Effect of liming and cadmium application in an acid soil on cadmium availability to sudangrass

A greenhouse pot experiment was conducted, using an acid sandy loam Dystric Cambisol derived from schist, in order to evaluate the effect of liming an d cadmium (Cd) application on Cd availability to sudangrass (Sorghum sudane nse cv. Tama). The soil was incubated with four levels of lime and three le vels of Cd. After soil incubation, sudangrass was then sown. During the exp eriment the pots were maintained at 70% of field moisture capacity. After h arvest, the air-dried soil samples were analyzed for extractable Cd using 0 .01 mol L-1 CaCl2, 0.43 mol L-1 HNO3, and 1 mol L-1 AcNH4 pH 7 reagents. Al though liming increased soil pH from 4.3 to 6.6, the effect of liming on so il pH was dependent on Cd level (p=0.05). Soil exchangeable calcium (Ca) in creased due, not only to CaCO3 addition, but also to the exchange sites cre ated by Al3+ desorption. However, a significant decrease of exchangeable Ca with added Cd was observed mainly for the first CaCO3 level. Liming signif icantly lowered exchangeable magnesium (Mg) and potassium (K), the latest b eing dependent on Cd application level. Cadmium sorption increased with the rate of Ca. Therefore, sorption was directly related to the pH and soil mi neralogy. Liming induced significantly higher values of DM yield, although depending on Cd application level. The plant Cd concentration decreased sig nificantly (p=0.05) with the application of 4.5 g kg(-1) of CaCO3 at 1.0 mg kg(-1) of Cd, reaching values of plant Cd within the range of critical con centrations. The decreasing of Cd uptake was only observed with rates of Ca CO3 higher than 1.5 g kg(-1). Soil pH of 5.1 is probably the critical value on Cd uptake.