Performance evaluation of automatic irrigation using capacitive probe soil moisture sensors

Abstract

Automatic irrigation systems play a crucial role in optimizing water usage and improving agricultural productivity. A solar powered smart irri-kit was established at Makerere University Agricultural Institute Kabanyolo with resistive soil moisture sensors to increase water use efficiency; however, susceptibility of these sensors to electrolytic dissolution questions its sustainability in precision irrigation. The resistive sensors are connected to the Microcontroller Unit by USB cables which limits expansion of the smart farm. This study aimed at evaluating the irri-kit’s performance with capacitive probe soil moisture sensors. The specific objectives included sensor calibration for accuracy, validation for consistency and building a wireless sensor network for sensor flexibility and mobility. The sensors were calibrated by gravimetric method and their results validated by comparing soil moisture readings by the irri-kit with gravimetric method. A Wireless Sensor Network was built using HC-05 Bluetooth modules in a single-slave Personal Area Network with breadboards, resistors, jumper wires and a potentiometer. The calibration gave an R2 value of 0.5996. A p value of 0.091 from a two-tailed t-test on validation data was obtained. Data transmission through the piconet was slow. This study contributes to advancement, development and adoption of sensor-based irrigation technologies in irrigated agriculture to optimize water usage, facilitate on-farm water conservation and farm expansion.