评估施用氮肥对水稻灌溉系统中CH4和N2O排放的影响翻译.doc

Assessing fertilizer N placement on CH4 and N2O emissions in irrigated rice systems ABSTRACT： Improved N fertilizer management practices can increase rice yields and mitigate global warming potential (GWP). While banding N has been shown to have positive effects on yield and nitrogen use efficiency (NUE),there is little information on how it affects green house gas (GHG) emissions from flooded rice systems. We tested the hypothesis that in continuously flooded rice systems where GWP is dominated by CH4 emissions , deep placement of urea in bands would reduce CH4 and N2O emissions. Rice yields and GHG emissions were measured from three field experiments which had three treatments : (1) no N(N0), (2) urea broadcast(U-BR) on soil surface and (3) urea banded at 7.5 cm soil depth (U-BA). All urea was applied in a single application before flooding in preparation for planting at N rates of 143–150 kg N ha?1. Throughout the rice growing season GHG emissions were measured using a vented flux chamber and gas chromatograph. Across all fields , N fertilizer application increased yield on average by 121%. Between the N placement methods, grain yields and NUE(37kg grain kg?1 ) were similar. Daily N2O emissions were low to negative and did not differ among treatments. CH4 emissions were the major source of GWP emissions and cumulative emissions ranged from 6.3 to 297 kg CH4–C ha?1 season?1 among fields. While in some cases fertilizer N increased CH4 emissions, there was no effect of N placement on them. 评估氮肥深施对水稻灌溉系统中CH4和N2O排放的影响 摘要： 提高氮肥管理措施能够增加水稻产量且减轻全球变暖趋势（GWP）。带状施氮已对产量和氮肥利用率（NUE）产生积极影响，但在淹水水稻系统下，如何影响温室气体（GHG）排放的信息还很少。我们检验假设在持续淹水水稻系统中GWP主要由CH4排放占主导地位，尿素深施会降低CH4和N2O的排放。3个田间试验各3个处理测定水稻产量和GHG排放：（1）不施氮（N0），（2）尿素播撒（U-BR）在土壤表层，（3）在7.5cm土壤深度处尿素带施（U-BA）。在准备种植淹水之前一次性施用所有尿素，施氮量为143-150 kg ha?1。利用排放通量室和气相色谱仪测定水稻整个生育期GHG排放量。在所有田间试验中，施用氮肥平均产量增加了121%。氮肥深施的方法、作物产量和NUE（每Kg施氮量产37Kg粮食）都有类似结果。每天N2O排放量很低，且和其他处理之间没有差别。CH4排放是GWP的主要来源，且每季每公顷CH4累积排放量范围为6.3-297Kg。虽然在某些情况下，施氮增加了CH4的排放，但氮肥深施对CH4的排放并没有影