Basic study on water distribution measurement in soil using SLDV

The global shortage of water is becoming the realistic fear. Because agriculture water occupies most of the consumption of the water, a saving of the agriculture water is demanded. In particular, if the negative pressure difference irrigation method that can supply water from the underground is used, water supply can be reduced than the surface drip irrigation method. However, dynamic optimal control cannot be performed by soil moisture sensor because it is difficult to grasp the water distribution in the soil. Therefore the water distribution in the soil is measured using sound wave vibration in this study. This time, using a plant (Japanese mustard spinach) cultivated in commercial soil, volume water content was measured when the root of the plant absorbed water. From the experimental result, a change of the propagation velocity of sound and the change of volume water content in the soil were inversely proportional unlike the case of the sand, but it was revealed that an absorbing water state of the plant could be estimated from a change of the propagation velocity of sound.