膜下滴灌对农田水碳氮耦合循环的影响机理与模拟

The pattern and simulation of water, carbon and nitrogen cycles in terrestrial ecosystems are the hot topic focused by the international academe. In recent years, the Chinese government invest heavily to extend the technology of drip irrigation under plastic film in northwest China, in order to solve the water scarcity in the region. However, how will water, carbon and nitrogen cycles change, how will these changes affect crop growth and how to quantify these processes, still remain uncertain. In order to reveal the scientific questions, our program will depend on the farmland flux network of China Agricultural University, use the eddy covariance system, Bowen-ratio and energy system, and flow analyzers to measure the water, carbon and nitrogen fluxes above the maize and wheat field continually, aims to reveal the differences between water, carbon and nitrogen cycles under the drip irrigation and that under border irrigation, and the effect of water, carbon and nitrogen cycles changes on crop growth. Additionally, the coupled models for simulating water, carbon and nitrogen cycles and crop growth under drip irrigation will be constructed after taken account of the effect of drip irrigation and film mulch on infiltration, boundary conditions and the growing environment. Our research will develop the traditional soil-plant-atmosphere continuum theory, and provide the scientific basis for effective utilization of agricultural water and fertilizer resources.

生态系统水碳氮耦合循环规律及模拟是国际学术界关注的前沿与热点。为解决我国西北干旱区水资源紧缺的问题，推广膜下滴灌技术已上升为国家节水战略。在由传统畦灌变为滴灌的情形下，农田水碳氮循环将如何变化，这些变化将如何影响作物生长以及如何定量表征，尚不明了。 为回答该问题，本项目拟依托中国农业大学西北旱区典型农田通量观测网络，以玉米和小麦等主粮作物为研究对象，应用涡度相关仪、波文比-能量平衡仪和流动分析仪等设备，对农田水碳氮通量，实施长期连续的野外定位对比观测， 主要研究：滴灌与畦灌两种不同灌溉方式下，农田水量平衡、能量平衡、辐射平衡、碳循环、氮循环以及生长过程的差异，水热碳氮循环过程的改变对作物生长的影响机理，并通过考虑滴灌和覆膜对入渗方式、边界条件和作物生长环境的影响，建立膜下滴灌条件下的水热碳氮与生长耦合过程模型。 以发展传统的土壤-植物-大气连续体理论，为农业水肥资源高效利用提供科学依据

为缓解西北干旱区水资源紧缺的问题，推广膜下滴灌技术已上升为国家节水战略，在由传统畦灌变为滴灌的过程下农田水碳氮循环和作物生长也将发生改变。本项目主要研究覆膜和滴灌条件下，农田水热碳氮的循环规律、机制机理及耦合模型。主要结果如下：（1）定量描述了农田水热碳氮和作物生长的变化规律，揭示了膜下滴灌条件下农田蒸散量减少，初级生产力提高，产量增加以及生态系统水分利用效率提高的机制，证实了膜下滴灌农田可以有效实现高产、高水、氮效率、低环境破坏的综合效益。（2）揭示了覆膜灌溉农田水和能量的耦合机理与敏感性参数，建立了适用于覆膜灌溉农田水热过程的模型结构和模拟实施方案，评价了机器学习模型与传统物理模型预测总初级生产力的准确性并改进了直角双曲线模型，构建了可以用于模拟营养生长时期玉米向根，茎和叶分配的耦合模型。成果对发展和完善传统的土壤-植物-大气连续体理论以及科学指导干旱地区典型农田管理实践具有重要意义。