Effects of soil pH and applied cadmium on cadmium concentration in wheat grain

The effects of pH and soil-applied Cd on Cd concentration in wheat grain were determined using 4 soils in a glasshouse study. Grain Cd concentrations increased significantly (P &lt; 0·001) with increasing applications of Cd for all soils. Generally, for the Alfisols the Cd concentration in grain decreased with increasing soil pH for all Cd treatments. The Cd concentrations in grain from plants grown on the Haploxerert showed variable responses to pH, depending on the Cd treatment. Smaller decreases in grain Cd concentration with increasing pH were seen on soils with native Cd compared with grain from soils to which Cd had been added. Generally, Cd uptake (mg/pot) by grain grown in the Alfisols showed the same trends with increasing pH as seen with grain Cd concentrations, indicating no yield dilution effect. On the Bordertown soil (a Palexeralf) the ratio of Cd in shoot material (excluding grain) to Cd concentration in grain was found to increase significantly (P &lt; 0·001) with increasing Cd treatments and decrease significantly (P &lt; 0·001) with increasing pH. The ratio on the Bordertown soil did not remain constant across Cd or pH treatments, which suggests that the use of soil tests to predict Cd concentration in grain may be problematical. The transfer coefficients for Kapinnie, Freeling, and Bordertown soils were dependent on pH, whereas that for the Inman Valley soil was independent of pH. The relationship between the reciprocal of the distribution coefficient (K¡ 1 d) and the transfer coefficients (Cd grain/Cd soil) was generally good for all soils except the Vertisol from Inman Valley. <keyword>distribution coefficient, EDTA-extractable Cd, transfer coefficient.</keyword>