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

Abstract

A greenhouse pot experiment was conducted, using an acid sandy loam Dystric Cambisol derived from schist, in order to evaluate the effect of liming and cadmium (Cd) application on Cd availability to sudangrass (Sorghum sudanense cv.Tama). The soil was incubated with four levels of lime and three levels of Cd. After soil incubation, sudangrass was then sown. During the experiment the pots were maintained at 70% of field moisture capacity. After harvest, 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 L¹ AcNH, pH 7 reagents. Although liming increased soil pH from 4.3 to 6.6, the effect of liming on soil pH was dependent on Cd level (p=0.05). Soil exchangeable calcium (Ca) increased due, not only to CaCO₃ addition, but also to the exchange sites created by Al³⁺ desorption. However, a significant decrease of exchangeable Ca with added Cd was observed mainly for the first CaCO₃ level. Liming significantly lowered exchangeable magnesium (Mg) and potassium (K), the latest being dependent on Cd application level. Cadmium sorption increased with the rate of Ca. Therefore, sorption was directly related to the pH and soil mineralogy. Liming induced significantly higher values of DM yield, although depending on Cd application level. The plant Cd concentration decreased significantly (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 concentrations. The decreasing of Cd uptake was only observed with rates of CaCO₃ higher than 1.5 g kg^‐1. Soil pH of 5.1 is probably the critical value on Cd uptake.