Oxisols
Oxisols develop in tropical and subtropical latitudes that experience an environment with high precipitation and temperature. The profiles of oxisols contain mixtures of quartz, kaolin clay, iron and aluminum oxides, and organic matter. For the most part they have a nearly featureless soil profile without clearly marked horizons. The abundance of iron and aluminum oxides found in these soils results from strong chemical weathering and heavy leaching. Many oxisols contain laterite layers because of a seasonally fluctuating water table.
Oxisols are only in the tropics. In the U.S.A. they have been found in Hawaii and Puerto Rico. The root comes from the French word oxide for oxides. They are intensely weathered, resulting in colors that are yellow to red from the accumulation of large amounts of iron oxides. Even if they are clayey, their ability to retain nutrients is low as the clay fraction consists of iron oxides and kaolinite. They frequently do not have very distinct horizons and are very deep. A variety of tropical crops can be grown in humid areas but generally much fertilizer is needed.