KMS XINJIANG INSTITUTE OF ECOLOGY AND GEOGRAPHY，CAS
| 水肥管理对西北干旱区棉田土壤 N2O 产生和排放的影响 | |
| Alternative Title | Effect of Water and Fertilizer Management on N2O Production and Emission from Cotton Fields in Arid Region of Northwest China |
| 匡文浓 | |
| Subtype | 博士 |
| Thesis Advisor | 高霄鹏 ; 曾凡江 |
| 2019-06-30 | |
| Degree Grantor | 中国科学院大学 |
| Place of Conferral | 北京 |
| Degree Discipline | 理学博士 |
| Keyword | 滴灌 排放因子 有机肥 Meta 分析 高效氮肥 Drip Irrigation Emission Factor Manure Meta-Analysis EnhancedEfficiency Fertilizer |
| Abstract | 氧化亚氮（N2O）是最重要的温室气体之一，其中 66%的人为 N2O 排放来自于农业生态系统。灌溉和施肥是保证干旱区作物生产最重要的两个因子，但全球尺度上灌溉方式对农田 N2O 排放的影响没有统一定论， 灌溉和施肥等管理措施对西北干旱区棉田 N2O 排放的综合影响及其影响机制尚不明确， 水分、 肥料类型及施肥位置对 N2O 排放及其与剖面 N2O 之间的关系尚不清楚，为制定合理的干旱区棉田水肥管理措施带来了困扰。本研究基于 Meta 分析的方法探讨不同灌溉方式对世界农业 N2O 排放的影响；以干旱区典型绿洲棉田为对象，研究灌溉方式（传统漫灌/滴灌）和肥料类型（有机肥/尿素）对西北干旱区棉田 N2O 排放的综合影响；利用自主设计的原位剖面气体采集系统，揭示水肥管理对干旱区棉田 N2O 产生和排放的影响机制；基于室内培养实验，揭示水分、肥料类型及施肥位置对干旱区棉田土壤 N2O 产生和排放的影响；基于长期观测数据，分析长期水肥投入对棉花产量和土壤质量的影响，在探明水肥管理对干旱区棉田 N2O产生和排放的影响机制的同时制定权衡棉花生产和控制 N2O 排放的水肥管理措施。研究结果表明： 1） Meta 分析结果表明， 全球尺度上看，滴灌较漫灌和喷灌降低了 43.50% 和 44.40% 的 N2O 排放；滴灌农业平均 N2O 排放因子（EF） 为0.30%，远低于 IPCC 参考值 1%， 但不同气候区域、作物类型、土壤特征及肥料因素等多个因素都显著影响了滴灌农业的 EF（P < 0.05）； 滴灌农业 N2O 排放随施氮量呈二项式增加，但其对施肥量增加的响应低于 Shcherbak 等(2014)对全球陆地作物的拟合结果；这意味着对特定区域特定作物的 N2O 监测有助于提高 N2O排放估算的精度以及制定更合理的农业管理措施。2）干旱区棉田 N2O 生长季累积排放量和排放因子较低，分别为 72-506 gN2O-N ha-1 和 0.04-0.15 %；与对照相比，施用不同类型氮肥（240 kg N ha-1）均显著增加了棉花产量和氮吸收量，但也增加了 N2O 排放量；与漫灌相比，滴灌增加了棉花产量或与之持平，但也增加了 N2O 排放量或与之持平；有机肥处理增加 N2O 排放主要是因为其提供了大量的有机碳促进了硝化和反硝化速率，在有机碳含量较低的干旱区棉田使用有机肥有增加 N2O 排放的潜在风险。3）西北干旱区棉田 N2O 排放较低是因为土壤 N2O 产生较少； 0-5 cm 土层贡献了 87-100%的地表 N2O 排放量；肥料和灌溉处理分别显著（P < 0.05） 影响了 5 和 15cm 土壤层 N2O 浓度； 5 cm 土层 N2O 浓度与温度显著（P < 0.05） 负相关，与 0-20 cm 土壤 NH4+-N 显著（P < 0.05） 正相关， 意味着硝化过程可能是地表 N2O 排放的主要来源。4）培养实验结果表明，氮肥深施有助于降低氮肥以 N2O 形态损失的风险；高效氮肥降低了剖面 N2O 的产生和累积；高土壤水分增加了土壤剖面 N2O 的积累但降低了地表排放； 44%土壤孔隙含水量（WFPS）下 N2O 排放量随剖面 N2O累积量指数增加， 77% WFPS 下二者没有显著相关关系。这意味着使用高效氮肥能有效降低 N2O 的累积，而灌溉引起的 N 素在土壤剖面上的下移能降低 N 素以N2O 形式的损失。5） 高肥料投入棉田产量是低肥料投入和不施肥棉田的 1.4 和 7.3 倍。 土壤有机碳、全氮、 有效磷含量以及碳氮比会随肥料投入年限的增加趋于稳定，其稳定值随施肥强度增加而增加；稳定后不施肥棉田土壤有效氮含量低于原生沙漠，施肥棉田土壤有效磷显著高于不施肥和原生沙漠。这意味着施肥是保证棉花稳产的关键因素，合适比例的 C:N:P 有机肥有稳产减排的潜力。全球尺度上滴灌较传统灌溉方式降低近 44.0%的全球 N2O 排放，但在西北干旱区棉田生产中滴灌并没有显示出有效的减排作用； 西北干旱区棉田 N2O 排放量及排放因子均处于较低水平，这主要与该地区土壤有机质含量较低、风沙土保水能力差等有关； 权衡棉花产量、水肥投入及 N2O 减排压力，推荐西北干旱区棉花生产中采用灌溉方式为滴灌，肥料类型为化肥+有机肥。 鉴于硝化过程可能是该地区棉田土壤 N2O 排放的主要来源，使用硝态氮肥作为干旱区棉花生产的化肥来源可能有进一步减排的潜力； 同时高效氮肥、 氮肥深施以及施用合适C:N:P 的有机肥等有降低该地区 N2O 排放的潜力，但这些措施需要进一步大田实验加以验证。 |
| Other Abstract | As one of the most important greenhouse gases, 66% of net anthropogenic nitrousoxide (N2O) emissions are from agricultural system. Irrigation and fertilization are thetwo most important management practices to ensure crop production in arid regions.However, the impact of irrigation methods on N2O emissions from farmland on a globalscale is not determined. In addition, the effects of irrigation and fertilizationmanagement on N2O emissions from cotton fields in the arid Northwest China remainsunclear. The relationship between soil profile accumulation and surface emission ofN2O, as affected by soil water content, and source and placement of fertilizer is alsounclear. These uncertainties have caused challenges in establishing the effective waterand fertilizer management measures for cotton production in arid region. This thesisconsists of four components. First, a meta-analysis was conducted to explore the impactof different irrigation methods on N2O emissions from the farmland on global scale.Second, a 2-yr field experiment was conducted on a typical oasis cotton field in aridNW China to study the comprehensive impacts of irrigation method (floodirrigation/drip irrigation) and fertilizer type (manure/urea) on N2O emissions. A selfdesigned in-situ soil profile gas collection system was used to reveal the mechanismhow irrigation and fertilizer management practices affect the production and emissionof N2O from the cotton field. Third, a soil column experiment was conducted toexamine the effects of fertilizer N source and depth of placement on soil profile N2Oaccumulation and surface emissions at two water-filled pore space (WFPS). Finally,data from a long-term field experiment in arid NW China were used to analyze theimpact of the intensity of nutrient and water inputs on cotton yield and soil quality. Thus,this study attempts to reveal the overall effect of irrigation and fertilizer managementon N2O production and emission from cotton production in arid region, and further toestablish the reasonable agricultural measures which can achieve high yield productionof cotton while reducing environmental impacts such as N2O emissions. The mainresults are listed as follows:1） Based on the meta-analysis on the global scale, drip irrigation reduced (P <0.001) N2O emissions by 43.5% (95% CI: 29.2-54.7%) and 44.4% (95% CI: 13.6-66.3 %), compared to furrow and sprinkler irrigation, respectively. The overall average EF for the drip irrigation was 0.30%, substantially lower than the IPCC Tier I defaultvalue of 1%. The EF for the drip irrigation was significantly (P < 0.05) affected bydifferent climatic regions, crop types, soil characteristics and fertilizer application rates.The N2O emission of drip irrigation increased with N addition rate in a binomialdistribution, whereas the response rate was lower than the fitting of Shcherbak et al.(2014) for global terrestrial crops. This means that monitoring of N2O emissions forspecific crops in specific regions is necessary to improve the accuracy of N2O emissionsestimates and develop more rational agricultural management practices.2） The overall N2O emission and EFs from the cotton fields in the arid zone ofNorthwest China ranged between 72-506 g N2O-N ha-1 and 0.04-0.15%, respectively,being generally lower than those of other climate zones. Cotton yield and N uptakewere generally increased by fertilizer or manure additions compared to the unfertilizedcontrol, but there were no significant differences between the three fertilized treatments.N2O emissions were generally increased by fertilizer or manure additions compared tothe unfertilized control. Compared to flood irrigation, drip irrigation was not effectivein reducing N2O emissions, even though it increased or maintained cotton yield. GreaterN2O emission with manure application was mainly attributed to the increased rates ofnitrification and denitrification through the manure’s increased supply of carbon forassociated microbes. These results suggest a potential risk of manure application toincrease N2O emission for irrigated crop production in soils with low soil organic matterand under dry climate.3） The lower N2O emission from cotton fields in the arid regions of NorthwestChina is due to less soil N2O production. The 0-5 cm soil layer contributed 87-100 %of surface N2O emissions. Fertilizer and irrigation treatments significantly (P < 0.05)affected N2O concentration at 5 and 15 cm soil depths. N2O concentration at 5 cm depthcorrelated negatively with temperature (P < 0.05) but positively (P < 0.05) with soilNH4+-N concentration, suggesting the nitrification was likely the main source of N2Oemissions.4） The results of soil incubation experiment showed that deep application of Nfertilizer can effectively reduce N2O emission. Compared to conventional urea, theenhanced-efficiency N fertilizers effectively reduced the production and accumulationof N2O in soil profile. Higher soil moisture at 77% WFPS increased the accumulationof N2O in soil profile but reduced surface N2O emissions. Cumulative N2O emissions increased exponentially with total accumulation at 44% but not 77% WFPS. Theseresults suggest that fertilizer N leached down the profile was less prone to N2O losswhile emission can be reduced by using the enhanced-efficiency N fertilizers.5） Cotton yield with high fertilizer and water input treatment was 1.4 and 7.3times greater compared to low input and no input control, respectively. Soil organiccarbon (SOC), total nitrogen (TN) and C:N ratio of different treatments were fluctuatedduring 2005–2009 and kept stable during 2010–2013 with the stable value increasedwith the input intensity. Soil available N in the native desert was even greater than thatin the unfertilized control, suggesting the N-fixing capacity of the leguminosae A.sparsifolia. Soil available phosphorus content in the fertilized fields was greater thanthat in the unfertilized control and native desert. These results suggest that water andfertilizer inputs are the key factors to ensure cotton production. Appropriate soil C:N:Pratio are particularly important to ensure cotton yield and reduction of N2O emission.On the global scale, drip irrigation reduced N2O emissions by nearly 44.0%compared to conventional irrigation methods. However, in our specific field experimentin arid NW China, drip irrigation was not effective in reducing N2O emissions from thecotton field compared to traditional flood irrigation. The overall N2O emission and EFwere generally lower than those of other climate zones, probably due to the lowavailable soil moisture and low soil organic carbon which restricted N2O production.Considering the trade-offs between cotton production, water and fertilizer inputs andN2O emission, drip irrigation and combinations of synthetic fertilizer with manureapplication are recommended as the best agricultural management for cotton productionin the arid region. Nitrification is the main source of N2O emissions from cotton fieldsin this region and thus use of nitrate-based nitrogen fertilizer should be avoided. Inaddition, agricultural management practices such as use of enhanced efficiencyfertilizers, deep application of fertilizer, combined application of manure with syntheticfertilizers, and maintaining appropriate soil C:N:P ratio are effective measures toreduce N2O emissions for agricultural production in arid regions. |
| Subject Area | 生态学 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.xjlas.org/handle/365004/15336 |
| Collection | 中国科学院新疆生态与地理研究所 研究系统 |
| Affiliation | 中国科学院新疆生态与地理研究所 |
| First Author Affilication | 中国科学院新疆生态与地理研究所 |
| Recommended Citation GB/T 7714 | 匡文浓. 水肥管理对西北干旱区棉田土壤 N2O 产生和排放的影响[D]. 北京. 中国科学院大学,2019. |
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