CADMIUM CONCENTRATION IN YELLOW LUPIN GRAIN IS DECREASED BY ZINC APPLICATIONS TO SOIL BUT IS INCREASED BY PHOSPHORUS APPLICATIONS TO SOIL

Yellow lupin (Lupinus luteus L.), which is grown as a grain legume in rotation with spring wheat (Triticum aestivum L.) on acidic, sandy soils of south-western Australia, accumulates cadmium (Cd) in grain. Application of fertilizer is required to combat zinc (Zn) and phosphorus (P) deficiency for yellow lupin production on these soils, which may affect Cd concentration in grain. In the same field experiment conducted at two sites on acidified sand over clay duplex soils, five Zn levels (0, 0.8, 1.6, 3.2, 6.4 kg Zn ha^-1), as Zn oxide, and three P levels (0, 10, and 20 kg P ha^-1), as triple superphosphate, were applied. At both sites, applying increasing Zn levels decreased Cd concentration in grain, whereas applying increasing P levels increased Cd concentration in grain. The ZnxP interaction was not significant for either grain yield or Cd concentration in grain. At the 8–10 leaf stage, Zn and P concentration was measured in whole shoots (WS), and Zn concentration was also measured in the youngest mature growth (YMG). The concentrations of the elements that were related to 90% of the maximum grain yield (critical prognostic plant test Zn and P) was i) for WS, 29 mg kg^-1for Zn and 3.5 g kg^-1for P; and ii) for YMG, was 23 mg kg^-1for Zn.