United States Department of Agriculture Natural Resources Conservation Service
Keys to Soil Taxonomy
Eighth Edition, 1998
Keys to Soil Taxonomy
By Soil Survey Staff
United States Department of Agriculture Natural Resources Conservation Service
Eighth Edition, 1998 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 326-W, 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: Map compiled by the World Soil Resources Staff, Natural Resources Conservation Service, Washington, D.C. 5
Table of Contents
Foreword ...... 7 Chapter 1: The Soils 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: Alfisols ...... 41 Chapter 6: Andisols ...... 83 Chapter 7: Aridisols ...... 103 Chapter 8: Entisols ...... 129 Chapter 9: Gelisols ...... 149 Chapter 10: Histosols ...... 159 Chapter 11: Inceptisols ...... 165 Chapter 12: Mollisols ...... 191 Chapter 13: Oxisols ...... 233 Chapter 14: Spodosols ...... 249 Chapter 15: Ultisols ...... 259 Chapter 16: Vertisols ...... 281 Chapter 17: Family and Series Differentiae and Names ...... 295 Chapter 18: Designations for Horizons and Layers ...... 311 Appendix ...... 317 Index ...... 319
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 classification of soils. This volume includes all revisions of the keys that so far have been approved, replacing the original keys in Soil Taxonomy: A Basic System of Soil Classification for Making and Interpreting Soil Surveys (1975), the work on which this and other abridged versions, the first of which was published in 1983, are based. We plan to continue issuing updated editions of the Keys to Soil Taxonomy as changes warrant new editions. Plans are under way to publish an updated version of Soil Taxonomy in its entirety in 1999. This publication incorporates all amendments approved to date and published in the National Soil Taxonomy Handbook (NSTH) Issues 1-18. It includes the recommendations of the International Committee on Low Activity Clays (NSTH Issue 8), the International Committee on Oxisols (NSTH Issue 11), the International Committee on Andisols (NSTH Issue 13), the International Committee on Vertisols (NSTH Issue 16), the International Committee on Aquic Moisture Regime (NSTH Issue 16), the International Committee on Spodosols (NSTH Issue 16), the International Committee on Aridisols (NSTH Issue 17), and the International Committee on Families (NSTH Issue 18). Editorial changes have been made throughout the Keys to Soil Taxonomy to correct grammatical errors and clarify the intent of the criteria. The keys reproduced here were extracted from a computerized copy of Soil Taxonomy, which is maintained in complete, up-to-date form. 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.
Horace Smith Director, Soil Survey Division Natural Resources Conservation Service 1998
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 meanings. In its traditional meaning, soil is the natural activity or current pedogenic processes extend to depths medium for the growth of land plants, whether or not it has greater than 200 cm, the lower limit of the soil for discernible soil horizons. This meaning is still the common classification purposes is still 200 cm. In some instances the understanding of the word, and the greatest interest in soil is more weakly cemented bedrocks (paralithic materials, defined centered on this meaning. People consider soil important later) have been described and used to differentiate soil series because it supports plants that supply food, fibers, drugs, and (series control section, defined later), even though the other wants of humans and because it filters water and recycles paralithic materials below a paralithic contact are not wastes. Soil covers the earth’s surface as a continuum, except considered soil in the true sense. In areas where soil has thin on bare rock, in areas of perpetual frost or deep water, or on the cemented horizons that are impermeable to roots, the soil bare ice of glaciers. In this sense, soil has a thickness that is extends as deep as the deepest cemented horizon, but not below determined by the rooting depth of plants. 200 cm. For certain management goals, layers deeper than the Soil in this text is a natural body comprised of solids lower boundary of the soil that is classified (200 cm) must also (minerals and organic matter), liquid, and gases that occurs on be described if they affect the content and movement of water the land surface, occupies space, and is characterized by one or and air or other 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 of many meters with no obvious changes below the upper 1 or additions, losses, transfers, and transformations of energy and 2 m, except for an occasional stone line. In many wet soils, matter or the ability to support rooted plants in a natural gleyed soil material may begin a few centimeters below the environment. This definition is expanded from the 1975 surface and, in some areas, continue down for several meters version of Soil Taxonomy to include soils in areas of Antarctica apparently unchanged with increasing depth. The latter where pedogenesis occurs but where the climate is too harsh to condition can arise through the gradual filling of a wet basin in support the higher plant forms. which the A horizon is gradually added to the surface and The upper limit of soil is the boundary between soil and air, becomes gleyed beneath. Finally, the A horizon rests on a thick shallow water, live plants, or plant materials that have not mass of gleyed material that may be relatively uniform. In both begun to decompose. Areas are not considered to have soil if of these situations, there is no alternative but to set the lower the surface is permanently covered by water too deep (typically limit of soil at the arbitrary limit of 200 cm. more than 2.5 m) for the growth of rooted plants. The Soil, as defined in this text, does not need to have horizontal boundaries of soil are areas where the soil grades to discernible horizons, although the presence or absence of deep water, barren areas, rock, or ice. In some places the horizons and their nature are of extreme importance in soil separation between soil and nonsoil is so gradual that clear classification. Plants can be grown under glass in pots filled distinctions cannot be made. with earthy materials, such as peat or sand, or even in water. The lower boundary that separates soil from the nonsoil Under proper conditions all these media are productive for underneath is most difficult to define. Soil consists of the plants, but they are nonsoil here in the sense that they cannot horizons near the earth’s surface that, in contrast to the be classified in the same system that is used for the soils of a underlying parent material, have been altered by the survey area, county, or even nation. Plants even grow on trees, interactions of climate, relief, and living organisms over time. but trees are regarded as nonsoil. Commonly, soil grades at its lower boundary to hard rock or to Soil has many properties that fluctuate with the seasons. It earthy materials virtually devoid of animals, roots, or other may be alternately cold and warm or dry and moist. Biological marks of biological activity. The lowest depth of biological activity is slowed or stopped if the soil becomes too cold or too activity, however, is difficult to discern and is often gradual. dry. The soil receives flushes of organic matter when leaves fall For purposes of classification, the lower boundary of soil is or grasses die. Soil is not static. The pH, soluble salts, amount 10
of organic matter and carbon-nitrogen ratio, numbers of micro- establish a phase of the mantled soil or even another soil series organisms, soil fauna, temperature, and moisture all change if the mantle affects the use of the soil. with the seasons as well as with more extended periods of time. Any horizons or layers underlying a plaggen epipedon are Soil must be viewed from both the short-term and long-term considered to be buried. perspective. A surface mantle of new material, as defined here, is largely unaltered, at least in the lower part. It may have a diagnostic Buried Soils surface horizon (epipedon) and/or a cambic horizon, but it has no other diagnostic subsurface horizons, all defined later. A buried soil is covered with a surface mantle of new soil However, there remains a layer 7.5 cm or more thick that fails material that either is 50 cm or more thick or is 30 to 50 cm the requirements for all diagnostic horizons, as defined later, thick and has a thickness that equals at least half the total overlying a horizon sequence that can be clearly identified as thickness of the named diagnostic horizons that are preserved the solum of a buried soil in at least half of each pedon. The in the buried soil. A surface mantle of new material that does recognition of a surface mantle should not be based only on not have the required thickness for buried soils can be used to studies of associated soils. 11
D I CHAPTER 2 F Differentiae for Mineral Soils1 and Organic Soils
Soil taxonomy differentiates between mineral soils and include what has been called litter or an O horizon. Material organic soils. To do this, first, it is necessary to distinguish that has more organic carbon than in item 2 has been called mineral soil material from organic soil material. Second, it is peat or muck. Not all organic soil material accumulates in or necessary to define the minimum part of a soil that should be under water. Leaf litter may rest on a lithic contact and support mineral if a soil is to be classified as a mineral soil and the forest vegetation. The soil in this situation is organic only in minimum part that should be organic if the soil is to be the sense that the mineral fraction is appreciably less than half classified as an organic soil. the weight and is only a small percentage of the volume of the Nearly all soils contain more than traces of both mineral soil. and organic components in some horizons, but most soils are dominantly one or the other. The horizons that are less than Distinction Between Mineral Soils and Organic about 20 to 35 percent organic matter, by weight, have Soils properties that are more nearly those of mineral than of organic soils. Even with this separation, the volume of organic matter Most soils are dominantly mineral material, but many at the upper limit exceeds that of the mineral material in the mineral soils have horizons of organic material. For simplicity fine-earth fraction. in writing definitions of taxa, a distinction between what is meant by a mineral soil and an organic soil is useful. To apply Mineral Soil Material the definitions of many taxa, one must first decide whether the soil is mineral or organic. An exception is the Andisols Mineral soil material (less than 2.0 mm in diameter) either: (defined later). These generally are considered to consist of mineral soils, but some may be organic if they meet other 1. Is saturated with water for less than 30 days (cumulative) criteria for Andisols. Those that exceed the organic carbon per year in normal years and contains less than 20 percent (by limit defined for mineral soils have a colloidal fraction weight) organic carbon; or dominated by short-range-order minerals or aluminum-humus 2. Is saturated with water for 30 days or more cumulative in complexes. The mineral fraction in these soils is believed to normal years (or is artificially drained) and, excluding live give more control to the soil properties than the organic roots, has an organic carbon content (by weight) of: fraction. Therefore, the soils are included with the Andisols rather than the organic soils defined later as Histosols. a. Less than 18 percent if the mineral fraction contains 60 If a soil has both organic and mineral horizons, the relative percent or more clay; or thickness of the organic and mineral soil materials must be b. Less than 12 percent if the mineral fraction contains no considered. At some point one must decide that the mineral clay; or horizons are more important. This point is arbitrary and depends in part on the nature of the materials. A thick layer of c. Less than 12 + (clay percentage multiplied by 0.1) sphagnum has a very low bulk density and contains less percent if the mineral fraction contains less than 60 percent organic matter than a thinner layer of well-decomposed muck. clay. It is much easier to measure the thickness of layers in the field than it is to determine tons of organic matter per hectare. The Organic Soil Material definition of a mineral soil, therefore, is based on the thickness of the horizons, or layers, but the limits of thickness must vary Soil material that contains more than the amounts of with the kinds of materials. The definition that follows is organic carbon described above for mineral soil material is intended to classify as mineral soils those that have both thick considered organic soil material. mineral soil layers and no more organic material than the In the definition of mineral soil material above, material amount permitted in the histic epipedon, which is defined in that has more organic carbon than in item 1 is intended to chapter 3. In the determination of whether a soil is organic or mineral, 1 Mineral soils include all soils except the suborder Histels and the order Histosols. the thickness of horizons is measured from the surface of the 12
soil whether that is the surface of a mineral or an organic a. Permafrost within 100 cm of the soil surface; or horizon, unless the soil is buried as defined in chapter 1. Thus, b. Gelic materials within 100 cm of the soil surface and any O horizon at the surface is considered an organic horizon permafrost within 200 cm of the soil surface. if it meets the requirements of organic soil material as defined 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: 1. Do not have andic soil properties in 60 percent or more of Definition of Mineral Soils the thickness between the soil surface and either a depth of 60 cm or a densic, lithic, or paralithic contact or duripan if Mineral soils are soils that have either of the following: shallower; and 1. Mineral soil materials that meet one or more of the 2. Meet one or more of the following: following: a. Overlie cindery, fragmental, or pumiceous materials a. Overlie cindery, fragmental, or pumiceous materials and/or fill their interstices2 and directly below these and/or have voids2 that are filled with 10 percent or less materials have a densic, lithic, or paralithic contact; or organic materials and directly below these materials have either a densic, lithic, or paralithic contact; or b. When added with the underlying cindery, fragmental, or pumiceous materials, total 40 cm or more between the soil b. When added with underlying cindery, fragmental, or surface and a depth of 50 cm; or pumiceous materials, total more than 10 cm between the soil surface and a depth of 50 cm; or c. Constitute two-thirds or more of the total thickness of the soil to a densic, lithic, or paralithic contact and have no c. Constitute more than one-third of the total thickness of mineral horizons or have mineral horizons with a total the soil to a densic, lithic, or paralithic contact or have a thickness of 10 cm or less; or total thickness of more than 10 cm; or d. Are saturated with water for 30 days or more per year in d. If they are saturated with water for 30 days or more per normal years (or are artificially drained), have an upper year in normal years (or are artificially drained) and have boundary within 40 cm of the soil surface, and have a total organic materials with an upper boundary within thickness of either: 40 cm of the soil surface, have a total thickness of either: (1) 60 cm or more if three-fourths or more of their (1) Less than 60 cm 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) 40 cm or more if they consist either of sapric or (2) Less than 40 cm if they consist either of sapric or hemic materials, or of fibric materials with less than hemic materials, or of fibric materials with less than three-fourths (by volume) moss fibers and a bulk density, three-fourths (by volume) moss fibers and a bulk density, moist, of 0.1 g/cm3 or more; or moist, of 0.1 g/cm3 or more; or e. Are 80 percent or more, by volume, from the soil 2. More than 20 percent, by volume, mineral soil materials surface to a depth of 50 cm or to a glacic layer or a densic, from the soil surface to a depth of 50 cm or to a glacic layer or lithic, or paralithic contact, whichever is shallowest. a densic, lithic, or paralithic contact, whichever is shallowest; and It is a general rule that a soil is classified as an organic soil (Histosol) 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 be on rock or on fragmental material having interstices filled with 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 subgroups. A soil with a mantle thick enough to have a buried both mineral and organic soils. It is divided into three parts— soil has no epipedon if the soil has rock structure to the surface horizons and characteristics diagnostic for mineral soils, or has an Ap horizon less than 25 cm thick that is underlain by characteristics diagnostic for organic soils, and horizons and soil material with rock structure. The melanic epipedon characteristics diagnostic for both mineral and organic soils. (defined below) is unique among epipedons. It forms The horizons and characteristics defined below are not in a commonly in volcanic deposits and can receive fresh deposits key format. Some diagnostic horizons are mutually exclusive, of ash. Therefore, this horizon is permitted to have layers and some are not. An umbric epipedon, for example, could within and above the epipedon that are not part of the melanic not also be a mollic epipedon. A kandic horizon with clay epipedon. films, however, could also meet the definition of an argillic A recent alluvial or eolian deposit that retains stratifications horizon. (5 mm or less thick) or an Ap horizon directly underlain by such stratified material is not included in the concept of the epipedon because time has not been sufficient for soil-forming Horizons and Characteristics processes to erase these transient marks of deposition and for Diagnostic for Mineral Soils diagnostic and accessory properties to develop. An epipedon is not the same as an A horizon. It may The criteria for some of the following horizons and include part or all of an illuvial B horizon if the darkening by characteristics, such as histic and folistic epipedons, can be met organic matter extends from the soil surface into or through the in organic soils. They are diagnostic, however, only for the B horizon. 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 horizon that forms at or near the surface and in which most of mollic epipedon, except for one or both of the following: the rock structure has been destroyed. It is darkened by organic matter or shows evidence of eluviation, or both. Rock structure 1. 1,500 milligrams per kilogram or more P2O5 soluble in 1 as used here and in other places in this taxonomy includes fine percent citric acid and a regular decrease in P2O5 to a depth of stratification (less than 5 mm) in unconsolidated sediments 125 cm; or (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 for 9 months or more in normal years. and pseudomorphs of weathered minerals retain their relative positions to each other. Any horizon may be at the surface of a truncated soil. The Folistic Epipedon following section, however, is concerned with eight diagnostic Required Characteristics horizons that have formed at or near the soil surface. These horizons can be covered by a surface mantle of new soil The folistic epipedon is defined as a layer (one or more material. If the surface mantle has rock structure, the top of the horizons) that is saturated for less than 30 days (cumulative) in epipedon is considered the soil surface unless the mantle meets normal years (and is not artificially drained) and either: 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 epipedon of the buried soil is considered a buried epipedon and a. Is 20 cm or more thick and either contains 75 percent or is not considered in selecting taxa unless the keys specifically more (by volume) Sphagnum fibers or has a bulk density, indicate buried horizons, such as those in Thapto-Histic moist, of less than 0.1; or 14 Keys to Soil Taxonomy
b. Is 15 cm or more thick; or with andic soil properties (defined below), whichever is shallower; and 2. Is an Ap horizon that, when mixed to a depth of 25 cm, has an organic-carbon content (by weight) of: 2. In layers with a cumulative thickness of 30 cm or more within a total thickness of 40 cm, all of the following: a. 16 percent or more if the mineral fraction contains 60 percent or more clay; or a. Andic soil properties throughout; and b. 8 percent or more if the mineral fraction contains no b. A color value, moist, and chroma (Munsell clay; or designations) of 2 or less throughout and a melanic index of 1.70 or less throughout; and c. 8 + (clay percentage divided by 7.5) percent or more if the mineral fraction contains less than 60 percent clay. c. 6 percent or more organic carbon as a weighted average 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 that is an Ap horizon consisting of mineral soil material. Mollic Epipedon 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 characterized by saturation (for 30 days or more, cumulative) a. Structural units with a diameter of 30 cm or less and reduction for some time during normal years (or is or secondary structure with a diameter of 30 cm or less; or artificially drained) and either: b. A moderately hard or softer rupture-resistance class; 1. Consists of organic soil material that: and a. Is 20 to 60 cm thick and either contains 75 percent or 2. Rock structure, including fine (less than 5 mm) more (by volume) Sphagnum fibers or has a bulk density, stratifications, in less than one-half of the volume of all parts; moist, of less than 0.1; or and b. Is 20 to 40 cm thick; or 3. One of the following: 2. Is an Ap horizon that, when mixed to a depth of 25 cm, a. All of the following: has an organic-carbon content (by weight) of: (1) Colors with a value of 3 or less, moist, and of 5 or a. 16 percent or more if the mineral fraction contains 60 less, dry; and 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 clay; or a color value at least 1 Munsell unit lower or chroma at c. 8 + (clay percentage divided by 7.5) percent or more if least 2 units lower (both moist and dry) than that of the C the mineral fraction contains less than 60 percent clay. horizon or the epipedon has at least 0.6 percent more organic carbon than the C horizon; or Most histic epipedons consist of organic soil material (defined in chapter 2). Item 2 provides for a histic epipedon b. A fine-earth fraction that has a calcium carbonate that is an Ap horizon consisting of mineral soil material. A equivalent of 15 to 40 percent and colors with a value and histic epipedon consisting of mineral soil material can also be chroma of 3 or less, moist; or 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
Required Characteristics 4. A base saturation (by NH4OAc) of 50 percent or more; 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 Horizons and Characteristics Diagnostic for the Higher Categories 15
b. 0.6 percent more than that of the C horizon (if one Ochric Epipedon occurs) if the mollic epipedon has a color value less than 1 Munsell unit lower or chroma less than 2 units lower (both The ochric epipedon fails to meet the definitions for any of moist and dry) than the C horizon; or the other seven epipedons because it is too thin or too dry, has D too high a color value or chroma, contains too little organic c. 0.6 percent or more; and I carbon, has too high an n value or melanic index, or is both A massive and hard or harder when dry . Many ochric epipedons 6. After mixing of the upper 18 cm of the mineral soil or of have either a Munsell color value of 4 or more, moist, and 6 or the whole mineral soil if its depth to a densic, lithic, or more, dry, or chroma of 4 or more, or they include an A or Ap paralithic contact, petrocalcic horizon, or duripan (all defined horizon that has both low color values and low chroma but is below) is less than 18 cm, the minimum thickness of the too thin to be recognized as a mollic or umbric epipedon (and epipedon is as follows: has less than 15 percent calcium carbonate equivalent in the a. 10 cm or the depth of the noncemented soil if the fine-earth fraction). Ochric epipedons also include horizons of epipedon is loamy very fine sand or finer and is directly organic materials that are too thin to meet the requirements for above a densic, lithic, or paralithic contact, a petrocalcic a histic or folistic epipedon. horizon, or a duripan that is within 18 cm of the mineral The ochric epipedon includes eluvial horizons that are at or soil surface; or near the soil surface, and it extends to the first underlying diagnostic illuvial horizon (defined below as an argillic, b. 25 cm or more if the epipedon is loamy fine sand or kandic, natric, or spodic horizon). If the underlying horizon is coarser throughout or if there are no underlying diagnostic a B horizon of alteration (defined below as a cambic or oxic horizons (defined below) and the organic-carbon content of horizon) and there is no surface horizon that is appreciably the underlying materials decreases irregularly with darkened by humus, the lower limit of the ochric epipedon is increasing depth; or the lower boundary of the plow layer or an equivalent depth c. 25 cm or more if all of the following are 75 cm or more (18 cm) in a soil that has not been plowed. Actually, the same below the mineral soil surface: horizon in an unplowed soil may be both part of the epipedon and part of the cambic horizon; the ochric epipedon and the (1) The upper boundary of any pedogenic lime that is subsurface diagnostic horizons are not all mutually exclusive. present as filaments, soft coatings, or soft nodules; and The ochric epipedon does not have rock structure and does not (2) The lower boundary of any argillic, cambic, natric, include finely stratified fresh sediments, nor can it be an Ap oxic, or spodic horizon (defined below); and horizon directly overlying such deposits. (3) The upper boundary of any petrocalcic horizon, duripan, or fragipan; or Plaggen Epipedon d. 18 cm if the epipedon is loamy very fine sand or finer in The plaggen epipedon is a human-made surface layer 50 cm some part and one-third or more of the total thickness or more thick that has been produced by long-continued between the top of the epipedon and the shallowest of any manuring. features listed in item 6-c is less than 75 cm below the A plaggen epipedon can be identified by several means. mineral soil surface; or Commonly, it contains artifacts, such as bits of brick and pottery, throughout its depth. There may be chunks of diverse e. 18 cm or more if none of the above conditions apply; materials, such as black sand and light gray sand, as large as and the 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 surface by beating rains and were later buried by spading. A soluble in 1 percent citric acid; or map unit delineation of soils with plaggen epipedons would b. Content decreasing irregularly with increasing depth tend to have straight-sided rectangular bodies that are higher below the epipedon; or than the 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: 6. Phosphate: a. Structural units with a diameter of 30 cm or less or a. Content less than 1,500 milligrams per kilogram secondary structure with a diameter of 30 cm or less; or soluble in 1 percent citric acid; or b. A moderately hard or softer rupture-resistance class; b. Content decreasing irregularly with increasing depth and below the epipedon; or 2. All of the following: c. Nodules are within the epipedon; and a. Colors with a value of 3 or less, moist, and of 5 or less, 7. Some part of the epipedon is moist for 90 days or more dry; and (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 b. Colors with chroma of 3 or less; and not irrigated; and c. If the soil has a C horizon, the umbric epipedon has a 8. The n value (defined below) is less than 0.7; and color value at least 1 Munsell unit lower or chroma at least 2 units lower (both moist and dry) than that of the C 9. The umbric epipedon does not have the artifacts, spade horizon or the epipedon has at least 0.6 percent more marks, and raised surfaces that are characteristic of the organic carbon than that of the C horizon; and plaggen epipedon.
3. A base saturation (by NH4OAc) of less than 50 percent in some or all parts; and Diagnostic Subsurface Horizons 4. An organic-carbon content of: The horizons described in this section form below the a. 0.6 percent more than that of the C horizon (if one surface of the soil, although in some areas they form directly occurs) if the umbric epipedon has a color value less than 1 below a layer of leaf litter. They may be exposed at the surface Munsell unit lower or chroma less than 2 units lower (both by truncation of the soil. Some of these horizons are generally moist and dry) than the C horizon; or regarded as B horizons, some are considered B horizons by many but not all pedologists, and others are generally regarded b. 0.6 percent or more; and as parts of the A horizon. 5. After mixing of the upper 18 cm of the mineral soil or of the whole mineral soil if its depth to a densic, lithic, or Agric Horizon paralithic contact or a duripan (all defined below) is less than 18 cm, the minimum thickness of the epipedon is as The agric horizon is an illuvial horizon that has formed follows: under cultivation and contains significant amounts of illuvial silt, clay, and humus. a. 10 cm or the depth of the noncemented soil if the epipedon is loamy very fine sand or finer and is directly Required Characteristics above a densic, lithic, or paralithic contact or a duripan that The agric horizon is directly below an Ap horizon and has is within 18 cm of the mineral soil surface; or the following properties: b. 25 cm or more if the epipedon is loamy fine sand or 1. A thickness of 10 cm or more and either: coarser throughout or if there are no underlying diagnostic horizons (defined below) and the organic-carbon content of a. 5 percent or more (by volume) wormholes, including the underlying materials decreases irregularly with coatings that are 2 mm or more thick and have a value, increasing depth; or moist, of 4 or less and chroma of 2 or less; or c. 25 cm or more if the lower boundary of any argillic, b. 5 percent or more (by volume) lamellae that have a cambic, natric, oxic, or spodic horizon (defined below) is 75 thickness of 5 mm or more and have a value, moist, of 4 or cm or more below the mineral soil surface; or less and chroma of 2 or less. d. 18 cm if the epipedon is loamy very fine sand or finer in some part and one-third or more of the total thickness Albic Horizon between the top of the epipedon and the shallowest of any The albic horizon is an eluvial horizon, 1.0 cm or more features listed in item 5-c is less than 75 cm below the thick, that has 85 percent or more (by volume) albic materials mineral soil surface; or (defined below). It generally occurs below an A horizon but e. 18 cm or more if none of the above conditions apply; may be at the mineral soil surface. Under the albic horizon and there generally is an argillic, cambic, kandic, natric, or spodic Horizons and Characteristics Diagnostic for the Higher Categories 17
horizon or a fragipan (defined below). The albic horizon may the ratio of fine clay to total clay in the illuvial horizon is lie between a spodic horizon and either a fragipan or an argillic greater by 1.2 times or more than the ratio in the eluvial horizon, or it may be between an argillic or kandic horizon and horizon; and a fragipan. It may lie between a mollic epipedon and an argillic 2. If an eluvial horizon remains and there is no lithologic D or natric horizon or between a cambic horizon and an argillic, discontinuity between it and the illuvial horizon and no plow I kandic, or natric horizon or a fragipan. The albic horizon may layer directly above the illuvial layer, then the illuvial horizon A separate horizons that, if they were together, would meet the must contain more total clay than the eluvial horizon within a requirements for a mollic epipedon. It may separate lamellae vertical distance of 30 cm or less, as follows: that together meet the requirements for an argillic horizon. These lamellae are not considered to be part of the albic a. If any part of the eluvial horizon has less than 15 horizon. percent total clay in the fine-earth fraction, the argillic horizon must contain at least 3 percent (absolute) more clay Argillic Horizon (10 percent versus 13 percent, for example); or b. If the eluvial horizon has 15 to 40 percent total clay in An argillic horizon is normally a subsurface horizon with a the fine-earth fraction, the argillic horizon must have at significantly higher percentage of phyllosilicate clay than the least 1.2 times more clay than the eluvial horizon; or overlying soil material. It shows evidence of clay illuviation. The argillic horizon forms below the soil surface, but it may be c. If the eluvial horizon has 40 percent or more total clay exposed at the surface later by erosion. in the fine-earth fraction, the argillic horizon must contain at least 8 percent (absolute) more clay (42 percent versus 50 Required Characteristics percent, for example). 1. All argillic horizons must meet both of the following requirements: Calcic Horizon a. One of the following: The calcic horizon is an illuvial horizon in which secondary (1) If the argillic horizon is coarse-loamy, fine-loamy, calcium carbonate or other carbonates have accumulated to a coarse-silty, fine-silty, fine, or very-fine or is loamy or significant extent. clayey, including skeletal counterparts, it must be at least 7.5 cm thick or at least one-tenth as thick as the sum of Required Characteristics the thickness of all overlying horizons, whichever is The calcic horizon has all of the following properties: greater. For example, if the eluvial and illuvial horizons together are more than 150 cm thick, then the argillic 1. Is 15 cm or more thick; and horizon must be 15 cm or more thick; or 2. Is not indurated or cemented to such a degree that it meets (2) If the argillic horizon is sandy or sandy-skeletal, it the requirements for a petrocalcic horizon; and 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 CaCO equivalent (see below), and lamellae, the combined thickness of the lamellae that are 3 its CaCO equivalent is 5 percent or more (absolute) higher 0.5 cm or more thick must be 15 cm or more; and 3 than that of an underlying horizon; or b. Evidence of clay illuviation in at least one of the b. 15 percent or more CaCO equivalent and 5 percent or following forms: 3 more (by volume) identifiable secondary carbonates; or (1) Oriented clay bridging the sand grains; or c. 5 percent or more calcium carbonate equivalent and (2) Clay films lining pores; or has: (3) Clay films on both vertical and horizontal surfaces (1) Less than 18 percent clay in the fine-earth fraction; of peds; or and (4) Thin sections with oriented clay bodies that are (2) A sandy, sandy-skeletal, coarse-loamy, or loamy- more than 1 percent of the section; or skeletal particle-size class; and (5) If the coefficient of linear extensibility is 0.04 or (3) 5 percent or more (by volume) identifiable higher and the soil has distinct wet and dry seasons, then secondary carbonates or a calcium carbonate equivalent 18 Keys to Soil Taxonomy
(by weight) that is 5 percent or more (absolute) higher (does not meet the color requirements for a mollic or umbric than that of an underlying horizon. epipedon), and is not brittle.
Cambic Horizon Duripan Required Characteristics A cambic horizon is the result of physical alterations, chemical transformations, or removals or of a combination of A duripan is a silica-cemented subsurface horizon with or two or more of these processes. without auxiliary cementing agents. It can occur in conjunction with a petrocalcic horizon. Required Characteristics A duripan must meet all of the following requirements: The cambic horizon is an altered horizon 15 cm or more 1. The pan is cemented or indurated in more than 50 percent thick. If it is composed of lamellae, the combined thickness of of the volume of some horizon; and the lamellae must be 15 cm or more. In addition, the cambic horizon must meet all of the following: 2. The pan shows evidence of the accumulation of opal or other forms of silica, such as laminar caps, coatings, lenses, 1. Has a texture of very fine sand, loamy very fine sand, or partly filled interstices, bridges between sand-sized grains, or finer; and coatings on rock and pararock fragments; and 2. Shows evidence of alteration in one of the following 3. Less than 50 percent of the volume of air-dry fragments forms: slakes in 1N HCl even during prolonged soaking, but more a. Aquic conditions within 50 cm of the soil surface or than 50 percent slakes in concentrated KOH or NaOH or in artificial drainage and all of the following: alternating acid and alkali; and (1) Soil structure or the absence of rock structure in 4. Because of lateral continuity, roots can penetrate the pan more than one-half of the volume; and only along vertical fractures with a horizontal spacing of 10 cm or more. (2) Colors that do not change on exposure to air; and Fragipan (3) Dominant color, moist, on faces of peds or in the 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 following characteristics: (b) Value of 4 or more and chroma of 1 or less; or 1. The layer is 15 cm or more thick; and (c) Any value, chroma of 2 or less, and redox concentrations; or 2. The layer shows evidence of pedogenesis within the horizon or, at a minimum, on the faces of structural units; and b. Does not have the combination of aquic conditions within 50 cm of the soil surface or artificial drainage and 3. The layer has very coarse prismatic, columnar, or blocky colors, moist, as defined in item 2-a-(3) above, and has soil structure of any grade, has weak structure of any size, or is structure or the absence of rock structure in more than one- massive. Separations between structural units that allow roots half of the volume and one or more of the following to enter have an average spacing of 10 cm or more on the properties: horizontal dimensions; and (1) Higher chroma, higher value, redder hue, or higher 4. Air-dry fragments of the natural soil fabric, 5 to 10 cm in clay content than the underlying horizon or an overlying diameter, from more than 50 percent of the horizon slake when horizon; or they are submerged in water; and (2) Evidence of the removal of carbonates or gypsum; 5. The layer has, in 60 percent or more of the volume, a firm and or firmer rupture-resistance class, a brittle manner of failure at or near field capacity, and virtually no roots. 3. Has properties that do not meet the requirements for an anthropic, histic, folistic, melanic, mollic, plaggen, or umbric epipedon, a duripan or fragipan, or an argillic, calcic, gypsic, Glossic Horizon natric, oxic, petrocalcic, petrogypsic, placic, or spodic horizon; The glossic horizon (Gr. glossa, tongue) develops as a result and of the degradation of an argillic, kandic, or natric horizon from 4. Is not part of an Ap horizon, is not appreciably darkened which clay and free iron oxides are removed. Horizons and Characteristics Diagnostic for the Higher Categories 19
Required Characteristics (1) 4 percent or more (absolute) higher than that in the 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 D constitute 15 to 85 percent (by volume) of the glossic horizon; surface horizon if that horizon has 20 to 40 percent total I and clay in the fine-earth fraction; or A 2. An illuvial part, i.e., remnants (pieces) of an argillic, (3) 8 percent or more (absolute) higher than that in the kandic, 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 (1) Between 100 cm and 200 cm from the mineral soil secondary gypsum has accumulated to a significant extent. surface if the particle-size class is sandy or sandy-skeletal Required Characteristics throughout the upper 100 cm; or A gypsic horizon has all of the following properties: (2) Within 100 cm from the mineral soil surface if the 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 content percentage of 150 or more. b. 15 cm or more if there is a densic, lithic, paralithic, or 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; volume) visible gypsum and is not cemented or indurated to and such a degree that it meets the requirements for a petrogypsic horizon. 4. Has a texture of loamy very fine sand or finer; and The gypsum percentage can be calculated by multiplying 5. Has an apparent CEC of 16 cmol(+) or less per kg clay (by the milliequivalents of gypsum per 100 g soil by the 1N NH OAc pH 7) and an apparent ECEC of 12 cmol(+) or . 4 milliequivalent weight of CaSO4 2H2O, which is 0.086. less per kg clay (sum of bases extracted with 1N NH4OAc pH 7 1 plus 1N KCl-extractable Al) in 50 percent or more of its Kandic Horizon thickness between the point where the clay increase requirements are met and either a depth of 100 cm below that Required Characteristics point or a densic, lithic, paralithic, or petroferric contact if The kandic horizon: shallower. (The percentage of clay is either measured by the pipette method or estimated to be 2.5 times [percent water 1. Is a vertically continuous subsurface horizon that underlies retained at 1500 kPa tension minus percent organic carbon], a coarser textured surface horizon. The minimum thickness of whichever is higher, but no more than 100); and the surface horizon is 18 cm after mixing or 5 cm if the textural transition to the kandic horizon is abrupt and there is 6. Has a regular decrease in organic-carbon content with no densic, lithic, paralithic, or petroferric contact (defined increasing depth, no fine stratification, and no overlying layers below) within 50 cm of the mineral soil surface; and more than 30 cm thick that have fine stratification and/or an organic-carbon content that decreases irregularly with 2. Has its upper boundary: increasing depth. a. At the point where the clay percentage in the fine-earth fraction, increasing with depth within a vertical distance of Natric Horizon 15 cm or less, is either: Required Characteristics 1 The concept of the kandic horizon and the “kandi” and “kanhapli” great groups of soils represent the work of the International Committee on the Classification of Low Activity Clays The natric horizon has, in addition to the properties of the (ICOMLAC), chaired by Dr. Frank R. Moormann. argillic horizon: 20 Keys to Soil Taxonomy
1. Either: if the fine-earth fraction of the surface horizon contains 20 to 40 percent clay; or a. Columns or prisms in some part (generally the upper part), which may break to blocks; or c. Less than 8 percent (absolute) in its fine-earth fraction if the fine-earth fraction of the surface horizon contains 40 b. Both blocky structure and eluvial materials, which percent or more clay); and contain uncoated silt or sand grains and extend more than 2.5 cm into the horizon; and 6. An apparent CEC of 16 cmol(+) or less per kg clay (by 1N NH OAc pH 7) and an apparent ECEC of 12 cmol(+) or less 2. Either: 4 per kg clay (sum of bases extracted with 1N NH4OAc pH 7 plus a. An exchangeable sodium percentage (ESP) of 15 1N KCl-extractable Al). (The percentage of clay is either percent or more (or a sodium adsorption ratio [SAR] of 13 measured by the pipette method or estimated to be 3 times or more) in one or more horizons within 40 cm of its upper [percent water retained at 1500 kPa tension minus percent boundary; or organic carbon], whichever value is higher, but no more than 100). b. More exchangeable magnesium plus sodium than calcium plus exchange acidity (at pH 8.2) in one or more horizons within 40 cm of its upper boundary if the ESP is Petrocalcic Horizon 15 or more (or the SAR is 13 or more) in one or more The petrocalcic horizon is an illuvial horizon in which horizons within 200 cm of the mineral soil surface. secondary calcium carbonate or other carbonates have accumulated to the extent that the horizon is cemented or Ortstein indurated. Required Characteristics Required Characteristics A petrocalcic horizon must meet the following Ortstein has all of the following: requirements: 1. Consists of spodic materials; and 1. The horizon is cemented or indurated by carbonates, with 2. Is in a layer that is 50 percent or more cemented; and or without silica or other cementing agents; and 3. Is 25 mm or more thick. 2. Because of lateral continuity, roots can penetrate only along vertical fractures with a horizontal spacing of 10 cm or Oxic Horizon more; and 3. The horizon has a thickness of: Required Characteristics a. 10 cm or more; or The oxic horizon is a subsurface horizon that does not have andic soil properties (defined below) and has all of the b. 1 cm or more if it consists of a laminar cap directly following characteristics: underlain by bedrock. 1. A thickness of 30 cm or more; and Petrogypsic Horizon 2. A texture of sandy loam or finer in the fine-earth fraction; and The petrogypsic horizon is an illuvial horizon, 10 cm or more thick, in which secondary gypsum has accumulated to the 3. Less than 10 percent weatherable minerals in the 50- extent that the horizon is cemented or indurated. to 200-micron fraction; and Required Characteristics 4. Rock structure in less than 5 percent of its volume, unless the lithorelicts with weatherable minerals are coated with A petrogypsic horizon must meet the following sesquioxides; and requirements: 5. A diffuse upper boundary, i.e., within a vertical distance 1. The horizon is cemented or indurated by gypsum, with or of 15 cm, a clay increase with increasing depth of: without other cementing agents; and a. Less than 4 percent (absolute) in its fine-earth fraction 2. Because of lateral continuity, roots can penetrate only if the fine-earth fraction of the surface horizon contains less along vertical fractures with a horizontal spacing of 10 cm or than 20 percent clay; or more; and b. Less than 20 percent (relative) in its fine-earth fraction 3. The horizon is 10 cm or more thick; and Horizons and Characteristics Diagnostic for the Higher Categories 21
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. In the field a sombric horizon is easily mistaken for a buried A horizon. It can be distinguished from some buried D Placic Horizon epipedons by lateral tracing. In thin sections the organic I matter of a sombric horizon appears more concentrated on A 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 spodic materials (defined below). 1. The horizon is cemented or indurated with iron or iron and manganese and organic matter, with or without other Required Characteristics cementing agents; and A spodic horizon is normally a subsurface horizon 2. Because of lateral continuity, roots can penetrate only underlying an O, A, Ap, or E horizon. It may, however, meet along vertical fractures with a horizontal spacing of 10 cm or the definition of an umbric epipedon. more; and A spodic horizon must have 85 percent or more spodic materials in a layer 2.5 cm or more thick that is not part of any 3. The horizon has a minimum thickness of 1 mm and, where Ap horizon. associated with spodic materials, is less than 25 mm thick.
Salic Horizon Other Diagnostic Soil Characteristics (Mineral Soils) A salic horizon is a horizon of accumulation of salts that are more soluble than gypsum in cold water. Diagnostic soil characteristics are features of the soil that are used in various places in the keys or in definitions of Required Characteristics 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 An abrupt textural change is a specific kind of change that dS/m in a saturated paste; and 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 equal to 900 or more. increase in clay content within a very short vertical distance in the zone of contact. If the clay content in the fine-earth fraction Sombric Horizon of the ochric epipedon or albic horizon is less than 20 percent, it doubles within a vertical distance of 7.5 cm or less. If the A sombric horizon (F. sombre, dark) is a subsurface horizon clay content in the fine-earth fraction of the ochric epipedon or in mineral soils that has formed under free drainage. It the albic horizon is 20 percent or more, there is an increase of contains illuvial humus that is neither associated with 20 percent or more (absolute) within a vertical distance of 7.5 aluminum, as is the humus in the spodic horizon, nor dispersed cm or less (e.g., an increase from 22 to 42 percent) and the clay by sodium, as is common in the natric horizon. Consequently, content in some part of the argillic horizon is 2 times or more the sombric horizon does not have the high cation-exchange the amount contained in the overlying horizon. capacity in its clay that characterizes a spodic horizon and does Normally, there is no transitional horizon between an ochric not have the high base saturation of a natric horizon. It does epipedon or an albic horizon and an argillic horizon, or the not underlie an 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 The sombric horizon has a lower color value or chroma, or might create the impression of a relatively thick transitional both, than the overlying horizon and commonly contains more horizon, whereas the thickness of the actual transition at the organic matter. It may have formed in an argillic, cambic, or contact may be no more than 1 mm. 22 Keys to Soil Taxonomy
Albic Materials Required Characteristics To be recognized as having andic soil properties, soil Albic (L. albus, white) materials are soil materials with a materials must contain less than 25 percent (by weight) organic color that is largely determined by the color of primary sand carbon and meet one or both of the following requirements: and silt particles rather than by the color of their coatings. This definition implies that clay and/or free iron oxides have been 1. In the fine-earth fraction, all of the following: removed from the materials or that the oxides have been 1 a. Aluminum plus /2 iron percentages (by ammonium segregated to such an extent that the color of the materials is oxalate) totaling 2.0 percent or more; and largely determined by the color of the primary particles. b. A bulk density, measured at 33 kPa water retention, of Required Characteristics 0.90 g/cm3 or less; and Albic materials have one of the following colors: c. A phosphate retention of 85 percent or more; or 1. Chroma of 2 or less; and either 2. In the fine-earth fraction, a phosphate retention of 25 a. A color value, moist, of 3 and a color value, dry, of 6 or percent or more, 30 percent or more particles 0.02 to 2.0 mm more; or in size, and one of the following:
1 b. A color value, moist, of 4 or more and a color value, a. Aluminum plus /2 iron percentages (by ammonium dry, of 5 or more; or oxalate) totaling 0.40 or more and, in the 0.02 to 2.0 mm fraction, 30 percent or more volcanic glass; or 2. Chroma of 3 or less; and either 1 b. Aluminum plus /2 iron percentages (by ammonium a. A color value, moist, of 6 or more; or oxalate) totaling 2.0 or more and, in the 0.02 to 2.0 mm b. A color value, dry, of 7 or more; or fraction, 5 percent or more volcanic glass; or
1 3. Chroma that is controlled by the color of uncoated grains c. Aluminum plus /2 iron percentages (by ammonium of silt or sand, hue of 5YR or redder, and the color values listed oxalate) totaling between 0.40 and 2.0 and, in the 0.02 to in item 1-a or 1-b above. 2.0 mm fraction, enough volcanic glass so that the glass percentage, when plotted against the value obtained by Relatively unaltered layers of light colored sand, volcanic 1 adding aluminum plus /2 iron percentages in the fine-earth ash, or other materials deposited by wind or water are not fraction, falls within the shaded area of figure 1. considered albic materials, although they may have the same color and apparent morphology. These deposits are parent materials that are not characterized by the removal of clay Anhydrous Conditions and/or free iron and do not overlie an illuvial horizon or other soil horizon, except for a buried soil. Light colored krotovinas Anhydrous conditions (Gr. anydros, waterless) refer to the or filled root channels should be considered albic materials active layer in soils of cold deserts and other areas with only if they have no fine stratifications or lamellae, if any permafrost (often dry permafrost) and low precipitation sealing along the krotovina walls has been destroyed, and if (usually less than 50 mm water equivalent). Anhydrous soil these intrusions have been leached of free iron oxides and/or conditions are similar to the aridic (torric) soil moisture clay after deposition. regimes, except that the soil temperature is less than 0 oC.
Andic Soil Properties Coefficient of Linear Extensibility (COLE)
Andic soil properties result mainly from the presence of The coefficient of linear extensibility (COLE) is the ratio of significant amounts of allophane, imogolite, ferrihydrite, or the difference between the moist length and dry length of a aluminum-humus complexes in soils. These materials, clod to its dry length. It is (Lm - Ld)/Ld, where Lm is the originally termed “amorphous” (but understood to contain length at 33 kPa tension and Ld is the length when dry. COLE allophane) in the 1975 edition of Soil Taxonomy (USDA, SCS, can be calculated from the differences in bulk density of the 1975), are commonly formed during the weathering of tephra clod when moist and when dry. An estimate of COLE can be and other parent materials with a significant content of calculated in the field by measuring the distance between two volcanic glass. Although volcanic glass is or was a common pins in a clod of undisturbed soil at field capacity and again component in many Andisols, it is not a requirement of the after the clod has dried. COLE does not apply if the shrinkage Andisol order. is irreversible. Horizons and Characteristics Diagnostic for the Higher Categories 23
Fragic Soil Properties
Fragic soil properties are the essential properties of a fragipan. They have neither the layer thickness nor volume D requirements for the fragipan. Fragic soil properties are in I subsurface horizons, although they can be at or near the surface A in truncated soils. Aggregates with fragic soil properties have a firm or firmer rupture-resistance class and a brittle manner of failure when soil water is at or near field capacity. Air-dry fragments of the natural fabric, 5 to 10 cm in diameter, slake when they are submerged in water. Aggregates with fragic soil properties show evidence of pedogenesis, including one or more of the following: oriented clay within the matrix or on faces of 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 soil properties regardless of whether or not the density and brittleness are pedogenic. 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. Figure 1.—Soils that are plotted in the shaded area have andic soil properties. A soil has these properties if the fraction less than 2.0 mm in size has phosphate retention of more than 25 percent and the 0.02 to Identifiable Secondary Carbonates 2.0 mm fraction is at least 30 percent of the fraction less than 2.0 mm in size. The term “identifiable secondary carbonates” is used in the definitions of a number of taxa. It refers to translocated Durinodes authigenic calcium carbonate that has been precipitated in place from the soil solution rather than inherited from a soil Durinodes (L. durus, hard, and nodus, knot) are weakly parent material, such as a calcareous loess or till. cemented to indurated nodules with a diameter of 1 cm or Identifiable secondary carbonates either may disrupt the soil more. The cement is SiO2, presumably opal and structure or fabric, forming masses, nodules, concretions, or microcrystalline forms of silica. Durinodes break down in hot spheroidal aggregates (white eyes) that are soft and powdery concentrated KOH after treatment with HCl to remove when dry, or may be present as coatings in pores, on structural carbonates but do not break down with concentrated HCl alone. faces, or on the undersides of rock or pararock fragments. If Dry durinodes do not slake appreciably in water, but prolonged present as coatings, the secondary carbonates cover a soaking can result in spalling of very thin platelets. Durinodes significant part of the surfaces. Commonly, they coat all of the are firm or firmer and brittle when wet, both before and after surfaces to a thickness of 1 mm or more. If little calcium treatment with acid. Most durinodes are roughly concentric carbonate is present in the soil, however, the surfaces may be when viewed in cross section, and concentric stringers of opal only partially coated. The coatings must be thick enough to be are visible under a hand lens. visible when moist. Some horizons are entirely engulfed by 24 Keys to Soil Taxonomy
carbonates. The color of these horizons is largely determined horizon is not required above the uppermost lamella if the soil by the carbonates. The carbonates in these horizons are within is truncated.) the concept of identifiable secondary carbonates. Lamellae may meet the requirements for either a cambic or The filaments commonly seen in a dry calcareous horizon an argillic horizon. A combination of two or more lamellae 15 are within the meaning of identifiable secondary carbonates if cm or more thick is a cambic horizon if the texture is very fine the filaments are thick enough to be visible when the soil is sand, loamy very fine sand, or finer. A combination of two or moist. Filaments commonly branch on structural faces. more lamellae meets the requirements for an argillic horizon if there is 15 cm or more cumulative thickness of lamellae that Interfingering of Albic Materials are 0.5 cm or more thick and that have a clay content of either: 1. 3 percent or more (absolute) higher than in the overlying The term “interfingering of albic materials” refers to albic eluvial horizon (e.g., 13 percent versus 10 percent) if any part materials that penetrate 5 cm or more into an underlying of the eluvial horizon has less than 15 percent clay in the fine- argillic, kandic, or natric horizon along vertical and, to a lesser earth fraction; or degree, horizontal faces of peds. There need not be a continuous overlying albic horizon. The albic materials 2. 20 percent or more (relative) higher than in the overlying constitute less than 15 percent of the layer that they penetrate, eluvial horizon (e.g., 24 percent versus 20 percent) if all parts but they form continuous skeletans (ped coatings of clean silt of the eluvial horizon have more than 15 percent clay in the or sand defined by Brewer, 1976) 1 mm or more thick on the fine-earth fraction. vertical faces of peds, which means a total width of 2 mm or more between abutting peds. Because quartz is such a common constituent of silt and sand, these skeletans are usually light Linear Extensibility (LE) gray when moist and nearly white when dry, but their color is Linear extensibility (LE) helps to predict the potential of a determined in large part by the color of the sand or silt soil to shrink and swell. The LE of a soil layer is the product of fraction. the thickness, in cm, multiplied by the COLE of the layer in Required Characteristics question. The LE of a soil is the sum of these products for all soil horizons. Interfingering of albic materials is recognized if albic materials: Lithologic Discontinuities 1. Penetrate 5 cm or more into an underlying argillic or natric horizon; and Lithologic discontinuities are significant changes in particle-size distribution or mineralogy that represent 2. Are 2 mm or more thick between vertical faces of abutting differences in lithology within a soil. A lithologic discontinuity peds; and can also denote an age difference. For information on using 3. Constitute less than 15 percent (by volume) of the layer horizon designations for lithologic discontinuities, see the Soil that they penetrate. Survey Manual (USDA, SCS, 1993). Not everyone agrees on the degree of change required for a Lamellae lithologic discontinuity. No attempt is made to quantify lithologic discontinuities. The discussion below is meant to A lamella is an illuvial horizon less than 7.5 cm thick. Each serve as a guideline. lamella contains an accumulation of oriented silicate clay on or Several lines of field evidence can be used to evaluate bridging sand and silt grains (and rock fragments if any are lithologic discontinuities. In addition to mineralogical and present). A lamella has more silicate clay than the overlying textural differences that may require laboratory studies, certain eluvial horizon. observations can be made in the field. These include but are not limited to the following: Required Characteristics 1. Abrupt textural contacts.—An abrupt change in A lamella is an illuvial horizon less than 7.5 cm thick particle-size distribution, which is not solely a change in clay formed in unconsolidated regolith more than 50 cm thick. content resulting from pedogenesis, can often be observed. Each lamella contains an accumulation of oriented silicate clay 2. Contrasting sand sizes.—Significant changes in sand on or bridging the sand and silt grains (and coarse fragments if size can be detected. For example, if material containing any are present). Each lamella is required to have more silicate mostly medium sand or finer sand abruptly overlies material clay than the overlying eluvial horizon. containing mostly coarse sand and very coarse sand, one can Lamellae occur in a vertical series of two or more, and each assume that there are two different materials. Although the lamella must have an overlying eluvial horizon. (An eluvial materials may be of the same mineralogy, the contrasting sand Horizons and Characteristics Diagnostic for the Higher Categories 25
sizes result from differences in energy at the time of deposition 2. Data on a clay-free basis.—A common manipulation by water and/or wind. in assessing lithologic change is computation of sand and silt 3. Bedrock lithology vs. rock fragment lithology in the separates on a carbonate-free, clay-free basis (percent fraction, soil.—If a soil with rock fragments overlies a lithic contact, e.g., fine sand and very fine sand, divided by percent sand plus D one would expect the rock fragments to have a lithology silt, times 100). Clay distribution is subject to pedogenic I similar to that of the material below the lithic contact. If many change and may either mask inherited lithologic differences or A of the rock fragments do not have the same lithology as the produce differences that are not inherited from lithology. The underlying bedrock, the soil is not derived completely from the numerical array computed on a clay-free basis can be inspected underlying bedrock. visually or plotted as a function of depth. 4. Stone lines.—The occurrence of a horizontal line of Another aid used to assess lithologic changes is computation rock fragments in the vertical sequence of a soil indicates that of the ratios of one sand separate to another. The ratios can be the soil may have developed in more than one kind of parent computed and examined as a numerical array, or they can be material. The material above the stone line is most likely plotted. The ratios work well if sufficient quantities of the two transported, and the material below may be of different origin. fractions are available. Low quantities magnify changes in 5. Inverse distribution of rock fragments.—A lithologic ratios, especially if the denominator is low. discontinuity is often indicated by an erratic distribution of rock fragments. The percentage of rock fragments decreases n Value with increasing depth. This line of evidence is useful in areas of soils that have relatively unweathered rock fragments. The n value (Pons and Zonneveld, 1965) characterizes the 6. Rock fragment weathering rinds.—Horizons relation between the percentage of water in a soil under field containing rock fragments with no rinds that overlie horizons conditions and its percentages of inorganic clay and humus. containing rocks with rinds suggest that the upper material is The n value is helpful in predicting whether a soil can be in part depositional and not related to the lower part in time grazed by livestock or can support other loads and in and perhaps in lithology. predicting what degree of subsidence would occur after 7. Shape of rock fragments.—A soil with horizons drainage. containing angular rock fragments overlying horizons For mineral soil materials that are not thixotropic, the n containing well rounded rock fragments may indicate a value can be calculated by the following formula: discontinuity. This line of evidence represents different n = (A - 0.2R)/(L + 3H) mechanisms of transport (colluvial vs. alluvial) or even In this formula, A is the percentage of water in the soil in different transport distances. field condition, calculated on a dry-soil basis; R is the 8. Soil color.—Abrupt changes in color that are not the percentage of silt plus sand; L is the percentage of clay; and H result of pedogenic processes can be used as indicators of is the percentage of organic matter (percent organic carbon discontinuity. multiplied by 1.724). 9. Micromorphological features.—Marked differences in Few data for calculations of the n value are available in the the size and shape of resistant minerals in one horizon and not United States, but the critical n value of 0.7 can be in another are indicators of differences in materials. approximated closely in the field by a simple test of squeezing a soil sample in the hand. If the soil flows between the fingers Use of Laboratory Data with difficulty, the n value is between 0.7 and 1.0 (slightly fluid Discontinuities are not always readily apparent in the field. manner of failure class); if the soil flows easily between the In these cases laboratory data are necessary. Even with fingers, the n value is 1 or more (moderately fluid or very fluid laboratory data, detecting discontinuities may be difficult. The manner of failure class). decision is a qualitative or perhaps a partly quantitative judgment. General concepts of lithology as a function of depth Petroferric Contact might include: 1. Laboratory data—visual scan.—The array of A petroferric (Gr. petra, rock, and L. ferrum, iron; implying laboratory data is assessed in an attempt to determine if a field- ironstone) contact is a boundary between soil and a continuous designated discontinuity is corroborated and if any data show layer of indurated material in which iron is an important evidence of a discontinuity not observed in the field. One must cement and organic matter is either absent or present only in sort changes in lithology from changes caused by pedogenic traces. The indurated layer must be continuous within the processes. In most cases the quantities of sand and coarser limits of each pedon, but it may be fractured if the average fractions are not altered significantly by soil-forming processes. lateral distance between fractures is 10 cm or more. The fact Therefore, an abrupt change in sand size or sand mineralogy is that this ironstone layer contains little or no organic matter a clue to lithologic change. Gross soil mineralogy and the distinguishes it from a placic horizon and an indurated spodic resistant mineral suite are other clues. horizon (ortstein), both of which contain organic matter. 26 Keys to Soil Taxonomy
Several features can aid in making the distinction between a soils. The less common ones include sphene, rutile, zircon, lithic contact and a petroferric contact. First, a petroferric tourmaline, and beryl. contact is roughly horizontal. Second, the material directly below a petroferric contact contains a high amount of iron Slickensides
(normally 30 percent or more Fe2O3). Third, the ironstone sheets below a petroferric contact are thin; their thickness Slickensides are polished and grooved surfaces and ranges from a few centimeters to very few meters. Sandstone, generally have dimensions exceeding 5 cm. They are produced on the other hand, may be thin or very thick, may be level- when one soil mass slides past another. Some slickensides bedded or tilted, and may contain only a small percentage of occur at the lower boundary of a slip surface where a mass of
Fe2O3. In the Tropics, the ironstone is generally more or less soil moves downward on a relatively steep slope. Slickensides vesicular. result directly from the swelling of clay minerals and shear failure. They are very common in swelling clays that undergo Plinthite marked changes in moisture content. Plinthite (Gr. plinthos, brick) is an iron-rich, humus-poor Spodic Materials mixture of clay with quartz and other minerals. It commonly occurs as dark red redox concentrations that usually form platy, Spodic materials form in an illuvial horizon that normally polygonal, or reticulate patterns. Plinthite changes irreversibly underlies a histic, ochric, or umbric epipedon or an albic to an ironstone hardpan or to irregular aggregates on exposure horizon. In most undisturbed areas, spodic materials underlie to repeated wetting and drying, especially if it is also exposed an albic horizon. They may occur within an umbric epipedon to heat from the sun. The lower boundary of a zone in which or an Ap horizon. plinthite occurs generally is diffuse or gradual, but it may be A horizon consisting of spodic materials normally has an abrupt at a lithologic discontinuity. optical-density-of-oxalate-extract (ODOE) value of 0.25 or Generally, plinthite forms in a horizon that is saturated with more, and that value is commonly at least 2 times as high as water for some time during the year. Initially, iron is normally the ODOE value in an overlying eluvial horizon. This increase segregated in the form of soft, more or less clayey, red or dark in ODOE value indicates an accumulation of translocated red redox concentrations. These concentrations are not organic materials in an illuvial horizon. Soils with spodic considered plinthite unless there has been enough segregation materials show evidence that organic materials and aluminum, of iron to permit their irreversible hardening on exposure to with or without iron, have been moved from an eluvial horizon repeated wetting and drying. Plinthite is firm or very firm to an illuvial horizon. when the soil moisture content is near field capacity and hard Definition of Spodic Materials when the moisture content is below the wilting point. Plinthite does not harden irreversibly as a result of a single cycle of Spodic materials are mineral soil materials that do not have drying and rewetting. After a single drying, it will remoisten all of the properties of an argillic or kandic horizon; are and then can be dispersed in large part if one shakes it in water dominated by active amorphous materials that are illuvial and with a dispersing agent. are composed of organic matter and aluminum, with or without In a moist soil, plinthite is soft enough to be cut with a iron; and have both of the following: spade. After irreversible hardening, it is no longer considered 1. A pH value in water (1:1) of 5.9 or less and an organic- plinthite but is called ironstone. Indurated ironstone materials carbon content of 0.6 percent or more; and can be broken or shattered with a spade but cannot be dispersed if one shakes tham in water with a dispersing agent. 2. One or both of the following: a. An overlying albic horizon that extends horizontally Resistant Minerals through 50 percent or more of each pedon and, directly under the albic horizon, colors, moist (crushed and Several references are made to resistant minerals in this smoothed sample), as follows: taxonomy. Obviously, the stability of a mineral in the soil is a partial function of the soil moisture regime. Where resistant (1) Hue of 5YR or redder; or minerals are referred to in the definitions of diagnostic (2) Hue of 5YR, color value of 5 or less, and chroma horizons and of various taxa, a humid climate, past or present, of 4 or less; or is always assumed. Resistant minerals are durable minerals in the 0.02 to 2.0 (3) Hue of 10YR or neutral and a color value and mm fraction. Quartz is the most common resistant mineral in chroma of 2 or less; or Horizons and Characteristics Diagnostic for the Higher Categories 27
(4) A color of 10YR 3/1; or Characteristics Diagnostic for b. With or without an albic horizon and one of the colors listed above or hue of 7.5YR, color value, moist, of 5 or less, Organic Soils chroma of 5 or 6 (crushed and smoothed sample), and one Following is a description of the characteristics that are D or more of the following morphological or chemical used only with organic soils. I properties: A (1) Cementation by organic matter and aluminum, with Kinds of Organic Soil Materials or without iron, in 50 percent or more of each pedon and a very firm or firmer rupture-resistance class in the Three different kinds of organic soil materials are cemented part; or distinguished in this taxonomy, based on the degree of decomposition of the plant materials from which the organic (2) 10 percent or more cracked coatings on sand grains; materials are derived. The three kinds are (1) fibric, (2) hemic, or and (3) sapric. Because of the importance of fiber content in 1 (3) Aluminum plus /2 iron percentages (by ammonium the definitions of these materials, fibers are defined before the oxalate) totaling 0.50 or more, and half that amount or kinds of organic soil materials. less in an overlying umbric (or subhorizon of an umbric) epipedon, ochric epipedon, or albic horizon; or Fibers (4) An optical-density-of-oxalate-extract (ODOE) value Fibers are pieces of plant tissue in organic soil materials of 0.25 or more, and a value half as high or lower in an (excluding live roots) that: overlying umbric (or subhorizon of an umbric) epipedon, ochric epipedon, or albic horizon. 1. Are large enough to be retained on a 100-mesh sieve (openings 0.15 mm across) when the materials are screened; Weatherable Minerals and 2. Show evidence of the cellular structure of the plants from Several references are made to weatherable minerals in this which they are derived; and taxonomy. Obviously, the stability of a mineral in a soil is a partial function of the soil moisture regime. Where weatherable 3. Either are 2 cm or less in their smallest dimension or are minerals are referred to in the definitions of diagnostic decomposed enough to be crushed and shredded with the horizons and of various taxa in this taxonomy, a humid fingers. climate, either present or past, is always assumed. The Pieces of wood that are larger than 2 cm in cross section minerals that are included in the meaning of weatherable and are so undecomposed that they cannot be crushed and minerals are as follows: shredded with the fingers, such as large branches, logs, and 1. Clay minerals: All 2:1 lattice clays, except for one that is stumps, are not considered fibers but are considered coarse currently considered to be an aluminum-interlayered chlorite. fragments (comparable to gravel, stones, and boulders in Sepiolite, talc, and glauconite are also included in this group of mineral soils). weatherable clay minerals, although they are not everywhere of clay size. Fibric Soil Materials 2. Silt- and sand-sized minerals (0.02 to 0.2 mm in Fibric soil materials are organic soil materials that either: diameter): Feldspars, feldspathoids, ferromagnesian minerals, glass, micas, zeolites, and apatite. 1. Contain three-fourths or more (by volume) fibers after rubbing, excluding coarse fragments; or Obviously, this definition of the term “weatherable minerals” is restrictive. The intent is to include, in the 2. Contain two-fifths or more (by volume) fibers after definitions of diagnostic horizons and various taxa, only rubbing, excluding coarse fragments, and yield color values those weatherable minerals that are unstable in a humid and chromas of 7/1, 7/2, 8/1, 8/2, or 8/3 (fig. 2) on white climate compared to other minerals, such as quartz and 1:1 chromatographic or filter paper that is inserted into a paste lattice clays, but that are more resistant to weathering than made of the soil materials in a saturated sodium-pyrophosphate calcite. solution. 28 Keys to Soil Taxonomy
Hemic Soil Materials
Hemic soil materials (Gr. hemi, half; implying intermediate decomposition) are intermediate in their degree of decomposition between the less decomposed fibric and more decomposed sapric materials. Their morphological features give intermediate values for fiber content, bulk density, and water content. Hemic soil materials are partly altered both physically and biochemically.
Sapric Soil Materials
Sapric soil materials (Gr. sapros, rotten) are the most highly decomposed of the three kinds of organic soil materials. They have the smallest amount of plant fiber, the highest bulk density, and the lowest water content on a dry-weight basis at saturation. Sapric soil materials are commonly very dark gray to black. They are relatively stable; i.e., they change very little physically and chemically with time in comparison to other organic soil materials. Sapric materials have the following characteristics: 1. The fiber content, after rubbing, is less than one-sixth (by volume), excluding coarse fragments; and 2. The color of the sodium-pyrophosphate extract on white chromatographic or filter paper is below or to the right of a line drawn to exclude blocks 5/1, 6/2, and 7/3 (Munsell designations, fig. 2). If few or no fibers can be detected and the color of the pyrophosphate extract is to the left of or above this line, the possibility that the material is limnic must be considered.
Humilluvic Material
Humilluvic material, i.e., illuvial humus, accumulates in the Figure 2.—Value and chroma of pyrophosphate solution of fibric and sapric lower parts of some organic soils that are acid and have been materials. drained and cultivated. The humilluvic material has a C14 age that is not older than the overlying organic materials. It has very high solubility in sodium pyrophosphate and rewets very such as algae or diatoms, or (2) derived from underwater and slowly after drying. Most commonly, it accumulates near a floating aquatic plants and subsequently modified by aquatic contact with a sandy mineral horizon. animals. They include coprogenous earth (sedimentary peat), To be recognized as a differentia in classification, the diatomaceous earth, and marl. humilluvic material must constitute one-half or more (by volume) of a layer 2 cm or more thick. Coprogenous Earth A layer of coprogenous earth (sedimentary peat) is a limnic Limnic Materials layer that: The presence or absence of limnic deposits is taken into 1. Contains many fecal pellets with diameters between a few account in the higher categories of Histosols but not Histels. hundredths and a few tenths of a millimeter; and The nature of such deposits is considered in the lower 2. Has a color value, moist, of 4 or less; and categories of Histosols. Limnic materials include both organic and inorganic materials that were either (1) deposited in water 3. Either forms a slightly viscous water suspension and is by precipitation or through the action of aquatic organisms, nonplastic or slightly plastic but not sticky, or shrinks upon Horizons and Characteristics Diagnostic for the Higher Categories 29
drying, forming clods that are difficult to rewet and often tend the control section only if the water extends below a depth of to crack along horizontal planes; and 130 or 160 cm, respectively. A densic, lithic, or paralithic contact, if shallower than 130 or 160 cm, constitutes the lower 4. Either yields a saturated sodium-pyrophosphate extract on boundary of the control section. In some soils the lower white chromatographic or filter paper that has a color value of D boundary is 25 cm below the upper limit of permafrost. An 7 or more and chroma of 2 or less (fig. 2) or has a cation- I unconsolidated mineral substratum shallower than those exchange capacity of less than 240 cmol(+) per kg organic A limits does not change the lower boundary of the control matter (measured by loss on ignition), or both. section. Diatomaceous Earth The control section of Histosols and Histels is divided somewhat arbitrarily into three tiers—surface, subsurface, and A layer of diatomaceous earth is a limnic layer that: bottom tiers. 1. If not previously dried, has a matrix color value of 3, 4, or 5, which changes irreversibly on drying as a result of the Surface Tier irreversible shrinkage of organic-matter coatings on diatoms The surface tier of a Histosol or Histel extends from the soil (identifiable by microscopic, 440 X, examination of dry surface to a depth of 60 cm if either (1) the materials within samples); and that depth are fibric and three-fourths or more of the fiber 2. Either yields a saturated sodium-pyrophosphate extract on volume is derived from Sphagnum or other mosses or (2) the white chromatographic or filter paper that has a color value of materials have a bulk density of less than 0.1. Otherwise, the 8 or more and chroma of 2 or less or has a cation-exchange surface tier extends from the soil surface to a depth of 30 cm. capacity of less than 240 cmol(+) per kg organic matter (by Some organic soils have a mineral surface layer less than 40 loss on ignition), or both. cm thick as a result of flooding, volcanic eruptions, additions of mineral materials to increase soil strength or reduce the Marl hazard of frost, or other causes. If such a mineral layer is less than 30 cm thick, it constitutes the upper part of the surface A layer of marl is a limnic layer that: tier; if it is 30 to 40 cm thick, it constitutes the whole surface 1. Has a color value, moist, of 5 or more; and tier and part of the subsurface tier.
2. Reacts with dilute HCl to evolve CO2. The color of marl usually does not change irreversibly on Subsurface Tier drying because a layer of marl contains too little organic The subsurface tier is normally 60 cm thick. If the control matter, even before it has been shrunk by drying, to coat the section ends at a shallower depth (at a densic, lithic, or carbonate particles. paralithic contact or a water layer or in permafrost), however, the subsurface tier extends from the lower boundary of the Thickness of Organic Soil Materials surface tier to the lower boundary of the control section. It (Control Section of Histosols and Histels) includes any unconsolidated mineral layers that may be present within those depths. The thickness of organic materials over limnic materials, mineral materials, water, or permafrost is used to define the Bottom Tier Histosols and Histels. For practical reasons, an arbitrary control section has been The bottom tier is 40 cm thick unless the control section has established for the classification of Histosols and Histels. its lower boundary at a shallower depth (at a densic, lithic, or Depending on the kinds of soil material in the surface layer, paralithic contact or a water layer or in permafrost). the control section has a thickness of either 130 cm or 160 cm Thus, if the organic materials are thick, there are two from the soil surface if there is no densic, lithic, or paralithic possible thicknesses of the control section, depending on the contact, thick layer of water, or permafrost within the presence or absence and the thickness of a surface mantle of respective limit. The thicker control section is used if the fibric moss or other organic material that has a low bulk surface layer to a depth of 60 cm either contains three-fourths density (less than 0.1). If the fibric moss extends to a depth of or more fibers derived from Sphagnum, Hypnum, or other 60 cm and is the dominant material within this depth (three- mosses or has a bulk density of less than 0.1. Layers of water, fourths or more of the volume), the control section is 160 cm which may be between a few centimeters and many meters thick. If the fibric moss is thin or absent, the control section thick in these soils, are considered to be the lower boundary of extends to a depth of 130 cm. 30 Keys to Soil Taxonomy
a. Endosaturation.—The soil is saturated with water in all Horizons and Characteristics layers from the upper boundary of saturation to a depth of Diagnostic for Both Mineral and 200 cm or more from the mineral soil surface. Organic Soils b. Episaturation.—The soil is saturated with water in one or more layers within 200 cm of the mineral soil surface and Following are descriptions of the horizons and also has one or more unsaturated layers, with an upper characteristics that are diagnostic for both mineral and organic boundary above a depth of 200 cm, below the saturated soils. layer. The zone of saturation, i.e., the water table, is perched on top of a relatively impermeable layer. Aquic Conditions2 c. Anthric saturation.—This term refers to a special kind Soils with aquic (L. aqua, water) conditions are those that of aquic conditions that occur in soils that are cultivated and currently undergo continuous or periodic saturation and irrigated (flood irrigation). Soils with anthraquic conditions reduction. The presence of these conditions is indicated by must meet the requirements for aquic conditions and in redoximorphic features, except in Histosols and Histels, and addition have both of the following: can be verified by measuring saturation and reduction, except (1) A tilled surface layer and a directly underlying in artificially drained soils. Artificial drainage is defined here slowly permeable layer that has, for 3 months or more in as the removal of free water from soils having aquic conditions normal years, both: by surface mounding, ditches, or subsurface tiles to the extent that water table levels are changed significantly in connection (a) Saturation and reduction; and with specific types of land use. In the keys, artificially drained (b) Chroma of 2 or less in the matrix; and soils are included with soils that have aquic conditions. Elements of aquic conditions are as follows: (2) A subsurface horizon with one or more of the following: 1. Saturation is characterized by zero or positive pressure in the soil water and can generally be determined by observing (a) Redox depletions with a color value, moist, of 4 free water in an unlined auger hole. Problems may arise, or more and chroma of 2 or less in macropores; or however, in clayey soils with peds, where an unlined auger (b) Redox concentrations of iron; or hole may fill with water flowing along faces of peds while the soil matrix is and remains unsaturated (bypass flow). Such free (c) 2 times or more the amount of iron (by dithionite water may incorrectly suggest the presence of a water table, citrate) contained in the tilled surface layer. while the actual water table occurs at greater depth. Use of well 2. The degree of reduction in a soil can be characterized by sealed piezometers or tensiometers is therefore recommended the direct measurement of redox potentials. Direct for measuring saturation. Problems may still occur, however, if measurements should take into account chemical equilibria as water runs into piezometer slits near the bottom of the expressed by stability diagrams in standard soil textbooks. piezometer hole or if tensiometers with slowly reacting Reduction and oxidation processes are also a function of soil manometers are used. The first problem can be overcome by pH. Obtaining accurate measurements of the degree of using piezometers with smaller slits and the second by using reduction in a soil is difficult. In the context of this taxonomy, transducer tensiometry, which reacts faster than manometers. however, only a degree of reduction that results in reduced iron Soils are considered wet if they have pressure heads greater is considered, because it produces the visible redoximorphic than -1 kPa. Only macropores, such as cracks between peds or features that are identified in the keys. A simple field test is channels, are then filled with air, while the soil matrix is available to determine if reduced iron ions are present. A usually still saturated. Obviously, exact measurements of the freshly broken surface of a field-wet soil sample is treated with wet state can be obtained only with tensiometers. For alpha,alpha-dipyridyl in neutral, 1-normal ammonium-acetate operational purposes, the use of piezometers is recommended solution. The appearance of a strong red color on the freshly as a standard method. broken surface indicates the presence of reduced iron ions. A The duration of saturation required for creating aquic positive reaction to the alpha,alpha-dipyridyl field test for conditions varies, depending on the soil environment, and is ferrous iron (Childs, 1981) may be used to confirm the not specified. existence of reducing conditions and is especially useful in Three types of saturation are defined: situations where, despite saturation, normal morphological indicators of such conditions are either absent or obscured (as 2 In 1992, the term “aquic conditions” was introduced and other changes were made by the dark colors characteristic of melanic great groups). A throughout this taxonomy as a result of recommendations submitted to NRCS by the International Committee on Aquic Moisture Regime (ICOMAQ), which was established in negative reaction, however, does not imply that reducing 1982 and was chaired initially by Dr. Frank Moormann, then by Dr. Johan Bouma. conditions are always absent. It may only mean that the level of Horizons and Characteristics Diagnostic for the Higher Categories 31
free iron in the soil is below the sensitivity limit of the test or that of the adjacent matrix (often referred to as albans or that the soil is in an oxidized phase at the time of testing. Use neoalbans); and of alpha,alpha-dipyridyl in a 10 percent acetic-acid solution is (2) Clay depletions, i.e., zones that contain low not recommended because the acid is likely to change soil amounts of Fe, Mn, and clay (often referred to as silt D conditions, for example, by dissolving CaCO . 3 coatings or skeletans). I The duration of reduction required for creating aquic A conditions is not specified. c. Reduced matrix.—This is a soil matrix that has low chroma in situ but undergoes a change in hue or chroma 3. Redoximorphic features associated with wetness result within 30 minutes after the soil material has been exposed from alternating periods of reduction and oxidation of iron and to air. manganese compounds in the soil. Reduction occurs during saturation with water, and oxidation occurs when the soil is not d. In soils that have no visible redoximorphic features, a saturated. The reduced iron and manganese ions are mobile reaction to an alpha,alpha-dipyridyl solution satisfies the and may be transported by water as it moves through the soil. requirement for redoximorphic features. Certain redox patterns occur as a function of the patterns in Field experience indicates that it is not possible to define a which the ion-carrying water moves through the soil and as a specific set of redoximorphic features that is uniquely function of the location of aerated zones in the soil. Redox characteristic of all of the taxa in one particular category. patterns are also affected by the fact that manganese is reduced Therefore, color patterns that are unique to specific taxa are more rapidly than iron, while iron oxidizes more rapidly upon referenced in the keys. aeration. Characteristic color patterns are created by these Anthraquic conditions are a variant of episaturation and are processes. The reduced iron and manganese ions may be associated with controlled flooding (for such crops as wetland removed from a soil if vertical or lateral fluxes of water occur, rice and cranberries), which causes reduction processes in the in which case there is no iron or manganese precipitation in saturated, puddled surface soil and oxidation of reduced and that soil. Wherever the iron and manganese are oxidized and mobilized iron and manganese in the unsaturated subsoil. precipitated, they form either soft masses or hard concretions or nodules. Movement of iron and manganese as a result of redox processes in a soil may result in redoximorphic features Cryoturbation that are defined as follows: Cryoturbation (frost churning) is the mixing of the soil a. Redox concentrations.—These are zones of apparent matrix within the pedon that results in irregular or broken accumulation of Fe-Mn oxides, including: horizons, involutions, accumulation of organic matter on the permafrost table, oriented rock fragments, and silt caps on rock (1) Nodules and concretions, which are cemented fragments. bodies that can be removed from the soil intact. Concretions are distinguished from nodules on the basis of internal organization. A concretion typically has Densic Contact concentric layers that are visible to the naked eye. A densic contact (L. densus, thick) is a contact between Nodules do not have visible organized internal structure. soil and densic materials (defined below). It has no cracks, Boundaries commonly are diffuse if formed in situ and or the spacing of cracks that roots can enter is 10 cm or sharp after pedoturbation. Sharp boundaries may be relict more. features in some soils; and (2) Masses, which are noncemented concentrations of Densic Materials substances within the soil matrix; and Densic materials are relatively unaltered materials (do not (3) Pore linings, i.e., zones of accumulation along pores meet the requirements for any other named diagnostic horizons that may be either coatings on pore surfaces or or any other diagnostic soil characteristic) that have a impregnations from the matrix adjacent to the pores. noncemented rupture-resistance class. The bulk density or the organization is such that roots cannot enter, except in cracks. b. Redox depletions.—These are zones of low chroma These are mostly earthy materials, such as till, volcanic (chromas less than those in the matrix) where either Fe-Mn mudflows, and some mechanically compacted materials, for oxides alone or both Fe-Mn oxides and clay have been example, mine spoils. Some noncemented rocks can be densic stripped out, including: materials if they are dense or resistant enough to keep roots (1) Iron depletions, i.e., zones that contain low amounts from entering, except in cracks. of Fe and Mn oxides but have a clay content similar to Densic materials are noncemented and thus differ from 32 Keys to Soil Taxonomy
paralithic materials and the material below a lithic contact, Paralithic Contact both of which are cemented. Densic materials have, at their upper boundary, a densic A paralithic (lithiclike) contact is a contact between soil and contact if they have no cracks or if the spacing of cracks that paralithic materials (defined below) where the paralithic roots can enter is 10 cm or more. These materials can be used materials have no cracks or the spacing of cracks that roots can to differentiate soil series if the materials are within the series enter is 10 cm or more. control section. Paralithic Materials Gelic Materials Paralithic materials are relatively unaltered materials (do Gelic materials are mineral or organic soil materials that not meet the requirements for any other named diagnostic show evidence of cryoturbation (frost churning) and/or ice horizons or any other diagnostic soil characteristic) that have segregation in the active layer (seasonal thaw layer) and/or the an extremely weakly cemented to moderately cemented upper part of the permafrost. Cryoturbation is manifested by rupture-resistance class. Cementation, bulk density, and the irregular and broken horizons, involutions, accumulation of organization are such that roots cannot enter, except in cracks. organic matter on top of and within the permafrost, oriented Paralithic materials have, at their upper boundary, a paralithic rock fragments, and silt-enriched layers. The characteristic contact if they have no cracks or if the spacing of cracks that structures associated with gelic materials include platy, blocky, roots can enter is 10 cm or more. Commonly, these materials or granular macrostructures; the structural results of sorting; are partially weathered bedrock or weakly consolidated and orbiculic, conglomeric, banded, or vesicular microfabrics. bedrock, such as sandstone, siltstone, or shale. Paralithic Ice segregation is manifested by ice lenses, vein ice, segregated materials can be used to differentiate soil series if the materials ice crystals, and ice wedges. Cryopedogenic processes that lead are within the series control section. Fragments of paralithic to gelic materials are driven by the physical volume change of materials 2.0 mm or more in diameter are referred to as water to ice, moisture migration along a thermal gradient in pararock fragments. the frozen system, or thermal contraction of the frozen material by continued rapid cooling. Permafrost Glacic Layer Permafrost is defined as a thermal condition in which a material (including soil material) remains below 0 oC for 2 or A glacic layer is massive ice or ground ice in the form of ice more years in succession. Those gelic materials having lenses or wedges. The layer is 30 cm or more thick and permafrost contain the unfrozen soil solution that drives contains 75 percent or more visible ice. cryopedogenic processes. Permafrost may be cemented by ice or, in the case of insufficient interstitial water, may be dry. The Lithic Contact frozen layer has a variety of ice lenses, vein ice, segregated ice crystals, and ice wedges. The permafrost table is in dynamic A lithic contact is the boundary between soil and a coherent equilibrium with the environment. underlying material. Except in Ruptic-Lithic subgroups, the underlying material must be virtually continuous within the Soil Moisture Regimes limits of a pedon. Cracks that can be penetrated by roots are few, and their horizontal spacing is 10 cm or more. The The term “soil moisture regime” refers to the presence or underlying material must be sufficiently coherent when moist absence either of ground water or of water held at a tension of to make hand-digging with a spade impractical, although the less than 1500 kPa in the soil or in specific horizons during material may be chipped or scraped with a spade. The material periods of the year. Water held at a tension of 1500 kPa or below a lithic contact must be in a strongly cemented or more more is not available to keep most mesophytic plants alive. The cemented rupture-resistance class. Commonly, the material is availability of water is also affected by dissolved salts. If a soil indurated. The underlying material considered here does not is saturated with water that is too salty to be available to most include diagnostic soil horizons, such as a duripan or a plants, it is considered salty rather than dry. Consequently, a petrocalcic horizon. horizon is considered dry when the moisture tension is 1500 A lithic contact is diagnostic at the subgroup level if it kPa or more and is considered moist if water is held at a is within 125 cm of the mineral soil surface in Oxisols and tension of less than 1500 kPa but more than zero. A soil may within 50 cm of the mineral soil surface in all other mineral be continuously moist in some or all horizons either throughout soils. In organic soils the lithic contact must be within the the year or for some part of the year. It may be either moist in control section to be recognized at the subgroup level. winter and dry in summer or the reverse. In the Northern Horizons and Characteristics Diagnostic for the Higher Categories 33
Hemisphere, summer refers to June, July, and August and Classes of Soil Moisture Regimes winter refers to December, January, and February. The soil moisture regimes are defined in terms of the level Normal Years of ground water and in terms of the seasonal presence or absence of water held at a tension of less than 1500 kPa in the D In the discussions that follow and throughout the keys, the moisture control section. It is assumed in the definitions that I term “normal years” is used. A normal year is defined as a year the soil supports whatever vegetation it is capable of A that has plus or minus one standard deviation of the long-term supporting, i.e., crops, grass, or native vegetation, and that the mean annual precipitation. (Long-term refers to 30 years or amount of stored moisture is not being increased by irrigation more.) Also, the mean monthly precipitation during a normal or fallowing. These cultural practices affect the soil moisture year must be plus or minus one standard deviation of the long- conditions as long as they are continued. term monthly precipitation for 8 of the 12 months. For the Aquic moisture regime.—The aquic (L. aqua, water) most part, normal years can be calculated from the mean moisture regime is a reducing regime in a soil that is virtually annual precipitation. When catastrophic events occur during a free of dissolved oxygen because it is saturated by water. Some year, however, the standard deviations of the monthly means soils are saturated with water at times while dissolved oxygen should also be calculated. The term “normal years” replaces is present, either because the water is moving or because the the terms “most years” and “6 out of 10 years,” which were environment is unfavorable for micro-organisms (e.g., if the used in the 1975 edition of Soil Taxonomy (USDA, SCS, temperature is less than 1 oC); such a regime is not considered 1975). aquic. It is not known how long a soil must be saturated before it is Soil Moisture Control Section said to have an aquic moisture regime, but the duration must The intent in defining the soil moisture control section is to be at least a few days, because it is implicit in the concept that facilitate estimation of soil moisture regimes from climatic dissolved oxygen is virtually absent. Because dissolved oxygen data. The upper boundary of this control section is the depth to is removed from ground water by respiration of micro- which a dry (tension of more than 1500 kPa, but not air-dry) organisms, roots, and soil fauna, it is also implicit in the soil will be moistened by 2.5 cm of water within 24 hours. The concept that the soil temperature is above biologic zero for lower boundary is the depth to which a dry soil will be some time while the soil is saturated. Biologic zero is defined moistened by 7.5 cm of water within 48 hours. These depths do as 5 oC in this taxonomy. In some of the very cold regions of not include the depth of moistening along any cracks or animal the world, however, biological activity occurs at temperatures burrows that are open to the surface. below 5 oC. If 7.5 cm of water moistens the soil to a densic, lithic, Very commonly, the level of ground water fluctuates with paralithic, or petroferric contact or to a petrocalcic or the seasons; it is highest in the rainy season or in fall, winter, petrogypsic horizon or a duripan, the contact or the upper or spring if cold weather virtually stops evapotranspiration. boundary of the cemented horizon constitutes the lower There are soils, however, in which the ground water is always boundary of the soil moisture control section. If a soil is at or very close to the surface. Examples are soils in tidal moistened to one of these contacts or horizons by 2.5 cm of marshes or in closed, landlocked depressions fed by perennial water, the soil moisture control section is the boundary or the streams. Such soils are considered to have a peraquic moisture contact itself. The control section of such a soil is considered regime. moist if the contact or upper boundary of the cemented horizon Aridic and torric (L. aridus, dry, and L. torridus, hot and has a thin film of water. If that upper boundary is dry, the dry) moisture regimes.—These terms are used for the same control section is considered dry. moisture regime but in different categories of the taxonomy. The moisture control section of a soil extends approximately In the aridic (torric) moisture regime, the moisture control (1) from 10 to 30 cm below the soil surface if the particle-size section is, in normal years: class of the soil is fine-loamy, coarse-silty, fine-silty, or clayey; (2) from 20 to 60 cm if the particle-size class is coarse-loamy; 1. Dry in all parts for more than half of the cumulative days and (3) from 30 to 90 cm if the particle-size class is sandy. If per year when the soil temperature at a depth of 50 cm from o the soil contains rock and pararock fragments that do not the soil surface is above 5 C; and absorb and release water, the limits of the moisture control 2. Moist in some or all parts for less than 90 consecutive days section are deeper. The limits of the soil moisture control when the soil temperature at a depth of 50 cm is above 8 oC. section are affected not only by the particle-size class but also by differences in soil structure or pore-size distribution or by Soils that have an aridic (torric) moisture regime normally other factors that influence the movement and retention of occur in areas of arid climates. A few are in areas of semiarid water in the soil. climates and either have physical properties that keep them 34 Keys to Soil Taxonomy
dry, such as a crusty surface that virtually precludes the If the mean annual soil temperature is lower than 22 oC and infiltration of water, or are on steep slopes where runoff is if the mean summer and winter soil temperatures differ by 6 oC high. There is little or no leaching in this moisture regime, and or more at a depth of 50 cm from the soil surface, the soil soluble salts accumulate in the soils if there is a source. moisture control section in areas of the ustic moisture regime is The limits set for soil temperature exclude from these dry in some or all parts for 90 or more cumulative days in moisture regimes soils in the very cold and dry polar regions normal years, but it is not dry in all parts for more than half of and in areas at high elevations. Such soils are considered to the cumulative days when the soil temperature at a depth of 50 have anhydrous conditions (defined earlier). cm is higher than 6 oC. If in normal years the moisture control Udic moisture regime.—The udic (L. udus, humid) section is moist in all parts for 45 or more consecutive days in moisture regime is one in which the soil moisture control the 4 months following the winter solstice, the moisture control section is not dry in any part for as long as 90 cumulative days section is dry in all parts for less than 45 consecutive days in in normal years. If the mean annual soil temperature is lower the 4 months following the summer solstice. than 22 oC and if the mean winter and mean summer soil In tropical and subtropical regions that have a monsoon temperatures at a depth of 50 cm from the soil surface differ by climate with either one or two dry seasons, summer and winter 5 oC or more, the soil moisture control section, in normal seasons have little meaning. In those regions the moisture years, is dry in all parts for less than 45 consecutive days in the regime is ustic if there is at least one rainy season of 3 months 4 months following the summer solstice. In addition, the udic or more. In temperate regions of subhumid or semiarid moisture regime requires, except for short periods, a three- climates, the rainy seasons are usually spring and summer or phase system, solid-liquid-gas, in part or all of the soil spring and fall, but never winter. Native plants are mostly moisture control section when the soil temperature is above annuals or plants that have a dormant period while the soil is 5 oC. dry. The udic moisture regime is common to the soils of humid Xeric moisture regime.—The xeric (Gr. xeros, dry) climates that have well distributed rainfall; have enough rain moisture regime is the typical moisture regime in areas of in summer so that the amount of stored moisture plus rainfall Mediterranean climates, where winters are moist and cool and is approximately equal to, or exceeds, the amount of summers are warm and dry. The moisture, which falls during evapotranspiration; or have adequate winter rains to recharge the winter, when potential evapotranspiration is at a minimum, the soils and cool, foggy summers, as in coastal areas. Water is particularly effective for leaching. In areas of a xeric moves downward through the soils at some time in normal moisture regime, the soil moisture control section, in normal years. years, is dry in all parts for 45 or more consecutive days in the In climates where precipitation exceeds evapotranspiration 4 months following the summer solstice and moist in all parts in all months of normal years, the moisture tension rarely for 45 or more consecutive days in the 4 months following the reaches 100 kPa in the soil moisture control section, although winter solstice. Also, in normal years, the moisture control there are occasional brief periods when some stored moisture is section is moist in some part for more than half of the used. The water moves through the soil in all months when it cumulative days per year when the soil temperature at a depth is not frozen. Such an extremely wet moisture regime is called of 50 cm from the soil surface is higher than 6 oC or for 90 or perudic (L. per, throughout in time, and L. udus, humid). In more consecutive days when the soil temperature at a depth of the names of most taxa, the formative element “ud” is used to 50 cm is higher than 8 oC. The mean annual soil temperature is indicate either a udic or a perudic regime; the formative lower than 22 oC, and the mean summer and mean winter soil element “per” is used in selected taxa. temperatures differ by 6 oC or more either at a depth of 50 cm Ustic moisture regime.—The ustic (L. ustus, burnt; from the soil surface or at a densic, lithic, or paralithic contact implying dryness) moisture regime is intermediate between the if shallower. aridic regime and the udic regime. Its concept is one of moisture that is limited but is present at a time when Soil Temperature Regimes conditions are suitable for plant growth. The concept of the ustic moisture regime is not applied to soils that have Classes of Soil Temperature Regimes permafrost or a cryic soil temperature regime (defined below). Following is a description of the soil temperature regimes If the mean annual soil temperature is 22 oC or higher or if used in defining classes at various categoric levels in this the mean summer and winter soil temperatures differ by less taxonomy. than 6 oC at a depth of 50 cm below the soil surface, the soil Cryic (Gr. kryos, coldness; meaning very cold soils).— moisture control section in areas of the ustic moisture regime is Soils in this temperature regime have a mean annual dry in some or all parts for 90 or more cumulative days in temperature lower than 8 oC but do not have permafrost. normal years. It is moist, however, in some part either for more than 180 cumulative days per year or for 90 or more 1. In mineral soils the mean summer soil temperature (June, consecutive days. July, and August in the Northern Hemisphere and December, Horizons and Characteristics Diagnostic for the Higher Categories 35
January, and February in the Southern Hemisphere) either at a Isomesic.—The mean annual soil temperature is 8 oC or depth of 50 cm from the soil surface or at a densic, lithic, or higher but lower than 15 oC. paralithic contact, whichever is shallower, is as follows: Isothermic.—The mean annual soil temperature is 15 oC or higher but lower than 22 oC. a. If the soil is not saturated with water during some part D Isohyperthermic.—The mean annual soil temperature is I of the summer and o 22 C or higher. A (1) If there is no O horizon: lower than 15 oC; or (2) If there is an O horizon: lower than 8 oC; or Sulfidic Materials b. If the soil is saturated with water during some part of Sulfidic materials contain oxidizable sulfur compounds. the summer and They are mineral or organic soil materials that have a pH value of more than 3.5 and that, if incubated as a layer (1) If there is no O horizon: lower than 13 oC; or 1 cm thick under moist aerobic conditions (field capacity) (2) If there is an O horizon or a histic epipedon: lower at room temperature, show a drop in pH of 0.5 or more than 6 oC. units to a pH value of 4.0 or less (1:1 by weight in water or in a minimum of water to permit measurement) within 8 2. In organic soils the mean annual soil temperature is lower weeks. than 6 oC. Sulfidic materials accumulate as a soil or sediment that is Cryic soils that have an aquic moisture regime commonly permanently saturated, generally with brackish water. The are churned by frost. sulfates in the water are biologically reduced to sulfides as the Isofrigid soils could also have a cryic temperature regime. A materials accumulate. Sulfidic materials most commonly few with organic materials in the upper part are exceptions. accumulate in coastal marshes near the mouth of rivers that The concepts of the soil temperature regimes described carry noncalcareous sediments, but they may occur in below are used in defining classes of soils in the low freshwater marshes if there is sulfur in the water. Upland categories. sulfidic materials may have accumulated in a similar manner Frigid.—A soil with a frigid temperature regime is in the geologic past. warmer in summer than a soil with a cryic regime, but its If a soil containing sulfidic materials is drained or if sulfidic mean annual temperature is lower than 8 oC and the difference materials are otherwise exposed to aerobic conditions, the between mean summer (June, July, and August) and mean sulfides oxidize and form sulfuric acid. The pH value, which winter (December, January, and February) soil temperatures is normally is near neutrality before drainage or exposure, may more than 6 oC either at a depth of 50 cm from the soil surface drop below 3. The acid may induce the formation of iron and or at a densic, lithic, or paralithic contact, whichever is aluminum sulfates. The iron sulfate, jarosite, may segregate, shallower. forming the yellow redoximorphic concentrations that Mesic.—The mean annual soil temperature is 8 oC or commonly characterize a sulfuric horizon. The transition from higher but lower than 15 oC, and the difference between mean sulfidic materials to a sulfuric horizon normally requires very summer and mean winter soil temperatures is more than 6 oC few years and may occur within a few weeks. A sample of either at a depth of 50 cm from the soil surface or at a densic, sulfidic materials, if air-dried slowly in shade for about 2 lithic, or paralithic contact, whichever is shallower. months with occasional remoistening, becomes extremely Thermic.—The mean annual soil temperature is 15 oC or acid. higher but lower than 22 oC, and the difference between mean summer and mean winter soil temperatures is more than 6 oC Sulfuric Horizon either at a depth of 50 cm from the soil surface or at a densic, lithic, or paralithic contact, whichever is shallower. Required Characteristics Hyperthermic.—The mean annual soil temperature is The sulfuric (L. sulfur) horizon is 15 cm or more thick and 22 oC or higher, and the difference between mean summer and is composed of either mineral or organic soil material that has mean winter soil temperatures is more than 6 oC either at a a pH value of 3.5 or less (1:1 by weight in water or in a depth of 50 cm from the soil surface or at a densic, lithic, or minimum of water to permit measurement) and shows evidence paralithic contact, whichever is shallower. that the low pH value is caused by sulfuric acid. The evidence If the name of a soil temperature regime has the prefix iso, is one or more of the following: the mean summer and mean winter soil temperatures differ by less than 6 oC at a depth of 50 cm or at a densic, lithic, or 1. Jarosite concentrations; or paralithic contact, whichever is shallower. 2. Directly underlying sulfidic materials (defined above); or Isofrigid.—The mean annual soil temperature is lower than 8 oC. 3. 0.05 percent or more water-soluble sulfate. 36
Deposits and a Classification of the Resulting Soils. Int. Inst. Literature Cited Land Reclam. and Impr. Pub. 13. Wageningen, The Brewer, R. 1976. Fabric and Mineral Analysis of Soils. Netherlands. Second edition. John Wiley and Sons, Inc. New York, New United States Department of Agriculture, Soil Conservation York. Service. 1975. Soil Taxonomy: A Basic System of Soil Childs, C.W. 1981. Field Test for Ferrous Iron and Ferric- Classification for Making and Interpreting Soil Surveys. Soil Organic Complexes (on Exchange Sites or in Water-Soluble Surv. Staff. U.S. Dep. Agric. Handb. 436. Forms) in Soils. Austr. J. of Soil Res. 19: 175-180. United States Department of Agriculture, Soil Conservation Pons, L.J., and I.S. Zonneveld. 1965. Soil Ripening Service. 1993. Soil Survey Manual. Soil Surv. Div. Staff. U.S. and Soil Classification. Initial Soil Formation in Alluvial 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 sections for classes used as components of a family must be by using the keys that follow in this and other chapters. It is used to determine the control section before use of the keys to assumed that the reader is familiar with the definitions of classes. diagnostic horizons and properties that are given in chapters 2 The descriptions and definitions of individual soil series are and 3 of this publication and with the meanings of the terms not included in this text. Definitions of the series and of the used for describing soils given in the Soil Survey Manual. The control section are given in chapter 17. Index at the back of this publication indicates the pages on In the “Key to Soil Orders” and the other keys that follow, which definitions of terms are given. the diagnostic horizons and the properties mentioned do not Standard rounding conventions should be used to determine include those below any densic, lithic, paralithic, or petroferric numerical values. contact. The properties of buried soils and the properties of a Soil colors (hue, value, and chroma) are used in many of surface mantle are considered on the basis of whether or not the criteria that follow. Soil colors typically change value and the soil meets the meaning of the term “buried soil” given in some change hue and chroma, depending on the water state. chapter 1. In many of the criteria of the keys, the water state is specified. If a soil has a surface mantle and is not a buried soil, the top If no water state is specified, the soil is considered to meet of the original surface layer is considered the “soil surface” for the criterion if it does so when moist or dry or both moist and determining depth to and thickness of diagnostic horizons and dry. most other diagnostic soil characteristics. The only properties All of the keys in this taxonomy are designed in such a way of the surface mantle that are considered are soil temperature, that the user can determine the correct classification of a soil soil moisture (including aquic conditions), and any andic or by going through the keys systematically. The user must start at vitrandic properties. the beginning of the “Key to Soil Orders” and eliminate, one If a soil profile includes a buried soil, the present soil by one, all classes that include criteria that do not fit the soil in surface is used to determine soil moisture and temperature as question. The soil belongs to the first class listed for which it well as depth to and thickness of diagnostic horizons and other meets all the required criteria. diagnostic soil characteristics. Diagnostic horizons of the In classifying a specific soil, the user of soil taxonomy buried soil are not considered in selecting taxa unless the begins by checking through the “Key to Soil Orders” to criteria in the keys specifically indicate buried horizons, such determine the name of the first order that, according to the as in Thapto-Histic subgroups. Most other diagnostic soil criteria listed, includes the soil in question. The next step is characteristics of the buried soil are not considered, but organic to go to the page indicated to find the “Key to Suborders” of carbon if of Holocene age, andic soil properties, base that particular order. Then the user systematically goes through saturation, and all properties used to determine family and the key to identify the suborder that includes the soil, i.e., the series placement are considered. first in the list for which it meets all the required criteria. The same procedure is used to find the great group class of the soil in the “Key to Great Groups” of the identified suborder. Key to Soil Orders Likewise, going through the “Key to Subgroups” of that great A. Soils that have: group, the user selects as the correct subgroup name the name of the first taxon for which the soil meets all of the required 1. Permafrost within 100 cm of the soil surface; or criteria. 2. Gelic materials within 100 cm of the soil surface and The family level is determined, in a similar manner, after permafrost within 200 cm of the soil surface. the subgroup has been determined. Chapter 17 can be used, Gelisols, p. 149 as one would use other keys in this taxonomy, to determine which components are part of the family. The family, B. Other soils that: however, typically has more than one component, and therefore the entire chapter must be used. The keys to control 1. Do not have andic soil properties in 60 percent or more 38 Keys to Soil Taxonomy
of the thickness between the soil surface and either a depth (4) A coarse-loamy, loamy-skeletal, or finer particle- of 60 cm or a densic, lithic, or paralithic contact or duripan size class and a frigid temperature regime in the soil; if shallower; and or 2. Have organic soil materials that meet one or more of (5) A cryic temperature regime in the soil; and the 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 b. When added with the underlying cindery, soil surface and the spodic horizon; and fragmental, 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 (1) Either at a depth of 25 cm or more below the of the soil to a densic, lithic, or paralithic contact and mineral soil surface or at the top of a duripan or have no mineral horizons or have mineral horizons with fragipan or at a densic, lithic, paralithic, or petroferric a total thickness of 10 cm or less; or contact, whichever is shallowest; or d. Are saturated with water for 30 days or more per (2) At any depth, year in normal years (or are artificially drained), have an (a) If the spodic horizon has a coarse-loamy, upper boundary within 40 cm of the soil surface, and loamy-skeletal, or finer particle-size class and the have a total 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 hemic materials, or of fibric materials with less than or 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 C. Other soils that do not have a plaggen epipedon or an surface or of the top of an organic layer with andic argillic or kandic horizon above a spodic horizon, and have soil properties, whichever is shallower, if there is one or more of the following: no 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. 249 characteristics: a. One or more of the following: D. Other soils that have andic soil properties in 60 percent or 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 (3) Cementation in 50 percent or more of each is shallower, if there is no densic, lithic, or paralithic pedon; or contact, duripan, or petrocalcic horizon within that depth; or 1 Materials that meet the definition of cindery, fragmental, or pumiceous but have more than 10 percent, by volume, voids that are filled with organic soil materials are considered to be 2. Between either the mineral soil surface or the top of an organic soil materials. organic layer with andic soil properties, whichever is Identification of the Taxonomic Class of a Soil 39
shallower, and a densic, lithic, or paralithic contact, a a. Saturation with water in one or more layers within duripan, or a petrocalcic horizon. 100 cm of the soil surface for 1 month or more during a Andisols, p. 83 normal year; and b. A moisture control section that is dry in some or all E. Other soils that have either: parts at some time during normal years; and 1. An oxic horizon that has its upper boundary within 150 c. No sulfuric horizon that has its upper boundary cm of the mineral soil surface and no kandic horizon that I within 150 cm of the mineral soil surface. has its upper boundary within that depth; or D Aridisols, p. 103 E 2. 40 percent or more (by weight) clay in the fine-earth fraction between the mineral soil surface and a depth of 18 H. Other soils that have either: cm (after mixing) and a kandic horizon that has the 1. An argillic or kandic horizon, but no fragipan, and a weatherable-mineral properties of an oxic horizon and has base saturation (by sum of cations) of less than 35 percent at its upper boundary within 100 cm of the mineral soil one of the following depths: surface. Oxisols, p. 233 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 horizon (but no deeper than 200 cm below the mineral 1. A layer 25 cm or more thick, with an upper boundary soil surface) or 180 cm below the mineral soil surface, within 100 cm of the mineral soil surface, that has either whichever is deeper; or slickensides or wedge-shaped peds that have their long axes tilted 10 to 60 degrees from the horizontal; and (2) At a densic, lithic, paralithic, or petroferric contact if shallower; or 2. A weighted average of 30 percent or more clay in the fine-earth fraction either between the mineral soil surface b. The shallowest of the following depths: and a depth of 18 cm or in an Ap horizon, whichever is (1) 125 cm below the upper boundary of the argillic thicker, and 30 percent or more clay in the fine-earth or kandic horizon; or fraction of all horizons between a depth of 18 cm and either a depth of 50 cm or a densic, lithic, or paralithic contact, a (2) 180 cm below the mineral soil surface; or duripan, or a petrocalcic horizon if shallower; and (3) At a densic, lithic, paralithic, or petroferric 3. Cracks2 that open and close periodically. contact; or Vertisols, p. 281 2. A fragipan and both of the following: G. Other soils that: a. Either an argillic or a kandic horizon above, within, or below it or clay films 1 mm or more thick in one or 1. Have: 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 (1) 75 cm below the upper boundary of the fragipan; boundary within 100 cm of the soil surface: a cambic or horizon with a lower depth of 25 cm or more; a cryic (2) 200 cm below the mineral soil surface; or temperature regime and a cambic horizon; a calcic, gypsic, petrocalcic, petrogypsic, or salic horizon; or a (3) At a densic, lithic, paralithic, or petroferric duripan; or contact. Ultisols, p. 259 d. An argillic or natric horizon; or 2. Have a salic horizon; and I. Other soils that have both of the following: 1. Either: 2 A crack is a separation between gross polyhedrons. If the surface is strongly self- mulching, i.e., a mass of granules, or if the soil is cultivated while cracks are open, the cracks a. A mollic epipedon; or 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 and b. Both a surface horizon that meets all the percolation of water in a dry, clayey soil. requirements for a mollic epipedon except thickness after 40
the soil has been mixed to a depth of 18 cm and a within a depth of 100 cm of the mineral soil surface; subhorizon more than 7.5 cm thick, within the upper part or of an argillic, kandic, or natric horizon, that meets the c. A fragipan or an oxic, sombric, or spodic horizon color, organic-carbon content, base saturation, and with an upper boundary within 200 cm of the mineral structure requirements of a mollic epipedon but is soil surface; or separated from the surface horizon by an albic horizon; and d. A sulfuric horizon that has its upper boundary within 150 cm of the mineral soil surface; or 2. A base saturation of 50 percent or more (by NH4OAc) in all horizons either between the upper boundary of any e. A cryic temperature regime and a cambic horizon; argillic, kandic, or natric horizon and a depth of 125 cm or below that boundary, or between the mineral soil surface 2. No sulfidic materials within 50 cm of the mineral soil and a depth of 180 cm, or between the mineral soil surface surface; and both: and a densic, lithic, or paralithic contact, whichever depth is shallowest. a. In one or more horizons between 20 and 50 cm Mollisols, p. 191 below the mineral soil surface, either an n value of 0.7 or less or less than 8 percent clay in the fine-earth fraction; J. Other soils that do not have a plaggen epipedon and that and have either: b. One or both of the following: 1. An argillic, kandic, or natric horizon; or (1) A salic horizon or a histic, mollic, plaggen, or 2. A fragipan that has clay films 1 mm or more thick in umbric epipedon; or some part. (2) In 50 percent or more of the layers between the Alfisols, p. 41 mineral soil surface and a depth of 50 cm, an exchangeable sodium percentage of 15 or more (or a K. Other soils that have either: sodium adsorption ratio of 13 or more), which 1. One or more of the following: decreases with increasing depth below 50 cm, and also ground water within 100 cm of the mineral soil a. A cambic horizon with its upper boundary within surface at some time during the year when the soil is 100 cm of the mineral soil surface and its lower boundary not frozen in any part. at a depth of 25 cm or more below the mineral soil Inceptisols, p. 165 surface; or b. A calcic, petrocalcic, gypsic, petrogypsic, or L. Other soils. placic horizon or a duripan with an upper boundary Entisols, p. 129 41
CHAPTER 5 Alfisols
Key to Suborders A L JA. Alfisols that have, in one or more horizons within 50 cm F of the mineral soil surface, aquic conditions (other than anthraquic conditions) for some time in normal years (or artificial drainage) and have one or both of the following: 1. Redoximorphic features in all layers between either the lower boundary of an Ap horizon or a depth of 25 cm below the mineral soil surface, whichever is deeper, and a depth of 40 cm; and one of the following within the upper 12.5 cm of the argillic, natric, glossic, or kandic horizon: a. 50 percent or more redox depletions with chroma of JAB. Other Aqualfs that have one or more horizons, at a 2 or less on faces of peds and redox concentrations depth between 30 and 150 cm from the mineral soil surface, in within peds; or which plinthite either forms a continuous phase or constitutes b. Redox concentrations and 50 percent or more redox one-half or more of the volume. depletions with chroma of 2 or less in the matrix; or Plinthaqualfs, p. 50 c. 50 percent or more redox depletions with chroma of JAC. Other Aqualfs that have a duripan. 1 or less on faces of peds or in the matrix, or both; or Duraqualfs, p. 43 2. In the horizons that have aquic conditions, enough active ferrous iron to give a positive reaction to alpha,alpha- JAD. Other Aqualfs that have a natric horizon. dipyridyl at a time when the soil is not being irrigated. Natraqualfs, p. 49 Aqualfs, p. 41 JAE. Other Aqualfs that have a fragipan with an JB. Other Alfisols that have a cryic or isofrigid temperature upper boundary within 100 cm of the mineral soil regime. surface. Cryalfs, p. 50 Fragiaqualfs, p. 47
JC. Other Alfisols that have an ustic moisture regime. JAF. Other Aqualfs that have a kandic horizon. Ustalfs, p. 65 Kandiaqualfs, p. 48
JD. Other Alfisols that have a xeric moisture regime. JAG. Other Aqualfs that have one or more layers, at least 25 Xeralfs, p. 76 cm thick (cumulative) within 100 cm of the mineral soil surface, that have 50 percent or more (by volume) recognizable JE. Other Alfisols. bioturbation, such as filled animal burrows, wormholes, or Udalfs, p. 54 casts. Vermaqualfs, p. 50 Aqualfs JAH. Other Aqualfs that have an abrupt textural change Key to Great Groups between the ochric epipedon or the albic horizon and the argillic horizon and have a moderately low or lower saturated JAA. Aqualfs that have a cryic temperature regime. hydraulic conductivity in the argillic horizon. Cryaqualfs, p. 43 Albaqualfs, p. 42 42 Keys to Soil Taxonomy
JAI. Other Aqualfs that have a glossic horizon. a. A color value, moist, of 4 or more; or Glossaqualfs, p. 48 b. A color value, dry, of 6 or more; or JAJ. Other Aqualfs that have episaturation. c. Chroma of 4 or more. Epiaqualfs, p. 45 Chromic Vertic Albaqualfs
JAK. Other Aqualfs. JAHD. Other Albaqualfs that have one or both of the Endoaqualfs, p. 43 following: 1. Cracks within 125 cm of the mineral soil surface that Albaqualfs are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or Key to Subgroups wedge-shaped aggregates in a layer 15 cm or more thick JAHA. Albaqualfs that have a sandy or sandy-skeletal that has its upper boundary within 125 cm of the mineral particle-size class throughout a layer extending from the soil surface; or mineral soil surface to the top of an argillic horizon at a depth 2. A linear extensibility of 6.0 cm or more between the of 50 cm or more below the mineral soil surface. mineral soil surface and either a depth of 100 cm or a Arenic Albaqualfs densic, lithic, or paralithic contact, whichever is shallower. Vertic Albaqualfs JAHB. Other Albaqualfs that have both of the following: 1. One or both: JAHE. Other Albaqualfs that have both: a. Cracks within 125 cm of the mineral soil surface that 1. Chroma of 3 or more in 40 percent or more of the are 5 mm or more wide through a thickness of 30 cm or matrix between the lower boundary of the A or Ap horizon more for some time in normal years, and slickensides or and a depth of 75 cm from the mineral soil surface; and 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 b. A linear extensibility of 6.0 cm or more between the meet these requirements after mixing. mineral soil surface and either a depth of 100 cm or a Udollic Albaqualfs densic, lithic, or paralithic contact, whichever is shallower; and JAHF. Other Albaqualfs that have chroma of 3 or more in 40 percent or more of the matrix between the lower boundary of 2. Chroma of 3 or more in 40 percent or more of the the A or Ap horizon and a depth of 75 cm from the mineral matrix between the lower boundary of the A or Ap horizon soil surface. and a depth of 75 cm from the mineral soil surface. Aeric Albaqualfs Aeric Vertic Albaqualfs JAHG. Other Albaqualfs that have, throughout one or more JAHC. Other Albaqualfs that have both of the following: horizons with a total thickness of 18 cm or more within 75 cm 1. One or both: of the mineral soil surface, one or more of the following: a. Cracks within 125 cm of the mineral soil surface that 1. A fine-earth fraction with both a bulk density of 1.0 are 5 mm or more wide through a thickness of 30 cm or g/cm3 or less, measured at 33 kPa water retention, and Al 1 more for some time in normal years, and slickensides or plus /2 Fe percentages (by ammonium oxalate) totaling wedge-shaped aggregates in a layer 15 cm or more thick more than 1.0; or 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, b. A linear extensibility of 6.0 cm or more between the pumice, and pumicelike fragments; or 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 more of the following: b. [(Al plus /2 Fe, percent extracted by ammonium Alfisols 43
oxalate) times 60] plus the volcanic glass (percent) is a. In the 0.02 to 2.0 mm fraction, 5 percent or more equal to 30 or more. volcanic glass; and
Aquandic Albaqualfs 1 b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is JAHH. Other Albaqualfs that have a mollic epipedon, an Ap equal to 30 or more. horizon that meets all of the requirements for a mollic Aquandic Endoaqualfs epipedon except thickness, or materials between the soil surface and a depth of 18 cm that meet these requirements after JAKB. Other Endoaqualfs that have both of the following: mixing. Mollic Albaqualfs 1. One or both: A a. Cracks within 125 cm of the mineral soil surface that JAHI. Other Albaqualfs that have an umbric epipedon, an Ap L are 5 mm or more wide through a thickness of 30 cm or horizon that meets all of the requirements for an umbric F more for some time in normal years, and slickensides or epipedon except thickness, or materials between the soil wedge-shaped aggregates in a layer 15 cm or more thick surface and a depth of 18 cm that meet these requirements after that has its upper boundary within 125 cm of the mineral mixing. soil surface; or Umbric Albaqualfs b. A linear extensibility of 6.0 cm or more between the 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. Chromic Vertic Endoaqualfs Key to Subgroups 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 Endoaqualfs are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or Key to Subgroups wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral JAKA. Endoaqualfs that have, throughout one or more soil surface; or horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or more of the 2. A linear extensibility of 6.0 cm or more between following: the mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is 1. A fine-earth fraction with both a bulk density of 1.0 shallower. g/cm3 or less, measured at 33 kPa water retention, and Al 1 Vertic Endoaqualfs 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 than 2.0 mm, of which more than 66 percent is cinders, 1. Fragic soil properties: pumice, and pumicelike fragments; or a. In 30 percent or more of the volume of a layer 15 cm 3. A fine-earth fraction containing 30 percent or more or more thick that has its upper boundary within 100 cm particles 0.02 to 2.0 mm in diameter; and of the mineral soil surface; or 44 Keys to Soil Taxonomy
b. In 60 percent or more of the volume of a layer 15 cm a. Hue of 7.5YR or redder in 50 percent or more of the or more thick; and matrix; and 2. In one or more horizons between the A or Ap horizon (1) If peds are present, chroma of 2 or more on 50 and a depth of 75 cm below the mineral soil surface, one or percent or more of ped exteriors or no redox a combination of the following colors: depletions with chroma of 2 or less in ped interiors; or a. Hue of 7.5YR or redder in 50 percent or more of the (2) If peds are absent, chroma of 2 or more in 50 matrix; and percent or more of the matrix; or (1) If peds are present, chroma of 2 or more on 50 b. In 50 percent or more of the matrix, hue of 10YR or percent or more of ped exteriors or no redox yellower and either: depletions with chroma of 2 or less in ped interiors; or (1) Both a color value of 3 or more (moist) and (2) If peds are absent, chroma of 2 or more in 50 chroma of 3 or more; or percent or more of the matrix; or (2) Chroma of 2 or more if there are no redox b. In 50 percent or more of the matrix, hue of 10YR or concentrations. yellower and either: Udollic Endoaqualfs (1) Both a color value of 3 or more (moist) and JAKI. Other Endoaqualfs that have both: chroma of 3 or more (moist and dry); or 1. An umbric epipedon, an Ap horizon that meets all of (2) Chroma of 2 or more if there are no redox the requirements for an umbric epipedon except thickness, concentrations. or materials between the soil surface and a depth of 18 cm Aeric Fragic Endoaqualfs 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 and a depth of 75 cm below the mineral soil surface, one or 1. In 30 percent or more of the volume of a layer 15 cm or a combination of the following colors: more thick that has its upper boundary within 100 cm of the mineral soil surface; or a. Hue of 7.5YR or redder in 50 percent or more of the matrix; and 2. In 60 percent or more of the volume of a layer 15 cm or 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 (2) If peds are absent, chroma of 2 or more in 50 particle-size class throughout a layer extending from the percent or more of the matrix; or mineral soil surface to the top of an argillic horizon at a depth of 50 to 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: (1) Both a color value of 3 or more (moist) and JAKG. Other Endoaqualfs that have a sandy or sandy- chroma of 3 or more; or skeletal particle-size class throughout a layer extending 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 1. A mollic epipedon, an Ap horizon that meets all of the or 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 redox depletions with chroma of 2 or less (both moist and a combination of the following colors: dry) in ped interiors; or Alfisols 45
b. If peds are absent, chroma of 2 or more (both moist or no redox depletions with chroma of 2 or less (both and dry); or moist and dry) in ped interiors; or 2. Hue of 10YR or yellower and either: (2) If peds are absent, chroma of 2 or more (both moist and dry); or a. Both a color value of 3 or more (moist) and chroma of 3 or more (moist and dry); or b. Hue of 10YR or yellower and either: b. Chroma of 2 or more (both moist and dry) and no (1) Both a color value of 3 or more (moist) redox concentrations. and chroma of 3 or more (moist and dry); Aeric Endoaqualfs or (2) Chroma of 2 or more (both moist and dry) and A JAKK. Other Endoaqualfs that have a mollic epipedon, an no redox concentrations; and L Ap horizon that meets all of the requirements for a mollic F epipedon except thickness, or materials between the soil 3. An Ap horizon or materials between the mineral soil surface and a depth of 18 cm that meet these requirements after surface and a depth of 18 cm that, after mixing, have one or mixing. more of the following: Mollic Endoaqualfs a. A color value, moist, of 4 or more; or JAKL. Other Endoaqualfs that have an umbric epipedon, an b. A color value, dry, of 6 or more; or Ap horizon that meets all of the requirements for an umbric c. Chroma of 4 or more. epipedon except thickness, or materials between the soil Aeric Chromic Vertic Epiaqualfs surface and a depth of 18 cm that meet these requirements after mixing. Umbric Endoaqualfs JAJB. Other Epiaqualfs that have both of the following: 1. One or both: JAKM. Other Endoaqualfs. Typic Endoaqualfs a. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or Epiaqualfs 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 soil surface; or JAJA. Epiaqualfs that have all of the following: b. A linear extensibility of 6.0 cm or more between the 1. One or both: 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 2. In one or more horizons between the A or Ap horizon wedge-shaped aggregates in a layer 15 cm or more thick and a depth of 75 cm below the mineral soil surface, in 50 that has its upper boundary within 125 cm of the mineral percent or more of the matrix, one or a combination of the soil surface; or following colors: b. A linear extensibility of 6.0 cm or more between the a. Hue of 7.5YR or redder; and mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is (1) If peds are present, chroma of 2 or more (both shallower; and moist and dry) on 50 percent or more of ped exteriors or no redox depletions with chroma of 2 or less (both 2. In one or more horizons between the A or Ap horizon moist and dry) in ped interiors; 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 (2) If peds are absent, chroma of 2 or more (both following colors: moist and dry); or a. Hue of 7.5YR or redder; and b. Hue of 10YR or yellower and either: (1) If peds are present, chroma of 2 or more (both (1) Both a color value of 3 or more (moist) and moist and dry) on 50 percent or more of ped exteriors chroma of 3 or more (moist and dry); or 46 Keys to Soil Taxonomy
(2) Chroma of 2 or more (both moist and dry) and 3. A fine-earth fraction containing 30 percent or more no redox concentrations. particles 0.02 to 2.0 mm in diameter; and Aeric Vertic Epiaqualfs a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and JAJC. Other Epiaqualfs that have both of the following: 1 b. [(Al plus /2 Fe, percent extracted by ammonium 1. One or both: oxalate) times 60] plus the volcanic glass (percent) is a. Cracks within 125 cm of the mineral soil surface that equal to 30 or more. are 5 mm or more wide through a thickness of 30 cm or Aquandic Epiaqualfs more for some time in normal years, and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick JAJF. Other Epiaqualfs that have: that has its upper boundary within 125 cm of the mineral 1. Fragic soil properties: soil surface; or a. In 30 percent or more of the volume of a layer 15 cm b. A linear extensibility of 6.0 cm or more between the or more thick that has its upper boundary within 100 cm mineral soil surface and either a depth of 100 cm or a of the mineral soil surface; or densic, lithic, or paralithic contact, whichever is shallower; and b. In 60 percent or more of the volume of a layer 15 cm or more thick; and 2. An Ap horizon or materials between the mineral soil surface and a depth of 18 cm that, after mixing, have one or 2. In one or more horizons between the A or Ap horizon more of the following: 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 a. A color value, moist, of 4 or more; or 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. (1) If peds are present, chroma of 2 or more (both Chromic Vertic Epiaqualfs 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 moist and dry); or are 5 mm or more wide through a thickness of 30 cm or b. Hue of 10YR or yellower and either: more for some time in normal years, and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick (1) Both a color value of 3 or more (moist) and that has its upper boundary within 125 cm of the mineral chroma of 3 or more (moist and dry); or soil surface; or (2) Chroma of 2 or more (both moist and dry) and 2. A linear extensibility of 6.0 cm or more between the no redox concentrations. mineral soil surface and either a depth of 100 cm or a Aeric Fragic Epiaqualfs densic, lithic, or paralithic contact, whichever is shallower. Vertic Epiaqualfs JAJG. Other Epiaqualfs that have fragic soil properties: 1. In 30 percent or more of the volume of a layer 15 cm or JAJE. Other Epiaqualfs that have, throughout one or more more thick that has its upper boundary within 100 cm of the horizons with a total thickness of 18 cm or more within mineral soil surface; or 75 cm of the mineral soil surface, one or more of the following: 2. In 60 percent or more of the volume of a layer 15 cm or more thick. 1. A fine-earth fraction with both a bulk density of 1.0 Fragic Epiaqualfs g/cm3 or less, measured at 33 kPa water retention, and Al 1 plus /2 Fe percentages (by ammonium oxalate) totaling JAJH. Other Epiaqualfs that have a sandy or sandy-skeletal more than 1.0; or particle-size class throughout a layer extending from the 2. More than 35 percent (by volume) fragments coarser mineral soil surface to the top of an argillic horizon at a depth than 2.0 mm, of which more than 66 percent is cinders, of 50 to 100 cm below the mineral soil surface. pumice, and pumicelike fragments; or Arenic Epiaqualfs Alfisols 47
JAJI. Other Epiaqualfs 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 concentrations. mineral soil surface to the top of an argillic horizon at a depth Udollic Epiaqualfs of 100 cm or more below the mineral soil surface. Grossarenic Epiaqualfs JAJL. Other Epiaqualfs that have, in one or more horizons between the A or Ap horizon and a depth of 75 cm below the JAJJ. Other Epiaqualfs that have: mineral soil surface, in 50 percent or more of the matrix, one or a combination of the following colors: 1. An umbric epipedon, an Ap horizon that meets all of the requirements for an umbric epipedon except thickness, 1. Hue of 7.5YR or redder; and or materials between the soil surface and a depth of 18 cm a. If peds are present, chroma of 2 or more (both moist A that meet these requirements after mixing; and and dry) on 50 percent or more of ped exteriors or no L 2. In one or more horizons between the A or Ap horizon redox depletions with chroma of 2 or less (both moist and F and a depth of 75 cm below the mineral soil surface, in 50 dry) in ped interiors; or percent or more of the matrix, one or a combination of the b. If peds are absent, chroma of 2 or more (both moist following colors: and dry); or a. Hue of 7.5YR or redder; and 2. Hue of 10YR or yellower and either: (1) If peds are present, chroma of 2 or more (both a. Both a color value of 3 or more (moist) and chroma moist and dry) on 50 percent or more of ped exteriors of 3 or more (moist and dry); or or no redox depletions with chroma of 2 or less (both moist and dry) in ped interiors; or b. Chroma of 2 or more (both moist and dry) and no redox concentrations. (2) If peds are absent, chroma of 2 or more (both Aeric Epiaqualfs moist and dry); or b. Hue of 10YR or yellower and either: JAJM. Other Epiaqualfs that have a mollic epipedon, an Ap horizon that meets all of the requirements for a mollic (1) Both a color value of 3 or more (moist) and epipedon except thickness, or materials between the soil chroma of 3 or more (moist and dry); or surface and a depth of 18 cm that meet these requirements after (2) Chroma of 2 or more (both moist and dry) and mixing. no redox concentrations. Mollic Epiaqualfs Aeric Umbric Epiaqualfs JAJN. Other Epiaqualfs that have an umbric epipedon, an Ap JAJK. Other Epiaqualfs that have both: horizon that meets all of the requirements for an umbric epipedon except thickness, or materials between the soil 1. A mollic epipedon, an Ap horizon that meets all of the surface and a depth of 18 cm that meet these requirements after requirements for a mollic epipedon except thickness, or 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 cm thick (cumulative) within 100 cm of the mineral soil depletions with chroma of 2 or less in ped interiors; or surface, 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 percent or more of the matrix; or casts. Vermic Fragiaqualfs b. Hue of 10YR or yellower and either: (1) Both a color value of 3 or more (moist) and JAEB. Other Fragiaqualfs that have, between the A or Ap chroma of 3 or more; or horizon and a fragipan, a horizon with 50 percent or more 48 Keys to Soil Taxonomy
chroma of 3 or more if hue is 10YR or redder or of 4 or more if (1) Both a color value of 3 or more (moist) and hue is 2.5Y or yellower. chroma of 3 or more (moist and dry); or Aeric Fragiaqualfs (2) Chroma of 2 or more if there are no redox concentrations. JAEC. Other Fragiaqualfs that have 5 percent or more (by Aeric Fragic Glossaqualfs volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. JAID. Other Glossaqualfs that have fragic soil properties: Plinthic Fragiaqualfs 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 JAED. Other Fragiaqualfs that have an Ap horizon with a mineral soil surface; 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. In 60 percent or more of the volume of a layer 15 cm or soil surface and a depth of 18 cm that have these color values more thick. after mixing. Fragic Glossaqualfs Humic Fragiaqualfs JAIE. Other Glossaqualfs that have, in one or more horizons JAEE. Other Fragiaqualfs. between the A or Ap horizon and a depth of 75 cm below the Typic Fragiaqualfs mineral soil surface, in 50 percent or more of the matrix, one or a combination of the following colors: Glossaqualfs 1. Hue of 7.5YR or redder; and Key to Subgroups a. If peds are present, chroma of 2 or more (both moist and dry) on 50 percent or more of ped exteriors or no JAIA. Glossaqualfs that have a histic epipedon. redox depletions with chroma of 2 or less (both moist and Histic Glossaqualfs dry) in ped interiors; or JAIB. Other Glossaqualfs that have a sandy or sandy-skeletal b. If peds are absent, chroma of 2 or more (both moist particle-size class throughout a layer extending from the and dry); or mineral soil surface to the top of an argillic horizon at a depth 2. Hue of 10YR or yellower and either: of 50 cm or more below the mineral soil surface. Arenic Glossaqualfs a. Both a color value of 3 or more (moist) and chroma of 3 or more (moist and dry); or JAIC. Other Glossaqualfs that have: b. Chroma of 2 or more (both moist and dry) and no 1. Fragic soil properties: redox concentrations. Aeric Glossaqualfs 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 JAIF. Other Glossaqualfs that have a mollic epipedon, an Ap of the mineral soil surface; or horizon that meets all of the requirements for a mollic b. In 60 percent or more of the volume of a layer 15 cm epipedon except thickness, or materials between the soil or more thick; and surface and a depth of 18 cm that meet these requirements after mixing. 2. In one or more horizons between the A or Ap horizon Mollic Glossaqualfs and a depth of 75 cm below the mineral soil surface, one or a combination of the following colors: JAIG. Other Glossaqualfs. a. Hue of 7.5YR or redder in 50 percent or more of the Typic Glossaqualfs matrix; and (1) If peds are present, chroma of 2 or more on 50 Kandiaqualfs percent or more of ped exteriors or no redox Key to Subgroups depletions with chroma of 2 or less in ped interiors; or JAFA. Kandiaqualfs that have a sandy or sandy-skeletal (2) If peds are absent, chroma of 2 or more in 50 particle-size class throughout a layer extending from the percent or more of the matrix; or mineral soil surface to the top of a kandic horizon at a depth of b. In 50 percent or more of the matrix, hue of 10YR or 50 to 100 cm below the mineral soil surface. yellower and either: Arenic Kandiaqualfs Alfisols 49
JAFB. Other Kandiaqualfs that have a sandy or sandy- b. Chroma of 2 or more (both moist and dry) and no skeletal particle-size class throughout a layer extending from redox concentrations. the mineral soil surface to the top of a kandic horizon at a Aeric Kandiaqualfs depth of 100 cm or more below the mineral soil surface. Grossarenic Kandiaqualfs JAFF. Other Kandiaqualfs that have an umbric epipedon, an Ap horizon that meets all of the requirements for an umbric JAFC. Other Kandiaqualfs that have 5 percent or more (by epipedon except thickness, or materials between the soil volume) plinthite in one or more horizons within 150 cm of the surface and a depth of 18 cm that meet these requirements after mineral soil surface. mixing. Plinthic Kandiaqualfs Umbric Kandiaqualfs A JAFD. Other Kandiaqualfs that have both: JAFG. Other Kandiaqualfs. L Typic Kandiaqualfs F 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 sample) or materials between the soil surface and a depth of Natraqualfs 18 cm that have these color values after mixing; and Key to Subgroups 2. In one or more horizons between the A or Ap horizon JADA. Natraqualfs that have one or both of the following: 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 1. Cracks within 125 cm of the mineral soil surface that following colors: are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or a. Hue of 7.5YR or redder; and wedge-shaped aggregates in a layer 15 cm or more thick (1) If peds are present, chroma of 2 or more (both that has its upper boundary within 125 cm of the mineral moist and dry) on 50 percent or more of ped exteriors soil surface; or or no redox depletions with chroma of 2 or less (both 2. A linear extensibility of 6.0 cm or more between the moist and dry) in ped interiors; or mineral soil surface and either a depth of 100 cm or a (2) If peds are absent, chroma of 2 or more (both densic, lithic, or paralithic contact, whichever is shallower. moist and dry); or Vertic Natraqualfs b. Hue of 10YR or yellower and either: JADB. Other Natraqualfs that have one or more layers, at (1) Both a color value of 3 or more (moist) and least 25 cm thick (cumulative) within 100 cm of the mineral chroma of 3 or more (moist and dry); or soil surface, that have 25 percent or more (by volume) recognizable bioturbation, such as filled animal burrows, (2) Chroma of 2 or more (both moist and dry) and wormholes, or casts. no redox concentrations. Vermic Natraqualfs Aeric Umbric Kandiaqualfs JADC. Other Natraqualfs that have both: JAFE. Other Kandiaqualfs that have, in one or more horizons between the A or Ap horizon and a depth of 75 cm below the 1. A glossic horizon or interfingering of albic materials mineral soil surface, in 50 percent or more of the matrix, one into the natric horizon; and or a combination of the following colors: 2. An exchangeable sodium percentage of less than 15 and 1. Hue of 7.5YR or redder; and less magnesium plus sodium than calcium plus extractable acidity either throughout the upper 15 cm of the natric a. If peds are present, chroma of 2 or more (both moist horizon or in all horizons within 40 cm of the mineral soil and dry) on 50 percent or more of ped exteriors or no surface, whichever is deeper. redox depletions with chroma of 2 or less (both moist and Albic Glossic Natraqualfs dry) in ped interiors; or b. If peds are absent, chroma of 2 or more (both moist JADD. Other Natraqualfs that have an exchangeable sodium and dry); or percentage of less than 15 and less magnesium plus sodium than calcium plus extractable acidity either throughout the 2. Hue of 10YR or yellower and either: upper 15 cm of the natric horizon or in all horizons within 40 a. Both a color value of 3 or more (moist) and chroma cm of the mineral soil surface, whichever is deeper. of 3 or more (moist and dry); or Albic Natraqualfs 50 Keys to Soil Taxonomy
JADE. Other Natraqualfs that have a glossic horizon 3. Either a glossic horizon or interfingering of albic or interfingering of albic materials into the natric materials into the argillic, kandic, or natric horizon. horizon. Palecryalfs, p. 53 Glossic Natraqualfs JBB. Other Cryalfs that have a glossic horizon. JADF. Other Natraqualfs that have a mollic epipedon, an Ap Glossocryalfs, p. 50 horizon that meets all of the requirements for a mollic epipedon except thickness, or materials between the soil JBC. Other Cryalfs. surface and a depth of 18 cm that meet these requirements after Haplocryalfs, p. 52 mixing. Mollic Natraqualfs Glossocryalfs JADG. Other Natraqualfs. Key to Subgroups Typic Natraqualfs JBBA. Glossocryalfs that have a lithic contact within 50 cm Plinthaqualfs of the mineral soil surface. Lithic Glossocryalfs Key to Subgroups JBBB. Other Glossocryalfs that have one or both of the JABA. All Plinthaqualfs (provisionally). following: Typic Plinthaqualfs 1. Cracks within 125 cm of the mineral soil surface that Vermaqualfs are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or Key to Subgroups wedge-shaped aggregates in a layer 15 cm or more thick JAGA. Vermaqualfs that have an exchangeable sodium that has its upper boundary within 125 cm of the mineral percentage of 7 or more (or a sodium adsorption ratio of 6 or soil surface; or more) either or both: 2. A linear extensibility of 6.0 cm or more between 1. Throughout the upper 15 cm of the argillic horizon; the mineral soil surface and either a depth of 100 cm and/or or a densic, lithic, or paralithic contact, whichever is shallower. 2. Throughout all horizons within 40 cm of the mineral Vertic Glossocryalfs soil surface. Natric Vermaqualfs JBBC. Other Glossocryalfs that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm JAGB. Other Vermaqualfs. of the mineral soil surface, a fine-earth fraction with both a Typic Vermaqualfs bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 retention, and Al plus /2 Fe percentages (by ammonium Cryalfs oxalate) totaling more than 1.0. Andic Glossocryalfs Key to Great Groups JBBD. Other Glossocryalfs that have, throughout one or JBA. Cryalfs that have all of the following: more horizons with a total thickness of 18 cm or more 1. An argillic, kandic, or natric horizon that has its upper within 75 cm of the mineral soil surface, one or both of the boundary 60 cm or more below both: following: a. The mineral soil surface; and 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, b. The lower boundary of any surface mantle pumice, and pumicelike fragments; or containing 30 percent or more vitric volcanic ash, cinders, or other vitric pyroclastic materials; and 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and 2. A texture (in the fine-earth fraction) finer than loamy fine sand in one or more horizons above the argillic, kandic, a. In the 0.02 to 2.0 mm fraction, 5 percent or more or natric horizon; and volcanic glass; and Alfisols 51
1 b. [(Al plus /2 Fe, percent extracted by ammonium JBBJ. Other Glossocryalfs that: oxalate) times 60] plus the volcanic glass (percent) is 1. Are dry in some part of the moisture control section for equal to 30 or more. 45 or more days (cumulative) in normal years; and Vitrandic Glossocryalfs 2. Have an Ap horizon with a color value, moist, of 3 or JBBE. Other Glossocryalfs that have, in one or more less and a color value, dry, of 5 or less (crushed and subhorizons within the upper 25 cm of the argillic, kandic, or smoothed sample) or materials between the soil surface and natric horizon, redox depletions with chroma of 2 or less a depth of 18 cm that have these color values after mixing; and also aquic conditions for some time in normal years and (or artificial drainage). 3. Have a base saturation of 50 percent or more (by Aquic Glossocryalfs A NH4OAc) in all parts from the mineral soil surface to a L depth of 180 cm or to a densic, lithic, or paralithic contact, JBBF. Other Glossocryalfs that are saturated with water in F whichever is shallower. one or more layers within 100 cm of the mineral soil surface in Ustollic Glossocryalfs normal years for either or both: 1. 20 or more consecutive days; or JBBK. Other Glossocryalfs that have a xeric moisture regime. 2. 30 or more cumulative days. Xeric Glossocryalfs Oxyaquic Glossocryalfs JBBL. Other Glossocryalfs that are dry in some part of the JBBG. Other Glossocryalfs that have fragic soil properties: moisture control section for 45 or more days (cumulative) in 1. In 30 percent or more of the volume of a layer 15 cm or normal years. more thick that has its upper boundary within 100 cm of the Ustic Glossocryalfs mineral soil surface; or JBBM. Other Glossocryalfs that: 2. In 60 percent or more of the volume of a layer 15 cm or more thick. 1. Have an Ap horizon with a color value, moist, of 3 or Fragic Glossocryalfs less and a color value, dry, of 5 or less (crushed and smoothed sample) or materials between the soil surface and JBBH. Other Glossocryalfs that have: a depth of 18 cm that have these color values after mixing; and 1. A xeric moisture regime; and 2. Have a base saturation of 50 percent or more (by 2. An Ap horizon with a color value, moist, of 3 or NH OAc) in all parts from the mineral soil surface to a less and a color value, dry, of 5 or less (crushed and 4 depth of 180 cm or to a densic, lithic, or paralithic contact, smoothed sample) or materials between the soil surface whichever is shallower. and a depth of 18 cm that have these color values after Mollic Glossocryalfs mixing; and
3. A base saturation of 50 percent or more (by NH4OAc) JBBN. Other Glossocryalfs that have an Ap horizon with a in all parts from the mineral soil surface to a depth of 180 color value, moist, of 3 or less and a color value, dry, of 5 or cm or to a densic, lithic, or paralithic contact, whichever is less (crushed and smoothed sample) or materials between the shallower. soil surface and a depth of 18 cm that have these color values Xerollic Glossocryalfs after mixing. Umbric Glossocryalfs JBBI. Other Glossocryalfs that have: JBBO. Other Glossocryalfs that have a base saturation of 50 1. A xeric moisture regime; and percent or more (by NH4OAc) in all parts from the mineral soil 2. An Ap horizon with a color value, moist, of 3 or surface to a depth of 180 cm or to a densic, lithic, or paralithic less and a color value, dry, of 5 or less (crushed and contact, whichever is shallower. smoothed sample) or materials between the soil surface Eutric Glossocryalfs and a depth of 18 cm that have these color values after mixing. JBBP. Other Glossocryalfs. Umbric Xeric Glossocryalfs Typic Glossocryalfs 52 Keys to Soil Taxonomy
Haplocryalfs JBCF. Other Haplocryalfs that are saturated with water in one or more layers within 100 cm of the mineral soil surface in Key to Subgroups normal years for either or both: JBCA. Haplocryalfs that have a lithic contact within 50 cm of 1. 20 or more consecutive days; or the mineral soil surface. 2. 30 or more cumulative days. Lithic Haplocryalfs Oxyaquic Haplocryalfs JBCB. Other Haplocryalfs that have one or both of the JBCG. Other Haplocryalfs that have an argillic horizon that: following: 1. Consists entirely of lamellae; or 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or 2. Is a combination of two or more lamellae and one or more for some time in normal years, and slickensides or more subhorizons with a thickness of 7.5 to 20 cm, each wedge-shaped aggregates in a layer 15 cm or more thick layer with an overlying eluvial horizon; or that has its upper boundary within 125 cm of the mineral 3. Consists of one or more subhorizons that are more than 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 or a densic, lithic, or paralithic contact, whichever is 5 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 argillic horizon 7.5 to 20 cm thick, each with an of the mineral soil surface, a fine-earth fraction with both a overlying eluvial horizon. bulk density of 1.0 g/cm3 or less, measured at 33 kPa water Lamellic Haplocryalfs 1 retention, 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 coarser than 2.0 mm, of which more than 66 percent less thick; and is cinders, pumice, and pumicelike fragments; or 2. No densic, lithic, or paralithic contact within 100 cm of the mineral soil surface. 2. A fine-earth fraction containing 30 percent or more Inceptic Haplocryalfs particles 0.02 to 2.0 mm in diameter; and a. In the 0.02 to 2.0 mm fraction, 5 percent or more JBCJ. Other Haplocryalfs that have: volcanic glass; and 1. A xeric moisture regime; and 1 b. [(Al plus /2 Fe, percent extracted by ammonium 2. An Ap horizon with a color value, moist, of 3 or less oxalate) times 60] plus the volcanic glass (percent) is and a color value, dry, of 5 or less (crushed and smoothed equal to 30 or more. sample) or materials between the soil surface and a depth of Vitrandic Haplocryalfs 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 NH4OAc) within 75 cm of the mineral soil surface, redox depletions with in all parts from the mineral soil surface to a depth of 180 chroma of 2 or less and also aquic conditions for some time in cm or to a densic, lithic, or paralithic contact, whichever is normal years (or artificial drainage). shallower. Aquic Haplocryalfs Xerollic Haplocryalfs Alfisols 53
JBCK. Other Haplocryalfs that have: surface to a depth of 180 cm or to a densic, lithic, or paralithic contact, whichever is shallower. 1. A xeric moisture regime; and Eutric Haplocryalfs 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 JBCR. Other Haplocryalfs. sample) or materials between the soil surface and a depth of Typic Haplocryalfs 18 cm that have these color values after mixing. Umbric Xeric Haplocryalfs Palecryalfs
JBCL. Other Haplocryalfs that: Key to Subgroups A 1. Are dry in some part of the moisture control section for JBAA. Palecryalfs that have, throughout one or more L 45 or more days (cumulative) in normal years; and horizons with a total thickness of 18 cm or more within 75 cm F of the mineral soil surface, a fine-earth fraction with both a 2. Have an Ap horizon with a color value, moist, of 3 or bulk density of 1.0 g/cm3 or less, measured at 33 kPa water less and a color value, dry, of 5 or less (crushed and 1 retention, and Al plus /2 Fe percentages (by ammonium smoothed sample) or materials between the soil surface and oxalate) totaling more than 1.0. a depth of 18 cm that have these color values after mixing; Andic Palecryalfs and 3. Have a base saturation of 50 percent or more (by JBAB. Other Palecryalfs that have, throughout one or
NH4OAc) in all parts from the mineral soil surface to a more horizons with a total thickness of 18 cm or more within depth of 180 cm or to a densic, lithic, or paralithic contact, 75 cm of the mineral soil surface, one or both of the whichever is shallower. following: Ustollic Haplocryalfs 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, JBCM. Other Haplocryalfs that have a xeric moisture regime. pumice, and pumicelike fragments; or Xeric Haplocryalfs 2. A fine-earth fraction containing 30 percent or more JBCN. Other Haplocryalfs that are dry in some part of the particles 0.02 to 2.0 mm in diameter; and moisture control section for 45 or more days (cumulative) in a. In the 0.02 to 2.0 mm fraction, 5 percent or more normal years. volcanic glass; and Ustic Haplocryalfs 1 b. [(Al plus /2 Fe, percent extracted by ammonium JBCO. Other Haplocryalfs that: oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. 1. Have an Ap horizon with a color value, moist, of 3 or Vitrandic Palecryalfs less and a color value, dry, of 5 or less (crushed and smoothed sample) or materials between the soil surface and JBAC. Other Palecryalfs that have, in one or more horizons a depth of 18 cm that have these color values after mixing; within 100 cm of the mineral soil surface, redox depletions and with chroma of 2 or less and also aquic conditions for some 2. Have a base saturation of 50 percent or more (by time in normal years (or artificial drainage).
NH4OAc) in all parts from the mineral soil surface to a Aquic Palecryalfs depth 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 NH4OAc) in all parts from the mineral soil JBAF. Other Palecryalfs that are dry in some part of the 54 Keys to Soil Taxonomy
moisture control section for 45 or more days (cumulative) in JED. Other Udalfs that have a fragipan with an upper normal years. boundary within 100 cm of the mineral soil surface. Ustic Palecryalfs Fragiudalfs, p. 55
JBAG. Other Palecryalfs that: JEE. Other Udalfs that: 1. Have an Ap horizon with a color value, moist, of 3 or 1. Do not have a densic, lithic, paralithic, or petroferric less and a color value, dry, of 5 or less (crushed and contact within 150 cm of the mineral soil surface; and smoothed sample) or materials between the soil surface and 2. Have a kandic horizon; and a depth of 18 cm that have these color values after mixing; and 3. Within 150 cm of the mineral soil surface, either: 2. Have a base saturation of 50 percent or more (by a. Do not have a clay decrease with increasing depth of
NH4OAc) in all parts from the mineral soil surface to a 20 percent or more (relative) from the maximum clay depth of 180 cm or to a densic, lithic, or paralithic contact, content [Clay is measured noncarbonate clay or based on whichever is shallower. the following formula: Clay % = 2.5(% water retained at Mollic Palecryalfs 1500 kPa tension - % organic carbon), whichever value is greater, but no more than 100]; or JBAH. Other Palecryalfs that have an Ap horizon with a b. Have 5 percent or more (by volume) skeletans on color value, moist, of 3 or less and a color value, dry, of 5 or faces of peds in the layer that has a 20 percent lower clay less (crushed and smoothed sample) or materials between the content and, below that layer, a clay increase of 3 percent soil surface and a depth of 18 cm that have these color values or more (absolute) in the fine-earth fraction. after mixing. Kandiudalfs, p. 61 Umbric Palecryalfs JEF. Other Udalfs that have a kandic horizon. JBAI. Other Palecryalfs. Kanhapludalfs, p. 62 Typic Palecryalfs
Udalfs JEG. Other Udalfs that: 1. Do not have a densic, lithic, or paralithic contact within Key to Great Groups 150 cm of the mineral soil surface; and JEA. Udalfs that have a natric horizon. 2. Within 150 cm of the mineral soil surface, either: 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 1. A glossic horizon; and the following formula: Clay % = 2.5(% water retained at 1500 kPa tension - % organic carbon), whichever value is 2. In the argillic or kandic horizon, discrete nodules, 2.5 greater, but no more than 100]; or to 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 b. Have exteriors with either a redder hue or a higher or more (absolute) in the fine-earth fraction; and chroma than the interiors. Ferrudalfs, p. 55 3. Have an argillic horizon with one or more of the following: JEC. Other Udalfs that have both: a. In 50 percent or more of the matrix of one or more 1. A glossic horizon; and subhorizons in its lower one-half, hue of 7.5YR or redder and chroma of 5 or more; or 2. A fragipan with an upper boundary within 100 cm of the mineral soil surface. b. In 50 percent or more of the matrix of horizons that Fraglossudalfs, p. 55 total more than one-half the total thickness, hue of Alfisols 55
2.5YR or redder, value, moist, of 3 or less, and value, Fragiudalfs dry, of 4 or less; or Key to Subgroups c. Many coarse redox concentrations with hue of 5YR or redder or chroma of 6 or more, or both, in one or more JEDA. Fragiudalfs that have, throughout one or more subhorizons; 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 4. Have a frigid temperature regime and all of the bulk density of 1.0 g/cm3 or less, measured at 33 kPa water following: 1 retention, and Al plus /2 Fe percentages (by ammonium a. An argillic horizon that has its upper boundary 60 oxalate) totaling more than 1.0. cm or more below both: Andic Fragiudalfs A (1) The mineral soil surface; and L JEDB. Other Fragiudalfs that have, throughout one or more F (2) The lower boundary of any surface mantle horizons with a total thickness of 18 cm or more within 75 cm containing 30 percent or more vitric volcanic of the mineral soil surface, one or both of the following: ash, cinders, or other vitric pyroclastic materials; 1. More than 35 percent (by volume) fragments coarser and than 2.0 mm, of which more than 66 percent is cinders, b. A texture (in the fine-earth fraction) finer than pumice, and pumicelike fragments; or loamy fine sand in one or more horizons above the 2. A fine-earth fraction containing 30 percent or more argillic horizon; and particles 0.02 to 2.0 mm in diameter; and c. Either a glossic horizon or interfingering of albic a. In the 0.02 to 2.0 mm fraction, 5 percent or more materials into the argillic horizon. volcanic glass; and Paleudalfs, p. 63 1 b. [(Al plus /2 Fe, percent extracted by ammonium JEH. Other Udalfs that have, in all subhorizons in the upper oxalate) times 60] plus the volcanic glass (percent) is 100 cm of the argillic horizon or throughout the entire argillic equal to 30 or more. horizon if less than 100 cm thick, more than 50 percent colors Vitrandic Fragiudalfs that have all of the following: JEDC. Other Fragiudalfs that have, in one or more horizons 1. Hue of 2.5YR or redder; and within 40 cm of the mineral soil surface, redox depletions with 2. Value, moist, of 3 or less; and chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). 3. Dry value no more than 1 unit higher than the moist Aquic Fragiudalfs value. Rhodudalfs, p. 65 JEDD. Other Fragiudalfs that are saturated with water in one or more layers above the fragipan in normal years for either or JEI. Other Udalfs that have a glossic horizon. both: Glossudalfs, p. 56 1. 20 or more consecutive days; or JEJ. Other Udalfs. 2. 30 or more cumulative days. Hapludalfs, p. 58 Oxyaquic Fragiudalfs
Ferrudalfs JEDE. Other Fragiudalfs. Typic Fragiudalfs Key to Subgroups JEBA. Ferrudalfs that have, in one or more horizons within 60 cm of the mineral soil surface, redox depletions with Fraglossudalfs chroma of 2 or less and also aquic conditions for some time in Key to Subgroups normal 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 JEBB. Other Ferrudalfs. of the mineral soil surface, a fine-earth fraction with both a Typic Ferrudalfs bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 56 Keys to Soil Taxonomy
1 retention, and Al plus /2 Fe percentages (by ammonium densic, lithic, or paralithic contact, whichever is oxalate) totaling more than 1.0. shallower; and Andic Fraglossudalfs 2. Redox depletions with chroma of 2 or less in layers that also have aquic conditions in normal years (or artificial JECB. Other Fraglossudalfs that have, throughout one or drainage) either: more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: a. Within the upper 25 cm of the argillic horizon if its upper boundary is within 50 cm of the mineral soil 1. More than 35 percent (by volume) fragments coarser surface; or than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or b. Within 75 cm of the mineral soil surface if the upper boundary of the argillic horizon is 50 cm or more below 2. A fine-earth fraction containing 30 percent or more the mineral soil surface. particles 0.02 to 2.0 mm in diameter; and Aquertic Glossudalfs a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and JEIB. Other Glossudalfs that have both:
1 b. [(Al plus /2 Fe, percent extracted by ammonium 1. Saturation with water in one or more layers within 100 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 soil surface; or either 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 2. 30 or more cumulative days. shallower. Oxyaquic Fraglossudalfs Oxyaquic Vertic Glossudalfs JECE. Other Fraglossudalfs. JEIC. Other Glossudalfs that have one or both of the Typic Fraglossudalfs following: Glossudalfs 1. 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 JEIA. Glossudalfs that have both: that has its upper boundary within 125 cm of the mineral 1. One or both of the following: 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 more for some time in normal years, and slickensides or densic, lithic, or paralithic contact, whichever is shallower. wedge-shaped aggregates in a layer 15 cm or more thick Vertic Glossudalfs that has its upper boundary within 125 cm of the mineral soil surface; or JEID. Other Glossudalfs that have both: b. A linear extensibility of 6.0 cm or more between the 1. In one or more subhorizons within the upper 25 cm of mineral soil surface and either a depth of 100 cm or a the argillic horizon, redox depletions with chroma of 2 or Alfisols 57
less and also aquic conditions for some time in normal years or more thick that has its upper boundary within 100 cm (or artificial 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 horizon if its more than 1.0; or upper boundary is within 50 cm of the mineral soil A b. More than 35 percent (by volume) fragments coarser 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 horizon is 50 cm or more below c. A fine-earth fraction containing 30 percent or more the mineral soil surface. particles 0.02 to 2.0 mm in diameter; and Fragiaquic Glossudalfs (1) In the 0.02 to 2.0 mm fraction, 5 percent or more JEIH. Other Glossudalfs that have, in one or more volcanic glass; and subhorizons within the upper 25 cm of the argillic horizon, 1 (2) [(Al plus /2 Fe, percent extracted by ammonium redox depletions with chroma of 2 or less and also aquic oxalate) times 60] plus the volcanic glass (percent) is conditions for some time in normal years (or artificial equal to 30 or more. drainage). Aquandic Glossudalfs Aquic Glossudalfs
JEIE. Other Glossudalfs that have, throughout one or more JEII. Other Glossudalfs that are saturated with water in one horizons with a total thickness of 18 cm or more within 75 cm or more layers within 100 cm of the mineral soil surface in of the mineral soil surface, a fine-earth fraction with both a normal years for either or both: bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 1. 20 or more consecutive days; or retention, and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. 2. 30 or more cumulative days. Andic Glossudalfs Oxyaquic Glossudalfs
JEIF. Other Glossudalfs that have, throughout one or more JEIJ. Other Glossudalfs that have fragic soil properties: horizons with a total thickness of 18 cm or more within 75 cm 1. In 30 percent or more of the volume of a layer 15 cm or of the mineral soil surface, one or both of the following: more thick that has its upper boundary within 100 cm of the 1. More than 35 percent (by volume) fragments coarser mineral soil surface; or than 2.0 mm, of which more than 66 percent is cinders, 2. In 60 percent or more of the volume of a layer 15 cm or pumice, and pumicelike fragments; or more thick. 2. A fine-earth fraction containing 30 percent or more Fragic Glossudalfs particles 0.02 to 2.0 mm in diameter; and JEIK. Other Glossudalfs 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 volcanic glass; and mineral soil surface to the top of an argillic horizon at a depth 1 b. [(Al plus /2 Fe, percent extracted by ammonium of 50 cm or more below the mineral soil surface. oxalate) times 60] plus the volcanic glass (percent) is Arenic Glossudalfs equal to 30 or more. Vitrandic Glossudalfs JEIL. Other Glossudalfs that have a glossic horizon less than 50 cm in total thickness. JEIG. Other Glossudalfs that have both: Haplic Glossudalfs 1. Fragic soil properties: JEIM. Other Glossudalfs. a. In 30 percent or more of the volume of a layer 15 cm Typic Glossudalfs 58 Keys to Soil Taxonomy
Hapludalfs densic, lithic, or paralithic contact, whichever is shallower; and Key to Subgroups 2. Redox depletions with chroma of 2 or less in layers that JEJA. Hapludalfs that have a lithic contact within 50 cm of also have aquic conditions in normal years (or artificial the mineral soil surface. drainage) either: Lithic Hapludalfs a. Within the upper 25 cm of the argillic horizon if its upper boundary is within 50 cm of the mineral soil JEJB. Other Hapludalfs that have all of the following: surface; or 1. One or both of the following: b. Within 75 cm of the mineral soil surface if the upper a. Cracks within 125 cm of the mineral soil surface that boundary of the argillic horizon is 50 cm or more below are 5 mm or more wide through a thickness of 30 cm or the mineral soil surface. more for some time in normal years, and slickensides or Aquertic Hapludalfs wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral JEJD. Other Hapludalfs that have both: soil surface; or 1. Saturation with water in one or more layers within 100 b. A linear extensibility of 6.0 cm or more between the cm of the mineral soil surface in normal years for either or mineral soil surface and either a depth of 100 cm or a both: densic, lithic, or paralithic contact, whichever is a. 20 or more consecutive days; or shallower; and b. 30 or more cumulative days; and 2. Redox depletions with chroma of 2 or less in layers that also have aquic conditions in normal years (or artificial 2. One or both of the following: drainage) either: a. Cracks within 125 cm of the mineral soil surface that a. Within the upper 25 cm of the argillic horizon if its are 5 mm or more wide through a thickness of 30 cm or upper boundary is within 50 cm of the mineral soil more for some time in normal years, and slickensides or surface; or wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral b. Within 75 cm of the mineral soil surface if the upper soil surface; or boundary of the argillic horizon is 50 cm or more below the mineral soil surface; 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 3. An Ap horizon or materials between the mineral soil densic, lithic, or paralithic contact, whichever is surface and a depth of 18 cm that, after mixing, have one or shallower. more of the following: Oxyaquic Vertic Hapludalfs a. A color value, moist, of 4 or more; or JEJE. Other Hapludalfs that have both: b. A color value, dry, of 6 or more; or 1. One or both of the following: c. Chroma of 4 or more. Aquertic Chromic Hapludalfs a. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or JEJC. Other Hapludalfs 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 the more for some time in normal years, and slickensides or mineral soil surface and either a depth of 100 cm or a wedge-shaped aggregates in a layer 15 cm or more thick densic, lithic, or paralithic contact, whichever is that has its upper boundary within 125 cm of the mineral shallower; and soil surface; or 2. An Ap horizon or materials between the mineral soil b. A linear extensibility of 6.0 cm or more between the surface and a depth of 18 cm that, after mixing, have one or mineral soil surface and either a depth of 100 cm or a more of the following: Alfisols 59
a. A color value, moist, of 4 or more; or 2. Redox depletions with chroma of 2 or less in layers that also have aquic conditions in normal years (or artificial b. A color value, dry, of 6 or more; or drainage) either: c. Chroma of 4 or more. a. Within the upper 25 cm of the argillic horizon if its Chromic Vertic Hapludalfs upper boundary is within 50 cm of the mineral soil 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 the mineral soil surface. are 5 mm or more wide through a thickness of 30 cm or Fragiaquic Hapludalfs A more for some time in normal years, and slickensides or L wedge-shaped aggregates in a layer 15 cm or more thick JEJJ. Other Hapludalfs that have both: F that has its upper boundary within 125 cm of the mineral soil surface; or 1. Fragic soil properties: 2. A linear extensibility of 6.0 cm or more between a. In 30 percent or more of the volume of a layer 15 cm the mineral soil surface and either a depth of 100 cm or or more thick that has its upper boundary within 100 cm a densic, lithic, or paralithic contact, whichever is of the mineral soil surface; or shallower. b. In 60 percent or more of the volume of a layer 15 cm Vertic Hapludalfs or more thick; and JEJG. Other Hapludalfs that have, throughout one or more 2. Saturation with water in one or more layers within 100 horizons with a total thickness of 18 cm or more within 75 cm cm of the mineral soil surface in normal years for either or of the mineral soil surface, a fine-earth fraction with both a both: bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 a. 20 or more consecutive days; or retention, and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. b. 30 or more cumulative days. Andic Hapludalfs Fragic Oxyaquic Hapludalfs
JEJH. Other Hapludalfs that have, throughout one or more JEJK. Other Hapludalfs that have both: horizons with a total thickness of 18 cm or more within 75 cm 1. In one or more horizons within 75 cm of the mineral of the mineral soil surface, one or both of the following: soil surface, redox depletions with chroma of 2 or less and 1. More than 35 percent (by volume) fragments coarser also aquic conditions for some time in normal years (or than 2.0 mm, of which more than 66 percent is cinders, artificial drainage); and pumice, and pumicelike fragments; or 2. A sandy or sandy-skeletal particle-size class 2. A fine-earth fraction containing 30 percent or more throughout a layer extending from the mineral soil surface particles 0.02 to 2.0 mm in diameter; and to the top of an argillic horizon at a depth of 50 cm or more. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Aquic Arenic Hapludalfs volcanic glass; and
1 b. [(Al plus /2 Fe, percent extracted by ammonium JEJL. Other Hapludalfs that have: oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. 1. An abrupt textural change; and Vitrandic Hapludalfs 2. Redox depletions with chroma of 2 or less in layers that also have aquic conditions in normal years (or artificial JEJI. Other Hapludalfs that have both: drainage) either: 1. Fragic soil properties: a. Within the upper 25 cm of the argillic horizon if its a. In 30 percent or more of the volume of a layer 15 cm upper boundary is within 50 cm of the mineral soil or more thick that has its upper boundary within 100 cm surface; or of the mineral soil surface; or b. Within 75 cm of the mineral soil surface if the upper b. In 60 percent or more of the volume of a layer 15 cm boundary of the argillic horizon is 50 cm or more below or more thick; and the mineral soil surface; and 60 Keys to Soil Taxonomy
3. A base saturation (by sum of cations) of less than 60 or directly above a densic, lithic, or paralithic contact, percent at a depth of 125 cm from the top of the argillic whichever is shallowest. horizon, at a depth of 180 cm from the mineral soil surface, Aquultic Hapludalfs or directly above a densic, lithic, or paralithic contact, whichever is shallowest. JEJP. Other Hapludalfs that have both: Albaquultic Hapludalfs 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 JEJM. Other Hapludalfs that have both: sample) or materials between the soil surface and a depth of 1. An abrupt textural change; and 18 cm that have these color values after mixing; and 2. Redox depletions with chroma of 2 or less in layers that 2. Redox depletions with chroma of 2 or less in layers that also have aquic conditions in normal years (or artificial also have aquic conditions in normal years (or artificial drainage) either: drainage) either: a. Within the upper 25 cm of the argillic horizon if its a. Within the upper 25 cm of the argillic horizon if its upper boundary is within 50 cm of the mineral soil upper boundary is within 50 cm of the mineral soil surface; or surface; or b. Within 75 cm of the mineral soil surface if the upper b. Within 75 cm of the mineral soil surface if the upper boundary of the argillic horizon is 50 cm or more below boundary of the argillic horizon is 50 cm or more below the mineral soil surface. the mineral soil surface. Albaquic Hapludalfs Aquollic Hapludalfs
JEJN. Other Hapludalfs that have both: JEJQ. Other Hapludalfs that have redox depletions with 1. Interfingering of albic materials in the upper part of the chroma of 2 or less in layers that also have aquic conditions in argillic horizon; and normal years (or artificial drainage) either: 2. Redox depletions with chroma of 2 or less in layers that 1. Within the upper 25 cm of the argillic horizon if its also have aquic conditions in normal years (or artificial upper boundary is within 50 cm of the mineral soil surface; drainage) either: or a. Within the upper 25 cm of the argillic horizon if its 2. Within 75 cm of the mineral soil surface if the upper upper boundary is within 50 cm of the mineral soil boundary of the argillic horizon is 50 cm or more below the surface; or mineral soil surface. Aquic Hapludalfs b. Within 75 cm of the mineral soil surface if the upper boundary of the argillic horizon is 50 cm or more below JEJR. Other Hapludalfs that have anthraquic conditions. the mineral soil surface. Anthraquic Hapludalfs Glossaquic Hapludalfs JEJS. Other Hapludalfs that are saturated with water in one JEJO. Other Hapludalfs that have both: or more layers within 100 cm of the mineral soil surface in normal years for either or both: 1. Redox depletions with chroma of 2 or less in layers that also have aquic conditions in normal years (or artificial 1. 20 or more consecutive days; or drainage) either: 2. 30 or more cumulative days. a. Within the upper 25 cm of the argillic horizon if its Oxyaquic Hapludalfs upper boundary is within 50 cm of the mineral soil surface; or JEJT. Other Hapludalfs that have fragic soil properties: b. Within 75 cm of the mineral soil surface if the upper 1. In 30 percent or more of the volume of a layer 15 cm or boundary of the argillic horizon is 50 cm or more below more thick that has its upper boundary within 100 cm of the the mineral soil surface; and mineral soil surface; or 2. A base saturation (by sum of cations) of less than 60 2. In 60 percent or more of the volume of a layer 15 cm or percent at a depth of 125 cm from the top of the argillic more thick. horizon, at a depth of 180 cm from the mineral soil surface, Fragic Hapludalfs Alfisols 61
JEJU. Other Hapludalfs that have an argillic horizon that: surface and a depth of 18 cm that meet these requirements after mixing. 1. Consists entirely of lamellae; or Mollic Hapludalfs 2. Is a combination of two or more lamellae and one or more subhorizons with a thickness of 7.5 to 20 cm, each JEJZb. Other Hapludalfs. layer with an overlying eluvial horizon; or Typic Hapludalfs 3. Consists of one or more subhorizons that are more than 20 cm thick, each with an overlying eluvial horizon, and Kandiudalfs above these horizons there are either: Key to Subgroups a. Two or more lamellae with a combined thickness of A JEEA. Kandiudalfs that have both: 5 cm or more (that may or may not be part of the argillic L horizon); or 1. In one or more horizons within 75 cm of the mineral F soil surface, redox depletions with chroma of 2 or less and b. A combination of lamellae (that may or may not be also aquic conditions for some time in normal years (or part of the argillic horizon) and one or more parts of the artificial drainage); and argillic horizon 7.5 to 20 cm thick, each with an overlying eluvial horizon. 2. 5 percent or more (by volume) plinthite in one or more Lamellic Hapludalfs horizons within 150 cm of the mineral soil surface. Plinthaquic Kandiudalfs JEJV. Other Hapludalfs that have a sandy particle-size class throughout the upper 75 cm of the argillic horizon or JEEB. Other Kandiudalfs that have, in one or more horizons throughout the entire argillic horizon if it is less than 75 cm within 75 cm of the mineral soil surface, redox depletions with thick. chroma of 2 or less and also aquic conditions for some time in Psammentic Hapludalfs normal years (or artificial drainage). Aquic Kandiudalfs JEJW. Other Hapludalfs that have a sandy or sandy-skeletal particle-size class throughout a layer extending from the JEEC. Other Kandiudalfs that are saturated with water in one mineral soil surface to the top of an argillic horizon at a depth or more layers within 100 cm of the mineral soil surface in of 50 cm or more. normal years for either or both: Arenic Hapludalfs 1. 20 or more consecutive days; or JEJX. Other Hapludalfs that have interfingering of 2. 30 or more cumulative days. albic materials in one or more subhorizons of the argillic Oxyaquic Kandiudalfs horizon. Glossic Hapludalfs JEED. Other Kandiudalfs that have both: 1. A sandy or sandy-skeletal particle-size class throughout JEJY. Other Hapludalfs that have: a layer extending from the mineral soil surface to the top of 1. An argillic, kandic, or natric horizon that is 35 cm or a kandic horizon at a depth of 50 to 100 cm; and less thick; and 2. 5 percent or more (by volume) plinthite in one or more 2. No densic, lithic, or paralithic contact within 100 cm of horizons within 150 cm of the mineral soil surface. the mineral soil surface. Arenic Plinthic Kandiudalfs Inceptic Hapludalfs JEEE. Other Kandiudalfs that have both: JEJZ. Other Hapludalfs that have a base saturation (by sum 1. A sandy or sandy-skeletal particle-size class throughout of cations) of less than 60 percent at a depth of 125 cm below a layer extending from the mineral soil surface to the top of the top of the argillic horizon, at a depth of 180 cm below the a kandic horizon at a depth of 100 cm or more; and mineral soil surface, or directly above a densic, lithic, or paralithic contact, whichever is shallowest. 2. 5 percent or more (by volume) plinthite in one or more Ultic Hapludalfs horizons within 150 cm of the mineral soil surface. Grossarenic Plinthic Kandiudalfs JEJZa. Other Hapludalfs that have a mollic epipedon, an Ap horizon that meets all of the requirements for a mollic JEEF. Other Kandiudalfs that have a sandy or sandy-skeletal epipedon except thickness, or materials between the soil particle-size class throughout a layer extending from the 62 Keys to Soil Taxonomy
mineral soil surface to the top of a kandic horizon at a depth of 1. 20 or more consecutive days; or 50 to 100 cm. 2. 30 or more cumulative days. Arenic Kandiudalfs Oxyaquic Kanhapludalfs JEEG. Other Kandiudalfs that have a sandy or sandy-skeletal JEFD. Other Kanhapludalfs that have, in all subhorizons in particle-size class throughout a layer extending from the the upper 100 cm of the kandic horizon or throughout the mineral soil surface to the top of a kandic horizon at a depth of entire kandic horizon if less than 100 cm thick, more than 50 100 cm or more. percent colors that have all of the following: Grossarenic Kandiudalfs 1. Hue of 2.5YR or redder; and JEEH. Other Kandiudalfs that have 5 percent or more (by 2. Value, moist, of 3 or less; and volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. 3. Dry value no more than 1 unit higher than the moist Plinthic Kandiudalfs value. Rhodic Kanhapludalfs JEEI. Other Kandiudalfs that have, in all subhorizons in the upper 100 cm of the kandic horizon or throughout the entire JEFE. Other Kanhapludalfs. kandic horizon if less than 100 cm thick, more than 50 percent Typic Kanhapludalfs colors that have all of the following: 1. Hue of 2.5YR or redder; and Natrudalfs 2. Value, moist, of 3 or less; and Key to Subgroups 3. Dry value no more than 1 unit higher than the moist JEAA. Natrudalfs that have one or both of the following: value. 1. Cracks within 125 cm of the mineral soil surface that Rhodic Kandiudalfs are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or JEEJ. Other Kandiudalfs that have a mollic epipedon, an Ap wedge-shaped aggregates in a layer 15 cm or more thick horizon that meets all of the requirements for a mollic that has its upper boundary within 125 cm of the mineral epipedon except thickness, or materials between the soil soil surface; or surface and a depth of 18 cm that meet these requirements after mixing. 2. A linear extensibility of 6.0 cm or more between the Mollic Kandiudalfs mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. JEEK. Other Kandiudalfs. Vertic Natrudalfs Typic Kandiudalfs JEAB. Other Natrudalfs that have: Kanhapludalfs 1. Either a glossic horizon or interfingering of albic materials into the natric horizon; and Key to Subgroups 2. Redox depletions with chroma of 2 or less in layers that JEFA. Kanhapludalfs that have a lithic contact within 50 cm also have aquic conditions in normal years (or artificial of the mineral soil surface. drainage) either: Lithic Kanhapludalfs a. Within the upper 25 cm of the natric horizon if its JEFB. Other Kanhapludalfs that have, in one or upper boundary is within 50 cm of the mineral soil more horizons within 75 cm of the mineral soil surface, surface; or redox depletions with chroma of 2 or less and also aquic b. Within 75 cm of the mineral soil surface if the upper conditions for some time in normal years (or artificial boundary of the natric horizon is 50 cm or more below drainage). the mineral soil surface. Aquic Kanhapludalfs Glossaquic Natrudalfs JEFC. Other Kanhapludalfs that are saturated with water in JEAC. Other Natrudalfs that have redox depletions with one or more layers within 100 cm of the mineral soil surface in chroma of 2 or less in layers that also have aquic conditions in normal years for either or both: normal years (or artificial drainage) either: Alfisols 63
1. Within the upper 25 cm of the natric horizon if its 1. Fragic soil properties: upper boundary is within 50 cm of the mineral soil surface; a. In 30 percent or more of the volume of a layer 15 cm or or more thick that has its upper boundary within 100 cm 2. Within 75 cm of the mineral soil surface if the upper of the mineral soil surface; or boundary of the natric horizon is 50 cm or more below the b. In 60 percent or more of the volume of a layer 15 cm mineral soil surface. or more thick; and Aquic Natrudalfs 2. Redox depletions with chroma of 2 or less in layers that JEAD. Other Natrudalfs. also have aquic conditions in normal years (or artificial Typic Natrudalfs drainage) either: A a. Within the upper 25 cm of the argillic horizon if its L Paleudalfs upper boundary is within 50 cm of the mineral soil F surface; or Key to Subgroups b. Within 75 cm of the mineral soil surface if the upper JEGA. Paleudalfs that have one or both of the following: boundary of the argillic horizon is 50 cm or more below 1. Cracks within 125 cm of the mineral soil surface that the mineral soil surface. are 5 mm or more wide through a thickness of 30 cm or Fragiaquic Paleudalfs more for some time in normal years, and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick JEGE. Other Paleudalfs that have both: that has its upper boundary within 125 cm of the mineral 1. In one or more horizons within 75 cm of the mineral soil surface; or soil surface, redox depletions with chroma of 2 or less and 2. A linear extensibility of 6.0 cm or more between the 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. 2. 5 percent or more (by volume) plinthite in one or more Vertic Paleudalfs horizons within 150 cm of the mineral soil surface. JEGB. Other Paleudalfs that have, throughout one or more Plinthaquic Paleudalfs 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 JEGF. Other Paleudalfs that have both: bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 1. In one or more horizons within 75 cm of the mineral retention, and Al plus /2 Fe percentages (by ammonium soil surface, redox depletions with chroma of 2 or less and oxalate) totaling more than 1.0. also aquic conditions for some time in normal years (or Andic Paleudalfs artificial drainage); and JEGC. Other Paleudalfs that have, throughout one or more 2. A glossic horizon or, in the upper part of the argillic horizons with a total thickness of 18 cm or more within 75 cm horizon, one or more subhorizons that have 5 percent or of the mineral soil surface, one or both of the following: more (by volume) clay depletions with chroma of 2 or less. Glossaquic Paleudalfs 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, JEGG. Other Paleudalfs that have both: pumice, and pumicelike fragments; or 1. In one or more horizons within 75 cm of the mineral 2. A fine-earth fraction containing 30 percent or more soil surface, redox depletions with chroma of 2 or less and particles 0.02 to 2.0 mm in diameter; and also aquic conditions for some time in normal years (or a. In the 0.02 to 2.0 mm fraction, 5 percent or more artificial drainage); and volcanic glass; and 2. A clay increase of 15 percent or more (absolute) in the 1 b. [(Al plus /2 Fe, percent extracted by ammonium fine-earth fraction within a vertical distance of 2.5 cm at the oxalate) times 60] plus the volcanic glass (percent) is upper boundary of the argillic horizon. equal to 30 or more. Albaquic Paleudalfs Vitrandic Paleudalfs JEGH. Other Paleudalfs that have, in one or more horizons JEGD. Other Paleudalfs that have both: within 75 cm of the mineral soil surface, redox depletions with 64 Keys to Soil Taxonomy
chroma of 2 or less and also aquic conditions for some time in 5 cm or more (that may or may not be part of the argillic normal years (or artificial drainage). horizon); or Aquic Paleudalfs b. A combination of lamellae (that may or may not be part of the argillic horizon) and one or more parts of the JEGI. Other Paleudalfs that have anthraquic conditions. argillic horizon 7.5 to 20 cm thick, each with an Anthraquic Paleudalfs overlying 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 JEGO. Other Paleudalfs that have a sandy particle-size class normal years for either or both: 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 soil surface to the top of an argillic horizon at a depth 1. In 30 percent or more of the volume of a layer 15 cm or of 50 to 100 cm. more thick that has its upper boundary within 100 cm of the Arenic Paleudalfs mineral soil surface; or 2. In 60 percent or more of the volume of a layer 15 cm or JEGQ. Other Paleudalfs that have a sandy or sandy-skeletal more thick. particle-size class throughout a layer extending from the Fragic Paleudalfs mineral soil surface to the top of an argillic horizon at a depth of 100 cm or more. JEGL. Other Paleudalfs that 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 JEGR. Other Paleudalfs that have 5 percent or more (by an 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 2. In the upper part of the argillic horizon, one or more a layer extending from the mineral soil surface to the top of subhorizons that have 5 percent or more (by volume) an argillic horizon at a depth of 100 cm or more; and skeletans with chroma of 2 or less; or 2. 5 percent or more (by volume) plinthite in one or more 3. 5 percent or more (by volume) albic materials in some horizons within 150 cm of the mineral soil surface. subhorizon of the argillic horizon. Grossarenic Plinthic Paleudalfs Glossic Paleudalfs
JEGN. Other Paleudalfs that have an argillic horizon that: JEGT. Other Paleudalfs that have, in all subhorizons in the 1. Consists entirely of lamellae; or upper 100 cm of the argillic horizon or throughout the entire argillic horizon if less than 100 cm thick, more than 50 percent 2. Is a combination of two or more lamellae and one or colors that have all of the following: more subhorizons with a thickness of 7.5 to 20 cm, each layer with an overlying eluvial horizon; or 1. Hue of 2.5YR or redder; and 3. Consists of one or more subhorizons that are more than 2. Value, moist, of 3 or less; and 20 cm thick, each with an overlying eluvial horizon, and 3. Dry value no more than 1 unit higher than the moist above these horizons there are either: value. a. Two or more lamellae with a combined thickness of Rhodic Paleudalfs Alfisols 65
JEGU. Other Paleudalfs that have a mollic epipedon, an Ap JCE. Other Ustalfs that have a kandic horizon. horizon that meets all of the requirements for a mollic Kanhaplustalfs, p. 70 epipedon except thickness, or materials between the soil surface and a depth of 18 cm that meet these requirements after JCF. Other Ustalfs that have one or more of the following: mixing. 1. A petrocalcic horizon that has its upper boundary Mollic Paleudalfs within 150 cm of the mineral soil surface; or JEGV. Other Paleudalfs. 2. No densic, lithic, or paralithic contact within 150 cm of Typic Paleudalfs the mineral soil surface and an argillic horizon that has both: Rhodudalfs A a. Within 150 cm of the mineral soil surface, either: L Key to Subgroups (1) With increasing depth, no clay decrease of 20 F percent or more (relative) from the maximum clay JEHA. All Rhodudalfs (provisionally). content [Clay is measured noncarbonate clay or based Typic Rhodudalfs on the following formula: Clay % = 2.5(% water retained at 1500 kPa tension - % organic carbon), Ustalfs whichever value is greater, but no more than 100]; or Key to Great Groups (2) 5 percent or more (by volume) skeletans on faces of peds in the layer that has a 20 percent lower clay JCA. Ustalfs that have a duripan that has its upper boundary content and, below that layer, a clay increase of 3 within 100 cm of the mineral soil surface. percent or more (absolute) in the fine-earth fraction; Durustalfs, p. 66 and b. In the lower one-half of the argillic horizon, one or JCB. Other Ustalfs that have one or more horizons within more subhorizons with either or both: 150 cm of the mineral soil surface in which plinthite either forms a continuous phase or constitutes one-half or more of the (1) Hue of 7.5YR or redder and chroma of 5 or more volume. in 50 percent or more of the matrix; or Plinthustalfs, p. 76 (2) Common or many coarse redox concentrations with hue of 7.5YR or redder or chroma of 6 or more, JCC. Other Ustalfs that have a natric horizon. or both; or Natrustalfs, p. 71 3. No densic, lithic, or paralithic contact within 50 cm of JCD. Other Ustalfs that: the mineral soil surface and an argillic horizon that has both: 1. Have a kandic horizon; and a. A clayey or clayey-skeletal particle-size class 2. Do not have a densic, lithic, paralithic, or petroferric throughout one or more subhorizons in its upper part; contact within 150 cm of the mineral soil surface; and and 3. Within 150 cm of the mineral soil surface, either: b. At its upper boundary, a clay increase (in the fine- a. Do not have a clay decrease with increasing depth of earth fraction) of either 20 percent or more (absolute) 20 percent or more (relative) from the maximum clay within a vertical distance of 7.5 cm or of 15 percent or content [Clay is measured noncarbonate clay or based on more (absolute) within a vertical distance of 2.5 cm. the following formula: Clay % = 2.5(% water retained at Paleustalfs, p. 73 1500 kPa tension - % organic carbon), whichever value is greater, but no more than 100]; or JCG. Other Ustalfs that have, in all subhorizons in the upper b. Have 5 percent or more (by volume) skeletans on 100 cm of the argillic horizon or throughout the entire argillic faces of peds in the layer that has a 20 percent lower horizon if less than 100 cm thick, more than 50 percent colors clay content and, below that layer, a clay increase that have all of the following: of 3 percent or more (absolute) in the fine-earth 1. Hue of 2.5YR or redder; and fraction. Kandiustalfs, p. 69 2. Value, moist, of 3 or less; and 66 Keys to Soil Taxonomy
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: a. 20 or more consecutive days; or JCH. Other Ustalfs. 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 2. One or both of the following: also aquic conditions for some time in normal years (or a. Cracks within 125 cm of the soil surface that are 5 artificial 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 JCHC. Other Haplustalfs that have both: that has its upper boundary within 125 cm of the soil surface; or 1. One or both of the following: b. A linear extensibility of 6.0 cm or more between the a. Cracks within 125 cm of the mineral soil surface that soil surface and either a depth of 100 cm or a densic, are 5 mm or more wide through a thickness of 30 cm or lithic, or paralithic contact, whichever is shallower. more for some time in normal years, and slickensides or Torrertic Haplustalfs wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral JCHE. Other Haplustalfs that have both: soil surface; or 1. When neither irrigated nor fallowed to store moisture, b. A linear extensibility of 6.0 cm or more between the either: mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is a. A mesic or thermic soil temperature regime and a shallower; and moisture control section that in normal years is dry in Alfisols 67
some part for four-tenths or less of the cumulative days 2. An argillic horizon that has a base saturation (by sum per year when the temperature at a depth of 50 cm below of cations) of less than 75 percent throughout. the soil surface is higher than 5 oC; or Aquultic Haplustalfs b. A hyperthermic, isomesic, or warmer iso soil JCHI. Other Haplustalfs that have, in one or more horizons temperature regime and a moisture control section that in within 75 cm of the mineral soil surface, redox depletions with normal years is dry in some or all parts for less than 120 chroma of 2 or less and also aquic conditions for some time in cumulative days per year when the temperature at a depth normal years (or artificial drainage). of 50 cm below the soil surface is higher than 8 oC; and Aquic Haplustalfs 2. One or both of the following: JCHJ. Other Haplustalfs that are saturated with water in one A a. Cracks within 125 cm of the mineral soil surface that or more layers within 100 cm of the mineral soil surface in L are 5 mm or more wide through a thickness of 30 cm or normal years for either or both: F more for some time in normal years, and slickensides or 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 2. 30 or more cumulative days. soil surface; or Oxyaquic Haplustalfs b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a JCHK. Other Haplustalfs that have, throughout one or more densic, lithic, or paralithic contact, whichever is horizons with a total thickness of 18 cm or more within 75 cm shallower. of the mineral soil surface, one or both of the following: Udertic Haplustalfs 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, JCHF. Other Haplustalfs that have one or both of the pumice, and pumicelike fragments; or following: 2. A fine-earth fraction containing 30 percent or more 1. Cracks within 125 cm of the mineral soil surface that particles 0.02 to 2.0 mm in diameter; and are 5 mm or more wide through a thickness of 30 cm or 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 b. [(Al plus /2 Fe, percent extracted by ammonium soil surface; or oxalate) times 60] plus the volcanic glass (percent) is 2. 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 Vitrandic Haplustalfs 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 more subhorizons with a thickness of 7.5 to 20 cm, each soil surface, redox depletions with chroma of 2 or less and layer with an overlying eluvial horizon; or also 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 above these horizons there are either: a 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 Aquic Arenic Haplustalfs 5 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 part of the argillic horizon) and one or more parts of the soil surface, redox depletions with chroma of 2 or less and argillic horizon 7.5 to 20 cm thick, each with an also aquic conditions for some time in normal years (or overlying eluvial horizon. artificial drainage); and Lamellic Haplustalfs 68 Keys to Soil Taxonomy
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 soil temperature at a depth of 50 cm below the soil throughout the entire argillic horizon if it is less than 75 cm surface is higher than 5 oC; or thick. b. A mesic or thermic soil temperature regime and a Psammentic Haplustalfs moisture control section that in normal years is dry in some part for six-tenths or more of the cumulative days JCHN. Other Haplustalfs that have both: per year when the soil temperature at a depth of 50 cm 1. A sandy or sandy-skeletal particle-size class throughout below the soil surface is higher than 5 oC; or a layer extending from the mineral soil surface to the top of c. A hyperthermic, isomesic, or warmer iso soil an argillic horizon at a depth of 50 cm or more; and temperature regime and a moisture control section that in 2. When neither irrigated nor fallowed to store moisture, normal years: one of the following: (1) Is moist in some or all parts for less than 90 a. A frigid temperature regime and a moisture control consecutive days per year when the 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 tenths or more of the cumulative days per year when the 8 oC; and soil temperature at a depth of 50 cm below the soil (2) Is dry in some part for six-tenths or more of the surface is higher than 5 oC; or cumulative days per year when the soil temperature at b. A mesic or thermic soil temperature regime a depth of 50 cm below the soil surface is higher than and a moisture control section that in normal years 5 oC. is dry in some part for six-tenths or more of the Calcidic Haplustalfs cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher JCHQ. Other Haplustalfs that, when neither irrigated nor than 5 oC; or fallowed to store moisture, have one of the following: c. A hyperthermic, isomesic, or warmer iso soil 1. 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-tenths normal years: or more of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is (1) Is moist in some or all parts for less than 90 higher than 5 oC; or consecutive days per year when the temperature at a depth of 50 cm below the soil surface is higher than 2. A mesic or thermic soil temperature regime and a 8 oC; and moisture control section that in normal years is dry in some part for six-tenths or more of the cumulative days per year (2) Is dry in some part for six-tenths or more of the when the soil temperature at a depth of 50 cm below the soil cumulative days per year when the soil temperature at surface is higher than 5 oC; or a depth of 50 cm below the soil surface is higher than 5 oC. 3. A hyperthermic, isomesic, or warmer iso soil Arenic Aridic Haplustalfs temperature regime and a moisture control section that in normal years: JCHO. Other Haplustalfs that have a sandy or sandy-skeletal a. Is moist in some or all parts for less than 90 particle-size class throughout a layer extending from the consecutive days per year when the temperature at a mineral soil surface to the top of an argillic horizon at a depth depth of 50 cm below the soil surface is higher than 8 oC; of 50 cm or more. and Arenic Haplustalfs b. Is dry in some part for six-tenths or more of the cumulative days per year when the soil temperature at a JCHP. Other Haplustalfs that have both: depth of 50 cm below the soil surface is higher than 5 oC. 1. A calcic horizon with its upper boundary within 100 cm Aridic Haplustalfs of the mineral soil surface; and JCHR. Other Haplustalfs that have a CEC of less than 24 2. When neither irrigated nor fallowed to store moisture, cmol(+)/kg clay (by 1N NH OAc pH 7) in 50 percent or more one of the following: 4 either of the argillic horizon if less than 100 cm thick or of its a. A frigid temperature regime and a moisture control upper 100 cm. section that in normal years is dry in all parts for four- Kanhaplic Haplustalfs Alfisols 69
JCHS. Other Haplustalfs that have: 3. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in 1. An argillic, kandic, or natric horizon that is 35 cm or normal years is dry in some or all parts for less than 120 less thick; and 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. Udic Haplustalfs Inceptic Haplustalfs JCHX. Other Haplustalfs. JCHT. Other Haplustalfs that have both: Typic Haplustalfs
1. A calcic horizon with its upper boundary within 100 cm A of the mineral soil surface; and Kandiustalfs L 2. When neither irrigated nor fallowed to store moisture, F 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 section that in normal years is dry in some or all parts for mineral soil surface to the top of a kandic horizon at a depth of less than 105 cumulative days per year when the 100 cm 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 some part for four-tenths or less of the cumulative days soil surface, redox depletions with chroma of 2 or less and per year when the temperature at a depth of 50 cm below also aquic conditions for some time in normal years (or the soil surface is higher than 5 oC; or artificial drainage); and c. A hyperthermic, isomesic, or warmer iso soil 2. A sandy or sandy-skeletal particle-size class throughout temperature regime and a moisture control section that in a layer extending from the mineral soil surface to the top of normal years is dry in some or all parts for less than 120 a 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 1. A frigid temperature regime and a moisture control a layer extending from the mineral soil surface to the top of section that in normal years is dry in some or all parts for a 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 2. When neither irrigated nor fallowed to store moisture, higher than 5 oC; or either: 2. A mesic or thermic soil temperature regime and a a. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in some moisture control section that in normal years is dry in part for four-tenths or less of the cumulative days per year some part for six-tenths or more of the cumulative days when the temperature at a depth of 50 cm below the soil per year when the soil temperature at a depth of 50 cm surface is higher than 5 oC; or below the soil surface is higher than 5 oC; or 70 Keys to Soil Taxonomy
b. A hyperthermic, isomesic, or warmer iso soil cumulative days per year when the temperature at a depth of temperature regime and a moisture control section that in 50 cm below the soil surface is higher than 8 oC. normal years: Udic Kandiustalfs (1) Is moist in some or all parts for less than 90 JCDI. Other Kandiustalfs that have, in all subhorizons in the consecutive days per year when the temperature at a upper 100 cm of the kandic horizon or throughout the entire depth of 50 cm below the soil surface is higher than kandic horizon if less than 100 cm thick, more than 50 percent 8 oC; and colors that have all of the following: (2) Is dry in some part for six-tenths or more of the 1. Hue of 2.5YR or redder; and cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 2. Value, moist, of 3 or less; and 5 oC. 3. Dry value no more than 1 unit higher than the moist Arenic Aridic Kandiustalfs value. Rhodic Kandiustalfs JCDF. Other Kandiustalfs that have a sandy or sandy-skeletal particle-size class throughout a layer extending from the JCDJ. Other Kandiustalfs. mineral soil surface to the top of a kandic horizon at a depth of Typic Kandiustalfs 50 to 100 cm. Arenic Kandiustalfs Kanhaplustalfs JCDG. Other Kandiustalfs that, when neither irrigated nor Key to Subgroups fallowed to store moisture, have either: JCEA. Kanhaplustalfs that have a lithic contact within 50 cm 1. A mesic or thermic soil temperature regime and a of the mineral soil surface. moisture control section that in normal years is dry in some Lithic Kanhaplustalfs 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 JCEB. Other Kanhaplustalfs that have, in one or more surface is higher than 5 oC; or horizons within 75 cm of the mineral soil surface, redox 2. A hyperthermic, isomesic, or warmer iso soil depletions with chroma of 2 or less and also aquic conditions temperature regime and a moisture control section that in for some time in normal years (or artificial drainage). normal years: Aquic Kanhaplustalfs a. Is moist in some or all parts for less than 90 JCEC. Other Kanhaplustalfs that, when neither irrigated nor consecutive days per year when the temperature at a fallowed to store moisture, have either: 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 six-tenths or more of the cumulative days per year cumulative days per year when the soil temperature at a when the soil temperature at a depth of 50 cm below the soil depth of 50 cm below the soil surface is higher than surface is higher than 5 oC; or 5 oC. Aridic Kandiustalfs 2. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in JCDH. Other Kandiustalfs 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 moisture control section that in normal years is dry in some depth of 50 cm below the soil surface is higher than 8 oC; part for 135 cumulative days or less per year when the and temperature at a depth of 50 cm below the soil surface is b. Is dry in some part for six-tenths or more of the higher than 5 oC; or cumulative days per year when the soil temperature at 2. A hyperthermic, isomesic, or warmer iso soil a depth of 50 cm below the soil surface is higher than temperature regime and a moisture control section that in 5 oC. normal years is dry in some or all parts for less than 120 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 normal years is dry in some or all parts for less than 120 a depth of 50 cm below the soil surface is higher than A cumulative days per year when the temperature at a depth of 5 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 more for some time in normal years, and slickensides or entire kandic horizon if less than 100 cm thick, more than 50 wedge-shaped aggregates in a layer 15 cm or more thick percent 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 value. shallower. Rhodic Kanhaplustalfs Leptic Torrertic Natrustalfs
JCEF. Other Kanhaplustalfs. JCCC. Other Natrustalfs that have both of the following: Typic Kanhaplustalfs 1. When neither irrigated nor fallowed to store moisture, Natrustalfs one of the following: a. A frigid temperature regime and a moisture control Key to Subgroups section that in normal years is dry in all parts for four- JCCA. Natrustalfs that have a salic horizon that has its upper tenths or more of the cumulative days per year when the boundary within 75 cm of the mineral soil surface. soil temperature at a depth of 50 cm below the soil Salidic Natrustalfs surface is higher than 5 oC; or b. A mesic or thermic soil temperature regime and a JCCB. Other Natrustalfs that have all of the following: moisture control section that in normal years is dry in 1. Visible crystals of gypsum or other salts more soluble some part for six-tenths or more of the cumulative days than gypsum, or both, within 40 cm of the soil surface; and per year when the soil 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, one of the following: c. A hyperthermic, isomesic, or warmer iso soil 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- tenths or more of the cumulative days per year when the (1) Is moist in some or all parts for less than 90 soil temperature at a depth of 50 cm below the soil consecutive days per year when the temperature at a surface is higher than 5 oC; or depth of 50 cm below the soil surface is higher than 8 oC; and b. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in (2) Is dry in some part for six-tenths or more of the some part for six-tenths or more of the cumulative days cumulative days per year when the soil temperature at per year when the soil temperature at a depth of 50 cm a depth of 50 cm below the soil surface is higher than below the soil surface is higher than 5 oC; or 5 oC; and 72 Keys to Soil Taxonomy
2. One or both of the following: c. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in a. 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 less than 90 wedge-shaped aggregates in a layer 15 cm or more thick consecutive days per year when the temperature at a that has its upper boundary within 125 cm of the mineral depth of 50 cm below the soil surface is higher than soil surface; or 8 oC; and b. A linear extensibility of 6.0 cm or more between the (2) Is dry in some part for six-tenths or more of the mineral soil surface and either a depth of 100 cm or a cumulative days per year when the soil temperature at densic, lithic, or paralithic contact, whichever is a depth of 50 cm below the soil surface is higher than shallower. 5 oC. Torrertic Natrustalfs Aridic Leptic Natrustalfs
JCCF. Other Natrustalfs that have one or both of the JCCD. Other Natrustalfs that have both: following: 1. In one or more horizons within 75 cm of the mineral 1. Cracks within 125 cm of the mineral soil surface that soil surface, redox depletions with chroma of 2 or less and are 5 mm or more wide through a thickness of 30 cm or also aquic conditions for some time in normal years (or more for some time in normal years, and slickensides or artificial drainage); and wedge-shaped aggregates in a layer 15 cm or more thick 2. 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 2. 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 Vertic Natrustalfs b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a JCCG. Other Natrustalfs that have both: densic, lithic, or paralithic contact, whichever is 1. In one or more horizons within 75 cm of the mineral shallower. soil surface, redox depletions with chroma of 2 or less and Aquertic Natrustalfs also aquic conditions for some time in normal years (or artificial drainage); and JCCE. Other Natrustalfs that have both of the following: 2. A sandy or sandy-skeletal particle-size class throughout 1. Visible crystals of gypsum or other salts more soluble a layer extending from the mineral soil surface to the top of than gypsum, or both, within 40 cm of the mineral soil an argillic horizon at a depth of 50 cm or more. surface; and Aquic Arenic Natrustalfs 2. When neither irrigated nor fallowed to store moisture, one of the following: JCCH. Other Natrustalfs that have, in one or more horizons a. A frigid temperature regime and a moisture control within 75 cm of the mineral soil surface, redox depletions with section that in normal years is dry in all parts for four- chroma of 2 or less and also aquic conditions for some time in tenths or more of the cumulative days per year when the normal years (or artificial drainage). soil temperature at a depth of 50 cm below the soil Aquic Natrustalfs surface is higher than 5 oC; or b. A mesic or thermic soil temperature regime and a JCCI. Other Natrustalfs that have a sandy or sandy-skeletal moisture control section that in normal years is dry in particle-size class throughout a layer extending from the some part for six-tenths or more of the cumulative days mineral soil surface to the top of an argillic horizon at a depth per year when the soil temperature at a depth of 50 cm of 50 cm or more. below the soil surface is higher than 5 oC; or Arenic Natrustalfs Alfisols 73
JCCJ. Other Natrustalfs that have a petrocalcic horizon that part for six-tenths or more of the cumulative days per year has its upper boundary within 150 cm of the mineral soil when the soil temperature at a depth of 50 cm below the soil surface. surface is higher than 5 oC; or Petrocalcic Natrustalfs 3. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in JCCK. Other Natrustalfs that have visible crystals of gypsum normal years: or other salts more soluble than gypsum, or both, within 40 cm of the mineral soil surface. a. Is moist in some or all parts for less than 90 Leptic Natrustalfs consecutive days per year when the temperature at a depth of 50 cm below the soil surface is higher than 8 oC; JCCL. Other Natrustalfs that have both of the following: and A L 1. An exchangeable sodium percentage of less than 15 (or b. Is dry in some part for six-tenths or more of the F a sodium adsorption ratio of less than 13) in 50 percent or cumulative days per year when the soil temperature at a more of the natric horizon; and depth of 50 cm below the soil surface is higher than 5 oC. Aridic Natrustalfs 2. When neither irrigated nor fallowed to store moisture, one of the following: JCCN. Other Natrustalfs that have an Ap horizon with a a. A frigid temperature regime and a moisture control color value, moist, of 3 or less and a color value, dry, of 5 or section that in normal years is dry in all parts for four- less (crushed and smoothed sample) or materials between the tenths or more of the cumulative days per year when the soil surface and a depth of 18 cm that have these color values soil temperature at a depth of 50 cm below the soil after mixing. surface is higher than 5 oC; or Mollic Natrustalfs b. A mesic or thermic soil temperature regime and a JCCO. Other Natrustalfs. moisture control section that in normal years is dry in Typic Natrustalfs some 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 surface is higher than 5 oC; or Paleustalfs c. A hyperthermic, isomesic, or warmer iso soil Key to Subgroups temperature regime and a moisture control section that in normal years: JCFA. Paleustalfs that have both: (1) Is moist in some or all parts for less than 90 1. One or both of the following: consecutive days per year when the temperature at a a. Cracks within 125 cm of the mineral soil surface that depth of 50 cm below the soil surface is higher than are 5 mm or more wide through a thickness of 30 cm or 8 oC; and more for some time in normal years, and slickensides or (2) Is dry in some part for six-tenths or more of the wedge-shaped aggregates in a layer 15 cm or more thick cumulative 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 5 oC. b. A linear extensibility of 6.0 cm or more between the Haplargidic Natrustalfs mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is JCCM. Other Natrustalfs that, when neither irrigated nor shallower; and fallowed to store moisture, have one of the following: 2. In one or more horizons within 75 cm of the mineral 1. A frigid temperature regime and a moisture control soil surface, redox depletions with chroma of 2 or less and section that in normal years is dry in all parts for four-tenths also aquic conditions for some time in normal years (or or more of the cumulative days per year when the soil artificial drainage). temperature at a depth of 50 cm below the soil surface is Aquertic Paleustalfs higher than 5 oC; or JCFB. Other Paleustalfs that have both: 2. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in some 1. One or both of the following: 74 Keys to Soil Taxonomy
a. Cracks within 125 cm of the mineral soil surface that that has its upper boundary within 125 cm of the mineral are 5 mm or more wide through a thickness of 30 cm or soil surface; or more for some time in normal years, and slickensides or 2. A linear extensibility of 6.0 cm or more between the wedge-shaped aggregates in a layer 15 cm or more thick mineral soil surface and either a depth of 100 cm or a that has its upper boundary within 125 cm of the mineral densic, lithic, or paralithic contact, whichever is shallower. soil surface; or Vertic Paleustalfs b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a JCFE. Other Paleustalfs that have both: densic, lithic, or paralithic contact, whichever is 1. In one or more horizons within 75 cm of the mineral shallower; and soil surface, redox depletions with chroma of 2 or less and 2. Saturation with water in one or more layers within 100 also aquic conditions for some time in normal years (or cm of the mineral soil surface in normal years for either or artificial drainage); and both: 2. A sandy or sandy-skeletal particle-size class throughout a. 20 or more consecutive days; or a layer extending from the mineral soil surface to the top of an argillic horizon at a depth of 50 to 100 cm. b. 30 or more cumulative days. Aquic Arenic Paleustalfs Oxyaquic Vertic Paleustalfs JCFF. Other Paleustalfs that have, in one or more horizons JCFC. Other Paleustalfs that have both: within 75 cm of the mineral soil surface, redox depletions with 1. When neither irrigated nor fallowed to store moisture, chroma of 2 or less and also aquic conditions for some time in either: normal years (or artificial drainage). Aquic Paleustalfs 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 time (cumulative) JCFG. Other Paleustalfs that are saturated with water in one per year when the temperature at a depth of 50 cm below or more layers within 100 cm of the mineral soil surface in the soil surface is higher than 5 oC; or normal years for either or both: b. A hyperthermic, isomesic, or warmer iso soil 1. 20 or more consecutive days; or temperature regime and a moisture control section that in 2. 30 or more cumulative days. normal years is dry in some or all parts for less than 120 Oxyaquic Paleustalfs cumulative days per year when the temperature at a depth of 50 cm below the soil surface is higher than 8 oC; and JCFH. Other Paleustalfs that have an argillic horizon that: 2. One or both of the following: 1. Consists entirely of lamellae; or a. Cracks within 125 cm of the mineral soil surface that 2. Is a combination of two or more lamellae and one or are 5 mm or more wide through a thickness of 30 cm or more subhorizons with a thickness of 7.5 to 20 cm, each more for some time in normal years, and slickensides or layer with an overlying eluvial horizon; or wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral 3. Consists of one or more subhorizons that are more than soil surface; or 20 cm thick, each with an overlying eluvial horizon, and above these horizons there are either: 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. Two or more lamellae with a combined thickness of densic, lithic, or paralithic contact, whichever is 5 cm or more (that may or may not be part of the argillic shallower. horizon); or Udertic Paleustalfs b. A combination of lamellae (that may or may not be part of the argillic horizon) and one or more parts of the JCFD. Other Paleustalfs that have one or both of the argillic horizon 7.5 to 20 cm thick, each with an following: overlying eluvial horizon. 1. Cracks within 125 cm of the mineral soil surface that Lamellic Paleustalfs are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or JCFI. Other Paleustalfs that have a sandy particle-size class wedge-shaped aggregates in a layer 15 cm or more thick throughout the upper 75 cm of the argillic horizon or Alfisols 75
throughout the entire argillic horizon if it is less than 75 cm JCFN. Other Paleustalfs that have a petrocalcic horizon that thick. has its upper boundary within 150 cm of the mineral soil Psammentic Paleustalfs surface. 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 layer extending from the mineral soil surface to the top of 1. When neither irrigated nor fallowed to store moisture, an argillic horizon at a depth of 50 to 100 cm; and either: 2. When neither irrigated nor fallowed to store moisture, a. A frigid temperature regime and a moisture control one of the following: section that in normal years is dry in all parts for four- A tenths or more of the time (cumulative) per year when L a. A frigid temperature regime and a moisture control the soil temperature at a depth of 50 cm below the soil F section that in normal years is dry in all parts for four- surface is higher than 5 oC; or tenths or more of the time (cumulative) per year when the soil temperature at a depth of 50 cm below the soil b. A mesic or thermic soil temperature regime and a surface is higher than 5 oC; or moisture control section that in normal years is dry in some part for six-tenths or more of the time (cumulative) b. A mesic or thermic soil temperature regime and a per year when the soil temperature at a depth of 50 cm moisture control section that in normal years is dry in below the soil surface is higher than 5 oC; or some part for six-tenths or more of the time (cumulative) per year when the soil temperature at a depth of 50 cm c. A hyperthermic, isomesic, or warmer iso soil below the soil surface is higher than 5 oC; or temperature regime and a moisture control section that in normal years: c. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in (1) Is moist in some or all parts for less than 90 normal years: consecutive days per year when the temperature at a depth of 50 cm below the soil surface is higher than (1) Is moist in some or all parts for less than 90 8 oC; and consecutive days per year when the temperature at a depth of 50 cm below the soil surface is higher than (2) Is dry in some part for six-tenths or more of the 8 oC; and cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than (2) Is dry in some part for six-tenths or more of the 5 oC; and cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 2. A calcic horizon either within 100 cm of the mineral 5 oC. soil surface if the weighted average particle-size class of the Arenic Aridic Paleustalfs upper 50 cm of the argillic horizon is sandy, or within 60 cm if it is loamy, or within 50 cm if it is clayey, and JCFK. Other Paleustalfs that have a sandy or sandy-skeletal carbonates in all horizons above the calcic horizon. particle-size class throughout a layer extending from the Calcidic Paleustalfs mineral soil surface to the top of an argillic horizon at a depth of 100 cm or more. JCFP. Other Paleustalfs that, when neither irrigated nor Grossarenic Paleustalfs fallowed to store moisture, have: 1. A frigid temperature regime and a moisture control JCFL. Other Paleustalfs that have a sandy or sandy-skeletal section that in normal years is dry in all parts for four-tenths particle-size class throughout a layer extending from the or more of the time (cumulative) per year when the soil mineral soil surface to the top of an argillic horizon at a depth temperature at a depth of 50 cm below the soil surface is of 50 to 100 cm. higher than 5 oC; or Arenic Paleustalfs 2. A mesic or thermic soil temperature regime and a JCFM. Other Paleustalfs that have 5 percent or more (by moisture control section that in normal years is dry in some volume) plinthite in one or more horizons within 150 cm of the part for six-tenths or more of the time (cumulative) per year mineral soil surface. when the soil temperature at a depth of 50 cm below the soil Plinthic Paleustalfs surface is higher than 5 oC; or 76 Keys to Soil Taxonomy
3. A hyperthermic, isomesic, or warmer iso soil Plinthustalfs temperature regime and a moisture control section that in normal years: Key to Subgroups a. Is moist in some or all parts for less than 90 JCBA. All Plinthustalfs (provisionally). consecutive days per year when the temperature at a Typic Plinthustalfs depth of 50 cm below the soil surface is higher than 8 oC; and Rhodustalfs b. Is dry in some part for six-tenths or more of the Key to Subgroups cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC. JCGA. Rhodustalfs that have a lithic contact within 50 cm of Aridic Paleustalfs the mineral soil surface. Lithic Rhodustalfs JCFQ. Other Paleustalfs that have a CEC of less than 24 cmol(+)/kg clay (by 1N NH4OAc pH 7) in 50 percent or more JCGB. Other Rhodustalfs that have a CEC of less than 24 either of the argillic horizon if less than 100 cm thick or of its cmol(+)/kg clay (by 1N NH4OAc pH 7) in 50 percent or more upper 100 cm. either of the argillic horizon if less than 100 cm thick or of its Kandic Paleustalfs upper 100 cm. Kanhaplic Rhodustalfs JCFR. Other Paleustalfs that have, in all subhorizons in the upper 100 cm of the argillic horizon or throughout the entire JCGC. Other Rhodustalfs that, when neither irrigated nor argillic horizon if less than 100 cm thick, more than 50 percent fallowed to store moisture, have either: colors that have all of the following: 1. A mesic or thermic soil temperature regime and a 1. Hue of 2.5YR or redder; and moisture control section that in normal years is dry in some part for four-tenths or less of the time (cumulative) per year 2. Value, moist, of 3 or less; and when the temperature at a depth of 50 cm below the soil 3. Dry value no more than 1 unit higher than the moist surface is higher than 5 oC; or value. 2. A hyperthermic, isomesic, or warmer iso soil Rhodic Paleustalfs temperature regime and a moisture control section that in normal years is dry in some or all parts for less than 120 JCFS. Other Paleustalfs that have an argillic horizon with a cumulative days per year when the temperature at a depth of base saturation (by sum of cations) of less than 75 percent 50 cm below the soil surface is higher than 8 oC. throughout. Udic Rhodustalfs Ultic Paleustalfs JCGD. Other Rhodustalfs. JCFT. Other Paleustalfs that, when neither irrigated nor Typic Rhodustalfs fallowed to store moisture, have either: 1. A mesic or thermic soil temperature regime and a Xeralfs moisture control section that in normal years is dry in some part for four-tenths or less of the time (cumulative) per year when the temperature at a depth of 50 cm below the soil Key to Great Groups surface is higher than 5 oC; or JDA. Xeralfs that have a duripan that has its upper boundary 2. A hyperthermic, isomesic, or warmer iso soil within 100 cm of the mineral soil surface. temperature regime and a moisture control section that in Durixeralfs, p. 77 normal years is dry in some or all parts for less than 120 cumulative days per year when the temperature at a depth of JDB. Other Xeralfs that have a natric horizon. 50 cm below the soil surface is higher than 8 oC. Natrixeralfs, p. 80 Udic Paleustalfs JDC. Other Xeralfs that have a fragipan with an upper JCFU. Other Paleustalfs. boundary within 100 cm of the mineral soil surface. Typic Paleustalfs Fragixeralfs, p. 78 Alfisols 77
JDD. Other Xeralfs that have one or more horizons within Durixeralfs 150 cm of the mineral soil surface in which plinthite either forms a continuous phase or constitutes one-half or more of the Key to Subgroups volume. JDAA. Durixeralfs that have a natric horizon. Plinthoxeralfs, p. 82 Natric Durixeralfs JDE. Other Xeralfs that have, in all subhorizons in the upper JDAB. Other Durixeralfs that have, above the duripan, one 100 cm of the argillic or kandic horizon or throughout the or both of the following: entire argillic or kandic horizon if less than 100 cm thick, more than 50 percent colors that have all of the following: 1. Cracks that are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and A 1. Hue of 2.5YR or redder; and slickensides or wedge-shaped aggregates in a layer 15 cm or L 2. Value, moist, of 3 or less; and more thick; or F 3. Dry value no more than 1 unit higher than the moist 2. A linear extensibility of 6.0 cm or more. value. Vertic Durixeralfs Rhodoxeralfs, p. 82 JDAC. Other Durixeralfs that have, in one or more JDF. Other Xeralfs that have one or more of the following: subhorizons within the argillic horizon, redox depletions with croma of 2 or less and also aquic conditions for some time in 1. A petrocalcic horizon that has its upper boundary normal years (or artificial drainage). within 150 cm of the mineral soil surface; or Aquic Durixeralfs 2. No densic, lithic, or paralithic contact within 150 cm of the mineral soil surface and an argillic or kandic horizon JDAD. Other Durixeralfs that have both: that has both: 1. An argillic horizon that has both: a. Within 150 cm of the mineral soil surface, either: a. A clayey particle-size class throughout some (1) With increasing depth, no clay decrease of 20 subhorizon 7.5 cm or more thick; and percent or more (relative) from the maximum clay content [Clay is measured noncarbonate clay or based b. At its upper boundary or within some part, a clay on the following formula: Clay % = 2.5(% water increase either of 20 percent or more (absolute) within a retained at 1500 kPa tension - % organic carbon), vertical distance of 7.5 cm or of 15 percent or more whichever value is greater, but no more than 100]; or (absolute) within a vertical distance of 2.5 cm, in the fine-earth fraction; and (2) 5 percent or more (by volume) skeletans on faces of peds in the layer that has a 20 percent lower clay 2. A duripan that is strongly cemented or less cemented in content and, below that layer, a clay increase of 3 all subhorizons. percent or more (absolute) in the fine-earth fraction; Abruptic Haplic Durixeralfs and b. A base at a depth of 150 cm or mre; or JDAE. Other Durixeralfs that have an argillic horizon that has both: 3. No densic, lithic, or paralithic contact within 50 cm of the mineral soil surface and an argillic or kandic horizon 1. A clayey particle-size class throughout some subhorizon that has within 15 cm of its upper boundary both: 7.5 cm or more thick; and a. A clayey, clayey-skeletal, fine, or very-fine particle- 2. At its upper boundary or within some part, a clay size class; and increase either of 20 percent or more (absolute) within a vertical distance of 7.5 cm or of 15 percent or more b. A clay increase, in the fine-earth fraction, of either (absolute) within a vertical distance of 2.5 cm, in the fine- 20 percent or more (absolute) within a vertical distance earth fraction. of 7.5 cm or of 15 percent or more (absolute) within a Abruptic Durixeralfs vertical distance of 2.5 cm. Palexeralfs, p. 80 JDAF. Other Durixeralfs that have a duripan that is strongly JDG. Other Xeralfs. cemented or less cemented in all subhorizons. Haploxeralfs, p. 78 Haplic Durixeralfs 78 Keys to Soil Taxonomy
JDAG. Other Durixeralfs. Haploxeralfs Typic Durixeralfs Key to Subgroups Fragixeralfs JDGA. Haploxeralfs that have both: Key to Subgroups 1. A lithic contact within 50 cm of the mineral soil surface; and JDCA. Fragixeralfs that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm 2. A color value, moist, of 3 or less and 0.7 percent or of the mineral soil surface, a fine-earth fraction with both a more organic carbon either throughout an Ap horizon or bulk density of 1.0 g/cm3 or less, measured at 33 kPa water throughout the upper 10 cm of an A horizon. 1 retention, and Al plus /2 Fe percentages (by ammonium Lithic Mollic Haploxeralfs oxalate) totaling more than 1.0. Andic Fragixeralfs JDGB. Other Haploxeralfs that have both: 1. A lithic contact within 50 cm of the mineral soil JDCB. Other Fragixeralfs that have, throughout one or surface; and more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the 2. An argillic or kandic horizon that is discontinuous following: horizontally in each pedon. Lithic Ruptic-Inceptic Haploxeralfs 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, JDGC. Other Haploxeralfs that have a lithic contact within pumice, and pumicelike fragments; or 50 cm of the mineral soil surface. 2. A fine-earth fraction containing 30 percent or more Lithic Haploxeralfs particles 0.02 to 2.0 mm in diameter; and JDGD. Other Haploxeralfs that have one or both of the a. In the 0.02 to 2.0 mm fraction, 5 percent or more following: volcanic glass; and
1 1. 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 Vitrandic Fragixeralfs that has its upper boundary within 125 cm of the mineral soil surface; or JDCC. Other Fragixeralfs that have an Ap horizon with a color value, moist, of 3 or less and a color value, dry, of 5 or 2. A linear extensibility of 6.0 cm or more between the ess (crushed and smoothed sample) or materials between the mineral soil surface and either a depth of 100 cm or a soil surface and a depth of 18 cm that have these color values densic, lithic, or paralithic contact, whichever is shallower. after mixing. Vertic Haploxeralfs Mollic Fragixeralfs JDGE. Other Haploxeralfs that have both: JDCD. Other Fragixeralfs that have, in one or more horizons within 40 cm of the mineral soil surface, redox depletions with 1. In one or more horizons within 75 cm of the mineral chroma of 2 or less and also aquic conditions for some time in soil surface, redox depletions with chroma of 2 or less and normal years (or artificial drainage). also aquic conditions for some time in normal years (or Aquic Fragixeralfs artificial drainage); and 2. Throughout one or more horizons with a total thickness JDCE. Other Fragixeralfs that, above the fragipan, do not of 18 cm or more within 75 cm of the mineral soil surface, have an argillic or kandic horizon with clay films on both one or more of the following: vertical and horizontal faces of any peds. Inceptic Fragixeralfs 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 JDCF. Other Fragixeralfs. plus /2 Fe percentages (by ammonium oxalate) totaling Typic Fragixeralfs more than 1.0; or Alfisols 79
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 or kandic horizon is 50 cm or pumice, and pumicelike fragments; or more below the mineral soil surface. Fragiaquic Haploxeralfs c. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and JDGI. Other Haploxeralfs that have both: (1) In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and 1. In one or more horizons within 75 cm of the mineral
1 soil surface, redox depletions with chroma of 2 or less and (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 A equal to 30 or more. L Aquandic Haploxeralfs 2. An argillic or kandic horizon that has a base saturation F (by sum of cations) of less than 75 percent in one or more JDGF. Other Haploxeralfs that have, throughout one or more subhorizons within its upper 75 cm or above a densic, lithic, horizons with a total thickness of 18 cm or more within 75 cm or paralithic contact, whichever is shallower. of the mineral soil surface, a fine-earth fraction with both a Aquultic Haploxeralfs bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 retention, and Al plus /2 Fe percentages (by ammonium JDGJ. Other Haploxeralfs that have, in one or more horizons oxalate) totaling more than 1.0. within 75 cm of the mineral soil surface, redox depletions with Andic Haploxeralfs chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). JDGG. Other Haploxeralfs that have, throughout one or more Aquic Haploxeralfs horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: JDGK. Other Haploxeralfs that have an exchangeable sodium percentage of 15 or more (or a sodium adsorption ratio of 13 or 1. More than 35 percent (by volume) fragments coarser more) in one or more subhorizons of the argillic or kandic than 2.0 mm, of which more than 66 percent is cinders, horizon. pumice, and pumicelike fragments; or Natric Haploxeralfs 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and JDGL. Other Haploxeralfs that have fragic soil properties: a. In the 0.02 to 2.0 mm fraction, 5 percent or more 1. In 30 percent or more of the volume of a layer 15 cm or volcanic glass; and more thick that has its upper boundary within 100 cm of the
1 mineral soil surface; or b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 2. In 60 percent or more of the volume of a layer 15 cm or equal to 30 or more. more thick. Vitrandic Haploxeralfs Fragic Haploxeralfs
JDGH. Other Haploxeralfs that have both: JDGM. Other Haploxeralfs that have an argillic horizon that: 1. Fragic soil properties: 1. Consists entirely of lamellae; or a. In 30 percent or more of the volume of a layer 15 cm 2. Is a combination of two or more lamellae and one or or more thick that has its upper boundary within 100 cm more subhorizons with a thickness of 7.5 to 20 cm, each of the mineral soil surface; or layer with an overlying eluvial horizon; or b. In 60 percent or more of the volume of a layer 15 cm 3. Consists of one or more subhorizons that are more than or more thick; and 20 cm thick, each with an overlying eluvial horizon, and above these horizons there are either: 2. Redox depletions with chroma of 2 or less in layers that also have aquic conditions in normal years (or artificial a. Two or more lamellae with a combined thickness of drainage) either: 5 cm or more (that may or may not be part of the argillic horizon); or a. Within the upper 25 cm of the argillic or kandic horizon if its upper boundary is within 50 cm of the b. A combination of lamellae (that may or may not be mineral soil surface; or part of the argillic horizon) and one or more parts of the 80 Keys to Soil Taxonomy
argillic horizon 7.5 to 20 cm thick, each with an more for some time in normal years, and slickensides or overlying eluvial horizon. wedge-shaped aggregates in a layer 15 cm or more thick Lamellic Haploxeralfs that has its upper boundary within 125 cm of the mineral soil surface; or JDGN. Other Haploxeralfs that have a sandy particle-size 2. A linear extensibility of 6.0 cm or more between the class throughout the upper 75 cm of the argillic horizon or mineral soil surface and either a depth of 100 cm or a throughout the entire argillic horizon if it is less than 75 cm densic, lithic, or paralithic contact, whichever is shallower. thick. Vertic Natrixeralfs Psammentic Haploxeralfs JDBB. Other Natrixeralfs that have, in one or more horizons JDGO. Other Haploxeralfs that have 5 percent or more (by within 75 cm of the mineral soil surface, redox depletions with volume) plinthite in one or more horizons within 150 cm of the chroma of 2 or less and also aquic conditions for some time in mineral soil surface. normal years (or artificial drainage). Plinthic Haploxeralfs Aquic Natrixeralfs JDGP. Other Haploxeralfs that have a calcic horizon that has JDBC. Other Natrixeralfs. its upper boundary within 100 cm of the mineral soil surface. Typic Natrixeralfs Calcic Haploxeralfs
JDGQ. Other Haploxeralfs that have: Palexeralfs 1. An argillic, kandic, or natric horizon that is 35 cm or Key to Subgroups less thick; and JDFA. Palexeralfs that have one or both of the following: 2. No densic, lithic, or paralithic contact within 100 cm of 1. Cracks within 125 cm of the mineral soil surface that the mineral soil surface. are 5 mm or more wide through a thickness of 30 cm or Inceptic Haploxeralfs more for some time in normal years, and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick JDGR. Other Haploxeralfs that have an argillic or kandic that has its upper boundary within 125 cm of the mineral horizon that has a base saturation (by sum of cations) of less soil surface; or than 75 percent in one or more subhorizons within its upper 75 cm or above a densic, lithic, or paralithic contact, whichever is 2. A linear extensibility of 6.0 cm or more between shallower. the mineral soil surface and either a depth of 100 cm Ultic Haploxeralfs or a densic, lithic, or paralithic contact, whichever is shallower. Vertic Palexeralfs JDGS. Other Haploxeralfs that have a color value, moist, of 3 or less and 0.7 percent or more organic carbon either JDFB. Other Palexeralfs that have both: throughout an Ap horizon or throughout the upper 10 cm of an A horizon. 1. In one or more horizons within 75 cm of the mineral Mollic Haploxeralfs soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or JDGT. Other Haploxeralfs. artificial drainage); and Typic Haploxeralfs 2. Throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, Natrixeralfs one or more of the following: a. A fine-earth fraction with both a bulk density of 1.0 Key to Subgroups g/cm3 or less, measured at 33 kPa water retention, and Al 1 JDBA. Natrixeralfs that have one or both of the following: plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0; or 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or b. More than 35 percent (by volume) fragments coarser Alfisols 81
than 2.0 mm, of which more than 66 percent is cinders, a. Within the upper 25 cm of the argillic or kandic pumice, and pumicelike fragments; or horizon if its upper boundary is within 50 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. Within 75 cm of the mineral soil surface if the upper boundary of the argillic or kandic horizon is 50 cm or (1) In the 0.02 to 2.0 mm fraction, 5 percent or more more below the mineral soil surface. volcanic glass; and Fragiaquic Palexeralfs 1 (2) [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is JDFF. Other Palexeralfs that have, in one or more horizons equal to 30 or more. within 75 cm of the mineral soil surface, redox depletions with A Aquandic Palexeralfs chroma of 2 or less and also aquic conditions for some time in L normal years (or artificial drainage). F JDFC. Other Palexeralfs that have, throughout one or more Aquic Palexeralfs horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction with both a JDFG. Other Palexeralfs that have a petrocalcic horizon that bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 has its upper boundary within 150 cm of the mineral soil retention, and Al plus /2 Fe percentages (by ammonium surface. oxalate) totaling more than 1.0. Petrocalcic Palexeralfs Andic Palexeralfs JDFH. Other Palexeralfs that have an argillic horizon that: JDFD. Other Palexeralfs that have, throughout one or more horizons with a total thickness of 18 cm or more 1. Consists entirely of lamellae; or within 75 cm of the mineral soil surface, one or both of the 2. Is a combination of two or more lamellae and one or following: more subhorizons with a thickness of 7.5 to 20 cm, each 1. More than 35 percent (by volume) fragments coarser layer with an overlying eluvial horizon; or 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 2. A fine-earth fraction containing 30 percent or more above these horizons there are either: particles 0.02 to 2.0 mm in diameter; and a. Two or more lamellae with a combined thickness of a. In the 0.02 to 2.0 mm fraction, 5 percent or more 5 cm or more (that may or may not be part of the argillic volcanic glass; and horizon); or
1 b. [(Al plus /2 Fe, percent extracted by ammonium b. A combination of lamellae (that may or may not be oxalate) times 60] plus the volcanic glass (percent) is part of the argillic horizon) and one or more parts of the equal to 30 or more. argillic horizon 7.5 to 20 cm thick, each with an Vitrandic Palexeralfs overlying eluvial horizon. 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 a. In 30 percent or more of the volume of a layer 15 cm throughout the entire argillic horizon if it is less than 75 cm or more thick that has its upper boundary within 100 cm thick. of the mineral soil surface; or Psammentic Palexeralfs b. In 60 percent or more of the volume of a layer 15 cm JDFJ. Other Palexeralfs that have a sandy or sandy-skeletal or more thick; and particle-size class throughout a layer extending from the 2. Redox depletions with chroma of 2 or less in layers that mineral soil surface to the top of an argillic or kandic horizon also have aquic conditions in normal years (or artificial at a depth of 50 cm or more. drainage) either: Arenic Palexeralfs 82
JDFK. Other Palexeralfs that have an exchangeable sodium Plinthoxeralfs percentage of 15 or more (or a sodium adsorption ratio of 13 or more) in one or more horizons within 100 cm of the mineral Key to Subgroups soil surface. JDDA. All Plinthoxeralfs (provisionally). Natric Palexeralfs Typic Plinthoxeralfs JDFL. Other Palexeralfs that have fragic soil properties: Rhodoxeralfs 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 Key to Subgroups mineral soil surface; or JDEA. Rhodoxeralfs that have a lithic contact within 50 cm 2. In 60 percent or more of the volume of a layer 15 cm or of the mineral soil surface. more thick. Lithic Rhodoxeralfs Fragic Palexeralfs JDEB. Other Rhodoxeralfs that have one or both of the JDFM. Other Palexeralfs that have a calcic horizon within following: 150 cm of the mineral soil surface. 1. Cracks within 125 cm of the mineral soil surface that Calcic Palexeralfs are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or JDFN. Other Palexeralfs that have 5 percent or more (by wedge-shaped aggregates in a layer 15 cm or more thick volume) plinthite in one or more horizons within 150 cm of the that has its upper boundary within 125 cm of the mineral mineral soil surface. soil surface; or Plinthic Palexeralfs 2. A linear extensibility of 6.0 cm or more between JDFO. Other Palexeralfs that have an argillic or kandic the mineral soil surface and either a depth of 100 cm horizon that has a base saturation (by sum of cations) of less or a densic, lithic, or paralithic contact, whichever is than 75 percent throughout. shallower. Ultic Palexeralfs Vertic Rhodoxeralfs
JDFP. Other Palexeralfs with an argillic or kandic horizon JDEC. Other Rhodoxeralfs that have a petrocalcic horizon that has, in the fine-earth fraction, either or both: 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 JDEE. Other Rhodoxeralfs that have an argillic or kandic or less and 0.7 percent or more organic carbon either horizon that is either less than 15 cm thick or is discontinuous throughout an Ap horizon or throughout the upper 10 cm of an horizontally in each pedon. A horizon. Inceptic Rhodoxeralfs Mollic Palexeralfs
JDFR. Other Palexeralfs. JDEF. Other Rhodoxeralfs. Typic Palexeralfs Typic Rhodoxeralfs 83
CHAPTER 6 Andisols1
Key to Suborders DA. Andisols that have either: 1. A histic epipedon; or A N 2. In a layer above a densic, lithic, or paralithic contact or D in a layer at a depth between 40 and 50 cm either from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever is shallowest, aquic conditions for some time in normal years (or artificial drainage) and one or more of the following: a. 2 percent or more redox concentrations; or contact, duripan, or petrocalcic horizon within that depth; b. A color value, moist, of 4 or more and 50 percent or or more chroma of 2 or less either in redox depletions on faces of peds or in the matrix if peds are absent; or 2. Between either the mineral soil surface or the top of an organic layer with andic soil properties, whichever is c. Enough active ferrous iron to give a positive reaction shallower, and a densic, lithic, or paralithic contact, a to alpha,alpha-dipyridyl at a time when the soil is not duripan, or a petrocalcic horizon. being irrigated. Vitrands, p. 99 Aquands, p. 83 DF. Other Andisols that have an ustic moisture regime. DB. Other Andisols that have a cryic soil temperature Ustands, p. 97 regime. Cryands, p. 86 DG. Other Andisols. Udands, p. 90 DC. Other Andisols that have an aridic moisture regime. Torrands, p. 89 Aquands DD. Other Andisols that have a xeric moisture regime. Xerands, p. 100 Key to Great Groups DE. Other Andisols that have a 1500 kPa water retention of DAA. Aquands that have a cryic soil temperature less than 15 percent on air-dried samples and less than 30 regime. percent on undried samples throughout 60 percent or more of Cryaquands, p. 84 the thickness either: 1. Within 60 cm either of the mineral soil surface or of the DAB. Other Aquands that have, in half or more of each top of an organic layer with andic soil properties, whichever pedon, a placic horizon within 100 cm either of the mineral is shallower, if there is no densic, lithic, or paralithic soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. Placaquands, p. 86
1 This chapter builds on the preliminary Andisol Proposal (1978) by Guy D. Smith (New DAC. Other Aquands that have, in 75 percent or more of Zealand Soil Bureau Record 96) and represents the work of the International Committee on the Classification of Andisols (ICOMAND), chaired by Michael L. Leamy, New Zealand Soil each pedon, a cemented horizon that has its upper boundary Bureau. within 100 cm either of the mineral soil surface or of the top of 84 Keys to Soil Taxonomy
an organic layer with andic soil properties, whichever is Duraquands shallower. Duraquands, p. 84 Key to Subgroups DACA. Duraquands that have a histic epipedon. DAD. Other Aquands that have a 1500 kPa water retention Histic Duraquands of less than 15 percent on air-dried samples and less than 30 percent on undried samples throughout 60 percent or more of DACB. Other Duraquands that have extractable bases (by the thickness either: 3+ NH4OAc) plus 1N KCl-extractable Al totaling less than 2.0 1. Within 60 cm either of the mineral soil surface or of the cmol(+)/kg in the fine-earth fraction of one or more horizons top of an organic layer with andic soil properties, whichever with a total thickness of 30 cm or more at a depth between 25 is shallower, if there is no densic, lithic, or paralithic and 100 cm either from the mineral soil surface or from the top contact within that depth; or of an organic layer with andic soil properties, whichever is shallower. 2. Between either the mineral soil surface or the top Acraquoxic Duraquands of an organic layer with andic soil properties, whichever is shallower, and a densic, lithic, or paralithic DACC. Other Duraquands that have, at a depth between 25 contact. and 100 cm either from the mineral soil surface or from the top Vitraquands, p. 86 of an organic layer with andic soil properties, whichever is shallower, a layer 10 cm or more thick with more than 3.0 DAE. Other Aquands that have a melanic epipedon. percent organic carbon and the colors of a mollic epipedon Melanaquands, p. 85 throughout, underlying one or more horizons with a total thickness of 10 cm or more that have a color value, moist, 1 DAF. Other Aquands that have episaturation. unit or more higher and an organic-carbon content 1 percent or Epiaquands, p. 85 more (absolute) lower. Thaptic Duraquands DAG. Other Aquands. Endoaquands, p. 84 DACD. Other Duraquands. Typic Duraquands Cryaquands Key to Subgroups Endoaquands DAAA. Cryaquands that have a lithic contact within 50 cm Key to Subgroups either of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. DAGA. Endoaquands that have a lithic contact within 50 cm Lithic Cryaquands either of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. DAAB. Other Cryaquands that have a histic epipedon. Lithic Endoaquands Histic Cryaquands DAGB. Other Endoaquands that have a horizon 15 cm or DAAC. Other Cryaquands that have, at a depth between 25 more thick that has 20 percent or more (by volume) cemented and 100 cm either from the mineral soil surface or from the top soil material and has its upper boundary within 100 cm either of an organic layer with andic soil properties, whichever is of the mineral soil surface or of the top of an organic layer with shallower, a layer 10 cm or more thick with more than 3.0 andic soil properties, whichever is shallower. percent organic carbon and the colors of a mollic epipedon Duric Endoaquands throughout, underlying one or more horizons with a total thickness of 10 cm or more that have a color value, moist, 1 DAGC. Other Endoaquands that have a histic epipedon. unit or more higher and an organic-carbon content 1 percent or Histic Endoaquands more (absolute) lower. Thaptic Cryaquands DAGD. Other Endoaquands that have more than 2.0 cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction of one DAAD. Other Cryaquands. or more horizons with a total thickness of 10 cm or more at a Typic Cryaquands depth between 25 and 50 cm either from the mineral soil Andisols 85
surface or from the top of an organic layer with andic soil DAFE. Other Epiaquands that have, at a depth between 25 properties, whichever is shallower. and 100 cm either from the mineral soil surface or from the top Alic Endoaquands of an organic layer with andic soil properties, whichever is shallower, a layer 10 cm or more thick with more than 3.0 DAGE. Other Endoaquands that have, on undried samples, a percent organic carbon and the colors of a mollic epipedon 1500 kPa water retention of 70 percent or more throughout a throughout, underlying one or more horizons with a total layer 35 cm or more thick within 100 cm either of the mineral thickness of 10 cm or more that have a color value, moist, 1 soil surface or of the top of an organic layer with andic soil unit or more higher and an organic-carbon content 1 percent or properties, whichever is shallower. more (absolute) lower. Hydric Endoaquands Thaptic Epiaquands
DAGF. Other Endoaquands that have, at a depth between 25 DAFF. 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 A shallower, a layer 10 cm or more thick with more than 3.0 N percent organic carbon and the colors of a mollic epipedon Melanaquands D 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 DAEA. Melanaquands that have a lithic contact within more (absolute) lower. 50 cm either of the mineral soil surface or of the top of an Thaptic Endoaquands organic layer with andic soil properties, whichever is shallower. DAGG. Other Endoaquands. Lithic Melanaquands Typic Endoaquands DAEB. Other Melanaquands that have extractable bases (by 3+ NH4OAc) plus 1N KCl-extractable Al totaling less than 2.0 Epiaquands 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 Key to Subgroups and 100 cm either from the mineral soil surface or from the top DAFA. Epiaquands that have a horizon 15 cm or more thick of an organic layer with andic soil properties, whichever is that has 20 percent or more (by volume) cemented soil material shallower. and has its upper boundary within 100 cm either of the mineral Acraquoxic Melanaquands soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. DAEC. Other Melanaquands that have both: Duric Epiaquands 1. On undried samples, a 1500 kPa water retention of 70 percent or more throughout a layer 35 cm or more thick DAFB. Other Epiaquands that have a histic epipedon. within 100 cm either of the mineral soil surface or of the top Histic Epiaquands of an organic layer with andic soil properties, whichever is shallower; and DAFC. Other Epiaquands that have more than 2.0 cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction of one 2. More than 6.0 percent organic carbon and the colors of or more horizons with a total thickness of 10 cm or more at a a mollic epipedon throughout a layer 50 cm or more thick depth between 25 and 50 cm either from the mineral soil within 60 cm either of the mineral soil surface or of 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. shallower. Alic Epiaquands Hydric Pachic Melanaquands
DAFD. Other Epiaquands that have, on undried samples, a DAED. Other Melanaquands that have, on undried samples, 1500 kPa water retention of 70 percent or more throughout a a 1500 kPa water retention of 70 percent or more throughout a layer 35 cm or more thick within 100 cm either of the mineral 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 soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. properties, whichever is shallower. Hydric Epiaquands Hydric Melanaquands 86 Keys to Soil Taxonomy
DAEE. Other Melanaquands that have more than 6.0 percent percent organic carbon and the colors of a mollic epipedon organic carbon and the colors of a mollic epipedon throughout throughout, underlying one or more horizons with a total a layer 50 cm or more thick within 60 cm either of the mineral thickness of 10 cm or more that have a color value, moist, 1 soil surface or of the top of an organic layer with andic soil unit or more higher and an organic-carbon content 1 percent or properties, whichever is shallower. more (absolute) lower. Pachic Melanaquands Thaptic Placaquands
DAEF. Other Melanaquands that have, at a depth between 40 DABF. Other Placaquands. and 100 cm either from the mineral soil surface or from the top Typic Placaquands of an organic layer with andic soil properties, whichever is shallower, a layer 10 cm or more thick with more than 3.0 Vitraquands 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 DADA. Vitraquands that have a lithic contact within unit or more higher and an organic-carbon content 1 percent or 50 cm either of the mineral soil surface or of the top of an more (absolute) lower. organic layer with andic soil properties, whichever is Thaptic Melanaquands shallower. Lithic Vitraquands DAEG. Other Melanaquands. Typic Melanaquands DADB. Other Vitraquands that have a horizon 15 cm or more thick that has 20 percent or more (by volume) cemented Placaquands soil material and has its upper boundary within 100 cm either of the mineral soil surface or of the top of an organic layer with Key to Subgroups andic soil properties, whichever is shallower. DABA. Placaquands that have a lithic contact within Duric Vitraquands 50 cm either of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is DADC. Other Vitraquands that have a histic epipedon. shallower. Histic Vitraquands Lithic Placaquands DADD. Other Vitraquands that have, at a depth between 25 DABB. 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 of the top of an organic layer with andic soil properties, unit or more higher and an organic-carbon content 1 percent or whichever is shallower. more (absolute) lower. Duric Histic Placaquands Thaptic Vitraquands
DABC. Other Placaquands that have a horizon 15 cm or DADE. Other Vitraquands. more thick that has 20 percent or more (by volume) cemented Typic Vitraquands soil 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. Cryands Duric Placaquands Key to Great Groups DABD. Other Placaquands that have a histic epipedon. Histic Placaquands DBA. Cryands that have, in 75 percent or more of each pedon, a cemented horizon that has its upper boundary within DABE. Other Placaquands that have, at a depth between 25 100 cm either of the mineral soil surface or of the top of an and 100 cm either from the mineral soil surface or from the top organic layer with andic soil properties, whichever is of an organic layer with andic soil properties, whichever is shallower. shallower, a layer 10 cm or more thick with more than 3.0 Duricryands, p. 87 Andisols 87
DBB. Other Cryands that have, on undried samples, a 1500 normal years (or artificial drainage) and one or more of the kPa water retention of 100 percent or more, by weighted following: average, throughout either: 1. 2 percent or more redox concentrations; or 1. One or more layers with a total thickness of 35 cm 2. A color value, moist, of 4 or more and 50 percent or between the mineral soil surface or the top of an organic more chroma of 2 or less either in redox depletions on faces layer with andic soil properties, whichever is shallower, of peds or in the matrix if peds are absent; or and 100 cm from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever 3. Enough active ferrous iron to give a positive reaction to is shallower, if there is no densic, lithic, or paralithic alpha,alpha-dipyridyl at a time when the soil is not being contact, duripan, or petrocalcic horizon within that depth; irrigated. or Aquic Duricryands 2. 60 percent or more of the horizon thickness between DBAB. Other Duricryands. either the mineral soil surface or the top of an organic layer A Typic Duricryands with andic soil properties, whichever is shallower, and a N densic, lithic, or paralithic contact, a duripan, or a D petrocalcic horizon. Fulvicryands Hydrocryands, p. 88 Key to Subgroups DBDA. Fulvicryands that have a lithic contact within 50 cm DBC. Other Cryands that have a melanic epipedon. either of the mineral soil surface or of the top of an organic Melanocryands, p. 89 layer with andic soil properties, whichever is shallower. Lithic Fulvicryands DBD. Other Cryands that have a layer that meets the depth, thickness, and organic-carbon requirements for a melanic DBDB. Other Fulvicryands that have, throughout a layer 50 epipedon. cm or more thick within 60 cm either of the mineral soil Fulvicryands, p. 87 surface or of the top of an organic layer with andic soil properties, whichever is shallower: DBE. Other Cryands that have a 1500 kPa water retention of less than 15 percent on air-dried samples and less than 30 1. More than 6.0 percent organic carbon, by weighted percent on undried samples throughout 60 percent or more of average; and the thickness either: 2. More than 4.0 percent organic carbon in all parts. 1. Within 60 cm either of the mineral soil surface or of the Pachic Fulvicryands top of an organic layer with andic soil properties, whichever is shallower, if there is no densic, lithic, or paralithic DBDC. Other Fulvicryands that have a 1500 kPa water contact, duripan, or petrocalcic horizon within that depth; retention of less than 15 percent on air-dried samples and less or than 30 percent on undried samples throughout one or more layers that have andic soil properties and have a total thickness 2. Between either the mineral soil surface or the top of an of 25 cm or more within 100 cm either of the mineral soil organic layer with andic soil properties, whichever is surface or of the top of an organic layer with andic soil shallower, and a densic, lithic, or paralithic contact, a properties, whichever is shallower. duripan, or a petrocalcic horizon. Vitric Fulvicryands Vitricryands, p. 89 DBDD. Other Fulvicryands. DBF. Other Cryands. Typic Fulvicryands Haplocryands, p. 87
Duricryands Haplocryands
Key to Subgroups Key to Subgroups DBAA. Duricryands that have, in some subhorizon at a depth DBFA. Haplocryands that have a lithic contact within 50 cm between 50 and 100 cm either from the mineral soil surface or either of the mineral soil surface or of the top of an organic from the top of an organic layer with andic soil properties, layer with andic soil properties, whichever is shallower. whichever is shallower, aquic conditions for some time in Lithic Haplocryands 88 Keys to Soil Taxonomy
DBFB. Other Haplocryands that have more than 2.0 DBFG. Other Haplocryands that have a xeric moisture cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction of one regime. or more horizons with a total thickness of 10 cm or more at a Xeric Haplocryands depth between 25 and 50 cm either from the mineral soil surface or from the top of an organic layer with andic soil DBFH. Other Haplocryands. properties, whichever is shallower. Typic Haplocryands Alic Haplocryands
DBFC. Other Haplocryands that have, in some subhorizon at Hydrocryands a depth between 50 and 100 cm either from the mineral soil Key to Subgroups surface or from the top of an organic layer with andic soil properties, whichever is shallower, aquic conditions for some DBBA. Hydrocryands that have a lithic contact within 50 cm time in normal years (or artificial drainage) and one or more of either of the mineral soil surface or of the top of an organic the following: layer with andic soil properties, whichever is shallower. Lithic Hydrocryands 1. 2 percent or more redox concentrations; or 2. A color value, moist, of 4 or more and 50 percent or DBBB. Other Hydrocryands that have a placic horizon within more chroma of 2 or less either in redox depletions on faces 100 cm either of the mineral soil surface or of the top of an of peds or in the matrix if peds are absent; or organic layer with andic soil properties, whichever is shallower. 3. Enough active ferrous iron to give a positive reaction to Placic Hydrocryands alpha,alpha-dipyridyl at a time when the soil is not being irrigated. DBBC. Other Hydrocryands that have, in one or more Aquic Haplocryands horizons at a depth between 50 and 100 cm either from the mineral soil surface or from the top of an organic layer with DBFD. Other Haplocryands that have extractable bases (by andic soil properties, whichever is shallower, aquic conditions NH OAc) plus 1N KCl-extractable Al3+ totaling less than 2.0 4 for some time in normal years (or artificial drainage) and one cmol(+)/kg in the fine-earth fraction of one or more horizons or more of the following: 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. 2 percent or more redox concentrations; or of an organic layer with andic soil properties, whichever is 2. A color value, moist, of 4 or more and 50 percent shallower. or more chroma of 2 or less either in redox depletions Acrudoxic Haplocryands on faces of peds or in the matrix if peds are absent; or DBFE. Other Haplocryands that have a 1500 kPa water retention of less than 15 percent on air-dried samples and less 3. Enough active ferrous iron to give a positive reaction to than 30 percent on undried samples throughout one or more alpha,alpha-dipyridyl at a time when the soil is not being layers that have andic soil properties and have a total thickness irrigated. of 25 cm or more within 100 cm either of the mineral soil Aquic Hydrocryands surface or of the top of an organic layer with andic soil properties, whichever is shallower. DBBD. Other Hydrocryands that have, at a depth between 25 Vitric Haplocryands and 100 cm either from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever is DBFF. Other Haplocryands that have, at a depth between 25 shallower, a layer 10 cm or more thick with more than 3.0 and 100 cm either from the mineral soil surface or from the top percent organic carbon and the colors of a mollic epipedon of an organic layer with andic soil properties, whichever is throughout, underlying one or more horizons with a total shallower, a layer 10 cm or more thick with more than 3.0 thickness of 10 cm or more that have a color value, moist, 1 percent organic carbon and the colors of a mollic epipedon unit or more higher and an organic-carbon content 1 percent or throughout, underlying one or more horizons with a total more (absolute) lower. thickness of 10 cm or more that have a color value, moist, 1 Thaptic Hydrocryands unit or more higher and an organic-carbon content 1 percent or more (absolute) lower. DBBE. Other Hydrocryands. Thaptic Haplocryands Typic Hydrocryands Andisols 89
Melanocryands DBED. Other Vitricryands that have, at a depth between 25 Key to Subgroups and 100 cm either from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever is DBCA. Melanocryands that have a lithic contact within shallower, a layer 10 cm or more thick with more than 3.0 50 cm either of the mineral soil surface or of the top of an percent organic carbon and the colors of a mollic epipedon organic layer that has andic soil properties, whichever is throughout, underlying one or more horizons with a total shallower. thickness of 10 cm or more that have a color value, moist, 1 Lithic Melanocryands unit or more higher and an organic-carbon content 1 percent or more (absolute) lower. DBCB. Other Melanocryands that have a 1500 kPa water Thaptic Vitricryands retention of less than 15 percent on air-dried samples and less than 30 percent on undried samples throughout one or more DBEE. Other Vitricryands that have a xeric moisture regime layers that have andic soil properties and have a total thickness and a mollic or umbric epipedon. A of 25 cm or more within 100 cm either of the mineral soil Humic Xeric Vitricryands N surface or of the top of an organic layer with andic soil D properties, whichever is shallower. DBEF. Other Vitricryands that have a xeric moisture regime. Vitric Melanocryands Xeric Vitricryands DBCC. Other Melanocryands. DBEG. Other Vitricryands that have an argillic or kandic Typic Melanocryands horizon that has both: Vitricryands 1. An upper boundary within 125 cm either of the mineral soil surface or of the top of an organic layer with andic soil Key to Subgroups properties, whichever is shallower; and DBEA. Vitricryands that have a lithic contact within 2. A base saturation (by sum of cations) of less than 50 cm either of the mineral soil surface or of the top of an 35 percent throughout the upper 50 cm or throughout the organic layer that has andic soil properties, whichever is entire argillic or kandic horizon if it is less than 50 cm shallower. thick. Lithic Vitricryands Ultic Vitricryands
DBEB. Other Vitricryands that have, in one or more horizons DBEH. Other Vitricryands that have an argillic or kandic at a depth between 50 and 100 cm either from the mineral soil horizon that has its upper boundary within 125 cm either of the surface or from the top of an organic layer with andic soil mineral soil surface or of the top of an organic layer with andic properties, whichever is shallower, aquic conditions for some soil properties, whichever is shallower. time in normal years (or artificial drainage) and one or more of Alfic Vitricryands the following: DBEI. Other Vitricryands that have a mollic or umbric 1. 2 percent or more redox concentrations; or epipedon. 2. A color value, moist, of 4 or more and 50 percent or Humic Vitricryands more chroma of 2 or less either in redox depletions on faces of peds or in the matrix if peds are absent; or DBEJ. Other Vitricryands. Typic Vitricryands 3. Enough active ferrous iron to give a positive reaction to alpha,alpha-dipyridyl at a time when the soil is not being irrigated. Torrands Aquic Vitricryands Key to Great Groups DBEC. Other Vitricryands that are saturated with water in one or more layers within 100 cm of the mineral soil surface in DCA. Torrands that have, in 75 percent or more of each normal years for either or both: pedon, a cemented horizon that has its upper boundary within 100 cm either of the mineral soil surface or of the top of an 1. 20 or more consecutive days; or organic layer with andic soil properties, whichever is 2. 30 or more cumulative days. shallower. Oxyaquic Vitricryands Duritorrands, p. 90 90 Keys to Soil Taxonomy
DCB. Other Torrands that have, on air-dried samples, a 1500 DCCC. Other Haplotorrands that have a calcic horizon that kPa water retention of less than 15 percent throughout 60 has its upper boundary within 125 cm of the mineral soil percent or more of the thickness either: surface. Calcic Haplotorrands 1. Within 60 cm either of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever DCCD. Other Haplotorrands. is shallower, if there is no densic, lithic, or paralithic Typic Haplotorrands contact, duripan, or petrocalcic horizon within that depth; or Vitritorrands 2. Between either the mineral soil surface or the top of an organic layer with andic soil properties, whichever is Key to Subgroups shallower, and a densic, lithic, or paralithic contact, a DCBA. Vitritorrands that have a lithic contact within 50 cm duripan, or a petrocalcic horizon. of the mineral soil surface. Vitritorrands, p. 90 Lithic Vitritorrands DCC. Other Torrands. DCBB. Other Vitritorrands that have a horizon 15 cm or Haplotorrands, p. 90 more thick that has 20 percent or more (by volume) cemented soil material and has its upper boundary within 100 cm of the Duritorrands mineral soil surface. Duric Vitritorrands Key to Subgroups DCAA. Duritorrands that have a petrocalcic horizon that has DCBC. Other Vitritorrands that have, in one or more its upper boundary within 100 cm of the mineral soil surface. horizons at a depth between 50 and 100 cm from the Petrocalcic Duritorrands mineral soil surface, aquic conditions for some time in normal years (or artificial drainage) and one or more of the DCAB. Other Duritorrands that have, on air-dried samples, a following: 1500 kPa water retention of less than 15 percent throughout 60 1. 2 percent or more redox concentrations; or percent or more of the thickness either: 2. A color value, moist, of 4 or more and 50 percent or 1. Between either the mineral soil surface or the top of an more chroma of 2 or less either in redox depletions on faces organic layer with andic soil properties, whichever is of peds or in the matrix if peds are absent; or shallower, if there is no paralithic contact or duripan within that depth, and a point 60 cm below that depth; or 3. Enough active ferrous iron to give a positive reaction to alpha,alpha-dipyridyl at a time when the soil is not being 2. Between either the mineral soil surface or the top of an irrigated. organic layer with andic soil properties, whichever is Aquic Vitritorrands shallower, and a paralithic contact or a duripan. Vitric Duritorrands DCBD. Other Vitritorrands that have a calcic horizon that has its upper boundary within 125 cm of the mineral soil DCAC. Other Duritorrands. surface. Typic Duritorrands Calcic Vitritorrands
Haplotorrands DCBE. Other Vitritorrands. Typic Vitritorrands Key to Subgroups DCCA. Haplotorrands that have a lithic contact within 50 cm Udands of the mineral soil surface. Lithic Haplotorrands Key to Great Groups
DCCB. Other Haplotorrands that have a horizon 15 cm or DGA. Udands that have, in half or more of each pedon, a more thick that has 20 percent or more (by volume) cemented placic horizon within 100 cm either of the mineral soil surface soil material and has its upper boundary within 100 cm of the or of the top of an organic layer with andic soil properties, mineral soil surface. whichever is shallower. Duric Haplotorrands Placudands, p. 97 Andisols 91
DGB. Other Udands that have, in 75 percent or more of each DGBB. Other Durudands that have extractable bases (by 3+ pedon, a cemented horizon that has its upper boundary within NH4OAc) plus 1N KCl-extractable Al totaling less than 2.0 100 cm either of the mineral soil surface or of the top of an cmol(+)/kg in the fine-earth fraction of one or more horizons organic layer with andic soil properties, whichever is with a total thickness of 30 cm or more at a depth between 25 shallower. cm either from the mineral soil surface or from the top of an Durudands, p. 91 organic layer with andic soil properties, whichever is shallower, and the cemented horizon. DGC. Other Udands that have a melanic epipedon. Acrudoxic Durudands Melanudands, p. 95 DGBC. Other Durudands that have, on undried samples, a DGD. Other Udands that have, on undried samples, a 1500 1500 kPa water retention of 70 percent or more throughout a kPa water retention of 100 percent or more, by weighted layer 35 cm or more thick above the cemented horizon. average, throughout either: Hydric Durudands A 1. One or more layers with a total thickness of 35 cm DGBD. Other Durudands that have more than 6.0 percent N between the mineral soil surface or the top of an organic organic carbon and the colors of a mollic epipedon throughout D layer with andic soil properties, whichever is shallower, a layer 50 cm or more thick within 60 cm either of the mineral and 100 cm from the mineral soil surface or from the soil surface or of the top of an organic layer with andic soil top of an organic layer with andic soil properties, properties, whichever is shallower. whichever is shallower, if there is no densic, lithic, or Pachic Durudands paralithic contact, duripan, or petrocalcic horizon within that depth; or DGBE. Other Durudands. 2. 60 percent or more of the horizon thickness between Typic Durudands either the mineral soil surface or the top of an organic layer with andic soil properties, whichever is shallower, and a Fulvudands densic, lithic, or paralithic contact, a duripan, or a petrocalcic horizon. Key to Subgroups Hydrudands, p. 94 DGEA. Fulvudands that have both: DGE. Other Udands that have a layer that meets the depth, 1. A lithic contact within 50 cm either of the mineral soil thickness, and organic-carbon requirements for a melanic surface or of the top of an organic layer with andic soil epipedon. properties, whichever is shallower; and Fulvudands, p. 91 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 DGF. Other Udands. 10 cm or more at a depth between 25 cm from the mineral Hapludands, p. 92 soil surface or from the top of an organic layer with andic soil properties, whichever is shallower, and the lithic Durudands contact. Eutric Lithic Fulvudands Key to Subgroups DGEB. Other Fulvudands that have a lithic contact within 50 DGBA. Durudands that have, in one or more horizons above cm either of the mineral soil surface or of the top of an organic the cemented horizon, aquic conditions for some time in layer with andic soil properties, whichever is shallower. normal years (or artificial drainage) and one or more of the Lithic Fulvudands following: 1. 2 percent or more redox concentrations; or DGEC. Other Fulvudands that have, in one or more horizons at a depth between 50 and 100 cm either from the mineral soil 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, aquic conditions for some of peds or in the matrix if peds are absent; or time in normal years (or artificial drainage) and one or more of 3. Enough active ferrous iron to give a positive reaction to the following: alpha,alpha-dipyridyl at a time when the soil is not being 1. 2 percent or more redox concentrations; or irrigated. Aquic Durudands 2. A color value, moist, of 4 or more and 50 percent or 92 Keys to Soil Taxonomy
more chroma of 2 or less either in redox depletions on faces top of an organic layer with andic soil properties, whichever is of peds or in the matrix if peds are absent; or shallower. Eutric Fulvudands 3. Enough active ferrous iron to give a positive reaction to alpha,alpha-dipyridyl at a time when the soil is not being DGEI. Other Fulvudands that have, throughout a layer 50 cm irrigated. or more thick within 60 cm either of the mineral soil surface or Aquic Fulvudands of the top of an organic layer with andic soil properties, whichever is shallower: DGED. Other Fulvudands that have, on undried samples, a 1500 kPa water retention of 70 percent or more throughout a 1. More than 6.0 percent organic carbon, by weighted layer 35 cm or more thick within 100 cm either of the mineral average; and soil surface or of the top of an organic layer with andic soil 2. More than 4.0 percent organic carbon in all parts. properties, whichever is shallower. Pachic Fulvudands Hydric Fulvudands
DGEE. Other Fulvudands that have extractable bases (by DGEJ. Other Fulvudands that have, at a depth between 40 3+ NH4OAc) plus 1N KCl-extractable Al totaling less than 2.0 and 100 cm either from the mineral soil surface or from the top cmol(+)/kg in the fine-earth fraction of one or more horizons of an organic layer with andic soil properties, whichever is with a total thickness of 30 cm or more at a depth between 25 shallower, a layer 10 cm or more thick with more than 3.0 and 100 cm either from the mineral soil surface or from the top percent organic carbon and the colors of a mollic epipedon of an organic layer with andic soil properties, whichever is throughout, underlying one or more horizons with a total shallower. thickness of 10 cm or more that have a color value, moist, 1 Acrudoxic Fulvudands unit or more higher and an organic-carbon content 1 percent or more (absolute) lower. DGEF. Other Fulvudands that have an argillic or kandic Thaptic Fulvudands horizon that has both: DGEK. Other Fulvudands. 1. An upper boundary within 125 cm either of the mineral Typic Fulvudands soil surface or of the top of an organic layer with andic soil properties, whichever is shallower; and 2. A base saturation (by sum of cations) of less than 35 Hapludands percent throughout its upper 50 cm. Key to Subgroups Ultic Fulvudands DGFA. Hapludands that have a lithic contact within 50 cm DGEG. Other Fulvudands that have both: either of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. 1. No horizons with more than 2.0 cmol(+)/kg Al3+ (by 1N Lithic Hapludands KCl) in the fine-earth fraction and with a total thickness of 10 cm or more at a depth between 25 and 50 cm either from the mineral soil surface or from the top of an organic layer DGFB. Other Hapludands that have anthraquic conditions. with andic soil properties, whichever is shallower; and Anthraquic Hapludands 2. Throughout a layer 50 cm or more thick within 60 cm either of the mineral soil surface or of the top of an organic DGFC. Other Hapludands that have both: layer with andic soil properties, whichever is shallower: 1. A horizon 15 cm or more thick that has 20 percent or a. More than 6.0 percent organic carbon, by weighted more (by volume) cemented soil material and has its upper average; and boundary within 100 cm either of the mineral soil surface or 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 DGEH. Other Fulvudands that have no horizons with more cm either from the mineral soil surface or from the top of an than 2.0 cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction organic layer with andic soil properties, whichever is and with a total thickness of 10 cm or more at a depth between shallower, aquic conditions for some time in normal years 25 and 50 cm either from the mineral soil surface or from the (or artificial drainage) and one or more of the following: Andisols 93
a. 2 percent or more redox concentrations; or of an organic layer with andic soil properties, whichever is shallower. b. A color value, moist, of 4 or more and 50 percent or Acrudoxic Hydric Hapludands more chroma of 2 or less either in redox depletions on faces of peds or in the matrix if peds are absent; or DGFH. Other Hapludands that have, at a depth between 25 c. Enough active ferrous iron to give a positive reaction and 100 cm either from the mineral soil surface or from the top to alpha,alpha-dipyridyl at a time when the soil is not of an organic layer with andic soil properties, whichever is being irrigated. shallower, both: Aquic Duric Hapludands 1. Extractable bases (by NH4OAc) plus 1N KCl- extractable Al3+ totaling less than 2.0 cmol(+)/kg in the DGFD. Other Hapludands that have a horizon 15 cm or more fine-earth fraction of one or more horizons with a total thick that has 20 percent or more (by volume) cemented soil thickness of 30 cm or more; and material and has its upper boundary within 100 cm either of the mineral soil surface or of the top of an organic layer with 2. A layer 10 cm or more thick with more than 3.0 percent A andic soil properties, whichever is shallower. organic carbon and the colors of a mollic epipedon N Duric Hapludands throughout, underlying one or more horizons with a total D thickness of 10 cm or more that have a color value, moist, 1 DGFE. Other Hapludands that have more than 2.0 unit or more higher and an organic-carbon content 1 percent cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction of one or more (absolute) lower. or more horizons with a total thickness of 10 cm or more at a Acrudoxic Thaptic Hapludands depth between 25 and 50 cm either from the mineral soil surface or from the top of an organic layer with andic soil DGFI. Other Hapludands that have both: properties, whichever is shallower. 1. Extractable bases (by NH OAc) plus 1N KCl- Alic Hapludands 4 extractable Al3+ totaling less than 2.0 cmol(+)/kg in the fine-earth fraction of one or more horizons with a total DGFF. Other Hapludands that have, in one or more horizons thickness of 30 cm or more at a depth between 25 and 100 at a depth between 50 and 100 cm either from the mineral soil cm either from the mineral soil surface or from the top of an surface or from the top of an organic layer with andic soil organic layer with andic soil properties, whichever is properties, whichever is shallower, aquic conditions for some shallower; and time in normal years (or artificial drainage) and one or more of the following: 2. An argillic or kandic horizon that has both: 1. 2 percent or more redox concentrations; or a. An upper boundary within 125 cm either of the mineral soil surface or of the top of an organic layer with 2. A color value, moist, of 4 or more and 50 percent or andic soil properties, whichever is shallower; and more chroma of 2 or less either in redox depletions on faces of peds or in the matrix if peds are absent; or b. A base saturation (by sum of cations) of less than 35 percent throughout its upper 50 cm. 3. Enough active ferrous iron to give a positive reaction to Acrudoxic Ultic Hapludands alpha,alpha-dipyridyl at a time when the soil is not being irrigated. DGFJ. Other Hapludands that have extractable bases (by Aquic Hapludands 3+ NH4OAc) plus 1N KCl-extractable Al totaling less than 2.0 cmol(+)/kg in the fine-earth fraction of one or more horizons DGFG. Other Hapludands that have both: with a total thickness of 30 cm or more at a depth between 25
1. Extractable bases (by NH4OAc) plus 1N KCl- and 100 cm either from the mineral soil surface or from the top extractable Al3+ totaling less than 2.0 cmol(+)/kg in the of an organic layer with andic soil properties, whichever is fine-earth fraction of one or more horizons with a total shallower. thickness of 30 cm or more at a depth between 25 and 100 Acrudoxic Hapludands cm either from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever is DGFK. Other Hapludands that have a 1500 kPa water 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 94 Keys to Soil Taxonomy
surface or of the top of an organic layer with andic soil thickness of 10 cm or more that have a color value, moist, 1 properties, whichever is shallower. unit or more higher and an organic-carbon content 1 percent or Vitric Hapludands more (absolute) lower. Thaptic Hapludands DGFL. Other Hapludands that have both: DGFP. Other Hapludands that have a sum of extractable 1. On undried samples, a 1500 kPa water retention of 70 bases of more than 25.0 cmol(+)/kg in the fine-earth fraction percent or more throughout a layer 35 cm or more thick throughout one or more horizons with a total thickness of 15 within 100 cm either of the mineral soil surface or of the top cm or more at a depth between 25 and 75 cm either from the of an organic layer with andic soil properties, whichever is mineral soil surface or from the top of an organic layer with shallower; and andic soil properties, whichever is shallower. 2. At a depth between 25 and 100 cm either from the Eutric Hapludands mineral soil surface or from the top of an organic layer with andic soil properties, whichever is shallower, a layer 10 cm DGFQ. Other Hapludands that have an oxic horizon that has or more thick with more than 3.0 percent organic carbon its upper boundary within 125 cm either of the mineral soil and the colors of a mollic epipedon throughout, underlying surface or of the top of an organic layer with andic soil one or more horizons with a total thickness of 10 cm or properties, whichever is shallower. more that have a color value, moist, 1 unit or more higher Oxic Hapludands and an organic-carbon content 1 percent or more (absolute) lower. DGFR. Other Hapludands that have an argillic or kandic Hydric Thaptic Hapludands horizon that has both: 1. An upper boundary within 125 cm either of the mineral DGFM. Other Hapludands that have, on undried samples, a soil surface or of the top of an organic layer with andic soil 1500 kPa water retention of 70 percent or more throughout a properties, whichever is shallower; and 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 2. A base saturation (by sum of cations) of less than 35 properties, whichever is shallower. percent throughout its upper 50 cm. Hydric Hapludands Ultic Hapludands
DGFN. Other Hapludands that have both: DGFS. Other Hapludands that have an argillic or kandic horizon that has its upper boundary within 125 cm either of the 1. A sum of extractable bases of more than 25.0 mineral soil surface or of the top of an organic layer with andic cmol(+)/kg in the fine-earth fraction throughout one or soil properties, whichever is shallower. more horizons with a total thickness of 15 cm or more at a Alfic Hapludands depth between 25 and 75 cm either from the mineral soil surface or from the top of an organic layer with andic soil DGFT. Other Hapludands. properties, whichever is shallower; and Typic Hapludands 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 or more thick with more than 3.0 percent organic carbon Key to Subgroups and the colors of a mollic epipedon throughout, underlying DGDA. Hydrudands that have a lithic contact within 50 cm one or more horizons with a total thickness of 10 cm or either of the mineral soil surface or of the top of an organic more that have a color value, moist, 1 unit or more higher layer with andic soil properties, whichever is shallower. and an organic-carbon content 1 percent or more (absolute) Lithic Hydrudands lower. Eutric Thaptic Hapludands DGDB. Other Hydrudands that have, in one or more horizons at a depth between 50 and 100 cm either from the DGFO. Other Hapludands that have, at a depth between 25 mineral soil surface or from the top of an organic layer with and 100 cm either from the mineral soil surface or from the top andic soil properties, whichever is shallower, aquic conditions of an organic layer with andic soil properties, whichever is for some time in normal years (or artificial drainage) and one shallower, a layer 10 cm or more thick with more than 3.0 or more of the following: percent organic carbon and the colors of a mollic epipedon throughout, underlying one or more horizons with a total 1. 2 percent or more redox concentrations; or Andisols 95
2. A color value, moist, of 4 or more and 50 percent or horizon that has both: more chroma of 2 or less either in redox depletions on faces 1. An upper boundary within 125 cm either of the mineral of peds or in the matrix if peds are absent; or soil surface or of the top of an organic layer with andic soil 3. Enough active ferrous iron to give a positive reaction to properties, whichever is shallower; and alpha,alpha-dipyridyl at a time when the soil is not being 2. A base saturation (by sum of cations) of less than 35 irrigated. percent throughout its upper 50 cm. Aquic Hydrudands Ultic Hydrudands DGDC. Other Hydrudands that have, at a depth between 25 DGDH. Other Hydrudands. and 100 cm either from the mineral soil surface or from the top Typic Hydrudands of an organic layer with andic soil properties, whichever is shallower, both:
Melanudands A 1. Extractable bases (by NH4OAc) plus 1N KCl- extractable Al3+ totaling less than 2.0 cmol(+)/kg in the N Key to Subgroups fine-earth fraction of one or more horizons with a total D thickness of 30 cm or more; and DGCA. Melanudands that have a lithic contact within 50 cm either of the mineral soil surface or of the top of an 2. A layer 10 cm or more thick with more than 3.0 percent organic layer that has andic soil properties, whichever is organic carbon and the colors of a mollic epipedon shallower. throughout, underlying one or more horizons with a total Lithic Melanudands thickness of 10 cm or more that have a color value, moist, 1 unit or more higher and an organic-carbon content 1 percent DGCB. Other Melanudands that have anthraquic conditions. or more (absolute) lower. Anthraquic Melanudands Acrudoxic Thaptic Hydrudands DGCC. Other Melanudands that have, in one or more DGDD. Other Hydrudands that have extractable bases (by horizons at a depth between 50 and 100 cm either from the NH OAc) plus 1N KCl-extractable Al3+ totaling less than 2.0 4 mineral soil surface or from the top of an organic layer with cmol(+)/kg in the fine-earth fraction of one or more horizons andic soil properties, whichever is shallower, aquic conditions with a total thickness of 30 cm or more at a depth between 25 for some time in normal years (or artificial drainage) and one and 100 cm either from the mineral soil surface or from the top or more of the following: of an organic layer with andic soil properties, whichever is shallower. 1. 2 percent or more redox concentrations; or Acrudoxic Hydrudands 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 DGDE. Other Hydrudands that have, at a depth between 25 of peds or in the matrix if peds are absent; or and 100 cm either from the mineral soil surface or from the top of an organic layer with andic soil properties, whichever is 3. Enough active ferrous iron to give a positive reaction to shallower, a layer 10 cm or more thick with more than 3.0 alpha,alpha-dipyridyl at a time when the soil is not being percent organic carbon and the colors of a mollic epipedon irrigated. throughout, underlying one or more horizons with a total Aquic Melanudands thickness of 10 cm or more that have a color value, moist, 1 unit or more higher and an organic-carbon content 1 percent or DGCD. Other Melanudands that have both: more (absolute) lower. 1. Extractable bases (by NH OAc) plus 1N KCl- Thaptic Hydrudands 4 extractable Al3+ totaling less than 2.0 cmol(+)/kg in the fine-earth fraction of one or more horizons with a total DGDF. Other Hydrudands that have a sum of extractable thickness of 30 cm or more at a depth between 25 and 100 bases of more than 25.0 cmol(+)/kg in the fine-earth fraction cm either from the mineral soil surface or from the top of an throughout one or more horizons with a total thickness of 15 organic layer with andic soil properties, whichever is cm or more at a depth between 25 and 75 cm either from the shallower; and mineral soil surface or from the top of an organic layer with andic soil properties, whichever is shallower. 2. A 1500 kPa water retention of less than 15 percent on Eutric Hydrudands air-dried samples and less than 30 percent on undried samples throughout one or more layers that have andic soil DGDG. Other Hydrudands that have an argillic or kandic properties and have a total thickness of 25 cm or more 96 Keys to Soil Taxonomy
within 100 cm either of the mineral soil surface or of the top DGCI. Other Melanudands that have both: of an organic layer with andic soil properties, whichever is 1. On undried samples, a 1500 kPa water retention of 70 shallower. percent or more throughout a layer 35 cm or more thick Acrudoxic Vitric Melanudands within 100 cm either of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is DGCE. Other Melanudands that have both: shallower; and 1. Extractable bases (by NH OAc) plus 1N KCl- 4 2. More than 6.0 percent organic carbon and the colors of extractable Al3+ totaling less than 2.0 cmol(+)/kg in the a mollic epipedon throughout a layer 50 cm or more thick fine-earth fraction of one or more horizons with a total within 60 cm either of the mineral soil surface or of the top thickness of 30 cm or more at a depth between 25 and 100 of an organic layer with andic soil properties, whichever is cm either from the mineral soil surface or from the top of an shallower. organic layer with andic soil properties, whichever is Hydric Pachic Melanudands shallower; and 2. On undried samples, a 1500 kPa water retention of 70 DGCJ. Other Melanudands that have more than 6.0 percent percent or more throughout a layer 35 cm or more thick organic carbon and the colors of a mollic epipedon throughout within 100 cm either of the mineral soil surface or of the top a layer 50 cm or more thick within 60 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. Acrudoxic Hydric Melanudands Pachic Melanudands
DGCF. Other Melanudands that have extractable bases (by DGCK. Other Melanudands that have, on undried samples, a NH OAc) plus 1N KCl-extractable Al3+ totaling less than 2.0 4 1500 kPa water retention of 70 percent or more throughout a cmol(+)/kg in the fine-earth fraction of one or more horizons layer 35 cm or more thick within 100 cm either of the mineral with a total thickness of 30 cm or more 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 Melanudands shallower. Acrudoxic Melanudands DGCL. Other Melanudands that have, at a depth between 40 and 100 cm either from the mineral soil surface or from the top DGCG. Other Melanudands that have both: of an organic layer with andic soil properties, whichever is 1. More than 6.0 percent organic carbon and the colors of shallower, a layer 10 cm or more thick with more than 3.0 a mollic epipedon throughout a layer 50 cm or more thick percent organic carbon and the colors of a mollic epipedon within 60 cm either of the mineral soil surface or of the top throughout, underlying one or more horizons with a total of an organic layer with andic soil properties, whichever is thickness of 10 cm or more that have a color value, moist, 1 shallower; and unit or more higher and an organic-carbon content 1 percent or more (absolute) lower. 2. A 1500 kPa water retention of less than 15 percent on Thaptic Melanudands air-dried samples and less than 30 percent on undried samples throughout one or more layers that have andic soil properties and have a total thickness of 25 cm or more DGCM. Other Melanudands that have an argillic or kandic within 100 cm either of the mineral soil surface or of the top horizon that has both: of an 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 DGCN. 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 Vitric Melanudands cm or more at a depth between 25 and 75 cm either from the Andisols 97
mineral soil surface or from the top of an organic layer with Ustands andic soil properties, whichever is shallower. Eutric Melanudands Key to Great Groups
DGCO. Other Melanudands. DFA. Ustands that have, in 75 percent or more of each Typic Melanudands pedon, a cemented horizon that has its upper boundary within 100 cm either of the mineral soil surface or of the top of an Placudands organic layer with andic soil properties, whichever is shallower. Key to Subgroups Durustands, p. 97 DGAA. Placudands that have a lithic contact within DFB. Other Ustands. 50 cm either of the mineral soil surface or of the top of an Haplustands, p. 98 organic layer that has andic soil properties, whichever is A shallower. N Lithic Placudands Durustands D Key to Subgroups DGAB. Other Placudands that have, in one or more horizons at a depth between 50 cm either from the mineral soil surface DFAA. Durustands that have, in one or more horizons at a or from the top of an organic layer with andic soil properties, depth between 50 and 100 cm either from the mineral soil whichever is shallower, and the placic horizon, aquic surface or from the top of an organic layer with andic soil conditions for some time in normal years (or artificial properties, whichever is shallower, aquic conditions for some drainage) and one or more of the following: time in normal years (or artificial drainage) and one or more of the following: 1. 2 percent or more redox concentrations; or 1. 2 percent or more redox concentrations; or 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 2. A color value, moist, of 4 or more and 50 percent or of peds or in the matrix if peds are absent; or more chroma of 2 or less either in redox depletions on faces of peds or in the matrix if peds are absent; or 3. Enough active ferrous iron to give a positive reaction to alpha,alpha-dipyridyl at a time when the soil is not being 3. Enough active ferrous iron to give a positive reaction to irrigated. alpha,alpha-dipyridyl at a time when the soil is not being Aquic Placudands irrigated. Aquic Durustands DGAC. Other Placudands that have extractable bases (by 3+ NH4OAc) plus 1N KCl-extractable Al totaling less than 2.0 DFAB. Other Durustands that have, at a depth between 25 cmol(+)/kg in the fine-earth fraction of one or more horizons and 100 cm either from the mineral soil surface or from the top with a total thickness of 30 cm or more at a depth between 25 of an organic layer with andic soil properties, whichever is cm either from the mineral soil surface or from the top of an shallower, a layer 10 cm or more thick with more than 3.0 organic layer with andic soil properties, whichever is percent organic carbon and the colors of a mollic epipedon shallower, and the placic horizon. throughout, underlying one or more horizons with a total Acrudoxic Placudands 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 DGAD. Other Placudands that have, on undried samples, a more (absolute) lower. 1500 kPa water retention of 70 percent or more throughout a Thaptic Durustands 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 DFAC. Other Durustands that have a melanic, mollic, or properties, whichever is shallower. umbric epipedon. Hydric Placudands Humic Durustands
DGAE. Other Placudands. DFAD. Other Durustands. Typic Placudands Typic Durustands 98 Keys to Soil Taxonomy
Haplustands soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. Key to Subgroups Pachic Haplustands DFBA. Haplustands that have a lithic contact within 50 cm DFBF. Other Haplustands that have, at a depth between 25 either of the mineral soil surface or of the top of an organic and 100 cm either from the mineral soil surface or from the top layer with andic soil properties, whichever is shallower. of an organic layer with andic soil properties, whichever is Lithic Haplustands shallower, a layer 10 cm or more thick with more than 3.0 percent organic carbon and the colors of a mollic epipedon DFBB. Other Haplustands that have, in one or more horizons throughout, underlying one or more horizons with a total at a depth between 50 and 100 cm either from the mineral soil thickness of 10 cm or more that have a color value, moist, 1 surface or from the top of an organic layer with andic soil unit or more higher and an organic-carbon content 1 percent or properties, whichever is shallower, aquic conditions for some more (absolute) lower. time in normal years (or artificial drainage) and one or more of Thaptic Haplustands the following: DFBG. Other Haplustands that have a calcic horizon that has 1. 2 percent or more redox concentrations; or its upper boundary within 125 cm either of the mineral soil 2. A color value, moist, of 4 or more and 50 percent or surface or of 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. of peds or in the matrix if peds are absent; or Calcic Haplustands 3. Enough active ferrous iron to give a positive reaction to DFBH. Other Haplustands that have extractable bases (by 3+ alpha,alpha-dipyridyl at a time when the soil is not being NH4OAc) plus 1N KCl-extractable Al totaling less than 15.0 irrigated. cmol(+)/kg in the fine-earth fraction throughout one or more Aquic Haplustands horizons with a total thickness of 60 cm or more within 75 cm either of the mineral soil surface or of the top of an organic DFBC. Other Haplustands that have both: layer with andic soil properties, whichever is shallower. Dystric Haplustands 1. Extractable bases (by NH4OAc) plus 1N KCl- extractable Al3+ totaling less than 15.0 cmol(+)/kg in the DFBI. Other Haplustands that have an oxic horizon that has fine-earth fraction throughout one or more horizons with a its upper boundary within 125 cm either of the mineral soil total 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 air-dried samples and less than 30 percent on undried DFBJ. Other Haplustands that have an argillic or kandic samples throughout one or more layers that have andic soil horizon that has both: properties and have a total thickness of 25 cm or more 1. An upper boundary within 125 cm either of the mineral within 100 cm either of the mineral soil surface or of 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; and shallower. Dystric Vitric Haplustands 2. A base saturation (by sum of cations) of less than 35 percent throughout the upper 50 cm or throughout the entire DFBD. Other Haplustands that have a 1500 kPa water argillic or kandic horizon if it is less than 50 cm thick. retention of less than 15 percent on air-dried samples and less Ultic Haplustands than 30 percent on undried samples throughout one or more layers that have andic soil properties and have a total thickness DFBK. Other Haplustands that have an argillic or kandic of 25 cm or more within 100 cm either of the mineral soil horizon that has its upper boundary within 125 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 andic properties, whichever is shallower. soil properties, whichever is shallower. Vitric Haplustands Alfic Haplustands
DFBE. Other Haplustands that have more than 6.0 percent DFBL. Other Haplustands that have a melanic, mollic, or organic carbon and the colors of a mollic epipedon throughout umbric epipedon. a layer 50 cm or more thick within 60 cm either of the mineral Humic Haplustands Andisols 99
DFBM. Other Haplustands. upper boundary of an organic layer with andic soil Typic Haplustands properties, whichever is shallower; and 2. A base saturation (by sum of cations) of less than 35 Vitrands percent throughout the upper 50 cm of the argillic or kandic horizon. Key to Great Groups Ultic Udivitrands DEA. Vitrands that have an ustic moisture regime. DEBE. Other Udivitrands that have an argillic or kandic Ustivitrands, p. 99 horizon that has its upper boundary within 125 cm of the mineral soil surface or of the upper boundary of an organic DEB. Other Vitrands. layer with andic soil properties, whichever is shallower. Udivitrands, p. 99 Alfic Udivitrands
A DEBF. Other Udivitrands that have a melanic, mollic, or Udivitrands N umbric epipedon. D Key to Subgroups Humic Udivitrands DEBA. Udivitrands that have a lithic contact within 50 cm DEBG. Other Udivitrands. either of the mineral soil surface or of the top of an organic Typic Udivitrands layer with andic soil properties, whichever is shallower. Lithic Udivitrands Ustivitrands DEBB. Other Udivitrands that have, in one or more horizons at a depth between 50 and 100 cm either from the mineral soil Key to Subgroups surface or from the top of an organic layer with andic soil DEAA. Ustivitrands that have a lithic contact within 50 cm properties, whichever is shallower, aquic conditions for some either of the mineral soil surface or of the top of an organic time in normal years (or artificial drainage) and one or more of layer with andic soil properties, whichever is shallower. the following: Lithic Ustivitrands 1. 2 percent or more redox concentrations; or DEAB. Other Ustivitrands that have, in one or more horizons 2. A color value, moist, of 4 or more and 50 percent or at a depth between 50 and 100 cm either from the mineral soil more chroma of 2 or less either in redox depletions on faces surface or from the top of an organic layer with andic soil of peds or in the matrix if peds are absent; or properties, whichever is shallower, aquic conditions for some 3. Enough active ferrous iron to give a positive reaction to time in normal years (or artificial drainage) and one or more of alpha,alpha-dipyridyl at a time when the soil is not being the following: irrigated. 1. 2 percent or more redox concentrations; or Aquic Udivitrands 2. A color value, moist, of 4 or more and 50 percent or DEBC. Other Udivitrands that have, at a depth between 25 more chroma of 2 or less either in redox depletions on faces and 100 cm either from the mineral soil surface or from the top of peds or in the matrix if peds are absent; or of an organic layer with andic soil properties, whichever is 3. Enough active ferrous iron to give a positive reaction to shallower, a layer 10 cm or more thick with more than 3.0 alpha,alpha-dipyridyl at a time when the soil is not being percent organic carbon and the colors of a mollic epipedon irrigated. throughout, underlying one or more horizons with a total Aquic Ustivitrands 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 DEAC. Other Ustivitrands that have, at a depth between 25 more (absolute) lower. and 100 cm either from the mineral soil surface or from the top Thaptic Udivitrands of an organic layer with andic soil properties, whichever is shallower, a layer 10 cm or more thick with more than 3.0 DEBD. Other Udivitrands that have both: percent organic carbon and the colors of a mollic epipedon 1. An argillic or kandic horizon that has its upper throughout, underlying one or more horizons with a total boundary within 125 cm of the mineral soil surface or of the thickness of 10 cm or more that have a color value, moist, 1 100 Keys to Soil Taxonomy
unit or more higher and an organic-carbon content 1 percent or andic soil properties, whichever is shallower, aquic conditions more (absolute) lower. for some time in normal years (or artificial drainage) and one Thaptic Ustivitrands or more of the following: 1. 2 percent or more redox concentrations; or DEAD. Other Ustivitrands that have a calcic horizon that has its upper boundary within 125 cm either of the mineral soil 2. A color value, moist, of 4 or more and 50 percent or surface or of 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. of peds or in the matrix if peds are absent; or Calcic Ustivitrands 3. Enough active ferrous iron to give a positive reaction to alpha,alpha-dipyridyl at a time when the soil is not being DEAE. Other Ustivitrands that have a melanic, mollic, or irrigated. umbric epipedon. Aquic Haploxerands Humic Ustivitrands DDCC. Other Haploxerands that have, at a depth between 25 DEAF. Other Ustivitrands. and 100 cm from the mineral soil surface or from the top of an Typic Ustivitrands organic layer with andic soil properties, whichever is shallower, a layer 10 cm or more thick with more than 3.0 Xerands percent organic carbon and the colors of a mollic epipedon throughout, underlying one or more horizons with a total Key to Great Groups 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 DDA. Xerands that have a 1500 kPa water retention of less more (absolute) lower. than 15 percent on air-dried samples and less than 30 percent Thaptic Haploxerands on undried samples throughout 60 percent or more of the thickness either: DDCD. Other Haploxerands that have a calcic horizon that 1. Within 60 cm either of the mineral soil surface or of the has its upper boundary within 125 cm of the mineral soil top of an organic layer with andic soil properties, whichever surface. is shallower, if there is no densic, lithic, or paralithic Calcic Haploxerands contact, duripan, or petrocalcic horizon within that depth; or DDCE. Other Haploxerands that have an argillic or kandic horizon that has both: 2. Between either the mineral soil surface or the top of an organic layer with andic soil properties, whichever is 1. An upper boundary within 125 cm of the mineral soil shallower, and a densic, lithic, or paralithic contact, a surface or of the top of an organic layer with andic soil duripan, or a petrocalcic horizon. properties, whichever is shallower; and Vitrixerands, p. 101 2. A base saturation (by sum of cations) of less than 35 percent throughout its upper 50 cm. DDB. Other Xerands that have a melanic epipedon. Ultic Haploxerands Melanoxerands, p. 101
DDC. Other Xerands. DDCF. Other Haploxerands that have both: Haploxerands, p. 100 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 Key to Subgroups top of an organic layer with andic soil properties, whichever is shallower. DDCA. 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. Lithic Haploxerands DDCG. Other Haploxerands that have an argillic or kandic horizon that has its upper boundary within 125 cm of the DDCB. Other Haploxerands that have, in one or more mineral soil surface or of the top of an organic layer with andic horizons at a depth between 50 and 100 cm either from the soil properties, whichever is shallower. mineral soil surface or from the top of an organic layer with Alfic Haploxerands Andisols 101
DDCH. Other Haploxerands that have a mollic or umbric DDAC. Other Vitrixerands that have, at a depth between 25 epipedon. and 100 cm from the mineral soil surface or from the top of an Humic Haploxerands organic layer with andic soil properties, whichever is shallower, a layer 10 cm or more thick with more than 3.0 DDCI. Other Haploxerands. percent organic carbon and the colors of a mollic epipedon Typic Haploxerands throughout, underlying one or more horizons with a total thickness of 10 cm or more that have a color value, moist, 1 Melanoxerands unit or more higher and an organic-carbon content 1 percent or more (absolute) lower. Key to Subgroups Thaptic Vitrixerands DDBA. Melanoxerands that have more than 6.0 percent organic carbon and the colors of a mollic epipedon throughout DDAD. Other Vitrixerands that have both: a layer 50 cm or more thick within 60 cm either of the mineral 1. A melanic, mollic, or umbric epipedon; and A soil surface or of the top of an organic layer with andic soil N properties, whichever is shallower. 2. An argillic or kandic horizon that has its upper D Pachic Melanoxerands boundary within 125 cm of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever DDBB. Other Melanoxerands. is shallower. Typic Melanoxerands Alfic Humic Vitrixerands
Vitrixerands DDAE. Other Vitrixerands that have an argillic or kandic horizon that has both: Key to Subgroups 1. An upper boundary within 125 cm either of the mineral DDAA. Vitrixerands that have a lithic contact within 50 cm soil surface or of the top of an organic layer with andic soil of the mineral soil surface or of the top of an organic layer with properties, whichever is shallower; and andic soil properties, whichever is shallower. 2. A base saturation (by sum of cations) of less than Lithic Vitrixerands 35 percent throughout the upper 50 cm or throughout the entire argillic or kandic horizon if it is less than 50 cm DDAB. Other Vitrixerands that have, in one or more thick. horizons at a depth between 50 and 100 cm either from the Ultic Vitrixerands mineral soil surface or from the top of an organic layer with andic soil properties, whichever is shallower, aquic conditions DDAF. Other Vitrixerands that have an argillic or kandic for some time in normal years (or artificial drainage) and one horizon that has its upper boundary within 125 cm of the or more of the following: mineral soil surface or of the top of an organic layer with andic 1. 2 percent or more redox concentrations; or soil properties, whichever is shallower. Alfic Vitrixerands 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 DDAG. Other Vitrixerands that have a melanic, mollic, or of peds or in the matrix if peds are absent; or umbric epipedon. 3. Enough active ferrous iron to give a positive reaction to Humic Vitrixerands alpha,alpha-dipyridyl at a time when the soil is not being irrigated. DDAH. Other Vitrixerands. Aquic Vitrixerands Typic Vitrixerands
103
CHAPTER 7 Aridisols1
Key to Suborders FA. Aridisols that have a cryic soil temperature regime. Cryids, p. 118
FB. Other Aridisols that have a salic horizon that has its upper boundary within 100 cm of the soil surface. Salids, p. 128 A R FC. Other Aridisols that have a duripan that has its upper I boundary within 100 cm of the soil surface. Durids, p. 121 FEB. Other Argids that have a natric horizon. FD. Other Aridisols that have a gypsic or petrogypsic horizon Natrargids, p. 108 that has its upper boundary within 100 cm of the soil surface and do not have a petrocalcic horizon overlying these horizons. Gypsids, p. 124 FEC. Other Argids that do not have a densic, lithic, or paralithic contact within 50 cm of the soil surface and have FE. Other Aridisols that have an argillic or natric horizon either: that has its upper boundary within 100 cm of the soil surface 1. A clay increase of 15 percent or more (absolute) within and do not have a petrocalcic horizon that has an upper a vertical distance of 2.5 cm either within the argillic boundary within 100 cm of the soil surface. horizon or at its upper boundary; or Argids, p. 103 2. An argillic horizon that extends to 150 cm or more FF. Other Aridisols that have a calcic or petrocalcic horizon from the soil surface, that does not have a clay decrease with that has its upper boundary within 100 cm of the soil surface. increasing depth of 20 percent or more (relative) from the Calcids, p. 111 maximum clay content, and that has, in 50 percent or more of the matrix in some part between 100 and 150 cm, either: FG. Other Aridisols. a. Hue of 7.5YR or redder and chroma of 5 or more; Cambids, p. 114 or Argids b. Hue of 7.5YR or redder and value, moist, of 3 or less and value, dry, of 4 or less. Paleargids, p. 109 Key to Great Groups FED. Other Argids that have a gypsic horizon that has its FEA. Argids that have a duripan or a petrocalcic or upper boundary within 150 cm of the soil surface. petrogypsic horizon that has its upper boundary within 150 cm Gypsiargids, p. 105 of the soil surface. Petroargids, p. 111 FEE. Other Argids that have a calcic horizon that has its upper boundary within 150 cm of the soil surface. Calciargids, p. 104
1 This chapter was rewritten in 1994 following recommendations of the International Committee on Aridisols (ICOMID), chaired by Dr. A. Osman. Major contributions were made FEF. Other Argids. by Dr. H. Eswaran and J. Nichols. Haplargids, p. 106 104 Keys to Soil Taxonomy
Calciargids soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact if shallower. Key to Subgroups Vertic Calciargids FEEA. Calciargids that have a lithic contact within 50 cm of FEEE. Other Calciargids that are either: the soil surface. Lithic Calciargids 1. Irrigated and have aquic conditions for some time in normal years in one or more layers within 100 cm of the soil FEEB. Other Calciargids that have both: surface; or 1. One or both of the following: 2. Saturated with water in one or more layers within 100 cm of the soil surface for 1 month or more in normal a. Cracks within 125 cm of the soil surface that are 5 years. mm or more wide through a thickness of 30 cm or more Aquic Calciargids for some time in normal years, and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick FEEF. Other Calciargids that have: that has its upper boundary within 125 cm of the soil surface; or 1. A sandy or sandy-skeletal particle-size class throughout a layer extending from the soil surface to the top of an b. A linear extensibility of 6.0 cm or more between the argillic horizon at a depth of 50 cm or more; and soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact if shallower; and 2. A moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) when the 2. A moisture control section that is dry in all parts for soil temperature at a depth of 50 cm is 5 oC or higher and a less than three-fourths of the time (cumulative) when the soil moisture regime that borders on ustic. soil temperature is 5 oC or higher at a depth of 50 cm and a Arenic Ustic Calciargids soil moisture regime that borders on xeric. Xerertic Calciargids FEEG. Other Calciargids that have a sandy or sandy-skeletal particle-size class throughout a layer extending from the soil FEEC. Other Calciargids that have both: surface to the top of an argillic horizon at a depth of 50 cm or 1. One or both of the following: more. Arenic Calciargids a. Cracks within 125 cm of the soil surface that are 5 mm or more wide through a thickness of 30 cm or more FEEH. Other Calciargids that have the following for some time in normal years, and slickensides or combination of characteristics: wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 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) durinodes or b. A linear extensibility of 6.0 cm or more between the are brittle and have at least a firm rupture-resistance class soil surface and either a depth of 100 cm or a densic, when 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 than three-fourths of the time (cumulative) when the less than three-fourths of the time (cumulative) when the soil temperature is 5 oC or higher at a depth of 50 cm and soil temperature is 5 oC or higher at a depth of 50 cm and a have a soil moisture regime that borders on xeric. soil moisture regime that borders on ustic. Durinodic Xeric Calciargids Ustertic Calciargids FEEI. Other Calciargids that have one or more horizons, FEED. Other Calciargids that have one or both of the within 100 cm of the soil surface and with a combined following: thickness of 15 cm or more, that contain 20 percent or more 1. Cracks within 125 cm of the soil surface that are 5 mm (by volume) durinodes or are brittle and have at least a firm or more wide through a thickness of 30 cm or more for some rupture-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 FEEJ. Other Calciargids that: 2. A linear extensibility of 6.0 cm or more between the 1. Are dry in all parts of the moisture control section Aridisols 105
for less than three-fourths of the time (cumulative) when than 2.0 mm, of which more than 66 percent is cinders, the soil temperature at a depth of 50 cm is 5 oC or higher pumice, and pumicelike fragments; or and have a soil moisture regime that borders on xeric; 2. A fine-earth fraction containing 30 percent or more and particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 2. Have one or more horizons, within 100 cm of the soil more is volcanic glass, and [(Al plus /2 Fe, percent surface and with a combined thickness of 15 cm or more, extracted by ammonium oxalate) times 60] plus the volcanic that contain 20 percent or more (by volume) nodules or glass (percent) is 30 or more. concretions. Vitrandic Calciargids Petronodic Xeric Calciargids FEEO. Other Calciargids that are dry in all parts of the FEEK. Other Calciargids that: moisture control section for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm is 1. Are dry in all parts of the moisture control section 5 oC or higher and have a soil moisture regime that borders on for less than three-fourths of the time (cumulative) when xeric. the soil temperature at a depth of 50 cm is 5 oC or higher Xeric Calciargids and have a soil moisture regime that borders on ustic; and FEEP. Other Calciargids that are dry in all parts of the A 2. Have one or more horizons, within 100 cm of the soil moisture control section for less than three-fourths of the time R surface and with a combined thickness of 15 cm or more, (cumulative) when the soil temperature at a depth of 50 cm is I that contain 20 percent or more (by volume) nodules or 5 oC or higher and have a soil moisture regime that borders on concretions. ustic. Petronodic Ustic Calciargids Ustic Calciargids
FEEL. Other Calciargids that have one or more horizons, FEEQ. Other Calciargids. within 100 cm of the soil surface and with a combined Typic Calciargid thickness of 15 cm or more, that contain 20 percent or more (by volume) nodules or concretions. Gypsiargids Petronodic Calciargids Key to Subgroups FEEM. Other Calciargids that have both: FEDA. Gypsiargids that are either: 1. A moisture control section that is dry in all parts for 1. Irrigated and have aquic conditions for some time in less than three-fourths of the time (cumulative) when the normal years in one or more layers within 100 cm of the soil soil temperature is 5 oC or higher at a depth of 50 cm and a surface; or soil moisture regime that borders on xeric; and 2. Are saturated with water in one or more layers within 2. Throughout one or more horizons with a total thickness 100 cm of the soil surface for 1 month or more in normal of 18 cm or more within 75 cm of the soil surface, one or years. both of the following: Aquic Gypsiargids a. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, FEDB. Other Gypsiargids that have one or more horizons, pumice, and pumicelike fragments; or within 100 cm of the soil surface and with a combined thickness of 15 cm or more, that either contain 20 percent or b. A fine-earth fraction containing 30 percent or more more (by volume) durinodes or are brittle and have at least a particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 firm rupture-resistance class when moist. or more is volcanic glass, and [(Al plus /2 Fe, percent Durinodic Gypsiargids extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. FEDC. Other Gypsiargids that have both: Vitrixerandic Calciargids 1. A moisture control section that is dry in all parts for FEEN. Other Calciargids that have, throughout one or more less than three-fourths of the time (cumulative) when the horizons with a total thickness of 18 cm or more within 75 cm soil temperature is 5 oC or higher at a depth of 50 cm and a of the soil surface, one or both of the following: soil moisture regime that borders on xeric; and 1. More than 35 percent (by volume) fragments coarser 2. Throughout one or more horizons with a total thickness 106 Keys to Soil Taxonomy
of 18 cm or more within 75 cm of the soil surface, one or FEFB. Other Haplargids that have: both of the following: 1. A lithic contact within 50 cm of the soil surface; a. More than 35 percent (by volume) fragments coarser and than 2.0 mm, of which more than 66 percent is cinders, 2. A moisture control section that is dry in all parts for pumice, and pumicelike fragments; or less than three-fourths of the time (cumulative) when the b. A fine-earth fraction containing 30 percent or more soil temperature is 5 oC or higher at a depth of 50 cm and a particles 0.02 to 2.0 mm in diameter, of which 5 percent soil moisture regime that borders on xeric. 1 or more is volcanic glass, and [(Al plus /2 Fe, percent Lithic Xeric Haplargids extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. FEFC. Other Haplargids that have: Vitrixerandic Gypsiargids 1. A lithic contact within 50 cm of the soil surface; and FEDD. Other Gypsiargids that have, throughout one or more 2. A moisture control section that is dry in all parts for horizons with a total thickness of 18 cm or more within 75 cm less than three-fourths of the time (cumulative) when the of the soil surface, one or both of the following: soil temperature is 5 oC or higher at a depth of 50 cm and a soil moisture regime that borders on ustic. 1. More than 35 percent (by volume) fragments coarser Lithic Ustic Haplargids than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or FEFD. Other Haplargids that have a lithic contact within 50 2. A fine-earth fraction containing 30 percent or more cm of the soil surface. particles 0.02 to 2.0 mm in diameter, of which 5 percent or Lithic Haplargids 1 more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic FEFE. Other Haplargids that have both: glass (percent) is 30 or more. 1. One or both of the following: Vitrandic Gypsiargids a. Cracks within 125 cm of the soil surface that are 5 FEDE. Other Gypsiargids that are dry in all parts of the mm or more wide through a thickness of 30 cm or more moisture control section for less than three-fourths of the time for some time in normal years, and slickensides or (cumulative) when the soil temperature at a depth of 50 cm is wedge-shaped aggregates in a layer 15 cm or more thick 5 oC or higher and have a soil moisture regime that borders on that has its upper boundary within 125 cm of the soil xeric. surface; or Xeric Gypsiargids b. A linear extensibility of 6.0 cm or more between the soil surface and either a depth of 100 cm or a densic, FEDF. Other Gypsiargids that are dry in all parts of the lithic, or paralithic contact if shallower; and moisture control section for less than three-fourths of the time (cumulative) when the soil temperature is 5 oC or higher at a 2. A moisture control section that is dry in all parts for depth of 50 cm and have a soil moisture regime that borders on less than three-fourths of the time (cumulative) when the ustic. soil temperature is 5 oC or higher at a depth of 50 cm and a Ustic Gypsiargids soil moisture regime that borders on xeric. Xerertic Haplargids FEDG. Other Gypsiargids. Typic Gypsiargids FEFF. Other Haplargids that have both: 1. One or both of the following: Haplargids 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 FEFA. Haplargids that have: that has its upper boundary within 125 cm of the soil 1. A lithic contact within 50 cm of the soil surface; and surface; or 2. An argillic horizon that is discontinuous throughout b. A linear extensibility of 6.0 cm or more between the each pedon. soil surface and either a depth of 100 cm or a densic, Lithic Ruptic-Entic Haplargids lithic, or paralithic contact if shallower; and Aridisols 107
2. A moisture control section that is dry in all parts for soil temperature is 5 oC or higher at a depth of 50 cm and a less than three-fourths of the time (cumulative) when the soil moisture regime that borders on xeric. soil temperature is 5 oC or higher at a depth of 50 cm and a Durinodic Xeric Haplargids soil moisture regime that borders on ustic. Ustertic Haplargids FEFL. Other Haplargids that have one or more horizons, within 100 cm of the soil surface and with a combined FEFG. Other Haplargids that have one or both of the thickness of 15 cm or more, that contain 20 percent or more following: (by volume) durinodes or are brittle and have at least a firm rupture-resistance class when moist. 1. Cracks within 125 cm of the soil surface that are 5 mm Durinodic Haplargids or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or wedge-shaped FEFM. Other Haplargids that: aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the soil surface; or 1. Have one or more horizons, within 100 cm of the soil surface and with a combined thickness of 15 cm or more, 2. A linear extensibility of 6.0 cm or more between the that contain 20 percent or more (by volume) nodules or soil surface and either a depth of 100 cm or a densic, lithic, concretions; and or paralithic contact if shallower. A Vertic Haplargids 2. Are dry in all parts of the moisture control section for R less than three-fourths of the time (cumulative) when the I FEFH. Other Haplargids that are either: soil temperature at a depth of 50 cm is 5 oC or higher and have a soil moisture regime that borders on ustic. 1. Irrigated and have aquic conditions for some time in Petronodic Ustic Haplargids normal years in one or more layers within 100 cm of the soil surface; or FEFN. Other Haplargids that have one or more horizons, 2. Saturated with water in one or more layers within 100 within 100 cm of the soil surface and with a combined cm of the soil surface for 1 month or more in normal years. thickness of 15 cm or more, that contain 20 percent or more Aquic Haplargids (by volume) nodules or concretions. Petronodic Haplargids FEFI. Other Haplargids that have: FEFO. Other Haplargids that have both: 1. A sandy or sandy-skeletal particle-size class throughout a layer extending from the soil surface to the top of an 1. A moisture control section that is dry in all parts for argillic horizon at a depth of 50 cm or more; and 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 2. A moisture control section that is dry in all parts for soil moisture regime that borders on xeric; and less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm is 5 oC or higher and a 2. Throughout one or more horizons with a total thickness soil moisture regime that borders on ustic. of 18 cm or more within 75 cm of the soil surface, one or Arenic Ustic Haplargids both of the following: a. More than 35 percent (by volume) fragments coarser FEFJ. Other Haplargids that have a sandy or sandy-skeletal than 2.0 mm, of which more than 66 percent is cinders, particle-size class throughout a layer extending from the soil pumice, and pumicelike fragments; or surface to the top of an argillic horizon at a depth of 50 cm or more. b. A fine-earth fraction containing 30 percent or more Arenic Haplargids 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 FEFK. Other Haplargids that have: extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. 1. One or more horizons, within 100 cm of the soil surface Vitrixerandic Haplargids and with a combined thickness of 15 cm or more, that contain 20 percent or more (by volume) durinodes or are brittle and have at least a firm rupture-resistance class when FEFP. Other Haplargids that have, throughout one or more 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 1. More than 35 percent (by volume) fragments coarser 108 Keys to Soil Taxonomy
than 2.0 mm, of which more than 66 percent is cinders, 1. Cracks within 125 cm of the soil surface that are 5 mm pumice, and pumicelike fragments; or or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or wedge-shaped 2. A fine-earth fraction containing 30 percent or more aggregates in a layer 15 cm or more thick that has its upper particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 boundary within 125 cm of the soil surface; or more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic 2. A linear extensibility of 6.0 cm or more between the glass (percent) is 30 or more. soil surface and either a depth of 100 cm or a densic, lithic, Vitrandic Haplargids or paralithic contact, whichever is shallower. Vertic Natrargids FEFQ. Other Haplargids that are dry in all parts of the moisture control section for less than three-fourths of the time FEBE. Other Natrargids that are either: (cumulative) when the soil temperature at a depth of 50 cm is 1. Irrigated and have aquic conditions for some time in 5 oC or higher and have a soil moisture regime that borders on normal years in one or more layers within 100 cm of the soil xeric. surface; or Xeric Haplargids 2. Saturated with water in one or more layers within FEFR. Other Haplargids that are dry in all parts of the 100 cm of the soil surface for 1 month or more in normal moisture control section for less than three-fourths of the time years. (cumulative) when the soil temperature is 5 oC or higher at a Aquic Natrargids depth of 50 cm and have a soil moisture regime that borders on ustic. FEBF. Other Natrargids that meet both of the following: Ustic Haplargids 1. Have one or more horizons, within 100 cm of the soil surface and with a combined thickness of 15 cm or more, FEFS. Other Haplargids. that contain 20 percent or more (by volume) durinodes or Typic Haplargids are brittle and have at least a firm rupture-resistance class when moist; and Natrargids 2. Are dry in all parts of the moisture control section for less than three-fourths of the time (cumulative) Key to Subgroups when the soil temperature is 5 oC or higher at a depth FEBA. Natrargids that have both of the following: of 50 cm and have a soil moisture regime that borders on xeric. 1. A lithic contact within 50 cm of the soil surface; and Durinodic Xeric Natrargids 2. A moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) when the FEBG. Other Natrargids that have one or more horizons, soil temperature is 5 oC or higher at a depth of 50 cm and a within 100 cm of the soil surface and with a combined soil moisture regime that borders on xeric. thickness of 15 cm or more, that contain 20 percent or more Lithic Xeric Natrargids (by volume) durinodes or are brittle and have at least a firm rupture-resistance class when moist. FEBB. Other Natrargids that have both of the following: Durinodic Natrargids 1. A lithic contact within 50 cm of the soil surface; and FEBH. Other Natrargids that have one or more horizons, 2. A moisture control section that is dry in all parts for within 100 cm of the soil surface and with a combined less than three-fourths of the time (cumulative) when the thickness of 15 cm or more, that contain 20 percent or more soil temperature is 5 oC or higher at a depth of 50 cm and a (by volume) nodules or concretions. soil moisture regime that borders on ustic. Petronodic Natrargids Lithic Ustic Natrargids FEBI. Other Natrargids that have: FEBC. Other Natrargids that have a lithic contact within 50 1. Skeletans covering 10 percent or more of the surfaces of cm of the soil surface. peds at a depth 2.5 cm or more below the upper boundary of Lithic Natrargids the natric horizon; and FEBD. Other Natrargids that have one or both of the 2. A moisture control section that is dry in all parts for following: less than three-fourths of the time (cumulative) when the Aridisols 109
soil temperature is 5 oC or higher at a depth of 50 cm and a 1. More than 35 percent (by volume) fragments coarser soil moisture regime that borders on ustic. than 2.0 mm, of which more than 66 percent is cinders, Glossic Ustic Natrargids pumice, and pumicelike fragments; or 2. A fine-earth fraction containing 30 percent or more FEBJ. Other Natrargids that have: particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 1. An exchangeable sodium percentage of less than 15 (or more is volcanic glass, and [(Al plus /2 Fe, percent an SAR of less than 13) in 50 percent or more of the natric extracted by ammonium oxalate) times 60] plus the volcanic horizon; and glass (percent) is 30 or more. Vitrandic Natrargids 2. A moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) when the FEBO. Other Natrargids that are dry in all parts of the soil temperature is 5 oC or higher at a depth of 50 cm and a moisture control section for less than three-fourths of the time soil moisture regime that borders on ustic. (cumulative) when the soil temperature at a depth of 50 cm is Haplic Ustic Natrargids 5 oC or higher and have a soil moisture regime that borders on xeric. FEBK. Other Natrargids that have: Xeric Natrargids 1. An exchangeable sodium percentage of less than 15 A (or an SAR of less than 13) in 50 percent or more of the FEBP. Other Natrargids that are dry in all parts of the R natric horizon; and moisture control section for less than three-fourths of the time I (cumulative) when the soil temperature at a depth of 50 cm is 2. A moisture control section that is dry in all parts for 5 oC or higher and have a soil moisture regime that borders on less than three-fourths of the time (cumulative) when the ustic. soil temperature is 5 oC or higher at a depth of 50 cm and a Ustic Natrargids soil moisture regime that borders on xeric. Haploxeralfic Natrargids FEBQ. Other Natrargids that have skeletans covering 10 percent or more of the surfaces of peds at a depth FEBL. Other Natrargids that have an exchangeable sodium 2.5 cm or more below the upper boundary of the natric percentage of less than 15 (or an SAR of less than 13) in 50 horizon. percent or more of the natric horizon. Glossic Natrargids Haplic Natrargids FEBR. Other Natrargids. FEBM. Other Natrargids that have both: Typic Natrargids 1. A moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) when the Paleargids soil temperature is 5 oC or higher at a depth of 50 cm and a Key to Subgroups soil moisture regime that borders on xeric; and FECA. Paleargids that have one or both of the following: 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 both 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 a. 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 soil pumice, and pumicelike fragments; or surface; or b. A fine-earth fraction containing 30 percent or more 2. A linear extensibility of 6.0 cm or more between the particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 soil surface and either a depth of 100 cm or a densic, lithic, or more is volcanic glass, and [(Al plus /2 Fe, percent or paralithic contact, whichever is shallower. extracted by ammonium oxalate) times 60] plus the Vertic Paleargids volcanic glass (percent) is 30 or more. Vitrixerandic Natrargids FECB. Other Paleargids that are either: FEBN. Other Natrargids that have, throughout one or more 1. Irrigated and have aquic conditions for some time in horizons with a total thickness of 18 cm or more within 75 cm normal years in one or more layers within 100 cm of the soil of the soil surface, one or both of the following: surface; or 110 Keys to Soil Taxonomy
2. Saturated with water in one or more layers within 100 soil temperature at a depth of 50 cm is 5 oC or higher and cm of the soil surface for 1 month or more in normal years. have a soil moisture regime that borders on ustic. Aquic Paleargids Petronodic Ustic Paleargids
FECC. Other Paleargids that have: FECI. Other Paleargids that have one or more horizons, within 100 cm of the soil surface and with a combined 1. A sandy or sandy-skeletal particle-size class throughout thickness of 15 cm or more, that contain 20 percent or more a layer extending from the mineral soil surface to the top of (by volume) nodules or concretions. an argillic horizon at a depth of 50 cm or more; and Petronodic Paleargids 2. A moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) when the FECJ. Other Paleargids that have both: soil temperature is 5 oC or higher at a depth of 50 cm and a 1. A moisture control section that is dry in all parts for soil moisture regime that borders on ustic. less than three-fourths of the time (cumulative) when the Arenic Ustic Paleargids soil temperature is 5 oC or higher at a depth of 50 cm and a soil moisture regime that borders on xeric; and FECD. Other Paleargids that have a sandy or sandy-skeletal particle-size class throughout a layer extending from the 2. Throughout one or more horizons with a total thickness mineral soil surface to the top of an argillic horizon at a depth of 18 cm or more within 75 cm of the soil surface, one or of 50 cm or more. both of the following: Arenic Paleargids a. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, FECE. Other Paleargids that have a calcic horizon that has pumice, and pumicelike fragments; or its upper boundary within 150 cm of the soil surface. Calcic Paleargids b. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 FECF. Other Paleargids that have: or more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the 1. One or more horizons, within 100 cm of the soil surface volcanic glass (percent) is 30 or more. and with a combined thickness of 15 cm or more, that Vitrixerandic Paleargids contain 20 percent or more (by volume) durinodes or are brittle and have at least a firm rupture-resistance class when FECK. Other Paleargids that have, throughout one or more moist; and horizons with a total thickness of 18 cm or more within 75 cm 2. A moisture control section that is dry in all parts for of the soil surface, one or both of the following: less than three-fourths of the time (cumulative) when the 1. More than 35 percent (by volume) fragments coarser soil temperature is 5 oC or higher at a depth of 50 cm and a than 2.0 mm, of which more than 66 percent is cinders, soil moisture regime that borders on xeric. pumice, and pumicelike fragments; or Durinodic Xeric Paleargids 2. A fine-earth fraction containing 30 percent or more FECG. Other Paleargids that have one or more horizons, particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 within 100 cm of the soil surface and with a combined more is volcanic glass, and [(Al plus /2 Fe, percent thickness of 15 cm or more, that contain 20 percent or more extracted by ammonium oxalate) times 60] plus the volcanic (by volume) durinodes or are brittle and have at least a firm glass (percent) is 30 or more. rupture-resistance class when moist. Vitrandic Paleargids Durinodic Paleargids FECL. Other Paleargids that are dry in all parts of the FECH. Other Paleargids that: moisture control section for less than three-fourths of the time (cumulative) when the soil temperature is 5 oC or higher at a 1. Have one or more horizons, within 100 cm of the soil depth of 50 cm and have a soil moisture regime that borders on surface and with a combined thickness of 15 cm or more, xeric. that contain 20 percent or more (by volume) nodules or Xeric Paleargids concretions; and 2. Are dry in all parts of the moisture control section for FECM. Other Paleargids that are dry in all parts of the less than three-fourths of the time (cumulative) when the moisture control section for less than three-fourths of the time Aridisols 111
(cumulative) when the soil temperature is 5 oC or higher at a FEAH. Other Petroargids. depth of 50 cm and have a soil moisture regime that borders on Typic Petroargids ustic. Ustic Paleargids Calcids FECN. Other Paleargids. Key to Great Groups Typic Paleargids FFA. Calcids that have a petrocalcic horizon that has its Petroargids upper boundary within 100 cm of the soil surface. Petrocalcids, p. 113 Key to Subgroups FEAA. Petroargids that meet both of the following: FFB. Other Calcids. Haplocalcids, p. 111 1. Have a petrogypsic horizon that has its upper boundary within 150 cm of the soil surface; and Haplocalcids 2. Are dry in all parts of the moisture control section for less than three-fourths of the time (cumulative) when the Key to Subgroups A soil temperature is 5 oC or higher at a depth of 50 cm and FFBA. Haplocalcids that have: R have a soil moisture regime that borders on ustic. I Petrogypsic Ustic Petroargids 1. A lithic contact within 50 cm of the soil surface; and 2. A moisture control section that is dry in all parts for FEAB. Other Petroargids that have a petrogypsic horizon less than three-fourths of the time (cumulative) when the that has its upper boundary within 150 cm of the soil surface. soil temperature is 5 oC or higher at a depth of 50 cm and a Petrogypsic Petroargids soil moisture regime that borders on xeric. Lithic Xeric Haplocalcids FEAC. Other Petroargids that have: 1. A duripan that has its upper boundary within 150 cm of FFBB. Other Haplocalcids that have: the soil surface; and 1. A lithic contact within 50 cm of the soil surface; and 2. A moisture control section that is dry in all parts for 2. A moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) when the 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 temperature is 5 oC or higher at a depth of 50 cm and a soil moisture regime that borders on xeric. soil moisture regime that borders on ustic. Duric Xeric Petroargids Lithic Ustic Haplocalcids FEAD. Other Petroargids that have a duripan that has its upper boundary within 150 cm of the soil surface. FFBC. Other Haplocalcids that have a lithic contact within Duric Petroargids 50 cm of the soil surface. Lithic Haplocalcids FEAE. Other Petroargids that have a natric horizon. Natric Petroargids FFBD. Other Haplocalcids that have: 1. Cracks within 125 cm of the soil surface that are 5 mm FEAF. Other Petroargids that have a moisture control section or more wide through a thickness of 30 cm or more for some that is dry in all parts for less than three-fourths of the time time in normal years, and slickensides or wedge-shaped (cumulative) when the soil temperature is 5 oC or higher at a aggregates in a layer 15 cm or more thick that has its upper depth of 50 cm and have a soil moisture regime that borders on boundary within 125 cm of the soil surface; or xeric. Xeric Petroargids 2. A linear extensibility of 6.0 cm or more between the soil surface and either a depth of 100 cm or a densic, lithic, FEAG. Other Petroargids that have a moisture control section or paralithic contact, whichever is shallower. that is dry in all parts for less than three-fourths of the time Vertic Haplocalcids (cumulative) when the soil temperature is 5 oC or higher at a depth of 50 cm and have a soil moisture regime that borders on FFBE. Other Haplocalcids that: ustic. Ustic Petroargids 1. Are either: 112 Keys to Soil Taxonomy
a. Irrigated and have aquic conditions for some time in (by volume) durinodes or are brittle and have at least a firm normal years in one or more layers within 100 cm of the rupture-resistance class when moist. soil surface; or Durinodic Haplocalcids b. Saturated with water in one or more layers within FFBK. Other Haplocalcids that have: 100 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 2. Have one or more horizons, within 100 cm of the soil contain 20 percent or more (by volume) nodules or surface and with a combined thickness of 15 cm or more, concretions; and that contain 20 percent or more (by volume) durinodes or are brittle and have at least a firm rupture-resistance class 2. A moisture control section that is dry in all parts for when moist. less than three-fourths of the time (cumulative) when the Aquic Durinodic Haplocalcids soil temperature is 5 oC or higher at a depth of 50 cm and a soil moisture regime that borders on xeric. FFBF. Other Haplocalcids that are either: Petronodic Xeric Haplocalcids 1. Irrigated and have aquic conditions for some time in FEBL. Other Haplocalids that: normal years in one or more layers within 100 cm of the soil surface; or 1. Have one or more horizons, within 100 cm of the soil surface and with a combined thickness of 15 cm or more, 2. Saturated with water in one or more layers within 100 that contain 20 percent or more (by volume) nodules or cm of the soil surface for 1 month or more in normal years. concretions; and Aquic Haplocalcids 2. Are dry in all parts of the moisture control section FFBG. Other Haplocalcids that have: for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm is 5 oC or 1. A duripan that has its upper boundary within 150 cm of higher and have a soil moisture regime that borders on the surface; and ustic. 2. A moisture control section that is dry in all parts for Petronodic Ustic Haplocalcids 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 FFBM. Other Haplocalcids that have one or more horizons, soil moisture regime that borders on xeric. within 100 cm of the soil surface and with a combined Duric Xeric Haplocalcids thickness of 15 cm or more, that contain 20 percent or more (by volume) nodules or concretions. FFBH. Other Haplocalcids that have a duripan that has its Petronodic Haplocalcids upper boundary within 150 cm of the surface. Duric Haplocalcids FFBN. Other Haplocalcids that have both: 1. A horizon at least 25 cm thick within 100 cm of the soil FFBI. Other Haplocalcids that have: surface that has an exchangeable sodium percentage of 15 1. One or more horizons, within 100 cm of the soil surface or more (or an SAR of 13 or more) during at least 1 month and with a combined thickness of 15 cm or more, that in normal years; and contain 20 percent or more (by volume) durinodes or are 2. A moisture control section that is dry in all parts for brittle and have at least a firm rupture-resistance class when less than three-fourths of the time (cumulative) when the moist; and soil temperature at a depth of 50 cm is 5 oC or higher and a 2. A moisture control section that is dry in all parts for soil moisture regime that borders on xeric. less than three-fourths of the time (cumulative) when the Sodic Xeric Haplocalcids soil temperature is 5 oC or higher at a depth of 50 cm and a soil moisture regime that borders on xeric. FFBO. Other Haplocalcids that meet both of the following: Durinodic Xeric Haplocalcids 1. Have, in a horizon at least 25 cm thick within 100 cm FFBJ. Other Haplocalcids that have one or more horizons, of the soil surface, an exchangeable sodium percentage of 15 within 100 cm of the soil surface and with a combined or more (or an SAR of 13 or more) during at least 1 month thickness of 15 cm or more, that contain 20 percent or more in normal years; and Aridisols 113
2. Are dry in all parts of the moisture control section for FFBT. Other Haplocalcids that are dry in all parts of the less than three-fourths of the time (cumulative) when the moisture control section for less than three-fourths of the time soil temperature at a depth of 50 cm is 5 oC or higher and (cumulative) when the soil temperature is 5 oC or higher at a have a soil moisture regime that borders on ustic. depth of 50 cm and have a soil moisture regime that borders on Sodic Ustic Haplocalcids ustic. Ustic Haplocalcids FFBP. Other Haplocalcids that have, in a horizon at least 25 cm thick within 100 cm of the mineral soil surface, an FFBU. Other Haplocalcids. exchangeable sodium percentage of 15 or more (or an SAR of Typic Haplocalcids 13 or more) during at least 1 month in normal years. Sodic Haplocalcids Petrocalcids
FFBQ. Other Haplocalcids that have both: Key to Subgroups 1. A moisture control section that is dry in all parts for FFAA. Petrocalcids that are either: less than three-fourths of the time (cumulative) when the 1. Irrigated and have aquic conditions for some time in soil temperature is 5 oC or higher at a depth of 50 cm and a normal years in one or more layers within 100 cm of the soil A soil moisture regime that borders on xeric; and surface; or R 2. Throughout one or more horizons with a total thickness I 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 than 2.0 mm, of which more than 66 percent is cinders, FFAB. Other Petrocalcids that have a natric horizon. pumice, and pumicelike fragments; or Natric Petrocalcids b. A fine-earth fraction containing 30 percent or more FFAC. Other Petrocalcids that have 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. An argillic horizon that has its upper boundary within extracted by ammonium oxalate) times 60] plus the 100 cm of the soil surface; and volcanic glass (percent) is 30 or more. 2. A moisture control section that is dry in all parts for Vitrixerandic Haplocalcids 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 FFBR. Other Haplocalcids that have, throughout one or more soil moisture regime that borders on xeric. horizons with a total thickness of 18 cm or more within 75 cm Xeralfic Petrocalcids of the soil surface, one or both of the following: 1. More than 35 percent (by volume) fragments coarser FFAD. Other Petrocalcids that have both of the following: than 2.0 mm, of which more than 66 percent is cinders, 1. An argillic horizon that has its upper boundary within pumice, and pumicelike fragments; or 100 cm of the soil surface; and 2. A fine-earth fraction containing 30 percent or more 2. A moisture control section that is dry in all parts for particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 less than three-fourths of the time (cumulative) when the more is volcanic glass, and [(Al plus /2 Fe, percent soil temperature is 5 oC or higher at a depth of 50 cm and a extracted by ammonium oxalate) times 60] plus the volcanic soil moisture regime that borders on ustic. glass (percent) is 30 or more. Ustalfic Petrocalcids Vitrandic Haplocalcids FFAE. Other Petrocalcids that have an argillic horizon that FFBS. Other Haplocalcids that are dry in all parts of the has its upper boundary within 100 cm of the soil surface. moisture control section for less than three-fourths of the time Argic Petrocalcids (cumulative) when the soil temperature is 5 oC or higher at a depth of 50 cm and have a soil moisture regime that borders on FFAF. Other Petrocalcids that have: xeric. Xeric Haplocalcids 1. A calcic horizon overlying the petrocalcic horizon; and 114 Keys to Soil Taxonomy
2. A lithic contact within 50 cm of the soil surface. Aquicambids Calcic Lithic Petrocalcids Key to Subgroups FFAG. Other Petrocalcids that have a calcic horizon FGAA. Aquicambids that have, in a horizon at least 25 cm overlying the petrocalcic horizon. thick within 100 cm of the soil surface, an exchangeable Calcic Petrocalcids sodium percentage of 15 or more (or an SAR of 13 or more) during at least 1 month in normal years. FFAH. Other Petrocalcids that are dry in all parts of the Sodic Aquicambids moisture control section for less than three-fourths of the time (cumulative) when the soil temperature is 5 oC or higher at a FGAB. Other Aquicambids that: depth of 50 cm and have a soil moisture regime that borders on xeric. 1. Have one or more horizons, within 100 cm of the soil Xeric Petrocalcids surface and with a combined thickness of 15 cm or more, that contain 20 percent or more (by volume) durinodes or FFAI. Other Petrocalcids that are dry in all parts of the are brittle and have at least a firm rupture-resistance class moisture control section for less than three-fourths of the time when moist; and (cumulative) when the soil temperature is 5 oC or higher at a 2. Are dry in all parts of the moisture control section for depth of 50 cm and have a soil moisture regime that borders on less than three-fourths of the time (cumulative) when the ustic. soil temperature is 5 oC or higher at a depth of 50 cm and Ustic Petrocalcids have a soil moisture regime that borders on xeric. Durinodic Xeric Aquicambids FFAJ. Other Petrocalcids. Typic Petrocalcids FGAC. Other Aquicambids that have one or more horizons, within 100 cm of the soil surface and with a combined Cambids thickness of 15 cm or more, that contain 20 percent or more (by volume) durinodes or are brittle and have at least a firm Key to Great Groups rupture-resistance class when moist. Durinodic Aquicambids FGA. Cambids that are either: 1. Irrigated and have aquic conditions for some time in FGAD. Other Aquicambids 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 surface; or thickness of 15 cm or more, that contain 20 percent or more (by volume) nodules or concretions. 2. Saturated with water in one or more layers within 100 Petronodic Aquicambids cm of the soil surface for 1 month or more in normal years. Aquicambids, p. 114 FGAE. Other Aquicambids that have both: 1. A moisture control section that is dry in all parts for FGB. Other Cambids that have a duripan or a petrocalcic or less than three-fourths of the time (cumulative) when the petrogypsic horizon that has its upper boundary within 150 cm soil temperature is 5 oC or higher at a depth of 50 cm and a of the soil surface. soil moisture regime that borders on xeric; and Petrocambids, p. 117 2. Throughout one or more horizons with a total thickness FGC. Other Cambids that have an anthropic epipedon. of 18 cm or more within 75 cm of the soil surface, one or Anthracambids, p. 114 both of the following: a. More than 35 percent (by volume) fragments coarser FGD. Other Cambids. than 2.0 mm, of which more than 66 percent is cinders, Haplocambids, p. 115 pumice, and pumicelike fragments; or b. A fine-earth fraction containing 30 percent or more Anthracambids 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 Key to Subgroups extracted by ammonium oxalate) times 60] plus the FGCA. All Anthracambids. volcanic glass (percent) is 30 or more. Typic Anthracambids Vitrixerandic Aquicambids Aridisols 115
FGAF. Other Aquicambids that have, throughout one or less than three-fourths of the time (cumulative) when the more horizons with a total thickness of 18 cm or more within soil temperature is 5 oC or higher at a depth of 50 cm and a 75 cm of the soil surface, one or both of the following: soil moisture regime that borders on ustic. Lithic Ustic Haplocambids 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, FGDC. Other Haplocambids that have a lithic contact within pumice, and pumicelike fragments; or 50 cm of the soil surface. 2. A fine-earth fraction containing 30 percent or more Lithic Haplocambids 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 FGDD. Other Haplocambids that have: extracted by ammonium oxalate) times 60] plus the volcanic 1. One or both of the following: glass (percent) is 30 or more. Vitrandic Aquicambids a. Cracks within 125 cm of the soil surface that are 5 mm or more wide through a thickness of 30 cm or more FGAG. Other Aquicambids that have an irregular decrease in for some time in normal years, and slickensides or content of organic carbon from a depth of 25 cm either to a wedge-shaped aggregates in a layer 15 cm or more thick depth of 125 cm or to a densic, lithic, or paralithic contact if that has its upper boundary within 125 cm of the soil A shallower. surface; or R Fluventic Aquicambids b. A linear extensibility of 6.0 cm or more between the I soil surface and either a depth of 100 cm or a densic, FGAH. Other Aquicambids that are dry in all parts of the lithic, or paralithic contact if shallower; and moisture control section for less than three-fourths of the time (cumulative) when the soil temperature is 5 oC or higher at a 2. A moisture control section that is dry in all parts for depth of 50 cm and have a soil moisture regime that borders on less than three-fourths of the time (cumulative) when the xeric. soil temperature is 5 oC or higher at a depth of 50 cm and a Xeric Aquicambids soil moisture regime that borders on xeric. Xerertic Haplocambids FGAI. Other Aquicambids that are dry in all parts of the moisture control section for less than three-fourths of the time FGDE. Other Haplocambids that have: (cumulative) when the soil temperature is 5 oC or higher at a 1. One or both of the following: depth of 50 cm and have a soil moisture regime that borders on ustic. a. Cracks within 125 cm of the soil surface that are 5 Ustic Aquicambids mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or FGAJ. Other Aquicambids. wedge-shaped aggregates in a layer 15 cm or more thick Typic Aquicambids that has its upper boundary within 125 cm of the soil surface; or Haplocambids b. A linear extensibility of 6.0 cm or more between the soil surface and either a depth of 100 cm or a densic, Key to Subgroups lithic, or paralithic contact if shallower; and FGDA. Haplocambids that have: 2. A moisture control section that is dry in all parts for 1. A lithic contact within 50 cm of the soil surface; less than three-fourths of the time (cumulative) when the and soil temperature is 5 oC or higher at a depth of 50 cm and a soil moisture regime that borders on ustic. 2. A moisture control section that is dry in all parts for Ustertic Haplocambids 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 FGDF. Other Haplocambids that have at least one of the soil moisture regime that borders on xeric. following: Lithic Xeric Haplocambids 1. Cracks within 125 cm of the soil surface that are 5 mm FGDB. Other Haplocambids that have: or more wide through a thickness of 30 cm or more for some 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 2. A moisture control section that is dry in all parts for boundary within 125 cm of the soil surface; or 116 Keys to Soil Taxonomy
2. A linear extensibility of 6.0 cm or more between the FGDL. Other Haplocambids that have both: soil surface and either a depth of 100 cm or a densic, lithic, 1. A horizon at least 25 cm thick within 100 cm of the soil or paralithic contact, whichever is shallower. surface that has an exchangeable sodium percentage of 15 Vertic Haplocambids or more (or an SAR of 13 or more) during at least 1 month in normal years; and FGDG. Other Haplocambids that have both of the following: 2. A moisture control section that is dry in all parts for 1. One or more horizons, within 100 cm of the soil surface less than three-fourths of the time (cumulative) when the and with a combined thickness of 15 cm or more, that soil temperature at a depth of 50 cm is 5 oC or higher and a contain 20 percent or more (by volume) durinodes or are soil moisture regime that borders on xeric. brittle and have at least a firm rupture-resistance class when Sodic Xeric Haplocambids moist; and 2. A moisture control section that is dry in all parts for FGDM. Other Haplocambids that meet both of the following: less than three-fourths of the time (cumulative) when the 1. Have, in a horizon at least 25 cm thick within 100 cm soil temperature at a depth of 50 cm is 5 oC or higher and a of the soil surface, an exchangeable sodium percentage of 15 soil moisture regime that borders on xeric. or more (or an SAR of 13 or more) during at least 1 month Durinodic Xeric Haplocambids in normal years; and FGDH. Other Haplocambids that have one or more horizons, 2. Are dry in all parts of the moisture control section for within 100 cm of the soil surface and with a combined less than three-fourths of the time (cumulative) when the thickness of 15 cm or more, that contain 20 percent or more soil temperature at a depth of 50 cm is 5 oC or higher and (by volume) durinodes or are brittle and have at least a firm have a soil moisture regime that borders on ustic. rupture-resistance class when moist. Sodic Ustic Haplocambids Durinodic Haplocambids FGDN. Other Haplocambids that have, in a horizon at least FGDI. Other Haplocambids that have: 25 cm thick within 100 cm of the soil surface, an exchangeable sodium percentage of 15 or more (or an SAR of 13 or more) 1. 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 Sodic Haplocambids contain 20 percent or more (by volume) nodules or concretions; and FGDO. Other Haplocambids that have both: 2. A moisture control section that is dry in all parts for 1. A moisture control section that is dry in all parts less than three-fourths of the time (cumulative) when the for less than three-fourths of the time (cumulative) when soil temperature at a depth of 50 cm is 5 oC or higher and a the soil temperature is 5 oC or higher at a depth of 50 soil moisture regime that borders on xeric. cm and a soil moisture regime that borders on xeric; Petronodic Xeric Haplocambids and FEDJ. Other Haplocambids that: 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. Have one or more horizons, within 100 cm of the soil both of the following: surface and with a combined thickness of 15 cm or more, that contain 20 percent or more (by volume) nodules or a. More than 35 percent (by volume) fragments coarser concretions; and than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or 2. Are dry in all parts of the moisture control section for less than three-fourths of the time (cumulative) when the b. A fine-earth fraction containing 30 percent or more soil temperature at a depth of 50 cm is 5 oC or higher and particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 have a soil moisture regime that borders on ustic. or more is volcanic glass, and [(Al plus /2 Fe, percent Petronodic Ustic Haplocambids extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. FGDK. Other Haplocambids that have one or more horizons, Vitrixerandic Haplocambids within 100 cm of the soil surface and with a combined thickness of 15 cm or more, that contain 20 percent or more FGDP. Other Haplocambids that have, throughout one or (by volume) nodules or concretions. more horizons with a total thickness of 18 cm or more within Petronodic Haplocambids 75 cm of the soil surface, one or both of the following: Aridisols 117
1. More than 35 percent (by volume) fragments coarser FGDV. Other Haplocambids. than 2.0 mm, of which more than 66 percent is cinders, Typic Haplocambids pumice, and pumicelike fragments; or 2. A fine-earth fraction containing 30 percent or more Petrocambids 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 Key to Subgroups extracted by ammonium oxalate) times 60] plus the volcanic FGBA. Petrocambids that have, in a horizon at least 25 cm glass (percent) is 30 or more. thick within 100 cm of the soil surface, an exchangeable Vitrandic Haplocambids sodium percentage of 15 or more (or an SAR of 13 or more) during at least 1 month in normal years. FGDQ. Other Haplocambids that: Sodic Petrocambids 1. Are dry in all parts of the moisture control section for less than three-fourths of the time (cumulative) when FGBB. Other Petrocambids that have both: the soil temperature at a depth of 50 cm is 5 oC or higher and have a soil moisture regime that borders on xeric; 1. A moisture control section that is dry in all parts for and less than three-fourths of the time (cumulative) when the A soil temperature is 5 oC or higher at a depth of 50 cm and a 2. Have an irregular decrease in content of organic R soil moisture regime that borders on xeric; and carbon from a depth of 25 cm either to a depth of I 125 cm or to a densic, lithic, or paralithic contact if 2. Throughout one or more horizons with a total thickness shallower. of 18 cm or more within 75 cm of the soil surface, one or Xerofluventic Haplocambids both of the following: a. More than 35 percent (by volume) fragments coarser FGDR. Other Haplocambids that: than 2.0 mm, of which more than 66 percent is cinders, 1. Are dry in all parts of the moisture control section for pumice, and pumicelike fragments; or less than three-fourths of the time (cumulative) when the b. A fine-earth fraction containing 30 percent or more soil temperature at a depth of 50 cm is 5 oC or higher and particles 0.02 to 2.0 mm in diameter, of which 5 percent have a soil moisture regime that borders on ustic; and 1 or more is volcanic glass, and [(Al plus /2 Fe, percent 2. Have an irregular decrease in content of organic carbon extracted by ammonium oxalate) times 60] plus the from a depth of 25 cm either to a depth of 125 cm or to a volcanic glass (percent) is 30 or more. densic, lithic, or paralithic contact if shallower. Vitrixerandic Petrocambids Ustifluventic Haplocambids FGBC. Other Petrocambids that have, throughout one or FGDS. Other Haplocambids that have an irregular decrease more horizons with a total thickness of 18 cm or more within in content of organic carbon from a depth of 25 cm either to a 75 cm of the soil surface, one or both of the following: depth of 125 cm or to a densic, lithic, or paralithic contact if 1. More than 35 percent (by volume) fragments coarser shallower. than 2.0 mm, of which more than 66 percent is cinders, Fluventic Haplocambids pumice, and pumicelike fragments; or FGDT. Other Haplocambids that are dry in all parts of the 2. A fine-earth fraction containing 30 percent or more moisture control section for less than three-fourths of the time particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 (cumulative) when the soil temperature at a depth of 50 cm is more is volcanic glass, and [(Al plus /2 Fe, percent 5 oC or higher and have a soil moisture regime that borders on extracted by ammonium oxalate) times 60] plus the volcanic xeric. glass (percent) is 30 or more. Xeric Haplocambids Vitrandic Petrocambids
FGDU. Other Haplocambids that are dry in all parts of the FGBD. Other Petrocambids that are dry in all parts of the moisture control section for less than three-fourths of the time moisture control section for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 cm is (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 5 oC or higher and have a soil moisture regime that borders on ustic. xeric. Ustic Haplocambids Xeric Petrocambids 118 Keys to Soil Taxonomy
FGBE. Other Petrocambids that are dry in all parts of the 2. A linear extensibility of 6.0 cm or more between the moisture control section for less than three-fourths of the time mineral soil surface and either a depth of 100 cm or a (cumulative) when the soil temperature at a depth of 50 cm is densic, lithic, or paralithic contact, whichever is shallower. 5 oC or higher and have a soil moisture regime that borders on Vertic Argicryids ustic. Ustic Petrocambids FADC. Other Argicryids that have a natric horizon that has its upper boundary within 100 cm of the soil surface. FGBF. Other Petrocambids. Natric Argicryids Typic Petrocambids FADD. Other Argicryids that have both: Cryids 1. A moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) when the Key to Great Groups soil temperature is 5 oC or higher at a depth of 50 cm and a soil moisture regime that borders on xeric; and FAA. Cryids that have a salic horizon that has its upper 2. Throughout one or more horizons with a total thickness boundary within 100 cm of the soil surface. of 18 cm or more within 75 cm of the soil surface, one or Salicryids, p. 121 both of the following: FAB. Other Cryids that have a duripan or a petrocalcic or a. More than 35 percent (by volume) fragments coarser petrogypsic horizon that has its upper boundary within 100 cm than 2.0 mm, of which more than 66 percent is cinders, of the soil surface. pumice, and pumicelike fragments; or Petrocryids, p. 120 b. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter, of which 5 percent FAC. Other Cryids that have a gypsic horizon that has its 1 or more is volcanic glass, and [(Al plus /2 Fe, percent upper boundary within 100 cm of the soil surface. extracted by ammonium oxalate) times 60] plus the Gypsicryids, p. 119 volcanic glass (percent) is 30 or more. Vitrixerandic Argicryids FAD. Other Cryids that have an argillic or natric horizon. Argicryids, p. 118 FADE. Other Argicryids that have, throughout one or more FAE. Other Cryids that have a calcic horizon that has its horizons with a total thickness of 18 cm or more within 75 cm upper boundary within 100 cm of the soil surface. of the soil surface, one or both of the following: Calcicryids, p. 119 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, FAF. Other Cryids. pumice, and pumicelike fragments; or Haplocryids, p. 120 2. A fine-earth fraction containing 30 percent or more Argicryids 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 Key to Subgroups extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. FADA. Argicryids that have a lithic contact within 50 cm of Vitrandic Argicryids the soil surface. Lithic Argicryids FADF. Other Argicryids that are dry in all parts of the moisture control section for less than three-fourths of the time FADB. Other Argicryids that have one or both of the (cumulative) when the soil temperature is 5 oC or higher at a following: depth of 50 cm and have a soil moisture regime that borders on 1. Cracks within 125 cm of the soil surface that are 5 mm xeric. or more wide throughout a thickness of 30 cm or more for Xeric Argicryids some time in normal years, and slickensides or wedge- shaped aggregates in a layer 15 cm or more thick that has FADG. Other Argicryids that are dry in all parts of the its upper boundary within 125 cm of the mineral 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 Aridisols 119
depth of 50 cm and have a soil moisture regime that borders on FAEE. Other Calcicryids that are dry in all parts of the ustic. moisture control section for less than three-fourths of the time Ustic Argicryids (cumulative) when the soil temperature is 5 oC or higher at a depth of 50 cm and have a soil moisture regime that borders on FADH. Other Argicryids. ustic. Typic Argicryids Ustic Calcicryids
Calcicryids FAEF. Other Calcicryids. Typic Calcicryids Key to Subgroups FAEA. Calcicryids that have a lithic contact within 50 cm of Gypsicryids the soil surface. Key to Subgroups Lithic Calcicryids FACA. Gypsicryids that have a calcic horizon. FAEB. Other Calcicryids that have both: Calcic Gypsicryids
1. A moisture control section that is dry in all parts for A less than three-fourths of the time (cumulative) when the FACB. Other Gypsicryids that have both: R soil temperature is 5 oC or higher at a depth of 50 cm and a 1. A moisture control section that is dry in all parts I soil moisture regime that borders on xeric; and for less than three-fourths of the time (cumulative) 2. Throughout one or more horizons with a total thickness when the soil temperature is 5 oC or higher at a depth of 18 cm or more within 75 cm of the soil surface, one or of 50 cm and a soil moisture regime that borders on xeric; both of the following: and a. More than 35 percent (by volume) fragments coarser 2. Throughout one or more horizons with a total thickness than 2.0 mm, of which more than 66 percent is cinders, of 18 cm or more within 75 cm of the soil surface, one or pumice, and pumicelike fragments; or both of the following: b. A fine-earth fraction containing 30 percent or more a. More than 35 percent (by volume) fragments coarser particles 0.02 to 2.0 mm in diameter, of which 5 percent than 2.0 mm, of which more than 66 percent is cinders, 1 or more is volcanic glass, and [(Al plus /2 Fe, percent pumice, and pumicelike fragments; or extracted by ammonium oxalate) times 60] plus the b. A fine-earth fraction containing 30 percent or more volcanic glass (percent) is 30 or more. particles 0.02 to 2.0 mm in diameter, of which 5 percent Vitrixerandic Calcicryids 1 or more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the FAEC. Other Calcicryids that have, throughout one or more volcanic glass (percent) is 30 or more. horizons with a total thickness of 18 cm or more within 75 cm Vitrixerandic Gypsicryids of the soil surface, one or both of the following: 1. More than 35 percent (by volume) fragments coarser FACC. Other Gypsicryids that have, throughout one or more than 2.0 mm, of which more than 66 percent is cinders, horizons with a total thickness of 18 cm or more within 75 cm pumice, and pumicelike fragments; or of the soil surface, one or both of the following: 2. A fine-earth fraction containing 30 percent or more 1. More than 35 percent (by volume) fragments coarser particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 than 2.0 mm, of which more than 66 percent is cinders, 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 Vitrandic Calcicryids 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 FAED. Other Calcicryids that are dry in all parts of the extracted by ammonium oxalate) times 60] plus the volcanic moisture control section for less than three-fourths of the time glass (percent) is 30 or more. (cumulative) when the soil temperature is 5 oC or higher at a Vitrandic Gypsicryids depth of 50 cm and have a soil moisture regime that borders on xeric. FACD. Other Gypsicryids. Xeric Calcicryids Typic Gypsicryids 120 Keys to Soil Taxonomy
Haplocryids FAFE. Other Haplocryids that are dry in all parts of the moisture control section for less than three-fourths of the time Key to Subgroups (cumulative) when the soil temperature is 5 oC or higher at a depth of 50 cm and have a soil moisture regime that borders on FAFA. Haplocryids that have a lithic contact within 50 cm of xeric. the soil surface. Xeric Haplocryids Lithic Haplocryids FAFF. Other Haplocryids that are dry in all parts of the FAFB. Other Haplocryids that have one or both of the moisture control section for less than three-fourths of the time following: (cumulative) when the soil temperature is 5 oC or higher at a 1. Cracks within 125 cm of the soil surface that are 5 mm depth of 50 cm and have a soil moisture regime that borders on or more wide throughout a thickness of 30 cm or more for ustic. some time in normal years, and slickensides or wedge- Ustic Haplocryids shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil FAFG. Other Haplocryids. surface; or 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 Petrocryids densic, lithic, or paralithic contact, whichever is shallower. Vertic Haplocryids Key to Subgroups FABA. Petrocryids that: FAFC. Other Haplocryids that have both: 1. Have a duripan that is strongly cemented or less 1. A moisture control section that is dry in all parts for cemented in all subhorizons and has its upper boundary less than three-fourths of the time (cumulative) when the within 100 cm of the soil surface; and soil temperature is 5 oC or higher at a depth of 50 cm and a soil moisture regime that borders on xeric; and 2. Are dry in all parts of the moisture control section for less than three-fourths of the time (cumulative) when the 2. Throughout one or more horizons with a total thickness soil temperature is 5 oC or higher at a depth of 50 cm and of 18 cm or more within 75 cm of the soil surface, one or have a soil moisture regime that borders on xeric. both of the following: Xereptic Petrocryids a. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, FABB. 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 2. Are dry in all parts of the moisture control section for or more is volcanic glass, and [(Al plus /2 Fe, percent less than three-fourths of the time (cumulative) when the extracted by ammonium oxalate) times 60] plus the soil temperature is 5 oC or higher at a depth of 50 cm and volcanic glass (percent) is 30 or more. have a soil moisture regime that borders on xeric. Vitrixerandic Haplocryids Duric Xeric Petrocryids FAFD. Other Haplocryids that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm FABC. Other Petrocryids that have a duripan that has its of the soil surface, one or both of the following: upper boundary within 100 cm of the soil surface. Duric Petrocryids 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, FABD. Other Petrocryids that have a petrogypsic horizon pumice, and pumicelike fragments; or that has its upper boundary within 100 cm of the soil 2. A fine-earth fraction containing 30 percent or more surface. particles 0.02 to 2.0 mm in diameter, of which 5 percent or Petrogypsic Petrocryids 1 more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic FABE. Other Petrocryids that are dry in all parts of the glass (percent) is 30 or more. moisture control section for less than three-fourths of the time Vitrandic Haplocryids (cumulative) when the soil temperature is 5 oC or higher at a Aridisols 121
depth of 50 cm and have a soil moisture regime that borders on 2. A linear extensibility of 6.0 cm or more between the xeric. soil surface and the top of the duripan. Xeric Petrocryids Vertic Argidurids
FABF. Other Petrocryids that are dry in all parts of the FCBB. Other Argidurids that are either: moisture control section for less than three-fourths of the time 1. Irrigated and have aquic conditions for some time in (cumulative) when the soil temperature is 5 oC or higher at a normal years in one or more layers within 100 cm of the soil depth of 50 cm and have a soil moisture regime that borders on surface; or ustic. Ustic Petrocryids 2. Saturated with water in one or more layers within 100 cm of the soil surface for 1 month or more in normal FABG. Other Petrocryids. years. Typic Petrocryids Aquic Argidurids
Salicryids FCBC. Other Argidurids that have the following combination of characteristics: Key to Subgroups 1. An argillic horizon that has 35 percent or more clay in A FAAA. Salicryids that are saturated with water in one or the fine-earth fraction of some part; and either R more layers within 100 cm of the soil surface for 1 month or I a. A clay increase of 15 percent or more (absolute) more in normal years. within a vertical distance of 2.5 cm either within the Aquic Salicryids argillic horizon or at its upper boundary; or FAAB. Other Salicryids. b. If there is an Ap horizon directly above the argillic Typic Salicryids horizon, a clay increase of 10 percent or more (absolute) at the upper boundary of the argillic horizon; and Durids 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 Key to Great Groups soil moisture regime that borders on xeric. Abruptic Xeric Argidurids FCA. Durids that have a natric horizon above the duripan. Natridurids, p. 123 FCBD. Other Argidurids that have an argillic horizon that has 35 percent or more clay in the fine-earth fraction of some FCB. Other Durids that have an argillic horizon above the part; and either duripan. 1. A clay increase of 15 percent or more (absolute) within Argidurids, p. 121 a vertical distance of 2.5 cm within the argillic horizon or at its upper boundary; or FCC. Other Durids. Haplodurids, p. 122 2. If there is an Ap horizon directly above the argillic horizon, a clay increase of 10 percent or more (absolute) at Argidurids the upper boundary of the argillic horizon. Abruptic Argidurids Key to Subgroups FCBE. Other Argidurids that have: FCBA. Argidurids that have, above the duripan, one or both of the following: 1. A duripan that is strongly cemented or less cemented in all subhorizons; 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. A moisture control section that is dry in all parts for 30 cm or more for some time in normal years, and less than three-fourths of the time (cumulative) when the slickensides or wedge-shaped aggregates in a layer 15 cm or soil temperature is 5 oC or higher at a depth of 50 cm and a more thick that has its upper boundary above the duripan; soil moisture regime that borders on xeric. or Haploxeralfic Argidurids 122 Keys to Soil Taxonomy
FCBF. Other Argidurids that have a duripan that is strongly Haplodurids cemented or less cemented in all subhorizons. Argidic Argidurids Key to Subgroups FCCA. Haplodurids that: FCBG. Other Argidurids that have both: 1. Have a duripan that is strongly cemented or less 1. A moisture control section that is dry in all parts for cemented in all subhorizons; and 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 2. Are either: soil moisture regime that borders on xeric; and a. Irrigated and have aquic conditions for some time in 2. Throughout one or more horizons with a total thickness normal years in one or more layers within 100 cm of the of 18 cm or more within 75 cm of the soil surface, one or soil surface; or both of the following: b. Saturated with water in one or more layers within a. More than 35 percent (by volume) fragments coarser 100 cm of the soil surface for 1 month or more in normal than 2.0 mm, of which more than 66 percent is cinders, years. pumice, and pumicelike fragments; or Aquicambidic Haplodurids b. A fine-earth fraction containing 30 percent or more FCCB. Other Haplodurids that are either: 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. Irrigated and have aquic conditions for some time in extracted by ammonium oxalate) times 60] plus the normal years in one or more layers within 100 cm of the soil volcanic glass (percent) is 30 or more. surface; or Vitrixerandic Argidurids 2. Saturated with water in one or more layers within 100 cm of the soil surface for 1 month or more in normal FCBH. Other Argidurids that have, throughout one or more years. horizons with a total thickness of 18 cm or more within 75 cm Aquic Haplodurids of the soil surface, one or both of the following: 1. More than 35 percent (by volume) fragments coarser FCCC. Other Haplodurids that have: than 2.0 mm, of which more than 66 percent is cinders, 1. A duripan that is strongly cemented or less cemented in pumice, and pumicelike fragments; or all subhorizons; and 2. A fine-earth fraction containing 30 percent or more 2. A mean annual soil temperature lower than 22 oC, a particles 0.02 to 2.0 mm in diameter, of which 5 percent or o 1 difference of 5 C or more between mean summer and mean more is volcanic glass, and [(Al plus /2 Fe, percent winter soil temperatures at a depth of 50 cm, and a soil extracted by ammonium oxalate) times 60] plus the volcanic moisture regime that borders on xeric. glass (percent) is 30 or more. Xereptic Haplodurids Vitrandic Argidurids FCCD. Other Haplodurids that have a duripan that is FCBI. Other Argidurids that have a moisture control section strongly cemented or less cemented in all subhorizons. that is dry in all parts for less than three-fourths of the time Cambidic Haplodurids (cumulative) when the soil temperature is 5 oC or higher at a depth of 50 cm and have a soil moisture regime that borders on FCCE. Other Haplodurids that have: xeric. Xeric Argidurids 1. A moisture control section that is dry in all parts for three-fourths of the time (cumulative) or less when the soil FCBJ. Other Argidurids that have a moisture control section temperature at a depth of 50 cm is 5 oC or higher and a soil that is dry in all parts for less than three-fourths of the time moisture regime that borders on xeric; and (cumulative) when the soil temperature at a depth of 50 cm is 2. Throughout one or more horizons with a total thickness 5 oC or higher and have a soil moisture regime that borders on of 18 cm or more within 75 cm of the soil surface, one or ustic. both of the following: Ustic Argidurids a. More than 35 percent (by volume) fragments coarser FCBK. Other Argidurids. than 2.0 mm, of which more than 66 percent is cinders, Typic Argidurids pumice, and pumicelike fragments; or Aridisols 123
b. A fine-earth fraction containing 30 percent or more FCAB. Other Natridurids that meet both of the following: particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 1. Have a duripan that is strongly cemented or less or more is volcanic glass, and [(Al plus /2 Fe, percent cemented in all subhorizons; and extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. 2. Are either: Vitrixerandic Haplodurids a. Irrigated and have aquic conditions for some time in normal years in one or more layers within 100 cm of the FCCF. Other Haplodurids that have, throughout one soil surface; or or more horizons with a total thickness of 18 cm or more within 75 cm of the soil surface, one or both of the b. Saturated with water in one or more layers within 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 Natrargidic Natridurids than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or FCAC. Other Natridurids that are either: 2. A fine-earth fraction containing 30 percent or more 1. Irrigated and have aquic conditions for some time in particles 0.02 to 2.0 mm in diameter, of which 5 percent or A 1 normal years in one or more layers within 100 cm of the soil more is volcanic glass, and [(Al plus /2 Fe, percent surface; or R extracted by ammonium oxalate) times 60] plus the volcanic I glass (percent) is 30 or more. 2. Saturated with water in one or more layers within 100 Vitrandic Haplodurids cm of the soil surface for 1 month or more in normal years. Aquic Natridurids FCCG. Other Haplodurids that have a mean annual soil temperature lower than 22 oC, a difference of 5 oC or more FCAD. Other Natridurids that have the following between mean summer and mean winter soil temperatures at a combination of characteristics: depth of 50 cm, and a soil moisture regime that borders on 1. A duripan that is strongly cemented or less cemented in xeric. all subhorizons; and Xeric Haplodurids 2. A moisture control section that is dry in all parts for FCCH. Other Haplodurids that have a moisture control less than three-fourths of the time (cumulative) when the section that is dry in all parts for less than three-fourths of the soil temperature is 5 oC or higher at a depth of 50 cm and a time (cumulative) when the soil temperature at a depth of 50 soil moisture regime that borders on xeric. cm is 5 oC or higher and have a soil moisture regime that Natrixeralfic Natridurids borders on ustic. Ustic Haplodurids FCAE. Other Natridurids that have a duripan that is strongly cemented or less cemented in all subhorizons. FCCI. Other Haplodurids. Natrargidic Natridurids Typic Haplodurids FCAF. Other Natridurids that have both: Natridurids 1. A moisture control section that is dry in all parts for Key to Subgroups 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 FCAA. Natridurids that have, above the duripan, one or both soil moisture regime that borders on xeric; and of the following: 2. Throughout one or more horizons with a total thickness 1. Cracks between the soil surface and the top of the of 18 cm or more within 75 cm of the soil surface, one or duripan that are 5 mm or more wide through a thickness of both of the following: 30 cm or more for some time in normal years, and slickensides or wedge-shaped aggregates in a layer 15 cm or a. More than 35 percent (by volume) fragments coarser more thick that has its upper boundary above the duripan; than 2.0 mm, of which more than 66 percent is cinders, or pumice, and pumicelike fragments; or 2. A linear extensibility of 6.0 cm or more between the b. A fine-earth fraction containing 30 percent or more soil surface and the top of the duripan. particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 Vertic Natridurids or more is volcanic glass, and [(Al plus /2 Fe, percent 124 Keys to Soil Taxonomy
extracted by ammonium oxalate) times 60] plus the Argigypsids volcanic glass (percent) is 30 or more. Vitrixerandic Natridurids Key to Subgroups FDCA. Argigypsids that have a lithic contact within 50 cm of FCAG. Other Natridurids that have, throughout one the soil surface. or more horizons with a total thickness of 18 cm or more Lithic Argigypsids within 75 cm of the soil surface, one or both of the following: FDCB. Other Argigypsids that have: 1. More than 35 percent (by volume) fragments coarser 1. Cracks within 125 cm of the soil surface that are 5 mm than 2.0 mm, of which more than 66 percent is cinders, or more wide through a thickness of 30 cm or more for some pumice, and pumicelike fragments; or time in normal years, and slickensides or wedge-shaped 2. A fine-earth fraction containing 30 percent or more aggregates in a layer 15 cm or more thick that has its upper particles 0.02 to 2.0 mm in diameter, of which 5 percent or boundary within 125 cm of the soil surface; or 1 more is volcanic glass, and [(Al plus /2 Fe, percent 2. A linear extensibility of 6.0 cm or more between the extracted by ammonium oxalate) times 60] plus the volcanic soil surface and either a depth of 100 cm or a densic, lithic, glass (percent) is 30 or more. or paralithic contact, whichever is shallower. Vitrandic Natridurids Vertic Argigypsids FCAH. Other Natridurids that have a moisture control FDCC. Other Argigypsids that have a calcic horizon section that is dry in all parts for less than three-fourths of the overlying the gypsic horizon. time (cumulative) when the soil temperature is 5 oC or higher Calcic Argigypsids at a depth of 50 cm and have a soil moisture regime that borders on xeric. FDCD. Other Argigypsids that have one or more horizons, Xeric Natridurids within 100 cm of the soil surface and with a combined thickness of 15 cm or more, that contain 20 percent or more FCAI. Other Natridurids. (by volume) durinodes, nodules, or concretions. Typic Natridurids Petronodic Argigypsids
Gypsids FDCE. Other Argigypsids that have both: 1. A moisture control section that is dry in all parts for Key to Great Groups 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 FDA. Gypsids that have a petrogypsic or petrocalcic soil moisture regime that borders on xeric; and horizon that has its upper boundary within 100 cm of the soil surface. 2. Throughout one or more horizons with a total thickness Petrogypsids, p. 127 of 18 cm or more within 75 cm of the soil surface, one or both of the following: FDB. Other Gypsids that have a natric horizon that has its a. More than 35 percent (by volume) fragments coarser upper boundary within 100 cm of the soil surface. than 2.0 mm, of which more than 66 percent is cinders, Natrigypsids, p. 126 pumice, and pumicelike fragments; or FDC. Other Gypsids that have an argillic horizon that has its b. A fine-earth fraction containing 30 percent or more upper boundary within 100 cm of the soil surface. particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 Argigypsids, p. 124 or more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the FDD. Other Gypsids that have a calcic horizon that has its volcanic glass (percent) is 30 or more. upper boundary within 100 cm of the soil surface. Vitrixerandic Argigypsids Calcigypsids, p. 125 FDCF. Other Argigypsids that have, throughout one or more FDE. Other Gypsids. horizons with a total thickness of 18 cm or more within 75 cm Haplogypsids, p. 125 of the soil surface, one or both of the following: Aridisols 125
1. More than 35 percent (by volume) fragments coarser b. A fine-earth fraction containing 30 percent or more than 2.0 mm, of which more than 66 percent is cinders, particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 pumice, and pumicelike fragments; or or more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the 2. A fine-earth fraction containing 30 percent or more volcanic glass (percent) is 30 or more. particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 Vitrixerandic Calcigypsids more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic FDDD. Other Calcigypsids that have, throughout one glass (percent) is 30 percent or more. or more horizons with a total thickness of 18 cm or more Vitrandic Argigypsids within 75 cm of the soil surface, one or both of the following: FDCG. Other Argigypsids that have a moisture control section that is dry in all parts for less than three-fourths of the 1. More than 35 percent (by volume) fragments coarser time (cumulative) when the soil temperature at a depth of 50 than 2.0 mm, of which more than 66 percent is cinders, cm is 5 oC or higher and have a soil moisture regime that pumice, and pumicelike fragments; or borders on xeric. 2. A fine-earth fraction containing 30 percent or more Xeric Argigypsids particles 0.02 to 2.0 mm in diameter, of which 5 percent or A 1 more is volcanic glass, and [(Al plus /2 Fe, percent FDCH. Other Argigypsids that have a moisture control R extracted by ammonium oxalate) times 60] plus the volcanic section that is dry in all parts for less than three-fourths of the I glass (percent) is 30 or more. time (cumulative) when the soil temperature at a depth of 50 Vitrandic Calcigypsids cm is 5 oC or higher and have a soil moisture regime that borders on ustic. FDDE. Other Calcigypsids that have a moisture control Ustic Argigypsids section that is dry in all parts for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 FDCI. Other Argigypsids. cm is 5 oC or higher and have a soil moisture regime that Typic Argigypsids borders on xeric. Xeric Calcigypsids Calcigypsids FDDF. Other Calcigypsids that have a moisture control Key to Subgroups section that is dry in all parts for less than three-fourths of the FDDA. Calcigypsids that have a lithic contact within 50 cm time (cumulative) when the soil temperature at a depth of 50 of the soil surface. cm is 5 oC or higher and have a soil moisture regime that Lithic Calcigypsids borders on ustic. Ustic Calcigypsids FDDB. Other Calcigypsids that have one or more horizons, within 100 cm of the soil surface and with a combined FDDG. Other Calcigypsids. thickness of 15 cm or more, that contain 20 percent or more Typic Calcigypsids (by volume) durinodes, nodules, or concretions. Petronodic Calcigypsids Haplogypsids FDDC. Other Calcigypsids that have both: Key to Subgroups 1. A moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) FDEA. Haplogypsids that have a lithic contact within 50 cm when the soil temperature is 5 oC or higher at a depth of the soil surface. of 50 cm and a soil moisture regime that borders on xeric; Lithic Haplogypsids and FDEB. Other Haplogypsids that have a gypsic horizon 2. Throughout one or more horizons with a total thickness that has its upper boundary within 18 cm of the soil of 18 cm or more within 75 cm of the soil surface, one or surface. both of the following: Leptic Haplogypsids a. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, FDEC. Other Haplogypsids that have, in a horizon at least pumice, and pumicelike fragments; or 25 cm thick within 100 cm of the mineral soil surface, an 126 Keys to Soil Taxonomy
exchangeable sodium percentage of 15 or more (or an SAR of FDEH. Other Haplogypsids that have a moisture control 13 or more) during at least 1 month in normal years. section that is dry in all parts for less than three-fourths of the Sodic Haplogypsids time (cumulative) when the soil temperature at a depth of 50 cm is 5 oC or higher and have a soil moisture regime that FDED. Other Haplogypsids that have one or more horizons, borders on ustic. within 100 cm of the soil surface and with a combined Ustic Haplogypsids thickness of 15 cm or more, that contain 20 percent or more (by volume) durinodes, nodules, or concretions. FDEI. Other Haplogypsids. Petronodic Haplogypsids Typic Haplogypsids
FDEE. Other Haplogypsids that have both: Natrigypsids 1. A moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) when the Key to Subgroups soil temperature is 5 oC or higher at a depth of 50 cm and a FDBA. Natrigypsids that have a lithic contact within 50 cm soil moisture regime that borders on xeric; and of the soil surface. 2. Throughout one or more horizons with a total thickness Lithic Natrigypsids of 18 cm or more within 75 cm of the soil surface, one or both of the following: FDBB. Other Natrigypsids that have: a. More than 35 percent (by volume) fragments coarser 1. Cracks within 125 cm of the soil surface that are 5 than 2.0 mm, of which more than 66 percent is cinders, mm or more wide through a thickness of 30 cm or more pumice, and pumicelike fragments; or for some time in normal years, and slickensides or wedge- shaped aggregates in a layer 15 cm or more thick that b. A fine-earth fraction containing 30 percent or more has its upper boundary within 125 cm of the soil surface; particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 or or more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the 2. A linear extensibility of 6.0 cm or more between the volcanic glass (percent) is 30 or more. soil surface and either a depth of 100 cm or a densic, lithic, Vitrixerandic Haplogypsids or paralithic contact, whichever is shallower. Vertic Natrigypsids FDEF. Other Haplogypsids that have, throughout one or more horizons with a total thickness of 18 cm or more FDBC. Other Natrigypsids that have one or more horizons, within 75 cm of the soil surface, one or both of the within 100 cm of the soil surface and with a combined following: thickness of 15 cm or more, that contain 20 percent or more (by volume) durinodes, nodules, or concretions. 1. More than 35 percent (by volume) fragments coarser Petronodic Natrigypsids than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or FDBD. Other Natrigypsids that have both: 2. A fine-earth fraction containing 30 percent or more 1. A moisture control section that is dry in all parts for particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 less than three-fourths of the time (cumulative) when the more is volcanic glass, and [(Al plus /2 Fe, percent soil temperature is 5 oC or higher at a depth of 50 cm and a extracted by ammonium oxalate) times 60] plus the volcanic soil moisture regime that borders on xeric; and glass (percent) is 30 or more. Vitrandic Haplogypsids 2. Throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of the soil surface, one or FDEG. Other Haplogypsids that have a moisture control both of the following: section that is dry in all parts for less than three-fourths of the a. More than 35 percent (by volume) fragments coarser time (cumulative) when the soil temperature at a depth of 50 than 2.0 mm, of which more than 66 percent is cinders, cm is 5 oC or higher and have a soil moisture regime that pumice, and pumicelike fragments; or borders on xeric. Xeric Haplogypsids b. A fine-earth fraction containing 30 percent or more Aridisols 127
particles 0.02 to 2.0 mm in diameter, of which 5 percent FDAC. Other Petrogypsids that have both: 1 or more is volcanic glass, and [(Al plus /2 Fe, percent 1. A moisture control section that is dry in all parts for extracted by ammonium oxalate) times 60] plus the less than three-fourths of the time (cumulative) when the volcanic glass (percent) is 30 or more. soil temperature is 5 oC or higher at a depth of 50 cm and a Vitrixerandic Natrigypsids soil moisture regime that borders on xeric; and FDBE. Other Natrigypsids that have, throughout one or more 2. Throughout one or more horizons with a total thickness horizons with a total thickness of 18 cm or more within 75 cm of 18 cm or more within 75 cm of the soil surface, one or of the soil surface, one or both of the following: both of the following: 1. More than 35 percent (by volume) fragments coarser a. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or pumice, and pumicelike fragments; or 2. A fine-earth fraction containing 30 percent or more b. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter, of which 5 percent or particles 0.02 to 2.0 mm in diameter, of which 5 percent 1 1 more is volcanic glass, and [(Al plus /2 Fe, percent or more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic extracted by ammonium oxalate) times 60] plus the A glass (percent) is 30 or more. volcanic glass (percent) is 30 or more. R Vitrandic Natrigypsids Vitrixerandic Petrogypsids I
FDBF. Other Natrigypsids that have a moisture control FDAD. Other Petrogypsids that have, throughout one section that is dry in all parts for less than three-fourths of the or more horizons with a total thickness of 18 cm or more time (cumulative) when the soil temperature at a depth of 50 within 75 cm of the soil surface, one or both of the cm is 5 oC or higher and have a soil moisture regime that following: borders on xeric. 1. More than 35 percent (by volume) fragments coarser Xeric Natrigypsids than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or FDBG. Other Natrigypsids that have a moisture control section that is dry in all parts for less than three-fourths of the 2. A fine-earth fraction containing 30 percent or more time (cumulative) when the soil temperature at a depth of 50 particles 0.02 to 2.0 mm in diameter, of which 5 percent or o 1 cm is 5 C or higher and have a soil moisture regime that more is volcanic glass, and [(Al plus /2 Fe, percent borders on ustic. extracted by ammonium oxalate) times 60] plus the volcanic Ustic Natrigypsids glass (percent) is 30 or more. Vitrandic Petrogypsids FDBH. Other Natrigypsids. Typic Natrigypsids FDAE. Other Petrogypsids that have a moisture control section that is dry in all parts for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 Petrogypsids cm is 5 oC or higher and have a soil moisture regime that borders on xeric. Key to Subgroups Xeric Petrogypsids FDAA. Petrogypsids that have a petrocalcic horizon that has its upper boundary within 100 cm of the soil surface. FDAF. Other Petrogypsids that have a moisture control Petrocalcic Petrogypsids section that is dry in all parts for less than three-fourths of the time (cumulative) when the soil temperature at a depth of 50 FDAB. Other Petrogypsids that have a calcic horizon cm is 5 oC or higher and have a soil moisture regime that overlying the petrogypsic horizon. borders on ustic. Calcic Petrogypsids Ustic Petrogypsids 128
FDAG. Other Petrogypsids. FBAC. Other Aquisalids. Typic Petrogypsids Typic Aquisalids
Salids Haplosalids Key to Great Groups Key to Subgroups FBBA. Haplosalids that have a duripan that has its upper FBA. Salids that are saturated with water in one or more boundary within 100 cm of the soil surface. layers within 100 cm of the mineral soil surface for 1 month or Duric Haplosalids more in normal years. Aquisalids, p. 128 FBBB. Other Haplosalids that have a petrogypsic horizon that has its upper boundary within 100 cm of FBB. Other Salids. the soil surface. Haplosalids, p. 128 Petrogypsic Haplosalids
Aquisalids FBBC. Other Haplosalids that have a gypsic horizon that has its upper boundary within 100 cm of the soil Key to Subgroups surface. FBAA. Aquisalids that have a gypsic or petrogypsic Gypsic Haplosalids horizon that has its upper boundary within 100 cm of the soil surface. FBBD. Other Haplosalids that have a calcic horizon Gypsic Aquisalids that has its upper boundary within 100 cm of the soil surface. FBAB. Other Aquisalids that have a calcic or petrocalcic Calcic Haplosalids horizon that has an upper boundary within 100 cm of the soil surface. FBBE. Other Haplosalids. Calcic Aquisalids Typic Haplosalids 129
CHAPTER 8 Entisols
Key to Suborders LA. Entisols that have one or more of the following: 1. Aquic conditions and sulfidic materials within 50 cm of the mineral soil surface; or 2. Permanent saturation with water and a reduced matrix in all horizons below 25 cm from the mineral soil surface; or 3. In a layer above a densic, lithic, or paralithic contact or E in a layer at a depth between 40 and 50 cm below the N mineral soil surface, whichever is shallower, aquic T conditions for some time in normal years (or artificial to alpha,alpha-dipyridyl at a time when the soil is not drainage) and one or more of the following: being irrigated. Aquents, p. 130 a. A texture finer than loamy fine sand and, in 50 percent or more of the matrix, one or more of the LB. Other Entisols that have, in one or more layers at a depth following: between 25 and 100 cm below the mineral soil surface, 3 (1) Chroma of 0; or percent or more (by volume) fragments of diagnostic horizons that are not arranged in any discernible order. (2) Chroma of 1 or less and a color value, moist, Arents, p. 133 of 4 or more; or (3) Chroma of 2 or less and redox concentrations; LC. Other Entisols that have less than 35 percent (by or volume) rock fragments and a texture of loamy fine sand or coarser in all layers within the particle-size control section. b. A texture of loamy fine sand or coarser and, in 50 Psamments, p. 144 percent or more of the matrix, one or more of the following: LD. Other Entisols that do not have a densic, lithic, or (1) Chroma of 0; or paralithic contact within 25 cm of the mineral soil surface and have: (2) Hue of 10YR or redder, a color value, moist, of 4 or more, and chroma of 1; or 1. A slope of less than 25 percent; and (3) Hue of 10YR or redder, chroma of 2 or less, 2. Either 0.2 percent or more organic carbon of Holocene and redox concentrations; or age at a depth of 125 cm below the mineral soil surface or an irregular decrease in content of organic carbon from a (4) Hue of 2.5Y or yellower, chroma of 3 or less, depth of 25 cm to a depth of 125 cm or to a densic, lithic, or and distinct or prominent redox concentrations; paralithic contact if shallower; and or 3. A soil temperature regime: (5) Hue of 2.5Y or yellower and chroma of 1; or a. That is warmer than cryic; or (6) Hue of 5GY, 5G, 5BG, or 5B; or b. That is cryic and the soil has: (7) Any color if it results from uncoated sand grains; or (1) No gelic material; and c. Enough active ferrous iron to give a positive reaction (2) Either a slope of less than 5 percent or less than 130 Keys to Soil Taxonomy
1 15 percent volcanic glass in the 0.02 to 2.0 mm plus /2 Fe percentages (by ammonium oxalate) totaling fraction in some part of the particle-size control more than 1.0; or section. 2. More than 35 percent (by volume) fragments coarser Fluvents, p. 134 than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or LE. Other Entisols. Orthents, p. 139 3. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and Aquents a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and
Key to Great Groups 1 b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is LAA. Aquents that have sulfidic materials within 50 cm of equal to 30 or more. the mineral soil surface. Aquandic Cryaquents Sulfaquents, p. 133 LACB. Other Cryaquents. LAB. Other Aquents that have, in all horizons at a depth Typic Cryaquents between 20 and 50 cm below the mineral soil surface, both an n value of more than 0.7 and 8 percent or more clay in the fine- earth fraction. Endoaquents Hydraquents, p. 132 Key to Subgroups LAC. Other Aquents that have a cryic soil temperature LAGA. Endoaquents that have, within 100 cm of the mineral regime. soil surface, one or both of the following: Cryaquents, p. 130 1. Sulfidic materials; or LAD. Other Aquents that have less than 35 percent (by 2. A horizon 15 cm or more thick that has all of the volume) rock fragments and a texture of loamy fine sand or characteristics of a sulfuric horizon, except that it has a pH coarser in all layers within the particle-size control section. value between 3.5 and 4.0. Psammaquents, p. 132 Sulfic Endoaquents LAE. Other Aquents that have either 0.2 percent or more LAGB. Other Endoaquents that have a lithic contact within organic carbon of Holocene age at a depth of 125 cm below the 50 cm of the mineral soil surface. mineral soil surface or an irregular decrease in content of Lithic Endoaquents organic carbon from a depth of 25 cm to a depth of 125 cm or to a densic, lithic, or paralithic contact if shallower. LAGC. Other Endoaquents that have, in one or more Fluvaquents, p. 131 horizons within 100 cm of the mineral soil surface, an exchangeable sodium percentage of 15 or more (or a sodium LAF. Other Aquents that have episaturation. adsorption ratio of 13 or more) for 6 or more months in normal Epiaquents, p. 131 years. Sodic Endoaquents LAG. Other Aquents. Endoaquents, p. 130 LAGD. Other Endoaquents that have, in one or more horizons between either the Ap horizon or a depth of 25 cm Cryaquents from the 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 LACA. Cryaquents that have, throughout one or more more, and chroma of 3 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: 2. Hue of 2.5Y or redder, a color value, moist, of 5 or less, and chroma of 2 or more; or 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 3. Hue of 5Y and chroma of 3 or more; or Entisols 131
4. Hue of 5Y or redder and chroma of 2 or more if there or less (crushed and smoothed) or materials in the upper 15 cm are no redox concentrations. that have these colors after mixing. Aeric Endoaquents Mollic Epiaquents
LAGE. Other Endoaquents that have both: LAFD. Other Epiaquents. Typic Epiaquents 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 materials in the upper 15 cm that have these colors after Fluvaquents mixing; and Key to Subgroups 2. A base saturation (by NH OAc) of less than 50 percent 4 LAEA. Fluvaquents that have, within 100 cm of the mineral in some part within 100 cm of the mineral soil surface. soil surface, one or both of the following: Humaqueptic Endoaquents 1. Sulfidic materials; or LAGF. Other Endoaquents that have either an Ap horizon 2. A horizon 15 cm or more thick that has all of the that has a color value, moist, of 3 or less and a color value, dry, characteristics of a sulfuric horizon, except that it has a pH of 5 or less (crushed and smoothed) or materials in the upper value between 3.5 and 4.0. 15 cm that have these colors after mixing. Sulfic Fluvaquents Mollic Endoaquents LAEB. Other Fluvaquents that have one or both of the E LAGG. Other Endoaquents. following: N Typic Endoaquents T 1. Cracks within 125 cm of the mineral soil surface that Epiaquents are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or Key to Subgroups wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral LAFA. Epiaquents that have, in one or more horizons soil surface; or between either the Ap horizon or a depth of 25 cm from the mineral soil surface, whichever is deeper, and a depth of 75 2. A linear extensibility of 6.0 cm or more between the cm, colors in 50 percent or more of the matrix as follows: mineral soil surface and either a depth of 100 cm or a densic, 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 2. Hue of 2.5Y or redder, a color value, moist, of 5 or less, LAEC. Other Fluvaquents that have a buried layer of organic and chroma of 2 or more; or soil materials, 20 cm or more thick, that has its upper boundary within 100 cm of the mineral soil surface. 3. Hue of 5Y and chroma of 3 or more; or Thapto-Histic Fluvaquents 4. Chroma of 2 or more if there are no redox concentrations. LAED. Other Fluvaquents that have, throughout one or more Aeric Epiaquents horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or more of the following: LAFB. Other Epiaquents that have both: 1. A fine-earth fraction with both a bulk density of 1.0 1. An Ap horizon that has a color value, moist, of 3 or less g/cm3 or less, measured at 33 kPa water retention, and Al 1 and a color value, dry, of 5 or less (crushed and smoothed) plus /2 Fe percentages (by ammonium oxalate) totaling or materials in the upper 15 cm that have these colors after more than 1.0; or mixing; and 2. More than 35 percent (by volume) fragments coarser
2. A base saturation (by NH4OAc) of less than than 2.0 mm, of which more than 66 percent is cinders, 50 percent in some part within 100 cm of the mineral soil pumice, and pumicelike fragments; or surface. 3. A fine-earth fraction containing 30 percent or more Humaqueptic Epiaquents particles 0.02 to 2.0 mm in diameter; and LAFC. Other Epiaquents that have either an Ap horizon that a. In the 0.02 to 2.0 mm fraction, 5 percent or more has a color value, moist, of 3 or less and a color value, dry, of 5 volcanic glass; and 132 Keys to Soil Taxonomy
1 b. [(Al plus /2 Fe, percent extracted by ammonium exchangeable sodium percentage of 15 or more (or a sodium oxalate) times 60] plus the volcanic glass (percent) is adsorption ratio of 13 or more) for 6 or more months in normal equal to 30 or more. years. Aquandic Fluvaquents Sodic Hydraquents
LAEE. Other Fluvaquents that have, in one or more horizons LABC. Other Hydraquents that have a buried layer of organic between either the Ap horizon or a depth of 25 cm from the soil materials, 20 cm or more thick, that has its upper boundary mineral soil surface, whichever is deeper, and a depth of 75 within 100 cm of the mineral soil surface. cm, colors in 50 percent or more of the matrix as follows: Thapto-Histic Hydraquents 1. Hue of 2.5Y or redder, a color value, moist, of 6 or LABD. Other Hydraquents. more, and chroma of 3 or more; or Typic Hydraquents 2. Hue of 2.5Y or redder, a color value, moist, of 5 or less, and chroma of 2 or more; or Psammaquents 3. Hue of 5Y and chroma of 3 or more; or Key to Subgroups 4. Chroma of 2 or more if there are no redox concentrations. LADA. Psammaquents that have a lithic contact within 50 Aeric Fluvaquents cm of the mineral soil surface. Lithic Psammaquents LAEF. Other Fluvaquents that have both: LADB. Other Psammaquents that have, in one or more 1. An Ap horizon that has a color value, moist, of 3 or less horizons within 100 cm of the mineral soil surface, an and a color value, dry, of 5 or less (crushed and smoothed) exchangeable sodium percentage of 15 or more (or a sodium or materials in the upper 15 cm that have these colors after adsorption ratio of 13 or more) for 6 or more months in normal mixing; and years.
2. A base saturation (by NH4OAc) of less than Sodic Psammaquents 50 percent in some part within 100 cm of the mineral soil surface. LADC. Other Psammaquents that have a horizon, 5 cm or Humaqueptic 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 LAEG. Other Fluvaquents that have either an Ap horizon has one or more of the following: that has a color value, moist, of 3 or less and a color value, dry, 1. In 25 percent or more of each pedon, cementation by of 5 or less (crushed and smoothed) or materials in the upper organic matter and aluminum, with or without iron; or 15 cm that have these colors after mixing. 1 Mollic Fluvaquents 2. Al plus /2 Fe percentages (by ammonium oxalate) totaling 0.25 or more, and half that amount or less in an LAEH. Other Fluvaquents. overlying horizon; or Typic Fluvaquents 3. An ODOE value of 0.12 or more, and a value half as high or lower in an overlying horizon. Hydraquents Spodic Psammaquents Key to Subgroups LADD. Other Psammaquents that have both: LABA. Hydraquents that have, within 100 cm of the mineral 1. An Ap horizon that has a color value, moist, of 3 or less soil surface, one or both of the following: and a color value, dry, of 5 or less (crushed and smoothed) 1. Sulfidic materials; or or materials in the upper 15 cm that have these colors after mixing; and 2. A horizon 15 cm or more thick that has all of the
characteristics of a sulfuric horizon, except that it has a pH 2. A base saturation (by NH4OAc) of less than 50 percent value between 3.5 and 4.0. in some part within 100 cm of the mineral soil surface. Sulfic Hydraquents Humaqueptic Psammaquents
LABB. Other Hydraquents that have, in one or more LADE. Other Psammaquents that have either an Ap horizon horizons within 100 cm of the mineral soil surface, an that has a color value, moist, of 3 or less and a color value, dry, Entisols 133
of 5 or less (crushed and smoothed) or materials in the upper LBCB. Other Torriarents that have, within 100 cm of the 15 cm that have these colors after mixing. mineral soil surface, 3 percent or more fragments of a duripan Mollic Psammaquents or a petrocalcic horizon; Duric Torriarents LADF. Other Psammaquents. Typic Psammaquents LBCC. Other Torriarents. Haplic Torriarents Sulfaquents Key to Subgroups Udarents LAAA. Sulfaquents that have, in some horizons at a depth Key to Subgroups between 20 and 50 cm below the mineral soil surface, either or both: LBDA. Udarents that have 3 percent or more fragments of an argillic horizon in some horizon within 100 cm of the mineral 1. An n value of 0.7 or less; or soil surface and have a base saturation (by sum of cations) of 2. Less than 8 percent clay in the fine-earth fraction. 35 percent or more in all parts within 100 cm of the mineral Haplic Sulfaquents soil surface. Alfic Udarents LAAB. Other Sulfaquents that have a histic epipedon. Histic Sulfaquents LBDB. Other Udarents that have 3 percent or more E fragments of an argillic horizon in some horizon within 100 N LAAC. Other Sulfaquents that have a buried layer of organic cm of the mineral soil surface. T soil materials, 20 cm or more thick, that has its upper boundary Ultic Udarents within 100 cm of the mineral soil surface. Thapto-Histic Sulfaquents LBDC. Other Udarents that have 3 percent or more fragments of a mollic epipedon in some horizon within 100 cm LAAD. Other Sulfaquents. of the mineral soil surface and have a base saturation (by sum Typic Sulfaquents of cations) of 35 percent or more in all parts within 100 cm of the mineral soil surface. Mollic Udarents Arents LBDD. Other Udarents. Key to Great Groups Haplic Udarents LBA. Arents that have an ustic moisture regime. Ustarents, p. 133 Ustarents Key to Subgroups LBB. Other Arents that have a xeric moisture regime. Xerarents, p. 133 LBAA. All Ustarents. Haplic Ustarents LBC. Other Arents that have an aridic (or torric) moisture 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 Torriarents fragments 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 mineral soil surface, 3 percent or more fragments of a duripan fragments of a natric horizon. or a petrocalcic horizon. Sodic Torriarents Duric Xerarents 134 Keys to Soil Taxonomy
LBBC. Other Xerarents that have fragments of an argillic oxalate) times 60] plus the volcanic glass (percent) is horizon with a base saturation (by sum of cations) of 35 percent equal to 30 or more. or more within 100 cm of the mineral soil surface. Vitrandic Cryofluvents Alfic Xerarents LDAC. Other Cryofluvents that have, in one or more LBBD. Other Xerarents. horizons within 50 cm of the mineral soil surface, Haplic Xerarents redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial Fluvents drainage). Aquic Cryofluvents
Key to Great Groups LDAD. Other Cryofluvents that are saturated with water in one or more layers within 100 cm of the mineral soil surface in LDA. Fluvents that have a cryic soil temperature regime. normal years for either or both: Cryofluvents, p. 134 1. 20 or more consecutive days; or LDB. Other Fluvents that have a xeric moisture regime. 2. 30 or more cumulative days. Xerofluvents, p. 138 Oxyaquic Cryofluvents LDC. Other Fluvents that have an ustic moisture regime. LDAE. Other Cryofluvents that have either an Ap horizon Ustifluvents, p. 137 that 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 LDD. Other Fluvents that have an aridic (or torric) moisture 15 cm that have these colors after mixing. regime. Mollic Cryofluvents Torrifluvents, p. 134 LDAF. Other Cryofluvents. LDE. Other Fluvents. Typic Cryofluvents Udifluvents, p. 136
Cryofluvents Torrifluvents Key to Subgroups Key to Subgroups LDDA. Torrifluvents that have: LDAA. Cryofluvents that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm 1. One or both of the following: of the mineral soil surface, a fine-earth fraction with both a a. Cracks within 125 cm of the mineral soil surface that bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 are 5 mm or more wide through a thickness of 30 cm or retention, and percent aluminum plus /2 the iron percentage more for some time in normal years, and slickensides or (by ammonium oxalate) totaling more than 1.0. wedge-shaped aggregates in a layer 15 cm or more thick Andic Cryofluvents that has its upper boundary within 125 cm of the mineral soil surface; or LDAB. Other Cryofluvents that have, throughout one or more horizons with a total thickness of 18 cm or more within b. A linear extensibility of 6.0 cm or more between the 75 cm of the mineral soil surface, one or both of the following: mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is 1. More than 35 percent (by volume) fragments coarser shallower; and than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or 2. A moisture control section that, in normal years, is dry in all its parts for less than three-fourths of the cumulative 2. A fine-earth fraction containing 30 percent or more days per year when the soil temperature at a depth of 50 cm particles 0.02 to 2.0 mm in diameter; and from the soil surface is 5 oC or higher; and a. In the 0.02 to 2.0 mm fraction, 5 percent or more 3. An aridic (or torric) moisture regime that borders on volcanic glass; and ustic. 1 b. [(Al plus /2 Fe, percent extracted by ammonium Ustertic Torrifluvents Entisols 135
LDDB. Other Torrifluvents that have one or both of the oxalate) times 60] plus the volcanic glass (percent) is following: equal to 30 or more. Vitrandic Torrifluvents 1. Cracks within 125 cm of the soil surface that are 5 mm or more wide through a thickness of 30 cm or more LDDE. Other Torrifluvents that have, in one or more for some time in most normal years, and slickensides or horizons within 100 cm of the soil surface, both redox wedge-shaped aggregates in a layer 15 cm or more thick depletions with chroma of 2 or less and aquic conditions for that has its upper boundary within 125 cm of the soil some time in normal years (or artificial drainage). surface; or Aquic Torrifluvents 2. A linear extensibility of 6.0 cm or more between the soil surface and either a depth of 100 cm or a densic, lithic, LDDF. Other Torrifluvents that are saturated with water in or paralithic contact, whichever is shallower. one or more layers within 150 cm of the soil surface in normal Vertic Torrifluvents years for either or both: 1. 20 or more consecutive days; or LDDC. Other Torrifluvents that have: 2. 30 or more cumulative days. 1. A moisture control section that, in normal years, is dry Oxyaquic Torrifluvents in all its parts for less than three-fourths of the cumulative days per year when the soil temperature at a depth of 50 cm LDDG. Other Torrifluvents that have: from the soil surface is 5 oC or higher; and 1. A horizon within 100 cm of the mineral soil surface E 2. A thermic, mesic, or frigid soil temperature regime and that is 15 cm or more thick and that either has 20 percent or N an aridic (or torric) moisture regime that borders on xeric; more (by volume) durinodes or is brittle and has a firm T and rupture-resistance class when moist; and 3. Throughout one or more horizons with a total thickness 2. A moisture control section that, in normal years, is dry of 18 cm or more within 75 cm of the mineral soil surface, in all its parts for less than three-fourths of the cumulative one or both of the following: days per year when the soil temperature at a depth of 50 cm from the soil surface is 5 oC or higher; and a. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, 3. A thermic, mesic, or frigid soil temperature regime and pumice, and pumicelike fragments; or an aridic (or torric) moisture regime that borders on xeric. Duric Xeric Torrifluvents b. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and LDDH. Other Torrifluvents that have a horizon within 100 (1) In the 0.02 to 2.0 mm fraction, 5 percent or more cm of the mineral soil surface that is 15 cm or more thick and volcanic glass; and that either has 20 percent or more (by volume) durinodes or is
1 brittle and has a firm rupture-resistance class when moist. (2) [(Al plus /2 Fe, percent extracted by ammonium Duric Torrifluvents oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. LDDI. Other Torrifluvents that have both: Vitrixerandic Torrifluvents 1. A moisture control section that, in normal years, is dry LDDD. Other Torrifluvents that have, throughout one or in all its parts for less than three-fourths of the cumulative more horizons with a total thickness of 18 cm or more within days per year when the soil temperature at a depth of 50 cm 75 cm of the mineral soil surface, one or both of the following: from the soil surface is 5 oC or higher; and 1. More than 35 percent (by volume) fragments coarser 2. An aridic (or torric) moisture regime that borders on than 2.0 mm, of which more than 66 percent is cinders, ustic. pumice, and pumicelike fragments; or Ustic Torrifluvents 2. A fine-earth fraction containing 30 percent or more LDDJ. Other Torrifluvents that have both: particles 0.02 to 2.0 mm in diameter; and 1. A moisture control section that, in normal years, is dry a. In the 0.02 to 2.0 mm fraction, 5 percent or more in all its parts for less than three-fourths of the cumulative volcanic glass; and days per year when the soil temperature at a depth of 50 cm 1 o b. [(Al plus /2 Fe, percent extracted by ammonium from the soil surface is 5 C or higher; and 136 Keys to Soil Taxonomy
2. A thermic, mesic, or frigid soil temperature regime and LDEC. 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 Xeric Torrifluvents 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 LDDK. Other Torrifluvents that have an anthropic epipedon. retention, and Al plus /2 Fe percentages (by ammonium Anthropic Torrifluvents oxalate) totaling more than 1.0. Andic Udifluvents LDDL. Other Torrifluvents. Typic Torrifluvents LDED. Other Udifluvents that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm Udifluvents of 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, LDEA. 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 LDEE. Other Udifluvents that have either: shallower; and 1. In one or more horizons within 50 cm of the mineral 2. Either or both of the following: soil surface, redox depletions with chroma of 2 or less and a. In one or more horizons within 50 cm of the mineral also aquic conditions for some time in normal years (or soil surface, redox depletions with chroma of 2 or less artificial drainage); or and also aquic conditions for some time in normal years 2. In one or more horizons within 100 cm of the mineral (or artificial drainage); or soil surface, a color value, moist, of 4 or more and either b. In one or more horizons within 100 cm of the chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and also aquic mineral soil surface, a color value, moist, of 4 or more conditions for some time in normal years (or artificial and either chroma of 0 or hue of 5GY, 5G, 5BG, or 5B drainage). and also aquic conditions for some time in normal years Aquic Udifluvents (or artificial drainage). Aquertic Udifluvents LDEF. Other Udifluvents that are saturated with water in one or more layers within 100 cm of the mineral soil surface in LDEB. Other Udifluvents that have one or both of the normal years for either or both: following: 1. 20 or more consecutive days; or 1. Cracks within 125 cm of the mineral soil surface that 2. 30 or more cumulative days. are 5 mm or more wide through a thickness of 30 cm or Oxyaquic Udifluvents more for some time in normal years, and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick LDEG. Other Udifluvents that have either an Ap horizon that that has its upper boundary within 125 cm of the mineral has a color value, moist, of 3 or less and a color value, dry, of 5 soil surface; or or less (crushed and smoothed) or materials in the upper 15 cm 2. A linear extensibility of 6.0 cm or more between that have these colors after mixing. the mineral soil surface and either a depth of 100 cm Mollic Udifluvents or a densic, lithic, or paralithic contact, whichever is shallower. LDEH. Other Udifluvents. Vertic Udifluvents Typic Udifluvents Entisols 137
Ustifluvents are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or Key to Subgroups wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral LDCA. Ustifluvents 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 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 more for some time in normal years, and slickensides or shallower. wedge-shaped aggregates in a layer 15 cm or more thick Torrertic Ustifluvents that has its upper boundary within 125 cm of the mineral soil surface; or LDCC. Other Ustifluvents that have 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 1. 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. Either or both of the following: that has its upper boundary within 125 cm of the mineral a. In one or more horizons within 50 cm of the mineral soil surface; or E soil surface, redox depletions with chroma of 2 or less 2. A linear extensibility of 6.0 cm or more between the N and also aquic conditions for some time in normal years mineral soil surface and either a depth of 100 cm or a T (or artificial drainage); or densic, lithic, or paralithic contact, whichever is shallower. b. In one or more horizons within 150 cm of the Vertic Ustifluvents mineral soil surface, a color value, moist, of 4 or more and either chroma of 0 or hue of 5GY, 5G, 5BG, or 5B LDCD. Other Ustifluvents that have anthraquic conditions. and also aquic conditions for some time in normal years Anthraquic Ustifluvents (or artificial drainage). Aquertic Ustifluvents LDCE. Other Ustifluvents that have either: 1. In one or more horizons within 50 cm of the mineral LDCB. Other Ustifluvents that have both of the following: soil surface, redox depletions with chroma of 2 or less and 1. When neither irrigated nor fallowed to store moisture, also aquic conditions for some time in normal years (or one of the following: artificial drainage); or a. A frigid temperature regime and a moisture control 2. In one or more horizons within 150 cm of the mineral section that, in normal years, is dry in all parts for four- soil surface, a color value, moist, of 4 or more and either tenths or more of the cumulative days per year when the chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and also aquic soil temperature at a depth of 50 cm below the soil conditions for some time in normal years (or artificial surface is higher than 5 oC; or drainage). Aquic Ustifluvents b. A mesic or thermic soil temperature regime and a moisture control section that, in normal years, is dry in LDCF. Other Ustifluvents that are saturated with water in some part for six-tenths or more of the cumulative days one or more layers within 150 cm of the mineral soil surface in per year when the soil temperature at a depth of 50 cm normal years for either or both: below the soil surface is higher than 5 oC; or 1. 20 or more consecutive days; or c. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that, 2. 30 or more cumulative days. in normal years, remains moist in some or all parts for Oxyaquic Ustifluvents less than 90 consecutive days per year when the temperature at a depth of 50 cm below the soil surface is LDCG. Other Ustifluvents that, when neither irrigated nor higher than 8 oC; and fallowed to store moisture, have one of the following: 2. One or both of the following: 1. A frigid soil temperature regime and a moisture control a. Cracks within 125 cm of the mineral soil surface that section that, in normal years, is dry in all parts for four- 138 Keys to Soil Taxonomy
tenths or more of the cumulative days per year when the soil that has its upper boundary within 125 cm of the mineral temperature at a depth of 50 cm below the soil surface is soil surface; or higher than 5 oC; or 2. A linear extensibility of 6.0 cm or more between 2. A mesic or thermic soil temperature regime and a the mineral soil surface and either a depth of 100 cm moisture control section that, in normal years, is dry in or a densic, lithic, or paralithic contact, whichever is some part for six-tenths or more of the cumulative days per shallower. year when the soil temperature at a depth of 50 cm below Vertic Xerofluvents the soil surface is higher than 5 oC; or LDBB. Other Xerofluvents that have: 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 normal years, is moist in some or all parts for less than 180 soil surface, redox depletions with chroma of 2 or less and cumulative days per year when the temperature at a depth of also aquic conditions for some time in normal years (or 50 cm below the soil surface is higher than 8 oC. artificial drainage); or Aridic 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 LDCH. Other Ustifluvents that, when neither irrigated nor chroma of 0 or hue bluer than 10Y and also aquic fallowed to store moisture, have one of the following: conditions for some time in normal years (or artificial 1. A frigid soil temperature regime and a moisture control drainage); and section that, in normal years, is dry in some or all parts for 3. Throughout one or more horizons with a total thickness less than 105 cumulative days per year when the soil of 18 cm or more within 75 cm of the mineral soil surface, temperature at a depth of 50 cm below the soil surface is one or more of the following: higher than 5 oC; or a. A fine-earth fraction with both a bulk density of 1.0 2. A mesic or thermic soil temperature regime and a g/cm3 or less, measured at 33 kPa water retention, and Al moisture control section that, in normal years, is dry in 1 plus /2 Fe percentages (by ammonium oxalate) totaling some part for less than four-tenths of the cumulative days more than 1.0; or per year when the temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or b. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, 3. A hyperthermic, isomesic, or warmer iso soil pumice, and pumicelike fragments; or temperature regime and a moisture control section that, in normal years, is dry in some or all parts for less than 120 c. A fine-earth fraction containing 30 percent or more cumulative days per year when the temperature at a depth of particles 0.02 to 2.0 mm in diameter; and 50 cm below the soil surface is higher than 8 oC. (1) In the 0.02 to 2.0 mm fraction, 5 percent or more Udic Ustifluvents volcanic glass; and
1 LDCI. Other Ustifluvents that have either an Ap horizon that (2) [(Al plus /2 Fe, percent extracted by ammonium has a color value, moist, of 3 or less and a color value, dry, of 5 oxalate) times 60] plus the volcanic glass (percent) is or less (crushed and smoothed) or materials in the upper 15 cm equal to 30 or more. that have these colors after mixing. Aquandic Xerofluvents Mollic Ustifluvents LDBC. Other Xerofluvents that have, throughout one or LDCJ. Other Ustifluvents. more horizons with a total thickness of 18 cm or more within Typic Ustifluvents 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 Xerofluvents 1 water retention, and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. Key to Subgroups Andic Xerofluvents LDBA. Xerofluvents that have one or both of the following: LDBD. Other Xerofluvents that have, throughout one or 1. Cracks within 125 cm of the mineral soil surface that more horizons with a total thickness of 18 cm or more within are 5 mm or more wide through a thickness of 30 cm or 75 cm of 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 Entisols 139
than 2.0 mm, of which more than 66 percent is cinders, LEB. Other Orthents that have an aridic (or torric) moisture pumice, and pumicelike fragments; or regime. Torriorthents, p. 140 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and LEC. Other Orthents that have a xeric moisture regime. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Xerorthents, p. 143 volcanic glass; and
1 LED. Other Orthents that have an ustic moisture regime. b. [(Al plus /2 Fe, percent extracted by ammonium Ustorthents, p. 141 oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. LEE. Other Orthents. Vitrandic Xerofluvents Udorthents, p. 141 LDBE. Other Xerofluvents that have either: 1. In one or more horizons within 50 cm of the mineral Cryorthents soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or Key to Subgroups artificial drainage); or LEAA. Cryorthents that have a lithic contact within 50 cm of 2. In one or more horizons within 150 cm of the mineral the mineral soil surface. soil surface, a color value, moist, of 4 or more and either Lithic Cryorthents E chroma of 0 or hue of 5GY, 5G, 5BG, or 5B or aquic N conditions for some time in normal years. LEAB. Other Cryorthents that have, throughout one T Aquic Xerofluvents or more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the LDBF. Other Xerofluvents that are saturated with water in following: one or more layers within 150 cm of the mineral soil surface in 1. More than 35 percent (by volume) fragments coarser normal years for either or both: than 2.0 mm, of which more than 66 percent is cinders, 1. 20 or more consecutive days; or pumice, and pumicelike fragments; or 2. 30 or more cumulative days. 2. A fine-earth fraction containing 30 percent or more Oxyaquic Xerofluvents particles 0.02 to 2.0 mm in diameter; and a. In the 0.02 to 2.0 mm fraction, 5 percent or more LDBG. Other Xerofluvents that have a horizon within 100 volcanic glass; and cm of the mineral soil surface that is 15 cm or more thick and 1 that either has 20 percent or more (by volume) durinodes or is b. [(Al plus /2 Fe, percent extracted by ammonium brittle and has a firm rupture-resistance class when moist. oxalate) times 60] plus the volcanic glass (percent) is Durinodic Xerofluvents equal to 30 or more. Vitrandic Cryorthents LDBH. Other Xerofluvents that have either an Ap horizon that has a color value, moist, of 3 or less and a color value, dry, LEAC. Other Cryorthents that have, in one or more horizons of 5 or less (crushed and smoothed) or materials in the upper within 50 cm of the mineral soil surface, redox depletions with 15 cm that have these colors after mixing. chroma of 2 or less and also aquic conditions for some time in Mollic Xerofluvents normal years (or artificial drainage). Aquic Cryorthents LDBI. Other Xerofluvents. Typic Xerofluvents LEAD. Other Cryorthents that are saturated with water in Orthents one or more layers within 100 cm of the mineral soil surface in normal years for either or both: Key to Great Groups 1. 20 or more consecutive days; or LEA. Orthents that have a cryic soil temperature regime. 2. 30 or more cumulative days. Cryorthents, p. 139 Oxyaquic Cryorthents 140 Keys to Soil Taxonomy
LEAE. Other Cryorthents that have lamellae within 200 cm days per year when the soil temperature at a depth of 50 cm of the mineral soil surface. from the soil surface is 5 oC or higher; and Lamellic Cryorthents 3. A thermic, mesic, or frigid soil temperature regime and an aridic (or torric) moisture regime that borders on xeric. LEAF. Other Cryorthents. Xerertic Torriorthents Typic Cryorthents LEBE. Other Torriorthents that have: Torriorthents 1. One or both of the following: Key to Subgroups a. Cracks within 125 cm of the soil surface that are 5 mm or more wide through a thickness of 30 cm or more LEBA. Torriorthents that have: for some time in normal years, and slickensides or 1. A lithic contact within 50 cm of the soil surface; and wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the soil 2. A moisture control section that, in normal years, is dry surface; or in all its parts for less than three-fourths 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 from the soil surface is 5 oC or higher; and soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower; and 3. A hyperthermic, thermic, mesic, frigid, or iso soil temperature regime and an aridic (or torric) moisture 2. A moisture control section that, in normal years, is dry regime that borders on ustic. in all its parts for less than three-fourths of the cumulative Lithic Ustic Torriorthents days per year when the soil temperature at a depth of 50 cm from the soil surface is 5 oC or higher; and LEBB. Other Torriorthents that have: 3. An aridic (or torric) moisture regime that borders on 1. A lithic contact within 50 cm of the soil surface; and ustic. Ustertic Torriorthents 2. A moisture control section that, in normal years, is dry in all its parts for less than three-fourths of the cumulative LEBF. Other Torriorthents that have one or both of the days per year when the soil temperature at a depth of 50 cm following: from the soil surface is 5 oC or higher; and 1. Cracks within 125 cm of the soil surface that are 5 mm 3. A thermic, mesic, or frigid soil temperature regime and or more wide through a thickness of 30 cm or more for some an aridic (or torric) moisture regime that borders on xeric. time in normal years, and slickensides or wedge-shaped Lithic Xeric Torriorthents aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the soil surface; or LEBC. Other Torriorthents that have a lithic contact within 50 cm of the soil surface. 2. A linear extensibility of 6.0 cm or more between the Lithic Torriorthents soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. LEBD. Other Torriorthents that have: Vertic Torriorthents 1. One or both of the following: LEBG. Other Torriorthents that have, throughout one or a. Cracks within 125 cm of the soil surface that are 5 more horizons with a total thickness of 18 cm or more within mm or more wide through a thickness of 30 cm or more 75 cm of the soil surface, one or both of the following: 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 soil pumice, and pumicelike fragments; or 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 soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower; and a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and 2. A moisture control section that, in normal years, is dry 1 in all its parts for less than three-fourths of the cumulative b. [(Al plus /2 Fe, percent extracted by ammonium Entisols 141
oxalate) times 60] plus the volcanic glass (percent) is LEEB. Other Udorthents that have, throughout one or more equal to 30 or more. horizons with a total thickness of 18 cm or more within 75 cm Vitrandic Torriorthents of the mineral soil surface, one or both of the following: 1. More than 35 percent (by volume) fragments coarser LEBH. Other Torriorthents that have, in one or more than 2.0 mm, of which more than 66 percent is cinders, horizons within 100 cm of the soil surface, redox depletions pumice, and pumicelike fragments; or with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). 2. A fine-earth fraction containing 30 percent or more Aquic Torriorthents particles 0.02 to 2.0 mm in diameter; and a. In the 0.02 to 2.0 mm fraction, 5 percent or more LEBI. Other Torriorthents that are saturated with water in volcanic glass; and one or more layers within 150 cm of the soil surface in normal 1 years for either or both: b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 1. 20 or more consecutive days; or equal to 30 or more. 2. 30 or more cumulative days. Vitrandic Udorthents Oxyaquic Torriorthents LEEC. Other Udorthents that have, in one or more horizons LEBJ. Other Torriorthents that have a horizon within 100 cm within 100 cm of the mineral soil surface, redox depletions of the soil surface that is 15 cm or more thick and that either with chroma of 2 or less and also aquic conditions for some E has 20 percent or more (by volume) durinodes or is brittle and time in normal years (or artificial drainage). N has a firm rupture-resistance class when moist. Aquic Udorthents T Duric Torriorthents LEED. Other Udorthents that are saturated with water in one LEBK. Other Torriorthents that have both: or more layers within 150 cm of the mineral soil surface in normal years for either or both: 1. A moisture control section that, in normal years, is dry in all its parts for less than three-fourths of the cumulative 1. 20 or more consecutive days; or days per year when the soil temperature at a depth of 50 cm 2. 30 or more cumulative days. from the soil surface is 5 oC or higher; and Oxyaquic Udorthents 2. A hyperthermic, thermic, mesic, frigid, or iso soil temperature regime and an aridic (or torric) moisture LEEE. Other Udorthents that have 50 percent or more (by regime that borders on ustic. volume) wormholes, wormcasts, and filled animal burrows Ustic Torriorthents between either the Ap horizon or a depth of 25 cm from the mineral soil surface, whichever is deeper, and either a depth of LEBL. Other Torriorthents that have both: 100 cm or a densic, lithic, paralithic, or petroferric contact, whichever is shallower. 1. A moisture control section that, in normal years, is dry Vermic Udorthents in all its parts for less than three-fourths of the cumulative days per year when the soil temperature at a depth of 50 cm LEEF. Other Udorthents. from the soil surface is 5 oC or higher; and Typic Udorthents 2. A thermic, mesic, or frigid soil temperature regime and an aridic (or torric) moisture regime that borders on xeric. Ustorthents Xeric Torriorthents Key to Subgroups LEBM. Other Torriorthents. LEDA. Ustorthents that have: Typic Torriorthents 1. A lithic contact within 50 cm of the mineral soil Udorthents surface; and Key to Subgroups 2. When neither irrigated nor fallowed to store moisture, one of the following: LEEA. Udorthents that have a lithic contact within 50 cm of the mineral soil surface. a. A frigid temperature regime and a moisture Lithic Udorthents control section that, in normal years, is dry in all parts 142 Keys to Soil Taxonomy
for four-tenths or more of the cumulative days per year temperature at a depth of 50 cm below the soil surface is when the soil temperature at a depth of 50 cm below the higher than 8 oC. soil surface is higher than 5 oC; or Torrertic Ustorthents b. A mesic or thermic soil temperature regime and a LEDD. Other Ustorthents that have one or both of the moisture control section that, in normal years, is dry in 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. Cracks within 125 cm of the mineral soil surface that below the soil surface is higher than 5 oC; or are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or c. A hyperthermic, isomesic, or warmer iso soil wedge-shaped aggregates in a layer 15 cm or more thick temperature regime and a moisture control section that, that has its upper boundary within 125 cm of the mineral in normal years, remains moist in some or all parts for soil surface; or less than 90 consecutive days per year when the temperature at a depth of 50 cm below the soil surface is 2. A linear extensibility of 6.0 cm or more between the higher than 8 oC. mineral soil surface and either a depth of 100 cm or a Aridic Lithic Ustorthents densic, lithic, or paralithic contact, whichever is shallower. Vertic Ustorthents LEDB. Other Ustorthents that have a lithic contact within 50 cm of the mineral soil surface. LEDE. Other Ustorthents that have anthraquic conditions. Lithic Ustorthents Anthraquic Ustorthents
LEDC. Other Ustorthents that have both: LEDF. Other Ustorthents that have, in one or more horizons within 100 cm of the mineral soil surface, redox depletions 1. One or both of the following: with chroma of 2 or less and also aquic conditions for some a. Cracks within 125 cm of the mineral soil surface that time in normal years (or artificial drainage). are 5 mm or more wide through a thickness of 30 cm or Aquic Ustorthents more for some time in normal years, and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick LEDG. Other Ustorthents that are saturated with water in that has its upper boundary within 125 cm of the mineral one or more layers within 150 cm of the mineral soil surface in soil surface; or normal years for either 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 2. 30 or more cumulative days. densic, lithic, or paralithic contact, whichever is Oxyaquic Ustorthents shallower; and 2. When neither irrigated nor fallowed to store moisture, LEDH. Other Ustorthents that have a horizon within 100 one of the following: cm of the mineral soil surface that is 15 cm or more thick and that either has 20 percent or more (by volume) durinodes a. A frigid temperature regime and a moisture control or is brittle and has a firm rupture-resistance class when section that, in normal years, is dry in all parts for four- moist. tenths or more of the cumulative days per year when the Durinodic Ustorthents soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or LEDI. Other Ustorthents that have both: b. A mesic or thermic soil temperature regime and a 1. When neither irrigated nor fallowed to store moisture, moisture control section that, in normal years, is dry in one 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 a. A frigid temperature regime and a moisture control below the soil surface is higher than 5 oC; or section that, in normal years, is dry in all parts for four- tenths or more of the cumulative days per year when the c. A hyperthermic, isomesic, or warmer iso soil soil temperature at a depth of 50 cm below the soil temperature regime and a moisture control section that, surface is higher than 5 oC; or in normal years, remains moist in some or all parts for less than 90 consecutive days per year when the b. A mesic or thermic soil temperature regime and a Entisols 143
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 per year when the soil temperature at a depth of 50 cm year when the soil temperature at a depth of 50 cm below below the soil surface is higher than 5 oC; or the soil surface is higher than 5 oC; or c. A hyperthermic, isomesic, or warmer iso soil 3. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that, temperature regime and a moisture control section that, in in normal years, remains moist in some or all parts for normal years, is moist in some or all parts for less than 180 less than 90 consecutive days per year when the cumulative days per year when the temperature at a depth of temperature at a depth of 50 cm below the soil surface is 50 cm below the soil surface is higher than 8 oC. higher than 8 oC; and Aridic Ustorthents 2. Throughout one or more horizons with a total thickness LEDL. Other Ustorthents that, when neither irrigated nor of 18 cm or more within 75 cm of the soil surface, one or fallowed to store moisture, have one of the following: both of the following: 1. A frigid soil temperature regime and a moisture control a. More than 35 percent (by volume) fragments coarser section that, in normal years, is dry in some or all parts for than 2.0 mm, of which more than 66 percent is cinders, less than 105 cumulative days per year when the soil pumice, and pumicelike fragments; or temperature at a depth of 50 cm below the soil surface is b. A fine-earth fraction containing 30 percent or more higher than 5 oC; or particles 0.02 to 2.0 mm in diameter; and 2. A mesic or thermic soil temperature regime and a E (1) In the 0.02 to 2.0 mm fraction, 5 percent or more moisture control section that, in normal years, is dry in N volcanic glass; and some part for less than four-tenths of the cumulative days T
1 per year when the temperature at a depth of 50 cm below the (2) [(Al plus /2 Fe, percent extracted by ammonium soil surface is higher than 5 oC; or oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. 3. A hyperthermic, isomesic, or warmer iso soil Vitritorrandic Ustorthents temperature regime and a moisture control section that, in normal years, is dry in some or all parts for less than 120 LEDJ. Other Ustorthents that have, throughout one or more cumulative days per year when the temperature at a depth of horizons with a total thickness of 18 cm or more within 75 cm 50 cm below the soil surface is higher than 8 oC. of the soil surface, one or both of the following: Udic Ustorthents 1. More than 35 percent (by volume) fragments coarser LEDM. Other Ustorthents that have 50 percent or more (by than 2.0 mm, of which more than 66 percent is cinders, volume) wormholes, wormcasts, and filled animal burrows pumice, and pumicelike fragments; or between either the Ap horizon or a depth of 25 cm from the 2. A fine-earth fraction containing 30 percent or more mineral soil surface, whichever is deeper, and either a depth of particles 0.02 to 2.0 mm in diameter; and 100 cm or a densic, lithic, paralithic, or petroferric contact, whichever is shallower. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Vermic Ustorthents volcanic glass; and
1 b. [(Al plus /2 Fe, percent extracted by ammonium LEDN. Other Ustorthents. oxalate) times 60] plus the volcanic glass (percent) is Typic Ustorthents equal to 30 or more. Vitrandic Ustorthents Xerorthents LEDK. Other Ustorthents that, when neither irrigated nor Key to Subgroups fallowed to store moisture, have one of the following: LECA. Xerorthents that have a lithic contact within 50 cm of 1. A frigid soil temperature regime and a moisture control the mineral soil surface. section that, in normal years, is dry in all parts for four- Lithic Xerorthents tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is LECB. Other Xerorthents that have, throughout one or more higher than 5 oC; or horizons with a total thickness of 18 cm or more within 75 cm 2. A mesic or thermic soil temperature regime and a of the mineral soil surface, one or both of the following: 144 Keys to Soil Taxonomy
1. More than 35 percent (by volume) fragments coarser LCC. Other Psamments that have, in the 0.02 to 2.0 mm than 2.0 mm, of which more than 66 percent is cinders, fraction within the particle-size control section, a total of more pumice, and pumicelike fragments; or than 90 percent (by weighted average) resistant minerals. 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. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Ustipsamments, p. 147 volcanic glass; and
1 LCE. Other Psamments that have a xeric moisture regime. b. [(Al plus /2 Fe, percent extracted by ammonium Xeropsamments, p. 147 oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. LCF. Other Psamments. Vitrandic Xerorthents Udipsamments, p. 146 LECC. Other Xerorthents that have, in one or more horizons within 100 cm of the mineral soil surface, redox depletions Cryopsamments with chroma of 2 or less and also aquic conditions for some Key to Subgroups time in normal years (or artificial drainage). Aquic Xerorthents LCAA. Cryopsamments that have a lithic contact within 50 cm of the mineral soil surface. LECD. Other Xerorthents that are saturated with water in Lithic Cryopsamments one or more layers within 150 cm of the mineral soil surface in normal years for either or both: LCAB. Other Cryopsamments that have, in one or more horizons within 50 cm of the mineral soil surface, redox 1. 20 or more consecutive days; or depletions with chroma of 2 or less and also aquic conditions 2. 30 or more cumulative days. for some time in normal years (or artificial drainage). Oxyaquic Xerorthents Aquic Cryopsamments
LECE. Other Xerorthents that have a horizon within 100 cm LCAC. Other Cryopsamments that are saturated with water of the mineral soil surface that is 15 cm or more thick and that in one or more layers within 100 cm of the mineral soil surface either has 20 percent or more (by volume) durinodes or is in normal years for either or both: brittle and has a firm rupture-resistance class when moist. 1. 20 or more consecutive days; or Durinodic Xerorthents 2. 30 or more cumulative days. LECF. Other Xerorthents that have a base saturation (by Oxyaquic Cryopsamments
NH4OAc) of less than 60 percent in all horizons at a depth between 25 and 75 cm below the mineral soil surface. LCAD. Other Cryopsamments that have, throughout one or Dystric Xerorthents more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction 1 LECG. Other Xerorthents. containing 5 percent or more volcanic glass, and [(Al plus /2 Typic Xerorthents Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 30 or more. Psamments Vitrandic Cryopsamments Key to Great Groups LCAE. Other Cryopsamments that have a horizon 5 cm or more thick that has one or more of the following: LCA. Psamments that have a cryic soil temperature 1. In 25 percent or more of each pedon, cementation regime. by organic matter and aluminum, with or without iron; Cryopsamments, p. 144 or
1 LCB. Other Psamments that have an aridic (or torric) 2. Al plus /2 Fe percentages (by ammonium oxalate) moisture regime. totaling 0.25 or more, and half that amount or less in an Torripsamments, p. 146 overlying horizon; or Entisols 145
3. An ODOE value of 0.12 or more, and a value half as high or lower in an overlying horizon. LCCE. Other Quartzipsamments that meet all of the Spodic Cryopsamments following: 1. Have an ustic moisture regime; and LCAF. Other Cryopsamments that have lamellae within 200 cm of the mineral soil surface. 2. Have a clay fraction with a CEC of 16 cmol(+) or less
Lamellic Cryopsamments per kg clay (by NH4OAc pH 7); and 3. The sum of the weighted average silt plus 2 times LCAG. Other Cryopsamments. the weighted average clay (both by weight) is more than 5. Typic Cryopsamments Ustoxic Quartzipsamments
Quartzipsamments LCCF. Other Quartzipsamments that meet all of the following: Key to Subgroups 1. Have a udic moisture regime; and LCCA. Quartzipsamments that have a lithic contact within 50 cm of the mineral soil surface. 2. Have a clay fraction with a CEC of 16 cmol(+) or less
Lithic Quartzipsamments per kg clay (by NH4OAc pH 7); and 3. The sum of the weighted average silt plus 2 times the LCCB. Other Quartzipsamments that have both: weighted average clay (both by weight) is more than 5. E 1. In one or more horizons within 100 cm of the mineral Udoxic Quartzipsamments N soil surface, redox depletions with chroma of 2 or less and T also aquic conditions for some time in normal years (or LCCG. Other Quartzipsamments that have 5 percent or more artificial drainage); and (by volume) plinthite in one or more horizons within 100 cm of the mineral soil surface. 2. A horizon, 5 cm or more thick, either below an Ap Plinthic Quartzipsamments 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 LCCH. Other Quartzipsamments that have both: following: 1. Lamellae within 200 cm of the mineral soil surface; and a. In 25 percent or more of each pedon, cementation by organic matter and aluminum, with or without iron; 2. An ustic moisture regime. or Lamellic Ustic Quartzipsamments
1 b. Al plus /2 Fe percentages (by ammonium oxalate) LCCI. Other Quartzipsamments that have lamellae within totaling 0.25 or more, and half that amount or less in an 200 cm of the mineral soil surface. overlying horizon; or Lamellic Quartzipsamments c. An ODOE value of 0.12 or more, and a value half as high or lower in an overlying horizon. LCCJ. Other Quartzipsamments that have an ustic moisture Aquodic Quartzipsamments regime. Ustic Quartzipsamments LCCC. Other Quartzipsamments that have, in one or more horizons within 100 cm of the mineral soil surface, LCCK. Other Quartzipsamments that have a xeric moisture redox depletions with chroma of 2 or less and also aquic regime. conditions for some time in normal years (or artificial Xeric Quartzipsamments drainage). Aquic Quartzipsamments LCCL. Other Quartzipsamments that have a horizon, 5 cm or more thick, either below an Ap horizon or at a depth of 18 cm LCCD. Other Quartzipsamments that are saturated with or more from the mineral soil surface, whichever is deeper, that water in one or more layers within 100 cm of the mineral soil has one or more of the following: surface in normal years for either or both: 1. In 25 percent or more of each pedon, cementation 1. 20 or more consecutive days; or by organic matter and aluminum, with or without iron; or 2. 30 or more cumulative days. 1 Oxyaquic Quartzipsamments 2. Al plus /2 Fe percentages (by ammonium oxalate) 146 Keys to Soil Taxonomy
totaling 0.25 or more, and half that amount or less in an 1. Hue of 2.5YR or redder; and overlying horizon; or 2. A color value, moist, of 3 or less; and 3. An ODOE value of 0.12 or more, and a value half as 3. A dry value no more than 1 unit higher than the moist high or lower in an overlying horizon. value. Spodic Quartzipsamments Rhodic Torripsamments LCCM. Other Quartzipsamments. LCBG. Other Torripsamments. Typic Quartzipsamments Typic Torripsamments
Torripsamments Udipsamments Key to Subgroups Key to Subgroups LCBA. Torripsamments that have a lithic contact within 50 LCFA. Udipsamments that have a lithic contact within 50 cm cm of the soil surface. of the mineral soil surface. Lithic Torripsamments Lithic Udipsamments LCBB. Other Torripsamments that have, throughout one or LCFB. Other Udipsamments that have, in one or more more horizons with a total thickness of 18 cm or more within horizons within 100 cm of the mineral soil surface, redox 75 cm of the mineral soil surface, a fine-earth fraction 1 depletions with chroma of 2 or less and also aquic conditions containing 5 percent or more volcanic glass, and [(Al plus /2 for some time in normal years (or artificial drainage). Fe, percent extracted by ammonium oxalate) times 60] plus the Aquic Udipsamments volcanic glass (percent) is 30 or more. Vitrandic Torripsamments LCFC. Other Udipsamments that are saturated with water in one or more layers within 100 cm of the mineral soil surface in LCBC. Other Torripsamments that have a horizon within normal years for either or both: 100 cm of the soil surface that is 15 cm or more thick and that either has 20 percent or more (by volume) durinodes or is 1. 20 or more consecutive days; or brittle and has a firm rupture-resistance class when moist. 2. 30 or more cumulative days. Haploduridic Torripsamments Oxyaquic Udipsamments LCBD. Other Torripsamments that have both: LCFD. Other Udipsamments that have a horizon, 5 cm or 1. A moisture control section that, in normal years, is dry more thick, either below an Ap horizon or at a depth of 18 cm in all its parts for less than three-fourths of the cumulative or more from the mineral soil surface, whichever is deeper, that days per year when the soil temperature at a depth of 50 cm has one or more of the following: from the soil surface is 5 oC or higher; and 1. In 25 percent or more of each pedon, cementation by 2. An aridic (or torric) moisture regime that borders on organic matter and aluminum, with or without iron; or
ustic. 1 2. Al plus /2 Fe percentages (by ammonium oxalate) Ustic Torripsamments totaling 0.25 or more, and half that amount or less in an overlying horizon; or LCBE. Other Torripsamments that have both: 3. An ODOE value of 0.12 or more, and a value half as 1. A moisture control section that, in normal years, is dry high or lower in an overlying horizon. in all its parts for less than three-fourths of the cumulative Spodic Udipsamments days per year when the soil temperature at a depth of 50 cm from the soil surface is 5 oC or higher; and LCFE. Other Udipsamments that have lamellae within 200 2. A thermic, mesic, or frigid soil temperature regime and cm of the mineral soil surface. an aridic (or torric) moisture regime that borders on xeric. Lamellic Udipsamments Xeric Torripsamments LCFF. Other Udipsamments that have a surface horizon LCBF. Other Torripsamments that have, in all horizons from between 25 and 50 cm thick that meets all of the requirements a depth of 25 to 100 cm, more than 50 percent colors that have for a plaggen epipedon except thickness. all of the following: Plagganthreptic Udipsamments Entisols 147
LCFG. Other Udipsamments. 1. Hue of 2.5YR or redder; and Typic Udipsamments 2. A color value, moist, of 3 or less; and 3. A dry value no more than 1 unit higher than the moist Ustipsamments value. Rhodic Ustipsamments Key to Subgroups LCDA. Ustipsamments that have a lithic contact within 50 LCDG. Other Ustipsamments. cm of the mineral soil surface. Typic Ustipsamments Lithic Ustipsamments Xeropsamments LCDB. Other Ustipsamments that have, in one or more horizons within 100 cm of the mineral soil surface, Key to Subgroups distinct or prominent redox concentrations and also aquic LCEA. Xeropsamments have a lithic contact within 50 cm of conditions for some time in normal years (or artificial the mineral soil surface. drainage). Lithic Xeropsamments Aquic Ustipsamments LCEB. Other Xeropsamments that have both: LCDC. Other Ustipsamments that are saturated with water in one or more layers within 100 cm of the mineral soil surface in 1. In one or more horizons within 100 cm of the mineral E normal years for either or both: soil surface, distinct or prominent redox concentrations and N also aquic conditions for some time in normal years (or 1. 20 or more consecutive days; or T artificial drainage); and 2. 30 or more cumulative days. 2. A horizon within 100 cm of the mineral soil surface Oxyaquic Ustipsamments that is 15 cm or more thick and that either has 20 percent or more (by volume) durinodes or is brittle and has a firm LCDD. Other Ustipsamments that, when neither irrigated rupture-resistance class when moist. nor fallowed to store moisture, have one of the following: Aquic Durinodic Xeropsamments 1. A frigid soil temperature regime and a moisture control section that, in normal years, is dry in all parts for four- LCEC. Other Xeropsamments that have, in one or more tenths or more of the cumulative days per year when the soil horizons within 100 cm of the mineral soil surface, distinct or temperature at a depth of 50 cm below the soil surface is prominent redox concentrations and also aquic conditions for higher than 5 oC; or some time in normal years (or artificial drainage). Aquic Xeropsamments 2. A mesic or thermic soil temperature regime and a moisture control section that, in normal years, is dry in LCED. Other Xeropsamments that are saturated with water some part for six-tenths or more of the cumulative days per in one or more layers within 100 cm of the mineral soil surface year when the soil temperature at a depth of 50 cm below in normal years for either or both: the soil surface is higher than 5 oC; or 1. 20 or more consecutive days; or 3. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that, in 2. 30 or more cumulative days. normal years, is moist in some or all parts for less than 180 Oxyaquic Xeropsamments cumulative days per year when the temperature at a depth of 50 cm below the soil surface is higher than 8 oC. LCEE. Other Xeropsamments that have, throughout one or Aridic Ustipsamments more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction 1 LCDE. Other Ustipsamments that have lamellae within 200 containing 5 percent or more volcanic glass, and [(Al plus /2 cm of the mineral soil surface. Fe, percent extracted by ammonium oxalate) times 60] plus the Lamellic Ustipsamments volcanic glass (percent) is 30 or more. Vitrandic Xeropsamments LCDF. Other Ustipsamments that have, in all horizons from a depth of 25 to 100 cm, more than 50 percent colors that have LCEF. Other Xeropsamments that have a horizon within all of the following: 100 cm of the mineral soil surface that is 15 cm or more thick 148
and that either has 20 percent or more (by volume) durinodes LCEH. Other Xeropsamments that have a base saturation or is brittle and has a firm rupture-resistance class when (by NH4OAc) of less than 60 percent in all horizons at moist. a depth between 25 and 75 cm below the mineral soil Durinodic Xeropsamments surface. Dystric Xeropsamments LCEG. Other Xeropsamments that have lamellae within 200 cm of the mineral soil surface. LCEI. Other Xeropsamments. Lamellic Xeropsamments Typic Xeropsamments 149
CHAPTER 9 Gelisols1
Key to Suborders AA. Gelisols that have organic soil materials that meet one or more of the following: 1. Overlie cindery, fragmental, or pumiceous materials and/or fill their interstices and directly below these materials have either a densic, lithic, or paralithic contact; or 2. When added with the underlying cindery, fragmental, or pumiceous materials, total 40 cm or more between the soil surface and a depth of 50 cm; or 3. Are saturated with water for 30 or more cumulative AAB. Other Histels that are saturated with water for 30 or days during normal years (or are artificially drained) and more cumulative days during normal years and that have both: G have 80 percent or more, by volume, organic soil materials E 1. A glacic layer with its upper boundary within 100 cm of from the soil surface to a depth of 50 cm or to a glacic layer L the soil surface; and or a densic, lithic, or paralithic contact, whichever is shallowest. 2. Less than three-fourths (by volume) Sphagnum fibers in Histels, p. 149 the organic soil materials to a depth of 50 cm or to a densic, lithic, or paralithic contact, whichever is shallower. AB. Other Gelisols that have one or more horizons showing Glacistels, p. 150 cryoturbation in the form of irregular, broken, or distorted horizon boundaries, involutions, the accumulation of organic AAC. Other Histels that have more thickness of fibric soil matter on top of the permafrost, ice or sand wedges, and materials than any other kind of organic soil material to a oriented rock fragments. depth of 50 cm or to a densic, lithic, or paralithic contact, Turbels, p. 154 whichever is shallowest. Fibristels, p. 149 AC. Other Gelisols. Orthels, p. 150 AAD. Other Histels that have more thickness of hemic soil materials than any other kind of organic soil material to a Histels depth of 50 cm or to a densic, lithic, or paralithic contact, whichever is shallowest. Key to Great Groups Hemistels, p. 150
AAA. Histels that are saturated with water for less than 30 cumulative days during normal years (and are not artificially AAE. Other Histels. drained). Sapristels, p. 150 Folistels, p. 150 . Fibristels
Key to Subgroups AACA. Fibristels that have a lithic contact within 100 cm of 1 This chapter is based on recommendations by the International Committee on Permafrost-Affected Soils (ICOMPAS), chaired by Dr. James G. Bockheim, University of the soil surface. Wisconsin. Lithic Fibristels 150 Keys to Soil Taxonomy
AACB. Other Fibristels that have a mineral layer 30 cm or Hemistels more thick within 100 cm of the soil surface. Terric Fibristels Key to Subgroups AADA. Hemistels that have a lithic contact within 100 cm of AACC. Other Fibristels that have, within the organic the soil surface. materials, either one mineral layer 5 cm or more thick or two Lithic Hemistels or more layers of any thickness within 100 cm of the soil surface. AADB. Other Hemistels that have a mineral layer 30 cm or Fluvaquentic Fibristels more thick within 100 cm of the soil surface. Terric Hemistels AACD. Other Fibristels in which three-fourths or more of the fibric material is derived from Sphagnum to a depth of 50 cm AADC. Other Hemistels that have, within the organic or to a densic, lithic, or paralithic contact, whichever is materials, either one mineral layer 5 cm or more thick or two shallowest. or more layers of any thickness within 100 cm of the soil Sphagnic Fibristels surface. Fluvaquentic Hemistels AACE. Other Fibristels. AADD. Other Hemistels. Typic Fibristels Typic Hemistels
Folistels Sapristels Key to Subgroups Key to Subgroups AAAA. Folistels that have a lithic contact within 50 cm of AAEA. Sapristels that have a lithic contact within 100 cm of the 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. Glacistels Fluvaquentic Sapristels Key to Subgroups AAED. Other Sapristels. AABA. Glacistels that have more thickness of hemic Typic Sapristels materials than any other kind of organic soil material in the upper 50 cm. Hemic Glacistels Orthels
AABB. Other Glacistels that have more thickness of sapric Key to Great Groups materials than any other kind of organic soil material in the ACA. Orthels that have in 30 percent or more of the pedon upper 50 cm. more than 40 percent, by volume, organic materials from the Sapric Glacistels soil surface to a depth of 50 cm. Historthels, p. 152 AABC. Other Glacistels Typic Glacistels ACB. Other Orthels that have, within 50 cm of the mineral Gelisols 151
soil surface, redox depletions with chroma of 2 or less and also ACCF. Other Anhyorthels that have a salic horizon that has aquic conditions during normal years (or artificial drainage). its upper boundary within 100 cm of the mineral soil surface. Aquorthels, p. 151 Salic Anhyorthels
ACC. Other Orthels that have anhydrous conditions. ACCG. Other Anhyorthels that have a calcic horizon with its Anhyorthels, p. 151 upper boundary within 100 cm of the mineral soil surface. Calcic Anhyorthels ACD. Other Orthels that have a mollic epipedon. Mollorthels, p. 152 ACCH. Other Anhyorthels. Typic Anhyorthels ACE. Other Orthels that have an umbric epipedon. Umbrorthels, p. 153 Aquorthels
ACF. Other Orthels that have an argillic horizon that has its Key to Subgroups upper boundary within 100 cm of the mineral soil surface. ACBA. Aquorthels that have a lithic contact within 50 cm of Argiorthels, p. 152 the mineral soil surface. Lithic Aquorthels ACG. Other Orthels that have, below the Ap horizon or below a depth of 25 cm, whichever is deeper, less than 35 ACBB. Other Aquorthels that have a glacic layer that has its percent (by volume) rock fragments and have a texture of upper boundary within 100 cm of the mineral soil surface. loamy fine sand or coarser in the particle-size control section. Glacic Aquorthels Psammorthels, p. 153 ACBC. Other Aquorthels that have a sulfuric horizon or ACH. Other Orthels. G sulfidic materials with an upper boundary within 100 cm of the Haplorthels, p. 152 E mineral soil surface. L Sulfuric Aquorthels Anhyorthels ACBD. Other Aquorthels that have either: Key to Subgroups 1. Organic soil materials that are discontinuous at the ACCA. Anhyorthels that have a lithic contact within 50 cm surface; or of the mineral soil surface. Lithic Anhyorthels 2. Organic soil materials at the surface that change in thickness fourfold or more within a pedon. ACCB. Other Anhyorthels that have a glacic layer that has Ruptic-Histic Aquorthels its upper boundary within 100 cm of the mineral soil surface. Glacic Anhyorthels ACBE. Other Aquorthels that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm ACCC. Other Anhyorthels that have a petrogypsic horizon of the mineral soil surface, a fine-earth fraction with both a that has its upper boundary within 100 cm of the mineral soil bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 surface. retention, and Al plus /2 Fe percentages (by ammonium Petrogypsic Anhyorthels oxalate) totaling more than 1.0. Andic Aquorthels ACCD. Other Anhyorthels that have a gypsic horizon that has its upper boundary within 100 cm of the mineral soil ACBF. Other Aquorthels that have, throughout one or more surface. horizons with a total thickness of 18 cm or more within 75 cm Gypsic Anhyorthels of the mineral soil surface, one or both of the following: 1. More than 35 percent (by volume) fragments coarser ACCE. Other Anhyorthels that have a horizon 15 cm or than 2.0 mm, of which more than 66 percent is cinders, more thick that contains 12 cmol(-)/L in 1:5 soil:water nitrate pumice, and pumicelike fragments; or and in which the product of its thickness (in cm) and its nitrate concentration is 3,500 or more. 2. A fine-earth fraction containing 30 percent or more Nitric Anhyorthels particles 0.02 to 2.0 mm in diameter; and 152 Keys to Soil Taxonomy
a. In the 0.02 to 2.0 mm fraction, 5 percent or more ACHD. Other Haplorthels. volcanic glass; and Typic Haplorthels
1 b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is Historthels equal to 30 or more. Key to Subgroups Vitrandic Aquorthels ACAA. Historthels that have a lithic contact within 50 cm of ACBG. Other Aquorthels that have a salic horizon that the soil surface. has its upper boundary within 100 cm of the mineral soil Lithic Historthels surface. Salic Aquorthels ACAB. Other Historthels that have a glacic layer that has its upper boundary within 100 cm of the soil surface. ACBH. Other Aquorthels that have less than 35 percent (by Glacic Historthels volume) rock fragments and a texture of loamy fine sand or coarser in all layers within the particle-size control section. ACAC. Other Historthels that have more than 40 percent, by Psammentic Aquorthels volume, organic soil materials from the soil surface to a depth of 50 cm in 75 percent or less of the pedon. ACBI. Other Aquorthels. Ruptic Historthels Typic Aquorthels ACAD. Other Historthels. Argiorthels Typic Historthels Key to Subgroups Mollorthels ACFA. Argiorthels that have a lithic contact within 50 cm of Key to Subgroups the mineral soil surface. Lithic Argiorthels ACDA. Mollorthels that have a lithic contact within 50 cm of the mineral soil surface. ACFB. Other Argiorthels that have a glacic layer that has its Lithic Mollorthels upper boundary within 100 cm of the mineral soil surface. Glacic Argiorthels ACDB. Other Mollorthels that have a glacic layer that has its upper boundary within 100 cm of the mineral soil ACFC. Other Argiorthels that have a natric horizon. surface. Natric Argiorthels Glacic Mollorthels
ACFD. Other Argiorthels. ACDC. Other Mollorthels that have one or both of the Typic Argiorthels following: Haplorthels 1. 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 during normal years, and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick ACHA. Haplorthels that have a lithic contact within 50 cm of that has its upper boundary within 125 cm of the mineral the mineral soil surface. soil surface; or Lithic Haplorthels 2. A linear extensibility of 6.0 cm or more between ACHB. Other Haplorthels that have a glacic layer that has its the mineral soil surface and either a depth of 100 cm upper boundary within 100 cm of the mineral soil surface. or a densic, lithic, or paralithic contact, whichever is Glacic Haplorthels shallowest. Vertic Mollorthels ACHC. Other Haplorthels that have, in one or more horizons within 75 cm of the mineral soil surface, redox depletions with ACDD. Other Mollorthels that have, throughout one or more chroma of 2 or less and also aquic conditions for some time horizons with a total thickness of 18 cm or more within 75 cm during normal years (or artificial drainage). of the mineral soil surface, a fine-earth fraction with both a Aquic Haplorthels bulk density of 1.0 g/cm3 or less, measured at 33 kPa water Gelisols 153
1 1 retention, and Al plus /2 Fe percentages (by ammonium 2. Al plus /2 Fe percentages (by ammonium oxalate) oxalate) totaling more than 1.0. totaling 0.25 or more, and half that amount or less in an Andic Mollorthels overlying horizon; or 3. An ODOE value of 0.12 or more, and a value half as ACDE. Other Mollorthels that have, throughout one or more high or lower in an overlying horizon. horizons with a total thickness of 18 cm or more within 75 cm Spodic Psammorthels of the mineral soil surface, one or both of the following: 1. More than 35 percent (by volume) fragments coarser ACGD. Other Psammorthels. than 2.0 mm, of which more than 66 percent is cinders, Typic Psammorthels pumice, and pumicelike fragments; or 2. A fine-earth fraction containing 30 percent or more Umbrorthels 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 ACEA. Umbrorthels that have a lithic contact within 50 cm volcanic glass; and of the mineral soil surface. 1 b. [(Al plus /2 Fe, percent extracted by ammonium Lithic Umbrorthels oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. ACEB. Other Umbrorthels that have a glacic layer that Vitrandic Mollorthels has its upper boundary within 100 cm of the mineral soil surface. ACDF. Other Mollorthels that have: Glacic Umbrorthels 1. A mollic epipedon 40 cm or more thick with a texture ACEC. Other Umbrorthels that have one or both of the G finer than loamy fine sand; and following: E 2. A slope of less than 25 percent. L 1. Cracks within 125 cm of the mineral soil surface that Cumulic Mollorthels are 5 mm or more wide through a thickness of 30 cm or more for some time during normal years, and slickensides ACDG. Other Mollorthels that have, in one or more horizons or wedge-shaped aggregates in a layer 15 cm or more thick within 100 cm of the mineral soil surface, distinct or that has its upper boundary within 125 cm of the mineral prominent redox concentrations and also aquic conditions for soil surface; or some time during normal years (or artificial drainage). Aquic Mollorthels 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a ACDH. Other Mollorthels. densic, lithic, or paralithic contact, whichever is shallowest. Typic Mollorthels Vertic Umbrorthels
Psammorthels ACED. Other Umbrorthels that have, throughout one or more horizons with a total thickness of 18 cm or more within Key to Subgroups 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 ACGA. Psammorthels that have a lithic contact within 50 cm 1 water retention, and Al plus /2 Fe percentages (by ammonium of the mineral soil surface. oxalate) totaling more than 1.0. Lithic Psammorthels Andic Umbrorthels ACGB. Other Psammorthels that have a glacic layer that ACEE. Other Umbrorthels that have, throughout one or more has its upper boundary within 100 cm of the mineral soil horizons with a total thickness of 18 cm or more within 75 cm surface. of the mineral soil surface, one or both of the following: Glacic Psammorthels 1. More than 35 percent (by volume) fragments coarser ACGC. Other Psammorthels that have a horizon 5 cm or than 2.0 mm, of which more than 66 percent is cinders, more thick that has one or more of the following: pumice, and pumicelike fragments; or 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 154 Keys to Soil Taxonomy
a. In the 0.02 to 2.0 mm fraction, 5 percent or more Anhyturbels volcanic glass; and
1 Key to Subgroups b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is ABCA. Anhyturbels that have a lithic contact within 50 cm equal to 30 or more. of the mineral soil surface. Vitrandic Umbrorthels Lithic Anhyturbels
ACEF. Other Umbrorthels that have: ABCB. Other Anhyturbels that have a glacic layer with its upper boundary within 100 cm of the mineral soil surface. 1. An umbric epipedon 40 cm or more thick with a texture Glacic Anhyturbels finer than loamy fine sand; and 2. A slope of less than 25 percent. ABCC. Other Anhyturbels that have a petrogypsic horizon Cumulic Umbrorthels with its upper boundary within 100 cm of the mineral soil surface. ACEG. Other Umbrorthels that have, in one or more Petrogypsic Anhyturbels horizons within 100 cm of the mineral soil surface, distinct or prominent redox concentrations and also aquic conditions for ABCD. Other Anhyturbels that have a gypsic horizon some time during normal years (or artificial drainage). with its upper boundary within 100 cm of the mineral soil Aquic Umbrorthels surface. Gypsic Anhyturbels ACEH. Other Umbrorthels. Typic Umbrorthels ABCE. Other Anhyturbels that have a horizon 15 cm or more thick that contains 12 cmol(-)/L nitrate in 1:5 soil:water extract Turbels and in which the product of its thickness (in cm) and its nitrate concentration is 3,500 or more. Key to Great Groups Nitric Anhyturbels
ABA. Turbels that have in 30 percent or more of the pedon ABCF. Other Anhyturbels that have a salic horizon more than 40 percent, by volume, organic materials from the that has its upper boundary within 100 cm of the mineral soil soil surface to a depth of 50 cm. surface. Histoturbels, p. 155 Salic Anhyturbels
ABB. Other Turbels that have, within 50 cm of the mineral ABCG. Other Anhyturbels that have a calcic horizon soil surface, redox depletions with chroma of 2 or less and also that has its upper boundary within 100 cm of the mineral soil aquic conditions during normal years (or artificial drainage). surface. Aquiturbels, p. 154 Calcic Anhyturbels
ABC. Other Turbels that have anhydrous conditions. ABCH. Other Anhyturbels. Anhyturbels, p. 154 Typic Anhyturbels
ABD. Other Turbels that have a mollic epipedon. Molliturbels, p. 155 Aquiturbels Key to Subgroups ABE. Other Turbels that have an umbric epipedon. Umbriturbels, p. 156 ABBA. Aquiturbels that have a lithic contact within 50 cm of the mineral soil surface. ABF. Other Turbels that have less than 35 percent (by Lithic Aquiturbels volume) rock fragments and a texture of loamy fine sand or coarser in all layers within the particle-size control section. ABBB. Other Aquiturbels that have a glacic layer with its Psammoturbels, p. 156 upper boundary within 100 cm of the mineral soil surface. Glacic Aquiturbels ABG. Other Turbels. Haploturbels, p. 155 ABBC. Other Aquiturbels that have a sulfuric horizon or Gelisols 155
sulfidic materials with an upper boundary within 100 cm of the ABAC. Other Histoturbels that have more than 40 percent, mineral soil surface. by volume, organic soil materials from the soil surface to a Sulfuric Aquiturbels depth of 50 cm in 75 percent or less of the pedon. Ruptic Histoturbels ABBD. Other Aquiturbels that have either: ABAD. Other Histoturbels. 1. Organic soil materials that are discontinous at the Typic Histoturbels surface; or 2. Organic soil materials at the surface that change in Molliturbels thickness fourfold or more within a pedon. Ruptic-Histic Aquiturbels Key to Subgroups ABDA. Molliturbels that have a lithic contact within 50 cm ABBE. Other Aquiturbels that have less than 35 percent (by of the mineral soil surface. volume) rock fragments and a texture of loamy fine sand or Lithic Molliturbels coarser in all layers within the particle-size control section. Psammentic Aquiturbels ABDB. Other Molliturbels that have a glacic layer that has its upper boundary within 100 cm of the mineral soil surface. ABBF. Other Aquiturbels. Glacic Molliturbels Typic Aquiturbels ABDC. Other Molliturbels that have one or both of the Haploturbels 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 G ABGA. Haploturbels that have a lithic contact within 50 cm more for some time during normal years, and slickensides E of the mineral soil surface. or wedge-shaped aggregates in a layer 15 cm or more thick L Lithic Haploturbels that has its upper boundary within 125 cm of the mineral soil surface; or ABGB. Other Haploturbels that have a glacic layer that has an upper boundary within 100 cm of the mineral soil 2. A linear extensibility of 6.0 cm or more between the surface. mineral soil surface and either a depth of 100 cm or a Glacic Haploturbels densic, lithic, or paralithic contact, whichever is shallowest. Vertic Molliturbels ABGC. Other Haploturbels that have, in one or more horizons within 100 cm of the mineral soil surface, distinct or ABDD. Other Molliturbels that have, throughout one or more prominent redox concentrations and also aquic conditions for horizons with a total thickness of 18 cm or more within 75 cm some time during normal years (or artificial drainage). of the mineral soil surface, a fine-earth fraction with both a Aquic Haploturbels bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 retention, and Al plus /2 Fe percentages (by ammonium ABGD. Other Haploturbels. oxalate) totaling more than 1.0. Typic Haploturbels Andic Molliturbels
ABDE. Other Molliturbels that have, throughout one or more Histoturbels horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: Key to Subgroups 1. More than 35 percent (by volume) fragments coarser ABAA. Histoturbels that have a lithic contact within 50 cm than 2.0 mm, of which more than 66 percent is cinders, of the soil surface. pumice, and pumicelike fragments; or Lithic Histoturbels 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and ABAB. Other Histoturbels that have a glacic layer with its upper boundary within 100 cm of the soil surface. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Glacic Histoturbels volcanic glass; and 156 Keys to Soil Taxonomy
1 b. [(Al plus /2 Fe, percent extracted by ammonium Umbriturbels oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. Key to Subgroups Vitrandic Molliturbels ABEA. Umbriturbels that have a lithic contact within 50 cm of the mineral soil surface. ABDF. Other Molliturbels that have: Lithic Umbriturbels 1. A mollic epipedon 40 cm or more thick with a texture finer than loamy fine sand; and ABEB. Other Umbriturbels that have a glacic layer that has its upper boundary within 100 cm of the mineral soil 2. A slope of less than 25 percent. surface. Cumulic Molliturbels Glacic Umbriturbels ABDG. Other Molliturbels that have, in one or more ABEC. Other Umbriturbels that have one or both of the horizons within 100 cm of the mineral soil surface, distinct or following: prominent redox concentrations and also aquic conditions for some time during normal years (or artificial drainage). 1. Cracks within 125 cm of the mineral soil surface that Aquic Molliturbels are 5 mm or more wide through a thickness of 30 cm or more for some time during normal years, and slickensides ABDH. Other Molliturbels. or wedge-shaped aggregates in a layer 15 cm or more thick Typic Molliturbels that has its upper boundary within 125 cm of the mineral soil surface; or Psammoturbels 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or Key to Subgroups a densic, lithic, or paralithic contact, whichever is shallowest. ABFA. Psammoturbels that have a lithic contact within 50 Vertic Umbriturbels cm of the mineral soil surface. Lithic Psammoturbels ABED. Other Umbriturbels that have, throughout one or more horizons with a total thickness of 18 cm or more within ABFB. Other Psammoturbels that have a glacic layer that 75 cm of the mineral soil surface, a fine-earth fraction with has its upper boundary within 100 cm of the mineral soil both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa surface. 1 water retention, and Al plus /2 Fe percentages (by ammonium Glacic Psammoturbels oxalate) totaling more than 1.0. Andic Umbriturbels ABFC. Other Psammoturbels that have a horizon 5 cm or more thick that has one or more of the following: ABEE. Other Umbriturbels that have, throughout one or 1. In 25 percent or more of each pedon, cementation more horizons with a total thickness of 18 cm or more within by organic matter and aluminum, with or without iron; 75 cm of the mineral soil surface, one or both of the or following:
1 2. Al plus /2 Fe percentages (by ammonium oxalate) 1. More than 35 percent (by volume) fragments coarser totaling 0.25 or more, and half that amount or less in an than 2.0 mm, of which more than 66 percent is cinders, overlying horizon; or pumice, and pumicelike fragments; or 3. An ODOE value of 0.12 or more, and a value half as 2. A fine-earth fraction containing 30 percent or more high or lower in an overlying horizon. particles 0.02 to 2.0 mm in diameter; and Spodic Psammoturbels a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and ABFD. Other Psammoturbels. 1 Typic Psammoturbels b. [(Al plus /2 Fe, percent extracted by ammonium Gelisols 157
oxalate) times 60] plus the volcanic glass (percent) is ABEG. Other Umbriturbels that have, in one or more equal to 30 or more. horizons within 100 cm of the mineral soil surface, distinct Vitrandic Umbriturbels or prominent redox concentrations and also aquic conditions for some time during normal years (or artificial ABEF. Other Umbriturbels that have: drainage). 1. An umbric epipedon 40 cm or more thick with a texture Aquic Umbriturbels finer than loamy fine sand; and 2. A slope of less than 25 percent. ABEH. Other Umbriturbels. Cumulic Umbriturbels Typic Umbriturbels
G E L
159
CHAPTER 10 Histosols
Key to Suborders BA. Histosols that are saturated with water for less than 30 cumulative days during normal years (and are not artificially drained). Folists, p. 160
BB. Other Histosols that: 1. Have more thickness of fibric soil materials than any other kind of organic soil material either: a. In the organic parts of the subsurface tier if there is no continuous mineral layer 40 cm or more thick that has its upper boundary within the subsurface tier; Fibrists or Key to Great Groups b. In the combined thickness of the organic parts of the surface and subsurface tiers if there is a BBA. Fibrists that have a cryic soil temperature H continuous mineral layer 40 cm or more thick that regime. I has its upper boundary within the subsurface tier; Cryofibrists, p. 159 S and BBB. Other Fibrists in which fibric Sphagnum constitutes 2. Do not have a sulfuric horizon that has its upper three-fourths or more of the volume to either a depth of 90 cm boundary within 50 cm of the soil surface; and from the soil surface or to a densic, lithic, or paralithic contact, 3. Do not have sulfidic materials within 100 cm of the fragmental materials, or other mineral soil materials if at a soil surface. depth of less than 90 cm. Fibrists, p. 159 Sphagnofibrists, p. 160
BC. Other Histosols that have more thickness of sapric BBC. Other Fibrists. soil materials than any other kind of organic soil materials Haplofibrists, p. 160 either: 1. In the organic parts of the subsurface tier if there is no continuous mineral layer 40 cm or more thick that has its Cryofibrists upper boundary within the subsurface tier; or Key to Subgroups 2. In the combined thickness of the organic parts of the BBAA. Cryofibrists that have a layer of water within the surface and subsurface tiers if there is a continuous mineral control section, below the surface tier. layer 40 cm or more thick that has its upper boundary Hydric Cryofibrists within the subsurface tier. Saprists, p. 162 BBAB. Other Cryofibrists that have a lithic contact within BD. Other Histosols. the control section. Hemists, p. 161 Lithic Cryofibrists 160 Keys to Soil Taxonomy
BBAC. Other Cryofibrists that have a mineral layer 30 cm or Sphagnofibrists more thick that has its upper boundary within the control section, below the surface tier. Key to Subgroups Terric Cryofibrists BBBA. Sphagnofibrists that have a layer of water within the control section, below the surface tier. BBAD. Other Cryofibrists that have, within the organic Hydric Sphagnofibrists materials, either one mineral layer 5 cm or more thick or two or more mineral layers of any thickness in the control section, BBBB. Other Sphagnofibrists that have a lithic contact below the surface tier. within the control section. Fluvaquentic Cryofibrists Lithic Sphagnofibrists 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 BBCA. Haplofibrists that have a layer of water within the BBBE. Other Sphagnofibrists that have, within the organic control section, below the surface tier. materials, either one mineral layer 5 cm or more thick or two Hydric Haplofibrists or more mineral layers of any thickness in the control section, below the surface tier. BBCB. Other Haplofibrists that have a lithic contact within Fluvaquentic Sphagnofibrists the control section. Lithic Haplofibrists BBBF. Other Sphagnofibrists that have one or more layers of hemic and sapric materials with a total thickness of 25 cm or BBCC. Other Haplofibrists that have one or more limnic more below the surface tier. layers with a total thickness of 5 cm or more within the control Hemic Sphagnofibrists 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 Folists section, below the surface tier. Terric Haplofibrists Key to Great Groups
BBCE. Other Haplofibrists that have, within the organic BAA. Folists that have a cryic soil temperature regime. materials, either one mineral layer 5 cm or more thick or two Cryofolists, p. 161 or more mineral layers of any thickness in the control section, below the surface tier. BAB. Other Folists that have an aridic (or torric) soil Fluvaquentic Haplofibrists moisture regime. Torrifolists, p. 161 BBCF. Other Haplofibrists that have one or more layers of hemic and sapric materials with a total thickness of 25 cm or BAC. Other Folists that have an ustic or xeric soil moisture more below the surface tier. regime. Hemic Haplofibrists Ustifolists, p. 161
BBCG. Other Haplofibrists. BAD. Other Folists. Typic Haplofibrists Udifolists, p. 161 Histosols 161
Cryofolists BDC. Other Hemists that have a horizon 2 cm or more thick in which humilluvic materials constitute one-half or more of Key to Subgroups the volume. Luvihemists, p. 162 BAAA. Cryofolists that have a lithic contact within 50 cm of the soil surface. BDD. Other Hemists that have a cryic temperature Lithic Cryofolists regime. Cryohemists, p. 161 BAAB. Other Cryofolists. Typic Cryofolists BDE. Other Hemists. Haplohemists, p. 161 Torrifolists
Key to Subgroups Cryohemists BABA. Torrifolists that have a lithic contact within 50 cm of Key to Subgroups the soil surface. BDDA. Cryohemists that have a layer of water within the Lithic Torrifolists control section, below the surface tier. Hydric Cryohemists BABB. Other Torrifolists. Typic Torrifolists BDDB. Other Cryohemists that have a lithic contact within the control section. Udifolists Lithic Cryohemists Key to Subgroups BDDC. Other Cryohemists that have a mineral layer 30 cm BADA. Udifolists that have a lithic contact within 50 cm of or more thick that has its upper boundary within the control the soil surface. section, below the surface tier. H Lithic Udifolists Terric Cryohemists I S BADB. Other Udifolists. BDDD. Other Cryohemists that have, within the organic Typic Udifolists materials, either one mineral layer 5 cm or more thick or two or more mineral layers of any thickness in the control section, Ustifolists below the surface tier. Fluvaquentic Cryohemists Key to Subgroups BDDE. Other Cryohemists. BACA. Ustifolists that have a lithic contact within 50 cm of Typic Cryohemists the soil surface. Lithic Ustifolists Haplohemists BACB. Other Ustifolists. Key to Subgroups Typic Ustifolists BDEA. Haplohemists that have a layer of water within the Hemists control section, below the surface tier. Hydric Haplohemists Key to Great Groups BDEB. Other Haplohemists that have a lithic contact within BDA. Hemists that have a sulfuric horizon that has its upper the control section. boundary within 50 cm of the soil surface. Lithic Haplohemists Sulfohemists, p. 162 BDEC. Other Haplohemists that have one or more limnic BDB. Other Hemists that have sulfidic materials within 100 layers with a total thickness of 5 cm or more within the control cm of the soil surface. section. Sulfihemists, p. 162 Limnic Haplohemists 162 Keys to Soil Taxonomy
BDED. Other Haplohemists that have a mineral layer 30 cm Saprists or more thick that has its upper boundary within the control section, below the surface tier. Key to Great Groups Terric Haplohemists BCA. Saprists that have a sulfuric horizon that has its upper BDEE. Other Haplohemists that have, within the organic boundary within 50 cm of the soil surface. materials, either one mineral layer 5 cm or more thick or two Sulfosaprists, p. 163 or more mineral layers of any thickness in the control section, below the surface tier. BCB. Other Saprists that have sulfidic materials within 100 Fluvaquentic Haplohemists cm of the soil surface. Sulfisaprists, p. 163 BDEF. Other Haplohemists that have one or more layers of fibric materials with a total thickness of 25 cm or more below BCC. Other Saprists that have a cryic temperature the surface tier. regime. Fibric Haplohemists Cryosaprists, p. 162
BDEG. Other Haplohemists that have one or more layers of BCD. Other Saprists. sapric materials with a total thickness of 25 cm or more below Haplosaprists, p. 162 the surface tier. Sapric Haplohemists Cryosaprists
BDEH. Other Haplohemists. Key to Subgroups Typic Haplohemists BCCA. Cryosaprists that have a lithic contact within the control section. Luvihemists Lithic Cryosaprists Key to Subgroups BCCB. Other Cryosaprists that have a mineral layer 30 cm or BDCA. All Luvihemists (provisionally). more thick that has its upper boundary within the control Typic Luvihemists section, below the surface tier. Terric Cryosaprists Sulfihemists BCCC. Other Cryosaprists that have, within the organic Key to Subgroups materials, either one mineral layer 5 cm or more thick or two BDBA. Sulfihemists that have a mineral layer 30 cm or more or more mineral layers of any thickness in the control section, thick that has its upper boundary within the control section, below the surface tier. below the surface tier. Fluvaquentic Cryosaprists Terric Sulfihemists BCCD. Other Cryosaprists. BDBB. Other Sulfihemists. Typic Cryosaprists Typic Sulfihemists Haplosaprists Sulfohemists Key to Subgroups Key to Subgroups BCDA. Haplosaprists that have a lithic contact within the BDAA. All Sulfohemists (provisionally). control section. Typic Sulfohemists Lithic Haplosaprists Histosols 163
BCDB. Other Haplosaprists that have one or more limnic or more mineral layers of any thickness in the control section, layers with a total thickness of 5 cm or more within the control below the surface tier. section. Fluvaquentic Haplosaprists Limnic Haplosaprists BCDG. Other Haplosaprists that have one or more layers of BCDC. Other Haplosaprists that have both: fibric or hemic materials with a total thickness of 25 cm or more below the surface tier. 1. Throughout a layer 30 cm or thick that has its upper Hemic Haplosaprists boundary within the control section, an electrical conductivity of 30 dS/m or more (1:1 soil:water) for 6 BCDH. Other Haplosaprists. months or more during normal years; and Typic Haplosaprists 2. A mineral layer 30 cm or more thick that has its upper boundary within the control section, below the Sulfisaprists surface tier. Halic Terric Haplosaprists Key to Subgroups BCBA. Sulfisaprists that have a mineral layer 30 cm or more BCDD. Other Haplosaprists that have throughout a layer 30 thick that has its upper boundary within the control section, cm or more thick within the control section, an electrical below the surface tier. conductivity of 30 dS/m or more (1:1 soil:water) for 6 months Terric Sulfisaprists or more during normal years. Halic Haplosaprists BCBB. Other Sulfisaprists. Typic Sulfisaprists BCDE. Other Haplosaprists that have a mineral layer 30 cm or more thick that has its upper boundary within the control section, below the surface tier. Sulfosaprists Terric Haplosaprists Key to Subgroups H I BCDF. Other Haplosaprists that have, within the organic BCAA. All Sulfosaprists (provisionally). S materials, either one mineral layer 5 cm or more thick or two Typic Sulfosaprists
165
CHAPTER 11 Inceptisols
Key to Suborders KA. Inceptisols that have one or more of the following: 1. In a layer above a densic, lithic, or paralithic contact or in a layer at a depth between 40 and 50 cm from the mineral soil surface, whichever is shallower, aquic conditions for some time in normal years (or artificial drainage) and one or more of the following: a. A histic epipedon; or b. A sulfuric horizon that has its upper boundary within 50 cm of the mineral soil surface; or c. A layer directly under the epipedon, or within 50 cm KE. Other Inceptisols that have a xeric soil moisture of the mineral soil surface, that has, on faces of peds or regime. in the matrix if peds are absent, 50 percent or more Xerepts, p. 184 chroma of either: KF. Other Inceptisols that have a udic soil moisture (1) 2 or less if there are redox concentrations; or regime. (2) 1 or less; or Udepts, p. 172 I d. Within 50 cm of the mineral soil surface, enough N active ferrous iron to give a positive reaction to Anthrepts C alpha,alpha-dipyridyl at a time when the soil is not being irrigated; or Key to Great Groups 2. An exchangeable sodium percentage (ESP) of 15 or more (or a sodium adsorption ratio [SAR] of 13 or more) in KBA. Anthrepts that have a plaggen epipedon. half or more of the soil volume within 50 cm of the mineral Plagganthrepts, p. 165 soil surface, a decrease in ESP (or SAR) values with increasing depth below 50 cm, and ground water within 100 KBB. Other Anthrepts. cm of the mineral soil surface for some time during the year. Haplanthrepts, p. 165 Aquepts, p. 166 Haplanthrepts KB. Other Inceptisols that have a plaggen or anthropic epipedon. Key to Subgroups Anthrepts, p. 165 KBBA. All Haplanthrepts (provisionally). Typic Haplanthrepts KC. Other Inceptisols that have a cryic soil temperature regime. Cryepts, p. 171 Plagganthrepts Key to Subgroups KD. Other Inceptisols that have an ustic soil moisture regime. KBAA. All Plagganthrepts (provisionally). Ustepts, p. 178 Typic Plagganthrepts 166 Keys to Soil Taxonomy
Aquepts 1. A sulfuric horizon; or 2. A horizon 15 cm or more thick that has all of the Key to Great Groups characteristics of a sulfuric horizon, except that it has a pH between 3.5 and 4.0; or KAA. Aquepts that have a sulfuric horizon that has its upper boundary within 50 cm of the mineral soil surface. 3. Sulfidic materials. Sulfaquepts, p. 170 Sulfic Cryaquepts
KAB. Other Aquepts that have, within 100 cm of the mineral KAEB. Other Cryaquepts that have both a histic epipedon soil surface, one or more horizons in which plinthite or a and a lithic contact within 50 cm of the mineral soil surface. cemented or indurated diagnostic horizon either forms a Histic Lithic Cryaquepts continuous phase or constitutes one-half or more of the volume. Petraquepts, p. 170 KAEC. Other Cryaquepts that have a lithic contact within 50 cm of the mineral soil surface. KAC. Other Aquepts that have either: Lithic Cryaquepts 1. A salic horizon; or KAED. Other Cryaquepts that have one or both of the 2. In one or more horizons with a total thickness of 25 cm following: or more within 50 cm of the mineral soil surface, an exchangeable sodium percentage (ESP) of 15 or more (or a 1. Cracks within 125 cm of the mineral soil surface that sodium adsorption ratio [SAR] of 13 or more) and a are 5 mm or more wide through a thickness of 30 cm or decrease in ESP (or SAR) values with increasing depth more for some time in normal years, and slickensides or below 50 cm. wedge-shaped aggregates in a layer 15 cm or more thick Halaquepts, p. 169 that has its upper boundary within 125 cm of the mineral soil surface; or KAD. Other Aquepts that have a fragipan with its upper 2. A linear extensibility of 6.0 cm or more between the boundary within 100 cm of the mineral soil surface. mineral soil surface and either a depth of 100 cm or a Fragiaquepts, p. 169 densic, lithic, or paralithic contact, whichever is shallower. Vertic Cryaquepts KAE. Other Aquepts that have a cryic soil temperature regime. KAEE. Other Cryaquepts that have a histic epipedon. Cryaquepts, p. 166 Histic Cryaquepts KAF. Other Aquepts that have, in one or more layers at least KAEF. Other Cryaquepts that have, throughout one or more 25 cm thick (cumulative) within 100 cm of the mineral soil horizons with a total thickness of 18 cm or more within surface, 25 percent or more (by volume) recognizable 75 cm of the mineral soil surface, one or more of the bioturbation, such as filled animal burrows, wormholes, or following: casts. 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 1 KAG. Other Aquepts that have a histic, melanic, mollic, or plus /2 Fe percentages (by ammonium oxalate) totaling umbric epipedon. more than 1.0; or Humaquepts, p. 170 2. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, KAH. Other Aquepts that have episaturation. pumice, and pumicelike fragments; or Epiaquepts, p. 168 3. A fine-earth fraction containing 30 percent or more KAI. 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 KAEA. 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
KAEG. Other Cryaquepts that have a slope of less than 25 1. Cracks within 125 cm of the mineral soil surface that percent; and are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or 1. At a depth of 125 cm below the mineral soil surface, an wedge-shaped aggregates in a layer 15 cm or more thick organic-carbon content (Holocene age) of 0.2 percent or that has its upper boundary within 125 cm of the mineral more and no densic, lithic, or paralithic contact within that soil surface; or depth; or 2. A linear extensibility of 6.0 cm or more between the 2. An irregular decrease in organic-carbon content mineral soil surface and either a depth of 100 cm or a (Holocene age) between a depth of 25 cm and either a depth densic, lithic, or paralithic contact, whichever is shallower. of 125 cm below the mineral soil surface or a densic, lithic, Vertic Endoaquepts or paralithic contact, whichever is shallower. Fluvaquentic Cryaquepts KAID. Other Endoaquepts that have, throughout one or more KAEH. Other Cryaquepts that have both: 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. Chroma of 3 or more in 40 percent or more of the matrix of one or more horizons at a depth between 15 and 1. A fine-earth fraction with both a bulk density of 1.0 50 cm from the mineral soil surface; and g/cm3 or less, measured at 33 kPa water retention, and Al 1 plus /2 Fe percentages (by ammonium oxalate) totaling 2. A mollic or umbric epipedon. more than 1.0; or Aeric Humic Cryaquepts 2. More than 35 percent (by volume) fragments coarser KAEI. Other Cryaquepts that have chroma of 3 or more than 2.0 mm, of which more than 66 percent is cinders, in 40 percent or more of the matrix of one or more horizons pumice, and pumicelike fragments; or at a depth between 15 and 50 cm from the mineral soil 3. A fine-earth fraction containing 30 percent or more surface. particles 0.02 to 2.0 mm in diameter; and Aeric Cryaquepts a. In the 0.02 to 2.0 mm fraction, 5 percent or more KAEJ. Other Cryaquepts that have a mollic or umbric volcanic glass; and epipedon. 1 b. [(Al plus /2 Fe, percent extracted by ammonium Humic Cryaquepts oxalate) times 60] plus the volcanic glass (percent) is I equal to 30 or more. N KAEK. Other Cryaquepts. Aquandic Endoaquepts C Typic Cryaquepts KAIE. Other Endoaquepts that have a slope of less than 25 Endoaquepts percent; and 1. At a depth of 125 cm below the mineral soil surface, an Key to Subgroups organic-carbon content (Holocene age) of 0.2 percent or KAIA. Endoaquepts that have, within 150 cm of the mineral more and no densic, lithic, or paralithic contact within that soil surface, one or more of the following: depth; or 1. A sulfuric horizon; or 2. An irregular decrease in organic-carbon content (Holocene age) between a depth of 25 cm and either a depth 2. A horizon 15 cm or more thick that has all of the of 125 cm below the mineral soil surface or a densic, lithic, characteristics of a sulfuric horizon, except that it has a pH or paralithic contact, whichever is shallower. between 3.5 and 4.0; or Fluvaquentic Endoaquepts 3. Sulfidic materials. Sulfic Endoaquepts KAIF. Other Endoaquepts that have fragic soil properties: 1. In 30 percent or more of the volume of a layer 15 cm or KAIB. Other Endoaquepts that have a lithic contact within more thick that has its upper boundary within 100 cm of the 50 cm of the mineral soil surface. mineral soil surface; or Lithic Endoaquepts 2. In 60 percent or more of the volume of a layer 15 cm or KAIC. Other Endoaquepts that have one or both of the more thick. following: Fragic Endoaquepts 168 Keys to Soil Taxonomy
KAIG. Other Endoaquepts that have, in one or more KAHB. Other Epiaquepts that have, throughout one or horizons between the A or Ap horizon and a depth of 75 cm more horizons with a total thickness of 18 cm or more below the mineral soil surface, one of the following colors: within 75 cm of the mineral soil surface, one or more of the following: 1. Hue of 7.5YR or redder in 50 percent or more of the matrix; and 1. A fine-earth fraction with both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water retention, and Al a. If peds are present, either chroma of 2 or more on 50 1 plus /2 Fe percentages (by ammonium oxalate) totaling percent or more of ped exteriors or no redox depletions more than 1.0; or with chroma of 2 or less in ped interiors; or 2. More than 35 percent (by volume) fragments coarser b. If peds are absent, chroma of 2 or more in 50 percent than 2.0 mm, of which more than 66 percent is cinders, or more of the matrix; or pumice, and pumicelike fragments; or 2. In 50 percent or more of the matrix, hue of 10YR or 3. A fine-earth fraction containing 30 percent or more yellower and either: particles 0.02 to 2.0 mm in diameter; and a. Both a color value, moist, and chroma of 3 or more; a. In the 0.02 to 2.0 mm fraction, 5 percent or more or volcanic glass; and
b. Chroma of 2 or more if there are no redox 1 b. [(Al plus /2 Fe, percent extracted by ammonium concentrations. oxalate) times 60] plus the volcanic glass (percent) is Aeric Endoaquepts equal to 30 or more. Aquandic Epiaquepts KAIH. Other Endoaquepts that have: 1. A color value, moist, of 3 or less and a color value, dry, KAHC. Other Epiaquepts that have a slope of less than 25 of 5 or less (crushed and smoothed) in the Ap horizon or in percent; and the upper 15 cm after mixing; and 1. At a depth of 125 cm below the mineral soil surface, an 2. A base saturation (by NH OAc) of less than 50 percent 4 organic-carbon content (Holocene age) of 0.2 percent or in some part within 100 cm of the mineral soil surface. more and no densic, lithic, or paralithic contact within that Humic Endoaquepts depth; or KAII. Other Endoaquepts that have a color value, moist, of 3 2. An irregular decrease in organic-carbon content or less and a color value, dry, of 5 or less (crushed and (Holocene age) between a depth of 25 cm and either a depth smoothed) either in the Ap horizon or in the upper 15 cm after of 125 cm below the mineral soil surface or a densic, lithic, mixing. or paralithic contact, whichever is shallower. Mollic Endoaquepts Fluvaquentic Epiaquepts
KAIJ. Other Endoaquepts. KAHD. Other Epiaquepts that have fragic soil properties: Typic Endoaquepts 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 Epiaquepts mineral soil surface; or Key to Subgroups 2. In 60 percent or more of the volume of a layer 15 cm or more thick. KAHA. Epiaquepts that have one or both of the following: Fragic Epiaquepts 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or KAHE. Other Epiaquepts that have, in one or more horizons more for some time in normal years, and slickensides or between the A or Ap horizon and a depth of 75 cm below the wedge-shaped aggregates in a layer 15 cm or more thick mineral soil surface, one of the following colors: that has its upper boundary within 125 cm of the mineral soil surface; or 1. Hue of 7.5YR or redder in 50 percent or more of the matrix; 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 a. If peds are present, either chroma of 2 or more on 50 densic, lithic, or paralithic contact, whichever is shallower. percent or more of ped exteriors or no redox depletions Vertic Epiaquepts with chroma of 2 or less in ped interiors; or Inceptisols 169
b. If peds are absent, chroma of 2 or more in 50 percent Halaquepts or more of the matrix; or Key to Subgroups 2. In 50 percent or more of the matrix, hue of 10YR or yellower and either: KACA. Halaquepts that have one or both of the following: a. Both a color value, moist, and chroma of 3 or more; 1. Cracks within 125 cm of the mineral soil surface that or are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or b. Chroma of 2 or more if there are no redox wedge-shaped aggregates in a layer 15 cm or more thick concentrations. that has its upper boundary within 125 cm of the mineral Aeric Epiaquepts soil surface; or KAHF. Other Epiaquepts that have both: 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a 1. A color value, moist, of 3 or less and a color value, dry, densic, lithic, or paralithic contact, whichever is shallower. of 5 or less (crushed and smoothed) in the Ap horizon or in Vertic Halaquepts the upper 15 cm after mixing; and 2. A base saturation (by NH OAc) of less than 4 KACB. Other Halaquepts that have, throughout one or more 50 percent in some part within 100 cm of the mineral horizons with a total thickness of 18 cm or more within 75 cm soil surface. of the mineral soil surface, one or more of the following: Humic Epiaquepts 1. A fine-earth fraction with both a bulk density of 1.0 KAHG. Other Epiaquepts that have a color value, moist, of 3 g/cm3 or less, measured at 33 kPa water retention, and Al 1 or less and a color value, dry, of 5 or less (crushed and plus /2 Fe percentages (by ammonium oxalate) totaling smoothed) either in the Ap horizon or in the upper 15 cm after more than 1.0; or mixing. 2. More than 35 percent (by volume) fragments coarser Mollic Epiaquepts than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or KAHH. Other Epiaquepts. Typic Epiaquepts 3. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and I N Fragiaquepts a. In the 0.02 to 2.0 mm fraction, 5 percent or more C volcanic glass; and
Key to Subgroups 1 b. [(Al plus /2 Fe, percent extracted by ammonium KADA. Fragiaquepts that have, in 50 percent or more of the oxalate) times 60] plus the volcanic glass (percent) is matrix of one or more horizons either between the plow layer equal to 30 or more. and a depth of 75 cm below the mineral soil surface or, if there Aquandic Halaquepts is no plow layer, between depths of 15 and 75 cm, chroma of either: KACC. Other Halaquepts that have a horizon 15 cm or more thick that has 20 percent or more (by volume) cemented or 1. 3 or more; or indurated soil material and has its upper boundary within 100 2. 2 or more if there are no redox concentrations. cm either of the mineral soil surface or of the top of an organic Aeric Fragiaquepts layer with andic soil properties, whichever is shallower. Duric Halaquepts KADB. Other Fragiaquepts that have a histic, mollic, or umbric epipedon. KACD. Other Halaquepts that have chroma of 3 or more Humic Fragiaquepts in 40 percent or more of the matrix of one or more horizons at a depth between 15 and 75 cm from the mineral soil KADC. Other Fragiaquepts. surface. Typic Fragiaquepts Aeric Halaquepts 170 Keys to Soil Taxonomy
KACE. Other Halaquepts. KAGE. Other Humaquepts that have a slope of less than 25 Typic Halaquepts percent; and 1. At a depth of 125 cm below the mineral soil surface, an Humaquepts organic-carbon content (Holocene age) of 0.2 percent or more and no densic, lithic, or paralithic contact within that Key to Subgroups depth; or KAGA. Humaquepts that have an n value of either: 2. An irregular decrease in organic-carbon content 1. More than 0.7 (and less than 8 percent clay) in one or (Holocene age) between a depth of 25 cm and either a depth more layers at a depth between 20 and 50 cm from the of 125 cm below the mineral soil surface or a densic, lithic, mineral soil surface; or or paralithic contact, whichever is shallower. Fluvaquentic Humaquepts 2. More than 0.9 in one or more layers at a depth between 50 and 100 cm. KAGF. Other Humaquepts that have hue of 5Y or redder and Hydraquentic Humaquepts chroma of 3 or more in more than 40 percent of the matrix of one or more subhorizons at a depth between 15 and 75 cm KAGB. Other Humaquepts that have a histic epipedon. from the mineral soil surface. Histic Humaquepts Aeric Humaquepts KAGC. Other Humaquepts that have, throughout one or KAGG. Other Humaquepts. more horizons with a total thickness of 18 cm or more within Typic Humaquepts 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 Petraquepts g/cm3 or less, measured at 33 kPa water retention, and Al 1 plus /2 Fe percentages (by ammonium oxalate) totaling Key to Subgroups more than 1.0; or KABA. Petraquepts that have both: 2. More than 35 percent (by volume) fragments coarser 1. A histic epipedon; and than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or 2. A placic horizon. Histic Placic Petraquepts 3. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and KABB. Other Petraquepts that have a placic horizon. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Placic Petraquepts volcanic glass; and
1 b. [(Al plus /2 Fe, percent extracted by ammonium KABC. Other Petraquepts that have one or more horizons oxalate) times 60] plus the volcanic glass (percent) is within 125 cm of the mineral soil surface in which plinthite equal to 30 or more. either forms a continuous phase or constitutes one-half or more Aquandic Humaquepts of the volume. Plinthic Petraquepts KAGD. Other Humaquepts that have a slope of less than 25 percent; and KABD. Other Petraquepts. Typic Petraquepts 1. An umbric or mollic epipedon 60 cm or more thick; and either 2. At a depth of 125 cm below the mineral soil surface, an Sulfaquepts organic-carbon content (Holocene age) of 0.2 percent or Key to Subgroups more and no densic, lithic, or paralithic contact within that depth; or KAAA. Sulfaquepts that have a salic horizon within 75 cm of the mineral soil surface. 3. An irregular decrease in organic-carbon content Salidic 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, KAAB. Other Sulfaquepts that have an n value of either: or paralithic contact, whichever is shallower. Cumulic Humaquepts 1. More than 0.7 (and less than 8 percent clay) in one or Inceptisols 171
more layers at a depth between 20 and 50 cm from the 75 cm of the mineral soil surface, a fine-earth fraction with mineral soil surface; or both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa 1 water retention, and Al plus /2 Fe percentages (by ammonium 2. More than 0.9 in one or more layers at a depth oxalate) totaling more than 1.0. between 50 and 100 cm from the mineral soil surface. Andic Dystrocryepts Hydraquentic Sulfaquepts KCBD. Other Dystrocryepts that have, throughout one or KAAC. Other Sulfaquepts. more horizons with a total thickness of 18 cm or more within Typic Sulfaquepts 75 cm of the mineral soil surface, one or both of the following: Vermaquepts 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, Key to Subgroups pumice, and pumicelike fragments; or KAFA. Vermaquepts that have an exchangeable sodium 2. A fine-earth fraction containing 30 percent or more percentage of 7 or more (or a sodium adsorption ratio [SAR] of particles 0.02 to 2.0 mm in diameter; and 6 or more) in one or more subhorizons within 100 cm of the a. In the 0.02 to 2.0 mm fraction, 5 percent or more mineral soil surface. volcanic glass; and Sodic Vermaquepts 1 b. [(Al plus /2 Fe, percent extracted by ammonium KAFB. Other Vermaquepts. oxalate) times 60] plus the volcanic glass (percent) is Typic Vermaquepts equal to 30 or more. Vitrandic Dystrocryepts Cryepts KCBE. Other Dystrocryepts that have, in one or more Key to Great Groups horizons within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions KCA. Cryepts that have one or both of the following: for some time in normal years (or artificial drainage). Aquic Dystrocryepts 1. Free carbonates within the soils; or
2. A base saturation (by NH4OAc) of 60 percent or more KCBF. Other Dystrocryepts that in normal years are saturated I in one or more horizons at a depth between 25 and 75 cm with water in one or more layers within 100 cm of the mineral N from the mineral soil surface. soil surface for either or both: C Eutrocryepts, p. 172 1. 20 or more consecutive days; or KCB. Other Cryepts. 2. 30 or more cumulative days. Dystrocryepts, p. 171 Oxyaquic Dystrocryepts
Dystrocryepts KCBG. Other Dystrocryepts that have lamellae (two or more) within 200 cm of the mineral soil surface. Key to Subgroups Lamellic Dystrocryepts KCBA. Dystrocryepts that have both: KCBH. Other Dystrocryepts that have a horizon 5 cm or 1. An umbric or mollic epipedon; and more thick that has one or more of the following: 2. A lithic contact within 50 cm of the mineral soil 1. In 25 percent or more of each pedon, cementation surface. by organic matter and aluminum, with or without iron; Humic Lithic Dystrocryepts or
1 2. Al plus /2 Fe percentages (by ammonium oxalate) KCBB. Other Dystrocryepts that have a lithic contact within totaling 0.25 or more, and half that amount or less in an 50 cm of the mineral soil surface. overlying horizon; or Lithic Dystrocryepts 3. An ODOE value of 0.12 or more, and a value half as KCBC. Other Dystrocryepts that have, throughout one or high or lower in an overlying horizon. more horizons with a total thickness of 18 cm or more within Spodic Dystrocryepts 172 Keys to Soil Taxonomy
KCBI. Other Dystrocryepts that have a xeric moisture KCAE. Other Eutrocryepts that have, in one or more regime. horizons within 75 cm of the mineral soil surface, redox Xeric Dystrocryepts depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). KCBJ. Other Dystrocryepts that are dry in some part of the Aquic Eutrocryepts moisture control section for 45 or more days (cumulative) in normal years. KCAF. Other Eutrocryepts that in normal years are saturated Ustic Dystrocryepts with water in one or more layers within 100 cm of the mineral soil surface for either or both: KCBK. Other Dystrocryepts that have an umbric or mollic 1. 20 or more consecutive days; or epipedon. Humic Dystrocryepts 2. 30 or more cumulative days. Oxyaquic Eutrocryepts KCBL. Other Dystrocryepts. Typic Dystrocryepts KCAG. Other Eutrocryepts that have lamellae (two or more) within 200 cm of the mineral soil surface. Eutrocryepts Lamellic Eutrocryepts
Key to Subgroups KCAH. Other Eutrocryepts that have a xeric moisture regime. KCAA. Eutrocryepts that have both: Xeric Eutrocryepts 1. An umbric or mollic epipedon; and KCAI. Other Eutrocryepts that are dry in some part of the 2. A lithic contact within 50 cm of the mineral soil moisture control section for 45 or more days (cumulative) in surface. normal years. Humic Lithic Eutrocryepts Ustic Eutrocryepts KCAB. Other Eutrocryepts that have a lithic contact within KCAJ. Other Eutrocryepts that have an umbric or mollic 50 cm of the mineral soil surface. epipedon. Lithic Eutrocryepts Humic Eutrocryepts KCAC. Other Eutrocryepts that have, throughout one or KCAK. Other Eutrocryepts. more horizons with a total thickness of 18 cm or more within Typic Eutrocryepts 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 1 water retention, and Al plus /2 Fe percentages (by ammonium Udepts oxalate) totaling more than 1.0. Andic Eutrocryepts Key to Great Groups
KCAD. Other Eutrocryepts that have, throughout one or KFA. Udepts that have a sulfuric horizon within 50 cm of the more horizons with a total thickness of 18 cm or more within mineral soil surface. 75 cm of the mineral soil surface, one or both of the following: Sulfudepts, p. 178 1. More than 35 percent (by volume) fragments coarser KFB. Other Udepts that have a duripan that has its upper than 2.0 mm, of which more than 66 percent is cinders, boundary within 100 cm of the mineral soil surface. pumice, and pumicelike fragments; or Durudepts, p. 173 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and KFC. Other Udepts that have a fragipan with its upper boundary within 100 cm of the mineral soil surface. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Fragiudepts, p. 177 volcanic glass; and
1 b. [(Al plus /2 Fe, percent extracted by ammonium KFD. Other Udepts that have one or both of the following: oxalate) times 60] plus the volcanic glass (percent) is 1. Free carbonates within the soils; or equal to 30 or more.
Vitrandic Eutrocryepts 2. A base saturation (by NH4OAc) of 60 percent or more Inceptisols 173
in one or more horizons at a depth between 25 and 75 cm 2. A fine-earth fraction containing 30 percent or more from the mineral soil surface. particles 0.02 to 2.0 mm in diameter; and Eutrudepts, p. 176 a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and KFE. Other Udepts. 1 Dystrudepts, p. 173 b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is Durudepts equal to 30 or more. Vitrandic Durudepts Key to Subgroups KFBD. Other Durudepts that have, in one or more horizons KFBA. Durudepts that have both: above the duripan and within 30 cm of the mineral soil surface, 1. In one or more horizons above the duripan and distinct or prominent redox concentrations and also aquic within 60 cm of the mineral soil surface, distinct or conditions for some time in normal years (or artificial prominent redox concentrations and also aquic conditions drainage). for some time in normal years (or artificial drainage); and Aquic Durudepts 2. Throughout one or more horizons with a total thickness KFBE. Other Durudepts. of 18 cm or more, above the duripan and within 75 cm of Typic Durudepts the mineral soil surface, one or more of the following: a. A fine-earth fraction with both a bulk density of 1.0 Dystrudepts g/cm3 or less, measured at 33 kPa water retention, and Al 1 plus /2 Fe percentages (by ammonium oxalate) totaling Key to Subgroups more than 1.0; or KFEA. Dystrudepts that have both: b. More than 35 percent (by volume) fragments coarser 1. A lithic contact within 50 cm of the mineral soil than 2.0 mm, of which more than 66 percent is cinders, surface; and pumice, and pumicelike fragments; or 2. An umbric or mollic epipedon. c. A fine-earth fraction containing 30 percent or more Humic Lithic Dystrudepts particles 0.02 to 2.0 mm in diameter; and I (1) In the 0.02 to 2.0 mm fraction, 5 percent or more N KFEB. Other Dystrudepts that have a lithic contact within 50 volcanic glass; and C cm of the mineral soil surface. 1 (2) [(Al plus /2 Fe, percent extracted by ammonium Lithic Dystrudepts oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. KFEC. Other Dystrudepts that have one or both of the Aquandic Durudepts following: 1. Cracks within 125 cm of the mineral soil surface that KFBB. Other Durudepts 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, above the more for some time in normal years, and slickensides or duripan and within 75 cm of the mineral soil surface, a fine- wedge-shaped aggregates in a layer 15 cm or more thick earth fraction with both a bulk density of 1.0 g/cm3 or less, 1 that has its upper boundary within 125 cm of the mineral measured at 33 kPa water retention, and Al plus /2 Fe soil surface; or percentages (by ammonium oxalate) totaling more than 1.0. Andic Durudepts 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm KFBC. Other Durudepts 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, above the shallower. duripan and within 75 cm of the mineral soil surface, one or Vertic Dystrudepts both of the following: KFED. Other Dystrudepts that have both: 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, 1. In one or more horizons within 60 cm of the mineral pumice, and pumicelike fragments; or soil surface, redox depletions with chroma of 2 or less and 174 Keys to Soil Taxonomy
also aquic conditions for some time in normal years (or or more thick that has its upper boundary within 100 cm artificial 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 60 cm of the mineral a. A fine-earth fraction with both a bulk density of 1.0 soil surface, redox depletions with chroma of 2 or less and g/cm3 or less, measured at 33 kPa water retention, and Al also aquic conditions in normal years (or artificial 1 plus /2 Fe percentages (by ammonium oxalate) totaling drainage). more than 1.0; or Fragiaquic Dystrudepts b. More than 35 percent (by volume) fragments coarser KFEH. Other Dystrudepts 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 60 cm of the mineral c. A fine-earth fraction containing 30 percent or more soil surface, redox depletions with chroma of 2 or less and particles 0.02 to 2.0 mm in diameter; and also aquic conditions for some time in normal years (or (1) In the 0.02 to 2.0 mm fraction, 5 percent or more artificial drainage); and 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 Dystrudepts that depth; or KFEE. Other Dystrudepts that have, throughout one or more b. An irregular decrease in organic-carbon content horizons with a total thickness of 18 cm or more within 75 cm (Holocene age) between a depth of 25 cm and either a of the mineral soil surface, a fine-earth fraction with both a depth of 125 cm below the mineral soil surface or a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water densic, lithic, or paralithic contact, whichever is 1 retention, and Al plus /2 Fe percentages (by ammonium shallower. oxalate) totaling more than 1.0. Fluvaquentic Dystrudepts Andic Dystrudepts KFEI. Other Dystrudepts that have both: KFEF. Other Dystrudepts that have, throughout one or more 1. An umbric or mollic epipedon; and horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: 2. In one or more horizons within 60 cm of the mineral soil surface, redox depletions with chroma of 2 or less and 1. More than 35 percent (by volume) fragments coarser also aquic conditions for some time in normal years (or than 2.0 mm, of which more than 66 percent is cinders, artificial drainage). pumice, and pumicelike fragments; or Aquic Humic Dystrudepts 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and KFEJ. Other Dystrudepts that have, in one or more horizons within 60 cm of the mineral soil surface, redox depletions with a. In the 0.02 to 2.0 mm fraction, 5 percent or more chroma of 2 or less and also aquic conditions for some time in volcanic glass; and normal years (or artificial drainage). 1 b. [(Al plus /2 Fe, percent extracted by ammonium Aquic Dystrudepts oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. KFEK. Other Dystrudepts that in normal years are saturated Vitrandic Dystrudepts with water in one or more layers within 100 cm of the mineral soil surface for either or both: KFEG. Other Dystrudepts that have both: 1. 20 or more consecutive days; or 1. Fragic soil properties: 2. 30 or more cumulative days. a. In 30 percent or more of the volume of a layer 15 cm Oxyaquic Dystrudepts Inceptisols 175
KFEL. Other Dystrudepts that have fragic soil 1. In 25 percent or more of each pedon, cementation properties: by organic matter and aluminum, with or without iron; or 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 2. Al plus /2 Fe percentages (by ammonium oxalate) mineral soil surface; or totaling 0.25 or more, and half that amount or less in an overlying horizon; or 2. In 60 percent or more of the volume of a layer 15 cm or more thick. 3. An ODOE value of 0.12 or more, and a value half as Fragic Dystrudepts high or lower in an overlying horizon. Spodic Dystrudepts KFEM. Other Dystrudepts that have lamellae (two or more) within 200 cm of the mineral soil surface. KFER. Other Dystrudepts that have in 50 percent or more of Lamellic Dystrudepts 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 KFEN. Other Dystrudepts that have both: paralithic contact if shallower:
1. An umbric or mollic epipedon; and 1. A CEC (by 1N NH4OAc pH 7) of less than 24 cmol(+) per kg clay; or 2. A sandy particle-size class throughout the particle-size control section. 2. Both a ratio of measured clay in the fine-earth fraction Humic Psammentic Dystrudepts to percent water retained at 1500 kPa tension of 0.6 or more
and the following: the CEC (by 1N NH4OAc pH 7) divided KFEO. Other Dystrudepts that have a slope of less than 25 by the product of three times [percent water retained at 1500 percent; and kPa tension minus percent organic carbon (but no more than 1.00)] is less than 24. 1. An umbric or mollic epipedon; and Oxic Dystrudepts 2. Either: KFES. Other Dystrudepts that have an umbric or mollic a. At a depth of 125 cm below the mineral soil surface, epipedon that is 50 cm or more thick. an organic-carbon content (Holocene age) of 0.2 percent Humic Pachic Dystrudepts or more and no densic, lithic, or paralithic contact within that depth; or I KFET. Other Dystrudepts that have an umbric or mollic N b. An irregular decrease in organic-carbon content epipedon. C (Holocene age) between a depth of 25 cm and either a Humic Dystrudepts depth of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is KFEU. Other Dystrudepts that have both: shallower. 1. In each pedon a cambic horizon that includes 10 to 50 Fluventic Humic Dystrudepts percent (by volume) illuvial parts that otherwise meet the requirements for an argillic, kandic, or natric horizon; and KFEP. Other Dystrudepts that have a slope of less than 25 percent; and either 2. A base saturation (by sum of cations) of 35 percent or more either at a depth of 125 cm from the top of the cambic 1. At a depth of 125 cm below the mineral soil surface, an horizon or directly above a densic, lithic, or paralithic organic-carbon content (Holocene age) of 0.2 percent or contact if shallower. more and no densic, lithic, or paralithic contact within that Ruptic-Alfic Dystrudepts depth; or 2. An irregular decrease in organic-carbon content KFEV. Other Dystrudepts that have in each pedon a cambic (Holocene age) between a depth of 25 cm and either a depth horizon that includes 10 to 50 percent (by volume) illuvial of 125 cm below the mineral soil surface or a densic, lithic, parts that otherwise meet the requirements for an argillic, or paralithic contact, whichever is shallower. kandic, or natric horizon. Fluventic Dystrudepts Ruptic-Ultic Dystrudepts
KEEQ. Other Dystrudepts that have a horizon 5 cm or more KFEW. Other Dystrudepts. thick that has one or more of the following: Typic Dystrudepts 176 Keys to Soil Taxonomy
1 Eutrudepts retention, and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. Key to Subgroups Andic Eutrudepts KFDA. Eutrudepts that have both: KFDF. Other Eutrudepts that have, throughout one or 1. An umbric or mollic epipedon; and more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the 2. A lithic contact within 50 cm of the mineral soil following: surface. Humic Lithic Eutrudepts 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, KFDB. Other Eutrudepts that have a lithic contact within 50 pumice, and pumicelike fragments; or cm of the mineral soil surface. 2. A fine-earth fraction containing 30 percent or more Lithic Eutrudepts particles 0.02 to 2.0 mm in diameter; and KFDC. Other Eutrudepts that have both: a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and 1. One or both of the following: 1 b. [(Al plus /2 Fe, percent extracted by ammonium a. Cracks within 125 cm of the mineral soil surface that oxalate) times 60] plus the volcanic glass (percent) is are 5 mm or more wide through a thickness of 30 cm or equal to 30 or more. more for some time in normal years, and slickensides or Vitrandic Eutrudepts wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral KFDG. Other Eutrudepts that have anthraquic conditions. soil surface; or Anthraquic Eutrudepts b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a KFDH. Other Eutrudepts that have both: densic, lithic, or paralithic contact, whichever is 1. Fragic soil properties: shallower; and a. In 30 percent or more of the volume of a layer 15 cm 2. In one or more horizons within 60 cm of the mineral or more thick that has its upper boundary within 100 cm soil surface, redox depletions with chroma of 2 or less and of the mineral soil surface; or also aquic conditions for some time in normal years (or artificial drainage). b. In 60 percent or more of the volume of a layer 15 cm Aquertic Eutrudepts or more thick; and 2. In one or more horizons within 60 cm of the mineral KFDD. Other Eutrudepts that have one or both of the soil surface, redox depletions with chroma of 2 or less and following: also aquic conditions in normal years (or artificial 1. Cracks within 125 cm of the mineral soil surface that drainage). are 5 mm or more wide through a thickness of 30 cm or Fragiaquic Eutrudepts more for some time in normal years, and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick KFDI. Other Eutrudepts that have a slope of less than 25 that has its upper boundary within 125 cm of the mineral percent; and soil surface; or 1. In one or more horizons within 60 cm of the mineral 2. A linear extensibility of 6.0 cm or more between the soil surface, redox depletions with chroma of 2 or less and mineral soil surface and either a depth of 100 cm or a also aquic conditions for some time in normal years (or densic, lithic, or paralithic contact, whichever is shallower. artificial drainage); and Vertic Eutrudepts 2. Either: KFDE. Other Eutrudepts that have, throughout one or more a. At a depth of 125 cm below the mineral soil surface, horizons with a total thickness of 18 cm or more within 75 cm an organic-carbon content (Holocene age) of 0.2 percent of the mineral soil surface, a fine-earth fraction with both a or more and no densic, lithic, or paralithic contact within bulk density of 1.0 g/cm3 or less, measured at 33 kPa water that depth; or Inceptisols 177
b. An irregular decrease in organic-carbon content 3. Have 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 depth depth of 125 cm below the mineral soil surface or a of 125 cm below the mineral soil surface or a densic, lithic, densic, lithic, or paralithic contact, whichever is or paralithic contact, whichever is shallower. shallower. Dystric Fluventic Eutrudepts Fluvaquentic Eutrudepts KFDP. Other Eutrudepts that have a slope of less than 25 percent; and either KFDJ. 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 KFDK. Other Eutrudepts that have, in one or more horizons within 60 cm of the mineral soil surface, redox depletions with KFDQ. Other Eutrudepts that have a sandy or sandy-skeletal chroma of 2 or less and also aquic conditions for some time in particle-size class in all horizons within 50 cm of the mineral normal years (or artificial drainage). soil surface. Aquic Eutrudepts Arenic Eutrudepts KFDL. Other Eutrudepts that in normal years are saturated KFDR. Other Eutrudepts that do not have free carbonates with water in one or more layers within 100 cm of the mineral throughout any horizon within 100 cm of the mineral soil soil surface for either or both: surface. 1. 20 or more consecutive days; or Dystric Eutrudepts 2. 30 or more cumulative days. KFDS. Other Eutrudepts that have 40 percent or more free Oxyaquic Eutrudepts I carbonates, including coarse fragments as much as 75 mm in N diameter, in all horizons between the top of the cambic horizon KFDM. Other Eutrudepts that have fragic soil properties: C and either a depth of 100 cm from the mineral soil surface or a 1. In 30 percent or more of the volume of a layer 15 cm or densic, lithic, or paralithic contact if shallower. more thick that has its upper boundary within 100 cm of the Rendollic Eutrudepts mineral soil surface; or KFDT. Other Eutrudepts that have an umbric or mollic 2. In 60 percent or more of the volume of a layer 15 cm or epipedon. more thick. Humic Eutrudepts Fragic Eutrudepts KFDU. Other Eutrudepts that have a cambic horizon that KFDN. Other Eutrudepts that have lamellae (two or more) includes 10 to 50 percent (by volume) illuvial parts that within 200 cm of the mineral soil surface. otherwise meet the requirements for an argillic, kandic, or Lamellic Eutrudepts natric horizon. Ruptic-Alfic Eutrudepts KFDO. Other Eutrudepts that have a slope of less than 25 percent; and KFDV. Other Eutrudepts. 1. Do not have free carbonates throughout any Typic Eutrudepts horizon within 100 cm of the mineral soil surface; and either Fragiudepts 2. Have, at a depth of 125 cm below the mineral soil Key to Subgroups surface, an organic-carbon content (Holocene age) of 0.2 percent or more and no densic, lithic, or paralithic contact KFCA. Fragiudepts that have, throughout one or more within that depth; or horizons with a total thickness of 18 cm or more within 75 cm 178 Keys to Soil Taxonomy
of the mineral soil surface, a fine-earth fraction with both a horizon that has its upper boundary within 150 cm of the bulk density of 1.0 g/cm3 or less, measured at 33 kPa water mineral soil surface; and 1 retention, and Al plus /2 Fe percentages (by ammonium 2. Are either calcareous or have a texture of loamy fine oxalate) totaling more than 1.0. sand or coarser in all parts above the calcic or petrocalcic Andic Fragiudepts horizon, after the soil between the mineral soil surface and a depth of 18 cm has been mixed. KFCB. Other Fragiudepts that have, throughout one or more Calciustepts, p. 178 horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: KDC. Other Ustepts that have both of the following: 1. More than 35 percent (by volume) fragments coarser 1. No free carbonates within 200 cm of the mineral soil than 2.0 mm, of which more than 66 percent is cinders, surface; and pumice, and pumicelike fragments; or 2. A base saturation (by NH OAc) of less than 60 percent 2. A fine-earth fraction containing 30 percent or more 4 in all horizons at a depth between 25 and 75 cm from the particles 0.02 to 2.0 mm in diameter; and mineral soil surface. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Dystrustepts, p. 179 volcanic glass; and
1 KDD. Other Ustepts. b. [(Al plus /2 Fe, percent extracted by ammonium Haplustepts, p. 180 oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. Vitrandic Fragiudepts Calciustepts
KFCC. Other Fragiudepts that have, in one or more horizons Key to Subgroups within 30 cm of the mineral soil surface, distinct or prominent KDBA. Calciustepts that have a petrocalcic horizon and a redox concentrations and also aquic conditions for some time lithic contact within 50 cm of the mineral soil surface. in normal years (or artificial drainage). Lithic Petrocalcic Calciustepts Aquic Fragiudepts KDBB. Other Calciustepts that have a lithic contact within KFCD. Other Fragiudepts that have an umbric or mollic 50 cm of the mineral soil surface. epipedon. Lithic Calciustepts Humic Fragiudepts KDBC. Other Calciustepts that have both: KFCE. Other Fragiudepts. Typic Fragiudepts 1. One or both of the following: a. Cracks within 125 cm of the mineral soil surface that Sulfudepts are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or Key to Subgroups wedge-shaped aggregates in a layer 15 cm or more thick KFAA. All Sulfudepts (provisionally). that has its upper boundary within 125 cm of the mineral Typic Sulfudepts soil surface; or b. A linear extensibility of 6.0 cm or more between the Ustepts mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is Key to Great Groups shallower; and KDA. Ustepts that have a duripan that has its upper 2. When neither irrigated nor fallowed to store moisture, boundary within 100 cm of the mineral soil surface. one of the following: Durustepts, p. 179 a. A frigid temperature regime and a moisture control section that in normal years is dry in all parts for four- KDB. Other Ustepts that both: tenths or more of the cumulative days per year when the 1. Have a calcic horizon with its upper boundary temperature at a depth of 50 cm below the soil surface is within 100 cm of the mineral soil surface or a petrocalcic higher than 5 oC; or Inceptisols 179
b. A mesic or thermic soil temperature regime and a temperature at a depth of 50 cm below the soil surface is moisture control section that in normal years is dry in higher than 5 oC; or some or all parts for six-tenths or more of the cumulative 2. A mesic or thermic soil temperature regime and a days per year when the 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 or all parts for six-tenths or more of the cumulative days per c. A hyperthermic, isomesic, or warmer iso soil year when the temperature at a depth of 50 cm below the temperature regime and a moisture control section that in soil surface is higher than 5 oC; or normal years: 3. A hyperthermic, isomesic, or warmer iso soil (1) Is moist in some or all parts for fewer 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 a. Is moist in some or all parts for fewer than 90 8 oC; and consecutive days per year when the temperature at a (2) Is dry in some or all parts for six-tenths or more depth of 50 cm below the soil surface is higher than 8 oC; of the cumulative days per year when the temperature and at a depth of 50 cm below the soil surface is higher b. Is dry in some or all parts for six-tenths or more than 5 oC. of the cumulative days per year when the temperature Torrertic Calciustepts at a depth of 50 cm below the soil surface is higher than 5 oC. KDBD. Other Calciustepts that have one or both of the Aridic Calciustepts following: 1. Cracks within 125 cm of the mineral soil surface that KDBI. Other Calciustepts that have, when neither irrigated are 5 mm or more wide through a thickness of 30 cm or nor fallowed to store moisture, either: more for some time in normal years, and slickensides or 1. 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 some that has its upper boundary within 125 cm of the mineral or all parts for four-tenths or less of the consecutive days per soil surface; or year when the temperature at a depth of 50 cm below the 2. A linear extensibility of 6.0 cm or more between the soil surface is higher than 5 oC; or mineral soil surface and either a depth of 100 cm or a I 2. A hyperthermic, isomesic, or warmer iso soil densic, lithic, or paralithic contact, whichever is shallower. N temperature regime and a moisture control section that Vertic Calciustepts C in normal years is dry in some or all parts for fewer than 120 cumulative days per year when the temperature KDBE. Other Calciustepts that have a petrocalcic horizon at a depth of 50 cm below the soil surface is higher than that has its upper boundary within 100 cm of the mineral soil 8 oC. surface. Udic Calciustepts Petrocalcic Calciustepts KDBJ. Other Calciustepts. KDBF. Other Calciustepts that have a gypsic horizon that has Typic Calciustepts its upper boundary within 100 cm of the mineral soil surface. Gypsic Calciustepts Durustepts KDBG. Other Calciustepts that have, in one or more Key to Subgroups horizons within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions KDAA. All Durustepts (provisionally). for some time in normal years (or artificial drainage). Typic Durustepts Aquic Calciustepts Dystrustepts KDBH. Other Calciustepts that have, when neither irrigated nor fallowed to store moisture, one of the following: Key to Subgroups 1. A frigid temperature regime and a moisture control KDCA. Dystrustepts that have a lithic contact within 50 cm section that in normal years is dry in all parts for four-tenths of the mineral soil surface. or more of the cumulative days per year when the Lithic Dystrustepts 180 Keys to Soil Taxonomy
KDCB. Other Dystrustepts that have, throughout one or more and the following: the CEC (by 1N NH4OAc pH 7) divided horizons with a total thickness of 18 cm or more within 75 cm by the product of three times [percent water retained at 1500 of the mineral soil surface, a fine-earth fraction with both a kPa tension minus percent organic carbon (but no more than bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1.00)] is less than 24. 1 retention, and Al plus /2 Fe percentages (by ammonium Oxic Dystrustepts oxalate) totaling more than 1.0. Andic Dystrustepts KDCG. Other Dystrustepts that have an umbric or mollic epipedon. KDCC. Other Dystrustepts that have, throughout one Humic Dystrustepts or more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the KDCH. Other Dystrustepts. following: Typic Dystrustepts 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, Haplustepts 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; and KDDA. Haplustepts that have: a. In the 0.02 to 2.0 mm fraction, 5 percent or more 1. A lithic contact within 50 cm of the mineral soil volcanic glass; and surface; and
1 b. [(Al plus /2 Fe, percent extracted by ammonium 2. When neither irrigated nor fallowed to store moisture, oxalate) times 60] plus the volcanic glass (percent) is either: equal to 30 or more. a. A frigid temperature regime and a moisture control Vitrandic Dystrustepts section that in normal years is dry in all parts for four- tenths or more of the cumulative days per year when the KDCD. Other Dystrustepts that have, in one or more temperature at a depth of 50 cm below the soil surface is horizons within 75 cm of the mineral soil surface, redox higher than 5 oC; or depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). b. A mesic or thermic soil temperature regime and a Aquic Dystrustepts moisture control section that in normal years is dry in some part for six-tenths or more of the cumulative days KDCE. Other Dystrustepts that have a slope of less than 25 per year when the temperature at a depth of 50 cm below percent; and either the soil surface is higher than 5 oC; or 1. At a depth of 125 cm below the mineral soil surface, an c. A hyperthermic, isomesic, or warmer iso soil organic-carbon content (Holocene age) of 0.2 percent or temperature regime and a moisture control section that in more and no densic, lithic, or paralithic contact within that normal years: depth; or (1) Is moist in some or all parts for fewer than 90 2. An irregular decrease in organic-carbon content consecutive days per year when the temperature at a (Holocene age) between a depth of 25 cm and either a depth depth of 50 cm below the soil surface is higher than of 125 cm below the mineral soil surface or a densic, lithic, 8 oC; and or paralithic contact, whichever is shallower. (2) Is dry in some part for six-tenths or more of the Fluventic Dystrustepts cumulative days per year when the temperature at a depth of 50 cm below the soil surface is higher than KDCF. Other Dystrustepts that have in 50 percent or more of 5 oC. the soil volume between a depth of 25 cm from the mineral soil Aridic Lithic Haplustepts surface and either a depth of 100 cm or a densic, lithic, or paralithic contact if shallower: KDDB. Other Haplustepts that have a lithic contact within 1. A CEC (by 1N NH OAc pH 7) of less than 24 cmol(+) 4 50 cm of the mineral soil surface. per kg clay; or Lithic Haplustepts 2. Both a ratio of measured clay in the fine-earth fraction to percent water retained at 1500 kPa tension of 0.6 or more KDDC. Other Haplustepts that have both: Inceptisols 181
1. When neither irrigated nor fallowed to store moisture, depth of 50 cm below the soil surface is higher than one of the following: 8 oC; and a. A frigid soil temperature regime and a moisture (2) Is dry in some part for six-tenths or more of the control section that in normal years is dry in some or all cumulative days per year when the temperature at a parts for fewer than 105 cumulative days per year when depth of 50 cm below the soil surface is higher than the temperature at a depth of 50 cm below the soil 5 oC; and 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 part for less than four-tenths of the cumulative days more for some time in normal years, and slickensides or per year when the temperature at a depth of 50 cm below wedge-shaped aggregates in a layer 15 cm or more thick the soil surface is higher than 5 oC; or that has its upper boundary within 125 cm of the mineral c. A hyperthermic, isomesic, or warmer iso soil soil surface; or temperature regime and a moisture control section that in b. A linear extensibility of 6.0 cm or more between the normal years is dry in some or all parts for fewer than mineral soil surface and either a depth of 100 cm or a 120 cumulative days per year when the temperature at a densic, lithic, or paralithic contact, whichever is depth of 50 cm below the soil surface is higher than 8 oC; shallower. and Torrertic Haplustepts 2. One or both of the following: KDDE. Other Haplustepts that have one or both of the a. Cracks within 125 cm of the mineral soil surface that following: are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or 1. Cracks within 125 cm of the mineral soil surface that wedge-shaped aggregates in a layer 15 cm or more thick are 5 mm or more wide through a thickness of 30 cm or that has its upper boundary within 125 cm of the mineral more for some time in normal years, and slickensides or soil surface; or wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral b. A linear extensibility of 6.0 cm or more between the soil surface; or mineral soil surface and either a depth of 100 cm or a I densic, lithic, or paralithic contact, whichever is 2. A linear extensibility of 6.0 cm or more between the N shallower. mineral soil surface and either a depth of 100 cm or a C Udertic Haplustepts densic, lithic, or paralithic contact, whichever is shallower. Vertic Haplustepts KDDD. Other Haplustepts that have both: KDDF. Other Haplustepts that have, throughout one or more 1. When neither irrigated nor fallowed to store moisture, horizons with a total thickness of 18 cm or more within 75 cm one of the following: of the mineral soil surface, a fine-earth fraction with both a a. A frigid soil temperature regime and a moisture bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 control section that in normal years is dry in all parts for retention, and Al plus /2 Fe percentages (by ammonium four-tenths or more of the cumulative days per year when oxalate) totaling more than 1.0. the temperature at a depth of 50 cm below the soil Andic Haplustepts surface is higher than 5 oC; or KDDG. Other Haplustepts that have, throughout one or more b. A mesic or thermic soil temperature regime and a horizons with a total thickness of 18 cm or more within 75 cm moisture control section that in normal years is dry in of the mineral soil surface, one or both of the following: some part for six-tenths or more of the cumulative days per year when the temperature at a depth of 50 cm below 1. More than 35 percent (by volume) fragments coarser the soil surface is higher than 5 oC; or than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or c. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in 2. A fine-earth fraction containing 30 percent or more normal years: particles 0.02 to 2.0 mm in diameter; and (1) Is moist in some or all parts for fewer than 90 a. In the 0.02 to 2.0 mm fraction, 5 percent or more consecutive days per year when the temperature at a volcanic glass; and 182 Keys to Soil Taxonomy
1 b. [(Al plus /2 Fe, percent extracted by ammonium some part for six-tenths or more of the cumulative days oxalate) times 60] plus the volcanic glass (percent) is per year when the temperature at a depth of 50 cm below equal to 30 or more. the soil surface is higher than 5 oC; or Vitrandic Haplustepts c. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in KDDH. Other Haplustepts that have anthraquic conditions. normal years: Anthraquic Haplustepts (1) Is moist in some or all parts for fewer than 90 consecutive days per year when the temperature at a KDDI. 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 normal years (or artificial drainage). (2) Is dry in some part for six-tenths or more of the Aquic Haplustepts cumulative days per year when the temperature at a depth of 50 cm below the soil surface is higher than KDDJ. Other Haplustepts that in normal years are saturated 5 oC; and 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 2. 30 or more cumulative days. or more and no densic, lithic, or paralithic contact within Oxyaquic Haplustepts that depth; or b. An irregular decrease in organic-carbon content KDDK. Other Haplustepts that have in 50 percent or more of (Holocene age) between a depth of 25 cm and either a the soil volume between a depth of 25 cm from the mineral soil depth of 125 cm below the mineral soil surface or a surface and either a depth of 100 cm or a densic, lithic, or densic, lithic, or paralithic contact, whichever is paralithic contact if shallower: shallower.
1. A CEC (by 1N NH4OAc pH 7) of less than 24 cmol(+) Torrifluventic Haplustepts per kg clay; or KDDN. Other Haplustepts that have a slope of less than 25 2. Both a ratio of measured clay in the fine-earth fraction percent; and to percent water retained at 1500 kPa tension of 0.6 or more
and the following: the CEC (by 1N NH4OAc pH 7) divided 1. When neither irrigated nor fallowed to store moisture, by the product of three times [percent water retained at 1500 one of the following: 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 KDDL. Other Haplustepts that have lamellae (two or more) surface is higher than 5 oC; or within 200 cm of the mineral soil surface. Lamellic Haplustepts b. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in KDDM. Other Haplustepts that have a slope of less than 25 some part for less than four-tenths of the cumulative days percent; and per year when the temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or 1. When neither irrigated nor fallowed to store moisture, one of the following: c. A hyperthermic, isomesic, or warmer iso soil 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 control section that in normal years is dry in all parts for 120 cumulative days per year when the temperature at a four-tenths or more of the cumulative days per year when depth of 50 cm below the soil surface is higher than 8 oC; the temperature at a depth of 50 cm below the soil and surface is higher than 5 oC; or 2. Either: b. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in a. At a depth of 125 cm below the mineral soil surface, Inceptisols 183
an organic-carbon content (Holocene age) of 0.2 percent (2) Is dry in some part for six-tenths or more of the or more and no densic, lithic, or paralithic contact within cumulative days per year when the temperature at a that depth; or depth of 50 cm below the soil surface is higher than 5 oC. b. An irregular decrease in organic-carbon content Haplocalcidic Haplustepts (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 KDDR. Other Haplustepts that have both: shallower. 1. A calcic horizon that has its upper boundary within 100 Udifluventic Haplustepts cm of the mineral soil surface; and KDDO. Other Haplustepts that have a slope of less than 25 2. When neither irrigated nor fallowed to store moisture, percent; and either one of the following: 1. At a depth of 125 cm below the mineral soil surface, an a. A frigid soil temperature regime and a moisture organic-carbon content (Holocene age) of 0.2 percent or control section that in normal years is dry in some or all more and no densic, lithic, or paralithic contact within that parts for fewer than 105 cumulative days per year when depth; or the temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or 2. An irregular decrease in organic-carbon content (Holocene age) between a depth of 25 cm and either a depth b. A mesic or thermic soil temperature regime and a of 125 cm below the mineral soil surface or a densic, lithic, moisture control section that in normal years is dry in or paralithic contact, whichever is shallower. some part for less than four-tenths of the cumulative days Fluventic Haplustepts per year when the temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or KDDP. Other Haplustepts that have a gypsic horizon that c. A hyperthermic, isomesic, or warmer iso soil has its upper boundary within 100 cm of the mineral soil temperature regime and a moisture control section that in surface. normal years is dry in some or all parts for fewer than Gypsic Haplustepts 120 cumulative days per year when the temperature at a depth of 50 cm below the soil surface is higher than 8 oC. KDDQ. Other Haplustepts that have both: Calcic Udic Haplustepts I 1. A calcic horizon that has its upper boundary within 100 N KDDS. Other Haplustepts that have a calcic horizon that has cm of the mineral soil surface; and C its upper boundary within 100 cm of the mineral soil surface. 2. When neither irrigated nor fallowed to store moisture, Calcic Haplustepts one of the following: KDDT. 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 four-tenths or more of the cumulative days per year when 1. A frigid soil temperature regime and a moisture control the temperature at a depth of 50 cm below the soil section that in normal years is dry in all parts for four-tenths surface is higher than 5 oC; or or more of the cumulative days per year when the 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 temperature at a depth of 50 cm below moisture control section that in normal years is dry in some the soil surface is higher than 5 oC; or part for six-tenths or more of the cumulative days per year 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 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 fewer 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 fewer than 90 8 oC; and consecutive days per year when the temperature at a 184 Keys to Soil Taxonomy
depth of 50 cm below the soil surface is higher than 8 oC; 2. Are calcareous in all parts above the calcic or and petrocalcic horizon, after the soil between the mineral soil surface and a depth of 18 cm has been mixed. b. Is dry in some part for six-tenths or more of the Calcixerepts, p. 184 cumulative days per year when the temperature at a depth of 50 cm below the soil surface is higher than KEC. Other Xerepts that have a fragipan that has its upper 5 oC. boundary within 100 cm of the mineral soil surface. Aridic Haplustepts Fragixerepts, p. 187 KDDU. Other Haplustepts that have a base saturation (by KED. Other Xerepts that have both of the following: sum of cations) of less than 60 percent in some horizon between either an Ap horizon or a depth of 25 cm from the 1. No free carbonates within 200 cm of the mineral soil mineral soil surface, whichever is deeper, and either a depth of surface; and 75 cm below the mineral soil surface or a densic, lithic, or 2. A base saturation (by NH OAc) of less than 60 percent paralithic contact, whichever is shallower. 4 in all horizons at a depth between 25 and 75 cm from the Dystric Haplustepts mineral soil surface. Dystroxerepts, p. 185 KDDV. Other Haplustepts that, when neither irrigated nor fallowed to store moisture, have one of the following: KEE. Other Xerepts. 1. A frigid soil temperature regime and a moisture control Haploxerepts, p. 187 section that in normal years is dry in some or all parts for fewer than 105 cumulative days per year when the Calcixerepts temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or Key to Subgroups 2. A mesic or thermic soil temperature regime and a KEBA. Calcixerepts that have a lithic contact within 50 cm moisture control section that in normal years is dry in some of the mineral soil surface. part for less than four-tenths of the cumulative days per year Lithic Calcixerepts when the temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or KEBB. Other Calcixerepts that have one or both of the following: 3. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in 1. Cracks within 125 cm of the mineral soil surface that normal years is dry in some or all parts for fewer than 120 are 5 mm or more wide through a thickness of 30 cm or cumulative days per year when the temperature at a depth of more for some time in normal years, and slickensides or 50 cm below the soil surface is higher than 8 oC. wedge-shaped aggregates in a layer 15 cm or more thick Udic Haplustepts that has its upper boundary within 125 cm of the mineral soil surface; or KDDW. Other Haplustepts. 2. A linear extensibility of 6.0 cm or more between Typic Haplustepts the mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is Xerepts shallower. Vertic Calcixerepts Key to Great Groups KEBC. Other Calcixerepts that have a petrocalcic horizon KEA. Xerepts that have a duripan that has its upper that has its upper boundary within 100 cm of the mineral soil boundary within 100 cm of the mineral soil surface. surface. Durixerepts, p. 185 Petrocalcic Calcixerepts KEB. Other Xerepts that both: KEBD. Other Calcixerepts that have an exchangeable 1. Have a calcic horizon with its upper boundary sodium percentage of 15 or more (or a sodium adsorption ratio within 100 cm of the mineral soil surface or a petrocalcic [SAR] of 13 or more) in one or more subhorizons within 100 horizon with its upper boundary within 150 cm of the cm of the mineral soil surface. mineral soil surface; and Sodic Calcixerepts Inceptisols 185
KEBE. Other Calcixerepts that have, throughout one or more oxalate) times 60] plus the volcanic glass (percent) is horizons with a total thickness of 18 cm or more within 75 cm equal to 30 or more. of the mineral soil surface, one or both of the following: Aquandic Durixerepts 1. More than 35 percent (by volume) fragments coarser KEAB. Other Durixerepts 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, above the pumice, and pumicelike fragments; or duripan and within 75 cm of the mineral soil surface, a fine- 2. A fine-earth fraction containing 30 percent or more earth fraction with both a bulk density of 1.0 g/cm3 or less, 1 particles 0.02 to 2.0 mm in diameter; and measured at 33 kPa water retention, and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Andic Durixerepts volcanic glass; and
1 b. [(Al plus /2 Fe, percent extracted by ammonium KEAC. Other Durixerepts that have, throughout one or more oxalate) times 60] plus the volcanic glass (percent) is horizons with a total thickness of 18 cm or more, above the equal to 30 or more. duripan and within 75 cm of the mineral soil surface, one or Vitrandic Calcixerepts both of the following: 1. More than 35 percent (by volume) fragments coarser KEBF. Other Calcixerepts that have, in one or more horizons than 2.0 mm, of which more than 66 percent is cinders, within 75 cm of the mineral soil surface, redox depletions with pumice, and pumicelike fragments; or chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). 2. A fine-earth fraction containing 30 percent or more Aquic Calcixerepts particles 0.02 to 2.0 mm in diameter; and a. In the 0.02 to 2.0 mm fraction, 5 percent or more KEBG. Other Calcixerepts. volcanic glass; and Typic Calcixerepts 1 b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is Durixerepts equal to 30 or more. Vitrandic Durixerepts Key to Subgroups I KEAA. Durixerepts that have both: KEAD. Other Durixerepts that have, in one or more horizons N above the duripan and within 30 cm of the mineral soil surface, 1. In one or more horizons above the duripan and C distinct or prominent redox concentrations and also aquic within 30 cm of the mineral soil surface, distinct or conditions for some time in normal years (or artificial prominent redox concentrations and also aquic conditions drainage). for 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 KEAE. Other Durixerepts that have a duripan that is strongly the 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 KEAF. 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 KEDA. 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 (1) In the 0.02 to 2.0 mm fraction, 5 percent or more surface; and volcanic glass; and 2. An umbric or mollic epipedon. 1 (2) [(Al plus /2 Fe, percent extracted by ammonium Humic Lithic Dystroxerepts 186 Keys to Soil Taxonomy
KEDB. 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
KEDC. Other Dystroxerepts that have both: KEDF. Other Dystroxerepts that have both: 1. In one or more horizons within 75 cm of the mineral 1. Fragic soil properties: soil surface, redox depletions with chroma of 2 or less and a. In 30 percent or more of the volume of a layer 15 cm also aquic conditions for some time in normal years (or or more thick that has its upper boundary within 100 cm artificial 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 a. A fine-earth fraction with both a bulk density of 1.0 soil surface, redox depletions with chroma of 2 or less and g/cm3 or less, measured at 33 kPa water retention, and Al 1 also aquic conditions in normal years (or artificial plus /2 Fe percentages (by ammonium oxalate) totaling drainage). more than 1.0; or Fragiaquic Dystroxerepts b. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, KEDG. Other Dystroxerepts that have a slope of less than 25 pumice, and pumicelike fragments; or percent; and c. A fine-earth fraction containing 30 percent or more 1. In one or more horizons within 75 cm of the mineral particles 0.02 to 2.0 mm in diameter; and soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or (1) In the 0.02 to 2.0 mm fraction, 5 percent or more artificial drainage); and volcanic glass; and
1 2. Either: (2) [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is a. At a depth of 125 cm below the mineral soil surface, equal to 30 or more. an organic-carbon content (Holocene age) of 0.2 percent Aquandic Dystroxerepts or more and no densic, lithic, or paralithic contact within that depth; or KEDD. Other Dystroxerepts that have, throughout one or b. An irregular decrease in organic-carbon content more horizons with a total thickness of 18 cm or more within (Holocene age) between a depth of 25 cm and either a 75 cm of the mineral soil surface, a fine-earth fraction with depth of 125 cm below the mineral soil surface or a both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa 1 densic, lithic, or paralithic contact, whichever is water retention, and Al plus /2 Fe percentages (by ammonium shallower. oxalate) totaling more than 1.0. Fluvaquentic Dystroxerepts Andic Dystroxerepts
KEDH. Other Dystroxerepts that have, in one or more KEDE. Other Dystroxerepts that have, throughout one or horizons within 75 cm of the mineral soil surface, redox more horizons with a total thickness of 18 cm or more within depletions with chroma of 2 or less and also aquic conditions 75 cm of the mineral soil surface, one or both of the following: for some time in normal years (or artificial drainage). 1. More than 35 percent (by volume) fragments coarser Aquic Dystroxerepts than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelik fragments; or KEDI. Other Dystroxerepts that in normal years are saturated 2. A fine-earth fraction containing 30 percent or more with water in one or more layers within 100 cm of the mineral particles 0.02 to 2.0 mm in diameter; and soil surface for either or both: a. In the 0.02 to 2.0 mm fraction, 5 percent or more 1. 20 or more consecutive days; or volcanic glass; and 2. 30 or more cumulative days. 1 b. [(Al plus /2 Fe, percent extracted by ammonium Oxyaquic Dystroxerepts Inceptisols 187
1 KEDJ. Other Dystroxerepts that have fragic soil properties: retention, and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. 1. In 30 percent or more of the volume of a layer 15 cm or Andic Fragixerepts more thick that has its upper boundary within 100 cm of the mineral soil surface; or KECB. Other Fragixerepts that have, throughout one or more 2. In 60 percent or more of the volume of a layer 15 cm or horizons with a total thickness of 18 cm or more within 75 cm more thick. of the mineral soil surface, one or both of the following: Fragic Dystroxerepts 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, KEDK. Other Dystroxerepts that have a slope of less than 25 pumice, and pumicelike fragments; or percent; and 2. A fine-earth fraction containing 30 percent or more 1. An umbric or mollic epipedon; and particles 0.02 to 2.0 mm in diameter; and 2. Either: a. In the 0.02 to 2.0 mm fraction, 5 percent or more a. At a depth of 125 cm below the mineral soil surface, volcanic glass; and
an organic-carbon content (Holocene age) of 0.2 percent 1 b. [(Al plus /2 Fe, percent extracted by ammonium or more and no densc, lithic, or paralithic contact within oxalate) times 60] plus the volcanic glass (percent) is that depth; or equal to 30 or more. b. An irregular decrease in organic-carbon content Vitrandic Fragixerepts (Holocene age) between a depth of 25 cm and either a depth of 125 cm below the mineral soil surface or a KECC. Other Fragixerepts that have, in one or more densic, lithic, or paralithic contact, whichever is horizons within 30 cm of the mineral soil surface, distinct or shallower. prominent redox concentrations and also aquic conditions for Fluventic Humic Dystroxerepts some time in normal years (or artificial drainage). Aquic Fragixerepts KEDL. Other Dystroxerepts that have a slope of less than 25 percent; and either KECD. Other Fragixerepts that have an umbric or mollic epipedon. 1. At a depth of 125 cm below the mineral soil surface, an Humic Fragixerepts organic-carbon content (Holocene age) of 0.2 percent or I more and no densic, lithic, or paralithic contact within that N KECE. Other Fragixerepts. depth; or C Typic Fragixerepts 2. An irregular decrease in organic-carbon content (Holocene age) between a depth of 25 cm and either a depth Haploxerepts of 125 cm below the mineral soil surface or a densic, lithic, or paralithic contact, whichever is shallower. Key to Subgroups Fluventic Dystroxerepts KEEA. Haploxerepts that have both: KEDM. Other Dystroxerepts that have an umbric or mollic 1. A lithic contact within 50 cm of the mineral soil epipedon. surface; and Humic Dystroxerepts 2. An umbric or mollic epipedon. Humic Lithic Haploxerepts KEDN. Other Dystroxerepts. Typic Dystroxerepts KEEB. Other Haploxerepts that have a lithic contact within 50 cm of the mineral soil surface. Fragixerepts Lithic Haploxerepts
Key to Subgroups KEEC. Other Haploxerepts that have one or both of the following: KECA. Fragixerepts that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm 1. Cracks within 125 cm of the mineral soil surface that of the mineral soil surface, a fine-earth fraction with both a are 5 mm or more wide through a thickness of 30 cm or bulk density of 1.0 g/cm3 or less, measured at 33 kPa water more for some time in normal years, and slickensides or 188 Keys to Soil Taxonomy
wedge-shaped aggregates in a layer 15 cm or more thick 2. A fine-earth fraction containing 30 percent or more that has its upper boundary within 125 cm of the mineral particles 0.02 to 2.0 mm in diameter; and soil surface; or a. In the 0.02 to 2.0 mm fraction, 5 percent or more 2. A linear extensibility of 6.0 cm or more between volcanic glass; and
the mineral soil surface and either a depth of 100 cm 1 b. [(Al plus /2 Fe, percent extracted by ammonium or a densic, lithic, or paralithic contact, whichever is oxalate) times 60] plus the volcanic glass (percent) is shallower. equal to 30 or more. Vertic Haploxerepts Vitrandic Haploxerepts KEED. Other Haploxerepts that have both: KEEG. Other Haploxerepts that have a gypsic horizon within 1. In one or more horizons within 75 cm of the mineral 100 cm of the mineral soil surface. soil surface, redox depletions with chroma of 2 or less and Gypsic Haploxerepts also aquic conditions for some time in normal years (or artificial drainage); and KEEH. Other Haploxerepts that have, in one or more horizons within 75 cm of the mineral soil surface, redox 2. Throughout one or more horizons with a total thickness depletions with chroma of 2 or less and also aquic conditions of 18 cm or more within 75 cm of the mineral soil surface, for some time in normal years (or artificial drainage). one or more of the following: Aquic Haploxerepts 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 KEEI. Other Haploxerepts that have lamellae (two or more) 1 plus /2 Fe percentages (by ammonium oxalate) totaling within 200 cm of the mineral soil surface. more than 1.0; or Lamellic Haploxerepts b. More than 35 percent (by volume) fragments coarser KEEJ. Other Haploxerepts that have fragic soil properties: than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or 1. In 30 percent or more of the volume of a layer 15 cm or more thick that has its upper boundary within 100 cm of the c. A fine-earth fraction containing 30 percent or more mineral soil surface; or particles 0.02 to 2.0 mm in diameter; and 2. In 60 percent or more of the volume of a layer 15 cm or (1) In the 0.02 to 2.0 mm fraction, 5 percent or more more thick. volcanic glass; and Fragic Haploxerepts 1 (2) [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is KEEK. Other Haploxerepts that have a slope of less than 25 equal to 30 or more. percent; and either Aquandic Haploxerepts 1. At a depth of 125 cm below the mineral soil surface, an organic-carbon content (Holocene age) of 0.2 percent or KEEE. Other Haploxerepts that have, throughout one or more and no densic, lithic, or paralithic contact within that more horizons with a total thickness of 18 cm or more within depth; or 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 2. An irregular decrease in organic-carbon content 1 water retention, and Al plus /2 Fe percentages (by ammonium (Holocene age) between a depth of 25 cm and either a depth oxalate) totaling more than 1.0. of 125 cm below the mineral soil surface or a densic, lithic, Andic Haploxerepts or paralithic contact, whichever is shallower. Fluventic Haploxerepts KEEF. Other Haploxerepts that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm KEEL. Other Haploxerepts that have a calcic horizon or of the mineral soil surface, one or both of the following: identifiable secondary carbonates within one of the following particle-size class and depth combinations: 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, 1. A sandy or sandy-skeletal particle-size class and pumice, and pumicelike fragments; or within 150 cm of the mineral soil surface; or Inceptisols 189
2. A clayey, clayey-skeletal, fine, or very-fine KEEM. Other Haploxerepts that have an umbric or mollic particle-size class and within 90 cm of the mineral soil epipedon. surface; or Humic Haploxerepts 3. Any other particle-size class and within 110 cm of the mineral soil surface. KEEN. Other Haploxerepts. Calcic Haploxerepts Typic Haploxerepts
I N C
191
CHAPTER 12 Mollisols
Key to Suborders IA. Mollisols that have: 1. An argillic or natric horizon; and 2. An albic horizon that has chroma of 2 or less and is 2.5 cm or more thick, has its lower boundary 18 cm or more below the mineral soil surface, and either lies directly below the mollic epipedon or separates horizons that together meet all of the requirements for a mollic epipedon; and 3. In one or more subhorizons of the albic horizon and/or of the argillic or natric horizon and within 100 cm of the mineral soil surface, redox concentrations in the form of (2) Either directly below the mollic epipedon or masses or concretions, or both, and also aquic conditions for within 75 cm of the mineral soil surface if a calcic some time in normal years (or artificial drainage). horizon intervenes, a color value, moist, of 4 or more Albolls, p. 192 and one of the following: IB. Other Mollisols that have, in a layer above a densic, (a) 50 percent or more chroma of 1 on faces of lithic, or paralithic contact or in a layer at a depth between 40 peds or in the matrix, hue of 10YR or redder, and and 50 cm from the mineral soil surface, whichever is redox concentrations; or shallower, aquic conditions for some time in normal years (or (b) 50 percent or more chroma of 2 or less on artificial drainage) and one or more of the following: faces of peds or in the matrix, hue of 2.5Y, and 1. A histic epipedon overlying the mollic epipedon; or redox concentrations; or M O 2. An exchangeable sodium percentage (ESP) of 15 or (c) 50 percent or more chroma of 1 on faces of L more (or a sodium adsorption ratio [SAR] of 13 or more) in peds or in the matrix and hue of 2.5Y or yellower; the upper part of the mollic epipedon and a decrease in ESP or (or SAR) values with increasing depth below 50 cm from (d) 50 percent or more chroma of 3 or less on the mineral soil surface; or faces of peds or in the matrix, hue of 5Y, and redox 3. A calcic or petrocalcic horizon that has its upper concentrations; or boundary within 40 cm of the mineral soil surface; or (e) 50 percent or more chroma of 0 on faces of 4. A mollic epipedon, with chroma of 1 or less, that peds or in the matrix; or extends to a lithic contact within 30 cm of the mineral soil (f) Hue of 5GY, 5G, 5BG, or 5B; or surface; or (g) Any color if it results from uncoated sand 5. One of the following colors: grains; or a. Chroma of 1 or less in the lower part of the mollic b. Chroma of 2 in the lower part of the mollic epipedon;1 and either epipedon; and either (1) Distinct or prominent redox concentrations in (1) Distinct or prominent redox concentrations in the lower part of the mollic epipedon; or the lower part of the mollic epipedon; or
1 If the mollic epipedon extends to a lithic contact within 30 cm of the mineral soil surface, (2) Directly below the mollic epipedon, one of the the requirement for redoximorphic features is waived. following matrix colors: 192 Keys to Soil Taxonomy
(a) A color value, moist, of 4, chroma of 2, and Argialbolls some redox depletions with a color value, moist, of 4 or more and chroma of 1 or less; or Key to Subgroups (b) A color value, moist, of 5 or more, chroma of IABA. Argialbolls that have both: 2 or less, and redox concentrations; or 1. One or both of the following: (c) A color value, moist, of 4 and chroma of 1 or a. Cracks within 125 cm of the mineral soil surface that less; or are 5 mm or more wide through a thickness of 30 cm or 6. At a depth between 40 and 50 cm from the mineral soil more for some time in normal years, and slickensides or surface, enough active ferrous iron to give a positive wedge-shaped aggregates in a layer 15 cm or more thick reaction to alpha,alpha-dipyridyl at a time when the soil is that has its upper boundary within 125 cm of the mineral not being irrigated. soil surface; or Aquolls, p. 193 b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a IC. Other Mollisols that: densic, lithic, or paralithic contact, whichever is 1. Have a mollic epipedon less than 50 cm thick; shallower; and and 2. If not irrigated, a moisture control section that in 2. Do not have an argillic or calcic horizon; and normal years is dry in all parts for 45 or more consecutive days during the 120 days following the summer solstice. 3. Have, either within or directly below the mollic Xerertic Argialbolls epipedon, mineral soil materials less than 7.5 cm in diameter that have a CaCO equivalent of 40 percent or 3 IABB. Other Argialbolls that have one or both of the more; and following: 4. Have either or both a udic moisture regime or a cryic 1. Cracks within 125 cm of the mineral soil surface that soil temperature regime. are 5 mm or more wide through a thickness of 30 cm or Rendolls, p. 200 more for some time in normal years, and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick ID. Other Mollisols that have a cryic soil temperature that has its upper boundary within 125 cm of the mineral regime. soil surface; or Cryolls, p. 197 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm IE. Other Mollisols that have either a xeric moisture regime or a densic, lithic, or paralithic contact, whichever is or an aridic moisture regime that borders on xeric. shallower. Xerolls, p. 222 Vertic Argialbolls IF. Other Mollisols that have either an ustic moisture regime IABC. Other Argialbolls that: or an aridic moisture regime that borders on ustic. Ustolls, p. 207 1. Do not have an abrupt textural change from the albic to the argillic horizon; and IG. Other Mollisols. 2. If not irrigated, have a moisture control section that in Udolls, p. 201 normal years is dry in all parts for 45 or more consecutive days during the 120 days following the summer solstice. Albolls Argiaquic Xeric Argialbolls Key to Great Groups IABD. Other Argialbolls that do not have an abrupt textural IAA. Albolls that have a natric horizon. change from the albic to the argillic horizon. Natralbolls, p. 193 Argiaquic Argialbolls
IAB. Other Albolls. IABE. Other Argialbolls that, if not irrigated, have a Argialbolls, p. 192 moisture control section that in normal years is dry in all parts Mollisols 193
for 45 or more consecutive days during the 120 days following IBD. Other Aquolls that have a calcic or gypsic horizon that the summer solstice. has its upper boundary within 40 cm of the mineral soil surface Xeric Argialbolls but do not have an argillic horizon unless it is a buried horizon. IABF. Other Argialbolls that have, throughout one or more Calciaquolls, p. 194 horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or more of the following: IBE. Other Aquolls that have an argillic horizon. Argiaquolls, p. 193 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 IBF. Other Aquolls that have episaturation. plus /2 Fe percentages (by ammonium oxalate) totaling Epiaquolls, p. 196 more than 1.0; or 2. More than 35 percent (by volume) fragments coarser IBG. Other Aquolls. than 2.0 mm, of which more than 66 percent is cinders, Endoaquolls, p. 195 pumice, and pumicelike fragments; or 3. A fine-earth fraction containing 30 percent or more Argiaquolls 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 IBEA. Argiaquolls that have a sandy or sandy-skeletal volcanic glass; and particle-size class throughout a layer extending from the 1 b. [(Al plus /2 Fe, percent extracted by ammonium mineral soil surface to the top of an argillic horizon at a depth oxalate) times 60] plus the volcanic glass (percent) is of 50 to 100 cm. equal to 30 or more. Arenic Argiaquolls Aquandic Argialbolls IBEB. Other Argiaquolls that have a sandy or sandy-skeletal IABG. Other Argialbolls. particle-size class throughout a layer extending from the Typic Argialbolls mineral soil surface to the top of an argillic horizon at a depth of 100 cm or more. Natralbolls Grossarenic Argiaquolls Key to Subgroups IBEC. Other Argiaquolls that have one or both of the IAAA. Natralbolls that have visible crystals of gypsum following: and/or more soluble salts within 40 cm of the mineral soil M 1. Cracks within 125 cm of the mineral soil surface that surface. O are 5 mm or more wide through a thickness of 30 cm or Leptic Natralbolls L more for some time in normal years, and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick IAAB. Other Natralbolls. that has its upper boundary within 125 cm of the mineral Typic Natralbolls soil surface; or Aquolls 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a Key to Great Groups densic, lithic, or paralithic contact, whichever is shallower. Vertic Argiaquolls IBA. Aquolls that have a cryic soil temperature regime. Cryaquolls, p. 194 IBED. Other Argiaquolls that have an argillic horizon that, with increasing depth, has a clay increase of 20 percent or IBB. Other Aquolls that have a duripan that has its upper more (absolute, in the fine-earth fraction) within its upper 7.5 boundary within 100 cm of the mineral soil surface. cm. Duraquolls, p. 194 Abruptic Argiaquolls
IBC. Other Aquolls that have a natric horizon. IBEE. Other Argiaquolls. Natraquolls, p. 197 Typic Argiaquolls 194 Keys to Soil Taxonomy
1 Calciaquolls plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0; or Key to Subgroups 2. More than 35 percent (by volume) fragments coarser IBDA. Calciaquolls that have a petrocalcic horizon that has than 2.0 mm, of which more than 66 percent is cinders, its upper boundary within 100 cm of the mineral soil surface. pumice, and pumicelike fragments; or Petrocalcic Calciaquolls 3. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and IBDB. Other Calciaquolls that have 50 percent or more chroma of 3 or more on faces of peds or in the matrix of one or a. In the 0.02 to 2.0 mm fraction, 5 percent or more more horizons within 75 cm of the mineral soil surface or that volcanic glass; and have the following colors directly below the mollic epipedon: 1 b. [(Al plus /2 Fe, percent extracted by ammonium 1. Hue of 2.5Y or yellower and chroma of 3 or more; or oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. 2. Hue of 10YR or redder and chroma of 2 or more; or Aquandic Cryaquolls 3. Hue of 2.5Y or yellower and chroma of 2 or more if there are no distinct or prominent redox concentrations. IBAE. Other Cryaquolls that have an argillic horizon. Aeric Calciaquolls Argic Cryaquolls
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 Key to Subgroups or more thick. IBAA. Cryaquolls that have one or both of the following: Cumulic Cryaquolls 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 has its upper boundary within 125 cm of the mineral Duraquolls soil surface; or Key to Subgroups 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm IBBA. Duraquolls that have a natric horizon. or a densic, lithic, or paralithic contact, whichever is Natric Duraquolls shallower. Vertic Cryaquolls IBBB. Other Duraquolls that have, above the duripan, one or both of the following: IBAB. Other Cryaquolls that have a histic epipedon. 1. Cracks that are 5 mm or more wide through a thickness Histic Cryaquolls of 30 cm or more for some time in normal years, and slickensides or wedge-shaped aggregates in a layer 15 cm or IBAC. Other Cryaquolls that have a buried layer of organic more thick; or soil materials, 20 cm or more thick, that has its upper boundary within 100 cm of the mineral soil surface. 2. A linear extensibility of 6.0 cm or more. Thapto-Histic Cryaquolls Vertic Duraquolls
IBAD. Other Cryaquolls that have, throughout one or more IBBC. Other Duraquolls that have an argillic horizon. horizons with a total thickness of 18 cm or more within 75 cm Argic Duraquolls of the mineral soil surface, one or more of the following: 1. A fine-earth fraction with both a bulk density of 1.0 IBBD. Other Duraquolls. g/cm3 or less, measured at 33 kPa water retention, and Al Typic Duraquolls Mollisols 195
Endoaquolls wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral Key to Subgroups soil surface; or IBGA. Endoaquolls that have a lithic contact within 50 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 Lithic Endoaquolls densic, lithic, or paralithic contact, whichever is shallower. Vertic Endoaquolls IBGB. Other Endoaquolls that have both: IBGE. Other Endoaquolls that have a histic epipedon. 1. One or both of the following: Histic Endoaquolls a. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or IBGF. Other Endoaquolls that have a buried layer of organic more for some time in normal years, and slickensides or soil materials, 20 cm or more thick, that has its upper boundary wedge-shaped aggregates in a layer 15 cm or more thick within 100 cm of the mineral soil surface. that has its upper boundary within 125 cm of the mineral Thapto-Histic Endoaquolls soil surface; or b. A linear extensibility of 6.0 cm or more between the IBGG. Other Endoaquolls that have, throughout one or more mineral soil surface and either a depth of 100 cm or a horizons with a total thickness of 18 cm or more within 75 cm densic, lithic, or paralithic contact, whichever is of the mineral soil surface, one or more of the following: shallower; and 1. A fine-earth fraction with both a bulk density of 1.0 2. A mollic epipedon 60 cm or more thick. g/cm3 or less, measured at 33 kPa water retention, and Al 1 Cumulic Vertic Endoaquolls plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0; or IBGC. Other Endoaquolls that have both of the following: 2. More than 35 percent (by volume) fragments coarser 1. One or both of the following: than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or a. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or 3. A fine-earth fraction containing 30 percent or more more for some time in normal years, and slickensides or particles 0.02 to 2.0 mm in diameter; and wedge-shaped aggregates in a layer 15 cm or more thick a. In the 0.02 to 2.0 mm fraction, 5 percent or more that has its upper boundary within 125 cm of the mineral volcanic glass; and soil surface; or M 1 b. [(Al plus /2 Fe, percent extracted by ammonium O b. A linear extensibility of 6.0 cm or more between the oxalate) times 60] plus the volcanic glass (percent) is L mineral soil surface and either a depth of 100 cm or a equal to 30 or more. densic, lithic, or paralithic contact, whichever is Aquandic Endoaquolls shallower; and 2. A slope of less than 25 percent; and either IBGH. Other Endoaquolls that have a horizon, 15 cm or more thick within 100 cm of the mineral soil surface, that a. An organic-carbon content of 0.3 percent or more in either has 20 percent or more (by volume) durinodes or is all horizons within 125 cm of the mineral soil surface; or brittle and has a firm rupture-resistance class when moist. b. An irregular decrease in organic-carbon content Duric Endoaquolls from a depth of 25 cm to a depth of 125 cm or to a densic, lithic, or paralithic contact if shallower. IBGI. Other Endoaquolls that have a mollic epipedon 60 cm Fluvaquentic Vertic Endoaquolls or more thick. Cumulic Endoaquolls IBGD. Other Endoaquolls that have one or both of the following: IBGJ. Other Endoaquolls that have a slope of less than 25 percent; and either 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or 1. An organic-carbon content of 0.3 percent or more in all more for some time in normal years, and slickensides or horizons within 125 cm of the mineral soil surface; or 196 Keys to Soil Taxonomy
2. An irregular decrease in organic-carbon content from a 1. Cracks within 125 cm of the mineral soil surface that depth of 25 cm to a depth of 125 cm or to a densic, lithic, or are 5 mm or more wide through a thickness of 30 cm or paralithic contact if shallower. more for some time in normal years, and slickensides or Fluvaquentic Endoaquolls wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral IBGK. Other Endoaquolls. soil surface; or Typic Endoaquolls 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a Epiaquolls densic, lithic, or paralithic contact, whichever is shallower. Vertic Epiaquolls Key to Subgroups IBFA. Epiaquolls that have both of the following: IBFD. Other Epiaquolls that have a histic epipedon. Histic Epiaquolls 1. One or both of the following: a. Cracks within 125 cm of the mineral soil surface that IBFE. Other Epiaquolls that have a buried layer of organic are 5 mm or more wide through a thickness of 30 cm or soil materials, 20 cm or more thick, that has its upper boundary more for some time in normal years, and slickensides or within 100 cm of the mineral soil surface. wedge-shaped aggregates in a layer 15 cm or more thick Thapto-Histic Epiaquolls that has its upper boundary within 125 cm of the mineral soil surface; or IBFF. Other Epiaquolls 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 mineral soil surface and either a depth of 100 cm or a of 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 Cumulic Vertic Epiaquolls more 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. An organic-carbon content of 0.3 percent or more in a 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 IBFH. Other Epiaquolls that have a mollic epipedon 60 cm or densic, 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 Mollisols 197
1. An organic-carbon content of 0.3 percent or more in all 2. In all parts above the calcic or petrocalcic horizon, after horizons within 125 cm of the mineral soil surface; or the materials between the soil surface and a depth of 18 cm have been mixed, either are calcareous or have a texture of 2. An irregular decrease in organic-carbon content from a loamy fine sand or coarser. depth of 25 cm to a depth of 125 cm or to a densic, lithic, or Calcicryolls, p. 198 paralithic contact if shallower. Fluvaquentic Epiaquolls IDF. Other Cryolls. Haplocryolls, p. 198 IBFJ. Other Epiaquolls. Typic Epiaquolls Argicryolls Natraquolls Key to Subgroups Key to Subgroups IDDA. Argicryolls that have a lithic contact within 50 cm of IBCA. Natraquolls that have one or both of the following: the mineral soil surface. Lithic Argicryolls 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or IDDB. Other Argicryolls that have one or both of the more for some time in normal years, and slickensides or following: wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral 1. Cracks within 125 cm of the mineral soil surface that soil surface; 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. A linear extensibility of 6.0 cm or more between the wedge-shaped aggregates in a layer 15 cm or more thick mineral soil surface and either a depth of 100 cm or a that has its upper boundary within 125 cm of the mineral densic, lithic, or paralithic contact, whichever is shallower. soil surface; or Vertic Natraquolls 2. A linear extensibility of 6.0 cm or more between the IBCB. Other Natraquolls. mineral soil surface and either a depth of 100 cm or a Typic Natraquolls densic, lithic, or paralithic contact, whichever is shallower. Vertic Argicryolls Cryolls IDDC. Other Argicryolls that have, throughout one or more Key to Great Groups horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction with both a M IDA. Cryolls that have a duripan that has its upper boundary bulk density of 1.0 g/cm3 or less, measured at 33 kPa water O within 100 cm of the mineral soil surface. 1 retention, and Al plus /2 Fe percentages (by ammonium L Duricryolls, p. 198 oxalate) totaling more than 1.0. Andic Argicryolls IDB. Other Cryolls that have a natric horizon. Natricryolls, p. 200 IDDD. Other Argicryolls that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm IDC. Other Cryolls that have both: of the soil surface, one or both of the following: 1. An argillic horizon that has its upper boundary 60 cm 1. More than 35 percent (by volume) fragments coarser or more below the mineral soil surface; and than 2.0 mm, of which more than 66 percent is cinders, 2. A texture finer than loamy fine sand in all horizons pumice, and pumicelike fragments; or above the argillic horizon. 2. A fine-earth fraction containing 30 percent or more Palecryolls, p. 200 particles 0.02 to 2.0 mm in diameter; and IDD. Other Cryolls that have an argillic horizon. a. In the 0.02 to 2.0 mm fraction, 5 percent or more Argicryolls, p. 197 volcanic glass; and
1 b. [(Al plus /2 Fe, percent extracted by ammonium IDE. Other Cryolls that: oxalate) times 60] plus the volcanic glass (percent) is 1. Have a calcic or petrocalcic horizon that has its upper equal to 30 or more. boundary within 100 cm of the mineral soil surface; and Vitrandic Argicryolls 198 Keys to Soil Taxonomy
IDDE. Other Argicryolls that have an argillic horizon that, has its upper boundary within 100 cm of the mineral soil with increasing depth, has a clay increase of 20 percent or surface. more (absolute, in the fine-earth fraction) within its upper Petrocalcic Calcicryolls 7.5 cm. Abruptic Argicryolls IDEC. Other Calcicryolls that have a mollic epipedon that is 40 cm or more thick and has a texture finer than loamy fine IDDF. Other Argicryolls that have, in one or more horizons sand. within 100 cm of the mineral soil surface, redox depletions Pachic Calcicryolls with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). IDED. Other Calcicryolls that have an ustic moisture regime. Aquic Argicryolls Ustic Calcicryolls
IDDG. Other Argicryolls that in normal years are saturated IDEE. Other Calcicryolls that have a xeric moisture regime. with water in one or more layers within 100 cm of the mineral Xeric Calcicryolls soil surface for either or both: IDEF. Other Calcicryolls. 1. 20 or more consecutive days; or Typic Calcicryolls 2. 30 or more cumulative days. Oxyaquic Argicryolls Duricryolls
IDDH. Other Argicryolls that have a mollic epipedon that is Key to Subgroups 40 cm or more thick and has a texture finer than loamy fine IDAA. Duricryolls that have an argillic horizon. sand. Argic Duricryolls Pachic Argicryolls IDAB. Other Duricryolls. IDDI. Other Argicryolls that have either: Typic Duricryolls 1. Above the argillic horizon, an albic horizon or a horizon that has color values too high for a mollic epipedon Haplocryolls and chroma too high for an albic horizon; or Key to Subgroups 2. A glossic horizon, or interfingering of albic materials into the upper part of the argillic horizon, or skeletans of IDFA. Haplocryolls that have a lithic contact within 50 cm of clean silt and sand covering 50 percent or more of the faces the mineral soil surface. of peds in the upper 5 cm of the argillic horizon. Lithic Haplocryolls Alfic Argicryolls IDFB. Other Haplocryolls that have one or both of the IDDJ. Other Argicryolls that have an ustic moisture regime. following: Ustic Argicryolls 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or IDDK. Other Argicryolls that have a xeric moisture regime. more for some time in normal years, and slickensides or Xeric Argicryolls wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral IDDL. Other Argicryolls. soil surface; or Typic Argicryolls 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm Calcicryolls or a densic, lithic, or paralithic contact, whichever is shallower. Key to Subgroups Vertic Haplocryolls IDEA. Calcicryolls that have a lithic contact within 50 cm of the mineral soil surface. IDFC. Other Haplocryolls that have, throughout one or more Lithic Calcicryolls 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 IDEB. Other Calcicryolls that have a petrocalcic horizon that bulk density of 1.0 g/cm3 or less, measured at 33 kPa water Mollisols 199
1 retention, and Al plus /2 Fe percentages (by ammonium b. An irregular decrease in organic-carbon content oxalate) totaling more than 1.0. from a depth of 25 cm to a depth of 125 cm or to a Andic Haplocryolls densic, lithic, or paralithic contact if shallower; and 2. In one or more horizons within 100 cm of the mineral IDFD. 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 also aquic conditions for some time in normal years (or of the mineral soil surface, one or both of the following: artificial drainage). 1. More than 35 percent (by volume) fragments coarser Fluvaquentic Haplocryolls than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or IDFH. Other Haplocryolls that have, in one or more horizons within 100 cm of the mineral soil surface, distinct or 2. A fine-earth fraction containing 30 percent or more prominent redox concentrations and also aquic conditions for particles 0.02 to 2.0 mm in diameter; and some time in normal years (or artificial drainage). a. In the 0.02 to 2.0 mm fraction, 5 percent or more Aquic Haplocryolls volcanic glass; and IDFI. Other Haplocryolls that in normal years are saturated 1 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. 1. 20 or more consecutive days; or Vitrandic Haplocryolls 2. 30 or more cumulative days. IDFE. Other Haplocryolls that have: Oxyaquic Haplocryolls 1. A mollic epipedon that is 40 cm or more thick and has IDFJ. Other Haplocryolls that have both: a texture finer than loamy fine sand; and 1. A mollic epipedon that is 40 cm or more thick and has 2. An irregular decrease in organic-carbon content from a a texture finer than loamy fine sand; and depth of 25 cm below the mineral soil surface to a depth of 125 cm or to a densic, lithic, or paralithic contact if 2. A calcic horizon either within or directly below the shallower; and mollic epipedon, but no argillic horizon in the lower part of the mollic epipedon. 3. A slope of less than 25 percent; and Calcic Pachic Haplocryolls 4. In one or more horizons within 100 cm of the mineral soil surface, distinct or prominent redox concentrations and IDFK. Other Haplocryolls that have a mollic epipedon that is M also aquic conditions for some time in normal years (or 40 cm or more thick and has a texture finer than loamy fine O artificial drainage). sand. L Aquic Cumulic Haplocryolls Pachic Haplocryolls IDFF. Other Haplocryolls that have: IDFL. Other Haplocryolls that have a slope of less than 25 1. A mollic epipedon that is 40 cm or more thick and has percent; and either a texture finer than loamy fine sand; and 1. An organic-carbon content of 0.3 percent or more at a 2. An irregular decrease in organic-carbon content from a depth of 125 cm below the mineral soil surface; or depth of 25 cm below the mineral soil surface to a depth of 2. An irregular decrease in organic-carbon content from a 125 cm or to a densic, lithic, or paralithic contact if depth of 25 cm to a depth of 125 cm or to a densic, lithic, or shallower; and paralithic contact if shallower. 3. A slope of less than 25 percent. Fluventic Haplocryolls Cumulic Haplocryolls IDFM. Other Haplocryolls that have a calcic horizon within IDFG. Other Haplocryolls that have both: 100 cm of the mineral soil surface. Calcic Haplocryolls 1. A slope of less than 25 percent; and either a. An organic-carbon content of 0.3 percent or more IDFN. Other Haplocryolls that have an ustic moisture at a depth of 125 cm below the mineral soil surface; regime. or Ustic Haplocryolls 200 Keys to Soil Taxonomy
IDFO. Other Haplocryolls that have a xeric moisture Rendolls regime. Xeric Haplocryolls Key to Great Groups
IDFP. Other Haplocryolls. ICA. Rendolls that have a cryic soil temperature regime. Typic Haplocryolls Cryrendolls, p. 200
Natricryolls ICB. Other Rendolls. Haprendolls, p. 200 Key to Subgroups IDBA. All Natricryolls. Cryrendolls Typic Natricryolls Key to Subgroups Palecryolls ICAA. Cryrendolls that have a lithic contact within 50 cm of the mineral soil surface. Key to Subgroups Lithic Cryrendolls IDCA. Palecryolls that have, in one or more horizons within ICAB. Other Cryrendolls. 100 cm of the mineral soil surface, redox depletions with Typic Cryrendolls chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). Aquic Palecryolls Haprendolls Key to Subgroups IDCB. Other Palecryolls that in normal years are saturated with water in one or more layers within 100 cm of the mineral ICBA. Haprendolls that have a lithic contact within 50 cm of soil surface for either or both: the mineral soil surface. Lithic Haprendolls 1. 20 or more consecutive days; or 2. 30 or more cumulative days. ICBB. Other Haprendolls that have one or both of the Oxyaquic Palecryolls following: 1. Cracks within 125 cm of the mineral soil surface that IDCC. Other Palecryolls that have an argillic horizon that, are 5 mm or more wide through a thickness of 30 cm or with increasing depth, has a clay increase of 20 percent or more for some time in normal years, and slickensides or more (absolute, in the fine-earth fraction) within its upper wedge-shaped aggregates in a layer 15 cm or more thick 7.5 cm. that has its upper boundary within 125 cm of the mineral Abruptic Palecryolls soil surface; or IDCD. Other Palecryolls that have a mollic epipedon that is 2. A linear extensibility of 6.0 cm or more between the 40 cm or more thick and has a texture finer than loamy fine mineral soil surface and either a depth of 100 cm or a sand. densic, lithic, or paralithic contact, whichever is shallower. Pachic Palecryolls Vertic Haprendolls
IDCE. Other Palecryolls that have an ustic moisture ICBC. Other Haprendolls that have a cambic horizon. regime. Inceptic Haprendolls Ustic Palecryolls ICBD. Other Haprendolls that have a color value, dry, of 6 or IDCF. Other Palecryolls that have a xeric moisture more either in the upper 18 cm of the mollic epipedon, after regime. mixing, or in an Ap horizon 18 cm or more thick. Xeric Palecryolls Entic Haprendolls
IDCG. Other Palecryolls. ICBE. Other Haprendolls. Typic Palecryolls Typic Haprendolls Mollisols 201
Udolls IGD. Other Udolls that have an argillic horizon. Argiudolls, p. 201 Key to Great Groups IGE. Other Udolls that have a mollic epipedon that: IGA. Udolls that have a natric horizon. 1. Either below an Ap horizon or below a depth of 18 cm Natrudolls, p. 206 from the mineral soil surface, contains 50 percent or more (by volume) wormholes, wormcasts, or filled animal IGB. Other Udolls that: burrows; and 1. Have a calcic or petrocalcic horizon that has its 2. Either rests on a lithic contact or has a transition zone upper boundary within 100 cm of the mineral soil surface; to the underlying horizon in which 25 percent or more of and the soil volume consists of discrete wormholes, wormcasts, 2. Do not have an argillic horizon above the calcic or or animal burrows filled with material from the mollic petrocalcic horizon; and epipedon and from the underlying horizon. Vermudolls, p. 207 3. In all parts above the calcic or petrocalcic horizon, after the materials between the soil surface and a depth of 18 cm IGF. Other Udolls. have been mixed, either are calcareous or have a texture of Hapludolls, p. 204 loamy fine sand or coarser. Calciudolls, p. 203 Argiudolls IGC. Other Udolls that have one or more of the following: Key to Subgroups 1. A petrocalcic horizon that has its upper boundary IGDA. Argiudolls that have a lithic contact within 50 cm of within 150 cm of the mineral soil surface; or the mineral soil surface. 2. All of the following: Lithic Argiudolls a. No densic, lithic, or paralithic contact within 150 cm IGDB. Other Argiudolls that have both: of the mineral soil surface; and 1. Aquic conditions for some time in normal years (or b. Within 150 cm of the mineral soil surface, a clay artificial drainage) either: decrease, with increasing depth, of less than 20 percent (relative) from the maximum clay content (noncarbonate a. Within 40 cm of the mineral soil surface, in horizons clay); and that also have redoximorphic features; or M c. An argillic horizon with one or more of the b. Directly below the mollic epipedon, in one or more O following: horizons with a total thickness of 15 cm or more that L have one or more of the following: (1) In 50 percent or more of the matrix of one or more subhorizons in its lower half, hue of 7.5YR or (1) A color value, moist, of 4 or more and redox redder and chroma of 5 or more; or depletions with chroma of 2 or less; or (2) In 50 percent or more of the matrix of horizons (2) Hue of 10YR or redder and chroma of 2 or less; that total more than one-half the total thickness, hue or of 2.5YR or redder, a value, moist, of 3 or less, and a (3) Hue of 2.5Y or yellower and chroma of 3 or less; value, dry, of 4 or less; or and (3) Many redox concentrations with hue of 5YR or 2. One or both of the following: redder or chroma of 6 or more, or both, in one or more subhorizons; or a. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or 3. A frigid temperature regime; and both more for some time in normal years, and slickensides or a. An argillic horizon that has its upper boundary 60 wedge-shaped aggregates in a layer 15 cm or more thick cm or more below the mineral soil surface; and that has its upper boundary within 125 cm of the mineral soil surface; or b. A texture finer than loamy fine sand in all horizons above the argillic horizon. b. A linear extensibility of 6.0 cm or more between the Paleudolls, p. 207 mineral soil surface and either a depth of 100 cm or a 202 Keys to Soil Taxonomy
densic, lithic, or paralithic contact, whichever is clean silt and sand covering 50 percent or more of the faces shallower. of peds in the upper 5 cm of the argillic horizon; and Aquertic Argiudolls 3. Either: IGDC. Other Argiudolls that have both: 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. One or both of the following: more for some time in normal years, and slickensides or a. Cracks within 125 cm of the mineral soil surface that wedge-shaped aggregates in a layer 15 cm or more thick are 5 mm or more wide through a thickness of 30 cm or that has its upper boundary within 125 cm of the mineral more for some time in normal years, and slickensides or soil surface; or wedge-shaped aggregates in a layer 15 cm or more thick b. A linear extensibility of 6.0 cm or more between the that has its upper boundary within 125 cm of the mineral mineral soil surface and either a depth of 100 cm or a soil surface; or densic, lithic, or paralithic contact, whichever is b. A linear extensibility of 6.0 cm or more between the shallower. mineral soil surface and either a depth of 100 cm or a Alfic Vertic Argiudolls densic, lithic, or paralithic contact, whichever is shallower; and IGDF. Other Argiudolls that have one or both of the following: 2. In normal years saturation with water in one or more layers within 100 cm of the mineral soil surface for either or 1. Cracks within 125 cm of the mineral soil surface that both: are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or a. 20 or more consecutive days; or wedge-shaped aggregates in a layer 15 cm or more thick b. 30 or more cumulative days. that has its upper boundary within 125 cm of the mineral Oxyaquic Vertic Argiudolls soil surface; or 2. A linear extensibility of 6.0 cm or more between the IGDD. Other Argiudolls that have: mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. 1. A texture finer than loamy fine sand and either: Vertic Argiudolls a. A frigid temperature regime and a mollic epipedon 40 cm or more thick; or IGDG. Other Argiudolls that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm b. A mollic epipedon 50 cm or more thick; and of the mineral soil surface, a fine-earth fraction with both a 2. One or both 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 a. Cracks within 125 cm of the mineral soil surface that oxalate) totaling more than 1.0. are 5 mm or more wide through a thickness of 30 cm or Andic Argiudolls more for some time in normal years, and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick IGDH. Other Argiudolls that have, throughout one or more that has its upper boundary within 125 cm of the mineral horizons with a total thickness of 18 cm or more within 75 cm soil surface; or of the mineral soil surface, one or both of the following: b. A linear extensibility of 6.0 cm or more between the 1. More than 35 percent (by volume) fragments coarser mineral soil surface and either a depth of 100 cm or a than 2.0 mm, of which more than 66 percent is cinders, densic, lithic, or paralithic contact, whichever is pumice, and pumicelike fragments; or shallower. Pachic Vertic Argiudolls 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and IGDE. Other Argiudolls that have: a. In the 0.02 to 2.0 mm fraction, 5 percent or more 1. Above the argillic horizon, an albic horizon or a volcanic glass; and
horizon that has color values too high for a mollic epipedon 1 b. [(Al plus /2 Fe, percent extracted by ammonium and chroma too high for an albic horizon; or oxalate) times 60] plus the volcanic glass (percent) is 2. A glossic horizon, or interfingering of albic materials equal to 30 or more. into the upper part of the argillic horizon, or skeletans of Vitrandic Argiudolls Mollisols 203
IGDI. Other Argiudolls that have aquic conditions for some throughout the entire argillic horizon if it is less than 75 cm time in normal years (or artificial drainage) either: thick. Psammentic Argiudolls 1. Within 40 cm of the mineral soil surface, in horizons that also have redoximorphic features; or IGDN. Other Argiudolls that have a sandy or sandy-skeletal 2. Directly below the mollic epipedon, in one or more particle-size class throughout a layer extending from the horizons with a total thickness of 15 cm or more that have mineral soil surface to the top of an argillic horizon at a depth one or more of the following: of 50 cm or more. Arenic Argiudolls a. A color value, moist, of 4 or more and redox depletions with chroma of 2 or less; or IGDO. Other Argiudolls that have an argillic horizon that, b. Hue of 10YR or redder and chroma of 2 or less; or with increasing depth, has a clay increase of 20 percent or more (absolute, in the fine-earth fraction) within its upper c. Hue of 2.5Y or yellower and chroma of 3 or less. 7.5 cm. Aquic Argiudolls Abruptic Argiudolls IGDJ. Other Argiudolls that have a texture finer than loamy IGDP. Other Argiudolls that have: fine sand and either: 1. Above the argillic horizon, an albic horizon or a 1. A frigid temperature regime and a mollic epipedon 40 horizon that has color values too high for a mollic epipedon cm or more thick; or and chroma too high for an albic horizon; or 2. A mollic epipedon 50 cm or more thick. 2. A glossic horizon, or interfingering of albic materials Pachic Argiudolls into the upper part of the argillic horizon, or skeletans of clean silt and sand covering 50 percent or more of the faces IGDK. Other Argiudolls that in normal years are saturated of peds in the upper 5 cm of the argillic horizon. with water in one or more layers within 100 cm of the mineral Alfic Argiudolls soil surface for either or both: 1. 20 or more consecutive days; or IGDQ. Other Argiudolls that have an apparent CEC of less than 24 cmol(+)/kg clay (by 1N NH OAc pH 7) in 50 percent 2. 30 or more cumulative days. 4 or more either of the argillic horizon if less than 100 cm thick Oxyaquic Argiudolls or of its upper 100 cm. Oxic Argiudolls IGDL. Other Argiudolls that have an argillic horizon that: M 1. Consists entirely of lamellae; or IGDR. Other Argiudolls that have a calcic horizon within O 100 cm of the mineral soil surface. 2. Is a combination of two or more lamellae and one or L Calcic Argiudolls more subhorizons with a thickness of 7.5 to 20 cm, each layer with an overlying eluvial horizon; or IGDS. Other Argiudolls. 3. Consists of one or more subhorizons that are more Typic Argiudolls 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 Key to Subgroups 5 cm or more (that may or may not be part of the argillic horizon); or IGBA. Calciudolls that have a lithic contact within 50 cm of 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 IGBB. Other Calciudolls that have one or both of the overlying eluvial horizon. following: Lamellic Argiudolls 1. Cracks within 125 cm of the mineral soil surface that IGDM. Other Argiudolls that have a sandy particle-size class are 5 mm or more wide through a thickness of 30 cm or throughout the upper 75 cm of the argillic horizon or more for some time in normal years, and slickensides or 204 Keys to Soil Taxonomy
wedge-shaped aggregates in a layer 15 cm or more thick a. Cracks within 125 cm of the mineral soil surface that that has its upper boundary within 125 cm of the mineral are 5 mm or more wide through a thickness of 30 cm or soil surface; or more for some time in normal years, and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick 2. A linear extensibility of 6.0 cm or more between the that has its upper boundary within 125 cm of the mineral mineral soil surface and either a depth of 100 cm or a soil surface; or densic, lithic, or paralithic contact, whichever is shallower. Vertic Calciudolls b. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a IGBC. Other Calciudolls that have, in one or more horizons densic, lithic, or paralithic contact, whichever is within 100 cm of the mineral soil surface, redox depletions shallower. with chroma of 2 or less and also aquic conditions for some Aquertic Hapludolls time in normal years (or artificial drainage). Aquic Calciudolls IGFC. Other Hapludolls that have one or both of the following: IGBD. Other Calciudolls that have a slope of less than 25 1. Cracks within 125 cm of the mineral soil surface that percent; and either: are 5 mm or more wide through a thickness of 30 cm or 1. An organic-carbon content of 0.3 percent or more at a more for some time in normal years, and slickensides or depth of 125 cm below the mineral soil surface; or wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral 2. An irregular decrease in organic-carbon content from a soil surface; or depth of 25 cm to a depth of 125 cm or to a lithic or paralithic contact if shallower. 2. A linear extensibility of 6.0 cm or more between the Fluventic Calciudolls mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. IGBE. Other Calciudolls. Vertic Hapludolls Typic Calciudolls IGFD. Other Hapludolls that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm Hapludolls 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 Key to Subgroups 1 retention, and aluminum plus /2 iron percentages (by IGFA. Hapludolls that have a lithic contact within 50 cm of ammonium oxalate) totaling more than 1.0. the mineral soil surface. Andic Hapludolls Lithic Hapludolls IGFE. Other Hapludolls that have, throughout one or more IGFB. Other Hapludolls that have both: horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: 1. Aquic conditions for some time in normal years (or artificial drainage) either: 1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, a. Within 40 cm of the mineral soil surface, in horizons pumice, and pumicelike fragments; or that also have redoximorphic features; or 2. A fine-earth fraction containing 30 percent or more b. Directly below the mollic epipedon, in one or more particles 0.02 to 2.0 mm in diameter; and horizons with a total thickness of 15 cm or more that have one or more of the following: a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and (1) A color value, moist, of 4 or more and redox 1 depletions with chroma of 2 or less; or b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is (2) Hue of 10YR or redder and chroma of 2 or less; equal to 30 or more. or Vitrandic Hapludolls (3) Hue of 2.5Y or yellower and chroma of 3 or less; and IGFF. Other Hapludolls that have: 2. One or both of the following: 1. Either: Mollisols 205
a. A frigid soil temperature regime and a mollic (1) A color value, moist, of 4 or more and redox epipedon 40 cm or more thick, of which less than 50 depletions with chroma of 2 or less; or percent has a sandy or sandy-skeletal particle-size class, (2) Hue of 10YR or redder and chroma of 2 or less; and there is no densic or paralithic contact and no sandy or or sandy-skeletal particle-size class at a depth between 40 and 50 cm from the mineral soil surface; or (3) Hue of 2.5Y or yellower and chroma of 3 or less; and b. A mollic epipedon 60 cm or more thick, of which 50 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 2. Either 0.3 percent or more organic carbon at a depth a 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 decrease in organic-carbon content from a depth of 25 cm to from a depth of 25 cm to a depth of 125 cm or to a a depth of 125 cm or to a densic, lithic, or paralithic contact densic, lithic, or paralithic contact if shallower. if shallower; and Fluvaquentic Hapludolls 3. A slope of 25 percent or less; and IGFI. Other Hapludolls that have aquic conditions for some 4. In one or more horizons within 100 cm of the mineral time in normal years (or artificial drainage) either: soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or 1. Within 40 cm of the mineral soil surface, in horizons artificial drainage). that also have redoximorphic features; or Aquic Cumulic Hapludolls 2. Directly below the mollic epipedon, in one or more horizons with a total thickness of 15 cm or more that have IGFG. Other Hapludolls that have: one or more of the following: 1. Either: a. A color value, moist, of 4 or more and redox a. A frigid soil temperature regime and a mollic depletions with chroma of 2 or less; or epipedon 40 cm or more thick, of which less than 50 b. Hue of 10YR or redder and chroma of 2 or less; or percent has a sandy or sandy-skeletal particle-size class, and there is no densic or paralithic contact and no sandy c. Hue of 2.5Y or yellower and chroma of 3 or less. or sandy-skeletal particle-size class at a depth between 40 Aquic Hapludolls and 50 cm from the mineral soil surface; or b. A mollic epipedon 60 cm or more thick, of which 50 IGFJ. Other Hapludolls that have a texture finer than loamy M percent or more of the thickness has a texture finer than fine sand and either: O loamy fine sand; and L 1. A frigid temperature regime and a mollic epipedon 40 2. Either 0.3 percent or more organic carbon at a depth cm or more thick; or of 125 cm below the mineral soil surface or an irregular 2. A mollic epipedon 50 cm or more thick. decrease in organic-carbon content from a depth of 25 cm to Pachic Hapludolls a depth of 125 cm or to a densic, lithic, or paralithic contact if shallower; and IGFK. Other Hapludolls that in normal years are saturated 3. A slope of 25 percent or less. with water in one or more layers within 100 cm of the mineral Cumulic Hapludolls soil surface for either or both: 1. 20 or more consecutive days; or IGFH. Other Hapludolls that have both: 2. 30 or more cumulative days. 1. Aquic conditions for some time in normal years (or Oxyaquic Hapludolls artificial drainage) either: IGFL. Other Hapludolls that have a slope of less than 25 a. Within 40 cm of the mineral soil surface, in horizons percent; and either that also have redoximorphic features; or 1. An organic-carbon content of 0.3 percent or more at a b. Directly below the mollic epipedon, in one or more depth of 125 cm below the mineral soil surface; or horizons with a total thickness of 15 cm or more that have one or more of the following: 2. An irregular decrease in organic-carbon content from a 206 Keys to Soil Taxonomy
depth of 25 cm to a depth of 125 cm or to a densic, lithic, or b. A linear extensibility of 6.0 cm or more between the paralithic contact if shallower. mineral soil surface and either a depth of 100 cm or a Fluventic Hapludolls densic, lithic, or paralithic contact, whichever is shallower. IGFM. Other Hapludolls that have both: Leptic Vertic Natrudolls 1. A mollic epipedon 60 cm or more thick that has a IGAC. Other Natrudolls that have: texture finer than loamy fine sand and contains 50 percent or more (by volume) wormholes, wormcasts, or filled 1. A glossic horizon or interfingering of albic materials animal burrows either below an Ap horizon or below a into the natric horizon; and depth of 18 cm from the mineral soil surface; and 2. One or both of the following: 2. Either do not have a cambic horizon and do not, in the a. Cracks within 125 cm of the mineral soil surface that lower part of the mollic epipedon, meet all of the are 5 mm or more wide through a thickness of 30 cm or requirements for a cambic horizon, except for the color more for some time in normal years, and slickensides or requirements, or have carbonates throughout either the wedge-shaped aggregates in a layer 15 cm or more thick cambic horizon or the lower part of the mollic epipedon. that has its upper boundary within 125 cm of the mineral Vermic Hapludolls soil surface; or IGFN. Other Hapludolls that have a calcic horizon within b. A linear extensibility of 6.0 cm or more between the 100 cm of the mineral soil surface. mineral soil surface and either a depth of 100 cm or a Calcic Hapludolls densic, lithic, or paralithic contact, whichever is shallower. IGFO. Other Hapludolls that either: Glossic Vertic Natrudolls 1. Do not have a cambic horizon and do not, in any part of IGAD. Other Natrudolls that have one or both of the the mollic epipedon below 25 cm from the mineral soil following: surface, meet all of the requirements for a cambic horizon, except for the color requirements; or 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or 2. Have free carbonates throughout the cambic horizon or more for some time in normal years, and slickensides or in all parts of the mollic epipedon below a depth of 25 cm wedge-shaped aggregates in a layer 15 cm or more thick from the mineral soil surface. that has its upper boundary within 125 cm of the mineral Entic Hapludolls soil surface; or IGFP. 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 or a densic, lithic, or paralithic contact, whichever is Natrudolls shallower. Vertic Natrudolls Key to Subgroups IGAA. Natrudolls that have a petrocalcic horizon that has its IGAE. Other Natrudolls that have visible crystals of gypsum upper boundary within 100 cm of the mineral soil surface. and/or more soluble salts within 40 cm of the mineral soil Petrocalcic Natrudolls surface. Leptic Natrudolls IGAB. Other Natrudolls that have both: IGAF. Other Natrudolls that have a glossic horizon or 1. Visible crystals of gypsum and/or more soluble salts interfingering of albic materials into the natric horizon. within 40 cm of the mineral soil surface; and Glossic Natrudolls 2. One or both of the following: a. Cracks within 125 cm of the mineral soil surface that IGAG. Other Natrudolls that have a calcic horizon within are 5 mm or more wide through a thickness of 30 cm or 100 cm of the mineral soil surface. more for some time in normal years, and slickensides or Calcic Natrudolls wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral IGAH. Other Natrudolls. soil surface; or Typic Natrudolls Mollisols 207
Paleudolls Vermudolls
Key to Subgroups Key to Subgroups IGCA. Paleudolls that have one or both of the following: IGEA. Vermudolls that have a lithic contact within 50 cm of the mineral soil surface. 1. Cracks within 125 cm of the mineral soil surface that Lithic Vermudolls are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or IGEB. Other Vermudolls that have a mollic epipedon less wedge-shaped aggregates in a layer 15 cm or more thick than 75 cm thick. that has its upper boundary within 125 cm of the mineral Haplic Vermudolls soil surface; or 2. A linear extensibility of 6.0 cm or more between the IGEC. Other Vermudolls. mineral soil surface and either a depth of 100 cm or a Typic Vermudolls densic, lithic, or paralithic contact, whichever is shallower. Vertic Paleudolls Ustolls IGCB. Other Paleudolls that have a petrocalcic horizon Key to Great Groups within 150 cm of the mineral soil surface. Petrocalcic Paleudolls IFA. Ustolls that have a duripan that has its upper boundary within 100 cm of the mineral soil surface. IGCC. Other Paleudolls that have, in one or more Durustolls, p. 212 subhorizons within the upper 50 cm of the argillic horizon, redox depletions with chroma of 2 or less and also aquic IFB. Other Ustolls that have a natric horizon. conditions for some time in normal years (or artificial Natrustolls, p. 217 drainage). Aquic Paleudolls IFC. Other Ustolls that: 1. Have either a calcic or gypsic horizon that has its upper IGCD. Other Paleudolls that have a texture finer than loamy boundary within 100 cm of the mineral soil surface or a fine sand and a mollic epipedon 50 cm or more thick. petrocalcic horizon that has its upper boundary within 150 Pachic Paleudolls cm of the mineral soil surface; and IGCE. Other Paleudolls that in normal years are saturated 2. Do not have an argillic horizon above the calcic, gypsic, with water in one or more layers within 100 cm of the mineral or petrocalcic horizon; and M soil surface for either or both: O 3. In all parts above the calcic, gypsic, or petrocalcic L 1. 20 or more consecutive days; or horizon, after the materials between the soil surface and a depth of 18 cm have been mixed, either are calcareous or 2. 30 or more cumulative days. have a texture of loamy fine sand or coarser. Oxyaquic Paleudolls Calciustolls, p. 211 IGCF. Other Paleudolls that: IFD. Other Ustolls that have either: 1. Have a calcic horizon that has its upper boundary 1. A petrocalcic horizon that has its upper boundary within 100 cm of the mineral soil surface; and within 150 cm of the mineral soil surface; or 2. In all parts above the calcic horizon, after the materials 2. An argillic horizon that has one or both of the between the soil surface and a depth of 18 cm have been following: mixed, either are calcareous or have a texture of loamy fine sand or coarser. a. With increasing depth, no clay decrease of 20 Calcic Paleudolls percent or more (relative) from the maximum clay content (noncarbonate clay) within 150 cm of the mineral IGCG. Other Paleudolls. soil surface (and there is no densic, lithic, or paralithic Typic Paleudolls contact within that depth); and either 208 Keys to Soil Taxonomy
(1) Hue of 7.5YR or redder and chroma of 5 or more some or all parts for six-tenths or more of the cumulative in the matrix; or days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or (2) Common redox concentrations with hue of 7.5YR or redder or chroma of 6 or more, or c. A hyperthermic, isomesic, or warmer iso soil both; or temperature regime and a moisture control section that in normal years: b. 35 percent or more clay in its upper part and a clay increase either of 20 percent or more (absolute) within a (1) Is moist in some or all parts for fewer than 90 vertical distance of 7.5 cm or of 15 percent or more consecutive days per year when the soil temperature at (absolute) within a vertical distance of 2.5 cm, in the a depth of 50 cm below the soil surface is higher than fine-earth fraction (and there is no densic, lithic, or 8 oC; and paralithic contact within 50 cm of the mineral soil (2) Is dry in some or all parts for six-tenths or more surface). of the cumulative days per year when the soil Paleustolls, p. 220 temperature at a depth of 50 cm below the soil surface is higher than 5 oC. IFE. Other Ustolls that have an argillic horizon. Aridic Lithic Argiustolls Argiustolls, p. 208 IFEB. Other Argiustolls that have both: IFF. Other Ustolls that have a mollic epipedon that: 1. A lithic contact within 50 cm of the mineral soil 1. Either below an Ap horizon or below a depth of 18 cm surface; and from the mineral soil surface, contains 50 percent or more (by volume) wormholes, wormcasts, or filled animal 2. Above the argillic horizon, either an albic horizon or a burrows; and horizon that has color values too high for a mollic epipedon and chroma too high for an albic horizon. 2. Either rests on a lithic contact or has a transition zone Alfic Lithic Argiustolls to the underlying horizon in which 25 percent or more of the soil volume consists of discrete wormholes, wormcasts, IFEC. Other Argiustolls that have a lithic contact within 50 or animal burrows filled with material from the mollic cm of the mineral soil surface. epipedon and from the underlying horizon. Lithic Argiustolls Vermustolls, p. 222 IFED. Other Argiustolls that have both: IFG. Other Ustolls. Haplustolls, p. 213 1. One or both of the following: a. Cracks within 125 cm of the mineral soil surface that Argiustolls are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or Key to Subgroups wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral IFEA. Argiustolls that have both: soil surface; or 1. A lithic contact within 50 cm of the mineral soil b. A linear extensibility of 6.0 cm or more between the surface; and mineral soil surface and either a depth of 100 cm or a 2. When neither irrigated nor fallowed to store moisture, densic, lithic, or paralithic contact, whichever is have one of the following: shallower; 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- have one of the following: tenths or more of the cumulative days per year when the a. A frigid temperature regime and a moisture control soil temperature at a depth of 50 cm below the soil section that in normal years is dry in all parts for four- surface is higher than 5 oC; or tenths or more of the cumulative days 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 moisture control section that in normal years is dry in surface is higher than 5 oC; or Mollisols 209
b. A mesic or thermic soil temperature regime and a more for some time in normal years, and slickensides or moisture control section that in normal years is dry in wedge-shaped aggregates in a layer 15 cm or more thick some or all parts for six-tenths or more of the cumulative that has its upper boundary within 125 cm of the mineral days per year when the soil temperature at a depth of 50 soil surface; or cm below the soil surface is higher than 5 oC; or 2. A linear extensibility of 6.0 cm or more between the c. A hyperthermic, isomesic, or warmer iso soil mineral soil surface and either a depth of 100 cm or a temperature regime and a moisture control section that in densic, lithic, or paralithic contact, whichever is shallower. normal years: Vertic Argiustolls (1) Is moist in some or all parts for fewer than 90 IFEG. Other Argiustolls that have, throughout one or more consecutive days per year when the soil temperature at horizons with a total thickness of 18 cm or more within 75 cm a depth of 50 cm below the soil surface is higher than of the mineral soil surface, a fine-earth fraction with both a 8 oC; and bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 (2) Is dry in some or all parts for six-tenths or more retention, and Al plus /2 Fe percentages (by ammonium of the cumulative days per year when the soil oxalate) totaling more than 1.0. temperature at a depth of 50 cm below the soil surface Andic Argiustolls is higher than 5 oC. Torrertic Argiustolls IFEH. Other Argiustolls that have both: 1. When neither irrigated nor fallowed to store moisture, IFEE. Other Argiustolls that have both: one of the following: 1. One or both of the following: a. A frigid temperature regime and a moisture control a. Cracks within 125 cm of the mineral soil surface that section that in normal years is dry in all parts for four- are 5 mm or more wide through a thickness of 30 cm or tenths or more of the cumulative days per year when the more for some time in normal years, and slickensides or soil temperature at a depth of 50 cm below the soil wedge-shaped aggregates in a layer 15 cm or more thick surface is higher than 5 oC; or that has its upper boundary within 125 cm of the mineral b. A mesic or thermic soil temperature regime and a soil surface; or moisture control section that in normal years is dry in b. A linear extensibility of 6.0 cm or more between the some or all parts for six-tenths or more of the cumulative mineral soil surface and either a depth of 100 cm or a days per year when the soil temperature at a depth of 50 densic, lithic, or paralithic contact, whichever is cm below the soil surface is higher than 5 oC; or shallower; and c. A hyperthermic, isomesic, or warmer iso soil M 2. When neither irrigated nor fallowed to store moisture, temperature regime and a moisture control section that in O either: normal years: L a. A mesic or thermic soil temperature regime and a (1) Is moist in some or all parts for fewer than 90 moisture control section that in normal years is dry in consecutive days per year when the soil temperature at some part for four-tenths or less of the cumulative days a depth of 50 cm below the soil surface is higher than per year when the soil temperature at a depth of 50 cm 8 oC; and below the soil surface is higher than 5 oC; or (2) Is dry in some or all parts for six-tenths or more b. A hyperthermic, isomesic, or warmer iso soil of the cumulative days per year when the soil temperature regime and a moisture control section that in temperature at a depth of 50 cm below the soil surface normal years is dry in some or all parts for fewer than is higher than 5 oC; and 120 cumulative days per year when the soil temperature 2. Throughout one or more horizons with a total thickness at a depth of 50 cm below the soil surface is higher than of 18 cm or more within 75 cm of the mineral soil surface, 8 oC. one or both of the following: Udertic Argiustolls a. More than 35 percent (by volume) fragments coarser IFEF. Other Argiustolls that have one or both of the than 2.0 mm, of which more than 66 percent is cinders, following: pumice, and pumicelike fragments; or 1. Cracks within 125 cm of the mineral soil surface that b. 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 210 Keys to Soil Taxonomy
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more clean silt and sand covering 50 percent or more of the faces volcanic glass; and of peds in the upper 5 cm of the argillic horizon.
1 Alfic Argiustolls (2) [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is IFEN. Other Argiustolls that have both: equal to 30 or more. Vitritorrandic Argiustolls 1. A calcic horizon with its upper boundary within 100 cm of the mineral soil surface; and IFEI. 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 following: a. A frigid temperature regime and a moisture control 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 pumice, and pumicelike fragments; or surface is higher than 5 oC; or 2. A fine-earth fraction containing 30 percent or more b. A mesic or thermic soil temperature regime and a particles 0.02 to 2.0 mm in diameter; and moisture control section that in normal years is dry in a. In the 0.02 to 2.0 mm fraction, 5 percent or more some part for six-tenths or more of the cumulative days volcanic glass; and per year when the soil temperature at a depth of 50 cm o 1 below the soil surface is higher than 5 C; or b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is c. A hyperthermic, isomesic, or warmer iso soil equal to 30 or more. temperature regime and a moisture control section that in Vitrandic Argiustolls normal years: (1) Is moist in some or all parts for fewer than 90 IFEJ. Other Argiustolls that have a texture finer than loamy consecutive days per year when the soil temperature at fine sand and either: a depth of 50 cm below the soil surface is higher than 1. A frigid temperature regime and a mollic epipedon 40 8 oC; and cm or more thick; or (2) Is dry in some part for six-tenths or more of the 2. A mollic epipedon 50 cm or more thick. cumulative days per year when the soil temperature at Pachic Argiustolls a depth of 50 cm below the soil surface is higher than 5 oC. IFEK. Other Argiustolls that have, in one or more horizons Calcidic Argiustolls within 100 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some IFEO. Other Argiustolls that, when neither irrigated nor time in normal years (or artificial drainage). fallowed to store moisture, have one of the following: Aquic Argiustolls 1. A frigid temperature regime and a moisture control section that in normal years is dry in all parts for four-tenths IFEL. Other Argiustolls that in normal years are saturated or more of the cumulative days per year when the soil with water in one or more layers within 100 cm of the mineral temperature at a depth of 50 cm below the soil surface is soil surface for either or both: higher than 5 oC; or 1. 20 or more consecutive days; or 2. 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 some Oxyaquic Argiustolls or all parts for six-tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm below IFEM. Other Argiustolls that have either: the soil surface is higher than 5 oC; or 1. Above the argillic horizon, an albic horizon or a 3. A hyperthermic, isomesic, or warmer iso soil horizon that has color values too high for a mollic epipedon temperature regime and a moisture control section that in and chroma too high for an albic horizon; or normal years: 2. A glossic horizon, or interfingering of albic materials a. Is moist in some or all parts for fewer than 90 into the upper part of the argillic horizon, or skeletans of consecutive days per year when the soil temperature at a Mollisols 211
depth of 50 cm below the soil surface is higher than 8 oC; wedge-shaped aggregates in a layer 15 cm or more thick and that has its upper boundary within 125 cm of the mineral soil surface; or b. Is dry in some or all parts for six-tenths or more of the cumulative days per year when the soil temperature at b. A linear extensibility of 6.0 cm or more between the a depth of 50 cm below the soil surface is higher than mineral soil surface and either a depth of 100 cm or a 5 oC. densic, lithic, or paralithic contact, whichever is Aridic Argiustolls shallower; and 2. When neither irrigated nor fallowed to store moisture, IFEP. Other Argiustolls that, when neither irrigated nor one of the following: fallowed to store moisture, have either: a. A frigid temperature regime and a moisture control 1. A mesic or thermic soil temperature regime and a section that in normal years is dry in all parts for four- moisture control section that in normal years is dry in some tenths or more of the cumulative days per year when the part for four-tenths or less of the cumulative days per year soil temperature at a depth of 50 cm below the soil when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or surface is higher than 5 oC; or b. 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 or all parts for six-tenths or more of the cumulative normal years is dry in some or all parts for fewer than 120 days per year when the soil temperature at a depth of 50 cumulative days per year when the soil temperature at a cm below the soil surface is higher than 5 oC; or depth of 50 cm below the soil surface is higher than 8 oC. Udic Argiustolls c. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in IFEQ. Other Argiustolls that have a brittle horizon that is normal years: within 100 cm of the mineral soil surface, is 15 cm or more (1) Is moist in some or all parts for fewer than 90 thick, and has either some opal coatings or 20 percent or more consecutive days per year when the soil temperature at (by volume) durinodes. a depth of 50 cm below the soil surface is higher than Duric Argiustolls 8 oC; and IFER. Other Argiustolls. (2) Is dry in some or all parts for six-tenths or more Typic Argiustolls of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC. M Calciustolls Torrertic Calciustolls O L Key to Subgroups IFCE. Other Calciustolls that have both: IFCA. Calciustolls that have a salic horizon that has its upper boundary within 75 cm of the mineral soil surface. 1. One or both of the following: Salidic Calciustolls a. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or IFCB. Other Calciustolls that have a petrocalcic horizon and more for some time in normal years, and slickensides or a lithic contact within 50 cm of the mineral soil surface. wedge-shaped aggregates in a layer 15 cm or more thick Lithic Petrocalcic Calciustolls that has its upper boundary within 125 cm of the mineral soil surface; or IFCC. Other Calciustolls that have a lithic contact within 50 cm of the mineral soil surface. b. A linear extensibility of 6.0 cm or more between the Lithic Calciustolls mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is IFCD. Other Calciustolls that have both: shallower; and 1. One or both of the following: 2. When neither irrigated nor fallowed to store moisture, either: 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. A mesic or thermic soil temperature regime and a more for some time in normal years, and slickensides or moisture control section that in normal years is dry in 212 Keys to Soil Taxonomy
some part for four-tenths or less of the cumulative days 2. 30 or more cumulative days. per year when the soil temperature at a depth of 50 cm Oxyaquic Calciustolls below the soil surface is higher than 5 oC; or IFCL. Other Calciustolls that, when neither irrigated nor b. 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 is dry in some or all parts for fewer than 1. A frigid temperature regime and a moisture control 120 cumulative days per year when the soil temperature section that in normal years is dry in all parts for four-tenths at a depth of 50 cm below the soil surface is higher than or more of the cumulative days per year when the soil 8 oC. temperature at a depth of 50 cm below the soil surface is Udertic Calciustolls higher than 5 oC; or 2. A mesic or thermic soil temperature regime and a IFCF. Other Calciustolls that have one or both of the moisture control section that in normal years is dry in some following: or all parts for six-tenths or more of the cumulative days per 1. Cracks within 125 cm of the mineral soil surface that year when the soil temperature at a depth of 50 cm below are 5 mm or more wide through a thickness of 30 cm or the soil surface is higher than 5 oC; or more for some time in normal years, and slickensides or 3. A hyperthermic, isomesic, or warmer iso soil wedge-shaped aggregates in a layer 15 cm or more thick temperature regime and a moisture control section that in that has its upper boundary within 125 cm of the mineral normal years: soil surface; or a. Is moist in some or all parts for fewer than 90 2. A linear extensibility of 6.0 cm or more between consecutive days per year when the soil temperature at a the mineral soil surface and either a depth of 100 cm depth of 50 cm below the soil surface is higher than 8 oC; or a densic, lithic, or paralithic contact, whichever is and shallower. Vertic Calciustolls b. Is dry in some or all parts for six-tenths or more of the cumulative days per year when the soil temperature at IFCG. Other Calciustolls that have a petrocalcic horizon that a depth of 50 cm below the soil surface is higher than has its upper boundary within 100 cm of the mineral soil 5 oC. surface. Aridic Calciustolls Petrocalcic Calciustolls IFCM. Other Calciustolls that, when neither irrigated nor IFCH. Other Calciustolls that have a gypsic horizon with its fallowed to store moisture, have either: upper boundary within 100 cm of the mineral soil surface. 1. A mesic or thermic soil temperature regime and a Gypsic Calciustolls moisture control section that in normal years is dry in some or all parts for four-tenths or less of the consecutive days per IFCI. Other Calciustolls that have a texture finer than loamy year when the soil temperature at a depth of 50 cm below fine sand and either: the soil surface is higher than 5 oC; or 1. A frigid temperature regime and a mollic epipedon 40 2. A hyperthermic, isomesic, or warmer iso soil cm or more thick; or temperature regime and a moisture control section that in 2. A mollic epipedon 50 cm or more thick. normal years is dry in some or all parts for fewer than 120 Pachic Calciustolls cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 8 oC. IFCJ. Other Calciustolls that have, in one or more horizons Udic Calciustolls within 75 cm of the mineral soil surface, redox concentrations IFCN. Other Calciustolls. and also aquic conditions for some time in normal years (or Typic Calciustolls artificial drainage). Aquic Calciustolls Durustolls
IFCK. Other Calciustolls that in normal years are saturated Key to Subgroups with water in one or more layers within 100 cm of the mineral IFAA. Durustolls that have a natric horizon above the soil surface for either or both: duripan. 1. 20 or more consecutive days; or Natric Durustolls Mollisols 213
IFAB. Other Durustolls that: section that in normal years is dry in all parts for four- tenths or more of the cumulative days per year when the 1. Do not have an argillic horizon above the duripan; and soil temperature at a depth of 50 cm below the soil 2. Have an aridic moisture regime that borders on ustic. surface is higher than 5 oC; or Haploduridic Durustolls b. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in IFAC. Other Durustolls that have an aridic moisture regime some or all parts for six-tenths or more of the cumulative that borders on ustic. days per year when the soil temperature at a depth of 50 Argiduridic Durustolls cm below the soil surface is higher than 5 oC; or IFAD. Other Durustolls that do not have an argillic horizon c. A hyperthermic, isomesic, or warmer iso soil above the duripan. temperature regime and a moisture control section that in Entic Durustolls normal years: (1) Is moist in some or all parts for fewer than 90 IFAE. Other Durustolls that have a duripan that is strongly consecutive days per year when the soil temperature at cemented or less cemented in all subhorizons. a depth of 50 cm below the soil surface is higher than Haplic Durustolls 8 oC; and IFAF. Other Durustolls. (2) Is dry in some or all parts for six-tenths or more Typic Durustolls of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC. Haplustolls Torrertic Haplustolls Key to Subgroups IFGE. Other Haplustolls that have all of the following: IFGA. Haplustolls that have a salic horizon that has its upper 1. A mollic epipedon with a texture finer than loamy fine boundary within 75 cm of the mineral soil surface. sand; and either Salidic Haplustolls a. A frigid temperature regime and a mollic epipedon IFGB. Other Haplustolls that have, in part of each pedon, a 40 cm or more thick; or lithic contact within 50 cm of the mineral soil surface. b. A mollic epipedon 50 cm or more thick; and Ruptic-Lithic Haplustolls 2. One or both of the following: M IFGC. Other Haplustolls that have a lithic contact within 50 a. Cracks within 125 cm of the mineral soil surface that O cm of the mineral soil surface. are 5 mm or more wide through a thickness of 30 cm or L Lithic Haplustolls more for some time in normal years, and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick IFGD. Other Haplustolls that have both: that has its upper boundary within 125 cm of the mineral 1. 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 3. When neither irrigated nor fallowed to store moisture, soil surface; or either: b. A linear extensibility of 6.0 cm or more between the a. A mesic or thermic soil temperature regime and a mineral soil surface and either a depth of 100 cm or a moisture control section that in normal years is dry in densic, lithic, or paralithic contact, whichever is some part for four-tenths or less of the cumulative days shallower; and per year when the soil temperature at a depth of 50 cm 2. When neither irrigated nor fallowed to store moisture, below the soil surface is higher than 5 oC; or one of the following: 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 214 Keys to Soil Taxonomy
normal years is dry in some or all parts for fewer than a. A frigid temperature regime and a moisture control 120 cumulative days per year when the soil temperature section that in normal years is dry in all parts for four- at a depth of 50 cm below the soil surface is higher than tenths or more of the cumulative days per year when the 8 oC. soil temperature at a depth of 50 cm below the soil Pachic Udertic Haplustolls surface is higher than 5 oC; or b. A mesic or thermic soil temperature regime and a IFGF. Other Haplustolls that have both: moisture control section that in normal years is dry in 1. One or both 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 a. Cracks within 125 cm of the mineral soil surface that below the soil surface is higher than 5 oC; or are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or c. A hyperthermic, isomesic, or warmer iso soil wedge-shaped aggregates in a layer 15 cm or more thick temperature regime and a moisture control section that in that has its upper boundary within 125 cm of the mineral normal years remains moist in some or all parts for fewer soil surface; or than 90 consecutive days per year when the soil temperature at a depth of 50 cm below the soil surface is b. A linear extensibility of 6.0 cm or more between the higher than 8 oC; and mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is 2. An apparent CEC (by 1N NH4OAc pH 7) of less shallower; and than 24 cmol(+)/kg clay in 50 percent or more of the soil volume between a depth of 25 cm from the mineral 2. When neither irrigated nor fallowed to store moisture, soil surface and either a depth of 100 cm or a densic, either: lithic, or paralithic contact if shallower. (If the ratio of a. A mesic or thermic soil temperature regime and a [percent water retained at 1500 kPa tension minus percent moisture control section that in normal years is dry in organic carbon] to the percentage of measured clay is 0.6 or some part for four-tenths or less of the cumulative days more, then the percentage of clay is considered to equal per year when the soil temperature at a depth of 50 cm either the measured percentage of clay or three times below the soil surface is higher than 5 oC; or [percent water retained at 1500 kPa tension minus percent organic carbon], whichever value is higher, but no more b. A hyperthermic, isomesic, or warmer iso soil than 100.) temperature regime and a moisture control section that in Torroxic Haplustolls normal years is dry in some or all parts for fewer than 120 cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than IFGI. Other Haplustolls that have an apparent CEC (by o 8 C. 1N NH4OAc pH 7) of less than 24 cmol(+)/kg clay in 50 Udertic Haplustolls percent or more of the soil volume between a depth of 25 cm from the mineral soil surface and either a depth of 100 IFGG. Other Haplustolls that have one or both of the cm or a densic, lithic, or paralithic contact if shallower. (If following: the ratio of [percent water retained at 1500 kPa tension minus percent organic carbon] to the percentage of measured 1. Cracks within 125 cm of the mineral soil surface that clay is 0.6 or more, then the percentage of clay is considered are 5 mm or more wide through a thickness of 30 cm or to equal either the measured percentage of clay or three times more for some time in normal years, and slickensides or [percent water retained at 1500 kPa tension minus percent wedge-shaped aggregates in a layer 15 cm or more thick organic carbon], whichever value is higher, but no more than that has its upper boundary within 125 cm of the mineral 100.) soil surface; or Oxic Haplustolls 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a IFGJ. Other Haplustolls that have, throughout one or more densic, lithic, or paralithic contact, whichever is shallower. horizons with a total thickness of 18 cm or more within 75 cm Vertic Haplustolls 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 IFGH. Other Haplustolls that have both: 1 retention, and Al plus /2 Fe percentages (by ammonium 1. When neither irrigated nor fallowed to store moisture, oxalate) totaling more than 1.0. one of the following: Andic Haplustolls Mollisols 215
IFGK. Other Haplustolls that have both: a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and 1. When neither irrigated nor fallowed to store moisture, 1 one of the following: b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is a. A frigid temperature regime and a moisture control equal to 30 or more. section that in normal years is dry in all parts for four- Vitrandic Haplustolls tenths or more of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil IFGM. Other Haplustolls that have: surface is higher than 5 oC; or 1. Either: b. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in a. A frigid soil temperature regime and a mollic some part for six-tenths or more of the cumulative days epipedon 40 cm or more thick, of which less than 50 per year when the soil temperature at a depth of 50 cm percent has a sandy or sandy-skeletal particle-size class, below the soil surface is higher than 5 oC; or and there is no densic or paralithic contact and no sandy or sandy-skeletal particle-size class at a depth between 40 c. A hyperthermic, isomesic, or warmer iso soil and 50 cm from the mineral soil surface; or temperature regime and a moisture control section that in normal years: b. A mollic epipedon that is 50 cm or more thick and has a texture finer than loamy fine sand; and (1) Is moist in some or all parts for fewer than 90 consecutive days per year when the soil temperature at 2. An irregular decrease in organic-carbon content from a a depth of 50 cm below the soil surface is higher than depth of 25 cm below the mineral soil surface to a depth of 8 oC; and 125 cm or to a densic, lithic, or paralithic contact if shallower; and (2) Is dry in some or all parts for six-tenths or more of the cumulative days per year when the soil 3. A slope of less than 25 percent; and temperature at a depth of 50 cm below the soil surface 4. In one or more horizons within 100 cm of the mineral is higher than 5 oC; and soil surface, redox depletions with chroma of 2 or less and 2. Throughout one or more horizons with a total thickness also aquic conditions for some time in normal years (or of 18 cm or more within 75 cm of the mineral soil surface, artificial drainage). one or both of the following: Aquic Cumulic Haplustolls a. More than 35 percent (by volume) fragments coarser IFGN. Other Haplustolls that have: than 2.0 mm, of which more than 66 percent is cinders, M pumice, and pumicelike fragments; or 1. Either: O b. A fine-earth fraction containing 30 percent or more a. A frigid soil temperature regime and a mollic L particles 0.02 to 2.0 mm in diameter; and epipedon 40 cm or more thick, of which less than 50 percent has a sandy or sandy-skeletal particle-size class, (1) In the 0.02 to 2.0 mm fraction, 5 percent or more and there is no densic or paralithic contact and no sandy volcanic glass; and or sandy-skeletal particle-size class at a depth between 40 1 (2) [(Al plus /2 Fe, percent extracted by ammonium and 50 cm from the mineral soil surface; or oxalate) times 60] plus the volcanic glass (percent) is b. A mollic epipedon that is 50 cm or more thick and equal to 30 or more. has a texture finer than loamy fine sand; and Vitritorrandic Haplustolls 2. An irregular decrease in organic-carbon content from a IFGL. Other Haplustolls that have, throughout one or more depth of 25 cm below the mineral soil surface to a depth of horizons with a total thickness of 18 cm or more within 75 cm 125 cm or to a densic, lithic, or paralithic contact if of the mineral soil surface, one or both of the following: shallower; and 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 IFGO. Other Haplustolls that have anthraquic conditions. particles 0.02 to 2.0 mm in diameter; and Anthraquic Haplustolls 216 Keys to Soil Taxonomy
IFGP. Other Haplustolls that have both: temperature regime and a moisture control section that in normal years: 1. In one or more horizons within 100 cm of the mineral soil surface, redox depletions with chroma of 2 or less and (1) Is moist in some or all parts for fewer than 90 also aquic conditions for some time in normal years (or consecutive days per year when the soil temperature at artificial drainage); and a depth of 50 cm below the soil surface is higher than 8 oC; and 2. A slope of less than 25 percent; and either (2) Is dry in some or all parts for six-tenths or more a. An organic-carbon content of 0.3 percent or more at of the cumulative days per year when the soil a depth of 125 cm below the mineral soil surface; or temperature at a depth of 50 cm below the soil surface b. An irregular decrease in organic-carbon content is higher than 5 oC; and from a depth of 25 cm to a depth of 125 cm or to a 2. A slope of less than 25 percent; and either densic, lithic, or paralithic contact if shallower. Fluvaquentic Haplustolls a. An organic-carbon content of 0.3 percent or more at a depth of 125 cm below the mineral soil surface; or IFGQ. Other Haplustolls that have a texture finer than loamy b. An irregular decrease in organic-carbon content fine sand and either: from a depth of 25 cm to a depth of 125 cm or to a 1. A frigid temperature regime and a mollic epipedon 40 densic, lithic, or paralithic contact if shallower. cm or more thick; or Torrifluventic Haplustolls 2. A mollic epipedon 50 cm or more thick. IFGU. Other Haplustolls that: Pachic Haplustolls 1. When neither irrigated nor fallowed to store moisture, IFGR. Other Haplustolls that have, in one or more horizons have one of the following: within 100 cm of the mineral soil surface, redox depletions a. A frigid temperature regime and a moisture control with chroma of 2 or less and also aquic conditions for some section that in normal years is dry in all parts for four- time in most years (or artificial drainage). tenths or more of the cumulative days per year when the Aquic Haplustolls soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or IFGS. Other Haplustolls that in normal years are saturated with water in one or more layers within 100 cm of the mineral b. A mesic or thermic soil temperature regime and a soil surface for either or both: moisture control section that in normal years is dry in some part for six-tenths or more of the cumulative days 1. 20 or more consecutive days; or per year when the soil temperature at a depth of 50 cm 2. 30 or more cumulative days. below the soil surface is higher than 5 oC; or Oxyaquic Haplustolls c. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in IFGT. Other Haplustolls that have both: normal years: 1. When neither irrigated nor fallowed to store moisture, (1) Is moist in some or all parts for fewer than 90 one of the following: consecutive days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than a. A frigid temperature regime and a moisture control 8 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 (2) Is dry in some or all parts for six-tenths or more soil temperature at a depth of 50 cm below the soil of the cumulative days per year when the soil surface is higher than 5 oC; or temperature at a depth of 50 cm below the soil surface is higher than 5 oC; and b. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in 2. Either: some part for six-tenths or more of the cumulative days a. Do not have a cambic horizon and do not, in any part per year when the soil temperature at a depth of 50 cm of the mollic epipedon below 25 cm from the mineral soil below the soil surface is higher than 5 oC; or surface, meet all of the requirements for a cambic c. A hyperthermic, isomesic, or warmer iso soil horizon except color; or Mollisols 217
b. Have free carbonates throughout the cambic horizon moisture control section that in normal years is dry in or in all parts of the mollic epipedon below a depth of 25 some part for four-tenths or less of the cumulative days cm from the mineral soil surface. per year when the soil temperature at a depth of 50 cm Torriorthentic Haplustolls below the soil surface is higher than 5 oC; or b. A hyperthermic, isomesic, or warmer iso soil IFGV. Other Haplustolls that, when neither irrigated nor temperature regime and a moisture control section that in fallowed to store moisture, have one of the following: normal years is dry in some or all parts for fewer than 1. A frigid temperature regime and a moisture control 120 days per year when the soil temperature at a depth of section that in normal years is dry in all parts for four-tenths 50 cm below the soil surface is higher than 8 oC; and or more of the cumulative days per year when the soil 2. Either do not have a cambic horizon and do not, in the temperature at a depth of 50 cm below the soil surface is lower part of the mollic epipedon, meet the requirements for higher than 5 oC; or a cambic horizon, except for the color requirements, or have 2. A mesic or thermic soil temperature regime and a carbonates throughout either the cambic horizon or the moisture control section that in normal years is dry in some lower part of the mollic epipedon. part for six-tenths or more of the cumulative days per year Udorthentic Haplustolls when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or IFGZ. Other Haplustolls that, when neither irrigated nor fallowed to store moisture, have either: 3. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in 1. A mesic or thermic soil temperature regime and a normal years: moisture control section that in normal years is dry in some part for four-tenths or less of the cumulative days per year a. Is moist in some or all parts for fewer than 90 when the soil temperature at a depth of 50 cm below the soil consecutive 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 8 oC; and 2. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in b. Is dry in some or all parts for six-tenths or more of normal years is dry in some or all parts for fewer than 120 the cumulative days per year when the soil temperature at days per year when the soil temperature at a depth of 50 cm a depth of 50 cm below the soil surface is higher than below the soil surface is higher than 8 oC. 5 oC. Udic Haplustolls Aridic Haplustolls
IFGW. Other Haplustolls that have a slope of less than 25 IFGZa. Other Haplustolls that either: M percent; and either O 1. Do not have a cambic horizon and do not, in any part of L 1. An organic-carbon content of 0.3 percent or more at a the mollic epipedon below 25 cm from the mineral soil depth of 125 cm below the mineral soil surface; or surface, meet all of the requirements for a cambic horizon except color; or 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 2. Have free carbonates throughout the cambic horizon or paralithic contact if shallower. in all parts of the mollic epipedon below a depth of 25 cm Fluventic Haplustolls from the mineral soil surface. Entic Haplustolls IFGX. Other Haplustolls that have a brittle horizon that is IFGZb. Other Haplustolls. within 100 cm of the mineral soil surface, is 15 cm or more Typic Haplustolls thick, and has either some opal coatings or 20 percent or more (by volume) durinodes. Duric Haplustolls Natrustolls
IFGY. Other Haplustolls that: Key to Subgroups 1. When neither irrigated nor fallowed to store moisture, IFBA. Natrustolls that have all of the following: have either: 1. Visible crystals of gypsum and/or more soluble salts a. A mesic or thermic soil temperature regime and a within 40 cm of the mineral soil surface; and 218 Keys to Soil Taxonomy
2. One or both of the following: 2. When neither irrigated nor fallowed to store moisture, have one of the following: 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. A frigid temperature regime and a moisture control more for some time in normal years, and slickensides or section that in normal years is dry in all parts for four- wedge-shaped aggregates in a layer 15 cm or more thick tenths or more of the cumulative days per year when the that has its upper boundary within 125 cm of the mineral soil temperature at a depth of 50 cm below the soil soil surface; or surface is higher than 5 oC; or b. A linear extensibility of 6.0 cm or more between the b. A mesic or thermic soil temperature regime and a mineral soil surface and either a depth of 100 cm or a moisture control section that in normal years is dry in densic, lithic, or paralithic contact, whichever is some or all parts for six-tenths or more of the cumulative shallower; days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or 3. When neither irrigated nor fallowed to store moisture, have one of the following: c. A hyperthermic, isomesic, or warmer iso soil 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- tenths or more of the cumulative days per year when the (1) Is moist in some or all parts for fewer than 90 soil temperature at a depth of 50 cm below the soil consecutive days per year when the soil temperature at surface is higher than 5 oC; or a depth of 50 cm below the soil surface is higher than 8 oC; and b. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in (2) Is dry in some or all parts for six-tenths or more some or all parts for six-tenths or more of the cumulative of the cumulative days per year when the soil days per year when the soil temperature at a depth of 50 temperature at a depth of 50 cm below the soil surface cm below the soil surface is higher than 5 oC; or is higher than 5 oC. Torrertic Natrustolls c. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in IFBC. Other Natrustolls that have both of the following: normal years: 1. Visible crystals of gypsum and/or more soluble salts (1) Is moist in some or all parts for fewer than 90 within 40 cm of the mineral soil surface; and consecutive days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 2. One or both of the following: 8 oC; and a. Cracks within 125 cm of the mineral soil surface that (2) Is dry in some or all parts for six-tenths or more are 5 mm or more wide through a thickness of 30 cm or of the cumulative days per year when the soil more for some time in normal years, and slickensides or temperature at a depth of 50 cm below the soil surface wedge-shaped aggregates in a layer 15 cm or more thick is higher than 5 oC. that has its upper boundary within 125 cm of the mineral Leptic Torrertic Natrustolls soil surface; or b. A linear extensibility of 6.0 cm or more between the IFBB. Other Natrustolls that have both: mineral soil surface and either a depth of 100 cm or a 1. One or both of the following: densic, lithic, or paralithic contact, whichever is shallower. a. Cracks within 125 cm of the mineral soil surface that Leptic Vertic Natrustolls are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or IFBD. Other Natrustolls 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. A glossic horizon or interfingering of albic materials soil surface; or into a natric horizon; and b. A linear extensibility of 6.0 cm or more between the 2. One or both of the following: mineral soil surface and either a depth of 100 cm or a 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 Mollisols 219
more for some time in normal years, and slickensides or temperature at a depth of 50 cm below the soil surface wedge-shaped aggregates in a layer 15 cm or more thick is higher than 5 oC. that has its upper boundary within 125 cm of the mineral Aridic Leptic Natrustolls soil surface; or IFBG. Other Natrustolls that have visible crystals of gypsum b. A linear extensibility of 6.0 cm or more between the or of more soluble salts, or both, within 40 cm of the mineral mineral soil surface and either a depth of 100 cm or a soil surface. densic, lithic, or paralithic contact, whichever is Leptic Natrustolls shallower. Glossic Vertic Natrustolls IFBH. Other Natrustolls that have, in one or more horizons at IFBE. Other Natrustolls that have one or both of the a depth between 50 and 100 cm from the mineral soil surface, following: aquic conditions for some time in normal years (or artificial drainage) and one of the following: 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or 1. 50 percent or more chroma of 1 or less and hue of 2.5Y more for some time in normal years, and slickensides or or yellower; or wedge-shaped aggregates in a layer 15 cm or more thick 2. 50 percent or more chroma of 2 or less and redox that has its upper boundary within 125 cm of the mineral concentrations; or soil surface; or 3. 50 percent or more chroma of 2 or less and also a 2. A linear extensibility of 6.0 cm or more between the higher exchangeable sodium percentage (or sodium mineral soil surface and either a depth of 100 cm or a adsorption ratio) between the mineral soil surface and a densic, lithic, or paralithic contact, whichever is shallower. depth of 25 cm than in the underlying horizon. Vertic Natrustolls Aquic Natrustolls IFBF. Other Natrustolls that have both: IFBI. Other Natrustolls that, when neither irrigated nor 1. Visible crystals of gypsum or of more soluble salts, or fallowed to store moisture, have one of the following: both, within 40 cm of the mineral soil surface; and 1. 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-tenths have one of the following: 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 four- higher than 5 oC; or M tenths or more of the cumulative days per year when the 2. A mesic or thermic soil temperature regime and a O soil temperature at a depth of 50 cm below the soil moisture control section that in normal years is dry in some L surface is higher than 5 oC; or 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 3. A hyperthermic, isomesic, or warmer iso soil days per year when the soil temperature at a depth of 50 temperature regime and a moisture control section that in cm below the soil surface is higher than 5 oC; or normal years: c. A hyperthermic, isomesic, or warmer iso soil a. Is moist in some or all parts for fewer than 90 temperature regime and a moisture control section that in consecutive days per year when the soil temperature at a normal years: 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 b. Is dry in some or all parts for six-tenths or more of a depth of 50 cm below the soil surface is higher than the cumulative days per year when the soil temperature at 8 oC; and a depth of 50 cm below the soil surface is higher than (2) Is dry in some or all parts for six-tenths or more 5 oC. of the cumulative days per year when the soil Aridic Natrustolls 220 Keys to Soil Taxonomy
IFBJ. Other Natrustolls that have a horizon, 15 cm or more temperature at a depth of 50 cm below the soil surface thick within 100 cm of the mineral soil surface, that either has is higher than 5 oC. 20 percent or more (by volume) durinodes or is brittle and has Torrertic Paleustolls a firm rupture-resistance class when moist. IFDB. Other Paleustolls that have both: Duric Natrustolls 1. One or both of the following: IFBK. Other Natrustolls that have a glossic horizon or a. Cracks within 125 cm of the mineral soil surface that interfingering of albic materials into a natric horizon. are 5 mm or more wide through a thickness of 30 cm or Glossic Natrustolls more for some time in normal years, and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick IFBL. Other Natrustolls. that has its upper boundary within 125 cm of the mineral Typic Natrustolls soil surface; or b. A linear extensibility of 6.0 cm or more between the Paleustolls mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is Key to Subgroups shallower; and IFDA. Paleustolls that have both: 2. When neither irrigated nor fallowed to store moisture, 1. One or both of the following: either: a. Cracks within 125 cm of the mineral soil surface that a. 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 four-tenths or less of the cumulative days wedge-shaped aggregates in a layer 15 cm or more thick per year when the soil temperature at a depth of 50 cm that has its upper boundary within 125 cm of the mineral below the soil surface is higher than 5 oC; or soil surface; or b. 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 densic, lithic, or paralithic contact, whichever is 120 cumulative days per year when the soil temperature shallower; and at a depth of 50 cm below the soil surface is higher than 8 oC. 2. When neither irrigated nor fallowed to store moisture, Udertic Paleustolls one of the following: a. A frigid temperature regime and a moisture control IFDC. Other Paleustolls that have one or both of the section that in normal years is dry in all parts for less following: than four-tenths of the cumulative days per year when the 1. Cracks within 125 cm of the mineral soil surface that soil temperature at a depth of 50 cm below the soil are 5 mm or more wide through a thickness of 30 cm or surface is higher than 5 oC; or more for some time in normal years, and slickensides or b. 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 that has its upper boundary within 125 cm of the mineral some or all parts for six-tenths or more of the cumulative soil surface; or days per year when the soil temperature at a depth of 50 2. A linear extensibility of 6.0 cm or more between the cm below the soil surface is higher than 5 oC; or mineral soil surface and either a depth of 100 cm or a c. A hyperthermic, isomesic, or warmer iso soil densic, lithic, or paralithic contact, whichever is temperature regime and a moisture control section that in shallower. normal years: Vertic Paleustolls (1) Is moist in some or all parts for fewer than 90 IFDD. Other Paleustolls that have a texture finer than loamy consecutive days per year when the soil temperature at fine sand and a mollic epipedon 50 cm or more thick. a depth of 50 cm below the soil surface is higher than Pachic Paleustolls 8 oC; and (2) Is dry in some or all parts for six-tenths or more IFDE. Other Paleustolls that have, in one or more horizons of the cumulative days per year when the soil within 100 cm of the mineral soil surface, redox depletions Mollisols 221
with chroma of 2 or less and also aquic conditions for some temperature at a depth of 50 cm below the soil surface is time in normal years (or artificial drainage). higher than 5 oC; or Aquic Paleustolls 2. A mesic or thermic soil temperature regime and a moisture control section that in normal years is dry in some IFDF. Other Paleustolls that have a petrocalcic horizon part for six-tenths or more of the cumulative days per year within 150 cm of the mineral soil surface. when the soil temperature at a depth of 50 cm below the soil Petrocalcic Paleustolls surface is higher than 5 oC; or IFDG. Other Paleustolls that: 3. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in 1. Have a calcic horizon within one of the following normal years: particle-size class (by weighted average in the particle-size control section) and depth combinations: a. Is moist in some or all parts for fewer than 90 consecutive days per year when the soil temperature at a a. Sandy or sandy-skeletal and within 100 cm of the depth of 50 cm below the soil surface is higher than 8 oC; mineral soil surface; or and b. Clayey, clayey-skeletal, fine, or very-fine and within b. Is dry in some or all parts for six-tenths or more of 50 cm of the mineral soil surface; or the cumulative days per year when the soil temperature at c. Any other class and within 60 cm of the mineral soil a depth of 50 cm below the soil surface is higher than surface; and 5 oC. Aridic Paleustolls 2. When neither irrigated nor fallowed to store moisture, have one of the following: IFDI. Other Paleustolls 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 less 1. A mesic or thermic soil temperature regime and a than four-tenths 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 part for four-tenths or less of the cumulative days per year surface 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 part for six-tenths or more of the cumulative days temperature regime and a moisture control section that in per year when the soil temperature at a depth of 50 cm normal years is dry in some or all parts for fewer than 120 below the soil surface is higher than 5 oC; or M cumulative days per year when the soil temperature at a O c. A hyperthermic, isomesic, or warmer iso soil depth of 50 cm below the soil surface is higher than 8 oC. L temperature regime and a moisture control section that in Udic Paleustolls normal years: IFDJ. Other Paleustolls have a calcic horizon within (1) Is moist in some or all parts for fewer than 90 one of the following particle-size class (by weighted consecutive days per year when the soil temperature at average in the particle-size control section) and depth a depth of 50 cm below the soil surface is higher than combinations: 8 oC; and 1. Sandy or sandy-skeletal and within 100 cm of the (2) Is dry in some or all parts for six-tenths or more mineral soil surface; or of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface 2. Clayey, clayey-skeletal, fine, or very-fine and within 50 is higher than 5 oC. cm of the mineral soil surface; or Calcidic Paleustolls 3. Any other class and within 60 cm of the mineral soil surface. IFDH. Other Paleustolls that, when neither irrigated nor Calcic Paleustolls fallowed to store moisture, have one of the following: 1. A frigid temperature regime and a moisture control IFDK. Other Paleustolls that are calcareous throughout after section that in normal years is dry in all parts for less than the surface soil has been mixed to a depth of 18 cm. four-tenths of the cumulative days per year when the soil Entic Paleustolls 222 Keys to Soil Taxonomy
IFDL. Other Paleustolls. of 7.5YR or redder or chroma of 6 or more, or both; Typic Paleustolls or b. A clayey or clayey-skeletal particle-size class in its Vermustolls upper part and, at its upper boundary, a clay increase either of 20 percent or more (absolute) within a vertical Key to Subgroups distance of 7.5 cm or of 15 percent or more (absolute) IFFA. Vermustolls that have a lithic contact within 50 cm of within a vertical distance of 2.5 cm, in the fine-earth the mineral soil surface. fraction (and there is no densic, lithic, or paralithic Lithic Vermustolls contact within 50 cm of the mineral soil surface). Palexerolls, p. 230 IFFB. Other Vermustolls that have, in one or more horizons within 100 cm of the mineral soil surface, redox depletions IED. Other Xerolls that: with chroma of 2 or less and also aquic conditions for some 1. Have a calcic or gypsic horizon that has its upper time in normal years (or artificial drainage). boundary within 150 cm of the mineral soil surface; and Aquic Vermustolls 2. In all parts above the calcic or gypsic horizon, after the IFFC. Other Vermustolls that have a mollic epipedon 75 cm surface soil has been mixed to a depth of 18 cm, either are or more thick. calcareous or have a texture of loamy fine sand or coarser. Pachic Vermustolls Calcixerolls, p. 224
IFFD. Other Vermustolls that have a mollic epipedon less IEE. Other Xerolls that have an argillic horizon. than 50 cm thick. Argixerolls, p. 222 Entic Vermustolls IEF. Other Xerolls. IFFE. Other Vermustolls. Haploxerolls, p. 226 Typic Vermustolls Argixerolls
Xerolls Key to Subgroups Key to Great Groups IEEA. Argixerolls that have both: 1. A lithic contact within 50 cm of the mineral soil IEA. Xerolls that have a duripan within 100 cm of the surface; and mineral soil surface. Durixerolls, p. 225 2. A base saturation (by sum of cations) of 75 percent or less in one or more horizons between either the mineral soil IEB. Other Xerolls that have a natric horizon. surface or an Ap horizon, whichever is deeper, and the lithic Natrixerolls, p. 230 contact. Lithic Ultic Argixerolls IEC. Other Xerolls that have either: IEEB. Other Argixerolls that have a lithic contact within 50 1. A petrocalcic horizon that has its upper boundary cm of the mineral soil surface. within 150 cm of the mineral soil surface; or Lithic Argixerolls 2. An argillic horizon that has one or both of the following: IEEC. Other Argixerolls that have both: a. With increasing depth, no clay decrease of 20 1. An aridic moisture regime; and percent or more (relative) from the maximum clay 2. One or both of the following: content (noncarbonate clay) within 150 cm of the mineral soil surface (and there is no densic, lithic, or paralithic a. Cracks within 125 cm of the mineral soil surface that contact within that depth); and either are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or (1) Hue of 7.5YR or redder and chroma of 5 or more wedge-shaped aggregates in a layer 15 cm or more thick in the matrix; or that has its upper boundary within 125 cm of the mineral (2) Common redox concentrations with hue soil surface; or Mollisols 223
b. A linear extensibility of 6.0 cm or more between the 2. A fine-earth fraction containing 30 percent or more mineral soil surface and either a depth of 100 cm or a particles 0.02 to 2.0 mm in diameter; and densic, lithic, or paralithic contact, whichever is a. In the 0.02 to 2.0 mm fraction, 5 percent or more shallower. volcanic glass; and Torrertic Argixerolls 1 b. [(Al plus /2 Fe, percent extracted by ammonium IEED. Other Argixerolls that have one or both of the oxalate) times 60] plus the volcanic glass (percent) is following: equal to 30 or more. Vitrandic Argixerolls 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or IEEH. Other Argixerolls 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. In one or more horizons within 75 cm of the mineral that has its upper boundary within 125 cm of the mineral soil surface, redox depletions with chroma of 2 or less and soil surface; or also aquic conditions for some time in normal years (or artificial drainage); 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 2. A base saturation (by sum of cations) of 75 percent densic, lithic, or paralithic contact, whichever is shallower. or less in one or more horizons between either an Ap Vertic Argixerolls horizon or a depth of 25 cm from the mineral soil surface, whichever is deeper, and either a depth of 75 IEEE. Other Argixerolls that have, throughout one or more cm or a densic, lithic, or paralithic contact, whichever horizons with a total thickness of 18 cm or more within 75 cm is shallower. of the mineral soil surface, a fine-earth fraction with both a Aquultic Argixerolls bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 retention, and Al plus /2 Fe percentages (by ammonium IEEI. Other Argixerolls that have, in one or more horizons oxalate) totaling more than 1.0. within 75 cm of the mineral soil surface, redox depletions with Andic Argixerolls chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). IEEF. Other Argixerolls that have both: Aquic Argixerolls 1. An aridic moisture regime; and IEEJ. Other Argixerolls that in normal years are saturated 2. Throughout one or more horizons with a total thickness with water in one or more layers within 100 cm of the mineral of 18 cm or more within 75 cm of the mineral soil surface, soil surface for either or both: M one or both of the following: 1. 20 or more consecutive days; or O a. More than 35 percent (by volume) fragments coarser L 2. 30 or more cumulative days. than 2.0 mm, of which more than 66 percent is cinders, Oxyaquic Argixerolls pumice, and pumicelike fragments; or b. A fine-earth fraction containing 30 percent or more IEEK. Other Argixerolls that have either: particles 0.02 to 2.0 mm in diameter; and 1. Above the argillic horizon, an albic horizon or a (1) In the 0.02 to 2.0 mm fraction, 5 percent or more horizon that has color values too high for a mollic epipedon volcanic glass; and and chroma too high for an albic horizon; or
1 (2) [(Al plus /2 Fe, percent extracted by ammonium 2. A glossic horizon, or interfingering of albic materials oxalate) times 60] plus the volcanic glass (percent) is into the upper part of the argillic horizon, or skeletans of equal to 30 or more. clean silt and sand covering 50 percent or more of the faces Vitritorrandic Argixerolls of peds in the upper 5 cm of the argillic horizon. Alfic Argixerolls IEEG. Other Argixerolls that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm IEEL. Other Argixerolls that have both: of the mineral soil surface, one or both of the following: 1. A calcic horizon or identifiable secondary carbonates 1. More than 35 percent (by volume) fragments coarser within one of the following particle-size class (by weighted than 2.0 mm, of which more than 66 percent is cinders, average in the particle-size control section) and depth pumice, and pumicelike fragments; or combinations: 224 Keys to Soil Taxonomy
a. Sandy or sandy-skeletal and within 150 cm of the c. Any other class and within 110 cm of the mineral mineral soil surface; or soil surface. Calciargidic Argixerolls b. Clayey, clayey-skeletal, fine, or very-fine and within 90 cm of the mineral soil surface; or IEER. Other Argixerolls that have an aridic moisture c. Any other class and within 110 cm of the mineral regime. soil surface; and Aridic Argixerolls 2. A mollic epipedon that is 50 cm or more thick and has IEES. Other Argixerolls that have a calcic horizon or a texture finer than loamy fine sand. identifiable secondary carbonates within one of the following Calcic Pachic Argixerolls particle-size class (by weighted average in the particle-size control section) and depth combinations: IEEM. Other Argixerolls that have both: 1. Sandy or sandy-skeletal and within 150 cm of the 1. A mollic epipedon that is 50 cm or more thick and has mineral soil surface; or a texture finer than loamy fine sand; and 2. Clayey, clayey-skeletal, fine, or very-fine and within 90 2. A base saturation (by sum of cations) of 75 percent or cm of the mineral soil surface; or less in one or more horizons between either an Ap horizon or a depth of 25 cm from the mineral soil surface, whichever 3. Any other class and within 110 cm of the mineral soil is deeper, and either a depth of 75 cm or a densic, lithic, or surface. paralithic contact, whichever is shallower. Calcic Argixerolls Pachic Ultic Argixerolls IEET. Other Argixerolls that have a base saturation (by sum IEEN. Other Argixerolls that have a mollic epipedon that is of cations) of 75 percent or less in one or more horizons 50 cm or more thick and has a texture finer than loamy fine between either an Ap horizon or a depth of 25 cm from the sand. mineral soil surface, whichever is deeper, and either a depth of Pachic Argixerolls 75 cm or a densic, lithic, or paralithic contact, whichever is shallower. IEEO. Other Argixerolls that have both: Ultic Argixerolls 1. An aridic moisture regime; and IEEU. Other Argixerolls. 2. A horizon within 100 cm of the mineral soil surface Typic Argixerolls that is 15 cm or more thick and either has 20 percent or more (by volume) durinodes or is brittle and has a firm rupture-resistance class when moist. Calcixerolls Argiduridic Argixerolls Key to Subgroups IEEP. Other Argixerolls that have a horizon within 100 cm of IEDA. Calcixerolls that have a lithic contact within 50 cm of the mineral soil surface that is 15 cm or more thick and either the mineral soil surface. has 20 percent or more (by volume) durinodes or is brittle and Lithic Calcixerolls has a firm rupture-resistance class when moist. Duric Argixerolls IEDB. Other Calcixerolls that have one or both of the following: IEEQ. Other Argixerolls that have both: 1. Cracks within 125 cm of the mineral soil surface that 1. An aridic moisture regime; and are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or 2. A calcic horizon or identifiable secondary carbonates wedge-shaped aggregates in a layer 15 cm or more thick within one of the following particle-size class (by weighted that has its upper boundary within 125 cm of the mineral average in the particle-size control section) and depth soil surface; or combinations: 2. A linear extensibility of 6.0 cm or more between a. Sandy or sandy-skeletal and within 150 cm of the the mineral soil surface and either a depth of 100 cm mineral soil surface; or or a densic, lithic, or paralithic contact, whichever is b. Clayey, clayey-skeletal, fine, or very-fine and within shallower. 90 cm of the mineral soil surface; or Vertic Calcixerolls Mollisols 225
IEDC. Other Calcixerolls that have, in one or more horizons slickensides or wedge-shaped aggregates in a layer 15 cm or within 75 cm of the mineral soil surface, redox concentrations more thick; or and also aquic conditions for some time in normal years (or 2. A linear extensibility of 6.0 cm or more. artificial drainage). Vertic Durixerolls Aquic Calcixerolls IEAB. Other Durixerolls that have both: IEDD. Other Calcixerolls that in normal years are saturated with water in one or more layers within 100 cm of the mineral 1. An aridic moisture regime; and soil surface for either or both: 2. Throughout one or more horizons with a total thickness 1. 20 or more consecutive days; or of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: 2. 30 or more cumulative days. Oxyaquic Calcixerolls a. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, IEDE. Other Calcixerolls that have a mollic epipedon that is pumice, and pumicelike fragments; or 50 cm or more thick and has a texture finer than loamy fine b. A fine-earth fraction containing 30 percent or more sand. particles 0.02 to 2.0 mm in diameter; and Pachic Calcixerolls (1) In the 0.02 to 2.0 mm fraction, 5 percent or more IEDF. Other Calcixerolls that have, throughout one or more volcanic glass; and horizons with a total thickness of 18 cm or more within 75 cm 1 (2) [(Al plus /2 Fe, percent extracted by ammonium of the mineral soil surface, one or both of the following: oxalate) times 60] plus the volcanic glass (percent) is 1. More than 35 percent (by volume) fragments coarser equal to 30 or more. than 2.0 mm, of which more than 66 percent is cinders, Vitritorrandic Durixerolls pumice, and pumicelike fragments; or IEAC. Other Durixerolls that have, throughout one or more 2. A fine-earth fraction containing 30 percent or more horizons with a total thickness of 18 cm or more within 75 cm particles 0.02 to 2.0 mm in diameter, of which 5 percent or 1 of the mineral soil surface, one or both of the following: more is volcanic glass, and [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic 1. More than 35 percent (by volume) fragments coarser glass (percent) is equal to 30 or more. than 2.0 mm, of which more than 66 percent is cinders, Vitrandic Calcixerolls pumice, and pumicelike fragments; or 2. A fine-earth fraction containing 30 percent or more M IEDG. Other Calcixerolls that have an aridic moisture particles 0.02 to 2.0 mm in diameter; and O regime. L Aridic Calcixerolls a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and
IEDH. Other Calcixerolls that have a mollic epipedon that 1 b. [(Al plus /2 Fe, percent extracted by ammonium has, below any Ap horizon, 50 percent or more (by volume) oxalate) times 60] plus the volcanic glass (percent) is wormholes, wormcasts, or filled animal burrows. equal to 30 or more. Vermic Calcixerolls Vitrandic Durixerolls IEDI. Other Calcixerolls. IEAD. Other Durixerolls that have, in one or more horizons Typic Calcixerolls above the duripan, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or Durixerolls artificial drainage). Aquic Durixerolls Key to Subgroups IEAE. Other Durixerolls that have: IEAA. Durixerolls that have, above the duripan, one or both of the following: 1. An aridic moisture regime; and 1. Cracks that are 5 mm or more wide through a thickness 2. An argillic horizon that, with increasing depth, has a of 30 cm or more for some time in normal years, and clay increase either of 20 percent or more (absolute) within 226 Keys to Soil Taxonomy
a vertical distance of 7.5 cm or of 15 percent or more or more (absolute) within a vertical distance of 7.5 cm or of 15 (absolute) within a vertical distance of 2.5 cm; and percent or more (absolute) within a vertical distance of 2.5 cm. Palexerollic Durixerolls 3. A duripan that is neither very strongly cemented nor indurated in any subhorizon. IEAM. Other Durixerolls that: Paleargidic Durixerolls 1. Have a duripan that is neither very strongly cemented IEAF. Other Durixerolls that have both: nor indurated in any subhorizon; and 1. An aridic moisture regime; and 2. Do not have an argillic horizon above the duripan. Haplic Haploxerollic Durixerolls 2. An argillic horizon that, with increasing depth, has a clay increase either of 20 percent or more (absolute) within IEAN. Other Durixerolls that do not have an argillic horizon a vertical distance of 7.5 cm or of 15 percent or more above the duripan. (absolute) within a vertical distance of 2.5 cm. Haploxerollic Durixerolls Abruptic Argiduridic Durixerolls IEAO. Other Durixerolls that have a duripan that is neither IEAG. Other Durixerolls that: very strongly cemented nor indurated in any subhorizon. 1. Have an aridic moisture regime; and Haplic Durixerolls 2. Do not have an argillic horizon above the duripan; and IEAP. Other Durixerolls. 3. Have a duripan that is neither very strongly cemented Typic Durixerolls nor indurated in any subhorizon. Cambidic Durixerolls Haploxerolls IEAH. Other Durixerolls that: Key to Subgroups 1. Have an aridic moisture regime; and IEFA. Haploxerolls that have both: 2. Do not have an argillic horizon above the duripan. 1. A lithic contact within 50 cm of the mineral soil Haploduridic Durixerolls surface; and IEAI. Other Durixerolls that have: 2. A base saturation (by sum of cations) of 75 percent or less in one or more horizons between either the mineral soil 1. An aridic moisture regime; and surface or an Ap horizon, whichever is deeper, and the lithic 2. A duripan that is neither very strongly cemented nor contact. indurated in any subhorizon. Lithic Ultic Haploxerolls Argidic Durixerolls IEFB. Other Haploxerolls that have a lithic contact within 50 IEAJ. Other Durixerolls that have an aridic moisture cm of the mineral soil surface. regime. Lithic Haploxerolls Argiduridic Durixerolls IEFC. Other Haploxerolls that have both: IEAK. Other Durixerolls that have both: 1. An aridic moisture regime; and 1. An argillic horizon that, with increasing depth, has a 2. One or both of the following: clay increase either of 20 percent or more (absolute) within a vertical distance of 7.5 cm or of 15 percent or more a. Cracks within 125 cm of the mineral soil surface that (absolute) within a vertical distance of 2.5 cm; and are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or 2. A duripan that is neither very strongly cemented nor wedge-shaped aggregates in a layer 15 cm or more thick indurated in any subhorizon. that has its upper boundary within 125 cm of the mineral Haplic Palexerollic Durixerolls soil surface; or IEAL. Other Durixerolls that have an argillic horizon that, b. A linear extensibility of 6.0 cm or more between the with increasing depth, has a clay increase either of 20 percent mineral soil surface and either a depth of 100 cm or a Mollisols 227
densic, lithic, or paralithic contact, whichever is IEFG. Other Haploxerolls that have: shallower. 1. A mollic epipedon that is 50 cm or more thick and has Torrertic Haploxerolls a texture finer than loamy fine sand; and IEFD. Other Haploxerolls that have one or both of the 2. An irregular decrease in organic-carbon content from a following: depth of 25 cm below the mineral soil surface to a depth of 125 cm or to a densic, lithic, or paralithic contact if 1. Cracks within 125 cm of the mineral soil surface that shallower; and are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or 3. A slope of less than 25 percent; and wedge-shaped aggregates in a layer 15 cm or more thick 4. In one or more horizons within 75 cm of the mineral that has its upper boundary within 125 cm of the mineral soil surface, redox depletions with chroma of 2 or less and soil surface; or also aquic conditions for some time in normal years (or 2. A linear extensibility of 6.0 cm or more between the artificial drainage). mineral soil surface and either a depth of 100 cm or a Aquic Cumulic Haploxerolls densic, lithic, or paralithic contact, whichever is shallower. Vertic Haploxerolls IEFH. Other Haploxerolls that have: 1. A mollic epipedon that is 50 cm or more thick and has IEFE. Other Haploxerolls that have both: a texture finer than loamy fine sand; and 1. An aridic moisture regime; and 2. An irregular decrease in organic-carbon content from a 2. Throughout one or more horizons with a total thickness depth of 25 cm below the mineral soil surface to a depth of of 18 cm or more within 75 cm of the mineral soil surface, 125 cm or to a densic, lithic, or paralithic contact if one or both of the following: shallower; and a. More than 35 percent (by volume) fragments coarser 3. A slope of less than 25 percent; and than 2.0 mm, of which more than 66 percent is cinders, 4. A base saturation (by sum of cations) of 75 percent or pumice, and pumicelike fragments; or less in one or more horizons between either an Ap horizon b. A fine-earth fraction containing 30 percent or more or a depth of 25 cm from the mineral soil surface, whichever particles 0.02 to 2.0 mm in diameter; and is deeper, and either a depth of 75 cm or a densic, lithic, or paralithic contact, whichever is shallower. (1) In the 0.02 to 2.0 mm fraction, 5 percent or more Cumulic Ultic Haploxerolls volcanic glass; and M 1 (2) [(Al plus /2 Fe, percent extracted by ammonium IEFI. Other Haploxerolls that have: O oxalate) times 60] plus the volcanic glass (percent) is L equal to 30 or more. 1. A mollic epipedon that is 50 cm or more thick and has Vitritorrandic Haploxerolls a texture finer than loamy fine sand; and 2. An irregular decrease in organic-carbon content from a IEFF. Other Haploxerolls that have, throughout one or more depth of 25 cm below the mineral soil surface to a depth of horizons with a total thickness of 18 cm or more within 75 cm 125 cm or to a densic, lithic, or paralithic contact if of the mineral soil surface, one or both of the following: shallower; and 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 Haploxerolls pumice, and pumicelike fragments; or IEFJ. Other Haploxerolls that have both: 2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and 1. In one or more horizons within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and a. In the 0.02 to 2.0 mm fraction, 5 percent or more also aquic conditions for some time in normal years (or volcanic glass; and artificial drainage); and 1 b. [(Al plus /2 Fe, percent extracted by ammonium 2. A slope of less than 25 percent; and either oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. a. An organic-carbon content of 0.3 percent or more in Vitrandic Haploxerolls all horizons within 125 cm of the mineral soil surface; or 228 Keys to Soil Taxonomy
b. An irregular decrease in organic-carbon content b. Clayey, clayey-skeletal, fine, or very-fine and within from a depth of 25 cm to a depth of 125 cm or to a 90 cm of the mineral soil surface; or densic, lithic, or paralithic contact if shallower. c. Any other class and within 110 cm of the mineral Fluvaquentic Haploxerolls soil surface. Calcic Pachic Haploxerolls IEFK. Other Haploxerolls that have both: 1. In one or more horizons within 75 cm of the mineral IEFP. Other Haploxerolls that have both: soil surface, redox depletions with chroma of 2 or less and 1. A mollic epipedon that is 50 cm or more thick and has also aquic conditions for some time in normal years (or a texture finer than loamy fine sand; and artificial drainage); and 2. A base saturation (by sum of cations) of 75 percent or 2. A horizon, 15 cm or more thick within 100 cm of the less in one or more horizons between either an Ap horizon mineral soil surface, that either has 20 percent or more (by or a depth of 25 cm from the mineral soil surface, whichever volume) durinodes or is brittle and has a firm rupture- is deeper, and either a depth of 75 cm or a densic, lithic, or resistance class when moist. paralithic contact, whichever is shallower. Aquic Duric Haploxerolls Pachic Ultic Haploxerolls IEFL. Other Haploxerolls that have both: IEFQ. Other Haploxerolls that have a mollic epipedon that is 1. In one or more horizons within 75 cm of the mineral 50 cm or more thick and has a texture finer than loamy fine soil surface, redox depletions with chroma of 2 or less and sand. also aquic conditions for some time in normal years (or Pachic Haploxerolls artificial drainage); and 2. A base saturation (by sum of cations) of 75 percent or IEFR. Other Haploxerolls that have: less in one or more horizons between either an Ap horizon 1. An aridic moisture regime; and or a depth of 25 cm from the mineral soil surface, whichever is deeper, and either a depth of 75 cm or a densic, lithic, or 2. A slope of less than 25 percent; and either paralithic contact, whichever is shallower. a. An organic-carbon content of 0.3 percent or more Aquultic Haploxerolls in all horizons within 125 cm of the mineral soil surface; or IEFM. Other Haploxerolls that have, in one or more horizons within 75 cm of the mineral soil surface, redox depletions with b. An irregular decrease in organic-carbon content chroma of 2 or less and also aquic conditions for some time in from a depth of 25 cm to a depth of 125 cm or to a normal years (or artificial drainage). densic, lithic, or paralithic contact if shallower. Aquic Haploxerolls Torrifluventic Haploxerolls
IEFN. Other Haploxerolls that in normal years are saturated IEFS. Other Haploxerolls that have both: with water in one or more layers within 100 cm of the mineral 1. An aridic moisture regime; and soil surface for either or both: 2. A horizon within 100 cm of the mineral soil surface 1. 20 or more consecutive days; or that is 15 cm or more thick and either has 20 percent or 2. 30 or more cumulative days. more (by volume) durinodes or is brittle and has a firm Oxyaquic Haploxerolls rupture-resistance class when moist. Duridic Haploxerolls IEFO. Other Haploxerolls that have both: IEFT. Other Haploxerolls that have both: 1. A mollic epipedon that is 50 cm or more thick and has a texture finer than loamy fine sand; and 1. An aridic moisture regime; and 2. A calcic horizon or identifiable secondary carbonates 2. A calcic horizon or identifiable secondary carbonates within one of the following particle-size class (by weighted within one of the following particle-size class (by weighted average in the particle-size control section) and depth average in the particle-size control section) and depth combinations: combinations: 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 Mollisols 229
b. Clayey, clayey-skeletal, fine, or very-fine and within IEFZa. Other Haploxerolls that have a mollic epipedon that 90 cm of the mineral soil surface; or has granular structure and that has, below any Ap horizon, 50 percent or more (by volume) wormholes, wormcasts, or filled c. Any other class and within 110 cm of the mineral animal burrows. soil surface. Vermic Haploxerolls Calcidic Haploxerolls IEFZb. Other Haploxerolls that have a calcic horizon or IEFU. Other Haploxerolls that have both: identifiable secondary carbonates within one of the following 1. An aridic moisture regime; and particle-size class (by weighted average in the particle-size control section) and depth combinations: 2. A sandy particle-size class in all horizons within 100 cm of the mineral soil surface. 1. Sandy or sandy-skeletal and within 150 cm of the Torripsammentic Haploxerolls mineral soil surface; or 2. Clayey, clayey-skeletal, fine, or very-fine and within 90 IEFV. Other Haploxerolls that: cm of the mineral soil surface; or 1. Have an aridic moisture regime; and 3. Any other class and within 110 cm of the mineral soil 2. Either: surface. Calcic Haploxerolls a. Do not have a cambic horizon and do not, in any part of the mollic epipedon below 25 cm from the mineral soil IEFZc. Other Haploxerolls that: surface, meet all of the requirements for a cambic horizon except color; or 1. Do not have a cambic horizon and do not, in the lower part of the mollic epipedon, meet all of the requirements for b. Have free carbonates throughout the cambic horizon a cambic horizon except color; and or in all parts of the mollic epipedon below a depth of 25 cm from the mineral soil surface. 2. Have a base saturation (by sum of cations) of Torriorthentic Haploxerolls 75 percent or less in one or more horizons between either an Ap horizon or a depth of 25 cm from the mineral soil IEFW. Other Haploxerolls that have an aridic moisture surface, whichever is deeper, and either a depth of 75 cm or regime. a densic, lithic, or paralithic contact, whichever is Aridic Haploxerolls shallower. Entic Ultic Haploxerolls IEFX. Other Haploxerolls that have a horizon within 100 cm of the mineral soil surface that is 15 cm or more thick and IEFZd. Other Haploxerolls that have a base saturation (by M either has 20 percent or more (by volume) durinodes or is sum of cations) of 75 percent or less in one or more horizons O brittle and has a firm rupture-resistance class when moist. between either an Ap horizon or a depth of 25 cm from the L Duric Haploxerolls mineral soil surface, whichever is deeper, and either a depth of 75 cm or a densic, lithic, or paralithic contact, whichever is IEFY. Other Haploxerolls that have a sandy particle-size shallower. class in all horizons within 100 cm of the mineral soil surface. Ultic Haploxerolls Psammentic Haploxerolls IEFZe. Other Haploxerolls that either: IEFZ. Other Haploxerolls that have a slope of less than 25 1. Do not have a cambic horizon and do not, in any part of percent; and either the mollic epipedon below 25 cm from the mineral soil 1. An organic-carbon content of 0.3 percent or more in all surface, meet all of the requirements for a cambic horizon horizons within 125 cm of the mineral soil surface; or except color; or 2. An irregular decrease in organic-carbon content from a 2. Have free carbonates throughout the cambic horizon or depth of 25 cm to a depth of 125 cm or to a densic, lithic, or in all parts of the mollic epipedon below a depth of 25 cm paralithic contact if shallower. from the mineral soil surface. Fluventic Haploxerolls Entic Haploxerolls 230 Keys to Soil Taxonomy
IEFZf. Other Haploxerolls. Palexerolls Typic Haploxerolls Key to Subgroups Natrixerolls IECA. Palexerolls that have one or both of the 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 IEBA. Natrixerolls that have one or both of the following: more for some time in normal years, and slickensides or 1. Cracks within 125 cm of the mineral soil surface that wedge-shaped aggregates in a layer 15 cm or more thick are 5 mm or more wide through a thickness of 30 cm or that has its upper boundary within 125 cm of the mineral more for some time in normal years, and slickensides or soil surface; or wedge-shaped aggregates in a layer 15 cm or more thick 2. A linear extensibility of 6.0 cm or more between the that has its upper boundary within 125 cm of the mineral mineral soil surface and either a depth of 100 cm or a soil surface; or densic, lithic, or paralithic contact, whichever is shallower. 2. A linear extensibility of 6.0 cm or more between the Vertic Palexerolls mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. IECB. Other Palexerolls that have, throughout one or more Vertic Natrixerolls horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following: IEBB. Other Natrixerolls that have both: 1. More than 35 percent (by volume) fragments coarser 1. In one or more horizons within 75 cm of the mineral than 2.0 mm, of which more than 66 percent is cinders, soil surface, redox depletions with chroma of 2 or less and pumice, and pumicelike fragments; or also aquic conditions for some time in normal years (or 2. A fine-earth fraction containing 30 percent or more artificial drainage); and particles 0.02 to 2.0 mm in diameter; and 2. A horizon, 15 cm or more thick within 100 cm of the a. In the 0.02 to 2.0 mm fraction, 5 percent or more mineral soil surface, that either has 20 percent or more (by volcanic glass; and volume) durinodes or is brittle and has a firm rupture- 1 resistance class when moist. b. [(Al plus /2 Fe, percent extracted by ammonium Aquic Duric Natrixerolls oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. IEBC. Other Natrixerolls that have, in one or more horizons Vitrandic Palexerolls within 75 cm of the mineral soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in IECC. Other Palexerolls that have, in one or more horizons normal years (or artificial drainage). within 75 cm of the mineral soil surface, redox depletions with Aquic Natrixerolls chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). IEBD. Other Natrixerolls that have an aridic moisture Aquic Palexerolls regime. Aridic Natrixerolls IECD. Other Palexerolls that have a mollic epipedon that is 50 cm or more thick and has a texture finer than loamy fine IEBE. Other Natrixerolls that have a horizon within sand. 100 cm of the mineral soil surface that is 15 cm or more Pachic Palexerolls thick and either has 20 percent or more (by volume) durinodes or is brittle and has a firm rupture-resistance class IECE. Other Palexerolls that have both: when moist. 1. An aridic moisture regime; and Duric Natrixerolls 2. A petrocalcic horizon that has its upper boundary IEBF. Other Natrixerolls. within 150 cm of the mineral soil surface. Typic Natrixerolls Petrocalcidic Palexerolls Mollisols 231
IECF. Other Palexerolls that have a horizon, 15 cm or more argillic horizon if more than 50 cm thick or within its upper 50 thick within 100 cm of the mineral soil surface, that either has cm. 20 percent or more (by volume) durinodes or is brittle and has Ultic Palexerolls a firm rupture-resistance class when moist. Duric Palexerolls IECJ. Other Palexerolls that have an argillic horizon that has either: IECG. Other Palexerolls that have an aridic moisture regime. 1. Less than 35 percent clay in the upper part; or Aridic Palexerolls 2. At its upper boundary, a clay increase that is both less IECH. Other Palexerolls that have a petrocalcic horizon that than 20 percent (absolute) within a vertical distance of 7.5 has its upper boundary within 150 cm of the mineral soil cm and less than 15 percent (absolute) within a vertical surface. distance of 2.5 cm, in the fine-earth fraction. Petrocalcic Palexerolls Haplic Palexerolls
IECI. Other Palexerolls that have a base saturation of 75 IECK. Other Palexerolls. percent or less in one or more subhorizons either within the Typic Palexerolls
M O L
233
CHAPTER 13 Oxisols1
Key to Suborders EA. Oxisols that have aquic conditions for some time in normal years (or artificial drainage) in one or more horizons within 50 cm of the mineral soil surface and have one or more of the following: 1. A histic epipedon; or 2. An epipedon with a color value, moist, of 3 or less and, directly below it, a horizon with chroma of 2 or less; or 3. Distinct or prominent redox concentrations within 50 cm of the mineral soil surface, an epipedon, and, directly soil surface, an apparent ECEC of less than 1.50 below it, a horizon with one or both of the following: cmol(+) per kg clay and a pH value (in 1N KCl) of a. 50 percent or more hue of 2.5Y or yellower; or 5.0 or more. Acraquox, p. 233 b. Chroma of 3 or less; or 4. Within 50 cm of the mineral soil surface, enough active EAB. Other Aquox that have plinthite forming a continuous ferrous iron to give a positive reaction to alpha,alpha- phase within 125 cm of the mineral soil surface. dipyridyl at a time when the soil is not being irrigated. Plinthaquox, p. 234 Aquox, p. 233
EAC. Other Aquox that have a base saturation (by NH4OAc) EB. Other Oxisols that have an aridic moisture regime. of 35 percent or more in all horizons within 125 cm of the Torrox, p. 238 mineral soil surface. Eutraquox, p. 234 EC. Other Oxisols that have an ustic or xeric moisture regime. EAD. Other Aquox. O Ustox, p. 243 Haplaquox, p. 234 X I ED. Other Oxisols that have a perudic moisture regime. Acraquox Perox, p. 234 Key to Subgroups EE. Other Oxisols. EAAA. Acraquox that have 5 percent or more (by volume) Udox, p. 239 plinthite in one or more horizons within 125 cm of the mineral soil surface. Aquox Plinthic Acraquox
Key to Great Groups EAAB. Other Acraquox that have, directly below an epipedon, a horizon 10 cm or more thick that has 50 percent or EAA. Aquox that have, in one or more subhorizons more chroma of 3 or more. of an oxic or kandic horizon within 150 cm of the mineral Aeric Acraquox
1 This chapter was rewritten in 1987 following recommendations of the International Committee on the Classification of Oxisols (ICOMOX), chaired by Hari Eswaran from 1978 to EAAC. Other Acraquox. 1981 and then by S.W. Buol until completion of the task in 1987. Typic Acraquox 234 Keys to Soil Taxonomy
Eutraquox EABB. Other Plinthaquox. Typic Plinthaquox Key to Subgroups EACA. Eutraquox that have a histic epipedon. Perox Histic Eutraquox Key to Great Groups EACB. Other Eutraquox that have 5 percent or more (by EDA. Perox that have a sombric horizon within 150 cm of volume) plinthite in one or more horizons within 125 cm of the the mineral soil surface. mineral soil surface. Sombriperox, p. 238 Plinthic Eutraquox EDB. Other Perox that have, in one or more subhorizons of EACC. Other Eutraquox that have, directly below an an oxic or kandic horizon within 150 cm of the mineral soil epipedon, a horizon 10 cm or more thick that has 50 percent or surface, an apparent ECEC of less than 1.50 cmol(+) per kg more chroma of 3 or more. clay and a pH value (1N KCl) of 5.0 or more. Aeric Eutraquox Acroperox, p. 234 EACD. Other Eutraquox that have 16 kg/m2 or more organic EDC. Other Perox that have a base saturation (by NH OAc) carbon between the mineral soil surface and a depth of 100 cm. 4 of 35 percent or more in all horizons within 125 cm of the Humic Eutraquox mineral soil surface. Eutroperox, p. 235 EACE. Other Eutraquox. Typic Eutraquox EDD. Other Perox that have a kandic horizon that has its upper boundary within 150 cm of the mineral Haplaquox soil surface. Kandiperox, p. 237 Key to Subgroups EADA. Haplaquox that have a histic epipedon. EDE. Other Perox. Histic Haplaquox Haploperox, p. 236
EADB. Other Haplaquox that have 5 percent or more (by Acroperox volume) plinthite in one or more horizons within 125 cm of the mineral soil surface. Key to Subgroups Plinthic Haplaquox EDBA. Acroperox that have, within 125 cm of the mineral soil surface, both: EADC. Other Haplaquox that have, directly below an epipedon, a horizon 10 cm or more thick that has 50 percent or 1. A petroferric contact; and more chroma of 3 or more. 2. Redox depletions with a color value, moist, of 4 or more Aeric Haplaquox and chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). EADD. Other Haplaquox that have 16 kg/m2 or more organic Aquic Petroferric Acroperox carbon between the mineral soil surface and a depth of 100 cm. Humic Haplaquox EDBB. Other Acroperox that have a petroferric contact within 125 cm of the mineral soil surface. EADE. Other Haplaquox. Petroferric Acroperox Typic Haplaquox EDBC. Other Acroperox that have, within 125 cm of the Plinthaquox mineral soil surface, both: Key to Subgroups 1. A lithic contact; and EABA. Plintaquox that have, directly below an epipedon, a 2. Redox depletions with a color value, moist, of 4 or more horizon 10 cm or more thick that has 50 percent or more and chroma of 2 or less and also aquic conditions for some chroma of 3 or more. time in normal years (or artificial drainage). Aeric Plinthaquox Aquic Lithic Acroperox Oxisols 235
EDBD. Other Acroperox that have a lithic contact within 125 EDBL. Other Acroperox that have 50 percent or more hue of cm of the mineral soil surface. 7.5YR or yellower and a color value, moist, of 6 or more at a Lithic Acroperox depth between 25 and 125 cm from the mineral soil surface. Xanthic Acroperox EDBE. Other Acroperox that have a delta pH (KCl pH minus 1:1 water pH) with a 0 or net positive charge in a layer 18 cm EDBM. Other Acroperox. or more thick within 125 cm of the mineral soil surface. Typic Acroperox Anionic Acroperox
EDBF. Other Acroperox that have 5 percent or more (by Eutroperox volume) plinthite in one or more horizons within 125 cm of the Key to Subgroups mineral soil surface. Plinthic Acroperox EDCA. Eutroperox that have, within 125 cm of the mineral soil surface, both: EDBG. Other Acroperox that have, in one or more horizons 1. A petroferric contact; and 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 2. Redox depletions with a color value, moist, of 4 or more and also aquic conditions for some time in normal years (or and chroma of 2 or less and also aquic conditions for some artificial drainage). time in normal years (or artificial drainage). Aquic Acroperox Aquic Petroferric Eutroperox
EDBH. Other Acroperox that have both: EDCB. Other Eutroperox that have a petroferric contact within 125 cm of the mineral soil surface. 1. 16 kg/m2 or more organic carbon between the mineral Petroferric Eutroperox soil surface and a depth of 100 cm; and 2. In all horizons at a depth between 25 and 125 cm from EDCC. Other Eutroperox that have, within 125 cm of the the mineral soil surface, more than 50 percent colors that mineral soil surface, both: have both of the following: 1. A lithic contact; and a. Hue of 2.5YR or redder; and 2. Redox depletions with a color value, moist, of 4 or more b. A value, moist, of 3 or less. and chroma of 2 or less and also aquic conditions for some Humic Rhodic Acroperox time in normal years (or artificial drainage). Aquic Lithic Eutroperox EDBI. Other Acroperox that have both: EDCD. Other Eutroperox that have a lithic contact within 1. 16 kg/m2 or more organic carbon between the mineral 125 cm of the mineral soil surface. soil surface and a depth of 100 cm; and Lithic Eutroperox O 2. 50 percent or more hue of 7.5YR or yellower and a X color value, moist, of 6 or more at a depth between 25 and EDCE. Other Eutroperox that have, in one or more horizons I 125 cm from the mineral soil surface. within 125 cm of the mineral soil surface, both: Humic Xanthic Acroperox 1. 5 percent or more (by volume) plinthite; and EDBJ. Other Acroperox that have 16 kg/m2 or more organic 2. Redox depletions with a color value, moist, of 4 or more carbon between the mineral soil surface and a depth of 100 cm. and chroma of 2 or less and also aquic conditions for some Humic Acroperox time in normal years (or artificial drainage). Plinthaquic Eutroperox EDBK. Other Acroperox that have, in all horizons at a depth between 25 and 125 cm from the mineral soil surface, more EDCF. Other Eutroperox that have 5 percent or more (by than 50 percent colors that have both of the following: volume) plinthite in one or more horizons within 125 cm of the mineral soil surface. 1. Hue of 2.5YR or redder; and Plinthic Eutroperox 2. A value, moist, of 3 or less. Rhodic Acroperox EDCG. Other Eutroperox that have, in one or more horizons 236 Keys to Soil Taxonomy
within 125 cm of the mineral soil surface, redox depletions 2. A value, moist, of 3 or less. with a color value, moist, of 4 or more and chroma of 2 or less Rhodic Eutroperox and also aquic conditions for some time in normal years (or artificial drainage). EDCO. Other Eutroperox that have 50 percent or more hue Aquic Eutroperox of 7.5YR or yellower and a color value, moist, of 6 or more at a depth between 25 and 125 cm from the mineral soil surface. EDCH. Other Eutroperox that have a kandic horizon Xanthic Eutroperox that has its upper boundary within 150 cm of the mineral soil surface. EDCP. Other Eutroperox. Kandiudalfic Eutroperox Typic Eutroperox
EDCI. Other Eutroperox that have both: Haploperox 1. 16 kg/m2 or more organic carbon between the mineral Key to Subgroups soil surface and a depth of 100 cm; and EDEA. Haploperox that have, within 125 cm of the mineral 2. An oxic horizon that has its lower boundary within 125 soil surface, both: cm of the mineral soil surface. Humic Inceptic Eutroperox 1. A petroferric contact; and 2. Redox depletions with a color value, moist, of 4 or more EDCJ. Other Eutroperox 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 Eutroperox Aquic Petroferric Haploperox EDCK. Other Eutroperox that have both: EDEB. Other Haploperox 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 Haploperox 2. In all horizons at a depth between 25 and 125 cm from EDEC. Other Haploperox that have, within 125 cm of the the mineral soil surface, more than 50 percent colors that mineral soil surface, both: have both of the following: 1. A lithic contact; and a. Hue of 2.5YR or redder; and 2. Redox depletions with a color value, moist, of 4 or more b. A value, moist, of 3 or less. and chroma of 2 or less and also aquic conditions for some Humic Rhodic Eutroperox time in normal years (or artificial drainage). Aquic Lithic Haploperox EDCL. Other Eutroperox that have both: 1. 16 kg/m2 or more organic carbon between the mineral EDED. Other Haploperox that have a lithic contact within soil surface and a depth of 100 cm; and 125 cm of the mineral soil surface. Lithic Haploperox 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 EDEE. Other Haploperox that have, in one or more horizons 125 cm from the mineral soil surface. within 125 cm of the mineral soil surface, both: Humic Xanthic Eutroperox 1. 5 percent or more (by volume) plinthite; and EDCM. Other Eutroperox 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 of and chroma of 2 or less and also aquic conditions for some 100 cm. time in normal years (or artificial drainage). Humic Eutroperox Plinthaquic Haploperox EDCN. Other Eutroperox that have, in all horizons at a EDEF. Other Haploperox that have 5 percent or more (by depth between 25 and 125 cm from the mineral soil surface, volume) plinthite in one or more horizons within 125 cm of the more than 50 percent colors that have both of the following: mineral soil surface. 1. Hue of 2.5YR or redder; and Plinthic Haploperox Oxisols 237
EDEG. Other Haploperox that have, in one or more horizons EDEN. Other Haploperox. within 125 cm of the mineral soil surface, redox depletions Typic Haploperox with 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 drainage). Kandiperox Aquic Haploperox Key to Subgroups EDEH. Other Haploperox that have, throughout one or more EDDA. Kandiperox that have, within 125 cm of the mineral horizons with a total thickness of 18 cm or more within 75 cm soil surface, both: of the mineral soil surface, a fine-earth fraction with both a 1. A petroferric contact; and bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 retention, and Al plus /2 Fe percentages (by ammonium 2. Redox depletions with a color value, moist, of 4 or more oxalate) totaling more than 1.0. and chroma of 2 or less and also aquic conditions for some Andic Haploperox time in normal years (or artificial drainage). Aquic Petroferric Kandiperox EDEI. Other Haploperox that have both: EDDB. Other Kandiperox 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 Kandiperox 2. In all horizons at a depth between 25 and 125 cm from the mineral soil surface, more than 50 percent colors that EDDC. Other Kandiperox 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 Haploperox and chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). EDEJ. Other Haploperox that have both: Aquic Lithic Kandiperox 1. 16 kg/m2 or more organic carbon between the mineral EDDD. Other Kandiperox that have a lithic contact within soil surface and a depth of 100 cm; and 125 cm of the mineral soil surface. 2. 50 percent or more hue of 7.5YR or yellower and a Lithic Kandiperox color value, moist, of 6 or more at a depth between 25 and 125 cm from the mineral soil surface. EDDE. Other Kandiperox that have, in one or more horizons Humic Xanthic Haploperox within 125 cm of the mineral soil surface, both: 1. 5 percent or more (by volume) plinthite; and EDEK. Other Haploperox that have 16 kg/m2 or more O organic carbon between the mineral soil surface and a depth of 2. Redox depletions with a color value, moist, of 4 or more X 100 cm. and chroma of 2 or less and also aquic conditions for some I Humic Haploperox time in normal years (or artificial drainage). Plinthaquic Kandiperox EDEL. Other Haploperox that have, in all horizons at a depth between 25 and 125 cm from the mineral soil surface, EDDF. Other Kandiperox that have 5 percent or more (by more than 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 2. A value, moist, of 3 or less. Rhodic Haploperox EDDG. Other Kandiperox that have, in one or more horizons within 125 cm of the mineral soil surface, redox depletions EDEM. Other Haploperox that have 50 percent or more hue with a color value, moist, of 4 or more and chroma of 2 or less of 7.5YR or yellower and a color value, moist, of 6 or more at a and also aquic conditions for some time in normal years (or depth between 25 and 125 cm from the mineral soil surface. artificial drainage). Xanthic Haploperox Aquic Kandiperox 238 Keys to Soil Taxonomy
EDDH. Other Kandiperox that have, throughout one or more Sombriperox 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 Key to Subgroups bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 EDAA. Sombriperox that have a petroferric contact within retention, and Al plus /2 Fe percentages (by ammonium 125 cm of the mineral soil surface. oxalate) totaling more than 1.0. Petroferric Sombriperox Andic Kandiperox EDAB. Other Sombriperox that have a lithic contact within EDDI. Other Kandiperox that have both: 125 cm of the mineral soil surface. 1. 16 kg/m2 or more organic carbon between the mineral Lithic Sombriperox soil surface and a depth of 100 cm; and EDAC. Other Sombriperox that have 16 kg/m2 or more 2. In all horizons at a depth between 25 and 125 cm from organic carbon between the mineral soil surface and a depth of the mineral soil surface, more than 50 percent colors that 100 cm. have both of the following: Humic Sombriperox a. Hue of 2.5YR or redder; and EDAD. Other Sombriperox. b. A value, moist, of 3 or less. Typic Sombriperox Humic Rhodic Kandiperox
EDDJ. Other Kandiperox that have both: Torrox 1. 16 kg/m2 or more organic carbon between the mineral Key to Great Groups soil surface and a depth of 100 cm; and EBA. Torrox that have, in one or more subhorizons of an 2. 50 percent or more hue of 7.5YR or yellower and a oxic or kandic horizon within 150 cm of the mineral soil color value, moist, of 6 or more at a depth between 25 and surface, an apparent ECEC of less than 1.50 cmol(+) per kg 125 cm from the mineral soil surface. clay and a pH value (1N KCl) of 5.0 or more. Humic Xanthic Kandiperox Acrotorrox, p. 238 EDDK. Other Kandiperox that have 16 kg/m2 or more EBB. Other Torrox that have a base saturation (by NH OAc) organic carbon between the mineral soil surface and a depth of 4 of 35 percent or more in all horizons within 125 cm of the 100 cm. mineral soil surface. Humic Kandiperox Eutrotorrox, p. 239 EDDL. Other Kandiperox that have, in all horizons EBC. Other Torrox. at a depth between 25 and 125 cm from the mineral soil Haplotorrox, p. 239 surface, more than 50 percent colors that have both of the following: Acrotorrox 1. Hue of 2.5YR or redder; and Key to Subgroups 2. A value, moist, of 3 or less. Rhodic Kandiperox EBAA. Acrotorrox that have a petroferric contact within 125 cm of the mineral soil surface. EDDM. Other Kandiperox that have 50 percent or more Petroferric Acrotorrox hue of 7.5YR or yellower and a color value, moist, of 6 or more at a depth between 25 and 125 cm from the mineral soil EBAB. Other Acrotorrox that have a lithic contact within surface. 125 cm of the mineral soil surface. Xanthic Kandiperox Lithic Acrotorrox
EDDN. Other Kandiperox. EBAC. Other Acrotorrox. Typic Kandiperox Typic Acrotorrox Oxisols 239
Eutrotorrox Acrudox
Key to Subgroups Key to Subgroups EBBA. Eutrotorrox that have a petroferric contact within 125 EEBA. Acrudox that have, within 125 cm of the mineral soil cm of the mineral soil surface. surface, both: Petroferric Eutrotorrox 1. A petroferric contact; and EBBB. Other Eutrotorrox that have a lithic contact within 2. Redox depletions with a color value, moist, of 4 or more 125 cm of the mineral soil surface. and chroma of 2 or less and also aquic conditions for some Lithic Eutrotorrox time in normal years (or artificial drainage). Aquic Petroferric Acrudox EBBC. Other Eutrotorrox. Typic Eutrotorrox EEBB. Other Acrudox that have a petroferric contact within 125 cm of the mineral soil surface. Haplotorrox Petroferric Acrudox Key to Subgroups EEBC. Other Acrudox that have, within 125 cm of the EBCA. Haplotorrox that have a petroferric contact within mineral soil surface, both: 125 cm of the mineral soil surface. 1. A lithic contact; and Petroferric Haplotorrox 2. Redox depletions with a color value, moist, of 4 or more EBCB. Other Haplotorrox that have a lithic contact within and chroma of 2 or less and also aquic conditions for some 125 cm of the mineral soil surface. time in normal years (or artificial drainage). Lithic Haplotorrox Aquic Lithic Acrudox
EBCC. Other Haplotorrox. EEBD. Other Acrudox that have a lithic contact within 125 Typic Haplotorrox cm of the mineral soil surface. Lithic Acrudox Udox EEBE. Other Acrudox that have, within 125 cm of the Key to Great Groups mineral soil surface, both: 1. A delta pH (KCl pH minus 1:1 water pH) with EEA. Udox that have a sombric horizon within 150 cm of the a 0 or net positive charge in a layer 18 cm or more thick; mineral soil surface. and Sombriudox, p. 243 2. Redox depletions with a color value, moist, of 4 or more O EEB. Other Udox that have, in one or more subhorizons of and chroma of 2 or less and also aquic conditions for some X an oxic or kandic horizon within 150 cm of the mineral soil time in normal years (or artificial drainage). I surface, an apparent ECEC of less than 1.50 cmol(+) per kg Anionic Aquic Acrudox clay and a pH value (1N KCl) of 5.0 or more. Acrudox, p. 239 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
EEC. Other Udox that have a base saturation (by NH4OAc) of or more thick within 125 cm of the mineral soil surface. 35 percent or more in all horizons within 125 cm of the Anionic Acrudox mineral soil surface. Eutrudox, p. 240 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 mineral soil surface. upper boundary within 150 cm of the mineral soil surface. Plinthic Acrudox Kandiudox, p. 242 EEBH. Other Acrudox that have, in one or more horizons EEE. Other Udox. within 125 cm of the mineral soil surface, redox depletions Hapludox, p. 241 with a color value, moist, of 4 or more and chroma of 2 or less 240 Keys to Soil Taxonomy
and also aquic conditions for some time in normal years (or Eutrudox artificial drainage). Aquic Acrudox Key to Subgroups EECA. Eutrudox that have, within 125 cm of the mineral soil EEBI. Other Acrudox that have a base saturation (by surface, both: NH4OAc) of 35 percent or more in all horizons within 125 cm of the mineral soil surface. 1. A petroferric contact; and Eutric Acrudox 2. Redox depletions with a color value, moist, of 4 or more and chroma of 2 or less and also aquic conditions for some EEBJ. Other Acrudox that have both: time in normal years (or artificial drainage). 1. 16 kg/m2 or more organic carbon between the mineral Aquic Petroferric Eutrudox soil surface and a depth of 100 cm; and EECB. Other Eutrudox 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 Eutrudox have both of the following: a. Hue of 2.5YR or redder; and EECC. Other Eutrudox that have, within 125 cm of the mineral soil surface, both: b. A value, moist, of 3 or less. Humic Rhodic Acrudox 1. A lithic contact; and 2. Redox depletions with a color value, moist, of 4 or more EEBK. 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 Lithic Eutrudox soil surface and a depth of 100 cm; and 2. 50 percent or more hue of 7.5YR or yellower and a EECD. Other Eutrudox that have a lithic contact within 125 color value, moist, of 6 or more at a depth between 25 and cm of the mineral soil surface. 125 cm from the mineral soil surface. Lithic Eutrudox Humic Xanthic Acrudox EECE. Other Eutrudox that have, in one or more horizons EEBL. Other Acrudox that have 16 kg/m2 or more within 125 cm of the mineral soil surface, both: organic carbon between the mineral soil surface and a 1. 5 percent or more (by volume) plinthite; and depth of 100 cm. Humic Acrudox 2. Redox depletions with a color value, moist, of 4 or more and chroma of 2 or less and also aquic conditions for some EEBM. Other Acrudox that have, in all horizons at a depth time in normal years (or artificial drainage). between 25 and 125 cm from the mineral soil surface, more Plinthaquic Eutrudox than 50 percent colors that have both of the following: EECF. Other Eutrudox 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 Acrudox Plinthic Eutrudox
EEBN. Other Acrudox that have 50 percent or more hue EECG. Other Eutrudox 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 at a depth between 25 and 125 cm from the mineral soil with a color value, moist, of 4 or more and chroma of 2 or less surface. and also aquic conditions for some time in normal years (or Xanthic Acrudox artificial drainage). Aquic Eutrudox EEBO. Other Acrudox. Typic Acrudox EECH. Other Eutrudox that have a kandic horizon that Oxisols 241
has its upper boundary within 150 cm of the mineral soil EECP. Other Eutrudox. surface. Typic Eutrudox Kandiudalfic Eutrudox
EECI. Other Eutrudox that have both: Hapludox 1. 16 kg/m2 or more organic carbon between the mineral Key to Subgroups soil surface and a depth of 100 cm; and EEEA. Hapludox that have, within 125 cm of the mineral 2. An oxic horizon that has its lower boundary within 125 soil 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 Hapludox
EECK. Other Eutrudox that have both: EEEB. Other Hapludox 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 Hapludox soil surface and a depth of 100 cm; and 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 EEEE. Other Hapludox that have, in one or more horizons 125 cm 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 O EECM. Other Eutrudox that have 16 kg/m2 or more organic 2. Redox depletions with a color value, moist, of 4 or more X carbon between the mineral soil surface and a depth of 100 cm. and chroma of 2 or less and also aquic conditions for some I 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 EEEF. Other Hapludox that have 5 percent or more (by than 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 EECO. Other Eutrudox that have 50 percent or more hue of with a color value, moist, of 4 or more and chroma of 2 or less 7.5YR or yellower and a color value, moist, of 6 or more at a and also aquic conditions for some time in normal years (or depth between 25 and 125 cm from the mineral soil surface. artificial drainage). Xanthic Eutrudox Aquic Hapludox 242 Keys to Soil Taxonomy
EEEH. Other Hapludox that have an oxic horizon that has its Kandiudox lower boundary within 125 cm of the mineral soil surface. Inceptic Hapludox Key to Subgroups EEDA. Kandiudox that have, within 125 cm of the mineral EEEI. Other Hapludox that have, throughout one or more soil surface, both: horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction with both a 1. A petroferric contact; and bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 2. Redox depletions with a color value, moist, of 4 or more retention, and Al plus /2 Fe percentages (by ammonium and chroma of 2 or less and also aquic conditions for some oxalate) totaling more than 1.0. time in normal years (or artificial drainage). Andic Hapludox Aquic Petroferric Kandiudox EEEJ. Other Hapludox that have both: EEDB. Other Kandiudox 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 Kandiudox 2. In all horizons at a depth between 25 and 125 cm from EEDC. Other Kandiudox 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 Hapludox time in normal years (or artificial drainage). Aquic Lithic Kandiudox EEEK. Other Hapludox that have both: 1. 16 kg/m2 or more organic carbon between the mineral EEDD. Other Kandiudox that have a lithic contact within soil surface and a depth of 100 cm; and 125 cm of the mineral soil surface. Lithic Kandiudox 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 EEDE. Other Kandiudox that have, in one or more horizons 125 cm from the mineral soil surface. within 125 cm of the mineral soil surface, both: Humic Xanthic Hapludox 1. 5 percent or more (by volume) plinthite; and EEEL. Other Hapludox 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 Hapludox time in normal years (or artificial drainage). Plinthaquic Kandiudox EEEM. Other Hapludox that have, in all horizons at a depth between 25 and 125 cm from the mineral soil surface, more EEDF. Other Kandiudox that have 5 percent or more (by than 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 Kandiudox 2. A value, moist, of 3 or less. Rhodic Hapludox EEDG. Other Kandiudox that have, in one or more horizons within 125 cm of the mineral soil surface, redox depletions EEEN. Other Hapludox that have 50 percent or more hue of with a color value, moist, of 4 or more and chroma of 2 or less 7.5YR or yellower and a color value, moist, of 6 or more at a and also aquic conditions for some time in normal years (or depth between 25 and 125 cm from the mineral soil surface. artificial drainage). Xanthic Hapludox Aquic Kandiudox
EEEO. Other Hapludox. EEDH. Other Kandiudox that have, throughout one or more Typic Hapludox horizons with a total thickness of 18 cm or more within 75 cm Oxisols 243
of the mineral soil surface, a fine-earth fraction with both a EEAB. Other Sombriudox that have a lithic contact within bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 125 cm of the mineral soil surface. 1 retention, and Al plus /2 Fe percentages (by ammonium Lithic Sombriudox oxalate) totaling more than 1.0. Andic Kandiudox EEAC. Other Sombriudox that have 16 kg/m2 or more organic carbon between the mineral soil surface and a depth of EEDI. Other Kandiudox that have both: 100 cm. Humic Sombriudox 1. 16 kg/m2 or more organic carbon between the mineral soil surface and a depth of 100 cm; and EEAD. Other Sombriudox. 2. In all horizons at a depth between 25 and 125 cm from Typic Sombriudox the mineral soil surface, more than 50 percent colors that have both of the following: Ustox a. Hue of 2.5YR or redder; and Key to Great Groups b. A value, moist, of 3 or less. Humic Rhodic Kandiudox ECA. Ustox that have a sombric horizon within 150 cm of the mineral soil surface. EEDJ. Other Kandiudox that have both: Sombriustox, p. 247 1. 16 kg/m2 or more organic carbon between the mineral ECB. Other Ustox that have, in one or more subhorizons of soil surface and a depth of 100 cm; and an oxic or kandic horizon within 150 cm of the mineral soil 2. 50 percent or more hue of 7.5YR or yellower and a surface, an apparent ECEC of less than 1.50 cmol(+) per kg color value, moist, of 6 or more at a depth between 25 and clay and a pH value (1N KCl) of 5.0 or more. 125 cm from the mineral soil surface. Acrustox, p. 243 Humic Xanthic Kandiudox
ECC. Other Ustox that have a base saturation (by NH4OAc) EEDK. Other Kandiudox that have 16 kg/m2 or more organic of 35 percent or more in all horizons within 125 cm of the carbon between the mineral soil surface and a depth of 100 cm. mineral soil surface. Humic Kandiudox Eutrustox, p. 244
EEDL. Other Kandiudox that have, in all horizons at a depth ECD. Other Ustox that have a kandic horizon that between 25 and 125 cm from the mineral soil surface, more has its upper boundary within 150 cm of the mineral than 50 percent colors that have both of the following: soil surface. Kandiustox, p. 246 1. Hue of 2.5YR or redder; and 2. A value, moist, of 3 or less. ECE. Other Ustox. O Rhodic Kandiudox Haplustox, p. 245 X I EEDM. Other Kandiudox that have 50 percent or more hue Acrustox of 7.5YR or yellower and a color value, moist, of 6 or more at a depth between 25 and 125 cm from the mineral soil Key to Subgroups 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 ECBB. Other Acrustox that have a petroferric contact within 125 cm of the mineral soil surface. 125 cm of the mineral soil surface. Petroferric Sombriudox Petroferric Acrustox 244 Keys to Soil Taxonomy
ECBC. Other Acrustox that have, within 125 cm of the b. A value, moist, of 3 or less. mineral soil surface, both: Humic Rhodic Acrustox 1. A lithic contact; and ECBK. Other Acrustox that have both: 2. Redox depletions with a color value, moist, of 4 or more 1. 16 kg/m2 or more organic carbon between the mineral and chroma of 2 or less and also aquic conditions for some soil surface and a depth of 100 cm; and time in normal years (or artificial drainage). Aquic Lithic Acrustox 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 ECBD. Other Acrustox that have a lithic contact within 125 125 cm from the mineral soil surface. cm of the mineral soil surface. Humic Xanthic Acrustox Lithic Acrustox ECBL. Other Acrustox that have 16 kg/m2 or more organic ECBE. Other Acrustox that have, within 125 cm of the carbon between the mineral soil surface and a depth of 100 cm. mineral soil surface, both: Humic Acrustox 1. A delta pH (KCl pH minus 1:1 water pH) with a 0 or ECBM. Other Acrustox that have, in all horizons at a depth net positive charge in a layer 18 cm or more thick; and between 25 and 125 cm from the mineral soil surface, more 2. Redox depletions with a color value, moist, of 4 or more than 50 percent colors that have both of the following: and chroma of 2 or less and also aquic conditions for some 1. Hue of 2.5YR or redder; and time in normal years (or artificial drainage). Anionic Aquic Acrustox 2. A value, moist, of 3 or less. Rhodic Acrustox ECBF. Other Acrustox that have a delta pH (KCl pH minus 1:1 water pH) with a 0 or net positive charge in a layer 18 cm ECBN. Other Acrustox that have 50 percent or more hue of or more thick within 125 cm of the mineral soil surface. 7.5YR or yellower and a color value, moist, of 6 or more at a Anionic Acrustox depth between 25 and 125 cm from the mineral soil surface. Xanthic Acrustox ECBG. Other Acrustox that have 5 percent or more (by volume) plinthite in one or more horizons within 125 cm of the ECBO. Other Acrustox. mineral soil surface. Typic Acrustox Plinthic Acrustox Eutrustox ECBH. Other Acrustox that have, in one or more horizons within 125 cm of the mineral soil surface, redox depletions Key to Subgroups with a color value, moist, of 4 or more and chroma of 2 or less ECCA. Eutrustox that have, within 125 cm of the mineral and also aquic conditions for some time in normal years (or soil surface, both: artificial drainage). Aquic Acrustox 1. A petroferric contact; and 2. Redox depletions with a color value, moist, of 4 or more ECBI. Other Acrustox that have a base saturation (by and chroma of 2 or less and also aquic conditions for some NH OAc) of 35 percent or more in all horizons within 125 cm 4 time in normal years (or artificial drainage). of the mineral soil surface. Aquic Petroferric Eutrustox Eutric Acrustox ECCB. Other Eutrustox that have a petroferric contact within ECBJ. Other Acrustox that have both: 125 cm of the mineral soil surface. 1. 16 kg/m2 or more organic carbon between the mineral Petroferric Eutrustox soil surface and a depth of 100 cm; and ECCC. Other Eutrustox 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 Oxisols 245
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 Eutrustox ECCL. Other Eutrustox that have both: ECCD. Other Eutrustox 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 Eutrustox 2. 50 percent or more hue of 7.5YR or yellower and a ECCE. Other Eutrustox that have, in one or more horizons color value, moist, of 6 or more at a depth between 25 and within 125 cm of the mineral soil surface, both: 125 cm from the mineral soil surface. 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 Eutrustox ECCN. Other Eutrustox that have, in all horizons at a depth ECCF. Other Eutrustox that have 5 percent or more (by between 25 and 125 cm from the mineral soil surface, more volume) plinthite in one or more horizons within 125 cm of the than 50 percent colors that have both of the following: mineral soil surface. 1. Hue of 2.5YR or redder; and Plinthic Eutrustox 2. A value, moist, of 3 or less. ECCG. Other Eutrustox that have, in one or more horizons Rhodic Eutrustox 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 ECCO. Other Eutrustox that have 50 percent or more hue of 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 ECCP. Other Eutrustox. its 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 O soil surface, both: 2. An oxic horizon that has its lower boundary within 125 X cm of the mineral soil surface. 1. A petroferric contact; and I 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 ECCK. Other Eutrustox that have both: within 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 246 Keys to Soil Taxonomy
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 Lithic Haplustox have both of the following: a. Hue of 2.5YR or redder; and ECED. Other Haplustox that have a lithic contact within 125 cm of the mineral soil surface. b. A value, moist, of 3 or less. Lithic Haplustox Humic Rhodic Haplustox
ECEE. Other Haplustox that have, in one or more horizons ECEL. Other Haplustox that have both: within 125 cm of the mineral soil surface, both: 1. 16 kg/m2 or more organic carbon between the mineral 1. 5 percent or more (by volume) plinthite; and soil surface and a depth of 100 cm; and 2. Redox depletions with a color value, moist, of 4 or more 2. 50 percent or more hue of 7.5YR or yellower and a and chroma of 2 or less and also aquic conditions for some color value, moist, of 6 or more at a depth between 25 and time in normal years (or artificial drainage). 125 cm from the mineral soil surface. Plinthaquic Haplustox Humic Xanthic Haplustox
ECEF. Other Haplustox that have 5 percent or more (by ECEM. Other Haplustox that have 16 kg/m2 or more volume) plinthite in one or more horizons within 125 cm of the organic carbon between the mineral soil surface and a depth mineral soil surface. of 100 cm. Plinthic Haplustox Humic Haplustox
ECEG. Other Haplustox that have, within 125 cm of the ECEN. Other Haplustox that have, in all horizons at a depth mineral soil surface, both: between 25 and 125 cm from the mineral soil surface, more than 50 percent colors that have both of the following: 1. The lower boundary of the oxic horizon; and 1. Hue of 2.5YR or redder; and 2. Redox depletions with a color value, moist, of 4 or more and chroma of 2 or less and also aquic conditions for some 2. A value, moist, of 3 or less. time in normal years (or artificial drainage). Rhodic Haplustox Aqueptic Haplustox ECEO. Other Haplustox that have 50 percent or more hue of ECEH. Other Haplustox that have, in one or more horizons 7.5YR or yellower and a color value, moist, of 6 or more at a within 125 cm of the mineral soil surface, redox depletions depth between 25 and 125 cm from the mineral soil surface. with a color value, moist, of 4 or more and chroma of 2 or less Xanthic Haplustox and 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 Kandiustox or 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 Oxisols 247
ECDC. Other Kandiustox that have, within 125 cm of the 1. 16 kg/m2 or more organic carbon between the mineral mineral soil surface, both: soil surface and a depth of 100 cm; and 1. A lithic contact; and 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 2. Redox depletions with a color value, moist, of 4 or more 125 cm from the mineral soil surface. and chroma of 2 or less and also aquic conditions for some Humic Xanthic Kandiustox time in normal years (or artificial drainage). Aquic Lithic Kandiustox ECDJ. Other Kandiustox that have 16 kg/m2 or more organic carbon between the mineral soil surface and a depth of ECDD. Other Kandiustox that have a lithic contact within 100 cm. 125 cm of the mineral soil surface. Humic Kandiustox Lithic Kandiustox ECDK. Other Kandiustox that have, in all horizons at a ECDE. Other Kandiustox that have, in one or more horizons depth between 25 and 125 cm from the mineral soil surface, within 125 cm of the mineral soil surface, both: more than 50 percent colors that have both of the following: 1. 5 percent or more (by volume) plinthite; and 1. Hue of 2.5YR or redder; and 2. Redox depletions with a color value, moist, of 4 or more 2. A value, moist, of 3 or less. and chroma of 2 or less and also aquic conditions for some Rhodic Kandiustox time in normal years (or artificial drainage). Plinthaquic Kandiustox 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 ECDF. Other Kandiustox that have 5 percent or more (by depth between 25 and 125 cm from the mineral soil surface. volume) plinthite in one or more horizons within 125 cm of the Xanthic Kandiustox mineral soil surface. Plinthic Kandiustox ECDM. Other Kandiustox. Typic Kandiustox ECDG. Other Kandiustox that have, in one or more horizons 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 Sombriustox and also aquic conditions for some time in normal years (or Key to Subgroups artificial drainage). Aquic Kandiustox ECAA. Sombriustox that have a petroferric contact within 125 cm of the mineral soil surface. ECDH. Other Kandiustox that have both: Petroferric Sombriustox 1. 16 kg/m2 or more organic carbon between the mineral ECAB. Other Sombriustox that have a lithic contact within O soil surface and a depth of 100 cm; and 125 cm of the mineral soil surface. X 2. In all horizons at a depth between 25 and 125 cm from Lithic Sombriustox I the mineral soil surface, more than 50 percent colors that have both of the following: ECAC. Other Sombriustox that have 16 kg/m2 or more organic carbon between the mineral soil surface and a depth of a. Hue of 2.5YR or redder; and 100 cm. b. A value, moist, of 3 or less. Humic Sombriustox Humic Rhodic Kandiustox ECAD. Other Sombriustox. ECDI. Other Kandiustox that have both: Typic Sombriustox
249
CHAPTER 14 Spodosols1
Key to Suborders CA. Spodosols that have aquic conditions for some time in normal years (or artificial drainage) in one or more horizons within 50 cm of the mineral soil surface and have one or both of the following: 1. A histic epipedon; or 2. Within 50 cm of the mineral soil surface, redoximorphic features in an albic or a spodic horizon. Aquods, p. 249
CB. Other Spodosols that have a cryic soil temperature cm of the mineral soil surface in 50 percent or more of each regime. pedon. Cryods, p. 251 Placaquods, p. 251
CC. Other Spodosols that have 6.0 percent or more organic CAE. Other Aquods that have, in 90 percent or more of each carbon in a layer 10 cm or more thick within the spodic pedon, a cemented soil layer that has its upper boundary within horizon. 100 cm of the mineral soil surface. Humods, p. 253 Duraquods, p. 250
CD. Other Spodosols. CAF. Other Aquods that have episaturation. Orthods, p. 254 Epiaquods, p. 251
Aquods CAG. Other Aquods. Endoaquods, p. 251 Key to Great Groups
CAA. Aquods that have a cryic soil temperature regime. Alaquods Cryaquods, p. 250 Key to Subgroups S P CAB. Other Aquods that have less than 0.10 percent iron (by CABA. Alaquods that have a lithic contact within 50 cm of O ammonium oxalate) in 75 percent or more of the spodic the mineral soil surface. horizon. Lithic Alaquods Alaquods, p. 249 CABB. Other Alaquods that have, in 90 percent or more of CAC. Other Aquods that have a fragipan with its upper each pedon, a cemented soil layer that does not slake in water boundary within 100 cm of the mineral soil surface. after air drying and has its upper boundary within 100 cm of Fragiaquods, p. 251 the mineral soil surface. Duric Alaquods CAD. Other Aquods that have a placic horizon within 100 CABC. Other Alaquods that have a histic epipedon. Histic Alaquods 1 This chapter was rewritten in 1992 following recommendations of the International Committee on the Classification of Spodosols (ICOMOD), chaired initially by F. Ted Miller, then by Robert V. Rourke (since 1986). CABD. Other Alaquods that have both: 250 Keys to Soil Taxonomy
1. Within 200 cm of the mineral soil surface, an argillic CABL. Other Alaquods. or kandic horizon that has a base saturation of 35 percent Typic Alaquods or more (by sum of cations) in some part; and 2. A sandy or sandy-skeletal particle-size class Cryaquods throughout a layer extending from the mineral soil Key to Subgroups surface to the top of a spodic horizon at a depth of 75 to 125 cm. CAAA. Cryaquods that have a lithic contact within 50 cm of Alfic Arenic Alaquods the mineral soil surface. Lithic Cryaquods CABE. Other Alaquods that have both: CAAB. Other Cryaquods that have a placic horizon within 1. An argillic or kandic horizon within 200 cm of the 100 cm of the mineral soil surface in 50 percent or more of mineral soil surface; and each pedon. 2. A sandy or sandy-skeletal particle-size class throughout Placic Cryaquods a layer extending from the mineral soil surface to the top of a spodic horizon at a depth of 75 to 125 cm. CAAC. Other Cryaquods that have, in 90 percent or more of Arenic Ultic Alaquods each pedon, a cemented soil layer that does not slake in water after air drying and has its upper boundary within 100 cm of CABF. Other Alaquods that have both: the mineral soil surface. Duric Cryaquods 1. An umbric epipedon; and 2. A sandy or sandy-skeletal particle-size class CAAD. Other Cryaquods that have andic soil properties throughout a layer extending from the mineral soil throughout horizons that have a total thickness of 25 cm or surface to the top of a spodic horizon at a depth of 75 more within 75 cm either of the mineral soil surface or of the cm or more. top of an organic layer with andic soil properties, whichever is Arenic Umbric Alaquods shallower. Andic Cryaquods CABG. Other Alaquods that have a sandy or sandy-skeletal particle-size class throughout a layer extending from the CAAE. Other Cryaquods that have a spodic horizon less than mineral soil surface to the top of a spodic horizon at a depth of 10 cm thick in 50 percent or more of each pedon. 75 to 125 cm. Entic Cryaquods Arenic Alaquods CAAF. Other Cryaquods. CABH. Other Alaquods that have a sandy or sandy-skeletal Typic Cryaquods 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 or more. Duraquods Grossarenic Alaquods Key to Subgroups CABI. Other Alaquods that have, within 200 cm of the CAEA. Duraquods that have a histic epipedon. mineral soil surface, an argillic or kandic horizon that has a Histic Duraquods base saturation of 35 percent or more (by sum of cations) in some part. CAEB. Other Duraquods that have andic soil properties Alfic Alaquods throughout horizons that have a total thickness of 25 cm or more within 75 cm either of the mineral soil surface or of the CABJ. Other Alaquods that have an argillic or kandic top of an organic layer with andic soil properties, whichever is horizon within 200 cm of the mineral soil surface. shallower. Ultic Alaquods Andic Duraquods
CABK. Other Alaquods that have an ochric epipedon. CAEC. Other Duraquods. Aeric Alaquods Typic Duraquods Spodosols 251
Endoaquods CAFE. Other Epiaquods that have an argillic or kandic horizon within 200 cm of the mineral soil surface. Key to Subgroups Ultic Epiaquods CAGA. Endoaquods that have a lithic contact within 50 cm CAFF. Other Epiaquods that have an umbric epipedon. of the mineral soil surface. Umbric Epiaquods Lithic Endoaquods CAFG. Other Epiaquods. CAGB. Other Endoaquods that have a histic epipedon. Typic Epiaquods Histic Endoaquods
CAGC. Other Endoaquods that have andic soil properties Fragiaquods throughout horizons that have a total thickness of 25 cm or Key to Subgroups more within 75 cm either of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is CACA. Fragiaquods that have a histic epipedon. shallower. Histic Fragiaquods Andic Endoaquods CACB. Other Fragiaquods that have a surface horizon 30 cm CAGD. Other Endoaquods that have an argillic or kandic or more thick that meets all of the requirements for a plaggen horizon within 200 cm of the mineral soil surface. epipedon except thickness. Argic Endoaquods Plagganthreptic Fragiaquods CACC. Other Fragiaquods that have an argillic or kandic CAGE. Other Endoaquods that have an umbric epipedon. horizon within 200 cm of the mineral soil surface. Umbric Endoaquods Argic Fragiaquods
CAGF. Other Endoaquods. CACD. Other Fragiaquods. Typic Endoaquods Typic Fragiaquods
Epiaquods Placaquods Key to Subgroups Key to Subgroups CADA. Placaquods that have andic soil properties CAFA. Epiaquods that have a lithic contact within 50 cm of throughout horizons that have a total thickness of 25 cm or the mineral soil surface. more within 75 cm either of the mineral soil surface or of the Lithic Epiaquods top of an organic layer with andic soil properties, whichever is shallower. CAFB. Other Epiaquods that have a histic epipedon. Andic Placaquods Histic Epiaquods CADB. Other Placaquods. CAFC. Other Epiaquods that have andic soil properties Typic Placaquods S throughout horizons that have a total thickness of 25 cm or P more within 75 cm either of the mineral soil surface or of the Cryods O top of an organic layer with andic soil properties, whichever is shallower. Key to Great Groups Andic Epiaquods CBA. Cryods that have a placic horizon within 100 cm of CAFD. Other Epiaquods that have, within 200 cm of the the mineral soil surface in 50 percent or more of each pedon. mineral soil surface, an argillic or kandic horizon that has a Placocryods, p. 253 base saturation of 35 percent or more (by sum of cations) in some part. CBB. Other Cryods that have, in 90 percent or more of each Alfic Epiaquods pedon, a cemented soil layer that does not slake in water after 252 Keys to Soil Taxonomy
air drying and has its upper boundary within 100 cm of the Haplocryods mineral soil surface. Duricryods, p. 252 Key to Subgroups CBDA. Haplocryods that have a lithic contact within 50 cm CBC. Other Cryods that have 6.0 percent or more organic of the mineral soil surface. carbon throughout a layer 10 cm or more thick within the Lithic Haplocryods spodic horizon. Humicryods, p. 252 CBDB. Other Haplocryods that have both: CBD. Other Cryods. 1. Redoximorphic features in one or more horizons Haplocryods, p. 252 within 75 cm of the mineral soil surface and also aquic conditions for some time in normal years (or artificial Duricryods drainage); and 2. Andic soil properties throughout horizons that have a Key to Subgroups total thickness of 25 cm or more within 75 cm either of the CBBA. Duricryods 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 Haplocryods within 75 cm of the mineral soil surface and also aquic conditions for some time in normal years (or artificial CBDC. Other Haplocryods 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 total thickness of 25 cm or more within 75 cm either of the top 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 Haplocryods Aquandic Duricryods CBDD. Other Haplocryods that have redoximorphic features CBBB. Other Duricryods that have andic soil properties in one or more horizons within 75 cm of the mineral soil throughout horizons that have a total thickness of 25 cm or surface and also aquic conditions for some time in normal more within 75 cm either of the mineral soil surface or of the years (or artificial drainage). top of an organic layer with andic soil properties, whichever is Aquic Haplocryods shallower. Andic Duricryods CBDE. Other Haplocryods that are saturated with water in one or more layers within 100 cm of the mineral soil surface in CBBC. Other Duricryods that have redoximorphic features in normal years for either or both: one or more horizons within 75 cm of the mineral soil surface 1. 20 or more consecutive days; or and also aquic conditions for some time in normal years (or artificial drainage). 2. 30 or more cumulative days. Aquic Duricryods Oxyaquic Haplocryods
CBBD. Other Duricryods that are saturated with water in one CBDF. Other Haplocryods that have 1.1 percent or or more layers within 100 cm of the mineral soil surface in less organic carbon in the upper 10 cm of the spodic normal years for either or both: horizon. Entic Haplocryods 1. 20 or more consecutive days; or CBDG. Other Haplocryods. 2. 30 or more cumulative days. Typic Haplocryods Oxyaquic Duricryods
CBBE. Other Duricryods that have 6.0 percent or more Humicryods organic carbon throughout a layer 10 cm or more thick within Key to Subgroups the spodic horizon. Humic Duricryods CBCA. Humicryods that have a lithic contact within 50 cm CBBF. Other Duricryods. of the mineral soil surface. Typic Duricryods Lithic Humicryods Spodosols 253
CBCB. Other Humicryods that have both: Humods 1. Redoximorphic features in one or more horizons within 75 cm of the mineral soil surface and also aquic Key to Great Groups conditions for some time in normal years (or artificial CCA. Humods that have a placic horizon within 100 cm drainage); and of the mineral soil surface in 50 percent or more of each 2. Andic soil properties throughout horizons that have a pedon. total thickness of 25 cm or more within 75 cm either of the Placohumods, p. 254 mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. CCB. Other Humods that have, in 90 percent or more of each Aquandic Humicryods pedon, a cemented soil layer that does not slake in water after air drying and has its upper boundary within 100 cm of the CBCC. Other Humicryods that have andic soil properties mineral soil surface. throughout horizons that have a total thickness of 25 cm or Durihumods, p. 253 more within 75 cm either of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is CCC. Other Humods that have a fragipan with its upper shallower. boundary within 100 cm of the mineral soil surface. Andic Humicryods Fragihumods, p. 253
CBCD. Other Humicryods that have redoximorphic features CCD. Other Humods. in one or more horizons within 75 cm of the mineral soil Haplohumods, p. 253 surface and also aquic conditions for some time in normal years (or artificial drainage). Aquic Humicryods Durihumods Key to Subgroups CBCE. Other Humicryods that are saturated with water in one or more layers within 100 cm of the mineral soil surface in CCBA. Durihumods that have andic soil properties normal years for either or both: throughout horizons that have a total thickness of 25 cm or more within 75 cm either of the mineral soil surface or of the 1. 20 or more consecutive days; or top of an organic layer with andic soil properties, whichever is 2. 30 or more cumulative days. shallower. Oxyaquic Humicryods Andic Durihumods
CBCF. Other Humicryods. CCBB. Other Durihumods. Typic Humicryods Typic Durihumods
Placocryods Fragihumods Key to Subgroups Key to Subgroups S CBAA. Placocryods that have andic soil properties CCCA. All Fragihumods (provisionally). P throughout horizons that have a total thickness of 25 cm or Typic Fragihumods O more within 75 cm either of the mineral soil surface or of the top of an organic layer with andic soil properties, whichever is shallower. Haplohumods Andic Placocryods Key to Subgroups CBAB. Other Placocryods that have 6.0 percent or more CCDA. Haplohumods that have a lithic contact within 50 cm organic carbon in a layer 10 cm or more thick within the of the mineral soil surface. spodic horizon. Lithic Haplohumods Humic Placocryods CCDB. Other Haplohumods that have andic soil properties CBAC. Other Placocryods. throughout horizons that have a total thickness of 25 cm or Typic Placocryods more within 75 cm either of the mineral soil surface or of the 254 Keys to Soil Taxonomy
top of an organic layer with andic soil properties, whichever is Alorthods shallower. Andic Haplohumods Key to Subgroups CDDA. Alorthods that are saturated with water in one or CCDC. Other Haplohumods that have a surface horizon 30 more layers within 100 cm of the mineral soil surface in cm or more thick that meets all of the requirements for a normal years for either or both: plaggen epipedon except thickness. Plagganthreptic Haplohumods 1. 20 or more consecutive days; or 2. 30 or more cumulative days. CCDD. Other Haplohumods. Oxyaquic Alorthods Typic Haplohumods CDDB. Other Alorthods that have both: Placohumods 1. A sandy or sandy-skeletal particle-size class throughout a layer extending from the mineral soil surface to the top of Key to Subgroups a spodic horizon at a depth of 75 to 125 cm; and CCAA. Placohumods that have andic soil properties 2. An argillic or kandic horizon below the spodic throughout horizons that have a total thickness of 25 cm or horizon. more within 75 cm either of the mineral soil surface or of the Arenic Ultic Alorthods top of an organic layer with andic soil properties, whichever is shallower. CDDC. Other Alorthods that have a sandy or sandy-skeletal Andic Placohumods particle-size class throughout a layer extending from the mineral soil surface to the top of a spodic horizon at a depth of CCAB. Other Placohumods. 75 to 125 cm. Typic Placohumods Arenic Alorthods
Orthods CDDD. Other Alorthods that have both: 1. A sandy or sandy-skeletal particle-size class throughout Key to Great Groups a layer extending from the mineral soil surface to the top of a spodic horizon at a depth of 125 cm or more; and CDA. Orthods that have, in 50 percent or more of each pedon, a placic horizon within 100 cm of the mineral soil 2. In 10 percent or more of each pedon, less than 3.0 surface. percent organic carbon in the upper 2 cm of the spodic Placorthods, p. 257 horizon. Entic Grossarenic Alorthods CDB. Other Orthods that have, in 90 percent or more of each pedon, a cemented soil layer that does not slake in water after CDDE. Other Alorthods that have, in 10 percent or more of air drying and has its upper boundary within 100 cm of the each pedon, less than 3.0 percent organic carbon in the upper 2 mineral soil surface. cm of the spodic horizon. Durorthods, p. 255 Entic Alorthods
CDC. Other Orthods that have a fragipan with its upper CDDF. Other Alorthods that have a sandy or sandy-skeletal boundary within 100 cm of the mineral soil surface. particle-size class throughout a layer extending from the Fragiorthods, p. 255 mineral soil surface to the top of a spodic horizon at a depth of 125 cm or more. CDD. Other Orthods that have less than 0.10 percent iron (by Grossarenic Alorthods ammonium oxalate) in 75 percent or more of the spodic horizon. Alorthods, p. 254 CDDG. Other Alorthods that have a surface horizon 30 cm or more thick that meets all of the requirements for a plaggen CDE. Other Orthods. epipedon except thickness. Haplorthods, p. 255 Plagganthreptic Alorthods Spodosols 255
CDDH. Other Alorthods that have, within 200 cm of the 2. 30 or more cumulative days. mineral soil surface, an argillic or kandic horizon that has a Oxyaquic Fragiorthods base saturation of 35 percent or more (by sum of cations) in some part. CDCD. Other Fragiorthods that have a surface horizon 30 Alfic Alorthods cm or more thick that meets all of the requirements for a plaggen epipedon except thickness. CDDI. Other Alorthods that have an argillic or kandic Plagganthreptic Fragiorthods horizon within 200 cm of the mineral soil surface. Ultic Alorthods CDCE. Other Fragiorthods that have, within 200 cm of the mineral soil surface, an argillic or kandic horizon that has a CDDJ. Other Alorthods. base saturation of 35 percent or more (by sum of cations) in Typic Alorthods some part. Alfic Fragiorthods Durorthods CDCF. Other Fragiorthods that have an argillic or kandic Key to Subgroups horizon within 200 cm of the mineral soil surface. Ultic Fragiorthods CDBA. Durorthods that have andic soil properties throughout horizons that have a total thickness of 25 cm or CDCG. Other Fragiorthods that have a spodic horizon that more within 75 cm either of the mineral soil surface or of the has one of the following: top of an organic layer with andic soil properties, whichever is shallower. 1. A texture of very fine sand, loamy very fine sand, or Andic Durorthods finer; and a. A thickness of 10 cm or less; and CDBB. Other Durorthods. Typic Durorthods b. A weighted average of less than 1.2 percent organic carbon; and Fragiorthods c. Within the upper 7.5 cm, either or both a moist color value or chroma of 4 or more (crushed and smoothed Key to Subgroups sample); or CDCA. Fragiorthods that have redoximorphic features in one 2. A texture of loamy fine sand, fine sand, or coarser and or more horizons within 75 cm of the mineral soil surface and either or both a moist color value or chroma of 4 or more also aquic conditions for some time in normal years (or (crushed and smoothed sample) in the upper 2.5 cm. artificial drainage). Entic Fragiorthods Aquic Fragiorthods CDCH. Other Fragiorthods. CDCB. Other Fragiorthods that: Typic Fragiorthods 1. Are saturated with water in one or more layers within 100 cm of the mineral soil surface in normal Haplorthods S years for either or both: P Key to Subgroups O a. 20 or more consecutive days; or CDEA. Haplorthods that have a lithic contact within 50 cm b. 30 or more cumulative days; and of the mineral soil surface; and either 2. Have, within 200 cm of the mineral soil surface, an 1. A spodic horizon with a texture of very fine sand, argillic or kandic horizon that has a base saturation of 35 loamy very fine sand, or finer; and percent or more (by sum of cations) in some part. a. A thickness of 10 cm or less; and Alfic Oxyaquic Fragiorthods b. A weighted average of less than 1.2 percent organic CDCC. Other Fragiorthods that are saturated with water in carbon; and one or more layers within 100 cm of the mineral soil surface in c. Within the upper 7.5 cm, either or both a moist color normal years for either or both: value or chroma of 4 or more (crushed and smoothed 1. 20 or more consecutive days; or sample); or 256 Keys to Soil Taxonomy
2. A spodic horizon with a texture of loamy fine sand, fine chroma of 4 or more (crushed and smoothed sample) in the sand, or coarser and either or both a moist color value or upper 2.5 cm. chroma of 4 or more (crushed and smoothed sample) in the Aquentic Haplorthods upper 2.5 cm. Entic Lithic Haplorthods CDEF. Other Haplorthods that have redoximorphic features in one or more horizons within 75 cm of the mineral soil CDEB. Other Haplorthods that have a lithic contact within surface and also aquic conditions for some time in normal 50 cm of the mineral soil surface. years (or artificial drainage). Lithic Haplorthods Aquic Haplorthods
CDEC. Other Haplorthods that have both: CDEG. Other Haplorthods that have: 1. Fragic soil properties: 1. Within 200 cm of the mineral soil surface, an argillic or kandic horizon that has a base saturation a. In 30 percent or more of the volume of a layer 15 cm of 35 percent or more (by sum of cations) in some part; or more thick that has its upper boundary within 100 cm and of the mineral soil surface; or 2. Saturation with water in one or more layers within 100 b. In 60 percent or more of the volume of a layer 15 cm cm of the mineral soil surface in normal years for either or or more thick; and both: 2. Redoximorphic features in one or more horizons a. 20 or more consecutive days; or within 75 cm of the mineral soil surface and also aquic conditions for some time in normal years (or artificial b. 30 or more cumulative days. drainage). Alfic Oxyaquic Haplorthods Fragiaquic Haplorthods CDEH. Other Haplorthods that have: CDED. Other Haplorthods that have both: 1. Within 200 cm of the mineral soil surface, an argillic or 1. Redoximorphic features in one or more horizons kandic horizon; and within 75 cm of the mineral soil surface and also aquic 2. Saturation with water in one or more layers within 100 conditions for some time in normal years (or artificial cm of the mineral soil surface in normal years for either or drainage); and both: 2. Within 200 cm of the mineral soil surface, an argillic or a. 20 or more consecutive days; or kandic horizon that has a base saturation of 35 percent or more (by sum of cations) in some part. b. 30 or more cumulative days. Aqualfic Haplorthods Oxyaquic Ultic Haplorthods
CDEI. Other Haplorthods that have fragic soil properties: CDEE. Other Haplorthods that have redoximorphic features in one or more horizons within 75 cm of the mineral soil 1. In 30 percent or more of the volume of a layer 15 cm or surface and also aquic conditions for some time in normal more thick that has its upper boundary within 100 cm of the years (or artificial drainage); and either mineral soil surface; or 1. A spodic horizon with a texture of very fine sand, 2. In 60 percent or more of the volume of a layer 15 cm or loamy very fine sand, or finer; and more thick. Fragic Haplorthods a. A thickness of 10 cm or less; and b. A weighted average of less than 1.2 percent organic CDEJ. Other Haplorthods that, below the spodic horizon but carbon; and not below an argillic horizon, have lamellae (two or more) within 200 cm of the mineral soil surface. c. Within the upper 7.5 cm, either or both a moist color Lamellic Haplorthods value or chroma of 4 or more (crushed and smoothed sample); or CDEK. Other Haplorthods that are saturated with water in 2. A spodic horizon with a texture of loamy fine sand, fine one or more layers within 100 cm of the mineral soil surface in sand, or coarser and either or both a moist color value or normal years for either or both: Spodosols 257
1. 20 or more consecutive days; or 1. A texture of very fine sand, loamy very fine sand, or finer; and 2. 30 or more cumulative days. Oxyaquic Haplorthods a. A thickness of 10 cm or less; and b. A weighted average of less than 1.2 percent organic CDEL. Other Haplorthods that have andic soil properties carbon; and throughout horizons that have a total thickness of 25 cm or more within 75 cm either of the mineral soil surface or of the c. Within the upper 7.5 cm, either or both a moist color top of an organic layer with andic soil properties, whichever is value or chroma of 4 or more (crushed and smoothed shallower. sample); or Andic Haplorthods 2. A texture of loamy fine sand, fine sand, or coarser and either or both a moist color value or chroma of 4 CDEM. Other Haplorthods that have, within 200 cm of the or more (crushed and smoothed sample) in the upper mineral soil surface, an argillic or kandic horizon that has a 2.5 cm. base saturation of 35 percent or more (by sum of cations) in Entic Haplorthods some part. Alfic Haplorthods CDEP. Other Haplorthods. Typic Haplorthods CDEN. Other Haplorthods that have an argillic or kandic horizon within 200 cm of the mineral soil surface. Placorthods Ultic Haplorthods Key to Subgroups CDEO. Other Haplorthods that have a spodic horizon that CDAA. All Placorthods (provisionally). has one of the following: Typic Placorthods
S P O
259
CHAPTER 15 Ultisols
Key to Suborders HA. Ultisols that have aquic conditions for some time in normal years (or artificial drainage) in one or more horizons within 50 cm of the mineral soil surface and one or both of the following: 1. Redoximorphic features in all layers between either the lower boundary of an Ap horizon or a depth of 25 cm from the mineral soil surface, whichever is deeper, and a depth of 40 cm and one of the following within the upper 12.5 cm of the argillic or kandic horizon: a. Redox concentrations and 50 percent or more redox Aquults depletions with chroma of 2 or less either on faces of peds or in the matrix; or Key to Great Groups b. 50 percent or more redox depletions with chroma of HAA. Aquults that have one or more horizons within 150 1 or less either on faces of peds or in the matrix; or cm of the mineral soil surface in which plinthite either forms c. Distinct or prominent redox concentrations and 50 a continuous phase or constitutes one-half or more of the percent or more hue of 2.5Y or 5Y in the matrix and also volume. a thermic, isothermic, or warmer soil temperature Plinthaquults, p. 263 regime; or HAB. Other Aquults that have a fragipan with an upper 2. Within 50 cm of the mineral soil surface, enough active boundary within 100 cm of the mineral soil surface. ferrous iron to give a positive reaction to alpha,alpha- Fragiaquults, p. 261 dipyridyl at a time when the soil is not being irrigated. Aquults, p. 259 HAC. Other Aquults that have an abrupt textural change between the ochric epipedon or albic horizon and the argillic or HB. Other Ultisols that have one or both of the following: kandic horizon and have 0.4 cm/hr or slower (low or very low) 1. 0.9 percent (by weighted average) or more organic saturated hydraulic conductivity in the argillic or kandic carbon in the upper 15 cm of the argillic or kandic horizon; horizon. or Albaquults, p. 260 2. 12 kg/m2 or more organic carbon between the mineral HAD. Other Aquults that: U soil surface and a depth of 100 cm. L Humults, p. 263 1. Do not have a densic, lithic, paralithic, or petroferric T contact within 150 cm of the mineral soil surface; and HC. Other Ultisols that have a udic moisture regime. 2. Have a kandic horizon; and Udults, p. 266 3. Within 150 cm of the mineral soil surface, either: HD. Other Ultisols that have an ustic moisture regime. a. With increasing depth, do not have a clay decrease of Ustults, p. 274 20 percent or more (relative) from the maximum clay content; or HE. Other Ultisols. Xerults, p. 278 b. Have 5 percent or more (by volume) clay depletions 260 Keys to Soil Taxonomy
on faces of peds in the layer that has a 20 percent lower the A or Ap horizon or a depth of 25 cm from the mineral soil clay content and, below that layer, a clay increase of 3 surface, whichever is deeper, and a depth of 75 cm. percent or more (absolute) in the fine-earth fraction. Aeric Albaquults Kandiaquults, p. 261 HACD. Other Albaquults. HAE. Other Aquults that have a kandic horizon. Typic Albaquults Kanhaplaquults, p. 262 Endoaquults HAF. Other Aquults that: Key to Subgroups 1. Do not have a densic, lithic, paralithic, or petroferric contact within 150 cm of the mineral soil surface; and HAIA. Endoaquults that have a sandy or sandy-skeletal particle-size class throughout a layer extending from the 2. Within 150 cm of the mineral soil surface, either: mineral soil surface to the top of an argillic horizon at a depth a. With increasing depth, do not have a clay decrease of of 50 to 100 cm. 20 percent or more (relative) from the maximum clay Arenic Endoaquults content; or HAIB. Other Endoaquults that have a sandy or sandy-skeletal b. Have 5 percent or more (by volume) clay depletions particle-size class throughout a layer extending from the on faces of peds in the layer that has a 20 percent lower mineral soil surface to the top of an argillic horizon at a depth clay content and, below that layer, a clay increase of 3 of 100 cm or more. percent or more (absolute) in the fine-earth fraction. Grossarenic Endoaquults Paleaquults, p. 262 HAIC. Other Endoaquults that have 50 percent or more HAG. Other Aquults that have an umbric or mollic epipedon. chroma of 3 or more in one or more horizons between either Umbraquults, p. 263 the A or Ap horizon or a depth of 25 cm from the mineral soil surface, whichever is deeper, and a depth of 75 cm. HAH. Other Aquults that have episaturation. Aeric Endoaquults Epiaquults, p. 260 HAID. Other Endoaquults. HAI. Other Aquults. Typic Endoaquults Endoaquults, p. 260 Epiaquults Albaquults Key to Subgroups Key to Subgroups HAHA. Epiaquults that have one or both of the following: HACA. Albaquults that have one or both of the following: 1. Cracks within 125 cm of the mineral soil surface that 1. Cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or more for some time in normal years, and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral that has its upper 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 2. A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower. densic, lithic, or paralithic contact, whichever is shallower. Vertic Epiaquults Vertic Albaquults HAHB. Other Epiaquults that have: HACB. Other Albaquults that have a kandic horizon. 1. Fragic soil properties: Kandic Albaquults a. In 30 percent or more of the volume of a layer 15 cm HACC. Other Albaquults that have 50 percent or more or more thick that has its upper boundary within 100 cm chroma of 3 or more in one or more horizons between either of the mineral soil surface; or Ultisols 261
b. In 60 percent or more of the volume of a layer 15 cm HABC. Other Fragiaquults that have a mollic or umbric or more thick; and epipedon. Umbric Fragiaquults 2. 50 percent or more chroma of 3 or more in one or more horizons between either the A or Ap horizon or a depth of HABD. Other Fragiaquults. 25 cm from the mineral soil surface, whichever is deeper, Typic Fragiaquults and a depth of 75 cm. Aeric Fragic Epiaquults Kandiaquults HAHC. Other Epiaquults that have a sandy or sandy-skeletal Key to Subgroups particle-size class throughout a layer extending from the mineral soil surface to the top of an argillic horizon at a depth HADA. Kandiaquults that have an ECEC of 1.5 cmol(+)/kg of 50 to 100 cm. clay or less (sum of bases extracted with 1N NH4OAc pH 7, Arenic Epiaquults plus 1N KCl-extractable Al) in one or more horizons within 150 cm of the mineral soil surface. HAHD. Other Epiaquults that have a sandy or sandy-skeletal Acraquoxic Kandiaquults particle-size class throughout a layer extending from the mineral soil surface to the top of an argillic horizon at a depth HADB. Other Kandiaquults that have both: of 100 cm or more. 1. A sandy or sandy-skeletal particle-size class throughout Grossarenic Epiaquults a layer extending from the mineral soil surface to the top of a kandic horizon at a depth of 50 to 100 cm; and HAHE. Other Epiaquults that have fragic soil properties: 2. 5 percent or more (by volume) plinthite in one or more 1. In 30 percent or more of the volume of a layer 15 cm or horizons within 150 cm of the mineral soil surface. more thick that has its upper boundary within 100 cm of the Arenic Plinthic Kandiaquults mineral soil surface; or 2. In 60 percent or more of the volume of a layer 15 cm or HADC. Other Kandiaquults that: more thick. 1. Have a mollic or umbric epipedon; and Fragic Epiaquults 2. Have a sandy or sandy-skeletal particle-size class HAHF. Other Epiaquults that have 50 percent or more throughout a layer extending from the mineral soil surface chroma of 3 or more in one or more horizons between either to the top of a kandic horizon at a depth of 50 to 100 cm. the A or Ap horizon or a depth of 25 cm from the mineral soil Arenic Umbric Kandiaquults surface, whichever is deeper, and a depth of 75 cm. Aeric Epiaquults HADD. Other Kandiaquults that have a sandy or sandy- skeletal particle-size class throughout a layer extending from HAHG. Other Epiaquults. the mineral soil surface to the top of a kandic horizon at a Typic Epiaquults depth of 50 to 100 cm. Arenic Kandiaquults
Fragiaquults HADE. Other Kandiaquults that have a sandy or sandy- skeletal particle-size class throughout a layer extending from Key to Subgroups the mineral soil surface to the top of a kandic horizon at a HABA. Fragiaquults that have 50 percent or more chroma of depth of 100 cm or more. U 3 or more in one or more horizons between either the A or Ap Grossarenic Kandiaquults L horizon or a depth of 25 cm from the mineral soil surface, T whichever is deeper, and the fragipan. HADF. Other Kandiaquults that have 5 percent or more (by Aeric Fragiaquults volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. HABB. Other Fragiaquults that have 5 percent or more (by Plinthic Kandiaquults volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. HADG. Other Kandiaquults that have 50 percent or more Plinthic Fragiaquults chroma of 3 or more in one or more horizons between either 262 Keys to Soil Taxonomy
the A or Ap horizon or a depth of 25 cm from the mineral soil the A or Ap horizon or a depth of 25 cm from the mineral soil surface, whichever is deeper, and a depth of 75 cm. surface, whichever is deeper, and a depth of 75 cm. Aeric Kandiaquults Aeric Kanhaplaquults
HADH. Other Kandiaquults that have a mollic or umbric HAEE. Other Kanhaplaquults that have a mollic or umbric epipedon. epipedon. Umbric Kandiaquults Umbric Kanhaplaquults
HADI. Other Kandiaquults. HAEF. Other Kanhaplaquults. Typic Kandiaquults Typic Kanhaplaquults
Kanhaplaquults Paleaquults Key to Subgroups Key to Subgroups HAFA. Paleaquults that have one or both of the following: HAEA. Kanhaplaquults that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm 1. Cracks within 125 cm of the mineral soil surface that of the mineral soil surface, one or more of the following: are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or 1. A fine-earth fraction with both a bulk density of 1.0 wedge-shaped aggregates in a layer 15 cm or more thick g/cm3 or less, measured at 33 kPa water retention, and Al 1 that has its upper boundary within 125 cm of the mineral plus /2 Fe percentages (by ammonium oxalate) totaling soil surface; or more 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 than 2.0 mm, of which more than 66 percent is cinders, densic, lithic, or paralithic contact, whichever is shallower. pumice, and pumicelike fragments; or Vertic Paleaquults 3. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and HAFB. Other Paleaquults that have both: a. In the 0.02 to 2.0 mm fraction, 5 percent or more 1. A sandy or sandy-skeletal particle-size class throughout volcanic glass; and a layer extending from the mineral soil surface to the top of
1 an argillic horizon at a depth of 50 to 100 cm; and b. [(Al plus /2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is 2. 5 percent or more (by volume) plinthite in one or more equal to 30 or more. horizons within 150 cm of the mineral soil surface. Aquandic Kanhaplaquults Arenic Plinthic Paleaquults
HAEB. Other Kanhaplaquults that have 5 percent or more HAFC. Other Paleaquults that: (by volume) plinthite in one or more horizons within 150 cm of 1. Have a mollic or umbric epipedon; and the mineral soil surface. Plinthic Kanhaplaquults 2. Have a sandy or sandy-skeletal particle-size class throughout a layer extending from the mineral soil surface HAEC. Other Kanhaplaquults that: to the top of an argillic horizon at a depth of 50 to 100 cm. Arenic Umbric Paleaquults 1. Have a mollic or umbric epipedon; and 2. Have 50 percent or more chroma of 3 or more in one or HAFD. Other Paleaquults that have a sandy or sandy-skeletal more horizons between either the A or Ap horizon or a particle-size class throughout a layer extending from the depth of 25 cm from the mineral soil surface, whichever is mineral soil surface to the top of an argillic horizon at a depth deeper, and a depth of 75 cm. of 50 to 100 cm. Aeric Umbric Kanhaplaquults Arenic Paleaquults
HAED. Other Kanhaplaquults that have 50 percent or more HAFE. Other Paleaquults that have a sandy or sandy-skeletal chroma of 3 or more in one or more horizons between either particle-size class throughout a layer extending from the Ultisols 263
mineral soil surface to the top of an argillic horizon at a depth HBB. Other Humults that have one or more horizons within of 100 cm or more. 150 cm of the mineral soil surface in which plinthite either Grossarenic Paleaquults forms a continuous phase or constitutes one-half or more of the volume. HAFF. Other Paleaquults that have 5 percent or more (by Plinthohumults, p. 266 volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. HBC. Other Humults that: Plinthic Paleaquults 1. Do not have a densic, lithic, paralithic, or petroferric contact within 150 cm of the mineral soil surface; and HAFG. Other Paleaquults that have 50 percent or more chroma of 3 or more in one or more horizons between either 2. Have a kandic horizon; and the A or Ap horizon or a depth of 25 cm from the mineral soil 3. Within 150 cm of the mineral soil surface, either: surface, whichever is deeper, and a depth of 75 cm. Aeric Paleaquults a. With increasing depth, do not have a clay decrease of 20 percent or more (relative) from the maximum clay HAFH. Other Paleaquults that have a mollic or umbric content; or epipedon. b. Have 5 percent or more (by volume) clay depletions Umbric Paleaquults on faces of peds in the layer that has a 20 percent lower clay content and, below that layer, a clay increase of 3 HAFI. Other Paleaquults. percent or more (absolute) in the fine-earth fraction. Typic Paleaquults Kandihumults, p. 264
Plinthaquults HBD. Other Humults that have a kandic horizon. Kanhaplohumults, p. 265 Key to Subgroups HAAA. Plinthaquults that have a kandic horizon or a CEC HBE. Other Humults that: (by 1N NH OAc pH 7) of less than 24 cmol(+)/kg clay in 50 4 1. Do not have a densic, lithic, paralithic, or petroferric percent or more (by volume) of the argillic horizon if less than contact within 150 cm of the mineral soil surface; and 100 cm thick or of its upper 100 cm. Kandic Plinthaquults 2. Within 150 cm of the mineral soil surface, either: 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 Umbraquults b. Have 5 percent or more (by volume) clay depletions on faces of peds in the layer that has a 20 percent lower Key to Subgroups clay content and, below that layer, a clay increase of 3 percent or more (absolute) in the fine-earth fraction. HAGA. Umbraquults that have 5 to 50 percent (by volume) Palehumults, p. 265 plinthite in one or more horizons within 150 cm of the mineral soil surface. HBF. Other Humults. Plinthic Umbraquults Haplohumults, p. 263 U HAGB. Other Umbraquults. Haplohumults L Typic Umbraquults T 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. 266 1. In one or more subhorizons within the upper 25 cm of 264 Keys to Soil Taxonomy
the argillic horizon, redox depletions with a color value, Kandihumults moist, of 4 or more and chroma of 2 or less, accompanied by redox concentrations, and also aquic conditions for some Key to Subgroups time in normal years (or artificial drainage); and HBCA. Kandihumults that meet all of the following: 2. Throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, 1. Throughout one or more horizons with a total thickness a fine-earth fraction with both a bulk density of 1.0 g/cm3 of 18 cm or more within 75 cm of the mineral soil surface, or less, measured at 33 kPa water retention, and Al plus have a fine-earth fraction with both a bulk density of 1.0 1 3 /2 Fe percentages (by ammonium oxalate) totaling more g/cm or less, measured at 33 kPa water retention, and Al 1 than 1.0. plus /2 Fe percentages (by ammonium oxalate) totaling Aquandic Haplohumults more than 1.0; and 2. In one or more horizons within 75 cm of the mineral HBFC. Other Haplohumults that have, in one or more soil surface, have redox concentrations, a color value, moist, subhorizons within the upper 25 cm of the argillic horizon, of 4 or more, and hue that is 10YR or yellower and becomes redox depletions with a color value, moist, of 4 or more and redder with increasing depth within 100 cm of the mineral chroma of 2 or less, accompanied by redox concentrations and soil surface; and by aquic conditions for some time in normal years (or artificial drainage). 3. In normal years are saturated with water in one or more Aquic Haplohumults layers within 100 cm of the mineral soil surface for either or both: HBFD. Other Haplohumults that have, throughout one or a. 20 or more consecutive days; 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 b. 30 or more cumulative days. both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa Andic Ombroaquic Kandihumults 1 water retention, and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. HBCB. Other Kandihumults that have both: Andic Haplohumults 1. Throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a HBFE. Other Haplohumults that have 5 percent or more (by fine-earth fraction with both a bulk density of 1.0 g/cm3 or volume) plinthite in one or more horizons within 150 cm of the 1 less, measured at 33 kPa water retention, and Al plus /2 Fe mineral soil surface. percentages (by ammonium oxalate) totaling more than 1.0; Plinthic Haplohumults and HBFF. Other Haplohumults that in normal years are 2. An ustic moisture regime. saturated with water in one or more layers within 100 cm of Ustandic Kandihumults the mineral soil surface for either or both: HBCC. Other Kandihumults that have, throughout one or 1. 20 or more consecutive days; or more horizons with a total thickness of 18 cm or more within 2. 30 or more cumulative days. 75 cm of the mineral soil surface, a fine-earth fraction with Oxyaquic Haplohumults both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa 1 water retention, and Al plus /2 Fe percentages (by ammonium HBFG. Other Haplohumults that have an ustic moisture oxalate) totaling more than 1.0. regime. Andic Kandihumults Ustic Haplohumults HBCD. Other Kandihumults that have, in one or more HBFH. Other Haplohumults that have a xeric moisture subhorizons within the upper 25 cm of the kandic horizon, regime. redox depletions with a color value, moist, of 4 or more and Xeric Haplohumults chroma of 2 or less, accompanied by redox concentrations and by aquic conditions for some time in normal years (or artificial HBFI. Other Haplohumults. drainage). Typic Haplohumults Aquic Kandihumults Ultisols 265
HBCE. Other Kandihumults that: 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 1. Have, in one or more horizons within 75 cm of the 1 water retention, and Al plus /2 Fe percentages (by ammonium mineral soil surface, redox concentrations, a color value, oxalate) totaling more than 1.0. moist, of 4 or more, and hue that is 10YR or yellower and Andic Kanhaplohumults becomes redder with increasing depth within 100 cm of the mineral soil surface; and HBDD. Other Kanhaplohumults that have, in one or more 2. In normal years are saturated with water in one or more subhorizons within the upper 25 cm of the kandic horizon, layers within 100 cm of the mineral soil surface for either or redox depletions with a color value, moist, of 4 or more and both: chroma of 2 or less, accompanied by redox concentrations and by aquic conditions for some time in normal years (or artificial a. 20 or more consecutive days; or drainage). b. 30 or more cumulative days. Aquic Kanhaplohumults Ombroaquic Kandihumults HBDE. Other Kanhaplohumults that: HBCF. Other Kandihumults that have 5 percent or more (by 1. Have, in one or more horizons within 75 cm of the volume) plinthite in one or more horizons within 150 cm of the mineral soil surface, redox concentrations, a color value, mineral soil surface. moist, of 4 or more, and hue that is 10YR or yellower and Plinthic Kandihumults becomes redder with increasing depth within 100 cm of the mineral soil surface; and HBCG. Other Kandihumults that have an ustic moisture regime. 2. In normal years are saturated with water in one or more Ustic Kandihumults layers within 100 cm of the mineral soil surface for either or both: HBCH. Other Kandihumults that have a xeric moisture a. 20 or more consecutive days; or regime. Xeric Kandihumults b. 30 or more cumulative days. Ombroaquic Kanhaplohumults 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: U L 1. An ustic moisture regime; and Palehumults T 2. Throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a Key to Subgroups fine-earth fraction with both a bulk density of 1.0 g/cm3 or 1 HBEA. Palehumults that have both: less, measured at 33 kPa water retention, and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. 1. In one or more subhorizons within the upper 25 cm of Ustandic Kanhaplohumults the argillic horizon, redox depletions with a color value, moist, of 4 or more and chroma of 2 or less, accompanied by HBDC. Other Kanhaplohumults that have, throughout one or redox concentrations, and also aquic conditions for some more horizons with a total thickness of 18 cm or more within time in normal years (or artificial drainage); and 266 Keys to Soil Taxonomy
2. Throughout one or more horizons with a total Sombrihumults thickness of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction with both a bulk density Key to Subgroups of 1.0 g/cm3 or less, measured at 33 kPa water retention, 1 HBAA. All Sombrihumults. and Al plus /2 Fe percentages (by ammonium oxalate) Typic Sombrihumults totaling more than 1.0. Aquandic Palehumults Udults HBEB. Other Palehumults that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm Key to Great Groups of the mineral soil surface, a fine-earth fraction with both a HCA. Udults that have one or more horizons within 150 cm bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 of the mineral soil surface in which plinthite either forms a retention, and Al plus /2 Fe percentages (by ammonium continuous phase or constitutes one-half or more of the volume. oxalate) totaling more than 1.0. Plinthudults, p. 274 Andic Palehumults HCB. Other Udults that have a fragipan with an upper HBEC. Other Palehumults that have, in one or more boundary within 100 cm of the mineral soil surface. subhorizons within the upper 25 cm of the argillic horizon, Fragiudults, p. 267 redox depletions with a color value, moist, of 4 or more and chroma of 2 or less, accompanied by redox concentrations and HCC. Other Udults that: by aquic conditions for some time in normal years (or artificial drainage). 1. Do not have a densic, lithic, paralithic, or petroferric Aquic Palehumults contact within 150 cm of the mineral soil surface; and 2. Have a kandic horizon; and HBED. Other Palehumults that have 5 percent or more (by volume) plinthite in one or more horizons within 150 cm of the 3. Within 150 cm of the mineral soil surface, either: mineral soil surface. a. With increasing depth, do not have a clay decrease of Plinthic Palehumults 20 percent or more (relative) from the maximum clay content; or HBEE. Other Palehumults that in normal years are saturated with water in one or more layers within 100 cm of the mineral b. Have 5 percent or more (by volume) clay depletions soil surface for either or both: on faces of peds in the layer that has a 20 percent lower clay content and, below that layer, a clay increase of 3 1. 20 or more consecutive days; or percent or more (absolute) in the fine-earth fraction. 2. 30 or more cumulative days. Kandiudults, p. 269 Oxyaquic Palehumults HCD. Other Udults that have a kandic horizon. HBEF. Other Palehumults that have an ustic moisture Kanhapludults, p. 271 regime. Ustic Palehumults HCE. Other Udults that: 1. Do not have a densic, lithic, paralithic, or petroferric HBEG. Other Palehumults that have a xeric moisture regime. contact within 150 cm of the mineral soil surface; and Xeric Palehumults 2. Within 150 cm of the mineral soil surface, either: HBEH. Other Palehumults. a. With increasing depth, do not have a clay decrease of Typic Palehumults 20 percent or more (relative) from the maximum clay content; or Plinthohumults b. Have 5 percent or more (by volume) clay depletions on faces of peds in the layer that has a 20 percent lower Key to Subgroups clay content and, below that layer, a clay increase of 3 HBBA. All Plinthohumults. percent or more (absolute) in the fine-earth fraction. Typic Plinthohumults Paleudults, p. 272 Ultisols 267
HCF. Other Udults that have both: soil surface, have redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or 1. An epipedon that has a color value, moist, of 3 or less artificial drainage). throughout; and Glossaquic Fragiudults 2. In all subhorizons in the upper 100 cm of the argillic horizon or throughout the entire argillic horizon if it is less HCBD. Other Fragiudults that have, in one or more than 100 cm thick, more than 50 percent colors that have all subhorizons above the fragipan and within the upper 25 cm of of the following: the argillic or kandic horizon, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal a. Hue of 2.5YR or redder; and years (or artificial drainage). b. A value, moist, of 3 or less; and Aquic Fragiudults c. A dry value no more than 1 unit higher than the HCBE. Other Fragiudults that have 5 percent or more (by moist value. volume) plinthite in one or more horizons within 150 cm of the Rhodudults, p. 274 mineral soil surface. Plinthic Fragiudults HCG. Other Udults. Hapludults, p. 267 HCBF. Other Fragiudults that meet one or more of the following: Fragiudults 1. Have a glossic horizon above the fragipan; or Key to Subgroups 2. Do not have, above the fragipan, an argillic or kandic HCBA. Fragiudults that have a sandy or sandy-skeletal horizon that has clay films on both vertical and horizontal particle-size class throughout a layer extending from the surfaces of any structural aggregates; or mineral soil surface to the top of an argillic or kandic horizon 3. Between the argillic or kandic horizon and the fragipan, at a depth of 50 to 100 cm. have one or more horizons with 50 percent or more chroma Arenic Fragiudults of 3 or less and with a clay content 3 percent or more (absolute, in the fine-earth fraction) lower than that in both HCBB. Other Fragiudults that have both of the following: the argillic or kandic horizon and the fragipan. 1. In one or more horizons within 40 cm of the mineral Glossic Fragiudults soil surface, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or HCBG. Other Fragiudults that have a color value, moist, of 3 artificial drainage); and or less and a color value, dry, of 5 or less (crushed and smoothed sample) in either: 2. 5 percent or more (by volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. 1. An Ap horizon that is 18 cm or more thick; or Plinthaquic Fragiudults 2. The surface layer after mixing of the upper 18 cm. Humic Fragiudults HCBC. Other Fragiudults that meet both of the following: 1. Meet one or more of the following: HCBH. Other Fragiudults. Typic Fragiudults a. Have a glossic horizon above the fragipan; or b. Do not have, above the fragipan, an argillic or U kandic horizon that has clay films on both vertical and Hapludults L horizontal surfaces of any structural aggregates; or T Key to Subgroups c. Between the argillic or kandic horizon and the HCGA. Hapludults that have either or both: fragipan, have one or more horizons with 50 percent or more chroma of 3 or less and with a clay content 3 1. In each pedon, a discontinuous lithic contact within 50 percent or more (absolute, in the fine-earth fraction) cm of the mineral soil surface; and lower than that in both the argillic or kandic horizon and 2. In each pedon, a discontinuous argillic horizon that is the fragipan; and interrupted by ledges of bedrock. 2. In one or more horizons within 40 cm of the mineral Lithic-Ruptic-Entic Hapludults 268 Keys to Soil Taxonomy
HCGB. Other Hapludults that have a lithic contact within 50 HCGG. Other Hapludults that have fragic soil properties: cm of the mineral soil surface. 1. In 30 percent or more of the volume of a layer 15 cm or Lithic Hapludults more thick that has its upper boundary within 100 cm of the mineral soil surface; or HCGC. Other Hapludults that have one or both of the following: 2. In 60 percent or more of the volume of a layer 15 cm or more thick. 1. Cracks within 125 cm of the mineral soil surface that Fragic Hapludults are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or HCGH. Other Hapludults that in normal years are saturated wedge-shaped aggregates in a layer 15 cm or more thick with water in one or more layers within 100 cm of the mineral that has its upper boundary within 125 cm of the mineral soil surface for either or both: soil surface; or 1. 20 or more consecutive days; 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 2. 30 or more cumulative days. densic, lithic, or paralithic contact, whichever is shallower. Oxyaquic Hapludults Vertic Hapludults HCGI. Other Hapludults that have an argillic horizon that: HCGD. Other Hapludults that have both: 1. Consists entirely of lamellae; or 1. Fragic soil properties: 2. Is a combination of two or more lamellae and one or a. In 30 percent or more of the volume of a layer 15 cm more subhorizons with a thickness of 7.5 to 20 cm, each or more thick that has its upper boundary within 100 cm layer with an overlying eluvial horizon; or of the mineral soil surface; or 3. Consists of one or more subhorizons that are more b. In 60 percent or more of the volume of a layer 15 cm than 20 cm thick, each with an overlying eluvial horizon, or more thick; and and above these horizons there are either: 2. In one or more layers within 75 cm of the mineral soil a. Two or more lamellae with a combined thickness of surface, redox depletions with a color value, moist, of 4 or 5 cm or more (that may or may not be part of the argillic more and chroma of 2 or less, accompanied by redox horizon); or concentrations, and also aquic conditions for some time in b. A combination of lamellae (that may or may not be normal years (or artificial drainage). part of the argillic horizon) and one or more parts of the Fragiaquic Hapludults argillic horizon 7.5 to 20 cm thick, each with an overlying eluvial horizon. HCGE. Other Hapludults that have both: Lamellic Hapludults 1. A sandy or sandy-skeletal particle-size class throughout a layer extending from the mineral soil surface to the top of HCGJ. Other Hapludults that have a sandy particle-size class an argillic horizon at a depth of 50 to 100 cm; and throughout the upper 75 cm of the argillic horizon or throughout the entire argillic horizon if it is less than 75 cm 2. In one or more subhorizons within the upper 60 cm thick. of the argillic horizon, redox concentrations with a color Psammentic Hapludults value, moist, of 4 or more and chroma of 2 or less, accompanied by redox concentrations, and also aquic conditions for some time in normal years (or artificial HCGK. Other Hapludults that have a sandy or sandy-skeletal drainage). particle-size class throughout a layer extending from the Aquic Arenic Hapludults mineral soil surface to the top of an argillic horizon at a depth of 50 to 100 cm. HCGF. Other Hapludults that have, in one or more Arenic Hapludults subhorizons within the upper 60 cm of the argillic horizon, redox depletions with a color value, moist, of 4 or more and HCGL. Other Hapludults that have a sandy or sandy-skeletal chroma of 2 or less, accompanied by redox concentrations and particle-size class throughout a layer extending from the by aquic conditions for some time in normal years (or artificial mineral soil surface to the top of an argillic horizon at a depth drainage). of 100 cm or more. Aquic Hapludults Grossarenic Hapludults Ultisols 269
HCGM. Other Hapludults that have: HCCC. Other Kandiudults that have both: 1. No densic, lithic, or paralithic contact within 50 cm of 1. A sandy or sandy-skeletal particle-size class throughout the mineral soil surface; and a layer extending from the mineral soil surface to the top of a kandic horizon at a depth of 50 to 100 cm; and 2. An argillic horizon 25 cm or less thick. Inceptic Hapludults 2. 5 percent or more (by volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. HCGN. Other Hapludults that have a color value, moist, of 3 Arenic Plinthic Kandiudults or less and a color value, dry, of 5 or less (crushed and smoothed sample) in either: HCCD. Other Kandiudults that have both: 1. An Ap horizon that is 18 cm or more thick; or 1. A sandy or sandy-skeletal particle-size class throughout a layer extending from the mineral soil surface 2. The surface layer after mixing of the upper 18 cm. to the top of a kandic horizon at a depth of 50 to 100 cm; Humic Hapludults and HCGO. Other Hapludults. 2. In all subhorizons in the upper 75 cm of the kandic Typic Hapludults horizon or throughout the entire kandic horizon if it is less than 75 cm thick, more than 50 percent colors that have all Kandiudults of the following: a. Hue of 2.5YR or redder; and Key to Subgroups b. A value, moist, of 3 or less; and HCCA. Kandiudults that have: c. A dry value no more than 1 unit higher than the 1. A sandy or sandy-skeletal particle-size class throughout moist value. a layer extending from the mineral soil surface to the top of Arenic Rhodic Kandiudults a kandic horizon at a depth of 50 to 100 cm; and 2. 5 percent or more (by volume) plinthite in one or HCCE. Other Kandiudults that have a sandy or sandy- more horizons within 150 cm of the mineral soil surface; skeletal particle-size class throughout a layer extending from and the mineral soil surface to the top of a kandic horizon at a depth of 50 to 100 cm. 3. In one or more layers either within 75 cm of the Arenic Kandiudults mineral soil surface or, if the chroma throughout the upper 75 cm results from uncoated sand grains, within the upper HCCF. Other Kandiudults that have both: 12.5 cm of the kandic horizon, redox depletions with a color value, moist, of 4 or more and chroma of 2 or less, 1. A sandy or sandy-skeletal particle-size class accompanied by redox concentrations, and also aquic throughout a layer extending from the mineral soil surface conditions for some time in normal years (or artificial to the top of a kandic horizon at a depth of 100 cm or more; drainage). and Arenic Plinthaquic Kandiudults 2. 5 percent or more (by volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. HCCB. Other Kandiudults that have both: Grossarenic Plinthic Kandiudults 1. A sandy or sandy-skeletal particle-size class throughout a layer extending from the mineral soil surface to the top of HCCG. Other Kandiudults that have a sandy or sandy- U a kandic horizon at a depth of 50 to 100 cm; and skeletal particle-size class throughout a layer extending from L the mineral soil surface to the top of a kandic horizon at a T 2. In one or more layers either within 75 cm of the depth of 100 cm or more. mineral soil surface or, if the chroma throughout the upper Grossarenic Kandiudults 75 cm results from uncoated sand grains, within the upper 12.5 cm of the kandic horizon, redox depletions with a color HCCH. Other Kandiudults that have both: value, moist, of 4 or more and chroma of 2 or less, accompanied by redox concentrations, and also aquic 1. An ECEC of 1.5 cmol(+)/kg clay or less (sum of bases
conditions for some time in normal years (or artificial extracted with 1N NH4OAc pH 7, plus 1N KCl-extractable drainage). Al) in one or more horizons within 150 cm of the mineral Aquic Arenic Kandiudults soil surface; and 270 Keys to Soil Taxonomy
1 2. 5 percent or more (by volume) plinthite in one or more retention, and Al plus /2 Fe percentages (by ammonium horizons within 150 cm of the mineral soil surface. oxalate) totaling more than 1.0. Acrudoxic Plinthic Kandiudults Andic Kandiudults
HCCI. Other Kandiudults that have an ECEC of 1.5 HCCM. Other Kandiudults that have, in one or more layers cmol(+)/kg clay or less (sum of bases extracted with 1N within 75 cm of the mineral soil surface, redox depletions with
NH4OAc pH 7, plus 1N KCl-extractable Al) in one or more a color value, moist, of 4 or more and chroma of 2 or less, horizons within 150 cm of the mineral soil surface. accompanied by redox concentrations and by aquic conditions Acrudoxic Kandiudults for some time in normal years (or artificial drainage). Aquic Kandiudults HCCJ. Other Kandiudults that have both: HCCN. Other Kandiudults that have 5 percent or more (by 1. 5 percent or more (by volume) plinthite in one or more volume) plinthite in one or more horizons within 150 cm of the horizons within 150 cm of the mineral soil surface; and mineral soil surface. 2. In one or more layers within 75 cm of the mineral soil Plinthic Kandiudults surface, redox depletions with a color value, moist, of 4 or more and chroma of 2 or less, accompanied by redox HCCO. Other Kandiudults that: concentrations, and also aquic conditions for some time in 1. Have, in one or more horizons within 75 cm of the normal years (or artificial drainage). mineral soil surface, redox concentrations, a color value, Plinthaquic Kandiudults moist, of 4 or more, and hue that is 10YR or yellower and becomes redder with increasing depth within 100 cm of the HCCK. Other Kandiudults that have both: mineral soil surface; and 1. In one or more layers within 75 cm of the mineral soil 2. In normal years are saturated with water in one or more surface, redox depletions with a color value, moist, of 4 or layers within 100 cm of the mineral soil surface for either or more and chroma of 2 or less, accompanied by redox both: concentrations, and also aquic conditions for some time in normal years (or artificial drainage); and a. 20 or more consecutive days; or 2. Throughout one or more horizons with a total thickness b. 30 or more cumulative days. of 18 cm or more within 75 cm of the mineral soil surface, Ombroaquic Kandiudults one or more of the following: HCCP. Other Kandiudults that in normal years are saturated a. A fine-earth fraction with both a bulk density of 1.0 with water in one or more layers within 100 cm of the mineral g/cm3 or less, measured at 33 kPa water retention, and Al 1 soil surface for either or both: plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0; or 1. 20 or more consecutive days; or b. More than 35 percent (by volume) fragments coarser 2. 30 or more cumulative days. than 2.0 mm, of which more than 66 percent is cinders, Oxyaquic Kandiudults pumice, and pumicelike fragments; or HCCQ. Other Kandiudults that have a sombric horizon c. A fine-earth fraction containing 30 percent or more within 150 cm of the mineral soil surface. particles 0.02 to 2.0 mm in diameter; and Sombric Kandiudults (1) In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and HCCR. Other Kandiudults that have, in all subhorizons in
1 the upper 75 cm of the kandic horizon or throughout the entire (2) [(Al plus /2 Fe, percent extracted by ammonium kandic horizon if it is less than 75 cm thick, more than 50 oxalate) times 60] plus the volcanic glass (percent) is percent colors that have all of the following: equal to 30 or more. Aquandic Kandiudults 1. Hue of 2.5YR or redder; and 2. A value, moist, of 3 or less; and HCCL. Other Kandiudults that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm 3. A dry value no more than 1 unit higher than the moist of the mineral soil surface, a fine-earth fraction with both a value. bulk density of 1.0 g/cm3 or less, measured at 33 kPa water Rhodic Kandiudults Ultisols 271
HCCS. Other Kandiudults. more and chroma of 2 or less, accompanied by redox Typic Kandiudults concentrations, and also aquic conditions for some time in normal years (or artificial drainage). Kanhapludults Fragiaquic Kanhapludults
Key to Subgroups HCDG. Other Kanhapludults that have, throughout one or more horizons with a total thickness of 18 cm or more within HCDA. Kanhapludults that have a lithic contact within 50 75 cm of the mineral soil surface, a fine-earth fraction with cm of the mineral soil surface. both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa Lithic Kanhapludults 1 water retention, and Al plus /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. HCDB. Other Kanhapludults that have both: Andic Kanhapludults 1. 5 percent or more (by volume) plinthite in one or more horizons within 150 cm of the mineral soil surface; and HCDH. Other Kanhapludults that have, in one or more layers within 75 cm of the mineral soil surface, redox depletions with 2. In one or more layers within 75 cm of the mineral soil a color value, moist, of 4 or more and chroma of 2 or less, surface, redox depletions with a color value, moist, of 4 or accompanied by redox concentrations and by aquic conditions more and chroma of 2 or less, accompanied by redox for some time in normal years (or artificial drainage). concentrations, and also aquic conditions for some time in Aquic Kanhapludults normal years (or artificial drainage). Plinthaquic Kanhapludults HCDI. Other Kanhapludults that: HCDC. Other Kanhapludults that have both: 1. Have, in one or more horizons within 75 cm of the mineral soil surface, redox concentrations, a color value, 1. A sandy or sandy-skeletal particle-size class throughout moist, of 4 or more, and hue that is 10YR or yellower and a layer extending from the mineral soil surface to the top of becomes redder with increasing depth within 100 cm of the a kandic horizon at a depth of 50 to 100 cm; and mineral soil surface; and 2. 5 percent or more (by volume) plinthite in one or more 2. In normal years are saturated with water in one or more horizons within 150 cm of the mineral soil surface. layers within 100 cm of the mineral soil surface for either or Arenic Plinthic Kanhapludults both: 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 b. 30 or more cumulative days. the mineral soil surface to the top of a kandic horizon at a Ombroaquic Kanhapludults depth of 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 HCDE. Other Kanhapludults that have an ECEC of 1.5 the mineral 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: U HCDK. Other Kanhapludults that have 5 percent or more (by L 1. Fragic soil properties: volume) plinthite in one or more horizons within 150 cm of the T 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 272 Keys to Soil Taxonomy
2. In 60 percent or more of the volume of a layer 15 cm or 12.5 cm of the argillic horizon, redox depletions with a more thick. color value, moist, of 4 or more and chroma of 2 or less, Fragic Kanhapludults accompanied by redox concentrations, and also aquic conditions for some time in normal years (or artificial HCDM. Other Kanhapludults that have, in all subhorizons in drainage); and the upper 50 cm of the kandic horizon or throughout the entire 2. A sandy or sandy-skeletal particle-size class throughout kandic horizon if it is less than 50 cm thick, more than 50 a layer extending from the mineral soil surface to the top of percent colors that have all of the following: an argillic horizon at a depth of 50 cm or more; and 1. Hue of 2.5YR or redder; and 3. 5 percent or more (by volume) plinthite in one or more 2. A value, moist, of 3 or less; and horizons within 150 cm of the mineral soil surface. Arenic Plinthaquic Paleudults 3. A dry value no more than 1 unit higher than the moist value. HCED. Other Paleudults that have both: Rhodic Kanhapludults 1. A sandy or sandy-skeletal particle-size class throughout HCDN. Other Kanhapludults. a layer extending from the mineral soil surface to the top of Typic Kanhapludults an argillic horizon that is 50 cm or more below the mineral soil surface; and Paleudults 2. In one or more layers either within 75 cm of the mineral soil surface or, if the chroma throughout the upper Key to Subgroups 75 cm results from uncoated sand grains, within the upper 12.5 cm of the argillic horizon, redox depletions with a HCEA. Paleudults that have one or both of the following: color value, moist, of 4 or more and chroma of 2 or less, 1. Cracks within 125 cm of the mineral soil surface that accompanied by redox concentrations, and also aquic are 5 mm or more wide through a thickness of 30 cm or conditions for some time in normal years (or artificial more for some time in normal years, and slickensides or drainage). wedge-shaped aggregates in a layer 15 cm or more thick Aquic Arenic Paleudults that has its upper boundary within 125 cm of the mineral soil surface; or HCEE. Other Paleudults that have both: 2. A linear extensibility of 6.0 cm or more between the 1. 5 percent or more (by volume) plinthite in one or more mineral soil surface and either a depth of 100 cm or a horizons within 150 cm of the mineral soil surface; and densic, lithic, or paralithic contact, whichever is shallower. Vertic Paleudults 2. In one or more layers either within 75 cm of the mineral soil surface or, if the chroma throughout the upper HCEB. Other Paleudults that have a horizon 5 cm or more 75 cm results from uncoated sand grains, within the upper thick, either below an Ap horizon or at a depth of 18 cm or 12.5 cm of the argillic horizon, redox depletions with a more from the mineral soil surface, whichever is deeper, that color value, moist, of 4 or more and chroma of 2 or less, has one or more of the following: accompanied by redox concentrations, and also aquic conditions for some time in normal years (or artificial 1. In 25 percent or more of each pedon, cementation by 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 HCEF. 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 HCEC. Other Paleudults that have: b. In 60 percent or more of the volume of a layer 15 cm or more thick; and 1. In one or more layers either within 75 cm of the mineral soil surface or, if the chroma throughout the upper 2. In one or more layers within 75 cm of the mineral soil 75 cm results from uncoated sand grains, within the upper surface, redox depletions with a color value, moist, of 4 or Ultisols 273
more and chroma of 2 or less, accompanied by redox throughout the entire argillic horizon if it is less than 75 cm concentrations, and also aquic conditions for some time in thick. normal years (or artificial drainage). Psammentic Paleudults Fragiaquic Paleudults HCEM. Other Paleudults that have both: HCEG. Other Paleudults that have, in one or more layers 1. A sandy or sandy-skeletal particle-size class throughout within 75 cm of the mineral soil surface, redox depletions a layer extending from the mineral soil surface to the top of with a color value, moist, of 4 or more and chroma of 2 or an argillic horizon at a depth of 100 cm or more; and less, accompanied by redox concentrations and by aquic conditions for some time in normal years (or artificial 2. 5 percent or more (by volume) plinthite in one or more drainage). horizons within 150 cm of the mineral soil surface. Aquic Paleudults Grossarenic Plinthic Paleudults
HCEH. Other Paleudults that have anthraquic conditions. HCEN. Other Paleudults that have 5 percent or more (by Anthraquic Paleudults volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. HCEI. Other Paleludults that in normal years are saturated Plinthic Paleudults with water in one or more layers within 100 cm of the mineral soil surface for either or both: HCEO. Other Paleudults that have both: 1. 20 or more consecutive days; or 1. A sandy or sandy-skeletal particle-size class throughout a layer extending from the mineral soil surface to the top of 2. 30 or more cumulative days. an argillic horizon at a depth of 50 to 100 cm; and Oxyaquic Paleudults 2. In all subhorizons in the upper 75 cm of the argillic HCEJ. Other Paleudults that have an argillic horizon that: horizon or throughout the entire argillic horizon if it is less than 75 cm thick, more than 50 percent colors that have all 1. Consists entirely of lamellae; or of the following: 2. Is a combination of two or more lamellae and one or a. Hue of 2.5YR or redder; and more subhorizons with a thickness of 7.5 to 20 cm, each layer with an overlying eluvial horizon; or b. A value, moist, of 3 or less; and 3. Consists of one or more subhorizons that are more c. A dry value no more than 1 unit higher than the than 20 cm thick, each with an overlying eluvial horizon, moist value. and above these horizons there are either: Arenic Rhodic Paleudults a. Two or more lamellae with a combined thickness of HCEP. Other Paleudults that have a sandy or sandy-skeletal 5 cm or more (that may or may not be part of the argillic particle-size class throughout a layer extending from the horizon); or mineral soil surface to the top of an argillic horizon at a depth b. A combination of lamellae (that may or may not be of 50 to 100 cm. part of the argillic horizon) and one or more parts of the Arenic Paleudults argillic horizon 7.5 to 20 cm thick, each with an overlying eluvial horizon. HCEQ. Other Paleudults that have a sandy or sandy-skeletal Lamellic Paleudults particle-size class throughout a layer extending from the mineral soil surface to the top of an argillic horizon at a depth U HCEK. Other Paleudults that have both: of 100 cm or more. L Grossarenic Paleudults T 1. A sandy or sandy-skeletal particle-size class throughout a layer extending from the mineral soil surface to the top of HCER. Other Paleudults that have fragic soil properties: an 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 HCEL. Other Paleudults that have a sandy particle-size class more thick. throughout the upper 75 cm of the argillic horizon or Fragic Paleudults 274 Keys to Soil Taxonomy
HCES. Other Paleudults that have, in all subhorizons in the 3. Within 150 cm of the mineral soil surface, either: upper 75 cm of the argillic horizon or throughout the entire a. With increasing depth, do not have a clay decrease of argillic horizon if it is less than 75 cm thick, more than 50 20 percent or more (relative) from the maximum clay percent colors that have all of the following: content; or 1. Hue of 2.5YR or redder; and b. Have 5 percent or more (by volume) skeletans on 2. A value, moist, of 3 or less; and faces of peds in the layer that has a 20 percent lower clay content and, below that layer, a clay increase of 3 percent 3. A dry value no more than 1 unit higher than the moist or more (absolute) in the fine-earth fraction. value. Kandiustults, p. 275 Rhodic Paleudults HDC. Other Ustults that have a kandic horizon. HCET. Other Paleudults. Kanhaplustults, p. 276 Typic Paleudults HDD. Other Ustults that: Plinthudults 1. Do not have a densic, lithic, paralithic, or petroferric contact within 150 cm of the mineral soil surface; and Key to Subgroups 2. Within 150 cm of the mineral soil surface, either: HCAA. All Plinthudults. a. With increasing depth, do not have a clay decrease of Typic Plinthudults 20 percent or more (relative) from the maximum clay content; or Rhodudults b. Have 5 percent or more (by volume) skeletans on Key to Subgroups faces of peds in the layer that has a 20 percent lower clay content and, below that layer, a clay increase of 3 percent HCFA. Rhodudults that have a lithic contact within 50 cm of or more (absolute) in the fine-earth fraction. the mineral soil surface. Paleustults, p. 277 Lithic Rhodudults HDE. Other Ustults that have both: HCFB. Other Rhodudults that have a sandy particle-size class throughout the upper 75 cm of the argillic horizon or 1. An epipedon that has a color value, moist, of 3 or less throughout the entire argillic horizon if it is less than 75 cm throughout; and thick. 2. In all subhorizons in the upper 100 cm of the argillic Psammentic Rhodudults horizon or throughout the entire argillic horizon if it is less than 100 cm thick, more than 50 percent colors that have all HCFC. Other Rhodudults. of the following: Typic Rhodudults a. Hue of 2.5YR or redder; and Ustults b. A value, moist, of 3 or less; and c. A dry value no more than 1 unit higher than the Key to Great Groups moist value. Rhodustults, p. 278 HDA. Ustults that have one or more horizons within 150 cm of the mineral soil surface in which plinthite either forms HDF. Other Ustults. a continuous phase or constitutes one-half or more of the Haplustults, p. 274 volume. Plinthustults, p. 277 Haplustults HDB. Other Ustults that: Key to Subgroups 1. Do not have a densic, lithic, paralithic, or petroferric HDFA. Haplustults that have a lithic contact within 50 cm of contact within 150 cm of the mineral soil surface; and the mineral soil surface. 2. Have a kandic horizon; and Lithic Haplustults Ultisols 275
HDFB. Other Haplustults that have a petroferric contact plus 1N KCl-extractable Al) in one or more horizons within within 100 cm of the mineral soil surface. 150 cm of the mineral soil surface. Petroferric Haplustults Acrustoxic Kandiustults
HDFC. Other Haplustults that have, in one or more layers HDBB. Other Kandiustults that have, in one or more layers both within the upper 12.5 cm of the argillic horizon and within 75 cm of the mineral soil surface, redox depletions with 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, a color value, moist, of 4 or more and chroma of 2 or less, accompanied by redox concentrations and by aquic conditions accompanied by redox concentrations and by aquic conditions for some time in normal years (or artificial drainage). for some time in normal years (or artificial drainage). Aquic Kandiustults Aquic Haplustults HDBC. Other Kandiustults that have both: HDFD. Other Haplustults that have a sandy or sandy-skeletal 1. A sandy or sandy-skeletal particle-size class throughout particle-size class throughout a layer extending from the a layer extending from the mineral soil surface to the top of mineral soil surface to the top of an argillic horizon at a depth a kandic horizon at a depth of 50 cm or more; and of 50 cm or more below the mineral soil surface. Arenic Haplustults 2. 5 percent or more (by volume) plinthite in one or more horizons within 150 cm of the mineral soil surface. HDFE. Other Haplustults that: Arenic Plinthic Kandiustults 1. Have, in one or more horizons within 75 cm of the HDBD. Other Kandiustults that have a sandy or sandy- mineral soil surface, redox concentrations, a color value, skeletal particle-size class throughout a layer extending from moist, of 4 or more, and hue that is 10YR or yellower and the mineral soil surface to the top of a kandic horizon at a becomes redder with increasing depth within 100 cm of the depth of 50 cm or more. mineral soil surface; and Arenic Kandiustults 2. In normal years are saturated with water in one or more layers within 100 cm of the mineral soil surface for either or HDBE. Other Kandiustults that have both: both: 1. Throughout one or more horizons with a total thickness a. 20 or more consecutive days; or of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction with both a bulk density of 1.0 g/cm3 or b. 30 or more cumulative days. 1 less, measured at 33 kPa water retention, and Al plus /2 Fe Ombroaquic Haplustults percentages (by ammonium oxalate) totaling more than 1.0; and HDFF. Other Haplustults that have 5 percent or more (by volume) plinthite in one or more horizons within 150 cm of the 2. When neither irrigated nor fallowed to store moisture, mineral soil surface. either: Plinthic Haplustults a. A mesic or thermic soil temperature regime and a moisture control section that is dry in some part for 135 HDFG. Other Haplustults that have a CEC (by 1N NH OAc 4 or fewer of the cumulative days per year when the pH 7) of less than 24 cmol(+)/kg clay in 50 percent or more of temperature at a depth of 50 cm below the soil surface is the entire argillic horizon if less than 100 cm thick or of its higher than 5 oC; or upper 100 cm. Kanhaplic Haplustults b. A hyperthermic, isomesic, or warmer iso soil U temperature regime and a moisture control section that is L HDFH. Other Haplustults. dry in some or all parts for fewer than 120 cumulative T Typic Haplustults days per year when the temperature at a depth of 50 cm below the soil surface is higher than 8 oC. Udandic Kandiustults Kandiustults HDBF. Other Kandiustults that have, throughout one or more Key to Subgroups horizons with a total thickness of 18 cm or more within 75 cm HDBA. Kandiustults that have an ECEC of 1.5 cmol(+)/kg of the mineral soil surface, a fine-earth fraction with both a 3 clay or less (sum of bases extracted with 1N NH4OAc pH 7, bulk density of 1.0 g/cm or less, measured at 33 kPa water 276 Keys to Soil Taxonomy
1 retention, and Al plus /2 Fe percentages (by ammonium 3. A dry value no more than 1 unit higher than the moist oxalate) totaling more than 1.0. value. Andic Kandiustults Rhodic Kandiustults
HDBG. Other Kandiustults that have 5 percent or more (by HDBK. Other Kandiustults. volume) plinthite in one or more horizons within 150 cm of the Typic Kandiustults mineral soil surface. Plinthic Kandiustults Kanhaplustults HDBH. Other Kandiustults that, when neither irrigated nor Key to Subgroups fallowed to store moisture, have either: HDCA. Kanhaplustults that have a lithic contact within 50 1. A thermic, mesic, or colder soil temperature regime and cm of the mineral soil surface. a moisture control section that in normal years is dry in Lithic Kanhaplustults some part for more than four-tenths of the cumulative days per year when the soil temperature at a depth of 50 cm HDCB. Other Kanhaplustults that have an ECEC of 1.5 below the soil surface is higher than 5 oC; or cmol(+)/kg clay or less (sum of bases extracted with 1N
2. A hyperthermic, isomesic, or warmer iso soil NH4OAc pH 7, plus 1N KCl-extractable Al) in one or more temperature regime and a moisture control section that in horizons within 150 cm of the mineral soil surface. normal years: Acrustoxic Kanhaplustults a. Is moist in some or all parts for fewer than 90 HDCC. Other Kanhaplustults that have, in one or more consecutive days per year when the temperature at a layers within 75 cm of the mineral soil surface, redox depth of 50 cm below the soil surface is higher than 8 oC; depletions with a color value, moist, of 4 or more and chroma and of 2 or less, accompanied by redox concentrations and by aquic b. Is dry in some part for six-tenths or more of the conditions for some time in normal years (or artificial cumulative days per year when the soil temperature at a drainage). depth of 50 cm below the soil surface is higher than 5 oC. Aquic Kanhaplustults Aridic Kandiustults HDCD. Other Kanhaplustults that have a sandy or sandy- HDBI. Other Kandiustults that, when neither irrigated nor skeletal particle-size class throughout a layer extending from fallowed to store moisture, have either: the mineral soil surface to the top of a kandic horizon at a depth of 50 to 100 cm. 1. A mesic or thermic soil temperature regime and a Arenic Kanhaplustults moisture control section that in normal years is dry in some part for 135 or fewer of the cumulative days per year when HDCE. Other Kanhaplustults that have both: the temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or 1. Throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a 2. A hyperthermic, isomesic, or warmer iso soil fine-earth fraction with both a bulk density of 1.0 g/cm3 or temperature regime and a moisture control section that in 1 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. Udic Kandiustults 2. When neither irrigated nor fallowed to store moisture, either: HDBJ. Other Kandiustults that have, in all subhorizons in a. A mesic or thermic soil temperature regime and a the 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 percent colors that have all of the following: year when the temperature at a depth of 50 cm below the 1. Hue of 2.5YR or redder; and soil surface is higher than 5 oC; or 2. A value, moist, of 3 or less; and b. A hyperthermic, isomesic, or warmer iso soil Ultisols 277
temperature regime and a moisture control section that in at a depth of 50 cm below the soil surface is higher than normal years is dry in some or all parts for fewer than 5 oC. 120 cumulative days per year when the temperature at a Aridic Kanhaplustults depth of 50 cm below the soil surface is higher than 8 oC. Udandic Kanhaplustults HDCJ. Other Kanhaplustults that, when neither irrigated nor fallowed to store moisture, have either: HDCF. Other Kanhaplustults that have, throughout one or 1. A mesic or thermic soil temperature regime and a more horizons with a total thickness of 18 cm or more within moisture control section that in normal years is dry in some 75 cm of the mineral soil surface, a fine-earth fraction with part for 135 or fewer of the cumulative days per year when both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa 1 the temperature at a depth of 50 cm below the soil surface is water retention, and Al plus /2 Fe percentages (by ammonium higher than 5 oC; or oxalate) totaling more than 1.0. Andic Kanhaplustults 2. A hyperthermic, isomesic, or warmer iso soil temperature regime and a moisture control section that in HDCG. Other Kanhaplustults that have 5 percent or more (by normal years is dry in some or all parts for fewer than 120 volume) plinthite in one or more horizons within 150 cm of the cumulative days per year when the temperature at a depth of mineral soil surface. 50 cm below the soil surface is higher than 8 oC. Plinthic Kanhaplustults Udic Kanhaplustults
HDCH. Other Kanhaplustults that: HDCK. Other Kanhaplustults that have, in all subhorizons in the upper 50 cm of the kandic horizon or throughout the entire 1. Have, in one or more horizons within 75 cm of the kandic horizon if it is less than 50 cm thick, more than 50 mineral soil surface, redox concentrations, a color value, percent colors that have all of the following: moist, of 4 or more, and hue that is 10YR or yellower and becomes redder with increasing depth within 100 cm of the 1. Hue of 2.5YR or redder; and mineral soil surface; and 2. A value, moist, of 3 or less; and 2. In normal years are saturated with water in one or more 3. A dry value no more than 1 unit higher than the moist layers within 100 cm of the mineral soil surface for either or value. both: Rhodic Kanhaplustults a. 20 or more consecutive days; or HDCL. Other Kanhaplustults. b. 30 or more cumulative days. Typic Kanhaplustults Ombroaquic Kanhaplustults
HDCI. Other Kanhaplustults that, when neither irrigated nor Paleustults fallowed to store moisture, have either: Key to Subgroups 1. A thermic, mesic, or colder soil temperature regime and HDDA. All Paleustults. a moisture control section that in normal years is dry in Typic Paleustults some part for more than four-tenths of the cumulative days per year when the soil temperature at a depth of 50 cm below the soil surface is higher than 5 oC; or Plinthustults
2. A hyperthermic, isomesic, or warmer iso soil Key to Subgroups U temperature regime and a moisture control section that in HDAA. Plinthustults that have: L normal years: T 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 depth of 50 cm below the soil surface is higher than 8 oC; 2. Within 150 cm of the mineral soil surface, both: and a. With increasing depth, a clay decrease of 20 b. Is dry in some part for six-tenths or more of the percent or more (relative) from the maximum clay cumulative days per year when the soil temperature content; and 278 Keys to Soil Taxonomy
b. Less than 5 percent (by volume) skeletans on faces of 1. A lithic contact within 50 cm of the mineral soil peds in the layer that has a 20 percent lower clay content surface; and or, below that layer, a clay increase of less than 3 percent 2. In each pedon, a discontinuous argillic or kandic (absolute) in the fine-earth fraction. horizon that is interrupted by ledges of bedrock. Haplic Plinthustults Lithic Ruptic-Inceptic Haploxerults HDAB. Other Plinthustults. HEBB. Other Haploxerults that have a lithic contact within Typic Plinthustults 50 cm of the mineral soil surface. Lithic Haploxerults Rhodustults HEBC. Other Haploxerults that have, in one or more Key to Subgroups subhorizons within the upper 25 cm of the argillic or kandic HDEA. Rhodustults that have a lithic contact within 50 cm horizon, redox depletions with a color value, moist, of 4 or of the mineral soil surface. more and chroma of 2 or less, accompanied by redox Lithic Rhodustults concentrations and by aquic conditions for some time in normal years (or artificial drainage). HDEB. Other Rhodustults that have a sandy particle-size Aquic Haploxerults class throughout the upper 75 cm of the argillic horizon or throughout the entire argillic horizon if it is less than 75 cm HEBD. Other Haploxerults that have, throughout one or thick. more horizons with a total thickness of 18 cm or more within Psammentic Rhodustults 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 1 HDEC. Other Rhodustults. water retention, and Al plus /2 Fe percentages (by ammonium Typic Rhodustults oxalate) totaling more than 1.0. Andic Haploxerults Xerults HEBE. Other Haploxerults that have an argillic or kandic Key to Great Groups horizon that: 1. Consists entirely of lamellae; or HEA. Xerults that: 2. Is a combination of two or more lamellae and one or 1. Do not have a densic, lithic, or paralithic contact more subhorizons with a thickness of 7.5 to 20 cm, each within 150 cm of the mineral soil surface; and layer with an overlying eluvial horizon; or 2. Within 150 cm of the mineral soil surface, either: 3. Consists of one or more subhorizons that are more a. With increasing depth, do not have a clay decrease of than 20 cm thick, each with an overlying eluvial horizon, 20 percent or more (relative) from the maximum clay andabove these horizons there are either: content; or a. Two or more lamellae with a combined thickness of b. Have 5 percent or more (by volume) skeletans on 5 cm or more (that may or may not be part of the argillic faces of peds or 5 percent or more (by volume) plinthite, or kandic horizon); or or both, in the layer that has a 20 percent lower clay b. A combination of lamellae (that may or may content and, below that layer, a clay increase of 3 percent not be part of the argillic or kandic horizon) and or more (absolute) in the fine-earth fraction. one or more parts of the argillic or kandic horizon Palexerults, p. 279 7.5 to 20 cm thick, each with an overlying eluvial horizon. HEB. Other Xerults. Lamellic Haploxerults Haploxerults, p. 278 HEBF. Other Haploxerults that have a sandy particle-size Haploxerults class throughout the upper 75 cm of the argillic or kandic horizon or throughout the entire horizon if it is less than 75 cm Key to Subgroups thick. HEBA. Haploxerults that have both: Psammentic Haploxerults Ultisols 279
HEBG. Other Haploxerults that have a sandy or sandy- 2. Throughout one or more horizons with a total thickness skeletal particle-size class throughout a layer extending from of 18 cm or more within 75 cm of the mineral soil surface, the mineral soil surface to the top of an argillic or kandic a fine-earth fraction with both a bulk density of 1.0 g/cm3 horizon at a depth of 50 to 100 cm. or less, measured at 33 kPa water retention, and Al plus 1 Arenic Haploxerults /2 Fe percentages (by ammonium oxalate) totaling more than 1.0. HEBH. Other Haploxerults that have a sandy or sandy- Aquandic Palexerults skeletal particle-size class throughout a layer extending from the mineral soil surface to the top of an argillic or kandic HEAB. Other Palexerults that have, in one or more horizon at a depth of 100 cm or more. subhorizons within the upper 25 cm of the argillic or kandic Grossarenic Haploxerults horizon, redox depletions with a color value, moist, of 4 or more and chroma of 2 or less, accompanied by redox HEBI. Other Haploxerults. concentrations and by aquic conditions for some time in Typic Haploxerults normal years (or artificial drainage). Aquic Palexerults Palexerults HEAC. Other Palexerults that have, throughout one or more Key to Subgroups 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 HEAA. Palexerults that have both: bulk density of 1.0 g/cm3 or less, measured at 33 kPa water 1 1. In one or more subhorizons within the upper 25 cm of retention, and Al plus /2 Fe percentages (by ammonium the argillic or kandic horizon, redox depletions with a color oxalate) totaling more than 1.0. value, moist, of 4 or more and chroma of 2 or less, Andic Palexerults accompanied by redox concentrations, and also aquic conditions for some time in normal years (or artificial HEAD. Other Palexerults. drainage); and Typic Palexerults
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281
CHAPTER 16 Vertisols1
Key to Suborders 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: 1. In more than half of each pedon, either on faces of peds or in the matrix if peds are absent, 50 percent or more chroma of either: a. 2 or less if redox concentrations are present; or b. 1 or less; or through a thickness of 25 cm or more within 50 cm of the 2. Enough active ferrous iron (Fe2+) to give a positive mineral soil surface, for 90 or more cumulative days per reaction to alpha,alpha-dipyridyl at a time when the soil is year. not being irrigated. Usterts, p. 288 Aquerts, p. 281 FF. Other Vertisols. FB. Other Vertisols that have a cryic soil temperature regime. Uderts, p. 286 Cryerts, p. 285 Aquerts FC. Other Vertisols that in normal years have both: 1. A thermic, mesic, or frigid soil temperature regime; and Key to Great Groups 2. If not irrigated during the year, cracks that remain both: FAA. Aquerts that have a salic horizon that has its upper boundary within 100 cm of the mineral soil surface. a. 5 mm or more wide, through a thickness of 25 cm or Salaquerts, p. 284 more within 50 cm of the mineral soil surface, for 60 or more consecutive days during the 90 days following the FAB. Other Aquerts that have a duripan that has its upper summer solstice; and boundary within 100 cm of the mineral soil surface. b. Closed for 60 or more consecutive days during the 90 Duraquerts, p. 282 days following the winter solstice. Xererts, p. 291 FAC. Other Aquerts that have a natric horizon or have an exchangeable sodium percentage of 15 percent or more (or a FD. Other Vertisols that, if not irrigated during the year, have sodium adsorption ratio of 13 or more) within 100 cm of the cracks in normal years that remain closed for less than 60 mineral soil surface. consecutive days during a period when the soil temperature at a Natraquerts, p. 284 V depth of 50 cm from the soil surface is higher than 8 oC. E Torrerts, p. 285 FAD. Other Aquerts that have a calcic horizon that has its R upper boundary within 100 cm of the mineral soil surface. FE. Other Vertisols that, if not irrigated during the year, Calciaquerts, p. 282 have cracks in normal years that are 5 mm or more wide, FAE. Other Aquerts that have, throughout one or more
1 This chapter was rewritten in 1992 following the recommendations of the International horizons with a total thickness of 25 cm or more within 50 cm Committee on the Classification of Vertisols (ICOMERT), chaired by Dr. Juan Comerma. of the mineral soil surface, both: 282 Keys to Soil Taxonomy
1. An electrical conductivity in the saturation extract of 2. Closed for 60 or more consecutive days during the 90 less than 4.0 dS/m at 25 oC; and days following the winter solstice. Xeric Duraquerts 2. A pH value of 4.5 or less in 0.01 M CaCl2 (5.0 or less in 1:1 water). FABC. Other Duraquerts that, if not irrigated during the Dystraquerts, p. 282 year, have cracks in normal years that are 5 mm or more wide, FAF. Other Aquerts that have episaturation. through a thickness of 25 cm or more within 50 cm of the Epiaquerts, p. 284 mineral soil surface, for 90 or more cumulative days per year. Ustic Duraquerts FAG. Other Aquerts. Endoaquerts, p. 283 FABD. Other Duraquerts that have, in one or more horizons between either an Ap horizon or a depth of 25 cm from the Calciaquerts mineral soil surface, whichever is deeper, and either a depth of 75 cm or the upper boundary of the duripan if shallower, 50 Key to Subgroups percent or more colors as follows: FADA. Calciaquerts that have, in one or more horizons 1. Hue of 2.5Y or redder and either: between either an Ap horizon or a depth of 25 cm from the a. A color value, moist, of 6 or more and chroma of 3 mineral soil surface, whichever is deeper, and either a depth of or more; or 75 cm or the upper boundary of a duripan if shallower, 50 percent or more colors as follows: b. A color value, moist, of 5 or less and chroma of 2 or 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 more; or 3. Chroma of 2 or more and no redox concentrations. Aeric Duraquerts b. A color value, moist, of 5 or less and chroma of 2 or more; or FABE. Other Duraquerts that have, in one or more horizons 2. Hue of 5Y and chroma of 3 or more; or within 30 cm of the mineral soil surface, one or both of the following in more than half of each pedon: 3. Chroma of 2 or more and no redox concentrations. Aeric Calciaquerts 1. A color value, moist, of 4 or more; or 2. A color value, dry, of 6 or more. FADB. Other Calciaquerts. Chromic Duraquerts Typic Calciaquerts FABF. Other Duraquerts. Duraquerts Typic Duraquerts
Key to Subgroups Dystraquerts FABA. Duraquerts that, if not irrigated during the year, have cracks in normal years that are 5 mm or more wide, through a Key to Subgroups thickness of 25 cm or more within 50 cm of the mineral soil FAEA. Dystraquerts that have, in one or more horizons surface, for 210 or more cumulative days per year. within 100 cm of the mineral soil surface, jarosite Aridic Duraquerts concentrations and a pH value of 4.0 or less (1:1 water, air- dried slowly in shade). FABB. Other Duraquerts that have a thermic, mesic, or frigid Sulfaqueptic Dystraquerts soil temperature regime and that, if not irrigated during the year, have cracks in normal years that remain both: FAEB. Other Dystraquerts that, if not irrigated during the 1. 5 mm or more wide, through a thickness of 25 cm or year, have cracks in normal years that are 5 mm or more wide, more within 50 cm of the mineral soil surface, for 60 or through a thickness of 25 cm or more within 50 cm of the more consecutive days during the 90 days following the mineral soil surface, for 210 or more cumulative days per year. summer solstice; and Aridic Dystraquerts Vertisols 283
FAEC. Other Dystraquerts that, if not irrigated during the sodium percentage of 15 or more (or a sodium adsorption ratio year, have cracks in normal years that are 5 mm or more wide, of 13 or more) for 6 or more months in normal years. through a thickness of 25 cm or more within 50 cm of the Sodic Endoaquerts mineral soil surface, for 90 or more cumulative days per year. Ustic Dystraquerts FAGC. Other Endoaquerts that, if not irrigated during the year, have cracks in normal years that are 5 mm or more wide, FAED. 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 210 or more cumulative days per year. mineral soil surface, whichever is deeper, and a depth of 75 Aridic Endoaquerts cm, 50 percent or more colors as follows: FAGD. Other Endoaquerts that have a thermic, mesic, or 1. Hue of 2.5Y or redder and either: frigid soil temperature regime and that, if not irrigated during a. A color value, moist, of 6 or more and chroma of 3 the year, have cracks in normal years that remain both: or 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; or more consecutive days during the 90 days following the summer solstice; and 2. Hue of 5Y and chroma of 3 or more; or 2. Closed for 60 or more consecutive days during the 90 3. Chroma of 2 or more and no redox concentrations. days following the winter solstice. Aeric Dystraquerts Xeric Endoaquerts FAEE. Other Dystraquerts that have a densic, lithic, or FAGE. Other Endoaquerts that, if not irrigated during the paralithic contact within 100 cm of the mineral soil surface. year, have cracks in normal years that are 5 mm or more wide, Leptic Dystraquerts through a thickness of 25 cm or more within 50 cm of the mineral soil surface, for 90 or more cumulative days per year. FAEF. Other Dystraquerts that have a layer 25 cm or more Ustic Endoaquerts thick that contains less than 27 percent clay in its fine-earth fraction and has its upper boundary within 100 cm of the FAGF. Other Endoaquerts that have, in one or more horizons mineral soil surface. between either an Ap horizon or a depth of 25 cm from the Entic Dystraquerts mineral soil surface, whichever is deeper, and a depth of 75 cm, 50 percent or more colors as follows: FAEG. Other Dystraquerts that have, in one or more horizons 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 1. A color value, moist, of 4 or more; or 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 2. Hue of 5Y and chroma of 3 or more; or FAEH. Other Dystraquerts. Typic Dystraquerts 3. Chroma of 2 or more and no redox concentrations. Aeric Endoaquerts
Endoaquerts FAGG. Other Endoaquerts that have a densic, lithic, or paralithic contact within 100 cm of the mineral soil surface. Key to Subgroups Leptic Endoaquerts V FAGA. Endoaquerts that have, throughout a layer 15 cm or E more thick within 100 cm of the mineral soil surface, an FAGH. Other Endoaquerts that have a layer 25 cm or more R electrical conductivity of 15 dS/m or more (saturated paste) for thick that contains less than 27 percent clay in its fine-earth 6 or more months in normal years. fraction and has its upper boundary within 100 cm of the Halic Endoaquerts mineral soil surface. Entic Endoaquerts FAGB. Other Endoaquerts that have, in one or more horizons within 100 cm of the mineral soil surface, an exchangeable FAGI. Other Endoaquerts that have, in one or more horizons 284 Keys to Soil Taxonomy
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 1. A color value, moist, of 4 or more; or 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 Endoaquerts more; or 2. Hue of 5Y and chroma of 3 or more; or FAGJ. Other Endoaquerts. Typic Endoaquerts 3. Chroma of 2 or more and no redox concentrations. Aeric Epiaquerts Epiaquerts FAFG. Other Epiaquerts that have a densic, lithic, or Key to Subgroups paralithic contact within 100 cm of the mineral soil surface. Leptic Epiaquerts FAFA. Epiaquerts that have, throughout a layer 15 cm or more thick within 100 cm of the mineral soil surface, an FAFH. Other Epiaquerts that have a layer 25 cm or more electrical conductivity of 15 dS/m or more (saturated paste) for thick that contains less than 27 percent clay in its fine-earth 6 or more months in normal years. fraction and has its upper boundary within 100 cm of the Halic Epiaquerts mineral soil surface. Entic Epiaquerts FAFB. Other Epiaquerts that have, in one or more horizons within 100 cm of the mineral soil surface, an exchangeable FAFI. Other Epiaquerts that have, in one or more horizons sodium percentage of 15 or more (or a sodium adsorption ratio within 30 cm of the mineral soil surface, one or both of the of 13 or more) for 6 or more months in normal years. following in more than half of each pedon: Sodic Epiaquerts 1. A color value, moist, of 4 or more; or FAFC. Other Epiaquerts that, if not irrigated during the year, 2. A color value, dry, of 6 or more. have cracks in normal years that are 5 mm or more wide, Chromic Epiaquerts through a thickness of 25 cm or more within 50 cm of the mineral soil surface, for 210 or more cumulative days per year. FAFJ. Other Epiaquerts. Aridic Epiaquerts Typic Epiaquerts FAFD. Other Epiaquerts that have a thermic, mesic, or frigid soil temperature regime and that, if not irrigated during the Natraquerts year, have cracks in normal years that remain both: Key to Subgroups 1. 5 mm or more wide, through a thickness of 25 cm or FACA. All Natraquerts. more within 50 cm of the mineral soil surface, for 60 or Typic Natraquerts more consecutive days during the 90 days following the summer solstice; and 2. Closed for 60 or more consecutive days during the 90 Salaquerts days following the winter solstice. Key to Subgroups Xeric Epiaquerts FAAA. Salaquerts that, if not irrigated during the year, have FAFE. Other Epiaquerts that, if not irrigated during the year, cracks in normal years that are 5 mm or more wide, through a have cracks in normal years that are 5 mm or more wide, thickness of 25 cm or more within 50 cm of the mineral soil through a thickness of 25 cm or more within 50 cm of the surface, for 210 or more cumulative days per year. mineral soil surface, for 90 or more cumulative days per year. Aridic Salaquerts Ustic Epiaquerts FAAB. Other Salaquerts that, if not irrigated during the year, FAFF. Other Epiaquerts that have, in one or more horizons have cracks in normal years that are 5 mm or more wide, between either an Ap horizon or a depth of 25 cm from the through a thickness of 25 cm or more within 50 cm of the mineral soil surface, whichever is deeper, and a depth of 75 mineral soil surface, for 90 or more cumulative days per year. cm, 50 percent or more colors as follows: Ustic Salaquerts Vertisols 285
FAAC. Other Salaquerts that have a densic, lithic, or Humicryerts paralithic contact within 100 cm of the mineral soil surface. Leptic Salaquerts Key to Subgroups FBAA. Humicryerts that have, in one or more horizons FAAD. Other Salaquerts that have a layer 25 cm or more within 100 cm of the mineral soil surface, an exchangeable thick that contains less than 27 percent clay in its fine-earth sodium percentage of 15 or more (or a sodium adsorption ratio fraction and has its upper boundary within 100 cm of the of 13 or more) for 6 or more months in normal years. mineral soil surface. Sodic Humicryerts Entic Salaquerts FBAB. Other Humicryerts. FAAE. Other Salaquerts that have, in one or more horizons Typic Humicryerts within 30 cm of the mineral soil surface, 50 percent or more colors as follows: Torrerts 1. A color value, moist, of 4 or more; or 2. A color value, dry, of 6 or more; or Key to Great Groups 3. Chroma of 3 or more. FDA. Torrerts that have a salic horizon that has its upper Chromic Salaquerts boundary within 100 cm of the soil surface. Salitorrerts, p. 286 FAAF. Other Salaquerts. Typic Salaquerts FDB. Other Torrerts that have a gypsic horizon that has its upper boundary within 100 cm of the soil surface. Cryerts Gypsitorrerts, p. 286 Key to Great Groups FDC. Other Torrerts that have a calcic or petrocalcic horizon that has its upper boundary within 100 cm of the soil surface. FBA. Cryerts that have 10 kg/m2 or more organic carbon Calcitorrerts, p. 285 between the mineral soil surface and a depth of 50 cm. Humicryerts, p. 285 FDD. Other Torrerts. Haplotorrerts, p. 286 FBB. Other Cryerts. Haplocryerts, p. 285 Calcitorrerts Haplocryerts Key to Subgroups FDCA. Calcitorrerts that have a petrocalcic horizon that has Key to Subgroups its upper boundary within 100 cm of the soil surface. FBBA. Haplocryerts that have, in one or more horizons Petrocalcic Calcitorrerts within 100 cm of the mineral soil surface, an exchangeable sodium percentage of 15 or more (or a sodium adsorption ratio FDCB. Other Calcitorrerts that have a densic, lithic, or of 13 or more) for 6 or more months in normal years. paralithic contact, or the upper boundary of a duripan, within Sodic Haplocryerts 100 cm of the soil surface. Leptic Calcitorrerts FBBB. Other Haplocryerts that have, in one or more horizons within 30 cm of the mineral soil surface, 50 percent or more FDCC. Other Calcitorrerts that have a layer 25 cm or more colors as follows: thick that contains less than 27 percent clay in its fine-earth V fraction and has its upper boundary within 100 cm of the soil 1. A color value, moist, of 4 or more; or E surface. R 2. A color value, dry, of 6 or more; or Entic Calcitorrerts 3. Chroma of 3 or more. FDCD. Other Calcitorrerts that have, in one or more Chromic Haplocryerts horizons within 30 cm of the soil surface, 50 percent or more colors as follows: FBBC. Other Haplocryerts. Typic Haplocryerts 1. A color value, moist, of 4 or more; or 286 Keys to Soil Taxonomy
2. A color value, dry, of 6 or more; or 1. A color value, moist, of 4 or more; or 3. Chroma of 3 or more. 2. A color value, dry, of 6 or more; or 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 FDAA. Salitorrerts that have, in one or more horizons within follows: 100 cm of the soil surface, aquic conditions for some time in normal years (or artificial drainage) and either: 1. A color value, moist, of 4 or more; or 1. Redoximorphic features; or 2. A color value, dry, of 6 or more; or 2. Enough active ferrous iron (Fe2+) to give a positive 3. Chroma of 3 or more. reaction to alpha,alpha-dipyridyl at a time when the soil is Chromic Gypsitorrerts not being irrigated. Aquic Salitorrerts FDBB. Other Gypsitorrerts. Typic Gypsitorrerts FDAB. Other Salitorrerts that have a densic, lithic, or paralithic contact, or the upper boundary of a duripan or Haplotorrerts petrocalcic horizon, within 100 cm of the soil surface. Leptic Salitorrerts Key to Subgroups 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 FDAD. Other Salitorrerts that have, in one or more horizons horizons within 100 cm of the soil surface, an exchangeable within 30 cm of the soil surface, 50 percent or more colors as sodium percentage of 15 or more (or a sodium adsorption ratio follows: of 13 or more) for 6 or more months in normal years. 1. A color value, moist, of 4 or more; or Sodic Haplotorrerts 2. A color value, dry, of 6 or more; or FDDC. Other Haplotorrerts that have a densic, lithic, or 3. Chroma of 3 or more. paralithic contact, or the upper boundary of a duripan, within Chromic Salitorrerts 100 cm of the soil surface. Leptic Haplotorrerts FDAE. Other Salitorrerts. Typic Salitorrerts FDDD. Other Haplotorrerts that have a layer 25 cm or more thick that contains less than 27 percent clay in its fine-earth fraction and has its upper boundary within 100 cm of the soil Uderts surface. Entic Haplotorrerts Key to Great Groups
FDDE. Other Haplotorrerts that have, in one or more FFA. Uderts that have, throughout one or more horizons with horizons within 30 cm of the soil surface, 50 percent or more a total thickness of 25 cm or more within 50 cm of the mineral colors as follows: soil surface, both: Vertisols 287
1. An electrical conductivity in the saturation extract of FFAF. Other Dystruderts. less than 4.0 dS/m at 25 oC; and Typic Dystruderts
2. A pH value of 4.5 or less in 0.01 M CaCl2 (5.0 or less in saturated paste). Hapluderts Dystruderts, p. 287 Key to Subgroups FFB. Other Uderts. FFBA. Hapluderts that have a lithic contact within 50 cm of Hapluderts, p. 287 the mineral soil surface. Lithic Hapluderts
Dystruderts FFBB. Other Hapluderts that have, in one or more horizons within 100 cm of the mineral soil surface, aquic conditions Key to Subgroups for some time in normal years (or artificial drainage) and FFAA. Dystruderts that have, in one or more horizons either: within 100 cm of the mineral soil surface, aquic conditions 1. Redoximorphic features; or for some time in normal years (or artificial drainage) and either: 2. Enough active ferrous iron (Fe2+) to give a positive reaction to alpha,alpha-dipyridyl at a time when the soil is 1. Redoximorphic features; or not being irrigated. 2. Enough active ferrous iron (Fe2+) to give a positive Aquic Hapluderts reaction to alpha,alpha-dipyridyl at a time when the soil is not being irrigated. FFBC. Other Hapluderts that are saturated with water in one Aquic Dystruderts or more layers within 100 cm of the mineral soil surface in normal years for: FFAB. Other Dystruderts that are saturated with water in one 1. 20 or more consecutive days; or or more layers within 100 cm of the mineral soil surface in normal years for either or both: 2. 30 or more cumulative days. Oxyaquic Hapluderts 1. 20 or more consecutive days; or 2. 30 or more cumulative days. FFBD. Other Hapluderts that have a densic, lithic, Oxyaquic Dystruderts or paralithic contact within 100 cm of the mineral soil surface. Leptic Hapluderts FFAC. Other Dystruderts that have a densic, lithic, or paralithic contact within 100 cm of the mineral soil surface. FFBE. Other Hapluderts that have a layer 25 cm or more Leptic Dystruderts thick that contains less than 27 percent clay in its fine-earth fraction and has its upper boundary within 100 cm of the FFAD. Other Dystruderts that have a layer 25 cm or more mineral soil surface. thick that contains less than 27 percent clay in its fine-earth Entic Hapluderts fraction and has its upper boundary within 100 cm of the mineral soil surface. FFBF. Other Hapluderts that have, in one or more horizons Entic Dystruderts within 30 cm of the mineral soil surface, 50 percent or more colors as follows: FFAE. Other Dystruderts that have, in one or more horizons 1. A color value, moist, of 4 or more; or within 30 cm of the mineral soil surface, 50 percent or more colors as follows: 2. A color value, dry, of 6 or more; or V 1. A color value, moist, of 4 or more; or 3. Chroma of 3 or more. E Chromic Hapluderts 2. A color value, dry, of 6 or more; or R 3. Chroma of 3 or more. FFBG. Other Hapluderts. Chromic Dystruderts Typic Hapluderts 288 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 Aridic Calciusterts with 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 through a thickness of 25 cm or more within 50 cm of the less than 4.0 dS/m at 25 oC; and mineral soil surface, for less than 150 cumulative days per
2. A pH value of 4.5 or less in 0.01 M CaCl2 (5.0 or less in year. saturated paste). Udic Calciusterts Dystrusterts, p. 288 FEDG. Other Calciusterts that have a densic, lithic, or FEB. Other Usterts that have a salic horizon that has its paralithic contact, or the upper boundary of a duripan, within upper boundary within 100 cm of the mineral soil surface. 100 cm of the mineral soil surface. Salusterts, p. 291 Leptic Calciusterts
FEC. Other Usterts that have a gypsic horizon that has its FEDH. Other Calciusterts that have a layer 25 cm or more upper boundary within 100 cm of the mineral soil surface. thick that contains less than 27 percent clay in its fine-earth Gypsiusterts, p. 289 fraction and has its upper boundary within 100 cm of the mineral soil surface. FED. Other Usterts that have a calcic or petrocalcic horizon Entic Calciusterts that has its upper boundary within 100 cm of the mineral soil surface. FEDI. Other Calciusterts that have, in one or more horizons Calciusterts, p. 288 within 30 cm of the mineral soil surface, 50 percent or more colors as follows: FEE. Other Usterts. 1. A color value, moist, of 4 or more; or Haplusterts, p. 289 2. A color value, dry, of 6 or more; or Calciusterts 3. Chroma of 3 or more. Chromic Calciusterts Key to Subgroups FEDJ. Other Calciusterts. FEDA. Calciusterts that have a lithic contact within 50 cm of Typic Calciusterts the mineral soil surface. Lithic Calciusterts Dystrusterts FEDB. Other Calciusterts that have, throughout a layer 15 Key to Subgroups cm or more thick within 100 cm of the mineral soil surface, an electrical conductivity of 15 dS/m or more (saturated paste) for FEAA. Dystrusterts that have a lithic contact within 50 cm of 6 or more months in normal years. the mineral soil surface. Halic Calciusterts Lithic Dystrusterts
FEDC. Other Calciusterts that have, in one or more horizons FEAB. Other Dystrusterts that have, in one or more horizons within 100 cm of the mineral soil surface, an exchangeable within 100 cm of the mineral soil surface, aquic conditions sodium percentage of 15 or more (or a sodium adsorption ratio for some time in normal years (or artificial drainage) and of 13 or more) for 6 or more months in normal years. either: Sodic Calciusterts 1. Redoximorphic features; or FEDD. Other Calciusterts that have a petrocalcic horizon 2. Enough active ferrous iron (Fe2+) to give a positive that has its upper boundary within 100 cm of the mineral soil reaction to alpha,alpha-dipyridyl at a time when the soil is surface. not being irrigated. Petrocalcic Calciusterts Aquic Dystrusterts Vertisols 289
FEAC. Other Dystrusterts that, if not irrigated during the sodium percentage of 15 or more (or a sodium adsorption ratio year, have cracks in normal years that are 5 mm or more wide, of 13 or more) for 6 or more months in normal years. through a thickness of 25 cm or more within 50 cm of the Sodic Gypsiusterts mineral soil surface, for 210 or more cumulative days per year. FECD. Other Gypsiusterts that, if not irrigated during the Aridic Dystrusterts 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 FEAD. Other Dystrusterts that, if not irrigated during the the mineral soil surface, for 210 or more cumulative days per year, have cracks in normal years that are 5 mm or more wide, year. through a thickness of 25 cm or more within 50 cm of the Aridic Gypsiusterts mineral soil surface, for less than 150 cumulative days. Udic Dystrusterts FECE. Other Gypsiusterts that, if not irrigated during the year, have cracks in normal years that are 5 mm or more wide, FEAE. Other Dystrusterts that have a densic, lithic, or through a thickness of 25 cm or more within 50 cm of the paralithic contact, or the upper boundary of a duripan, within mineral soil surface, for less than 150 cumulative days per 100 cm of the mineral soil surface. year. Leptic Dystrusterts Udic Gypsiusterts
FEAF. Other Dystrusterts that have a layer 25 cm or more FECF. Other Gypsiusterts that have a densic, lithic, or thick that contains less than 27 percent clay in its fine-earth paralithic contact, or the upper boundary of a duripan or fraction and has its upper boundary within 100 cm of the petrocalcic horizon, within 100 cm of the mineral soil mineral soil surface. surface. Entic Dystrusterts Leptic Gypsiusterts
FEAG. Other Dystrusterts that have, in one or more horizons FECG. Other Gypsiusterts 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: fraction and has its upper boundary within 100 cm of the mineral soil surface. 1. A color value, moist, of 4 or more; or Entic Gypsiusterts 2. A color value, dry, of 6 or more; or FECH. Other Gypsiusterts that have, in one or more horizons 3. Chroma of 3 or more. within 30 cm of the mineral soil surface, 50 percent or more Chromic Dystrusterts colors as follows: FEAH. Other Dystrusterts. 1. A color value, moist, of 4 or more; or Typic Dystrusterts 2. A color value, dry, of 6 or more; or Gypsiusterts 3. Chroma of 3 or more. Chromic Gypsiusterts Key to Subgroups FECI. Other Gypsiusterts. FECA. Gypsiusterts that have a lithic contact within 50 cm of Typic Gypsiusterts the mineral soil surface. Lithic Gypsiusterts Haplusterts FECB. Other Gypsiusterts that have, throughout a layer 15 Key to Subgroups cm or more thick within 100 cm of the mineral soil surface, an V electrical conductivity of 15 dS/m or more (saturated paste) for FEEA. Haplusterts that have a lithic contact within 50 cm of E 6 or more months in normal years. the mineral soil surface. R Halic Gypsiusterts Lithic Haplusterts
FECC. Other Gypsiusterts that have, in one or more horizons FEEB. Other Haplusterts that have, throughout a layer 15 cm within 100 cm of the mineral soil surface, an exchangeable or more thick within 100 cm of the mineral soil surface, an 290 Keys to Soil Taxonomy
electrical conductivity of 15 dS/m or more (saturated paste) for percent clay in its fine-earth fraction and has its upper 6 or more months in normal years. boundary within 100 cm of the mineral soil surface; and Halic Haplusterts 2. If not irrigated during the year, cracks in normal years that are 5 mm or more wide, through a thickness of 25 cm FEEC. Other Haplusterts that have, in one or more horizons or more within 50 cm of the mineral soil surface, for less within 100 cm of the mineral soil surface, an exchangeable than 150 cumulative days per year. sodium percentage of 15 or more (or a sodium adsorption ratio Entic Udic Haplusterts of 13 or more) for 6 or more months in normal years. Sodic Haplusterts FEEK. Other Haplusterts that have both: FEED. Other Haplusterts that have a petrocalcic horizon that 1. In one or more horizons within 30 cm of the mineral has its upper boundary within 150 cm of the mineral soil soil surface, 50 percent or more colors as follows: surface. a. A color value, moist, of 4 or more; or Petrocalcic Haplusterts b. A color value, dry, of 6 or more; or FEEE. Other Haplusterts that have a gypsic horizon that has c. Chroma of 3 or more; and its upper boundary within 150 cm of the mineral soil surface. Gypsic Haplusterts 2. If not irrigated during the year, cracks in normal years that are 5 mm or more wide, through a thickness of 25 cm FEEF. Other Haplusterts that have a calcic horizon that has or more within 50 cm of the mineral soil surface, for less its upper boundary within 150 cm of the mineral soil surface. than 150 cumulative days per year. Calcic Haplusterts Chromic Udic Haplusterts
FEEG. Other Haplusterts that have both: FEEL. Other Haplusterts that, if not irrigated during the year, have cracks in normal years that are 5 mm or more wide, 1. A densic, lithic, or paralithic contact within 100 cm of through a thickness of 25 cm or more within 50 cm of the the mineral soil surface; and mineral soil surface, for less than 150 cumulative days per 2. If not irrigated during the year, cracks in normal years year. that are 5 mm or more wide, through a thickness of 25 cm Udic Haplusterts or more within 50 cm of the mineral soil surface, for 210 or more cumulative days per year. FEEM. Other Haplusterts that have a densic, lithic, or Aridic Leptic Haplusterts paralithic contact, or the upper boundary of a duripan, within 100 cm of the mineral soil surface. FEEH. Other Haplusterts that, if not irrigated during the Leptic 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 FEEN. Other Haplusterts that have a layer 25 cm or more mineral soil surface, for 210 or more cumulative days per thick that contains less than 27 percent clay in its fine-earth year. fraction and has its upper boundary within 100 cm of the Aridic Haplusterts mineral soil surface. Entic Haplusterts FEEI. Other Haplusterts that have both: FEEO. Other Haplusterts that have, in one or more horizons 1. A densic, lithic, or paralithic contact within 100 cm of within 30 cm of the mineral soil surface, 50 percent or more the mineral soil surface; and colors as follows: 2. If not irrigated during the year, cracks in 6 or more out 1. A color value, moist, of 4 or more; or of 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, 2. A color value, dry, of 6 or more; or for less than 150 cumulative days per year. 3. Chroma of 3 or more. Leptic Udic Haplusterts Chromic Haplusterts FEEJ. Other Haplusterts that have both: FEEP. Other Haplusterts. 1. A layer 25 cm or more thick that contains less than 27 Typic Haplusterts Vertisols 291
Salusterts Xererts Key to Subgroups Key to Great Groups FEBA. Salusterts that have a lithic contact within 50 cm of FCA. Xererts that have a duripan that has its upper boundary the mineral soil surface. within 100 cm of the mineral soil surface. Lithic Salusterts Durixererts, p. 292 FEBB. Other Salusterts that have, in one or more horizons FCB. Other Xererts that have a calcic or petrocalcic horizon within 100 cm of the mineral soil surface, an exchangeable that has its upper boundary within 100 cm of the mineral soil sodium percentage of 15 or more (or a sodium adsorption ratio surface. of 13 or more) for 6 or more months in normal years. Calcixererts, p. 291 Sodic Salusterts FCC. Other Xererts. FEBC. Other Salusterts that have, in one or more horizons Haploxererts, p. 292 within 100 cm of the mineral soil surface, aquic conditions for some time in normal years (or artificial drainage) and either: Calcixererts 1. Redoximorphic features; or Key to Subgroups 2. Enough active ferrous iron (Fe2+) to give a positive reaction to alpha,alpha-dipyridyl at a time when the soil is 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 year, have cracks in normal years that are 5 mm or more that has its upper boundary within 100 cm of the mineral soil wide, through a thickness of 25 cm or more within 50 cm of surface. the 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 wide, through a thickness of 25 cm or more within 50 cm of paralithic contact, or the upper boundary of a duripan or the mineral soil surface, for 180 or more consecutive days. petrocalcic 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: FCBF. Other Calcixererts that have, in one or more horizons 1. A color value, moist, of 4 or more; or within 30 cm of the mineral soil surface, 50 percent or more V 2. A color value, dry, of 6 or more; or colors as follows: E R 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 292 Keys to Soil Taxonomy
FCBG. Other Calcixererts. 3. Chroma of 3 or more. Typic Calcixererts Chromic Durixererts
Durixererts FCAH. Other Durixererts. Typic Durixererts Key to Subgroups FCAA. Durixererts that have, throughout a layer 15 cm or Haploxererts more thick above the duripan, an electrical conductivity of 15 Key to Subgroups dS/m or more (saturated paste) for 6 or more months in normal years. FCCA. Haploxererts that have a lithic contact within 50 cm Halic Durixererts of the mineral soil surface. Lithic Haploxererts FCAB. Other Durixererts that have, in one or more horizons above the duripan, an exchangeable sodium percentage of 15 or FCCB. Other Haploxererts that have, throughout a layer 15 more (or a sodium adsorption ratio of 13 or more) for 6 or cm or more thick within 100 cm of the mineral soil surface, an more months in normal years. electrical conductivity of 15 dS/m or more (saturated paste) for Sodic Durixererts 6 or more months in normal years. Halic Haploxererts FCAC. Other Durixererts that have, in one or more horizons above the duripan, aquic conditions for some time in normal FCCC. Other Haploxererts that have, in one or more years (or artificial drainage) and either: horizons within 100 cm of the mineral soil surface, an exchangeable sodium percentage of 15 or more (or a sodium 1. Redoximorphic features; or adsorption ratio of 13 or more) for 6 or more months in normal 2. Enough active ferrous iron (Fe2+) to give a positive years. reaction to alpha,alpha-dipyridyl at a time when the soil is Sodic Haploxererts not being irrigated. Aquic Durixererts FCCD. Other Haploxererts that, if not irrigated during the year, have cracks in normal years that remain 5 mm or FCAD. Other Durixererts that, if not irrigated during the more wide, through a thickness of 25 cm or more within 50 year, have cracks in normal years that remain 5 mm or more cm of the mineral soil surface, for 180 or more consecutive wide, through a thickness of 25 cm or more above the duripan, days. for 180 or more consecutive days. Aridic Haploxererts Aridic Durixererts FCCE. Other Haploxererts that have, in one or more FCAE. Other Durixererts that, if not irrigated during the horizons within 100 cm of the mineral soil surface, aquic year, have cracks in normal years that remain 5 mm or more conditions for some time in normal years (or artificial wide, through a thickness of 25 cm or more above the duripan, drainage) and either: for less than 90 consecutive days. 1. Redoximorphic features; or Udic Durixererts 2. Enough active ferrous iron (Fe2+) to give a positive FCAF. Other Durixererts that have a duripan that is not reaction to alpha,alpha-dipyridyl at a time when the soil is indurated in any subhorizon. not being irrigated. Haplic Durixererts Aquic Haploxererts
FCAG. Other Durixererts that have, in one or more horizons FCCF. Other Haploxererts that, if not irrigated during within 30 cm of the mineral soil surface, 50 percent or more the year, have cracks in normal years that remain 5 mm or colors as follows: more wide, through a thickness of 25 cm or more within 50 cm of the mineral soil surface, for less than 90 consecutive 1. A color value, moist, of 4 or more; or days. 2. A color value, dry, of 6 or more; or Udic Haploxererts Vertisols 293
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 3. Chroma of 3 or more. fraction and has its upper boundary within 100 cm of the Chromic Haploxererts mineral soil surface. Entic Haploxererts FCCJ. Other Haploxererts. FCCI. Other Haploxererts that have, in one or more horizons Typic Haploxererts
V E R
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CHAPTER 17 Family and Series Differentiae and Names
Families and series serve purposes that are largely engineering classifications. Engineering classifications have pragmatic, the series name is abstract, and the technical family set the limit between sand and silt at a diameter of 74 microns, name is descriptive. In this chapter the descriptive terms used while pedologic classifications have set it at either 50 or 20 in the names of families are defined, the control sections to microns. Engineering classifications have been based on grain- which the terms apply are given, and the criteria, including the size percentages, by weight, in the soil fraction less than 74 taxa in which they are used, are indicated. mm in diameter, while textural classes in pedologic classifications have been based on percentages, by weight, in Family Differentiae for Mineral Soils and the fraction less than 2.0 mm in diameter. In engineering classifications, the separate very fine sand (diameter between Mineral Layers of Some Organic Soils 50 and 100 microns or 0.05 and 0.1 mm) has been subdivided at 74 microns. In defining the particle-size classes for this The following differentiae are used to distinguish families of taxonomy, a similar division has been made, but in a different mineral soils and the mineral layers of some organic soils way. Soil materials that have a texture of fine sand or loamy within a subgroup. The class names of these components are fine sand normally have an appreciable amount of very fine used to form the family name. The components are listed and sand, most of which is coarser than 74 microns. A silty defined in the same sequence in which the components appear sediment, such as loess, may also contain an appreciable in the family names. amount of very fine sand, most of which is finer than 74 Particle-size classes microns. Thus, in the design of particle-size classes for this Mineralogy classes taxonomy, the very fine sand has been allowed to “float.” It is Cation-exchange activity classes included with the sand if the texture (fine-earth fraction) of a Calcareous and reaction classes soil is sand, loamy fine sand, or coarser. It is treated as silt, Soil temperature classes however, if the texture is very fine sand, loamy very fine sand, Soil depth classes sandy loam, silt loam, or finer. Rupture-resistance classes No single set of particle-size classes seems adequate to serve Classes of coatings as family differentiae for all of the different kinds of soil. Thus, Classes of cracks this taxonomy provides 2 generalized and 11 more narrowly defined classes, which permit relatively fine distinctions Particle-Size Classes and Their Substitutes between families of soils for which particle size is important, while providing broader groupings for soils in which narrowly defined particle-size classes would produce undesirable Definition of Particle-Size Classes and Their Substitutes for separations. Thus, the term “clayey” is used for some soil Mineral Soils families to indicate a clay content of 35 percent (30 percent in The first part of the family name is the name of either a Vertisols) or more in specific horizons, while in other families particle-size class or a substitute for a particle-size class. The the more narrowly defined terms “fine” and “very-fine” term particle-size class is used to characterize the grain-size indicate that these horizons have a clay content either of 35 (30 composition of the whole soil, including both the fine earth and percent in Vertisols) to 60 percent or of 60 percent or more in the rock and pararock fragments up to the size of a pedon, but their fine-earth fraction. Fine earth refers to particles smaller it excludes organic matter and salts more soluble than gypsum. than 2.0 mm in diameter. Rock fragments are particles 2.0 mm Substitutes for particle-size classes are used for soils that have or more in diameter that are strongly cemented or more andic soil properties or a high content of volcanic glass, resistant to rupture and include all particles with horizontal F pumice, or cinders. dimensions smaller than the size of a pedon. Cemented A The particle-size classes of this taxonomy represent a fragments 2.0 mm or more in diameter that are in a rupture- M compromise between conventional divisions in pedologic and resistance class that is less cemented than the strongly 296 Keys to Soil Taxonomy
cemented class are referred to as pararock fragments. Pararock clayey; and the transition zone is less than 12.5 cm thick. If a fragments, like rock fragments, include all particles between substitute name applies to one or more parts of the particle-size 2.0 mm and a horizontal dimension smaller than the size of a control section and the parts are not strongly contrasting pedon. Most pararock fragments are broken into fragments 2.0 classes, the name of the thickest part (cumulative) is used as mm or less in diameter during the preparation of samples for the soil family name. particle-size analysis in the laboratory. Therefore, pararock Aniso Class fragments are generally included with the fine earth in the particle-size classes, although cinders, pumice, and pumicelike If the particle-size control section includes more than one fragments are treated as fragments in the substitutes for pair of the strongly contrasting classes, listed below, then the classes, regardless of their rupture-resistance class. soil is assigned to an aniso class named for the pair of adjacent Substitutes for particle-size classes are used for soils that classes that contrast most strongly. The aniso class is have andic soil properties or a high content of volcanic glass, considered part of the particle-size class name and is set off by pumice, or cinders. These materials cannot be readily commas after the particle-size name. An example is a sandy dispersed, and the results of dispersion vary. Consequently, over clayey, aniso, mixed, active, mesic Aridic Haplustoll. normal particle-size classes do not adequately characterize Generalized Particle-Size Classes these components. Substitutes for particle-size class names are used for those parts of soils that have andic soil properties or a Two generalized particle-size classes, loamy and clayey, are high amount of volcanic glass, pumice, or cinders, as is the used for shallow classes (defined below) and for soils in case with Andisols and many Andic and Vitrandic subgroups Arenic, Grossarenic, and Lithic subgroups. The clayey class is of other soil orders. Some Spodosols, whether identified in used for all strongly contrasting particle-size classes with more Andic subgroups or not, have andic soil properties in some than 35 percent clay (30 percent in Vertisols). The loamy horizons within the particle-size control section, and particle- particle-size class is used for contrasting classes, where size substitute class names are used for these horizons. appropriate, to characterize the lower part of the particle-size Neither a particle-size class name nor a substitute for a control section. The generalized classes, where appropriate, are particle-size class name is used for Psamments, also used for all strongly contrasting particle-size classes that Psammaquents, and Psammentic subgroups that are in a sandy include a substitute class. For example, loamy over pumiceous particle-size class. These taxa have, by definition, either a or cindery (not fine-loamy over pumiceous or cindery) is used. sandy particle-size class or an ashy substitute class. The sandy Six generalized classes, defined later in this chapter, are particle-size class is considered redundant in the family name. used for Terric subgroups of Histosols and Histels. The ashy substitute class, however, is named, if appropriate in Control Section for Particle-Size Classes or Their these taxa. Substitutes in Mineral Soils Particle-size class names are applied, although with reservations, to spodic horizons and other horizons that do not The particle-size and substitute class names listed below are have andic soil properties but contain significant amounts of applied to certain horizons, or to the soil materials within allophane, imogolite, ferrihydrite, or aluminum-humus specific depth limits, that have been designated as the particle- complexes. The isotic mineralogy class (defined below) is size control section. The lower boundary of the control section helpful in identifying these particle-size classes. may be at a specified depth (in centimeters) below the mineral In general, the weighted average particle-size class of the soil surface or below the upper boundary of an organic layer whole particle-size control section (defined below) determines with andic soil properties, or it may be at the upper boundary what particle-size class name is used as a component of the of a root-limiting layer. Unless otherwise indicated, the family name. following are considered root-limiting layers in this chapter: a duripan; a fragipan; petrocalcic, petrogypsic, and placic Strongly Contrasting Particle-Size Classes horizons; continuous ortstein; and densic, lithic, paralithic, If the particle-size control section consists of two parts with and petroferric contacts. The following list of particle-size strongly contrasting particle-size or substitute classes (listed control sections for particular kinds of mineral soils is below), if both parts are 12.5 cm or more thick (including parts arranged as a key. This key, like other keys in this taxonomy, is not in the control section), and if the transition zone between designed in such a way that the reader makes the correct them is less than 12.5 cm thick, both class names are used. For classification by going through the key systematically, starting example, the family particle-size class is sandy over clayey if at the beginning and eliminating one by one all classes that all of the following criteria are met: the soil meets criterion D include criteria that do not fit the soil in question. The soil (listed below) under the control section for particle-size classes belongs to the first class for which it meets all of the criteria or their substitutes; any Ap horizon is less than 30 cm thick; listed. The upper boundary of an argillic, natric, or kandic the weighted average particle-size class of the upper 30 cm of horizon is used in the following key. This boundary is not the soil is sandy; the weighted average of the lower part is always obvious. If one of these horizons is present but the Family and Series Differentiae and Names 297
upper boundary is irregular or broken, as in an A/B or B/A the mineral soil surface or a root-limiting layer, whichever is horizon, the depth at which half or more of the volume has the shallower; or fabric of an argillic, natric, or kandic horizon should be E. For other soils that have an argillic or natric horizon that considered the upper boundary. has its lower boundary at a depth of less than 25 cm from the Key to the Control Section for Particle-Size Classes or mineral surface: Between the upper boundary of the argillic Their Substitutes in Mineral Soils or natric horizon and a depth of 100 cm below the mineral soil surface or a root-limiting layer, whichever is shallower; A. For mineral soils that have a root-limiting layer (listed or above) within 36 cm of the mineral soil surface or below the upper boundary of organic soil materials with andic soil F. All other mineral soils: Between the lower boundary of an properties, whichever is shallower: From the mineral soil Ap horizon or a depth of 25 cm below the mineral soil surface, surface or the upper boundary of the organic soil materials with whichever is deeper, and the shallower of the following: (a) a andic soil properties, whichever is shallower, to the root- depth of 100 cm below the mineral soil surface or (b) a root- limiting layer; or limiting layer. B. For Andisols: Between either the mineral soil surface or Key to the Particle-Size and Substitute Classes of Mineral the upper boundary of an organic layer with andic soil Soils properties, whichever is shallower, and the shallower of the This key, like other keys in this taxonomy, is designed in following: (a) a depth 100 cm below the starting point or (b) a such a way that the reader makes the correct classification by root-limiting layer; or going through the key systematically, starting at the beginning C. For those Alfisols, Ultisols, and great groups of Aridisols and eliminating one by one all classes that include criteria that and Mollisols, excluding soils in Lamellic subgroups, that have do not fit the soil or layer in question. The class or substitute an argillic, kandic, or natric horizon that has its upper name for each layer within the control section must be boundary within 100 cm of the mineral soil surface and its determined from the key. If any two layers meet the criteria for lower boundary at a depth of 25 cm or more below the mineral strongly contrasting particle-size classes (listed below), the soil soil surface or that are in a Grossarenic or Arenic subgroup, is named for that strongly contrasting class. If more than one use 1 through 4 below. For other soils, go to D below. pair meets the criteria for strongly contrasting classes, the soil is also in an aniso class named for the pair of adjacent classes 1. Strongly contrasting particle-size classes (defined and that contrast most strongly. If the soil has none of the strongly listed later) within or below the argillic, kandic, or natric contrasting classes, the weighted average soil materials within horizon and within 100 cm of the mineral soil surface: The the particle-size control section generally determine the class. upper 50 cm of the argillic, kandic, or natric horizon or to a Exceptions are soils that are not strongly contrasting and that depth of 100 cm, whichever is deeper, but not below the have a substitute class name for one or more parts of the upper boundary of a root-limiting layer; or control section. In these soils the class or substitute name of the 2. All parts of the argillic, kandic, or natric horizon in or thickest (cumulative) part within the control section is used to below a fragipan: Between a depth of 25 cm from the determine the family name. mineral soil surface and the top of the fragipan; or A. Mineral soils that have, in the thickest part of the control 3. A fragipan at a depth of less than 50 cm below the top section (if the control section is not in one of the strongly of the argillic, kandic, or natric horizon: Between the upper contrasting particle-size classes listed below), or in a part of boundary of the argillic, kandic, or natric horizon and the the control section that qualifies as an element in one of the top the fragipan; or strongly contrasting particle-size classes listed below, or throughout the control section, a fine-earth component 4. Other soils that meet C above: Either the whole argillic, (including associated medium and finer pores) of less than 10 kandic, or natric horizon if 50 cm or less thick or the upper percent of the total volume and that meet one of the following 50 cm of the horizon if more than 50 cm thick. sets of substitute class criteria: D. For those Alfisols, Ultisols, and great groups of Aridisols 1. Have, in the whole soil, more than 60 percent (by and Mollisols that are in a Lamellic subgroup or have an weight) volcanic ash, cinders, lapilli, pumice, and argillic, kandic, or natric horizon that has its upper boundary pumicelike1 fragments and, in the fraction coarser than 2.0 at a depth of 100 cm or more from the mineral surface and that F are not in a Grossarenic or Arenic subgroup: Between the A lower boundary of an Ap horizon or a depth of 25 cm from the 1 Pumicelike—vesicular pyroclastic materials other than pumice that have an apparent M mineral soil surface, whichever is deeper, and 100 cm below specific gravity (including vesicles) of less than 1.0 g/cm3. 298 Keys to Soil Taxonomy
mm, two-thirds or more (by volume) pumice and/or (3) Less than 35 percent (by volume) rock pumicelike fragments. fragments. Pumiceous Ashy or or
2. Have, in the whole soil, more than 60 percent (by 2. Have a fine-earth fraction that has andic soil properties weight) volcanic ash, cinders, lapilli, pumice, and and that has a water content at 1500 kPa tension of 12 pumicelike fragments and, in the fraction coarser than 2.0 percent or more on air-dried samples or of 30 to 100 percent mm, less than two-thirds (by volume) pumice and on undried samples; and pumicelike fragments. a. Have a total of 35 percent or more (by volume) rock Cindery and pararock fragments, of which two-thirds or more (by or volume) is pumice or pumicelike fragments. Medial-pumiceous 3. Other mineral soils that have a fine-earth component of or less than 10 percent (including associated medium and finer pores) of the total volume. b. Have 35 percent or more (by volume) rock Fragmental fragments. or Medial-skeletal or B. Other mineral soils that have a fine-earth component of 10 percent or more (including associated medium and finer pores) c. Have less than 35 percent (by volume) rock of the total volume and meet, in the thickest part of the control fragments. section (if the control section is not in one of the strongly Medial contrasting particle-size classes listed below), or in a part of or the control section that qualifies as an element in one of the strongly contrasting particle-size classes listed below, or 3. Have a fine-earth fraction that has andic soil properties throughout the control section, one of the following sets of and that has a water content at 1500 kPa tension of 100 substitute class criteria: percent or more on undried samples; and 1. They: a. Have a total of 35 percent or more (by volume) rock a. Have andic soil properties and have a water and pararock fragments, of which two-thirds or more (by content at 1500 kPa tension of less than 30 percent on volume) is pumice or pumicelike fragments. undried samples and less than 12 percent on dried Hydrous-pumiceous samples; or or b. Do not have andic soil properties, have a total of 30 b. Have 35 percent or more (by volume) rock percent or more of the fine-earth fraction in the 0.02 to fragments. 2.0 mm fraction, and have (by grain count) 30 percent or Hydrous-skeletal more of that fraction consisting of volcanic glass, glass or aggregates, glass-coated grains, and other vitric volcaniclastics; and c. Have less than 35 percent (by volume) rock c. Have one of the following; fragments. Hydrous (1) A total of 35 percent or more (by volume) rock or and pararock fragments, of which two-thirds or more (by volume) is pumice or pumicelike fragments. Ashy-pumiceous Note: In the following classes, “clay” excludes clay-size or carbonates. Carbonates of clay size are treated as silt. If the ratio of percent water retained at 1500 kPa tension to the (2) 35 percent or more (by volume) rock fragments. percentage of measured clay is 0.25 or less or 0.6 or more in Ashy-skeletal half or more of the particle-size control section or part of the or particle-size control section in strongly contrasting classes, Family and Series Differentiae and Names 299
then the percentage of clay is estimated by the following percent or more (by weight) particles with diameters of 0.1 formula: Clay % = 2.5(% water retained at 1500 kPa tension - to 75 mm (fine sand or coarser, including rock fragments up % organic carbon). to 7.5 cm in diameter) and 18 to 35 percent (by weight) clay (Vertisols are excluded). C. Other mineral soils that, in the thickest part of the control Fine-loamy section (if part of the control section has a substitute for or particle-size class and is not in one of the strongly contrasting particle-size classes listed below), or in a part of the control 8. Have, in the fraction less than 75 mm in diameter, less section that qualifies as an element in one of the strongly than 15 percent (by weight) particles with diameters of 0.1 contrasting particle-size classes listed below, or throughout the to 75 mm (fine sand or coarser, including rock fragments up control section, meet one of the following sets of particle-size to 7.5 cm in diameter) and, in the fine-earth fraction, less class criteria: than 18 percent (by weight) clay. 1. Have 35 percent or more (by volume) rock fragments Coarse-silty and a fine-earth fraction with a texture of sand or loamy or sand, including less than 50 percent (by weight) very fine sand. 9. Have, in the fraction less than 75 mm in diameter, less Sandy-skeletal than 15 percent (by weight) particles with diameters of 0.1 or to 75 mm (fine sand or coarser, including rock fragments up to 7.5 cm in diameter) and, in the fine-earth fraction, 18 to 2. Have 35 percent or more (by volume) rock fragments 35 percent (by weight) clay (Vertisols are excluded). and less than 35 percent (by weight) clay. Fine-silty Loamy-skeletal or or 10. Have 35 percent or more (by weight) clay (more 3. Have 35 percent or more (by volume) rock fragments. than 30 percent in Vertisols) and are in a shallow family Clayey-skeletal (defined below) or in a Lithic, Arenic, or Grossarenic or subgroup, or the layer is an element in a strongly contrasting particle-size class (listed below). 4. Have a texture of sand or loamy sand, including less Clayey than 50 percent (by weight) very fine sand in the fine-earth or fraction. Sandy 11. Have (by weighted average) less than 60 percent (by or weight) clay in the fine-earth fraction. Fine 5. Have a texture of loamy very fine sand, very fine sand, or or finer, including less than 35 percent (by weight) clay in the fine-earth fraction (excluding Vertisols), and are in a 12. Have 60 percent or more clay. shallow family (defined below) or in a Lithic, Arenic, or Very-fine Grossarenic subgroup, or the layer is an element in a Strongly Contrasting Particle-Size Classes strongly contrasting particle-size class (listed below) and the layer is the lower element or the other element is a The purpose of strongly contrasting particle-size classes is substitute for particle-size class. to identify changes in pore-size distribution or composition that Loamy are not identified in higher soil categories and that seriously or affect the movement and retention of water and/or nutrients. The following particle-size or substitute classes are 6. Have, in the fraction less than 75 mm in diameter, 15 considered strongly contrasting if both parts are 12.5 cm or percent or more (by weight) particles with diameters of 0.1 more thick (including parts not in the particle-size control to 75 mm (fine sand or coarser, including rock fragments up section; however, substitute class names are used only if the to 7.5 cm in diameter) and, in the fine-earth fraction, less soil materials to which they apply extend 10 cm or more into than 18 percent (by weight) clay. the upper part of the particle-size control section) and if the F Coarse-loamy transition zone between the two parts of the particle-size A or control section is less than 12.5 cm thick. M Some classes, such as sandy and sandy-skeletal, have been 7. Have, in the fraction less than 75 mm in diameter, 15 combined in the following list. In those cases the combined 300 Keys to Soil Taxonomy
name is used as the family class if part of the control section 25. Fine-loamy over fragmental meets the criteria for either class. 26. Fine-loamy over sandy or sandy-skeletal 1. Ashy over clayey 27. Fine-silty over clayey (if there is an absolute difference of 2. Ashy over clayey-skeletal 25 percent or more between clay percentages of the fine-earth fraction in the two parts of the control section) 3. Ashy over loamy-skeletal 28. Fine-silty over fragmental 4. Ashy over loamy 29. Fine-silty over sandy or sandy-skeletal 5. Ashy over medial-skeletal 30. Hydrous over clayey-skeletal 6. Ashy over medial (if the water content at 1500 kPa tension in dried samples of the fine-earth fraction is 10 percent or less 31. Hydrous over clayey for the ashy materials and 15 percent or more for the medial 32. Hydrous over fragmental materials) 33. Hydrous over loamy-skeletal 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 the fine-earth fraction is 35 percent or more [absolute] greater 36. Loamy over sandy or sandy-skeletal (if the loamy in the ashy-skeletal part than in the fragmental or cindery part) material contains less than 50 percent fine sand or coarser sand) 10. Cindery over loamy 37. Loamy over pumiceous or cindery 11. Cindery over medial-skeletal 38. Loamy-skeletal over cindery (if the volume of the fine- 12. Cindery over medial earth fraction is 35 percent or more [absolute] greater in the 13. Clayey over fine-silty (if there is an absolute difference of loamy-skeletal part than in the cindery part) 25 percent or more between clay percentages of the fine-earth 39. Loamy-skeletal over clayey (if there is an absolute fraction in the two parts of the control section) difference of 25 percent or more between clay percentages of 14. Clayey over fragmental the fine-earth fraction in the two parts of the control section) 15. Clayey over loamy (if there is an absolute difference of 25 40. Loamy-skeletal over fragmental (if the volume of the percent or more between clay percentages of the fine-earth fine-earth fraction is 35 percent or more [absolute] greater in fraction in the two parts of the control section) the loamy-skeletal part than in the fragmental part) 16. Clayey over loamy-skeletal (if there is an absolute 41. Loamy-skeletal over sandy or sandy-skeletal (if the loamy difference of 25 percent or more between clay percentages of material has less than 50 percent fine sand or coarser sand) the fine-earth fraction in the two parts of the control section) 42. Medial over ashy (if the water content at 1500 kPa 17. Clayey over sandy or sandy-skeletal tension in dried samples of the fine-earth fraction is 15 percent or more for the medial materials and 10 percent or less for the 18. Clayey-skeletal over sandy or sandy-skeletal ashy materials) 19. Coarse-loamy over clayey 43. 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-earth fraction is 15 percent or more for the medial materials and 10 21. Coarse-loamy over sandy or sandy-skeletal (if the coarse- percent or less for the ashy part) loamy material contains less than 50 percent fine sand or coarser sand) 44. Medial over clayey-skeletal 22. Coarse-silty over clayey 45. Medial over clayey 23. Coarse-silty over sandy or sandy-skeletal 46. Medial over fragmental 24. Fine-loamy over clayey (if there is an absolute difference 47. 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) Family and Series Differentiae and Names 301
48. Medial over loamy-skeletal clayey, mixed (if both the ashy and clayey parts are mixed), superactive, mesic Typic Vitraquand and a clayey over sandy or 49. Medial over loamy sandy-skeletal, smectitic over mixed, thermic Vertic 50. Medial over pumiceous or cindery Haplustept. 51. Medial over sandy or sandy-skeletal A. Oxisols and “kandi” and “kanhap” great groups of Alfisols and Ultisols that in the mineralogy control section 52. Medial-skeletal over fragmental or cindery (if the volume have: of the fine-earth fraction is 35 percent or more [absolute] greater in the medial-skeletal part than the fragmental or 1. More than 40 percent iron oxide (more than 28 percent cindery part) Fe), by dithionite citrate, in the fine-earth fraction. Ferritic 53. Pumiceous or ashy-pumiceous over loamy or 54. Pumiceous or ashy-pumiceous over medial-skeletal 2. More than 40 percent gibbsite in the fine-earth fraction. 55. Pumiceous or ashy-pumiceous over medial Gibbsitic 56. Pumiceous or ashy-pumiceous over sandy or sandy- or skeletal 3. Both: 57. Sandy over clayey a. 18 to 40 percent iron oxide (12.6 to 28 percent Fe), 58. Sandy over loamy (if the loamy material contains less by dithionite citrate, in the fine-earth fraction; and than 50 percent fine sand or coarser sand) b. 18 to 40 percent gibbsite in the fine-earth fraction. 59. Sandy-skeletal over loamy (if the loamy material contains Sesquic less than 50 percent fine sand or coarser sand) or
Mineralogy Classes 4. 18 to 40 percent iron oxide (12.6 to 28 percent Fe), by dithionite citrate, in the fine-earth fraction. The mineralogy of soils is known to be useful in making Ferruginous predictions about soil behavior and responses to management. or Some mineralogy classes occur or are important only in certain taxa or particle-size classes, and others are important in all 5. 18 to 40 percent gibbsite in the fine-earth 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 halloysite, dickite, nacrite, and other 1:1 and nonexpanding that defined for the particle-size classes and their substitutes. 2:1 layer minerals and gibbsite in the fraction less than 0.002 in size and more kaolinite than halloysite. Key to Mineralogy Classes Kaolinitic This key, like other keys in this taxonomy, is designed in or such a way that the reader makes the correct classification by 7. More than 50 percent (by weight) halloysite plus going through the key systematically, starting at the beginning kaolinite and allophane in the fraction less than 0.002 in and eliminating one by one any classes that include criteria size. that do not fit the soil in question. The soil belongs to the first Halloysitic class for which it meets all of the required criteria. The user or should first check the criteria in section A and, if the soil in question does not meet the criteria listed there, proceed on to 8. All other properties. sections B, C, D, and E, until the soil meets the criteria listed. Mixed All criteria are based on a weighted average. or For soils with strongly contrasting particle-size classes, the F mineralogy for both named particle-size classes or substitutes A are given, unless they are the same. Examples are an ashy over B. Other soil layers or horizons, in the mineralogy control M 302 Keys to Soil Taxonomy
section, that have a substitute class that replaces the particle- 4. Any particle-size class, except for fragmental, and more size class and that: than 40 percent (by weight) hydrated aluminum oxides, reported as gibbsite and bohemite, in the fine-earth 1. Have a sum of 8 times the Si (percent by weight fraction. extracted by acid oxalate) plus 2 times the Fe (percent by Gibbsitic weight extracted by acid oxalate) of 5 or more, and 8 times or the Si is more than 2 times the Fe. Amorphic 5. Any particle-size class, except for fragmental, and more or than 40 percent (by weight) magnesium-silicate minerals, such as the serpentine minerals (antigorite, chrysotile, and 2. Other soils that have a sum of 8 times the Si (percent lizardite) plus talc, olivines, Mg-rich pyroxenes, and Mg- by weight extracted by acid oxalate) plus 2 times the Fe rich amphiboles, in the fine-earth fraction. (percent by weight extracted by acid oxalate) of 5 or Magnesic more. or Ferrihydritic or 6. Any particle-size class, except for fragmental, and a total iron oxide, by weight (Fe extracted by citrate-dithionite 3. Other soils that have 30 percent or more (by grain times 1.43 is used to determine the iron oxide), plus percent count) volcanic glass in the 0.02 to 2.0 mm fraction. (by weight) gibbsite of more than 10 percent in the fine- Glassy earth fraction. or Parasesquic or 4. All other soils that have a substitute class. Mixed 7. Any particle-size class, except for fragmental, and more or than 20 percent (by weight) glauconitic pellets in the fine- earth fraction. C. Other mineral soil layers or horizons, in the mineralogy Glauconitic control section, in all other mineral soil orders and in Terric or subgroups of Histosols and Histels that have: 1. Any particle-size class and more than 40 percent (by D. Other mineral soil layers or horizons, in the mineralogy weight) carbonates (expressed as CaCO ) plus gypsum, with 3 control section, of soils in all other mineral orders and in gypsum constituting more than 35 percent of the total Terric subgroups of Histosols and Histels, in a clayey, clayey- weight of carbonates plus gypsum, either in the fine-earth skeletal, fine or very-fine particle-size class, that in the fraction fraction or in the fraction less than 20 mm in size, less than 0.002 mm in size: whichever has a higher percentage of carbonates plus gypsum. 1. Have more than one-half (by weight) halloysite plus Gypsic kaolinite and allophane and more halloysite than any other or single mineral. Halloysitic 2. Any particle-size class and more than 40 percent (by or
weight) carbonates (expressed as CaCO3) plus gypsum, either in the fine-earth fraction or in the fraction less than 2. Have more than one-half (by weight) kaolinite plus 20 mm in size, whichever has a higher percentage of halloysite, dickite, and nacrite, and other 1:1 or carbonates plus gypsum. nonexpanding 2:1 layer minerals or gibbsite, and less than Carbonatic 10 percent (by weight) smectite. or Kaolinitic or 3. Any particle-size class, except for fragmental, and more than 40 percent (by weight) iron oxide (extractable by 3. Have more smectite (montmorillonite, beidellite, and
dithionite citrate), reported as Fe2O3 (or 28 percent reported nontronite), by weight, than any other single kind of clay as Fe), in the fine-earth fraction. mineral. Ferritic Smectitic or or Family and Series Differentiae and Names 303
4. Have more than one-half (by weight) illite (hydrous minerals that are resistant to weathering, in the 0.02 to 2.0
mica) and commonly more than 4 percent K2O. mm fraction. Illitic Siliceous or or
5. Have more vermiculite than any other single kind of 5. All other properties. clay mineral. Mixed Vermiculitic or Cation-Exchange Activity Classes
6. In more than one-half of the thickness, meet all of the The cation-exchange activity classes help in making following: interpretations of mineral assemblages and of the nutrient- holding capacity of soils in mixed and siliceous mineralogy a. Have no free carbonates; and classes of clayey, clayey-skeletal, coarse-loamy, coarse-silty, b. The pH of a suspension of 1 g soil in 50 ml 1 M NaF fine, fine-loamy, fine-silty, loamy, loamy-skeletal, and very-fine is more than 8.4 after 2 minutes; and particle-size classes. Cation-exchange activity classes are not assigned to Histosols and Histels, and they are not assigned to c. The ratio of 1500 kPa water to measured clay is 0.6 Oxisols and “kandi” and “kanhap” great groups and subgroups or 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 E. All other mineral soil layers or horizons, in the determination. The criteria for the classes use ratios of CEC to mineralogy control section, that have: the percent, by weight, of silicate clay, both by weighted 1. More than 40 percent (by weight) (80 percent by grain average in the control section. In the following classes “clay” count) mica and stable mica pseudomorphs in the 0.02 to excludes clay-size carbonates. If the ratio of percent water 2.0 mm fraction. retained at 1500 kPa tension to the percentage of measured Micaceous clay is 0.25 or less or 0.6 or more in half or more of the or particle-size control section (or part in contrasting families), then the percentage of clay is estimated by the following 2. More than 25 percent (by weight) (65 percent by grain formula: Clay % = 2.5(% water retained at 1500 kPa tension - count) mica and stable mica pseudomorphs in the 0.02 to % organic carbon). 2.0 mm fraction. Paramicaceous Control Section for Cation-Exchange Activity Classes or The control section for cation-exchange activity classes is the same as that used to determine the particle-size and 3. In more than one-half of the thickness, all of the mineralogy classes. For soils with strongly contrasting particle- following: size classes, where both named parts of the control section use a. No free carbonates; and a cation-exchange activity class, the class associated with the particle-size class that has the most clay is named. For b. The pH of a suspension of 1 g soil in 50 ml 1 M NaF example, in a pedon with a classification of loamy over clayey, is more than 8.4 after 2 minutes; and mixed, active, calcareous, thermic Typic Udorthent, the cation- c. A ratio of 1500 kPa water to measured clay of 0.6 or exchange activity class “active” is associated with the clayey more. part of the control section. Isotic Key to Cation-Exchange Activity Classes F or A A. Soils that are not Histosols, Histels, or Oxisols, that are M 4. More than 90 percent (by weight) silica minerals not in “kandi” or “kanhap” great groups or subgroups of (quartz, chalcedony, or opal) and other extremely durable Alfisols and Ultisols, that are in either a mixed or siliceous 304 Keys to Soil Taxonomy
mineralogy class, that are not in a fragmental, sandy, or sandy- 1. Soils with a root-limiting layer that is 25 cm or less below skeletal particle-size class or any substitute for a particle-size the mineral soil surface: A 2.5-cm-thick layer directly above class, and that have a ratio of cation-exchange capacity (by the root-limiting layer. NH OAc at pH 7) to clay (percent by weight) of: 4 2. Soils with a root-limiting layer that is 26 to 50 cm below 1. 0.60 or more. the mineral soil surface: The layer between a depth of 25 cm Superactive below the mineral soil surface and the root-limiting layer. 3. All other listed soils: Between a depth of 25 and 50 cm 2. 0.40 to 0.60. below the mineral soil surface. Active The control section for the acid, nonacid, and allic classes is 3. 0.24 to 0.40. the same as that for particle-size classes. Semiactive Key to Calcareous and Reaction Classes 4. Less than 0.24. A. Oxisols that have a layer, 30 cm or more thick within the Subactive control section, that contains more than 2 cmol(+) of KCl- or extractable Al per kg soil in the fine-earth fraction. Allic B. All other soils: No cation-exchange activity classes used. B. Other listed soils that, in the fine-earth fraction, effervesce Calcareous and Reaction Classes of Mineral Soils (in cold dilute HCl) in all parts of the control section. Calcareous The presence or absence of carbonates, soil reaction, and the presence of high concentrations of aluminum in mineral soils C. Other listed soils with a pH of less than 5.0 in 0.01 M are treated together because they are so intimately related. CaCl2 (1:2) (about pH 5.5 in H2O, 1:1) throughout the control There are four classes—calcareous, acid, nonacid, and allic. section. These are defined later in the key to calcareous and reaction Acid classes. The 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 CaCl (1:2) in some or all layers in the control section. Use of the Calcareous and Reaction Classes 2 Nonacid The calcareous, acid, and nonacid classes are used in the names of the families of Entisols, Aquands, and Aquepts, It should be noted that a soil containing dolomite is except 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 class. 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 in the names of the families of Aquolls, except it is not used as part of the family name in both mineral and organic used with any of the following: soils. Temperature class names are used as part of the family name unless the criteria for a higher taxon carry the same 1. Calciaquolls, Natraquolls, and Argiaquolls limitation. Thus, frigid is implied in all cryic suborders, great 2. Cryaquolls and Duraquolls that have an argillic horizon groups, and 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 following: of 50 cm from the soil surface or is at the upper boundary of a Family and Series Differentiae and Names 305
root-limiting layer, whichever is shallower. The soil 3. 15 oC (59 oF) to 22 oC (72 oF). temperature classes, defined in terms of the mean annual soil Isothermic temperature and the difference between mean summer and or mean winter temperatures, are determined by the following key. 4. 22 oC (72 oF) or higher. Isohyperthermic Key to Soil Temperature Classes A. Gelisols that have a mean annual soil temperature as Soil Depth Classes follows: Soil depth classes are used in all families that have a root- 1. -10 oC or lower. limiting layer at a specified depth from the mineral soil Hypergelic surface, except for those families in Lithic subgroups and those or with a fragipan. The root-limiting layers included in soil depth classes are duripans; petrocalcic, petrogypsic, and placic 2. -4 oC to -10 oC. horizons; continuous ortstein (90 percent or more); and densic, Pergelic lithic, paralithic, and petroferric contacts. Soil depth classes for or Histosols and Histels are given later in this chapter. One soil depth class name, “shallow,” is used to characterize certain 3. +1 oC to -4 oC. mineral soil families that have one of the depths indicated in Subgelic the following key. or Key to Soil Depth Classes B. Other soils that have a difference in soil temperature of A. Oxisols that are less than 100 cm deep (from the mineral 5 oC or more between mean summer (June, July, and August in soil surface) to a root-limiting layer and are not in a Lithic the Northern Hemisphere) and mean winter (December, subgroup. January, and February in the Northern Hemisphere) and a Shallow mean annual soil temperature of: or 1. Lower than 8 oC (47 oF). Frigid B. Soils in all other mineral soil orders that are less than 50 or cm deep (from the mineral soil surface) to a root-limiting layer and are not in a Lithic subgroup. 2. 8 oC (47 oF) to 15 oC (59 oF). Shallow Mesic or or C. All other mineral soils: No soil depth class used. 3. 15 oC (59 oF) to 22 oC (72 oF). Thermic Rupture-Resistance Classes or In this taxonomy, some partially cemented soil 4. 22 oC (72 oF) or higher. materials, such as durinodes, serve as differentiae in Hyperthermic categories above the family, while others, such as partially or cemented spodic materials (ortstein), do not. No single family, however, should include soils both with and without C. All other soils that have a mean annual soil temperature partially cemented horizons. In Spodosols, a partially as follows: cemented spodic horizon is used as a family differentia. The following rupture-resistance class is defined for families 1. Lower than 8 oC (47 oF). of Spodosols: Isofrigid or A. Spodosols that have an ortstein horizon. Ortstein F o o o o 2. 8 C (47 F) to 15 C (59 F). or A Isomesic M or B. All other soils: No rupture-resistance class used. 306 Keys to Soil Taxonomy
Classes of Coatings (on Sands) Key to Classes of Permanent Cracks A. Fluvaquents or Humaquepts that have, throughout a layer Despite the emphasis given to particle-size classes in this 50 cm or more thick, continuous, permanent, lateral and taxonomy, variability remains in the sandy particle-size class, vertical cracks 2 mm or more wide, spaced at average lateral which includes sands and loamy sands. Some sands are very intervals of less than 50 cm. clean, i.e., almost completely free of silt and clay, while others Cracked are mixed with appreciable amounts of finer grains. Clay is or more efficient at coating sand than is silt. A weighted average silt (by weight) plus 2 times the weighted average clay (by B. All other Fluvaquents and Humaquepts: No class of weight) of more than 5 makes a reasonable division of the permanent cracks used. sands at the family level. Two classes of Quartzipsamments are defined in terms of their content of silt plus 2 times their content of clay. Family Differentiae for Histosols and Control Section for Classes of Coatings Histels The control section for classes of coatings is the same as Most of the differentiae that are used to distinguish families that for particle-size classes or their substitutes and for of Histosols and Histels have already been defined, either mineralogy classes. because they are used as differentiae in mineral soils as well as Histosols and Histels or because their definitions are used for Key to Classes of Coatings the classification of some Histosols and Histels in categories A. Quartzipsamments that have a sum of the weighted higher than the family. In the following descriptions, average silt (by weight) plus 2 times the weighted average clay differentiae not previously mentioned are defined and the of more than 5. classes in which they are used are enumerated. Coated The order in which family classes, if appropriate for a or particular family, are placed in the technical family names of Histosols and Histels is as follows: B. Other Quartzipsamments. Particle-size classes Uncoated Mineralogy classes, including the nature of limnic deposits in Histosols Classes of Permanent Cracks Reaction classes Soil temperature classes Some Hydraquents consolidate or shrink after drainage and Soil depth classes (used only in Histosols) become Fluvaquents or Humaquepts. In the process they can form polyhedrons roughly 12 to 50 cm in diameter, depending Particle-Size Classes on their n value and texture. These polyhedrons are separated by cracks that range in width from 2 mm to more than 1 cm. Particle-size classes are used only for the family names of The polyhedrons may shrink and swell with changes in the Terric subgroups of Histosols and Histels. The classes are moisture content of the soils, but the cracks are permanent and determined from the properties of the mineral soil materials in can persist for several hundreds of years, even if the soils are the control section through use of the key to particle-size cultivated. The cracks permit rapid movement of water through classes. The classes are more generalized than those for soils in the soils, either vertically or laterally. Such soils may have the other orders. same texture, mineralogy, and other family properties as soils Control Section for Particle-Size Classes that do not form cracks or that have cracks that open and close with the seasons. Soils with permanent cracks are very rare in The particle-size control section is the upper 30 cm of the the United States. mineral layer or of that part of the mineral layer that is within the control section for Histosols and Histels (given in chapter Control Section for Classes of Permanent Cracks 3), whichever is thicker. The control section for classes of permanent cracks is from Key to Particle-Size Classes of Histosols and Histels the base of any plow layer or 25 cm from the soil surface, whichever is deeper, to 100 cm below the soil surface. A. Terric subgroups of Histosols and Histels that Family and Series Differentiae and Names 307
have (by weighted average) in the particle-size control mixed with organic matter, either dispersed and soft or section: cemented into large aggregates, in a mineral or organic layer that has all of the following characteristics: 1. A fine-earth component of less than 10 percent (including associated medium and finer pores) of the total 1. Saturation with water for more than 6 months per year (or volume. artificial drainage); Fragmental 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 2. A texture (of the fine earth) of sand or loamy sand, oxide (7 percent or more Fe) and 1 percent or more (by weight) including less than 50 percent (by weight) very fine sand in organic matter; and the fine-earth fraction. Sandy or sandy-skeletal 3. A dark reddish or brownish color that changes little on or drying. The ferrihumic mineralogy class is used for families of 3. Less than 35 percent clay in the fine-earth fraction and Fibrists, Hemists, and Saprists, but it is not used for a content of rock fragments of 35 percent or more of the Sphagnofibrists and Sphagnic subgroups of other great groups. total volume. If the ferrihumic class is used in the family name of a Histosol, Loamy-skeletal no other mineralogy classes are used in that family because the or presence of iron is considered to be by far the most important mineralogical characteristic. 4. A content of rock fragments of 35 percent or more of the total volume. Mineralogy Classes Applied Only to Limnic Subgroups Clayey-skeletal Limnic materials (defined in chapter 3) with a thickness of or 5 cm or more are mineralogy class criteria if the soil does not also have ferrihumic mineralogy. The following family classes 5. A clay content of 35 percent or more in the fine-earth are used: coprogenous, diatomaceous, and marly. fraction. Clayey Control Section for the Ferrihumic Mineralogy Class and or Mineralogy Classes Applied to Limnic Subgroups The control section for the ferrihumic mineralogy class and 6. All other Terric subgroups of Histosols and Histels. the classes applied to Limnic subgroups is the same as the Loamy control section for Histosols. or Mineralogy Classes Applied Only to Terric Subgroups B. All other Histosols and Histels: No particle-size class For Histosols and Histels in Terric subgroups, use the same used. key to mineralogy classes as that used for mineral soils unless a Histosol also has ferrihumic mineralogy. Mineralogy Classes Control Section for Mineralogy Classes Applied Only to Terric Subgroups There are three different kinds of mineralogy classes recognized for families in certain great groups and subgroups For Terric subgroups of Histosols and Histels, use the same of Histosols. The first kind is the ferrihumic soil material control section for mineralogy classes as that used for the defined below. The second is three types of limnic materials— particle-size classes. coprogenous earth, diatomaceous earth, and marl, defined in Key to Mineralogy Classes chapter 3. The third is mineral layers of Terric subgroups. The key to mineralogy classes for these mineral layers is the same A. Histosols (except for Folists), Sphagnofibrists, and as that for mineral soils. Terric subgroups of Histels also have Sphagnic subgroups of other great groups that have ferrihumic the same mineralogy classes as those for mineral soils. soil material within the control section for Histosols. Ferrihumic F Ferrihumic Mineralogy Class or A Ferrihumic soil material, i.e., bog iron, is an authigenic M (formed in place) deposit consisting of hydrated iron oxide B. Other Histosols that have, within the control section for 308 Keys to Soil Taxonomy
Histosols, limnic materials, 5 cm or more thick, that consist of: Key to Soil Depth Classes 1. Coprogenous earth. A. Histosols that are less than 18 cm deep to a root-limiting Coprogenous layer, to a fragmental particle-size class, or to a cindery or or pumiceous substitute class. Micro 2. Diatomaceous earth. or Diatomaceous or B. Other Histosols, excluding Folists, that have a root- limiting layer, a fragmental particle-size class, or a cindery or 3. Marl. pumiceous substitute class at a depth between 18 and 50 cm Marly from the soil surface. or Shallow or C. Histels and other Histosols in Terric subgroups: Use the key to mineralogy classes for mineral soils. C. All other Histosols: No soil depth class used. or Series Differentiae Within a Family D. All other Histels and Histosols: No mineralogy class used. The function of the series is pragmatic, and differences Reaction Classes within a family that affect the use of a soil should be considered in classifying soil series. The separation of soils at Reaction classes are used in all families of Histosols and the series level of this taxonomy can be based on any property Histels. The two classes recognized are defined in the that is used as criteria at higher levels in the system. The following key: criteria most commonly used include presence of, depth to, thickness of, and expression of horizons and properties A. Histosols and Histels that have a pH value, on undried diagnostic for the higher categories and differences in texture, samples, of 4.5 or more (in 0.01 M CaCl ) in one or more 2 mineralogy, soil moisture, soil temperature, and amounts of layers of organic soil materials within the control section for organic matter. The limits of the properties used as differentiae Histosols. must be more narrowly defined than the limits for the family. Euic The properties used, however, must be reliably observable or be or inferable from other soil properties or from the setting or vegetation. B. All other Histosols and Histels. The differentiae used must be within the series control Dysic section. Differences in soil or regolith that are outside the series control section and that have not been recognized as Soil Temperature Classes series differentiae but are relevant to potential uses of certain soils are considered as a basis for phase distinctions. The soil temperature classes of Histosols are determined through use of the same key and definitions as those used for mineral soils. Histels have the same temperature classes as Control Section for the Differentiation of Series other Gelisols. The control section for the soil series is similar to that for the family, but it differs in a few important respects. The Soil Depth Classes particle-size and mineralogy control sections for families end at the upper boundary of a fragipan, duripan, or petrocalcic Soil depth classes refer to the depth to a root-limiting layer, horizon because these horizons have few roots. In contrast to a fragmental particle-size class, or a cindery or pumiceous the control section for the series, the thickness of such horizons substitute class. The root-limiting layers included in soil depth is not taken into account in the control sections for the family. classes of Histosols are duripans; petrocalcic, petrogypsic, and The series control section includes materials starting at the soil placic horizons; continuous ortstein; and densic, lithic, surface and also the first 25 cm below a densic or paralithic paralithic, and petroferric contacts. The following key is used contact if its upper boundary is less than 125 cm below the for families in all subgroups of Histosols. The shallow class is mineral soil surface. Properties of horizons and layers below not used in the suborder Folists. the particle-size control section, a depth between 100 and 150 Family and Series Differentiae and Names 309
cm (or to 200 cm if in a diagnostic horizon) from the mineral contact or 150 cm below the soil surface, whichever is soil surface, also are considered. shallower, if there is a densic or paralithic contact within 150 cm; or Key to the Control Section for the Differentiation of Series 3. A depth of 150 cm if the bottom of the deepest The part of a soil to be considered in differentiating series diagnostic horizon is less than 150 cm from the soil surface; within a family is as follows: or A. Mineral soils that have permafrost within 150 cm of the 4. The lower boundary of the deepest diagnostic horizon soil surface: From the soil surface to the shallowest of the or a depth of 200 cm, whichever is shallower, if the lower following: boundary of the deepest diagnostic horizon is 150 cm or more below the soil surface; or 1. A lithic or petroferric contact; or C. Organic soils (Histosols and Histels): From the soil surface 2. A depth of 100 cm if the depth to permafrost is less to the shallowest of the following: than 75 cm; or 1. A lithic or petroferric contact; or 3. 25 cm below the upper boundary of permafrost if that boundary is 75 cm or more below the soil surface; or 2. A depth of 25 cm below a densic or paralithic contact; or 4. 25 cm below a densic or paralithic contact; or 3. A depth of 100 cm if the depth to permafrost is less 5. A depth of 150 cm; or than 75 cm; or B. Other mineral soils: From the soil surface to the 4. 25 cm below the upper boundary of permafrost if that shallowest of the following: boundary is between a depth of 75 and 125 cm below the 1. A lithic or petroferric contact; or soil surface; or 2. A depth of either 25 cm below a densic or paralithic 5. The base of the bottom tier
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CHAPTER 18 Designations for Horizons and Layers
This chapter describes soil layers and genetic soil horizons. the following: (1) an accumulation of humified organic matter The genetic horizons are not the equivalent of the diagnostic closely mixed with the mineral fraction and not dominated by horizons of Soil Taxonomy. While designations of genetic properties characteristic of E or B horizons (defined below) or horizons express a qualitative judgment about the kinds of (2) properties resulting from cultivation, pasturing, or similar changes that are believed to have taken place in a soil, kinds of disturbance. diagnostic horizons are quantitatively defined features that are If a surface horizon has properties of both A and E horizons used to differentiate between taxa. A diagnostic horizon may but the feature emphasized is an accumulation of humified encompass several genetic horizons, and the changes implied organic matter, it is designated as an A horizon. In some areas, by genetic horizon designations may not be large enough to such as areas of warm, arid climates, the undisturbed surface justify recognition of different diagnostic horizons. horizon is less dark than the adjacent underlying horizon and contains only small amounts of organic matter. It has a Master Horizons and Layers morphology distinct from the C layer, although the mineral fraction is unaltered or only slightly altered by weathering. The capital letters O, A, E, B, C, R, and W represent the Such a horizon is designated as an A horizon because it is at master horizons and layers of soils. These letters are the base the surface. Recent alluvial or eolian deposits that retain fine symbols to which other characters are added to complete the stratification are not considered to be A horizons unless designations. Most horizons and layers are given a single cultivated. capital-letter symbol; some require two. E horizons: Mineral horizons in which the main feature is O horizons or layers: Layers dominated by organic the loss of silicate clay, iron, aluminum, or some combination material. Some are saturated with water for long periods or of these, leaving a concentration of sand and silt particles. were once saturated but are now artificially drained; others These horizons exhibit obliteration of all or much of the have never been saturated. original rock structure. Some O layers consist of undecomposed or partially An E horizon is most commonly differentiated from an decomposed litter (such as leaves, needles, twigs, moss, and underlying B horizon in the same sequum by a color of higher lichens) that has been deposited on the surface. They may be value or lower chroma, or both, by coarser texture, or by a on top of either mineral or organic soils. Other O layers consist combination of these properties. In some soils the color of the of organic material that was deposited under saturated E horizon is that of the sand and silt particles, but in many conditions and has decomposed to varying stages. The mineral soils coatings of iron oxides or other compounds mask the fraction of such material constitutes only a small percentage of color of the primary particles. An E horizon is most commonly the volume of the material and generally much less than half of differentiated from an overlying A horizon by its lighter color. its weight. Some soils consist entirely of materials designated It generally contains less organic matter than the A horizon. as O horizons or layers. An E horizon is commonly near the surface, below an O or A An O layer may be on the surface of a mineral soil, or it horizon and above a B horizon, but eluvial horizons that are may be at any depth below the surface if it is buried. A horizon within or between parts of the B horizon or extend to depths formed by the illuviation of organic material into a mineral greater than those of normal observation can be assigned the subsoil is not an O horizon, although some horizons that have letter E if they are pedogenic. formed in this manner contain considerable amounts of organic B horizons: Horizons that have formed below an A, E, or O matter. horizon. They are dominated by the obliteration of all or much A horizons: Mineral horizons that have formed at the of the original rock structure and show one or more of the surface or below an O horizon. They exhibit obliteration of all following: or much of the original rock structure1 and show one or both of 1. Illuvial concentration of silicate clay, iron, aluminum, humus, carbonates, gypsum, or silica, alone or in 1 Rock structure includes fine stratification in unconsolidated soil materials as well as combination; H pseudomorphs of weathered minerals that retain their positions relative to each other and to O unweathered minerals in saprolite. 2. Evidence of the removal or addition of carbonates; R 312 Keys to Soil Taxonomy
3. Residual concentration of oxides; too small to allow root penetration. The cracks may be coated or filled with clay or other material. 4. Coatings of sesquioxides that make the horizon W layers: Water conspicuously lower in color value, higher in chroma, or This symbol indicates water layers within or beneath the redder in hue, without apparent illuviation of iron; soil. The water layer is designated as Wf if it is permanently 5. Alteration that forms silicate clay or liberates oxides, or frozen and as W if it is not permanently frozen. The W (or Wf) both, and that forms a granular, blocky, or prismatic designation is not used for shallow water, ice, or snow above structure if volume changes accompany changes in moisture the soil surface. 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 properties of the horizon so designated dominate the result of pedogenic processes (and may or may not be transitional horizon. An AB horizon, for example, has cemented) and brittle layers that show other evidence of characteristics of both an overlying A horizon and an alteration, such as prismatic structure or illuvial accumulation underlying B horizon, but it is more like the A horizon than of clay. 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 stratified unconsolidated sediments, regardless of whether the forms a transition is not present. A BE horizon may be films were formed in place or by illuviation; layers into which recognized in a truncated soil if its properties are similar to carbonates have been illuviated but that are not contiguous to those of a BE horizon in a soil from which the overlying E an overlying genetic horizon; and layers with gleying but no horizon has not been removed by erosion. A BC horizon may other pedogenic changes. be recognized even if no underlying C horizon is present; it is C horizons or layers: Horizons or layers, excluding transitional to assumed parent materials. strongly cemented and harder bedrock, that are little affected Horizons with two distinct parts that have recognizable by pedogenic processes and lack the properties of O, A, E, or properties of the two kinds of master horizons indicated by the B horizons. Most are mineral layers. The material of C layers capital letters.—The two capital letters designating such may be either like or unlike the material from which the solum combination horizons are separated by a virgule (/), e.g., E/B, has presumably formed. The C horizon may have been B/E, or B/C. Most of the individual parts of one horizon modified, even if there is no evidence of pedogenesis. component are surrounded by the other. The designation may Included as C layers are sediment, saprolite, bedrock, and be 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 the requirements for A, E, or B horizons, it is designated by the situations; therefore, some improvising is needed. For example, letter C. Changes that are not considered pedogenic are those Argic Udipsamments have lamellae that are separated from not related to the overlying horizons. Some layers that have each other by eluvial layers. Because it is generally not accumulations of silica, carbonates, gypsum, or more soluble practical to describe each lamella and eluvial layer as a salts are included in C horizons, even if cemented. If a separate horizon, the horizons can be combined but the cemented layer formed through pedogenic processes, however, components described separately. One horizon then has several it is considered a B horizon. lamellae and eluvial layers and can be designated an “E and R layers: Strongly cemented to indurated bedrock. Bt” horizon. The complete horizon sequence for these soils Granite, basalt, quartzite, limestone, and sandstone are could be: Ap-Bw-E and Bt1-E and Bt2-C. examples of bedrock designated by the letter R. The excavation difficulty commonly exceeds high. The R layer is sufficiently Suffix Symbols coherent when moist to make hand-digging with a spade impractical, although the layer may be chipped or scraped. Lowercase letters are used as suffixes to designate specific Some R layers can be ripped with heavy power equipment. The kinds of master horizons and layers. The term “accumulation” bedrock may have cracks, but these are generally too few and is used in many of the definitions of such horizons to indicate Designations for Horizons and Layers 313
that these horizons must contain more of the material in reduced state. Most of the affected layers have chroma of question than is presumed to have been present in the parent 2 or less, and many have redox concentrations. The low material. The suffix symbols and their meanings are as follows: chroma can represent either the color of reduced iron or the color of uncoated sand and silt particles from which a Highly decomposed organic material iron has been removed. The symbol g is not used for This symbol is used with O to indicate the most highly materials of low chroma that have no history of wetness, decomposed organic materials, which have a fiber such as some shales or E horizons. If g is used with B, content of less than 17 percent (by volume) after rubbing. pedogenic change in addition to gleying is implied. If no other pedogenic change besides gleying has taken place, b Buried genetic horizon the horizon is designated Cg. This symbol is used in mineral soils to indicate h Illuvial accumulation of organic matter identifiable buried horizons with major genetic features that were developed before burial. Genetic horizons may This symbol is used with B to indicate the or may not have formed in the overlying material, which accumulation of illuvial, amorphous, dispersible may be either like or unlike the assumed parent material complexes of organic matter and sesquioxides if the of the buried soil. This symbol is not used in organic sesquioxide component is dominated by aluminum but is soils, nor is it used to separate an organic layer from a present only in very small quantities. The organo- mineral layer. sesquioxide material coats sand and silt particles. In some horizons these coatings have coalesced, filled c Concretions or nodules pores, and cemented the horizon. The symbol h is also This symbol indicates a significant accumulation of used in combination with s as “Bhs” if the amount of the concretions or nodules. Cementation is required. The sesquioxide component is significant but the color value cementing agent commonly is iron, aluminum, and chroma, moist, of the horizon are 3 or less. manganese, or titanium. It cannot be silica, dolomite, i Slightly decomposed organic material calcite, or more soluble salts. This symbol is used with O to indicate the least d Physical root restriction decomposed of the organic materials. The fiber content of This symbol indicates noncemented, root-restricting these materials is 40 percent or more (by volume) after layers in naturally occurring or human-made sediments rubbing. or materials. Examples are dense basal till, plowpans, j Accumulation of jarosite and other mechanically compacted zones. Jarosite is a potassium or iron sulfate mineral that is e Organic material of intermediate decomposition commonly an alteration product of pyrite that has been This symbol is used with O to indicate organic exposed to an oxidizing environment. Jarosite has hue of materials of intermediate decomposition. The fiber 2.5YR or yellower and normally has chroma of 6 or content of these materials is 17 to 40 percent (by volume) more, although chromas as low as 3 or 4 have been after rubbing. reported. f Frozen soil or water jj Evidence of cryoturbation This symbol indicates that a horizon or layer contains Evidence of cryoturbation includes irregular and permanent ice. The symbol is not used for seasonally broken horizon boundaries, sorted rock fragments, and frozen layers or for dry permafrost. organic soil materials occurring as bodies and broken layers within and/or between mineral soil layers. The ff Dry permafrost organic bodies and layers are most commonly at the This symbol indicates a horizon or layer that is contact between the active layer and the permafrost. continually colder than 0 oC and does not contain enough k Accumulation of carbonates ice to be cemented by ice. This suffix is not used for horizons or layers that have a temperature warmer than This symbol indicates an accumulation of alkaline- 0 oC at some time of the year. earth carbonates, commonly calcium carbonate. g Strong gleying m Cementation or induration This symbol indicates either that iron has been This symbol indicates continuous or nearly continuous reduced and removed during soil formation or that cementation. It is used only for horizons that are more H saturation with stagnant water has preserved it in a than 90 percent cemented, although they may be O R 314 Keys to Soil Taxonomy
fractured. The cemented layer is physically root- other vertic characteristics, such as wedge-shaped peds restrictive. The predominant cementing agent (or the two and surface cracks, may be present. dominant cementing agents) may be indicated by adding t Accumulation of silicate clay defined letter suffixes, singly or in pairs. The horizon suffix km indicates cementation by carbonates; qm, This symbol indicates an accumulation of silicate clay cementation by silica; sm, cementation by iron; ym, that either has formed within a horizon and subsequently cementation by gypsum; kqm, cementation by lime and has been translocated within the horizon or has been silica; and zm, cementation by salts more soluble than moved into the horizon by illuviation, or both. At least gypsum. some part of the horizon should show evidence of clay accumulation either as coatings on surfaces of peds or in n Accumulation of sodium pores, as lamellae, or as bridges between mineral grains. This symbol indicates an accumulation of v Plinthite exchangeable sodium. This symbol indicates the presence of iron-rich, o Residual accumulation of sesquioxides humus-poor, reddish material that is firm or very firm This symbol indicates a residual accumulation of when moist and hardens irreversibly when exposed to the sesquioxides. atmosphere and to repeated wetting and drying. p Tillage or other disturbance w Development of color or structure This symbol indicates a disturbance of the surface This symbol is used with B to indicate the layer by mechanical means, pasturing, or similar uses. A development of color or structure, or both, with little or disturbed organic horizon is designated Op. A disturbed no apparent illuvial accumulation of material. It should mineral horizon is designated Ap even though it is not be used to indicate a transitional horizon. clearly a former E, B, or C horizon. x Fragipan character q Accumulation of silica This symbol indicates a genetically developed layer This symbol indicates an accumulation of secondary that has a combination of firmness and brittleness and silica. commonly a higher bulk density than the adjacent layers. 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 (moderately cemented or less cemented). Examples This symbol indicates an accumulation of gypsum. are weathered igneous rock and partly consolidated z Accumulation of salts more soluble than gypsum sandstone, siltstone, or shale. The excavation difficulty is low to high. This symbol indicates an accumulation of salts that are more soluble than gypsum. s Illuvial accumulation of sesquioxides and organic matter Conventions for Using Letter Suffixes This symbol is used with B to indicate an accumulation of illuvial, amorphous, dispersible Many master horizons and layers that are symbolized by a complexes of organic matter and sesquioxides if both the single capital letter have one or more lowercase letter suffixes. organic-matter and sesquioxide components are The following rules apply: significant and if either the color value or chroma, moist, 1. Letter suffixes should directly follow the capital letter. of the horizon is 4 or more. The symbol is also used in combination with h as “Bhs” if both the organic-matter 2. More than three suffixes are rarely used. and sesquioxide components are significant and if the 3. If more than one suffix is needed, the following letters, color value and chroma, moist, are 3 or less. if used, are written first: a, d, e, h, i, r, s, t, and w. Except in ss Presence of slickensides the Bhs or Crt2 horizon designations, none of these letters are used in combination in a single horizon. This symbol indicates the presence of slickensides. Slickensides result directly from the swelling of clay 4. If more than one suffix is needed and the horizon is not minerals and shear failure, commonly at angles of 20 to 60 degrees above horizontal. They are indicators that 2 Indicates weathered bedrock or saprolite in which clay films are present. Designations for Horizons and Layers 315
buried, the following symbols, if used, are written last: c, f, Discontinuities g, m, v, and x. Some examples: Btc, Bkm, and Bsv. Arabic numerals are used as prefixes to horizon 5. If a horizon is buried, the suffix b is written last. It is designations (preceding the letters A, E, B, C, and R) to used only for buried mineral soils. indicate discontinuities in mineral soils. These prefixes are A B horizon that has a significant accumulation of clay and distinct from the Arabic numerals that are used as suffixes also shows evidence of a development of color or structure, or denoting vertical subdivisions. both, is designated Bt (t has precedence over w, s, and h). A B A discontinuity that can be identified by a number prefix is horizon that is gleyed or has accumulations of carbonates, a significant change in particle-size distribution or mineralogy sodium, silica, gypsum, or salts more soluble than gypsum or that indicates a difference in the material from which the residual accumulations of sesquioxides carries the appropriate horizons have formed and/or a significant difference in age, symbol: g, k, n, q, y, z, or o. If illuvial clay also is present, t unless that difference in age is indicated by the suffix b. precedes the other symbol: Bto. Symbols that identify discontinuities are used only when they Unless needed for explanatory purposes, the suffixes h, s, can contribute substantially to an understanding of the and w are not used with g, k, n, q, y, z, or o. relationships among horizons. The stratification common to soils that formed in alluvium is not designated as a Vertical Subdivision discontinuity, unless particle-size distribution differs markedly from layer to layer (i.e., particle-size classes are strongly Commonly, a horizon or layer identified by a single letter or contrasting), even though genetic horizons may have formed in a combination of letters has to be subdivided. For this purpose, the contrasting layers. Arabic numerals are added to the letters of the horizon Where a soil has formed entirely in one kind of material, the designation. These numerals follow all the letters. Within a C whole profile is understood to be material 1 and the number horizon, for example, successive layers may be designated C1, prefix is omitted from the symbol. Similarly, the uppermost C2, C3, etc. If the lower part is gleyed and the upper part is material in a profile consisting of two or more contrasting not gleyed, the layers may be designated C1-C2-Cg1-Cg2 or materials is understood to be material 1, but the number is C-Cg1-Cg2-R. omitted. Numbering starts with the second layer of contrasting These conventions apply whatever the purpose of the material, which is designated 2. Underlying contrasting layers subdivision. In many soils a horizon that could be identified are numbered consecutively. Even when the material of a layer by a single set of letters is subdivided because of the need to below material 2 is similar to material 1, it is designated 3 in recognize differences in morphological features, such as the sequence; the numbers indicate a change in materials, not structure, color, or texture. These divisions are numbered types of material. Where two or more consecutive horizons consecutively with Arabic numerals, but the numbering starts have formed in the same kind of material, the same prefix again with 1 wherever in the profile any letter of the horizon number is applied to all the designations of horizons in that symbol changes, e.g., Bt1-Bt2-Btk1-Btk2 (not Bt1-Bt2-Btk3- material: Ap-E-Bt1-2Bt2-2Bt3-2BC. The suffix numbers Btk4). The numbering of vertical subdivisions within a designating subdivisions of the Bt horizon continue in horizon is not interrupted at a discontinuity (indicated by a consecutive order across the discontinuity. numerical prefix) if the same letter combination is used in If an R layer is present below a soil that has formed in both materials, e.g., Bs1-Bs2-2Bs3-2Bs4 (not Bs1-Bs2-2Bs1- residuum and if the material of the R layer is judged to be like 2Bs2). the material from which the soil has developed, the Arabic- During sampling for laboratory analyses, thick soil horizons number prefix is not used. The prefix is used, however, if it is are sometimes subdivided even though differences in thought that the R layer would produce material unlike that in morphology are not evident in the field. These subdivisions are the solum, e.g., A-Bt-C-2R or A-Bt-2R. If part of the solum identified by Arabic numerals that follow the respective has formed in residuum, the symbol R is given the appropriate horizon designations. For example, four layers of a Bt horizon prefix: Ap-Bt1-2Bt2-2Bt3-2C1-2C2-2R. sampled by 10-cm increments are designated Bt1, Bt2, Bt3, A buried horizon (designated by the letter b) presents and Bt4. If the horizon has already been subdivided because of special problems. It is obviously not in the same deposit as the differences in morphological features, the set of Arabic overlying horizons. Some buried horizons, however, have numerals that identifies the additional sampling subdivisions formed in material that is lithologically like the overlying follows the first numeral. For example, three layers of a Bt2 deposit. A prefix is not used to distinguish material of such a horizon sampled by 10-cm increments are designated Bt21, buried horizon. If the material in which a horizon of a buried Bt22, and Bt23. The descriptions for each of these sampling soil has formed is lithologically unlike the overlying material, subdivisions can be the same, and a statement indicating that however, the discontinuity is indicated by a number prefix and the horizon has been subdivided only for sampling purposes the symbol for the buried horizon also is used, e.g., Ap-Bt1- H can be added. Bt2-BC-C-2ABb-2Btb1-2Btb2-2C. O R 316
Discontinuities between different kinds of layers in organic after the master-horizon symbol of the lower of the two soils are not identified. In most cases such differences are horizons that have identical designations, e.g., A-E-Bt-E´-Btx- identified either by letter-suffix designations if the different C. The prime symbol, when appropriate, is applied to the layers are organic or by the master symbol if the different capital-letter horizon designation, and any lowercase letter layers are mineral. symbols follow it: B´t. The prime symbol is used only when the letter designations of the two layers in question are completely Use of the Prime Symbol identical. In the rare cases when three layers have identical letter symbols, double prime symbols can be used for the lowest If two or more horizons of the same kind are separated by of these layers: E´´. one or more horizons of a different kind in a pedon, identical The same principle applies in designating layers of organic letter and number symbols can be used for those horizons that soils. The prime symbol is used only to distinguish two or more have the same characteristics. For example, the sequence A-E- horizons that have identical symbols, e.g., Oi-C-O´i-C´ (when Bt-E-Btx-C identifies a soil that has two E horizons. To the soil has two identical Oi layers) or Oi-C-Oe-C´ (when the emphasize this characteristic, the prime symbol (´) is added two C layers are of the same kind). 317
Appendix
SI unit conversion table
CEC and ECEC: 1 meq/100 g soil = 1 cmol(+)/kg soil Pressure: 15-bar water = 1500 kPa water retention 1 Conductivity: 1 mmho/cm = 1 dS/m /3-bar water = 33 kPa water retention
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
319
Index
A Argicryids ...... 118 Argicryolls ...... 197 A horizons. See Horizons and layers. Argids ...... 103 Abrupt textural change...... 21 Argidurids ...... 121 Acraquox ...... 233 Argigypsids...... 124 Acroperox ...... 234 Argillic horizon ...... 17 Acrotorrox ...... 238 Argiorthels ...... 152 Acrudox ...... 239 Argiudolls ...... 201 Acrustox ...... 243 Argiustolls ...... 208 Agric horizon ...... 16 Argixerolls ...... 222 Alaquods ...... 249 Aridic moisture regime. See Soil moisture regimes. Albaqualfs...... 42 Aridisols ...... 103 Albaquults ...... 260 Albic horizon ...... 16 B Albic materials ...... 22 Albolls ...... 192 B horizons. See Horizons and layers. Alfisols ...... 41 Bottom tier ...... 29 Alorthods ...... 254 Buried soils ...... 10 Andic soil properties ...... 22 Andisols ...... 83 C Anhydrous conditions ...... 22 Anhyorthels ...... 151 C horizons or layers. See Horizons and layers. Anhyturbels ...... 154 Calcareous and reaction classes for mineral soils ...... 304 Aniso class ...... 296 Calciaquerts ...... 282 Anthracambids ...... 114 Calciaquolls ...... 194 Anthrepts ...... 165 Calciargids ...... 104 Anthropic epipedon ...... 13 Calcic horizon ...... 17 Aqualfs ...... 41 Calcicryids ...... 119 Aquands ...... 83 Calcicryolls ...... 198 Aquents ...... 130 Calcids ...... 111 Aquepts ...... 166 Calcigypsids ...... 125 Aquerts ...... 281 Calcitorrerts ...... 285 Aquic conditions ...... 30 Calciudolls ...... 203 Aquic moisture regime. See Soil moisture regimes. Calciustepts ...... 178 Aquicambids ...... 114 Calciusterts ...... 288 Aquisalids ...... 128 Calciustolls ...... 211 Aquiturbels ...... 154 Calcixerepts ...... 184 Aquods ...... 249 Calcixererts...... 291 Aquolls ...... 193 Calcixerolls ...... 224 Aquorthels ...... 151 Cambic horizon ...... 18 Aquox ...... 233 Cambids ...... 114 Aquults ...... 259 Cation-exchange activity classes for mineral soils ...... 303 Arents ...... 133 Coatings (classes) on sands ...... 306 Argialbolls ...... 192 Coefficient of linear extensibility (COLE)...... 22 Argiaquolls ...... 193 Control section of Histosols and Histels ...... 29 320 Keys to Soil Taxonomy
Coprogenous earth. See Organic soil material. Durudands ...... 91 Cryalfs ...... 50 Durudepts ...... 173 Cryands ...... 86 Durustalfs ...... 66 Cryaqualfs...... 43 Durustands...... 97 Cryaquands ...... 84 Durustepts...... 179 Cryaquents ...... 130 Durustolls ...... 212 Cryaquepts ...... 166 Dystraquerts...... 282 Cryaquods ...... 250 Dystrocryepts ...... 171 Cryaquolls...... 194 Dystroxerepts ...... 185 Cryepts ...... 171 Dystrudepts ...... 173 Cryerts ...... 285 Dystruderts ...... 287 Cryic temperature regime. See Soil temperature Dystrustepts ...... 179 regimes. Dystrusterts ...... 288 Cryids ...... 118 Cryods ...... 251 E Cryofibrists ...... 159 Cryofluvents ...... 134 E horizons. See Horizons and layers. Cryofolists...... 161 Endoaqualfs ...... 43 Cryohemists ...... 161 Endoaquands ...... 84 Cryolls ...... 197 Endoaquents ...... 130 Cryopsamments ...... 144 Endoaquepts ...... 167 Cryorthents ...... 139 Endoaquerts ...... 283 Cryosaprists ...... 162 Endoaquods ...... 251 Cryoturbation...... 31 Endoaquolls ...... 195 Cryrendolls ...... 200 Endoaquults ...... 260 Entisols ...... 129 D Epiaqualfs ...... 45 Epiaquands ...... 85 Densic contact ...... 31 Epiaquents ...... 131 Densic materials ...... 31 Epiaquepts ...... 168 Diagnostic subsurface horizons ...... 16 Epiaquerts ...... 284 Diagnostic surface horizons ...... 13 Epiaquods ...... 251 Diatomaceous earth. See Organic soil material. Epiaquolls ...... 196 Discontinuities identified by horizon designators ...... 315 Epiaquults ...... 260 Duraqualfs ...... 43 Epipedon ...... 13 Duraquands ...... 84 Eutraquox ...... 234 Duraquerts ...... 282 Eutrocryepts ...... 172 Duraquods ...... 250 Eutroperox ...... 235 Duraquolls ...... 194 Eutrotorrox ...... 239 Duricryands ...... 87 Eutrudepts ...... 176 Duricryods ...... 252 Eutrudox ...... 240 Duricryolls ...... 198 Eutrustox ...... 244 Durids ...... 121 Durihumods ...... 253 F Durinodes ...... 23 Duripan ...... 18 Family differentiae for Histosols and Histels ...... 306 Duritorrands ...... 90 Family differentiae for mineral soils ...... 295 Durixeralfs ...... 77 Ferrudalfs ...... 55 Durixerepts ...... 185 Fibers. See Organic soil material. Durixererts...... 292 Fibric soil materials. See Organic soil material. Durixerolls ...... 225 Fibristels ...... 149 Durorthods ...... 255 Fibrists ...... 159 Index 321
Fluvaquents ...... 131 Haplocryolls ...... 198 Fluvents ...... 134 Haplodurids ...... 122 Folistels...... 150 Haplofibrists ...... 160 Folistic epipedon ...... 13 Haplogypsids ...... 125 Folists ...... 160 Haplohemists ...... 161 Fragiaqualfs ...... 47 Haplohumods ...... 253 Fragiaquepts ...... 169 Haplohumults ...... 263 Fragiaquods ...... 251 Haploperox ...... 236 Fragiaquults ...... 261 Haplorthels ...... 152 Fragic soil properties ...... 23 Haplorthods ...... 255 Fragihumods ...... 253 Haplosalids ...... 128 Fragiorthods ...... 255 Haplosaprists ...... 162 Fragipan ...... 18 Haplotorrands ...... 90 Fragiudalfs ...... 55 Haplotorrerts...... 286 Fragiudepts ...... 177 Haplotorrox ...... 239 Fragiudults...... 267 Haploturbels ...... 155 Fragixeralfs...... 78 Haploxeralfs ...... 78 Fragixerepts ...... 187 Haploxerands ...... 100 Fraglossudalfs ...... 55 Haploxerepts ...... 187 Frigid temperature regime. See Soil temperature regimes. Haploxererts ...... 292 Fulvicryands ...... 87 Haploxerolls ...... 226 Fulvudands ...... 91 Haploxerults ...... 278 Hapludalfs...... 58 G Hapludands ...... 92 Hapluderts ...... 287 Gelic materials ...... 32 Hapludolls ...... 204 Gelisols ...... 149 Hapludox ...... 241 Glacic layer ...... 32 Hapludults ...... 267 Glacistels ...... 150 Haplustalfs ...... 66 Glossaqualfs ...... 48 Haplustands ...... 98 Glossic horizon ...... 18 Haplustepts ...... 180 Glossocryalfs ...... 50 Haplusterts ...... 289 Glossudalfs ...... 56 Haplustolls ...... 213 Gypsiargids ...... 105 Haplustox ...... 245 Gypsic horizon ...... 19 Haplustults ...... 274 Gypsicryids ...... 119 Haprendolls ...... 200 Gypsids ...... 124 Hemic soil materials. See Organic soil material. Gypsitorrerts ...... 286 Hemistels ...... 150 Gypsiusterts ...... 289 Hemists ...... 161 Histels ...... 149 H Histic epipedon ...... 14 Historthels ...... 152 Halaquepts ...... 169 Histosols ...... 159 Haplanthrepts ...... 165 Histoturbels...... 155 Haplaquox...... 234 Horizons and layers ...... 311 Haplargids ...... 106 A horizons ...... 311 Haplocalcids ...... 111 B horizons ...... 311 Haplocambids ...... 115 C horizons or layers ...... 312 Haplocryalfs ...... 52 E horizons ...... 311 Haplocryands ...... 87 O horizons or layers ...... 311 Haplocryerts...... 285 R layers ...... 312 Haplocryids ...... 120 W layers ...... 312 Haplocryods ...... 252 Humaquepts ...... 170 322 Keys to Soil Taxonomy
Humicryerts ...... 285 M Humicryods...... 252 Humilluvic material. See Organic soil material. Marl. See Organic soil material. Humods ...... 253 Melanaquands ...... 85 Humults ...... 263 Melanic epipedon ...... 14 Hydraquents ...... 132 Melanocryands ...... 89 Hydrocryands ...... 88 Melanoxerands ...... 101 Hydrudands ...... 94 Melanudands ...... 95 Hyperthermic temperature regime. See Soil temperature Mesic temperature regime. See Soil temperature regimes. regimes. Mineral soil material ...... 11 I Mineral soils ...... 12 Mineralogy classes for Histosols and Histels ...... 307 Identifiable secondary carbonates ...... 23 Mineralogy classes for mineral soils...... 301 Inceptisols ...... 165 Mollic epipedon ...... 14 Interfingering of albic materials ...... 24 Mollisols ...... 191 Isofrigid temperature regime. See Soil temperature Molliturbels ...... 155 regimes. Mollorthels ...... 152 Isohyperthermic temperature regime. See Soil temperature regimes. N Isomesic temperature regime. See Soil temperature regimes. n value ...... 25 Isothermic temperature regime. See Soil temperature Natralbolls ...... 193 regimes. Natraqualfs ...... 49 Natraquerts ...... 284 K Natraquolls ...... 197 Natrargids ...... 108 Kandiaqualfs ...... 48 Natric horizon ...... 19 Kandiaquults ...... 261 Natricryolls ...... 200 Kandic horizon ...... 19 Natridurids ...... 123 Kandihumults ...... 264 Natrigypsids...... 126 Kandiperox ...... 237 Natrixeralfs ...... 80 Kandiudalfs ...... 61 Natrixerolls ...... 230 Kandiudox ...... 242 Natrudalfs ...... 62 Kandiudults ...... 269 Natrudolls ...... 206 Kandiustalfs ...... 69 Natrustalfs ...... 71 Kandiustox ...... 246 Natrustolls ...... 217 Kandiustults ...... 275 Normal years ...... 33 Kanhaplaquults ...... 262 Kanhaplohumults ...... 265 O Kanhapludalfs ...... 62 Kanhapludults ...... 271 O horizons or layers. See Horizons and layers. Kanhaplustalfs ...... 70 Ochric epipedon ...... 15 Kanhaplustults...... 276 Organic soil material ...... 11 Key to soil orders...... 37 Fibers ...... 27 Fibric soil materials ...... 27 L Hemic soil materials ...... 28 Humilluvic material ...... 28 Lamellae ...... 24 Limnic materials ...... 28 Limnic materials. See Organic soil material. Coprogenous earth ...... 28 Linear extensibility (LE) ...... 24 Diatomaceous earth ...... 29 Lithic contact ...... 32 Marl ...... 29 Lithologic discontinuities ...... 24 Sapric soil materials ...... 28 Luvihemists ...... 162 Organic soils ...... 12 Index 323
Orthels ...... 150 Plinthohumults ...... 266 Orthents ...... 139 Plinthoxeralfs ...... 82 Orthods ...... 254 Plinthudults ...... 274 Ortstein ...... 20 Plinthustalfs ...... 76 Oxic horizon ...... 20 Plinthustults...... 277 Oxisols ...... 233 Prime symbol in horizon designators ...... 316 Psammaquents ...... 132 P Psamments ...... 144 Psammorthels ...... 153 Paleaquults ...... 262 Psammoturbels ...... 156 Paleargids ...... 109 Palecryalfs ...... 53 Q Palecryolls ...... 200 Palehumults ...... 265 Quartzipsamments...... 145 Paleudalfs ...... 63 Paleudolls ...... 207 R Paleudults ...... 272 Paleustalfs ...... 73 R layers. See Horizons and layers. Paleustolls ...... 220 Reaction classes for Histosols and Histels ...... 308 Paleustults...... 277 Rendolls ...... 200 Palexeralfs ...... 80 Resistant minerals ...... 26 Palexerolls ...... 230 Rhodoxeralfs...... 82 Palexerults ...... 279 Rhodudalfs ...... 65 Paralithic contact ...... 32 Rhodudults...... 274 Paralithic materials ...... 32 Rhodustalfs ...... 76 Particle-size classes for Histosols and Histels ...... 306 Rhodustults ...... 278 Particle-size classes for mineral soils ...... 295 Rupture-resistance classes for mineral soils ...... 305 Permafrost ...... 32 Permanent cracks (classes) in mineral soils ...... 306 S Perox ...... 234 Petraquepts ...... 170 Salaquerts ...... 284 Petroargids ...... 111 Salic horizon ...... 21 Petrocalcic horizon ...... 20 Salicryids ...... 121 Petrocalcids...... 113 Salids ...... 128 Petrocambids ...... 117 Salitorrerts ...... 286 Petrocryids ...... 120 Salusterts ...... 291 Petroferric contact ...... 25 Sapric soil materials. See Organic soil material. Petrogypsic horizon ...... 20 Sapristels ...... 150 Petrogypsids...... 127 Saprists ...... 162 Placaquands ...... 86 Series control section ...... 308 Placaquods ...... 251 Series differentiae within a family ...... 308 Placic horizon ...... 21 Slickensides ...... 26 Placocryods ...... 253 Soil ...... 9 Placohumods ...... 254 Soil depth classes for Histosols and Histels ...... 308 Placorthods ...... 257 Soil depth classes for mineral soils ...... 305 Placudands ...... 97 Soil moisture regimes ...... 32 Plagganthrepts ...... 165 Aquic ...... 33 Plaggen epipedon ...... 15 Aridic and torric ...... 33 Plinthaqualfs...... 50 Udic ...... 34 Plinthaquox ...... 234 Ustic ...... 34 Plinthaquults ...... 263 Xeric ...... 34 Plinthite ...... 26 Soil temperature classes for Histosols and Histels...... 308 324 Keys to Soil Taxonomy
Soil temperature classes for mineral soils ...... 304 Turbels ...... 154 Soil temperature regimes ...... 34 Cryic ...... 34 U Frigid ...... 35 Hyperthermic ...... 35 Udalfs...... 54 Isofrigid ...... 35 Udands ...... 90 Isohyperthermic ...... 35 Udarents ...... 133 Isomesic ...... 35 Udepts ...... 172 Isothermic ...... 35 Uderts ...... 286 Mesic ...... 35 Udic moisture regime. See Soil moisture regimes. Thermic ...... 35 Udifluvents ...... 136 Sombric horizon ...... 21 Udifolists ...... 161 Sombrihumults ...... 266 Udipsamments ...... 146 Sombriperox ...... 238 Udivitrands ...... 99 Sombriudox ...... 243 Udolls...... 201 Sombriustox ...... 247 Udorthents ...... 141 Sphagnofibrists ...... 160 Udox ...... 239 Spodic horizon ...... 21 Udults ...... 266 Spodic materials ...... 26 Ultisols ...... 259 Spodosols ...... 249 Umbraquults ...... 263 Strongly contrasting particle-size classes ...... 299 Umbric epipedon ...... 15 Subsurface tier ...... 29 Umbriturbels ...... 156 Suffix symbols in horizon designators ...... 312 Umbrorthels ...... 153 Conventions for using letter suffixes ...... 314 Ustalfs ...... 65 Vertical subdivision ...... 315 Ustands ...... 97 Sulfaquents ...... 133 Ustarents ...... 133 Sulfaquepts ...... 170 Ustepts ...... 178 Sulfidic materials ...... 35 Usterts ...... 288 Sulfihemists ...... 162 Ustic moisture regime. See Soil moisture regimes. Sulfisaprists ...... 163 Ustifluvents...... 137 Sulfohemists ...... 162 Ustifolists ...... 161 Sulfosaprists ...... 163 Ustipsamments ...... 147 Sulfudepts ...... 178 Ustivitrands ...... 99 Sulfuric horizon ...... 35 Ustolls ...... 207 Surface tier ...... 29 Ustorthents ...... 141 Ustox ...... 243 T Ustults ...... 274
Thermic temperature regime. See Soil temperature V regimes. Torrands...... 89 Vermaqualfs...... 50 Torrerts ...... 285 Vermaquepts ...... 171 Torriarents ...... 133 Vermudolls...... 207 Torric moisture regime. See Soil moisture regimes. Vermustolls ...... 222 Torrifluvents ...... 134 Vertisols ...... 281 Torrifolists ...... 161 Vitrands ...... 99 Torriorthents ...... 140 Vitraquands ...... 86 Torripsamments ...... 146 Vitricryands ...... 89 Torrox ...... 238 Vitritorrands ...... 90 Transitional and combination horizons ...... 312 Vitrixerands ...... 101 Index 325
W Xerarents ...... 133 Xerepts ...... 184 W layers. See Horizons and layers. Xererts ...... 291 Weatherable minerals ...... 27 Xeric moisture regime. See Soil moisture regimes. Xerofluvents ...... 138 X Xerolls ...... 222 Xeropsamments ...... 147 Xeralfs ...... 76 Xerorthents ...... 143 Xerands...... 100 Xerults ...... 278 326 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