Temporal and spatial dynamics of enzyme activities under long-term fertilization in a maize growing brown soil

A long-term fertilizer location experiment (31 years) was carried out to study the temporal and spatial dynamics of enzyme activities under long-term fertilization in a maize growing brown soil. Results showed that enzyme activities changed regularly with the growing of maize. The highest urease and invertase activities were observed at jointing stage, while the highest acid phosphatase activity at the huge bellbottom period. Urease and invertase activities were higher after harvest than before sowing, however acid phosphatase activity was lower after harvest. With same application rate of chemical fertilizer, application of organic fertilizer could increase urease and invertase activities, but decrease acid phosphatase activity. All of the three enzyme activities decreased with the depth soil profile. Long-term fertilization could also affect the enzyme activities at deeper layer of soil. Correlation analysis results indicated that there was a very significant positive correlation between urease and invertase (r=0.636**). A significant correlation was also observed between urease, invertase and soil organic carbon, pH, water content, Alkali-hydro nitrogen, available phosphorus. No significant correlation was found between acid phosphatase activity and these soil fertility factors. Soil enzyme activities closely related with soil fertility status, and could be chosen as sensitive indexes on soil fertility.