Cadmium concentrations in New Zealand wheat: effect of cultivar type, soil properties, and crop management

Wheat grain is a contributing source of dietary cadmium (Cd) in New Zealand, but despite this there is a dearth of information on Cd concentrations in wheat and the factors that affect uptake. We measured Cd uptake in 12 wheat cultivars grown in field sites across New Zealand, and also assessed the soil, plant and crop factors that have been reported to affect Cd uptake. We found there was a wide range in grain Cd concentrations (0.004 to 0.205 mg kg-1 FW). The overall mean concentration, (0.066 mg kg-1 FW) was below the maximum limit (ML) of 0.1 mg kg-1 FW, although 7% of grain samples across eight sites exceeded the ML. There were significant differences (2.5-fold) in Cd uptake in wheat grain between cultivars. No strong significant relationships were found between soil properties and Cd concentrations in grain, while the effects of management factors on Cd uptake were inconsistent. Given the lack of relationships, the most effective way to manage Cd in wheat grain at sites where Cd exceeds MLs may be the use of low-Cd-accumulating cultivars. Further studies could determine if management factors, such as irrigation or type and rates of fertiliser affect Cd uptake in wheat, as well as research to explore the mechanisms of Cd uptake in wheat which may assist with management.