河套灌区盐碱地膜下滴灌土壤水热盐过程模拟与调控

The Hetao Irrigation District is one of the important commodity grain bases in China. In recent years, with the increase of irrigation area and the decrease of water quota from the Yellow River, several agro-ecological issues, such as water scarcity and soil salinization, are becoming more and more severe. Rational utilization of groundwater and promotion of mulched drip irrigation are among the important measures to alleviate the water resource crisis in the Hetao Irrigation District. In a typical salt-affected land selected in the district, different soil water and salt regulation methods were implemented in the field experiment. The effects of different soil-water matric potentials (SMP) on the spatial and temporal distribution and transport of soil water, heat and salt will be studied. The changes of soil boundary conditions under the farming pattern of “ridged cultivation + film mulching + drip irrigation” will be investigated. The related input parameters of the Hydrus-3D model will be adjusted accordingly. Consequently, the coupled processes of soil water, heat and salt under mulched drip irrigation will be simulated more accurately and predicted more reasonably. Then, the responding mechanism of maize growth and yield to different soil water and salt regulation methods will be analyzed, with the aim of finding the threshold of SMP that can simultaneously meet the requirements of salt leaching and maize water consumption. Finally, an optimal regulation method of soil water and salt based on soil water potential will be proposed. This study will contribute to the perfection and promotion of mulched drip irrigation in the Hetao Irrigation District so as to realize the goals of agricultural water-saving and amelioration of salt-affected lands. On the other hand, it will help improve the fundamental principles of coupled transfer of soil water, heat and salt under mulched drip irrigation, and provide a scientific guidance for the comprehensive regulations of soil water and salt in salt-affected soils.

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。合理利用地下水发展膜下滴灌是缓解河套灌区水资源危机的重要举措。本研究针对河套灌区典型盐碱地，通过设置不同的膜下滴灌水盐调控方法处理，研究不同土壤水基质势控制水平对土壤水热盐分布和运移规律的影响；探讨“垄作+覆膜+滴灌”模式下土壤边界条件的变化，修正Hydrus-3D模型输入参数，实现对膜下滴灌土壤水热盐耦合过程的准确模拟和合理预测；分析玉米生长和产量对不同土壤水盐调控方法的响应，寻求既能有效淋洗盐分又能满足玉米生长需水的土壤水基质势下限，提出基于土壤水势的膜下滴灌水盐调控方法。该研究一方面将有助于河套灌区膜下滴灌技术的完善和推广，以实现灌区农业节水和盐碱地治理的目标；另一方面也有助于进一步完善膜下滴灌土壤水热盐耦合迁移理论，为盐碱地土壤水热盐的综合调控提供科学依据。

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。合理利用地下水发展膜下滴灌是缓解河套灌区水资源危机的重要举措。通过连续3年的田间试验，本研究针对河套灌区典型盐碱地，通过设置基于土壤基质势水平的不同膜下滴灌水盐调控方法处理，研究了土壤水热盐分布和运移规律，结果发现生长季内不同基质势水平下土壤含水率差异明显，基质势越高土壤剖面平均体积含水率越高。采用田间实测数据对Hydrus-2D 模型进行标定并验证模型的有效性。结果表明，Hydrus-2D 模型模拟值与实测值之间吻合较好，可以较为准确地模拟河套灌区不同膜下滴灌方法对土壤水、盐、热运移规律的影响。不同土壤水基质势下限控制的灌水水平显著影响玉米生长，随着生育期内土壤水基质势控制下限的降低，玉米株高与叶面积指数显著降低（p < 0.05），其中基质势下限为-50 kPa的处理玉米发生早衰现象。土壤水基质势水平越高，玉米产量越高，其中S1、S2和S3处理玉米产量显著高于S4和S5，但是前三者之间不存在显著差异（p < 0.05）。随着土壤水基质势的降低水分利用效率先增大后减小，-30 kPa时水分利用效率最高。综合考虑作物产量和水分利用效率，建议将河套灌区玉米膜下滴灌土壤水基质势下限控制在-30 kPa。该研究成果完善了河套灌区膜下滴灌技术，有利于膜下滴灌在灌区的推广，助推实现农业节水和盐碱地治理的目标；另一方面，进一步完善了膜下滴灌土壤水热盐耦合迁移理论，为盐碱地土壤水热盐的综合调控提供科学依据。