Agriculture Reference
In-Depth Information
Table 6.5.
Tentative leaf nutrient standards for atemoya (Pink's Mammoth) in
Queensland, Australia, presented as a guide (Sanewski, 1991).
Nutrient
Acceptable range
Nitrogen
2.5-3.0%
Phosphorus
0.16-0.2%
Potassium
1.0-1.5%
Calcium
0.6-1.0%
Magnesium
0.35-0.5%
Sodium
< 0.02%
Chloride
< 0.3%
Manganese
30-90 ppm
Copper
10-20 ppm
Zinc
15-30 ppm
Iron
50-70 ppm
Boron
15-40 ppm
The primary sink for K in the atemoya is the fruit, rather than the leaves,
and thus there is a high requirement, with defi ciency likely. About 60% of
the K requirement is applied during the fruit-development period. Atemoyas
also have a fairly high requirement for magnesium (Mg) and calcium (Ca).
Heavy vegetative growth during the fruit-development period competes for
nutrients such as boron (B) and Ca, resulting in boron-defi cient fruit. Boron-
defi cient fruit develop hard, brown, lumpy tissues around the central core.
Defi ciency in B and, to some degree, Ca is considered a causal factor for these
lumps (Cresswell and Sanewski, 1991). Applying B at a slight excess can be
phytotoxic, especially in sandy soils. A desirable practice is to use organic
fertilizers, with inorganic fertilizer as a supplement to maintain a balance and
to control cropping (Sanewski, 1991).
For sweetsop, a periodic application of NPK is best, split into three parts
applied every 4 months. The early-spring application would include all the P
for the year and 20% of the N and K requirements. In summer, the other 70%
of N and 40% of K are applied, and the rest of K is left for autumn application.
A physiological disorder called black speck is caused by Ca defi ciency, which
is corrected by spraying with a foliar Ca solution. This physiological disorder
causes small, dark spots in the shoulder and waist of the fruit, but it can invade
the whole skin in extreme cases.
Pest management
Diseases
A number of diseases have been reported in the literature (Table 6.6).
Anthracnose, caused by
Colletotrichum gloeosporioides
(
Glomerella cingulata
),
