Design and validation of an IoT-enabled soil moisture sensor for precision agriculture

The research paper describe the soil moisture sensor in accordance with the field conditions and the capacity to measure soil moisture on a real-time basis. In this study, the Arduino-based soil moisture sensors with Copper-Based Probe (CBP) are introduced, which fit best with the conventional method for measuring soil moisture. The paper also presents a low-cost design, laboratory calibration, and field validation of an IoT-enabled resistive soil moisture sensor. The developed soil moisture sensor consists of a microcontroller ATmega328p, a resistive soil probe, an OLED display, a GPS, and LoRa WAN data transmission module integrated with IoT technology. The sensor was calibrated using a gravimetric method with nine steps of soil moisture content ranging from 0% to 40% in a clay-loam soil type. The laboratory calibration revealed linear equations in which ADC (-) 2.067, moisture (+) 1029.40, and voltage (-) 0.10083, Moisture (+) 5.020, with an R² value equal to 0.9996. Residual values of linear and quadratic equations are within (±) 0.15% and (±) 0.14%, respectively. For embedded irrigation systems, linear equations are sufficient and efficient, as quadratic equations are of little use. Thus, the developed soil moisture sensor shows satisfactory results in laboratory conditions. Preliminary field evaluation showed close agreement with gravimetric measurements, with deviations within (±) 1.2%, indicating promising field applicability. The developed IoT-enabled soil moisture sensor has great potential to play a vital role in data-driven irrigation management, to enhance resource use efficiency in precision agriculture.