Performance Analysis of Capacitive Sensors for Continuous Soil Moisture Measurement

Accurate soil moisture data is fundamental for improving management of water and soil resources in rainfed agrosystems and water and energy saving in irrigated schemes. Having an effective tool to measure the soil moisture content is essential to assist farmers and water users towards better agricultural water management. The soil moisture can be measured using gravimetric measurement which is one of the most accurate methods, however, it is soil destructive and doesn’t give up-to-date data. A variety of indirect methods which use soil moisture sensors installed in the plot at different depths are available on the market. They measure the soil water content frequently and continuously. However, their cost is high and the evaluation of their performance is needed. The present study aims to provide an analysis of the performance of the Sentek Drill and Drop probe capacitive sensors. We analyzed datasets from in-situ measurements under two various climatic and soil conditions within rainfed and irrigated agrosystems in Tunisia. The soil moisture values were calculated using the calibration curve parameters from the supplier when available, and site-specific soil calibration procedures were performed. Results indicated that soil moisture at the upper layers shows larger dynamics than the soil moisture at deeper layers. The results of this baseline study indicated a clear correlation between the soil temperature, the soil salinity, gravimetric soil moisture content and the soil moisture content data provided by the Sentek Drill and Drop capacitive sensors. It is, therefore, necessary to deepen our analysis of these correlations before concluding on the performance of the capacitive sensors.