Abstract: To explore the effect of biochar on the transfer of copper (Cu) in soil-rice system, a pot experiment was conducted with three rice cultivars, namely Teyou 009, Donglian 5, and Yiyou 673 planted in Cu-contaminated soils that had been amended with biochar applications (w=0, 2.5%, and 5% ). The results show that biochar applications increased soil pH and water-soluble soil organic carbon (WSOC) and decreased the soil available Cu significantly. Compared with the control, the CaCl₂-extractable Cu content of 5% biochar application at tillering and maturity stage were reduced by 73.78%-78.96% and 87.61%-96.97%, respectively. At maturity stage under 5% biochar treatment the proportion of acid soluble Cu decreased by 38.34%-48.72%, while the proportion of oxidizable Cu increased by 34.24%-46.04% as compared to the control. With the increasing of biochar applications, the concentration of Cu in rice root, husk and brown rice was reduced significantly. Among the 3 rice varieties, the effect of biochar on inhibiting Cu uptake by root was strongest for Teyou 009. The result of spatial distribution of Cu in rice root show that biochar application apparently decreased the abundance of Cu across the root section, leading to lower Cu levels near the stele, which decreased the probability of Cu transfer to shoot. As a result, Cu content in brown rice of Teyou 009, Donglian 5, and Yiyou 673 under 5% biochar application was decreased by 33.99%, 28.39%, and 40.22%, respectively.

Key words: biochar, copper, rice, accumulation