TDR method monitors soil moisture by measuring the transmission time of electromagnetic pulse in soil medium. When measuring soils with high organic carbon content and especially high or low density, the energy dissipation of the input electromagnetic wave is large, which results in the ambiguity of the reflected information and the distortion of the data. In the process of measuring high salinity soil, salt attenuates the reflected pulse signal, affects the pulse reflection time, and affects the monitoring of soil moisture content.
Salinization of soils leads to an increase in apparent permeability in the frequency range of TDR and to an overestimation of the moisture values measured by the TDR sensor. This increase is highly dependent on the clay content in the soil and other factors. Therefore, for reliable measurement of moisture, it is necessary to pre-calibrate the TDR sensor by comparing its readings with the moisture values found by the thermogravimetric method. With great salinization, the TDR may not work due to strong pulse attenuation.
Please see the following paper:
- DOI: 10.1111/j.1365-2389.1997.tb00555.x
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