1. In order to establish a method of plant hasbandry for the direct sowing of rice on dry land, the use of a tractor fitted with experimented iron row crop tires (provisional name is star-wheel) was investigated.<br>It was found that vehicle mobility, fertilization and herbicide application were stablized on both the dry sown and the wet transplanting field.<br>1. It was found that a tractor (22kw) fitted with the star-wheels could run stably on the dry sown field, when the corn index of soil layers at a depth of 10-30cm was more than about 0.5MPa (5kg f/cm²) before flooding, about 0.6-0.7MPa (6-7kg f/cm²) after flooding, and on the wet trans-planting field, when the born index of soil layers at a depth of 10-30cm was about 0.6-0.7MPa (6-7kg f/cm²).<br>2. The more the tractor fitted with the star-wheels run on the wheel ruts, the more the corn index on the wheel rut decreased and the more the wheel ruts width increased.<br>After the tractor ran three times on the wheel ruts, the width of the wheel rut increased to 15-20cm, the lug root of the star-wheel sank to 24-20cm, and the lug top of that sunk to 36-37cm.<br>3. The tractor could run until three times on the wheel ruts. But if the tractor has to run more than four times on the wheel ruts, it would be necessary to do farther study on tire design and running methods.<br>4. Fertilization and herbicide application on a large lot could be worked by one-man operation used the tractor fitted with the star-wheels.<br>When fertilizer was applied by a broadcaster mounted on tractor, work width was 8m, verlocity of work was 0.43-0.77m/s, effective field capacity was 0.98-1.53ha/h.<br>When herbicide was applied by a boom sprayer mounted on tractor, width work was 8m, velocity of work was 0.46-0.48m/s, and effective field capacity was 0.75ha/h.<br>When ditch was trenched with furrow opener mounted on tractor, the working interval was 7.5m, velocity of work was 0.46m/s, and rate of work capacity was 0.79ha/h.<br>5. In order to experiment on rice stubble damage by running of the tractor fitted with star-wheels, a control area where no tractor ran was established for the purpose of comparison.<br>The percentage of rice stubble damaged by running of the tractor fitted with star-wheels two or three times was 0.23-0.55% in the straightaway area, and was 4.2-12.9% in the turning area.<br>The damade rate of rice stubble for the total area of a large lot was 0.23-2.1%.<br>6. Then decrease in the rate of ear numbers of 1.9-5.3% and that in the rate of yield of 1.9-3.9% was noted.