京津冀地区农业生产与水资源利用: 历史与适水转型

Crop production and agricultural water consumption in the Beijing-Tianjin-Hebei region: History and water-adapting routes

  • 摘要: 京津冀地区是资源型缺水地区, 也是我国的主要农业区之一。本文对京津冀地区农业生产和灌溉水资源利用的历史阶段特征和适水转型进行了分析, 对京津冀地区农业适水转型路线提出建议。1970年代末以来, 井灌为主的灌溉体系基本覆盖平原农区, 小麦玉米占优的作物结构形成, 蔬果产能快速扩大。粮食产量从2136.2万t增加至3944.8万t, 蔬菜产量从1093.7万t增加至5508.4万t, 水果产量从144.0万t增加至1505.2万t。灌溉占地下水消耗的70%, 是京津冀平原区地下水超采的主要原因。近40年来, 京津冀三地农业的差异化发展强化了河北省在京津冀农业生产中的重要性和基础性功能, 也加重了河北平原农业生产和资源节水压力。现有田间试验和作物模型研究结果表明, 通过优化轮作模式, 降低复种指数, 将小麦-玉米一年两熟灌溉高产模式调整为两年三熟或者三年四熟, 减少高耗水的小麦, 适度增加杂粮、薯类或将夏玉米改为春玉米等措施, 可在较小产量损失下, 达到农业耗水与水资源条件的平衡。现有研究明确了通过压缩高耗水作物构建适水种植结构的总体方向, 但对于不同适水轮作模式在中长期时间尺度上的产粮能力与耗水强度的交互关系仍不明晰, 实用高效的适水田间管理与生产技术支撑体系也需不断完善。在政策层面, 需健全京津冀地区农业综合规划与产业发展体系, 统筹长期目标和短期措施, 在保障区域粮食安全和农产品生产稳定的前提下, 有序地推进京津冀地区农业生产的适水转型。

     

    Abstract: The amount of water resources in the Beijing-Tianjin-Hebei (BTH) region is less than 1% of China, but support approximately 8% of the national population produces 10% of gross domestic product (GDP). Water shortages and groundwater overexploitation are key constraints to the sustainable development of the BTH region. Agricultural water use dominates regional water withdrawal, accounting for 70% of all water use, and the irrigation of high-intensity cropping systems has caused notable groundwater depletion over the past several decades. In this study, the historical stage characteristics of agricultural production scale and irrigation expansion were analyzed based on statistical data. Before 1949, irrigated farmland was mainly located in the piedmont plain of the Taihang Mountains for high-value crop production, irrigation scale and water withdrawal were limited. After 1949, electromechanical irrigation wells gradually replaced traditional shallow wells, and irrigation became a conventional measure for crop production. Since the end of the 1970s, a well-irrigated system has covered the BTH region. Groundwater irrigation provided dominant support for stable agricultural production and sustained high yield. The wheat-maize double-cropping system was enhanced. Simultaneously, the production capacity of fruits and vegetables increased rapidly. The output of grain crops increased from 2.1362×107 t to 3.9448×107 t, an increase of 84.7%. Vegetable production increased from 1.0937×107 t to 5.5084×107 t, an increase of 403.6%. The fruit output increased from 1.440×106 t to 1.5052×107 t, with a 945.6% increase. High yields depended on adequate irrigation, and groundwater depletion occurred as a result of a trade-off between water and agricultural products in the BTH region. Over the last four decades, agricultural production in Beijing, Tianjin, and Hebei has diverged in terms of scale and structure. The crop planting areas of Beijing and Tianjin decreased by 85.0% and 38.7%, respectively. Beijing has almost abandoned grain crop production, but the agricultural production capacity of Hebei Province has further increased. In 2018, 93.8% of grains, 99.1% of oilseeds, 92.9% of cotton, 93.1% of vegetables, and 91.7% of fruits in the BTH region were contributed by Hebei Province. This pattern of differentiation intensified the importance of agricultural production in Hebei Province in the BTH region, which has reliably increased the pressure on agricultural production and water withdrawal in Hebei Province. Studies have explored cropping systems that are more sustainable for groundwater sustainability. Based on field experiments and crop models, it was confirmed that reducing planting intensity can help mitigate groundwater decline, and winter wheat has been reported to be the main contributor to groundwater consumption. The cropping system of three harvests over two years has been suggested as a better alternative cropping system for water savings than the current winter wheat-summer maize double cropping system, which could save more water each year with a slight grain yield loss. However, the interaction between grain production capacity and water consumption intensity on medium- and long-term time scales for different water-adapting rotations of crops remains unclear and insufficient. From a policy-making perspective, it is necessary to improve the comprehensive agricultural plan under the conditions of the BTH coordinated development strategy. To ensure regional food security and stable agriculture, the water-adapting transformation of agricultural production in the BTH region should be promoted in an orderly and efficient manner.

     

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