基于“节水-减排-经济”三维视角的华北平原不同种植模式分析研究

In the North China Plain, food production with high yield pursuing and intensified agricultural production resulted in huge resources and environment pressure and ecological cost. All these factors, such as the increasing serious groundwater table decline, the growing greenhouses gas emissions from the farmland, the low economic benefits of the current sole winter wheat-summer maize double cropping system, can affect the ecosystem health and the agricultural sustainable development. This project aims to analysis the ecological benefits and economic benefits of different crop rotations based on the field crop rotation experiment which will be carried out in the North China Plain with the serious groundwater depression cone. The new established crop rotation experiment covers food crops (winter wheat, summer maize, spring maize), economic crops (cotton, peanuts), feed crop (ryegrass). The project focuses on the analysis and compare the water-saving benefits of different crop rotations including the characteristic of farmland water consumption, the annual average economic water use efficiency and the net groundwater depletion based on the field cropping system experiment interpreted with the soil-water-balance model (Kendy model), and the effect of diversified crop rotations on groundwater table decline combined with groundwater table changes model. Moreover, the modified calculation of “Carbon footprint of Farmland ecosystem” with the localized greenhouse gas emissions parameters will be introduced in the analysis of the effects of different crop rotations on carbon sequestration and mitigation by per unit area, per kg biomass and per unit economic output. It aims to screen for the optimized cropping system for carbon fixation and greenhouse gas emissions reduction in the North China Plain. In addition, based on the comprehensive analysis of ecological benefits and economic benefits, the project will filter the optimized alternative crop rotations which could significantly lower the water consumption and reduce the carbon footprint, meanwhile, improve the economic benefit and keep food production. The alternative crop rotation will be analyzed the potential to partially substitute the conventional winter wheat-summer maize double cropping system. This project will play the critically important role in adjusting planting structure, optimizing crop planting scale and distribution, and policy-making in the North China Plain.

针对华北平原传统麦玉一年两熟模式导致的地下水位持续下降、温室气体排放加剧及经济效益低下等生态经济问题，本研究拟在华北平原地下水漏斗严重区开展不同轮作模式田间定位试验，兼顾粮食作物、经济作物、饲料作物，结合农田水量平衡模型，对不同轮作模式的农田水分消耗特征、经济水分利用效率及周年地下水净消耗量进行分析，同时结合“地下水位模型”分析不同轮作模式对地下水位的影响，并揭示轮作的节水机理；引入国际前沿的“农田生态系统碳足迹”评价方法，结合本地化排放参数对不同轮作模式的单位面积、单位生物量、单位经济产值的碳足迹进行评估，筛选最优固碳减排种植模式；通过生态及经济效益的综合分析筛选出适合华北平原节水减排且兼顾粮食生产和经济效益的优化种植模式，探讨其能否替代或者部分替代传统麦玉模式，为华北平原合理优化作物布局、适当调整种植结构提供可靠的理论依据。

针对华北平原传统冬小麦-夏玉米一年两熟制的高耗水、高排放、经济效益低下、种植结构单一等现实生产问题和科学问题，本项目设置了3年田间定位试验，设置了涵盖粮、经、饲、能四元结构的多样化种植制度，结合农田水分+地下水位模型，分析了不同轮作模式相比传统麦玉模式可节水27-34%，可缓解地下水位下降量14-15%。阐明了不同轮作模式的节水潜力，通过浅根与深根作物的搭配种植，可形成土壤水分利用的时空互补，提高土壤水分利用效率。通过实时监测农田温室气体排放通量，得到多样化轮作模式可有效降低农田总温室气体排放16-44%，降低农田单位面积碳足迹25-50%。多样化轮作模式可提高表层土壤的全氮、速效钾、速效磷等养分含量；同时，也可提高经济水分利用效率28-64%。多样化轮作模式通过前茬作物的轮作，可提高后茬作物产量冬小麦15-24%、夏玉米产量14-31%，提高经济水分利用效率冬小麦14-22%、夏玉米17-64%。粮薯、粮油、粮豆、粮粮模式各方面表现最优。因此，在华北平原发展多样化种植制度是该地区平衡粮食安全、水资源可持续利用以及节能减排的最主要农艺途径。