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Determination of Soil Pore Water Salinity Using an FDR Sensor Working at Various Frequencies up to 500 MHz
Institute of Agrophysics, Polish Academy of Sciences, ul. Doświadczalna 4, 20-290 Lublin, Poland
Department of Natural Environment, Faculty of Forestry, Technical University Zvolen, T. G. Masaryka 24, 960 53 Zvolen, Slovakia
Institute of Environmental Protection and Development, Wroclaw University of Environmental and Life Sciences, Pl. Grunwaldzki 24, 50-363 Wrocław, Poland
* Author to whom correspondence should be addressed.
Received: 18 June 2012; in revised form: 27 July 2012 / Accepted: 1 August 2012 / Published: 7 August 2012
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.
Keywords: dielectric spectroscopy; frequency-domain reflectometry; complex dielectric permittivity; salinity index approach; soil salinity; soil water content
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Wilczek, A.; Szypłowska, A.; Skierucha, W.; Cieśla, J.; Pichler, V.; Janik, G. Determination of Soil Pore Water Salinity Using an FDR Sensor Working at Various Frequencies up to 500 MHz. Sensors 2012, 12, 10890-10905.
Wilczek A, Szypłowska A, Skierucha W, Cieśla J, Pichler V, Janik G. Determination of Soil Pore Water Salinity Using an FDR Sensor Working at Various Frequencies up to 500 MHz. Sensors. 2012; 12(8):10890-10905.
Wilczek, Andrzej; Szypłowska, Agnieszka; Skierucha, Wojciech; Cieśla, Jolanta; Pichler, Viliam; Janik, Grzegorz. 2012. "Determination of Soil Pore Water Salinity Using an FDR Sensor Working at Various Frequencies up to 500 MHz." Sensors 12, no. 8: 10890-10905.