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Blohuis, W. A.
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In the new soil classification system of the United States Department of Agriculture (Soil Survey Staff, 1960 ; 1967) and in the french system of the 'Commission de Pedologie et de Cartographie des Sols' (CPCS, 1967) the name Vertisols has been given to a group of soils on the highest level of abstraction, 'Order' and 'Classes', respectively. In both classification systems the concept is the same: dark-colored, fine textured soils with a clay fraction dominated by swelling clay minerals and occurring in climates where the annual rainfall is seasonal. In the dry season these soils have wide and deep cracks; they have a specific soil structure and often show a typical micro relief (gilgai), both resulting from internal mass movements in the soil caused by alternate swelling and shrinking of the clays. Local names for these soils abound; some of the most well-known are: black cotton soils (India, Africa), dark cracking clays, 'argiles noires tropicales' (Africa) and similar terms: 'melanites' (Ghana), 'badobes' (Sudan), 'mbuga' (Tanzania), 'regur' (India), 'tirs' (Morocco), 'smonitza' or 'smolnitza' (S. E. Europe). The name 'Grumusols' was introduced by Oakes and Thorp (1950) and has had some international recognition. The name 'Vertisols' is now widely used; apart from the classification systems mentioned it also occurs in the legend of the soil map of the world, which is in preparation by FAO and UNESCO (1968) and on the soil map of Africa 1 : 5,000,000 prepared by d'Hoore (1964).
Library Journal, p. 92-98