Pires Luiz F, Auler André C, Roque Waldir L, Mooney Sacha J
Laboratory of Physics Applied to Soils and Environmental Sciences, Department of Physics, State University of Ponta Grossa (UEPG), 84.030-900, Ponta Grossa, PR, Brazil.
Department of Soils and Agricultural Engineering, Federal University of Paraná, 80.035-050, Curitiba, PR, Brazil.
Geoderma. 2020 Mar 15;362:114103. doi: 10.1016/j.geoderma.2019.114103.
The soil water retention curve is one of the most important properties used to predict the amount of water available to plants, pore size distribution and hydraulic conductivity, as well as knowledge for drainage and irrigation modeling. Depending on the method of measurement adopted, the water retention curve can involve the application of several wetting and drying (W-D) cycles to a soil sample. The method assumes soil pore structure is constant throughout however most of the time soil structure is dynamic and subjected to change when submitted to continuous W-D. Consequently, the pore size distribution, as well as other soil morphological properties can be affected. With this in mind, high resolution X-ray Computed micro-Tomography was utilized to evaluate changes in the soil pore architecture following W-D cycles during the procedure of the water retention curve evaluation. Two different soil sample volumes were analyzed: ROI (whole sample) and ROI (the region close to the bottom of the sample). The second region was selected due to its proximity to the hydraulic contact of the soil with the water retention curve measurement apparatus. Samples were submitted to the following W-D treatments: 0, 6 and 12 W-D. Results indicated the soil changed its porous architecture after W-D cycles. The image-derived porosity did not show differences after W-D cycles for ROI; while for ROI it increased porosity. The porosity was also lower in ROI in comparison to ROI Pore connectivity improved after W-D cycles for ROI, but not for ROI. W-D cycles induced more aligned pores for both ROIs as observed by the tortuosity results. Pore shape showed changes mainly for ROI for the equant and triaxial shaped pores; while pore size was significantly influenced by the W-D cycles. Soil water retention curve measurements showed that W-D cycles can affect water retention evaluation and that the changes in the soil morphological properties can play an important role in it.
土壤水分保持曲线是用于预测植物可利用水量、孔径分布和水力传导率的最重要特性之一，也是排水和灌溉模型的相关知识。根据所采用的测量方法，水分保持曲线可能涉及对土壤样品施加多个湿润和干燥（W-D）循环。该方法假定土壤孔隙结构始终保持不变，但在大多数情况下，土壤结构是动态的，在连续的W-D过程中会发生变化。因此，孔径分布以及其他土壤形态特性可能会受到影响。考虑到这一点，在水分保持曲线评估过程中，利用高分辨率X射线计算机显微断层扫描技术来评估W-D循环后土壤孔隙结构的变化。分析了两种不同体积的土壤样品：感兴趣区域（整个样品）和感兴趣区域（靠近样品底部的区域）。选择第二个区域是因为它靠近土壤与水分保持曲线测量装置的水力接触处。样品接受以下W-D处理：0、6和12次W-D。结果表明，经过W-D循环后土壤的多孔结构发生了变化。对于感兴趣区域，图像得出的孔隙率在W-D循环后没有显示出差异；而对于感兴趣区域，孔隙率增加了。与感兴趣区域相比，感兴趣区域的孔隙率也较低。对于感兴趣区域，W-D循环后孔隙连通性得到改善，但对于感兴趣区域则没有。通过曲折度结果观察到，W-D循环使两个感兴趣区域的孔隙排列更整齐。孔隙形状的变化主要发生在感兴趣区域的等轴状和三轴状孔隙上；而孔径受W-D循环的影响显著。土壤水分保持曲线测量表明，W-D循环会影响水分保持评估，并且土壤形态特性的变化在其中可能起重要作用。
