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ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Soil, Water & Air Resources Research » Research » Publications at this Location » Publication #210474

Title: Water content reflectometer calibration and field use

item Logsdon, Sally

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/8/2007
Publication Date: 11/8/2007
Citation: Logsdon, S.D. 2007. Water content reflectometer calibration and field use [CD-ROM]. In: ASA-CSSA-SSSA Annual Meeting Abstracts, Nov. 4-8, New Orleans, LA.

Interpretive Summary:

Technical Abstract: Automated soil water content can be used to help determine upward water movement from a shallow water table. Apparent permittivity determined from dielectric probes is related to more than soil water content for soils high in smectite clays. The purpose of this study was to calibrate and use CS616 water content reflectometers in high-smectite soils to assist in determining water movement up from the water table. The probes were installed at an angle centered around 30, 50, 70, and 90 cm depth at three positions on a low hill: summit, backslope, and toeslope. In addition we installed neutron access tubes, wells with automated well depth transducers, and thermocouples at the same depths as the CS616s. After harvest we removed undisturbed soil columns at the location of the probes for the 30, 50, and 70 cm depths. These were used for laboratory calibration across a range of water contents and temperatures. The temperature response was linear as a function of the square root of apparent permittivity. Different calibration equations were needed for each site and depth, but the calibrated data appeared reliable. The range of soil water was less at the toeslope position than summit or backslope positions because of water movement up from the shallow water table.