The Effects Of Different Cultivation Measures On Greenhouse Gas Emissions In Dryland Winter Wheat Fields

Agricultural production is one of the important sources of greenhouse gases emission.An important scientific problem we faced of agriculture sustainable development is how to guarantee food production and reduce greenhouse gas emissions,and to achieve the harmonious development between economy and environment.This study is based on the dry winter wheat fields as the research object in the Changwu Ecological Test Station of Shaanxi Province.In this research,CO₂,CH₄,N₂O emissions regularity were monitored by static chamber-gas chromatography technique,and Global Warming Potential（GWP）and Greenhouse Gases Intensity（GHGI）were then calculated.The experiment inclued five cultivation measures(N:urea nitrogen fertilizer 180 kg·hm^-2,NM:urea nitrogen fertilizer 180kg·hm^-2+manure 45×10³kg·hm^-2,NMW:urea nitrogen fertilizer 180 kg·hm^-2+manure 45×10³ kg·hm^-2+supplementary irrigation in wheat jointing stage,NSR:urea nitrogen fertilizer 180 kg·hm^-2+straw returned,NBC:urea nitrogen fertilizer 180 kg·hm^-2+biochar 45×10³ kg·hm^-2).It is clear that different cultivation measures have the potential to increase crop productionl and mitigate the greenhouse gas emissions,so as to achieve coordinated development of economic and environmental benefits on the basis of high yield and stable production.The research mainly draws the following conclusions:（1）The agricultural soil is the source of CO₂ and N₂O emission,and is the sink of CH₄uptake in the Loess Plateau.The greenhouse gases of CO₂,N₂O and CH₄ emission fluxes have obvious seasonal variation rule,and the trend of each treatment is basically the same.The fluxes of CO₂ emission increased with the growth process and decreased at the beginning of maturity.Compared with the N treament,the cumulative CO₂ emission of NM,NMW and NBC treaments were increased by 22.2%,27.0%,13.4%,arrived at 17148.97 kg C hm^-2,17828.47 kg C hm^-2,15915.60 kg C hm^-2,respectively.The fluxes of N₂O emission were suddenly increased after fertilization,rainfall and irrigation,and three peak emissions have occurred in the monitoring period.Compared with the N treament,the cumulative N₂O emissions of NM,NMW and NBC treaments were decreased by 21.3%,14.7%,28.0%,arrived at 0.59 kg N hm^-2,0.64 kg N hm^-2,0.54 kg N hm^-2,respectively.The cumulative CH₄absorption of NM,NMW,NSR and NBC treaments were decreased by 15.9%,10.6%,14.6%,16.2%,arrived at 2.7 kg C hm^-2,2.87 kg C hm^-2,2.74 kg C hm^-2,2.69 kg C hm^-2,respectively.The cumulative emissions of CO₂ and N₂O in the growth period of winter wheat accounted for more than 80%of the total annual emissions,and the CH₄absorption accounted for more than 50%of the total annual absorption.（2）The CO₂emission rate and CH₄ absorption rate were positive correlation with soil temperature,atmospheric temperature and negative correlation with soil moisture content.Meanwhile,The CO₂ emission rate was positive correlation with soil microbial biomass carbon content（MBC）,soil dissolved organic carbon content（DOC）.The N₂O emission rate was positive correlation with soil temperature,atmospheric temperature,soil moisture content and NO₃^--N content.Therefore,the main reasons for the difference in emission flux of CO₂,N₂O and CH₄ are temperature,soil moisture content and fertilization.（3）The crop yields of NM,NMW and NSR treaments were significantly increased by24.6%,36.7%,21.3%,respectively.Compared with the N treament,the GWP in NM,NMW and NBC treaments were significantly decreased by 23.9%,17.3%,34.9%.and the GHGI were significantly decreased by 38.9%,39.5%,39.8%,respectively.The GWP in NSR treatment was increased by 20.4%than that of N treament.Compared with NM treatment,the crop yields in NMW treament increased significantly,while the GWP was not significant with NM treament.Therefore,the result of this study showed that the application of manure and supplementary irrigation can further increase crop yields and mitigate greenhouse gases simultaneously,which is the best cultivation measure.