Agriculture Reference
In-Depth Information
1. Dormant Pruning is carried out to retain the number of nodes necessary
to achieve an estimated 200% of the final desired yield level. Figure 7.1b
shows the shear pruning attachment in a Vineyard System chassis.
2. Shoot Thinning is used to achieve an estimated 130-140% of the desired
final yield level. The shoot thinner shown in Figure 7.1c is used without
hand follow-up when the new shoots were 10-20 cm.
3. Fruit Thinning attachment is used to reach the desired crop levels, if the vine
still exceeded the target yield after dormant pruning and shoot thinning.
7.2.2 H
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Pruning of fruit trees (1) adjusts tree shape and the ratio of framework to fruit bear-
ing area of the canopy, (2) alters the top/root ratio, and (3) changes the food storage
status of the tree (Tucker et al., 1994). Proper control of crop growth is essential for
the maintenance of a healthy and productive orchard. In addition, pruning improves
sunlight access of the tree, which provides the energy for photosynthesis. Light
becomes a limiting factor in crowded groves.
The mechanization of pruning began in California in the early 1960s through an
effort to mechanically top lemon trees (Jutras and Kretchman, 1962). Mechanical
toppers were used to eliminate hand pruning of vigorous shoots at the top of the tree.
The machine consisted of a modified sickle-bar mower blade mounted on towers that
were adjustable for height. In later years, topping machines used a series of circular
saws mounted on a horizontal boom (Sansavini, 1978). Mechanical pruning is based
on a predetermined cutting plan: horizontal top cutting (topping) and vertical walls,
or oblique hedging (house top). Consequently, hedging is normally surface pruning.
However, certain crops such as citrus often use deep cuttings on alternating sides
of the tree on an every other year basis. Figure 7.2 illustrates a citrus hedger system
built by Northern Motors that can cut various canopy profiles.
Hand thinning is a necessary but costly management practice in peach produc-
tion. Organic apple production also may require hand thinning to adjust crop load.
Mechanical devices to aid in thinning have been developed but have not proven
efficient and capable of completely replacing hand thinning. The introduction of nar-
row canopy training systems and novel peach tree growing approaches will create
new opportunities to examine mechanical methods for thinning peach and apple
trees (Schupp et al., 2008). A spiked-drum shaker was used to thin pillar peach trees
at 52 to 55 days after full blossom. The spiked drum was a vibrating direct drive
double spiked-drum shaker designed for harvesting citrus. The shaker was mounted
on a tractor-towed trailer and consisted of two rotating drums each measuring 8 ft
in diameter and 5 ft in height. Each drum was composed of six whorls of nylon rods
spaced 12 in apart on a central axis. Each whorl was made up of 16 individual rods
and were radially spaced at equal angles around the axis of the drum. Results of the
drum shaker trial, conducted at a commercial orchard, showed that although this
type of mechanical thinning generated larger-sized fruits, the level of crop reduction
and disproportionate removal of fruit over the canopy were a concern. It also broke
some small shoots and twigs, and caused bark damage when rods became entangled
in the branches.
