水田におけるトラクタ性能判定に関する研究 (第7報)

沈下と土壌条件

抄録

In order to find the relation of the soil hardness which is measured by the cone penetrometer to the tractor sinkage on the soft paddy field, the tests were repeated by the methods produced by the Waterways Experimental Station. Test fields were the low swampy ground scattered near the Lake Biwa which had been harvested the rice plants and located as the dots in Fig. 1. Thirteen test tractors were used and they had the various running elements, such as pneumatic single tires, dual tires, half tracks, strake type wheels, girdles and tracks and they had the dimensions as in Table 1. Vehicle cone index of each tractor on the same Table were calculated according to the WES methods. Abscissa of Fig. 3 shows the cone index calculated from the cone penetrating resistance and ordinate is the depth measured from the land surface. These diagrams are recorded by the self recording penetrating devices produced by the way of experiment in our laboratory and called TN-4. reported previously.
Fig. 4 is the result of these tests and the abscissa of the coordinate is the actual measured sinkage of the tractors and the ordinate is the presumed sinkage from the cone diagrams and the vehicle cone index. Fig. 6 shows the increases of sinkage with the increases of slippage of the wheel or other running elements of the tractors on the test field having the cone diagrams as the upper part of the same figures.
1. Tractor sinkages presumed by the cone index and vehicle cone index are almost agreed with the actual sinkages except special examples, such as the large sinkage caused when the running elements excavate the soil surface at the time of 100 percent or large slippage.
2. On the surface we can get the cross point to the cone diagrams of the vertical line drawing to the scale corresponding to the vehicle cone index of the tractor which crosses on that surface, the depth of that cross point were agreed with the actual sinkage of the tractor having no load, however, when the tractors had the large drawbar pull and the hard layers of the surface of soil were excavated by the slippage of the running elements of that tractors, they sank to the second cross point we can get at the deeper layer. If we can not get the cross point at that layer, they can not cross on that surface.
3. On the surface having the hard cone diagrams, slip sinkage according to the excavation of the running elements were affected by the hardness of the soil.
4. Rotary tiller is not need to be treated as the drawbar load, it rather may be available as the means of increase of floatation.
5. As the combine harvester had generally less slippage and less excavation of soil, they can cross the surface which have the hard layer on the top of the surface, even if the deeper layer are extremely soft.