江苏省稻麦轮作系统产量和CH4、N2O排放对施氮的响应OA

To explore the quantitative relationship between CH4 and N2O emissions with nitrogen fertilizer application rates in the rice-wheat rotation system in Jiangsu Province and to determine the optimal fertilization scheme,a multi-level quan-titative nitrogen application experiment was conducted to accurately estimate the relationship between N2 O and CH4 emis-sions with nitrogen application in the rice-wheat rotation system.A carbon footprint(CF)and net ecosystem economic benefits(NEEB)model for the rice-wheat rotation system was constructed.Based on this model,an optimized fertilization scheme was put forward,with the objective of providing theoretical support for measures to reduce emissions.A field ex-periment was carried out during the wheat and rice seasons between November 2022 and October 2023.The wheat season test was conducted with six nitrogen level treatments,specifically N0(0 kg·hm-2),N180(180 kg·hm-2),N240(240 kg·hm-2),N270(270 kg·hm-2),N300(300 kg·hm-2)and N360(360 kg·hm-2).The rice season test was con-ducted with five nitrogen level treatments,specifically N0(0 kg·hm-2),N180(180 kg·hm-2),N240(240 kg·hm-2),N300(300 kg·hm-2)and N360(360 kg·hm-2).The same nitrogen level was applied in the same experimen-tal plot for rotation.Continuous monitoring of CH4 and N2O emissions in agricultural fields was conducted using static closed chamber/GC technique,with a comprehensive analysis of greenhouse gas emissions intensity based on rice-wheat yield and global warming potential.The results indicate that the N2O emissions from the rice-wheat rotation system in-creased significantly with the increase of nitrogen application,and an exponential relationship was observed between N2O emissions and nitrogen application.CH4 emissions exhibited a pattern of initial decrease followed by an increase with rising nitrogen fertilizer application,and the most suitable equation for the methane-nitrogen relationship was found to be cubic function of one variable,which indicates that an appropriate nitrogen application rate can reduce CH4 emissions.Through-out the rice-wheat rotation cycle,as nitrogen application increased,the contribution rate of N2O to GWP gradually rose,while the contribution rate of CH4 further declined.CH4 emissions during the rice season consistently played a dominant role in GWP contribution.Therefore,when studying greenhouse gas emission reduction in a rice-wheat rotation system,it is essential to focus on CH4 emissions during the rice season.The dominance of CH4 emissions in the rice season on GWP was consistent across all nitrogen fertilizer treatments.Therefore,when studying greenhouse gas emission reduction in a rice-wheat rotation system,it is essential to focus on CH4 emissions during the rice season.Synergizing the net ecosystem economic benefits and carbon emissions,a nitrogen application rate ranging from 267 to 283 kg·hm-2 is the optimal ferti-lization scheme.