Campus Units

Agronomy

Document Type

Article

Publication Version

Published Version

Publication Date

2012

Journal or Book Title

Soil Science Society of America Journal

Volume

76

Issue

6

First Page

1929

Last Page

1937

DOI

10.2136/sssaj2011.0361

Abstract

Time domain reflectometry (TDR) is a well-established electromagnetic technique used to measure soil water content. Time domain reflectometry sensors have been combined with heat pulse sensors to produce thermo-TDR sensors. Thermo-TDR sensors are restricted to having relatively short needles to accurately measure soil thermal properties. Short needle lengths, however, can limit the accuracy of the TDR measurement of soil water content. Frequency domain reflectometry (FDR) sensors are an alternative to TDR sensors that can provide an inexpensive measurement of soil water content. The objective of this study was to determine whether short FDR sensors can accurately measure soil water content. We designed and constructed a short FDR sensor. For four soil types across a range of water contents, temperatures, and salt contents, we measured soil dielectric spectra with the short FDR sensor. A vector network analyzer was used to obtain soil dielectric spectra in the 1-MHz to 3-GHz frequency range. The ideal frequency of a short FDR sensor is the frequency at which the permittivity is not altered by changing temperature or salt content. The 47- to 200-MHz range was an ideal frequency range for measuring soil water content, and 70 MHz was the frequency least influenced by temperature and salt content. The short FDR sensor provided quick, continuous, stable, and cheap measurements of soil water content. Because of the promising performance of the short thermo-FDR sensor in laboratory studies, sensors should be evaluated in future field studies.

Comments

This article is published as Xu, Jinghui, Xiaoyi Ma, Sally D. Logsdon, and Robert Horton. "Short, multineedle frequency domain reflectometry sensor suitable for measuring soil water content." Soil Science Society of America Journal 76, no. 6 (2012): 1929-1937. doi: 10.2136/sssaj2011.0361. Posted with permission.

Rights

Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.

Language

en

File Format

application/pdf

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