水分状况对水田土壤N2O排放的影响

通过室内培养试验，研究了不同水分含量下水稻土的Ｎ２Ｏ排放，结果表明，在水分含量相当于田间持水量时，土壤具有最大的Ｎ２Ｏ排放速率，当水分含量在田间持水量之上时，反硝化作用是Ｎ２Ｏ的主要来源。水分含量在田间持水量之下时，尽管硝倾作用强烈，但Ｎ２Ｏ排放量较小。通过温室盆栽试验研究了不同水分管理措施下，水稻土Ｎ２Ｏ和ＣＨ４的排放，同常规水分管理方式相比，长期淹水显著增加ＣＨ４的排放而减少了Ｎ２Ｏ的排放。相反，湿润灌溉的处理在整个水稻生长期内没有明显的ＣＨ４排放，但其Ｎ２Ｏ排放对水分状况敏感，出现数次峰值，从而总排放量远高于其它两处理。

N2O EMISSION FROM PADDY SOIL AS AFFECTED BY WATER REGIME

N2O emissions from paddy soils with various water contents incubated at 30℃ were measured. During the 39 days’ incubation, soil with water content up to its field capacity had the highest N2O emission. When soil water content was above the field capacity, dentrification was the dominant process for N2O formation. And when soil water content was below the field capacity, there was only a small amount of N2O emission, though the nitrification was most significant. In a pot experiment, N2O and CH4 fluxes from paddy soils under normal water management, continuous flooding and moist irrigation were measured over the rice杇rowing season. There was little N2O emission from paddy soil under continuous flooding. Unfortunately, the emission of CH4, another important greenhouse gas, dramatically increased. In contrast, there was no significant CH4 emission from paddy soil under moist irrigation whereas its N2O emission was much higher than other treatments.