滴灌节水技术应用对北方典型旱作农田综合温室效应及碳汇潜力变化的影响与机制

Irrigation is one of the important means for dry farming in Northern China to get high yield. Wide application of water-saving irrigation technology would be the inevitable trend of the future agriculture development because of the increasing shortage of water resources in the world.The carbon pool of agro-ecosystem is the most active part of global carbon pool and very sensitive to the change of management measures. As one of the most effective means for agricultural water-saving, drip irrigation and its popularization certainly will have a significant impact on the carbon budget of ecosystem and its atmospheric greenhouse effect, but the relative data and corresponding mechanism analysis are rarely seen up to know. In our project, wheat-maize rotation field, which is widely distributed and representative in Northern China, will be selected as the object of research, and through the comparison between drip irrigation and the traditional flooding irrigation, we try to reveal the quantitative effect of water-saving drip irrigation application on the soil respiration rates and its component change, spatial heterogeneity as well as the ecosystem carbon budget, elaborate the main driving mechanism of irrigation methods change on the temporal-spatial variation of CO2, N2O and CH4 and their synthetic global warming potential, and comprehensively evaluate the quantitative contribution of water-saving irrigation technology in the climate change and the grain production, making up for the lack of relevant research data in China. The results are not only advantageous to reveal the inherent mechanism of farmland water management and greenhouse gases emission characteristics, but also could provide important scientific basis for the establishment of appropriate agricultural management measures which are in favor of mitigating greenhouse effect in the future, amd provide important data support for the extensive popularization of water-saving drip irrigation technology.

农田碳库是全球碳库最活跃的部分，对管理措施的变化响应十分敏感。节水灌溉技术广泛应用是水资源日益短缺背景下我国旱作农业发展的必然趋势。滴灌作为目前我国旱作农田最有效的一种节水灌溉方式，其推广应用势必会对农田温室效应贡献及其碳源汇产生显著影响，但相关试验数据及机理研究迄今十分缺乏。研究拟选择我国华北平原冬小麦-夏玉米轮作田为研究对象，通过滴灌与传统漫灌方式的比较，揭示滴灌技术应用对农田土壤呼吸不同组分、空间异质性及碳收支变化的定量影响；明确CO2、CH4、N2O通量及其综合增温潜势对灌溉方式变化的响应规律；探讨不同气体的响应与耦合变化机制；综合评估滴灌技术对北方农田气候变化及粮食生产变化的定量贡献。研究成果有利于深入揭示农田水分管理方式与温室气体源汇贡献间的内在联系机制，为完善相关预测模型提供机理认识与关键参数，同时也可为农业减排管理措施的制定提供科学依据，为滴灌技术的推广提供环境效应数据支持

本研究以华北平原夏玉米-冬小麦田为研究对象，采用静态暗箱法对漫灌、微喷、滴灌三种灌溉方式下土壤主要温室气体排放的时间及空间变化特征进行了系统观测，分析了不同灌溉方式下农田土壤不同组分碳氮养分的分布特征，探讨了灌溉方式改变情景下不同环境因子对温室气体排放驱动效应的变化，明确了温室气体综合增温潜势（GWPs）及生态系统碳源汇对灌溉方式变化的响应。结果表明：与漫灌相比，滴灌与微喷改变了土壤碳氮养分的空间分布规律，但除个别时段外，同一灌溉方式下不同空间部位碳氮养分含量差异并不显著；玉米生长季，滴灌和微喷均促进了土壤关键温室气体的排放。冬小麦生长季，除滴灌降低了土壤N2O累积排放外，滴灌和微喷对土壤温室气体排放通量均表现出促进作用；滴灌方式下，玉米生长季土壤主要温室气体排放通量均表现为滴灌管上显著高于滴灌管间（P<0.05），小麦生长季不同空间处理温室气体排放通量差异不显著；在微喷方式下，距离微喷管越远，温室气体排放通量越小；漫灌方式下，不同温室气体排放通量均表现为漫灌行上>漫灌行间，但与滴灌相类似，微喷与漫灌方式下只有玉米生长季不同空间处理间各温室气体累积排放量表现出显著差异；滴灌和微喷灌溉均增加了农田的综合温室潜势，滴灌和微喷降低了玉米生长季农田碳汇，但增加了小麦生长季农田碳汇；灌溉方式改变了不同生长季土壤温室气体排放的主要驱动因子及其作用贡献。