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 gra in were determined using 4 soils in a glasshouse study. Grain Cd conce ntrations increased significantly (P < 0.001) with increasing applicat ions of Cd for all soils. Generally, for the Alfisols the Cd concentra tion in grain decreased with increasing soil pH for all Cd treatments. The Cd concentrations in grain from plants grown on the Haploxerert s howed variable responses to pH, depending on the Cd treatment. Smaller decreases in grain Cd concentration with increasing pH were seen on s oils with native Cd compared with grain from soils to which Cd had bee n added. Generally, Cd uptake (mg/pot) by grain grown in the Alfisols showed the same trends with increasing pH as seen with grain Cd concen trations, 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 < 0.0 01) with increasing Cd treatments and decrease significantly (P < 0.00 1) with increasing pH. The ratio on the Bordertown soil did not remain constant across Cd or pH treatments, which suggests that the use of s oil tests to predict Cd concentration in grain may be problematical. T he transfer coefficients for Kapinnie, Freeling, and Bordertown soils were dependent on pH, whereas that for the Inman Valley soil was indep endent of pH. The relationship between the reciprocal of the distribut ion coefficient (K-d(-1)) and the transfer coefficients (Cd grain/Cd s oil) was generally good for all soils except the Vertisol from Inman V alley.