CALCISOL

one of the 30 soil groups in the classification system of the Food and Agriculture Organization (FAO). Calcisols are characterized by a layer of translocated (migrated) calcium carbonatewhether soft and powdery or hard and cementedat some depth in the soil profile. They are usually well-drained soils with fine to medium texture, and they are relatively fertile because of their high calcium content. Their chief use is for animal grazing. Occupying about 6.4 percent of the continental land surface of the Earth, these soils are typically encountered in arid or Mediterranean climatic zones (southwestern United States, central and southern Argentina, central China, northern Africa, and the Arabian Peninsula). Soils in the Aridisol, Inceptisol, and Mollisol orders of the U.S. Soil Taxonomy show strong calcium carbonate accumulation and are therefore closely related to the Calcisols. Related FAO soil groups originating in arid regions and conditioned by limited leaching are Solonchak, Solonetz, Durisol, and Gypsisol.