江苏省稻麦轮作系统产量和CH4、N2O排放对施氮的响应

Responses of Yield and CH4, N2O Emissions to Nitrogen Application in Rice-wheat Rotation System in Jiangsu Province

  • 摘要: 为探究江苏省稻麦轮作系统CH4以及N2O排放与氮肥用量之间的定量关系以及最佳施肥方案, 基于多水平定量施氮试验对稻麦轮作种植模式N2O以及CH4排放和施氮的关系进行精确估算, 构建稻麦轮作系统碳足迹(CF)与生态经济净收益(NEEB)模型, 并提出施肥优化方案。田间试验于2022年11月至2023年10月进行, 为稻麦轮作体系。麦季试验设置6个施氮水平处理, 分别为N0(0 kg·hm-2)、N180(180 kg·hm-2)、N240(240 kg·hm-2)、N270(270 kg·hm-2)、N300(300 kg·hm-2)和N360(360 kg·hm-2)。稻季试验设置5个施氮水平处理, 分别为N0(0 kg·hm-2)、N180(180 kg·hm-2)、N240(240 kg·hm-2)、N300(300 kg·hm-2)和N360(360 kg·hm-2), 同一施氮水平试验均在同一小区进行轮作。采用静态箱/气相色谱法连续监测农田中CH4和N2O排放量, 并综合稻麦产量和全球增温潜势(GWP)对温室气体排放强度(GHGI)进行分析。结果表明, 稻麦轮作系统N2O排放随着施氮水平的提高而显著增加, N2O的排放和施氮水平呈指数关系。甲烷排放随氮肥水平提高呈现先降低再升高的趋势, 甲烷排放量和施氮水平的最佳拟合方程为一元三次函数, 这表明适宜的施氮水平可以减少CH4排放。在整个稻麦轮作周期内, 随着施氮量的增加, N2O对GWP的贡献率逐步提升, CH4的贡献率进一步下降, 各氮肥处理稻季CH4排放对GWP的贡献率始终占主导地位。因此, 在稻麦轮作系统温室气体减排的研究中应该重点关注稻季CH4排放。综合稻麦产量与全球增温潜势, 协同构建碳足迹与生态经济净收益模型, 分析表明267~283 kg·hm-2的施氮量为最优施肥方案。

     

    Abstract: To explore the quantitative relationship between CH4 and N2O emissions with nitrogen fertilizer application rates in the rice-wheat rotation system in Jiangsu Province and to determine the optimal fertilization scheme, a multi-level quantitative nitrogen application experiment was conducted to accurately estimate the relationship between N2O and CH4 emissions with nitrogen application in the rice-wheat rotation system. A carbon footprint (CF) and net ecosystem economic benefits (NEEB) model for the rice-wheat rotation system was constructed. Based on this model, an optimized fertilization scheme was put forward, with the objective of providing theoretical support for measures to reduce emissions. A field experiment was carried out during the wheat and rice seasons between November 2022 and October 2023. The wheat season test was conducted with six nitrogen level treatments, specifically N0 (0 kg·hm-2), N180 (180 kg·hm-2), N240 (240 kg·hm-2), N270 (270 kg·hm-2), N300 (300 kg·hm-2) and N360 (360 kg·hm-2). The rice season test was conducted with five nitrogen level treatments, specifically N0 (0 kg·hm-2), N180 (180 kg·hm-2), N240 (240 kg·hm-2), N300 (300 kg·hm-2) and N360 (360 kg·hm-2). The same nitrogen level was applied in the same experimental plot for rotation. Continuous monitoring of CH4 and N2O emissions in agricultural fields was conducted using static closed chamber/GC technique, with a comprehensive analysis of greenhouse gas emissions intensity based on rice-wheat yield and global warming potential. The results indicate that the N2O emissions from the rice-wheat rotation system increased significantly with the increase of nitrogen application, and an exponential relationship was observed between N2O emissions and nitrogen application. CH4 emissions exhibited a pattern of initial decrease followed by an increase with rising nitrogen fertilizer application, and the most suitable equation for the methane-nitrogen relationship was found to be cubic function of one variable, which indicates that an appropriate nitrogen application rate can reduce CH4 emissions. Throughout the rice-wheat rotation cycle, as nitrogen application increased, the contribution rate of N2O to GWP gradually rose, while the contribution rate of CH4 further declined. CH4 emissions during the rice season consistently played a dominant role in GWP contribution. Therefore, when studying greenhouse gas emission reduction in a rice-wheat rotation system, it is essential to focus on CH4 emissions during the rice season. The dominance of CH4 emissions in the rice season on GWP was consistent across all nitrogen fertilizer treatments. Therefore, when studying greenhouse gas emission reduction in a rice-wheat rotation system, it is essential to focus on CH4 emissions during the rice season. Synergizing the net ecosystem economic benefits and carbon emissions, a nitrogen application rate ranging from 267 to 283 kg·hm-2 is the optimal fertilization scheme.

     

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