PHAEOZEM

one of the 30 soil groups in the classification system of the Food and Agriculture Organization (FAO). Phaeozems are characterized by a humus-rich surface layer covered in the natural state with abundant grass or deciduous forest vegetation. They are highly arable soils and are used for growing wheat, soybeans, and pasture for cattle, as well as for wood and fuel production. Occupying about 1.5 percent of the continental land area on Earth, Phaeozems are found principally in the North American prairies, the South American pampas, and the subtropical steppes of Asia. Phaeozems have a high content of available calcium ions bound to soil particles, resulting in a very permeable, well-aggregated structure. These soils occur in association with Chernozems but under more humid climatic conditions (more than 550 mm [22 inches] of rainfall per year), which results in the absence of calcium carbonate or salt accumulation in subsurface layers. They may exhibit a layer of clay accumulation, however. Their surface layers are usually higher in humus than those of Chernozems.