Soil & Water Res., 2008, 3(4):199-214 | DOI: 10.17221/18/2008-SWR

Field and laboratory ad hoc calibrations of Virrib and ThetaProbe dielectric sensors for soil moisture measurementsOriginal Paper

František Doležal1, Tomáš Litschmann2, Jiří Kučera3, Jana Peterková1, Josef Zavadil1, Josef Vacek4, Pavel Pražák1, Eva Pilná1, Tomáš Bayer1, Marek Nechvátal1
1 Research Institute for Soil and Water Conservation, Prague, Czech Republic
2 AMET - Consortium Litschmann-Suchý, Velké Bílovice, Czech Republic
3 Environmental Measuring Systems, Brno, Czech Republic
4 Potato Research Institute Havlíčkův Brod Ltd., Havlíčkův Brod, Czech Republic

For the research of irrigation optimization and nitrate leaching it is important to know the short-term soil moisture variation during percolation episodes as well as its seasonal pattern. Dielectric soil moisture sensors Virrib (AMET - Consortium) and ThetaProbe ML2x (Delta-T) were used for this purpose over several years for measuring soil moisture content at hourly intervals in Valečov (49°38'40" N, 14°30'25" E, 461 m a.s.l.), Czech Republic, in a deep loamy Stagnosol soil underlain by weathered paragneiss. One-point field calibration was made each spring at the time of sensor installation over three (for Virribs) or two (for ThetaProbes) consecutive years by taking sensor readings and soil samples (at least one 100 cm3 core sample near to each sensor) in parallel. A supplementary check was then made in the laboratory by taking readings of individual sensors, inserted into pre-made loamy-sand mixtures with various moisture contents. During both the field calibration and the laboratory check, the readings were taken manually, using either the AMET hand-held meter or the EMS ModuLog datalogger. The results suggest that the average slope of the secondary Virrib calibration curve (defined as the plot of y = sensor readings in terms of moisture content vs. x = soil moisture content determined gravimetrically) is near to unity, but the offsets are quite large and vary from probe to probe. The axial zone of influence of the Virrib sensors is up to about 30 cm, as it follows from both laboratory and field observations. The results of the laboratory check of Virribs were biased, because the volume of the soil was not large enough and the soil had different dry bulk densities at different moisture contents. The field secondary calibration curve of ThetaProbes appears to be roughly linear, in contrast to the laboratory calibration curve, because of absence of very low moisture contents in the field. If the same calibration line is applied to several different depths, then its slope is statistically significantly lower then unity, due to the dependence of ThetaProbe readings on the soil bulk density. The overall accuracy of the sensors and its components due to different factors is estimated from the statistics of repeated measurements.

Keywords: Virrib; ThetaProbe; one-point; loam; loamy sand; zone of influence; bulk density; offset; FertOrgaNic

Published: December 31, 2008  Show citation

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Doležal F, Litschmann T, Kučera J, Peterková J, Zavadil J, Vacek J, et al.. Field and laboratory ad hoc calibrations of Virrib and ThetaProbe dielectric sensors for soil moisture measurements. Soil & Water Res. 2008;3(4):199-214. doi: 10.17221/18/2008-SWR.
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    References

    1. Cunnane C. (1989): Statistical distributions for flood frequency analysis. Operational Hydrology Report No. 33, WMO, Geneva.
    2. Delta-T (1999): ThetaProbe Soil Moisture Sensor, Type ML2x. User Manual ML2x-UM-1.21. Delta-T Devices Ltd., Cambridge.
    3. Doležal F., Vacek J., Zavadil J. (2005): Problems of potato growing and irrigation in highland regions of Czechia with regard to water resources protection. In: Integrated Land and Water Resources Management: Towards Sustainable Rural Development. Proc. (CD) 21st European Regional Conf. ICID, Frankfurt(Oder) and Słubice, May 15-19, 2005, ICID German National Committee, Müncheberg.
    4. Hazen A. (1930): Flood Flows. A Study of Frequency and Magnitudes. Wiley, New York. Cited after Cunnane (1989), who, however, indicates a wrong year of publication (1932).
    5. IUSS Working Group WRB (2007): World reference base for soil resources 2006. First update 2007. A framework for international classification, correlation and communication. World Soil Resources Reports No. 103, FAO, Rome. Available at http://www.fao.org/ag/agl/agll/wrb/doc/wrb2007_corr.pdf
    6. Klika J., Novák V., Gregor A. (eds) (1954): Handbook of Phytocenology, Ecology, Climatology and Soil Science. Nakladatelství Československé akademie věd, Praha. (in Czech)
    7. Kučera J., Doležal F., Vlčková M., Nechvátal M., Bayer T., Pražák P. (2007): Accuracy and reproducibility of readings of several dielectric soil moisture sensors tested in the laboratory. In: Proc. 2nd Int. Symp. Soil Water Measurement Using Capacitance, Impedance and Time Domain Transmission. October 28-November 2, 2007, Beltsville.
    8. Maidment D.R. (ed) (1993): Handbook of Hydrology. McGraw-Hill, New York.
    9. Miller J.D., Gaskin G.J. (2007): ThetaProbe ML2x. Principles of Operation and Applications. MLURI Technical Note. 2nd Ed. Macaulay Land Use Research Institute, Aberdeen. Available at http://www.macaulay.ac.uk/MRCS/pdf/tprobe.pdf. (accessed June 27, 2007)
    10. Muñoz-Carpena R. (2004): Field devices for monitoring soil water content. Extension Bulletin 343 of the Department of Agricultural and Biological Engineering, University of Florida. Available at http://edis.ifas.ufl. edu/AE266. (accessed April 24, 2008)
    11. Plauborg F.L., Battilani A., Doležal F., Mazurczyk W., Bízik J., Coutinho J., Hansen S. (2006): New strategies for potatoes growing compared with conventional systems. Results from the EU project FertOrgaNic "Improved organic fertiliser management for high nitrogen and water use efficiency and reduced pollution in crop systems" (QLK5-2002-01799). Deliverable D1_4, August 2006, 57 p. Available at www. fertorganic.org.
    12. Váša J. (1960): Soil moisture characteristics. Vodohospodársky časopis SAV, 8: 235-243. (in Czech)
    13. Zumr D., Dohnal M., Hrnčíř M., Císlerová M., Vogel T., Doležal F. (2006): Simulation of soil water dynamics in structured heavy soils with respect to root water uptake. Biologia, 61(Suppl. 19): S320-S323. Go to original source...

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