Application of Time Domain Reflectometry to Soilless Substrate Moisture Measurement

Time Domain Reflectometry (TDR) technology was investigated for monitoring volumetric moisture content in soilless substrates used in container nursery production. Water desorption curves and TDR wave-traces were simultaneously derived for six soilless substrate source materials. Calibration curves for actual substrates were generated so that set points could be identified to allow automatic control of cyclic irrigation scheduling in real time. Good relationships with volumetric moistures were established and good control was obtained.