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Determination of soil pore water salinity using an FDR sensor working at various frequencies up to 500 MHz.

Wilczek A, Szypłowska A, Skierucha W, Cieśla J, Pichler V, Janik G - Sensors (Basel) (2012)

Bottom Line: The soil salinity status was determined using the salinity index, defined as a partial derivative of the soil bulk electrical conductivity with respect to the real part of the soil complex dielectric permittivity.For the five sandy mineral soils that have been tested, the relationship between bulk electrical conductivity and the real part of dielectric permittivity is essentially linear.As a result, the salinity index method applied for FDR measurements may be adapted to field use after examination of loam and clayey soils.

View Article: PubMed Central - PubMed

Affiliation: Institute of Agrophysics, Polish Academy of Sciences, ul. Doświadczalna 4, 20-290 Lublin, Poland. a.wilczek@ipan.lublin.pl

ABSTRACT
This paper presents the application of a frequency-domain reflectometry (FDR) sensor designed for soil salinity assessment of sandy mineral soils in a wide range of soil moisture and bulk electrical conductivity, through the determination of soil complex dielectric permittivity spectra in the frequency range 10-500 MHz. The real part of dielectric permittivity was assessed from the 380-440 MHz, while the bulk electrical conductivity was calculated from the 165-325 MHz range. The FDR technique allows determination of bulk electrical conductivity from the imaginary part of the complex dielectric permittivity, without disregarding the dielectric losses. The soil salinity status was determined using the salinity index, defined as a partial derivative of the soil bulk electrical conductivity with respect to the real part of the soil complex dielectric permittivity. The salinity index method enables determining the soil water electrical conductivity value. For the five sandy mineral soils that have been tested, the relationship between bulk electrical conductivity and the real part of dielectric permittivity is essentially linear. As a result, the salinity index method applied for FDR measurements may be adapted to field use after examination of loam and clayey soils.

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Determination of bulk electrical conductivity of a sample of soil no. 601 wetted with distilled water to 50% of saturation water content; Cb is directly proportional to the intercept, according to Equation (5). The regression equation, R2 and standard error of regression are given on the plot. The standard error of determination of Cb is about 2%.
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f2-sensors-12-10890: Determination of bulk electrical conductivity of a sample of soil no. 601 wetted with distilled water to 50% of saturation water content; Cb is directly proportional to the intercept, according to Equation (5). The regression equation, R2 and standard error of regression are given on the plot. The standard error of determination of Cb is about 2%.

Mentions: Assuming that εd is not frequency dependent in the analyzed frequency range up to 500 MHz, one can find the values of Cb by fitting a straight line into a plot of the above function, as shown in Figure 2. The regression equation, coefficient of determination R2 and standard error of regression σ, defined as the square root of the sum of the squared residuals divided by the number of degrees of freedom, were presented on the graph. To calculate bulk electrical conductivity with the artifacts removed, frequencies from 165 to 180 and from 245 to 325 MHz were selected. In this frequency range, which is narrow enough and distant from relaxation frequencies of various polarization mechanisms which may occur in the tested soils, the assumption that the dielectric loss εd does not depend on frequency is reasonable and gives good fits, as presented by the example in Figure 2.


Determination of soil pore water salinity using an FDR sensor working at various frequencies up to 500 MHz.

Wilczek A, Szypłowska A, Skierucha W, Cieśla J, Pichler V, Janik G - Sensors (Basel) (2012)

Determination of bulk electrical conductivity of a sample of soil no. 601 wetted with distilled water to 50% of saturation water content; Cb is directly proportional to the intercept, according to Equation (5). The regression equation, R2 and standard error of regression are given on the plot. The standard error of determination of Cb is about 2%.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472864&req=5

f2-sensors-12-10890: Determination of bulk electrical conductivity of a sample of soil no. 601 wetted with distilled water to 50% of saturation water content; Cb is directly proportional to the intercept, according to Equation (5). The regression equation, R2 and standard error of regression are given on the plot. The standard error of determination of Cb is about 2%.
Mentions: Assuming that εd is not frequency dependent in the analyzed frequency range up to 500 MHz, one can find the values of Cb by fitting a straight line into a plot of the above function, as shown in Figure 2. The regression equation, coefficient of determination R2 and standard error of regression σ, defined as the square root of the sum of the squared residuals divided by the number of degrees of freedom, were presented on the graph. To calculate bulk electrical conductivity with the artifacts removed, frequencies from 165 to 180 and from 245 to 325 MHz were selected. In this frequency range, which is narrow enough and distant from relaxation frequencies of various polarization mechanisms which may occur in the tested soils, the assumption that the dielectric loss εd does not depend on frequency is reasonable and gives good fits, as presented by the example in Figure 2.

Bottom Line: The soil salinity status was determined using the salinity index, defined as a partial derivative of the soil bulk electrical conductivity with respect to the real part of the soil complex dielectric permittivity.For the five sandy mineral soils that have been tested, the relationship between bulk electrical conductivity and the real part of dielectric permittivity is essentially linear.As a result, the salinity index method applied for FDR measurements may be adapted to field use after examination of loam and clayey soils.

View Article: PubMed Central - PubMed

Affiliation: Institute of Agrophysics, Polish Academy of Sciences, ul. Doświadczalna 4, 20-290 Lublin, Poland. a.wilczek@ipan.lublin.pl

ABSTRACT
This paper presents the application of a frequency-domain reflectometry (FDR) sensor designed for soil salinity assessment of sandy mineral soils in a wide range of soil moisture and bulk electrical conductivity, through the determination of soil complex dielectric permittivity spectra in the frequency range 10-500 MHz. The real part of dielectric permittivity was assessed from the 380-440 MHz, while the bulk electrical conductivity was calculated from the 165-325 MHz range. The FDR technique allows determination of bulk electrical conductivity from the imaginary part of the complex dielectric permittivity, without disregarding the dielectric losses. The soil salinity status was determined using the salinity index, defined as a partial derivative of the soil bulk electrical conductivity with respect to the real part of the soil complex dielectric permittivity. The salinity index method enables determining the soil water electrical conductivity value. For the five sandy mineral soils that have been tested, the relationship between bulk electrical conductivity and the real part of dielectric permittivity is essentially linear. As a result, the salinity index method applied for FDR measurements may be adapted to field use after examination of loam and clayey soils.

Show MeSH
Related in: MedlinePlus