Cadmium concentrations in some New Zealand wheat grain

The variation in wheat (Triticum aestivum L.) grain cadmium (Cd) concentrations between different cultivars was investigated along with a preliminary ranking of soil properties in terms of their importance in controlling wheat grain Cd concentrations. Results indicate that there is considerable variation in Cd concentrations in New Zealand wheat grain samples. The mean Cd concentration for wheat in this study is 54 mug kg(-1) fresh weight (FW). Ten percent of the grain samples examined in this study are non-compliant with the maximum permissible concentration (MPC) for Cd in wheat grain. However almost 50% of non-compliant samples were found at a single site, and at a number of sites no samples exceeded MPC. There was a 4-fold range in the abilities of different wheat cultivars to accumulate Cd in grain. There was also seasonal variation in Cd uptake for wheat cultivars grown at the same site. Extractable soil Cd using a weak salt reagent yielded the highest correlation with grain Cd concentrations in spring wheat across all soils, whereas no significant relationships were found for winter wheat. There were no significant simple correlations between major soil properties and wheat grain Cd concentrations for either winter or spring wheat. For winter wheat, a multiple regression model with terms for total zinc (Zn) and CaCl2-extractable Cd yielded the highest correlation with winter wheat Cd concentrations (r(2) = 0.59 P < 0.05). Low Cd accumulating wheat cultivars can be selected for use at sites where the Cd concentration in grain exceeds the MPC. Future work is required to determine which soil properties are important in controlling wheat grain Cd concentrations.