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

Figure 63. The use of bolts to save an embedded-bark limb, practiced
by Ralph Moltzau in the 1930s.
(Courtl'SY of Ralph 1-1. Molt,.au)
canopy of small branches.
To sustain yield by pruning, when necessary,
limbs or large branches should be pruned and
eliminated at the point of their attachment to
another branch to permit more light to go through
the void thus created. In this manner the remaining
older branches will set flowers and thus
increase yield. This system of branch pruning
will also extend yield by forcing top growth in
the proper direction and will enable trees to maintain
total productivity over a longer period of time
by better utilization of airspace.
Fertilization
Fertility requirements of macadamia have been
studied and reported over the years by Cooil and
his co-workers (9, 10, 11), Shigeura et a1. (69, 70,
72, 74), and Warner and Fox (86), suggesting leaf
analyses values that can be used in a more objective
fertilization program. Cooil and his coworkers,
working on M. integrifolia at Keaau
Orchard on the island of Hawaii in the early 1950s,
established leaf analyses values for nitrogen (N),
phosphorus (P), potassium (K), and magnesium
(Mg) using leaves at the time the major flush of
growth is beginning, generally in March. In this
sampling procedure, a mature leaf is taken from
the second whorl below the newly emerging flush.
A total of 10 leaves is suggested for each sample.
Cooil's values for ,P, K, and Mg have been found
to be accura te and useful in predicting nutritional
needs of trees growing on the many soil types
found in the state. This sampling procedure has
now been extended and applied to leaf sampling
throughout the year.
Shigeura et aI., using Cooil's leaf val ues,
developed a system using the leaves from the most
recently matured terminal, which is distinct and
identifiable since new terminals continue to
develop on macadamia throughout the year, and
the new leaves are glossier green than older leaves.
The overriding advantage of using recently matured
terminals is that the sampled leaves will be
of the same vegetative age irrespective of the time
of sampling, and represent the nutritional status
of the tree at that time. Values thus obtained can
be reasonably compared with leaves sampled at
any time during the year. On the other hand, the
age of leaves in Cooil's method cannot be accurately
determined since the leaves may be of recent
origin or may be more than a year old at sampling
time. Consequently, leaf calcium (Ca) values on
Cooil's "prior to fl ushing" samples are erratic and
seem to be affected by the difference in the age of
leaves. Cooil's difficulty in determining a critical
leaf Ca value lends support to this statement.
Fortunately, the value differences in N, P, K,
and Mg between "March sampling" and "recently
matured terminal" samplings are not discernible.
Calcium, however, differs very strongly. Data
gathered by Shigeura et al. (72) in Kohala,
Hawaii, suggest that leaf phosphate can be 0.07
percent to 0.08 percent (Cooil, 0.08 percent) to
obtain maximum nut quality (Fig. 64) and yield
(Fig. 65). The difference in P noted here is hardl y
anything and not important by itself; but it should
be monitored closely because phosphate approaching
0.10 percent in leaves becomes a problem,
since high leaf P indicates an accumulation of
phosphate in the substrate as soluble phosphate.
Jones et al. (28) report work done with the electron
microprobe showing that there is actually a depletion
of iron (Fe) and an accumulation of P in the
vicinity of the roots on Fe-chlorotic trees growing
on aa lava land. Shigeura et a1. (70) showed tha t
under this condition the strong, healthy leaves at
the very terminals of branches will begin to yellow
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