Agriculture Reference
In-Depth Information
irrigation is desirable after the infl orescence appears and as fl owers begin to
set fruit. During the fi rst 4-6 weeks of fruit development, cell division is most
rapid and moisture stress should be avoided. Four-year-old trees may require
around 400-500 l water/tree at 2-week intervals. Irrigation is completely cut
of as the fruits approach maturity, since dry conditions favour higher sugar
content. Heavy irrigation is resumed immediately after harvest to encourage
new vegetative growth (Fig. 10.4). In the monsoon tropics, termination of
harvest coincides with the rainy season, so irrigation is usually unnecessary.
As soon as a major vegetative fl ush occurs, reduction in soil moisture content
is desirable to mature the new fl ush. The choice of irrigation equipment and its
management is based on capacity and ei ciency of water delivery, and cost of
the system plus installation. Irrigation should be programmed in accordance
with the phenological growth cycle (Fig. 10.4) to achieve maximum yield.
Pruning
In most subtropical areas, the tendency is to use narrower plant spacings
and keep the trees small by pruning. In the hot tropics, the trees are also kept
smaller than before by pruning, but they are normally larger than in the
subtropics.
Formation pruning can start in the nursery, at transplanting time or
shortly after transplanting. All lateral shoots from the main stem are removed
until the plants reach a height of 70-100 cm, to train the tree to a single
trunk. For varieties with long hanging branches, at this height the top 10-20
cm is cut of below a node. In the subtropics this should not be done in autumn
or winter, otherwise fl oral shoots might develop (Galán Saúco, 2009). Later
lateral buds will sprout and three well-oriented and well-distanced shoots are
left to become the primary tree branches. These shoots should be oriented in
dif erent directions, hopefully separated by a 120° angle; at the same time
there should be a distance of 20-30 cm between them along the main stem, so
that the weight of the adult tree is not concentrated at one point. For varieties
that tend to produce very long shoots at a narrow angle, the selected primary
branches can be forced to grow at a 45° angle. This forcing will slow their
growth and induce more laterals to arise and reduce excessive tree height.
To obtain compact trees for narrow plant spacing, once the main lateral
branches have stopped growing and mature, the terminal buds are pinched
of , with as few leaves as possible being removed. From these pinched main
lateral branches, three shoots are left to grow, and they will be pinched the
same way, so that nine secondary branches are formed, and fi nally these can
also be pinched, leaving three equally spaced new shoots on them, completing
a total of 27 tertiary branches. This process is repeated during the fi rst 2-3
years until a well-balanced plant is obtained.
