3.2.Soil enzymatic activities
Intercropping and nitrogen application increased the activity of urease (SUR) (Table 2). Compared to MN0, SUR activities increased by 28.32% (P < 0.05), 29.13% (P < 0.05), and 119.47% (P < 0.01) in MNE, M0, and ME, respectively, while, SUR activities in ANE, A0, and AE increased by 2.31% (P < 0.05), 3.11% (P < 0.05), and 23.25% (P < 0.05), respectively. The SUR activities were higher in mulberry than in alfalfa soil. Nitrogen application increased peroxidase (POD) activity in mulberry soil, while POD activity was decreased in alfalfa soil. The activities of catalase (CAT) were lower in intercropping systems and in mulberry soil with nitrogen application, but there were no significant differences between the alfalfa treatments.