控制灌溉稻田的甲烷减排效果

    Mitigation of methane emissions from paddy fieldsunder controlled irrigation

    • 摘要: 为探讨节水灌溉水分调控对稻田甲烷(CH4)排放的影响,寻找节水减排的稻田灌溉模式,依据5a田间原位观测资料,分析控制灌溉稻田CH4排放规律及其减排效果。结果表明,控制灌溉稻田稻季CH4排放量为1.07±0.17 g/m2,较淹水灌溉稻田(6.49±0.17 g/m2)降低83.5%,差别极显著。本研究得到的中国东南部稻田稻季和全年CH4排放量均低于已有报道中的中国稻田CH4排放量,其中控制灌溉稻田全年CH4排放量低于世界大部分地区稻田。根据本研究结果估算中国稻田CH4排放总量为2.06 Tg/a,大面积推广控制灌溉后,中国稻田CH4排放量还将进一步下降。控制灌溉模式显著影响水稻全生育期稻田CH4排放通量的变化,削峰效果显著。控制灌溉稻田CH4排放通量在返青期至分蘖中期(移栽后18 d内)逐渐上升至最大值,然后逐渐减小,从水稻分蘖后期(移栽后21 d)开始至生育期结束均维持在较低水平。控制灌溉稻田CH4排放通量峰值为3.69 mg/m2·h,较淹水灌溉稻田降低69.0%。在持续降雨的作用下,控制灌溉和淹水灌溉模式下稻田CH4排放通量均呈现下降趋势。控制灌溉模式的土壤水分调控,使稻田经历一系列的脱水过程,改变了根层土壤的水气状况,减小了稻田CH4排放。控制灌溉模式在水稻全生育期的应用可显著地减少稻田CH4排放。

       

      Abstract: Abstract: In order to explore the influence of soil moisture regulation on methane (CH4) emissions under water-saving irrigation and look for an irrigation mode for rice that would save water while simultaneously limiting CH4 emissions, the regularity of CH4 emissions from paddy fields under controlled irrigation was analyzed based on 5 years' of field experiment data. Two different irrigation managements were conducted as follows with the same rice variety, cultivation practices and plant protection measures: controlled irrigation (CI) and irrigated intermittently flooded single aeration irrigation (FI). Rice was cultivated in a 150 m2 (20 m×7.5 m) plot between 2006 and 2007, each plot was separated by brick concrete with a height of 30 cm and width of 30 cm. Plastic anti-seepage films were inserted into soil plough layer to a depth of 50cm to isolate water exchange between the plots. For exploring the influence of rainfall on CH4 emissions from irrigated paddy fields and controlling soil moisture accurately, experiments were conducted in lysimeter with mobile canopy between 2009 and 2011, and each plot area was 5 m2(2.5 m×2 m). Gas samples were collected using manual static chamber and were analyzed by a gas chromatograph (ShimadzuGC-14B) with a flame ionization detector (FID) for CH4 concentration. The results showed that the total CH4 emissions from CI paddy fields were 1.07±0.17g/m2, which was significantly reduced by 83.5% compared with FI paddy fields (6.49±0.17 g/m2). Total seasonal and annual CH4 emissions from CI and FI paddy fields located in Southeast China were lower than the reported values. Meanwhile, the total annual CH4 emissions from controlled irrigation paddy fields was lower than that of paddy filed in most parts of the World. When compared to irrigated intermittently flooded multiple aeration, irrigated intermittently flooded single aeration and irrigated continuously flooded paddy fields, seasonal CH4 emissions from CI paddy fields decreased 94.7%, 97.1% and 99.0% respectively. Annual total CH4 emissions from CI paddy fields was reduced by 87.4%, 84.0% and 33.8% than that of irrigated continuously flooded, irrigated intermittently flooded single aeration and irrigated intermittently flooded multiple aeration paddy fields in most parts of the World. The controlled irrigation mode significantly changed CH4 emissions law from paddy fields and also reduced the emission peak. The CH4 emissions from paddy fields under controlled irrigation were high between turning-green stage and middle tillering stage (DAP≤18), then reduced and maintained low level beginning from late tillering stage (DAP=21). The peak flux of methane emission from paddy fields under controlled irrigation was 3.69 mg/(m2?h), which was 69.0% lower than that of irrigated intermittently flooded single aeration irrigation. The CH4 emissions from paddy fields under controlled irrigation and irrigated intermittently flooded single aeration irrigation were began to reduce due to persistent rainfall. The increase of water depth due to the persistent rainfall, and decrease of CH4 emissions was observed in the rainfall. Meanwhile, the low soil temperature maintained in the progress of persistent rainfall also impeded CH4 production. The soil moisture regulation under controlled irrigation resulted in a series of dewatering in paddy field and changed the oxygen supply in soil rooting profile, finally reduced the total CH4 emissions from paddy fields. The controlled irrigation mode could significantly reduce CH4 emissions from paddy fields.

       

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