Effects Of Nitrogen Fertilizer Types On Greenhouse Gas Emissions And Nitrogen Use Efficiency Of Rice And Oilseed Rape Cropping Syste

Through field experiments,this study clarified the effects of different nitrogen fertilizer types on crop yield,nitrogen absorption efficiency and greenhouse gas emissions in the rice oil system,in order to provide a theoretical basis for slowing down the greenhouse effect and improving crop nitrogen absorption,and explore a nitrogen fertilizer combined application model with maximum benefits.There were five treatments in this study:（1）No nitrogen fertilizer（CK）;（2）Inorganic nitrogen fertilizer+biochar（IB）;（3）Inorganic nitrogen fertilizer+carbon based fertilizer（IS）;（4）Inorganic nitrogen fertilizer+organic nitrogen fertilizer（IO）;（5）Single application of organic nitrogen fertilizer（O）.The main results are as follows:1.Biochar addition treatment significantly reduced greenhouse gas emissions.There was no significant difference in CH₄ emission among fertilization treatments in rape season;Compared with IS,IO and O treatment,IB treatment reduced N₂O emissions by 19.5%,17.2%and 23.7%respectively.In the rice season,the cumulative emission of CH₄ and N₂O in IB treatment decreased by 6.7%～16.3%and 17.9%～36.1%respectively compared with other fertilization treatments;IB treatment significantly reduced the global warming potential by 14.5%～20.6%compared with IS,IO and O treatment.2.Biochar addition significantly reduced the carbon footprint of rice oil system.The carbon footprint per unit yield of IO treatment and O treatment was significantly higher than that of IS and IB treatment,in which the carbon footprint per unit yield of O treatment was the highest,and the carbon footprint per unit yield of IB treatment was significantly reduced by 4.9%～87.1%compared with other fertilization treatments.3.Biochar addition treatment significantly increased crop yield,and the yield increase effect was the best.IB treatment(2803.3 kg hm^-2)significantly increased the yield of rape,which was 3.6%,2.2%and 19.0%higher than that of IS,IO and O treatment,respectively.The rice yield of IB treatment reached 11091.57 kg hm^-2,which was significantly increased by 7.7%～36.3%compared with other fertilization treatments.4.Biochar addition treatment significantly improved the nitrogen use efficiency of crops.In rape season,compared with IS,IO and O treatments,the nitrogen uptake and utilization efficiency of IB treatment increased significantly by 25.8%～162.7%,the partial productivity of nitrogen fertilizer increased significantly by 3.6%～20.0%,and the agronomic utilization efficiency of nitrogen fertilizer increased significantly by 5.7%～38.5%;In the rice season,the nitrogen uptake and utilization efficiency,agronomic utilization efficiency and partial productivity of nitrogen fertilizer in IB treatment increased significantly by 24.2%～208.9%,24.3%～117.1%and 9.3%～41.8%respectively compared with other fertilization treatments.In conclusion,biochar addition treatment significantly reduces the greenhouse gas emissions and carbon footprint of rice oil system,and improves the nitrogen use efficiency and yield of crops.It is a sustainable fertilization method and worthy of popularization.