稻田水氮耦合尺度效应及其机理

The scientific water-nitrogen management in paddy field is an important measure to improve water-nitrogen use efficiency and reduce nitrogen loss in paddy field. To improve the water-nitrogen use efficiency on different scales, it has theoretical and practical significance studying on the coupling effects of the water-nitrogen management of paddy with the water management system in district and the scale effect of water-nitrogen translation and movement and the mechanism of scale effect. In this work, we conducted the field experiments and observations related to water and nitrogen management in paddy field. Accordingly, we constructed the distributed hydrological model in district based on a modified hydrological model in river basin. Furthermore, we proposed a technical coupling the crop-growth model with the distributed hydrological model in district. According to the different combinations of water-nitrogen management in field and water management system in district, the coupling model was used to analyze the effects of water-nitrogen management model in field on the water transformation and nitrogen loss in different scales. Additionally, the rules of the water-nitrogen use efficiency and nitrogen loss indices varying with different combination sets and scales were evaluated. The results identified the coupling effects of the water-nitrogen management mode in field and water management system in district, and revealed the impacting mechanism and scale effects of water-nitrogen transportation and transformation. From the perspective of irrigation district, by taking account of some indices, e.g., water saving, yield stimulation, water-nitrogen use efficiency and nitrogen-emission reduction; we proposed the best combination of the water-nitrogen management mode in field and water management system in district. Finally, the results in this work had theoretical and practical significance on increasing the water-nitrogen use efficiency, expanding the application of field experiment achievement and making scientific decision on the water-nitrogen management in different scales.

合理的稻田水氮管理是提高水肥利用率、减少氮素流失的重要措施之一，其与灌区水管理制度耦合效应、水氮迁移转化尺度效应及机理研究，对提高灌区不同尺度水氮利用率具有重要意义。本项目通过开展水氮管理模式田间试验和野外观测，在改进流域水文模型基础上研发灌区分布式水文模型，提出田间作物生长模型与灌区分布式水文模型耦合技术。根据田间水氮管理和灌区水管理制度拟定不同组合模式，基于耦合模型模拟分析田间水氮管理模式对不同尺度水量转化、氮素排放的影响规律，以及不同组合模式不同尺度水氮利用率及氮素排放的变化规律，探明田间水氮管理与灌区水管理制度的耦合效应，揭示水氮迁移转化的尺度效应及机理。从灌区角度，综合考虑节水、增产、水氮利用率、氮素减排效果等指标，提出田间水氮管理与灌区水管理制度的最佳组合模式。研究成果对协同提升灌区不同尺度水氮利用率，实现田间试验成果扩展应用，及不同尺度水氮管理决策具有重要的理论和现实意义。

合理的稻田水氮管理模式是提高水肥利用率、减少氮素流失的重要措施之一，其与灌区水管理制度耦合效应、水氮迁移转化尺度效应及机理研究，对提高灌区不同尺度水氮利用率具有重要意义。本项目开展了2年的（2018年和2019年）水氮管理模式田间试验和野外观测分析，在改进流域水文模型基础上研发灌区分布式水文模型，提出了田间作物生长模型与灌区分布式水文模型联合应用模拟技术。根据田间水氮管理和灌区水管理制度拟定了16种组合模式，基于模型联合应用模拟分析了田间水氮管理模式对不同尺度水量转化、氮素排放的影响规律，以及不同组合模式不同尺度水氮利用率及氮素排放的变化规律，探明了田间水氮管理与灌区水管理制度的耦合效应，揭示了水氮迁移转化的尺度效应及机理。综合考虑节水、增产、水氮利用率、氮素减排效果、农民接收意愿等指标，提出了田间水氮管理与灌区水管理制度的最佳组合模式。同时针对南方地区新兴的虾稻共作模式，研究了其用水模式及灌溉定额计算方法。研究成果对协同提升灌区不同尺度水氮利用率，实现田间试验成果扩展应用，及不同尺度水氮管理决策具有重要的理论和现实意义。