Agriculture Reference
In-Depth Information
may have fewer than ten fruits developing at a time on the fruit column, with
new fl owers abscising.
Fertilization
Papaya is a fast and continuously growing tree that provides fruits all the
year round. An abundant supply of nutrients at regular intervals is needed
to sustain good growth and production. In general, an adequate supply of
nitrogen and phosphorus should be provided during the early stages to ensure
optimum foliage, trunk and root development. However, at the fruiting stage,
the level of potassium should be raised, while the level of phosphorus should
be reduced, as high levels reduce fruit size. The level of nitrogen remains
somewhat unchanged through the juvenile and fruiting stages because foliage
is continuously produced. Tentative ranges of critical levels for bearing plants
of 'Kapoho' Solo are: N = 1.10-1.40%, P = 0.15-0.18% and K = 2.5-3.5%
(Awada and Long, 1980).
Papaya is sensitive to boron defi ciency, especially when cultivated
on sandy soil. Plants suf ering from this defi ciency exhibit characteristic
symptoms: slight yellowing and downward curling of the leaf tips, with very
slight necrosis of the leaf tips and margins. The leaves are brittle in texture
and claw-like. During fruiting, secretion of milky latex often occurs on the
fruit surface, which subsequently turns brown in colour. At the later stage, the
fruit surface becomes rough or 'bumpy', giving the fruit an overall distorted
or malformed appearance. Treatment of boron defi ciency is by soil or foliar
application of borate.
Diversity of soil types, climatic conditions and practices make it necessary
to develop recommendations for specifi c areas based upon soil analysis and
preferably foliar analysis. In the sandy loam soils of North Moreton, Australia,
a pre-plant application of 0.5 kg of 5:7:4 complete fertilizer, 0.25 kg of single
superphosphate and 1.0 kg of lime per individual plant (over 1 m 2 area) is
recommended. For post-plant application, 100 g/plant of 10:2:16 complete
fertilizer is given at about 2-month intervals, with monthly application of
150-200 g per plant site during summer and autumn. In the second year,
250 g per plant is given at 2-3-month intervals. Because of boron defi ciency
problems in this area, 20 g of borax is applied at 3-4-month intervals and
30g/plant is given the second year at about 7-8-month intervals.
Pest management
Diseases
The importance of frequently reported papaya diseases (Table 11.6) varies,
and they may be widespread or localized. Phytophthora commonly causes
 
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