Abstract
The crumbling action caused by a slight cultivation helps erosion control. Its effect is very remarkable in Hokkaido, where we have a heavy precipitation in a short time. Further, this effect depends upon the time cultivation is performed. It is effective for reducing erosion to cultivate after the first excessive rain-fall. But cultivating tends to reduce the effect when it is done to much. However, the erosion in the contour ridge is heavier than in the up and down hill when it is left after the ridge is fallen. It is necessary for keeping the effect of contour lister that we repair fallen ridge by cultivation as soon as they are fallen.
