银北灌区土地整治土壤水盐运动模拟与排盐空间配置

This study is to be carried out in the region of land consolidation of Pingluo County located in Yinchuan North Irrigation District, where is key land consolidation area under water and salt constraints. The objectives are to address scientific problems such as the spatial allocation of cultivated land and salt discharge area, responding mechanism of soil water and salt movement, and also the reality of severe soil salinization of cultivated land due to blind land consolidation in a way of high newly increased cultivated land rate. Multiple methods such as geostatistics and fractal theory and neural network analysis will be compared to investigate the spatial analysis of soil water and salt in the region of land consolidation. Spatial heterogeneity of soil water and salt and corresponding effect factors will be disclosed. Regional parameters of soil water and salt movement will be obtained. Referring to Sahysmod and other models, a localized regional soil water and salt movement and balance analysis model will be established and, employed to analyze the regularity of soil water and salt movement in the region of land consolidation. Different land consolidation scenarios of cultivated land and salt discharge reservation will be set up. The responding mechanism of soil water and salt movement on spatial allocation between cultivated land and salt discharge area will be analyzed based on the scenarios simulation results. The spatial allocation parameters of cultivated land and salt discharge area will be optimized in the land consolidation area under water and salt constraints. The implementation of this research is expected to 1) improve the allocation theory of cultivated land and salt discharge area of land consolidation, 2) prevent soil salinity of cultivated land, and 3) achieve the comprehensive land consolidation goals of efficient flood drainage and steeping reduction, and win-win of agricultural production and ecology.

针对银北灌区水盐约束下土地整治中的耕地与排盐空间配置及土壤水盐响应机制等科学问题，以及由于盲目追求新增耕地率导致的耕地土壤盐渍化严重等现实问题，选择宁夏平罗县土地整治片区开展相关研究。通过地统计学、分形理论和神经网络等方法对比分析，探讨土地整治片区土壤水盐空间分析方法，揭示土壤水盐空间变异规律及其影响因素，获取区域土壤水盐运动参数。参考Sahysmod等模型，构建本地化的区域土壤水盐运动与平衡分析模型或参数，模拟分析区域土壤水盐运动规律。设置不同耕地与排盐地配置的土地整治情景，基于模型模拟，揭示不同情景下耕地土壤水盐运移规律，分析耕地与排盐空间配置的土壤水盐响应机制，优化水盐约束下土地整治中耕地与排盐空间配置参数。预期结果将完善水盐约束下土地整治耕地与排盐空间配置理论，有效防止耕地土壤盐渍化，实现涝能排、渍能降、生产生态双赢的土地综合整治目标。

针对盐渍土地区水盐约束下土地整治中耕地与排盐地空间配置不合理及相应的土壤水盐动态响应机制缺失等问题，本项目设计实施了三方面研究内容，包括关键土壤属性空间预测方法研究、土壤水盐运移模拟研究和土地整治片区排盐地空间配置研究。在关键土壤属性空间预测方法研究方面，在典型土地整治片区空间尺度上比较了OK_BP(Ordinary Kriging Combined with Back-Propagation Network)、RK(Regression Kriging)、BP(Back-Propagation Network)、OK(Ordinary Kriging)四种方法预测土壤盐分的精度，结果表明OK_BP方法可以有效去除OK的平滑效应、提供更多局部细节、预测的数据更贴近实际情况；在银北灌区尺度上利用多元线性回归、地理加权回归、随机森林回归等方法结合64个与盐碱地形成相关的辅助变量（如地形、土壤基质、气候等）和盐碱地的表观光谱特征来估计土壤EC，结果表明从旱季遥感影像提取的光谱特征更适于预测土壤EC，随机森林模型预测精度更高。在土壤水盐运移模拟研究方面，以典型土地整治片区—宁夏平罗县西大滩为例，建立了研究区土壤水盐运移SahysMod模型，模拟了不同灌排管理模式下土壤水盐动态变化，结果表明在现有灌排管理模式下，研究区土壤EC逐年增加，2024年以后作物生长就会受到盐害胁迫，加大灌水量和加深排水沟深度，可以有效延迟土壤电导率达到障碍水平的时间。在土地整治片区排盐地空间配置研究方面，采用SahysMod模型研究不同耕地与排盐地的面积比例、耕地与排盐地的高度差、排盐地位置布局等情景模式下的土壤水盐动态变化，结果表明同一整治区域内排盐地占比越大，排盐效果越好，本项目中典型土地整治片区耕地与荒地的比例为1.5、高度差为0.3米，耕地的排盐效果最好，此外，排盐地插花分布于耕地中，排盐效果更好。研究成果为完善盐渍土地区土地整治工程项目评价指标体系以及农田水利建设工程提供了技术支撑，为有效防止耕地土壤盐渍化，实现涝能排、渍能降、生产生态双赢的土地综合整治目标提供了解决方案。

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