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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]
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 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 ...
Lamella clay-sandy soil. The dominant material is the montmorillonite clay material which has a high swell and shrinks characteristics depending on the soil water content. In the dry season, evaporation moves water from the deep horizon toward the soil surface through capillary action.
For instance, soils with a small amount of expansive clay minerals will not expand as much when exposed to moisture as a soil with a large amount of the same clay minerals. [5] If a soil is composed of at least 5 percent of these clay minerals by weight, it could have the ability to shrink and swell. [3]
Ultisol, commonly known as red clay soil, is one of twelve soil orders in the United States Department of Agriculture soil taxonomy. The word "Ultisol" is derived from "ultimate", because Ultisols were seen as the ultimate product of continuous weathering of minerals in a humid, temperate climate without new soil formation via glaciation .
If the soil has 5–12% by weight of fines passing a #200 sieve (5% < P #200 < 12%), both grain size distribution and plasticity have a significant effect on the engineering properties of the soil, and dual notation may be used for the group symbol.
Soil sieve nests with dry soil aggregates after removal from a laboratory drying oven. Soil aggregate stability is a measure of the ability of soil aggregates—soil particles that bind together—to resist breaking apart when exposed to external forces such as water erosion and wind erosion, shrinking and swelling processes, and tillage.