Abstract: Soil samples were collected from a long term experimental field to study the effects of different fertilization system on the fertility and microbial activity of aquic brown soil. Long-term fertilization, both inorganic and organic, decreased soil pH significantly. Chemical fertilization did not increase the contents of soil total carbon and nitrogen, while organic fertilization increased soil organic matter content significantly. Long term non-fertilization with chemical P and K induced the deficit of soil P and K. Organic fertilization, including manure (M), N+M, and NPK+M, increased soil microbial biomass (MB) significantly, compared with non-fertilization (CK). However, the difference in MB among treatments M, N+M, and NPK+M was not significant. No significant difference in MB was also observed between treatments NPK and CK. Soil microbial respiration was increased significantly in treatments M, N+M, NPK, and NPK+M, but had less change in treatment N. Comparing with CK, all fertilization treatments increased soil ammonification significantly, especially in treatment NPK+M. All fertilization treatments except treatment N increased soil nitrification significantly. Correlation analysis showed that soil microbial biomass C and N, microbial respiration, ammonification, and nitrification were significantly correlated with the contents of soil total carbon and nitrogen (P<0.01), suggesting that they could better reflect the changes of soil fertility, while soil microbial activity was discrepantly related to the other physical and chemical factors, suggesting that they had different responses to the changes of soil physical and chemical factors.

Key words: Contaminated soil, Remediation standard, Methodology, Ecological risk assessment