Heavy metals input with phosphate fertilizers used in Argentina.

Sustainability of conventional agriculture is based upon a high input of agrochemicals, such as phosphate fertilizers. Conventional inorganic phosphorus fertilizers may cause an inadvertent addition of heavy metals, which are contained as impurities. Fertilizers commonly used in Argentina were analyzed to determine concentrations of chromium, cadmium, copper, zinc, nickel and lead. Rock phosphate contained the highest levels of cadmium and zinc, chromium was enhanced in diammonium phosphate and copper and lead were high in one superphosphate sample. Urea-phosphate contained the lowest levels of heavy metals. Concentrations of heavy metals varied considerably and the levels of Cd and Pb in some analyzed materials were significant relative to those naturally present in soils. Continuous fertilization of soils could increase the heavy metal contents exceeding natural abundances in soils, and transfer of these metals to the human food chain must not be overlooked.