CAMBISOL

one of the 30 soil groups in the classification system of the Food and Agriculture Organization (FAO). Cambisols are characterized by the absence of a layer of accumulated clay, humus, soluble salts, or iron and aluminum oxides. They differ from unweathered parent material in their aggregate structure, colour, clay content, carbonate content, or other properties that give some evidence of soil-forming processes. Because of their favourable aggregate structure and high content of weatherable minerals, they usually can be exploited for agriculture subject to the limitations of terrain and climate. Cambisols are the second most extensive soil group on Earth, occupying 12 percent of the total continental land areamainly in boreal polar regions, in landscapes with high rates of erosion, and in regions of parent material resistant to clay movement. They are not common in humid tropical climates. In order for a soil to qualify as a Cambisol, the texture of the subsurface horizons must be sandy loam or finer, with at least 8 percent clay by mass and a thickness of 15 cm (6 inches) or more. These soils naturally form on medium- to fine-textured parent materials under any climatic, topographic, and vegetative-cover conditions. They differ from Leptosols and Regosols by their greater depth and finer texture and are often found in conjunction with Luvisols.