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. 2016 Nov 15;16(11):1912.
doi: 10.3390/s16111912.

Laboratory Performance of Five Selected Soil Moisture Sensors Applying Factory and Own Calibration Equations for Two Soil Media of Different Bulk Density and Salinity Levels

Svatopluk Matula  1 , Kamila Báťková  2 , Wossenu Lemma Legese  3   4
Affiliations

Laboratory Performance of Five Selected Soil Moisture Sensors Applying Factory and Own Calibration Equations for Two Soil Media of Different Bulk Density and Salinity Levels

Svatopluk Matula et al. Sensors (Basel). .

Abstract

Non-destructive soil water content determination is a fundamental component for many agricultural and environmental applications. The accuracy and costs of the sensors define the measurement scheme and the ability to fit the natural heterogeneous conditions. The aim of this study was to evaluate five commercially available and relatively cheap sensors usually grouped with impedance and FDR sensors. ThetaProbe ML2x (impedance) and ECH₂O EC-10, ECH₂O EC-20, ECH₂O EC-5, and ECH₂O TE (all FDR) were tested on silica sand and loess of defined characteristics under controlled laboratory conditions. The calibrations were carried out in nine consecutive soil water contents from dry to saturated conditions (pure water and saline water). The gravimetric method was used as a reference method for the statistical evaluation (ANOVA with significance level 0.05). Generally, the results showed that our own calibrations led to more accurate soil moisture estimates. Variance component analysis arranged the factors contributing to the total variation as follows: calibration (contributed 42%), sensor type (contributed 29%), material (contributed 18%), and dry bulk density (contributed 11%). All the tested sensors performed very well within the whole range of water content, especially the sensors ECH₂O EC-5 and ECH₂O TE, which also performed surprisingly well in saline conditions.

Keywords: Frequency Domain Reflectometry (FDR); bulk density; comparison; factory calibration; impedance; own calibration; performance; salinity; sand; soil; water content sensors.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
ThetaProbe scheme and dimensions [33].
Figure 2
Figure 2
Scheme of tested soil water sensors from the ECH2O family (Decagon Devices Inc., Pullman, WA, USA).
Figure 3
Figure 3
Graphical comparison of the real volumetric water contents obtained on the basis of the gravimetric method and volumetric water contents measured by ThetaProbe using factory and our own linear and polynomial calibration equations.
Figure 4
Figure 4
Graphical comparison of the real volumetric water contents obtained on the basis of gravimetric method and volumetric water contents measured by the sensors from the ECH2O family using factory and our own linear calibration equations.
Figure 5
Figure 5
Performance of all tested sensors for three rounds of saline water applications for a sand media and compact packing using factory and our own linear calibration equations.
Figure 6
Figure 6
Real and measured volumetric water contents determined by ECH2O EC-5 for all three rounds of the drying/wetting cycle with saline water application with an indication of a reference line that was based on non-saline water application.
Figure 7
Figure 7
Sensor performance comparison based on RMSE (vol %) values for saline conditions.
Figure 8
Figure 8
ThetaProbe—means and 95.0% LSD intervals of analysis of variance for RMSE and calibration type.
Figure 9
Figure 9
ThetaProbe—means and 95.0% LSD intervals of analysis of variance for RMSE and packing.
Figure 10
Figure 10
Sensors from the ECH2O family—sensor performance comparison based on RMSE (vol %) values for factory and our own calibrations.
Figure 11
Figure 11
Sensors from the ECH2O family—sensor performance comparison based on RMSE (vol %) values for different dry bulk density levels.
Figure 12
Figure 12
Factory and our own calibration comparison based on RMSE (vol %) values for saline conditions.
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References

    1. Robinson D.A., Jones S.B., Wraith J.M., Or D., Friedman S.P. A review of advances in dielectric and electrical conductivity measurement in soils using Time Domain Reflectometry. Vadose Zone J. 2003;2:444–475. doi: 10.2136/vzj2003.4440. - DOI
    1. Walker J.P., Willgoose G.R., Kalma J.D. In situ measurement of soil moisture: A comparison of techniques. J. Hydrol. 2004;293:85–99. doi: 10.1016/j.jhydrol.2004.01.008. - DOI
    1. Bogena H.R., Huisman J.A., Oberdörster C., Vereecken H. Evaluation of a low-cost soil water content sensor for wireless network applications. J. Hydrol. 2007;344:32–42. doi: 10.1016/j.jhydrol.2007.06.032. - DOI
    1. Roth C.H., Malicki M.A., Plagge R. Empirical evaluation of the relationship between soil dielectric constant and volumetric water content as the basis for calibrating soil moisture measurements by TDR. J. Soil Sci. 1992;43:1–13. doi: 10.1111/j.1365-2389.1992.tb00115.x. - DOI
    1. Topp G.C., Davis J.L., Annan A.P. Electromagnetic determination of soil water content: Measurements in coaxial transmission lines. Water Resour. Res. 1980;16:574–582. doi: 10.1029/WR016i003p00574. - DOI

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