Towards pervasive soil moisture sensing using RFID tag antenna-based sensors

An RFID-based passive sensor for pervasive soil moisture monitoring is proposed. Variations in moisture cause a change in soil permittivity which in turn affects the impedance match/mismatch between the tag chip and the sensor probe. This manifests itself as a change in the RFID tag backscatter signal strength which can be detected at the reader. The concept is validated through a series of experiments conducted on sand and clay in two different settings. Variations in soil moisture content, as small as 20mL could be detected from a distance of 0.8 m.