Abstract:In order to explore the effects of long-term interaction between controlled-release urea blended fertilizer and maize straw on soil enzyme activities and soil nutrient status in wheat season, based on 8-year experiment of positioned fertilization experiment of wheat-maize rotation in brown soil of North China Plain, the effects of controlled-release urea blended with urea (CRF) and bulk blending urea (BBF) on soil enzyme activities and soil nutrients in wheat season were compared under maize straw returning (S) and non-returning conditions. The results showed that under the condition of no straw returning, compared with BBF treatment, the CRF treatment significantly increased the neutral phosphatase activity (rejuvenation and maturity stages), sucrase activity and cellulase activity (rejuvenation and booting stages) and the content of soil organic matter, NO3-—N and Olsen phosphorus (Olsen—P) at maturity. At maturity, the neutral phosphatase activity and NO3-—N content increased by 29.6% and 34.8%, respectively. Under the condition of straw returning, activities of urease and cellulase at maturity and neutral phosphatase activity at booting stage were significantly higher in the BBF+S treatment than that in the CRF+S treatment, but there was no significant difference in soil enzyme activities between the two types of blended nitrogen fertilizers at other stages. The content of soil total nitrogen, soil organic matter, NO3-—N and Olsen—P at maturity was significantly higher in the CRF+S treatment than that in the BBF+S treatment. The interaction of nitrogen fertilizer types and maize straw returning had significant effects on the activities of neutral phosphatase, sucrase and cellulase in soil and the contents of total nitrogen, NO3-—N, NH4+—N, Olsen—P and available potassium in soil. Straw returning significantly increased the activities of neutral phosphatase and sucrase and the contents of available potassium and Olsen—P compared with non-returning treatment. In summary, under the conditions of straw returning and non-returning, CRF treatment could significantly increase soil organic matter content, improve the supply intensity and supply capacity of available nitrogen and phosphorus nutrients in late stage of wheat compared with the BBF treatment, and the treatment of CRF+S showed the best performance in improving soil enzyme activity and soil nutrients. The research results could provide a theoretical basis for the optimal application of nitrogen fertilizer under straw returning.