אסיף מאגר המחקר החקלאי

A review of advances in dielectric and electrical conductivity measurement in soils using time domain reflectometry

Year:

2003

Source of publication :

Authors :

Volume :

2

Co-Authors:

Robinson, D.A., U.S. Salinity Laboratory, USDA-ARS, 450 W. Big Springs Road, Riverside, CA 92507, United States
Jones, S.B., Dep. Plants, Soils and Biometeorology, Utah State University, Logan, UT 84322-4820, United States
Wraith, J.M., Land Resources and Environmental Sciences Dep, Montana State University, Bozeman, MT 59717-3120, United States
Or, D., Dep. of Civil and Environmental Engineering, University of Connecticut, 261 Glenbrook Road, Unit 2037, Storrs, CT06269, United States
Friedman, S.P., Institute of Soil, Water and Environmental Sciences, The Volcani Center (ARO), Bet Dagan 50250, Israel

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Abstract:

Substantial advances in the measurement of water content and bulk soil electrical conductivity (EC) using time domain reflectometry (TDR) have been made in the last two decades. The key to TDR's success is its ability to accurately measure the permittivity of a material and the fact that there is a good relationship between the permittivity of a material and its water content. A further advantage is the ability to estimate water content and measure bulk soil EC simultaneously using TDR. The aim of this review is to summarize and examine advances that have been made in terms of measuring permittivity and bulk EC. The review examines issues such as the effective frequency of the TDR measurement and waveform analysis in dispersive dielectrics. The growing importance of both waveform simulation and inverse analysis of waveforms is highlighted. Such methods hold great potential for obtaining far more information from TDR waveform analysis. Probe design is considered in some detail and practical guidance is given for probe construction. The importance of TDR measurement sampling volume is considered and the relative energy storage density is modeled for a range of probe designs. Tables are provided that compare some of the different aspects of commercial TDR equipment, and the units are discussed in terms of their performance and their advantages and disadvantages. It is hoped that the review will provide an informative guide to the more technical aspects of permittivity and EC measurement using TDR for the novice and expert alike. © Soil Science Society of America.

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