Abstract: The effects of bio-char derived from rice straw on soil physical properties and clomazone residual degradation were studied by barrel column and pot experiments simulating the degradation of persistent herbicides in soil environment. The results showed that when applying 2-32 mg·kg^-1 of bio-char in soil, the soil bulk density was decreased on average by 0.126 g·cm^-3, the solid phase ratio was reduced by an average of 21.2%, and the gas and liquid phase ratios were increased by 29.8% and 15.3%, respectively, which meant that soil physical properties were improved. The barrel column test indicated that clomazone was mainly distributed in the soil layer above 30 cm, and its residue in soil was greater when its initial concentration was higher. Bio-char promoted the degradation of clomazone in the soil. With the increase of biochar content in soil, clomazone residue in soil was reduced, decreasing its biological hazard to crops.

Key words: tillage practice, root surface area, yield., root length