Studies on the perfection of radiography for soil macropores and on the application to the soil physical problems.

1. 大孔成像方法的完善。(1)立方体土的原状取样。立方体土壤样品适合于x射线立体放射成像，本研究开发了方形圆柱形取样器法和刀切法。这两种方法之后，在实验室进行土样修剪，得到4.15cm的未扰动土样立方。(2)对比剂渗入样品的方法。对立方试样的粘土板涂层和试样的含水饱和度进行了标准化，并将该方法命名为“干燥法”。这一标准化提高了造影剂渗透的效率和大孔成像的准确性。大孔成像方法的应用。(1)在火山灰土田中，沿土层全深度密集发育着具有植物根系形状的大孔。此外，在全水平土壤中同时检测到本地植物的植物蛋白石。这些结果表明，大孔可能是由老植物的根形成的。(2)采用上述方法研究了压实土中水侵大孔隙的形态。即在渗透试验结束后，用造影剂代替水，并对土样进行射线照相。在土壤含水量较低时，颗粒单位的空隙发育。高含水率时，膜状空隙向水平方向生长。(3)在农田、水田、旱地和草地上，由作物根系形成的大孔生长旺盛。其中，草地大孔隙发育最活跃，深度为1 m。(4)用上述方法可以观察到火山灰土的初始空气进入空洞，它们是植物根系形成的最粗的大孔。

1. Perfection of the macropore imaging method. (1) Undisturbed sampling of cubic form soil. Cubic form soil samples are suitable for x-ray stereoradiography, and in this study the square cylindrical sampler method and knife cutting method have been developed. These two methods are followed by soil sample trimming in the laboratory, and 4.15cm cube sample of undisturbed soil is obtained. (2) Infiltrating method of contrast medium into the sample. Clay plate coating of cubic sample and water saturation of sample were standardized, and the method was named "Drying method". This standardization raised the efficiency of contrast medium infiltration and the accuracy of macropore imaging.2. Application of the macropore imaging method. (1) In the fields of volcanic ash soils, it was found that macropores having shape of plant roots developed densely through the whole depth of tephra horizon. Further, the plants opals of native plants were detected simultaneously in the soils of whole horizon. These results indicate that the macropores would have been formed by the old plants roots. (2) The shapes of macropores infiltrated with water in the compacted soils were investigated using above method. Namely, after permeability test the water was replaced with contrast medium, and the sample soil was radiographed. At the low water content of soil, the interspaces of granulated units developed. However at the high water content, the membrane-like voids grew into horizontal direction. (3) In the farmland, the rice paddy field, upland field and grass land, macropores formed by the c rop roots grew vigorously. Among them, grass land shows the most active and deepest (1 m) development of those macropores. (4) Initially air entering voids of volcanic ash soils were visualized by the above method, and they were most thick macropores formed by the plants roots.