Temperature calibration of capacitance probes to measure soilless substrate water

Dielectric sensors have been widely used for nondestructive determination of volumetric water content. Previous work has shown that temperature can affect these sensors, but relatively little has been done to correct these effects. This study evaluated a new probe (ECH₂O EC-5 sensor) in terms of changing soilless substrate actual water content and temperature. To demonstrate the importance of temperature calibration, a calibration equation combing the temperature, the output of probe and the slope values of linear response to temperature depended on apparent water content was developed and analyzed the effect of increasing substrate temperature on the output of probe. We found that the EC-5 probe output increased when temperature was increased at fixed water content. Measurements in four soilless substrates demonstrated that the accurate of ECH₂O EC-5 probes increase to 90% at least after calibration. The sensor can be useful for accurate measurements of soilless substrate water content.