MANGO PRODUCTION
1. Introduction
Mango is the fifth most important fruit crop having a world production of over 15 million tonnes annually. It is generally classified as one of the most common delicious fruits. Its consumption has however been limited to within its production regions. Generally mango is a fragile fruit and transportation by ship is up to now only practical over short distance even under refrigerated conditions. Consequently, despite its quality it has for a long time been ignored by consumers from temperate countries until when air transport developed.
Fresh fruits; are very palatable, rich in vitamin C and A. can be eaten when green-mature as fresh food in the Philippines, in chutneys, flavoring and in sauces. Other uses include, shade for sub storey crops, wind break. In India the stones are used as cattle feed.
2. Botanical description
2.1 Classification
Mango belongs to the family: Anacardiaceae (with 430 species), the genus Mangifera , which is known to have 16 species and the species indica . Thus the binomial name for mango is Mangifera indica L.
The family Anacardiaceae is generally composed of trees and shrubs. Other important fruit species are:
- Anacardiumoccidental (Cashewnut)
- Spondiasdulcis (forst) or S.cytherea (Sonner) (custard apple or golden apple)
- Pistaciavera L. (Pistachio), which is a temperate nut.
2.2 Plant characteristics
2.2.1 Plant structure
Mango is a large spreading evergreen tree with a dense canopy. The tree ranges in height from 9-18 m. Trees taller than this (up to 21m) are not rare. The tree’s spread is of 4-5 m in diameter. Usually the plant is characterized by dense canopy (low branching), with foliage of shade column depending on the season. The size varies considerably depending mainly on variety and growing conditions. The tree life span (longevity) can be up to more than 100 years.
2.2.2 Leaves
Leaves are alternative and simple, with a phyllotaxy of 3/8. They measure 12-40 cm long, up to 10 cm wide. They are petiolate. The petioles are 10 cm long, with a pulvinus at their base. As will be seen later, they are produced at irregular flushes. At the beginning (when they unfold) they are thin flaccid, reddish – coloured. They then gradually become stiff and dark green as they mature.
2.2.3 Inflorescence
Is a widely branched, terminal panicle 10-60cm long, constituted of 1000-6000 reddish –pink or almost white flowers. Both male and hermaphrodite flowers occur on the same inflorescence. About 1-36% of them depending on cultivars, are hermaphrodite (perfect with both stamen and pistils) flowers, the rest being male (unisexual). The male flowers have 6-7 stamens,with only one bearing fertile pollen (5-6 staminodes). In most varieties more flowers are perfect towards the apex of the inflorescence, then towards the base. That is why more fruits are borne on the terminal ends of the inflorescences.
For fruit set, pollination is necessary. Most varieties are self-fertilized. But it has been observed that cross pollination result in better reproduction.Pollination is chiefly entomophilous. The most effective insects are flies, thrips, while other small insects are hardly attracted by the mango flowers. Bees dislike mango flowers.
2.2.4 The fruit
The fruit is a large drupe. The outer most part is the epicarp, the fresh is known as the mesocarp, and is followed by the hard stone or the endocarp to which many fibres are attached. The endocarp encloses the seed (Fig. 1)
The mango fruit is extremely variable size and other characteristics. In terms of size, the fruit weighs between 100g – 3.5 kg, while in shape, it varies from ovate, oblong to roundish, with prominent or fused (flat) beak as well as shoulders. The skin (epicarp) is smooth with a colour that varies from yellow, green, scarlet to deep carmine.The pigmentation is more intense on the exposed side of the fruit. The intensity of colour further depends on the climate.
The flesh is yellow or orange yellow in colour. In some varieties the flesh is fibrous while in others it is free from fibres.
2.2.5 The seed
The seed can be monoembryonic (sexual embryo) or polyembryonic (sexual embryo and several nucellar embryos), numbering 9 to 12.
2.2.6 The root system
A mango tree developing from seed will develop a very strong tap root system, which in absence of obstacles will penetrate very deep into the soil. It has been observed that the tap root will usually continue to penetrate deep into the soil till it reaches water bearing layer or hard pan. Roots have usually been found at a depth of more than 6m.
The effective rooting zone is situated towards 1.2m of depth while 2-3 roots (primary roots) can develop up to beyond 6m of depth.
3. Origin and Distribution
Mango is a native of South Asia, more specifically in Indonesia, Burma and the Malaysian archipelago. It is in this region that the largest multitude of cultivated varieties and wild species are found.From the Indian sub-continent, it is said to have been introduced in the Middle East (Yemen) towards the end of 18th C. It was introduced in the Queensland (Australia) towards 1870. In Africa, it was imported by Arab traders much earlier during the 10thC. Initially it was established along the east coast, in Mombasa and Kilwa as well as on the islands in the Indian Ocean in particular in Madagascar. Further north on the East Africa coast, it was first observed in Somalia.It should have been introduced into the interior much later. At the beginning of the 19thcentury, it had spread up to the Western shores of Lake Tanganyika. It is suggested that it is from there and at that time it spread further to the west up to the upper Niger before the arrival of the Europeans. In the America and the Caribbean mango is said to have been introduced from Goa by Portuguese.
To date mango is cultivated almost entirely in lower altitude areas (except the driest) of the inter-tropical region of the world. It is grown in limited areas outside the inter tropics. The areas include:Israel and Lebanon, Egypt, Hawaii and Florida, the Indian Ocean islands of Madagascar and La Reunion and in South Africa in the Transvaal region.
4. Ecology and Physiology
Mango is a fruit tree of the tropical climate that is characterized by a quite clear succession of dry and wet seasons. The north and south limits of its cultivation is essentially the tropics. The furthest region north of the equator is in Israel 31o50’N.
The tree can grow and produce under wide range of climate, but for commercial production, the limits are more restraint and a function of temperature, rainfall, Altitude as well as wind, solar radiation and relative humidity.
Mango is very sensitive to freezing temperatures. Trees of less than 5years will never resist to temperature of -3oC. These plants are killed outright if temperature falls to 1oC. Optimum temperatures for vegetative growth are those between 24 and 27oC.The average temperature influences the length of time interval between flowering and fruit maturing (Harvesting). Temperature above 21oC will shorten the time interval, while low temperature will prolong it.
4.2 Altitude
In East Africa mango are limited to the lower attitude areas (0-1500m). Mango trees are seldom seen above 1500m. In Kenya two varieties (Harries mango and sabre) can be grown as high as 1800m.
It has been observed that attitude retards the time to flowering for 4 days for every 120m rise. Likewise latitude delays flowering for 4 days/degree.
4.3 Rainfall
Mango grows well in areas which receives different rates of average annual rainfall. Mango grows well in central Tanzania where the average annual rainfall is only 650mm.
Commercial mango production is considered impossible in areas receiving an average annual rainfall of 750mm or below. In such areas irrigation will always be necessary to meet plant water requirement. Irrigation can make possible the commercial growing of mango (even in areas with 200-250mm/annum). The best example is in Israel, where it would otherwise not have survived.
The distribution of rainfall over the year is more important than total precipitation.Mango like other fruit trees needs a resting period (during which vegetative growth is arrested) in order to induce flowering. This indispensable (essential) rest is provoked by dry period of at least 2.5 to 3 months.
Therefore for proper flowering and fruit production there should be approximately 3 months of dry (water stress) period without rainfall each year. In areas where rainfall is well (uniformly) distributed throughout the year, as is the case in the equatorial climate or in very humid areas of certain Islands (e.g., in Madagascar (Tamatave region) where average rainfall per annum is approximately 3000 mm) trees never enter rest period. As a consequence they are usually continuously in vegetative growth. They do not flower or do so very poorly.
Rains during flowering period are destructive, because can prevent pollination, rain water washes away pollen and floral secretion which attracts pollinating insects. Wet conditions promote fungal attack at a time when flowers and the young fruits are very susceptible. Therefore: where irrigation is applied it should be stopped during the period of rest.
Where water supply is solely dependent on rainfall;
· When dry period is prolonged after fruit set it should be less felt by the tree, if water reserves in the soil are sufficient.
· In fact fungal attacks will develop to a lesser extent in particular if the relative humidity is low (mist and dew do not occur). As a result,the development of fruits occurs under favourable conditions and the fruits are eventually of good quality. Thus, early varieties are usually better adapted.
· When the soil water reserves are insufficient, fruit development will be important at the early stage, while filling of those fruits which will be retained will be poor. In such a case, irrigation should be started at flowering.
It can be considered that, a long well marked dry season is very favourable to fruit formation (fruiting) in mango. Irrigation can be applied when there is need inorder to ensure normal development of fruit. Long cloud period will also be unfavourable at flowering and fruit set.
4.4 Soils
Mango is much more adapted to wide range of soil types as long as they sufficiently deep and free draining. A depth of 1.2 – 1.5m is adequate if the underlying horizons do not impair the penetration of the tap root and do not provoke the formation of water layers (rising water level) during the rains.
Soil pH of 5.5-7.5 is preferred(higher pH results to deficiency of Fe and Zn). Soil salinity should not exceed 500 ppm. Water holding capacity of the soil should be moderate, ground water table should be at 3-4m. Steep slopes are unsuitable. The suitable slope should not exceed 6-10%.
5. Plant growth and development
The growth habit of mango differs from most fruit trees.It is not continuous within a season, but it occurs in periodic flushes from the terminal auxiliary buds on young branches.The number of these periodic growth flushes during the growth season (varies from 2-5 per year). They are determined by:
- Varietals characteristic
- Climate
- Cultural practices
- Age
- Crop load on the tree
Each vegetative flush continues for some times after its initiation, become quiescent and then breaks out again until growth ceases for that season, followed by the initiation of flowering
The growth flushes which make their appearance and cease early in the season are the once more likely to be fruitful in the subsequent year.This is because the growth made in early flushes matures and accumulates sufficient carbohydrates before the initiation of flowering.
On bearing trees shoots of the fruit flushes can arise from terminal buds of shoots of the preceding year that did not flower.
The second flushes arise from the lateral buds on shoots that have each a terminal inflorescence that is setting some or no fruit. Third flush may grow from the lateral buds on the shoots that have produced or ripeneda crop (have been harvested), while a fourth flush will originate from lateral shoots that have been greatly weakened by a crop in the current or preceding year.
The presence of foliage of different shades (colours) on the same tree shows that all the branches do not flush at the same time.
6. Cultivation
6.1 Varieties
There are several hundreds of cultivars known in the world. The biggest number is known in India (200 Cv.).Mango types in cultivation are generally placed in 3 main groups:
(i) Monoembryonic seedling races
Seed of this type give rise to only a single sexual seedling. Since mango is a free cross-pollinated plant, the gametic seedlings differ from the female parent, and the tree does not breed true to type from seed. Most mango varieties in India sub-continent are monoembryonic.
(ii) Polyembryonic seedling races;
These races breed true to type from the seed and generally found in the moist tropics. More than one seedling is produced from one seed. These seedlings are called nucellar seedling since, except one seedling which is zygotic all develop from the cells of the nucellus and are thus identical with the parent tree.It is generally believed that in most polyembryonic types the sexual embryo degenerates early in development, with the result that in same varieties all the seedlings are nucellar.
In early stages of growth it is not possible to distinguish between the sexual and nucellar seedlings, but it is generally believed that the sexual seedling is relatively weak and stunted in growth.
(iii) Horticultural varieties
In monoembryonic cultivars, seedlings invariably differ from each other, and from the mother tree. The varieties among the seedlings progenies are responsible for development of chance seedlings possessing desirable yield and fruit characters. These have been further multiplied vegetatively. They form clonal progenies or the Horticultural varieties.
Famous cultivars
Other classification systems are based on shape of fruits (Round – fruited, longfruited, indefinite-fruits).
6.2 Propagation
6.2.1 Propagation through seeds
This is a traditional method in many countries and is employed in the multiplication of polyembryonic types. These reproduce true to type by this sexual method. It is employed in the production of the root stock for the grafting of monoembryonic varieties.
Mango seeds have however very short viability. To improve the viability of mango seeds, seeds can be stored in moist charcoal for up to100 days. However it is better to sow them fresh.
Preparation consist of
- Washing
- Drying in the shade (1-2) days)
- The endocarp should preferably be removed (Decorticated). This facilitates to eliminate damaged or too small seeds, roots development without malformation and rapid germination (that is, 18 against 40 days for non-decorticated seeds.
6.2.2 Grafting
The most common grafting methods are approach grafting, budding, Side grafting, Top working and side veneer
6.3 Plantation Establishment
6.3.1 Time of planting
To ensure quick growth of young plants it is better to plant at the beginning of the wet and hot season. These conditions are favourable for vegetative growth.
6.3.2 Spacing
A density of 100 tree/ha is the most common. Square planting of trees at 8-10 m apart is recommended. Closer spacing of 6.1 x 4.8 = 340 trees/ha which is gradually thinned out has been described.
6.4 Plantation maintenance and management
`6.4.1 Weeding
The area around plants must be kept clean; mulching, shallow cultivation, slashing and use of herbicides are the most common ways of controlling weeds.
6.4.2 Fertilization
Before trees bear fruits, fertilization must be done to permit optimum development of young trees.The recommended balance of the major nutrients (N.P.K) = 4:1:4
From year 4, trees can bear fruits consequently. Nutrients applied must compensate the need of the trees for its development and the exportation occurring during harvest.1 ton of fruits exports: 1,735 kg of N, 0.174 kg of P2O5 and 2,050 kg of K2O
The nutrients should be applied in 3 times:
- Half the total Annual dose will be applied after harvest (in Tanzania) to enable the tree restore their reserves before the resting period, and to be able to produce important blossoming at the end of the rest period.
- A quarter of the total dose will be applied during the lengthening of the flower panicles (Normally August). This will avoid excessive young fruit formation. If simple fertilizers are used the total P2O5 dose can be applied at this time.
- The last quarter of the total dose will be applied when the fruit begin to enlarge in order to encourage the process.
6.4.3 Irrigation
Before the first bearing age, young trees can always be irrigated throughout the year to encourage their growth and absorption of nutrients.
For bearing trees, we have seen that trees need a resting period in order to properly flower. During this period, irrigation (where provided) should be stopped.
7. Harvesting
Yield = 400-600 fruits/ tree/year.
Fruits are picked when they start to change colour and the first fruit start to soften. After harvesting, disinfection at 52oC for 15 minutes by immersing in hot water (52oC) to control anthracnose may be necessary.
Pests
Important parasites:
Fruit flies,Mites, Mealy bugs and Mango weevils.
The fruit fly; Bactrocerainvadensis currently the most devastating insect pest.
Diseases: Bacteriosis, Powdery mildew andAnthracnose.
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