World’s Soil Resources

KASTANOZEMS (Ustolls and Xerolls)
Kastanozems are humus-rich soils that were originally covered with early-maturing native grassland
vegetation which produced a characteristic brown topsoil 20-40 cm thick in which the organic matter
content ranges between 2 and 6 percent. Kastanozems have a brown topsoil with a granular or fine blocky
structure. The rest of the profile is lighter in colour and is characterized by the secondary accumulation of
calcite (Figure A 19). Kastanozems are chemically rich soils with a pH slightly above neutral. Near the surface,
soil pH may reach a value of 8.0.
These soils are found in relatively dry climatic zones (annual precipitation 200–400 mm). Kastanozems
are mostly used for irrigated farming and grazing. Kastanozems have relatively high levels of available calcium
ions and other nutrients. Carbonates weakly move down in the soil profile with percolating water to form
layers of secondary carbonates; gypsum is also common in these soils. Kastanozems form in semi-arid regions
under relatively sparse grasses and shrubs.
The total extent of Kastanozems is estimated to be about 465 million ha. Major areas are in the Eurasian
short-grass steppe belt (southern Ukraine, the south of the Russian Federation, Kazakhstan and Mongolia),
in the Great Plains of the United States of America, in Mexico, and in the southwestern pampas and Chaco
regions of Argentina, in Paraguay and southeastern Bolivia (FAO, 2014).
The main obstacle to the agricultural use of these potentially rich soils is drought (Encyclopaedia of Soil
Science, 2008). Irrigation, which brings the threat of secondary salinization, is nearly always necessary to
obtain high yields. Another serious problem on Kastanozems is overgrazing (Wang and Batkhishig, 2014),
extensive grazing being another important use for these soils. Overgrazing on light-textured soils often
produces deflation, destroying the topsoil.
Status of the World’s Soil Resources | Main Report Annex | Soil groups, characteristics,
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distribution and ecosystem services