Abstract: 【Objective】To investigate the changing of soil enzyme activity in central Inner Mongolia when density-sowing date coupling of Cyperus esculentus.【Methods】The experiment was carried out with a split plot group design. With a total of 16 treatments,the primary treatment was sowing date（S1：April 30,S2：May 10,S3：May 20,S4：May 30）,while the secondary treatment was density（D1：60 000 plants/hm²,D2：90 000 plants/hm²,D3：120 000 plants/hm²,D4：150 000 plants/hm²）. The yields of the 16 treatments,as well as the changes of soil urease,catalase,alkaline phosphatase and sucrase activity were all analyzed.【Results】Soil enzyme activities increased gradually with increasing density under S1,S2,S3 sowing date. Under the same density,other soil enzyme activities,except urease activity,increased first and then decreased with the delay of sowing date,and the distribution trend of different enzyme activities was slightly different. Under the density-sowing date coupling,soil urease activity peaked at 9.81 mg/（g·24 h）in S4D4. S3D4 had the highest soil catalase activity of 38.20 mg/（g·24 h）and the highest soil sucrase activity of 52.02 mg/（g·24 h）. S3D4 had significantly higher（P<0.05）soil alkaline phosphatase activity than the other treatments,which was 0.45 mg/（g·24 h）. The yield of Cyperus esculentus increased as density grew at the same sowing date,and increased first,then reduced if the sowing date was delayed at the same density. The yield of S3D4 was 16 333.42 kg/hm²,which was significantly higher（P<0.05）than the yield of the other treatments.【Conclusion】When Cyperus esculentus was sown on May 20 in central Inner Mongolia at a density of 150 000 plants/hm²,the soil enzyme activity was at its peak,and the yield increased dramatically.

Key words: Cyperus esculentus, Sowing date, Planting density, Soil enzyme activities