抄録
Field studies were carried out to know the effect of the continued non-tilled direct seeding rice culture on the soil compactness and water requirement in depth. The outline will be described below.
1) The compactness of topsoil was become harder due to the continuing of the non-tilled direct seeding rice culture. The compactness of the topsoil was about 500-1000 KPa.
2) The distribution of root system was not limited by the high compactness at the non-tilled direct seeding rice culture. The amount of root was converged into the surface of topsoil,0-3 cm, by continuing the nontilled direct seeding rice culture.
3) The thickness of organic layer on topsoil was about 14-18 mm in the way of surface application with rice straw, but about 6 mm in the way of carrying out of rice straw.
4) The water requirement in depth was increased due to the continuing of the non-tilled direct seeding rice culture. That was remarkable in the paddy field with low groundwater level, but there was no problem in the paddy field with high groundwater level.
5) The increase in the water requirement in depth was mainly due to the increase in the percolation through border.
