The crops which produce these commodities can all be classed as cash or export crops although many of them such as ginger and sugar cane are also used for domestic consumption.
The major cash crops which will be dealt with in this section are: cocoa, coffee, ginger and sugar cane and the main characteristics of these crops are as follows.
Cocoa
A number of cultivars and selections of cocoa have been grown in West Africa for many years but the introduction of the 'Amazon' selections during recent
years has resulted in a general increase in yield; these are about early maturing and more vigorous than most of the original Amelonado types.
Cocoa is normally grown in moderate to high rainfall areas under light shade, preferably leguminous, since the leaves and roots are both sensitive to excessive water loss, If the planted area is not exposed to ATFong winds, the shade trees over established cocoa can be removed but fertilisers, mulching and possibly irrigation will be required in order to maintain the necessary level of soil fertility. Soils should be deep and well provided with organic material.
They should also be well-drained but clay loams rather than sandy loums are preferable.
Propagation is normally by seeds sown in plastic containers, although stem cuttings are used for multiplying high yielding selections or clones. These cuttings may be from semi mature wood or short stem cuttings with one or two leaves attached; these are also normally rooted in containers.
Hormones may be used to promote rooting. When the seedlings or rooted cuttings are 50-60 cm in height they are transferred to prepared planting holes. Shade should be provided by bananas or other food crops, or leguminous trees, which should have been planted to become well established before the cocoa is transplanted between them. If being transplanted where secondary bush is established, traces should be cut and
cleared before transplanting begins. It is important not to disturb the cocoa roots on transplanting. The initial planting may be fairly close, to allow for later thinning of the trees as they become more mature.
Mulching is generally recommended and fertilisers should be applied if the soils are lacking in any of the major nutrients. Pruning is rarely required, except for the removal of Diseases, dead or crossing branches.
The mature pods are removed from the tree with a sharp knife and the beans, after removal from the pods, are fermented in baskets or boxes for 3-4 days before being dried in the sun. Diseases and pests are controlled by using a regular spraying programme, particularly against Black pod and capsid's.
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Coffee
The main type of coffee grown in lowland areas in West Africa is the 'Robusta' coffee; other types such as 'Arabica', which is adapted to growing at elevations ever 800 m and 'Liberica' arc also grown, but not on a large scale. Soils should be fairly deep, well drained but with a good organic content and, in exposed areas, a light shade is required.
Areas of moderate to high rainfall are generally suitable ie. from 170-220 cm,
but coffee is sensitive to dry periods and shade should be provided if the dry season is pronounced. Seeds are plant in either nursery beds or plastic containers and shaded, irrigated and mulched until transplanted to prepared planting holes when they are about 15-20cm high. They require immediate shading and watering unless planted during wet weather. Some form of shade trees e.g. bananas or leguminous trees should have been established before transplanting takes place.
Pruning, to shape the young trees and produce lateral branches which are within reach for harvesting the crop, should begin at a fairly early age, normally two or three main or primary branches are required.
Weeding to reduce competition and the application of fertiliser at intervals are the main cultural operations required, with the exception of spraying to control any diseases. The wet method of processing, in which the coffee berries are passed through a pulping machine which removes the outer pericarp layer, followed by fermentation to remove the remaining mucilage, is used for producing high quality beans. The more traditional method of sun drying, followed by removal of the dried pericarp by hulling is still widely used, but produces a lower quality product.
Ginger
This spice crop, which is largely exported, is normally grown on flat land and alluvial soils are generally preferred, although it is tolerant to a wide range of soil and climatic conditions. Soils with a good organic content are preferable and elevations up to 1,200 m are generally suitable.
The rhizomes, sometimes referred to as 'hands', form the solvable commodity
and vary in size, shape and colour. Two main types, white and yellow, are in common cultivation. Propagation is by means of pieces of mature rhizome,
these are planted about 5 cm deep at the beginning of the rains, low ridges or beds are often used. The beds or ridges are generally covered with mulch after
planting. Weeding should be carried out until the plants are established, the value of the crop does not normally justify the use of fertilisers or irrigation. Few pests or diseases affect the crop which is lifted when the leaves become dry; the hands are washed and scraped several times before being cured by drying in the sun.
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Sugar Cane
This is an increasingly important export crop and large scale cultivation and extraction operations have been established in various parts of West Africa.
The level of rainfall required for satisfactory crop production is within the range 110-150 cm per annum, areas with a long dry season are not suitable, unless irrigation is available. Clay loams are generally suitable for this crop, but a good level of organic content and satisfactory drainage are also required. Many new cultivars are now available, many of them are very high yielding if given suitable growing conditions..
Plants are propagated from stem cuttings 25-30 cm in length and taken from the upper portion of the stem. They are often laid end to end along prepared trenches where the plants are to grow. These are then gradually filled in and slightly ridged after the plants have become established. Alternatively, cuttings may be raised in the nursery and transplanted. Weeds should be controlled and fertiliser applied as a top dressing as required. The canes are harvested during dry weather and before flowering begins, otherwise the sugar content is likely to fall rapidly.
The juice should be extracted from the cane within 24 hours of harvesting.
Some of the new cultivars are resistant to virus diseases and to Red Rot, one of the most serious diseases of sugar cane in West Africa.