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To support crop-rotation systems using rice, wheat, and soybean in paddy fields, we developed a sowing device that can be attached to a rototiller ; the device cuts small ditches on both sides of groups of rows of plants, while tilling to a depth of approximately 5cm, planting seeds, and compressing the soil around the seeds. This device includes a pressurized roller which compacts the soil with sowing, and we examined the effect of this compaction on germination rate after seeding. The roller provides three settings : The setting of strong pressure is compressing the soil to the level of the original topsoil. The setting of weaker pressure is compressing to leave the tilled soil 1.5cm above the original topsoil level. The non pressure setting does not apply pressure during seeding. The strong pressure produced a higher rice germination rate than the weaker pressure and the non pressure in March 2011, but did not affect rice yield. The weaker pressure produced higher germination and growth rates than with the strong pressure and non pressure settings for wheat. In a soybean, it was not able to be recognized which pressurized setting was higher a germination rate. The strong pressure increased soil volumetric water content in the surface layer to a depth of 5 cm layer from topsoil compared with the weaker pressure and non pressure. The setting of pressurized roller made contracting soil from topsoil to depth 6-8 cm, and this condition was retained after 3 months from sowing.
