Effects of long-term fertilization on soil microorganisms and enzyme activities in an upland red soil

Soil samples were collected from the Red Soil Ecology Experimental Station of Chinese Academy of Sciences (CAS) at Yingtan County, Jiangxi Province. The soil microbial colony forming units (CFUs), soil microbial biomass carbon (SMBC) and enzyme activities, including urease, acid phosphatase, catalase, dehydrogenase and invertase were determined. Results showed that the organic manure fertilizer treatment could enhance soil organic matter content and SMBC significantly, increase fungal CFUs and soil enzyme activities. The least soil cultivable microbial CFUs, SMBC and soil enzyme activities were found in the inorganic fertilizer NK (lack of P element) treatment. Therefore, P element was considered as the most important limiting nutrient element in the tested soils, and P element may be vital to keep healthy soil biochemical environment. Significant positive correlations were found among all tested soil enzyme activities. Furthermore, there were also significant positive correlations among soil organic matter content, SMBC, fungal CFUs and soil enzyme activities, which indicated that soil enzyme activities could be considered as good indicators for soil quality.