil surface and either a depth of 100 cm or a densic, soil surface to the top of an argillic horizon at a depth of 50 cm lithic, or paralithic contact, whichever is shallower. or more. Vertic Calciudolls Arenic Argiudolls IHBC. Other Calciudolls that have, in one or more horizons IHDP. Other Argiudolls that have an argillic horizon that, with within 75 cm of the mineral soil surface, redox depletions with increasing depth, has a clay increase of 20 percent or more chroma of 2 or less and also aquic conditions for some time in (absolute, in the fine-earth fraction) within its upper 7.5 cm. normal years (or artificial drainage). Abruptic Argiudolls Aquic Calciudolls

IHDQ. Other Argiudolls that have: IHBD. Other Calciudolls that have a slope of less than 25 percent; and either: 1. Above the argillic horizon, an albic horizon or a horizon that has color values too high for a mollic epipedon and 1. An organic-carbon content of 0.3 percent or more at a depth chroma too high for an albic horizon; or of 125 cm below the mineral soil surface; or 2. A glossic horizon, or interfingering of albic materials 2. An irregular decrease in organic-carbon content from a into the upper part of the argillic horizon, or skeletans of depth of 25 cm to a depth of 125 cm or to a lithic or paralithic clean silt and sand covering 50 percent or more of the faces contact if shallower. of peds in the upper 5 cm of the argillic horizon. Fluventic Calciudolls Alfic Argiudolls IHBE. Other Calciudolls. IHDR. Other Argiudolls that have an apparent CEC of less Typic Calciudolls Mollisols 207

Hapludolls a. 40 cm or more thick in a frigid temperature regime; or b. 50 cm or more thick. Key to Subgroups Pachic Vertic Hapludolls IHFA. Hapludolls that have a lithic contact within 50 cm of the mineral soil surface. IHFD. Other Hapludolls that have one or both of the Lithic Hapludolls following: 1. Cracks within 125 cm of the mineral soil surface that IHFB. Other Hapludolls that have both: are 5 mm or more wide through a thickness of 30 cm or 1. Aquic conditions for some time in normal years (or more for some time in normal years and slickensides or artificial drainage) either: wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil a. Within 40 cm of the mineral soil surface, in horizons surface; or that also have redoximorphic features; or 2. A linear extensibility of 6.0 cm or more between the b. Within 75 cm of the mineral soil surface, in one or mineral soil surface and either a depth of 100 cm or a densic, more horizons with a total thickness of 15 cm or more that lithic, or paralithic contact, whichever is shallower. have one or more of the following: 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 horizons with a total thickness of 18 cm or more within 75 cm of (2) Hue of 10YR or redder and chroma of 2 or less; the mineral soil surface, a fine-earth fraction with both a bulk or density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 (3) Hue of 2.5Y or yellower and chroma of 3 or less; and aluminum plus /2 iron percentages (by ammonium oxalate) and totaling more than 1.0. Andic Hapludolls 2. One or both of the following: 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 of more for some time in normal years and slickensides or the mineral soil surface, one or both of the following: wedge-shaped aggregates in a layer 15 cm or more thick 1. More than 35 percent (by volume) fragments coarser that has its upper boundary within 125 cm of the mineral than 2.0 mm, of which more than 66 percent is cinders, soil surface; or pumice, and pumicelike fragments; or M b. A linear extensibility of 6.0 cm or more between the 2. A fine-earth fraction containing 30 percent or more O mineral soil surface and either a depth of 100 cm or a particles 0.02 to 2.0 mm in diameter; and L densic, lithic, or paralithic contact, whichever is shallower. 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 equal to 30 or more. a. Cracks within 125 cm of the mineral soil surface that Vitrandic Hapludolls are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or IHFG. Other Hapludolls that have: wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral 1. Either: soil surface; or a. A frigid soil temperature regime and a mollic b. A linear extensibility of 6.0 cm or more between the epipedon 40 cm or more thick, of which less than 50 mineral soil surface and either a depth of 100 cm or a percent has a sandy or sandy-skeletal particle-size class, densic, lithic, or paralithic contact, whichever is and there is no densic or paralithic contact and no sandy shallower; and or sandy-skeletal particle-size class at a depth between 40 and 50 cm from the mineral soil surface; or 2. A mollic epipedon that has a texture finer than loamy fine sand and that is either: b. A mollic epipedon 60 cm or more thick, of which 50 208 Keys to Soil Taxonomy

percent or more of the thickness has a texture finer than 2. A slope of less than 25 percent; and either loamy fine sand; and a. An organic-carbon content of 0.3 percent or more at a 2. Either 0.3 percent or more organic carbon at a depth depth of 125 cm below the mineral soil surface; or of 125 cm below the mineral soil surface or an irregular b. An irregular decrease in organic-carbon content from decrease in organic-carbon content from a depth of 25 cm to a depth of 25 cm to a depth of 125 cm or to a densic, a depth of 125 cm or to a densic, lithic, or paralithic contact lithic, or paralithic contact if shallower. if shallower; and Fluvaquentic Hapludolls 3. A slope of 25 percent or less; and IHFJ. Other Hapludolls that have a slope of less than 25 4. In one or more horizons within 75 cm of the mineral soil percent; and either surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial 1. An organic-carbon content of 0.3 percent or more at a depth drainage). of 125 cm below the mineral soil surface; or Aquic Cumulic Hapludolls 2. An irregular decrease in organic-carbon content from a depth of 25 cm to a depth of 125 cm or to a densic, lithic, or IHFH. Other Hapludolls that have: paralithic contact if shallower. 1. Either: Fluventic Hapludolls a. A frigid soil temperature regime and a mollic IHFK. Other Hapludolls that have both: epipedon 40 cm or more thick, of which less than 50 percent has a sandy or sandy-skeletal particle-size class, 1. Aquic conditions for some time normal years (or and there is no densic or paralithic contact and no sandy artificial drainage) either: or sandy-skeletal particle-size class at a depth between 40 a. Within 40 cm of the mineral soil surface, in horizons and 50 cm from the mineral soil surface; or that also have redoximorphic features; or b. A mollic epipedon 60 cm or more thick, of which 50 b. Within 75 cm of the mineral soil surface, in one or percent or more of the thickness has a texture finer than more horizons with a total thickness of 15 cm or more that loamy fine sand; and have one or more of the following: 2. Either 0.3 percent or more organic carbon at a depth (1) A color value, moist, of 4 or more and redox of 125 cm below the mineral soil surface or an irregular depletions with chroma of 2 or less; or decrease in organic-carbon content from a depth of 25 cm to a depth of 125 cm or to a densic, lithic, or paralithic contact (2) Hue of 10YR or redder and chroma of 2 or less; if shallower; and or 3. A slope of 25 percent or less. (3) Hue of 2.5Y or yellower and chroma of 3 or less; Cumulic Hapludolls and 2. A mollic epipedon that has a texture finer than loamy IHFI. Other Hapludolls that have both: fine sand and that is either: 1. Aquic conditions for some time in normal years (or a. 40 cm or more thick in a frigid temperature regime; or artificial drainage) either: b. 50 cm or more thick. a. Within 40 cm of the mineral soil surface, in horizons Aquic Pachic Hapludolls that also have redoximorphic features; or b. Within 75 cm of the mineral soil surface, in one or IHFL. Other Hapludolls that have a mollic epipedon that has a more horizons with a total thickness of 15 cm or more that texture finer than loamy fine sand and that is either: have one or more of the following: 1. 40 cm or more thick in a frigid temperature regime; or (1) A color value, moist, of 4 or more and redox depletions with chroma of 2 or less; or 2. 50 cm or more thick. Pachic Hapludolls (2) Hue of 10YR or redder and chroma of 2 or less; or (3) Hue of 2.5Y or yellower and chroma of 3 or less; IHFM. Other Hapludolls that have aquic conditions for some and time in normal years (or artificial drainage) either: Mollisols 209

1. Within 40 cm of the mineral soil surface, in horizons that Natrudolls also have redoximorphic features; or Key to Subgroups 2. Within 75 cm of the mineral soil surface, in one or more horizons with a total thickness of 15 cm or more that have IHAA. Natrudolls that have a petrocalcic horizon that has its one or more of the following: upper boundary within 100 cm of the mineral soil surface. Petrocalcic Natrudolls a. A color value, moist, of 4 or more and redox depletions with chroma of 2 or less; or IHAB. Other Natrudolls that have both: b. Hue of 10YR or redder and chroma of 2 or less; or 1. Visible crystals of gypsum and/or more soluble salts c. Hue of 2.5Y or yellower and chroma of 3 or less. within 40 cm of the mineral soil surface; and Aquic Hapludolls 2. One or both of the following: a. Cracks within 125 cm of the mineral soil surface that IHFN. Other Hapludolls that in normal years are saturated are 5 mm or more wide through a thickness of 30 cm or with water in one or more layers within 100 cm of the mineral more for some time in normal years and slickensides or soil surface for either or both: wedge-shaped aggregates in a layer 15 cm or more thick 1. 20 or more consecutive days; or that has its upper boundary within 125 cm of the mineral soil surface; or 2. 30 or more cumulative days. Oxyaquic Hapludolls b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a IHFO. Other Hapludolls that have both: densic, lithic, or paralithic contact, whichever is shallower. Leptic Vertic Natrudolls 1. A mollic epipedon 60 cm or more thick that has a texture finer than loamy fine sand and contains 50 percent or more IHAC. Other Natrudolls that have: (by volume) wormholes, wormcasts, or filled animal burrows either below an Ap horizon or below a depth of 18 cm from 1. A glossic horizon or interfingering of albic materials into the mineral soil surface; and the natric horizon; and 2. Either do not have a cambic horizon and do not, in the 2. One or both of the following: lower part of the mollic epipedon, meet all of the a. Cracks within 125 cm of the mineral soil surface that requirements for a cambic horizon, except for the color are 5 mm or more wide through a thickness of 30 cm or requirements, or have carbonates throughout either the more for some time in normal years and slickensides or cambic horizon or the lower part of the mollic epipedon. M wedge-shaped aggregates in a layer 15 cm or more thick Vermic Hapludolls O that has its upper boundary within 125 cm of the mineral L soil surface; or IHFP. Other Hapludolls that have a calcic horizon within 100 cm of the mineral soil surface. b. A linear extensibility of 6.0 cm or more between Calcic Hapludolls the mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is IHFQ. Other Hapludolls that either: shallower. Glossic Vertic Natrudolls 1. Do not have a cambic horizon and do not, in any part of the mollic epipedon below 25 cm from the mineral soil IHAD. Other Natrudolls that have one or both of the surface, meet all of the requirements for a cambic horizon, following: except for the color requirements; or 1. Cracks within 125 cm of the mineral soil surface that are 2. Have free carbonates throughout the cambic horizon or 5 mm or more wide through a thickness of 30 cm or more for in all parts of the mollic epipedon below a depth of 25 cm some time in normal years and slickensides or wedge-shaped from the mineral soil surface. aggregates in a layer 15 cm or more thick that has its upper Entic Hapludolls boundary within 125 cm of the mineral soil surface; or IHFR. Other Hapludolls. 2. A linear extensibility of 6.0 cm or more between Typic Hapludolls the mineral soil surface and either a depth of 100 cm 210 Keys to Soil Taxonomy

or a densic, lithic, or paralithic contact, whichever is (3) Hue of 2.5Y or yellower and chroma of 3 or less; shallower. and Vertic Natrudolls 2. A mollic epipedon that has a texture 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 temperature regime; or surface. b. 50 cm or more thick. Leptic Natrudolls Aquic Pachic Paleudolls IHAF. Other Natrudolls that have a glossic horizon or IHCD. Other Paleudolls that have a mollic epipedon that has a interfingering of albic materials into the natric horizon. texture finer than loamy fine sand and that is 50 cm or more thick. Glossic Natrudolls Pachic Paleudolls IHAG. Other Natrudolls that have a calcic horizon within 100 IHCE. Other Paleudolls that have, in one or more subhorizons cm of the mineral soil surface. within 75 cm of the mineral soil surface, redox depletions with Calcic Natrudolls chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). IHAH. Other Natrudolls. Aquic Paleudolls Typic Natrudolls IHCF. Other Paleudolls that in normal years are saturated with Paleudolls water in one or more layers within 100 cm of the mineral soil surface for either or both: Key to Subgroups 1. 20 or more consecutive days; or IHCA. Paleudolls that have one or both of the following: 2. 30 or more cumulative days. 1. Cracks within 125 cm of the mineral soil surface that are Oxyaquic Paleudolls 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge-shaped IHCG. Other Paleudolls that: aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil surface; or 1. Have a calcic horizon that has its upper boundary within 100 cm of the mineral soil surface; and 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, 2. In all parts above the calcic horizon, after the materials lithic, or paralithic contact, whichever is shallower. between the soil surface and a depth of 18 cm have been Vertic Paleudolls mixed, either are calcareous or have a texture of loamy fine sand or coarser. IHCB. Other Paleudolls that have a petrocalcic horizon within Calcic Paleudolls 150 cm of the mineral soil surface. Petrocalcic Paleudolls IHCH. Other Paleudolls. Typic Paleudolls IHCC. Other Paleudolls that have both: 1. Aquic conditions for some time normal years (or Vermudolls artificial drainage) either: Key to Subgroups a. Within 40 cm of the mineral soil surface, in horizons IHEA. Vermudolls that have a lithic contact within 50 cm of that also have redoximorphic features; or the mineral soil surface. b. Within 75 cm of the mineral soil surface, in one or Lithic Vermudolls more horizons with a total thickness of 15 cm or more that have one or more of the following: IHEB. Other Vermudolls that have a mollic epipedon less than 75 cm thick. (1) A color value, moist, of 4 or more and redox Haplic Vermudolls depletions with chroma of 2 or less; or (2) Hue of 10YR or redder and chroma of 2 or less; IHEC. Other Vermudolls. or Typic Vermudolls Mollisols 211

Ustolls 1. Either below an Ap horizon or below a depth of 18 cm from the mineral soil surface, contains 50 percent or more Key to Great Groups (by volume) wormholes, wormcasts, or filled animal burrows; and IGA. Ustolls that have a duripan that has its upper boundary 2. Either rests on a lithic contact or has a transition zone to within 100 cm of the mineral soil surface. the underlying horizon in which 25 percent or more of the Durustolls, p. 216 soil volume consists of discrete wormholes, wormcasts, or animal burrows filled with material from the mollic epipedon IGB. Other Ustolls that have a natric horizon. and from the underlying horizon. Natrustolls, p. 222 Vermustolls, p. 226 IGC. Other Ustolls that: IGG. Other Ustolls. 1. Have either a calcic or gypsic horizon that has its upper Haplustolls, p. 217 boundary within 100 cm of the mineral soil surface or a petrocalcic horizon that has its upper boundary 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: 3. In all parts above the calcic, gypsic, or petrocalcic 1. A lithic contact within 50 cm of the mineral soil surface; horizon, after the materials between the soil surface and a and depth of 18 cm have been mixed, either are calcareous or 2. When neither irrigated nor fallowed to store moisture, have a texture of loamy fine sand or coarser. have one of the following: Calciustolls, p. 215 a. A frigid temperature regime and a moisture control IGD. Other Ustolls that have either: section that in normal years is dry in all parts for four- tenths or more of the cumulative days per year when the 1. A petrocalcic horizon that has its upper boundary within soil temperature at a depth of 50 cm below the soil surface 150 cm of the mineral soil surface; or 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 M (noncarbonate clay) within 150 cm of the mineral soil days per year when the soil temperature at a depth of 50 O surface (and there is no densic, lithic, or paralithic contact cm below the soil surface is higher than 5 oC; or L 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 (1) Is moist in some or all parts for fewer than 90 of 7.5YR or redder or chroma of 6 or more, or consecutive days per year when the soil temperature at both; or a depth of 50 cm below the soil surface is higher than 8 oC; and b. 35 percent or more clay in its upper part and a clay increase either of 20 percent or more (absolute) within a (2) Is dry in some or all parts for six-tenths or more vertical distance of 7.5 cm or of 15 percent or more of the cumulative days per year when the soil (absolute) within a vertical distance of 2.5 cm, in the fine- temperature at a depth of 50 cm below the soil surface earth fraction (and there is no densic, lithic, or paralithic is higher than 5 oC. contact within 50 cm of the mineral soil surface). Aridic Lithic Argiustolls Paleustolls, p. 224 IGEB. Other Argiustolls that have both: IGE. Other Ustolls that have an argillic horizon. 1. A lithic contact within 50 cm of the mineral soil surface; Argiustolls, p. 211 and IGF. Other Ustolls that have a mollic epipedon that: 2. Above the argillic horizon, either an albic horizon or a 212 Keys to Soil Taxonomy

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: (1) Is moist in some or all parts for fewer than 90 IGEC. Other Argiustolls that have a lithic contact within 50 consecutive days per year when the soil temperature at cm of the mineral soil surface. a depth of 50 cm below the soil surface is higher than Lithic Argiustolls 8 oC; and (2) Is dry in some or all parts for six-tenths or more IGED. Other Argiustolls that have both: of the cumulative days per year when the soil 1. In one or more horizons within 100 cm of the mineral temperature at a depth of 50 cm below the soil surface soil surface, redox depletions with a chroma of 2 or less and is higher than 5 oC. also aquic conditions for some time in normal years (or Torrertic Argiustolls artificial drainage); and: IGEF. Other Argiustolls that have all of the following: 2. One or both of the following: 1. A mollic epipedon that has a texture finer than loamy a. Cracks within 125 cm of the mineral soil surface that fine sand and that is either: are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or a. 40 cm or more thick in a frigid temperature regime; or wedge-shaped aggregates in a layer 15 cm or more thick b. 50 cm or more thick; and. that has its upper boundary within 125 cm of the mineral soil surface; or 2. 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 mineral soil surface and either a depth of 100 cm or a 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 Aquertic Argiustolls wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral IGEE. Other Argiustolls that have both: soil surface; or 1. One or both 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. Cracks within 125 cm of the mineral soil surface that densic, lithic, or paralithic contact, whichever is are 5 mm or more wide through a thickness of 30 cm or shallower; and more for some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick 3. When neither irrigated nor fallowed to store moisture, that has its upper boundary within 125 cm of the mineral either: soil surface; or a. A mesic or thermic temperature regime and a moisture b. A linear extensibility of 6.0 cm or more between the control section that in normal years is dry in some part for mineral soil surface and either a depth of 100 cm or a four-tenths or less of the cumulative days per year when densic, lithic, or paralithic contact, whichever is the soil temperature at a depth of 50 cm below the soil shallower; and surface is higher than 5 oC; or 2. When neither irrigated nor fallowed to store moisture, b. A hyperthermic, isomesic, or warmer iso soil have one of the following: temperature regime and a moisture control section that in normal years is dry in some or all parts for fewer than 120 a. A frigid temperature regime and a moisture control cumulative days per year when the soil temperature at a section that in normal years is dry in all parts for four- depth of 50 cm below the soil surface is higher than 8 oC. tenths or more of the cumulative days per year when the Pachic Udertic Argiustolls soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or IGEG. Other Argiustolls that have both: b. A mesic or thermic soil temperature regime and a 1. One or both of the following: moisture control section that in normal years is dry in some or all parts for six-tenths or more of the cumulative a. Cracks within 125 cm of the mineral soil surface that days per year when the soil temperature at a depth of 50 are 5 mm or more wide through a thickness of 30 cm or cm below the soil surface is higher than 5 oC; or more for some time in normal years and slickensides or Mollisols 213

wedge-shaped aggregates in a layer 15 cm or more thick mineral soil surface and either a depth of 100 cm or a densic, that has its upper boundary within 125 cm of the mineral lithic, or paralithic contact, whichever is shallower. soil surface; or Vertic Argiustolls b. A linear extensibility of 6.0 cm or more between the IGEJ. Other Argiustolls 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 of densic, lithic, or paralithic contact, whichever is the mineral soil surface, a fine-earth fraction with both a bulk shallower; and density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 2. When neither irrigated nor fallowed to store moisture, and Al plus /2 Fe percentages (by ammonium oxalate) totaling either: more than 1.0. Andic Argiustolls a. 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 IGEK. Other Argiustolls that have both: per year when the soil temperature at a depth of 50 cm 1. When neither irrigated nor fallowed to store moisture, below the soil surface is higher than 5 oC; or one of the following: b. A hyperthermic, isomesic, or warmer iso soil a. A frigid 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 cumulative days per year when the soil temperature at a soil temperature at a depth of 50 cm below the soil surface depth of 50 cm below the soil surface is higher than 8 oC. is higher than 5 oC; or Udertic Argiustolls b. A mesic or thermic soil temperature regime and a IGEH. Other Argiustolls that have both: moisture control section that in normal years is dry in some or all parts for six-tenths or more of the cumulative 1. One or both of the following: 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 c. A hyperthermic, isomesic, or warmer iso soil more for some time in normal years and slickensides or temperature regime and a moisture control section that in wedge-shaped aggregates in a layer 15 cm or more thick normal years: that has its upper boundary within 125 cm of the mineral soil surface; or (1) Is moist in some or all parts for fewer than 90 consecutive days per year when the soil temperature at b. A linear extensibility of 6.0 cm or more between the M a depth of 50 cm below the soil surface is higher than mineral soil surface and either a depth of 100 cm or a O 8 oC; and densic, lithic, or paralithic contact, whichever is L shallower; and (2) Is dry in some or all parts for six-tenths or more of the cumulative days per year when the soil 2. A mollic epipedon that has a texture finer than loamy temperature at a depth of 50 cm below the soil surface fine sand and that is either: is higher than 5 oC; and a. 40 cm or more thick in a frigid temperature regime; 2. Throughout one or more horizons with a total thickness or of 18 cm or more within 75 cm of the mineral soil surface, b. 50 cm or more thick. one or both of the following: Pachic Vertic Argiustolls a. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, IGEI. Other Argiustolls 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 b. A fine-earth fraction containing 30 percent or more 5 mm or more wide through a thickness of 30 cm or more for particles 0.02 to 2.0 mm in diameter; and some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick that has its upper (1) In the 0.02 to 2.0 mm fraction, 5 percent or more boundary within 125 cm of the mineral soil surface; or volcanic glass; and

1 2. A linear extensibility of 6.0 cm or more between the (2) [(Al plus /2 Fe, percent extracted by ammonium 214 Keys to Soil Taxonomy

oxalate) times 60] plus the volcanic glass (percent) is IGEQ. Other Argiustolls that have both: equal to 30 or more. 1. A calcic horizon with its upper boundary within 100 cm Vitritorrandic Argiustolls of the mineral soil surface; and IGEL. Other Argiustolls that have, throughout one or 2. When neither irrigated nor fallowed to store moisture, more horizons with a total thickness of 18 cm or more one of the following: within 75 cm of the mineral soil surface, one or both of the a. A frigid temperature regime and a moisture control following: section that in normal years is dry in all parts for four- 1. More than 35 percent (by volume) fragments coarser tenths or more of the cumulative days per year when the than 2.0 mm, of which more than 66 percent is cinders, soil temperature at a depth of 50 cm below the soil surface pumice, and pumicelike fragments; or 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 some part for six-tenths or more of the cumulative days a. In the 0.02 to 2.0 mm fraction, 5 percent or more per year when the soil temperature at a depth of 50 cm volcanic glass; and below the soil surface is higher than 5 oC; or 1 b. [(Al plus /2 Fe, percent extracted by ammonium c. A hyperthermic, isomesic, or warmer iso soil oxalate) times 60] plus the volcanic glass (percent) is temperature regime and a moisture control section that in equal to 30 or more. normal years: Vitrandic Argiustolls (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). (2) Is dry in some part for six-tenths or more of the Aquic Argiustolls cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than IGEN. Other Argiustolls that in normal years are saturated 5 oC. with water in one or more layers within 100 cm of the mineral Calcidic Argiustolls soil surface for either or both: 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 temperature regime and a moisture control section that in normal years is dry in all parts for four-tenths IGEO. Other Argiustolls that have a mollic epipedon that has a or more of the cumulative days per year when the soil texture 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 temperature regime; or higher than 5 oC; or 2. 50 cm or more thick. 2. A mesic or thermic soil temperature regime and a Pachic Argiustolls moisture control section that in normal years is dry in some or all parts for six-tenths or more of the cumulative days per IGEP. Other Argiustolls that have either: year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or 1. Above the argillic horizon, an albic horizon or a horizon that has color values too high for a mollic epipedon and 3. A hyperthermic, isomesic, or warmer iso soil chroma too high for an albic horizon; or temperature regime and a moisture control section that in normal years: 2. A glossic horizon, or interfingering of albic materials into the upper part of the argillic horizon, or skeletans of a. Is moist in some or all parts for fewer than 90 clean silt and sand covering 50 percent or more of the faces consecutive days per year when the soil temperature at a of peds in the upper 5 cm of the argillic horizon. depth of 50 cm below the soil surface is higher than 8 oC; Alfic Argiustolls and Mollisols 215

b. Is dry in some or all parts for six-tenths or more of the that has its upper boundary within 125 cm of the mineral cumulative days per year when the soil temperature at a soil surface; or depth of 50 cm below the soil surface is higher than b. A linear extensibility of 6.0 cm or more between the 5 oC. mineral soil surface and either a depth of 100 cm or a Aridic Argiustolls densic, lithic, or paralithic contact, whichever is shallower; and IGES. Other Argiustolls that, when neither irrigated nor fallowed to store moisture, have either: 2. When neither irrigated nor fallowed to store moisture, one of the following: 1. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in some a. A frigid temperature regime and a moisture control part for four-tenths or less of the cumulative days per year section that in normal years is dry in all parts for four- when the soil temperature at a depth of 50 cm below the soil tenths or more of the cumulative days per year when the surface is higher than 5 oC; or soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or 2. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in b. 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 cumulative days per year when the soil temperature at a depth some or all parts for six-tenths or more of the cumulative of 50 cm below the soil surface is higher than 8 oC. days per year when the soil temperature at a depth of 50 Udic Argiustolls cm below the soil surface is higher than 5 oC; or c. A hyperthermic, isomesic, or warmer iso soil IGET. Other Argiustolls that have a brittle horizon that is temperature regime and a moisture control section that in within 100 cm of the mineral soil surface, is 15 cm or more normal years: thick, and has either some opal coatings or 20 percent or more (by volume) durinodes. (1) Is moist in some or all parts for fewer than 90 Duric Argiustolls consecutive days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than IGEU. Other Argiustolls. 8 oC; and Typic Argiustolls (2) Is dry in some or all parts for six-tenths or more of the cumulative days per year when the soil Calciustolls temperature at a depth of 50 cm below the soil surface is higher than 5 oC. Key to Subgroups Torrertic Calciustolls M O IGCA. Calciustolls that have a salic horizon that has its upper IGCE. Other Calciustolls that have both: L boundary within 75 cm of the mineral soil surface. Salidic Calciustolls 1. One or both of the following: a. Cracks within 125 cm of the mineral soil surface that IGCB. Other Calciustolls that have a petrocalcic horizon and a are 5 mm or more wide through a thickness of 30 cm or lithic contact within 50 cm of the mineral soil surface. more for some time in normal years and slickensides or Lithic Petrocalcic Calciustolls wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral IGCC. Other Calciustolls that have a lithic contact within 50 soil surface; or cm of the mineral soil surface. Lithic Calciustolls b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a IGCD. Other Calciustolls that have both: densic, lithic, or paralithic contact, whichever is shallower; and 1. 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 more for some time in normal years and slickensides or a. A mesic or thermic soil temperature regime and a wedge-shaped aggregates in a layer 15 cm or more thick moisture control section that in normal years is dry in 216 Keys to Soil Taxonomy

some part for four-tenths or less of the cumulative days IGCL. Other Calciustolls that, when neither irrigated nor per year when the soil temperature at a depth of 50 cm fallowed to store moisture, have one of the following: below the soil surface is higher than 5 oC; or 1. A frigid temperature regime and a moisture control b. A hyperthermic, isomesic, or warmer iso soil section that in normal years is dry in all parts for four-tenths temperature regime and a moisture control section that in or more of the cumulative days per year when the soil normal years is dry in some or all parts for fewer than 120 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 8 oC. 2. A mesic or thermic soil temperature regime and a Udertic Calciustolls moisture control section that in normal years is dry in some or all parts for six-tenths or more of the cumulative days per IGCF. Other Calciustolls that have one or both of the year when the soil temperature at a depth of 50 cm below the following: soil surface is higher than 5 oC; or 1. Cracks within 125 cm of the mineral soil surface that are 3. A hyperthermic, isomesic, or warmer iso soil 5 mm or more wide through a thickness of 30 cm or more for temperature regime and a moisture control section that in some time in normal years and slickensides or wedge-shaped normal years: aggregates in a layer 15 cm or more thick that has its upper a. Is moist in some or all parts for fewer than 90 boundary within 125 cm of the mineral soil surface; or consecutive days per year when the soil temperature at a 2. A linear extensibility of 6.0 cm or more between depth of 50 cm below the soil surface is higher than 8 oC; the mineral soil surface and either a depth of 100 cm and or a densic, lithic, or paralithic contact, whichever is b. Is dry in some or all parts for six-tenths or more of shallower. the cumulative days per year when the soil temperature at Vertic Calciustolls a depth of 50 cm below the soil surface is higher than 5 oC. IGCG. Other Calciustolls that have a petrocalcic horizon that Aridic Calciustolls has its upper boundary within 100 cm of the mineral soil surface. IGCM. Other Calciustolls that, when neither irrigated nor Petrocalcic Calciustolls fallowed to store moisture, have either: IGCH. Other Calciustolls that have a gypsic horizon with its 1. A mesic or thermic soil temperature regime and a upper boundary within 100 cm of the mineral soil surface. moisture control section that in normal years is dry in some Gypsic Calciustolls or all parts for four-tenths or less of the consecutive days per year when the soil temperature at a depth of 50 cm below the IGCI. Other Calciustolls that have, in one or more horizons soil surface is higher than 5 oC; or within 75 cm of the mineral soil surface, redox concentrations 2. A hyperthermic, isomesic, or warmer iso soil and also aquic conditions for some time in normal years (or temperature regime and a moisture control section that in artificial drainage). normal years is dry in some or all parts for fewer than 120 Aquic Calciustolls cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 8 oC. IGCJ. Other Calciustolls that in normal years are saturated Udic Calciustolls with water in one or more layers within 100 cm of the mineral soil surface for either or both: IGCN. Other Calciustolls. Typic Calciustolls 1. 20 or more consecutive days; or 2. 30 or more cumulative days. Durustolls Oxyaquic Calciustolls Key to Subgroups IGCK. Other Calciustolls that have a mollic epipedon that has IGAA. Durustolls that have a natric horizon above the a texture finer than loamy fine sand and that is either: duripan. 1. 40 cm or more thick in a frigid temperature regime; or Natric Durustolls IGAB. Other Durustolls that: 2. 50 cm or more thick. Pachic Calciustolls 1. Do not have an argillic horizon above the duripan; and Mollisols 217

2. Have an aridic moisture regime that borders on ustic. cumulative days per year when the temperature at a Haploduridic Durustolls depth of 50 cm below the soil surface is higher than 5 oC; and IGAC. Other Durustolls that have an aridic moisture regime 2. A lithic contact within 50 cm of the mineral soil surface. that borders on ustic. Aridic Lithic Haplustolls Argiduridic Durustolls IGGD. Other Haplustolls that have a lithic contact within 50 IGAD. Other Durustolls that do not have an argillic horizon cm of the mineral soil surface. above the duripan. Lithic Haplustolls Entic Durustolls IGGE. Other Haplustolls that have both: IGAE. Other Durustolls that have a duripan that is strongly cemented or less cemented in all subhorizons. 1. In one or more horizons within 100 cm of the mineral Haplic Durustolls soil surface, redox depletions with a chroma of 2 or less and also aquic conditions for some time in normal years (or IGAF. Other Durustolls. artificial drainage); and: Typic Durustolls 2. One or both of the following: Haplustolls 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 aggregates in a layer 15 cm or more thick IGGA. Haplustolls that have a salic horizon that has its upper that has its upper boundary within 125 cm of the mineral boundary within 75 cm of the mineral soil surface. soil surface; or Salidic Haplustolls b. A linear extensibility of 6.0 cm or more between the IGGB. Other Haplustolls that have, in part of each pedon, a mineral soil surface and either a depth of 100 cm or a lithic contact within 50 cm of the mineral soil surface. densic, lithic, or paralithic contact, whichever is shallower. Ruptic-Lithic Haplustolls Aquertic Haplustolls

IGGC. Other Haplustolls that have both: IGGF. Other Haplustolls that have both: 1. When neither irrigated nor fallowed to store moisture, 1. One or both of the following: one of the following: a. Cracks within 125 cm of the mineral soil surface that M a. A frigid soil temperature regime and a moisture are 5 mm or more wide through a thickness of 30 cm or O control section that in normal years is dry in all parts for more for some time in normal years and slickensides or L four-tenths or more of the cumulative days per year when wedge-shaped aggregates in a layer 15 cm or more thick the temperature at a depth of 50 cm below the soil surface that has its upper boundary within 125 cm of the mineral is higher than 5 oC; or soil surface; or b. A mesic or thermic soil temperature regime and a b. A linear extensibility of 6.0 cm or more between the moisture control section that, in 6 normal years, is dry in mineral soil surface and either a depth of 100 cm or a some part for six-tenths or more of the cumulative days densic, lithic, or paralithic contact, whichever is per year when the soil temperature at a depth of 50 cm shallower; and below the soil surface is higher than 5 oC; or 2. When neither irrigated nor fallowed to store moisture, c. A hyperthermic, isomesic, or warmer iso soil one of the following: temperature regime and a moisture control section that, in a. A frigid temperature regime and a moisture control normal years: section that in normal years is dry in all parts for four- (1) Is moist in some or all parts for fewer than 90 tenths or more of the cumulative days per year when the consecutive days per year when the temperature at a soil temperature at a depth of 50 cm below the soil surface depth of 50 cm below the soil surface is higher than is higher than 5 oC; or 8 oC; and b. A mesic or thermic soil temperature regime and a (2) Is dry in some part for six-tenths or more of the moisture control section that in normal years is dry in 218 Keys to Soil Taxonomy

some or all parts for six-tenths or more of the cumulative 1. One or both of the following: 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 c. A hyperthermic, isomesic, or warmer iso soil more for some time in normal years and slickensides or temperature regime and a moisture control section that in wedge-shaped aggregates in a layer 15 cm or more thick normal years: that has its upper boundary within 125 cm of the mineral soil surface; or (1) Is moist in some or all parts for fewer than 90 consecutive days per year when the soil temperature at b. A linear extensibility of 6.0 cm or more between the a depth of 50 cm below the soil surface is higher than mineral soil surface and either a depth of 100 cm or a 8 oC; and densic, lithic, or paralithic contact, whichever is shallower; and (2) Is dry in some or all parts for six-tenths or 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 either: 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 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 a. 40 cm or more thick in a frigid temperature regime; or in normal years is dry in some or all parts for fewer than 120 cumulative days per year when the soil temperature b. 50 cm or more thick. at a depth of 50 cm below the soil surface is higher than 2. One or both of the following: 8 oC. Udertic Haplustolls a. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or IGGI. Other Haplustolls that have both: more for some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick 1. A mollic epipedon that has a texture finer than loamy that has its upper boundary within 125 cm of the mineral fine sand and that is either: soil surface; or a. 40 cm or more thick in a frigid temperature regime; or b. A linear extensibility of 6.0 cm or more between the b. 50 cm or more thick; and mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is 2. One or both of the following: shallower; and a. Cracks within 125 cm of the mineral soil surface that 3. When neither irrigated nor fallowed to store moisture, are 5 mm or more wide through a thickness of 30 cm or either: more for some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick a. A mesic or thermic soil temperature regime and a that has its upper boundary within 125 cm of the mineral moisture control section that in normal years is dry in soil surface; or some part for four-tenths or less of the cumulative days per year when the soil temperature at a depth of 50 cm b. A linear extensibility of 6.0 cm or more between the below the soil surface is 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. b. A hyperthermic, isomesic, or warmer iso soil Pachic Vertic Haplustolls temperature regime and a moisture control section that in normal years is dry in some or all parts for fewer than 120 IGGJ. Other Haplustolls that have one or both of the cumulative days per year when the soil temperature at a following: depth of 50 cm below the soil surface is higher than 8 oC. Pachic Udertic Haplustolls 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 IGGH. Other Haplustolls that have both: for some time in normal years and slickensides or wedge- Mollisols 219

shaped aggregates in a layer 15 cm or more thick that has its IGGM. Other Haplustolls that have, throughout one or more upper boundary within 125 cm of the mineral soil surface; or 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 2. A linear extensibility of 6.0 cm or more between the density of 1.0 g/cm3 or less, measured at 33 kPa water retention, mineral soil surface and either a depth of 100 cm or a densic, 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling lithic, or paralithic contact, whichever is shallower. more than 1.0. Vertic Haplustolls Andic Haplustolls IGGN. Other Haplustolls that have both: IGGK. Other Haplustolls that have both: 1. When neither irrigated nor fallowed to store moisture, 1. When neither irrigated nor fallowed to store moisture, one of the following: one of the following: a. A frigid temperature regime and a moisture control a. A frigid temperature regime and a moisture control section that in normal years is dry in all parts for four- section that in normal years is dry in all parts for four- tenths or more of the cumulative days per year when the tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or is higher than 5 oC; or b. 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 moisture control section that in normal years is dry in some part for six-tenths or more of the cumulative days some part for six-tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or below the soil surface is higher than 5 oC; or c. 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 in normal years: normal years remains moist in some or all parts for fewer than 90 consecutive days per year when the soil (1) Is moist in some or all parts for fewer than 90 temperature at a depth of 50 cm below the soil surface is consecutive days per year when the soil temperature at higher than 8 oC; and a depth of 50 cm below the soil surface is higher than 8 oC; and 2. An apparent CEC (by 1N NH4OAc pH 7) of less than 24 cmol(+)/kg clay in 50 percent or more of the (2) Is dry in some or all parts for six-tenths or more soil volume between a depth of 25 cm from the mineral of the cumulative days per year when the soil soil surface and either a depth of 100 cm or a densic, temperature at a depth of 50 cm below the soil surface M lithic, or paralithic contact if shallower. (If the ratio of is higher than 5 oC; and O [percent water retained at 1500 kPa tension minus percent 2. Throughout one or more horizons with a total thickness L organic carbon] to the percentage of measured clay is 0.6 or of 18 cm or more within 75 cm of the mineral soil surface, more, then the percentage of clay is considered to equal one or both of the following: either the measured percentage of clay or three times [percent water retained at 1500 kPa tension minus percent organic a. More than 35 percent (by volume) fragments coarser carbon], whichever value is higher, but no more than 100.) than 2.0 mm, of which more than 66 percent is cinders, Torroxic Haplustolls pumice, and pumicelike fragments; or b. A fine-earth fraction containing 30 percent or more IGGL. Other Haplustolls that have an apparent CEC (by particles 0.02 to 2.0 mm in diameter; and 1N NH OAc pH 7) of less than 24 cmol(+)/kg clay in 50 percent 4 (1) In the 0.02 to 2.0 mm fraction, 5 percent or more or more of the soil volume between a depth of 25 cm from the volcanic glass; and mineral soil surface and either a depth of 100 cm or a densic, 1 lithic, or paralithic contact if shallower. (If the ratio of [percent (2) [(Al plus /2 Fe, percent extracted by ammonium water retained at 1500 kPa tension minus percent organic oxalate) times 60] plus the volcanic glass (percent) is carbon] to the percentage of measured clay is 0.6 or more, then equal to 30 or more. the percentage of clay is considered to equal either the measured Vitritorrandic Haplustolls percentage of clay or three times [percent water retained at 1500 kPa tension minus percent organic carbon], whichever value is IGGO. Other Haplustolls that have, throughout one or more higher, but no more than 100.) horizons with a total thickness of 18 cm or more within 75 cm of Oxic Haplustolls the mineral soil surface, one or both of the following: 220 Keys to Soil Taxonomy

1. More than 35 percent (by volume) fragments coarser 3. A slope of less than 25 percent. than 2.0 mm, of which more than 66 percent is cinders, Cumulic Haplustolls pumice, and pumicelike fragments; or 2. A fine-earth fraction containing 30 percent or more IGGR. Other Haplustolls that have anthraquic conditions. particles 0.02 to 2.0 mm in diameter; and Anthraquic Haplustolls a. In the 0.02 to 2.0 mm fraction, 5 percent or more IGGS. Other Haplustolls that have both: volcanic glass; and

1 1. In one or more horizons within 100 cm of the mineral b. [(Al plus /2 Fe, percent extracted by ammonium soil surface, redox depletions with chroma of 2 or less and oxalate) times 60] plus the volcanic glass (percent) is also aquic conditions for some time in normal years (or equal to 30 or more. artificial drainage); and Vitrandic Haplustolls 2. A slope of less than 25 percent; and either IGGP. Other Haplustolls that have: a. An organic-carbon content of 0.3 percent or more at a depth of 125 cm below the mineral soil surface; or 1. Either: b. An irregular decrease in organic-carbon content from a. A frigid soil temperature regime and a mollic a depth of 25 cm to a depth of 125 cm or to a densic, epipedon 40 cm or more thick, of which less than 50 lithic, or paralithic contact if shallower. percent has a sandy or sandy-skeletal particle-size class, Fluvaquentic Haplustolls and there is no densic or paralithic contact and no sandy or sandy-skeletal particle-size class at a depth between 40 IGGT. Other Haplustolls that have, in one or more horizons and 50 cm from the mineral soil surface; or within 100 cm of the mineral soil surface, redox depletions b. A mollic epipedon that is 50 cm or more thick and has with chroma of 2 or less and also aquic conditions for some a texture finer than loamy fine sand; and time in most years (or artificial drainage). Aquic Haplustolls 2. An irregular decrease in organic-carbon content from a depth of 25 cm below the mineral soil surface to a depth of IGGU. Other Haplustolls that have a mollic epipedon that has 125 cm or to a densic, lithic, or paralithic contact if a texture finer than loamy fine sand and that is either: shallower; and 1. 40 cm or more thick in a frigid temperature regime; or 3. A slope of less than 25 percent; and 2. 50 cm or more thick. 4. In one or more horizons within 100 cm of the mineral Pachic Haplustolls soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or IGGV. Other Haplustolls that in normal years are saturated artificial drainage). with water in one or more layers within 100 cm of the mineral Aquic Cumulic Haplustolls soil surface for either or both: IGGQ. Other Haplustolls that have: 1. 20 or more consecutive days; or 1. Either: 2. 30 or more cumulative days. Oxyaquic Haplustolls a. A frigid soil temperature regime and a mollic epipedon 40 cm or more thick, of which less than 50 IGGW. Other Haplustolls that have both: percent has a sandy or sandy-skeletal particle-size class, and there is no densic or paralithic contact and no sandy 1. When neither irrigated nor fallowed to store moisture, or sandy-skeletal particle-size class at a depth between 40 one of the following: and 50 cm from the mineral soil surface; or a. A frigid temperature regime and a moisture control b. A mollic epipedon that is 50 cm or more thick and has section that in normal years is dry in all parts for four- a texture finer than loamy fine sand; and tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface 2. An irregular decrease in organic-carbon content from a is higher than 5 oC; or depth of 25 cm below the mineral soil surface to a depth of 125 cm or to a densic, lithic, or paralithic contact if b. A mesic or thermic soil temperature regime and a shallower; and moisture control section that in normal years is dry in Mollisols 221

some part for six-tenths or more of the cumulative days 2. Either: per year when the soil temperature at a depth of 50 cm a. Do not have a cambic horizon and do not, in any part below the soil surface is higher than 5 oC; or of the mollic epipedon below 25 cm from the mineral soil c. A hyperthermic, isomesic, or warmer iso soil surface, meet all of the requirements for a cambic horizon temperature regime and a moisture control section that in except color; 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 Torriorthentic Haplustolls 8 oC; and IGGY. Other Haplustolls that, when neither irrigated nor (2) Is dry in some or all parts for six-tenths or more fallowed to store moisture, have one of the following: of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface 1. A frigid temperature regime and a moisture control is higher than 5 oC; and section that in normal years is dry in all parts for four-tenths or more of the cumulative days per year when the soil 2. A slope of less than 25 percent; and either temperature at a depth of 50 cm below the soil surface is a. An organic-carbon content of 0.3 percent or more at a higher than 5 oC; or depth of 125 cm below the mineral soil surface; or 2. A mesic or thermic soil temperature regime and a b. An irregular decrease in organic-carbon content from moisture control section that in normal years is dry in some a depth of 25 cm to a depth of 125 cm or to a densic, part for six-tenths or more of the cumulative days per year lithic, or paralithic contact if shallower. when the soil temperature at a depth of 50 cm below the soil Torrifluventic Haplustolls surface is higher than 5 oC; or 3. A hyperthermic, isomesic, or warmer iso soil IGGX. Other Haplustolls that: temperature regime and a moisture control section that in normal years: 1. When neither irrigated nor fallowed to store moisture, have one of the following: a. Is moist in some or all parts for fewer than 90 consecutive days per year when the soil temperature at a a. A frigid temperature regime and a moisture control depth of 50 cm below the soil surface is higher than 8 oC; section that in normal years is dry in all parts for four- and tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface b. Is dry in some or all parts for six-tenths or more of the M is higher than 5 oC; or cumulative days per year when the soil temperature at a O depth of 50 cm below the soil surface is higher than 5 oC. L b. A mesic or thermic soil temperature regime and a Aridic Haplustolls moisture control section that in normal years is dry in some part for six-tenths or more of the cumulative days IGGZ. Other Haplustolls that have a slope of less than 25 per year when the soil temperature at a depth of 50 cm percent; and either below the soil surface is higher than 5 oC; or 1. An organic-carbon content of 0.3 percent or more at a c. A hyperthermic, isomesic, or warmer iso soil depth of 125 cm below the mineral soil surface; or temperature regime and a moisture control section that in normal years: 2. An irregular decrease in organic-carbon content from a depth of 25 cm to a depth of 125 cm or to a densic, lithic, or (1) Is moist in some or all parts for fewer than 90 paralithic contact if shallower. consecutive days per year when the soil temperature at Fluventic Haplustolls a depth of 50 cm below the soil surface is higher than 8 oC; and IGGZa. Other Haplustolls that have a brittle horizon that is (2) Is dry in some or all parts for six-tenths or more within 100 cm of the mineral soil surface, is 15 cm or more of the cumulative days per year when the soil thick, and has either some opal coatings or 20 percent or more temperature at a depth of 50 cm below the soil surface (by volume) durinodes. is higher than 5 oC; and Duric Haplustolls 222 Keys to Soil Taxonomy

IGGZb. Other Haplustolls that: Natrustolls 1. When neither irrigated nor fallowed to store moisture, Key to Subgroups have either: IGBA. Natrustolls that have all of the following: a. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in 1. Visible crystals of gypsum and/or more soluble salts some part for four-tenths or less of the cumulative days within 40 cm of the mineral soil surface; and per year when the soil temperature at a depth of 50 cm 2. 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 b. 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 is dry in some or all parts for fewer than 120 wedge-shaped aggregates in a layer 15 cm or more thick days per year when the soil temperature at a depth of 50 that has its upper boundary within 125 cm of the mineral cm below the soil surface is higher than 8 oC; and soil surface; or 2. Either do not have a cambic horizon and do not, in the b. A linear extensibility of 6.0 cm or more between the lower part of the mollic epipedon, meet the requirements for mineral soil surface and either a depth of 100 cm or a a cambic horizon, except for the color requirements, or have densic, lithic, or paralithic contact, whichever is carbonates throughout either the cambic horizon or the lower shallower; part of the mollic epipedon. Udorthentic Haplustolls 3. When neither irrigated nor fallowed to store moisture, have one of the following: IGGZc. Other Haplustolls that, when neither irrigated nor a. A frigid temperature regime and a moisture control fallowed to store moisture, have either: section that in normal years is dry in all parts for four- 1. A mesic or thermic soil temperature regime and a tenths or more of the cumulative days per year when the moisture control section that in normal years is dry in some soil temperature at a depth of 50 cm below the soil surface part for four-tenths or less of the cumulative days per year is higher than 5 oC; or 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 2. A hyperthermic, isomesic, or warmer iso soil some or all parts for six-tenths or more of the cumulative temperature regime and a moisture control section that in days per year when the soil temperature at a depth of 50 normal years is dry in some or all parts for fewer than 120 cm below the soil surface is higher than 5 oC; or days 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 8 oC. temperature regime and a moisture control section that in Udic Haplustolls normal years: IGGZd. Other Haplustolls that either: (1) Is moist in some or all parts for fewer than 90 consecutive days per year when the soil temperature at 1. Do not have a cambic horizon and do not, in any part of a depth of 50 cm below the soil surface is higher than the mollic epipedon below 25 cm from the mineral soil 8 oC; and surface, meet all of the requirements for a cambic horizon except color; or (2) Is dry in some or all parts for six-tenths or more of the cumulative days per year when the soil 2. Have free carbonates throughout the cambic horizon or temperature at a depth of 50 cm below the soil surface in all parts of the mollic epipedon below a depth of 25 cm is higher than 5 oC. from the mineral soil surface. Leptic Torrertic Natrustolls Entic Haplustolls IGBB. Other Natrustolls that have both: IGGZe. Other Haplustolls. Typic Haplustolls 1. One or both of the following: Mollisols 223

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 aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral 2. One or both of the following: soil surface; or a. Cracks within 125 cm of the mineral soil surface that b. 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 more for some time in normal years and slickensides or densic, lithic, or paralithic contact, whichever is wedge-shaped aggregates in a layer 15 cm or more thick shallower; and that has its upper boundary within 125 cm of the mineral soil surface; or 2. When neither irrigated nor fallowed to store moisture, have 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 frigid temperature regime and a moisture control a densic, lithic, or paralithic contact, whichever is section that in normal years is dry in all parts for four- shallower. tenths or more of the cumulative days per year when the Glossic Vertic Natrustolls soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or IGBE. Other Natrustolls that have one or both of the b. A mesic or thermic soil temperature regime and a following: moisture control section that in normal years is dry in some or all parts for six-tenths or more of the cumulative 1. Cracks within 125 cm of the mineral soil surface that are days per year when the soil temperature at a depth of 50 5 mm or more wide through a thickness of 30 cm or more for cm below the soil surface is higher than 5 oC; or some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick that has its upper c. A hyperthermic, isomesic, or warmer iso soil boundary within 125 cm of the mineral soil surface; or temperature regime and a moisture control section that in normal years: 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) Is moist in some or all parts for fewer than 90 lithic, or paralithic contact, whichever is shallower. consecutive days per year when the soil temperature at Vertic Natrustolls a depth of 50 cm below the soil surface is higher than 8 oC; and IGBF. Other Natrustolls that have both: (2) Is dry in some or all parts for six-tenths or more M 1. Visible crystals of gypsum or of more soluble salts, or of the cumulative days per year when the soil O both, within 40 cm of the mineral soil surface; and temperature at a depth of 50 cm below the soil surface L is higher than 5 oC. 2. When neither irrigated nor fallowed to store moisture, Torrertic Natrustolls have one of the following: a. A frigid temperature regime and a moisture control IGBC. Other Natrustolls that have both of the following: section that in normal years is dry in all parts for four- 1. Visible crystals of gypsum and/or more soluble salts tenths or more of the cumulative days per year when the within 40 cm of the mineral soil surface; and soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or 2. One or both of the following: b. A mesic or thermic soil temperature regime and a a. Cracks within 125 cm of the mineral soil surface that moisture control section that in normal years is dry in are 5 mm or more wide through a thickness of 30 cm or some or all parts for six-tenths or more of the cumulative more for some time in normal years and slickensides or days per year when the soil temperature at a depth of 50 wedge-shaped aggregates in a layer 15 cm or more thick cm below the soil surface is higher than 5 oC; or 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 in b. A linear extensibility of 6.0 cm or more between the normal years: mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. (1) Is moist in some or all parts for fewer than 90 Leptic Vertic Natrustolls consecutive days per year when the soil temperature at 224 Keys to Soil Taxonomy

a depth of 50 cm below the soil surface is higher than IGBJ. Other Natrustolls that have a horizon, 15 cm or more 8 oC; and thick within 100 cm of the mineral soil surface, that either has 20 percent or more (by volume) durinodes or is brittle and has a (2) Is dry in some or all parts for six-tenths or more firm rupture-resistance class when moist. of the cumulative days per year when the soil Duric Natrustolls temperature at a depth of 50 cm below the soil surface is higher than 5 oC. IGBK. Other Natrustolls that have a glossic horizon or Aridic Leptic Natrustolls interfingering of albic materials into a natric horizon. Glossic Natrustolls IGBG. Other Natrustolls that have visible crystals of gypsum or of more soluble salts, or both, within 40 cm of the mineral IGBL. Other Natrustolls. soil surface. Typic Natrustolls Leptic Natrustolls

IGBH. Other Natrustolls that have, in one or more horizons at Paleustolls a depth between 50 and 100 cm from the mineral soil surface, aquic conditions for some time in normal years (or artificial Key to Subgroups drainage) and one of the following: IGDA. Paleustolls that have both: 1. 50 percent or more chroma of 1 or less and hue of 2.5Y 1. One or both of the following: or yellower; or a. Cracks within 125 cm of the mineral soil surface that 2. 50 percent or more chroma of 2 or less and redox are 5 mm or more wide through a thickness of 30 cm or concentrations; or more for some time in normal years and slickensides or 3. 50 percent or more chroma of 2 or less and also a higher wedge-shaped aggregates in a layer 15 cm or more thick exchangeable sodium percentage (or sodium adsorption that has its upper boundary within 125 cm of the mineral ratio) between the mineral soil surface and a depth of 25 cm soil surface; or than in the underlying horizon. b. A linear extensibility of 6.0 cm or more between the Aquic Natrustolls mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is IGBI. Other Natrustolls that, when neither irrigated nor shallower; and fallowed to store moisture, have one of the following: 2. When neither irrigated nor fallowed to store moisture, 1. A frigid temperature regime and a moisture control one of the following: section that in normal years is dry in all parts for four-tenths or more of the cumulative days per year when the soil a. A frigid temperature regime and a moisture control temperature at a depth of 50 cm below the soil surface is section that in normal years is dry in all parts for less than higher than 5 oC; or four-tenths of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is 2. A mesic or thermic soil temperature regime and a higher than 5 oC; 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. 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 or all parts for six-tenths or more of the cumulative days per year when the soil temperature at a depth of 50 3. A hyperthermic, isomesic, or warmer iso soil cm 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 a. Is moist in some or all parts for fewer 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 8 oC; (1) Is moist in some or all parts for fewer than 90 and consecutive days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than b. Is dry in some or all parts 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 5 oC. (2) Is dry in some or all parts for six-tenths or more Aridic Natrustolls of the cumulative days per year when the soil Mollisols 225

temperature at a depth of 50 cm below the soil surface texture finer than loamy fine sand and that is 50 cm or more is higher than 5 oC. 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 aggregates in a layer 15 cm or more thick particle-size class (by weighted average in the particle-size that has its upper boundary within 125 cm of the mineral control section) and depth combinations: soil surface; or a. Sandy or sandy-skeletal and within 100 cm of the b. A linear extensibility of 6.0 cm or more between the mineral soil surface; or 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 2. When neither irrigated nor fallowed to store moisture, c. Any other class and within 60 cm of the mineral soil 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 temperature regime and a moisture control per year when the soil temperature at a depth of 50 cm section that in normal years is dry in all parts for less than below the soil surface is higher than 5 oC; or four-tenths of the cumulative days per year when the soil b. 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 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 M IGDC. Other Paleustolls that have one or both of the O following: c. A hyperthermic, isomesic, or warmer iso soil L 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 wedge-shaped aggregates in a layer 15 cm or more thick consecutive days per year when the soil temperature at that has its upper boundary within 125 cm of the mineral a depth of 50 cm below the soil surface is higher than soil surface; or 8 oC; and 2. A linear extensibility of 6.0 cm or more between the (2) Is dry in some or all parts for six-tenths or more mineral soil surface and either a depth of 100 cm or a of the cumulative days per year when the soil densic, lithic, or paralithic contact, whichever is shallower. temperature at a depth of 50 cm below the soil surface Vertic Paleustolls is higher than 5 oC. Calcidic Paleustolls IGDD. Other Paleustolls that have, in one or more horizons within 100 cm of the mineral soil surface, redox depletions with IGDH. Other Paleustolls that, when neither irrigated nor chroma of 2 or less and also aquic conditions for some time in fallowed to store moisture, have one of the following: normal years (or artificial drainage). Aquic Paleustolls 1. A frigid temperature regime and a moisture control section that in normal years is dry in all parts for less than IGDE. Other Paleustolls that have a mollic epipedon that has a four-tenths of the cumulative days per year when the soil 226 Keys to Soil Taxonomy

temperature at a depth of 50 cm below the soil surface is Vermustolls higher than 5 oC; or Key to Subgroups 2. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in some IGFA. Vermustolls that have a lithic contact within 50 cm of part for six-tenths or more of the cumulative days per year the mineral soil surface. when the soil temperature at a depth of 50 cm below the soil Lithic Vermustolls surface is higher than 5 oC; or IGFB. Other Vermustolls that have, in one or more horizons 3. A hyperthermic, isomesic, or warmer iso soil within 100 cm of the mineral soil surface, redox depletions with temperature regime and a moisture control section that in chroma of 2 or less and also aquic conditions for some time in normal years: normal years (or artificial drainage). a. Is moist in some or all parts for fewer than 90 Aquic Vermustolls consecutive days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 8 oC; IGFC. Other Vermustolls that have a mollic epipedon 75 cm or and more thick. Pachic Vermustolls b. Is dry in some or all parts for six-tenths or more of the cumulative days per year when the soil temperature at a IGFD. Other Vermustolls that have a mollic epipedon less than depth of 50 cm below the soil surface is higher than 5 oC. 50 cm thick. Aridic Paleustolls Entic Vermustolls IGDI. Other Paleustolls that, when neither irrigated nor IGFE. Other Vermustolls. fallowed to store moisture, have either: 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 surface is higher than 5 oC; or Key to Great Groups 2. A hyperthermic, isomesic, or warmer iso soil IFA. Xerolls that have a duripan within 100 cm of the mineral temperature regime and a moisture control section that in soil surface. normal years is dry in some or all parts for fewer than 120 Durixerolls, p. 229 cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 8 oC. IFB. Other Xerolls that have a natric horizon. Udic Paleustolls Natrixerolls, p. 234 IGDJ. Other Paleustolls have a calcic horizon within one of IFC. Other Xerolls that have either: the following particle-size class (by weighted average in the particle-size control section) and depth combinations: 1. A petrocalcic horizon that has its upper boundary within 150 cm of the mineral soil surface; or 1. Sandy or sandy-skeletal and within 100 cm of the mineral soil surface; or 2. An argillic horizon that has one or both of the following: 2. Clayey, clayey-skeletal, fine, or very-fine and within 50 a. With increasing depth, no clay decrease of 20 percent cm of the mineral soil surface; or or more (relative) from the maximum clay content (noncarbonate clay) within 150 cm of the mineral soil 3. Any other class and within 60 cm of the mineral soil surface (and there is no densic, lithic, or paralithic contact surface. within that depth); and either Calcic Paleustolls (1) Hue of 7.5YR or redder and chroma of 5 or more IGDK. Other Paleustolls that are calcareous throughout after in the matrix; or the surface soil has been mixed to a depth of 18 cm. (2) Common redox concentrations with hue Entic Paleustolls of 7.5YR or redder or chroma of 6 or more, or both; or IGDL. Other Paleustolls. Typic Paleustolls b. A clayey or clayey-skeletal particle-size class in its Mollisols 227

upper part and, at its upper boundary, a clay increase a densic, lithic, or paralithic contact, whichever is either of 20 percent or more (absolute) within a vertical shallower. distance of 7.5 cm or of 15 percent or more (absolute) Torrertic Argixerolls within a vertical distance of 2.5 cm, in the fine-earth fraction (and there is no densic, lithic, or paralithic contact IFED. Other Argixerolls that have one or both of the within 50 cm of the mineral soil surface). following: Palexerolls, p. 234 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 IFD. Other Xerolls that: some time in normal years and slickensides or wedge-shaped 1. Have a calcic or gypsic horizon that has its upper aggregates in a layer 15 cm or more thick that has its upper boundary within 150 cm of the mineral soil surface; and boundary within 125 cm of the mineral soil surface; or 2. In all parts above the calcic or gypsic horizon, after the 2. A linear extensibility of 6.0 cm or more between the surface soil has been mixed to a depth of 18 cm, either are mineral soil surface and either a depth of 100 cm or a densic, calcareous or have a texture of loamy fine sand or coarser. lithic, or paralithic contact, whichever is shallower. Calcixerolls, p. 229 Vertic Argixerolls

IFE. Other Xerolls that have an argillic horizon. IFEE. Other Argixerolls that have, throughout one or more Argixerolls, p. 227 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 IFF. Other Xerolls. density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 Haploxerolls, p. 231 and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. Andic Argixerolls Argixerolls IFEF. Other Argixerolls that have both: Key to Subgroups 1. An aridic moisture regime; and IFEA. Argixerolls that have both: 2. Throughout one or more horizons with a total thickness 1. A lithic contact within 50 cm of the mineral soil surface; of 18 cm or more within 75 cm of the mineral soil surface, and one or both of the following: 2. A base saturation (by sum of cations) of 75 percent or a. More than 35 percent (by volume) fragments coarser less in one or more horizons between either the mineral soil than 2.0 mm, of which more than 66 percent is cinders, M surface or an Ap horizon, whichever is deeper, and the lithic pumice, and pumicelike fragments; or O contact. L Lithic Ultic Argixerolls b. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and IFEB. Other Argixerolls that have a lithic contact within 50 cm (1) In the 0.02 to 2.0 mm fraction, 5 percent or more of the mineral soil surface. volcanic glass; and Lithic Argixerolls 1 (2) [(Al plus /2 Fe, percent extracted by ammonium IFEC. Other Argixerolls that have both: oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. 1. An aridic moisture regime; and Vitritorrandic Argixerolls 2. One or both of the following: IFEG. Other Argixerolls 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 of are 5 mm or more wide through a thickness of 30 cm or the mineral soil surface, one or both of the following: more for some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick 1. More than 35 percent (by volume) fragments coarser that has its upper boundary within 125 cm of the mineral than 2.0 mm, of which more than 66 percent is cinders, soil surface; or pumice, and pumicelike fragments; or b. A linear extensibility of 6.0 cm or more between 2. A fine-earth fraction containing 30 percent or more the mineral soil surface and either a depth of 100 cm or particles 0.02 to 2.0 mm in diameter; and 228 Keys to Soil Taxonomy

a. In the 0.02 to 2.0 mm fraction, 5 percent or more b. Clayey, clayey-skeletal, fine, or very-fine and within volcanic glass; and 90 cm of the mineral soil surface; or

1 b. [(Al plus /2 Fe, percent extracted by ammonium c. Any other class and within 110 cm of the mineral soil oxalate) times 60] plus the volcanic glass (percent) is surface; and equal to 30 or more. 2. A mollic epipedon that is 50 cm or more thick and has a Vitrandic Argixerolls texture finer than loamy fine sand. Calcic Pachic Argixerolls IFEH. Other Argixerolls that have both: IFEM. Other Argixerolls that have both: 1. In one or more horizons within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also 1. A mollic epipedon that is 50 cm or more thick and has a aquic conditions for some time in normal years (or artificial texture finer than loamy fine sand; and drainage); and 2. A base saturation (by sum of cations) of 75 percent or 2. A base saturation (by sum of cations) of 75 percent less in one or more horizons between either an Ap horizon or or less in one or more horizons between either an Ap horizon a depth of 25 cm from the mineral soil surface, whichever is or a depth of 25 cm from the mineral soil surface, whichever 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. Pachic Ultic Argixerolls Aquultic Argixerolls IFEN. Other Argixerolls that have a mollic epipedon that is 50 IFEI. Other Argixerolls that have, in one or more horizons cm or more thick and has a texture finer than loamy fine sand. within 75 cm of the mineral soil surface, redox depletions with Pachic Argixerolls chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). IFEO. Other Argixerolls that have both: Aquic Argixerolls 1. An aridic moisture regime; and IFEJ. Other Argixerolls that in normal years are saturated with 2. A horizon within 100 cm of the mineral soil surface that water in one or more layers within 100 cm of the mineral soil is 15 cm or more thick and either has 20 percent or more (by surface for either or both: volume) durinodes or is brittle and has a firm rupture- resistance class when moist. 1. 20 or more consecutive days; or Argiduridic Argixerolls 2. 30 or more cumulative days. Oxyaquic Argixerolls IFEP. Other Argixerolls that have 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 volume) durinodes or is brittle and IFEK. Other Argixerolls that have either: has a firm rupture-resistance class when moist. 1. Above the argillic horizon, an albic horizon or a horizon Duric Argixerolls that has color values too high for a mollic epipedon and chroma too high for an albic horizon; or IFEQ. Other Argixerolls that have both: 2. A glossic horizon, or interfingering of albic materials 1. An aridic moisture regime; and into the upper part of the argillic horizon, or skeletans of 2. A calcic horizon or identifiable secondary carbonates clean silt and sand covering 50 percent or more of the faces within one of the following particle-size class (by weighted of peds in the upper 5 cm of the argillic horizon. average in the particle-size control section) and depth Alfic Argixerolls combinations: IFEL. Other Argixerolls that have both: a. Sandy or sandy-skeletal and within 150 cm of the mineral soil surface; or 1. A calcic horizon or identifiable secondary carbonates within one of the following particle-size class (by weighted b. Clayey, clayey-skeletal, fine, or very-fine and within average in the particle-size control section) and depth 90 cm of the mineral soil surface; or combinations: c. Any other class and within 110 cm of the mineral soil a. Sandy or sandy-skeletal and within 150 cm of the surface. mineral soil surface; or Calciargidic Argixerolls Mollisols 229

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

Calcixerolls IFDG. Other Calcixerolls that have an aridic moisture regime. Aridic Calcixerolls Key to Subgroups IFDH. Other Calcixerolls that have a mollic epipedon that has, IFDA. Calcixerolls that have a lithic contact within 50 cm of below any Ap horizon, 50 percent or more (by volume) the mineral soil surface. wormholes, wormcasts, or filled animal burrows. Lithic Calcixerolls M Vermic Calcixerolls O IFDB. Other Calcixerolls that have one or both of the L IFDI. Other Calcixerolls. following: Typic Calcixerolls 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 some time in normal years and slickensides or Durixerolls wedge-shaped aggregates in a layer 15 cm or more thick that Key to Subgroups has its upper boundary within 125 cm of the mineral soil surface; or IFAA. Durixerolls that have, above the duripan, 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 1. Cracks that are 5 mm or more wide through a thickness or a densic, lithic, or paralithic contact, whichever is of 30 cm or more for some time in normal years and shallower. slickensides or wedge-shaped aggregates in a layer 15 cm or Vertic Calcixerolls more thick; or 2. A linear extensibility of 6.0 cm or more. IFDC. Other Calcixerolls that have, in one or more horizons Vertic Durixerolls within 75 cm of the mineral soil surface, redox concentrations and also aquic conditions for some time in normal years (or IFAB. Other Durixerolls that have both: artificial drainage). Aquic Calcixerolls 1. An aridic moisture regime; and 230 Keys to Soil Taxonomy

2. Throughout one or more horizons with a total thickness 2. An argillic horizon that, with increasing depth, has a clay of 18 cm or more within 75 cm of the mineral soil surface, increase either of 20 percent or more (absolute) within a one or both of the following: vertical distance of 7.5 cm or of 15 percent or more (absolute) within a vertical distance of 2.5 cm. a. More than 35 percent (by volume) fragments coarser Abruptic Argiduridic Durixerolls than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or IFAG. Other Durixerolls that: b. A fine-earth fraction containing 30 percent or more 1. Have an aridic moisture regime; and particles 0.02 to 2.0 mm in diameter; and 2. Do not have an argillic horizon above the duripan; and (1) In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and 3. Have a duripan that is neither very strongly cemented

1 nor indurated in any subhorizon. (2) [(Al plus /2 Fe, percent extracted by ammonium Cambidic Durixerolls oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. IFAH. Other Durixerolls that: Vitritorrandic Durixerolls 1. Have an aridic moisture regime; and IFAC. Other Durixerolls that have, throughout one or more 2. Do not have an argillic horizon above the duripan. horizons with a total thickness of 18 cm or more within 75 cm of Haploduridic Durixerolls the mineral soil surface, one or both of the following: 1. More than 35 percent (by volume) fragments coarser IFAI. Other Durixerolls that have: than 2.0 mm, of which more than 66 percent is cinders, 1. An aridic moisture regime; and pumice, and pumicelike fragments; or 2. A duripan that is neither very strongly cemented nor 2. A fine-earth fraction containing 30 percent or more indurated in any subhorizon. particles 0.02 to 2.0 mm in diameter; and Argidic Durixerolls a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and IFAJ. Other Durixerolls that have an aridic moisture

1 regime. b. [(Al plus /2 Fe, percent extracted by ammonium Argiduridic Durixerolls oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. IFAK. Other Durixerolls that have both: Vitrandic Durixerolls 1. An argillic horizon that, with increasing depth, has a clay increase either of 20 percent or more (absolute) within a IFAD. Other Durixerolls that have, in one or more horizons vertical distance of 7.5 cm or of 15 percent or more above the duripan, redox depletions with chroma of 2 or less (absolute) within a vertical distance of 2.5 cm; and and also aquic conditions for some time in normal years (or artificial drainage). 2. A duripan that is neither very strongly cemented nor Aquic Durixerolls indurated in any subhorizon. Haplic Palexerollic Durixerolls IFAE. Other Durixerolls that have: IFAL. Other Durixerolls that have an argillic horizon that, 1. An aridic moisture regime; and with increasing depth, has a clay increase either of 20 percent 2. An argillic horizon that, with increasing depth, has a clay or more (absolute) within a vertical distance of 7.5 cm or of increase either of 20 percent or more (absolute) within a 15 percent or more (absolute) within a vertical distance of 2.5 vertical distance of 7.5 cm or of 15 percent or more cm. (absolute) within a vertical distance of 2.5 cm; and Palexerollic Durixerolls 3. A duripan that is neither very strongly cemented nor IFAM. Other Durixerolls that: indurated in any subhorizon. Paleargidic Durixerolls 1. Have a duripan that is neither very strongly cemented nor indurated in any subhorizon; and IFAF. Other Durixerolls that have both: 2. Do not have an argillic horizon above the duripan. 1. An aridic moisture regime; and Haplic Haploxerollic Durixerolls Mollisols 231

IFAN. Other Durixerolls that do not have an argillic horizon mineral soil surface and either a depth of 100 cm or a densic, above the duripan. lithic, or paralithic contact, whichever is shallower. Haploxerollic Durixerolls Vertic Haploxerolls

IFAO. Other Durixerolls that have a duripan that is neither IFFE. Other Haploxerolls that have throughout one or more very strongly cemented nor indurated in any subhorizon. horizons with a total thickness of 18 cm or more within 75 cm of Haplic Durixerolls 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 IFAP. Other Durixerolls. and Al plus /2 Fe percentages (by ammonium oxalate) totaling Typic Durixerolls more than 1.0. Andic Haploxerolls

Haploxerolls IFFF. Other Haploxerolls that have both: Key to Subgroups 1. An aridic moisture regime; and IFFA. Haploxerolls 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 Haploxerolls particles 0.02 to 2.0 mm in diameter; and (1) In the 0.02 to 2.0 mm fraction, 5 percent or more IFFB. Other Haploxerolls that have a lithic contact within 50 volcanic glass; and cm of the mineral soil surface. 1 Lithic Haploxerolls (2) [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is IFFC. Other Haploxerolls that have both: equal to 30 or more. Vitritorrandic Haploxerolls 1. An aridic moisture regime; and 2. One or both of the following: IFFG. Other Haploxerolls that have, throughout one or more M horizons with a total thickness of 18 cm or more within 75 cm of a. Cracks within 125 cm of the mineral soil surface that O the mineral soil surface, one or both of the following: are 5 mm or more wide through a thickness of 30 cm or L more for some time in normal years and slickensides or 1. More than 35 percent (by volume) fragments coarser wedge-shaped aggregates in a layer 15 cm or more thick than 2.0 mm, of which more than 66 percent is cinders, that has its upper boundary within 125 cm of the mineral pumice, and pumicelike fragments; or soil surface; or 2. A fine-earth fraction containing 30 percent or more b. A linear extensibility of 6.0 cm or more between the particles 0.02 to 2.0 mm in diameter; and mineral soil surface and either a depth of 100 cm or a a. In the 0.02 to 2.0 mm fraction, 5 percent or more densic, lithic, or paralithic contact, whichever is shallower. volcanic glass; and Torrertic Haploxerolls 1 b. [(Al plus /2 Fe, percent extracted by ammonium IFFD. Other Haploxerolls that have one or both of the oxalate) times 60] plus the volcanic glass (percent) is following: equal to 30 or more. Vitrandic Haploxerolls 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 IFFH. Other Haploxerolls that have: some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick that has its upper 1. A mollic epipedon that is 50 cm or more thick and has a boundary within 125 cm of the mineral soil surface; or texture finer than loamy fine sand; and 2. A linear extensibility of 6.0 cm or more between the 2. An irregular decrease in organic-carbon content from a 232 Keys to Soil Taxonomy

depth of 25 cm below the mineral soil surface to a depth of a depth of 25 cm to a depth of 125 cm or to a densic, 125 cm or to a densic, lithic, or paralithic contact if lithic, or paralithic contact if shallower. shallower; and Fluvaquentic Haploxerolls 3. A slope of less than 25 percent; and IFFL. Other Haploxerolls that have both: 4. In one or more horizons within 75 cm of the mineral soil 1. In one or more horizons within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial aquic conditions for some time in normal years (or artificial drainage). drainage); and Aquic Cumulic Haploxerolls 2. A horizon, 15 cm or more thick within 100 cm of the IFFI. Other Haploxerolls that have: mineral soil surface, that either has 20 percent or more (by volume) durinodes or is brittle and has a firm rupture- 1. A mollic epipedon that is 50 cm or more thick and has a resistance class when moist. texture finer than loamy fine sand; and Aquic Duric Haploxerolls 2. An irregular decrease in organic-carbon content from a depth of 25 cm below the mineral soil surface to a depth of IFFM. Other Haploxerolls that have both: 125 cm or to a densic, lithic, or paralithic contact if shallower; and 1. In one or more horizons within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also 3. A slope of less than 25 percent; and aquic conditions for some time in normal years (or artificial 4. A base saturation (by sum of cations) of 75 percent or drainage); and less in one or more horizons between either an Ap horizon or 2. A base saturation (by sum of cations) of 75 percent or a depth of 25 cm from the mineral soil surface, whichever is less in one or more horizons between either an Ap horizon or deeper, and either a depth of 75 cm or a densic, lithic, or a depth of 25 cm from the mineral soil surface, whichever is paralithic contact, whichever is shallower. deeper, and either a depth of 75 cm or a densic, lithic, or Cumulic Ultic Haploxerolls paralithic contact, whichever is shallower. Aquultic Haploxerolls IFFJ. Other Haploxerolls that have: 1. A mollic epipedon that is 50 cm or more thick and has a IFFN. Other Haploxerolls that have, in one or more horizons texture finer than loamy fine sand; 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 2. An irregular decrease in organic-carbon content from a normal years (or artificial drainage). depth of 25 cm below the mineral soil surface to a depth of Aquic Haploxerolls 125 cm or to a densic, lithic, or paralithic contact if shallower; and IFFO. Other Haploxerolls that in normal years are saturated 3. A slope of less than 25 percent. with water in one or more layers within 100 cm of the mineral Cumulic Haploxerolls soil surface for either or both: 1. 20 or more consecutive days; or IFFK. Other Haploxerolls that have both: 2. 30 or more cumulative days. 1. In one or more horizons within 75 cm of the mineral soil Oxyaquic Haploxerolls surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial IFFP. Other Haploxerolls that have both: drainage); and 1. A mollic epipedon that is 50 cm or more thick and has a 2. A slope of less than 25 percent; and either texture finer than loamy fine sand; and a. An organic-carbon content of 0.3 percent or more 2. A calcic horizon or identifiable secondary carbonates in all horizons within 125 cm of the mineral soil surface; within one of the following particle-size class (by weighted or average in the particle-size control section) and depth b. An irregular decrease in organic-carbon content from combinations: Mollisols 233

a. Sandy or sandy-skeletal and within 150 cm of the a. Sandy or sandy-skeletal and within 150 cm of the mineral soil surface; or mineral soil surface; or b. Clayey, clayey-skeletal, fine, or very-fine and within b. Clayey, clayey-skeletal, fine, or very-fine and within 90 cm of the mineral soil surface; or 90 cm of the mineral soil surface; or c. Any other class and within 110 cm of the mineral soil c. Any other class and within 110 cm of the mineral soil surface. surface. Calcic Pachic Haploxerolls Calcidic Haploxerolls

IFFQ. Other Haploxerolls that have both: IFFV. Other Haploxerolls that have both: 1. A mollic epipedon that is 50 cm or more thick and has a 1. An aridic moisture regime; and texture finer than loamy fine sand; and 2. A sandy particle-size class in all horizons within 100 cm 2. A base saturation (by sum of cations) of 75 percent or of the mineral soil surface. less in one or more horizons between either an Ap horizon or Torripsammentic Haploxerolls 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 IFFW. Other Haploxerolls that: paralithic contact, whichever is shallower. 1. Have an aridic moisture regime; and Pachic Ultic Haploxerolls 2. Either: IFFR. Other Haploxerolls that have a mollic epipedon that is a. Do not have a cambic horizon and do not, in any part 50 cm or more thick and has a texture finer than loamy fine of the mollic epipedon below 25 cm from the mineral soil sand. surface, meet all of the requirements for a cambic horizon Pachic Haploxerolls except color; or IFFS. Other Haploxerolls that have: b. Have free carbonates throughout the cambic horizon or in all parts of the mollic epipedon below a depth of 25 1. An aridic moisture regime; and cm from the mineral soil surface. 2. A slope of less than 25 percent; and either Torriorthentic Haploxerolls a. An organic-carbon content of 0.3 percent or more IFFX. Other Haploxerolls that have an aridic moisture regime. in all horizons within 125 cm of the mineral soil surface; Aridic Haploxerolls or M b. An irregular decrease in organic-carbon content from IFFY. Other Haploxerolls that have a horizon within 100 cm O a depth of 25 cm to a depth of 125 cm or to a densic, of the mineral soil surface that is 15 cm or more thick and either L lithic, or paralithic contact if shallower. has 20 percent or more (by volume) durinodes or is brittle and Torrifluventic Haploxerolls has a firm rupture-resistance class when moist. Duric Haploxerolls IFFT. Other Haploxerolls that have both: IFFZ. Other Haploxerolls that have a sandy particle-size class 1. An aridic moisture regime; and in all horizons within 100 cm of the mineral soil surface. 2. A horizon within 100 cm of the mineral soil surface that Psammentic Haploxerolls is 15 cm or more thick and either has 20 percent or more (by volume) durinodes or is brittle and has a firm rupture- IFFZa. Other Haploxerolls that have a slope of less than 25 resistance class when moist. percent; and either Duridic Haploxerolls 1. An organic-carbon content of 0.3 percent or more in all horizons within 125 cm of the mineral soil surface; or IFFU. Other Haploxerolls that have both: 2. An irregular decrease in organic-carbon content from a 1. An aridic moisture regime; and depth of 25 cm to a depth of 125 cm or to a densic, lithic, or 2. A calcic horizon or identifiable secondary carbonates paralithic contact if shallower. within one of the following particle-size class (by weighted Fluventic Haploxerolls average in the particle-size control section) and depth combinations: IFFZb. Other Haploxerolls that have a mollic epipedon that 234 Keys to Soil Taxonomy

has granular structure and that has, below any Ap horizon, 50 Natrixerolls percent or more (by volume) wormholes, wormcasts, or filled animal burrows. Key to Subgroups Vermic Haploxerolls IFBA. Natrixerolls that have one or both of the following: IFFZc. Other Haploxerolls that have a calcic horizon or 1. Cracks within 125 cm of the mineral soil surface that are identifiable secondary carbonates within one of the following 5 mm or more wide through a thickness of 30 cm or more for particle-size class (by weighted average in the particle-size some time in normal years and slickensides or wedge-shaped control section) and depth combinations: aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil surface; or 1. Sandy or sandy-skeletal and within 150 cm of the mineral soil surface; 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, 2. Clayey, clayey-skeletal, fine, or very-fine and within 90 lithic, or paralithic contact, whichever is shallower. cm of the mineral soil surface; or Vertic Natrixerolls 3. Any other class and within 110 cm of the mineral soil surface. IFBB. Other Natrixerolls that have both: Calcic Haploxerolls 1. In one or more horizons within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also IFFZd. Other Haploxerolls that: aquic conditions for some time in normal years (or artificial 1. Do not have a cambic horizon and do not, in the lower drainage); and part of the mollic epipedon, meet all of the requirements for a 2. A horizon, 15 cm or more thick within 100 cm of the cambic horizon except color; and mineral soil surface, that either has 20 percent or more (by 2. Have a base saturation (by sum of cations) of volume) durinodes or is brittle and has a firm rupture- 75 percent or less in one or more horizons between either resistance class when moist. an Ap horizon or a depth of 25 cm from the mineral soil Aquic Duric Natrixerolls surface, whichever is deeper, and either a depth of 75 cm or a densic, lithic, or paralithic contact, whichever is shallower. IFBC. Other Natrixerolls that have, in one or more horizons Entic Ultic Haploxerolls within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in IFFZe. Other Haploxerolls that have a base saturation (by sum normal years (or artificial drainage). of cations) of 75 percent or less in one or more horizons Aquic Natrixerolls between either an Ap horizon or a depth of 25 cm from the mineral soil surface, whichever is deeper, and either a depth of IFBD. Other Natrixerolls that have an aridic moisture regime. 75 cm or a densic, lithic, or paralithic contact, whichever is Aridic Natrixerolls shallower. Ultic Haploxerolls IFBE. Other Natrixerolls that have a horizon within 100 cm of the mineral soil surface that is 15 cm or more thick and either IFFZf. Other Haploxerolls that either: has 20 percent or more (by volume) durinodes or is brittle and has a firm rupture-resistance class when moist. 1. Do not have a cambic horizon and do not, in any part of Duric Natrixerolls the mollic epipedon below 25 cm from the mineral soil surface, meet all of the requirements for a cambic horizon IFBF. Other Natrixerolls. except color; or Typic Natrixerolls 2. Have free carbonates throughout the cambic horizon or in all parts of the mollic epipedon below a depth of 25 cm Palexerolls from the mineral soil surface. Entic Haploxerolls Key to Subgroups IFCA. Palexerolls that have one or both of the following: IFFZg. Other Haploxerolls. Typic Haploxerolls 1. Cracks within 125 cm of the mineral soil surface that are Mollisols 235

5 mm or more wide through a thickness of 30 cm or more for 1. An aridic moisture regime; and some time in normal years and slickensides or wedge-shaped 2. A petrocalcic horizon that has its upper boundary within aggregates in a layer 15 cm or more thick that has its upper 150 cm of the mineral soil surface. boundary within 125 cm of the mineral soil surface; or Petrocalcidic Palexerolls 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, IFCF. Other Palexerolls that have a horizon, 15 cm or more lithic, or paralithic contact, whichever is shallower. thick within 100 cm of the mineral soil surface, that either has Vertic Palexerolls 20 percent or more (by volume) durinodes or is brittle and has a firm rupture-resistance class when moist. IFCB. Other Palexerolls that have, throughout one or more Duric Palexerolls horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: IFCG. Other Palexerolls that have an aridic moisture regime. Aridic Palexerolls 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, IFCH. Other Palexerolls that have a petrocalcic horizon that pumice, and pumicelike fragments; or has its upper boundary within 150 cm of the mineral soil 2. A fine-earth fraction containing 30 percent or more surface. particles 0.02 to 2.0 mm in diameter; and Petrocalcic Palexerolls a. In the 0.02 to 2.0 mm fraction, 5 percent or more IFCI. Other Palexerolls that have a base saturation of 75 volcanic glass; and percent or less in one or more subhorizons either within the 1 b. [(Al plus /2 Fe, percent extracted by ammonium argillic horizon if more than 50 cm thick or within its upper 50 oxalate) times 60] plus the volcanic glass (percent) is cm. equal to 30 or more. Ultic Palexerolls Vitrandic Palexerolls IFCJ. Other Palexerolls that have an argillic horizon that has IFCC. Other Palexerolls that have, in one or more horizons either: within 75 cm of the mineral soil surface, redox depletions with 1. Less than 35 percent clay in the upper part; or chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). 2. At its upper boundary, a clay increase that is both less Aquic Palexerolls than 20 percent (absolute) within a vertical distance of 7.5 cm and less than 15 percent (absolute) within a vertical IFCD. Other Palexerolls that have a mollic epipedon that is 50 distance of 2.5 cm, in the fine-earth fraction. M cm or more thick and has a texture finer than loamy fine sand. Haplic Palexerolls O Pachic Palexerolls L IFCK. Other Palexerolls. IFCE. Other Palexerolls that have both: Typic Palexerolls

237

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. 238 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 mineral soil surface. 1. A histic epipedon; or Eutraquox, p. 237 2. An epipedon with a color value, moist, of 3 or less and, directly below it, a horizon with chroma of 2 or less; EAD. Other Aquox. or Haplaquox, p. 238 3. Distinct or prominent redox concentrations within 50 cm of the mineral soil surface, an epipedon, and, directly below Acraquox it, a horizon with one or both of the following: Key to Subgroups a. 50 percent or more hue of 2.5Y or yellower; or 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 soil surface. 4. Within 50 cm of the mineral soil surface, enough active Plinthic Acraquox ferrous iron to give a positive reaction to alpha,alpha- dipyridyl at a time when the soil is not being irrigated. EAAB. Other Acraquox that have, directly below an epipedon, Aquox, p. 237 a horizon 10 cm or more thick that has 50 percent or more chroma of 3 or more. EB. Other Oxisols that have an aridic moisture regime. Aeric Acraquox Torrox, p. 242 EAAC. Other Acraquox. EC. Other Oxisols that have an ustic or xeric moisture regime. Typic Acraquox O Ustox, p. 247 X I ED. Other Oxisols that have a perudic moisture regime. Eutraquox Perox, p. 238 Key to Subgroups EE. Other Oxisols. EACA. Eutraquox that have a histic epipedon. Udox, p. 243 Histic Eutraquox

Aquox EACB. Other Eutraquox that have 5 percent or more (by volume) plinthite in one or more horizons within 125 cm of the Key to Great Groups mineral soil surface. 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 (in 1N KCl) of 5.0 or more. more chroma of 3 or more. Acraquox, p. 237 Aeric Eutraquox 238 Keys to Soil Taxonomy

EACD. Other Eutraquox that have 16 kg/m2 or more oxic or kandic horizon within 150 cm of the mineral soil organic carbon between the mineral soil surface and a depth surface, an apparent ECEC of less than 1.50 cmol(+) per kg clay of 100 cm. and a pH value (1N KCl) of 5.0 or more. Humic Eutraquox Acroperox, p. 238

EACE. Other Eutraquox. EDC. Other Perox that have a base saturation (by NH4OAc) of Typic Eutraquox 35 percent or more in all horizons within 125 cm of the mineral soil surface. Haplaquox Eutroperox, p. 239

Key to Subgroups EDD. Other Perox that have a kandic horizon that has its upper boundary within 150 cm of the mineral soil surface. EADA. Haplaquox that have a histic epipedon. Kandiperox, p. 241 Histic Haplaquox EDE. Other Perox. EADB. Other Haplaquox that have 5 percent or more (by Haploperox, p. 240 volume) plinthite in one or more horizons within 125 cm of the mineral soil surface. Plinthic Haplaquox Acroperox Key to Subgroups EADC. Other Haplaquox that have, directly below an epipedon, a horizon 10 cm or more thick that has 50 percent or EDBA. Acroperox that have, within 125 cm of the mineral more chroma of 3 or more. soil surface, both: Aeric Haplaquox 1. A petroferric contact; and EADD. Other Haplaquox that have 16 kg/m2 or more 2. Redox depletions with a color value, moist, of 4 or more organic carbon between the mineral soil surface and a depth and chroma of 2 or less and also aquic conditions for some of 100 cm. time in normal years (or artificial drainage). Humic Haplaquox Aquic Petroferric Acroperox

EADE. Other Haplaquox. EDBB. Other Acroperox that have a petroferric contact within Typic Haplaquox 125 cm of the mineral soil surface. Petroferric Acroperox Plinthaquox EDBC. Other Acroperox that have, within 125 cm of the Key to Subgroups mineral soil surface, both: EABA. Plintaquox that have, directly below an epipedon, a 1. A lithic contact; and horizon 10 cm or more thick that has 50 percent or more chroma 2. Redox depletions with a color value, moist, of 4 or more of 3 or more. and chroma of 2 or less and also aquic conditions for some Aeric Plinthaquox time in normal years (or artificial drainage). Aquic Lithic Acroperox EABB. Other Plinthaquox. Typic Plinthaquox EDBD. Other Acroperox that have a lithic contact within 125 cm of the mineral soil surface. Perox Lithic Acroperox Key to Great Groups EDBE. Other Acroperox that have a delta pH (KCl pH minus 1:1 water pH) with a 0 or net positive charge in a EDA. Perox that have a sombric horizon within 150 cm of the layer 18 cm or more thick within 125 cm of the mineral soil mineral soil surface. surface. Sombriperox, p. 242 Anionic Acroperox

EDB. Other Perox that have, in one or more subhorizons of an EDBF. Other Acroperox that have 5 percent or more (by Oxisols 239

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

EDBL. Other Acroperox that have 50 percent or more hue EDCG. Other Eutroperox that have, in one or more horizons of 7.5YR or yellower and a color value, moist, of 6 or more within 125 cm of the mineral soil surface, redox depletions with at a depth between 25 and 125 cm from the mineral soil a color value, moist, of 4 or more and chroma of 2 or less and surface. also aquic conditions for some time in normal years (or artificial Xanthic Acroperox drainage). Aquic Eutroperox EDBM. Other Acroperox. Typic Acroperox EDCH. Other Eutroperox that have a kandic horizon that 240 Keys to Soil Taxonomy

has its upper boundary within 150 cm of the mineral soil EDCP. Other Eutroperox. surface. Typic Eutroperox Kandiudalfic Eutroperox Haploperox EDCI. Other Eutroperox that have both: Key to Subgroups 1. 16 kg/m2 or more organic carbon between the mineral soil surface and a depth of 100 cm; and EDEA. Haploperox that have, within 125 cm of the mineral soil surface, both: 2. An oxic horizon that has its lower boundary within 125 cm of the mineral soil surface. 1. A petroferric contact; and Humic Inceptic Eutroperox 2. Redox depletions with a color value, moist, of 4 or more and chroma of 2 or less and also aquic conditions for some EDCJ. Other Eutroperox 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 Haploperox Inceptic Eutroperox EDEB. Other Haploperox that have a petroferric contact EDCK. Other Eutroperox that have both: within 125 cm of the mineral soil surface. Petroferric Haploperox 1. 16 kg/m2 or more organic carbon between the mineral soil surface and a depth of 100 cm; and EDEC. Other Haploperox 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 b. A value, moist, of 3 or less. 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 cm of the mineral soil surface. 1. 16 kg/m2 or more organic carbon between the mineral Lithic Haploperox soil surface and a depth of 100 cm; and 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. 1. 5 percent or more (by volume) plinthite; and Humic Xanthic Eutroperox 2. Redox depletions with a color value, moist, of 4 or more EDCM. Other Eutroperox that have 16 kg/m2 or more and chroma of 2 or less and also aquic conditions for some organic carbon between the mineral soil surface and a depth time in normal years (or artificial drainage). of 100 cm. Plinthaquic Haploperox Humic Eutroperox EDEF. Other Haploperox that have 5 percent or more (by EDCN. Other Eutroperox 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 Haploperox 1. Hue of 2.5YR or redder; and EDEG. Other Haploperox that have, in one or more horizons 2. A value, moist, of 3 or less. within 125 cm of the mineral soil surface, redox depletions with Rhodic Eutroperox a color value, moist, of 4 or more and chroma of 2 or less and also aquic conditions for some time in normal years (or artificial EDCO. Other Eutroperox that have 50 percent or more hue of drainage). 7.5YR or yellower and a color value, moist, of 6 or more at a Aquic Haploperox depth between 25 and 125 cm from the mineral soil surface. Xanthic Eutroperox EDEH. Other Haploperox that have, throughout one or more Oxisols 241

horizons with a total thickness of 18 cm or more within 75 cm of 1. A petroferric contact; and the mineral soil surface, a fine-earth fraction with both a bulk 2. Redox depletions with a color value, moist, of 4 or more density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 and chroma of 2 or less and also aquic conditions for some and Al plus /2 Fe percentages (by ammonium oxalate) totaling time in normal years (or artificial drainage). more than 1.0. Aquic Petroferric Kandiperox Andic Haploperox EDDB. Other Kandiperox that have a petroferric contact EDEI. Other Haploperox that have both: within 125 cm of the mineral soil surface. 1. 16 kg/m2 or more organic carbon between the mineral Petroferric Kandiperox soil surface and a depth of 100 cm; and EDDC. Other Kandiperox 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 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 and chroma of 2 or less and also aquic conditions for some b. A value, moist, of 3 or less. time in normal years (or artificial drainage). Humic Rhodic Haploperox Aquic Lithic Kandiperox EDEJ. Other Haploperox that have both: EDDD. Other Kandiperox 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 Kandiperox 2. 50 percent or more hue of 7.5YR or yellower and a color EDDE. Other Kandiperox 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 Haploperox 1. 5 percent or more (by volume) plinthite; and 2. Redox depletions with a color value, moist, of 4 or more EDEK. Other Haploperox that have 16 kg/m2 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 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 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 Kandiperox O 2. A value, moist, of 3 or less. X Rhodic Haploperox EDDG. Other Kandiperox that have, in one or more horizons I within 125 cm of the mineral soil surface, redox depletions with EDEM. Other Haploperox 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 Haploperox Aquic Kandiperox

EDEN. Other Haploperox. EDDH. Other Kandiperox that have, throughout one or more Typic Haploperox 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 density of 1.0 g/cm3 or less, measured at 33 kPa water retention, Kandiperox 1 and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. Key to Subgroups Andic Kandiperox EDDA. Kandiperox that have, within 125 cm of the mineral soil surface, both: EDDI. Other Kandiperox that have both: 242 Keys to Soil Taxonomy

1. 16 kg/m2 or more organic carbon between the mineral organic carbon between the mineral soil surface and a depth of soil surface and a depth of 100 cm; and 100 cm. Humic Sombriperox 2. In all horizons at a depth between 25 and 125 cm from the mineral soil surface, more than 50 percent colors that EDAD. Other Sombriperox. have both of the following: Typic Sombriperox a. Hue of 2.5YR or redder; and b. A value, moist, of 3 or less. Torrox Humic Rhodic Kandiperox Key to Great Groups EDDJ. Other Kandiperox that have both: EBA. Torrox that have, in one or more subhorizons of an oxic 1. 16 kg/m2 or more organic carbon between the mineral or kandic horizon within 150 cm of the mineral soil surface, an soil surface and a depth of 100 cm; and apparent ECEC of less than 1.50 cmol(+) per kg clay and a pH value (1N KCl) of 5.0 or more. 2. 50 percent or more hue of 7.5YR or yellower and a color Acrotorrox, p. 242 value, moist, of 6 or more at a depth between 25 and 125 cm from the mineral soil surface. EBB. Other Torrox that have a base saturation (by NH OAc) Humic Xanthic Kandiperox 4 of 35 percent or more in all horizons within 125 cm of the mineral soil surface. EDDK. Other Kandiperox that have 16 kg/m2 or more Eutrotorrox, p. 242 organic carbon between the mineral soil surface and a depth of 100 cm. EBC. Other Torrox. Humic Kandiperox Haplotorrox, p. 243 EDDL. Other Kandiperox that have, in all horizons at a depth between 25 and 125 cm from the mineral soil surface, Acrotorrox more than 50 percent colors that have both of the following: Key to Subgroups 1. Hue of 2.5YR or redder; and EBAA. Acrotorrox that have a petroferric contact within 125 2. A value, moist, of 3 or less. cm of the mineral soil surface. Rhodic Kandiperox Petroferric Acrotorrox

EDDM. Other Kandiperox that have 50 percent or more EBAB. Other Acrotorrox that have a lithic contact within 125 hue of 7.5YR or yellower and a color value, moist, of 6 or more cm of the mineral soil surface. at a depth between 25 and 125 cm from the mineral soil surface. Lithic Acrotorrox Xanthic Kandiperox EBAC. Other Acrotorrox. EDDN. Other Kandiperox. Typic Acrotorrox Typic Kandiperox Eutrotorrox Sombriperox Key to Subgroups Key to Subgroups EBBA. Eutrotorrox that have a petroferric contact within 125 EDAA. Sombriperox that have a petroferric contact within cm of the mineral soil surface. 125 cm of the mineral soil surface. Petroferric Eutrotorrox Petroferric Sombriperox EBBB. Other Eutrotorrox that have a lithic contact within 125 EDAB. Other Sombriperox that have a lithic contact within cm of the mineral soil surface. 125 cm of the mineral soil surface. Lithic Eutrotorrox Lithic Sombriperox EBBC. Other Eutrotorrox. EDAC. Other Sombriperox that have 16 kg/m2 or more Typic Eutrotorrox Oxisols 243

Haplotorrox EEBB. Other Acrudox that have a petroferric contact within 125 cm of the mineral soil surface. Key to Subgroups Petroferric Acrudox EBCA. Haplotorrox that have a petroferric contact within 125 EEBC. Other Acrudox that have, within 125 cm of the mineral cm of the mineral soil surface. soil surface, both: Petroferric Haplotorrox 1. A lithic contact; and EBCB. Other Haplotorrox that have a lithic contact within 125 2. Redox depletions with a color value, moist, of 4 or more cm of the mineral soil surface. and chroma of 2 or less and also aquic conditions for some Lithic Haplotorrox time in normal years (or artificial drainage). Aquic Lithic Acrudox EBCC. Other Haplotorrox. Typic Haplotorrox EEBD. Other Acrudox that have a lithic contact within 125 cm of the mineral soil surface. Udox Lithic Acrudox Key to Great Groups EEBE. Other Acrudox that have, within 125 cm of the mineral soil surface, both: EEA. Udox that have a sombric horizon within 150 cm of the 1. A delta pH (KCl pH minus 1:1 water pH) with mineral soil surface. a 0 or net positive charge in a layer 18 cm or more thick; and Sombriudox, p. 247 2. Redox depletions with a color value, moist, of 4 or more EEB. Other Udox that have, in one or more subhorizons of an and chroma of 2 or less and also aquic conditions for some oxic or kandic horizon within 150 cm of the mineral soil time in normal years (or artificial drainage). surface, an apparent ECEC of less than 1.50 cmol(+) per kg clay Anionic Aquic Acrudox and a pH value (1N KCl) of 5.0 or more. Acrudox, p. 243 EEBF. Other Acrudox 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

EEC. Other Udox that have a base saturation (by NH4OAc) of more thick within 125 cm of the mineral soil surface. 35 percent or more in all horizons within 125 cm of the mineral Anionic Acrudox soil surface. Eutrudox, p. 244 EEBG. Other Acrudox that have 5 percent or more (by volume) plinthite in one or more horizons within 125 cm of the EED. Other Udox that have a kandic horizon that has its upper mineral soil surface. boundary within 150 cm of the mineral soil surface. Plinthic Acrudox Kandiudox, p. 246 O EEBH. Other Acrudox that have, in one or more horizons X EEE. Other Udox. within 125 cm of the mineral soil surface, redox depletions with I Hapludox, p. 245 a color value, moist, of 4 or more and chroma of 2 or less and also aquic conditions for some time in normal years (or artificial Acrudox drainage). Aquic Acrudox Key to Subgroups EEBI. Other Acrudox that have a base saturation (by EEBA. Acrudox that have, within 125 cm of the mineral soil NH OAc) of 35 percent or more in all horizons within 125 cm surface, both: 4 of the mineral soil surface. 1. A petroferric contact; and Eutric Acrudox 2. Redox depletions with a color value, moist, of 4 or more EEBJ. Other Acrudox that have both: 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 Petroferric Acrudox soil surface and a depth of 100 cm; and 244 Keys to Soil Taxonomy

2. In all horizons at a depth between 25 and 125 cm from EECC. Other Eutrudox 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 Acrudox time in normal years (or artificial drainage). Aquic Lithic Eutrudox EEBK. Other Acrudox that have both: EECD. Other Eutrudox 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 Eutrudox 2. 50 percent or more hue of 7.5YR or yellower and a color EECE. Other Eutrudox 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 Acrudox 1. 5 percent or more (by volume) plinthite; and 2. Redox depletions with a color value, moist, of 4 or more EEBL. Other Acrudox that have 16 kg/m2 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 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 also aquic conditions for some time in normal years (or artificial of 7.5YR or yellower and a color value, moist, of 6 or more drainage). at a depth between 25 and 125 cm from the mineral soil surface. Aquic Eutrudox Xanthic Acrudox EECH. Other Eutrudox that have a kandic horizon that has its EEBO. Other Acrudox. upper boundary within 150 cm of the mineral soil surface. Typic Acrudox Kandiudalfic Eutrudox

Eutrudox EECI. Other Eutrudox that have both: 1. 16 kg/m2 or more organic carbon between the mineral Key to Subgroups soil surface and a depth of 100 cm; and EECA. Eutrudox that have, within 125 cm of the mineral soil 2. An oxic horizon that has its lower boundary within 125 surface, both: cm of the mineral soil surface. 1. A petroferric contact; and Humic Inceptic Eutrudox 2. Redox depletions with a color value, moist, of 4 or more EECJ. Other Eutrudox 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 Eutrudox Aquic Petroferric Eutrudox EECK. Other Eutrudox that have both: EECB. Other Eutrudox 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 Eutrudox soil surface and a depth of 100 cm; and Oxisols 245

2. In all horizons at a depth between 25 and 125 cm from EEEC. Other Hapludox 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 Eutrudox time in normal years (or artificial drainage). Aquic Lithic Hapludox EECL. Other Eutrudox that have both: EEED. Other Hapludox 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 Hapludox 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 EEEE. Other Hapludox that have, in one or more horizons from the mineral soil surface. within 125 cm of the mineral soil surface, both: Humic Xanthic Eutrudox 1. 5 percent or more (by volume) plinthite; and 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 O X Hapludox EEEI. Other Hapludox that have, throughout one or more I horizons with a total thickness of 18 cm or more within 75 cm of Key to Subgroups the mineral soil surface, a fine-earth fraction with both a bulk EEEA. Hapludox that have, within 125 cm of the mineral soil density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 surface, both: and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. 1. A petroferric contact; and Andic 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 EEEJ. Other Hapludox that have both: time in normal years (or artificial drainage). 1. 16 kg/m2 or more organic carbon between the mineral Aquic Petroferric Hapludox soil surface and a depth of 100 cm; and EEEB. Other Hapludox that have a petroferric contact within 2. In all horizons at a depth between 25 and 125 cm from 125 cm of the mineral soil surface. the mineral soil surface, more than 50 percent colors that Petroferric Hapludox have both of the following: 246 Keys to Soil Taxonomy

a. 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 b. A value, moist, of 3 or less. time in normal years (or artificial drainage). Humic Rhodic Hapludox Aquic Lithic Kandiudox EEEK. Other Hapludox that have both: EEDD. Other Kandiudox 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 Kandiudox 2. 50 percent or more hue of 7.5YR or yellower and a color EEDE. Other Kandiudox 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 Hapludox 1. 5 percent or more (by volume) plinthite; and 2. Redox depletions with a color value, moist, of 4 or more EEEL. Other Hapludox that have 16 kg/m2 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 Hapludox Plinthaquic Kandiudox EEEM. Other Hapludox that have, in all horizons at a depth EEDF. Other Kandiudox 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 Kandiudox 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 of Typic Hapludox 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, Kandiudox 1 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 Oxisols 247

2. 50 percent or more hue of 7.5YR or yellower and a color surface, an apparent ECEC of less than 1.50 cmol(+) per kg clay value, moist, of 6 or more at a depth between 25 and 125 cm and a pH value (1N KCl) of 5.0 or more. from the mineral soil surface. Acrustox, p. 247 Humic Xanthic Kandiudox

ECC. Other Ustox that have a base saturation (by NH4OAc) of EEDK. Other Kandiudox that have 16 kg/m2 or more organic 35 percent or more in all horizons within 125 cm of the mineral carbon between the mineral soil surface and a depth of 100 cm. soil surface. Humic Kandiudox Eutrustox, p. 248

EEDL. Other Kandiudox that have, in all horizons at a depth ECD. Other Ustox that have a kandic horizon that has its between 25 and 125 cm from the mineral soil surface, more than upper boundary within 150 cm of the mineral soil surface. 50 percent colors that have both of the following: Kandiustox, p. 250 1. Hue of 2.5YR or redder; and ECE. Other Ustox. 2. A value, moist, of 3 or less. Haplustox, p. 249 Rhodic Kandiudox Acrustox EEDM. Other Kandiudox that have 50 percent or more hue 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. ECBA. Acrustox that have, within 125 cm of the mineral soil Xanthic Kandiudox surface, both: EEDN. Other Kandiudox. 1. A petroferric contact; and Typic Kandiudox 2. Redox depletions with a color value, moist, of 4 or more and chroma of 2 or less and also aquic conditions for some Sombriudox time in normal years (or artificial drainage). Aquic Petroferric Acrustox Key to Subgroups EEAA. Sombriudox that have a petroferric contact within 125 ECBB. Other Acrustox that have a petroferric contact within cm of the mineral soil surface. 125 cm of the mineral soil surface. Petroferric Sombriudox Petroferric Acrustox

EEAB. Other Sombriudox that have a lithic contact within 125 ECBC. Other Acrustox that have, within 125 cm of the cm of the mineral soil surface. mineral soil surface, both: Lithic Sombriudox 1. A lithic contact; and O 2 EEAC. Other Sombriudox that have 16 kg/m or more 2. Redox depletions with a color value, moist, of 4 or more X organic carbon between the mineral soil surface and a depth and chroma of 2 or less and also aquic conditions for some I of 100 cm. 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 ECBE. Other Acrustox that have, within 125 cm of the mineral Key to Great Groups soil surface, both: 1. A delta pH (KCl pH minus 1:1 water pH) with a 0 or net ECA. Ustox that have a sombric horizon within 150 cm of the positive charge in a layer 18 cm or more thick; and mineral soil surface. Sombriustox, 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 ECB. Other Ustox that have, in one or more subhorizons of an time in normal years (or artificial drainage). oxic or kandic horizon within 150 cm of the mineral soil Anionic Aquic Acrustox 248 Keys to Soil Taxonomy

ECBF. Other Acrustox that have a delta pH (KCl pH minus ECBN. Other Acrustox that have 50 percent or more hue of 1:1 water pH) with a 0 or net positive charge in a layer 18 cm or 7.5YR or yellower and a color value, moist, of 6 or more at a more thick within 125 cm of the mineral soil surface. depth between 25 and 125 cm from the mineral soil surface. Anionic Acrustox Xanthic Acrustox

ECBG. Other Acrustox that have 5 percent or more (by ECBO. Other Acrustox. volume) plinthite in one or more horizons within 125 cm of the Typic Acrustox mineral soil surface. Plinthic Acrustox Eutrustox

ECBH. Other Acrustox that have, in one or more horizons Key to Subgroups within 125 cm of the mineral soil surface, redox depletions with ECCA. Eutrustox that have, within 125 cm of the mineral a color value, moist, of 4 or more and chroma of 2 or less and soil surface, both: also aquic conditions for some time in normal years (or artificial drainage). 1. A petroferric contact; and Aquic Acrustox 2. Redox depletions with a color value, moist, of 4 or more and chroma of 2 or less and also aquic conditions for ECBI. Other Acrustox that have a base saturation (by some time in normal years (or artificial drainage). NH OAc) of 35 percent or more in all horizons within 125 cm 4 Aquic Petroferric Eutrustox of the mineral soil surface. Eutric Acrustox ECCB. Other Eutrustox that have a petroferric contact within 125 cm of the mineral soil surface. ECBJ. Other Acrustox that have both: Petroferric Eutrustox 1. 16 kg/m2 or more organic carbon between the mineral soil surface and a depth of 100 cm; and ECCC. Other Eutrustox that have, within 125 cm of the mineral soil surface, both: 2. In all horizons at a depth between 25 and 125 cm from 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 a. Hue of 2.5YR or redder; and more 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 Eutrustox Humic Rhodic Acrustox ECCD. Other Eutrustox that have a lithic contact within ECBK. Other Acrustox that have both: 125 cm of the mineral soil surface. 1. 16 kg/m2 or more organic carbon between the mineral Lithic Eutrustox soil surface and a depth of 100 cm; and ECCE. Other Eutrustox 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 Acrustox 2. Redox depletions with a color value, moist, of 4 or more and chroma of 2 or less and also aquic conditions for ECBL. Other Acrustox that have 16 kg/m2 or more organic some time in normal years (or artificial drainage). carbon between the mineral soil surface and a depth of 100 cm. Plinthaquic Eutrustox Humic Acrustox ECCF. Other Eutrustox that have 5 percent or more (by ECBM. Other Acrustox that have, in all horizons at a depth volume) plinthite in one or more horizons within 125 cm of between 25 and 125 cm from the mineral soil surface, more than the mineral soil surface. 50 percent colors that have both of the following: Plinthic Eutrustox 1. Hue of 2.5YR or redder; and ECCG. Other Eutrustox that have, in one or more horizons 2. A value, moist, of 3 or less. within 125 cm of the mineral soil surface, redox depletions Rhodic Acrustox with a color value, moist, of 4 or more and chroma of 2 or Oxisols 249

less and also aquic conditions for some time in normal years (or 7.5YR or yellower and a color value, moist, of 6 or more at a artificial drainage). depth between 25 and 125 cm from the mineral soil surface. Aquic Eutrustox Xanthic Eutrustox

ECCH. Other Eutrustox that have a kandic horizon that has its ECCP. Other Eutrustox. upper boundary within 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 soil surface and a depth of 100 cm; and ECEA. Haplustox that have, within 125 cm of the mineral soil surface, both: 2. An oxic horizon that has its lower boundary within 125 cm of the mineral soil surface. 1. A petroferric contact; and 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. 1. 16 kg/m2 or more organic carbon between the mineral Petroferric Haplustox 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 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 and chroma of 2 or less and also aquic conditions for some b. A value, moist, of 3 or less. time in normal years (or artificial drainage). Humic Rhodic Eutrustox Aquic Lithic Haplustox ECCL. Other Eutrustox that have both: ECED. Other Haplustox 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 Haplustox 2. 50 percent or more hue of 7.5YR or yellower and a color O ECEE. Other Haplustox that have, in one or more horizons value, moist, of 6 or more at a depth between 25 and 125 cm X within 125 cm of the mineral soil surface, both: from the mineral soil surface. I Humic Xanthic Eutrustox 1. 5 percent or more (by volume) plinthite; and 2. Redox depletions with a color value, moist, of 4 or more ECCM. Other Eutrustox that have 16 kg/m2 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 Eutrustox Plinthaquic Haplustox ECCN. Other Eutrustox that have, in all horizons at a depth ECEF. Other Haplustox 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 Haplustox 2. A value, moist, of 3 or less. ECEG. Other Haplustox that have, within 125 cm of the Rhodic Eutrustox mineral soil surface, both: ECCO. Other Eutrustox that have 50 percent or more hue of 1. The lower boundary of the oxic horizon; and 250 Keys to Soil Taxonomy

2. Redox depletions with a color value, moist, of 4 or more 2. A value, moist, of 3 or less. and chroma of 2 or less and also aquic conditions for some Rhodic Haplustox time in normal years (or artificial drainage). Aqueptic Haplustox ECEO. Other Haplustox that have 50 percent or more hue of 7.5YR or yellower and a color value, moist, of 6 or more ECEH. Other Haplustox that have, in one or more horizons at a depth between 25 and 125 cm from the mineral soil within 125 cm of the mineral soil surface, redox depletions with 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 soil surface, both: 2. 30 or more cumulative days. Oxyaquic Haplustox 1. A petroferric contact; and 2. Redox depletions with a color value, moist, of 4 or more ECEJ. Other Haplustox that have an oxic horizon that has and chroma of 2 or less and also aquic conditions for some its lower boundary within 125 cm of the mineral soil surface. time in normal years (or artificial drainage). Inceptic Haplustox Aquic Petroferric Kandiustox ECEK. Other Haplustox that have both: ECDB. Other Kandiustox that have a petroferric contact 1. 16 kg/m2 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 ECDC. Other Kandiustox 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 Haplustox time in normal years (or artificial drainage). Aquic Lithic Kandiustox ECEL. Other Haplustox that have both: 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. Lithic Kandiustox 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 ECDE. Other Kandiustox that have, in one or more horizons from the mineral soil surface. within 125 cm of the mineral soil surface, both: Humic Xanthic Haplustox 1. 5 percent or more (by volume) plinthite; and ECEM. Other Haplustox that have 16 kg/m2 or more 2. Redox depletions with a color value, moist, of 4 or more organic carbon between the mineral soil surface and a depth and chroma of 2 or less and also aquic conditions for some of 100 cm. time in normal years (or artificial drainage). Humic Haplustox Plinthaquic Kandiustox ECEN. Other Haplustox that have, in all horizons at a depth ECDF. Other Kandiustox 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 Kandiustox Oxisols 251

ECDG. Other Kandiustox that have, in one or more horizons between 25 and 125 cm from the mineral soil surface, more than within 125 cm of the mineral soil surface, redox depletions with 50 percent colors that have both of the following: 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 b. A value, moist, of 3 or less. Sombriustox Humic Rhodic Kandiustox Key to Subgroups ECDI. Other Kandiustox that have both: ECAA. Sombriustox 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 Sombriustox soil surface and a depth of 100 cm; and 2. 50 percent or more hue of 7.5YR or yellower and a color ECAB. Other Sombriustox 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 Sombriustox Humic Xanthic Kandiustox ECAC. Other Sombriustox that have 16 kg/m2 or more organic ECDJ. Other Kandiustox that have 16 kg/m2 or more organic carbon between the mineral soil surface and a depth of 100 cm. carbon between the mineral soil surface and a depth of 100 cm. Humic Sombriustox Humic Kandiustox ECAD. Other Sombriustox. ECDK. Other Kandiustox that have, in all horizons at a depth Typic Sombriustox

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CHAPTER 14 Spodosols

Key to Suborders CAD. Other Aquods that have a placic horizon within 100 cm of the mineral soil surface in 50 percent or more of each pedon. CA. Spodosols that have aquic conditions for some time in Placaquods, p. 255 normal years (or artificial drainage) in one or more horizons within 50 cm of the mineral soil surface and have one or both of CAE. Other Aquods that have, in 90 percent or more of each the following: pedon, a cemented soil layer that has its upper boundary within 100 cm of the mineral soil surface. 1. A histic epipedon; or Duraquods, p. 254 2. Within 50 cm of the mineral soil surface, redoximorphic features in an albic or a spodic horizon. CAF. Other Aquods that have episaturation. Aquods, p. 253 Epiaquods, p. 255

CB. Other Spodosols that have, in normal years, a mean CAG. Other Aquods. annual soil temperature of 0 oC or colder and a mean summer Endoaquods, p. 254 soil temperature that: 1. Is 8 oC or colder if there is no O horizon; or Alaquods 2. Is 5 oC or colder if there is an O horizon. Key to Subgroups Gelods, p. 257 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. 255 CABB. Other Alaquods that have, in 90 percent or more of each pedon, a cemented soil layer that does not slake in water CD. Other Spodosols that have 6.0 percent or more organic after air drying and has its upper boundary within 100 cm of the carbon in a layer 10 cm or more thick within the spodic horizon. mineral soil surface. Humods, p. 257 Duric Alaquods CE. Other Spodosols. CABC. Other Alaquods that have a histic epipedon. Orthods, p. 258 Histic Alaquods S P Aquods CABD. Other Alaquods that have both: O Key to Great Groups 1. Within 200 cm of the mineral soil surface, an argillic or kandic horizon that has a base saturation of 35 percent or CAA. Aquods that have a cryic soil temperature regime. more (by sum of cations) in some part; and Cryaquods, p. 254 2. A sandy or sandy-skeletal particle-size class throughout a layer extending from the mineral soil surface to the top of a CAB. Other Aquods that have less than 0.10 percent iron (by spodic horizon at a depth of 75 to 125 cm. ammonium oxalate) in 75 percent or more of the spodic horizon. Alfic Arenic Alaquods Alaquods, p. 253 CABE. Other Alaquods that have both: CAC. Other Aquods that have a fragipan with its upper boundary within 100 cm of the mineral soil surface. 1. An argillic or kandic horizon within 200 cm of the Fragiaquods, p. 255 mineral soil surface; and 254 Keys to Soil Taxonomy

2. A sandy or sandy-skeletal particle-size class throughout a each pedon, a cemented soil layer that does not slake in water layer extending from the mineral soil surface to the top of a after air drying and has its upper boundary within 100 cm of the spodic horizon at a depth of 75 to 125 cm. mineral soil surface. Arenic Ultic Alaquods Duric Cryaquods

CABF. Other Alaquods that have both: CAAD. Other Cryaquods that have andic soil properties throughout horizons that have a total thickness of 25 cm or more 1. An umbric epipedon; and within 75 cm either of the mineral soil surface or of the top of an 2. A sandy or sandy-skeletal particle-size class throughout a organic layer with andic soil properties, whichever is shallower. layer extending from the mineral soil surface to the top of a Andic Cryaquods 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 have a sandy or sandy-skeletal Entic Cryaquods particle-size class throughout a layer extending from the mineral soil surface to the top of a spodic horizon at a depth of 75 to 125 CAAF. Other Cryaquods. cm. Typic Cryaquods Arenic Alaquods

CABH. Other Alaquods that have a sandy or sandy-skeletal Duraquods particle-size class throughout a layer extending from the mineral Key to Subgroups soil surface to the top of a spodic horizon at a depth of 125 cm or more. CAEA. Duraquods that have a histic epipedon. Grossarenic Alaquods Histic Duraquods

CABI. Other Alaquods that have, within 200 cm of the mineral CAEB. Other Duraquods that have andic soil properties soil surface, an argillic or kandic horizon that has a base throughout horizons that have a total thickness of 25 cm or saturation of 35 percent or more (by sum of cations) 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 top of an CAAB. Other Cryaquods that have a placic horizon within organic layer with andic soil properties, whichever is shallower. 100 cm of the mineral soil surface in 50 percent or more of each Andic Endoaquods pedon. Placic Cryaquods CAGD. Other Endoaquods that have an argillic or kandic horizon within 200 cm of the mineral soil surface. CAAC. Other Cryaquods that have, in 90 percent or more of Argic Endoaquods Spodosols 255

CAGE. Other Endoaquods that have an umbric epipedon. CACD. Other Fragiaquods. Umbric Endoaquods Typic Fragiaquods

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 more within 75 Key to Subgroups cm either of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. CAFA. Epiaquods that have a lithic contact within 50 cm of Andic Placaquods the mineral soil surface. Lithic Epiaquods CADB. Other Placaquods. Typic Placaquods CAFB. Other Epiaquods that have a histic epipedon. Histic Epiaquods Cryods CAFC. Other Epiaquods that have andic soil properties throughout horizons that have a total thickness of 25 cm or more Key to Great Groups within 75 cm either of the mineral soil surface or of the top of an CCA. Cryods that have a placic horizon within 100 cm of organic layer with andic soil properties, whichever is shallower. the mineral soil surface in 50 percent or more of each pedon. Andic Epiaquods Placocryods, p. 257 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 soil layer that does not slake in water after saturation of 35 percent or more (by sum of cations) in some air drying and has its upper boundary within 100 cm of the part. mineral soil surface. Alfic Epiaquods Duricryods, p. 255 CAFE. Other Epiaquods that have an argillic or kandic CCC. Other Cryods that have 6.0 percent or more organic horizon within 200 cm of the mineral soil surface. carbon throughout a layer 10 cm or more thick within the spodic Ultic Epiaquods horizon. Humicryods, p. 256 CAFF. Other Epiaquods that have an umbric epipedon. Umbric Epiaquods CCD. Other Cryods. Haplocryods, p. 256 CAFG. Other Epiaquods. Typic Epiaquods Duricryods S Key to Subgroups Fragiaquods P CCBA. Duricryods that have both: O Key to Subgroups 1. Redoximorphic features in one or more horizons CACA. Fragiaquods that have a histic epipedon. within 75 cm of the mineral soil surface and also aquic Histic Fragiaquods conditions for some time in normal years (or artificial drainage); and CACB. Other Fragiaquods that have a surface horizon 30 cm or more thick that meets all of the requirements for a plaggen 2. Andic soil properties throughout horizons that have a epipedon except thickness. total thickness of 25 cm or more within 75 cm either of the Plagganthreptic Fragiaquods mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. CACC. Other Fragiaquods that have an argillic or kandic Aquandic Duricryods horizon within 200 cm of the mineral soil surface. Argic Fragiaquods CCBB. Other Duricryods that have andic soil properties 256 Keys to Soil Taxonomy

throughout horizons that have a total thickness of 25 cm or more and also aquic conditions for some time in normal years (or within 75 cm either of the mineral soil surface or of the top of an artificial drainage). organic layer with andic soil properties, whichever is shallower. Aquic Haplocryods Andic Duricryods CCDE. Other Haplocryods that are saturated with water in one CCBC. Other Duricryods that have redoximorphic features in or more layers within 100 cm of the mineral soil surface 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 1. 20 or more consecutive days; or artificial drainage). Aquic Duricryods 2. 30 or more cumulative days. Oxyaquic Haplocryods CCBD. Other Duricryods that are saturated with water in one or more layers within 100 cm of the mineral soil surface in CCDF. Other Haplocryods that have 1.1 percent or less normal years for either or both: organic carbon in the upper 10 cm of the spodic horizon. Entic Haplocryods 1. 20 or more consecutive days; or 2. 30 or more cumulative days. CCDG. Other Haplocryods. Oxyaquic Duricryods Typic Haplocryods

CCBE. Other Duricryods that have 6.0 percent or more Humicryods organic carbon throughout a layer 10 cm or more thick within the spodic horizon. Key to Subgroups Humic Duricryods CCCA. Humicryods that have a lithic contact within 50 cm of the mineral soil surface. CCBF. Other Duricryods. Lithic Humicryods Typic Duricryods CCCB. Other Humicryods that have both: Haplocryods 1. Redoximorphic features in one or more horizons Key to Subgroups within 75 cm of the mineral soil surface and also aquic conditions for some time in normal years (or artificial CCDA. Haplocryods that have a lithic contact within 50 cm of drainage); and the mineral soil surface. 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 andic soil properties, whichever is shallower. 1. Redoximorphic features in one or more horizons Aquandic Humicryods within 75 cm of the mineral soil surface and also aquic conditions for some time in normal years (or artificial CCCC. Other Humicryods that have andic soil properties drainage); and throughout horizons that have a total thickness of 25 cm or 2. Andic soil properties throughout horizons that have a more within 75 cm either of the mineral soil surface or of the top total thickness of 25 cm or more within 75 cm either of the of an organic layer with andic soil properties, whichever is mineral soil surface or of the top of an organic layer with shallower. andic soil properties, whichever is shallower. Andic Humicryods Aquandic Haplocryods CCCD. Other Humicryods that have redoximorphic features in CCDC. Other Haplocryods that have andic soil properties one or more horizons within 75 cm of the mineral soil surface throughout horizons that have a total thickness of 25 cm or more and also aquic conditions for some time in normal years (or within 75 cm either of the mineral soil surface or of the top of an artificial drainage). organic layer with andic soil properties, whichever is shallower. Aquic Humicryods Andic Haplocryods CCCE. Other Humicryods that are saturated with water in one CCDD. Other Haplocryods that have redoximorphic features 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: Spodosols 257

1. 20 or more consecutive days; or in one or more horizons within 75 cm of the mineral soil surface and also aquic conditions for some time in normal years (or 2. 30 or more cumulative days. artificial drainage). Oxyaquic Humicryods Aquic Haplogelods CCCF. Other Humicryods. CBBD. Other Haplogelods. Typic Humicryods 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 CBAD. Other Humigelods. throughout a layer 10 cm or more thick within the spodic Typic Humigelods horizon. Humigelods, p. 257 Humods CBB. Other Gelods. Key to Great Groups Haplogelods, p. 257 CDA. Humods that have a placic horizon within 100 cm of the Haplogelods mineral soil surface in 50 percent or more of each pedon. Placohumods, p. 258 Key to Subgroups S CDB. Other Humods that have, in 90 percent or more of each P CBBA. Haplogelods that have a lithic contact within 50 cm of pedon, a cemented soil layer that does not slake in water after O the mineral soil surface. air drying and has its upper boundary within 100 cm of the Lithic Haplogelods mineral soil surface. Durihumods, p. 258 CBBB. Other Haplogelods that have andic soil properties throughout horizons that have a total thickness of 25 cm or more CDC. Other Humods that have a fragipan with its upper within 75 cm either of the mineral soil surface or of the top of an boundary within 100 cm of the mineral soil surface. organic layer with andic soil properties, whichever is shallower. Fragihumods, p. 258 Andic Haplogelods CDD. Other Humods. CBBC. Other Haplogelods that have redoximorphic features Haplohumods, p. 258 258 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. 261 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 soil layer that does not slake in water after CDBB. Other Durihumods. air drying and has its upper boundary within 100 cm of the Typic Durihumods mineral soil surface. Durorthods, p. 259 Fragihumods CEC. Other Orthods that have a fragipan with its upper Key to Subgroups boundary within 100 cm of the mineral soil surface. CDCA. All Fragihumods (provisionally). Fragiorthods, p. 259 Typic Fragihumods CED. Other Orthods that have less than 0.10 percent iron (by Haplohumods ammonium oxalate) in 75 percent or more of the spodic horizon. Alorthods, p. 258 Key to Subgroups CEE. Other Orthods. CDDA. Haplohumods that have a lithic contact within 50 cm Haplorthods, p. 260 of the mineral soil surface. 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 top of an CEDA. Alorthods that are saturated with water in one or more organic layer with andic soil properties, whichever is shallower. layers within 100 cm of the mineral soil surface in normal years Andic Haplohumods for either or both: 1. 20 or more consecutive days; or CDDC. Other Haplohumods that have a surface horizon 30 cm or more thick that meets all of the requirements for a plaggen 2. 30 or more cumulative days. epipedon except thickness. Oxyaquic Alorthods Plagganthreptic Haplohumods CEDB. Other Alorthods that have both: CDDD. Other Haplohumods. 1. A sandy or sandy-skeletal particle-size class throughout a Typic Haplohumods layer extending from the mineral soil surface to the top of a spodic horizon at a depth of 75 to 125 cm; and Placohumods 2. 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 have a sandy or sandy-skeletal throughout horizons that have a total thickness of 25 cm or particle-size class throughout a layer extending from the mineral more within 75 cm either of the mineral soil surface or of the soil surface to the top of a spodic horizon at a depth of 75 to 125 top of an organic layer with andic soil properties, whichever is cm. shallower. Arenic Alorthods Andic Placohumods CEDD. Other Alorthods that have both: CDAB. Other Placohumods. Typic Placohumods 1. A sandy or sandy-skeletal particle-size class throughout a Spodosols 259

layer extending from the mineral soil surface to the top of a Fragiorthods spodic horizon at a depth of 125 cm or more; and Key to Subgroups 2. In 10 percent or more of each pedon, less than 3.0 percent organic carbon in the upper 2 cm of the spodic CECA. Fragiorthods that have redoximorphic features in one horizon. or more horizons within 75 cm of the mineral soil surface and Entic Grossarenic Alorthods also aquic conditions for some time in normal years (or artificial drainage). CEDE. Other Alorthods that have, in 10 percent or more of Aquic Fragiorthods each pedon, less than 3.0 percent organic carbon in the upper 2 cm of the spodic horizon. CECB. Other Fragiorthods that: Entic Alorthods 1. Are saturated with water in one or more layers within 100 cm of the mineral soil surface in normal years for either CEDF. Other Alorthods that have a sandy or sandy-skeletal or both: particle-size class throughout a layer extending from the mineral soil surface to the top of a spodic horizon at a depth of 125 cm a. 20 or more consecutive days; or or more. b. 30 or more cumulative days; and Grossarenic Alorthods 2. Have, within 200 cm of the mineral soil surface, an CEDG. Other Alorthods that have a surface horizon 30 cm or argillic or kandic horizon that has a base saturation of 35 more thick that meets all of the requirements for a plaggen percent or more (by sum of cations) in some part. epipedon except thickness. Alfic Oxyaquic Fragiorthods Plagganthreptic Alorthods CECC. Other Fragiorthods that are saturated with water in one CEDH. Other Alorthods that have, within 200 cm of the or more layers within 100 cm of the mineral soil surface in mineral soil surface, an argillic or kandic horizon that has a base normal years for either or both: saturation of 35 percent or more (by sum of cations) in some 1. 20 or more consecutive days; or part. Alfic Alorthods 2. 30 or more cumulative days. Oxyaquic Fragiorthods CEDI. Other Alorthods that have an argillic or kandic horizon within 200 cm of the mineral soil surface. CECD. Other Fragiorthods that have a surface horizon 30 cm Ultic Alorthods or more thick that meets all of the requirements for a plaggen epipedon except thickness. CEDJ. Other Alorthods. Plagganthreptic Fragiorthods Typic Alorthods CECE. Other Fragiorthods that have, within 200 cm of the Durorthods mineral soil surface, an argillic or kandic horizon that has a base saturation of 35 percent or more (by sum of cations) in some part. Key to Subgroups Alfic Fragiorthods S CEBA. Durorthods that have andic soil properties P CECF. Other Fragiorthods that have an argillic or kandic throughout horizons that have a total thickness of 25 cm or O horizon within 200 cm of the mineral soil surface. more within 75 cm either of the mineral soil surface or of the Ultic Fragiorthods top of an organic layer with andic soil properties, whichever is shallower. CECG. Other Fragiorthods that have a spodic horizon that has Andic Durorthods one of the following: CEBB. Other Durorthods. 1. A texture of very fine sand, loamy very fine sand, or Typic Durorthods finer; and 260 Keys to Soil Taxonomy

a. A thickness of 10 cm or less; and CEED. Other Haplorthods that have both: b. A weighted average of less than 1.2 percent organic 1. Redoximorphic features in one or more horizons carbon; and within 75 cm of the mineral soil surface and also aquic conditions for some time in normal years (or artificial c. Within the upper 7.5 cm, either or both a moist color drainage); and value or chroma of 4 or more (crushed and smoothed sample); or 2. Within 200 cm of the mineral soil surface, an argillic or kandic horizon that has a base saturation of 35 percent or 2. A texture of loamy fine sand, fine sand, or coarser and more (by sum of cations) in some part. either or both a moist color value or chroma of 4 or more Aqualfic Haplorthods (crushed and smoothed sample) in the upper 2.5 cm. Entic Fragiorthods CEEE. Other Haplorthods that have redoximorphic features in one or more horizons within 75 cm of the mineral soil surface CECH. Other Fragiorthods. and also aquic conditions for some time in normal years (or Typic Fragiorthods artificial drainage); and either Haplorthods 1. A spodic horizon with a texture of very fine sand, loamy very fine sand, or finer; and Key to Subgroups a. A thickness of 10 cm or less; and CEEA. Haplorthods that have a lithic contact within 50 cm of b. A weighted average of less than 1.2 percent organic the mineral soil surface; and either carbon; and 1. A spodic horizon with a texture of very fine sand, loamy c. Within the upper 7.5 cm, either or both a moist color very fine sand, or finer; and value or chroma of 4 or more (crushed and smoothed a. A thickness of 10 cm or less; and sample); or b. A weighted average of less than 1.2 percent organic 2. A spodic horizon with a texture of loamy fine sand, fine carbon; and sand, or coarser and either or both a moist color value or chroma of 4 or more (crushed and smoothed sample) in the c. Within the upper 7.5 cm, either or both a moist color upper 2.5 cm. value or chroma of 4 or more (crushed and smoothed Aquentic Haplorthods sample); or 2. A spodic horizon with a texture of loamy fine sand, fine CEEF. Other Haplorthods that have redoximorphic features in sand, or coarser and either or both a moist color value or one or more horizons within 75 cm of the mineral soil surface chroma of 4 or more (crushed and smoothed sample) in the and also aquic conditions for some time in normal years (or upper 2.5 cm. artificial drainage). Entic Lithic Haplorthods Aquic Haplorthods

CEEB. Other Haplorthods that have a lithic contact within 50 CEEG. Other Haplorthods that have: cm of the mineral soil surface. Lithic Haplorthods 1. Within 200 cm of the mineral soil surface, an argillic or kandic horizon that has a base saturation of 35 percent or CEEC. Other Haplorthods that have both: more (by sum of cations) in some part; and 1. Fragic soil properties: 2. Saturation with water in one or more layers within 100 cm of the mineral soil surface in normal years for either or a. In 30 percent or more of the volume of a layer 15 cm both: or more thick that has its upper boundary within 100 cm of the mineral soil surface; or a. 20 or more consecutive days; or b. In 60 percent or more of the volume of a layer 15 cm b. 30 or more cumulative days. or more thick; and Alfic Oxyaquic Haplorthods 2. Redoximorphic features in one or more horizons within CEEH. Other Haplorthods that have: 75 cm of the mineral soil surface and also aquic conditions for some time in normal years (or artificial drainage). 1. Within 200 cm of the mineral soil surface, an argillic or Fragiaquic Haplorthods kandic horizon; and Spodosols 261

2. Saturation with water in one or more layers within 100 throughout horizons that have a total thickness of 25 cm or cm of the mineral soil surface in normal years for either or more within 75 cm either of the mineral soil surface or of the both: top of an organic layer with andic soil properties, whichever is shallower. a. 20 or more consecutive days; or Andic Haplorthods b. 30 or more cumulative days. Oxyaquic Ultic Haplorthods CEEN. Other Haplorthods that have, within 200 cm of the mineral soil surface, an argillic or kandic horizon that has a base CEEI. Other Haplorthods that have fragic soil properties: saturation of 35 percent or more (by sum of cations) in some part. 1. In 30 percent or more of the volume of a layer 15 cm or Alfic Haplorthods more thick that has its upper boundary within 100 cm of the mineral soil surface; or CEEO. Other Haplorthods that have an argillic or kandic 2. In 60 percent or more of the volume of a layer 15 cm or horizon within 200 cm of the mineral soil surface. more thick. Ultic Haplorthods Fragic Haplorthods CEEP. Other Haplorthods that have a spodic horizon that has CEEJ.Other Haplorthods that have both: one of the following: 1. Saturation with water in 1 or more layers within 100 cm 1. A texture of very fine sand, loamy very fine sand, or of the mineral soil surface in normal years for either or both: finer; and a. 20 or more consecutive days; or a. A thickness of 10 cm or less; and b. 30 or more cumulative days; and b. A weighted average of less than 1.2 percent organic carbon; and 2. Below the spodic horizon but not below an argillic horizon, lamellae (two or more) within 200 cm of the mineral c. Within the upper 7.5 cm, either or both a moist color soil surface. value or chroma of 4 or more (crushed and smoothed Lamellic Oxyaquic Haplorthods sample); or 2. A texture of loamy fine sand, fine sand, or coarser CEEK. Other Haplorthods that, below the spodic horizon but and either or both a moist color value or chroma of 4 not below an argillic horizon, have lamellae (two or more) or more (crushed and smoothed sample) in the upper within 200 cm of the mineral soil surface. 2.5 cm. Lamellic Haplorthods Entic Haplorthods CEEL. Other Haplorthods that are saturated with water in one CEEQ. Other Haplorthods. or more layers within 100 cm of the mineral soil surface in Typic Haplorthods normal years for either or both: 1. 20 or more consecutive days; or Placorthods 2. 30 or more cumulative days. S Key to Subgroups Oxyaquic Haplorthods P CEAA. All Placorthods (provisionally). O CEEM. Other Haplorthods that have andic soil properties Typic Placorthods

263

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 cm following: 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. 267 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 with an upper 40 cm and one of the following within the upper 12.5 cm of boundary within 100 cm of the mineral soil surface. the argillic or kandic horizon: Fragiaquults, p. 265 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 0.4 cm/hr or slower (moderately low or b. 50 percent or more redox depletions with chroma of 1 lower) saturated hydraulic conductivity in the argillic or kandic or less either on faces of peds or in the matrix; or horizon. c. Distinct or prominent redox concentrations and 50 Albaquults, p. 264 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. 263 3. Within 150 cm of the mineral soil surface, either: a. With increasing depth, do not have a clay decrease of HB. Other Ultisols that have one or both of the following: 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 2. 12 kg/m 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. 267 Kandiaquults, p. 265 T

HC. Other Ultisols that have a udic moisture regime. HAE. Other Aquults that have a kandic horizon. Udults, p. 270 Kanhaplaquults, p. 265

HD. Other Ultisols that have an ustic moisture regime. HAF. Other Aquults that: Ustults, p. 278 1. Do not have a densic, lithic, paralithic, or petroferric contact within 150 cm of the mineral soil surface; and HE. Other Ultisols. Xerults, p. 281 2. Within 150 cm of the mineral soil surface, either: 264 Keys to Soil Taxonomy

a. With increasing depth, do not have a clay decrease of HAIB. Other Endoaquults that have a sandy or sandy-skeletal 20 percent or more (relative) from the maximum clay particle-size class throughout a layer extending from the mineral content; or 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 the Paleaquults, p. 266 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. 267 HAID. Other Endoaquults. HAH. Other Aquults that have episaturation. Typic Endoaquults Epiaquults, p. 264

HAI. Other Aquults. Epiaquults Endoaquults, p. 264 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 Key to Subgroups are 5 mm or more wide through a thickness of 30 cm or HACA. Albaquults that have one or both of the following: more for some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick that 1. Cracks within 125 cm of the mineral soil surface that are has its upper boundary within 125 cm of the mineral soil 5 mm or more wide through a thickness of 30 cm or more for surface; or some time in normal years and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick that has its upper 2. A linear extensibility of 6.0 cm or more between the boundary within 125 cm of the mineral soil surface; or mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. 2. A linear extensibility of 6.0 cm or more between the Vertic Epiaquults mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. HAHB. Other Epiaquults that have: Vertic Albaquults 1. Fragic soil properties: HACB. Other Albaquults that have a kandic horizon. a. In 30 percent or more of the volume of a layer 15 cm Kandic Albaquults or more thick that has its upper boundary within 100 cm of the mineral soil surface; or HACC. Other Albaquults that have 50 percent or more chroma of 3 or more in one or more horizons between either the A or Ap b. In 60 percent or more of the volume of a layer 15 cm horizon or a depth of 25 cm from the mineral soil surface, or more thick; and whichever is deeper, and a depth of 75 cm. 2. 50 percent or more chroma of 3 or more in one or more Aeric Albaquults horizons between either the A or Ap horizon or a depth of 25 cm from the mineral soil surface, whichever is deeper, and a HACD. Other Albaquults. depth of 75 cm. Typic Albaquults Aeric Fragic Epiaquults

Endoaquults HAHC. Other Epiaquults that have a sandy or sandy-skeletal particle-size class throughout a layer extending from the mineral Key to Subgroups soil surface to the top of an argillic horizon at a depth of 50 to HAIA. Endoaquults that have a sandy or sandy-skeletal 100 cm. particle-size class throughout a layer extending from the mineral Arenic Epiaquults soil surface to the top of an argillic horizon at a depth of 50 to 100 cm. HAHD. Other Epiaquults that have a sandy or sandy-skeletal Arenic Endoaquults particle-size class throughout a layer extending from the mineral Ultisols 265

soil surface to the top of an argillic horizon at a depth of 100 cm 1. A sandy or sandy-skeletal particle-size class throughout a or more. layer extending from the mineral soil surface to the top of a Grossarenic Epiaquults kandic horizon at a depth of 50 to 100 cm; and 2. 5 percent or more (by volume) plinthite in one or more HAHE. Other Epiaquults that have fragic soil properties: horizons within 150 cm of the mineral soil surface. 1. In 30 percent or more of the volume of a layer 15 cm or Arenic Plinthic Kandiaquults more thick that has its upper boundary within 100 cm of the mineral soil surface; or HADC. Other Kandiaquults that: 2. In 60 percent or more of the volume of a layer 15 cm or 1. Have a mollic or umbric epipedon; and more thick. 2. Have a sandy or sandy-skeletal particle-size class Fragic Epiaquults throughout a layer extending from the mineral soil surface to the top of a kandic horizon at a depth of 50 to 100 cm. HAHF. Other Epiaquults that have 50 percent or more chroma Arenic Umbric Kandiaquults 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 surface, HADD. Other Kandiaquults that have a sandy or sandy- whichever is deeper, and a depth of 75 cm. skeletal particle-size class throughout a layer extending from the Aeric Epiaquults mineral soil surface to the top of a kandic horizon at a depth of 50 to 100 cm. HAHG. Other Epiaquults. Arenic Kandiaquults Typic Epiaquults HADE. Other Kandiaquults that have a sandy or sandy- Fragiaquults skeletal particle-size class throughout a layer extending from the mineral soil surface to the top of a kandic horizon at a depth of Key to Subgroups 100 cm or more. HABA. Fragiaquults that have 50 percent or more chroma of 3 Grossarenic Kandiaquults or more in one or more horizons between either the A or Ap horizon or a depth of 25 cm from the mineral soil surface, HADF. Other Kandiaquults that have 5 percent or more (by whichever is deeper, and the fragipan. volume) plinthite in one or more horizons within 150 cm of the Aeric Fragiaquults mineral soil surface. Plinthic Kandiaquults HABB. Other Fragiaquults that have 5 percent or more (by volume) plinthite in one or more horizons within 150 cm of the HADG. Other Kandiaquults that have 50 percent or more mineral soil surface. chroma of 3 or more in one or more horizons between either the Plinthic Fragiaquults A or Ap horizon or a depth of 25 cm from the mineral soil surface, whichever is deeper, and a depth of 75 cm. HABC. Other Fragiaquults that have a mollic or umbric Aeric Kandiaquults epipedon. Umbric Fragiaquults HADH. Other Kandiaquults that have a mollic or umbric epipedon. HABD. Other Fragiaquults. Umbric Kandiaquults Typic Fragiaquults HADI. Other Kandiaquults. U Kandiaquults Typic Kandiaquults L T Key to Subgroups Kanhaplaquults HADA. Kandiaquults that have an ECEC of 1.5 cmol(+)/kg clay or less (sum of bases extracted with 1N NH4OAc pH 7, plus Key to Subgroups 1N KCl-extractable Al) in one or more horizons within 150 cm HAEA. Kanhaplaquults that have, throughout one or more of the mineral soil surface. horizons with a total thickness of 18 cm or more within 75 cm of Acraquoxic Kandiaquults the mineral soil surface, one or more of the following: HADB. Other Kandiaquults that have both: 1. A fine-earth fraction with both a bulk density of 1.0 266 Keys to Soil Taxonomy

g/cm3 or less, measured at 33 kPa water retention, and Al has its upper boundary within 125 cm of the mineral soil 1 plus /2 Fe percentages (by ammonium oxalate) totaling more surface; or than 1.0; or 2. A linear extensibility of 6.0 cm or more between the 2. More than 35 percent (by volume) fragments coarser mineral soil surface and either a depth of 100 cm or a densic, than 2.0 mm, of which more than 66 percent is cinders, lithic, or paralithic contact, whichever is shallower. pumice, and pumicelike fragments; or Vertic Paleaquults 3. A fine-earth fraction containing 30 percent or more HAFB. Other Paleaquults that have both: particles 0.02 to 2.0 mm in diameter; and 1. A sandy or sandy-skeletal particle-size class throughout a a. In the 0.02 to 2.0 mm fraction, 5 percent or more layer extending from the mineral soil surface to the top of an volcanic glass; and argillic horizon at a depth of 50 to 100 cm; and 1 b. [(Al plus /2 Fe, percent extracted by ammonium 2. 5 percent or more (by volume) plinthite in one or more oxalate) times 60] plus the volcanic glass (percent) is horizons within 150 cm of the mineral soil surface. equal to 30 or more. Arenic Plinthic Paleaquults Aquandic Kanhaplaquults HAFC. Other Paleaquults that: HAEB. Other Kanhaplaquults that have 5 percent or more (by volume) plinthite in one or more horizons within 150 cm of the 1. Have a mollic or umbric epipedon; and mineral soil surface. 2. Have a sandy or sandy-skeletal particle-size class Plinthic Kanhaplaquults throughout a layer extending from the mineral soil surface to the top of an argillic horizon at a depth of 50 to 100 cm. HAEC. Other Kanhaplaquults that: Arenic Umbric Paleaquults 1. Have a mollic or umbric epipedon; and HAFD. Other Paleaquults that have a sandy or sandy-skeletal 2. Have 50 percent or more chroma of 3 or more in one or particle-size class throughout a layer extending from the mineral more horizons between either the A or Ap horizon or a depth soil surface to the top of an argillic horizon at a depth of 50 to of 25 cm from the mineral soil surface, whichever is deeper, 100 cm. and a depth of 75 cm. Arenic Paleaquults Aeric Umbric Kanhaplaquults HAFE. Other Paleaquults that have a sandy or sandy-skeletal HAED. Other Kanhaplaquults that have 50 percent or more particle-size class throughout a layer extending from the mineral chroma of 3 or more in one or more horizons between either the soil surface to the top of an argillic horizon at a depth of 100 cm A or Ap horizon or a depth of 25 cm from the mineral soil or more. surface, whichever is deeper, and a depth of 75 cm. Grossarenic Paleaquults Aeric Kanhaplaquults HAFF. Other Paleaquults that have 5 percent or more (by HAEE. Other Kanhaplaquults that have a mollic or umbric volume) plinthite in one or more horizons within 150 cm of the epipedon. mineral soil surface. Umbric Kanhaplaquults Plinthic Paleaquults HAEF. Other Kanhaplaquults. HAFG. Other Paleaquults that have 50 percent or more Typic Kanhaplaquults 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 Paleaquults surface, whichever is deeper, and a depth of 75 cm. Aeric Paleaquults Key to Subgroups HAFH. Other Paleaquults that have a mollic or umbric HAFA. Paleaquults that have one or both of the following: epipedon. 1. Cracks within 125 cm of the mineral soil surface that Umbric Paleaquults are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or HAFI. Other Paleaquults. wedge-shaped aggregates in a layer 15 cm or more thick that Typic Paleaquults Ultisols 267

Plinthaquults HBD. Other Humults that have a kandic horizon. Kanhaplohumults, p. 269 Key to Subgroups HBE. Other Humults that: HAAA. Plinthaquults that have a kandic horizon or a CEC (by 1N NH OAc pH 7) of less than 24 cmol(+)/kg clay in 50 percent 1. Do not have a densic, lithic, paralithic, or petroferric 4 or more (by volume) of the argillic horizon if less than 100 cm contact within 150 cm of the mineral soil surface; and thick or of its upper 100 cm. 2. Within 150 cm of the mineral soil surface, either: Kandic Plinthaquults a. With increasing depth, do not have a clay decrease of HAAB. Other Plinthaquults. 20 percent or more (relative) from the maximum clay Typic Plinthaquults content; or b. Have 5 percent or more (by volume) skeletans on Umbraquults faces of peds 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. HAGA. Umbraquults that have 5 to 50 percent (by volume) Palehumults, p. 269 plinthite in one or more horizons within 150 cm of the mineral soil surface. HBF. Other Humults. Plinthic Umbraquults Haplohumults, p. 267

HAGB. Other Umbraquults. Haplohumults Typic Umbraquults Key to Subgroups Humults HBFA. Haplohumults that have a lithic contact within 50 cm of the mineral soil surface. Key to Great Groups Lithic Haplohumults HBA. Humults that have a sombric horizon within 100 cm of HBFB. Other Haplohumults that have both: the mineral soil surface. Sombrihumults, p. 270 1. In one or more subhorizons within the upper 25 cm of the argillic horizon, redox depletions with a color value, HBB. Other Humults that have one or more horizons within moist, of 4 or more and chroma of 2 or less, accompanied by 150 cm of the mineral soil surface in which plinthite either redox concentrations, and also aquic conditions for some forms a continuous phase or constitutes one-half or more of the time in normal years (or artificial drainage); and volume. 2. Throughout one or more horizons with a total thickness Plinthohumults, p. 270 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 HBC. Other Humults that: or less, measured at 33 kPa water retention, and Al plus 1 1. Do not have a densic, lithic, paralithic, or petroferric /2 Fe percentages (by ammonium oxalate) totaling more than contact within 150 cm of the mineral soil surface; and 1.0. Aquandic Haplohumults 2. Have a kandic horizon; and U 3. Within 150 cm of the mineral soil surface, either: HBFC. Other Haplohumults that have, in one or more L subhorizons within the upper 25 cm of the argillic horizon, T a. With increasing depth, do not have a clay decrease of redox depletions with a color value, moist, of 4 or more and 20 percent or more (relative) from the maximum clay chroma of 2 or less, accompanied by redox concentrations and content; or by aquic conditions for some time in normal years (or artificial b. Have 5 percent or more (by volume) skeletans on drainage). faces of peds in the layer that has a 20 percent lower clay Aquic Haplohumults content and, below that layer, a clay increase of 3 percent or more (absolute) in the fine-earth fraction. HBFD. Other Haplohumults that have, throughout one or Kandihumults, p. 268 more horizons with a total thickness of 18 cm or more within 75 268 Keys to Soil Taxonomy

cm of the mineral soil surface, a fine-earth fraction with both a HBCB. Other Kandihumults that have both: bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 1. Throughout one or more horizons with a total thickness retention, and Al plus /2 Fe percentages (by ammonium oxalate) of 18 cm or more within 75 cm of the mineral soil surface, a totaling more than 1.0. fine-earth fraction with both a bulk density of 1.0 g/cm3 or Andic Haplohumults 1 less, measured at 33 kPa water retention, and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0; HBFE. Other Haplohumults that have 5 percent or more (by and volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. 2. An ustic 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 75 soil surface for either or both: cm 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 1. 20 or more consecutive days; or 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 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 redox concentrations and HBFH. Other Haplohumults that have a xeric moisture regime. by aquic conditions for some time in normal years (or artificial Xeric Haplohumults drainage). Aquic Kandihumults HBFI. Other Haplohumults. Typic Haplohumults HBCE. Other Kandihumults that: 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: g/cm3 or less, measured at 33 kPa water retention, and Al 1 a. 20 or more consecutive days; or 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 4 HBCF. Other Kandihumults that have 5 percent or more (by 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 layers within 100 cm of the mineral soil surface for either or HBCG. Other Kandihumults that have an ustic moisture both: regime. Ustic Kandihumults a. 20 or more consecutive days; or b. 30 or more cumulative days. HBCH. Other Kandihumults that have a xeric moisture regime. Andic Ombroaquic Kandihumults Xeric Kandihumults Ultisols 269

HBCI. Other Kandihumults that have an anthropic epipedon. HBDF. Other Kanhaplohumults that have an ustic moisture Anthropic Kandihumults regime. Ustic Kanhaplohumults HBCJ. Other Kandihumults. Typic Kandihumults HBDG. Other Kanhaplohumults that have a xeric moisture regime. Kanhaplohumults Xeric Kanhaplohumults

Key to Subgroups HBDH. Other Kanhaplohumults that have an anthropic epipedon. HBDA. Kanhaplohumults that have a lithic contact within 50 Anthropic Kanhaplohumults cm of the mineral soil surface. Lithic Kanhaplohumults HBDI. Other Kanhaplohumults. Typic Kanhaplohumults HBDB. Other Kanhaplohumults that have both: 1. An ustic moisture regime; and Palehumults 2. Throughout one or more horizons with a total thickness Key to Subgroups 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 HBEA. Palehumults that have both: 1 less, measured at 33 kPa water retention, and Al plus /2 Fe 1. In one or more subhorizons within the upper 25 cm of percentages (by ammonium oxalate) totaling more than 1.0. the argillic horizon, redox depletions with a color value, Ustandic Kanhaplohumults moist, of 4 or more and chroma of 2 or less, accompanied by redox concentrations, and also aquic conditions for some HBDC. Other Kanhaplohumults that have, throughout one or time in normal years (or artificial drainage); and 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 a 2. Throughout one or more horizons with a total bulk density of 1.0 g/cm3 or less, measured at 33 kPa water thickness of 18 cm or more within 75 cm of the mineral 1 retention, and Al plus /2 Fe percentages (by ammonium oxalate) soil surface, a fine-earth fraction with both a bulk density totaling more than 1.0. of 1.0 g/cm3 or less, measured at 33 kPa water retention, and 1 Andic Kanhaplohumults Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. HBDD. Other Kanhaplohumults that have, in one or more Aquandic Palehumults subhorizons within the upper 25 cm of the kandic horizon, redox depletions with a color value, moist, of 4 or more and HBEB. Other Palehumults that have, throughout one or more chroma of 2 or less, accompanied by redox concentrations and horizons with a total thickness of 18 cm or more within 75 cm of by aquic conditions for some time in normal years (or artificial the mineral soil surface, a fine-earth fraction with both a bulk drainage). density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 Aquic Kanhaplohumults and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. HBDE. Other Kanhaplohumults that: Andic Palehumults 1. Have, in one or more horizons within 75 cm of the HBEC. Other Palehumults that have, in one or more mineral soil surface, redox concentrations, a color value, subhorizons within the upper 25 cm of the argillic horizon, U moist, of 4 or more, and hue that is 10YR or yellower and redox depletions with a color value, moist, of 4 or more and L becomes redder with increasing depth within 100 cm of the chroma of 2 or less, accompanied by redox concentrations and T mineral soil surface; and by aquic conditions for some time in normal years (or artificial 2. In normal years are saturated with water in one or more drainage). layers within 100 cm of the mineral soil surface for either or Aquic Palehumults both: HBED. Other Palehumults that have 5 percent or more (by a. 20 or more consecutive days; or volume) plinthite in one or more horizons within 150 cm of the b. 30 or more cumulative days. mineral soil surface. Ombroaquic Kanhaplohumults Plinthic Palehumults 270 Keys to Soil Taxonomy

HBEE. Other Palehumults that in normal years are saturated faces of peds in the layer that has a 20 percent lower clay with water in one or more layers within 100 cm of the mineral content and, below that layer, a clay increase of 3 percent soil surface for either or both: or more (absolute) in the fine-earth fraction. Kandiudults, p. 272 1. 20 or more consecutive days; or 2. 30 or more cumulative days. HCD. Other Udults that have a kandic horizon. Oxyaquic Palehumults Kanhapludults, p. 274

HBEF. Other Palehumults that have an ustic moisture regime. HCE. Other Udults that: Ustic Palehumults 1. Do not have a densic, lithic, paralithic, or petroferric contact within 150 cm of the mineral soil surface; and HBEG. Other Palehumults that have a xeric moisture regime. Xeric Palehumults 2. Within 150 cm of the mineral soil surface, either: a. With increasing depth, do not have a clay decrease of HBEH. Other Palehumults. 20 percent or more (relative) from the maximum clay Typic Palehumults content; or Plinthohumults b. Have 5 percent or more (by volume) skeletans on faces of peds in the layer that has a 20 percent lower clay Key to Subgroups content and, below that layer, a clay increase of 3 percent or more (absolute) in the fine-earth fraction. HBBA. All Plinthohumults. Paleudults, p. 275 Typic Plinthohumults HCF. Other Udults that have both: Sombrihumults 1. An epipedon that has a color value, moist, of 3 or less Key to Subgroups throughout; and HBAA. All Sombrihumults. 2. In all subhorizons in the upper 100 cm of the argillic Typic Sombrihumults horizon or throughout the entire argillic horizon if it is less than 100 cm thick, more than 50 percent colors that have all Udults of the following: a. Hue of 2.5YR or redder; and Key to Great Groups b. A value, moist, of 3 or less; and HCA. Udults that have one or more horizons within 150 cm of c. A dry value no more than 1 unit higher than the moist the mineral soil surface in which plinthite either forms a value. continuous phase or constitutes one-half or more of the volume. Rhodudults, p. 277 Plinthudults, p. 277 HCG. Other Udults. HCB. Other Udults that have a fragipan with an upper Hapludults, p. 271 boundary within 100 cm of the mineral soil surface. Fragiudults, p. 270 Fragiudults HCC. Other Udults that: Key to Subgroups 1. Do not have a densic, lithic, paralithic, or petroferric HCBA. Fragiudults that have a sandy or sandy-skeletal contact within 150 cm of the mineral soil surface; and particle-size class throughout a layer extending from the mineral 2. Have a kandic horizon; and soil surface to the top of an argillic or kandic horizon at a depth of 50 to 100 cm. 3. Within 150 cm of the mineral soil surface, either: Arenic Fragiudults a. With increasing depth, do not have a clay decrease of 20 percent or more (relative) from the maximum clay HCBB. Other Fragiudults that have both of the following: content; or 1. In one or more horizons within 40 cm of the mineral soil b. Have 5 percent or more (by volume) skeletans on surface, redox depletions with chroma of 2 or less and also Ultisols 271

aquic conditions for some time in normal years (or artificial or less and a color value, dry, of 5 or less (crushed and drainage); and smoothed sample) in either: 2. 5 percent or more (by volume) plinthite in one or more 1. An Ap horizon that is 18 cm or more thick; or horizons within 150 cm of the mineral soil surface. 2. The surface layer after mixing of the upper 18 cm. Plinthaquic Fragiudults Humic Fragiudults HCBC. Other Fragiudults that meet both of the following: HCBH. Other Fragiudults. 1. Meet one or more of the following: Typic Fragiudults a. Have a glossic horizon above the fragipan; or Hapludults b. Do not have, above the fragipan, an argillic or kandic horizon that has clay films on both vertical and horizontal Key to Subgroups surfaces of any structural aggregates; or HCGA. Hapludults that have either or both: c. Between the argillic or kandic horizon and the 1. In each pedon, a discontinuous lithic contact within 50 fragipan, have one or more horizons with 50 percent or cm of the mineral soil surface; and more chroma of 3 or less and with a clay content 3 percent or more (absolute, in the fine-earth fraction) lower than 2. In each pedon, a discontinuous argillic horizon that is that in both the argillic or kandic horizon and the fragipan; interrupted by ledges of bedrock. and Lithic-Ruptic-Entic Hapludults 2. In one or more horizons within 40 cm of the mineral soil HCGB. Other Hapludults that have a lithic contact within 50 surface, have redox depletions with chroma of 2 or less and cm of the mineral soil surface. also aquic conditions for some time in normal years (or Lithic Hapludults artificial drainage). Glossaquic Fragiudults HCGC. Other Hapludults that have one or both of the following: HCBD. Other Fragiudults that have, in one or more subhorizons above the fragipan and within the upper 25 cm of 1. Cracks within 125 cm of the mineral soil surface that the argillic or kandic horizon, redox depletions with chroma of 2 are 5 mm or more wide through a thickness of 30 cm or or less and also aquic conditions for some time in normal years more for some time in normal years and slickensides or (or artificial drainage). wedge-shaped aggregates in a layer 15 cm or more thick that Aquic Fragiudults has its upper boundary within 125 cm of the mineral soil surface; or HCBE. Other Fragiudults that have 5 percent or more (by 2. A linear extensibility of 6.0 cm or more between the volume) plinthite in one or more horizons within 150 cm of the mineral soil surface and either a depth of 100 cm or a densic, mineral soil surface. lithic, or paralithic contact, whichever is shallower. Plinthic Fragiudults Vertic Hapludults HCBF. Other Fragiudults that meet one or more of the HCGD. Other Hapludults that have both: following: 1. Fragic soil properties: 1. Have a glossic horizon above the fragipan; or a. In 30 percent or more of the volume of a layer 15 cm U 2. Do not have, above the fragipan, an argillic or kandic or more thick that has its upper boundary within 100 cm L horizon that has clay films on both vertical and horizontal of the mineral soil surface; or T surfaces of any structural aggregates; or b. In 60 percent or more of the volume of a layer 15 cm 3. Between the argillic or kandic horizon and the fragipan, or more thick; and have one or more horizons with 50 percent or more chroma of 3 or less and with a clay content 3 percent or more 2. In one or more layers within 75 cm of the mineral soil (absolute, in the fine-earth fraction) lower than that in both surface, redox depletions with a color value, moist, of 4 or the argillic or kandic horizon and the fragipan. more and chroma of 2 or less, accompanied by redox Glossic Fragiudults concentrations, and also aquic conditions for some time in normal years (or artificial drainage). HCBG. Other Fragiudults that have a color value, moist, of 3 Fragiaquic Hapludults 272 Keys to Soil Taxonomy

HCGE. Other Hapludults that have both: argillic horizon 7.5 to 20 cm thick, each with an overlying eluvial horizon. 1. A sandy or sandy-skeletal particle-size class throughout a Lamellic Hapludults layer extending from the mineral soil surface to the top of an argillic horizon at a depth of 50 to 100 cm; and HCGJ. Other Hapludults that have a sandy particle-size class 2. In one or more subhorizons within the upper 60 cm throughout the upper 75 cm of the argillic horizon or throughout of the argillic horizon, redox depletions with a color value, the entire argillic horizon if it is less than 75 cm thick. moist, of 4 or more and chroma of 2 or less, accompanied by Psammentic Hapludults redox concentrations, and also aquic conditions for some time in normal years (or artificial drainage). HCGK. Other Hapludults that have a sandy or sandy-skeletal Aquic Arenic Hapludults particle-size class throughout a layer extending from the mineral soil surface to the top of an argillic horizon at a depth of 50 to HCGF. Other Hapludults that have, in one or more 100 cm. subhorizons within the upper 60 cm of the argillic horizon, Arenic Hapludults redox depletions with a color value, moist, of 4 or more and chroma of 2 or less, accompanied by redox concentrations and HCGL. Other Hapludults that have a sandy or sandy-skeletal by aquic conditions for some time in normal years (or artificial particle-size class throughout a layer extending from the mineral drainage). soil surface to the top of an argillic horizon at a depth of 100 cm Aquic Hapludults or more. Grossarenic Hapludults HCGG. Other Hapludults that have fragic soil properties: 1. In 30 percent or more of the volume of a layer 15 cm or HCGM. Other Hapludults that have: more thick that has its upper boundary within 100 cm of the 1. No densic, lithic, or paralithic contact within 50 cm of mineral soil surface; or the mineral soil surface; and 2. In 60 percent or more of the volume of a layer 15 cm or 2. An argillic horizon 25 cm or less thick. more thick. Inceptic Hapludults Fragic Hapludults HCGN. Other Hapludults that have a color value, moist, of 3 HCGH. Other Hapludults that in normal years are saturated or less and a color value, dry, of 5 or less (crushed and with water in one or more layers within 100 cm of the mineral smoothed sample) in either: soil surface for either or both: 1. An Ap horizon that is 18 cm or more thick; or 1. 20 or more consecutive days; or 2. The surface layer after mixing of the upper 18 cm. 2. 30 or more cumulative days. Humic Hapludults Oxyaquic Hapludults HCGO. Other Hapludults. HCGI. Other Hapludults that have an argillic horizon that: Typic Hapludults 1. Consists entirely of lamellae; or 2. Is a combination of two or more lamellae and one or Kandiudults more subhorizons with a thickness of 7.5 to 20 cm, each layer Key to Subgroups with an overlying eluvial horizon; or HCCA. Kandiudults that have: 3. Consists of one or more subhorizons that are more than 20 cm thick, each with an overlying eluvial horizon, and 1. A sandy or sandy-skeletal particle-size class throughout a above these horizons there are either: layer extending from the mineral soil surface to the top of a kandic horizon at a depth of 50 to 100 cm; 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 2. 5 percent or more (by volume) plinthite in one or horizon); or more horizons within 150 cm of the mineral soil surface; and b. A combination of lamellae (that may or may not be 3. 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 Ultisols 273

results from uncoated sand grains, within the upper 12.5 cm 1. A sandy or sandy-skeletal particle-size class of the kandic horizon, redox depletions with a color value, throughout a layer extending from the mineral soil surface to moist, of 4 or more and chroma of 2 or less, accompanied by the top of a kandic horizon at a depth of 100 cm or more; and redox concentrations, and also aquic conditions for some 2. 5 percent or more (by volume) plinthite in one or more time in normal years (or artificial drainage). horizons within 150 cm of the mineral soil surface. Arenic Plinthaquic Kandiudults Grossarenic Plinthic Kandiudults HCCB. Other Kandiudults that have both: HCCG. Other Kandiudults that have a sandy or sandy-skeletal 1. A sandy or sandy-skeletal particle-size class throughout a particle-size class throughout a layer extending from the mineral layer extending from the mineral soil surface to the top of a soil surface to the top of a kandic horizon at a depth of 100 cm kandic horizon at a depth of 50 to 100 cm; and or more. Grossarenic Kandiudults 2. In one or more layers either within 75 cm of the mineral soil surface or, if the chroma throughout the upper 75 cm HCCH. Other Kandiudults that have both: results from uncoated sand grains, within the upper 12.5 cm of the kandic horizon, redox depletions with a color value, 1. An ECEC of 1.5 cmol(+)/kg clay or less (sum of bases

moist, of 4 or more and chroma of 2 or less, accompanied by extracted with 1N NH4OAc pH 7, plus 1N KCl-extractable redox concentrations, and also aquic conditions for some Al) in one or more horizons within 150 cm of the mineral soil time in normal years (or artificial drainage). surface; and Aquic Arenic Kandiudults 2. 5 percent or more (by volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. HCCC. Other Kandiudults that have both: Acrudoxic Plinthic Kandiudults 1. A sandy or sandy-skeletal particle-size class throughout a layer extending from the mineral soil surface to the top of a HCCI. Other Kandiudults that have an ECEC of 1.5 kandic horizon at a depth of 50 to 100 cm; and cmol(+)/kg clay or less (sum of bases extracted with 1N NH OAc pH 7, plus 1N KCl-extractable Al) in one or more 2. 5 percent or more (by volume) plinthite in one or more 4 horizons within 150 cm of the mineral soil surface. horizons within 150 cm of the mineral soil surface. Acrudoxic Kandiudults Arenic Plinthic Kandiudults

HCCD. Other Kandiudults that have both: HCCJ. Other Kandiudults that have both: 1. A sandy or sandy-skeletal particle-size class 1. 5 percent or more (by volume) plinthite in one or more throughout a layer extending from the mineral soil surface to horizons within 150 cm of the mineral soil surface; and the top of a kandic horizon at a depth of 50 to 100 cm; and 2. In one or more layers within 75 cm of the mineral soil 2. In all subhorizons in the upper 75 cm of the kandic surface, redox depletions with a color value, moist, of 4 or horizon or throughout the entire kandic horizon if it is less more and chroma of 2 or less, accompanied by redox than 75 cm thick, more than 50 percent colors that have all of concentrations, and also aquic conditions for some time in the following: normal years (or artificial drainage). Plinthaquic Kandiudults a. Hue of 2.5YR or redder; and b. A value, moist, of 3 or less; and HCCK. Other Kandiudults that have both: c. A dry value no more than 1 unit higher than the moist 1. In one or more layers within 75 cm of the mineral soil U value. surface, redox depletions with a color value, moist, of 4 or L Arenic Rhodic Kandiudults more and chroma of 2 or less, accompanied by redox T concentrations, and also aquic conditions for some time in HCCE. Other Kandiudults that have a sandy or sandy-skeletal normal years (or artificial drainage); and particle-size class throughout a layer extending from the mineral 2. Throughout one or more horizons with a total thickness soil surface to the top of a kandic horizon at a depth of 50 to of 18 cm or more within 75 cm of the mineral soil surface, 100 cm. one or more of the following: Arenic Kandiudults a. A fine-earth fraction with both a bulk density of 1.0 HCCF. Other Kandiudults that have both: g/cm3 or less, measured at 33 kPa water retention, and Al 274 Keys to Soil Taxonomy

1 plus /2 Fe percentages (by ammonium oxalate) totaling with water in one or more layers within 100 cm of the mineral more than 1.0; or soil surface for either or both: b. 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, 2. 30 or more cumulative days. pumice, and pumicelike fragments; or Oxyaquic Kandiudults c. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and HCCQ. Other Kandiudults that have a sombric horizon within 150 cm of the mineral soil surface. (1) In the 0.02 to 2.0 mm fraction, 5 percent or more Sombric Kandiudults volcanic glass; and

1 (2) [(Al plus /2 Fe, percent extracted by ammonium HCCR. Other Kandiudults that have, in all subhorizons in the oxalate) times 60] plus the volcanic glass (percent) is upper 75 cm of the kandic horizon or throughout the entire equal to 30 or more. kandic horizon if it is less than 75 cm thick, more than 50 Aquandic Kandiudults percent colors that have all of the following: 1. Hue of 2.5YR or redder; and HCCL. Other Kandiudults that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of 2. A value, moist, of 3 or less; and the mineral soil surface, a fine-earth fraction with both a bulk 3. A dry value no more than 1 unit higher than the moist density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 value. and Al plus /2 Fe percentages (by ammonium oxalate) totaling Rhodic Kandiudults more than 1.0. Andic Kandiudults HCCS. Other Kandiudults. Typic Kandiudults HCCM. Other Kandiudults that have, in one or more layers 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, Kanhapludults accompanied by redox concentrations and by aquic conditions Key to Subgroups for some time in normal years (or artificial drainage). Aquic Kandiudults HCDA. Kanhapludults that have a lithic contact within 50 cm of the mineral soil surface. HCCN. Other Kandiudults that have 5 percent or more (by Lithic Kanhapludults volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. HCDB. Other Kanhapludults that have both: Plinthic Kandiudults 1. 5 percent or more (by volume) plinthite in one or more horizons within 150 cm of the mineral soil surface; and HCCO. Other Kandiudults that: 2. In one or more layers within 75 cm of the mineral soil 1. Have, in one or more horizons within 75 cm of the surface, redox depletions with a color value, moist, of 4 or mineral soil surface, redox concentrations, a color value, more and chroma of 2 or less, accompanied by redox moist, of 4 or more, and hue that is 10YR or yellower and concentrations, and also aquic conditions for some time in becomes redder with increasing depth within 100 cm of the normal years (or artificial drainage). mineral soil surface; and Plinthaquic Kanhapludults 2. In normal years are saturated with water in one or more layers within 100 cm of the mineral soil surface for either or HCDC. Other Kanhapludults that have both: both: 1. A sandy or sandy-skeletal particle-size class throughout a a. 20 or more consecutive days; or layer extending from the mineral soil surface to the top of a kandic horizon at a depth of 50 to 100 cm; and b. 30 or more cumulative days. Ombroaquic Kandiudults 2. 5 percent or more (by volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. HCCP. Other Kandiudults that in normal years are saturated Arenic Plinthic Kanhapludults Ultisols 275

HCDD. Other Kanhapludults that have a sandy or sandy- a. 20 or more consecutive days; or skeletal particle-size class throughout a layer extending from the b. 30 or more cumulative days. mineral soil surface to the top of a kandic horizon at a depth of Ombroaquic Kanhapludults 50 to 100 cm. Arenic Kanhapludults HCDJ. Other Kanhapludults that in normal years are saturated with water in one or more layers within 100 cm of the mineral HCDE. Other Kanhapludults that have an ECEC of 1.5 soil surface for either or both: cmol(+)/kg clay or less (sum of bases extracted with 1N

NH4OAc pH 7, plus 1N KCl-extractable Al) in one or more 1. 20 or more consecutive days; or horizons within 150 cm of the mineral soil surface. 2. 30 or more cumulative days. Acrudoxic Kanhapludults Oxyaquic Kanhapludults HCDF. Other Kanhapludults that have both: HCDK. Other Kanhapludults that have 5 percent or more (by 1. Fragic soil properties: volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. a. In 30 percent or more of the volume of a layer 15 cm Plinthic Kanhapludults or more thick that has its upper boundary within 100 cm of the mineral soil surface; or HCDL. Other Kanhapludults that have fragic soil b. In 60 percent or more of the volume of a layer 15 cm properties: or more thick; and 1. In 30 percent or more of the volume of a layer 15 cm or 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 redox 2. In 60 percent or more of the volume of a layer 15 cm or concentrations, and also aquic conditions for some time in more thick. normal years (or artificial drainage). Fragic Kanhapludults Fragiaquic Kanhapludults HCDM. Other Kanhapludults that have, in all subhorizons in HCDG. Other Kanhapludults that have, throughout one or the upper 50 cm of the kandic horizon or throughout the entire more horizons with a total thickness of 18 cm or more within 75 kandic horizon if it is less than 50 cm thick, more than 50 cm of the mineral soil surface, a fine-earth fraction with both a percent colors that have all of the following: 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 a Rhodic Kanhapludults color value, moist, of 4 or more and chroma of 2 or less, accompanied by redox concentrations and by aquic conditions HCDN. Other Kanhapludults. for some time in normal years (or artificial drainage). Typic Kanhapludults Aquic Kanhapludults Paleudults U HCDI. Other Kanhapludults that: L Key to Subgroups 1. Have, in one or more horizons within 75 cm of the T 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 becomes redder with increasing depth within 100 cm of the are 5 mm or more wide through a thickness of 30 cm or mineral soil surface; and more for some time in normal years and slickensides or 2. In normal years are saturated with water in one or more wedge-shaped aggregates in a layer 15 cm or more thick that layers within 100 cm of the mineral soil surface for either or has its upper boundary within 125 cm of the mineral soil both: surface; or 276 Keys to Soil Taxonomy

2. A linear extensibility of 6.0 cm or more between the HCEF. Other Paleudults that have both: mineral soil surface and either a depth of 100 cm or a densic, 1. 5 percent or more (by volume) plinthite in one or more lithic, or paralithic contact, whichever is shallower. horizons within 150 cm of the mineral soil surface; and Vertic Paleudults 2. In one or more layers either within 75 cm of the mineral HCEB. Other Paleudults that have a horizon 5 cm or more soil surface or, if the chroma throughout the upper 75 cm thick, either below an Ap horizon or at a depth of 18 cm or more results from uncoated sand grains, within the upper 12.5 cm from the mineral soil surface, whichever is deeper, that has one of the argillic horizon, redox depletions with a color value, or more of the following: moist, of 4 or more and chroma of 2 or less, accompanied by redox concentrations, and also aquic conditions for some 1. In 25 percent or more of each pedon, cementation by time in normal years (or artificial drainage). organic matter and aluminum, with or without iron; or Plinthaquic Paleudults 1 2. Al plus /2 Fe percentages (by ammonium oxalate) totaling 0.25 or more, and half that amount or less in an HCEG. Other Paleudults that have both: overlying horizon; or 1. Fragic soil properties: 3. An ODOE value of 0.12 or more, and a value half as a. In 30 percent or more of the volume of a layer 15 cm high or lower in an overlying horizon. or more thick that has its upper boundary within 100 cm Spodic Paleudults of the mineral soil surface; or b. In 60 percent or more of the volume of a layer 15 cm HCEC. Other Paleudults that have: or more thick; and 1. In one or more layers either within 75 cm of the mineral 2. In one or more layers within 75 cm of the mineral soil soil surface or, if the chroma throughout the upper 75 cm surface, redox depletions with a color value, moist, of 4 or results from uncoated sand grains, within the upper 12.5 cm more and chroma of 2 or less, accompanied by redox of the argillic horizon, redox depletions with a color value, concentrations, and also aquic conditions for some time in moist, of 4 or more and chroma of 2 or less, accompanied by normal years (or artificial drainage). redox concentrations, and also aquic conditions for some Fragiaquic Paleudults time in normal years (or artificial drainage); and 2. A sandy or sandy-skeletal particle-size class throughout a HCEH. Other Paleudults that have, in one or more layers layer extending from the mineral soil surface to the top of an within 75 cm of the mineral soil surface, redox depletions argillic horizon at a depth of 50 cm or more; and with a color value, moist, of 4 or more and chroma of 2 or less, accompanied by redox concentrations and by aquic 3. 5 percent or more (by volume) plinthite in one or more conditions for some time in normal years (or artificial drainage). horizons within 150 cm of the mineral soil surface. Aquic Paleudults Arenic Plinthaquic Paleudults HCEI. Other Paleludults that in normal years are saturated HCED. Other Paleudults that have both: with water in one or more layers within 100 cm of the mineral 1. A sandy or sandy-skeletal particle-size class throughout a soil surface for either or both: layer extending from the mineral soil surface to the top of an 1. 20 or more consecutive days; or argillic horizon that is 50 cm or more below the mineral soil surface; and 2. 30 or more cumulative days. Oxyaquic Paleudults 2. In one or more layers either within 75 cm of the mineral soil surface or, if the chroma throughout the upper 75 cm HCEJ. Other Paleudults that have an argillic horizon that: results from uncoated sand grains, within the upper 12.5 cm of the argillic horizon, redox depletions with a color value, 1. Consists entirely of lamellae; or moist, of 4 or more and chroma of 2 or less, accompanied by 2. Is a combination of two or more lamellae and one or redox concentrations, and also aquic conditions for some more subhorizons with a thickness of 7.5 to 20 cm, each layer time in normal years (or artificial drainage). with an overlying eluvial horizon; or Aquic Arenic Paleudults 3. Consists of one or more subhorizons that are more HCEE. Other Paleudults that have anthraquic conditions. than 20 cm thick, each with an overlying eluvial horizon, and Anthraquic Paleudults above these horizons there are either: Ultisols 277

a. Two or more lamellae with a combined thickness of 5 HCEP. Other Paleudults that have a sandy or sandy-skeletal cm or more (that may or may not be part of the argillic particle-size class throughout a layer extending from the mineral horizon); or soil surface to the top of an argillic horizon at a depth of 50 to 100 cm. b. A combination of lamellae (that may or may not be Arenic Paleudults part of the argillic horizon) and one or more parts of the argillic horizon 7.5 to 20 cm thick, each with an overlying HCEQ. Other Paleudults that have a sandy or sandy-skeletal eluvial horizon. particle-size class throughout a layer extending from the mineral Lamellic Paleudults soil surface to the top of an argillic horizon at a depth of 100 cm or more. HCEK. Other Paleudults that have both: Grossarenic Paleudults 1. A sandy or sandy-skeletal particle-size class throughout a layer extending from the mineral soil surface to the top of an HCER. Other Paleudults that have fragic soil properties: argillic horizon at a depth of 50 to 100 cm; and 1. In 30 percent or more of the volume of a layer 15 cm or 2. 5 percent or more (by volume) plinthite in one or more more thick that has its upper boundary within 100 cm of the horizons within 150 cm of the mineral soil surface. mineral soil surface; or Arenic Plinthic Paleudults 2. In 60 percent or more of the volume of a layer 15 cm or more thick. HCEL. Other Paleudults that have a sandy particle-size class Fragic Paleudults throughout the upper 75 cm of the argillic horizon or throughout the entire argillic horizon if it is less than 75 cm thick. HCES. Other Paleudults that have, in all subhorizons in the Psammentic Paleudults upper 75 cm of the argillic horizon or throughout the entire argillic horizon if it is less than 75 cm thick, more than 50 HCEM. Other Paleudults that have both: percent colors that have all of the following: 1. A sandy or sandy-skeletal particle-size class throughout a 1. Hue of 2.5YR or redder; and layer extending from the mineral soil surface to the top of an 2. A value, moist, of 3 or less; and argillic horizon at a depth of 100 cm or more; and 3. A dry value no more than 1 unit higher than the moist 2. 5 percent or more (by volume) plinthite in one or more value. horizons within 150 cm of the mineral soil surface. Rhodic Paleudults Grossarenic Plinthic Paleudults HCET. Other Paleudults. HCEN. Other Paleudults that have 5 percent or more (by Typic Paleudults volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. Plinthic Paleudults Plinthudults Key to Subgroups HCEO. Other Paleudults that have both: HCAA. All Plinthudults. 1. A sandy or sandy-skeletal particle-size class throughout a Typic Plinthudults layer extending from the mineral soil surface to the top of an argillic horizon at a depth of 50 to 100 cm; and Rhodudults U 2. In all subhorizons in the upper 75 cm of the argillic L horizon or throughout the entire argillic horizon if it is less Key to Subgroups T than 75 cm thick, more than 50 percent colors that have all of HCFA. Rhodudults that have a lithic contact within 50 cm of the following: the mineral soil surface. a. Hue of 2.5YR or redder; and Lithic Rhodudults b. A value, moist, of 3 or less; and HCFB. Other Rhodudults that have a sandy particle-size class c. A dry value no more than 1 unit higher than the moist throughout the upper 75 cm of the argillic horizon or throughout value. the entire argillic horizon if it is less than 75 cm thick. Arenic Rhodic Paleudults Psammentic Rhodudults 278 Keys to Soil Taxonomy

HCFC. Other Rhodudults. than 100 cm thick, more than 50 percent colors that have all Typic Rhodudults of the following: a. Hue of 2.5YR or redder; and Ustults 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 value. HDA. Ustults that have one or more horizons within 150 Rhodustults, p. 281 cm of the mineral soil surface in which plinthite either forms a continuous phase or constitutes one-half or more of the HDF. Other Ustults. volume. Haplustults, p. 278 Plinthustults, p. 281 Haplustults HDB. Other Ustults that: Key to Subgroups 1. Do not have a densic, lithic, paralithic, or petroferric contact within 150 cm of the mineral soil surface; and HDFA. Haplustults that have a lithic contact within 50 cm of the mineral soil surface. 2. Have a kandic horizon; and Lithic Haplustults 3. Within 150 cm of the mineral soil surface, either: HDFB. Other Haplustults that have a petroferric contact a. With increasing depth, do not have a clay decrease of within 100 cm of the mineral soil surface. 20 percent or more (relative) from the maximum clay Petroferric Haplustults content; or b. Have 5 percent or more (by volume) skeletans on HDFC. Other Haplustults that have, in one or more layers both faces of peds in the layer that has a 20 percent lower clay within the upper 12.5 cm of the argillic horizon and within 75 content and, below that layer, a clay increase of 3 percent cm of the mineral soil surface, redox depletions with a color or more (absolute) in the fine-earth fraction. value, moist, of 4 or more and chroma of 2 or less, accompanied Kandiustults, p. 279 by redox concentrations and by aquic conditions for some time in normal years (or artificial drainage). HDC. Other Ustults that have a kandic horizon. Aquic Haplustults Kanhaplustults, p. 280 HDFD. Other Haplustults that have a sandy or sandy-skeletal HDD. Other Ustults that: particle-size class throughout a layer extending from the mineral soil surface to the top of an argillic horizon at a depth of 50 cm 1. Do not have a densic, lithic, paralithic, or petroferric or more below the mineral soil surface. contact within 150 cm of the mineral soil surface; and Arenic Haplustults 2. Within 150 cm of the mineral soil surface, either: HDFE. Other Haplustults that: a. With increasing depth, do not have a clay decrease of 20 percent or more (relative) from the maximum clay 1. Have, in one or more horizons within 75 cm of the content; or mineral soil surface, redox concentrations, a color value, moist, of 4 or more, and hue that is 10YR or yellower and b. Have 5 percent or more (by volume) skeletans on becomes redder with increasing depth within 100 cm of the faces of peds in the layer that has a 20 percent lower clay mineral soil surface; and content and, below that layer, a clay increase of 3 percent or more (absolute) in the fine-earth fraction. 2. In normal years are saturated with water in one or more Paleustults, p. 281 layers within 100 cm of the mineral soil surface for either or both: HDE. Other Ustults that have both: a. 20 or more consecutive days; or 1. An epipedon that has a color value, moist, of 3 or less b. 30 or more cumulative days. throughout; and Ombroaquic Haplustults 2. In all subhorizons in the upper 100 cm of the argillic horizon or throughout the entire argillic horizon if it is less HDFF. Other Haplustults that have 5 percent or more (by Ultisols 279

volume) plinthite in one or more horizons within 150 cm of the a. A mesic or thermic soil temperature regime and a mineral soil surface. moisture control section that is dry in some part for 135 or Plinthic Haplustults fewer of the cumulative days per year when the temperature at a depth of 50 cm below the soil surface is o HDFG. Other Haplustults that have a CEC (by 1N NH4OAc higher than 5 C; or pH 7) of less than 24 cmol(+)/kg clay in 50 percent or more of b. A hyperthermic, isomesic, or warmer iso soil the entire argillic horizon if less than 100 cm thick or of its temperature regime and a moisture control section that is upper 100 cm. dry in some or all parts for fewer than 120 cumulative Kanhaplic Haplustults days per year when the temperature at a depth of 50 cm below the soil surface is higher than 8 oC. HDFH. Other Haplustults. Udandic Kandiustults Typic Haplustults HDBF. Other Kandiustults that have, throughout one or more Kandiustults 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 Key to Subgroups density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 HDBA. Kandiustults that have an ECEC of 1.5 cmol(+)/kg and Al plus /2 Fe percentages (by ammonium oxalate) totaling clay or less (sum of bases extracted with 1N NH4OAc pH 7, plus more than 1.0. 1N KCl-extractable Al) in one or more horizons within 150 cm Andic Kandiustults of the mineral soil surface. Acrustoxic Kandiustults HDBG. Other Kandiustults that have 5 percent or more (by volume) plinthite in one or more horizons within 150 cm of the HDBB. Other Kandiustults that have, in one or more layers mineral soil surface. within 75 cm of the mineral soil surface, redox depletions with a Plinthic Kandiustults color value, moist, of 4 or more and chroma of 2 or less, accompanied by redox concentrations and by aquic conditions HDBH. Other Kandiustults that, when neither irrigated nor for some time in normal years (or artificial drainage). fallowed to store moisture, have either: Aquic Kandiustults 1. A thermic, mesic, or colder soil temperature regime and a moisture control section that in normal years is dry in some HDBC. Other Kandiustults that have both: part for more than four-tenths of the cumulative days per year 1. A sandy or sandy-skeletal particle-size class throughout a when the soil temperature at a depth of 50 cm below the soil layer extending from the mineral soil surface to the top of a surface is higher than 5 oC; or kandic horizon at a depth of 50 cm or more; and 2. A hyperthermic, isomesic, or warmer iso soil 2. 5 percent or more (by volume) plinthite in one or more temperature regime and a moisture control section that in horizons within 150 cm of the mineral soil surface. normal years: Arenic Plinthic Kandiustults a. Is moist in some or all parts for fewer than 90 consecutive days per year when the temperature at a depth HDBD. Other Kandiustults that have a sandy or sandy-skeletal of 50 cm below the soil surface is higher than 8 oC; and particle-size class throughout a layer extending from the mineral soil surface to the top of a kandic horizon at a depth of 50 cm or b. Is dry in some part for six-tenths or more of the more. cumulative days per year when the soil temperature at a Arenic Kandiustults depth of 50 cm below the soil surface is higher than 5 oC. U Aridic Kandiustults L HDBE. Other Kandiustults that have both: T HDBI. Other Kandiustults that, when neither irrigated nor 1. Throughout one or more horizons with a total thickness fallowed to store moisture, have either: 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. A mesic or thermic soil temperature regime and a 1 less, measured at 33 kPa water retention, and Al plus /2 Fe moisture control section that in normal years is dry in some percentages (by ammonium oxalate) totaling more than 1.0; part for 135 or fewer of the cumulative days per year when and the temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or 2. When neither irrigated nor fallowed to store moisture, either: 2. A hyperthermic, isomesic, or warmer iso soil 280 Keys to Soil Taxonomy

1 temperature regime and a moisture control section that in less, measured at 33 kPa water retention, and Al plus /2 Fe normal years is dry in some or all parts for fewer than 120 percentages (by ammonium oxalate) totaling more than 1.0; cumulative days per year when the temperature at a depth of and 50 cm below the soil surface is higher than 8 oC. 2. When neither irrigated nor fallowed to store moisture, Udic Kandiustults either: HDBJ. Other Kandiustults that have, in all subhorizons in the a. A mesic or thermic soil temperature regime and a upper 50 cm of the kandic horizon or throughout the entire moisture control section that in normal years is dry in kandic horizon if it is less than 75 cm thick, more than 50 some part for 135 or fewer of the cumulative days per year percent colors that have all of the following: when the temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or 1. Hue of 2.5YR or redder; and b. A hyperthermic, isomesic, or warmer iso soil 2. A value, moist, of 3 or less; and temperature regime and a moisture control section that in 3. A dry value no more than 1 unit higher than the moist normal years is dry in some or all parts for fewer than 120 value. cumulative days per year when the temperature at a depth Rhodic Kandiustults of 50 cm below the soil surface is higher than 8 oC. Udandic Kanhaplustults HDBK. Other Kandiustults. Typic Kandiustults HDCF. Other Kanhaplustults that have, throughout one or 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 a Kanhaplustults 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 a becomes redder with increasing depth within 100 cm of the color value, moist, of 4 or more and chroma of 2 or less, mineral soil surface; and accompanied by redox concentrations and by 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 have a sandy or sandy- a. 20 or more consecutive days; or skeletal particle-size class throughout a layer extending from the mineral soil surface to the top of a kandic horizon at a depth of b. 30 or more cumulative days. 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 a moisture control section that in normal years is dry in some 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 year Ultisols 281

when the soil temperature at a depth of 50 cm below the soil Plinthustults surface is higher than 5 oC; or Key to Subgroups 2. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in HDAA. Plinthustults that have: normal years: 1. A densic, lithic, paralithic, or petroferric contact a. Is moist in some or all parts for fewer than 90 within 150 cm of the mineral soil surface; or consecutive days per year when the temperature at a 2. Within 150 cm of the mineral soil surface, both: depth of 50 cm below the soil surface is higher than 8 oC; and a. With increasing depth, a clay decrease of 20 percent or more (relative) from the maximum clay b. Is dry in some part for six-tenths or more of the content; and cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than b. Less than 5 percent (by volume) skeletans on faces of 5 oC. peds in the layer that has a 20 percent lower clay content Aridic Kanhaplustults or, below that layer, a clay increase of less than 3 percent (absolute) in the fine-earth fraction. HDCJ. Other Kanhaplustults that, when neither irrigated nor Haplic Plinthustults fallowed to store moisture, have either: HDAB. Other Plinthustults. 1. A mesic or thermic soil temperature regime and a Typic Plinthustults moisture control section that in normal years is dry in some part for 135 or fewer of the cumulative days per year when the temperature at a depth of 50 cm below the soil surface is Rhodustults higher than 5 oC; or Key to Subgroups 2. A hyperthermic, isomesic, or warmer iso soil HDEA. Rhodustults that have a lithic contact within 50 cm of temperature regime and a moisture control section that in the mineral soil surface. normal years is dry in some or all parts for fewer than 120 Lithic Rhodustults cumulative days per year when the temperature at a depth of 50 cm below the soil surface is higher than 8 oC. HDEB. Other Rhodustults that have a sandy particle-size class Udic Kanhaplustults throughout the upper 75 cm of the argillic horizon or throughout the entire argillic horizon if it is less than 75 cm thick. HDCK. Other Kanhaplustults that have, in all subhorizons in Psammentic Rhodustults 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 HDEC. Other Rhodustults. percent colors that have all of the following: Typic Rhodustults 1. Hue of 2.5YR or redder; and 2. A value, moist, of 3 or less; and Xerults 3. A dry value no more than 1 unit higher than the moist value. Key to Great Groups Rhodic Kanhaplustults HEA. Xerults that: U HDCL. Other Kanhaplustults. 1. Do not have a densic, lithic, or paralithic contact L Typic Kanhaplustults within 150 cm of the mineral soil surface; and T 2. Within 150 cm of the mineral soil surface, either: Paleustults a. With increasing depth, do not have a clay decrease of Key to Subgroups 20 percent or more (relative) from the maximum clay content; or HDDA. All Paleustults. Typic Paleustults b. Have 5 percent or more (by volume) skeletans on 282 Keys to Soil Taxonomy

faces of peds or 5 percent or more (by volume) plinthite, cm or more (that may or may not be part of the argillic or or both, in the layer that has a 20 percent lower clay kandic horizon); or content and, below that layer, a clay increase of 3 percent b. A combination of lamellae (that may or may or more (absolute) in the fine-earth fraction. not be part of the argillic or kandic horizon) and Palexerults, p. 282 one or more parts of the argillic or kandic horizon 7.5 to 20 cm thick, each with an overlying eluvial horizon. HEB. Other Xerults. Lamellic Haploxerults Haploxerults, p. 282 HEBF. Other Haploxerults that have a sandy particle-size class Haploxerults throughout the upper 75 cm of the argillic or kandic horizon or throughout the entire horizon if it is less than 75 cm thick. Key to Subgroups Psammentic Haploxerults HEBA. Haploxerults that have both: HEBG. Other Haploxerults that have a sandy or sandy-skeletal 1. A lithic contact within 50 cm of the mineral soil surface; particle-size class throughout a layer extending from the mineral and soil surface to the top of an argillic or kandic horizon at a depth 2. In each pedon, a discontinuous argillic or kandic horizon of 50 to 100 cm. that is interrupted by ledges of bedrock. Arenic Haploxerults Lithic Ruptic-Inceptic Haploxerults HEBH. Other Haploxerults that have a sandy or sandy-skeletal HEBB. Other Haploxerults that have a lithic contact within 50 particle-size class throughout a layer extending from the mineral cm of the mineral soil surface. soil surface to the top of an argillic or kandic horizon at a depth Lithic Haploxerults of 100 cm or more. Grossarenic Haploxerults HEBC. Other Haploxerults that have, in one or more subhorizons within the upper 25 cm of the argillic or kandic HEBI. Other Haploxerults. horizon, redox depletions with a color value, moist, of 4 or more Typic Haploxerults and chroma of 2 or less, accompanied by redox concentrations and by aquic conditions for some time in normal years (or artificial drainage). Palexerults Aquic Haploxerults Key to Subgroups HEBD. Other Haploxerults that have, throughout one or more HEAA. Palexerults that have both: horizons with a total thickness of 18 cm or more within 75 cm of 1. In one or more subhorizons within the upper 25 cm of the mineral soil surface, a fine-earth fraction with both a bulk the argillic or kandic horizon, redox depletions with a color density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 value, moist, of 4 or more and chroma of 2 or less, and Al plus /2 Fe percentages (by ammonium oxalate) totaling accompanied by redox concentrations, and also aquic more than 1.0. conditions for some time in normal years (or artificial Andic Haploxerults drainage); and HEBE. Other Haploxerults that have an argillic or kandic 2. Throughout one or more horizons with a total thickness horizon that: 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 1. Consists entirely of lamellae; or or less, measured at 33 kPa water retention, and Al plus 1 2. Is a combination of two or more lamellae and one or /2 Fe percentages (by ammonium oxalate) totaling more than more subhorizons with a thickness of 7.5 to 20 cm, each layer 1.0. with an overlying eluvial horizon; or Aquandic Palexerults 3. Consists of one or more subhorizons that are more HEAB. Other Palexerults that have, in one or more than 20 cm thick, each with an overlying eluvial horizon, subhorizons within the upper 25 cm of the argillic or kandic andabove these horizons there are either: horizon, redox depletions with a color value, moist, of 4 or more a. Two or more lamellae with a combined thickness of 5 and chroma of 2 or less, accompanied by redox concentrations Ultisols 283

and by aquic conditions for some time in normal years (or density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 artificial drainage). and Al plus /2 Fe percentages (by ammonium oxalate) totaling Aquic Palexerults more than 1.0. Andic Palexerults HEAC. Other Palexerults that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of HEAD. Other Palexerults. the mineral soil surface, a fine-earth fraction with both a bulk Typic Palexerults

U L T

285

CHAPTER 16 Vertisols

Key to Suborders FF. Other Vertisols. Uderts, p. 291 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) and one or both of the following: Aquerts 1. In more than half of each pedon, either on faces of peds Key to Great Groups or in the matrix if peds are absent, 50 percent or more chroma of either: FAA. Aquerts that have within 100 cm of the mineral soil surface either: a. 2 or less if redox concentrations are present; or 1. A sulfuric horizon; or b. 1 or less; or 2. Sulfidic materials. 2. Enough active ferrous iron (Fe2+) to give a positive Sulfaquerts, p. 289 reaction to alpha,alpha-dipyridyl at a time when the soil is not being irrigated. FAB. Aquerts that have a salic horizon that has its upper Aquerts, p. 285 boundary within 100 cm of the mineral soil surface. Salaquerts, p. 288 FB. Other Vertisols that have a cryic soil temperature regime. Cryerts, p. 289 FAC. Other Aquerts that have a duripan that has its upper boundary within 100 cm of the mineral soil surface. FC. Other Vertisols that in normal years have both: Duraquerts, p. 286 1. A thermic, mesic, or frigid soil temperature regime; and FAD. Other Aquerts that have a natric horizon or have an 2. If not irrigated during the year, cracks that remain both: exchangeable sodium percentage of 15 percent or more (or a a. 5 mm or more wide, through a thickness of 25 cm or sodium adsorption ratio of 13 or more) within 100 cm of the more within 50 cm of the mineral soil surface, for 60 or mineral soil surface. more consecutive days during the 90 days following the Natraquerts, p. 288 summer solstice; and FAE. Other Aquerts that have a calcic horizon that has its b. Closed for 60 or more consecutive days during the 90 upper boundary within 100 cm of the mineral soil surface. days following the winter solstice. Calciaquerts, p. 286 Xererts, p. 295 FAF. Other Aquerts that have, throughout one or more FD. Other Vertisols that, if not irrigated during the year, have horizons with a total thickness of 25 cm or more within 50 cm of cracks in normal years that remain closed for less than 60 the mineral soil surface, both: consecutive days during a period when the soil temperature at a depth of 50 cm from the soil surface is higher than 8 oC. 1. An electrical conductivity in the saturation extract of less V Torrerts, p. 289 than 4.0 dS/m at 25 oC; and E R 2. A pH value of 4.5 or less in 0.01 M CaCl (5.0 or less in FE. Other Vertisols that, if not irrigated during the year, have 2 1:1 water). cracks in normal years that are 5 mm or more wide, through a Dystraquerts, p. 286 thickness of 25 cm or more within 50 cm of the mineral soil surface, for 90 or more cumulative days per year. FAG. Other Aquerts that have episaturation. Usterts, p. 292 Epiaquerts, p. 288 286 Keys to Soil Taxonomy

FAH. Other Aquerts. FACD. Other Duraquerts that have, in one or more horizons Endoaquerts, p. 287 between either an Ap horizon or a depth of 25 cm from the mineral soil surface, whichever is deeper, and either a depth of Calciaquerts 75 cm or the upper boundary of the duripan if shallower, 50 percent or more colors as follows: Key to Subgroups 1. Hue of 2.5Y or redder and either: FAEA. Calciaquerts that have, in one or more horizons a. A color value, moist, of 6 or more and chroma of 3 or between either an Ap horizon or a depth of 25 cm from the more; or mineral soil surface, whichever is deeper, and either a depth of 75 cm or the upper boundary of a duripan if shallower, 50 b. A color value, moist, of 5 or less and chroma of 2 or percent or more colors as follows: more; or 1. Hue of 2.5Y or redder and either: 2. Hue of 5Y and chroma of 3 or more; or a. A color value, moist, of 6 or more and chroma of 3 or 3. Chroma of 2 or more and no redox concentrations. more; or Aeric Duraquerts b. A color value, moist, of 5 or less and chroma of 2 or FACE. Other Duraquerts that have, in one or more horizons more; or within 30 cm of the mineral soil surface, one or both of the 2. Hue of 5Y and chroma of 3 or more; or following in more than half of each pedon: 3. Chroma of 2 or more and no redox concentrations. 1. A color value, moist, of 4 or more; or Aeric Calciaquerts 2. A color value, dry, of 6 or more. Chromic Duraquerts FAEB. Other Calciaquerts. Typic Calciaquerts FACF. Other Duraquerts. Typic Duraquerts Duraquerts

Key to Subgroups Dystraquerts FACA. Duraquerts that, if not irrigated during the year, have Key to Subgroups 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 FAFA. Dystraquerts that have, in one or more horizons within surface, for 210 or more cumulative days per year. 100 cm of the mineral soil surface, jarosite concentrations and a Aridic Duraquerts pH value of 4.0 or less (1:1 water, air-dried slowly in shade). Sulfaqueptic Dystraquerts FACB. Other Duraquerts that have a thermic, mesic, or frigid soil temperature regime and that, if not irrigated during the year, FAFB. Other Dystraquerts that, if not irrigated during the year, have cracks in normal years that remain both: 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 1. 5 mm or more wide, through a thickness of 25 cm or mineral soil surface, for 210 or more cumulative days per year. more within 50 cm of the mineral soil surface, for 60 or more Aridic Dystraquerts consecutive days during the 90 days following the summer solstice; and FAFC. Other Dystraquerts that, if not irrigated during the year, 2. Closed for 60 or more consecutive days during the 90 have cracks in normal years that are 5 mm or more wide, days following the winter solstice. through a thickness of 25 cm or more within 50 cm of the Xeric Duraquerts mineral soil surface, for 90 or more cumulative days per year. Ustic Dystraquerts FACC. Other Duraquerts that, if not irrigated during the year, have cracks in normal years that are 5 mm or more wide, FAFD. Other Dystraquerts that have, in one or more horizons through a thickness of 25 cm or more within 50 cm of the between either an Ap horizon or a depth of 25 cm from the mineral soil surface, for 90 or more cumulative days per year. mineral soil surface, whichever is deeper, and a depth of 75 cm, Ustic Duraquerts 50 percent or more colors as follows: Vertisols 287

1. Hue of 2.5Y or redder and either: FAHD. Other Endoaquerts that have a thermic, mesic, or frigid soil temperature regime and that, if not irrigated during the year, a. A color value, moist, of 6 or more and chroma of 3 or have cracks in normal years that remain both: more; or 1. 5 mm or more wide, through a thickness of 25 cm or b. A color value, moist, of 5 or less and chroma of 2 or more within 50 cm of the mineral soil surface, for 60 or more more; or consecutive days during the 90 days following the summer 2. Hue of 5Y and chroma of 3 or more; or solstice; and 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 year, Leptic Dystraquerts 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 that contains less than 27 percent clay in its fine-earth Ustic Endoaquerts fraction and has its upper boundary within 100 cm of the mineral soil surface. FAHF. Other Endoaquerts that have, in one or more horizons Entic Dystraquerts between either an Ap horizon or a depth of 25 cm from the mineral soil surface, whichever is deeper, and a depth of 75 cm, FAFG. Other Dystraquerts that have, in one or more horizons 50 percent or more colors as follows: within 30 cm of the mineral soil surface, one or both of the 1. Hue of 2.5Y or redder and either: following in more than half of each pedon: a. A color value, moist, of 6 or more and chroma of 3 or 1. A color value, moist, of 4 or more; or more; or 2. A color value, dry, of 6 or more. b. A color value, moist, of 5 or less and chroma of 2 or Chromic Dystraquerts 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. Aeric Endoaquerts Endoaquerts FAHG. Other Endoaquerts that have a densic, lithic, or Key to Subgroups paralithic contact within 100 cm of the mineral soil surface. FAHA. Endoaquerts that have, throughout a layer 15 cm or Leptic Endoaquerts 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 that contains less than 27 percent clay in its fine-earth Halic Endoaquerts fraction and has its upper boundary within 100 cm of the mineral soil surface. FAHB. Other Endoaquerts that have, in one or more horizons Entic Endoaquerts within 100 cm of the mineral soil surface, an exchangeable sodium percentage of 15 or more (or a sodium adsorption ratio FAHI. Other Endoaquerts that have, in one or more horizons of 13 or more) for 6 or more months in normal years. within 30 cm of the mineral soil surface, one or both of the Sodic Endoaquerts following in more than half of each pedon: V E 1. A color value, moist, of 4 or more; or FAHC. Other Endoaquerts that, if not irrigated during the R year, have cracks in normal years that are 5 mm or more 2. A color value, dry, of 6 or more. wide, through a thickness of 25 cm or more within 50 cm of Chromic Endoaquerts the mineral soil surface, for 210 or more cumulative days per year. FAGJ. Other Endoaquerts. Aridic Endoaquerts Typic Endoaquerts 288 Keys to Soil Taxonomy

Epiaquerts FAGG. Other Epiaquerts that have a densic, lithic, or paralithic contact within 100 cm of the mineral soil surface. Key to Subgroups Leptic Epiaquerts FAGA. Epiaquerts that have, throughout a layer 15 cm or FAGH. Other Epiaquerts that have a layer 25 cm or more thick more thick within 100 cm of the mineral soil surface, an that contains less than 27 percent clay in its fine-earth fraction electrical conductivity of 15 dS/m or more (saturated paste) for and has its upper boundary within 100 cm of the mineral soil 6 or more months in normal years. surface. Halic Epiaquerts Entic Epiaquerts 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. Sodic Epiaquerts 1. A color value, moist, of 4 or more; or 2. A color value, dry, of 6 or more. FAGC. Other Epiaquerts that, if not irrigated during the year, Chromic Epiaquerts 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

FAGD. Other Epiaquerts that have a thermic, mesic, or frigid Natraquerts 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 solstice; and Salaquerts 2. Closed for 60 or more consecutive days during the 90 Key to Subgroups 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 year, surface, for 210 or more cumulative days per 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 year, Ustic Epiaquerts 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 1. Hue of 2.5Y or redder and either: contact within 100 cm of the mineral soil surface. 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 b. A color value, moist, of 5 or less and chroma of 2 or that contains less than 27 percent clay in its fine-earth fraction more; or and has its upper boundary within 100 cm of the mineral soil surface. 2. Hue of 5Y and chroma of 3 or more; or Entic Salaquerts 3. Chroma of 2 or more and no redox concentrations. Aeric Epiaquerts FABE. Other Salaquerts that have, in one or more horizons Vertisols 289

within 30 cm of the mineral soil surface, 50 percent or more 3. Chroma of 3 or more. colors as follows: Chromic Haplocryerts 1. A color value, moist, of 4 or more; or FBBC. Other Haplocryerts. 2. A color value, dry, of 6 or more; or Typic Haplocryerts 3. Chroma of 3 or more. Chromic Salaquerts Humicryerts Key to Subgroups FABF. Other Salaquerts. Typic Salaquerts FBAA. Humicryerts that have, in one or more horizons within 100 cm of the mineral soil surface, an exchangeable sodium Sulfaquerts percentage of 15 or more (or a sodium adsorption ratio of 13 or more) for 6 or more months in normal years. Key to Subgroups Sodic Humicryerts FAAA. Sulfaquerts that have a salic horizon within 75 cm of FBAB. Other Humicryerts. the mineral soil surface. Typic Humicryerts Salic Sulfaquerts

FAAB. Other Sulfaquerts that do not have a sulfuric horizon Torrerts within 100 cm of the mineral soil surface. Sulfic Sulfaquerts Key to Great Groups

FAAC. Other Sulfaquerts. FDA. Torrerts that have a salic horizon that has its upper Typic Sulfaquerts boundary within 100 cm of the soil surface. Salitorrerts, p. 290 Cryerts FDB. Other Torrerts that have a gypsic horizon that has its Key to Great Groups upper boundary within 100 cm of the soil surface. Gypsitorrerts, p. 290 FBA. Cryerts that have 10 kg/m2 or more organic carbon between the mineral soil surface and a depth of 50 cm. FDC. Other Torrerts that have a calcic or petrocalcic horizon Humicryerts, p. 289 that has its upper boundary within 100 cm of the soil surface. Calcitorrerts, p. 289 FBB. Other Cryerts. Haplocryerts, p. 289 FDD. Other Torrerts. Haplotorrerts, p. 290 Haplocryerts Calcitorrerts Key to Subgroups Key to Subgroups FBBA. Haplocryerts that have, in one or more horizons within 100 cm of the mineral soil surface, an exchangeable sodium FDCA. Calcitorrerts that have a petrocalcic horizon that has percentage of 15 or more (or a sodium adsorption ratio of 13 or its upper boundary within 100 cm of the soil surface. more) for 6 or more months in normal years. Petrocalcic Calcitorrerts Sodic Haplocryerts FDCB. Other Calcitorrerts that have a densic, lithic, or V FBBB. Other Haplocryerts that have, in one or more horizons paralithic contact, or the upper boundary of a duripan, within E within 30 cm of the mineral soil surface, 50 percent or more 100 cm of the soil surface. R colors as follows: Leptic Calcitorrerts 1. A color value, moist, of 4 or more; or FDCC. Other Calcitorrerts that have a layer 25 cm or more 2. A color value, dry, of 6 or more; or thick that contains less than 27 percent clay in its fine-earth 290 Keys to Soil Taxonomy

fraction and has its upper boundary within 100 cm of the soil thick that contains less than 27 percent clay in its fine-earth surface. fraction and has its upper boundary within 100 cm of the soil Entic Calcitorrerts surface. Entic Haplotorrerts FDCD. Other Calcitorrerts that have, in one or more horizons within 30 cm of the soil surface, 50 percent or more colors as FDDE. Other Haplotorrerts that have, in one or more horizons follows: within 30 cm of the soil surface, 50 percent or more 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. Chromic Calcitorrerts 3. Chroma of 3 or more. Chromic Haplotorrerts FDCE. Other Calcitorrerts. Typic Calcitorrerts FDDF. Other Haplotorrerts. Typic Haplotorrerts Gypsitorrerts Salitorrerts Key to Subgroups Key to Subgroups FDBA. Gypsitorrerts that have, in one or more horizons within 30 cm of the soil surface, 50 percent or more colors as follows: FDAA. Salitorrerts that have, in one or more horizons within 100 cm of the soil surface, aquic conditions for some time in 1. A color value, moist, of 4 or more; or normal years (or artificial drainage) and either: 2. A color value, dry, of 6 or more; or 1. Redoximorphic features; or 3. Chroma of 3 or more. 2. Enough active ferrous iron (Fe2+) to give a positive Chromic Gypsitorrerts reaction to alpha,alpha-dipyridyl at a time when the soil is not being irrigated. FDBB. Other Gypsitorrerts. Aquic Salitorrerts Typic Gypsitorrerts FDAB. Other Salitorrerts that have a densic, lithic, or Haplotorrerts paralithic contact, or the upper boundary of a duripan or petrocalcic horizon, within 100 cm of the soil surface. Key to Subgroups Leptic Salitorrerts FDDA. Haplotorrerts that have, throughout a layer 15 cm or FDAC. Other Salitorrerts that have a layer 25 cm or more more thick within 100 cm of the soil surface, an electrical thick that contains less than 27 percent clay in its fine-earth conductivity of 15 dS/m or more (saturated paste) for 6 or more fraction and has its upper boundary within 100 cm of the soil months in normal years. surface. Halic Haplotorrerts Entic Salitorrerts FDDB. Other Haplotorrerts that have, in one or more horizons FDAD. Other Salitorrerts that have, in one or more horizons within 100 cm of the soil surface, an exchangeable sodium within 30 cm of the soil surface, 50 percent or more colors as percentage of 15 or more (or a sodium adsorption ratio of 13 or follows: more) for 6 or more months in normal years. Sodic Haplotorrerts 1. A color value, moist, of 4 or more; or 2. A color value, dry, of 6 or more; or FDDC. Other Haplotorrerts that have a densic, lithic, or paralithic contact, or the upper boundary of a duripan, within 3. Chroma of 3 or more. 100 cm of the soil surface. Chromic Salitorrerts Leptic Haplotorrerts FDAE. Other Salitorrerts. FDDD. Other Haplotorrerts that have a layer 25 cm or more Typic Salitorrerts Vertisols 291

Uderts 2. A color value, dry, of 6 or more; or 3. Chroma of 3 or more. Key to Great Groups Chromic Dystruderts FFA. Uderts that have, throughout one or more horizons with a FFAF. Other Dystruderts. total thickness of 25 cm or more within 50 cm of the mineral Typic Dystruderts soil surface, both: 1. An electrical conductivity in the saturation extract of less Hapluderts than 4.0 dS/m at 25 oC; and Key to Subgroups 2. A pH value of 4.5 or less in 0.01 M CaCl2 (5.0 or less in saturated paste). FFBA. Hapluderts that have a lithic contact within 50 cm of Dystruderts, p. 291 the mineral soil surface. Lithic Hapluderts FFB. Other Uderts. Hapluderts, p. 291 FFBB. Other Hapluderts that have, in one or more horizons within 100 cm of the mineral soil surface, aquic conditions for some time in normal years (or artificial drainage) and either: Dystruderts 1. Redoximorphic features; or Key to Subgroups 2. Enough active ferrous iron (Fe2+) to give a positive FFAA. Dystruderts that have, in one or more horizons reaction to alpha,alpha-dipyridyl at a time when the soil is within 100 cm of the mineral soil surface, aquic conditions not being irrigated. for some time in normal years (or artificial drainage) and Aquic Hapluderts either: FFBC. Other Hapluderts that are saturated with water in one 1. Redoximorphic features; or 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: reaction to alpha,alpha-dipyridyl at a time when the soil is 1. 20 or more consecutive days; or not being irrigated. 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, normal years for either or both: or paralithic contact within 100 cm of the mineral soil surface. Leptic Hapluderts 1. 20 or more consecutive days; or 2. 30 or more cumulative days. FFBE. Other Hapluderts that have a layer 25 cm or more thick Oxyaquic Dystruderts that contains less than 27 percent clay in its fine-earth fraction and has its upper boundary within 100 cm of the mineral soil FFAC. Other Dystruderts that have a densic, lithic, or surface. paralithic contact within 100 cm of the mineral soil surface. Entic Hapluderts Leptic Dystruderts FFBF. Other Hapluderts that have, in one or more horizons FFAD. Other Dystruderts that have a layer 25 cm or more within 30 cm of the mineral soil surface, 50 percent or more thick that contains less than 27 percent clay in its fine-earth colors as follows: V fraction and has its upper boundary within 100 cm of the 1. A color value, moist, of 4 or more; or E mineral soil surface. R Entic Dystruderts 2. A color value, dry, of 6 or more; or 3. Chroma of 3 or more. FFAE. Other Dystruderts that have, in one or more horizons Chromic Hapluderts within 30 cm of the mineral soil surface, 50 percent or more colors as follows: FFBG. Other Hapluderts. 1. A color value, moist, of 4 or more; or Typic Hapluderts 292 Keys to Soil Taxonomy

Usterts FEDE. Other Calciusterts that, if not irrigated during the year, have cracks in normal years that are 5 mm or more wide, Key to Great Groups through a thickness of 25 cm or more within 50 cm of the mineral soil surface, for 210 or more cumulative days per year. FEA. Usterts that have, throughout one or more horizons with Aridic Calciusterts a total thickness of 25 cm or more within 50 cm of the mineral soil surface, both: FEDF. Other Calciusterts that, if not irrigated during the year, have cracks in normal years that are 5 mm or more wide, 1. An electrical conductivity in the saturation extract of less through a thickness of 25 cm or more within 50 cm of the than 4.0 dS/m at 25 oC; and mineral soil surface, for less than 150 cumulative days per year.

2. A pH value of 4.5 or less in 0.01 M CaCl2 (5.0 or less in Udic Calciusterts saturated paste). Dystrusterts, p. 292 FEDG. Other Calciusterts that have a densic, lithic, or paralithic contact, or the upper boundary of a duripan, within FEB. Other Usterts that have a salic horizon that has its upper 100 cm of the mineral soil surface. boundary within 100 cm of the mineral soil surface. Leptic Calciusterts Salusterts, p. 294 FEDH. Other Calciusterts that have a layer 25 cm or more FEC. Other Usterts that have a gypsic horizon that has its thick that contains less than 27 percent clay in its fine-earth upper boundary within 100 cm of the mineral soil surface. fraction and has its upper boundary within 100 cm of the Gypsiusterts, p. 293 mineral soil surface. Entic Calciusterts FED. Other Usterts that have a calcic or petrocalcic horizon that has its upper boundary within 100 cm of the mineral soil FEDI. Other Calciusterts that have, in one or more horizons surface. within 30 cm of the mineral soil surface, 50 percent or more Calciusterts, p. 292 colors as follows: 1. A color value, moist, of 4 or more; or FEE. Other Usterts. Haplusterts, p. 293 2. A color value, dry, of 6 or more; or 3. Chroma of 3 or more. Calciusterts Chromic Calciusterts

Key to Subgroups FEDJ. Other Calciusterts. Typic Calciusterts FEDA. Calciusterts that have a lithic contact within 50 cm of the mineral soil surface. Lithic Calciusterts Dystrusterts Key to Subgroups FEDB. Other Calciusterts that have, throughout a layer 15 cm or more thick within 100 cm of the mineral soil surface, an FEAA. Dystrusterts that have a lithic contact within 50 cm of electrical conductivity of 15 dS/m or more (saturated paste) for the mineral soil surface. 6 or more months in normal years. Lithic Dystrusterts Halic Calciusterts FEAB. Other Dystrusterts that have, in one or more horizons FEDC. Other Calciusterts that have, in one or more horizons within 100 cm of the mineral soil surface, aquic conditions within 100 cm of the mineral soil surface, an exchangeable for some time in normal years (or artificial drainage) and either: sodium percentage of 15 or more (or a sodium adsorption ratio 1. Redoximorphic features; or of 13 or more) for 6 or more months in normal years. Sodic Calciusterts 2. Enough active ferrous iron (Fe2+) to give a positive reaction to alpha,alpha-dipyridyl at a time when the soil is FEDD. Other Calciusterts that have a petrocalcic horizon that not being irrigated. has its upper boundary within 100 cm of the mineral soil Aquic Dystrusterts surface. Petrocalcic Calciusterts FEAC. Other Dystrusterts that, if not irrigated during the year, Vertisols 293

have cracks in normal years that are 5 mm or more wide, FECD. Other Gypsiusterts 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 are 5 mm or more mineral soil surface, for 210 or more cumulative days per wide, through a thickness of 25 cm or more within 50 cm of the year. mineral soil surface, for 210 or more cumulative days per year. Aridic Dystrusterts Aridic Gypsiusterts

FEAD. Other Dystrusterts that, if not irrigated during the year, FECE. Other Gypsiusterts that, if not irrigated during the year, have cracks in normal years that are 5 mm or more wide, 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. mineral soil surface, for less than 150 cumulative days per year. Udic Dystrusterts Udic Gypsiusterts

FEAE. Other Dystrusterts that have a densic, lithic, or FECF. Other Gypsiusterts that have a densic, lithic, or paralithic contact, or the upper boundary of a duripan, within paralithic contact, or the upper boundary of a duripan or 100 cm of the mineral soil surface. petrocalcic horizon, within 100 cm of the mineral soil surface. Leptic Dystrusterts Leptic Gypsiusterts

FEAF. Other Dystrusterts that have a layer 25 cm or more FECG. Other Gypsiusterts that have a layer 25 cm or more thick that contains less than 27 percent clay in its fine-earth thick that contains less than 27 percent clay in its fine-earth fraction and has its upper boundary within 100 cm of the fraction and has its upper boundary within 100 cm of the mineral soil surface. mineral soil surface. 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 cm FEEB. Other Haplusterts that have, throughout a layer 15 cm or more thick within 100 cm of the mineral soil surface, an 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 V 6 or more months in normal years. 6 or more months in normal years. E Halic Gypsiusterts Halic Haplusterts R FECC. Other Gypsiusterts that have, in one or more horizons FEEC. Other Haplusterts 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 Gypsiusterts Sodic Haplusterts 294 Keys to Soil Taxonomy

FEED. Other Haplusterts that have a petrocalcic horizon that a. A color value, moist, of 4 or more; or has its upper boundary within 150 cm of the mineral soil b. A color value, dry, of 6 or more; or surface. Petrocalcic Haplusterts c. Chroma of 3 or more; and 2. If not irrigated during the year, cracks in normal years FEEE. Other Haplusterts that have a gypsic horizon that has that are 5 mm or more wide, through a thickness of 25 cm or its upper boundary within 150 cm of the mineral soil surface. more within 50 cm of the mineral soil surface, for less than Gypsic Haplusterts 150 cumulative days per year. Chromic Udic Haplusterts FEEF. Other Haplusterts that have a calcic horizon that has its upper boundary within 150 cm of the mineral soil surface. FEEL. Other Haplusterts that, if not irrigated during the Calcic Haplusterts 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 FEEG. Other Haplusterts that have both: mineral soil surface, for less than 150 cumulative days per 1. A densic, lithic, or paralithic contact within 100 cm of year. the mineral soil surface; and Udic Haplusterts 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 or paralithic contact, or the upper boundary of a duripan, within more within 50 cm of the mineral soil surface, for 210 or 100 cm of the mineral soil 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 year, thick that contains less than 27 percent clay in its fine-earth have cracks in normal years that are 5 mm or more wide, fraction and has its upper boundary within 100 cm of the through a thickness of 25 cm or more within 50 cm of the mineral soil surface. mineral soil surface, for 210 or more cumulative days per year. Entic Haplusterts Aridic Haplusterts FEEO. Other Haplusterts that have, in one or more horizons FEEI. Other Haplusterts that have both: within 30 cm of the mineral soil surface, 50 percent or more 1. A densic, lithic, or paralithic contact within 100 cm of colors as follows: the mineral soil surface; and 1. A color value, moist, of 4 or more; or 2. If not irrigated during the year, cracks in 6 or more out of 2. A color value, dry, of 6 or more; or 10 years that are 5 mm or more wide, through a thickness of 25 cm or more within 50 cm of the mineral soil surface, for 3. Chroma of 3 or more. less than 150 cumulative days per year. Chromic Haplusterts Leptic Udic Haplusterts FEEP. Other Haplusterts. FEEJ. Other Haplusterts that have both: Typic Haplusterts 1. A layer 25 cm or more thick that contains less than 27 percent clay in its fine-earth fraction and has its upper Salusterts boundary within 100 cm of the mineral soil surface; and Key to Subgroups 2. If not irrigated during the year, cracks in normal years FEBA. Salusterts that have a lithic contact within 50 cm of the that are 5 mm or more wide, through a thickness of 25 cm or mineral soil surface. more within 50 cm of the mineral soil surface, for less than Lithic Salusterts 150 cumulative days per year. Entic Udic Haplusterts FEBB. Other Salusterts that have, in one or more horizons within 100 cm of the mineral soil surface, an exchangeable FEEK. Other Haplusterts that have both: sodium percentage of 15 or more (or a sodium adsorption ratio 1. In one or more horizons within 30 cm of the mineral soil of 13 or more) for 6 or more months in normal years. surface, 50 percent or more colors as follows: Sodic Salusterts Vertisols 295

FEBC. Other Salusterts that have, in one or more horizons FCC. Other Xererts. within 100 cm of the mineral soil surface, aquic conditions for Haploxererts, p. 296 some time in normal years (or artificial drainage) and either: 1. Redoximorphic features; or Calcixererts 2. Enough active ferrous iron (Fe2+) to give a positive Key to Subgroups reaction to alpha,alpha-dipyridyl at a time when the soil is FCBA. Calcixererts that have a lithic contact within 50 cm of not being irrigated. the mineral soil surface. Aquic Salusterts Lithic Calcixererts FEBD. Other Salusterts that, if not irrigated during the FCBB. Other Calcixererts that have a petrocalcic horizon that year, have cracks in normal years that are 5 mm or more wide, has its upper boundary within 100 cm of the mineral soil through a thickness of 25 cm or more within 50 cm of the surface. mineral soil surface, for 210 or more cumulative days per Petrocalcic Calcixererts year. Aridic Salusterts FCBC. Other Calcixererts that, if not irrigated during the year, have cracks in normal years that remain 5 mm or more FEBE. Other Salusterts that have a densic, lithic, or paralithic wide, through a thickness of 25 cm or more within 50 cm of contact, or the upper boundary of a duripan or petrocalcic the mineral soil surface, for 180 or more consecutive days. horizon, within 100 cm of the mineral soil surface. Aridic Calcixererts Leptic Salusterts FCBD. Other Calcixererts that have a densic, lithic, or FEBF. Other Salusterts that have a layer 25 cm or more thick paralithic contact within 100 cm of the mineral soil surface. that contains less than 27 percent clay in its fine-earth fraction Leptic Calcixererts and has its upper boundary within 100 cm of the mineral soil surface. FCBE. Other Calcixererts that have a layer 25 cm or more Entic Salusterts thick that contains less than 27 percent clay in its fine-earth fraction and has its upper boundary within 100 cm of the FEBG. Other Salusterts that have, in one or more horizons mineral soil surface. within 30 cm of the mineral soil surface, 50 percent or more Entic Calcixererts colors as follows: 1. A color value, moist, of 4 or more; or FCBF. Other Calcixererts that have, in one or more horizons within 30 cm of the mineral soil surface, 50 percent or more 2. A color value, dry, of 6 or more; or colors as follows: 3. Chroma of 3 or more. 1. A color value, moist, of 4 or more; or Chromic Salusterts 2. A color value, dry, of 6 or more; or FEBH. Other Salusterts. 3. Chroma of 3 or more. Typic Salusterts Chromic Calcixererts

Xererts FCBG. Other Calcixererts. Typic Calcixererts Key to Great Groups

FCA. Xererts that have a duripan that has its upper boundary Durixererts V within 100 cm of the mineral soil surface. Key to Subgroups E Durixererts, p. 295 R FCAA. Durixererts that have, throughout a layer 15 cm or FCB. Other Xererts that have a calcic or petrocalcic horizon more thick above the duripan, an electrical conductivity of 15 that has its upper boundary within 100 cm of the mineral soil dS/m or more (saturated paste) for 6 or more months in normal surface. years. Calcixererts, p. 295 Halic Durixererts 296

FCAB. Other Durixererts that have, in one or more horizons electrical conductivity of 15 dS/m or more (saturated paste) for above the duripan, an exchangeable sodium percentage of 15 or 6 or more months in normal years. more (or a sodium adsorption ratio of 13 or more) for 6 or more Halic Haploxererts months in normal years. Sodic Durixererts FCCC. Other Haploxererts that have, in one or more horizons within 100 cm of the mineral soil surface, an exchangeable FCAC. Other Durixererts that have, in one or more horizons sodium percentage of 15 or more (or a sodium adsorption ratio above the duripan, aquic conditions for some time in normal of 13 or more) for 6 or more months in normal years. years (or artificial drainage) and either: Sodic Haploxererts 1. Redoximorphic features; or FCCD. Other Haploxererts that, if not irrigated during the 2. Enough active ferrous iron (Fe2+) to give a positive year, have cracks in normal years that remain 5 mm or more reaction to alpha,alpha-dipyridyl at a time when the soil is wide, through a thickness of 25 cm or more within 50 cm of the not being irrigated. mineral soil surface, for 180 or more consecutive days. Aquic Durixererts Aridic Haploxererts

FCAD. Other Durixererts that, if not irrigated during the year, FCCE. Other Haploxererts that have, in one or more horizons have cracks in normal years that remain 5 mm or more wide, within 100 cm of the mineral soil surface, aquic conditions for through a thickness of 25 cm or more above the duripan, for 180 some time in normal years (or artificial drainage) and either: or more consecutive days. 1. Redoximorphic features; or Aridic Durixererts 2. Enough active ferrous iron (Fe2+) to give a positive FCAE. Other Durixererts that, if not irrigated during the year, reaction to alpha,alpha-dipyridyl at a time when the soil is have cracks in normal years that remain 5 mm or more wide, not being irrigated. through a thickness of 25 cm or more above the duripan, for less Aquic Haploxererts than 90 consecutive days. Udic Durixererts FCCF. Other Haploxererts that, if not irrigated during the year, have cracks in normal years that remain 5 mm or more FCAF. Other Durixererts that have a duripan that is not wide, through a thickness of 25 cm or more within 50 indurated in any subhorizon. cm of the mineral soil surface, for less than 90 consecutive days. Haplic Durixererts Udic Haploxererts

FCAG. Other Durixererts that have, in one or more horizons FCCG. Other Haploxererts that have a densic, lithic, or within 30 cm of the mineral soil surface, 50 percent or more paralithic contact within 100 cm of the mineral soil surface. colors as follows: Leptic Haploxererts 1. A color value, moist, of 4 or more; or FCCH. Other Haploxererts that have a layer 25 cm or more 2. A color value, dry, of 6 or more; or thick that contains less than 27 percent clay in its fine-earth fraction and has its upper boundary within 100 cm of the 3. Chroma of 3 or more. mineral soil surface. Chromic Durixererts Entic Haploxererts FCAH. Other Durixererts. FCCI. Other Haploxererts that have, in one or more horizons Typic Durixererts within 30 cm of the mineral soil surface, 50 percent or more colors as follows: Haploxererts 1. A color value, moist, of 4 or more; or Key to Subgroups 2. A color value, dry, of 6 or more; or FCCA. Haploxererts that have a lithic contact within 50 cm of 3. Chroma of 3 or more. the mineral soil surface. Chromic Haploxererts Lithic Haploxererts

FCCB. Other Haploxererts that have, throughout a layer 15 cm FCCJ. Other Haploxererts. or more thick within 100 cm of the mineral soil surface, an Typic Haploxererts 297

CHAPTER 17 Family and Series Differentiae and Names

Families and series serve purposes that are largely pragmatic, while pedologic classifications have set it at either 50 or 20 the series name is abstract, and the technical family name is microns. Engineering classifications have been based on grain- descriptive. In this chapter the descriptive terms used in the size percentages, by weight, in the soil fraction less than 74 mm names of families are defined, the control sections to which the in diameter, while textural classes in pedologic classifications terms apply are given, and the criteria, including the taxa in have been based on percentages, by weight, in the fraction less which they are used, are indicated. than 2.0 mm in diameter. In engineering classifications, the separate very fine sand (diameter between 50 and 100 microns Family Differentiae for Mineral Soils and or 0.05 and 0.1 mm) has been subdivided at 74 microns. In defining the particle-size classes for this taxonomy, a similar Mineral Layers of Some Organic Soils division has been made, but in a different way. Soil materials that have a texture of fine sand or loamy fine sand normally The following differentiae are used to distinguish families of have an appreciable amount of very fine sand, most of which is mineral soils and the mineral layers of some organic soils within coarser than 74 microns. A silty sediment, such as loess, may a subgroup. The class names of these components are used to also contain an appreciable amount of very fine sand, most of form the family name. The components are listed and defined in which is finer than 74 microns. Thus, in the design of particle- the same sequence in which the components appear in the family size classes for this taxonomy, the very fine sand has been names. allowed to “float.” It is included with the sand if the texture Particle-size classes (fine-earth fraction) of a soil is sand, loamy fine sand, or Mineralogy classes coarser. It is treated as silt, however, if the texture is very fine Cation-exchange activity classes sand, loamy very fine sand, sandy loam, silt loam, or finer. Calcareous and reaction classes No single set of particle-size classes seems adequate to serve Soil temperature classes as family differentiae for all of the different kinds of soil. Thus, Soil depth classes this taxonomy provides 2 generalized and 11 more narrowly Rupture-resistance classes defined classes, which permit relatively fine distinctions Classes of coatings between families of soils for which particle size is important, Classes of cracks while providing broader groupings for soils in which narrowly defined particle-size classes would produce undesirable Particle-Size Classes and Their Substitutes separations. Thus, the term “clayey” is used for some soil families to indicate a clay content of 35 percent (30 percent in Vertisols) or more in specific horizons, while in other families Definition of Particle-Size Classes and Their Substitutes for the more narrowly defined terms “fine” and “very-fine” indicate Mineral Soils that these horizons have a clay content either of 35 (30 percent The first part of the family name is the name of either a in Vertisols) to 60 percent or of 60 percent or more in their fine- particle-size class or a substitute for a particle-size class. The earth fraction. Fine earth refers to particles smaller than 2.0 mm term particle-size class is used to characterize the grain-size in diameter. Rock fragments are particles 2.0 mm or more in composition of the whole soil, including both the fine earth and diameter that are strongly cemented or more resistant to rupture the rock and pararock fragments up to the size of a pedon, but it and include all particles with horizontal dimensions smaller than excludes organic matter and salts more soluble than gypsum. the size of a pedon. Cemented fragments 2.0 mm or more in Substitutes for particle-size classes are used for soils that have diameter that are in a rupture-resistance class that is less andic soil properties or a high content of volcanic glass, pumice, cemented than the strongly cemented class are referred to as F or cinders. pararock fragments. Pararock fragments, like rock fragments, A The particle-size classes of this taxonomy represent a include all particles between 2.0 mm and a horizontal dimension M compromise between conventional divisions in pedologic and smaller than the size of a pedon. Most pararock fragments are engineering classifications. Engineering classifications have set broken into fragments 2.0 mm or less in diameter during the the limit between sand and silt at a diameter of 74 microns, preparation of samples for particle-size analysis in the 298 Keys to Soil Taxonomy

laboratory. Therefore, pararock fragments are generally included Aniso Class with the fine earth in the particle-size classes, although cinders, If the particle-size control section includes more than one pumice, and pumicelike fragments are treated as fragments in pair of the strongly contrasting classes, listed below, then the the substitutes for classes, regardless of their rupture-resistance soil is assigned to an aniso class named for the pair of adjacent class. classes that contrast most strongly. The aniso class is considered Substitutes for particle-size classes are used for soils that part of the particle-size class name and is set off by commas have andic soil properties or a high content of volcanic glass, after the particle-size name. An example is a sandy over clayey, pumice, or cinders. These materials cannot be readily dispersed, aniso, mixed, active, mesic Aridic Haplustoll. and the results of dispersion vary. Consequently, normal particle-size classes do not adequately characterize these Generalized Particle-Size Classes components. Substitutes for particle-size class names are used for those parts of soils that have andic soil properties or a high Two generalized particle-size classes, loamy and clayey, are amount of volcanic glass, pumice, or cinders, as is the case with used for shallow classes (defined below) and for soils in Arenic, Andisols and many Andic and Vitrandic subgroups of other soil Grossarenic, and Lithic subgroups. The clayey class is used for orders. Some Spodosols, whether identified in Andic subgroups all strongly contrasting particle-size classes with more than 35 or not, have andic soil properties in some horizons within the percent clay (30 percent in Vertisols). The loamy particle-size particle-size control section, and particle-size substitute class class is used for contrasting classes, where appropriate, to names are used for these horizons. characterize the lower part of the particle-size control section. Neither a particle-size class name nor a substitute for a The generalized classes, where appropriate, are also used for all particle-size class name is used for Psamments, Psammaquents, strongly contrasting particle-size classes that include a substitute and Psammentic subgroups that are in a sandy particle-size class. For example, loamy over pumiceous or cindery (not fine- class. These taxa have, by definition, either a sandy particle-size loamy over pumiceous or cindery) is used. class or an ashy substitute class. The sandy particle-size class is Six generalized classes, defined later in this chapter, are used considered redundant in the family name. The ashy substitute for Terric subgroups of Histosols and Histels. class, however, is named, if appropriate in these taxa. Control Section for Particle-Size Classes or Their Particle-size class names are applied, although with Substitutes in Mineral Soils reservations, to spodic horizons and other horizons that do not have andic soil properties but contain significant amounts of The particle-size and substitute class names listed below are allophane, imogolite, ferrihydrite, or aluminum-humus applied to certain horizons, or to the soil materials within complexes. The isotic mineralogy class (defined below) is specific depth limits, that have been designated as the particle- helpful in identifying these particle-size classes. size control section. The lower boundary of the control section In general, the weighted average particle-size class of the may be at a specified depth (in centimeters) below the mineral whole particle-size control section (defined below) determines soil surface or below the upper boundary of an organic layer what particle-size class name is used as a component of the with andic soil properties, or it may be at the upper boundary of family name. a root-limiting layer. Unless otherwise indicated, the following are considered root-limiting layers in this chapter: a duripan; a Strongly Contrasting Particle-Size Classes fragipan; petrocalcic, petrogypsic, and placic horizons; If the particle-size control section consists of two parts with continuous ortstein; and densic, lithic, paralithic, and petroferric strongly contrasting particle-size or substitute classes (listed contacts. The following list of particle-size control sections for below), if both parts are 12.5 cm or more thick (including parts particular kinds of mineral soils is arranged as a key. This key, not in the control section), and if the transition zone between like other keys in this taxonomy, is designed in such a way that them is less than 12.5 cm thick, both class names are used. For the reader makes the correct classification by going through the example, the family particle-size class is sandy over clayey if all key systematically, starting at the beginning and eliminating one of the following criteria are met: the soil meets criterion D by one all classes that include criteria that do not fit the soil in (listed below) under the control section for particle-size classes question. The soil belongs to the first class for which it meets all or their substitutes; any Ap horizon is less than 30 cm thick; the of the criteria listed. The upper boundary of an argillic, natric, or weighted average particle-size class of the upper 30 cm of the kandic horizon is used in the following key. This boundary is not soil is sandy; the weighted average of the lower part is clayey; always obvious. If one of these horizons is present but the upper and the transition zone is less than 12.5 cm thick. If a substitute boundary is irregular or broken, as in an A/B or B/A horizon, the name applies to one or more parts of the particle-size control depth at which half or more of the volume has the fabric of an section and the parts are not strongly contrasting classes, the argillic, natric, or kandic horizon should be considered the upper name of the thickest part (cumulative) is used as the soil family boundary. name. Family and Series Differentiae and Names 299

Key to the Control Section for Particle-Size Classes or Their soil surface or a root-limiting layer, whichever is shallower; Substitutes in Mineral Soils or A. For mineral soils that have a root-limiting layer (listed F. All other mineral soils: Between the lower boundary of an above) within 36 cm of the mineral soil surface or below the Ap horizon or a depth of 25 cm below the mineral soil surface, upper boundary of organic soil materials with andic soil whichever is deeper, and the shallower of the following: (a) a properties, whichever is shallower: From the mineral soil depth of 100 cm below the mineral soil surface or (b) a root- surface or the upper boundary of the organic soil materials with limiting layer. 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 such upper boundary of an organic layer with andic soil properties, a way that the reader makes the correct classification by going whichever is shallower, and the shallower of the following: (a) a through the key systematically, starting at the beginning and depth 100 cm below the starting point or (b) a root-limiting eliminating one by one all classes that include criteria that do layer; or not fit the soil or layer in question. The class or substitute name C. For those Alfisols, Ultisols, and great groups of Aridisols for each layer within the control section must be determined and Mollisols, excluding soils in Lamellic subgroups, that have from the key. If any two layers meet the criteria for strongly an argillic, kandic, or natric horizon that has its upper boundary contrasting particle-size classes (listed below), the soil is named within 100 cm of the mineral soil surface and its lower boundary for that strongly contrasting class. If more than one pair meets at a depth of 25 cm or more below the mineral soil surface or the criteria for strongly contrasting classes, the soil is also in an that are in a Grossarenic or Arenic subgroup, use 1 through 4 aniso class named for the pair of adjacent classes that contrast below. For other soils, go to D below. most strongly. If the soil has none of the strongly contrasting classes, the weighted average soil materials within the particle- 1. Strongly contrasting particle-size classes (defined and size control section generally determine the class. Exceptions listed later) within or below the argillic, kandic, or natric are soils that are not strongly contrasting and that have a horizon and within 100 cm of the mineral soil surface: The substitute class name for one or more parts of the control upper 50 cm of the argillic, kandic, or natric horizon or to a section. In these soils the class or substitute name of the thickest 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 3. A fragipan at a depth of less than 50 cm below the top of control section that qualifies as an element in one of the strongly the argillic, kandic, or natric horizon: Between the upper contrasting particle-size classes listed below, or throughout the boundary of the argillic, kandic, or natric horizon and the top control section, a fine-earth component (including associated the fragipan; or medium and finer pores) of less than 10 percent of the total volume and that meet one of the following sets of substitute 4. Other soils that meet C above: Either the whole argillic, class criteria: kandic, or natric horizon if 50 cm or less thick or the upper 50 cm of the horizon if more than 50 cm thick. 1. Have, in the whole soil, more than 60 percent (by weight) volcanic ash, cinders, lapilli, pumice, and D. For those Alfisols, Ultisols, and great groups of Aridisols pumicelike1 fragments and, in the fraction coarser than 2.0 and Mollisols that are in a Lamellic subgroup or have an argillic, mm, two-thirds or more (by volume) pumice and/or kandic, or natric horizon that has its upper boundary at a depth pumicelike fragments. of 100 cm or more from the mineral surface and that are not in a Pumiceous Grossarenic or Arenic subgroup: Between the lower boundary of or an Ap horizon or a depth of 25 cm from the mineral soil surface, whichever is deeper, and 100 cm below the mineral soil surface 2. Have, in the whole soil, more than 60 percent (by or a root-limiting layer, whichever is shallower; or weight) volcanic ash, cinders, lapilli, pumice, and pumicelike F E. For other soils that have an argillic or natric horizon that A has its lower boundary at a depth of less than 25 cm from the M mineral surface: Between the upper boundary of the argillic 1 Pumicelike—vesicular pyroclastic materials other than pumice that have an apparent or natric horizon and a depth of 100 cm below the mineral specific gravity (including vesicles) of less than 1.0 g/cm3. 300 Keys to Soil Taxonomy

fragments and, in the fraction coarser than 2.0 mm, less than and pararock fragments, of which two-thirds or more (by two-thirds (by volume) pumice and pumicelike fragments. volume) is pumice or pumicelike fragments. Cindery Medial-pumiceous or or

3. Other mineral soils that have a fine-earth component of b. Have 35 percent or more (by volume) rock less than 10 percent (including associated medium and finer fragments. pores) of the total volume. Medial-skeletal Fragmental or or c. Have less than 35 percent (by volume) rock B. Other mineral soils that have a fine-earth component of 10 fragments. percent or more (including associated medium and finer pores) Medial of the total volume and meet, in the thickest part of the control or section (if the control section is not in one of the strongly contrasting particle-size classes listed below), or in a part of the 3. Have a fine-earth fraction that has andic soil properties control section that qualifies as an element in one of the strongly and that has a water content at 1500 kPa tension of 100 contrasting particle-size classes listed below, or throughout the percent or more on undried samples; and control section, one of the following sets of substitute class a. Have a total of 35 percent or more (by volume) rock criteria: and pararock fragments, of which two-thirds or more (by 1. They: volume) is pumice or pumicelike fragments. Hydrous-pumiceous a. Have andic soil properties and have a water or content at 1500 kPa tension of less than 30 percent on undried samples and less than 12 percent on dried b. Have 35 percent or more (by volume) rock fragments. samples; or Hydrous-skeletal b. Do not have andic soil properties, have a total of 30 or percent or more of the fine-earth fraction in the 0.02 to 2.0 mm fraction, and have (by grain count) 30 percent or more c. Have less than 35 percent (by volume) rock of that fraction consisting of volcanic glass, glass fragments. aggregates, glass-coated grains, and other vitric Hydrous volcaniclastics; and or c. Have one of the following; Note: In the following classes, “clay” excludes clay-size (1) A total of 35 percent or more (by volume) rock carbonates. Carbonates of clay size are treated as silt. If the ratio and pararock fragments, of which two-thirds or more of percent water retained at 1500 kPa tension to the percentage (by volume) is pumice or pumicelike fragments. of measured clay is 0.25 or less or 0.6 or more in half or more of Ashy-pumiceous the particle-size control section or part of the particle-size or control section in strongly contrasting classes, then the percentage of clay is estimated by the following formula: Clay (2) 35 percent or more (by volume) rock fragments. % = 2.5(% water retained at 1500 kPa tension - % organic Ashy-skeletal carbon). or C. Other mineral soils that, in the thickest part of the control (3) Less than 35 percent (by volume) rock fragments. section (if part of the control section has a substitute for Ashy particle-size class and is not in one of the strongly contrasting or particle-size classes listed below), or in a part of the control section that qualifies as an element in one of the strongly 2. Have a fine-earth fraction that has andic soil properties contrasting particle-size classes listed below, or throughout the and that has a water content at 1500 kPa tension of 12 control section, meet one of the following sets of particle-size percent or more on air-dried samples or of 30 to 100 percent class criteria: on undried samples; and 1. Have 35 percent or more (by volume) rock fragments a. Have a total of 35 percent or more (by volume) rock and a fine-earth fraction with a texture of sand or loamy Family and Series Differentiae and Names 301

sand, including less than 50 percent (by weight) very fine 9. Have, in the fraction less than 75 mm in diameter, less sand. than 15 percent (by weight) particles with diameters of 0.1 to Sandy-skeletal 75 mm (fine sand or coarser, including rock fragments up to or 7.5 cm in diameter) and, in the fine-earth fraction, 18 to 35 percent (by weight) clay (Vertisols are excluded). 2. Have 35 percent or more (by volume) rock fragments Fine-silty and less than 35 percent (by weight) clay. or Loamy-skeletal or 10. Have 35 percent or more (by weight) clay (more than 30 percent in Vertisols) and are in a shallow family 3. Have 35 percent or more (by volume) rock fragments. (defined below) or in a Lithic, Arenic, or Grossarenic Clayey-skeletal subgroup, or the layer is an element in a strongly contrasting or particle-size class (listed below). Clayey 4. Have a texture of sand or loamy sand, including less than or 50 percent (by weight) very fine sand in the fine-earth fraction. 11. Have (by weighted average) less than 60 percent (by Sandy weight) clay in the fine-earth fraction. or Fine or 5. Have a texture of loamy very fine sand, very fine sand, or finer, including less than 35 percent (by weight) clay in the 12. Have 60 percent or more clay. fine-earth fraction (excluding Vertisols), and are in a shallow Very-fine family (defined below) or in a Lithic, Arenic, or Grossarenic Strongly Contrasting Particle-Size Classes subgroup, or the layer is an element in a strongly contrasting particle-size class (listed below) and the layer is the lower The purpose of strongly contrasting particle-size classes is to element or the other element is a substitute for particle-size identify changes in pore-size distribution or composition that are class. not identified in higher soil categories and that seriously affect Loamy the movement and retention of water and/or nutrients. or The following particle-size or substitute classes are considered strongly contrasting if both parts are 12.5 cm or 6. Have, in the fraction less than 75 mm in diameter, 15 more thick (including parts not in the particle-size control percent or more (by weight) particles with diameters of 0.1 to section; however, substitute class names are used only if the soil 75 mm (fine sand or coarser, including rock fragments up to materials to which they apply extend 10 cm or more into the 7.5 cm in diameter) and, in the fine-earth fraction, less than upper part of the particle-size control section) and if the 18 percent (by weight) clay. transition zone between the two parts of the particle-size control Coarse-loamy section is less than 12.5 cm thick. or Some classes, such as sandy and sandy-skeletal, have been combined in the following list. In those cases the combined 7. Have, in the fraction less than 75 mm in diameter, 15 name is used as the family class if part of the control section percent or more (by weight) particles with diameters of 0.1 to meets the criteria for either class. 75 mm (fine sand or coarser, including rock fragments up to 1. Ashy over clayey 7.5 cm in diameter) and 18 to 35 percent (by weight) clay (Vertisols are excluded). 2. Ashy over clayey-skeletal Fine-loamy 3. Ashy over loamy-skeletal or 4. Ashy over loamy 8. Have, in the fraction less than 75 mm in diameter, less 5. Ashy over medial-skeletal than 15 percent (by weight) particles with diameters of 0.1 to 75 mm (fine sand or coarser, including rock fragments up to 6. Ashy over medial (if the water content at 1500 kPa tension F 7.5 cm in diameter) and, in the fine-earth fraction, less than in dried samples of the fine-earth fraction is 10 percent or A 18 percent (by weight) clay. less for the ashy materials and 15 percent or more for the M Coarse-silty medial materials) or 302 Keys to Soil Taxonomy

7. Ashy over pumiceous or cindery 34. Hydrous over loamy 8. Ashy over sandy or sandy-skeletal 35. Hydrous over sandy or sandy-skeletal 9. Ashy-skeletal over fragmental or cindery (if the volume of 36. Loamy over ashy or ashy-pumiceous the fine-earth fraction is 35 percent or more [absolute] 37. Loamy over sandy or sandy-skeletal (if the loamy material greater in the ashy-skeletal part than in the fragmental or contains less than 50 percent fine sand or coarser sand) cindery part) 38. Loamy over pumiceous or cindery 10. Ashy-skeletal over loamy-skeletal 39. Loamy-skeletal over cindery (if the volume of the fine- 11. Cindery over loamy earth fraction is 35 percent or more [absolute] greater in the 12. Cindery over medial-skeletal loamy-skeletal part than in the cindery part) 13. Cindery over medial 40. Loamy-skeletal over clayey (if there is an absolute difference of 25 percent or more between clay percentages 14. Clayey over fragmental of the fine-earth fraction in the two parts of the control 15. Clayey over loamy (if there is an absolute difference of 25 section) percent or more between clay percentages of the fine-earth 41. Loamy-skeletal over fragmental (if the volume of the fine- fraction in the two parts of the control section) earth fraction is 35 percent or more [absolute] greater in the 16. Clayey over loamy-skeletal (if there is an absolute loamy-skeletal part than in the fragmental part) difference of 25 percent or more between clay percentages 42. Loamy-skeletal over sandy or sandy-skeletal (if the loamy of the fine-earth fraction in the two parts of the control material has less than 50 percent fine sand or coarser sand) section) 43. Medial over ashy (if the water content at 1500 kPa tension 17. Clayey over sandy or sandy-skeletal in dried samples of the fine-earth fraction is 15 percent or 18. Clayey-skeletal over sandy or sandy-skeletal more for the medial materials and 10 percent or less for the ashy materials) 19. Coarse-loamy over clayey 44. Medial over ashy-pumiceous or ashy-skeletal (if the water 20. Coarse-loamy over fragmental content at 1500 kPa tension in dried samples of the fine- 21. Coarse-loamy over sandy or sandy-skeletal (if the coarse- earth fraction is 15 percent or more for the medial materials loamy material contains less than 50 percent fine sand or and 10 percent or less for the ashy part) coarser sand) 45. Medial over clayey-skeletal 22. Coarse-silty over clayey 46. Medial over clayey 23. Coarse-silty over sandy or sandy-skeletal 47. Medial over fragmental 24. Fine-loamy over clayey (if there is an absolute difference 48. Medial over hydrous (if the water content at 1500 kPa of 25 percent or more between clay percentages of the fine- tension in undried samples of the fine-earth fraction is 75 earth fraction in the two parts of the control section) percent or less for the medial materials) 25. Fine-loamy over fragmental 49. Medial over loamy-skeletal 26. Fine-loamy over sandy or sandy-skeletal 50. Medial over loamy 27. Fine-silty over clayey (if there is an absolute difference of 51. Medial over pumiceous or cindery 25 percent or more between clay percentages of the fine- earth fraction in the two parts of the control section) 52. Medial over sandy or sandy-skeletal 28. Fine-silty over fragmental 53. Medial-skeletal over fragmental or cindery (if the volume of the fine-earth fraction is 35 percent or more [absolute] 29. Fine-silty over sandy or sandy-skeletal greater in the medial-skeletal part than the fragmental or 30. Hydrous over clayey-skeletal cindery part) 31. Hydrous over clayey 54. Medial-skeletal over loamy-skeletal 32. Hydrous over fragmental 55. Pumiceous or ashy-pumiceous over loamy 33. Hydrous over loamy-skeletal 56. Pumiceous or ashy-pumiceous over medial-skeletal Family and Series Differentiae and Names 303

57. Pumiceous or ashy-pumiceous over medial 3. Both: 58. Pumiceous or ashy-pumiceous over sandy or sandy- a. 18 to 40 percent (by weight) iron oxide as Fe O (12.6 2 3 skeletal to 28 percent Fe), by dithionite citrate, in the fine-earth fraction; and 59. Sandy over clayey b. 18 to 40 percent (by weight) gibbsite in the fine-earth 60. Sandy over loamy (if the loamy material contains less than fraction. 50 percent fine sand or coarser sand) Sesquic 61. Sandy-skeletal over loamy (if the loamy material contains or less than 50 percent fine sand or coarser sand) 4. 18 to 40 percent (by weight) iron oxide as Fe O (12.6 2 3 to 28 percent Fe), by dithionite citrate, in the fine-earth Mineralogy Classes fraction. Ferruginous The mineralogy of soils is known to be useful in making or predictions about soil behavior and responses to management. Some mineralogy classes occur or are important only in certain 5. 18 to 40 percent (by weight) gibbsite in the fine-earth taxa or particle-size classes, and others are important in all fraction. particle-size classes. The following key to mineralogy classes is Allitic designed to make those distinctions. or Control Section for Mineralogy Classes 6. More than 50 percent (by weight) kaolinite plus The control section for mineralogy classes is the same as that halloysite, dickite, nacrite, and other 1:1 or nonexpanding 2:1 defined for the particle-size classes and their substitutes. layer minerals and gibbsite and less than 10 percent (by Key to Mineralogy Classes weight) smectite in the fraction less than 0.002 mm in size; and more kaolinite than halloysite. This key, like other keys in this taxonomy, is designed in such Kaolinitic a way that the reader makes the correct classification by going or through the key systematically, starting at the beginning and eliminating one by one any classes that include criteria that do 7. More than 50 percent (by weight) halloysite plus not fit the soil in question. The soil belongs to the first class for kaolinite and allophane and less than 10 percent (by weight) which it meets all of the required criteria. The user should first smectite in the fraction less than 0.002 mm in size. check the criteria in section A and, if the soil in question does Halloysitic not meet the criteria listed there, proceed on to sections B, C, D, or and E, until the soil meets the criteria listed. All criteria are based on a weighted average. 8. All other properties in this category. For soils with strongly contrasting particle-size classes, the Mixed mineralogy for both named particle-size classes or substitutes or are given, unless they are the same. Examples are an ashy over clayey, mixed (if both the ashy and clayey parts are mixed), B. Other soil layers or horizons, in the mineralogy control superactive, mesic Typic Vitraquand and a clayey over sandy or section, that have a substitute class that replaces the particle-size sandy-skeletal, smectitic over mixed, thermic Vertic Haplustept. class, other than fragmental, and that: A. Oxisols and “kandi” and “kanhap” great groups of Alfisols 1. Have a sum of 8 times the Si (percent by weight and Ultisols that in the mineralogy control section have: extracted by ammonium oxalate from the fine-earth fraction) 1. More than 40 percent (by weight) iron oxide as Fe O plus 2 times the Fe (percent by weight extracted by 2 3 (more than 28 percent Fe), by dithionite citrate, in the fine- ammonium oxalate from the fine-earth fraction) of 5 or more, earth fraction. and 8 times the Si is more than 2 times the Fe. Ferritic Amorphic or or F A 2. More than 40 percent (by weight) gibbsite in the fine- 2. Other soils that have a sum of 8 times the Si M earth fraction. (percent by weight extracted by ammonium oxalate from the Gibbsitic fine-earth fraction) plus 2 times the Fe (percent by weight or 304 Keys to Soil Taxonomy

extracted by ammonium oxalate from the fine-earth fraction) 6. Any particle-size class, except for fragmental, and a total of 5 or more. percent (by weight) iron oxide as Fe O (percent Fe by 2 3 Ferrihydritic dithionate citrate times 1.43) plus the percent (by weight) or gibbsite of more than 10 in the fine-earth fraction. Parasesquic 3. Other soils that have 30 percent or more (by grain count) or volcanic glass, glass-coated grains, glassy materials, and glassy aggregates in the 0.02 to 2.0 mm fraction. 7. Any particle-size class, except for fragmental, and more Glassy than 20 percent (by weight) glauconitic pellets in the fine- or earth fraction. Glauconitic 4. All other soils that have a substitute class. 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 C. Other mineral soil layers or horizons, in the mineralogy subgroups of Histosols and Histels, in a clayey, clayey-skeletal, control section, in all other mineral soil orders and in Terric fine or very-fine particle-size class, that in the fraction less than subgroups of Histosols and Histels that have: 0.002 mm in size: 1. Any particle-size class and more than 40 percent (by 1. Have more than one-half (by weight) halloysite plus weight) carbonates (expressed as CaCO ) plus gypsum, with kaolinite and allophane, less than 10 percent (by weight) 3 gypsum constituting more than 35 percent of the total weight smectite, and more halloysite than any other single mineral. of carbonates plus gypsum, either in the fine-earth fraction or Halloysitic in the fraction less than 20 mm in size, whichever has a or higher percentage of carbonates plus gypsum. Gypsic 2. Have more than one-half (by weight) kaolinite plus or halloysite, dickite, and nacrite, and other 1:1 or nonexpanding 2:1 layer minerals and gibbsite and less than 2. Any particle-size class and more than 40 percent (by 10 percent (by weight) smectite. weight) carbonates (expressed as CaCO ) plus gypsum, either Kaolinitic 3 in the fine-earth fraction or in the fraction less than 20 mm in or size, whichever has a higher percentage of carbonates plus gypsum. 3. Have more smectite (montmorillonite, beidellite, and Carbonatic nontronite), by weight, than any other single kind of clay or mineral. Smectitic 3. Any particle-size class, except for fragmental, and more or than 40 percent (by weight) iron oxide as Fe O (extractable 2 3 by dithionite citrate) in the fine-earth fraction. 4. Have more than one-half (by weight) illite (hydrous Ferritic mica) and commonly more than 4 percent K O. 2 or Illitic or 4. Any particle-size class, except for fragmental, and more than 40 percent (by weight) gibbsite and boehmite in the fine- 5. Have more vermiculite than any other single kind of clay earth fraction. mineral. Gibbsitic Vermiculitic or or

5. Any particle-size class, except for fragmental, and more 6. In more than one-half of the thickness, meet all of the than 40 percent (by weight) magnesium-silicate minerals, following: such as the serpentine minerals (antigorite, chrysotile, and a. Have no free carbonates; and lizardite) plus talc, olivines, Mg-rich pyroxenes, and Mg-rich amphiboles, in the fine-earth fraction. b. The pH of a suspension of 1 g soil in 50 ml 1 M NaF Magnesic is more than 8.4 after 2 minutes; and or Family and Series Differentiae and Names 305

c. The ratio of 1500 kPa water to measured clay is 0.6 or Oxisols and “kandi” and “kanhap” great groups and subgroups more. of Alfisols and Ultisols because assigning such classes to them Isotic would be redundant. Cation-exchange activity classes are not or assigned to the sandy, sandy-skeletal, or fragmental particle-size class because the low clay content causes cation-exchange 7. All other soils in this category. activity classes to be less useful and less reliable. Mixed The cation-exchange capacity (CEC) is determined by or NH4OAc at pH 7 on the fine-earth fraction. The CEC of the organic matter, sand, silt, and clay is included in the determination. The criteria for the classes use ratios of CEC to E. All other mineral soil layers or horizons, in the mineralogy the percent, by weight, of silicate clay, both by weighted average control section, that have: in the control section. In the following classes “clay” excludes 1. More than 40 percent (by weight) (70 percent by grain clay-size carbonates. If the ratio of percent water retained at count) mica and stable mica pseudomorphs in the 0.02 to 1500 kPa tension to the percentage of measured clay is 0.25 or 0.25 mm fraction. less or 0.6 or more in half or more of the particle-size control Micaceous section (or part in contrasting families), then the percentage of or clay is estimated by the following formula: Clay % = 2.5(% water retained at 1500 kPa tension - % organic carbon). 2. More than 25 percent (by weight) (45 percent by grain count) mica and stable mica pseudomorphs in the 0.02 to Control Section for Cation-Exchange Activity Classes 0.25 mm fraction. The control section for cation-exchange activity classes is the Paramicaceous same as that used to determine the particle-size and mineralogy or classes. For soils with strongly contrasting particle-size classes, where both named parts of the control section use a cation- 3. In more than one-half of the thickness, all of the exchange activity class, the class associated with the particle- following: size class that has the most clay is named. For example, in a a. No free carbonates; and pedon with a classification of loamy over clayey, mixed, active, calcareous, thermic Typic Udorthent, the cation-exchange b. The pH of a suspension of 1 g soil in 50 ml 1 M NaF activity class “active” is associated with the clayey part of the is more than 8.4 after stirring for 2 minutes; and control section. c. A ratio of 1500 kPa water to measured clay of 0.6 or Key to Cation-Exchange Activity Classes more. Isotic A. Soils that are not Histosols, Histels, or Oxisols, that are not or in “kandi” or “kanhap” great groups or subgroups of Alfisols and Ultisols, that are in either a mixed or siliceous mineralogy 4. More than 90 percent (by weight or grain count) silica class, that are not in a fragmental, sandy, or sandy-skeletal minerals (quartz, chalcedony, or opal) and other resistant particle-size class or any substitute for a particle-size class, and

minerals in the 0.02 to 2.0 mm fraction. that have a ratio of cation-exchange capacity (by NH4OAc at pH Siliceous 7) to clay (percent by weight) of: or 1. 0.60 or more. Superactive 5. All other properties. Mixed 2. 0.40 to 0.60. Active Cation-Exchange Activity Classes 3. 0.24 to 0.40. The cation-exchange activity classes help in making Semiactive interpretations of mineral assemblages and of the nutrient- holding capacity of soils in mixed and siliceous mineralogy 4. Less than 0.24. F classes of clayey, clayey-skeletal, coarse-loamy, coarse-silty, Subactive A fine, fine-loamy, fine-silty, loamy, loamy-skeletal, and very-fine or M particle-size classes. Cation-exchange activity classes are not assigned to Histosols and Histels, and they are not assigned to B. All other soils: No cation-exchange activity classes used. 306 Keys to Soil Taxonomy

Calcareous and Reaction Classes of Mineral Soils effervesce (in cold dilute HCl) in all parts of the control section. The presence or absence of carbonates, soil reaction, and the Calcareous presence of high concentrations of aluminum in mineral soils are treated together because they are so intimately related. There are C. Other listed soils with a pH of less than 5.0 in 0.01 M CaCl2 four classes—calcareous, acid, nonacid, and allic. These are (1:2) (about pH 5.5 in H2O, 1:1) throughout the control section. defined later, in the key to calcareous and reaction classes. The Acid classes are not used in all taxa, nor is more than one used in the same taxa. D. Other listed soils with a pH of 5.0 or more in 0.01 M CaCl2 (1:2) in some or all layers in the control section. Use of the Calcareous and Reaction Classes Nonacid The calcareous, acid, and nonacid classes are used in the names of the families of Entisols, Aquands, and Aquepts, except It should be noted that a soil containing dolomite is they are not used in any of the following: calcareous and that effervescence of dolomite, when treated with cold dilute HCl, is slow. 1. Duraquands and Placaquands The calcareous, acid, nonacid, and allic classes are listed in 2. Sulfaquepts, Fragiaquepts, and Petraquepts the family name, when appropriate, following the mineralogy and cation-exchange activity classes. 3. Sandy, sandy-skeletal, cindery, pumiceous, or fragmental families 4. Families with carbonatic or gypsic mineralogy Soil Temperature Classes The calcareous class, in addition to those listed above, is Soil temperature classes, as named and defined here, are used used in the names of the families of Aquolls, except it is not as part of the family name in both mineral and organic soils. used with any of the following: Temperature class names are used as part of the family name unless the criteria for a higher taxon carry the same limitation. 1. Calciaquolls, Natraquolls, and Argiaquolls Thus, frigid is implied in all cryic suborders, great groups, and 2. Cryaquolls and Duraquolls that have an argillic horizon subgroups and would be redundant if used in the names of families within these classes. 3. Families with carbonatic or gypsic mineralogy The Celsius (centigrade) scale is the standard. It is assumed The allic class is used only in families of Oxisols. that the temperature is that of a soil that is not being irrigated. Control Section for Calcareous and Reaction Classes Control Section for Soil Temperature The control section for the calcareous class is one of the The control section for soil temperature either is at a depth of following: 50 cm from the soil surface or is at the upper boundary of a 1. Soils with a root-limiting layer that is 25 cm or less below root-limiting layer, whichever is shallower. The soil temperature the mineral soil surface: A 2.5-cm-thick layer directly above the classes, defined in terms of the mean annual soil temperature root-limiting layer. and the difference between mean summer and mean winter temperatures, are determined by the following key. 2. Soils with a root-limiting layer that is 26 to 50 cm below the mineral soil surface: The layer between a depth of 25 cm Key to Soil Temperature Classes below the mineral soil surface and the root-limiting layer. A. Gelisols and Gelic suborders and great groups that have a 3. All other listed soils: Between a depth of 25 and 50 cm mean annual soil temperature as follows: below the mineral soil surface. 1. -10 oC or lower. The control section for the acid, nonacid, and allic classes is Hypergelic the same as that for particle-size classes. or Key to Calcareous and Reaction Classes 2. -4 oC to -10 oC. A. Oxisols that have a layer, 30 cm or more thick within the Pergelic control section, that contains more than 2 cmol(+) of KCl- or extractable Al per kg soil in the fine-earth fraction. Allic 3. +1 oC to -4 oC. Subgelic B. Other listed soils that, in the fine-earth fraction, or Family and Series Differentiae and Names 307

B. Other soils that have a difference in soil temperature of Key to Soil Depth Classes 6 oC or more between mean summer (June, July, and August in A. Oxisols that are less than 100 cm deep (from the mineral the Northern Hemisphere) and mean winter (December, January, soil surface) to a root-limiting layer and are not in a Lithic and February in the Northern Hemisphere) and a mean annual subgroup. soil temperature of: Shallow 1. Lower than 8 oC (47 oF). or Frigid or B. Soils in all other mineral soil orders that are less than 50 cm deep (from the mineral soil surface) to a root-limiting layer and 2. 8 oC (47 oF) to 15 oC (59 oF). are not in a Lithic subgroup. Mesic Shallow or or

3. 15 oC (59 oF) to 22 oC (72 oF). C. All other mineral soils: No soil depth class used. Thermic or Rupture-Resistance Classes

4. 22 oC (72 oF) or higher. In this taxonomy, some partially cemented soil Hyperthermic materials, such as durinodes, serve as differentiae in or categories above the family, while others, such as partially cemented spodic materials (ortstein), do not. No single C. All other soils that have a mean annual soil temperature as family, however, should include soils both with and without follows: partially cemented horizons. In Spodosols, a partially cemented spodic horizon is used as a family differentia. 1. Lower than 8 oC (47 oF). The following rupture-resistance class is defined for families Isofrigid of Spodosols: or A. Spodosols that have an ortstein horizon. 2. 8 oC (47 oF) to 15 oC (59 oF). Ortstein Isomesic or or B. All other soils: No rupture-resistance class used. 3. 15 oC (59 oF) to 22 oC (72 oF). Isothermic Classes of Coatings (on ) or Despite the emphasis given to particle-size classes in this 4. 22 oC (72 oF) or higher. taxonomy, variability remains in the sandy particle-size class, Isohyperthermic which includes sands and loamy sands. Some sands are very clean, i.e., almost completely free of silt and clay, while others Soil Depth Classes are mixed with appreciable amounts of finer grains. Clay is more efficient at coating sand than is silt. A weighted average Soil depth classes are used in all families that have a root- silt (by weight) plus 2 times the weighted average clay (by limiting layer at a specified depth from the mineral soil surface, weight) of more than 5 makes a reasonable division of the sands except for those families in Lithic subgroups and those with a at the family level. Two classes of Quartzipsamments are fragipan. The root-limiting layers included in soil depth classes defined in terms of their content of silt plus 2 times their content are duripans; petrocalcic, petrogypsic, and placic horizons; of clay. continuous ortstein (90 percent or more); and densic, lithic, Control Section for Classes of Coatings paralithic, and petroferric contacts. Soil depth classes for Histosols and Histels are given later in this chapter. One soil The control section for classes of coatings is the same as that depth class name, “shallow,” is used to characterize certain for particle-size classes or their substitutes and for mineralogy F mineral soil families that have one of the depths indicated in the classes. A following key. M 308 Keys to Soil Taxonomy

Key to Classes of Coatings not previously mentioned are defined and the classes in which they are used are enumerated. A. Quartzipsamments that have a sum of the weighted average The order in which family classes, if appropriate for a silt (by weight) plus 2 times the weighted average clay of more particular family, are placed in the technical family names of than 5. Histosols and Histels is as follows: Coated or Particle-size classes Mineralogy classes, including the nature of limnic deposits in B. Other Quartzipsamments. Histosols Uncoated Reaction classes Soil temperature classes Soil depth classes (used only in Histosols) Classes of Permanent Cracks

Some Hydraquents consolidate or shrink after drainage and Particle-Size Classes become Fluvaquents or Humaquepts. In the process they can Particle-size classes are used only for the family names of form polyhedrons roughly 12 to 50 cm in diameter, depending Terric subgroups of Histosols and Histels. The classes are on their n value and texture. These polyhedrons are separated by determined from the properties of the mineral soil materials in cracks that range in width from 2 mm to more than 1 cm. The the control section through use of the key to particle-size polyhedrons may shrink and swell with changes in the moisture classes. The classes are more generalized than those for soils in content of the soils, but the cracks are permanent and can persist other orders. for several hundreds of years, even if the soils are cultivated. The cracks permit rapid movement of water through the soils, Control Section for Particle-Size Classes either vertically or laterally. Such soils may have the same The particle-size control section is the upper 30 cm of the texture, mineralogy, and other family properties as soils that do mineral layer or of that part of the mineral layer that is within not form cracks or that have cracks that open and close with the the control section for Histosols and Histels (given in chapter 3), seasons. Soils with permanent cracks are very rare in the United whichever is thicker. States. Key to Particle-Size Classes of Histosols and Histels Control Section for Classes of Permanent Cracks A. Terric subgroups of Histosols and Histels that The control section for classes of permanent cracks is from have (by weighted average) in the particle-size control the base of any plow layer or 25 cm from the soil surface, section: whichever is deeper, to 100 cm below the soil surface. 1. A fine-earth component of less than 10 percent Key to Classes of Permanent Cracks (including associated medium and finer pores) of the total A. Fluvaquents or Humaquepts that have, throughout a layer volume. 50 cm or more thick, continuous, permanent, lateral and vertical Fragmental cracks 2 mm or more wide, spaced at average lateral intervals of or less than 50 cm. Cracked 2. A texture (of the fine earth) of sand or loamy sand, or including less than 50 percent (by weight) very fine sand in the fine-earth fraction. B. All other Fluvaquents and Humaquepts: No class of Sandy or sandy-skeletal permanent cracks used. or

3. Less than 35 percent clay in the fine-earth fraction and a Family Differentiae for Histosols and content of rock fragments of 35 percent or more of the total Histels volume. Loamy-skeletal Most of the differentiae that are used to distinguish families or of Histosols and Histels have already been defined, either because they are used as differentiae in mineral soils as well as 4. A content of rock fragments of 35 percent or more of the Histosols and Histels or because their definitions are used for total volume. the classification of some Histosols and Histels in categories Clayey-skeletal higher than the family. In the following descriptions, differentiae or Family and Series Differentiae and Names 309

5. A clay content of 35 percent or more in the fine-earth Control Section for the Ferrihumic Mineralogy Class and fraction. Mineralogy Classes Applied to Limnic Subgroups Clayey The control section for the ferrihumic mineralogy class and or the classes applied to Limnic subgroups is the same as the control section for Histosols. 6. All other Terric subgroups of Histosols and Histels. Loamy Mineralogy Classes Applied Only to Terric Subgroups or For Histosols and Histels in Terric subgroups, use the same key to mineralogy classes as that used for mineral soils unless a B. All other Histosols and Histels: No particle-size class used. Histosol also has ferrihumic mineralogy. Control Section for Mineralogy Classes Applied Only to Mineralogy Classes Terric Subgroups There are three different kinds of mineralogy classes For Terric subgroups of Histosols and Histels, use the same recognized for families in certain great groups and subgroups of control section for mineralogy classes as that used for the Histosols. The first kind is the ferrihumic soil material defined particle-size classes. below. The second is three types of limnic materials— Key to Mineralogy Classes coprogenous earth, diatomaceous earth, and marl, defined in chapter 3. The third is mineral layers of Terric subgroups. The A. Histosols (except for Folists), Sphagnofibrists, and key to mineralogy classes for these mineral layers is the same as Sphagnic subgroups of other great groups that have ferrihumic that for mineral soils. Terric subgroups of Histels also have the soil material within the control section for Histosols. same mineralogy classes as those for mineral soils. Ferrihumic or Ferrihumic Mineralogy Class 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 1. Coprogenous earth. into large aggregates, in a mineral or organic layer that has all of Coprogenous the following characteristics: or 1. Saturation with water for more than 6 months per year (or artificial drainage); 2. Diatomaceous earth. Diatomaceous 2. 2 percent or more (by weight) iron concretions having or lateral dimensions ranging from less than 5 to more than 100 mm and containing 10 percent or more (by weight) free iron 3. Marl. oxide (7 percent or more Fe) and 1 percent or more (by weight) Marly organic matter; and or 3. A dark reddish or brownish color that changes little on drying. C. Histels and other Histosols in Terric subgroups: Use the key to mineralogy classes for mineral soils. The ferrihumic mineralogy class is used for families of Fibrists, Hemists, and Saprists, but it is not used for or Sphagnofibrists and Sphagnic subgroups of other great groups. If the ferrihumic class is used in the family name of a Histosol, D. All other Histels and Histosols: No mineralogy class used. no other mineralogy classes are used in that family because the presence of iron is considered to be by far the most important mineralogical characteristic. Reaction Classes Mineralogy Classes Applied Only to Limnic Subgroups Reaction classes are used in all families of Histosols and Histels. The two classes recognized are defined in the following F Limnic materials (defined in chapter 3) with a thickness of 5 key: A cm or more are mineralogy class criteria if the soil does not also M have ferrihumic mineralogy. The following family classes are A. Histosols and Histels that have a pH value, on undried used: coprogenous, diatomaceous, and marly. samples, of 4.5 or more (in 0.01 M CaCl2) in one or more 310 Keys to Soil Taxonomy

layers of organic soil materials within the control section for defined than the limits for the family. The properties used, Histosols. however, must be reliably observable or be inferable from other Euic soil properties or from the setting or vegetation. or The differentiae used must be within the series control section. Differences in soil or regolith that are outside the series B. All other Histosols and Histels. control section and that have not been recognized as series Dysic differentiae but are relevant to potential uses of certain soils are considered as a basis for phase distinctions. Soil Temperature Classes Control Section for the Differentiation of Series The soil temperature classes of Histosols are determined through use of the same key and definitions as those used for The control section for the soil series is similar to that for the mineral soils. Histels have the same temperature classes as other family, but it differs in a few important respects. The particle- Gelisols. size and mineralogy control sections for families end at the upper boundary of a fragipan, duripan, or petrocalcic horizon because these horizons have few roots. In contrast to the control Soil Depth Classes section for the series, the thickness of such horizons is not taken into account in the control sections for the family. The series Soil depth classes refer to the depth to a root-limiting layer, a control section includes materials starting at the soil surface and fragmental particle-size class, or a cindery or pumiceous also the first 25 cm below a densic or paralithic contact if its substitute class. The root-limiting layers included in soil depth upper boundary is less than 125 cm below the mineral soil classes of Histosols are duripans; petrocalcic, petrogypsic, and surface. Properties of horizons and layers below the particle-size placic horizons; continuous ortstein; and densic, lithic, control section, a depth between 100 and 150 cm (or to 200 cm paralithic, and petroferric contacts. The following key is used if in a diagnostic horizon) from the mineral soil surface, also are for families in all subgroups of Histosols. The shallow class is considered. not used in the suborder Folists. Key to Soil Depth Classes Key to the Control Section for the Differentiation of Series A. Histosols that are less than 18 cm deep to a root-limiting The part of a soil to be considered in differentiating series layer, to a fragmental particle-size class, or to a cindery or within a family is as follows: pumiceous substitute class. A. Mineral soils that have permafrost within 150 cm of the Micro soil surface: From the soil surface to the shallowest of the or following: B. Other Histosols, excluding Folists, that have a root-limiting 1. A lithic or petroferric contact; or layer, a fragmental particle-size class, or a cindery or pumiceous 2. A depth of 100 cm if the depth to permafrost is less than substitute class at a depth between 18 and 50 cm from the soil 75 cm; or surface. Shallow 3. 25 cm below the upper boundary of permafrost if or that boundary is 75 cm or more below the soil surface; 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 used contact or 150 cm below the soil surface, whichever is 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; or expression of horizons and properties diagnostic for the higher 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 of diagnostic horizon is less than 150 cm from the soil surface; the properties used as differentiae must be more narrowly or Family and Series Differentiae and Names 311

4. The lower boundary of the deepest diagnostic horizon or 2. A depth of 25 cm below a densic or paralithic contact; or a depth of 200 cm, whichever is shallower, if the lower 3. A depth of 100 cm if the depth to permafrost is less than boundary of the deepest diagnostic horizon is 150 cm or 75 cm; or more below the soil surface; or 4. 25 cm below the upper boundary of permafrost if that C. Organic soils (Histosols and Histels): From the soil surface boundary is between a depth of 75 and 125 cm below the soil to the shallowest of the following: surface; or 1. A lithic or petroferric contact; or 5. The base of the bottom tier

F A M

313

CHAPTER 18 Designations for Horizons and Layers

This chapter describes soil layers and genetic soil horizons. aquatic organisms, such as algae and diatoms, or (2) derived The genetic horizons are not the equivalent of the diagnostic from underwater and floating aquatic plants and subsequently horizons of Soil Taxonomy. While designations of genetic modified by aquatic animals. horizons express a qualitative judgment about the kinds of L horizons or layers include coprogenous earth, (sedimentary changes that are believed to have taken place in a soil, peat), diatomaceous earth, and marl. They occur only in diagnostic horizons are quantitatively defined features that are Histosols. They have only the following subordinate used to differentiate between taxa. A diagnostic horizon may distinctions: co, di, or ma. They do not have the subordinate encompass several genetic horizons, and the changes implied by distinctions of the other master horizons and layers. genetic horizon designations may not be large enough to justify A horizons: Mineral horizons that have formed at the recognition of different diagnostic horizons. surface or below an O horizon. They exhibit obliteration of all or much of the original rock structure1 and show one or both of Master Horizons and Layers the following: (1) an accumulation of humified organic matter closely mixed with the mineral fraction and not dominated by The capital letters O, L, A, E, B, C, R, and W represent the properties characteristic of E or B horizons (defined below) or master horizons and layers of soils. These letters are the base (2) properties resulting from cultivation, pasturing, or similar symbols to which other characters are added to complete the kinds of disturbance. designations. Most horizons and layers are given a single If a surface horizon has properties of both A and E horizons capital-letter symbol; some require two. but the feature emphasized is an accumulation of humified O horizons or layers: Layers dominated by organic organic matter, it is designated as an A horizon. In some areas, material. Some are saturated with water for long periods or such as areas of warm, arid climates, the undisturbed surface were once saturated but are now artificially drained; others horizon is less dark than the adjacent underlying horizon and have never been saturated. contains only small amounts of organic matter. It has a Some O layers consist of undecomposed or partially morphology distinct from the C layer, although the mineral decomposed litter (such as leaves, needles, twigs, moss, and fraction is unaltered or only slightly altered by weathering. Such lichens) that has been deposited on the surface. They may be on a horizon is designated as an A horizon because it is at the top of either mineral or organic soils. Other O layers consist of surface. Recent alluvial or eolian deposits that retain fine organic material that was deposited under saturated conditions stratification are not considered to be A horizons unless and has decomposed to varying stages. The mineral fraction of cultivated. such material constitutes only a small percentage of the volume E horizons: Mineral horizons in which the main feature is of the material and generally much less than half of its weight. the loss of silicate clay, iron, aluminum, or some combination of Some soils consist entirely of materials designated as O these, leaving a concentration of sand and silt particles. These horizons or layers. horizons exhibit obliteration of all or much of the original rock An O layer may be on the surface of a mineral soil, or it may structure. be at any depth below the surface if it is buried. A horizon An E horizon is most commonly differentiated from an formed by the illuviation of organic material into a mineral underlying B horizon in the same sequum by a color of higher subsoil is not an O horizon, although some horizons that have value or lower chroma, or both, by coarser texture, or by a formed in this manner contain considerable amounts of organic combination of these properties. In some soils the color of the E matter. horizon is that of the sand and silt particles, but in many soils L horizons or layers: Limnic horizons or layers include coatings of iron oxides or other compounds mask the color of both organic and mineral limnic materials that were either (1) the primary particles. An E horizon is most commonly deposited in water by precipitation or through the actions of differentiated from an overlying A horizon by its lighter color. It generally contains less organic matter than the A horizon. An E horizon is commonly near the surface, below an O or A horizon 1 Rock structure includes fine stratification in unconsolidated soil materials as well as H and above a B horizon, but eluvial horizons that are within or pseudomorphs of weathered minerals that retain their positions relative to each other and to O unweathered minerals in saprolite. between parts of the B horizon or extend to depths greater than R 314 Keys to Soil Taxonomy

those of normal observation can be assigned the letter E if they layer formed through pedogenic processes, however, it is are pedogenic. considered a B horizon. B horizons: Horizons that have formed below an A, E, or O R layers: Strongly cemented to indurated bedrock. horizon. They are dominated by the obliteration of all or much Granite, basalt, quartzite, limestone, and sandstone are of the original rock structure and show one or more of the examples of bedrock designated by the letter R. The excavation following: difficulty commonly exceeds high. The R layer is sufficiently coherent when moist to make hand-digging with a spade 1. Illuvial concentration of silicate clay, iron, aluminum, impractical, although the layer may be chipped or scraped. humus, carbonates, gypsum, or silica, alone or in Some R layers can be ripped with heavy power equipment. The combination; bedrock may have cracks, but these are generally too few and 2. Evidence of the removal or addition of carbonates; too small to allow root penetration. The cracks may be coated or filled with clay or other material. 3. Residual concentration of oxides; W layers: Water 4. Coatings of sesquioxides that make the horizon This symbol indicates water layers within or beneath the soil. conspicuously lower in color value, higher in chroma, or The water layer is designated as Wf if it is permanently frozen redder in hue, without apparent illuviation of iron; and as W if it is not permanently frozen. The W (or Wf) designation is not used for shallow water, ice, or snow above the 5. Alteration that forms silicate clay or liberates oxides, or soil surface. both, and that forms a granular, blocky, or prismatic structure if volume changes accompany changes in moisture content; 6. Brittleness; or Transitional and Combination Horizons 7. Strong gleying. Horizons dominated by properties of one master horizon but All of the different kinds of B horizons are, or were having subordinate properties of another.—Two capital-letter originally, subsurface horizons. Included as B horizons, where symbols are used for such transitional horizons, e.g., AB, EB, contiguous to other genetic horizons, are layers of illuvial BE, or BC. The first of these symbols indicates that the concentration of carbonates, gypsum, or silica that are the result properties of the horizon so designated dominate the transitional of pedogenic processes (and may or may not be cemented) and horizon. An AB horizon, for example, has characteristics of both brittle layers that show other evidence of alteration, such as an overlying A horizon and an underlying B horizon, but it is prismatic structure or illuvial accumulation of clay. more like the A horizon than the B horizon. Examples of layers that are not B horizons are layers in In some cases a horizon can be designated as transitional which clay films either coat rock fragments or cover finely even if one of the master horizons to which it presumably forms stratified unconsolidated sediments, regardless of whether the a transition is not present. A BE horizon may be recognized in a films were formed in place or by illuviation; layers into which truncated soil if its properties are similar to those of a BE carbonates have been illuviated but that are not contiguous to an horizon in a soil from which the overlying E horizon has not overlying genetic horizon; and layers with gleying but no other been removed by erosion. A BC horizon may be recognized pedogenic changes. even if no underlying C horizon is present; it is transitional to C horizons or layers: Horizons or layers, excluding strongly assumed parent materials. cemented and harder bedrock, that are little affected by Horizons with two distinct parts that have recognizable pedogenic processes and lack the properties of O, A, E, or B properties of the two kinds of master horizons indicated by the horizons. Most are mineral layers. The material of C layers may capital letters.—The two capital letters designating such be either like or unlike the material from which the solum has combination horizons are separated by a virgule (/), e.g., E/B, B/ presumably formed. The C horizon may have been modified, E, or B/C. Most of the individual parts of one horizon even if there is no evidence of pedogenesis. component are surrounded by the other. The designation may be Included as C layers are sediment, saprolite, bedrock, and used even when horizons similar to one or both of the other geologic materials that are moderately cemented or less components are not present, provided that the separate cemented. The excavation difficulty in these materials components can be recognized in the combination horizon. The commonly is low or moderate. Some soils form in material that first symbol is that of the horizon with the greater volume. is already highly weathered, and if such material does not meet Single sets of horizon designators do not cover all situations; the requirements for A, E, or B horizons, it is designated by the therefore, some improvising is needed. For example, Argic letter C. Changes that are not considered pedogenic are those Udipsamments have lamellae that are separated from each other not related to the overlying horizons. Some layers that have by eluvial layers. Because it is generally not practical to accumulations of silica, carbonates, gypsum, or more soluble describe each lamella and eluvial layer as a separate horizon, the salts are included in C horizons, even if cemented. If a cemented horizons can be combined but the components described Designations for Horizons and Layers 315

separately. One horizon then has several lamellae and eluvial of these materials is 17 to 40 percent (by volume) after layers and can be designated an “E and Bt” horizon. The rubbing. 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 Suffix Symbols permanent ice. The symbol is not used for seasonally 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 used in many of the definitions of such horizons to indicate that This symbol indicates a horizon or layer that is these horizons must contain more of the material in question continually colder than 0 oC and does not contain enough than is presumed to have been present in the parent material. ice to be cemented by ice. This suffix is not used for The suffix symbols and their meanings are as follows: horizons or layers that have a temperature warmer than 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 decomposed organic materials, which have a fiber content This symbol indicates either that iron has been reduced of less than 17 percent (by volume) after rubbing. and removed during soil formation or that saturation with stagnant water has preserved it in a reduced state. Most of b Buried genetic horizon the affected layers have chroma of 2 or less, and many This symbol is used in mineral soils to indicate have redox concentrations. The low chroma can represent identifiable buried horizons with major genetic features either the color of reduced iron or the color of uncoated that were developed before burial. Genetic horizons may sand and silt particles from which iron has been removed. or may not have formed in the overlying material, which The symbol g is not used for materials of low chroma that may be either like or unlike the assumed parent material of have no history of wetness, such as some shales or E the buried soil. This symbol is not used in organic soils, horizons. If g is used with B, pedogenic change in nor is it used to separate an organic layer from a mineral addition to gleying is implied. If no other pedogenic layer. change besides gleying has taken place, the horizon is designated Cg. c Concretions or nodules h Illuvial accumulation of organic matter This symbol indicates a significant accumulation of concretions or nodules. Cementation is required. The This symbol is used with B to indicate the cementing agent commonly is iron, aluminum, manganese, accumulation of illuvial, amorphous, dispersible or titanium. It cannot be silica, dolomite, calcite, or more complexes of organic matter and sesquioxides if the soluble salts. sesquioxide component is dominated by aluminum but is present only in very small quantities. The organo- co Coprogenous earth sesquioxide material coats sand and silt particles. In some This symbol, used only with L, indicates a limnic layer horizons these coatings have coalesced, filled pores, and of coprogenous earth (or sedimentary peat). cemented the horizon. The symbol h is also used in combination with s as “Bhs” if the amount of the d Physical root restriction sesquioxide component is significant but the color value This symbol indicates noncemented, root-restricting and chroma, moist, of the horizon are 3 or less. layers in naturally occurring or human-made sediments or i Slightly decomposed organic material materials. Examples are dense basal till, plowpans, and other mechanically compacted zones. This symbol is used with O to indicate the least decomposed of the organic materials. The fiber content of di Diatomaceous earth these materials is 40 percent or more (by volume) after This symbol, used only with L, indicates a limnic layer rubbing. of diatomaceous earth. j Accumulation of jarosite e Organic material of intermediate decomposition Jarosite is a potassium or iron sulfate mineral that is This symbol is used with O to indicate organic commonly an alteration product of pyrite that has been materials of intermediate decomposition. The fiber content exposed to an oxidizing environment. Jarosite has hue of H O R 316 Keys to Soil Taxonomy

2.5Y or yellower and normally has chroma of 6 or more, (moderately cemented or less cemented). Examples are although chromas as low as 3 or 4 have been reported. weathered igneous rock and partly consolidated sandstone, siltstone, or shale. The excavation difficulty is jj Evidence of cryoturbation low to high. Evidence of cryoturbation includes irregular and s Illuvial accumulation of sesquioxides and organic matter broken horizon boundaries, sorted rock fragments, and organic soil materials occurring as bodies and broken This symbol is used with B to indicate an accumulation layers within and/or between mineral soil layers. The of illuvial, amorphous, dispersible complexes of organic organic bodies and layers are most commonly at the matter and sesquioxides if both the organic-matter and contact between the active layer and the permafrost. sesquioxide components are significant and if either the color value or chroma, moist, of the horizon is 4 or more. k Accumulation of carbonates The symbol is also used in combination with h as “Bhs” if This symbol indicates an accumulation of alkaline- both the organic-matter and sesquioxide components are earth carbonates, commonly calcium carbonate. significant and if the color value and chroma, moist, are 3 or less. m Cementation or induration ss Presence of slickensides This symbol indicates continuous or nearly continuous cementation. It is used only for horizons that are more This symbol indicates the presence of slickensides. than 90 percent cemented, although they may be fractured. Slickensides result directly from the swelling of clay The cemented layer is physically root-restrictive. The minerals and shear failure, commonly at angles of 20 to 60 predominant cementing agent (or the two dominant degrees above horizontal. They are indicators that other cementing agents) may be indicated by adding defined vertic characteristics, such as wedge-shaped peds and letter suffixes, singly or in pairs. The horizon suffix km surface cracks, may be present. indicates cementation by carbonates; qm, cementation by t Accumulation of silicate clay silica; sm, cementation by iron; ym, cementation by gypsum; kqm, cementation by lime and silica; and zm, This symbol indicates an accumulation of silicate clay cementation by salts more soluble than gypsum. that either has formed within a horizon and subsequently has been translocated within the horizon or has been ma Marl moved into the horizon by illuviation, or both. At least This symbol, used only with L, indicates a limnic layer some part of the horizon should show evidence of clay of marl. accumulation either as coatings on surfaces of peds or in pores, as lamellae, or as bridges between mineral grains. n Accumulation of sodium v Plinthite This symbol indicates an accumulation of exchangeable sodium. This symbol indicates the presence of iron-rich, humus- poor, reddish material that is firm or very firm when moist o Residual accumulation of sesquioxides and hardens irreversibly when exposed to the atmosphere This symbol indicates a residual accumulation of and to repeated wetting and drying. sesquioxides. w Development of color or structure p Tillage or other disturbance This symbol is used with B to indicate the development This symbol indicates a disturbance of the surface layer of color or structure, or both, with little or no apparent by mechanical means, pasturing, or similar uses. A illuvial accumulation of material. It should not be used to disturbed organic horizon is designated Op. A disturbed indicate a transitional horizon. mineral horizon is designated Ap even though it is clearly x Fragipan character a former E, B, or C horizon. This symbol indicates a genetically developed layer q Accumulation of silica that has a combination of firmness and brittleness and This symbol indicates an accumulation of secondary commonly a higher bulk density than the adjacent layers. silica. Some part of the layer is physically root-restrictive. r Weathered or soft bedrock y Accumulation of gypsum This symbol is used with C to indicate cemented layers This symbol indicates an accumulation of gypsum. Designations for Horizons and Layers 317

z Accumulation of salts more soluble than gypsum again with 1 wherever in the profile any letter of the horizon symbol changes, e.g., Bt1-Bt2-Btk1-Btk2 (not Bt1-Bt2-Btk3- This symbol indicates an accumulation of salts that are Btk4). The numbering of vertical subdivisions within a more soluble than gypsum. horizon is not interrupted at a discontinuity (indicated by a numerical prefix) if the same letter combination is used in Conventions for Using Letter Suffixes both materials, e.g., Bs1-Bs2-2Bs3-2Bs4 (not Bs1-Bs2-2Bs1- 2Bs2). Many master horizons and layers that are symbolized by a During sampling for laboratory analyses, thick soil horizons single capital letter have one or more lowercase letter suffixes. are sometimes subdivided even though differences in The following rules apply: morphology are not evident in the field. These subdivisions are 1. Letter suffixes should directly follow the capital letter. identified by Arabic numerals that follow the respective horizon designations. For example, four layers of a Bt horizon sampled 2. More than three suffixes are rarely used. by 10-cm increments are designated Bt1, Bt2, Bt3, and Bt4. If 3. If more than one suffix is needed, the following letters, if the horizon has already been subdivided because of differences used, are written first: a, d, e, h, i, r, s, t, and w. Except in the in morphological features, the set of Arabic numerals that Bhs or Crt2 horizon designations, none of these letters are identifies the additional sampling subdivisions follows the first used in combination in a single horizon. numeral. For example, three layers of a Bt2 horizon sampled by 10-cm increments are designated Bt21, Bt22, and Bt23. The 4. If more than one suffix is needed and the horizon is not descriptions for each of these sampling subdivisions can be the buried, the following symbols, if used, are written last: c, f, g, same, and a statement indicating that the horizon has been m, v, and x. Some examples: Btc, Bkm, and Bsv. subdivided only for sampling purposes can be added. 5. If a horizon is buried, the suffix b is written last. It is used only for buried mineral soils. Discontinuities A B horizon that has a significant accumulation of clay and Arabic numerals are used as prefixes to horizon designations also shows evidence of a development of color or structure, or (preceding the letters A, E, B, C, and R) to indicate both, is designated Bt (t has precedence over w, s, and h). A B discontinuities in mineral soils. These prefixes are distinct from horizon that is gleyed or has accumulations of carbonates, the Arabic numerals that are used as suffixes denoting vertical sodium, silica, gypsum, or salts more soluble than gypsum or subdivisions. residual accumulations of sesquioxides carries the appropriate A discontinuity that can be identified by a number prefix is a symbol: g, k, n, q, y, z, or o. If illuvial clay also is present, t significant change in particle-size distribution or mineralogy that precedes the other symbol: Bto. indicates a difference in the material from which the horizons Unless needed for explanatory purposes, the suffixes h, s, and have formed and/or a significant difference in age, unless that w are not used with g, k, n, q, y, z, or o. difference in age is indicated by the suffix b. Symbols that identify discontinuities are used only when they can contribute Vertical Subdivision substantially to an understanding of the relationships among horizons. The stratification common to soils that formed in Commonly, a horizon or layer identified by a single letter or alluvium is not designated as a discontinuity, unless particle-size a combination of letters has to be subdivided. For this purpose, distribution differs markedly from layer to layer (i.e., particle- Arabic numerals are added to the letters of the horizon size classes are strongly contrasting), even though genetic designation. These numerals follow all the letters. Within a C horizons may have formed in the contrasting layers. horizon, for example, successive layers may be designated C1, Where a soil has formed entirely in one kind of material, the C2, C3, etc. If the lower part is gleyed and the upper part is whole profile is understood to be material 1 and the number not gleyed, the layers may be designated C1-C2-Cg1-Cg2 or prefix is omitted from the symbol. Similarly, the uppermost C-Cg1-Cg2-R. material in a profile consisting of two or more contrasting These conventions apply whatever the purpose of the materials is understood to be material 1, but the number is subdivision. In many soils a horizon that could be identified omitted. Numbering starts with the second layer of contrasting by a single set of letters is subdivided because of the need to material, which is designated 2. Underlying contrasting layers recognize differences in morphological features, such as are numbered consecutively. Even when the material of a layer structure, color, or texture. These divisions are numbered below material 2 is similar to material 1, it is designated 3 in the consecutively with Arabic numerals, but the numbering starts sequence; the numbers indicate a change in materials, not types of material. Where two or more consecutive horizons have 2 Indicates weathered bedrock or saprolite in which clay films are present. formed in the same kind of material, the same prefix number is H O R 318

applied to all the designations of horizons in that material: Ap- layers are organic or by the master symbol if the different layers E-Bt1-2Bt2-2Bt3-2BC. The suffix numbers designating are mineral. subdivisions of the Bt horizon continue in consecutive order across the discontinuity. Use of the Prime Symbol If an R layer is present below a soil that has formed in residuum and if the material of the R layer is judged to be like If two or more horizons of the same kind are separated by the material from which the soil has developed, the Arabic- one or more horizons of a different kind in a pedon, identical number prefix is not used. The prefix is used, however, if it is letter and number symbols can be used for those horizons that thought that the R layer would produce material unlike that in have the same characteristics. For example, the sequence A-E- the solum, e.g., A-Bt-C-2R or A-Bt-2R. If part of the solum has Bt-E-Btx-C identifies a soil that has two E horizons. To formed in residuum, the symbol R is given the appropriate emphasize this characteristic, the prime symbol (´) is added prefix: Ap-Bt1-2Bt2-2Bt3-2C1-2C2-2R. after the master-horizon symbol of the lower of the two A buried horizon (designated by the letter b) presents special horizons that have identical designations, e.g., A-E-Bt-E´-Btx-C. problems. It is obviously not in the same deposit as the The prime symbol, when appropriate, is applied to the capital- overlying horizons. Some buried horizons, however, have letter horizon designation, and any lowercase letter symbols formed in material that is lithologically like the overlying follow it: B´t. The prime symbol is used only when the letter deposit. A prefix is not used to distinguish material of such a designations of the two layers in question are completely buried horizon. If the material in which a horizon of a buried identical. In the rare cases when three layers have identical letter soil has formed is lithologically unlike the overlying material, symbols, double prime symbols can be used for the lowest of however, the discontinuity is indicated by a number prefix and these layers: E´´. the symbol for the buried horizon also is used, e.g., Ap-Bt1-Bt2- The same principle applies in designating layers of organic BC-C-2ABb-2Btb1-2Btb2-2C. soils. The prime symbol is used only to distinguish two or more Discontinuities between different kinds of layers in organic horizons that have identical symbols, e.g., Oi-C-O´i-C´ (when soils are not identified. In most cases such differences are the soil has two identical Oi layers) or Oi-C-Oe-C´ (when the identified either by letter-suffix designations if the different two C layers are of the same kind). 319

Appendix

Laboratory Methods for Soil Taxonomy Each method is listed by code on the data sheet at the beginning of the chapters describing soil orders. On the data sheets The standard laboratory methods upon which the operational presented with each order, the method code is shown for each definitions of this edition of Soil Taxonomy are based are determination made. These data sheets should be consulted for described in the Soil Survey Laboratory Methods Manual reference to the Soil Survey Laboratory Methods Manual. This (USDA, in press). Copies of standard laboratory data sheets are manual specifies method codes for pedon sampling, sample included with the typifying pedons in the chapters on soil orders handling, site selection, sample collection, and sample in this edition of Soil Taxonomy. For specific information about preparation. an analytical procedure, these data sheets should be checked and The units of measure reported on the data sheets are not SI reference should be made to the Soil Survey Laboratory units. Following are SI conversions: Methods Manual. Much of the information included in this 1 meq/100 g = 1 cmol(+)/kg appendix is derived from “Soil Survey Laboratory Methods for 1 mmho/cm = 1 dS/m Characterizing Physical and Chemical Properties and 15 bar = 1500 kPa Mineralology of Soils” (Kimble, Knox, and Holzhey, 1993). 1 /3 bar = 33 kPa Also, the information is summarized the Soil Survey Laboratory 1 /10 bar = 10 kPa Information Manual (USDA, NRCS, 1995). Pedon characterization data, or any soil survey data, are most In this taxonomy the terms (1) particle-size analysis (size useful when the operations for collecting the data are well separates), (2) texture, and (3) particle-size classes are all used. understood. The mental pictures and conceptual definitions that Particle-size analysis is needed to determine texture and aid in visualizing properties and processes often differ from the particle-size classes. Texture differs from particle-size class in information supplied by an analysis. Also, results differ by that texture includes only the fine-earth fraction (less than 2 method, even though two methods may carry the same name or mm), while particle size includes both the fraction less than 2 the same concept. There is uncertainty in comparing one bit of mm in size and the fraction equal to or more than 2 mm. data with another without knowledge of how both bits were Atterberg limits are determined on the fraction less than 0.4 gathered. Operational definitions, definitions tied to a specific mm in size. Plasticity index is the difference in water content method, are needed. This soil taxonomy has many class limits between liquid limit and plastic limit. It is the range of water (at all levels) that are based on chemical or physical properties content over which a soil paste can be deformed without determined in the laboratory. One can question a given limit, but breaking, but it does not include flow as a liquid under that is not the purpose of this appendix. This appendix is written operationally defined conditions. Liquid limit is the minimum to show what procedures are used for given class limits. By water content at which the paste begins to flow as a liquid. using specific class limits, everyone will come to the same Samples that do not deform without breaking at any water classification if they follow the same procedures. content are reported as NP, nonplastic. Operational definitions This taxonomy is based almost entirely on criteria that are are in the Annual Book of ASTM Standards (ASTM, 1998). defined operationally. One example is the definition of particle- Bulk density is obtained typically by equilibration of Saran- size classes. There is no one definition of clay that works well coated natural fabric clods at designated pressure differentials. for all soils. Hence, an operation for testing the validity of a clay Bulk densities are determined at two or more water contents. measurement and a default operation for those situations where For coarse textured and moderately coarse textured soils, they the clay measurement is not valid are defined. The default are determined when the sample is at 10 kPa suction and when method is based on a water content at 1500 kPa and on content ovendry. For soils of medium and finer texture, the bulk of organic carbon. densities are determined when the sample is at 33 kPa suction and when ovendry. Data Elements Used in Classifying Soils Bulk density determined at 33 kPa suction is used to convert other analytical results to a volumetric basis (for example, kg of Detailed explanations of laboratory methods are given in the organic carbon per m3). Soil Survey Laboratory Methods Manual (USDA, in press). Coefficient of linear extensibility (COLE) is a derived value. 320 Keys to Soil Taxonomy

It is computed from the difference in bulk density between a barium chloride-triethanolamine solution buffered at pH 8.2. It moist clod and an ovendry clod. It is based on the shrinkage of a includes all the acidity generated by replacement of the natural soil clod between a water content of 33 kPa (10 kPa for hydrogen and aluminum from permanent and pH-dependent sandier soils) and ovendry. exchange sites. It is reported as meq/100 g soil. Extractable Linear extensibility (LE) of a soil layer is the product of the acidity data are reported on some data sheets as exchangeable thickness, in centimeters, multiplied by the COLE of the layer in acidity and on others as exchangeable H+. question. The LE of a soil is the sum of these products for all Extractable aluminum is exchangeable aluminum extracted soil horizons. COLE multiplied by 100 is called linear by 1N KCl. It is a major constituent only in strongly acid soils extensibility percent (LEP). (pH of less than 5.0). Aluminum will precipitate if the pH rises Water retention difference (WRD) is computed from water above 4.5 to 5.0 during analysis. The extractant KCl usually retentions at 33 kPa (10 kPa for sandier soils) and 1500 kPa affects the soil pH 1 unit or less. Extractable aluminum is suction. It is converted to cm of water per cm of soil through use measured at the NSSL by atomic absorption. Many laboratories of the bulk density. The 33 or 10 kPa water is determined by measure the aluminum by titration with a base to the desorption of the natural fabric clods, and the 1500 kPa water is phenopthalein end point. Titration measures exchangeable determined by desorption of crushed soil. acidity as well as extractable aluminum. Soils with a pH below Organic carbon data in the National Soil Survey Laboratory 4.0 or 4.5 are likely to have values determined by atomic (NSSL) data base have been determined mostly by wet digestion absorption similar to values determined by titration because very (Walkley, 1935). Because of environmental concerns about little hydrogen is typically on the exchange complex. If there is a waste products, however, that procedure is no longer in use. The large percentage of organic matter, however, some hydrogen only procedure that is currently used to determine organic may be present. For some soils it is important to know which carbon is a dry combustion procedure that determines the procedure was used. Extractable aluminum is reported as meq/ percent of total carbon. The content of organic carbon is 100 g soil. determined by subtracting the amount of carbon contributed by Aluminum saturation is the amount of KCl-extractable Al carbonates from total carbon data. The content of organic divided by extractable bases (extracted by ammonium acetate) carbon determined by this computation is very close to the plus the KCl-extractable Al. It is expressed as percent. A general content determined by the wet digestion procedure. rule of thumb is that if there is more than 50 percent Al Nitrogen in the NSSL data base is reported as a percentage of saturation, Al problems in the soil are likely. The problems may the total dry weight. A soil sample is combusted at high not be related to Al toxicity but to a deficiency of calcium and/ temperature with oxygen to release NOx, and the N2 is or magnesium. measured by thermal conductivity detection. Cation-exchange capacity (CEC) by ammonium acetate (at Iron and aluminum extracted by citrate dithionite are pH 7), by sum of cations (at pH 8.2), and by bases plus removed in a single extraction. They are measured by atomic aluminum is given on the data sheets in the chapters on soil absorption and reported as a percentage of the total dry weight. orders. The CEC depends on the method of analysis as well as The iron is primarily from ferric oxides (hematite, magnetite) the nature of the exchange complex. CEC by sum of cations at and iron oxyhydroxides (goethite). Aluminum substituted into pH 8.2 is calculated by adding the sum of bases and the these minerals is extracted simultaneously. The dithionite extractable acidity. CEC by ammonium acetate is measured at reduces the ferric iron, and the citrate stabilizes the iron by pH 7. CEC by bases plus aluminum, or effective cation- chelation. Iron and aluminum bound in organic matter are exchange capacity (ECEC), is derived by adding the sum of extracted if the citrate is a stronger chelator than the organic bases and KCl-extractable Al. Aluminum extracted by 1N KCl is molecules. Manganese extracted by this procedure also is negligible if the extractant pH rises toward 5.5. ECEC then is recorded. The iron extracted is commonly related to the clay equal to extractable bases. CEC and ECEC are reported on the distribution within a pedon. data sheets as meq/100 g soil. Extractable bases (calcium, magnesium, sodium, and The reported CEC may differ from the CEC of the soil at its potassium) are extracted with ammonium acetate buffered at pH natural pH. The standard methods allow the comparison of one 7. They are equilibrated, filtered in an auto-extractor, and soil with another even though the pH of the extractant differs measured by atomic absorption. They are reported as meq/100 g from the pH of the natural soil. Cation-exchange capacity by soil. The bases are extracted from the cation-exchange complex ammonium acetate and by sum of cations applies to all soils. by displacement with ammonium ions. The term “extractable CEC at pH 8.2 is not reported if the soil contains free carbonates bases” is used instead of “exchangeable bases” because soluble because bases are extracted from the carbonates. The effective salts and some bases from carbonates can be included in the CEC (ECEC) is reported only for acid soils. ECEC is not extract. reported for soils having soluble salts, although it can be Sum of bases is the sum of the calcium, magnesium, sodium, calculated by subtracting the soluble components from the and potassium described in the previous paragraph. extractable components. ECEC also may be defined as bases Extractable acidity is the acidity released from the soil by a plus aluminum plus hydrogen. That is the more common Appendix 321

definition for agronomic interpretations. This taxonomy water and precipitation in acetone. The amount of gypsum is specifies bases plus aluminum. reported as a percentage of the total dry weight of the fraction Generally, the ECEC is less than the CEC at pH 7, which in less than 2 mm in size and the fraction less than 20 mm in size. turn is less than the CEC at pH 8.2. If the soil is dominated by Drying soils to oven-dryness, the standard base for reporting the positively charged colloids (e.g., iron oxides), however, the data, removes part of the water of hydration from the gypsum. trend is reversed. Most soils have negatively charged colloids, Many measured values, particularly water retention values, must which cause the CEC to increase with increasing pH. This be recalculated to compensate for the weight of the water of difference in CEC is commonly called the pH-dependent or hydration lost during drying. variable charge. The CEC at the soil pH can be estimated by pH is measured in water and in salts. The pH measured in plotting the CEC of the soil vs. the pH of the extractant on a water is determined in distilled water typically mixed 1:1 with graph and reading the CEC at the soil pH. dry soil. The pH measured in potassium chloride is determined CEC measurements at pH levels other than those described in in 1N KCl solution mixed 1:1 with soil. The pH measured in the paragraphs above and CEC derived by use of other cations calcium chloride is determined in 0.01M CaCl2 solution mixed will yield somewhat different results. It is important to know the 2:1 with soil. procedure, pH, and cation used before evaluating CEC data or The pH is measured by a pH meter in a soil-water or soil-salt comparing data from different sources. solution. The extent of the dilution is shown in the heading on Base saturation is reported on the data sheets as percent of the data sheets. A ratio of 1:1 means one part dry soil and one the CEC. It is reported as CEC by sum of cations at pH 8.2 and part water, by weight. by ammonium acetate at pH 7. Base saturation by ammonium Measurement of pH in a dilute salt solution is common acetate is equal to the sum of the bases extracted by ammonium because it tends to mask seasonal variations in pH. Readings in acetate, divided by the CEC (by ammonium acetate), and 0.01M CaCl2 tend to be uniform regardless of the time of year. multiplied by 100. If extractable calcium is not reported on the Readings in 1N KCl also tend to be uniform. The former are data sheet because of free carbonates or salts in the sample, then more popular in regions with less acid soils. The latter are more the base saturation is assumed to be 100 percent. popular in regions with more acid soils. If KCl is used to extract Base saturation percentage by sum of cations is equal to the exchangeable aluminum, the pH reading (in KCl) shows the pH sum of bases extracted by ammonium acetate, divided by the at which the aluminum was extracted. CEC (by sum of cations), and multiplied by 100. This value is The pH may also be measured in 1N sodium fluoride. This not reported if either extractable calcium or extractable acidity measurement is usually used to identify soils that are dominated is omitted. by short-range-order minerals, such as Andisols and Spodosols. Differences between the two methods of determining base In soils that have a significant component of poorly ordered saturation reflect the amount of the pH-dependent CEC. Class minerals, such as the soils in the isotic mineralogy class, the pH definitions in this taxonomy specify which method is used. in NaF will be greater than 8.5. Soils with free carbonates also The sum of exchangeable cations is considered equal to the have high pH values in NaF. Therefore, care must be taken in sum of bases extracted by ammonium acetate unless carbonates, interpreting these data. gypsum, or other salts are present. When these salts are present, Water-soluble cations and anions are determined in water the sum of the bases extracted by ammonium acetate typically extracted from a saturated paste. The cations include calcium, exceeds 100 percent of the CEC. Therefore, a base saturation of magnesium, sodium, and potassium, and the anions include 100 percent is assumed. The amount of calcium from carbonates carbonate, bicarbonate, sulfate, chloride, nitrate, fluoride, is usually much larger than the amount of magnesium from the phosphate, silicate, and borate. The cations and anions can be carbonates. Extractable calcium is not shown on the data sheet if reported as cmol(+)/l. more than a trace (more than 0.4 percent) of carbonates Exchangeable sodium percentage (ESP) is reported as a (reported as calcium carbonate) is present or if calculated base percentage of the CEC by ammonium acetate at pH 7. Water- saturation exceeds 110 percent, based on CEC by ammonium soluble sodium is converted to meq/100 g soil. This value is acetate at pH 7. subtracted from extractable sodium, divided by the CEC (by Calcium carbonate equivalent is the amount of carbonates in ammonium acetate), and multiplied by 100. An ESP of more the soil as measured by treating the sample with HCl. The than 15 percent is used in this taxonomy as a criterion for the evolved carbon dioxide is measured manometrically. The natric horizon. amount of carbonate is then calculated as a calcium carbonate Sodium adsorption ratio (SAR) was developed as a measure equivalent regardless of the form of carbonates (dolomite, of irrigation water quality. Water-soluble sodium is divided by sodium carbonate, magnesium carbonate, etc.) in the sample. water-soluble calcium and magnesium. The formula is SAR = Calcium carbonate equivalent is reported as a percentage of the Na/[(Ca+Mg)/2]0.5. An SAR of 13 or more is used as an alternate total dry weight of the sample. It can be reported on material to the ESP criterion for the natric horizon. that is less than 2 mm or less than 20 mm in size. Electrical conductivity (EC) is the conductivity of the water Calcium sulfate as gypsum is determined by extraction in extracted from saturated paste. The EC is used to determine the 322 Keys to Soil Taxonomy

total content of salts. It is reported as mmhos/cm, which is equal acetate. See the paragraphs about extractable acidity and to dS/m. exchangeable bases. Total salts is calculated from the electrical conductivity of the Color of sodium-pyrophosphate extract is used as a criterion saturation extract. It is reported as a weight percentage of the in the separation of different types of organic materials. A total water-soluble salts in the soil. saturated solution is made by adding 1 g of sodium Phosphate retention (P ret.) refers to the percent phosphorus pyrophosphate to 4 ml of distilled water, and a moist organic retained by soil after equilibration with 1,000 mg/kg phosphorus matter sample is added to the solution. The sample is mixed and solution for 24 hours. This procedure is used in the classification allowed to stand overnight, chromatographic paper is dipped in of andic soil materials. It identifies soils in which phosphorus the solution, and the color of the paper is ascertained through fixation may be a problem affecting agronomic uses. use of a Munsell color chart. Ammonium-oxalate-extractable aluminum, iron, and silicon Water-soluble sulfate is used in the definition of the sulfuric are determined by a single extraction made in the dark with 0.2 horizon. The sulfate is determined in the saturation extract and molar ammonium oxalate at a pH of 3.5. The amount of is reported as one of the anions. aluminum, iron, and silicon is measured by atomic absorption Mineralogy of the clay, silt, and sand fractions is required and reported as a percentage of the total dry weight. These in some taxa. The different techniques employed are X-ray values are used as criteria in identifying soils in the Andisol and diffraction analysis, thermal analysis, and petrographic Spodosol orders and in the andic and spodic subgroups in other analysis. orders. The procedure extracts iron, aluminum, and silicon from X-ray diffraction analysis (XRD) is reported in a five-class organic matter and from amorphous mineral material. It is used system based mostly on relative peak intensities. It is useful in in conjunction with dithionite-citrate and pyrophosphate determining relative amounts of clay minerals. It is used to extractions to identify the sources of iron and aluminum in the differentiate between the smectitic and vermiculitic mineralogy soil. Pyrophosphate extracts iron and aluminum from organic classes. matter. Dithionite citrate extracts iron from iron oxides and Thermal analysis is reported as weight percent of the clay oxyhydroxides as well as from organic matter. fraction. It helps to determine kaolinitic, gibbsitic, and other Sodium-pyrophosphate-extractable iron and aluminum are mineralogy classes. determined by a single extraction and measured by atomic Petrographic analysis is reported as percent of grains absorption. Results are reported as a percentage of the total dry counted. Minerals are identified by use of a petrographic weight. This procedure has been used widely to extract iron and microscope. At least 300 grains of a coarse silt, very fine sand, aluminum from organic matter. It successfully removes much of or fine sand separate are identified and counted. Weatherable the organo-metal accumulations in spodic horizons but extracts minerals, resistant minerals, and volcanic glass are identified by little of the inorganically bound iron and aluminum. this procedure. A complete list of these is in the Soil Survey Potassium-hydroxide-extractable aluminum is determined by Laboratory Methods Manual (USDA, in press). atomic absorption spectrophotometry. This procedure has been used in the past but is not used in this taxonomy. The data can be Other Information Useful in Classifying Soils used in the field to estimate the amount of ammonium-oxalate- extractable aluminum. Volumetric amounts of organic carbon are used in some Melanic index is used in the identification of the melanic taxonomic criteria. The following calculation is used: (Datum epipedon. The index is related to the ratio of the humic and [percent] times bulk density [at 33 or 10 kPa] times thickness fulvic acids in the organic fraction of the soil (Honna, [cm]) divided by 10. This calculation is normally used for Yamamoto, and Matsui, 1988). About 0.50 gram of air-dried soil organic carbon, but it can be used for some other measurements. material that is less than 2 mm in size is shaken with 25 ml of Each horizon is calculated separately, and the product of the 0.5 percent NaOH solution in a 50-ml centrifuge tube for 1 hour calculations can be summed to any desired depth, commonly at room temperature. One drop of a flocculating agent is added, 100 cm. and the mixture is centrifuged at 4,000 rpm for 10 minutes. The Ratios that can be developed from the data are useful in melanic index is the ratio of the absorbance at 450 nm over that making internal checks of the data, in making management- at 520 nm. related interpretations, and in answering taxonomic questions. Citric-acid-extractable phosphorus (acid-soluble phosphate) Some of the ratios are used as criteria in determining argillic, is used to separate the mollic epipedon (less than 1,500 mg/kg kandic, or oxic horizons. P O ) from the anthropic epipedon (equal to or more than 1,500 The ratio of 1500 kPa water to clay is used to indicate the 2 5 mg/kg). relevancy of the particle-size determination. If the ratio is 0.6 or Exchangeable manganese and calcium plus exchangeable more and the soil does not have andic soil properties, acidity (at pH 8.2) is used as a criterion for the natric horizon. incomplete dispersion of the clay is assumed and clay is The exchangeable acidity is measured at pH 8.2, and the estimated by the following formula: Clay % = 2.5(% water manganese and calcium are extracted at pH 7.0 with ammonium retained at 1500 kPa tension - % organic carbon). For a typical Appendix 323

soil with well dispersed clays, the ratio is 0.4. Some soil-related extractable Al imply a soil with a high pH-dependent charge. factors that can cause deviation from the 0.4 value are: (1) low- Along with bulk density data, they help to distinguish soils that activity clays (kaolinites, chlorites, and some micas), which tend have andic and spodic materials or soils that have materials with to have a ratio of 0.35 or below; (2) iron oxides and clay-size an isotic mineralogy class from soils with minerals that are more carbonates, which tend to decrease the ratio; (3) organic matter, crystalline. which increases the ratio because it increases the water content at 1500 kPa; (4) andic and spodic materials and materials with Literature Cited an isotic mineralogy class, which increase the ratio because they do not disperse well; (5) large amounts of gypsum; and (6) clay American Society for Testing and Materials. 1998. Annual minerals within grains of sand and silt. These clay minerals hold Book of ASTM Standards. Vol. 4.08, D 4318-95a. water at 1500 kPa and thus increase the ratio. They are most Honna,T., S. Yamamoto, and K. Matsui. 1988. A Simple common in shale and in pseudomorphs of primary minerals in Procedure to Determine Melanic Index That Is Useful for saprolite. Differentiating Melanic from Fulvic Andisols. Pedol. 32: 69-78. The ratio of CEC by ammonium acetate at pH 7 to clay can Kimble, J.M, E.G. Knox, and C.S. Holzhey. 1993. Soil be used to estimate clay mineralogy and clay dispersion. If the Survey Laboratory Methods for Characterizing Physical and ratio is multiplied by 100, the product is cmol(+)/kg clay. The Chemical Properties and Mineralology of Soils. In Applications following ratios are typical for the following classes of clay of Agriculture Analysis in Environmental Studies, ASTM Spec. mineralogy: less than 0.2, kaolinitic; 0.2-0.3, kaolinitic or Pub. 1162, K.B. Hoddinott and T.A. O’Shay, eds. mixed; 0.3-0.5, mixed or illitic; 0.5-0.7, mixed or smectitic; and United States Department of Agriculture, Natural Resources more than 0.7, smectitic. These ratios are most valid when some Conservation Service. 1995. Soil Survey Laboratory detailed mineralogy data are available. If the ratio of 1500 kPa Information Manual. National Soil Survey Center, Soil Survey water to clay is 0.25 or less or 0.6 or more, the ratio of CEC by Laboratory, Soil Survey Investigations Report 45. ammonium acetate to clay is not valid. Ratios of 1500 kPa water United States Department of Agriculture, Natural Resources to clay of 0.6 or more are typical of poorly dispersed clays, Conservation Service, National Soil Survey Center. (In press.) andic and spodic materials, and materials with an isotic Soil Survey Laboratory Methods Manual. Soil Survey mineralogy class, and ratios of less than 0.3 are common in Investigations Report 42, Version 4.0. some soils that contain large amounts of gypsum. Walkley, A. 1935. An Examination of Methods for A ratio of CEC at pH 8.2 to 1500 kPa water of more than 1.5 Determining Organic Carbon and Nitrogen in Soils. J. Agr. Sci. and more exchange acidity than the sum of bases plus KCl- 25: 598-609. 324

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 textural classes 325

Index

A Argicryids ...... 118 Argicryolls ...... 199 A horizons. See Horizons and layers. Argids ...... 103 Abrupt textural change ...... 21 Argidurids ...... 121 Acraquox ...... 237 Argigypsids ...... 124 Acroperox ...... 238 Argillic horizon ...... 17 Acrotorrox ...... 242 Argiorthels ...... 152 Acrudox ...... 243 Argiudolls ...... 204 Acrustox...... 247 Argiustolls...... 211 Agric horizon ...... 16 Argixerolls ...... 227 Alaquods ...... 253 Aridic moisture regime. See Soil moisture regimes. Albaqualfs ...... 41 Aridisols ...... 103 Albaquults ...... 264 Albic horizon ...... 17 B Albic materials ...... 22 Albolls ...... 194 B horizons. See Horizons and layers. Alfisols...... 41 Bottom tier ...... 29 Alorthods ...... 258 Buried soils ...... 10 Andic soil properties...... 22 Andisols ...... 83 C Anhydrous conditions ...... 22 Anhyorthels...... 151 C horizons or layers. See Horizons and layers. Anhyturbels...... 155 Calcareous and reaction classes for mineral soils ...... 306 Aniso class ...... 298 Calciaquerts ...... 286 Anthracambids ...... 114 Calciaquolls ...... 195 Anthrepts ...... 165 Calciargids ...... 103 Anthropic epipedon ...... 13 Calcic horizon ...... 17 Aqualfs...... 41 Calcicryids ...... 119 Aquands ...... 83 Calcicryolls ...... 200 Aquents ...... 129 Calcids ...... 111 Aquepts ...... 165 Calcigypsids...... 125 Aquerts...... 285 Calcitorrerts ...... 289 Aquic conditions ...... 29 Calciudolls ...... 206 Aquic moisture regime. See Soil moisture regimes. Calciustepts ...... 180 Aquicambids ...... 114 Calciusterts ...... 292 Aquisalids ...... 128 Calciustolls ...... 215 Aquiturbels ...... 155 Calcixerepts ...... 186 Aquods ...... 253 Calcixererts ...... 295 Aquolls...... 195 Calcixerolls ...... 229 Aquorthels ...... 151 Cambic horizon...... 18 Aquox ...... 237 Cambids ...... 114 Aquults...... 263 Cation-exchange activity classes for mineral soils ...... 305 Arents...... 133 Coatings (classes) on sands ...... 307 Argialbolls ...... 194 Coefficient of linear extensibility (COLE) ...... 22 Argiaquolls ...... 195 Control section of Histosols and Histels ...... 29 326 Keys to Soil Taxonomy

Coprogenous earth. See Organic soil material. Durustalfs...... 66 Cryalfs ...... 50 Durustands ...... 98 Cryands ...... 87 Durustepts ...... 181 Cryaqualfs ...... 43 Durustolls...... 216 Cryaquands ...... 84 Dystraquerts ...... 286 Cryaquents ...... 130 Dystrocryepts ...... 172 Cryaquepts ...... 166 Dystrogelepts ...... 173 Cryaquods ...... 254 Dystroxerepts ...... 187 Cryaquolls ...... 196 Dystrudepts ...... 175 Cryepts ...... 171 Dystruderts...... 292 Cryerts ...... 289 Dystrustepts ...... 181 Cryic temperature regime. See Soil temperature Dystrusterts ...... 291 regimes. Cryids...... 118 E Cryods ...... 255 Cryofibrists ...... 159 E horizons. See Horizons and layers. Cryofluvents ...... 134 Endoaqualfs ...... 43 Cryofolists ...... 160 Endoaquands...... 84 Cryohemists ...... 161 Endoaquents...... 130 Cryolls ...... 199 Endoaquepts ...... 167 Cryopsamments ...... 145 Endoaquerts ...... 287 Cryorthents ...... 139 Endoaquods ...... 254 Cryosaprists ...... 162 Endoaquolls ...... 196 Cryoturbation ...... 31 Endoaquults ...... 264 Cryrendolls ...... 203 Entisols ...... 129 Epiaqualfs ...... 45 D Epiaquands ...... 85 Epiaquents ...... 131 Densic contact...... 31 Epiaquepts ...... 168 Densic materials...... 31 Epiaquerts ...... 288 Diagnostic subsurface horizons ...... 16 Epiaquods ...... 255 Diagnostic surface horizons ...... 13 Epiaquolls ...... 197 Diatomaceous earth. See Organic soil material. Epiaquults ...... 264 Discontinuities identified by horizon designators...... 317 Epipedon ...... 13 Duraqualfs ...... 43 Eutraquox...... 237 Duraquands ...... 84 Eutrocryepts ...... 172 Duraquerts ...... 286 Eutrogelepts ...... 173 Duraquods...... 254 Eutroperox ...... 239 Duraquolls ...... 196 Eutrotorrox ...... 242 Duricryands ...... 87 Eutrudepts ...... 177 Duricryods ...... 255 Eutrudox ...... 244 Duricryolls ...... 200 Eutrustox ...... 248 Durids ...... 121 Durihumods ...... 258 F Durinodes ...... 22 Duripan ...... 18 Family differentiae for Histosols and Histels ...... 308 Duritorrands ...... 90 Family differentiae for mineral soils ...... 297 Durixeralfs ...... 77 Ferrudalfs ...... 55 Durixerepts ...... 187 Fibers. See Organic soil material. Durixererts ...... 295 Fibric soil materials. See Organic soil material. Durixerolls ...... 229 Fibristels ...... 149 Durorthods ...... 259 Fibrists ...... 159 Durudands ...... 91 Fluvaquents ...... 131 Durudepts ...... 174 Fluvents ...... 134 Index 327

Folistels ...... 150 Haplocambids ...... 115 Folistic epipedon ...... 13 Haplocryalfs...... 51 Folists ...... 160 Haplocryands ...... 88 Fragiaqualfs ...... 47 Haplocryerts ...... 289 Fragiaquepts...... 169 Haplocryids ...... 120 Fragiaquods ...... 255 Haplocryods ...... 256 Fragiaquults ...... 265 Haplocryolls ...... 201 Fragic soil properties ...... 23 Haplodurids ...... 122 Fragihumods ...... 258 Haplofibrists ...... 160 Fragiorthods ...... 259 Haplogelods ...... 257 Fragipan ...... 18 Haplogelolls ...... 202 Fragiudalfs ...... 55 Haplogypsids ...... 125 Fragiudepts ...... 179 Haplohemists ...... 161 Fragiudults ...... 270 Haplohumods ...... 258 Fragixeralfs ...... 78 Haplohumults ...... 267 Fragixerepts ...... 189 Haploperox ...... 240 Fraglossudalfs ...... 55 Haplorthels ...... 152 Frigid temperature regime. See Soil temperature regimes. Haplorthods ...... 260 Fulvicryands ...... 87 Haplosalids ...... 128 Fulvudands...... 92 Haplosaprists ...... 162 Haplotorrands ...... 91 G Haplotorrerts ...... 290 Haplotorrox...... 243 Gelands ...... 90 Haploturbels ...... 155 Gelaquands ...... 85 Haploxeralfs ...... 78 Gelaquents ...... 132 Haploxerands ...... 101 Gelaquepts ...... 169 Haploxerepts ...... 189 Gelepts ...... 173 Haploxererts ...... 296 Gelic materials ...... 31 Haploxerolls ...... 231 Gelifluvents...... 134 Haploxerults...... 282 Gelisols ...... 149 Hapludalfs ...... 58 Gelods ...... 257 Hapludands ...... 93 Gelolls...... 202 Hapluderts...... 291 Gelorthents...... 140 Hapludolls...... 207 Glacic layer ...... 31 Hapludox ...... 245 Glacistels ...... 150 Hapludults ...... 271 Glossaqualfs...... 48 Haplustalfs ...... 66 Glossic horizon ...... 19 Haplustands ...... 98 Glossocryalfs ...... 50 Haplustepts ...... 182 Glossudalfs ...... 56 Haplusterts ...... 293 Gypsiargids ...... 105 Haplustolls ...... 217 Gypsic horizon ...... 19 Haplustox ...... 249 Gypsicryids ...... 119 Haplustults ...... 278 Gypsids ...... 124 Haprendolls...... 203 Gypsitorrerts ...... 290 Hemic soil materials. See Organic soil material. Gypsiusterts ...... 293 Hemistels ...... 150 Hemists ...... 161 H Histels ...... 149 Histic epipedon ...... 14 Halaquepts ...... 170 Historthels ...... 152 Haplanthrepts ...... 165 Histosols ...... 159 Haplaquox...... 238 Histoturbels ...... 155 Haplargids ...... 106 Horizons and layers ...... 313 Haplocalcids ...... 111 A horizons ...... 313 328 Keys to Soil Taxonomy

B horizons ...... 314 L C horizons or layers ...... 314 E horizons ...... 313 L horizons or layers. See Horizons and layers. L horizons or layers ...... 313 Lamellae ...... 24 O horizons or layers ...... 313 Limnic materials. See Organic soil material and Horizons R layers ...... 314 and layers. W layers ...... 314 Linear extensibility (LE) ...... 24 Humaquepts ...... 170 Lithic contact ...... 31 Humicryerts ...... 289 Lithologic discontinuities ...... 24 Humicryods...... 256 Luvihemists ...... 162 Humigelods ...... 257 Humilluvic material. See Organic soil material. M Humods ...... 257 Humults ...... 267 Marl. See Organic soil material. Hydraquents ...... 132 Melanaquands ...... 85 Hydrocryands...... 89 Melanic epipedon ...... 14 Hydrudands ...... 95 Melanocryands...... 89 Hyperthermic temperature regime. See Soil temperature Melanoxerands...... 101 regimes. Melanudands ...... 96 Mesic temperature regime. See Soil temperature I regimes. Mineral soil material ...... 11 Identifiable secondary carbonates ...... 23 Mineral soils ...... 12 Inceptisols ...... 165 Mineralogy classes for Histosols and Histels ...... 309 Interfingering of albic materials ...... 23 Mineralogy classes for mineral soils ...... 303 Isofrigid temperature regime. See Soil temperature Mollic epipedon ...... 14 regimes. Mollisols ...... 193 Isohyperthermic temperature regime. See Soil temperature Molliturbels ...... 156 regimes. Mollorthels ...... 153 Isomesic temperature regime. See Soil temperature regimes. N Isothermic temperature regime. See Soil temperature regimes. n value ...... 25 Natralbolls ...... 195 K Natraqualfs...... 49 Natraquerts ...... 288 Kandiaqualfs ...... 48 Natraquolls ...... 198 Kandiaquults ...... 265 Natrargids ...... 108 Kandic horizon ...... 19 Natric horizon ...... 20 Kandihumults ...... 268 Natricryolls ...... 202 Kandiperox ...... 241 Natridurids ...... 123 Kandiudalfs ...... 61 Natrigypsids ...... 126 Kandiudox ...... 246 Natrixeralfs ...... 80 Kandiudults ...... 272 Natrixerolls ...... 234 Kandiustalfs ...... 69 Natrudalfs ...... 62 Kandiustox ...... 250 Natrudolls ...... 209 Kandiustults ...... 279 Natrustalfs ...... 71 Kanhaplaquults ...... 265 Natrustolls ...... 222 Kanhaplohumults ...... 269 Normal years...... 32 Kanhapludalfs ...... 62 Kanhapludults ...... 274 O Kanhaplustalfs ...... 70 Kanhaplustults ...... 280 O horizons or layers. See Horizons and layers. Key to soil orders...... 37 Ochric epipedon...... 15 Index 329

Organic soil material ...... 11 Placohumods ...... 258 Fibers ...... 27 Placorthods ...... 261 Fibric soil materials ...... 27 Placudands ...... 97 Hemic soil materials ...... 27 Plagganthrepts ...... 165 Humilluvic material ...... 27 Plaggen epipedon...... 15 Limnic materials ...... 28 Plinthaqualfs ...... 50 Coprogenous earth ...... 28 Plinthaquox ...... 238 Diatomaceous earth ...... 28 Plinthaquults ...... 267 Marl ...... 28 Plinthite ...... 25 Sapric soil materials ...... 27 Plinthohumults ...... 270 Organic soils ...... 12 Plinthoxeralfs ...... 82 Orthels ...... 150 Plinthudults ...... 277 Orthents ...... 139 Plinthustalfs ...... 76 Orthods ...... 258 Plinthustults ...... 281 Ortstein ...... 20 Prime symbol in horizon designators...... 318 Oxic horizon ...... 20 Psammaquents ...... 132 Oxisols ...... 237 Psamments ...... 144 Psammorthels ...... 153 P Psammoturbels ...... 156

Paleaquults ...... 266 Q Paleargids...... 110 Palecryalfs ...... 53 Quartzipsamments ...... 145 Palecryolls ...... 202 Palehumults...... 269 R Paleudalfs ...... 63 Paleudolls ...... 210 R layers. See Horizons and layers. Paleudults ...... 275 Ratio, 15 kPa water to clay ...... 300 Paleustalfs ...... 73 Ratio, CEC to clay ...... 305 Paleustolls ...... 224 Reaction classes for Histosols and Histels...... 309 Paleustults ...... 281 Rendolls ...... 203 Palexeralfs ...... 80 Resistant minerals ...... 26 Palexerolls ...... 234 Rhodoxeralfs ...... 82 Palexerults ...... 282 Rhodudalfs ...... 65 Paralithic contact ...... 32 Rhodudults ...... 277 Paralithic materials ...... 32 Rhodustalfs ...... 76 Particle-size classes for Histosols and Histels ...... 308 Rhodustults ...... 281 Particle-size classes for mineral soils ...... 297 Rock fragments ...... 297 Permafrost ...... 32 Rock structure ...... 13 Permanent cracks (classes) in mineral soils ...... 308 Rounding ...... 37 Perox ...... 238 Rupture-resistance classes for mineral soils ...... 307 Petraquepts ...... 171 Petroargids ...... 111 S Petrocalcic horizon ...... 20 Petrocalcids ...... 113 Salaquerts ...... 288 Petrocambids ...... 117 Salic horizon ...... 21 Petrocryids ...... 120 Salicryids ...... 121 Petroferric contact ...... 25 Salids ...... 127 Petrogypsic horizon ...... 20 Salitorrerts ...... 290 Petrogypsids ...... 127 Salusterts ...... 294 Placaquands ...... 86 Sapric soil materials. See Organic soil material. Placaquods ...... 255 Sapristels...... 150 Placic horizon ...... 21 Saprists ...... 162 Placocryods...... 257 Series control section ...... 310 330 Keys to Soil Taxonomy

Series differentiae within a family ...... 310 Torrands ...... 90 Slickensides ...... 26 Torrerts ...... 289 Soil ...... 9 Torriarents...... 133 Soil color, water state criteria ...... 37 Torric moisture regime. See Soil moisture regimes. Soil depth classes for Histosols and Histels ...... 310 Torrifluvents ...... 134 Soil depth classes for mineral soils ...... 307 Torrifolists ...... 161 Soil moisture regimes ...... 32 Torriorthents ...... 140 Aquic ...... 33 Torripsamments ...... 146 Aridic and torric ...... 33 Torrox ...... 242 Udic ...... 33 Transitional and combination horizons ...... 314 Ustic ...... 33 Turbels ...... 154 Xeric ...... 34 Soil temperature classes for Histosols and Histels ...... 310 Soil temperature classes for mineral soils...... 306 U Soil temperature regimes ...... 34 Udalfs ...... 54 Cryic ...... 34 Udands ...... 91 Frigid ...... 34 Udarents ...... 133 Hyperthermic ...... 34 Udepts ...... 174 Isofrigid ...... 34 Uderts ...... 291 Isohyperthermic ...... 35 Udic moisture regime. See Soil moisture regimes. Isomesic ...... 35 Udifluvents ...... 136 Isothermic ...... 35 Udifolists ...... 161 Mesic ...... 34 Udipsamments ...... 147 Thermic ...... 34 Udivitrands ...... 99 Sombric horizon ...... 21 Udolls ...... 203 Sombrihumults ...... 270 Udorthents ...... 141 Sombriperox ...... 242 Udox ...... 243 Sombriudox ...... 247 Udults ...... 270 Sombriustox ...... 251 Ultisols ...... 263 Sphagnofibrists ...... 160 Umbraquults ...... 267 Spodic horizon ...... 21 Umbric epipedon ...... 15 Spodic materials ...... 26 Umbriturbels ...... 156 Spodosols ...... 253 Umbrorthels ...... 154 Strongly contrasting particle-size classes ...... 301 Ustalfs ...... 65 Subsurface tier ...... 29 Ustands ...... 98 Suffix symbols in horizon designators ...... 315 Ustarents ...... 133 Conventions for using letter suffixes ...... 317 Ustepts ...... 179 Vertical subdivision ...... 317 Usterts ...... 292 Sulfaquents ...... 133 Ustic moisture regime. See Soil moisture regimes. Sulfaquepts ...... 171 Ustifluvents ...... 137 Sulfaquerts ...... 289 Ustifolists ...... 161 Sulfidic materials ...... 35 Ustipsamments ...... 147 Sulfihemists ...... 162 Ustivitrands ...... 100 Sulfisaprists ...... 163 Ustolls ...... 211 Sulfohemists ...... 162 Ustorthents ...... 142 Sulfosaprists...... 163 Ustox...... 247 Sulfudepts ...... 179 Ustults ...... 278 Sulfuric horizon ...... 35 Surface tier ...... 29 V T Vermaqualfs ...... 50 Thermic temperature regime. See Soil temperature Vermaquepts ...... 171 regimes. Vermudolls ...... 210 Index 331

Vermustolls ...... 226 X Vertisols ...... 285 Vitrands ...... 99 Xeralfs ...... 77 Vitraquands ...... 86 Xerands ...... 101 Vitricryands ...... 89 Xerarents...... 133 Vitrigelands ...... 90 Xerepts ...... 186 Vitritorrands ...... 91 Xererts ...... 295 Vitrixerands ...... 102 Xeric moisture regime. See Soil moisture regimes. Xerofluvents ...... 138 W Xerolls ...... 226 Xeropsamments ...... 148 W layers. See Horizons and layers. Xerorthents ...... 144 Weatherable minerals...... 26 Xerults ...... 281 332 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