Effect of land-use type on enzyme activity in black soil

Based on long-term experiment at Hailun Agricultural Ecology Station of Chinese Academy of Sciences, the characteristics of soil enzyme activity in black soil under different land-use types were investigated. The results show significant differences among the soil enzyme activity under different land-use types. In comparison with bare-land (BL), urease, invertase and phosphatase activity in grassland (GL) respectively increases by 24.66%, 29.56% and 34.67% in April, and 56.12%, 128.40% and 30.42% in July. This suggests that after natural restoration, soil bioactivity increases and soil fertility improves significantly. Compared, however, with the control (i.e. zero-fertilizer; ZF), soil enzyme activity in the cropping treatments follow the same order: nitrogen and phosphorus fertilizers plus organic manure (NPM) > nitrogen and phosphorus fertilizers (NP) > zero-fertilizer (ZF) application. Invertase and phosphatase activity in the ecosystems have the following order: GL > cropping system > BL, and urease activity is the order of: NPM treatment in cropping system > GL > NP treatment in cropping system > ZF treatment in cropping system > BL. This indicates that some fertilization patterns and natural restoration increase soil enzyme activity thereby improving soil fertility. Urease, invertase and phosphatase activity is significantly positively correlated with soil organic matter and total N content, largely reflecting soil property.