双季稻区“稻萍”共生系统固碳减排效应研究

发布时间：2018-08-25 07:23

【摘要】：水稻可持续生产对保障我国粮食安全具有十分重要的作用。稻田是温室气体排放的重要源,在全球温室气体排放中占有重要份额。水稻集约化种植,化肥过量施用及施肥结构不合理均增加稻田温室气体排放。"稻萍"共生在我国具有悠久的历史,是高效生态稻作模式。本研究以我国南方双季稻种植系统为研究对象,在早、晚稻行间放养红萍,构建"稻萍"共生复合系统,通过4年田间定位试验,研究"稻萍"共生对稻田土壤理化性质、水稻产量、CH4和N2O排放以及土壤有机碳贮量的影响;利用盆栽试验探索养萍影响温室气体排放的机理。主要结论如下:1.在双季稻生产中,"稻萍"共生可以降低土壤容重,增加土壤孔隙度、土壤有机碳和铵态氮含量,具有培肥地力作用。养萍4年后,"稻萍"共生不施氮和"稻萍"共生减半施氮处理土壤容重分别降低6.3%和7.7%,孔隙度增加5.7%和7.0%;"稻萍"共生不施氮和"稻萍"共生减半施氮处理土壤有机碳较试验前分别增加了 8.1%和12.2%。"稻萍"共生减半施氮处理土壤的铵态氮和全氮含量逐渐增加,与常规稻作习惯施氮处理的差异不显著。2.与常规稻作相比,"稻萍"共生增加稻谷产量,早稻与晚稻产量分别增加4.7%-8.9%和2.3%-7.4%,"稻萍"共生双季稻产量连续4年在12549.8~(-1)3006.6 kg ha~(-1)范围内,较常规稻作增产3.2%-8.0%。在不同施氮水平下,"稻萍"共生较常规稻作均表现出增产效应。"稻萍"共生提高早稻和晚稻产量的原因是增加了每穗粒数。与常规稻作相比,早稻和晚稻季"稻萍"共生每穗粒数分别增加 3.3%~(-1)5.9%和 2.8%~(-1)5.2%。3.连续3年稻田CH4和N2O排放结果表明:与常规稻作相比,在不同施氮水平下,"稻萍"共生均显著减少早稻季和晚稻季CH4排放(P0.05),早稻季和晚稻季CH4排放分别减少21.2%-49.9%和19.2%-37.3%;"稻萍"共生较常规稻作显著增加早、晚稻季N2O排放量,早稻季增加10.5%-63.8%,晚稻季增加14.5%-62.3%;整个双季稻生长期间全球增温潜势(GWP)计算结果表明,CH4排放贡献了 87.9%-98.7%的GWP。"稻萍"共生减半施氮处理的温室气体排放强度(GHGI)较常规稻作习惯施氮处理降低了 14.3%-20.6%。4.盆栽试验结果表明早稻季和晚稻季CH4排放通量与表面水中溶解氧含量及土壤氧化还原电位呈极显著负相关关系(P0.01),与土壤pH值呈极显著正相关关系(P0.01)。养萍处理增加了表面水中溶解氧含量,提高土壤氧化还原电位和降低土壤pH值,进而减少CH4排放。其中,早稻季,养萍处理表面水中溶解氧含量增加30.64%-34.17%,土壤氧化还原电位提高19.8%-31.2%,土壤pH值降低0.25%-2.18%;晚稻季,养萍处理表面水中溶解氧含量增加44.57%-60.23%,土壤氧化还原电位提高20.6%-29.6%,土壤pH值降低0.41%~(-1).13%。5.应用碳足迹-生命周期分析法对"稻萍"共生系统温室气体排放清单进行分析,结果表明:稻萍"共生减少水稻生产过程中农资投入,早稻季和晚稻季农资投入引起的间接碳排放量分别为425.59 和 405.30 kg CO2-eq ha~(-1),较常规稻作减少 13.19 和 13.20 kg CO2-eq ha~(-1)。"稻萍"共生的稻田土壤有机碳固定速率高于常规稻作。其中"稻萍"共生减半施氮处理有机碳固定速率最高,为3148.9kgCO2-eq ha~(-1)a~(-1)。从碳足迹分析结果可以看出,在双季稻生产系统中,"稻萍"共生减半施氮处理的碳足迹值最低,为0.57 kg CO2-eq kg~(-1) grain yield a~(-1),较常规稻作习惯性施氮减少37.8%,是既能保障水稻产量,又能达到减排与减氮目标的高效生态种植模式。
[Abstract]:Sustainable rice production plays an important role in ensuring China's food security. Paddy field is an important source of greenhouse gas emissions and occupies an important share in global greenhouse gas emissions. In this study, Azolla was raised between rows of early and late rice to construct a symbiotic rice-azolla complex system. The effects of Azolla symbiosis on the physicochemical properties of paddy soil, rice yield, CH4 and N2O emissions and soil organic carbon storage were studied by four-year field experiment. The main conclusions are as follows: 1. In double-cropping rice production, Azolla symbiosis can reduce soil bulk density, increase soil porosity, soil organic carbon and ammonium nitrogen content, and has the effect of fertilizing soil fertility. Soil bulk density decreased by 6.3% and 7.7%, soil porosity increased by 5.7% and 7.0%, and soil organic carbon increased by 8.1% and 12.2% respectively under the symbiotic nitrogen-free and symbiotic Nitrogen-Reducing treatments of "azolla" and "azolla". The content of ammonium nitrogen and total nitrogen increased gradually under the symbiotic Nitrogen-Reducing treatments of "azolla" and the conventional nitrogen-applying treatments. Compared with conventional rice, the yield of early rice and late rice increased by 4.7% - 8.9% and 2.3% - 7.4%, respectively. The yield of "azolla" symbiotic double cropping rice increased by 3.2% - 8.0% in the range of 12549.8 ~(- 1) 3006.6 kg ha ~(- 1) for four consecutive years. Compared with conventional rice, the number of grains per panicle in early rice and late rice increased by 3.3%~(-1) 5.9% and 2.8%~(-1) 5.2% respectively. 3. The results of CH4 and N2O emission from rice fields for three consecutive years showed that compared with conventional rice, the number of grains per panicle increased by 3.3%~(-1) 5.9% and 2.8%~(-1) 5.2% respectively. The CH4 emission of early rice and late rice decreased by 21.2% - 49.9% and 19.2% - 37.3% in early rice and late rice, respectively; the N2O emission of late rice increased by 10.5% - 63.8% and 14.5% - 62.3% in early rice and late rice, respectively; and the global warming during the whole double rice growing period increased by 14.5% - 62.3%. The results of GWP calculation showed that CH4 emission contributed 87.9% - 98.7% of GWP. GHGI of the symbiotic halving nitrogen treatment of Azolla decreased by 14.3% - 20.6% compared with conventional nitrogen treatment. 4. Pot experiment showed that CH4 emission flux in early rice and late rice season, dissolved oxygen content in surface water and soil oxidation returned. There was a very significant negative correlation (P 0.01) between the original potential and soil pH (P 0.01). The treatment of duckweed increased the dissolved oxygen content in surface water, increased the soil redox potential and decreased the soil pH value, thereby reducing CH4 emissions. In early rice season, the treatment of duckweed increased the dissolved oxygen content in surface water by 30.64% - 34.17%, and soil pH increased. Redox potential increased by 19.8% - 31.2%, soil pH value decreased by 0.25% - 2.18%; dissolved oxygen content increased by 44.57% - 60.23%, soil oxidation-reduction potential increased by 20.6% - 29.6%, soil pH value decreased by 0.41% - 1.13% in late rice season. Carbon footprint-life cycle analysis was applied to the greenhouse gas emission inventory of "rice-duckweed" symbiotic system. The row analysis showed that the indirect carbon emissions from rice production were 425.59 kg CO2-eq-ha~(-1) and 405.30 kg CO2-eq-ha~(-1), 13.19 kg CO2-eq-ha~(-1) and 13.20 kg CO2-eq-ha~(-1). Compared with conventional rice, the organic carbon fixation rate of rice-azolla symbiotic rice was higher than that of conventional rice. Rice cultivation. Among them, the highest rate of organic carbon fixation was 3148.9 kg CO2-eq HA-1 a-1. The results of carbon footprint analysis showed that in double cropping rice production system, the lowest carbon footprint was 0.57 kg CO2-eq kg-1 grain yield a-1, which was higher than that of conventional rice. The reduction of 37.8% is an efficient ecological planting mode which can not only guarantee rice yield, but also achieve the goal of reducing emission and nitrogen.
【学位授予单位】：中国农业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：S511

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