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

The cadmium concentrations in wheat grain were determined from three c rop rotation x tillage experiments in South Australia. Generally, the concentrations in grain were highest in wheat grown after lupins and l owest in wheat grown after cereal. The high cadmium concentrations in grain from wheat/lupins plots could not be explained solely by acidifi cation, thus indicating involvement of other processes in cadmium avai lability. While cadmium concentration in grain also increased with inc reasing rates of nitrogenous fertilizers, the results of cultivation p ractices were generally too inconsistent to allow conclusions to be dr awn. Cadmium concentrations exceed the maximum permissible concentrati on (MPC) of 0.05 mg kg-1 set by the National Health and Medical Resear ch Council (NHMRC) for unspecified foods in only one of the three till age experiments. This study indicates that crop rotation is an importa nt factor affecting cadmium uptake. Under certain soil conditions and with particular wheat varieties, the cadmium concentration in grain ma y exceed the MPC as the result of the crop rotation used.