On-site measurement of soil moisture content using an acoustic system

Abstract

Precision agriculture is a farming management concept based on observing and responding to intra-field variations.  One of the most important soil properties in farming is soil moisture content and it is necessary to develop new technique for measuring this property in a precision farming system.  This study investigates the measurement of moisture content in soil using an on-site, easy to use and real-time acoustic wave system.  The system consists of the propagation of acoustic waves such as sweep frequency sound wave (10-300 Hz) and multiple tone sound waves (120 Hz) through the soil.  Some properties of these acoustic waves enable estimation of soil water content such as peak amplitude (A), total power (TP), total harmonic distortion (THD) and signal to noise ratio (SNR).  The results showed that the best model for estimating the soil moisture content was the model that expressed relationship between A and soil moisture content with R² = 0.999 (using sweep frequency) and relationship between TP and soil moisture content with R² = 0.999 (using multiple tone).  It is argued that the change in the sound characteristics related to the soil moisture content can be used for a continuous monitoring and control of irrigation of crops.

Keywords: acoustic waves, soil moisture content, sound properties