Rapid laboratory calibration of time domain reflectometry using upward infiltration

We propose an upward infiltration method to calibrate a time domain reflectometry (TDR) system. The method is rapid, allows the soil to remain unchanged during the experiment, and provides hundreds of data points. Three experiments were conducted using 18.7-cm-long probes in soils of three textures (nine experiments total). Calibrations also were performed by packing soil cores with soil at progressively higher water contents. The data from the two methods were fitted using regression techniques to two published models of the dielectric constant-water content relationship. The results show that the calibration curves of all three soils, fitted simultaneously to replicate experiments, mere similar in shape and statistically the same. A single calibration curve, fitted simultaneously to the replicate experiments of the three soils, was compared with Topps equation and was statistically the same. The results support the conclusion that the upward infiltration method provides a fast and repeatable calibration method, consistent with conventional calibration.