Our data have practical application for
greenhouse production of tomatoes. Where
fruit cracking is a problem, irrigation should
be reduced. Overirrigating is particularly
tempting late in the season in the spring crop
as the plants become older and days become
longer and hotter. By the end of the season,
however, few fruit remain on the plant, and
leaf area is either the same or may be less if
lower leaves have been removed, a normal
cultural practice. The remaining leaves are
older, leathery, and may transpire less. Thus,
it would probably be safer in terms of preventing
fruit cracking to reduce irrigation at the
end of the crop than to automatically raise it.
This concept has several implications for automatic
greenhouse watering. If the concept is
correct, models that predict watering requirements
on the basis of evapotranspiration and
leaf area would overpredict water usage unless
they take into account changes in plant
transpiration. Lysimeter-based control systems,
which add water only as it is actually
used by the plant, may lead to reduced cracking
if properly set.