Calibration of the dielectric sensor ECH2O in two types of soil

Abstract

The ECH2O sensor (Decagon Devices, Inc.) is a low-cost dielectric probe, which is easily adapted to automatic data acquisition systems. However, to present satisfactory results, the sensor manufacturer recommends its calibration for soils with distinct characteristics of texture and salinity. The study aimed to calibrate the dielectric sensor ECH2O, model EC-10 for two types of soil with distinct textures, Quartzipsament and Cambisol. It was evaluated the sensor response to decreasing soil water content, measured by determining the mass of a known soil volume, using an electronic scale. The results showed that, when it is properly calibrated, the ECH2O sensor can perform adequately for soil water content measurements. For the Quartzipsament the ECH2O sensor presented a linear response to soil water content variation, according to the equation q = 0,0009x- 0,2778, where Q is the soil water content in m3 m-3 and x is the sensor voltage output in mV, with r2 = 0,9899. For the Cambisol the calibration equation was Q = 8,2890 x 10-6 x2 – 0,0106 x + 3,5291, with r2 = 0,9475.