全面、准确分析重要农业管理措施对于农业固碳减排的影响特征,对于中国农业可持续发展具有重要意义。该文以华北平原冬小麦-夏玉米生产为对象,研究硝化/脲酶抑制剂对土壤温室气体(CO₂、N2O和CH4)排放、土壤有机碳和作物产量的影响；在此基础上利用土壤碳库排放法(soil based approach, SBA)、生物量排放法(crop based approach, CBA)和土壤&生物量排放法(soil & crop based approach, S&CBA)3种方法对农田净温室气体效应(net greenhouse gas warming potential,NGWP)进行评价。研究发现,相比只施尿素(U)处理,尿素+硝化抑制剂(NI)、尿素+脲酶抑制剂(UI)和尿素+硝化抑制剂+脲酶抑制剂(NIUI)均能增加粮食产量和降低净温室气体排放。用S&CBA方法计算得到的农田温室气体净排放的潜力最大(15 704~17 860 kg/hm²),CBA法次之(4 195~7 107 kg/hm²),SBA法最低(-7 304~-6 599 kg/hm²)。由于3种方法的固碳单元不一样,评估结果差异较大、一致性差。S&CBA方法更适于评价强调粮食生产条件下的农田净温室气体效应。增加作物籽粒和秸秆产量,降低化肥使用和减少灌溉量是提高当前华北平原农田温室气体系统净排放潜力的主要措施。

It is of great importance that Comprehensive and accurate analyzing the quantitative impacts of major agricultural management practices on carbon sequestration and greenhouse gas(GHG) emission within agricultural system for the sustainable agricultural development in China.A field experiment was designed to study the effects of nitrification and urease inhibitor on GHG emission, soil organic carbon change and crops yield of winter wheat summer maize system at the North China Field Experimental Station for Intensive Agricultural Ecosystems Research(located in the Xilujia village of the Xincheng town, Huantai county, Shangdong province; 36°58N, 117°59E; altitude: 9 m above the average sea level).Four treatments were arranged, including urea(U), urea plus nitrification inhibitor (DMPP, NI), urea plus urease inhibitor (NBPT, UI) and urea plus nitrification inhibitor and urease inhibitor (DMPP and NBPT, NIUI).We monitored the emission of CO₂, N2O and CH4, soil organic carbon change and crop yields of wheat and maize during the period of October 2012 to October 2013.Three methods, i.e., soil based approach(SBA), crop based approach(CBA) and soil & crop based approach (S&CBA), were employed to assess the net greenhouse gas warming potential(NGWP) of different nitrification and urease inhibitors in the intensified agricultural system.The monitoring data revealed that there were two N2O emission peaks for wheat and one for maize, all after the farming activities of fertilization or irrigation during winter wheat summer maize production.Cumulative N2O emissions of NI, UI and NIUI were 48.3%, 25.1% and 38.2% lower than that of U treatment, and all treatments were the sink of CH4.Irrigation and fertilization also increased the emission of CH4.Compared with U treatment, NI, UI and NIUI significantly decreased the uptake of CH4 by soil, and the decrease was 29.7%, 18.8% and 13.9%, respectively.All treatments had a seasonal induced change of soil CO₂ emission, i.e., lower in winter and higher in summer season.Similar to CH4, irrigation and fertilization also enhanced the soil respiration.During the research period, average soil respiration rates were 383.9, 385.4, 420.2 and 392.0 mg/(m2·h) for the U, NI, UI and NIUI treatment, respectively.UI treatment emitted significantly higher quantity of CO₂ than other three treatments(U, NI and NIUI) and the differences between these three treatments were not significant.Soil GHGs emissions were significantly correlated with the soil water content and temperature(P<0.01).The crop yields of NI, UI and NIUI treatments were 4.0% (0.59 t/hm²), 2.0% (0.29 t/hm²) and 6.7% (0.99 t/hm²) higher than that of U treatment, respectively.The NGWP quantified by S&CBA was the highest(15 704-17 860 kg/hm²), followed by CBA(4 195-7 107 kg/hm²) and SBA approach (-7 304-(-6 599) kg/hm²).Different NGWP results of the three assessment methods were because of the different carbon sequestration carriers.S&CBA and CBA calculated NGWP on the basis of the removed and returned crop biomass(grain for S&CBA and straw for CBA) and estimated considerably higher GHG mitigation potential than that the change of soil organic carbon stock defined by SBA.The NGWP of NI and NIUI were higher than that of U and UI treatments whatever the method was chosen.Chemical fertilizers application and irrigation were the two main sources of indirect greenhouse gas emission in current study.These results reveal that urea plus DMPP and urea plus DMPP and NBPT could be the promising farming measures to reduce GHG emission and improve the crop yield in North China.S&CBA method is more appropriate for the farmland system with the goal of high yield grain production.Increasing the production of crop grain and straw, reducing chemical fertilizers application and saved irrigation are the main farming measures to decrease the NGWP of farmland system in North China.

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