Abstract
Regarding the continuous sub-irrigation method using low positive pressure set in porous pipe and negative pressure in soil, this study was carried out to clarify its principle, extent of water supply and infiltration state under a different pressure set and different permeability of the porous pipe. Experiments were also carried out to investigate a better way of setting the low positive pressure in porous pipe or deciding the suitable permeability of porous pipe. The results obtained under the bare soil conditions are as follows.
1) The bigger the pressure set in the porous pipe is, the more the water supply and infiltration distance tend to become larger. However, it was found that their values are not always in proportion to the magnitude of the pressure.
2) The bigger the porous pipe's permeability is, the more water supply and infiltration distance tend to become bigger. However, it was found that their values are not always in proportion to the magnitude of the permeability.
3) It was found that the water supply was dependent on the degree of the dry or wet soil condition as well as the magnitude of pressure set in the porous pipe.
4) It was considered that a greater water supply could be had by increasing pressure in the porous pipe and the use of a negative pressure for the soil in case of porous pipe having a lower permeability.
