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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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Conductivities of the moistening solutions calculated from the linear salinity index model vs. assumed conductivities for all tested soils. The straight line has a slope equal to 1 and corresponds to the perfect agreement.
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f5-sensors-12-10890: Conductivities of the moistening solutions calculated from the linear salinity index model vs. assumed conductivities for all tested soils. The straight line has a slope equal to 1 and corresponds to the perfect agreement.

Mentions: The results can be then compared with CS assumed from the molarity of the solutions (Table 2). The values corresponding to distilled water are equal to zero from definition. The results, calculated for the salinity index obtained as a slope of Cb vs. ε′ relation (linear model), are presented in Figure 5. The values of R2 and the standard errors σ presented in the figure describe how well the assumed values of CS explain the calculated quantities. As can be seen from the values, the agreement is very good. The worst case is soil no. 568, which exhibits both high errors in the calculated CS, as shown by the error bars, and the worst fit for the assumed values. The best case is soil no. 605, which has 95% sand fraction. This occurrence, along with the errors of Cw presented in Figure 4, shows that the salinity index method is generally the most reliable for soils with the highest sand content. Because the calculated electrical conductivities of the moistening solutions have been determined from linear model, the values corresponding to distilled water are equal to zero from definition


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)

Conductivities of the moistening solutions calculated from the linear salinity index model vs. assumed conductivities for all tested soils. The straight line has a slope equal to 1 and corresponds to the perfect agreement.
© Copyright Policy
Related In: Results  -  Collection

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

f5-sensors-12-10890: Conductivities of the moistening solutions calculated from the linear salinity index model vs. assumed conductivities for all tested soils. The straight line has a slope equal to 1 and corresponds to the perfect agreement.
Mentions: The results can be then compared with CS assumed from the molarity of the solutions (Table 2). The values corresponding to distilled water are equal to zero from definition. The results, calculated for the salinity index obtained as a slope of Cb vs. ε′ relation (linear model), are presented in Figure 5. The values of R2 and the standard errors σ presented in the figure describe how well the assumed values of CS explain the calculated quantities. As can be seen from the values, the agreement is very good. The worst case is soil no. 568, which exhibits both high errors in the calculated CS, as shown by the error bars, and the worst fit for the assumed values. The best case is soil no. 605, which has 95% sand fraction. This occurrence, along with the errors of Cw presented in Figure 4, shows that the salinity index method is generally the most reliable for soils with the highest sand content. Because the calculated electrical conductivities of the moistening solutions have been determined from linear model, the values corresponding to distilled water are equal to zero from definition

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