Apart from frequency and amplitude, other factors are also
important. Rumsey and Barnes (1970) studied several parameters
related with detachment in ‘Valencia’ and ’Navel’ oranges
and ‘Marsh’ grapefruits. They measured the traction
force necessary to detach the fruit as a function of the direction
in which this force was applied, that is, following the
calyx-pistil axis or following lines at 45 and 90 from the
calyx-pistil line. They noted that the force decreased as the
angle increased. In addition, they observed that a lower rate of
detachment was achieved in fruits with longer peduncles,
higher amplitudes being more effective. Moreover, they analysed
the detachment point of the fruit in the traction tests
and found that they were mostly detached without calyx
whatever the traction angle. On the other hand, in torsion
tests, most of the fruits were detached with calyx and the rest
with peduncle, while in the vibratory tests the fruit detached
with calyx decreased. Alper and Foux (1976) analysed the
mechanical resistance of ‘Shamouti’ oranges to axial, flexion,
torsion and combined forces. They separated the branches
from the tree and performed the tests under laboratory conditions
and found that axial strength was the main component
to detach the fruit. When the force was applied with
some inclination with respect to the calyx-bottom axis, the
variety and the traction force. High amplitudes and low frequencies
achieved a higher percentage of fruit detached with
the peduncle, but the effect was not significant so that these
parameters could be used to control the detachment point.