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United States Department of Agriculture

Agricultural Research Service

Title: Soil Water Measurement by Time Domain Reflectometry

Author
item Evett, Steven

Submitted to: Encyclopedia of Water Science
Publication Type: Book / Chapter
Publication Acceptance Date: December 11, 2001
Publication Date: August 1, 2003
Citation: EVETT, S.R. SOIL WATER MEASUREMENT BY TIME DOMAIN REFLECTOMETRY. STEWART, B.A., HOWELL, T.A., EDITORS. MARCEL-DEKKER, INC., NEW YORK, NY. ENCYCLOPEDIA OF WATER SCIENCE. 2003. P. 894-898.

Interpretive Summary: This encyclopedia article describes the time domain reflectometry (TDR) for soil water content measurement. Details of principles, theory, accuracy and repeatability are given. Equipment and its use and capabilities are described, including unique features of TDR that make it useful in studies of how plants take up water from the soil, studies of water movement into the soil from rainfall and irrigation or water loss from the soil due to evaporation, and studies of soil salt content. The article will be a useful reference for scientists, engineers and agricultural consultants needing an introduction to the use of TDR to accurately measure water content in a variety of agricultural and non-agricultural situations.

Technical Abstract: The time domain reflectometry (TDR) method for soil water content measurement is described. Principles, theory, accuracy and repeatability are discussed. Equipment and its use and capabilities are concisely described. Theoretical and empirical calibrations are discussed. Volume of measurement is discussed, and how this may be changed is described. Also, presented are unique features of TDR that make it useful in studies of how plants take up water from the soil, and studies of water movement into the soil from rainfall and irrigation or water loss from the soil due to evaporation. The use of TDR for measurement of bulk electrical conductivity is discussed. The chapter will be a useful reference for scientists, engineers and agricultural consultants needing an introduction to the use of TDR to accurately measure water content in a variety of agricultural and non-agricultural situations.

Last Modified: 7/12/2014
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