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Distribution of nitisols. Nitisol, in the World Reference Base for Soil Resources (WRB), is a deep, red, well-drained soil with a clay content of at least 30% and a polyhedral structure or a blocky structure, breaking into a polyhedral or a flat-edged structure. The soil aggregates show pressure faces.
Vertisols have a high content of expansive clay minerals, many of them belonging to the montmorillonites that form deep cracks in drier seasons or years. In a phenomenon known as argillipedoturbation, alternate shrinking and swelling causes self-ploughing, where the soil material consistently mixes itself, causing some vertisols to have an extremely deep A horizon and no B horizon.
The shrink–swell capacity of soils refers to the extent certain clay minerals will expand when wet and retract when dry. Soil with a high shrink–swell capacity is problematic and is known as shrink–swell soil, or expansive soil. [1]
Expansive clays have an expanding crystal lattice in a 2:1 ratio; however, there are 2:1 non-expansive clays. [2] Mitigation of the effects of expansive clay on structures built in areas with expansive clays is a major challenge in geotechnical engineering. Some areas mitigate foundation cracking by watering around the foundation with a soaker ...
The formation of soil aggregates (or so-called secondary soil particles or peds) occurs due to interactions of primary soil particles (i.e., clay) through rearrangement, flocculation and cementation. Aggregate stability has a direct impact on soil pore size distribution, which affects soil water retention and water movement in soil, therefore ...
Distribution of Durisols. A Durisol is a Reference Soil Group under the World Reference Base for Soil Resources (WRB) [1] referring to free-draining soils in arid and semi-arid environments that contain grains cemented together by secondary silica (SiO 2) in the upper metre of soil, occurring either as concretions (durinodes – duric horizon) or as a continuously cemented layer (duripan ...
Mapping of the distribution and extent of natural vegetation of South Africa started in 1918 when the Botanical Survey of the Union of South Africa was established. Maps by Pole-Evans (1936), Acocks (1953), and Low and Rebelo (1996) preceded the current system, which is the combined effort of participants from various centres in the country. [2]
Leptosol in Agbe (Ethiopia). A Leptosol in the World Reference Base for Soil Resources (WRB) is a very shallow soil over continuous rock or a deeper soil that is extremely rich in coarse fragments (gravelly and/or stony).