Abstract: An orthogonal experiment, including three treatments of biogas slurry application rate and three combinations of biogas slurry application time, was carried out to study the effects of biogas slurry application rate and time on yield and quality of machine\|transplanted single cropping late rice as well as soil fertility. The results showed that application rate of biogas slurry showed a significant effect on yield of single cropping late rice, but combinations of biogas slurry application time showed no significant effect on rice yield. Application of biogas slurry could significantly improve tillering, and increase earbearing percentage, productive panicle number and spikelet number per panicle. However, over-application of biogas slurry could impact the quality of brown rice. Application of biogas slurry slightly increased the concentrations of Cd and Pb in the grains, but the concentrations of heavy metals in the grain for all treatments were lower than their safety limits. As compared with chemical fertilizer, application of biogas slurry could slightly decrease the quality of soil fertility. It was suggested that the optimum rate of biogas slurry application ranged from 15.5 to 27.7 t· 667m-2(equivalent N of 11.5～20.7 kg·667m-2), and optimum combinations of biogas slurry application time was 3-3-2-2 and 4-2-3-1．

Key words: biogas slurry, machine-transplanted single cropping late rice, application method, quality, soil fertility