Calibration and field validation of smart soil moisture monitoring system

Agriculture is one of the crucial sectors of Pakistan’s economy – accounting for about 21% of GDP and engaging approximately 50% of work force and is the major source of livelihood of a substantial segment (67%) of population. Traditionally farmers use the classical methods for irrigation like flood irrigation, border irrigation, and furrow bed irrigation, which are less efficient and cause more water losses due to surface runoff and infiltration of water beyond the root zone of the crop. Furthermore, excessive pumping of water from the wells caused high consumption of energy. Due to lack of proper monitoring system for irrigation water management, farmers use more water than required water to the crop. High rate of water losses in irrigation systems is due to heterogeneity of soil in the agricultural field and water infiltration beyond the root zone of the crop.

This paper presents the calibration and field validation of soil moisture sensors for smart irrigation system using IoT (Internet of Things). Field soil samples were collected to calibrate soil moisture sensors. Different amount of water was added to oven-dried soil samples to create soil moisture variability and the voltage values of the capacitive soil moisture sensor were measured to establish a calibration curve. After the calibration of sensors, an array of soil moisture sensors was installed vertically to monitor soil moisture dynamics within the root zone of the crop. The Wi-Fi/LORA module is used to transfer the data to a cloud server at a frequency of 60sec/cycle. The data from the cloud server can be accessed via the mobile phone application “BLYNK”. Results show that the vertical dynamics of soil moisture were clearly measured by the smart soil moisture monitoring system at different depths. The calibrated sensors can be used for smart irrigation systems and can be easily adapted for different irrigation methods.