Design of an acoustic soil moisture sensor to measure over a relatively larger coverage

Abstract

Water is among the resources that have to be managed if the world is to achieve Sustainable Development Goal 6; Clean water and sanitation. One of the means of managing water in agriculture is through the use of smart irrigation practices. However, these are not without their limitations, one of which is limited area of coverage of most sensor systems employed currently. The objective of this study was to address this limitation by design, assembly and operationalization of a sound-based soil moisture sensor. The principle and design of the sensor was based on earlier models identified through literature review. Components were identified and assembled in a workshop, and field tests were carried out at Makerere University Agricultural Research Institute Kabanyolo. Calibration was done on-site dependent on soil characteristics obtained by literature review. Readings were visualized for comparison for consistency with existing models. Post-testing, the prototype was able to achieve a 90% (1 meter) increase in the coverage as compared to watermark and tensiometer sensors (0.05m to 0.1m), with potential for even greater distances upon transmitter modification. The study thus presents an opportune candidate for deployment of a wide-area coverage sensor on agricultural fields for soil moisture monitoring and integration with smart irrigation systems. With appropriate modifications, this system could easily be applied to rural and remote areas, with a lower number of units per area of field.