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Using infrared canopy temperature and leaf water potential for irrigation scheduling in peppermint (Mentha piperita L.)Gallardo, Ivan T. 14 July 1992 (has links)
Several methods of infering plant water stress for
irrigation scheduling are based upon measurements of the
environment in which the plants grow. These measurements
include parameters such as soil water content, air
temperature, pan evaporation and incident radiation. It is
hypothesized that improved estimates of plant water deficit
can be obtained by direct measurements made on the plants.
The main objective of this study was to test the
performance of measurements of canopy temperature and leaf
water potential for irrigation scheduling. This study seeks
to establish whether a correlation exists between these
monitoring methods and measurements of soil moisture
content, leaf area, and evapotranspiration. The experiments
were conducted in first-year peppermint irrigated at five
different rates. Canopy and air temperatures were measured
with a hand-held infrared thermometer. Leaf water potential
was measured with a pressure bomb.
A non-stressed baseline for the difference between
canopy temperature and air temperature using data from well-watered
plants was used together with the vapor pressure
deficit to determine the crop water stress index (CWSI).
The results of this study show that the CWSI is well
correlated to evapotranspiration deficit and is useful for
irrigation scheduling. The relationship between leaf area
yield and CWSI in peppermint was described by a quadratic
function.
Leaf water potential varied during the day in such a
way that it was not possible to establish a relationship
with water stress, differences in soil moisture content, or
different irrigation levels. Leaf water potential was
influenced by the daily weather conditions and represented
the current demand more than the cumulative demand. The
results of this study indicate that mid-day pressure bomb
measurements cannot be used in irrigation scheduling.
Predawn measurements of leaf water potential were stable,
were well correlated with the different irrigation levels
and soil moisture content, and therefore may be useful in
irrigation scheduling. / Graduation date: 1993
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