Abstract
The Subsurface Irrigation based on the Different Negative Pressure (S. I. D. N. P.) between water fed by a porous pipe irrigation system and that (soil moisture) in the neighborhood of root zone in soil is characterized by the effect of self-controlled (mainly controlled by that water gradient) continuous irrigation.
In the conditions of popular cultivation modes in vinylhouse, various porous pipes were examined regarding the fundamental relationships between the above difference of water and the quantities of water supply, the distribution of water in soil, and daily variation of evaporation from the soil's surface. This system was analyzed theoretically by conformal mapping.These results are summarized as follows:
1) The suitable shape of porous pipe of S. I. D. N. P. for use in the above-mentioned conditions in order to maintain the effective low moisture tention zone is a porous ceramic pipe having length 10-20cm, outer radius of about 3cm, coefficient of water permeability above 10-4cm/sec with one of its ends being sealed.
2) Changing given water pressure in pipes controlled the quantity of the water supply very sensitively and varied the area of the wet soil surface above the porous pipes and the seepage zone in soil.
3) Daily variation and its peak time of water supply occurred almost simultaneous with those of evaporation from soil surface and so weather conditions affected its quantity which was supplied continuously day and night.
4) Theoretical analyses by conformal mapping are nearly simultaneous with the above experimental results. And so experiments of cultivation by S. I. N. D. P. are planned to be put into practical use.
