Measurement of soil water content and electrical conductivity by time domain reflectometry: a review

Non-destructive measurement of soil water content and electrical conductivity has been desired for many years. Recent development of time domain reflectometry (TDR) enables us to simultaneously obtain soil water content and electrical conductivity using a single probe with a minimal disturbance of soil. Research on water and solute transport in porous media using TDR has flourished in the last few years. In this review article, an overview of theoretical background for measuring water content and electrical conductivity is presented as well as characteristics of different types of probes. Limitations of applying TDR techniques to measuring soil water content and salinity are also addressed. The review is designed to equip other scientists and engineers with background information so that the development of TDR for studies on water and chemical movement can continue.