Abstract:In order to investigate the effect of grass return under different conditions on soil microorganism, enzyme activities and available nutrients in peach orchard, taking the cleaning tillage as the control, grass return naturally, grass return by mowing, grass return by mowing combined with organic matter-decomposing agent were set up in this study with a 3-year experiment. The effect of grass return under different conditions on soil microbial biomass, soil enzyme activities, and different forms of nitrogen and potassium content in soils were studied by collecting rhizosphere and non-rhizosphere region soils in the peach orchard. The results showed that grass return under different conditions could all increase the rhizosphere region soil microorganism quantity. Compared with the other treatments, grass return by mowing combined with organic matter-decomposing agent improved the quantity of rhizosphere and non-rhizosphere region soil bacteria and fungi significantly, which increased by 21.2%~48.2% and 11.7%~17.0% respectively. Grass return by mowing combined with organic matter-decomposing agent accelerated the decomposition and microbial reproduction of straw. Compared with the cleaning tillage, grass return by mowing combined with organic matter-decomposing agent increased soil urease, catalase and sucrose activities by 10.2%~45.4%, 26.8%~56.9% and 20.5%~30.7% respectively. Grass return had a positive effect on the accumulation of soil nutrients in peach orchard, and the result was especially obvious on the grass return by mowing combined with organic matter-decomposing agent treatment, which could not only increase the contents of soil inorganic nitrogen and organic nitrogen, but also reduce the nitrogen loss. Meanwhile, it significantly increased the contents of soil available potassium and water-soluble potassium, which were 12.6%~15.6% and 11.4%~39.1% higher than those of other treatments, respectively. In conclusion, grass return by mowing combined with organic matter-decomposing agent was the better way to improve soil microbial biomass, soil enzymes activities and nitrogen and potassium nutrients supply, which could provide a scientific basis for the better management of orchard grass.