干湿交替灌溉与控释氮肥施用对稻田氮素运移流失的影响及作用机制

Optimizing management of water and fertilizers is one of the most effective measures for reducing agricultural non-point source pollution from cropland by source. Systematic study of the effects and mechanism of water and fertilizer coupling managements on the migration and loss of nitrogen (MLN) in paddy fields is crucial to improve water and N use efficiencies and to reduce N loss from cropland. This project will carry out a field plot experiment with two water regimes (conventional continuous flooding irrigation, CF; and alternate wetting and drying irrigation, AWD) and three N managements (control, N0; conventional urea, UREA; and polymer-coated urea, PCU) in a typical rice producing area in the middle reaches of the Changjiang River. By investigating the surface runoff and leaching of N, ammonia (NH3) volatilization, and nitrous oxide (N2O) emission as well as analysising the dynamic characteristics of plant N uptake and soil N residue at different growth stages of rice, the study aims to ascertain the multidimensional migration regularity of N in paddy fields applied with different water and N fertilizer managements, obtain the quantitative distribution ratios of N in those pathways of runoff, leaching, NH3 volatilization and N2O emission, and figure out the reduction of N loss of the optimized water and N fertilizer management (AWD irrigation + PCU application) relative to conventional water and N fertilizr management (CF irrigation + UREA application). On this basis, the response relationship between the dynamic changes of soil physico-chemical parameters as well as microbial traits and the MLN was comprehensively analysed in order to reveal the mechanism of nitrogen-loss reduction from paddy fields by the AWD and PCU coupling management. The research will provide theoretical basis for the efficient use of water and fertilizers in cropland and the reduction of agricultural non-point source pollution.

水肥优化管理是目前农田面源污染源头减量最经济有效的措施之一。研究水肥耦合调控对稻田氮素运移流失的影响及作用机制，对提高作物水肥利用效率，减少农田氮素损失至关重要。项目拟在长江中游典型稻作区开展不同灌溉模式（常规连续淹灌、干湿交替节灌）和施氮管理（不施氮、常规氮肥、控释氮肥）的田间原位实验，通过系统研究水稻季氮素地表径流、渗漏淋溶、NH3挥发与N2O排放，结合植株氮吸收量和土壤氮残留量动态特征分析，探明不同水肥耦合管理下氮素在稻田土壤-水体-作物-大气的多维运移规律，明确氮素在径流、渗漏、氨挥发、硝化反硝化、作物吸收和土壤残留途径的量化分配比例，阐明干湿交替节灌与控释氮肥施用的优化水肥管理对氮素流失的减排效果。在此基础上，综合分析土壤理化参数和微生物性状指标动态变化与氮素运移流失的响应关系，揭示水肥优化调控降低稻田氮素流失的作用机制，为区域农田水肥资源高效利用和农业面源污染减排提供理论基础。

水肥优化管理是目前农业面源污染源头减量最经济有效的措施之一。系统深入研究水肥耦合调控对稻田氮素运移流失的影响及作用机制，对提高作物水肥利用效率，减少农田氮素损失至关重要。本项目自2016年起在长江中游梁子湖流域的典型水稻种植区开展田间试验，研究了两种灌溉模式（常规连续淹灌、干湿交替节灌）和三种氮肥管理（不施氮、常规尿素和树脂包膜尿素）下氮素在稻田土壤-水体-作物-大气的多维运移规律以及氮素在径流、渗漏、氨挥发、N2O排放、作物吸收和土壤残留途径的量化分配比例，阐明了干湿交替节灌与树脂包膜尿素施用的优化水肥管理对稻田氮素流失的减排效果，初步探讨了水肥优化调控对稻田氮素流失减排的影响机制，同时考察了水稻产量、水分和氮肥利用效率。主要研究结果如下：.水稻生育期内，各施氮处理稻田氮素流失总量（径流流失+渗漏淋失+NH3挥发+N2O排放）为39.43~64.45 kg·hm-2，氮素流失率为16.4%~26.8%。干湿交替节灌较常规淹灌处理稻田TN径流流失量降低2.8%、TN渗漏淋失量降低10.1%、NH3挥发损失量降低19.3%、N2O排放损失量提高22.0%。树脂包膜尿素较常规尿素处理稻田TN径流流失量降低25.3%、TN渗漏淋失量降低33.8%、NH3挥发损失量降低16.8%、N2O排放损失量降低13.3%。水肥优化调控（干湿交替节灌+树脂包膜尿素）较常规水肥管理（常规连续淹灌+常规尿素）稻田氮素径流流失量降低25.9%、渗漏淋失量减少41.0%、NH3挥发损失量下降32.7%、N2O排放总量提高5.0%，田间氮素总流失量（径流、渗漏、NH3挥发、N2O排放）合计降低30.8%。同时，水肥优化调控较常规水肥管理水稻增产16.4%、水分利用效率提高29.3%、氮肥利用效率提高19.0%。水肥优化调控稻田土壤脲酶活性和微生物量碳、微生物量氮含量更高，表观微生物学性状更优。.综上，干湿交替节水灌溉与树脂包膜尿素施用的水肥耦合调控显著降低了稻田氮素损失、增加了水稻产量，提高了水肥利用效率，为农业面源污染负荷减量与水质改善提供了技术支撑，可作为经济适用的稻作农田水肥管理方式推广运用。.