分期施用氮肥对农田土壤有机碳/氮激发效应的影响研究

The split application of nitrogen fertilizer according to crop demand not only increase the nitrogen use efficiency and yield of crop, but is one of the important methods to deal with the challenges of food security, environmental degradation and global warming with the development of agriculture in China. However, the effect of split fertilization on the priming effects of soil organic carbon/nitrogen remains unclear. In this study, in a C4 plant and C3 soil system, we plan to single or split application of nitrogen fertilizer to the soil. Based on static chamber-gas chromatograph technique, isotope technology and phospholipid fatty acid analysis methods, we can measure the soil organic carbon/nitrogen mineralization and immobilization, quantify the priming effects of soil organic carbon/nitrogen after single or split application of nitrogen fertilizer, analyze soil microbial community structures and extracellular enzyme activities. The objective of this project is to understand the mechanisms of priming effects of soil organic carbon/nitrogen under different fertilization frequencies using structural equation modeling, assist in improving soil organic carbon sequestration and improving agricultural sustainability.

根据农作物需肥规律分期施用氮肥，既能有效提高农作物氮素利用效率和产量，也是解决我国农业发展面临的粮食安全、环境退化和气候变暖等问题的重要措施之一，但该措施对农田土壤有机碳/氮激发效应的影响机理尚不清楚。本项目拟在C3土壤种植C4植物，优化氮肥施用次数。利用静态箱-气相色谱法、同位素法和磷脂脂肪酸分析法等技术，测定土壤有机碳/氮矿化和固持速率，量化不同氮肥施用次数下土壤有机碳/氮的激发效应强度，分析土壤微生物群落结构及酶活性，运用结构方程模型分析方法阐明土壤有机碳/氮激发效应的微生物驱动机制，为科学合理施肥、农田土壤有机碳长期有效固持和保障农业可持续发展提供科学依据。

适当增加施用氮肥次数可通过调节土壤元素化学平衡，降低外源氮对土壤微生物群落的刺激程度，进而减少土壤有机质矿化的激发效应强度，对农田土壤有机碳长期有效固持和养分循环过程产生重要影响。本项目基于微宇宙培养试验及高通量定量PCR方法，系统研究了不同氮素添加方式下土壤有机质矿化速率、激发效应强度以及编码碳分解有关的功能基因丰度。结果表明，低氮添加量下，分期施用氮肥使得土壤有机质矿化速率及其激发效应强度分别增加了7.2-18.8%和43.8-172.8%，不利于农田土壤有机碳的长期有效固持；高氮添加量下，分期添加氮素通过维持较低的土壤铵态氮含量和降低编码半纤维素分解的xylA功能基因丰度，使得土壤有机质矿化速率及其激发效应强度分别降低了15.9-20.7%和27.3-49.2%，可能是有效降低土壤碳排放、提升农田土壤固碳功能的有效措施。回归分析结果表明，土壤铵态氮及编码半纤维素分解的xylA功能基因是驱动施肥土壤有机质矿化的关键因素。本研究结果为科学合理施肥、农田土壤有机碳长期有效固持和保障农业可持续发展提供科学依据。结果表明，低氮添加量下，分期施用氮肥使得土壤有机质矿化速率及其激发效应强度分别增加了7.2-18.8%和43.8-172.8%，不利于农田土壤有机碳的长期有效固持；高氮添加量下，分期添加氮素通过维持较低的土壤铵态氮含量和降低编码半纤维素分解的xylA功能基因丰度，使得土壤有机质矿化速率及其激发效应强度分别降低了15.9-20.7%和27.3-49.2%，可能是有效降低土壤碳排放、提升农田土壤固碳功能的有效措施。回归分析结果表明，土壤铵态氮及编码半纤维素分解的xylA功能基因是驱动施肥土壤有机质矿化的关键因素。