Variable charge soils: Their mineralogy, chemistry and management

Soils in the Oxisols, Ultisols, Alfisols, Spodosols and Andisols orders that are rich in constituents with surface reactive groups with amphoteric properties are considered variable charge soils (VCS). They have developed under intensive weathering in subtropical and tropical regions or from volcanic ash parent material. The magnitude and sign of the surface charge of variable charge constituents depend on the chemistry of the contacting solution (pH and ionic strength). The mineralogical, physical and chemical characteristics of these soil systems are different from those observed in soil systems of temperate regions. In this chapter, the mineralogy, chemistry and management of VCS are reviewed and discussed, focusing on the chemistry of these systems. (C) 2004 by Elsevier Inc.