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

that stimulate the phenomena and processes observed in the soil-plant-atmosphere
system.
Monitoring of water status is accomplished using digital systems. The digital
data acquisition systems react only on electric signals and the applied sensors
must convert the measured value into the proportional electric signal.
Water status of soil, as a porous material should be expressed by minimum
five variables: amount of water in the soil (ie soil water content), soil potential,
salinity, oxygenation and temperature (Malicki and Bieganowski [55]).
The most difficult are the electric measurement of soil water potential and soil
water content (soil water content), therefore they are the subject of permanent
research. It is assumed here, that the method successfully verified for soils will be
also applicable for other porous agricultural materials because their structure is
not so complex as soil.
1.1.1. Minimal number of variables describing the water status
The number of variables for water status description in the porous material
depends on the specificity of the analysed problem and, up till now, is arbitrary
chosen. In majority of practical cases the status of water is described by one
variable: water content of the material. One variable - water content – is enough
for wood as building material. Two variables are practically enough to describe
the status of water in grain: water content and temperature. Soil is a material in
which water status should be describes by minimum five variables: amount of
water (soil water content), its potential, salinity, oxygenation and temperature.
Soil is the most difficult biological material for water status monitoring
because soil is diverse and its properties are not stable in time and space. Soil
water content is the most challenging soil water status parameter for
determination because the measurement results must be in the form of electric
signal, while the current flow though the soil depends not only on its water
content.
Assuming that:
− the methods effective for soil water content measurements are also
effective for water content measurements of other biological materials
−
characterized by simpler construction, and
sensors, methods and instrumentation requirements in soil water content
monitoring are not stronger than in water content monitoring of other
biological materials
we can concentrate further discussion on soil water content measurement and
monitoring.
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