Soil moisture assessment by means of compressional and shear wave velocities: a theoretical analysis

This paper deals with the problem of measuring the moisture of agricultural soils by an accurate theoretical method valid for different kinds of soils in different physical conditions. In this work we propose a theoretical analysis based on the propagation of seismic waves in a complex medium as the agricultural soil is. Particularly we prove that the use of both compressional and shear waves simplifies the analysis (by reducing the number of parameters affecting the moisture measurement) and increases the accuracy of the assessment without increasing the computational charge. Moreover we have noticed that, to obtain a complete and accurate mathematical model, it is necessary to focus on the Z factor, which accounts for the influence of air and water content in the soil on the sound velocities. The aim is to demonstrate that velocity of propagation of compressional and shear waves are influenced differently for the different physical factors. Moreover, we will show that the Z factor has to be taken into account for this different dependence on parameters and microclimatic characteristics of the soil.