ZUPANC, V. in sod.: Comparison of laboratory TDR soil water measurements
373
4 CONCLUSIONS
TDR 100 Reflectometer measurements were compared to gravimetrically determined
soil VWC, the latter taken as a standard (Topp and Ferré, 2002). During the
experiment the importance of waveguide form interpretation and determination was
shown to be of extreme importance, which agrees with findings of Evett (2001) and
Noborio (2001). Manual interpretation of waveguide’s form enabled better readings,
adapting the analysis to each reading.
TDR 100 10 cm rods gave better results in both Clay Loam and Silt Loam soil,
comparing to 20 cm results, which underestimated VWC. The difference can be
contributed to the fact that shorter rods are more suitable for soil VWC measurements,
due to their form, length and rod distance (Noboria, 2001). All TDR 100
Reflectometer measurements showed substantially higher VWC in Sand soil as
Gravimetric method.
The results comparison of soil VWC measurements showed differences between
original steel rods and homemade steel rods to be minimal and negligible. The one
exception were 10 cm rods measurements in Silt Loam soil.
5 REFERENCES
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Chandler, D.G., Seyfried, M., Murdock, M. and McNamara, J.P. 2004. Field Calibration of
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Noborio, K. 2001. Measurement of soil water content and electrical conductivity by time
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