Sonic Sensor for Soil Moisture Measurement

The work deals with the problem of measuring the moisture of agricultural soils by an accurate, on-site, real-time method. The idea is to estimate the moisture by measuring the speed of propagation of seismic waves in the medium applying a new model based on both compressional and shear waves velocity measurement. In a previous paper, starting from the Brutsaert's model for elastic waves propagation in unconsolidated, unsaturated, granular and porous medium, the authors derived the relationship between compressional wave’s speed and moisture content for various kind of soils; they also derived the conditions for the actual validity of the curves and the suitable sound frequency for performing the measurement, for a wide range of agricultural soils in different physical conditions. In this paper, the use of shear wave velocity is proposed aiming to increase the accuracy of moisture estimation and to reduce the number of soil parameters affecting the measurement without increasing the computational charge. Finally, using the results obtained they propose a portable, accurate and very cheap sensor for farmers.