蓄水坑入渗表层土壤体积质量和饱和导水率的变化

Changes of topsoil bulk density and saturated hydraulic conductivity under infiltration condition of water storage pit

表层土壤体积质量和导水率是影响土壤入渗及水分运动的重要物理参数。该文采用土壤切片技术和数字图像分析技术,分析了蓄水坑灌条件下入渗水头对砂壤土表层土壤体积质量的影响,进行了不同入渗水头、土壤体积质量对砂壤土表层土壤饱和导水率的试验研究,并对蓄水坑侧向水平入渗湿润锋变化的试验结果与数值模拟结果进行对比分析。结果表明:该研究试验条件下(土壤体积质量为1.345g/cm3),入渗水头对土壤体积质量和表层土壤饱和导水率有较明显的影响。随着入渗水头的增大,其作用下的表层土壤体积质量趋于增大,土壤结构趋于密实,表层土壤的饱和导水率趋于减小;表层土壤饱和导水率与入渗水头和土壤体积质量之间呈乘幂关系,且表层土壤饱和导水率对土壤体积质量的变化较为敏感,当土壤体积质量达到某一程度时(1.466g/cm3),入渗水头对表层土壤饱和导水率的影响甚微。研究成果揭示了入渗水头影响蓄水坑土壤入渗的微观机制,为进一步研究蓄水坑灌法提供了理论依据。

The bulk density and saturated hydraulic conductivity of topsoil are important physical parameters in studying water infiltration and soil water movement. Soil sections and digital images analysis techniques were used to study the effects of different infiltration heads on bulk density of the topsoil in sandy loam under water storage pit irrigation condition. The effects of different infiltration heads and soil bulk density on saturated hydraulic conductivity were tested. The comparative analysis between tested and computer simulated results of horizontal wetting front was conducted. The results indicated that infiltration head had a remarkable influence on the bulk density and saturated hydraulic conductivity of topsoil in sandy loam （soil bulk density was 1.345 g/cm^3）. With the increasing of infiltration head, the topsoil bulk density increased, soil became compact, and the saturated hydraulic conductivity of topsoil decreased. The power function could be used to describe the relationship between topsoil saturated hydraulic conductivity and infiltration head and soil bulk density. With the increasing of soil bulk density, the effect of infiltration head on saturated hydraulic conductivity decreased. When soil bulk density up to 1.466 g/cm^3, infiltration head had few influence on saturated hydraulic conductivity. The results explore the micromechanism of the effect of infiltration head on the infiltration characteristics, and provide theoretical foundation for the further research in water storage pit irrigation.