Study on the relationships between soil enzyme activities and soil fertility
in Zhifanggou Watershed

The relationships between soil enzyme activities and soil fertility under the different land uses (forest, shrub, grass and farmland) in the Zhifanggou watershed were studied through field investigation and laboratory analysis. The correlation between soil enzyme activities and soil fertility were evaluated by the methods of correlation analysis and path analysis. The results there are significant positive correlations between soil organic matter, total N, available N, available K, urease, invertase, alkaline-phosphatase and catalase. Soil organic matter, total N and available N are important factors of affecting activities of urease, invertase, alkaline-phosphatase and catalase, and their direct path coefficients to the four enzymes are 0.148, 0.415, 0.345, -0.018; 0.241, 0.202, 0.190, 0.318 and 0.394, 0.375, 0.507, 0.277, respectively. The direct impacts of pH values upon four enzymes are largely minimized by the indirect effects of other factors. The results derived from correlation analysis and path analysis indicate that the four enzyme activities can be used to evaluate soil fertility in the loess hilly region.