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Vertisols of the world A more detailed map of the global distribution of Vertisols. A vertisol is a Soil Order in the USDA soil taxonomy [1] and a Reference Soil Group in the World Reference Base for Soil Resources (WRB). [2] It is also defined in many other soil classification systems. In the Australian Soil Classification it is called ...
Expansive clay, also called expansive soil, is a clay soil prone to large volume changes (swelling and shrinking) directly related to changes in water content. [1] Soils with a high content of expansive minerals can form deep cracks in drier seasons or years; such soils are called vertisols.
Soils with this shrink-swell capacity fall under the soil order of Vertisols. [6] As these soils dry, deep cracks can form on the surface, which then allows water to penetrate to deeper levels of the soil. [7] This can cause the swelling of these soils to become cyclical, with periods of both shrinking and swelling.
Cation-exchange capacity (CEC) is a measure of how many cations can be retained on soil particle surfaces. [1] Negative charges on the surfaces of soil particles bind positively-charged atoms or molecules (cations), but allow these to exchange with other positively charged particles in the surrounding soil water. [2]
In both the World Reference Base for Soil Resources (WRB) [1] and the USDA soil taxonomy, [2] a Histosol is a soil consisting primarily of organic materials. They are defined as having 40 centimetres (16 in) or more of organic soil material starting within 40 cm from the soil surface.
However, some ground-water gley soils have permeable lower horizons, including, for example, some sands in hollows within sand dune systems (known as slacks), and in some alluvial situations. Groundwater gleysoils develop where drainage is poor because the water table ( phreatic surface) is high, whilst surface-water gleying occurs when ...
Water-reactive substances [1] are those that spontaneously undergo a chemical reaction with water, often noted as generating flammable gas. [2] Some are highly reducing in nature. [ 3 ] Notable examples include alkali metals , lithium through caesium , and alkaline earth metals , magnesium through barium .
The physical category of soil quality indicators consists of tests that measure soil texture, bulk density, porosity, water content at saturation, aggregate stability, penetration resistance, and more. [9] These measures provide hydrological information, such the level of water infiltration and water availability to plants.