养殖废水灌溉对玉米-小麦轮作农田CO2、CH4、N2O通量的影响及作用机理

Global change and greenhouse gas emission have gained increasing concerns from governments and scientists. Livestock and poultry breeding is one of the most important factors that impacts the emissions of greenhouse gases. Most attentions have been paid on the fermentation in gastrointestinal tract of livestock and poultry, manure compost disposition, and manure application to farmland etc., however, effects of breeding wastewater irrigation on the greenhouse gas emission have barely investigated. Objects of this project are to investigate the relationship between the greenhouse gas fluxes (CO2、CH4、N2O) in farmland and the irrigation time, degree of treatment and irrigation volume of breeding wastewater. This project will be carried out in a corn-wheat rotation field in North China region where selected typical large scale cattle farm/hoggery are located around, and the produced breeding wastewater will be used for this project. Research will foucs on the relationship of the emission of CO2、CH4 and N2O after breeding wastewater irrigation in farmland with soil physicochemical properties, soil aggregate, carbon and nitrogen speciation and their mineralization and nitrification rates, and structure and diversity of soil microbial communities. Results from this project will provide theoretical basis for assessing the effects of breeding wastewater irrigation on the emission fluxes of main greenhouse gas, and explore the contribution of breeding/planting coupling process to greenhouse gas emissions. In addition, it can also provide the scientific foundation for our country to make policies on greenhouse gas reduction and carbon and nitrogen management in soils.

全球变化和温室气体减排日益受到各国政府和科学家的广泛关注。畜禽养殖业是影响温室气体排放的重要因素之一，现有研究主要集中在畜禽胃肠道发酵、粪便堆肥以及粪便农田施用等方面，对于养殖废水灌溉农田过程中的温室气体排放及其机理研究鲜见报道。项目以华北地区典型玉米-小麦轮作农田和猪场养殖废水为研究对象，研究农田CO2、CH4、N2O通量变化特征与猪场养殖废水处理程度、养殖废水灌溉量及灌溉时间之间的关系。重点研究养殖废水灌溉条件下，土壤理化性状、土壤团聚体组成、土壤碳氮形态及矿化速率和硝化速率、土壤微生物群落结构和多样性等指标与温室气体通量变化间的内在关系，阐明猪场养殖废水灌溉对玉米-小麦轮作农田CO2、CH4、N2O通量的影响及作用机理。研究结果可为评估养殖废水灌溉影响主要温室气体通量提供理论基础，补充养殖/种植业耦合过程对温室气体排放的贡献份额，为我国制定温室气体减排、农田碳氮管理政策提供科学依据。

为阐明养殖废水灌溉对农田温室气体排放的影响及作用机理，本项目以华北地区典型玉米-小麦轮作农田为研究对象，研究了不同牛场养殖废水处理下农田CO2、N2O和CH4通量变化特征，明确了温室气体排放与土壤理化性状、微生物群落结构的动态关联，圆满完成了项目预定科研目标，为我国制定温室气体减排、农田碳氮管理政策提供科学依据。具体来说：.（1）明确了沼液灌溉后农田土壤CO2、N2O和CH4的排放特征；日排放特征为昼高夜低的单峰曲线；周变化特征为沼液灌溉后麦田土壤温室气体排放通量显著增加，并且随着时间的延长逐渐下降。.（2）中、低强度养殖废水灌溉未显著增加温室气体年累积排放量；与常规施肥相比，中、低强度养殖废水灌溉不会引起CO2和N2O累积排放量增加；沼液灌溉会增加小麦季土壤CH4的排放通量，但在整个轮作周期CH4累积排放无显著变化。.（3）适量养殖废水灌溉下粮食产量与常规施肥相当；中、高强度废水处理下粮食产量与常规施肥相比无显著差异，说明中浓度养殖废水灌溉即可达到常规施肥增产效果。.（4）温室气体排放与土壤理化性状相关；土壤CO2排放与DOC和温度正相关；N2O排放与DOC和土壤NO3--N含量正相关；CH4的排放与土壤NH4+-N含量和含水量正相关。.（5）养殖废水对土壤氮素循环微生物作用存在差异；养殖废水增加氨氧化细菌数量、降低氨氧化古菌数量，而对群落结构影响不大；养殖废水未显著改变nirK及nirS型反硝化细菌数量，但nirK及nirS型反硝化细菌群落结构发生明显变化；.综合来看，养殖废水灌溉在一定程度上改变了土壤性质、微生物数量、群落结构和多样性，最终影响温室气体排放。科学、合理的养殖废水灌溉能够在保证作物产量的同时控制温室气体排放，保持土壤氮素循环相关微生物的活性，并调整群落结构、增加多样性。项目的实施为我国制定温室气体减排、农田碳氮管理提供科学依据。