Chile imports almost all of the phosphate fertilizers essential to satisfy its agricultural requirements for a value close to US$60 million annually. The greatest use of these fertilizers is made on soils of volcanic origin -Andosols, Ultisols- which comprise about 55-60% of the country’s arable surface (5,400,000 ha; Peralta, 1976).

The need for phosphorus in non-volcanic soils (Alfisols, Entisols, Vertisols…) in the central area is much lower. Measured in the laboratory, phosphorus retention in Andosols exceeds 90% and since the very availability of P in these soils is limited, agricultural production without phosphorus supplementation is extremely low. The implications for agriculture and the country’s economy are quite serious.