Application of Time Domain Transmissiometry to Coupled Measurements of Soil Moisture and Electrical Conductivity

Abstract

Time domain transmissiometry (TDT), a method of measuring transmitted broadband signal in microwave frequency, was used to measure volumetric water contents (θ) and liquid-phase electrical conductivities (σ_w) in sand. The θ and σ_w were determined independently with travel time and amplitude of impulse-signal transmission, although the determination of both θ and σ_w with saline sand (θ ≥ 0.32 m³ m^-3 for σ_w = 1.19 S m^-1) was difficult due to the loss of transmitted signals. Judging from the versatility and the simplicity of signal analyses, we believe that the TDT technique would be a more convenient method than time domain reflectometry (TDR) to monitor θ and σ_w in soils.