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Tropical Plant "Banana"
Musa X paradisiaca
The word "banana" is a general term embracing a number of
species or hybrids in the genus Musa of the family
Musaceae. Some species such as M. Basjoo Sieb. &
Zucc. of Japan and M. ornata Roxb., native from Pakistan
to Burma, are grown only as ornamental plants or for fiber.
M. textilis Nee of the Philippines is grown only for
its fiber, prized for strong ropes and also for tissue-thin
tea bags. The so-called Abyssinian banana, Ensete ventricosum
Cheesman, formerly E. edule Horan, Musa ensete
Gmel., is cultivated in Ethiopia for fiber and for the staple
foods derived from the young shoot, the base of the stem,
and the corm.
Most
edible-fruited bananas, usually seedless, belong to the species
M. acuminata Colla (M. cavendishii Lamb. ex
Paxt., M. chinensis Sweet, M. nana Auth. NOT
Lour., M. zebrina Van Houtee ex Planch.), or to the
hybrid M. X paradisiaca L. (M. X sapientum
L.; M. acumianta X M. balbisiana Colla).
M.
balbisiana Colla of southern Asia and the East Indies,
bears a seedy fruit but the plant is valued for its disease-resistance
and therefore plays an important role as a ";parent"; in the
breeding of edible bananas.
M.
fehi Bertero ex Vieill. and M. troglodytarum L.
have been applied to the group of bananas known as fehi or
fe'i but taxonomists have yet to make final decisions as to
the applicability of these binomials.
To
the American consumer, ";banana"; seems a simple name for
the yellow fruits so abundantly marketed for consumption raw,
and ";plantain"; for the larger, more angular fruits intended
for cooking but also edible raw when fully ripe. However,
the distinction is not that clear and the terms may even be
reversed. The types we call ";banana"; are known by similar
or very different names in banana-growing areas. Spanish-speaking
people say banana china (Paraguay), banano enano
(Costa Rica), cambur or camburi (Colombia, Venezuela),
cachaco, colicero, cuatrofilos (Colombia); carapi
(Paraguay), curro (Panama), guineo (Costa Rico,
Puerto Rico, E1 Salvador); murrapo (Colombia); mampurro
(Dominican Republic); patriota (Panama); platano
(Mexico); platano de seda (Peru); platano enano
(Cuba); suspiro (Dominican Republic); zambo
(Honduras). Portuguese names in Brazil are: banana maca,
banana de Sao Tome', banana da Prata. In French
islands or areas, the terms may be bananier nain, bananier
de Chine (Guadaloupe), figue, figue banane, figue naine
(Haiti). Where German is spoken, they say: echte banane,
feige, or feigenbaum. In the Sudan, baranda.
The
types Americans call ";plantain";, Plate IV, may be known
as banaan (Surinam); banano macho (Panama);
banane or bananier (Haiti, Guadeloupe, Martinique);
banane misquette or banane musquee, or pie
banane (Haiti); bananeira de terra (Brazil); banano
indio (Costa Rica); barbaro (Mexico); butuco
(Honduras); parichao (Venezuela); plantain (Guyana,
Jamaica, Trinidad); platano (Cuba, Puerto Rico, Dominican
Republic); platano burro, platano hembra (Cuba);
platano macho (Cuba, Panama); platano de la isla
(Peru); topocho or yapuru (Venezuela); zapolote
(Mexico). Numerous other vernacular names, according to geographical
region, are provided by N.W. Simmonds in his textbook, Bananas.
In
India, there is no distinction between bananas and plantains.
All cultivars are merely rated as to whether they are best
for dessert or for cooking.
Banana Description
The
banana plant, often erroneously referred to as a "tree", is
a large herb, with succulent, very juicy stem (properly "pseudostem")
which is a cylinder of leaf-petiole sheaths, reaching a height
of 20 to 25 ft (6-7.5 m) and arising from a fleshy rhizome
or corm. Suckers spring up around the main plant forming a
clump or "stool'', the eldest sucker replacing the main plant
when it fruits and dies, and this process of succession continues
indefinitely. Tender, smooth, oblong or elliptic, fleshy-stalked
leaves, numbering 4 or 5 to 15, are arranged spirally. They
unfurl, as the plant grows, at the rate of one per week in
warm weather, and extend upward and outward, becoming as much
as 9 ft (2.75 m) long and 2 ft (60 cm) wide. They may be entirely
green, green with maroon splotches, or green on the upperside
and red purple beneath. The inflorescence, a transformed growing
point, is a terminal spike shooting out from the heart in
the tip of the stem. At first, it is a large, long-oval, tapering,
purple-clad bud. As it opens, it is seen that the slim, nectar-rich,
tubular, toothed, white flowers are clustered in whorled double
rows along the floral stalk, each cluster covered by a thick,
waxy, hoodlike bract, purple outside, deep-red within. Normally,
the bract will lift from the first hand in 3 to 10 days. If
the plant is weak, opening may not occur until 10 or 15 days.
Female flowers occupy the lower 5 to 15 rows; above them may
be some rows of hermaphrodite or neuter flowers; male flowers
are borne in the upper rows. In some types the inflorescence
remains erect but generally, shortly after opening, it begins
to bend downward. In about one day after the opening of the
flower clusters, the male flowers and their bracts are shed,
leaving most of the upper stalk naked except at the very tip
where there usually remains an unopened bud containing the
last-formed of the male flowers. However, there are some mutants
such as 'Dwarf Cavendish' with persistent male flowers and
bracts which wither and remain, filling the space between
the fruits and the terminal bud.
As
the young fruits develop from the female flowers, they look
like slender green fingers. The bracts are soon shed and the
fully grown fruits in each cluster become a "hand" of bananas,
and the stalk droops with the weight until the bunch is upside
down. The number of "hands" varies with the species and variety.
The
fruit (technically a "berry") turns from deep-green to yellow
or red, or, in some forms, green-and white-striped, and may
range from 2 1/2 to 12 in (6.4-30 cm) in length and 3/4 to
2 in (1.9-5 cm) in width, and from oblong, cylindrical and
blunt to pronouncedly 3-angled, somewhat curved and hornlike.
The flesh, ivory-white to yellow or salmon-yellow, may be
firm, astringent, even gummy with latex, when unripe, turning
tender and slippery, or soft and mellow or rather dry and
mealy or starchy when ripe. The flavor may be mild and sweet
or subacid with a distinct apple tone. Wild types may be nearly
filled with black, hard, rounded or angled seeds 1/8 to 5/8
in (3-16 mm) wide and have scant flesh. The common cultivated
types are generally seedless with just minute vestiges of
ovules visible as brown specks in the slightly hollow or faintly
pithy center, especially when the fruit is overripe. Occasionally,
cross-pollination by wild types will result in a number of
seeds in a normally seedless variety such as 'Gros Michel',
but never in the Cavendish type.
Banana Origin
and Distribution
Edible
bananas originated in the Indo-Malaysian region reaching to
northern Australia. They were known only by hearsay in the
Mediterranean region in the 3rd Century B.C., and are believed
to have been first carried to Europe in the 10th Century A.D.
Early in the 16th Century, Portuguese mariners transported
the plant from the West African coast to South America. The
types found in cultivation in the Pacific have been traced
to eastern Indonesia from where they spread to the Marquesas
and by stages to Hawaii.
Bananas
and plantains are today grown in every humid tropical region
and constitute the 4th largest fruit crop of the world, following
the grape, citrus fruits and the apple. World production is
estimated to be 28 million tons-65% from Latin America, 27
% from Southeast Asia, and 7 % from Africa. One-fifth of the
crop is exported to Europe, Canada, the United States and
Japan as fresh fruit. India is the leading banana producer
in Asia. The crop from 400,000 acres (161,878 ha) is entirely
for domestic consumption. Indonesia produces over 2 million
tons annually, the Philippines about 1/2 million tons, exporting
mostly to Japan. Taiwan raises over 1/2 million tons for export.
Tropical Africa (principally the Ivory Coast and Somalia)
grows nearly 9 million tons of bananas each year and exports
large quantities to Europe.
Brazil
is the leading banana grower in South America-about 3 million
tons per year, mostly locally consumed, while Colombia and
Ecuador are the leading exporters. Venezuela's crop in 1980
reached 983,000 tons. Large scale commercial production for
export to North America is concentrated in Honduras (where
banana fields may cover 60 sq mi) and Panama, and, to a lesser
extent, Costa Rica. In the West Indies, the Windward Islands
of Martinique and Guadeloupe are the main growers and for
many years have regularly exported to Europe. Green bananas
are the basic food of the people of Western Samoa and large
quantities are exported.
In
Ghana, the plantain is a staple food but up to the late 1960's
the crop was grown only in home gardens or as a shade for
cacao. When the cacao trees declined, solid plantings of plantain
were established in their place and in newly cleared forest
land where the richness of organic matter greatly promotes
growth. By 1977, Ghana was harvesting 2,204,000 tons (2,000,000
MT) annually.
The
plantain is the most important starchy food of Puerto Rico
and is third in monetary value among agricultural crops, being
valued at $30,000,000 annually. While improved methods of
culture have been adopted in recent years and production has
been increased by 15% in 1980, it was still necessary to import
1,328 tons (1,207 MT) to meet local demand. Annual per capita
consumption is said to be 65 lbs (29.5 kg). In the past, most
of the plantains in Puerto Rico were grown on humid mountainsides.
High prices have induced some farmers to develop plantations
on level irrigated land formerly devoted to sugarcane.
In
tropical zones of Colombia, plantains are not only an important
part of the human diet but the fruits and the plants furnish
indispensable feed for domestic animals as well. The total
plantain area is about 1,037,820 acres (420,000 ha) with a
yield of 5,500 lbs per acre (5,500) kg/ha). Mexico grows about
1/6 as much, 35% under irrigation, and the crop is valued
at $1,335 US per acre ($3,300 US/ha). Venezuela has somewhat
less of a crop 517,000 tons from 146,000 acres (59,000 ha)
in 1980-and the Dominican Republic is fourth in order with
about 114,600 acres (46,200 ha). Bananas and plantains are
casually grown in some home gardens in southern Florida. There
are a few small commercial plantations furnishing local markets.
Banana Varieties
Edible
bananas are classified into several main groups and subgroups.
Simmonds placed first the diploid M. acuminata group
'Sucrier', represented in Malaya, Indonesia, the Philippines,
southern India, East Africa, Burma, Thailand, the West Indies,
Colombia and Brazil. The sheaths are dark-brown, the leaves
yellowish and nearly free of wax. The bunches are small and
the fruits small, thin-skinned and sweet. Cultivars of this
group are more important in New Guinea than elsewhere.
Here
belongs one of the smallest of the well-known bananas, the
'Lady Finger', also known as'Date'or'Fig', and, in
Spanish, as 'Dedo de Dama', 'Datil', 'Nino', Bocadillo', 'Manices',
'Guineo Blanco', or 'Cambur Titiaro'. The plant reaches 25
ft (7.5 m) in height, has a slender trunk but a heavy root
system that fortifies the plant against strong winds. The
outer sheaths have streaks or patches of reddish brown. The
bunch consists of 10 to 14 hands each of 12 to 20 fingers.
The fruit is 4 to 5 in (10-12.5 cm) long, with thin, light-yellow
skin and sweet flesh. This cultivar is resistant to drought,
Panama disease and the black weevil but subject to Sigatoka
(leaf spot). It is common in Latin America and commercial
in Queensland and New South Wales.
In
second place, there is the group represented by the prominent
and widely cultivated 'Gros Michel' originally from
Burma, Thailand, Malaya, Indonesia and Ceylon. It was introduced
into Martinique early in the 19th Century by a French naval
officer and, a few years later, was taken to Jamaica; from
there it was carried to Fiji, Nicaragua, Hawaii and Australia,
in that sequence. It is a large, tall plant bearing long bunches
of large, yellow fruits, and it was formerly the leading commercial
cultivar in Central Africa, Latin America and the Caribbean,
but has been phased out because of its great susceptibility
to Panama disease. It has given rise to several named sports
or mutants.
The
Cavendish subgroup includes several important bananas:
a)
The 'Dwarf Cavendish', Plate III, first known from
China and widely cultivated, especially in the Canary Islands,
East Africa and South Africa. The plant is from 4 to 7 ft
(1.2-2.1 m) tall, with broad leaves on short petioles. It
is hardy and wind resistant. The fruit is of medium size,
of good quality, but thin-skinned and must be handled and
shipped with care. This cultivar is easily recognized because
the male bracts and flowers are not shed.
b)
The 'Giant Cavendish', also known as 'Mons Mari, 'Williams',
'Williams Hybrid', or 'Grand Naine', is of uncertain origin,
closely resembles the 'Gros Michel', and has replaced the
'Dwarf' in Colombia, Australia, Martinique, in many Hawaiian
plantations, and to some extent in Ecuador. It is the commercial
banana of Taiwan. The plant reaches 10 to 16 ft (2.7-4.9 m).
The pseudostem is splashed with darkbrown, the bunch is long
and cylindrical, and the fruits are larger than those of the
'Dwarf' and not as delicate. Male bracts and flowers are shed,
leaving a space between the fruits and the terminal bud.
c)
'Pisang masak hijau', or 'Bungulan', the triploid Cavendish
clone of the Philippines, Indonesia and Malaya, is erroneously
called 'Lacatan' in Jamaica where it replaced 'Gros Michel'
because of its immunity to Panama disease, though it is subject
to Sigatoka (leaf spot). The plant is tall and slender and
prone to wind injury. Its fruits ripen unevenly in winter,
bruise easily and are inclined to spoil in storage. It is
no longer grown commercially in Jamaica and the Windward Islands.
The fruits are commonly used as cooking bananas in Jamaican
households. Simmonds declares this cultivar is not the true
'Lacatan' of the Philippines. He suggested that 'Pisang masak
hijau' may have been the primary source of all the members
of the Cavendish group.
d)
'Robusta', very similar to the so-called 'Lacatan',
has largely replaced that cultivar in Jamaica and the Windward
Islands and the 'Gros Michel' in Central America because it
is shorter, thick-stemmed, less subject to wind. It is being
grown commercially also in Brazil, eastern Australia, Samoa
and Fiji. It is resistant to Panama disease but prone to Sigatoka.
e)
'Valery', also a triploid Cavendish clone, closely
resembles 'Robusta' and some believe it may be the same. However,
it is being grown as a successor to 'Robusta'. It is already
more widely cultivated than 'Lacatan' for export. As compared
with other clones in cooking trials, it has low ratings because
cooking hardens the flesh and gives it a waxy texture.
The
Banana Breeding Research Scheme in Jamaica has developed a
number of tetraploid banana clones with superior disease-resistance
and some are equal in dessert quality to the so-called 'Lacatan'
and 'Valery'.
The
tall 'Maricongo' and the 'Common Dwarf' are
leading commercial cultivars. A dwarf mutant is the 'Plantano
enano of Puerto Rico ('banane cochon' of Haiti). Ordinary
plantains are called 'cuadrado', 'chato', and 'topocho'
in Mexico. The leading commercial cultivars are 'Pelipita'
and 'Saba' which are resistant to Black Sigatoka but they
do not have the high culinary quality of 'Harton', 'Dominico-Harton',
'Currare', and 'Horn'. 'Laknau' is a fertile plantain that
resembles 'Horn' but is of inferior quality. It has opened
up possibilities for hybridizing and is being crossed with
'Pelipita' and 'Saba'.
Banana
and plantain cultivars most often grown in Florida are the
'Dwarf Cavendish', 'Apple', and 'Orinoco' bananas and the
'Macho' plantain. The 'Red' and 'Lady Finger' bananas are
very occasionally grown in sheltered locations.
There
are five major collections of banana and plantain clones in
the world. United Brands maintains a collection of 470 cultivars
and 100 species at La Lima, Honduras.
Banana Climate
The
edible bananas are restricted to tropical or neartropical
regions, roughly the area between latitudes 30°N and 30°S.
Within this band, there are varied climates with different
lengths of dry season and different degrees and patterns of
precipitation. A suitable banana climate is a mean temperature
of 80°F (26.67°C) and mean rainfall of 4 in (10 cm) per month.
There should not be more than 3 months of dry season.
Cool
weather and prolonged drought retard growth. Banana plants
produce only one leaf per month in winter, 4 per month in
summer. If low temperatures occur just at flowering time,
the bud may not be able to emerge from the stem. If fruits
have already formed, maturity may be delayed several months
or completely suspended. If only the leaves are destroyed,
the fruits will be exposed to sunburn. Smudging, by burning
dry trash covered with green clippings to create smoke, can
raise the temperature 2 to 4 degrees. Flooding the field in
advance of a cold snap will keep the ground warm if the chill
weather is brief. In Australia, bananas are planted on sunny
hill sides at elevations of 200 to 1,000 ft (60 to 300 m)
to avoid the cold air that settles at lower levels. Brief
frosts kill the plants to the ground but do not destroy the
corm. 'Dwarf Cavendish' and the 'Red' banana are particularly
sensitive to cold, whereas the dwarf cultivar 'Walha', or
'Kullen', of India is successful up to 4,000 ft (1,220 m)
in the outer range of the Western Ghats. 'Vella vazhai' is
extensively cultivated in the Lower Pulneys between 3,200
and 5,500 ft (975 and 1,616 m). A cooking banana, 'Plankel',
survives winters in home gardens in northern India. In South
Africa, the main banana-producing area is along the southeast
coast at 3,000 ft (915 m) above sea level with summer rainfall
of 35 to 45 in (90-115 cm). The major part of the crop in
East Africa is grown between 4,000 and 5,000 ft (1,220 and
1,524 m) and the total range extends from sea-level to 7,500
ft (2,286 m).
Wind
is detrimental to banana plants. Light winds shred the leaves,
interfering with metabolism; stronger winds may twist and
distort the crown. Winds to 30 mph break the petioles; winds
to 40 mph will topple a pseudostem that is supporting the
weight of a heavy bunch unless the stem is propped, and may
cause root damage in non fruiting plants that are not blown
down; winds of 60 mph or over will uproot entire plantations,
especially when the soil is saturated by rain. Windbreaks
are often planted around banana fields to provide some protection
from cold and wind. Cyclones and hurricanes are devastating
and the latter were the main reason for the shift of large
scale banana production from the West Indies to Central America,
Colombia and Ecuador. Hail results from powerful convection
currents in the tropics, especially in the spring, and does
much damage to bananas.
Banana Soil
The
banana plant will grow and fruit under very poor conditions
but will not flourish and be economically productive without
deep, well-drained soil-loam, rocky sand, marl, red laterite,
volcanic ash, sandy clay, even heavy clay-but not fine sand
which holds water. Over head irrigation is said to improve
the filth of heavy clay and has made possible the use of clay
soils that would never have been considered for banana culture
in the past. Alluvial soils of river valleys are ideal for
banana growing. Bananas prefer an acid soil but if the pH
is below 5.0 lime should be applied the second year. Low pH
makes bananas more susceptible to Panama disease. Where waterlogging
is likely, bananas and plantains are grown on raised beds.
Low, perennially wet soils require draining and dry soils
require irrigation.
Banana Propagation
Banana
seeds are employed for propagation only in breeding programs.
Corms are customarily used for planting and Mexican studies
with 'Giant Cavendish' have shown that those over 17.5 lbs
(8 kg) in weight come into bearing early and, in the first
year, the bunches are longer, heavier, with more hands than
those produced from smaller corms. From the second year on,
the advantage disappears. Most growers prefer "bits" 2- to
4-lb (0.9-1.8 kg) sections of the corm. When corms are scarce,
smaller sections-1 to 2 lbs (454-908 g) have been utilized
and early fertilization applied to compensate for the smaller
size. But in Queensland it is specified that "bits" of 'Dwarf
Cavendish' shall not be less than 4 x 3 x 3 in (10 x 7.5 x
7.5 cm) and "bits" of 'Lady Finger' and other tall cultivars
shall be not less than 5 x 5 x 3 1/2 in ( 12.5 x 12.5 x 9
cm). The corm has a number of buds, or "eyes", which develop
into new shoots. The two upper buds are the youngest and have
a pinkish tint. These develop rapidly and become vigorous
plants.
To
obtain the "bits", a selected, healthy banana plant, at least
7 months old but prior to fruiting, is uprooted and cut off
about 4 to 5 in (10-12.5 cm) above the corm. The outer layer
of leaf bases is peeled off to expose the buds, leaving just
a little to protect the buds during handling and transport.
The corm is split between the 2 upper buds and trimmed with
square sides, removing the lower, inferior buds and any parts
affected by pests or disease, usually indicated by discoloration.
Then the "bits" are fumigated by immersing for 20 minutes
in hot water at about 130°F (54.44°C) or in a commercial nematicide
solution. Sometimes it is advisable to apply a fungicide to
prevent spoilage. They should then be placed in a sanitary
place (away from all diseased trash) in the shade for 48 hrs
before planting.
Inasmuch
as "bits" are not often available in quantity, the second
choice is transplantation of suckers. These should not be
too young nor too old.
The
sucker first emerges as a conical shoot which opens and releases
leaves that are mostly midribs with only vestiges of blade.
These juvenile leaves are called "sword", "spear", or "arrow",
leaves. Just before the sucker produces wide leaves resembling
those of the mature plant but smaller, it has sufficient corm
development to be transplanted. Sometimes suckers from old,
deteriorating corms have broad leaves from the outset. These
are called "water" suckers, are insubstantial, with very little
vigor, and are not desirable propagating material. "Maiden"
suckers that have passed the "sword"-leaved stage and have
developed broad leaves must be large to be acceptably productive.
In banana trials at West Bengal, India, suckers 3 to 4 months
old with well-developed rhizomes proved to be the best yielders.
In comparison, small, medium, or large "sword" suckers develop
thicker stems, and give much higher yields of marketable fruits
per land parcel. "Bits' grow slowly at first, but in 2 years'
time they catch up to plants grown from suckers or "butts"
and are much more economical. "Butts" (entire corms, or rhizomes,
of mature plants), called "bull heads" in the Windward Islands,
are best used to fill in vacancies in a plantation. For quick
production, some farmers will use "butts" with several "sword"
suckers attached. Very young suckers, called "peepers", are
utilized only for establishing nurseries.
Instead
of waiting for normal sucker development, multiplication has
been artificially stimulated in the field by removing the
soil and outer leaf sheaths covering the upper buds of the
corm, packing soil around them and harvesting them when they
have reached the "sword' sucker stage. A greenhouse technique
involves cleaning and injuring a corm to induce callus formation
from which many new plants will develop. As many as 180 plantlets
have been derived from one corm in this manner.
Diseases
are often spread by vegetative propagation of bananas, and
this fact has stimulated efforts to create disease-free planting
material on a large scale by means of tissue culture. Some
commercial banana cultivars have been cultured in Hawaii.
A million 'Giant Cavendish' banana plants were produced by
meristem culture in Taiwan in 1983. In the field, these laboratory
plantlets showed 95% survival, grew faster than suckers in
the first 5 months, had bigger stems and more healthy leaves.
Rapid
multiplication of 'Philippine Lacatan' and 'Grand Naine' bananas,
and the Sigatoka-resistant 'Saba' and 'Pelipita' plantains
by shoot-tip culture has been achieved by workers at State
University of New York.
Banana Culture
On
level land where the soil is compact, deep ploughing is needed
to improve aeration and water filtration, whereas on a sloping
terrain minimum tillage is advised as well as contouring of
rows to minimize erosion. Planting is best done at the end
of the dry season and beginning of the wet season for adequate
initial moisture and to avoid waterlogging of the young plants.
Puerto Rico, because of its favorable climate, is able to
make monthly plantings of plantains the year around in order
to produce a continuous supply for processing factories. However,
some consideration has been given to manipulation of planting
dates to avoid a summer surplus (June-September) caused by
March and May plantings and to take advantage of higher prices
in winter and spring (February to April). To achieve this,
it is suggested that plantings be made only in the first or
second weeks of January, July, September, November and December.
Generally, the banana requires 10 to 12 months from planting
to harvest. Summer plantings of plantains in Puerto Rico take
14 to 16 months; winter plantings 17 to 19. In regions where
there may be periods of low temperatures in winter, planting
time is chosen to allow flowering and fruiting before predictable
cold periods.
Spacing
varies with the ultimate size of the cultivar, the fertility
of the soil, and other factors. Close planting protects plantations
exposed to high winds, but results in fewer suckers, hinders
disease control, and has been found to be profitable for only
the first year. In subsequent years, fruits are shorter, the
flesh is softer and bunches ripen prematurely. The standard
practice in Puerto Rico is 500 plants of 'Maricongo' plantain
per acre (1,235 plants/ha). Increasing to 800 plants/acre
(1,976/ha) has increased yield by 4 tons, but elevating density
to 1,300 plants/acre (3,212 plants/ha) has not shown any further
increase. In Surinam, most of the plantains are grown at a
density of 809 to 1,012 plants per acre (2,000-2,500/ha),
but density may range from 243 to 1,780 plants per acre (600-4,400/ha).
The
higher the number of plants in the field, the larger the volume
of fertilizer that must be applied. The crop suffers severely
from root competition, for the roots of a fully grown banana
plant may extend outward 18 ft (5.5 m). The higher the altitude,
the lower the density must be because solar radiation is reduced.
Too much space between plants allows excessive evaporation
from uncovered soil and increases the weed problem. Growers
must determine the most economical balance between sufficient
light for good yields and efficient land managemeet. Spacing
distances for 'Dwarf Cavendish' range from 10 x 6 ft (3 x
1.8 m) to 15 x 12 ft (4.5 x 3.6 m). A spacing of 12 ft (3.6
m) between rows and 8 ft (2.4 m) between plants allows 450
plants per acre (1,112 plants/ha). Studies conducted with
the so called 'Lacatan' ('Pisang masak hijau') over a 3-year
period in Jamaica, demonstrated the optimum density to be
680 plants per acre (2,680/ha). At closer spacings, yield
increased but profits declined. Hexagonal spacing gives the
maximum number of plants per area. Double- and triple-row
plantings provide alleys for mechanical operations and harvesting.
Planting
holes should be at least 18 in (45 cm) wide and 15 in (38
cm) deep, but may be as much as 3 ft (0.91 m) wide and 2 ft
(0.6 m) deep for extra wind resistance. They should be enriched
in advance of planting. On hillsides, suckers are set with
the cut surface facing downhill; the bud or "eye" of a "bit"
must point uphill; so that the "follower" sucker will emerge
on the uphill side where the soil is deepest. A surface cover
of about 4 in (10 cm) of soil is trampled down firmly.
Weed
control is essential. Geese have been installed as weeders
because they do not eat the banana plants. However, they consume
mostly grass and fail to eliminate certain broad-leaved weeds
which still require cleaning out. Certain herbicides, including
Diuron and Ametryne, have been approved for banana fields.
They are applied immediately after planting but great care
must be taken to minimize adverse effects on the crop. Ametryne
has been shown to be relatively safe for the plants and it
has a short life in the soil. The most persistent weed is
Cyperus rotundus L. (nutgrass, yellow nutgrass, purple
nutsedge, coqui or coyolillo) which decreases yields and competes
with the crop for nitrogen.
In
some plantations, a mulch of dry banana leaves is maintained
to discourage weeds. Some growers resort to live groundcovers
such as Glycine javanica L. (Rhodesian kodzu), Commelina
spp., or Zebrina pendula Schnizl. or other creepers,
but these tend to climb the banana stems and become a nuisance.
Sometimes short-term crops are interplanted in young banana
fields, for example, maize, eggplant, peppers, tomatoes, okra,
sweetpotato, pineapple or upland rice. A space of at least
3 ft (0.91 m) must be kept clear around each banana plant.
However, there are banana authorities who are opposed to interplanting.
Bananas
and plantains are heavy feeders. It has been calculated that
a harvest of 5 tons of fruit from an acre leaves the soil
depleted by 22 lbs (10 kg) nitrogen, 4 lbs (1.8 kg) phosphorus,
55 lbs (25 kg) potash and 11 oz (312 kg) calcium. In general,
it can be said that banana plants have high nitrogen and phosphorus
requirements and a fertilizer formula of 8:10:8 NPK is usually
suitable and normally 1 to 1 1/2 tons/acre (1 1 1/2 MT/ha)
may be adequate. One-third of the fertilizer is worked into
each planting site when most of the plants appear above ground,
one third in a circle about 1 ft (30 cm) out from each plant
2 months later, and one-third at double the distance 2 months
after that. Supplementary feedings will depend on signs of
deficiencies (often determined by leaf analyses) as the plantation
develops. Fertilization needs vary with the soil. In Puerto
Rico, most plantains are grown on humid Oxisols and Ultisols
in the interior. These soils are well drained but relatively
infertile and highly acid, the pH being about 4.8. On such
soils, potassium uptake may be too high and N and Mg deficiencies
occur. But experts have shown that these soils respond to
good fertilization practices and can be very productive. As
an example, 224 lbs N per acre (224 kg/ha) applied in circular
bands 1.5 ft (0.46 m) from the base of the pseudostem gives
a significantly higher yield than broadcast N, and there is
good response to Mg applied at time of planting and again
7 months later.
In
the humid mountain regions of Puerto Rico, 250 to 325 lbs
N per acre (250 325 kg/ha), 125 to 163 lbs phosphorus per
acre (125 163 kg/ha), and 500 to 650 lbs potassium per acre
(500 650 kg/ha) are recommended for plantains. On lowland
sandy clay, phosphorus and magnesium applications appear ineffective.
Applications of N at the rate of 168 to 282 lbs/acre (168-282
kg/ha) increase size and number of fruits harvested, but higher
rates of N decrease yield because of the number of plants
that bend over halfway or are stunted or fail to flower. Applications
of 1,121 1bs N per acre (1,121 kg/ha) reduce production by
46%. Potassium at the rate of 405 to 420 lbs/acre (405 420
kg/ha) has the effect of increasing weight and number of fruits.
However, there appear to be factors, possibly soil magnesium
and calcium, which inhibit the uptake of potassium. One study
showed that it took one year for heavy applications of K to
reach down to a depth of 8 in (20 cm) where most of the roots
were found in a banana plantation on clay loam. One benefit
of added potassium is that it makes bananas more buoyant.
In cool, dry seasons in Honduras, the fruit tissue is abnormally
dense and there is a high rate of "sinkers" when hands are
floated through a washing tank. Such fruits have been found
deficient in potassium and increased potassium in the fertilizer
has reduced the problem. Irrigation by costly overhead sprinkler
systems is standard practice in large scale banana culture
in Central America. Without such equipment, irrigation basins
may be necessary throughout the field and they should be able
to hold at least 3 in (7.5 cm) of water. During the first
2 months, the plants should be irrigated every 7 to 10 days;
older plants need irrigation only every 3 to 4 weeks in dry
seasons. On heavy soils, too frequent irrigations decrease
yields. For maximum root development, the water table must
be between 14 and 19 in (36 48 cm) below ground level.
To
preserve the original density, the plants are pruned; that
is, only the most deep seated sucker and one or more of its
offshoots ("peepers") are permitted to exist beside each parent
plant to serve as replacements and maintain a steady succession.
All other suckers are killed to prevent competition with the
pseudostem and its "followers", and a bunch of fruits will
be ready for harvest every 6 to 8 months. Various methods
of de-suckering have been employed: 1) wrenching by hand;
2) cutting at soil level with a banana knife; 3) cutting at
soil level and filling the base with kerosene; 4) cutting
at soil level and killing the under ground terminal bud by
thrusting in and twisting a gouging tool.
As
the older leaves wither and droop, they must be removed because
they interfere with spraying, they shade the suckers, cause
blemishes on the fruits, harbor disease, insects and other
creatures, and constitute a fire hazard.
Bearing
bananas require propping. This has been done with simple wooden
or bamboo poles, forked poles, or two stakes fastened together
to form an "X" at the top, a system much less harmful to the
pseudostem. Or the plant may be tied back to pickets driven
into the ground, to prevent falling with the weight of the
bunch.
Various
types of covering-dry banana leaves, canvas, drill cloth,
sisal sacks, or burlap or so-called "Hessian' bags (made of
jute), have been put over banana bunches intended for export,
especially to enhance fruit development in winter and avoid
blemishes. In 1955, Queensland led the trend toward adoption
of tubular poly vinylchloride (PVC), then the cheaper blue
polyethylene covers after trials produced record bunches.
At first, the transparent covering caused sunburn on the first
two hands and it was found necessary to protect these with
newspaper before pulling on the plastic sleeve. The use of
plastic covers became standard practice not only in Australia
but in Africa, India and the American tropics. In 1963, Queensland
growers were turning to covers made of High Wet Strength (formaldehyde-treated)
kraft paper which was already in use for garbage bags. These
bags were easily stapled at the top, prevented sunburn, resisted
adverse weather, and were reusable for at least another season.
Some growers still prefer the burlap. It is cautioned that
the cover should not be put on until the bracts have lifted
from the fruits (about 21 days after "shooting") so that the
young fingers will be firm enough to resist the friction of
the cover.
If
bunches are composed of more than 7 hands, debudding, or "de-belling"
that is, removal of the terminal male bud (which keeps on
extending and growing) will result in somewhat fuller bananas,
thus increasing bunch weight. The cut should be made several
inches below the last hand so that the rotting tip of the
severed stalk will not affect the fruits.
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