滴灌技术对华北农田碳氮气体排放与氮淋失的协同影响与调控机制

Carbon and Nitrogen gases emissions and nitrogen(N) losses by leaching are the most important issues of contemporary environmental safety. Within the restriction of water resources, how to ensure food security, quantify gases emissions and N leaching and search for appropriate mitigation measures has become a relatively big challenge for the sustainable development of China's agriculture. In comparison to the conventional flooding irrigation mode, the drip irrigation as a new developed technology recently, which not only could save water, but also increase rice yield, has played an important role in environment protection. So far, however, few investigations about the coordinated effect of drip irrigation on the C and N gases (i.e., N2O, CH4, CO2 and NH3) and N leaching have been reported. The related controlling mechanism also needs to be further studied. Therefore, the project will conduct the experiments of gases fluxes and N loss from the fields of 2 typical cropping systems (i.e., the winter wheat and summer maize rotation system and the greenhouse vegetables system) in the North China Plain region, using in situ field measurements, laboratory analysis coupled with process-based model methods. The objectives of this project are to (1) characterize the annual dynamics of the C and N gases emissions as well as the key processes of N leaching from the two production systems within the condition of the change of irrigation modes,(2)reveal the comprehensive response mechanism and relationships between not only gases, but also gases and N leaching, (3)verify and perfect carbon and nitrogen cycle process-based model (DNDC model) according to the measured data, and(4)finally, based on the establishment of the key parameters embedded in DNDC model, accurately evaluate the effects of drip irrigation mode on gases emissions and N loss, and finally reveal the comprehensive controlling mechanism on carbon and nitrogen. The results obtained from this project will provide not only the scientific foundation and decision support for the drip irrigation technology extension in North China Plain, and but also the basic data and technological reservation for optimizing carbon and nitrogen management.

如何在农业水资源硬约束下保障农产品的有效供给，同时有效削减农业碳氮气体排放和控制氮素损失已成为当前研究热点。与传统大水漫灌管理方式相比，滴灌技术被认为是既能节水节肥提高产量又能保护环境的多赢措施，对滴灌条件下农田生态系统碳氮循环规律及调控机制亟待研究。本研究针对农田碳氮气体排放和氮淋失协同过程研究不深入，综合调控机制不明晰的科学问题，以水资源短缺的华北平原为研究区域，选择两种典型的作物种植模式冬小麦夏玉米轮作和设施菜地为研究对象，通过田间原位观测、室内培养、过程机理模型相结合的方法，探明滴灌条件下不同种植类型农田碳氮气体排放和氮淋失通量特征、主控因素及时空差异特征，识别碳氮气体排放及其与氮淋失之间的协同过程，并揭示其综合调控机制。研究成果不仅为滴灌技术在华北区域的应用提供科学依据，而且能为我国农业碳氮优化调控提供技术储备和科学支撑。

针对滴灌条件下农田碳氮气体排放和氮淋失协同过程研究不深入，调控机制不明晰的科学问题，以水资源短缺的华北平原为研究区域，在山东桓台和京郊顺义房山分别选择两种典型的作物种植模式——冬小麦夏玉米轮作和设施蔬菜，通过田间原位观测、室内实验和过程机理模型相结合的方法，研究了滴灌条件下2种不同种植模式农田碳氮气体交换通量特征及关键影响因素，氮淋溶流失的形态、主控因素及年度动态特征，以及滴灌施肥对碳氮气体排放及其与氮淋失之间的协同影响与综合调控机制。研究表明，设施菜地氮素的损失途径（N2O排放、NH3挥发、氮淋溶）中，氮淋溶损失占主导地位，占氮肥投入的3.2%-7.5%，其次有1.5%-4.4%和0.07%-0.46%的氮素以NH3和N2O的形式排放到大气中。对于冬小麦-夏玉米轮作系统，滴灌施肥条件下碳氮损失途径以N2O排放为主，占氮肥投入的0.29%-0.47%。滴灌施肥技术在设施蔬菜和粮食作物系统均具有显著的减排效果，但减排贡献不一致，在设施蔬菜和粮食作物系统中减排量分别可达30.2%和45.8%。同时发现，碳氮气体之间及其与NO3--N淋溶存在着互为消涨或协同的关系，土壤NO3--N运移转化是关键影响和调控因子，制定协调作物产量和环境效应目标下调控措施和策略需要综合考虑碳氮气体排放和N淋溶损失。利用设施蔬菜和冬小麦夏玉米系统碳氮循环监测数据校验了DNDC模型，模型能够较好地模拟出作物产量、土壤温度和水分变化、NO3--N的迁移淋失过程等。基于模型定量化分析，综合考虑不同灌溉方式对碳氮损失的影响，在提高土壤SOC和优化施肥的条件下，滴灌技术可以在保证作物产量的前提下，具有较好的同时削减碳氮气体损失和氮淋失的效应，是设施菜地和冬小麦夏玉米作物系统值得推荐的管理策略。研究结果可为农田碳氮综合调控提供基础数据和决策依据，同时为农业碳氮气体减排、面源氮素流失控制等提供技术参考。