3.2.3 Soil enzyme activity
Soil enzyme activity is a living index to reflect soil environmental changes and fertility conditions, and they are more sensitive to soil environment. In MSSL, with N addition rates increasing, soil urease and sucrase activities increased significantly (P <0.05), and soil catalase activity decreased gradually (Table 1). The soil urease activities in the N addition treatments with 90-210 kg ha-1 increased by 91.5%-110.6% compared with that in no N addition treatment, and the soil sucrase activities increased by 3.74-5.42 times, respectively. On the contrary, the soil catalase activities in the N addition treatments with 90-210 kg ha-1 decreased by 3.2%-13.6% compared with that in no N addition treatment.