Field evaluation of N2O, CO2 and CH4 emissions and enzyme activities under corn-soybean intercropping system

Artemio A. Martin, Jr 1Diane S, Stott2

Isabela State University, Echague, Isabela, Philippines

NRS-USDA, Purdue University, West Lafayette, Indiana, USA


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 (β-glucosidase,  β-glucosamidase, 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.  Rye   grass   showed   higher   activity   in   acid   phosphatase,   β-glucosidase   and   β-glucosaminidase. Rye grass and hairy vetch significantly increased organic C and N, and MBC.  Level of mineralized C and N were the same in rye grass 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   CHfluxes   manifest   the   soil   as   CHsink.   No significant   differences  among   cover   crop   treatments   in   terms   of   CO2-C,   N2O-N   and   CH4C 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.