基于斥水程度强弱的土壤水分运动过程模型

There are directly and indirectly negative effects of soil water repellency on scoped water cycle process, solute transfer, even crop production in the field, but the study on the characteristics of water movement of water repellent soil is still not very deep. Different indices obtained using methods of Water Droplet Penetration Time, Ethanol Morality Test and capillary rise experiment were combined to assess water repellency levels, soil physico -chemical properties and soil hydraulic properties will be measured accurately and systematically, infiltration of water repellent soil will be conducted. Statistical analysis will be utilized so that the key physical-chemical factors which are significantly related to soil water repellency will be selected to reveal the intrinsic causes and mechanics of soil water repellency. Combining with traditional hydraulic property models, based on similarity theory to determine scaling factors, the new hydraulic property models taking account the weakness and strength of soil water repellency will be established. The developed new models for water repellent soils will be further used in the simulations of 1-and 2-dimensional soil water movement based on the Richards equation and Darcy’s law, to testify the applicability of the new models and the accuracy of Richards equation and Darcy’s law when extensively used in water repellency soils. The research achievement of this project will supply more accurate key parameters for simulation of water movement of water repellent soils in the field, it is also reference for the coupled transport of water, solute and heat.

土壤斥水性对农田水分和溶质迁移、水土环境及作物产量有直接和间接的负面影响，但目前对斥水土壤水分运动规律的研究并不深入。本项目拟采用滴水穿透时间、酒精摩尔浓度及毛管上升法得出的不同指标综合判定土壤斥水级别，测定相关土壤理化性质和土壤水力性质，并进行斥水土壤的入渗实验。基于统计分析筛选影响斥水性的关键理化性质因子，揭示土壤斥水的内在机理；得出不同质地及有机质含量下的土壤斥水性特征曲线；在亲水土壤的水力性质模型基础上，根据相似原理确定标定系数，提出考虑斥水性强弱的水力参数新模型；将水力参数新模型应用于Richards方程和Darcy定律，模拟斥水土壤的一维和二维水分运动过程，并与实测土壤水分入渗过程做对比，从而检验Richards方程模拟斥水土壤水分运动的适用性。所得研究成果可为农田斥水土壤的水分运动规律模拟提供更准确的关键参数，也是斥水土壤水、盐、热耦合运移的依据之一。

土壤斥水性（SWR）对农田水分循环过程、溶质迁移、甚至作物产量有直接和间接的负面影响，与SWR相关的研究极为必要。项目采用滴水穿透时间（WDPT）、酒精溶液浓度（MED）及毛管上升实验得出的接触角（θ）等指标综合判定SWR级别，测定相关土壤理化性质和水力性质，基于统计分析筛选了影响SWR的关键理化性质因子，揭示了SWR的内在机理；分析推导了滞后作用影响下的土壤斥水性特征曲线；在亲水土壤的传统水力性质模型基础上，提出考虑斥水性强弱的水力参数新模型；进行均质和层状斥水土壤的水平和垂直入渗试验和优先流试验，分析SWR对入渗的影响，探讨优先流出现的斥水性土壤条件。进行了土壤斥水性影响下蔬菜类、花草类、树木类和作物类等四类植物种子发芽率的试验。将水力参数新模型应用于Richards方程，基于HYDRUS-1D模型模拟了均质及层状斥水性土壤的水分运动过程，并与实测数据对比，评价HYDRUS-1D模拟斥水土壤水分运动的准确性，并进一步模拟其他斥水级别下的水分运动过程。结果表明：（1）在多种理化性质中，粘粒含量比其他土壤属性更显著地影响WDPT和θ，K+及Na+浓度均与θ呈正相关；蒙脱石含量与WDPT、MED呈负相关。（2）滞后作用对不同质地土壤斥水性特征曲线形状有明显影响，在实际分析中应考虑其影响。（3）van Genuchten模型对亲水和斥水土壤均适用，优于Brooks-Corey模型，两模型均可用于描述斥水性土壤水分运动参数。（4）斥水性砂土比粘土更容易出现非均匀流；斥水性壤土覆盖亲水砂土的层状结构会导致指流产生，但指流的长、宽及数量等的发展规律不一致。（5）SWR越强,四类植物的种子发芽率越低。（6）SWR越强，夏玉米的株高、茎粗和叶面积指数越小，干物质量显著减少，产量、水分利用效率、耗水量也相应降低。（7）随着SWR的增加，HYDRUS-1D模拟的效果有所降低，但整体模拟效果仍较好。（8）玛纳斯河流域0-10cm土层WDPT从东南和西北分别向西南和东北方向逐渐减小，WDPT变幅和变异程度较大，属于强变异。本项目系统地揭示了SWR对土壤水分和植物生长的影响规律。