This Oral Presentation -
"EVALUATIONS OF DIELECTRIC SOIL MOISTURE SENSORS FOR IRRIGATION SCHEDULING" was presented as Topic 3 at:

International Symposium on Irrigation of Horticultural Crops, Estoril., Portugal 1999
Author:
Hanson, B.; Douglas, P. and Serrarens, D.

address
email address

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EVALUATIONS OF DIELECTRIC SOIL MOISTURE SENSORS FOR IRRIGATION SCHEDULINGS

Many different types of dielectric soil moisture sensors, generally classified as time-domain-reflectometry (TDR) and frequency-domain-reflectometry instruments, are now being promoted for irrigation scheduling. These devices were evaluated for their appropriateness for farm-level irrigation scheduling. Evaluation criteria were response and accuracy of instrument to changes in soil moisture content, ease of installation, ease of operation, and cost. The procedure consisted of installing these devices in a variety of soil textures and comparing their readings with soil moisture content measurements made with a neutron moisture meter calibrated for each site or soil samples, depending on instrument configuration. Eleven instruments have been evaluated thus far. Results show that most of the sensors were reasonably accurate in sandy soil, but in fine textured soil, their performance was inconsistent with very poor accuracy in some cases. However, the ThetaProbe was consistently accurate under a variety of soil types. A conclusion is that caution should used in purchasing these devices without first determining their site-specific behavior.