The results of the author's experiments indicated that two-year rotaion of sawa-millet, wheat and soybean brought about soil erosion in a lower extent comared with that by the conventional cropping systems in Tohoku District. The explantion of the good results may be as folows: (1) Either millet or soybean itself protect soil effectively against erosion; (2) Wheat was planted by trashy cultivation, and soybean was interplanted before the wheat harvest, both the procedures tending to protect the soil.
