1. Humus-rich soils which were originally covered with early-maturing native grassland vegetation, that produces a characteristic brown surface layer.

They are found in relatively dry climatic zones (200–400 millimeters [8–16 inches] of rainfall per year), usually bordering arid regions; such as, southern and central Asia, northern Argentina, the western United States, and Mexico.

Kastanozems are principally used for irrigated agriculture and grazing and have relatively high levels of available calcium ions bound to soil particles.

These and other nutrient ions move downward with percolating water to form layers of accumulated calcium carbonate or gypsum.

Kastanozems are related to the soils in the Mollisol order of the U.S. Soil Taxonomy which form in semiarid regions under relatively scarce grasses and shrubs.

Related FAO soil groups originating in a steppe environment are Chernozems and Phaeozems.

2. From the classification system of the Food and Agriculture Organization, FAO.
3. Etymology: from Latin-Russian castanea zemlja, "chestnut earth".