黄土高原南部旱地冬小麦生长期N_2O排放特征与基于优化施氮的减排方法研究

N_2O emission characteristics and mitigation methods in South Loess Plateau under rain-fed winter wheat conditions

为了解陕西黄土高原南部旱地冬小麦季N2O排放规律,探索旱地N2O减排方法,采用密闭式静态箱法,以不同施氮处理[CK:对照,不施氮;CON:当地农民习惯施氮,施氮量220 kg·hm-2;OPT:优化施氮加秸秆还田,施氮量150 kg·hm-2;OPT+DCD:优化施氮加秸秆还田,同时施用施氮量5%的硝化抑制剂DCD;OPT(SR):优化施氮(所用肥料为包膜型缓控释肥)加秸秆还田]为基础,研究黄土高原南部旱地冬小麦农田N2O季节排放特征和减排措施。结果表明:黄土高原南部旱地冬小麦季N2O排放具有首月持续、大量排放,末月雨后瞬间排放,中期低排放的特点。各处理中,OPT+DCD和OPT(SR)在播种—返青期能显著减少N2O排放水平,而返青—成熟期,各优化处理差异不显著。从整个小麦季N2O排放总量来看,各优化处理能够减少N2O排放量,提高作物产量,降低单位产量N2O排放量。具体表现为:1与CON处理的N2O排放量相比,OPT、OPT+DCD和OPT(SR)处理分别减排29.2%(P<0.01)、38.7%(P<0.01)和39.3%(P<0.01),但3个优化处理间差异不显著;2与CON处理的产量相比,OPT、OPT+DCD和OPT(SR)处理分别增产3.8%(P>0.05)、15.2%(P<0.05)和9.5%(P<0.05);3与CON处理的单位产量N2O排放量相比,OPT处理单位产量N2O排放量减少31.7%(P<0.05);而相对于OPT处理,OPT+DCD处理和OPT(SR)处理分别减少了单位产量排放量的22.1%(P<0.05)和18.9%(P<0.05)。本研究表明,减少施氮量至150 kg·hm-2,并施用秸秆是减少N2O排放的重要手段,而施用缓控释肥或一定量的DCD可提升作物产量。

Quantifying N2O emissions and searching for appropriate emission-reduction measures have gained high international interest in global climate change studies. Therefore understanding the impacts of human activities on N2O emissions from arable soils was vital for mitigating any negative effects on climate change. In this paper, N2O emissions from soil under different nitrogen treatments：no nitrogen （CK）, conventional treatment of 220 kg（N）·hm-2 （CON）, optimized treatment with 150 kg（N）·hm-2 and straw return （OPT）, optimized treatment with DCD （OPT＋DCD） and optimized treatment by coated slow release fertilizer [OPT（SR）], in central Shaanxi of South Loess Plateau were observed during winter wheat season using the static opaque chamber/gas chromatography （GC） method. Results showed that in the first month of winter wheat growth, emissions were of large amount and lasted for longer times. In the last month, emission peaks rapidly occurred and disappeared after precipitation. Then during other times of winter wheat season, emissions were generally low. During seedling to re-greening stage, OPT＋DCD and OPT（SR） significantly reduced N2O emission. Then during re-greening to maturing stage, emissions under the three optimized treatments were not significantly different. In terms of total emissions of different treatments of winter wheat, all the three optimized treatments＂nbsp;reduced N2O emission, increased crop yield and decreased N2O intensity （N2O emission for per unit grain yield）. Compared with CON, the optimized treatments of OPT, OPT＋DCD and OPT（SR） reduced N2O emission by 29.2%（P〈0.01）, 38.7%（P〈0.01） and 39.3%（P〈0.01）, respectively, with not significant differences among the three optimized treatments. Compared with CON, the op-timized treatments of OPT, OPT＋DCD and OPT（SR） increased crop yield by 3.8%（P〉0.05）, 15.2%（P〈0.05） and 9.5%（P〈0.05）, respectively. Also compared with CON, the optimized treatment of OPT reduced N2O intensity by 31.7%（P〈0.05）. Then compared with OPT, OPT＋DCD and OPT（SR） reduced N2O intensity by 22.1%（P〈0.05） and 18.9%（P〈0.05）, separately. The results sug-gested that returning straw to soils in combination with reducing nitrogen application rate to 150 kg（N）·hm-2 most reduced N2O emission. Using slow release fertilizer or adding certain amounts of DCD increased crop yield.