Pot and adsorpt ion- exchange experiments were carried out by collecting the soil samples from the surfacelayer (0~15 cm) of red soil at the Ecological Experiment Station of Red Soil, the Chinese Academy of Sciences,in Jiangxi Province of China. When concentration of the exogenous La3+ exceeded 400 mg kg-1, therewas less non-exchangeable La3+ than exchangeable La3+ in the soil. Cation exchange capacity of the soilchanged slightly with increasing concentration of the exogenous La3+ in both experiments. However, in theadsorption-exchange experiment, when concentration of the exogenous La3+ was higher than 3Oo mg kg-1 ,exchangeable basic cations decreased significantly, while exchangeable hydrogen and exchangeable aluminumincreased significantly compared with the control treatments. The amounts of base cations (Ca2+ ) Mg2+, K+and Na+) exchanged by La3+ in the supernatant solution increased with the concentration of the exogenousLa3+, especially when concentration of the exogenous La3+ was higher than 50 mg kg-1.
