Cadmium accumulation in agricultural soils in Western Australia

Phosphatic fertilizers contain appreciable concentrations of cadmium (Cd) which may elevate the Cd concentrations of soils and crops, yet the impact of Cd on poorly buffered Western Australian soils is not known. We measured soil Cd, P and Zn concentrations at different depths and with total (mixed acid) and partial extractants (CaCl2, EDTA and HCl) at sites with a known phosphate fertilizer history. Accumulation of Cd in soils where P fertilizers had been applied varied greatly, with the Cd content of fertilized soils generally having significantly higher Cd contents than for unfertilized soils. In a ferruginous sandy loam, the highest concentrations of Cd were in the top 2 cm and these concentrations increased with increasing amounts of fertilizer application. A gravelly lateritic soil in an orchard contained 3.6 mg Cd kg(-1), which was 20-fold higher than the equivalent unfertilized soil. Very sandy horticultural soils which are characteristic of Western Australia did not have higher exchangeable Cd, and showed small increases in total Cd, despite the high amounts of phosphatic fertilizers applied. The largest proportional increases in soil Cd were generally for analyses using partial extractants rather than for total Cd.