Macadamia Nuts in Hawaii: History and Production - ctahr ...

Figure 68. Tree showing early P deficiency symptoms: a declining
terminal growth with defoliation in the stems of these
branches and normal-appearing branches at the lower
third of the tree.
Figure 69. A P-deficient tree with dead, dry twigs at the terminal.
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Table 3. Suggested leaf analyses values for macadamia
on oven-dried leaf tissue
Nutrient
N,%
P,%
K,%
Ca,%
Mg,%
S, %
Mn, ppm
ln, ppm
B, ppm
Cu, ppm
Cooil
1.50
0.08
0.45
0.095
Shigeura
0.07-0.08
0.55
Warner, Fox
0.10
0.24
100.00
15.00
75.00
4.50
A fertilization program based on leaf analysis is
the more exact and desirable procedure to follow.
However, the farmer may not be able to have his
leaves analyzed to meet his needs. In these situations,
although it is not as reliable as leaf analysis,
visual examination of trees for symptoms may be
used for some needs or deficiencies.
Nitrogen. Trees deficient in N are yellow-green
throughout, with decidedly smaller leaves. Occasionally,
in severe cases, trees may appear burnt.
Phosphorus. When P is deficient, trees respond
wi th smaller leaves a t the apex of the tree and mild
to major defoliation of leaves on these branches.
At the same time, the branches on the lower third
of the tree have largerand healthier leaves (Fig. 68).
These trees invariably have leaf P val ues of 0.05
percent or below, and definitely need immediate
phosphate fertilization. Figure 69 shows trees
becoming progressively worse due to phosphate
deficiency. Figure 70 shows a tree recovering after
phosphate fertilization.
Potassium. Symptoms of K deficiency are seen
only in older leaves as marginal necrosis and are
usually more confined to the margins of leaves.
Field experience indicates that Hawaiian soils are
high in available K for macadamia nutrition, and
the K requirement for macadamia is low, with 0.5
percent being adequate for good production (9).
Magnesium. When the older leaves become
generally yellow with green veinal tissues and
yellow to orange interveinal tissues, Mg is deficient.
This latter symptom is especially pronounced
in 'Kakea' (HAES 508), becoming
especially bad with heavy phosphate fertilization.
In this situation, a Mg fertilizer such as magnesium
sulfate (Epsom salt) should be applied
immediately to correct the deficiency. Within a
year, trees should respond by greening. When