From the Handbook of Energy Crops, unpublished
by James A. Duke
Macadamia integrifolia Maiden & Betche
Macadamia tetraphylla L. Johnson
Proteaceae
Macadamia nuts, Australian nuts
Uses
Folk
Medicine
Chemistry
Description
Germplasm
Distribution
Ecology
Cultivation
Harvesting
Yields
and Economics
Energy
Biotic
Factors
Chemical Analysis of Biomass Fuels
References
Uses
Macadamia
nuts are eaten raw or after cooking in oil are roasted and salted; also
used to make an edible bland salad oil. Rumsey (1927) recommends it as
well as a timber tree and ornamental. Years ago a coffee-like beverage
known as "almond coffee" was marketed from the seeds.
Folk Medecine
No data available.
Chemistry
Per
100 g, the nut is reported to contain 691 calories, 3.0–3.1 g H2O,
7.8–8.7 g protein, 71.4–71.6 g fat, 15.1–15.9 g total carbohydrate, 2.5
g fiber, 1.7 g ash, 48 mg Ca, 161 mg P, 20 mg Fe, 264 mg K, 0 mg
b-carotene equivalent, 0.34 mg thiamine, 0.11 mg riboflavin, 1.3 mg
niacin, and 0 mg ascorbic acid. According to MacFarlane and Harris
(1981), the oil is high in monounsaturates (79%) and palmitoleic acid
(16–25%). The composition ranges from 0.1–1.4% lauric, 0.7–0.8
myristic, 8.0–9.2 palmitic, 15.6–24.6 palmitoleic, 3.3– 3.4 stearic,
54.8–64.2 oleic, 1.5–1.9 linoleic, 2.4–2.7 arachidic, 2.1–3.1
eicosenoic, and 0.3–0.7% behenic acids. The oilcake contains 8.1%
moisture, 12.6% oil, 2.6% crude fiber, 33.4% crude protein, and 43.3%
N-free extract.
Description
Macadamia integrifolia:
Trees up to 20 m tall, with spread of 13 m; leaves opposite in
seedings, later in whorls of 3, pale green or bronze when young, 10–30
cm long, margins with few or no spines, petioles about 1.3 cm long;
flowers creamy white, apetalous, borne in groups of 3 or 4 along a long
axis in racemes, much like grapes; fruit consisting of a fleshy green
husk enclosing a spherical seed; nuts round or nearly so, surface
smooth or nearly so, 1.3–2.5 cm in diameter; shell tough, fibrous,
difficult to crack; kernel white, of uniform quality, shrinking only
slightly after harvesting. Fl. June through to March, some strains
almost ever-bearing, flowering while fruiting.
Macadamia tetraphylla:
Trees up to 20 m tall, with spread of 13 m; leaves opposite in
seedlings, commonly in 4's rarely in 3's or 5's, purple or reddish when
young, margins serrate with many spines, up to 50 cm long, sessile or
on very short petioles; flowers pink, in large racemes; fruit
consisting of a fleshy green husk enclosing one seed; nuts usually
elliptical or spindle-shaped, surface pebbled; kernel grayish; variable
in quality and shrinking some after harvest. Fl. between August and
October, producing one main crop. Between these two distinct types are
numerous intermediate forms varying in spininess of leaves, color of
flower, size of nut and thickness of shell.
Germplasm
Reported
from the Australian Center of Diversity, macadamias or cvs thereof are
reported to tolerate drought, slope and wind. (Duke, 1978). After 1956,
Macadamia integrifolia (smooth-shelled type) and Macadamia tetraphylla
L. (rough-shelled type) are the names properly applied to the
cultivated Macadamia nuts. Prior to this time they had been generally
referred to Macadamia ternifolia.
F. Muell., a distinct different species, bearing small, bitter,
cyanogenic seeds less than 1.3 cm in diameter, inedible and never
cultivated. Many cultivars have been developed and grafted trees of
promising selections have been made. Three varieties of M. integrifolia,
'Kakea', 'Ikaika' and 'Keauhou', have been planted extensively in
Hawaii, all giving satisfactory production under a variety of favorable
conditions;. 'Keaau' has been more recently recommended for commercial
planting in Hawaii, since it is highly resistant to wind and yields
5–10% more than previous varieties, the entire crop maturing and
dropping before end of November.
Most of the Australian crop is based upon M. tetraphylla, with some orchards of grafted M. integrifolia
varieties. Among the medium-to-thick shelled selections, used mainly
for processing, are: 'Richard', 'Tinana', 'Our Choice' and 'Hinde'. For
rough-shelled types, mostly grown for table purposes, are: 'Collard',
'Howard', 'Sewell' and 'Ebony'. Varieties showing hybrid
characteristics are: 'Oakhurst' and 'Nutty Glen'. 'Teddington' is a
hybrid with thin shell. (2n = 28, 36, 56).
Distribution
Native
to coastal rainforests of central east Australia (New South Wales and
Queensland). Introduced in other parts of tropics, as Ceylon, and
commercially grown in Hawaii and France, at medium elevation.
Ecology
Ranging
from Warm Temperate Dry (without frost) through Tropical Moist Forest
Life Zones, macadamias are reported to tolerate annual precipitation of
7 to 26 dm annual temperature of 15 to 25°C and pH of 4.5 to 8.0.
Macadamia grows best in rainforest areas, along coasts with high
humidity and heavy rainfall. However, it is tolerant of adverse
conditions when once established. Inland, tree thrives in some
localities but crops are usually lighter than when grown near coast.
Trees produce a deep taproot and relatively few lateral roots;
therefore, they need protection of windbreaks in exposed areas. Under
orchard conditions, trees are shapely, robust, and more heavily
foliaged than they are in rainforest. Grows well on wide range of soil,
but fails on infertile coastal sands, heavy clays or gravelly ridges.
Yields well on deep, well-drained loams and sandy loams. Slopes steeper
than 1 in 25 should be planted on the contour, and every precaution
taken to prevent soil erosion.
Cultivation
Propagation
by seed is not difficult, but seedlings are variable in production and
nut characteristics, and so of little value for commercial plantings.
Freshly harvested nuts are best for germination, but require 30–90 days
before germination. Propagation usually by cuttings, marcottage and
side-tongue grafts. Rootstocks for grafting are readily grown from seed
by ordinary nursery means. Grafting in Macadamia is more difficult than
in most nut trees due to hardness of wood. Best results obtained when
seedling rootstocks are side-wedge grafted with selected scions.
After-care of graft similar to that practiced in other trees. Budding
is much less satisfactory than grafting. Most suitable time for
transplanting young trees to orchard is from February to April in
Australia and in Hawaii, when rainfall is good and sufficient soil
moisture available. Taproot should be severed about 30 cm below ground
about 6 weeks before time to transplant to allow fibrous roots to
develop. Roots are very susceptible to exposure and should not be
allowed to dry out during transplanting. Grafted trees should be
planted with the union well above ground level and watered immediately.
Since trees have a tendency to grow tall, young trees when about 75
cm tall, should be topped little by little to produce a few evenly
spaced limbs, thus developing a strong, rounded symmetrical tree.
Little pruning is required in bearing trees except to discourage
leaders, to reduce lateral growth, to let in light, and to make
cultural and harvesting operations more favorable. Pruning should be
done toward end of winter after crop is harvested. Macadamia grows best
in soils with good supply of humus. Farmyard manure may be added and
green manure crops can be grown between trees in summer. Under orchard
conditions, regular applications of fertilizer are required, as a
8:10:5 formula, at rate of .45 kg per tree per year of age, a maximum
of 4.5 kg. Fertilizer should be applied in early spring just before
trees make new growth and start flowering. Zinc deficiencies seem to be
a problem with this tree, the symptoms being small, yellowish or
slightly mottled leaves which are bunched together, crop retardation
and poor shoot growth. Condition corrected by application of foliar
spray in early spring after first flush of growth, at rate of 4.5 kg
zinc sulfate, 1.3 kg soda ash (or 1.7 kg hydrate lime) in 100 gal
water. However, spray is effective at any period of year if symptoms
are obvious. Since root system is rather close to surface, shallow
cultivation for weed control should be practiced. Summer cover crops,
as cowpeas, and autumn green manure crops may be grown between trees
until harvest time. Grazing cattle on weeds and grass in orchards has
the advantage of adding animal manure.
Harvesting
Nuts
mature in 6–7 months after flowering and must be allowed to ripen on
the trees. Usually the nuts fall to the ground when mature, but in some
cvs remain on trees and must be removed with rake. Nuts are picked up
from the ground by hand or are raked up. After harvesting, nuts are
dehusked, usually with an improvised corn-sheller, washed, placed on
wire trays for about 6 weeks to dry out, graded and shipped to market.
Machinery for cracking shells has been designed for processing
purposes, in addition to several efficient hand-operated crackers,
which produce a kernel undamaged. Kernels which are broken during
cracking are used by confectioners. Shelled kernels deteriorate rather
quickly unless kept in vacuum-sealed jars. Processed nuts when roasted
and slightly salted keep extremely well.
Yields and Economics
Most
trees begin bearing at 6–7 years, others at 10–15, vegetatively
propagated trees bearing earlier. Yield records vary widely. Trees
flower for 3 to 12 months, various strains producing fruits over a long
period. Some cvs have a definite fruiting season. With great commercial
potential in the tropics, macadamia makes an excellent dooryard tree.
In addition to production of nuts in Australia, production in Hawaii in
1970 amounted to 5750 tons valued at $.217/lb. Production is being
developed in South Africa, Paraguay, Costa Rica, Jamaica, Samoa and
Rhodesia.
Energy
According to Saleeb et al. (1973), nuts of M. integrifolia and M. tetraphylla
are equal in oil content with an iodine value of 75.4 and 71.8,
respectively. They describe a method for partially extracting the oil
(6–14% of the weight of intact oven dry kernels), rendering them more
attractive, digestible, and less fattening, while diverting 14% of the
weight to oil production. Australian estimated yield of about 45
kg/tree annually; in Hawaii, yields average 135 kg/tree. New cvs are
known to yield as much as 3.75 MT/ha, averaging 1 ton of kernels, which
should contain more than 700 kg oil/ha renewably (oil makes up 65–75%
of the kernel).
Biotic Factors
Macadamia trees are attacked by Gloeosporium sp. (Blossom blight) and Macrophoma macadamiae. Nematodes isolated from trees include: Helicotylenchus dihystera, H. erythrinae, and Xiphinema americanum
(Golden, p.c. 1984). In Hawaii, the Southern green stinkbug is a
serious problem, damaging about 10% of the seed (Monroe et al., 1972)
Chemical Analysis of Biomass Fuels
Analysing
62 kinds of biomass for heating value, Jenkins and Ebeling (1985)
reported a spread of 21.01 to 20.00 MJ/kg, compared to 13.76 for
weathered rice straw to 23.28 MJ/kg for prune pits. On a % DM basis,
the shells contained 75.92% volatiles, 0.40% ash, 23.68% fixed carbon,
54.41% C, 4.99% H, 39.69% O, 0.36% N, 0.01% S, and undetermined residue.
References
•
Duke, J.A. 1978. The quest for tolerant germplasm. p. 1–61. In: ASA
Special Symposium 32, Crop tolerance to suboptimal land conditions. Am.
Soc. Agron. Madison, WI
• Jenkins, B.M. and Ebeling, J.M. 1985. Thermochemical properties of biomass fuels. Calif. Agric. 39(5/6):14–16.
• Monroe, G.E., Tung Liang, and Cavaletto, C.G. 1972. Quality and yield of tree-harvested macadamia nuts. USDA, ARS 42–196:1–9.
• Rumsey, H.J. 1927. Australian nuts and nut growing in Australia. Part I. The Australian nut. Sidney.
• Saleeb, W.F., Yermanos, D.M., Huszar, C.K., Storey, W.B., and Habanauskas, C.K. 1973. The oil and protein in nuts of Macadamia tetraphylla • L. Johnson, Macadamia integrifolia Maiden and Betche, and their F1 Hybrid. J. Am. Soc. Hort. Sci. 98(5):453–456.
Last update Wednesday, January 7, 1998 by aw
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