Large Scale Spatial Variability of Accumulated Cadmium in the Wheat Farm Grains

Cadmium (Cd) accumulation in edible crops is undesirable due to its hazardous influences on human health. The objectives of this study were: i) to evaluate the spatial variability of grain Cd and its relationships with soil properties in 4000 km2 wheat farms; ii) to evaluate the effect of wheat cultivar on the soil properties vs. grain Cd relationships. A number of 255 soil (0-20 cm) and grain samples were taken and Cd concentrations in grain samples and some soil properties were measured. Grain Cd concentrations in 95 percent of the samples exceeded the threshold of 0.2 mg kg-1. Durum wheat had more potential to accumulate Cd in grain (0.76 mg kg-1) than bread (0.69 mg kg-1). There was significant (p 0.01) correlation between grain Cd and organic carbon (r= 0.66), CEC (r= 0.77) and DTPA-extractable Cd (p 0.05) (r= 0.57) of the soils. Greater Pearson coefficient values for durum wheat showed that, in the studied calcareous soils, organic carbon, CEC, Cd-DTPA had more effects on durum wheat than bread wheat cultivar. The obtained Kriging map of grain Cd identified three hotspots at the east (durum wheat cultivation), the west (intensive irrigated wheat farms), and south (wheat farms around petrochemical industries) of the region. Agricultural mismanagement due to overusing P-fertilizers increased Cd concentration in the topsoils and grains of wheat farms in the study area.