中文摘要：

【目的】农田水肥的高投入在保障粮食产量的同时也伴随着温室气体的排放。本研究以农田投入品的生产和运输—作物生长的整个过程为研究对象,对农田生态系统中不同水氮管理措施的温室效应开展了评价。【方法】在已经确定粮食产量和温室气体排放强度评价指标的基础上,对土壤固碳深度和减排措施评价的时间尺度进行了分析,将土壤固碳深度确定为30 cm以上,温室效应评价的时间尺度确定为20年,提出了以田间试验与过程模型相结合,辅以调研的评价方法,来反映产量和温室气体排放强度对不同管理措施的响应。常规农民措施的农田投入量（灌溉量和施氮量等）通过问卷调研和文献数据来获得。以华北平原冬小麦/夏玉米轮作模式为例,利用验证后的农田生态系统管理模型（APSIM）对不同措施（氮肥利用、灌溉和有机肥配施）进行20年（1990 2010）尺度的模拟,并结合农田投入品在生产和运输过程的排放,遵照评价方法对不同水氮管理措施的温室效应进行了分析。【结果】与当前常规农民措施相比,将常规施氮量从520 kg/hm-2减少为400 kg/hm-2,粮食产量在20 a间不存在显著性差异（P=0.39）,但年均温室气体排放总量（AE-GHG）可减少约1.45 t/hm-2,温室气体排放强度（GHGI）可减少约0.08 t/t;若将该地区常规灌溉量从300 mm减少到240 mm,粮食产量在20年间不存在显著性差异（P=0.39）,年均温室气体排放总量（AE-GHG）可减少约0.29 t/hm-2,温室气体排放强度（GHGI）可减少约0.01 t/t,主要归因于电力消耗的降低,减少了生产和传输过程中温室气体排放;若将常规措施中的底肥（N）全部替换为有机肥,粮食产量在20年间不存在显著性差异（P=0.63）,年均温室气体排放总量（AE-GHG）可减少约0.03 t/hm-2,温室气体排放强度（GHGI）则基本无变化,虽然有机肥可带来更多的土壤固碳,但是若考?

英文摘要：

【Objectives 】 High-input of ground water and nitrogen（ N） fertilizer in cropland maintains crop productivity,while it also increases greenhouse gas（ GHG） emission. In this study,we used life-cycle analysis method（ from the production and transportation of cropland inputs to crop growth） to accurately evaluate the effect of management practices on the mitigation of GHG emission in agricultural ecosystem. 【Methods】We analyzed the effect of soil depth on carbon sequestration and the effect of time scale for evaluating mitigation practices on thebasis of the proposed evaluation indices,including grain yield and GHG intensity（ GHG emission per unit yield）.The soil depth of ≥30 cm and the time frame of 20-year were chosen because it is appropriate to reflect changes in soil organic carbon content,in crop yield and N_2O emissions as a consequence of management practices. We developed a method that combined the survey data,field measurements and process-based modelling in order to investigate how crop yield and GHG intensity change in the response to management practices for the winter wheat /summer maize rotation at Zhengzhou in North China Plain. Cropland input rates were obtained from common farmer＇s practices by questionnaire survey and from published data in the literatures,including irrigation and N application etc. 20-year ＇s simulation（ 1990- 2010） was conducted with the validated process-based cropping systems model（ APSIM） to obtain crop yield,N_2O emissions and the change in SOC content in the response to different N application rates（ including chemical N and organic N） and irrigation amounts. The simulation results,combined with the indirect CO- eq2 emissions from production and transportation of cropland inputs,were used to evaluate crop productivity and GHG intensity. 【Results】Compared to the current practices of local farmers,when the annual N application rate is reduced from 520 kg / hm-2 to 400 kg / hm-2,there is no significant difference in grain yields in