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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 merging of the 'ARD List' (approved, revalidated and discredited) with the 'GQN List' resulted in the first 'IMA/CNMNC List of Mineral Names'. The 2007 draft of the 'IMA/CNMNC List of Mineral Names' was a courtesy of the Materials Data, Inc. (MDI), its 2009 review had important modifications.
Since the 19th century, several countries developed national soil classification systems. During the 20th century, the need for an international soil classification system became more and more obvious. From 1971 to 1981, the Food and Agriculture Organization (FAO) and UNESCO published the Soil Map of the World, 10 volumes, scale 1 : 5 M). [2]
Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class of soil or soil type; i.e., a soil containing more than 85 percent sand-sized particles by mass. [2]
Soil texture triangle showing the USDA classification system based on grain size Map of global soil regions from the USDA. For soil resources, experience has shown that a natural system approach to classification, i.e. grouping soils by their intrinsic property (soil morphology), behaviour, or genesis, results in classes that can be interpreted for many diverse uses.
Soil structure describes the arrangement of the solid parts of the soil and of the pore spaces located between them (Marshall & Holmes, 1979). [1] Aggregation is the result of the interaction of soil particles through rearrangement, flocculation and cementation.
In USDA soil taxonomy, Psamments are divided into: Cryopsamments: Psamments that have a cryic soil temperature regime Quartzipsamments: other Psamments that have, in the 0.02 to 2.0 mm fraction within the particle-size control section, a total of more than 90 percent (by weighted average) resistant minerals
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 the amounts of soil water available to plants during a given year in a particular region.