2.3 Effect of soil microbial biomass carbon and nitrogen on enzyme activity unde different water and fertilizer optimal management
The Mantel analysis method was used to obtain correlation and explanation values for the relationship between soil microbial biomass carbon and nitrogen and soil enzyme activity under different water and fertilizer optimal management conditions. It could be seen from Fig.2a that the Mantel significant values of soil acid phosphatase, catalase, and microbial carbon were the smallest (Mantel’s p<0.01). Soil sucrase, acid phosphatase, catalase, and microbial nitrogen had the least Mantel’s p<0.01, while sucrase (Sue) had less than 0.05, and urease had less than 0.05. The maximum interpretation values of soil microbial biomass C and N by acid phosphatase and catalase (Mantel’s r≥0.5) indicated that soil microbial biomass C and N content determined soil acid phosphatase and catalase activities, and the maximum interpretation value of soil microbial biomass N by sucrase (Mantel’s r≥0.5) indicated that soil microbial biomass N content determined soil sucrase (Sue) activity. However, Mantel significant and interpreted values of urease and soil microbial biomass carbon and nitrogen were (Mantel’s p<0.05, Mantel’s r = 0.25~0.5), which were important factors affecting microbial biomass carbon and nitrogen. The results in Fig.2b showed that soil enzyme activities and soil microbial biomass C and N had different degrees of correlation. The correlation coefficient of soil acid phosphatase and catalase activity to soil microbial biomass carbon and nitrogen were between 0.90 and 1.00, indicating that there was a very significant positive correlation between soil acid phosphatase and catalase activities and soil microbial biomass carbon and nitrogen content (p<0.01), which was consistent with that results in Fig.2a. The correlation coefficient of urease and sucrase activities to soil microbial biomass c and n were 0.80~0.95, indicating that urease and sucrase activities had a significant positive correlation with soil microbial biomass c and n (p<0.05).