Study On Ghg Emission And Mitigation In Winter Wheat-summer Fallow Region Of South Loess Plateau

Due to the contribution of greenhouse gas (GHG) to the greenhouse effect and to thedestruction of global environment, GHG have attracted worldwide attention. To understandregular patten of GHG emission in winter wheat-summer fallow region of south Loess Plateau,and to explore relevant mitigation methods,static chamber-gas chromatography method wasused.Five treatments were designed：CK: No nitrogen, CON: Conventional treatment, OPT:Optimized treatment, OPT+DCD: Optimized treatment with DCD, OPT(SR): Optimizedtreatment by slow release fertilizer, to clarify the relationships between GHG emission andsoil moisture, and temperature,and other emivromental factors, and to test the effects of strawreturning and of reducing nitrogen on GHG emission. Main conclusions are as follow:1. Of each treatment, annual cumulative N2O emissions were:394.13,671.74,473.44g,486.07,468.50g N2O-N ha-1. Emission factors of CON, OPT, OPT+DCD, OPT(SR) were:0.13%,0.05%,0.06%and0.05%, which were much smaller than the IPCC default value of1.00%. Emission intensity of CON, OPT, OPT+DCD, OPT(SR) were:0.10、0.12、0.08、0.08、0.08g kg-1。 N2O flux was significantly correlated with WFPS, rather than withtemperature.Straw returning conbained with fertilization promoted N2O emission for “primingeffect”. However straw returning reduced emission from greening stage to the end of summerfallow season.DCD and slow-release fertilizers significantly inhibited the response of N2O onfertilization, and inproved crop yield.2. Of each treatment, annual cumulative CO2emissions were:5.84,7.01,6.80,7.00,6.88t CO2-C ha-1. CO2flux was significantly correlated with air temperature, rather than withWFPS. Straw returning promoted CO2emission for “priming effect”during seeding-greeningstage, while it had no significant contribution to annual cumulative CO2emission. DCD couldsignificantly reduce the “priming effect”, but no significant effect on annual cumulative CO2emission, either.3. Of each treatment, annual cumulative CH4emissions were:-0.93,-1.11,-1.31,-1.21,-1.05kg CH4-C ha-1. CH4flux was significantly correlated with air temperature, rather thanwith WFPS. However, after precipitation， CH4emission fluctuated rapidly. Slow-releasefertilizer signficantly reduced CH4emission correlation with air temperature. 4. In winter wheat-summer fallow region of south Loess Plateau, of each treatment,global warming potential for N2O and CH4（GWP） were:153.63、277.53、177.90、187.40、184.32kg CO2-eq ha-1, green house gas intensity for N2O and CH4(GHGI:GWP of per unit ofyield) were:40.89、51.11、31.65、29.95、30.95kg CO2-eq t-1.The estimatedNet-GWP(considering N2O,CH4, soil respairation, irrigation, fuel, fertilizers, and cropresidues) of each treatment were:10.51、12.20、3.56、3.16、3.16、3.12t CO2-eq ha-1, estimatedNet-GHGI(Net-GWP of per unit of yield) were:2.73、2.09、0.53、0.41、0.42t CO2-eq t-1。Straw returning mitigated the Net-GWP of-8.25t CO2-eq ha-1, was the most important carbonsequestration measure.