Agriculture Reference
In-Depth Information
these shoots can grow taller and more vigorously than the grafted canopy.
Another objective is to eliminate all excessive primary branches and all water
sprouts that are very vigorous and succulent shoots in a juvenile stage that
will take time to become adult branches.
The modern tendency is to have canopies close to the ground. In the case
of trees that tend to have a main stem with vigorous upright growth, they
are tipped at about 80-90 cm in order to induce lateral branching that starts
below that point and close to the ground (Fig. 4.2a). If the branching starts
higher on the main stem, as in non-pruned trees, the canopy will leave too
much empty space between the canopy and the ground. This space is wasted
and results in a higher tree, and it is more dii cult to carry out spraying,
fertilization, pruning and harvesting.
Once the tree has been tipped, several lateral branches will develop.
Three to four of these lateral branches are retained to become the main
scaf olds of the tree (Fig. 4.2b). The lateral branches are selected so as to
form a glass shape, with a 120 or 90° angle between the third and fourth
branches (Fig. 4.2c). The branches should not arise too close to each other
on the main stem, with 20-30 cm between them or between at least of one
of them and the other two branches. If all the main lateral branches come out
too close together on the main stem, too much of the canopy weight will be
concentrated at one point. This concentration of weight can become a problem
in later years when the trees are large, and they often break at this junction or
form a water pocket that accumulates water, which is undesirable.
If a primary branch grows too fast in relation to the others, it should be
checked by tipping or bending, in order to promote a balanced growth of all
the primary branches. In some species these primary branches have to be cut
back to about 60 cm, in order to induce them to form secondary branches (Fig.
4.2d), and this is followed by further pinching (Fig. 4.2e) to form a canopy
closer to the ground. A more open growth angle of the primary branches is
achieved by pulling them with strings attached to the ground or with strings
that have a weight hanging at the other end or by putting pieces of twigs
or bamboo between the branches in order to open their growth angles.
Sometimes the inner part of used tyres is put between the branches so that the
insertion angle to the stem is wider.
Formation pruning can start in the nursery or at planting time if the
plants are large or already show unwanted growth proportions, or after they
have achieved a certain size in the fi eld. During the fi rst years of growth in the
orchard, every 3 or 4 months the plants should be inspected and any water
sprout or sprout coming from below the graft union removed. If this is done
frequently, it can be done with the hands and no tools are needed. Longer
intervals will require pruning shears. The shoots should be cut at their base, to
prevent re-sprouting of more than one shoot.
