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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.

Show MeSH
Soil water conductivities Cw versus ε′ = Re(ε*) for linear and quadratic salinity index models for all moistening solutions. Solid lines represent Cw values calculated with the use of XS obtained from the slopes of Cb vs. ε′ linear relations.
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f4-sensors-12-10890: Soil water conductivities Cw versus ε′ = Re(ε*) for linear and quadratic salinity index models for all moistening solutions. Solid lines represent Cw values calculated with the use of XS obtained from the slopes of Cb vs. ε′ linear relations.

Mentions: On the left panel of Figure 4, the values of soil water electrical conductivity Cw for all tested soils are shown. The “linear model” phrase at the top of the figure means that the values of Cw were calculated with the assumption that the relation Cb vs. ε′ is linear as in the left panel of Figure 3. Possible quadratic effects are taken into account in the “quadratic model” elaborated in the next section. The straight lines on all graphs represent the values of Cw (these values are also written on the right side of the lines) calculated from Equation (7) with the use of the salinity index XS obtained from the regression equations from the left panel of Figure 3 and l values determined from the slopes of the regression lines from the right panel of Figure 3. Since the salinity index calculated from the slope of a straight line fitted through the data points obtained from the whole series of samples moistened to various water contents (to various values of ε′) by the same solution, the value of Cw is from definition independent of the water content (or ε′, equivalently). The errors of Cw, represented by the dashed lines, depend on the standard error of determination of XS as a slope of the fitted straight line and on the standard error of determination of slope l of the XS vs. CS relation.


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)

Soil water conductivities Cw versus ε′ = Re(ε*) for linear and quadratic salinity index models for all moistening solutions. Solid lines represent Cw values calculated with the use of XS obtained from the slopes of Cb vs. ε′ linear relations.
© Copyright Policy
Related In: Results  -  Collection

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

f4-sensors-12-10890: Soil water conductivities Cw versus ε′ = Re(ε*) for linear and quadratic salinity index models for all moistening solutions. Solid lines represent Cw values calculated with the use of XS obtained from the slopes of Cb vs. ε′ linear relations.
Mentions: On the left panel of Figure 4, the values of soil water electrical conductivity Cw for all tested soils are shown. The “linear model” phrase at the top of the figure means that the values of Cw were calculated with the assumption that the relation Cb vs. ε′ is linear as in the left panel of Figure 3. Possible quadratic effects are taken into account in the “quadratic model” elaborated in the next section. The straight lines on all graphs represent the values of Cw (these values are also written on the right side of the lines) calculated from Equation (7) with the use of the salinity index XS obtained from the regression equations from the left panel of Figure 3 and l values determined from the slopes of the regression lines from the right panel of Figure 3. Since the salinity index calculated from the slope of a straight line fitted through the data points obtained from the whole series of samples moistened to various water contents (to various values of ε′) by the same solution, the value of Cw is from definition independent of the water content (or ε′, equivalently). The errors of Cw, represented by the dashed lines, depend on the standard error of determination of XS as a slope of the fitted straight line and on the standard error of determination of slope l of the XS vs. CS relation.

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