Agriculture Reference
In-Depth Information
cultivar. In Florida, litchi are planted at 7 m × 4 m, with regular mechanical
pruning to avoid overcrowding (Campbell and Knight, 1987), and in
subtropical areas 6 m × 6 m spacing is possible (Galán Saúco, 1990).
Windbreaks are necessary for young and mature trees for both crops. This
is essential because trees propagated by air-layering do not have a tap root and
are easily uprooted by winds.
Irrigation
Regular irrigation is essential during the growth of young trees. During dry
periods irrigation may be needed at 2- or 3-week intervals. Moisture control
is applied when the trees reach fl owering age. In China, litchis are grown
along canals, on dykes around paddy fi elds and around village ponds, and
no irrigation is practised. Moisture should be withheld during autumn and
winter to discourage vegetative growth and promote fl owering (Fig. 9.1).
High soil moisture tension for 6 months, beginning mid-summer, or even for
3 months, beginning in late summer, promotes fl oral initiation and fruit set
by inhibiting emergence of vegetative fl ushes (Nakata and Suehisa, 1969).
Once the infl orescence has appeared and throughout fruit development,
adequate moisture is necessary. Irrigation should be terminated a few weeks
before harvesting. Moisture stress under non-irrigated situations can cause
developing fruit to ripen prematurely, even before the aril has fully developed.
Fruit growth will resume if water is provided, leading to fruit splitting. Copious
irrigation immediately after harvest is desirable to encourage new shoot
growth (Fig. 9.1). In areas with dry summers, irrigation is necessary, followed
by limb girdling in late summer to discourage further vegetative fl ushing and
to accumulate carbohydrates in the trees during the autumn months (Nakata,
1953). This practice is necessary in areas where climatic conditions do not
enforce a natural period of tree dormancy in the winter.
Pruning
Less research has been done on the need for and ef ectiveness of pruning
longan trees than litchi. During the fi rst 2-3 years, all side shoots up to
0.8-1.0m should be removed from litchi, as these will form low-hanging
branches, which interfere with cultivation. In bearing litchi trees, even
branches 1.5 m high will bend to the ground when laden with fruit. In
Australia, the main terminals of 3-4-year-old trees are headed back in the
spring (prior to fl ushing) in vigorous cultivars, to create a more compact tree
with many terminals, thus increasing the potential bearing surface (Menzel
et al.
, 1988a). Approximately 16 cm is pruned from the tip, and from each
pruned branch an average of three new terminals are produced. A pruning
