Measurement of the Dielectric Properties of Wyoming Soils Using Electromagnetic Probes.

Accurate soil water content estimates are important for agricultural water management, ecosystem studies, and climate research. Electromagnetic techniques for measuring soil water content are fast, safe, non-destructive, and easily automated. The relationship between the measured dielectric properties of the soil and the soil water content depends on the frequency of the applied stimulus, soil structure, soil texture, clay mineralogy, and the ion composition of the soil water. In this work we related the dielectric properties of 18 Wyoming soils to soil water content through a laboratory calibration using Time Domain Reflectometry (TDR), a Water Content Reflectometer (WCR), and a Hydra probe. Measurement frequency and the ability to distinguish between real and imaginary permittivity were important factors in explaining the observed differences in the permittivity versus water content relationship for the different probes.