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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
Real and imaginary parts of the complex dielectric permittivity of a sample of soil no. 601 wetted with distilled water to approximately 50% of saturation water content.
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f1-sensors-12-10890: Real and imaginary parts of the complex dielectric permittivity of a sample of soil no. 601 wetted with distilled water to approximately 50% of saturation water content.

Mentions: The FDR measurement technique allowed determining the real and imaginary parts of the dielectric permittivity directly and independently. Figure 1 presents the real and imaginary parts of the dielectric permittivity measured for a sample of soil no. 601 wetted with distilled water to approximately 50% of the saturation water content. The other soil samples were tested in a similar way. On the graph one can notice artifacts located near frequencies of 150, 205, 360 and 500 MHz for both parts of ε*. They are related to resonances in the experimental set-up, due mostly to the length of the coax cable connecting the sensor with the VNA; the details and discussion are presented in [17]. This was later confirmed by introducing a magnetic shield on the coax cable, which substantially decreased the effect of the artifacts. The frequencies for which the artifacts occur will be excluded from further analysis, without negatively influencing the obtained results.


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)

Real and imaginary parts of the complex dielectric permittivity of a sample of soil no. 601 wetted with distilled water to approximately 50% of saturation water content.
© Copyright Policy
Related In: Results  -  Collection

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

f1-sensors-12-10890: Real and imaginary parts of the complex dielectric permittivity of a sample of soil no. 601 wetted with distilled water to approximately 50% of saturation water content.
Mentions: The FDR measurement technique allowed determining the real and imaginary parts of the dielectric permittivity directly and independently. Figure 1 presents the real and imaginary parts of the dielectric permittivity measured for a sample of soil no. 601 wetted with distilled water to approximately 50% of the saturation water content. The other soil samples were tested in a similar way. On the graph one can notice artifacts located near frequencies of 150, 205, 360 and 500 MHz for both parts of ε*. They are related to resonances in the experimental set-up, due mostly to the length of the coax cable connecting the sensor with the VNA; the details and discussion are presented in [17]. This was later confirmed by introducing a magnetic shield on the coax cable, which substantially decreased the effect of the artifacts. The frequencies for which the artifacts occur will be excluded from further analysis, without negatively influencing the obtained results.

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