不同施肥措施下甘蔗田土壤温室气体排放过程机理及其调控因素

China is the third largest sugarcane producer in the world, while Guangxi is the main production area of sugarcane in China. Research on the characteristics of soil greenhouse gas emission from sugarcane field is of great importance for assessing the impact of sugarcane cropping system on climate change. So far, the study on soil greenhouse gas fluxes from China’s sugarcane field and its biochemical process is really scarce. This research project will be conducted in the sugarcane experimental fields under various fertilization practices located in Laibin and Fangchenggang in Guangxi. The impacts of different fertilization practices on soil greenhouse gas (CO2, CH4 and N2O) emissions from sugarcane field will be quantitatively clarified by in situ measuring using static chamber-gas chromatography. The effects of different fertilization practices on soil greenhouse gas source proportion and soil carbon sequestration will be investigated by measuring stable carbon and nitrogen isotope ratios using stable isotope analysis techniques. Based upon the field measured data, the process-based DeNitrification-DeComposition (DNDC) model will be calibrated and validated for sugarcane cropping systems. Then, the simulation and scenario analysis will be conducted using DNDC model. The objective is to reveal the response process mechanism of soil greenhouse gas emission from sugarcane field to long-term fertilizer application and its key controlling factors, and the soil greenhouse gas emission reduction measures will be explored and assessed as well. The project will make a contribution to assessment of soil greenhouse gas emission from sugarcane cropping systems and its reduction measures, and provide scientific basis for achieving green, high yield and efficient production of sugarcane.

中国是世界上第三大甘蔗生产国，广西是全国甘蔗主产区。研究甘蔗田土壤温室气体排放特征对于评估甘蔗系统对气候变化的影响具有重要意义。目前国内关于甘蔗田土壤温室气体排放通量及其过程机理的研究还很缺乏。本项目拟以广西来宾市和防城港市不同施肥措施下的甘蔗试验地为研究对象，采用静态箱-气相色谱法原位测定温室气体（CO2、CH4和N2O）通量，阐明不同施肥措施对甘蔗田土壤温室气体排放通量的影响；利用稳定同位素分析技术测定样品中稳定碳和氮同位素比值，探明不同施肥措施对甘蔗田土壤温室气体来源比例和土壤碳固存的影响；利用田间实测数据校正和验证反硝化-分解过程（DNDC）模型，开展模拟研究和情景分析，目的是揭示甘蔗田土壤温室气体排放对长期施肥的响应过程机理及其关键调控因素, 探索和评估减排措施。本研究将为广西甘蔗田土壤温室气体排放及其减排措施的评估作出贡献，并为实现甘蔗绿色高产高效发展提供科学依据。

中国是世界上第三大甘蔗生产国，广西是全国甘蔗主产区。研究甘蔗田土壤温室气体排放特征对于评估甘蔗系统对气候变化的影响具有重要意义。本项目以广西甘蔗主产区具有代表性的甘蔗种植地为研究对象，设置4个施氮水平梯度处理，分别为常规施氮量500 kg N ha–1 （N500），减量施氮量400 kg N ha–1 （N400）和300 kg N ha–1 （N300），以及不施氮肥处理（N0），采用静态箱-气相色谱法原位测定温室气体（CO2、CH4和N2O）通量，利用稳定同位素分析技术和反硝化-分解过程（DNDC）模型模拟，目的是阐明不同施氮量对甘蔗田土壤温室气体排放通量的影响及其关键调控因素，探明施氮量对甘蔗田土壤N2O来源的影响，评估减排措施。2019–2021年连续3个甘蔗生长季的观测研究结果表明：（1）不同施氮处理对甘蔗产量和含糖量没有显著影响； N0甘蔗茎全氮和全磷含量分别低于和高于施氮处理。（2）甘蔗田土壤温室气体（CH4、CO2、N2O）呈季节性动态变化，土壤排放CO2在苗期较弱（0.3–3.2 g C m–2 d–1），伸长期最强达6.8 g C m–2 d–1，成熟期下降，与气温呈指数关系； N2O排放高峰发生在施氮肥后3至4周期间，N2O排放通量与施氮量呈现显著正相关关系。（3）不同处理下的生长季温室气体累积排放量具有明显的处理间和年际间差异。总体上，N0排放CH4，N500吸收CH4。同一年份，不同处理之间土壤CO2累积排放量没有显著差异。土壤N2O累积排放量与施氮量呈显著的正相关关系。N500土壤N2O累积排放量显著高于其它三个处理，而N300、N400和N0之间差异均不显著。（4）施肥后3周期间，土壤排放的N2O主要来源于施入的氮肥，由硝化和反硝化共同作用。（5）DNDC模拟结果表明，施氮量和土壤含水量是调控土壤排放N2O的主要因子，可以通过减少施氮量和优化灌溉措施来降低N2O排放量。结论：甘蔗田土壤CO2排放动态主要受到气温的影响；N2O排放动态和排放量主要分别受到施氮时间和施氮量的影响，减少施氮量到400 kg N ha–1，结合优化施氮后的灌溉措施，可以显著减少N2O排放量，但对产量没有明显影响。