Andisols

In USA soil taxonomy, Andisols are soils formed in volcanic ash and defined as soils containing high proportions of glass and amorphous colloidal materials, including allophane, imogolite, and ferrihydrite. In the FAO soil classification, Andisols are known as Andosols.Because they are generally quite young, Andisols typically are very fertile except in cases where phosphorus is easily fixed (this sometimes occurs in the tropics). They can usually support intensive cropping, with areas used for wet rice in Java supporting some of the densest populations in the world. Other Andisol areas support crops of fruit, maize, tea, coffee or tobacco.
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Un andisol, ou andosol, est un sol humique peu évolué de montagne comportant :un horizon supérieur riche en matière organique ;un roche mère d'origine voclanique.
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Soil order (type) of the United States Department of Agriculture Comprehensive Soil Classification System. These soils develop from parent materials that are volcanic in origin.