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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 World Reference Base for Soil Resources (WRB) is an international soil classification system for naming soils and creating legends for soil maps. The currently valid version is the fourth edition 2022. [1]
The Unified Soil Classification System (USCS) is a soil classification system used in engineering and geology to describe the texture and grain size of a soil.The classification system can be applied to most unconsolidated materials, and is represented by a two-letter symbol.
The Food and Agriculture Organization of the United Nations (FAO) developed a supra-national classification, which offers useful generalizations about pedogenesis in relation to the interactions between the main soil-forming factors.
The AASHTO Soil Classification System was developed by the American Association of State Highway and Transportation Officials, and is used as a guide for the classification of soils and soil-aggregate mixtures for highway construction purposes.
Soil texture is a classification instrument used both in the field and laboratory to determine soil classes based on their physical texture. Soil texture can be determined using qualitative methods such as texture by feel, and quantitative methods such as the hydrometer method based on Stokes' law.
An Acrisol is a Reference Soil Group of the World Reference Base for Soil Resources (WRB). [1] It has a clay-rich subsoil and is associated with humid, tropical climates, such as those found in Brazil, and often supports forested areas. [2]
Alfisol between flows of middle Miocene Picture Gorge Basalt in Picture Gorge, Oregon. The fossil record of Alfisols extends back to the Late Devonian.