ekS - Instytut Agrofizyki im. Bohdana Dobrzańskiego PAN w Lublinie ...

The solution to the problem of electric measurement of the physical quantity
in selective way is to find such an electric property of the medium conditioning it,
which is specific to the considered medium. For example, the specific property of
molecular oxygen in electrolyte (“soil water”) is small activation energy of
electrode reaction of its reduction. It can be concluded that electric measurement
of oxygenation may be based on the amperometric measurement of the current of
electrode reaction of oxygen molecules reduction (Malicki and Bieganowski
[55]).
Similarly, concerning the issue of electric measurement of soil salinity, the
media conditioning salinity are salts present in soils and the specific property is
their ionic form. The ability to transport electric charge by the ions in “soil water”
allows the soil to conduct electric current. Therefore the electric measurement of
soil salinity should be based on the measurement of its electric conductivity.
2.1.1. Electrical measurement of soil water content
Concerning the problem of electric soil water content measurement, the
medium conditioning water content is water and its specific property is the polar
structure of water molecules (a water molecule has a permanent dipole moment of
1.87 D). Polarity of water molecules is the reason that dielectric permittivity
(dielectric constant) of water is much higher than permittivity of soil solid phase
(the relative dielectric constant of water in the electric field of frequency below
10 GHz and 18 ºC temperature is 81, while the relative dielectric constant of solid
phase is 4 ÷ 5 at the same conditions). The dielectric constant of soil strongly
depends on its water content, therefore it may be concluded that electric
measurement of soil water content should be based on the measurement of its
dielectric constant.
The medium conditioning its water content is water and its unique property is
the polar structure of water molecules. The real part of water dielectric
permittivity (dielectric constant) is much higher than dielectric constant of soil
solid phase therefore it can be concluded that electrical measurement of soil water
content should be based on the measurement of its dielectric constant.
The efforts to measure soil water content indirectly, on the base of the
resistance or electrical capacitance between the electrodes inserted into the soil,
has been continuously undertaken since the end of nineteen age (Whitney et al.
[102]).
2.1.2. Electrical measurement of soil salinity
Similarly, referring to the problem of electrical measurement of soil salinity,
the medium conditioning its salinity is salt present in the soil and the unique
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