Efects of organic material Oil the forms of added cd and its bioavailability in soil

The effects of rice straw and the Chinesemilk vecth on the forms of added Cd and its bioavailability in soil were studied in pot experiment．The results indicate that the rice straw and the Chinese milk vecth can significantly reduce the Ex(exchangeable)-Cd contents of fluvo-aquic soil and red-soil in tillering stage．But the influence is different between the soils．The effects ofrice straw and the Chinese milk vecth on the forms of added Cd in tillering stage are not stable．From tillering to mature stage，Sob-Cd (strong organic bound)and Mn-Cd are released andtransformed into Ex-Cd with the decomposition of strong organic material and red uction of active Mn．The Cd uptake by rice is closely related to the forms of Cd ．In tillering stage，these two kinds of organic materials can inhibit the Cd uptake by root and stelTl of rice．But in mature stage，Cd contents in root，steinan dlear，and grain of ricerise rapidly，which results from the increase of Ex-Cd and decrease of Sob-Cd ．