Calcium chloride extractable cadmium as an estimate of cadmium uptake by subterranean clover

Abstract

Cadmium (Cd) may accumulate in soils which have been regularly fertilized with phosphate fertilizers which contain Cd originating in rock phosphate. Soil was taken from three sites in the wheatbelt of Western Australia which were estimated to have received different amounts of phosphate fertilizer over the past decade. The pH was adjusted with dilute HCl or CaCO3. No Cd was added experimentally. The concentration of Cd in the whole tops of Trifolium subterraneum cv Mt Barker grown in a glasshouse pot experiment increased from 0-2-0.8 µg g-1 dry wt at pH 6 -6-6.9 (1:50-01 M CaCl2) to 2-4 µg g-1 at pH 4.1-4.2. The highest concentration of Cd in the plant tops at any particular pH occurred on the soil which had the highest concentration of P in the CaCl2 extract. There was a linear relationship between the concentration of Cd in the whole tops of sub-clover and the concentration of Cd in the CaCl2 extracts which was independent of site. The concentration of Cd in the CaCl2 extracts was a function of pH and concentration of P in the CaCl2 extract.