Forms of cadmium in sandy soils after amendment with soils of higher fixing capacity.

Most of the Cd applied through phosphatic fertilizers in sandy soils tends to stay in mobile forms (soluble or exchangeable) and hence the risk of it leaching to underground water or its uptake by plants is higher. A sequential extraction procedure was used to assess the efficacy of amending materials (soils containing inorganic or organic adsorption components) on the re-distribution of forms of Cd in a sandy soil. Amendment of the sandy soil with each of the three soils (yellow earth, lateritic podzolic and peaty sand) was generally effective in altering the more mobile or available forms of Cd to immobile or unavailable forms. The extent of alteration varied with the type of component present in the amendment soil, pH and the rate of Cd addition. The yellow earth was more effective at pH 7, whereas the peaty sand was equally effective at both pH 4 and 7 in altering the mobile to immobile forms. The lateritic podzolic soil was the least effective of the soils used at any of the pH values.