Hydrolases Related to C and N Cycles and Soil Fertility Amendment: Responses to Different Management Styles of Agro-Ecosystems

Extracellular enzyme activity is proposed as a universe index of soil fertility and contamination. To ascertain and to make a comparison of bioactivity variation during vegetation period, a variety of soil samples (including Hapli-Epihypogleyic Luvisol, Albi-Epihypogleyic Luvisol, and Hapli Albic Luvisol) were collected from rotation fields of different fertilizing and farming systems, namely extensive (ExF), conventional (CF) and organic (OF). The objective of this study was to determine soil bioactivity responses (saccharase and urease activity) on different land management systems and the main recourses of ecological factors such as soil genesis type, content of soil organic carbon (SOC), total nitrogen (N), and C/N ratio. The trial was comprised of eight experimental plots (three land management systems and two or three crop groups: legumes, gramineous, rapeseed, and bare fallow). The lowest mean of urease (1.13 mg NH4--N g(-1)) and saccharase (8.40 mg CG g(-1).24 h(-1)) activity was observed in abandoned grassland soil where mineral fertilizers were not applied. A general increase of hydrolytic enzyme activity has been observed in soil under conventional (144-413% of urease and 49-50% of saccharase) and organic (219-269% of urease and 78-221% of saccharase) management as compared with abandoned grassland. A strong correlation between enzyme activity and SOC (r = 0.7) was determined. Therefore, it can be concluded that farming management and soil fertility might be responsible for the different levels of enzyme activities in soil.