水稻控制灌溉对稻田N_2O排放的影响机理研究

Influence mechanism of controlled irrigation on N_2O emissions from paddy fields

为了揭示水稻控制灌溉对稻田N2O排放的影响机理,采用静态暗箱-气相色谱法对控制灌溉稻田N2O排放进行原位观测,同时观测土壤水分状况、表层土温和土壤氧化还原电位(Eh)等影响因子,分析控制灌溉稻田N2O排放通量与影响因子间的定量关系.结果表明,与常规灌溉稻田相比,控制灌溉稻田土壤脱水促进了稻田N2O排放,而复水则导致N2O排放通量迅速减小;控制灌溉稻田N2O排放通量的峰值均出现在肥后8~10 d土壤脱水至土壤充水孔隙度WFPS为78.1%~85.3%时;表层土温不是控制灌溉稻田N2O排放的决定性因素,两者之间无显著相关关系(p>0.05);控制灌溉稻田N2O排放通量的峰值主要出现在土壤Eh为+207.5^+275.2m V,低于+120或高于+300 m V时没有明显的N2O排放.将施肥后控制灌溉稻田的WFPS保持在85.3%以上能有效地减少其N2O排放,从而降低其温室效应.

In order to study the effects of controlled irrigation （CI） on seasonal variations of N2O emissions from paddy fields, N2O emissions from CI paddy fields were investigated by the method of static chamber/gas chromatography. Soil moisture, soil temperature and soil redox potential （Eh） were also measured. The quantitative relationships between N2O emissions and affecting factors were analysed. Soil drying incurred substantial N2O emissions, while no substantial N2O emission was observed after the soil was re-wetted following the drying phase. The peaks of N2O emissions from the CI paddy fields were all observed 8-10 days after soil drying with the WFPS ranging from 78.1% to 85.3%. However, no significant correlation was found between soil temperature and N2O emissions （p 〉 0.05）, indicating that soil temperature is not a critical factor in N2O emission. N2O peaks were observed at soil Eh values ranging from ＋207.5 to ＋275.2 mV in CI paddy fields. No significant N2O emission occurred at Eh values higher than ＋300 mV or lower than ＋120 mV. These results suggest that N2O emissions may be reduced obviously by keeping the WFPS higher than 83.5% after each fertilizer application.