An acoustic method for soil moisture measurement

The paper 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 sound in the medium: the main issue is therefore to determine a precise relationship between the two quantities. To this purpose, the Brutsaert´s model for elastic waves in porous media is applied, taking into consideration different kinds of soil of common interest in agriculture. The authors have derived the speed-moisture curves, 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. The paper results are therefore the basis to realize an inexpensive and accurate moisture sensor for farmers.