抄録
Plastic coated moldboard plows were developed in order to prevent soil sticking when plowing the volcanic light soils, and the problem of wear of plastic sheet was occured. The writers carried out the study on the effect of the qualities of the particles in volcanic ashes on the plastic coated moldboard plows, and the following results were obtained.
It was found out that the wears of plastic sheet were very different in districts, that is, the amount of wear was 6.7%/10ha in Yuni town, but was only 1.1%/10ha, in Memuro town and it seemed that this difference was dued to the qualities of volcanic soils. To pursue the cause, the qualities of typical volcanic soils in Hokkaido (i. e. soil texture, compressive breaking solidity of soil particle, and shape of particle) were studied.
1) The content of coarse sand (0.2-2.0mm) of Yuni town volcanic soils was 61.4% and that of Memuro was 21.1%. Therefore, it was concluded that the more content of coarse sand the more the wear of plastic sheet.
2) Both the compressive breaking solidity and the content of such particles effect the wear of the plastic remarkably. The breaking solidity of Yuni town soil was about 791gr and that of Memuro was 221gr, i. e. the former was 3 times as strong as the latter.
3) When the shape of the particles is more angular, the scraping or scratching effect on the surface of plastics becomes stronger, and the life of plastics is shortened. The shape of particles of Yuni was angular, but that of Meruro was roundish.
4) The factors 1)-3) may act on the wear of plastics individually, but generally they interact to increase the wear of plastics.
