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Evaluating soil salinity status from bulk electrical conductivity and permittivity
Author(s) -
Malicki M. A.,
Walczak R. T.
Publication year - 1999
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1046/j.1365-2389.1999.00245.x
Subject(s) - salinity , soil salinity , electrical resistivity and conductivity , water content , soil science , saturation (graph theory) , soil water , conductivity , bulk density , reflectometry , chemistry , analytical chemistry (journal) , environmental science , geology , time domain , mathematics , environmental chemistry , physics , geotechnical engineering , oceanography , quantum mechanics , combinatorics , computer science , computer vision
Summary In the range of volumetric water content, θ , from about 0.12 cm 3 cm –3 to saturation the relation between bulk electrical conductivity, C b , and bulk electrical permittivity, ε , of mineral soils was observed to be linear. The partial derivative ∂ C b /∂ ε appeared independent of the moisture content and directly proportional to soil salinity. We found that the variable X s = ∂ C b /∂ ε determined from in situ measurements of C b ( θ > 0.2) and ε ( θ > 0.2) can be considered as an index of soil salinity, and we call it the ‘salinity index’. Knowing the index and sand content for a given soil we could calculate the electrical conductivity of the soil water, C w , which is a widely accepted measure of soil salinity. The two variables from which the salinity index can be calculated, i.e. C b and ε , can be read simultaneously from the same sensor by time‐domain reflectometry. Quantities and symbols a constant /dS m –1 b constant c constant /dS m –1 Cb electrical conductivity of bulk soil /dS m –1 Cb ′ constant equal to 0.08 dS m –1 Cs electrical conductivity of a solution used to moisten soil samples /dS m –1 Cw electrical conductivity of soil water defined as the soil salinity /dS m –1 Cwref reference salinity (that truly existing) resulting from the procedure of moistening samples, expressed as C s + C r /dS m –1 Cr baseline value of C s due to residual soluble salts present in the soil /dS m –1 d constant D dry soil bulk density /g cm –3 l slope r ratio S sand content /% by weight t time /s Xs salinity index /dS m –1 Xsi initial salinity index when distilled water is used to moisten soil samples /dS m –1 Y a moisture‐independent salinity‐dependent variable /dS m –1 z coordinate along direction of flow of the soil solution ε′ constant equal to 6.2 ε relative bulk electrical permittivity (dielectric constant) of the soil θ volumetric water content determined thermogravimetrically using oven‐drying /cm 3 cm –3