生物炭对节水灌溉稻田氮素迁移转化及损失的影响机理与调控研究

Low irrigation use efficiency and non-point pollution are two serious problems of paddy fields. Rice water-saving irrigation and biochar application will combined in this research. Rice water-saving irrigation can significantly reduce irrigation water input, and water-saving irrigation and biochar application both can decrease non-point pollution from paddy fields. But mitigating effect and reasonable regulation of non-point pollution from paddy fields with combination of the above two measures need intensive study. Migration and transformation variations of nitrogen element in soil and nitrogen loss from paddy fields with combination of water-saving irrigation and biochar application will be analysed based on field tests, laboratory analysis and model simulation in this study. In addition, dynamic changes of nitrogen transformation bacteria and soil enzyme, soil environment, crop growth and meteorological factors will be measured. And the relationships between nitrogen element migration, transformation, loss and above impact factors will be illuminated to reveal the infulence mechanism of nitrogen element migration, transformation and loss of paddy fields with combination of water-saving irrigation and biochar. DeNitrification-DeComposition model (DNDC) will be improved to simulated rice yield, nitrogen loss, water and nitrogen use efficiencies dynamically with combination of water-saving irrigation and biochar. Detailed scene of water and biochar regulation will be set to simulate the change of rice yield, nitrogen loss, water and nitrogen use efficiencies with long-term use (20 years) of above different simulating scenarios. And reasonable application amount of biochar to saving irrigation water, increasing rice yield, reducing nitrogen loss from paddy fields will be put forward. The results will enrich the theory of rice water-saving irrigation. And it also has important meaning for the reduction of non-point pollution and sustainable utilization of soil and water resources of paddy fields.

针对稻田灌溉水利用率低与面源污染严重的问题，将水稻节水灌溉技术与生物炭施用技术相结合，节水灌溉具有显著的节水效果，两者均具有减污效应，两者结合的稻田面源污染减排效应与合理调控有待深入研究。本项目采用田间、室内试验与模型模拟的方法，分析生物炭施用后节水灌溉稻田土壤氮素迁移转化及损失规律，结合氮素转化相关功能菌与酶、土壤环境、作物生长与气象等因子的同步变化，研究其与氮素迁移转化及损失的关系，揭示生物炭对节水灌溉稻田氮素迁移转化与损失的影响机理。改进土壤碳氮循环模型-DNDC，实现对两种措施结合稻田水稻产量、氮素损失及水氮利用效率的动态模拟，设定细化的水碳调控情景，模拟并分析不同情景长期应用（20年）后稻田水稻产量、氮素损失及水氮利用效率的变化，提出稻田节水、高产、减少氮素损失的合理生物炭施用量。研究结果对于丰富水稻节水灌溉理论，实现稻田面源污染减排及水土资源可持续利用具有重要的理论和现实意义。

本项目针对稻田灌溉水利用率低与面源污染严重的问题，将水稻节水灌溉技术与生物炭施用技术相结合，采用田间、室内试验与模型模拟的方法，探究了水炭联合调控模式下稻田氮素迁移转化及淋失规律，发现生物炭对稻田氮素淋失具强有力的控制效果，施用20t/hm2和40t/hm2生物炭使稻田全氮淋失量降低10.10%~12.27%和13.89%~33.81%。生物炭增强了土壤对氮素的固持且抑制了土壤溶液中氮素的深层运移是导致淋失量降低的主要原因。引入高通量测序技术，分析了不同水炭管理条件下水稻三个典型生育期土壤固氮及氨氧化过程的nifH、AOA-amoA和AOB-amoA基因OUT丰度、物种多样性及群落组成，发现AOA倾向于主导稻田土壤生态系统中的氨氧化反应，并证实了施炭对氮转化功能菌的影响主要体现在增加物种多样性并提高优势物种相对丰度。阐明了控制灌溉技术与生物炭施用相结合条件下的稻田氨挥发特征，生物炭施用对节水灌溉稻田氨挥发影响存在年际变化。探究了稻田氨挥发与土壤、土壤溶液、气象、酶活性和细菌数量等影响因素之间的关系，阐释了了生物炭对节水灌溉稻田氨挥发的影响机理。稻田氨挥发通量和土壤铵态氮、土壤脲酶活性存在显著正相关关系。基于田间试验数据，构建了生物地球化学模型DNDC的控制灌溉与生物炭模块，实现了对生物炭施用控制灌溉稻田水量平衡、作物生长及氮素损失的模拟，模拟效果较好。基于改进模型，研究了未来气候条件下生物炭与节水灌溉长期应用对水稻生长及稻田氮素损失的影响，提出了适应未来气候变化的稻田节水、高产、减少氮素损失的合理生物炭施用量。研究结果对于丰富水稻节水灌溉理论，实现稻田面源污染减排及水土资源可持续利用具有重要的理论和现实意义。