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

Experimental Studies on the Measuring Soil Moisture Tension by the Use of the Pressure Membrane Method and the Centrifuging Method

Soil matric potential is necessary to be measured with undisturbed core samples taken from the field as possible. And also, to measure soil matric potential in laboratory, soil structure should not be distroyed under the experiments as possible, because the soil moisture retension properties are much influenced by the change of soil structure. Then, the study was carried out to make clear the difference of the results obtained from the pressure membrane method and the centrifuging method. Their differences were made clear to be about 1-2% at pF 2.5-3.0 and to be about 2-5% at pF 3.0-4.2