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with an eye on the actual evapotranspiration
(ET) of the tree and the amount of
soil-water salinity in its growing environment.
Optimal photosynthesis and maximum
carbon dioxide uptake are critical
to crop production. What Zaccaria and
others who study plant water needs have
learned is that salts increase the soil
osmotic potential retaining water tighter,
costing the plant more biological energy
and interfering with optimal water uptake.
That limits critical physiologic and
growth processes including cell multiplication
and expansion, canopy growth
and leaf conductance to transfer water
vapor from the plant to the surrounding
atmosphere. Split percent and nut weight
are most affected by those stressors.
UC researchers report that high
soil-water salinity reduces tree evapotranspiration
rates in pistachios by 10-30
percent, depending on the level of salinity,
relative to those of orchards grown on
non-salt affected conditions. Irrigation
scheduling and management need to be
accurate and precise to compensate for
high salinity levels. The trees may need
less water during irrigation season to
produce a profitable yield, but Zaccaria
said additional water needs to be
applied during the trees’ dormant period
to leach salts from the root zone and
maintain acceptable growth and produc-
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38 West Coast Nut December 2017