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ARS Home » Plains Area » Bushland, Texas » Conservation and Production Research Laboratory » Soil and Water Management Research » Research » Publications at this Location » Publication #270564
Title: Field tests of a down-hole TDR profiling water content measurement system

Author
item Casanova, Joaquin
item Evett, Steven - Steve
item Schwartz, Robert

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 7/19/2011
Publication Date: 10/18/2011
Citation: Casanova, J.J., Evett, S.R., Schwartz, R.C. 2011. Field tests of a down-hole TDR profiling water content measurement system [abstract]. ASA-CSSA-SSSA Annual Meeting Abstracts. Paper No. 243-6.

Interpretive Summary: Measuring the amount of water in soil is important in managing crop irrigation. Current methods of soil water estimation are limited by accuracy, precision, ease of installation and cost. This paper presents the results of field tests, a new sensor design.

Technical Abstract: Accurate soil profile water content monitoring at multiple depths has previously been possible only using the neutron probe (NP), but with great effort and at unsatisfactory intervals. Despite the existence of several capacitance systems for profile water content measurements, accuracy and spatial representativeness has been precluded by fundamental problems related to conductivity and soil structure effects on the volume explored by the static electromagnetic (EM) field of these sensors, which causes unrealistic spatial variation in profile water contents. Time domain reflectometry (TDR) methods have the distinct advantage of employing a moving EM field that must pass through and be affected by both the drier and wetter soil structures in which the TDR electrodes are embedded. This gives rise to the expectation that a profiling water content system based on TDR methods will provide realistic spatial variations in profile water content and may be competitive with the NP for accuracy, while providing unattended, real-time, wireless data acquisition. Such a system is described and results of field tests are reported.