soil - Lublin

DETERMINATION OF ENERGETIC STATUS AND EVAPORATION
FROM POROUS BODIES ON THE BASE OF INFRARED IMAGING
Baranowski P., Lamorski K., Mazurek W., Walczak R.T.
INTRODUCTION
Determination of heat and water properties of agrophysical objects is closely
connected with their composition. Frequently, the objects of agrophysical studies
(e.g. plants tissues, seed material, soil matrix, etc.) are characterized by cellular or
granular composition. In natural conditions these physical bodies are situated in
complicated systems and many various factors influence the transport of energy
and mass in them. The energetic status of these porous bodies, which is expressed
by the heat balance equation, can be indirectly evaluated by the measurement of the
radiation temperature of their surface providing the knowledge of other agrometeorological
parameters (Baranowski et al. 1996, 1998, 2001).
In case of limited availability of soil water for the rooting system, the transpiration
intensity decreases and canopy temperature becomes higher. The application
of radiation temperature measurement of plant cover with thermography makes
possible to evaluate actual evapotranspiration because plant itself is the best sensor
of the physiological processes taking place in it. The main factors influencing transpiration
intensity are: water potential in the soil and in plants, water vapour pressure
deficit in the air and stability conditions of the near surface atmosphere.
Radiation temperature of canopy can be used to evaluate evaporation from soil
surface and transpiration from plants (jointly evapotranspiration). The quantitative
determination of evapotranspiration rate is essential in the investigations of water
balance. Thermal images of agricultural areas, available from airborne or satellite
levels, contain information about physical status of cultivated fields. However,
their proper interpretation requires the basic studies, to obtain the knowledge of
interactions between different soil and meteorological factors, affecting the actual
value of crop radiation temperature.
Recently, some trials have been undertaken to use thermography for the detection
of inhomogeneity of heat properties within the soil on the base of temperature
distribution on surface of the soil or plant cover. These studies are based on the
assumption that heat transfer under the temperature gradient in a body with the intrusion
is strongly modified if the intrusion’s thermal properties are different than
the rest of the medium. The detection of military intrusions in the soil (e.g. mines)
has an important practical aspect.
FACTORS INFLUENCING RADIATION TEMPERATURE OF PLANT
COVER AND BARE SOIL
Numerous factors influence radiation temperature of plant surface. They can be
divided into three groups:
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