Abstract
Actual ridging, furrowing and ditching practices were observed on steep farmland of deep Kuroboku soil, rhe farmland had been reclaimed at original slope in 1972 and has ununiformed sloping fields with small valleys aside or inside. Airphotograph taken 3 years after reclamation showed that many gullies had occurred along these concave valley bottoms. Analysing the directions and the geomorphic features of furrowing practices shows that ridge and furrow tended to be formed in the steeper side direction of a field lot. In these fields, many ditches were observed to be dug across ridges and furrows. The troublesome ditching practices were suggested to be done in the sense of safety drainage; the steeper or the more gentle these ditches became, the shorter they were because a steep ditch would be eroded to cause a gully and a long gentle ditch would cause downside erosion by an overflow. The actual furrowing and ditching practices are supposed to be affected by the field lot arrangement and the replant failure of a monocultural cropping system but also show that the both soil conservation and water drainage practices are necessary together. These are implicated with the safe overland flow control and the effective subsoiling not to cause overland flow at a concave valley bottom.
