"薄浅湿晒"与干湿交替灌溉稻田甲烷和氧化亚氮排放机制和水氮运筹模式

"Thin-shallow-wet-dry" and alternate drying and wetting irrigation methods are two water-saving irrigation methods widely used in paddy soil. Systematical and deep studies about investigate soil microbial characteristics, soil properties and the mechanism of methane (CH4) and nitrous oxide (N2O) emissions from paddy soil and its mangement mode of water and nitrogen under the two water-saving irrigation methods have important significance in precisely estimating the emissions of CH4 and N2O from paddy soils in China, exploring and extending the reduction technology of greenhouse gas emission and controlling global warming. This project will investigate the effects of the two water-saving irrigation methods and nitrogen mangement and on the emmisons of CH4 and N2O in paddy soil, soil properties such as soil Eh and active organic C and N fraction, soil microbial numbers such as the numbers of methane producing bacteria, nitrifying bacteria and denitrifying bacteria, soil enzyme activity such as nitrate reductase and nitrite reductase, and community of ammonia oxidizing bacteria at different growth stages of rice. Our project aims to reveal the variations of CH4 and N2O emissions in paddy soil at different growth stages of rice and their comprehensive global warming potential, explore mechanism of CH4 and N2O emissions from paddy field explained by the changes of soil microbial characteristics and soil properties and their interaction induced by water and nitrogen management and propose optimal mangement mode of water and nitrogen that is benefical for water-saving and yield incresing of rice and the reduction of CH4 and N2O emission in paddy soil, so as to provide the scientific basis in precisely estimating and reducing CH4 and N2O emissions from irrigated paddy fields in China.

"薄浅湿晒"和干湿交替灌溉模式是稻田应用较广的两种节灌模式，系统深入地研究这两种节灌模式稻田土壤微生物特性、土壤性质以及甲烷（CH4）和氧化亚氮（N2O）排放机制及水氮运筹模式，对于准确估算我国稻田CH4和N2O排放量、探索和推广稻田温室气体减排技术和控制全球变暖具有重要的意义。本项目拟研究这两种节灌模式和氮肥运筹对不同生育期稻田CH4和N2O排放、土壤性质如土壤Eh值和活性有机C和N组分，土壤微生物数量如产甲烷细菌、硝化细菌和反硝化细菌，土壤酶活性如硝酸还原酶和亚硝酸还原酶，以及氨氧化细菌群落等的影响，揭示不同生育期稻田CH4和N2O排放规律及其综合增温潜势变化规律，探讨水氮运筹引起的土壤微生物特性和土壤性质变化及其相互作用对稻田CH4和N2O排放的影响机制以及提出利于水稻节水增产和稻田CH4和N2O减排的最佳水氮运筹模式，为我国灌溉稻田CH4和N2O排放量的准确估算和减排奠定科学基础。

“薄浅湿晒”和干湿交替灌溉模式是两种稻田节灌模式。本项目通过不同灌溉模式（常规灌溉，“薄浅湿晒”灌溉和干湿交替灌溉）和氮肥运筹（氮肥（N）用量，施氮方式以及有机无机氮肥配施）的早晚稻田间试验，系统深入地研究了稻田土壤微生物特性如微生物数量和酶活性和土壤理化性质如土壤Eh值和碳氮组分对不同水氮运筹的响应规律，甲烷（CH4）和氧化亚氮（N2O）排放规律和机制，以及探讨了节水、增产、稻田CH4和N2O减排的水氮运筹模式。研究发现，与常规灌溉相比，“薄浅湿晒”灌溉和干湿交替灌溉产量和N2O排放增加，但是降低CH4排放、CH4和N2O综合增温潜势和排放强度。在这两种灌溉方式下，N1（120 kg hm-2）处理，单施尿素处理和FN2（120 kg N hm-2，50%基肥、50%追肥）稻田CH4和N2O综合增温潜势和排放强度分别较N2（150 kg hm-2），猪粪尿素配施处理和FN1（120 kg N hm-2，20%基肥、80%追肥）降低。水氮运筹通过影响土壤性质，从而进一步影响甲烷（CH4）和氧化亚氮（N2O）排放。土壤温度、Eh，可溶性碳、还原性物质总量、全氮、碱解氮、甲烷氧化菌数量和淀粉酶活性是影响稻田甲烷排放的重要因子，而土壤NH4+-N、微生物量氮、非酸解性氮、还原性物质总量、全氮、碱解氮、速效磷、速效钾、氨氧化潜势、硝化细菌、氨氧化细菌、羟胺还原酶和硝酸还原酶是影响稻田N2O排放的重要因子。因此，不同施氮管理下，应采用“薄浅湿晒”和干湿交替灌溉模式替代常规灌溉，以减缓稻田CH4和N2O排放；不同灌溉模式下，应合理减施氮肥用量，控制有机肥用量，氮肥应少施基肥、多施追肥方案，以减缓稻田CH4和N2O排放。研究结果可以为我国灌溉稻田CH4和N2O排放准确估算和减排奠定科学基础。