Effect of liming on plant accumulation of cadmium under upland or flooded conditions.
Liming a Cd-amended red earth (typical hapludalf) decreased plant shoot Cd content both in upland and in flooded conditions. The effect was due to the restriction of the total uptake of Cd from soil and the Cd transfer from roots to shoots following liming. Pot soil samples were sequentially extracted with 1 M ammonium acetate, 0.125 M Cu(II) acetate, and 1 m HNO3 to fractionate Cd into exchangeable, complexed, and acid-soluble forms. Results showed that soil flooding decreased exchangeable Cd and increased Cd in the complexed fraction. Liming also transferred Cd from exchangeable fraction to other lower available fractions depending on water regimes. With upland conditions, the Cd was transferred to the residual fraction, and to a lesser extent to the acid-soluble fraction, whereas in flooded soil the lost exchangeable Cd was recovered mainly in complexed fraction where the Cd was potentially more available for plants compared with that in residual and in acid-soluble fractions. Therefore, soil liming for controlling plant Cd uptake would be more favourable in upland rather than flooded conditions.
Li-Ming Xiong
Institute of Soil Science, Academia Sinica, PO Box 821, Nanjing, People's Republic of China.
Ru-Kun Lu