Abstract: Sb-contaminated soils incubated with/without wheat straw-derived biochar (SBC) and fruit tree-derived biochar (FBC) were used to plant Lycopersicum esculentum. Sb- fractions in soil were measured by sequential chemical extractions. The correlation between the contents of Sb fractions in soil and the accumulation of Sb in L. esculentum was analyzed. The chlorophyll content, antioxidant system,and root cell morphology of L. esculentum were investigated to examine the effects of biochar on biochemical characteristics of L. esculentum in Sb-contaminated soil. Compared to the control, the accumulation of Sb was decreased by 66% (P<0.01) in treatment with 10% SBC and 32% (P<0.01) in treatment with 10% FBC, respectively. Sb accumulation distribution was in order of root>leaf>stem for all treatments. Sb fraction was changed by biochar, and FBC had greater effect on Sb fraction than SBC. The correlation analysis showed that the change of Sb fraction in soil induced by biochar affected the phytoavailability of Sb. Biochar increased chlorophyll content and CAT activity, while reduced SOD and POD activities of L. esculentum. Stressed root cell morphology by Sb was alleviated by biochar.

Key words: straw mulching, soil moisture, yield, watermelon.