Field evaluation of the SoilVUE10 time domain reflectometry soil moisture profiling sensor under different installation methods

Accurate monitoring of soil profile water content is essential for agronomic and environmental applications. Time domain reflectometry (TDR) sensors estimate volumetric water content from bulk soil dielectric permittivity. The SoilVUE10 is a high-frequency TDR sensor designed to measure volumetric water content at multiple depths. However, its performance under varying soil types, irrigation systems, and installation methods is not well documented. We evaluated the performance of the 50-cm-long SoilVUE10 sensor at depths of 5, 10, 20, 30, 40, and 50 cm by comparison with gravimetric measurements and Acclima TDR (315H and 310S) estimates in two field experiments encompassing different soil types, irrigation systems (subsurface drip and flood irrigation), and sensor installation methods. Results showed that the performance of the SoilVUE10 in soils with high clay content (>22%) was strongly affected by installation method. In fine-textured soils (sandy clay and sandy clay loam), the manufacturer-recommended installation method under drip irrigation led to large underestimations, likely due to the formation of a thin compacted soil layer around the sensor waveguides, which impeded proper hydraulic contact between the soil and sensor. In soils with low clay content (sandy loam), the SoilVUE10, when installed using the manufacturer-recommended method under flood irrigation, showed slightly better agreement with gravimetric data (root mean square error [RMSE] 0.038 cm³ cm⁻³) than the Acclima TDR (RMSE = 0.044 cm³ cm⁻³) across all depths. Installation by auguring a larger borehole and backfilling with parent soil improved sensor-soil hydraulic contact and reduced the RMSE by 27% in soils with low clay content.