施肥对稻田甲烷与氧化亚氮排放的影响

大气温室气体浓度的升高引起太阳辐射加强,导致全球变暖已成为不争的事实。农田是温室气体排放的重要来源之一,采用静态箱-气相色谱法探讨不同氮肥类型与施氮水平对华南稻田甲烷（CH4）与氧化亚氮（N2O）排放的影响。试验共设置5个处理,每处理3次重复,分别（以N计）为U6（90 kg·hm-2）,U10（150 kg·hm-2）,U12（180 kg·hm-2）,SR10（150 kg·hm-2,缓释肥）,CR10（150 kg·hm-2,控释肥）。各处理磷钾肥用量一致,分别为45 kg·hm-2（以P2O5计）和127.5 kg·hm-2（以K2O计）。研究结果表明：稻田CH4与N2O排放量随氮肥用量的增加呈增加趋势。晚稻CH4排放呈单峰型,其峰值出现在水稻移栽后16~23 d,N2O排放并未出现明显的排放峰。CH4累积排放主要发生在返青-分蘖初期和分蘖盛期-幼穗分化期两个时段,而N2O的累积排放主要集中在灌浆-成熟期（U6处理除外）。不同氮肥类型处理CH4季节排放总量与平均排放量表现为：处理SR10〉处理U10〉处理CR10,其中,控释肥处理甲烷排放总量较常规尿素处理减少了11.3%;而N2O季节排放总量与平均排放量表现为：处理CR10〉处理U10〉处理SR10。综上,初步认为氮肥的施用能够促进CH4与N2O的释放,缓释肥处理能有效减少稻田N2O的排放,而控释尿素处理能明显降低稻田CH4气体的排放,且稻田CH4与N2O的排放存在一定的互为消长关系,因此如何平衡稻田甲烷与氧化亚氮释放,使稻田增温潜势最小化是下一步研究的重点和方向。

Methane and nitrous oxide emissions in paddy field as influenced by fertilization

It is an indisputable fact that the increase in greenhouse gases concentration leads to the rising atmospheric temperature and causing global warming. It is believed that farmland is one of the most important sources of greenhouse gases; methane （CH4） and nitrous oxide （1,120）. In this study, closed-chamber technology with gas chromatography method was used to study the effect of different nitrogen fertilizer sources and nitrogen application rates on CH4 and N20 emissions from paddy field. The experiment con- sisted of five treatments with three replicates： U6 （90 kg N.hm-2, Urea）, U10 （150 kg N hm2, Urea）, U12 （180 kg N hm2, Urea）, SR10 （150 kg N hm2, Slow release fertilizer）, and CR10 （150 kg N hm2, Controlled-release urea）. The total P and K application rate in each plot were 45 kg P2Os.hm2 and 127.5 kg K20.hm-2. The results showed that methane and nitrous oxide emissions from paddy field tended to increase with the increase of nitrogen application rate. The flux emission of CH4 occurred as a single peak dur- ing growing season of late rice between 16 and 23 days after transplanting, while no obvious flux peak was observed for N20. The accumulative emission of CH4 was observed mainly at two phases; one from regreening stage to early tillering stage and the other from tillering stage to panicle initiation stage. However, the accumulative emission of N20 concentrated around the period from heading stage to harvest （except for treatment U6）. The seasonal and average fluxes of CH4 with different fertilizers followed the trend： SR10 〉 U10 〉 CR10, while the trend was opposite for N20. In addition, the total CH4 emission of CR10 treatment was 11.3% lower compared to U10 treatment. The result suggests that nitrogen application contributed to the release of CH4 and N20 in paddy field. The slow release fertilizer could reduce N20 emission significantly, while the controlled release Urea could reduce methane emission In addition, there＇s a negative relationship between methane and nitrous oxide emissions to some extent. Hence, future re- search should be focused on how to reduce emissions from both CH4 and N20 through appropriate fertilization to minimize the glob- al warming contribution of paddy field.