Calibração do sensor capacitivo EC-5 em um latossolo em função da densidade do solo

Abstract

In a non-destructive and instantaneous way, the determination of the water content in the soil facilitates the water management in the soil, as well as the understanding of the water dynamics in the soil. The objective of the study was to calibrate the ECH2O EC-5 (Decagon) capacitive sensor for a dystrophic Red Oxisol at different densities. The sensor was calibrated in the laboratory for soil densities: 1.10; 1.20; 1.25; 1.30 and 1.35 Mg m-3. The soil was saturated and oven dried at 40 °C at 2 hours intervals, waiting 1 hour for the samples to cool to room temperature. At each interval, the water content was determined by gravimetry and by the sensor. The results showed that the manufacturer’s standard calibration equation overestimates the soil water content by 38.4%. However, after calibration, for this soil, the sensor presented high accuracy in the estimation of soil water content. The results also demonstrated that the soil density influences the calibration of the sensors. Therefore, in order to obtain soil water content at different densities, the data collected in the field should be corrected for this soil by the following equation: θe = 0.652376 θo + 2.12808 ρs2 - 5.2077 ρs + 3.19237. This equation presents the coefficient of determination equal to 0.9488 and, for the worst case, an average accuracy of 0.024 m3 m-3.