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)立方体土样原状取样。立方土样适合于X射线立体照相，本研究发展了方柱取样器取样器和切割法。采用这两种方法对土样进行了室内修剪，得到了4.15 cm的原状土样。(2)对比剂渗入方法。对立方体样品的粘土板包衣和样品的含水饱和度进行了标准化，并将其命名为“干燥法”。这种标准化提高了造影剂渗透的效率和大孔成像的准确性。大孔成像法的应用(1)在火山灰土田中，植物根状的大孔隙在整个苔藓层深度内密集发育。此外，在整个土层的土壤中同时检测到了乡土植物的蛋白石。这些结果表明，大孔可能是由老植物的根形成的。(2)利用上述方法对压实土中入渗水的大孔隙形态进行了研究。即渗透性试验后，用对比剂代替水，并对土样进行X光摄影。土壤含水率低时，颗粒单元间隙发育。但在高含水率时，膜状空洞向水平方向生长。(3)在农田、水田、旱地和草地上，根部形成的大孔隙生长旺盛。其中，草地表现出最活跃、最深(1m)的大孔隙发育。(4)用上述方法可以直观地看到火山灰土最初进入的空隙，它们是植物根部形成的最厚的大孔隙。

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.