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Cadmium accumulation in wheat grain as affected by mineral N fertilizer and soil characteristics

Li, X., Ziadi, N., Bélanger, G., Cai, Z. and Xu, H. 2011. Cadmium accumulation in wheat grain as affected by mineral N fertilizer and soil characteristics. Can. J. Soil Sci. 91: 521-531. Cadmium (Cd) is a heavy metal distributed in soil by natural processes and anthropogenic activities. It can accumulate in crops, such as spring milling wheat (Triticum aestivum L.), and its accumulation depends on crop species, soil factors, and agricultural practices like fertilizer inputs. Our objective was to study the effect of mineral N fertilizer and soil characteristics on wheat grain Cd concentration. A field study was conducted over 12 site-years (2004-2006) in Québec, with four N application rates (0, 40, 120, and 200 kg N ha-1). Wheat grain samples (n=192) were analysed for their Cd and N concentrations. Soil samples (n=48) taken before N fertilizer application were characterised for their chemical and physical properties, including Mehlich-3 extractable Cd concentration. Wheat grain Cd concentration increased significantly with increasing N application rates at 11 of the 12 site-years. Averaged across the 12 site-years, Cd concentration ranged from 53 µg kg-1 dry matter (DM) without N applied up to 87 µg kg-1 DM when 200 kg N ha-1 was applied. Wheat grain Cd concentration also varied significantly with site-years (34-99 µg kg-1 DM), but never exceeded the proposed tolerance for wheat grain of 235 µg kg-1 DM. Wheat grain Cd concentration was significantly related to Mehlich-3 extractable Cd in soil (R2=0.44, P=0.021) and nitrogen nutrition index (R2=0.69, P=0.001). We conclude that soil Cd concentration and the crop N nutrition status affect Cd accumulation in spring wheat grain produced in eastern Canada.