| Co-Investigator(Kenkyū-buntansha) |
MIZOGUCHI Masaru Graduate School of Agricultural and Life Sciences, University of Tokyo, Associate Professor, 大学院・農学生命科学研究科, 助教授 (00181917)
NAKANO Masashi Faculty of Agriculture, Kobe University, Professor, 農学部, 教授 (00011908)
NISHIMURA Taku Graduate School of Agriculture, Tokyo University of Agriculture & Technology, Associate Professor, 農学部, 助教授 (40237730)
SEKI Katsutoshi Graduate School of Agricultural and Life Sciences, University of Tokyo, Assistant Professor, 大学院・農学生命科学研究科, 助手 (40313069)
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| Research Abstract |
The purpose of this study were to (1) find the causes why soils are undergoing serious degradation recently in the 380 ha upland fields in Fukaya, Saitama Prefecture, (2) classify the effects of soil degradation on the migration of such environmental materials as water, solutes (including salts, nitrogen, phosphorous, etc.), and gasses (including OィイD22ィエD2,COィイD22ィエD2, NィイD22ィエD2O etc.), and (3) propose the ways of soil restoration by which physical properties and drainage efficiency of the soils are recovered.
The main results are as follows.
1. The suffering from deterioration of drainage efficiency and excess water in upland fields were due to not only by soil degradation but also configurations of structures such as roads, drainage canals, green houses etc.
2. The saturated hydraulic conductivities of soil samples from well drained fields were not necessary higher than those from poorly drained fields. This contradiction was explained by other physical properties of soils.
3. The poor efficiency of drainage from upland fields were attributed to the low stability of aggregation, high sensitivity to the application of salts, the tendency of easy-to-form surface crusts, and high consistencies.
4. The soil degradation was classified into two types : one is the surface soil degradation where the soils are mechanically disturbed, directly compacted and periodically fertilized, and other is the subsurface soils degradation where the soils are indirectly compacted resulting in the increase of bulk density.
5. The deep plowing was effective for the restoration of subsurface soils but plowing with organic matter did not show any advantage for the physical properties of soils.
6. Application of polyacrylamid (PAM) may be effective for the soil restoration especially in its permeability. Further investigation of the PAM efficiency is needed.
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