Evaluation of the performance of soil moisture sensors in laboratory-scale lysimeters

Abstract

Soil moisture sensors were evaluated in laboratory-scale lysimeters. The performances of tensiometers, granular matrix sensors (GMS), capacitance sensors, phase transmission sensors, and of a portable capacitance probe and a frequency-domain reflectometry (FDR) sensor was observed in loam (31.5% sand, 45.2% silt, and 23.1% clay) and silt loam (20% sand, 54% silt, and 26% clay) of the Ramada Series. The experiment was conducted over two drying cycles in loam for moisture contents decreasing from 34.0 to 17.0% by volume for the 1999 trial and decreasing from 43.1 to 20.0% by volume for the 2000 trial and over a single drying cycle in silt loam for moisture decreasing from 45.8 to 19.5% by volume. The lysimeters were designed with hydraulic weighing systems to facilitate continuous monitoring of the soil moisture content. A conversion equation was developed, based on texture-specific calibration curves published by the manufacturer, to calibrate the readings of the Aqua-Tel sensors. The procedure followed for converting the readings of the Aquaterr probe was also partially developed by the experimenter to obtain more accuracy. (Abstract shortened by UMI.)