Despite the increased use of time domain reflectometry (TDR) for measurement of soil water content and bulkelectrical conductivity (BEC), there are few public releases of software for TDR system control. Even though graphicalinterpretation of the waveform to find pulse travel times is key to success with the method, the few published descriptionsof computer methods are incomplete. The TACQ program, under development since the early 1990s on a wide variety ofsoils, allows control of multiplexed systems supporting up to 256 TDR probes. Waveform interpretation methods are user-controlledand allow interpretation using various methods reported in the literature or methods available only in TACQ.The default methods allow automatic interpretation of waveforms from a variety of media including loose, air-dry soil,and wet clay. The present study shows that interpretation methods can have a large effect on reported water contents. Theadditive effects can result in water content change errors as large as 0.08 m 3 m 3 as the soil wets and dries, and as TDRsystem temperature changes over a season. Thus, the interpretation methods used should be reported in rigorous studiesinvolving TDR water content determination, calibration, and temperature effects. The TACQ program, anddocumentation, may be downloaded from http://www.cprl.ars.usda.gov/programs/.
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Steven R. Evett (2000) studied this question.