Influence of different cropping patterns on soil enzyme activities and yield of broomcorn millet

【Objectives】 Soil enzymes involve in a variety of biological processes in soil, their activities are one of soil quality evaluation index. In this paper, the dynamic changes of soil enzyme activities at different growing stages of broomcorn millet, soil nutrients contents at the maturity and the crop yields under different cropping patterns were analysed, to provide a theoretical basis for high-yield broomcorn millet. 【Methods】 A long-term experiment of minor grain crops was carried out at theFirst Station of Northwest A F University. Broomcorn millet was planted by rotation (T1), every two years (T2), continuously two years (T3) and continuously three years (T4). Soil catalase, urease, alkaline phosphatase and invertase activities in 0-20 cm rhizosphere soil layer were measured at sowing stage, seeding stage, jointing stage, heading stage, filling stage and maturing stage, and soil nutrient contents were determined at maturing stage.Soil organic matter, total nitrogen, alkali solution nitrogen, total phosphorus, available phosphorus, total potassium, available potassium content and pH value at the maturing stage were determined.【Results】 The activities of soil catalase, urease and invertase were decreased with the elongation of the continuous-cropping year, while the polyphenol oxidase activity was reverse, and the alkaline phosphatase activity was the lowest in the second year of the continuous-cropping. With the increase of the continuous-cropping year, soil pH was increased, soil available-potassium was obviously accumulated and soil available-phosphorus was consumed much. The catalase, urease, and alkaline phosphatase activities were significantly and positively correlated with the grain yield, while soil pH is negatively correlated with the grain yield. The correlations between soil invertase, organic matter content and the yield were not significant. 【Conclusions】Thecontinuous cropping of milletaffects the activities of soil enzymes and soil nutrients contents,slows downthe soil humification and amelioration degree,aggravatessoil secondary salinization and soil nutrient imbalance,and decreases the grain yields as a result. So the reasonable rotation for millet is very important, for slowing the succession cropping obstacle and achieving a high yield and quality on broomcorn millet.