1. INTRODUCTION
The banana is an herbaceous perennial of the Musicale family. The crop is tropical which requires a warm, humid, frost free climate. South Africa does not have the ideal conditions for banana production although there are some areas that grow bananas successfully. The areas that grow bananas are the coastal and Northern regions of Kwa‐Zulu Natal, the coastal regions of the Eastern Cape and Graskop, Malelane and Soutpansburg in Mpumalanga. The Dwarf Cavendish is the most popular variety. The plant consists of:
A rhizome, the true plant stem which is an underground storage organ from which the leaves, roots, flowers and suckers develop;
The main roots are thick and fleshy which branch into hair roots; and
Leaves which develop concentrically around the apex of the rhizome, the stems of which form the trunk or pseudostem of the plant.
Flowers develop in a series of double rows arranged spirally around the fruit stalk. The first flowers are formed at the top of the bunch which are female and develop into the banana ‘fingers’. If cold temperatures occur at this time, few fingers will be formed. Fruits develop from the female flowers only and the plant propagates itself by producing suckers at the base of the rhizome. When a bunch is harvested, a new sucker emerges and becomes the next bearing plant. The banana originated in the humid tropics and has high heat and water requirements.
The two sucker types that are recognized are:
Sword Suckers, which have a broad stem base and narrow leaves; and Water Suckers, which have a narrow base and broad leaves.
Below is a figure of a developing banana bunch with and a picture of a Sword Sucker and a Water Sucker.
Figure 1: The Developing Banana Plant
2. VARIETIES
Two commercial cultivars are grown in Southern and Central Africa and these are the Dwarf Cavendish and Williams. The latter being a mutant selection of Dwarf Cavendish.
Dwarf Cavendish are small plants which grow to a height of approximately 3 metres and grow their bunches at approximately 2 metres. Williams’s plants are larger about 5 metres tall and bunch at a height of about 3 to 3.5 metres. The Williams bunches are much larger and bunches of 100 kg and more, have been harvested. A 39 – 40 kg bunch is exceptional for the Dwarf Cavendish variety.
3. PLANTING
The time of planting can be timed hopefully so that first crop is produced out of season. This is important as the grower can usually obtain a better price for fruit produced in Winter.
The physical condition of the soil is very important since root development is chiefly determined by the degree of soil aeration. Poorly aerated soils caused by over‐irrigation or compaction of poorly drained soils restrict the root development. Soils should be at least 1 metre deep as roots normally grow to depths of 600 – 800 mm and most of the water is extracted from the upper 0.5 metres.
Although sandy loam soils are preferable bananas can be grown on a wide range of soil types. Before land preparation and planting begin it is advisable to have the soil analysed and the appropriate liming and fertilizer recommendations can be made. Bananas are gross feeders and make heavy demands on the available soil nutrients. Nitrogen and potassium are most important for the production of good quality fruit and phosphorus increases the number of hands and fingers per bunch.
Recommended: Spacing is 3.0 metres x (1.5 – 1.75 metres) resulting in 2222 to 1905 plants/ha.
A number of disadvantages are associated with too close spacing:
Fruit size and weight are reduced;
The production cycle of the following crops is prolonged; The fruit does not fill properly;
Sucker development is sparse and poor;
Fungal disease occurs more often and control is difficult; and Orchard management becomes complicated and difficult.
Although the yield per hectare is smaller at the wider spacing the crop cycle is much quicker. Bananas are tropical plants which require additional water (irrigation), when grown in low‐rainfall areas. Water should be applied regularly and adequately since the plants have a shallow root system and the roots are poor drawers of water. Sprinkler irrigation is probably the best method. Clean cultivation is essential throughout the life of the plantation and this removes possible sources of virus diseases and miminises water and nutrient competition which would affect the crop.
The optimum temperature range should be 20 ‐ 35⁰C. Below 12⁰C growth ceases. If the mean monthly temperature drops below 21ºC it will result in retarded growth. Temperatures between 15 and 20oC lead to a moderate growth rate. Bananas require a humidity level of 60% for fruit setting and a minimum humidity of 50% at 14h00 is required.
The required rainfall is 125 mm of water per month (1500 mm per annum) although 1200 mm a year is satisfactory. In most areas irrigation is necessary as dry spells of longer than a week can be detrimental. Soil moisture at 70% of field capacity must be maintained.
4. FERTILIZATION
Well‐rotted kraal manure which is worked into the soil at the rate of 10 – 20 tons/ha is recommended as a pre‐planting treatment. Bananas require large quantities of nitrogen in order to reduce losses caused by leaching and prevent deficiency in the soil.
The general fertilizer recommendation bananas at a population density of approximately 1 905 – 2222 plants/ha are as follows:
Nitrogen: is required at a rate of 340 – 400 kg/ha in 4 equal top dressings in January, March, September and November;
Potassium:is required at a rate of 430 – 500 kg/ha. For heavier textured soils half is applied at planting and the balance 6 months later. For light‐textured soils and initial planting, application of 75
– 100 kg/ha may be given followed by the remainder in 4 equal top‐dressings in January, March, September and November. Subsequent annual dressings should be applied at the rate of 430 – 500 kg/ha at the same time as the nitrogen top‐dressing;
Phosphate:38 – 45 kg/ha Single Superphosphate applied at half the rate as an initial application and ploughed in before planting. Single Superphosphate is subsequently applied at the rate of 38 – 45 kg/ha each year in August or September;
Lime: should be only applied on the basis of soil analysis. Depending on the soil pH and texture,recommended applications vary between 0.5 and 2.0 tons/ha. Where the magnesium status is low the Dolomitic limestone should be used; and
Fumigation of the soil with EDB is recommended as a pre‐planting treatment against possible nematode attack.
5. PESTS AND DISEASES
Fortunately no serious pest or disease problems have emerged in the hotter regions.
Nematodes: The burrowing nematode causes damage to plantations. This nematode causes toppling disease which destroys the plant’s roots. The inevitable result is that the plants fall over with a consequent loss of yield. The degree of damage caused by nematode attack depends on many factors including soil type, age of plant, water supply, fertilizer, rainfall, mulching and the species of nematode present. Other pests are Slugs, Thrips, Mites and Banana Root Borer.
Sigatoga Cigar‐end rot: This is caused by a fungus disease. Removal of the pistil and perianth parts of the flower 8 – 11 days after bunch emergence provides a means of control. Other diseases include Panama wilt, Armillarielle and Erwinia soft rot.
Virus diseases have not been a problem but in order to prevent infection all plantations should be kept weed‐free and not be inter‐planted with vegetables or other crops. The economic lifespan of a plantation can vary from 5 years and upwards. Good soil and climatic conditions, a good site and management practices by the individual farmer, all contribute to a long lifespan.
6. HARVESTING
Banana bunches are harvested when the fruit is about three quarters ripe. When the colour of the fruit changes from green to yellow but the ridges on the fruit are still prominent. The bunches are loaded into trucks padded with a layer of thick foam rubber to minimise bruising and placed in an upright position. The hands are removed from the bunch stalk at a central pack shed and dipped in a warm bath containing a fungicide, are sized, graded and finally packed into boxes.
The ripening cycle varies from 5 ‐ 7 days depending on the stage of ripeness required. An easy way to ripen bananas is to dip them in an ethyl solution and leave them in an ordinary room for 3 ‐ 4 days.
Growers generally sell green bananas to the wholesalers who ripen and distribute the fruit.
