An <i>in situ</i> probe‐spacing‐correction thermo‐TDR sensor to measure soil water content accurately

Abstract

Summary To reduce the possibility of probe deflections, conventional thermo‐time domain reflectometry (T‐TDR) sensors have relatively short probe lengths (≤4 cm). However, short probes lead to large errors in TDR‐estimated soil water content ( θ v ). In this study, two new 6‐cm‐long probe‐spacing‐correction T‐TDR (CT‐TDR) sensors were investigated. Compared with conventional 4‐cm‐long T‐TDR sensors, the 6‐cm‐long CT‐TDR sensors reduced errors in TDR‐estimated θ v . Errors in heat pulse (HP)‐estimated θ v because of probe deflections were reduced when linear or nonlinear probe‐spacing‐correction algorithms were implemented. The 6‐cm‐long CT‐TDR sensors provided more accurate θ v estimations than do the conventional 4‐cm‐long T‐TDR sensors. Highlights Short thermo‐TDR sensor has shortcomings in determining soil water content. Changes in thermo‐TDR probe spacing caused by deflections can be determined in situ . Correcting changed thermo‐TDR probe spacing determined soil water content accurately. The 6‐cm‐long thermo‐TDR sensors determined soil water content more accurately than 4‐cm‐long sensors.