Study on long-term experiment of crop rotation and fertilizationin the Loess PlateauI Ⅰ. Effect of crop rotation and continuous planting on soil enzyme activities

The effect of longterm crop rotation and fertilization on the activity of enzymes in soil was studied Soil samples (0～20 cm) were collected from plots where various crop and rotation combinations had been continuously applied to a black loessial soil (for 15 years) The results indicated that longterm rotation and fertilization reduced catalase activity by 1.2%～20.6% compared with fallow treatment Other soil enzyme activities including invertase, urease, alkaline phosphatase, and protease increased by 26.0%～138.3%, 22.5%～321.7%, 31.4～157.8%, and 15.2%～483.3% after different fertilizers were applied and different plants were cropped for 15 years continuously The effect of organic manure on soil enzyme activities was higher than that of chemical fertilizer and the enzyme activities affected by alfalfa, pea, and sainfoin (Onobrychis sativa) were higher than that of wheat and maize