Abstract:Through fixed field experiment, the effects of organic fertilizer substitute part of chemical fertilizer on soil extracellular enzyme activity and multi-functionality was analyzed, and this study could provide theoretical basis for soil fertility improvement and rational fertilization in rice-rapeseed rotation. Based on the principle of total nutrient substitution amount of nutrients, 4 treatments, which including no fertilizer (CK), full amount of chemical fertilizer (CF), organic fertilizer substitute 20% chemical fertilizer (CFM1), and organic fertilizer substitute 40% chemical fertilizer (CFM2) were set up. Soil chemical properties, microbial properties, and extracellular enzyme activity were assessed, and the Multiple regression analysis was used to explore the effects of soil properties on soil extracellular enzyme activity and multi-functionality. The results showed that compared with CF, soil microbial biomass carbon, microbial biomass nitrogen, and soil respiration of CFM1 and CFM2 increased 275.27%, 41.90%, and 64.29% in rapeseed season, and increased 115.06%, 338.32%, and 60.87% in rice season. Organic fertilizer application increased the contents of soil organic matter, total nitrogen, total phosphorus, and available nutrients by 13.25%~95.48%. Compared with the single application of chemical fertilizer, the replacement of part of chemical fertilizer by organic fertilizer significantly increased the activity of β-glucosidase, cellulase, xylanase, leucine aminopeptidase, N-acetyl-aminoglucosidase, and acid phosphatase in the carbon, nitrogen, and phosphorus cycle, with an increase of 20.33%~140.31% in rapeseed season, while in rice season, only xylanase activity was significantly increased, with an increase of 133.63%~159.86%. The key factors for the changes of soil extracellular enzyme activities was soil microbial biomass carbon in rapeseed season, and was soil available phosphorus in rice season. Compared with no fertilizer treatment and full amount of chemical fertilizer, organic fertilizer replacement treatment significantly increased soil multi-functionality, the main predictive factors of soil multi-functionality were available potassium and available nitrogen in rapeseed season, and were available phosphorus and microbial biomass nitrogen content in rice season. In a word, the substitution of organic fertilizer for part of chemical fertilizer is beneficial to the improvement of soil nutrients, microbial biomass, and soil extracellular enzyme activity, which is an important measure to maintain stable crop yield and soil biological health.