Effects of cover croppping on nitrogen dioxide, carbon dioxide and methane fluxes and soil enzyme activities in corn-soybean rotation system

The effect of cover crops (ryegrass, hairy vetch, and oilseed radish) in terms of microbial biomass carbon (MBC), C and N mineralization, and enzymatic activities in a corn-wheat-soybean cropping systems under a Mollisol was evaluated. The distributions of total organic C (TOC), total Kjeldahl N (TKN), microbial biomass C (MBC), readily mineralizable C and N, and five enzyme activities (?-glucosidase, ?-glucosaminidase, acid phosphatase, arylamidase, and fluorescein diacetate hydrolysis) involved in the cycling of C, N, P and S were studied in three soil depths (0-5. 5-10, 10-20 cm) while soil surface fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) were estimated. Ryegrass showed higher activity in acid phosphatase, ?-glucosidase and ?-glucosaminidase. Ryegrass and hairy vetch significantly increased organic C and N, and MBC. Level of mineralized C and N were the same in ryegrass and hairy vetch. There was no clear variation in CO2, N2O and CH4 fluxes from the cover crop treatments. N2O fluxes increased with an increase in soil moisture. The negative CH4 fluxes manifest the soil as CH4 sink. No significant differences among cover crop treatments in terms of CO2-C, N2O-N and CH4-C emissions, a reflection that their emissions are highly variable. Empirical data on carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes are important in management systems to evaluate mitigation strategies, while microbial biomass and enzyme activities can be used as sensitive indicators of ecological stability