节水灌溉对农田土壤温室气体排放的影响

农田是温室气体的重要排放源,如何通过有效的管理措施降低农田温室气体的排放成为当前应对气候变化研究的热点之一。不同灌溉方式导致土壤水分差异较大,进而引起温室气体排放的差异。目的]系统总结分析不同节水灌溉方式对温室气体排放的影响效果有助于对节水灌溉方式优化选择及未来研究方向的聚焦。方法]在前人研究基础上,进行文献搜集和整理,综述分析了节水灌溉方式对稻田和旱作农田温室气体排放的影响。结果]与长期淹水相比,现有的水稻节水灌溉方式增加了稻田土壤CO2排放,增幅为20.83%~104.00%,平均增加48.40%,对N2O排放的影响有增加也有降低,其影响率范围为-41.30%~3078.41%,平均增加269.10%,但却显著降低了CH4的排放,降幅为14.19%~78.92%,平均降低51.66%。综合考虑稻田的全球净增温潜势(GWP),节水灌溉较长期淹水降低了稻田的GWP。与漫灌/沟灌相比,滴灌可改变旱作农田CO2和N2O排放及对CH4的吸收,其变化率范围分别为-31.19%~2.81%、-46.51%~52.56%和-150.00%~43.39%,平均分别降低12.84%、18.63%和24.93%。综合考虑旱作农田的GWP,由于N2O是旱作农田的主要温室气体,因此,滴灌降低了旱作农田的GWP。结论]节水灌溉在节水的同时,还可降低农田温室气体排放的全球净增温潜势。基于研究现状,亟须对不同节水灌溉方式的温室排放效应及其机制开展定量研究。

Response of Greenhouse Gas Emissions to Water-saving Irrigation in Croplands: A Review

【Objective】Croplands emit greenhouse gases, and improving agronomical management to ameliorate emission has thus been touted as an alternative to mitigate climate change. It has received increased interest over the past decades. In this paper, we review how water-saving irrigations could alter gas emission from cropland.【Method】We analyzed previous research published in the literature with the focus on paddy field and upland.【Result】Compared with flooding irrigation, water-saving irrigation increased CO_2 emissions from paddy field by20.83%～104.00% with an average of 48.40%; its impact on N_2O emission varied from-41.30% to 3 078.41%with a mean 269.10%. In contrast, water-saving irrigation reduced CH_4 emission by 14.19%～78.92% with an average of 51.66%. In terms of net global warming potential(GWP), water-saving irrigation reduced GWP of paddy field compared to flooding irrigation. In upland, drip irrigation changed the emission of CO_2, N_2O and CH_4 by-31.19%～2.81%,-46.51%～52.56% and-150.00%～43.39%, respectively, compared to flooding irrigation. Since N_2O is a more potent greenhouse gas, drip irrigation still reduces GWP compared to flooding irrigation.【Conclusion】Water-saving irrigation can not only save water but also mitigate greenhouse gas emissions from cropland.