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The taxonomic class of a specific soil can be determined by using the keys that follow in this and other chapters. It is assumed that the reader is familiar with the definitions of diagnostic horizons and properties that are given in chapters 2 and 3 of this publication and with the meanings of the terms used for describing soils given in the Soil Survey Manual. The Index at the back of this publication indicates the pages on which definitions of terms are given. Standard rounding conventions should be used to determine numerical values. Soil colors (hue, value, and chroma) are used in many of the criteria that follow. Soil colors typically change value and some change hue and chroma, depending on the water state. In many of the criteria of the keys, the water state is specified. If no water state is specified, the soil is considered to meet the criterion if it does so when moist or dry or both moist and dry. All of the keys in this taxonomy are designed in such a way that the user can determine the correct classification of a soil by going through the keys systematically. The user must start at the beginning of the "Key to Soil Orders" and eliminate, one by one, all classes that include criteria that do not fit the soil in question. The soil belongs to the first class listed for which it meets all the required criteria. In classifying a specific soil, the user of soil taxonomy begins by checking through the "Key to Soil Orders" to determine the name of the first order that, according to the criteria listed, includes the soil in question. The next step is to go to the page indicated to find the "Key to Suborders" of that particular order. Then the user systematically goes through the key to identify the suborder that includes the soil, i.e., the first in the list for which it meets all the required criteria. The same procedure is used to find the great group class of the soil in the "Key to Great Groups" of the identified suborder. Likewise, going through the "Key to Subgroups" of that great group, the user selects as the correct subgroup name the name of the first taxon for which the soil meets all of the required criteria. The family level is determined, in a similar manner, after the subgroup has been determined. Chapter 17 can be used, as one would use other keys in this taxonomy, to determine which components are part of the family. The family, however, typically has more than one component, and therefore the entire chapter must be used. The keys to control sections for classes used as components of a family must be used to determine the control section before use of the keys to classes. The descriptions and definitions of individual soil series are not included in this text. Definitions of the series and of the control section are given in chapter 17. In the "Key to Soil Orders" and the other keys that follow, the diagnostic horizons and the properties mentioned do not include those below any densic, lithic, paralithic, or petroferric contact. The properties of buried soils and the properties of a surface mantle are considered on the basis of whether or not the soil meets the meaning of the term "buried soil" given in chapter 1. If a soil has a surface mantle and is not a buried soil, the top of the original surface layer is considered the "soil surface" for determining depth to and thickness of diagnostic horizons and most other diagnostic soil characteristics. The only properties of the surface mantle that are considered are soil temperature, soil moisture (including aquic conditions), and any andic or vitrandic properties and family criteria. If a soil profile includes a buried soil, the present soil surface is used to determine soil moisture and temperature as well as depth to and thickness of diagnostic horizons and other diagnostic soil characteristics. Diagnostic horizons of the buried soil are not considered in selecting taxa unless the criteria in the keys specifically indicate buried horizons, such as in Thapto-Histic subgroups. Most other diagnostic soil characteristics of the buried soil are not considered, but organic carbon if of Holocene age, andic soil properties, base saturation, and all properties used to determine family and series placement are considered.
Pedosphere.com is proud to present a searchable database for the US Taxonomy System. Click on the links to go into a deeper level, or simply enter the name of the soil Subgroup.
Citations: Online Source: Pedosphere.com. 2001. Searchable Keys to Soil Taxonomy, Eighth Edition [Online WWW]. Available URL: http://www.pedosphere.com/resources/sg_usa/ [cite access date]. Links: |
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