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Clay is a type of fine-grained natural soil material containing clay minerals [1] (hydrous aluminium phyllosilicates, e.g. kaolinite, Al 2 Si 2 O 5 4). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impurities, such as a reddish or brownish colour from small amounts of iron oxide .
The terra rossa classification was still, as of 1997, a part of the national soil classifications of countries such as Israel and Italy. The UNESCO/FAO World map equivalents are the chromic luvisols (a sub-order of the luvisols), and the USDA soil taxonomy equivalent is the rhodustalfs (a sub-order of the ustalfs). [11]
The soil texture is determined by the relative proportions of the individual particles of sand, silt, and clay that make up the soil. A soil texture triangle plot is a visual representation of the proportions of sand, silt, and clay in a soil sample.
Subsoil is the layer of soil under the topsoil on the surface of the ground. Like topsoil, it is composed of a variable mixture of small particles such as sand, silt and clay, but with a much lower percentage of organic matter and humus. The subsoil is labeled the B Horizon in most soil mapping systems.
The soil of the Blackland Prairies, from which the "blackland" gets its name, contains black or dark-gray, alkaline clay in both upland and bottomland areas. [4] Some western areas have shallow soils over chalk, while some soils in eastern areas are slightly acidic to neutral, grayish clays and loams over mottled clay subsoils (occasionally ...
Dark soil color imparted by organic matter in Illinois, US. Dark brown or black colors typically indicate that the soil has a high organic matter content. [4] Organic matter coats mineral soil particles, which masks or darkens the natural mineral colors. [1] Sodium content also influences the depth of organic matter and therefore the soil color.
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The benefits of improving soil structure for the growth of plants, particularly in an agricultural setting, include: reduced erosion due to greater soil aggregate strength and decreased overland flow; improved root penetration and access to soil moisture and nutrients; improved emergence of seedlings due to reduced crusting of the surface; and ...