Agriculture Reference
In-Depth Information
the urea. Fertilizer in subtropical areas is withheld during cold months to
prevent fl ushing.
In Australia, general recommendations for 5-year-old trees are: 150 g
urea, 300 g single superphosphate and 150-200 g potassium sulfate per
application. These amounts are increased by 20-30% each year until year 15,
when each application rate increases to 1200 g urea, 1200 g superphosphate
and 600-800 g potassium sulfate. No fertilizer is applied to bearing trees in
the spring, to prevent vegetative fl ushing in the autumn, in order to increase
the prospect of good fl owering. Three applications of a complete fertilizer,
such as triple-14 at 114 g per tree the fi rst year and increasing to 227 g per
application in the second year, are used in Hawaii. In the third year, two or
three applications at 454 g per application are applied. For bearing trees a
general rule of thumb of 0.90 kg of a complete fertilizer for every 2.54 cm
of trunk diameter is given upon completion of harvest to encourage summer
fl ush. An application in late winter or early spring before fl oral initiation has
begun can result in a vegetative fl ush rather than a fl ower fl ush. The main
fertilization is applied immediately after harvest in the summer (Fig. 9.1),
followed by irrigation and the annual limb girdling.
Critical nutrient periods are before fl owering and fruit set, several weeks
after fruit set and after harvest. Litchi leaf nitrogen should be
ca.
1%. Leaf
samples for analysis are taken twice a year, once at the end of harvest and
the second at fl owering, with only P and K applied during fruit set to avoid
vegetative growth from N application. Minor elements are applied once a year
at the end of the cold period.
Erratic bearing
Litchi trees 7-8 years old can produce up to 45 kg. Potential yields for 10-year-
old trees are 50-70 kg, 15-year-old trees at 100 kg, and 20-24-year-old trees
at 150-180 kg (Campbell and Knight, 1987). Occasionally, yields can be as
high as 500 kg in very old trees. Apparently, potential yields can continue to
increase with older trees, as has been demonstrated in China.
The litchi can be a heavy bearer when conditions are favourable for
fruiting; however, considerable year-to-year variation in yields occurs wherever
grown (Fig. 9.9). Erratic fl owering can be due to unfavourable weather
conditions, and even if fl ower production is consistent, fruit set problems
contribute to variable yields (Chapman, 1984). Cultivars are very particular
about their climactic requirement (Table 9.1); trees propagated from good
bearing trees and planted in another location are known to have produced
fruit for a few years and later ceased to produce for years.
Fruit bearing is dependent upon a number of crucial phases, which need
to be optimized throughout the year (Fig. 9.1). The infl uence of cultivar,
pruning and tree management needs to be integrated. Both species need to be
