chernozem (chĕrˈnəzĕmˌ) [key] or black earth, variety of soil rich in organic matter in the form of humus. It is generally a modified type of loess. True chernozem is black in color, but there are various grades, shading off into gray and chestnut-brown soils. It forms in areas that have cold winters, hot summers, and rapid evaporation of precipitation; generally only tall grass is found native on chernozem. It has large quantities of nutrients, excellent structure, and good water-holding capacity, making it very suitable for agriculture. It is most widely distributed in Russia, where it forms a large part of the good agricultural soil, but soils similar to the Russian are also found in India and the central and N central United States.