Studies on the Effect of Saving Water in Mulching Culture under the Sub-irrigation Method by Using Negative Pressure Difference

This study was carried out to clarify the effect of saving water by the mulching cultivation under the sub-irrigation method by using negative pressure difference resulting from porous pipes which are buried at the shallow depth from soil surface. Experiments were conducted in the vinylhouse under the mulching or unmulching condition. Ten plants each of tomatoes in autumn and Andes melons in spring were used in the experiments. In the experiments, water supply, the daily fluctuations of soil moisture tension. and others were measured at each season. Consequently, the luxuriant growth of stalks and leaves in the first stage of growing after taking roots was observed more under the mulching condition in both case than that under the unmulching condition. With respect to the culture of tomatoes, the mean amount of water supply saved in the mulching plot was recognized to be about 35% in contrast to that in the unmulching plot, but soil moisture environment was sustained at the wet conditions in spite of there being less water supply. With respect to the culture of melons, the mean amount of water supply saved in the mulching plot was also recognized to be about 7%. Moreover, the soil moisture environment in the mulching plot was sustained at the wet conditons

Optimization of Soil Moisture Environment by Applying Simulation on Sub-irrigation Method (III) : Reappearance Trial by Using Finite Element Method in Distributions of Soil Moisture Tension

This study was conducted by using the finite element method in order to reappear and predict the distributions of soil moisture tension under the application of sub-irrigation method. The reason which applied the finite element method in order to reappear the distribution of soil moisture tension is able to use the unsaturated permeability in response to the extent of soil moisture tension in the analysis region. Consequently, the results obtained by using finite element method are very different from those obtained by using mapping method. Further, the effects which the different extent of negative pressure, water supply and others influences were clarified, and then the distributions of soil moisture tension could be reappeared and predicted like nearly actual distributions