The effects of clay, organic matter and time on adsorption and plant uptake of cadmium added to the soil

In a 2-yr pot experiment the effects of texture and organic matter content on adsorption in soil and uptake in Perennial ryegrass (Lolium perenne ) and Winter rape (Brassica napus ) of Cd added to the soil were studied. The soils used were a clay, a loamy sand and a sapric peat mixed in different proportions. One mg kg super(-1) of Cd was added to each soil mixture. The organic matter showed a greater ability than clay to adsorb Cd in an unavailable form and thereby reduce plant uptake. The effect per unit of organic matter added was greatest at low organic matter content. Most of the Cd was adsorbed in a non-exchangeable form indicating the presence of strong organic complexing. The addition of organic matter reduced plant uptake more efficiently in sand than in clay even though the exchangeable Cd did not differ between the two soils. Increasing the clay content in sand from 9 to 63% led to slightly decreased water leachability but did not significantly decrease non-exchangeable Cd. Neither was plant uptake notably affected.