Locations of Aluminum Rich Soils

According to FAO/UNESCO recent maps (277), most Oxisols and Ultisols are located in the Tropics and Subtropics (Figure 16.2 and Figure 16.3). More specifically, about one third of the Tropics (1.5 billion ha) has sufficiently strong soil acidity for soluble aluminum to be toxic to most crops (278). Geographically, Latin America has 821 million ha, Africa 479 million ha, South and Southeast Asia 236 million ha (278). In the United States (Figure 16.4), a major portion of acid Ultisols is in the Southeast (88 million ha), from Alabama, Arkansas to Virginia (279). Other states, such as California, New York, Oregon, Pennsylvania, and Washington, also have acid Ultisols, but to a much smaller extent (280). In contrast, only Hawaii and Puerto Rico have Oxisols (Figure 16.5). A detailed review of global distribution of acid soils was given by Sumner and Noble (281).