THE EFFECT OF CROP ROTATIONS AND TILLAGE PRACTICES ON CADMIUM CONCENTRATION IN WHEAT-GRAIN

The cadmium concentrations in wheat grain were determined from three crop rotation x tillage experiments in South Australia. Generally, the concentrations in grain were highest in wheat grown after lupins and lowest in wheat grown after cereal. The high cadmium concentrations in grain from wheat/lupins plots could not be explained solely by acidification, thus indicating involvement of other processes in cadmium availability. While cadmium concentration in grain also increased with increasing rates of nitrogenous fertilizers, the results of cultivation practices were generally too inconsistent to allow conclusions to be drawn. Cadmium concentrations exceed the maximum permissible concentration (MPC) of 0.05 mg kg-1 set by the National Health and Medical Research Council (NHMRC) for unspecified foods in only one of the three tillage experiments. This study indicates that crop rotation is an important factor affecting cadmium uptake. Under certain soil conditions and with particular wheat varieties, the cadmium concentration in grain may exceed the MPC as the result of the crop rotation used.