Long-term changes in cadmium bioavailability in soil

A study was conducted to examine changes in total and phytoavailable Cd in a soil that had received inputs of Cd due to fertilization with single supe rphosphate (SSP) at various rates since 1948. Accumulation of Cd in the soi l was highly correlated to the application rate of SSP. No evidence was fou nd to indicate off site movement of Cd, either through horizontal transfer or via leaching through the profile. Increases in soil Cd led to an increas e in the Cd content of wheat that was grown in the soil. However, using a r adioisotope dilution technique, a significant proportion of the added Cd wa s found to exist in a non bioavailable pool in the soil. A model was develo ped which estimated that Cd was being fixed in this soil at a rate of 1-1.5 % of the total added Cd per year.