Studies Oil N₂O Emissions And Mitigation Of Spring Maize Field In North Of China

Global climate change is a serious problem that humanity faces, and greenhouse gases could havegreat impacts on global climate change. Agriculture is one of the most important emission sources ofgreenhouse gase. Agriculture contributes60%of N₂O emissions caused by human activities, thusassessing the impacts of agricultural production on N₂O emissions and searching for appropriatemitigation measures are important in dealing with global climate change. This paper investigates howthe fertilizer application strategies could affect N₂O emissions from the agricultural soils in north ofChina. The field experiment was conducted at the spring maize fields with seven different treatments,i.e., control （CK）, farmer’s practice （NPK）, nitrogen reduction （60%N+PK）, straw return （NPKS）,adding manure fertilizer to farmer’s practice （NPKM）, combined application of manure and inorganicfertilizer （50%M+50%U）and manure （M）. The static chamber-gas chromatography method wasemployed to conduct the measurements of N₂O and CO₂emissions. The DNDC model, which wasvalidated against data sets of N₂O and CO₂fluxes observed in the fields, was then adopted to quantifythe net greenhouse effects of different management practices and their long term impacts on SOCdynamics of local agricultural soils. The main results are as follows:N₂O emissions from spring maize field under different treatments had similar seasonal emissionpatterns, varying from^-17.56to515.62μg·m^-2·h^-1. N₂O emission peaks were observed15days beforeand after the topdressing during the growing season. And the highest N₂O emission flux was observedin NPKS treatment with515.62μg·m^-2·h^-1. Obvious N₂O emission peaks could be observed during thefreeze-thaw period. N₂O emission during non-growing season could not be ignored. Besides, theemission factor of M,50%M+50%U, NPK, NPKM, NPKS are0.12%,0.33%,0.49%,0.27%and0.97%,respectively, which are far below the value1%recommended by IPCC.The cumulative N₂O emissions of50%M+50%U was1.20kgN·ha^-1·yr^-1，decreasing sharply by19.5%compared with NPK, while the yield kept stable. Although M could reduce cumulative N₂Oemissions，the yield decreased sharply. The cumulative N₂O emissions of NPKM was1.57kgN·ha^-1·yr^-1which has no obvious difference with NPK while the NPKS treatment could significantly promote N₂Oemissions. Both of NPKM and NPKS could not only increase the content of soil organic carbon, theycould also keep the yield stable. The technique of60%+PK was not a sustainable strategy according tothe DNDC model simulations, because the yield would decrease sharply by22%in the third year.During the entire observation period, N₂O fluxes and soil moisture （WFPS） had a highlysignificant positive correlation if WFPS ranged from19%to37%. In addition, there was a significantpositive correlation between N₂O fluxes and soil temperature （5cm） under the condition of suitable soilmoisture and abundant substrate;DNDC model provided a sound basis for simulating the variance of N₂O and CO₂emissionsaccording to the comparison between observed values and model values.50%M+50%U treatment couldreduce the net greenhouse effect by33.5%while at the same time maintaining existing crop yields according to the model simulations. In addition, this treatment had positive effects on long-term SOCdynamics （50years） due to the application of manure; The net greenhouse effect of NPKM was1.06tCO₂-eq·ha^-1·yr^-1which had decreased by53.9%because of the large quantity of organic carbon addedto the soil. NPKS had the most significant decline in the net greenhouse effect by87.4%；The netgreenhouse effect of60%N+S was0.047tCO₂-eq·ha^-1·yr^-1，which was far less than that of NPKtreatment.