TDR probes calibration in laboratory conditions

Abstract

Among the indirect methods to evaluate the volumetric soil water content (?v), the Time Domain Reflectometry (TDR) technique is receiving growing attention. As any technique, it presents advantages and disadvantages: the most serious disadvantage is the calibration necessity. At the present study, values of apparent dielectric constant (Ka) and volumetric water content (?v) for a Red Latosol were obtained in a laboratory experiment, using seventeen probes of TDR, from which two were original and fifteen were manufactured by the staff. This study aimed: a) to calibrate the seventeen probes, in laboratory conditions, comparing six regression models for each probe; b) to verify the viability to use the manufactured probes. It was found out that the best regression model was the cubic polynomial model and that the manufactured probes presented performances comparable to the original ones.