USDA soil taxonomy (ST) developed by the United States Department of Agriculture and the National Cooperative Soil Survey provides an elaborate classification of soil types according to several parameters (most commonly their properties) and in several levels: Order , Suborder , Great Group , Subgroup , Family , and Series . The classification was originally developed by Guy Donald Smith , former director of the U.S. Department of Agriculture's soil survey investigations.
12-574: Aridisols (or desert soils ) are a soil order in USDA soil taxonomy . Aridisols (from the Latin aridus , for "dry", and solum ) form in an arid or semi-arid climate. Aridisols dominate the deserts and xeric shrublands , which occupy about one-third of the Earth's land surface. Aridisols have a very low concentration of organic matter , reflecting the paucity of vegetative production on these dry soils. Water deficiency
24-453: Is the central defining characteristic of Aridisols. Also required is sufficient age to exhibit subsoil weathering and development. Limited leaching in aridisols often results in one or more subsurface soil horizons in which suspended or dissolved minerals have been deposited: silicate clays, sodium, calcium carbonate, gypsum, or soluble salts. These subsoil horizons can also be cemented by carbonates, gypsum, or silica. Accumulation of salts on
36-492: The United States. A soil family category is a group of soils within a subgroup and describes the physical and chemical properties which affect the response of soil to agricultural management and engineering applications. The principal characteristics used to differentiate soil families include texture, mineralogy, pH, permeability, structure, consistency, the locale's precipitation pattern, and soil temperature. For some soils
48-406: The United States. Horizons marked by clay, iron, humus and hard pans and soil features such as the expansion-contraction of clays (that produce self-mixing provided by clay), temperature, and marked quantities of various salts are used as distinguishing features. The great group categories are divided into three kinds of soil subgroups : typic, intergrade and extragrade. A typic subgroup represents
60-440: The United States. This permits very specific descriptions of soils. A soil phase of series , originally called 'soil type' describes the soil surface texture, slope, stoniness, saltiness, erosion, and other conditions. Name of soil orders in soil taxonomy with their major characteristics: Order: Entisols Order: Alfisols Soil temperature regimes, such as frigid, mesic, and thermic, are used to classify soils at some of
72-442: The above at any time during their development. The soil suborders within an order are differentiated on the basis of soil properties and horizons which depend on soil moisture and temperature. Forty-seven suborders are recognized in the United States. The soil great group category is a subdivision of a suborder in which the kind and sequence of soil horizons distinguish one soil from another. About 185 great groups are recognized in
84-574: The basic or 'typical' concept of the great group to which the described subgroup belongs. An intergrade subgroup describes the properties that suggest how it grades towards (is similar to) soils of other soil great groups, suborders or orders. These properties are not developed or expressed well enough to cause the soil to be included within the great group towards which they grade, but suggest similarities. Extragrade features are aberrant properties which prevent that soil from being included in another soil classification. About 1,000 soil subgroups are defined in
96-598: The criteria also specify the percentage of silt, sand and coarse fragments such as gravel, cobbles and rocks. About 4,500 soil families are recognised in the United States. A family may contain several soil series which describe the physical location using the name of a prominent physical feature such as a river or town near where the soil sample was taken. An example would be Merrimac for the Merrimack River in New Hampshire. More than 14,000 soil series are recognised in
108-473: The difference between mean summer and winter temperatures is less than 6 °C, then add "Iso" at the front of the name of the Soil Temperature Class. The soil moisture regime, often reflective of climatic factors, is a major determinant of the productivity of terrestrial ecosystems, including agricultural systems. The soil moisture regimes are defined based on the levels of the groundwater table and
120-515: The lower levels of the Soil Taxonomy. The cryic temperature regime distinguishes some higher-level groups. These regimes are based on the mean annual soil temperature (MAST), mean summer temperature, and the difference between mean summer and winter temperatures all at a soil depth of 50 cm. It is normally assumed that the MAST (in °C) equals the sum of the mean annual air temperature plus 2 °C. If
132-604: The orders end with the suffix -sol . The criteria for the different soil orders include properties that reflect major differences in the genesis of soils. The orders are: The percentages listed above are for land area free of ice. "Soils of Mountains", which constitute the balance (11.6%), have a mixture of those listed above, or are classified as "Rugged Mountains" which have no soil. The above soil orders in sequence of increasing degree of development are Entisols, Inceptisols, Aridisols, Mollisols, Alfisols, Spodosols, Ultisols, and Oxisols. Histosols and Vertisols may appear in any of
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#1732858603208144-885: The surface can result in salinization . In the World Reference Base for Soil Resources (WRB), most Aridisols belong to the Calcisols , Gypsisols , Durisols and Solonchaks . USDA soil taxonomy A taxonomy is an arrangement in a systematic manner; the USDA soil taxonomy has six levels of classification. They are, from most general to specific: order, suborder, great group, subgroup, family and series. Soil properties that can be measured quantitatively are used in this classification system – they include: depth, moisture, temperature, texture, structure, cation exchange capacity, base saturation, clay mineralogy, organic matter content and salt content. There are 12 soil orders (the top hierarchical level) in soil taxonomy. The names of
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