华北平原农田管理措施对冬小麦-夏玉米轮作系统N2O和CH4排放的影响

华北平原是我国重要的粮食生产基地,其农业生产对N_2O和CH_4也具有重要影响.本研究设置包括3类不同农田管理措施的田间试验,即免耕(No-tillage,N)/旋耕(Rotary,T)、秸秆清茬(Cleaning,S0)/还田(Straw,S1)以及不同氮肥水平(常规氮肥(F2),优化氮肥(F1)和空白处理(F0)),分析对产量、N_2O和CH_4排放的影响以及与土壤性状的关系.结果表明,优化氮肥能保持和当地常规氮肥水平相同的粮食产量,同时可以有效降低温室气体CO2-eq(45.4%).秸秆还田可以显著降低N_2O的排放,其中在夏玉米季效果尤为明显.施用氮肥能够抑制土壤对CH_4的吸收.夏玉米季是N_2O排放的主要时期(N_2O累积排放占全年的59%~78%).土壤NO-3含量、WFPS和土壤温度都对N_2O有显著影响.主效应和交互作用分析证明,氮肥水平对两季作物产量、秸秆还田对冬小麦的产量有显著影响;耕作方式与氮肥水平、秸秆还田分别对两季作物产量和CH_4有极显著的交互作用,秸秆处理和氮肥水平对CH_4排放和冬小麦产量有显著的交互作用;三因素的交互作用体现在对冬小麦产量和两季作物的总产量有显著影响.在华北平原当前氮肥水平上降低30%仍能维持和当地常规农业管理措施相同的作物产量,降低N_2O和CH_4排放45%以上,秸秆还田体现出降低N_2O排放以及长期提高土壤有机碳水平的效益.

Effect of farmland management on N2O and CH4 emission from winter wheat-summer maize rotation system in North China Plain

North China Plain is an important grain production area in China with significant N₂O and CH₄ emissions. In this study, a field experiment with three farming factors were arranged, i.e., no-tillage (N)/rotary (T), straw clear (S0)/return (S1) and different nitrogen (N) levels (conventional rate (F2); optimized rate (F1) and control (F0)). The study aimed to investigate the influences of these farming measures on crop yield, N₂O and CH₄ emissions and the relationship of N₂O and CH₄ emission with soil properties. The result indicated that optimized N rate could maintain a similar crop yield to conventional N rate and also reduce annual GHG emission (about 45.4% decrease of CO₂-eq). Straw return significantly lowered the N₂O emission peak, especially in the summer maize season. Higher N fertilizer could inhibit the CH₄ uptake via soil. Summer maize season was the main period of N₂O emission (59%~78% of annual N₂O cumulative emission). Soil NO^-₃ content, WFPS and soil temperature significantly affected N₂O emission. Main and interaction analysis found that N rate and straw return had a significant effect on annual crop yield and winter wheat yield, respectively. Tillage and N rate had a significant interactive effect on annual crop yield. CH₄ uptake was also interactively influenced by tillage and straw management. The interactive effects of straw return and N rate on CH₄ uptake and wheat yield were significant. The interactive effect of these three factors was found on the yield of winter wheat and annual yield. We concluded that in North China Plain, crop yield could be maintained at the optimized N rate (about 30% lower than current conventional rate) while N₂O and CH₄ emissions were reduced by about 45%. Straw return had the benefits of reducing N₂O emission and improving soil organic carbon level over the long period.