Agriculture Reference
In-Depth Information
The models of tree growth habits provide a basis for comparing pruning
and training protocols for dif erent tropical fruit trees. Pruning to shape a
tree aims to control the number, orientation, size and angle of branches
and thereby improve the trees' structural strength to carry a fruit load,
reduce wind damage, increase light penetration, improve air circulation,
stimulate fl ower-shoot development and enhance fruit yield and quality. Too
much pruning can delay fl owering and lead to vegetative growth. Pruning
is not practised in monoaxial crops with short life cycles (banana, plantain,
pineapple and papaya), except that excess suckers are removed in bananas
and plantains; in papayas normally short lateral branches arising from the
main stem are removed. Broken, weak, drooping and diseased branches and
leaves should be removed. Pruning of many tropical trees may reduce yields
during the following season (mango, litchi), but some form of tree size control
is necessary to maintain a manageable tree size and structure. The trend is to
maintain the trees at a 3-5 m height by yearly or more frequent pruning for
ease of fl ower cycling, pruning and harvesting.
Avocados, mango and litchi have monopodial rhythmic growth (Table
4.2). In avocado, the branches are morphologically identical to the main
trunk, with fl owers borne laterally with only minor ef ects on the vegetative
shoot. In the case of guava, mango and rambutan, the rhythmic fl ushing
of vegetative growth and fl owering infl uences when and how pruning is
carried out. Flowers develop on shoots that are not fl ushing, and the objective
of pruning should be to increase the number of shoots that can fl ower
simultaneously. Carambola can be extensively pruned to remove overlapping
branches and topped to maintain 2-4 m height without signifi cantly reducing
yield, and it can also be trellised.
In the past, it was said that only deciduous fruit trees had to be pruned;
nowadays most of the evergreen tropical trees are being pruned in modern
orchards. Normally there has to be a formation pruning at the beginning
of the plantation, and later production and sanitary pruning has to be
performed.
Formation pruning
This practice is of major importance in deciduous fruit trees, where it takes
several cycles to achieve the desired form. Most tropical fruit species have a
natural tendency to develop a desired form, but often they need to be helped to
achieve well-balanced and anatomically proportioned canopies. This canopy
should be not too tall, without structural faults that might cause the trees
or main branches to break easily with a full fruit load. The object is to prune
the trees to achieve the right form and avoid overcrowding of branches in the
canopy. The main pruning actions eliminate all shoots arising below the graft
union. Shoots below the graft union can lead to a loss of a grafted canopy as
