Effect of soil structure on water and solutes movement

土壤结构对水分和溶质运动的影响是土壤水分运动的基础。结果如下：本文所建立的方法可以更容易地定量评价大孔结构。(1)利用软x射线将造影剂注入未受扰动的土样中，有效地获得立体x线图像，从而用三维图像观察孔隙结构。(2)根据不同的土地利用类型，形成了不同的土壤结构，如水田和旱田。(3)无论是显微照片还是射线照相照片，都能在稻田的大孔内发现腐烂的水稻根。这些事实表明，大孔是水稻根系在稻田中形成的，对土壤中物质的转运起着重要作用。(4)观察到土壤内部的流体运动，这是迄今为止尚未报道的。它显示了一个事实，即流体在少数大孔隙中运动，其中流体的运动速度比其他流体快。此外，还可以通过测量大孔隙的直径直接在照片上计算渗透率。通过与常规渗透率试验结果的比较，讨论了渗透率的一些特征。在这一点上，期望进一步讨论两个基准之间的关系。(5)由于保水力取决于微孔，因此很难解释水分特征曲线与土壤结构之间的关系。

Effect of soil structure on water and solutes movement was examined visually as the basis of soil water movement. Consequently following results were obtained. The method developed here made it easier to evaluate macropore structure quantitatively.(1) Stereo radiograph was obtained efficiently by infiltlating a contrast medium into undisturbed soil sample using soft X-ray, so pore structure was observed with 3-D images.(2) It was shown that specific soil structure was made with time according to land-use, such as paddy field and upland field.(3) Rotted rice roots are found inside the macropores in paddy field not only on the microscopic photos but also on the radiographic photos. These facts reveals macropores are made by rice roots in paddy field, and that it contributed significantly in transferring the matter in soils.(4) Fluid movement inside the soil which has not been reported until now was observed. It shows the fact that fluid moves inside rather small number of macropores in which fluids moves faster than others. Furthermore, it also became possible to calculate the permeability directly on photos by measuring the diameters of macropores. Some features were discussed on permeability comparing these datum with the results of usual permeability tests. At this point, further discussion is expected on relationships between two datum.(5) Because water retentivity depends on micropores, difficulty in explaining the relationships between moisture characteristic curve and soil structure is recognized.