Mitigation Of Greenhouse Gas Intensity From Typical Double Rice Field Of Central China

To investigate the regularity of greenhouse gas intensity (GHGI) from typical double rice system of Central China under various field managements and to find a way to optimize the mitigation practices, five continuous rice growing seasons'measurement on greenhouse gases (GHGs) emission initiated from 2007 was conducted using manual static-GC (gas chromatography) method. Simultaneously, the seasonal variation of GHGs fluxes was monitored. Furthermore, the relationship of GHGs emission and environmental factors was analyzed by using the multivariate regression. There were 7 treatments involved, viz. CWS (Conventional tillage + without Straw residue + Urea), NWS (No till + without straw residue + Urea), SCU (Conventional tillage + without straw residue + Controled release urea), HN (High stubble residue + No till + Urea), HC (High stubble residue + Conventional tillage + Urea), SN (Straw cover + No till + Urea) and SNF (Straw cover + No till + Urea + Continuous flooding). The environmental elements include air temperature, soil temperature, soil redox potential (Eh), soil pH, field water table (H), soil organic matter and activity and population of soil microbes related to the production of GHGs emission from soil. The following were the main conclusions generated from this study:1) Pronounced seasonal and annual variation of GHGs emission has been observed, i.e. different regularity exists between early rice and late rice. Climate and soil water situation of each year contrlled the annual variance of GHGs emission. Most of methane fluxes occurred during the rice growing stage before the end of tiller, the water regime predominanted the emission of methane in the late rice growing stage. However, there was great variance and uncertainty of nitrous oxide from rice paddy, tons of negative fluxes of nitrous oxide have been measured over years, while, the average emission factor of nitrous oxide from early and late rice was less than the default value of IPCC. Furthermore, there was no significant trade-off between seasonal variation of methane and nitrous flux under the effect of same treatment.2) By the regression analysis, the largest average of methane emission occurred in the range of -100 mv