优化施氮对宁夏引黄灌区稻田CO2、CH4和N2O通量的影响

针对宁夏引黄灌区稻田施氮严重过量现象,在宁夏引黄灌区的青铜峡稻田,采用静态箱-气相色谱法,通过田间试验研究常规施氮(N300)、优化施氮(N240)和不施氮(N0)对水稻不同生育期CO_2、CH_4和N_2O通量以及稻田增温潜势(GWP)的影响。结果表明:CO_2排放主要在水稻灌浆和成熟期,CH_4排放主要发生在水稻孕穗期,而N_2O排放关键期在水稻的分蘖和拔节期。与N0处理相比,施氮能显著增加稻田CO_2、CH_4和N_2O排放通量以及稻田GWP;常规施氮处理中CO_2、CH_4和N_2O的累积排放量分别为18 446.87、146.57 kg C·hm~(-2)和2.93 kg N·hm~(-2);为期一年的优化施氮没有显著增加水稻生育期内稻田CO_2排放,但使灌区稻田CH_4和N_2O排放分别显著降低了24.42%和36.28%。总的来看,为期一年的优化施氮使宁夏引黄灌区稻田GWP显著降低了26.70%。未来应结合土壤有机碳氮形态和含量变化以及土壤微生物技术,分析长期优化施氮对土壤温室气体通量的影响机制。

Effects of optimized N fertilization on carbon dioxide, methane and nitrous oxide fluxes in paddy fields in Yellow River water irrigation region of Ningxia

Excessive nitrogen(N) fertilizer application is a widespread practice in Yellow River water irrigation region of Ningxia. Previous studies have demonstrated that optimized N fertilization can not only improve rice yield but also reduce nitrogen leaching. However, there was little information available about the responses of soil greenhouse gas fluxes to optimized N fertilization in this region. A field experiment was conducted to evaluate the effects of different N fertilization on carbon dioxide(CO₂), methane(CH₄) and nitrous oxide(N₂O) fluxes and global warming potential(GWP) in paddy field in Yellow River water irrigation region of Ningxia, using static chamber technique and gas chromatography. Treatments included conventional N fertilization(N300), optimized N fertilization(N240) and no N fertilization(N0). Our results showed obvious differences in greenhouse gas fluxes during the rice growth period. Higher CO₂ emissions appeared at filling and mature stages, but CH₄ emissions mainly occurred at booting stage. However, the peak of N₂O emissions was observed at tillering and elongation stages. Applying nitrogen significantly increased soil CO₂, CH₄, and N₂O emissions and the global warming potential. During the experimental period, average CO₂, CH₄, and N₂O fluxes were 18 446.87 kg C·hm^-2, 146.57 kg C·hm^-2, and 2.93 kg N·hm^-2, respectively. One-season optimized N fertilization did not affect CO₂ emissions, but significantly reduced CH₄ and N₂O emissions by 24.42% and 36.28%, respectively, as compared with conventional N fertilization. Overall, our results indicate that the global warming potential of paddy field was significantly reduced by 26.70% by optimized N fertilization in Yellow River water irrigation region of Ningxia. Further research is needed to analyze the mechanisms of soil greenhouse gas fluxes under long-term optimized N fertilization by integrating the variations of soil organic carbon and N availability and soil microbiology methods.