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ARS Home » Pacific West Area » Boise, Idaho » Northwest Watershed Research Center » Research » Publications at this Location » Publication #168373

Title: measurement of soil water content in the field

item Seyfried, Mark

Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 2/19/2004
Publication Date: 4/27/2004
Citation: Seyfried, M.S., 2004. Measurement of soil water content in the field, relative merits of newer sensors. Abstract H33B-02, In: EOS Transactions, v. 85(17) supplement, American Geophysical Union, CD-ROM abstract

Interpretive Summary:

Technical Abstract: Measurement of soil water content is a critical component of much hydrologic research that also has important practical applications. The combination of advances in electronics and the success of time domain reflectometry (TDR) has lead to the development of numerous new, relatively inexpensive soil water sensors, most of which are based on soil dielectric properties and therefore claim to be 'like TDR'. Unfortunately, published research has not kept pace with instrument development so that choice of instruments is often based on limited information concerning instrument accuracy and precision. We discuss the merits of TDR relative to other, non electronic approaches. We then discuss, in a general manner, some advantages and disadvantages of the newer dielectric sensors relative to TDR. These relative advantages are fundamentally related to differences in measurement frequency, which is much lower for the newer sensors (usually 50 to 100 MHz) than for TDR (1 GHz). Although current understanding of soil dielectric properties as a function of measurement frequency is evolving, some generalizations related to calibration and temperature sensitivity are established. It is clear, for example, that the optimal choice of sensors depends on site soil properties in addition to other experimental considerations. We also address issues related to calibration, field variability and installation considerations.