冬小麦/大葱轮作体系N_2O排放特征及影响因素研究

采用静态暗箱-气相色谱法研究了冬小麦/大葱轮作体系不同施肥处理下农田N2O排放特征及排放系数,分析了土壤湿度和土壤温度等环境因子对N2O排放的影响。结果表明,农田N2O排放高峰值主要出现在每次施肥＋灌溉或强降雨之后的一段时间,大葱生长季排放峰值高且出现的频率比小麦生长季密集;N2O排放通量变化范围为-3.85～507.11μg N·m-2·h-1,平均值为251.63μgN·m-2·h-1,对于不同施肥处理,其年度N2O排放总量介于1.71 kg N·hm-2到4.60 kg N·hm-2之间。整个轮作体系不同处理N2O排放系数介于0.31%到0.48%之间,均值为0.43%;相对比农民习惯（FP）处理,优化施肥（OPT）、优化减氮（OPT-N）以及秸秆还田（C/N）处理均能显著减少N2O的排放,秸秆还田处理和优化减氮处理N2O排放总量比优化处理分别减少了17%和10%。在10℃〈土壤温度（T）s〈20℃时,N2O排放随温度的升高而增加;整个小麦生长季N2O排放随土壤湿度的增加而增加,且达到0.05的显著水平;大葱生长季在20℃〈Ts〈30℃时,土壤水分含量成为主要限制因素,N2O排放与土壤孔隙含水量（WFPS）呈显著指数正相关关系。秸秆还田处理作物产量高于其他处理,是具有减排增产＂双赢＂效果的农田管理措施。

Analysis of the Characteristics of Nitrous Oxide Emissions from a Winter Wheat-Green Onion Rotation Sys- tem and the Influencing Factors

Quantifying greenhouse gas（GHG） emissions and searching for appropriate mitigation measures have become a relatively hot issue in international global climate change studies. Therefore, understanding the impacts of human activities on greenhouse gas emissions from productive soils is vital for mitigating negative effects on climate change. In this paper, N=O emissions in winter wheat-green onion rotation system were observed using static opaque chamber/gas chromatography （GC） method. The effects of relative environmental factors such as soil moisture and temperature etc. on N20 emissions were also discussed. The results indicated that the observed N20 emissions peaks fol- lowed each time of fertilizer application and irrigation or heavy rainfall. The frequency of the peaks in green onion growing season was higher than that in winter wheat. The highest N20 emission flux was observed in green onion growing season with 507.11 I~g N＂ m-2＂ h-~. Annual cu- mulative N20 emissions in the 5 treatments of Control （CK）, farmer＇s practice （FP）, optimized fertilization （OPT）, optimized fertilization ＋re- ducing fertilizer（OPT-N）, and straw returned（ C/N ） were 1.71, 4.6, 3.62, 3.24 kg N＂ hm-2 and 3.02 kg N＂ hm-~, respectively. The annual emission factor（EF） of N fertilizer ranged from 0.31% to 0.48%, with an average of 0.43%. The OPT-N and C/N treatments could reduce N20 emissions by 10% and 17%, respectively, comparing with OPT treatment. But the C/N treatment was regarded as the best management prac- tice because it not only had significantly effect on reducing N20 emissions, but also maintaining crop yield. Multiple regression analysis re- vealed that soil temperature and soil moisture （WFPS） were also the factors affecting N20 emissions besides nitrogen fertilizer. When soil temperature changed in the range of 10-20 ℃, N20 emissions increased greatly with temperature rise, but soil temperature changed in therange of 20-30 ℃, soil moisture （WFPS） became a limiting factor and there was a significant positive correlation between NzO emissions and soil moisture （WFPS）. We expect these efforts will provide basic data for aecurately predieting N20 emissions at regional scales that are at- tracting more attention across China.