不同灌溉生产方式影响农田N2O排放特征及驱动机制

Nitrous Oxide (N2O) is one of the important atmospheric greenhouse gases, agriculture is an important source of atmospheric N2O emissions, it is the focus of governments and scientists that the transformation of the mode of agricultural production retard greenhouse gas emission. Sprinkler irrigation has small water infiltration rate and water use characteristics of high utilization rate, drip irrigation has better water saving effect and flood irrigation resulted in the low water use rate. The potato field of the research object which was applied with sprinkler irrigation, drip irrigation and flood irrigation is selected as the project in Dalate irrigation area of the Yellow River basin in China, it is observed and compared that different irrigation modes effect soil carbon and nitrogen process and N2O emission flux, project will be completed: (1) to compare N2O emission characteristics and emission intensity and N2O emission mitigation potential on the transformation of the mode of agricultural production in potato field; (2) to reveal driving mechanism and the dynamic characteristics on soil function changes, and the temporal variation of migration and transformation of soil carbon and nitrogen on different irrigation modes of production in potato fields; (3) to clarify microbiology association mechanism of N2O emission and soil carbon and nitrogen process on different irrigation modes of production in Potato Field. The results will provide data support of the evaluation of environmental effects about popularization of water saving irrigation production, and help to reduce uncertainty of farmland N2O emission estimation in our country, and provide scientific basis of slowing down farmland N2O emission in order to seek the transformation of the mode of agricultural production.

氧化亚氮(N2O)是大气重要温室气体之一, 农业是大气N2O重要排放源, 通过农业生产方式转变减缓农田温室气体排放是各国政府和科学家关注焦点。本项目针对不同灌溉生产方式“喷灌水分入渗速率小、水分利用率高, 滴灌具有更高的节水效果及漫灌生产水分入渗速率大、利用率低”的特点，以黄河流域达拉特灌域喷灌、滴灌和漫灌生产方式马铃薯田为研究对象，采用静态箱-气相色谱法原位观测土壤碳氮过程及N2O排放通量, 完成: (1)比较不同灌溉生产方式马铃薯田N2O排放特征和排放强度, 以及灌溉生产方式转变对马铃薯田N2O减排潜力; (2)揭示不同灌溉生产方式马铃薯田土壤碳氮迁移转化时空变化规律，土壤功能变化动态特征和驱动机制；(3)阐明不同灌溉生产方式马铃薯田N2O排放与土壤碳氮迁移转化过程关联的微生物学机制。研究结果为节水灌溉生产推广提供环境评价数据支撑,为寻求农业生产方式转变减缓农田N2O排放提供科学依据。

本研究针对干旱半干旱区喷滴灌施肥灌溉和传统漫灌马铃薯田，研究土壤温室气体N2O排放通量、强度和过程。采取野外原位观测和室内机制实验相结合的研究方法，阐释不同灌溉生产方式马铃薯田土壤N2O排放规律。(1)喷滴灌施肥灌溉是减缓温室气体N2O排放的重要措施。不同灌溉生产方式马铃薯田土壤N2O排放通量存在明显季节变化，均在7、8月份出现显著的N2O排放高峰。滴灌施肥灌溉土壤(NF-DI)N2O排放通量峰值平均为108.87 µg∙m-2∙hr-1，喷灌施肥灌溉土壤(NF-SI)N2O排放通量峰值平均为117.23 µg∙m-2∙hr-1，传统沟灌施肥土壤(NF-FI)N2O排放通量峰值平均为494.70 µg∙m-2∙hr-1。(2)土壤水分和土壤温度是不同灌溉生产方式马铃薯田土壤N2O排放的驱动因子。三种灌溉方式土壤N2O排放通量季节变化规律显示，7-8月，研究区域土壤温度和水分含量较高，N2O排放季节性变化规律与土壤水分、温度季节性变化趋势一致。5月-6月以及9月-10月N2O排放通量较小。不同灌溉生产方式土壤N2O通量与土壤水分以及土壤温度之间存在显著正相关关系(p＜0.001) (3) 喷滴灌施肥灌溉与传统漫灌比较，能够降低农田土壤中N2O排放强度，滴、喷灌施肥灌溉具有明显减排N2O效果。滴灌施肥灌溉土壤N2O平均累积排放量为137.29 mg m−2，喷灌施肥灌溉土壤为164.63 mg m−2，传统漫灌土壤为323.72 mg m−2。滴灌施肥灌溉土壤N2O排放系数比传统沟灌平均降低72%-81%，喷灌施肥灌溉土壤N2O排放系数比传统沟灌降低53-74%。滴灌施肥灌溉土壤N2O排放强度平均为0.20 kg N∙t−1∙year−1，喷灌施肥土壤N2O排放强度平均为0.38 kg N∙t−1∙year−1，沟灌施肥土壤的N2O排放强度平均为0.91 kg N∙t−1∙year−1。(4) 确定了喷滴灌施肥灌溉马铃薯田土壤具有N2O减排潜力。与传统漫灌比较，滴灌施肥灌溉增温潜势降低50.0%-65.5%；喷灌施肥灌溉降低40.7%-59.7%。本研究实施不仅为不同灌溉生产方式马铃薯田土壤N2O减排提供科学依据，也为干旱半干旱区节水节肥水肥一体化推广提供环境效应数据支撑。