The combined effect on a soil of the strong leaching and intense weathering found in the tropics. Ferrallitic soils are a characteristic of the tropical rain forest. Destruction of organic residues is very rapid, so that there is little humus. Most of the bases and some of the silica is leached away. The B2 horizon is massively impregnated with sesquioxides which form a hardpan rich in clays. This pan is often exposed by erosion of the upper horizons. In US soil classification, ferrallitic soils are oxisols.
