Abstract:

An outdoor pot experiment was conducted to study effects of biochar on Cd form and Cd uptake by rapeseed（ Xiangyou 27） in the heavily Cd polluted soil collected from a field nearby a metal melting plant in Hunan,relative to type and dosage of the biochar. In the pots,caragana biochar or bamboo biochar was amended,separately at a rate of0. 1% and 1%,7 days before rapeseed seedlings were transplanted. Then soil samples were analyzed for Cd forms and rapeseed plants were analyzed for Cd contents in various organs at the mature stage. Results show that amendment of biochar may reduce soil Cd availability and Cd contents in various organs of the plant. The effect of caragana biochar reducing Cd uptake and accumulation by the plant was more obvious than that of bamboo biochar. Moreover,the effect became more obvious with increasing biochar amendment rate. Compared with CK,amendment of biochar reduced the content of exchangeable Cd in the soil by as high as 16. 64%; and decreased the Cd concentrations in roots,stems,hulls and seeds of the rapeseed by as much as 34. 06%,39. 74%,33. 15% and 49. 81%,respectively. In short,Treatment of amendment of 1% caragana biochar is the most effective in the experiment.

Key words: bamboo biochar, caragana biochar, cadmium, rapeseed