Abstracts

Artemio A. Martin, Jr ¹, Diane S, Stott²

Isabela State University, Echague, Isabela, Philippines

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

Abstract

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   CH₄ fluxes   manifest   the   soil   as   CH₄ sink.   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.