[Effects of organic manure on the conformation and biological availability of soil Cd]

Pot experiments were conducted to investigate the effect of organic manure on the conformation and availability of both native and added Cd in red soil and moisture soil under rice planting. Most of the added Cd existed in exchangeable form, while the native Cd existed more evenly in four forms. The organic manure did not influence apparently on the forms of native Cd, whereas influenced significantly on those of the added Cd. From tillering to mature stage, the exchangeable form of the native Cd increased, while that of the added Cd decreased. The application of organic manure could promote the uptake of Cd under the treatments without adding Cd. Under the treatments of adding Cd, the application of the organic manure could depress the uptake of Cd, and the effect of applying pig's manure was stronger than that of applying peat. There existed a significant antagonism between the accumulation of Cd and Fe in rice roots.