垄膜沟灌对河套灌区盐渍土水盐运移过程的影响及调控

With the decrease of water quota from the Yellow River, soil salinization is becoming more and more severe. Water and salt regulation based on ridge with plastic mulch-furrow irrigation is the key technique to alleviate soil salinization situation in Hetao Irrigation District and plays an important role in improving the soil water and salt environment. In a typical salt-affected land selected in Hetao Irrigation District, different soil water and salt regulation methods were implemented in the field experiment. The effects of ridge with plastic mulch-furrow irrigation on the spatial and temporal distribution and transport processes of soil water and salt will be studied. The unique boundary conditions of soil water and salt under the farming pattern of ridge with plastic mulch-furrow irrigation will be investigated. The specific coupling strategy which can reasonably describe the continuous system of surface flow-soil water and salt transport in ridge with plastic mulch-furrow irrigation will be developed. Then the coupled surface flow-subsurface water and salt transport model under the condition of ridge with plastic mulch-furrow irrigation will be developed. The different irrigation performance indexes which are suitable for ridge with plastic mulch-furrow irrigation will be determined, with the aim of finding the different combinations of technique parameters that can simultaneously meet the requirements of salt leaching and agricultural water-saving. Then, an optimal regulation method of soil water and salt based on the different combinations of technique parameters will be proposed. The expected results of this project will add new knowledge to the regulation theory of ridge with plastic mulch-furrow irrigation and will be a contribution to regulating water and salt in Hetao Irrigation District.

随着引黄水量指令性减少，河套灌区土壤盐渍化等问题日益突出。利用垄膜沟灌开展水盐调控是缓解河套灌区土壤盐渍化状况的重要措施，可有效抑制土壤水盐环境的进一步恶化。本研究针对河套灌区盐渍化农田，通过设置不同的垄膜沟灌水盐调控方案，研究垄膜沟灌对土壤水盐运移过程与时空分布特征的影响。在此基础上，探究“垄体覆膜+沟灌”模式下特有的水盐初始与边界条件，提出能合理描述垄膜沟灌地表水流-土壤水盐连续系统的特定耦合模式，构建垄膜沟灌地表水流-土壤水盐运移耦合模拟模型，实现对垄膜沟灌地表水流-土壤水盐运移过程的准确模拟与合理预测。通过构造适宜于垄膜沟灌的性能评价指标，寻求既能有效淋洗盐分又能节水、控制地下水位的垄膜沟灌技术要素优化组合，提出基于不同技术要素优化组合的垄膜沟灌水盐综合调控模式。预期研究结果对丰富河套灌区垄膜沟灌技术理论、实现河套灌区水盐综合调控具有重要意义。

河套灌区是我国重要的商品粮基地之一。近年来随着灌溉面积的增加和引黄水量的减少，水资源紧缺、土壤盐渍化等问题日益突出。改良河套灌区盐渍化土壤、提高灌水效率，有助于营造适宜作物生长的水盐环境、提高河套灌区的粮食产量。垄膜沟灌可有效缓解强烈蒸发、漫灌渗漏对作物生长环境的影响，提高灌溉水利用效率与作物产量。通过多年田间试验，发现土壤水盐主要在0-80 cm土层波动较大。在春玉米生育期内，灌溉水深层渗漏量约占9.3％-29.5％。灌水量较少时通常会造成0-40 cm土层出现盐分累积。春玉米收获时，垄膜沟灌低水处理的盐分累积最严重，高水处理的累积情形较为和缓。与覆膜畦灌高水处理相比，垄膜沟灌处理的春玉米产量增加4.2%以上。因此，充分考虑河套灌区的土壤蓄水量、土壤盐分、玉米产量和水分利用效率，建议采用垄膜沟灌+300mm左右灌水量，可以满足河套灌区轻度盐渍化农田春玉米生长需要。同时，在掌握了垄膜沟灌地表水流-土壤水盐运移过程基础上，构建了垄膜沟灌一维地表水流-二维土壤水流溶质运移耦合模型，并采用田间试验数据对其加以验证，模拟发现沟长50 m左右、单沟流量2.5-4.0 L/(s.m)时，能够获得较好的节水控盐效果。综合试验与模拟数据，建议可将河套灌区春玉米垄膜沟灌灌水量控制在300 mm左右，垄沟长度50m左右、单沟流量2.5-4.0 L/(s.m)。该研究成果完善了河套灌区垄膜沟灌技术，有利于垄膜沟灌在河套灌区的推广，助推实现农业节水和盐碱地治理的目标；另一方面，完善了垄膜沟灌土壤水盐耦合迁移理论，为盐碱地土壤水盐的综合调控提供科学依据。