Method for Calibrating an Arduino-based Soil Moisture Sensor Using van Genuchten’s Equation

Calibrating an Arduino-based Soil Moisture Sensor

Abstract

Instructions on building a do-it-yourself soil moisture sensor using Arduino microcontrollers abound on the Internet. These do-it-yourself soil moisture sensors are favorite projects by both plant and microcontroller enthusiasts because the parts are affordable and the end product is functional. In the absence of proper calibration, these soil moisture sensors cannot generate usable information on the status of plant-availablewater in the soil. This research demonstrates the calibration of an Arduino-based soil moisture sensor using the soil moisture characteristic curve of a clay loam soil. Van Genuchten’s model was used to generate an equation and various parameters specific to the soil. An acceptable correlation was achieved between the soil volumetric moisture content and raw sensor value, with an R² = 0.63. A highly significant result was achieved on the correlation between the actual and predicted soil moisture tension with a Mean Absolute Percentage Error (MAPE) of 7.5% and a p-value of less than the alpha value of 0.05. It is recommended that the technique demonstrated in this research be used by other researchers working on a similar setup.