Accuracy of capacitive sensors for estimating soil moisture in northeastern Brazil

Abstract

Commercial capacitive sensors are used to determinate soil moisture, but the probes can be expensive. The objective of this study was to calibrate the YL-69 sensor and compare its accuracy with two commercial ECH2O probes. The sensors were used to determinate soil moisture in an Entisol Orthent and an Oxisol Ustox, representative soils of Northeast Brazil. The greenhouse study was conducted at the Federal Rural University of Pernambuco, Northeast Brazil, with two soils (Entisol Orthent and Oxisol Ustox). The experimental plots consisted of 5 replicates of 5 L pots, daily soil moisture was monitored from saturation to air dried. The soil textural classes were determined using the hydrometer method and the textural triangle of the Brazilian classification. After calibration, the YL-69 sensor performed well in both soils, obtaining a coefficient of determination (R2) value > 0.90 and root mean square error (RMSE) ≤0.01 m3 m−3; however, this sensor did not perform well if not calibrated. As such, the YL-69 sensor performed as well as the EC-5 and 5TE probes. The low cost of the YL-69 sensor makes it an attractive replacement for the EC-5 and 5TE sensors in determining the water content in Entisol Orthent and Oxisol Ustox.