This study aimed to develop a non-destructive and fast methodology for measurements of soil electrical conductivity mostly based on Electromagnetic Induction (EM). Simultaneous Time-Domain Reflectometry (TDR) readings of bulk electrical conductivity (ECb) and water content by TDR probes were used as ground-truth data for calibration of the EM sensor and for the subsequent validation of the calibration equations. Calibration and validation of the EM sensor were carried out on three transects irrigated with water at three different salinity levels (FW, 3dSm-1 and 6dSm-1), allowing exploring a wide range of salinity values and distributions. Different calibration equations were obtained for the depth intervals of 0-20, 20-40 and 40-60 cm, respectively.
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In the first case, it was observed that the calibration parameters obtained for the transect irrigated with a water salinity corresponding to 6dSm-1 were suitable even to describe salinity behavior in the other two transects, thus implying that along that transect the EM and TDR sensors explored all the possible salinity variability existing in all the three transects. Validation was carried out for the depth interval 0-20 cm with direct EC measurements and EM readings in the same sites used for calibration but for different times and proved the predictive effectiveness of the calibration parameters. Finally, a calibration was also carried out for translating ECb values estimated by EM to the corresponding ECw (soil water EC) values.
