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CASHEW NUTS IN THE TROPICS

  BY: Joseph Mulopi

  Agriculture Officer - Youth in Act-Uganda

  Snake River Music Gardens

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Cashew nut is a hardy tropical evergreen perennial tree which spreads vigorously; old trees can have canopies with diameters of up to 12m and their roots grow up to a radius which is often twice that of canopy. It can grow to a height of 12 m with alternate leaves which are simple, leathery and ovate in shape. The lamina is glabrous, 6-20cm long and 4-15cm broad, rounded and often notched at the apex. It is tapering at the base with Promina veins, lateral veins spreading. The petiole is 1-2cm long swollen at the base and flattened on an upper surface.

Cashew nut is a cross pollination species and is highly heterozygous; it produces a mixture of male and female hermaphrodite flowers at the tip of the inflorescence. The inflorescence is a lax terminal with many flowered panicles. The flowers are sweet scented and has pubescent bracts. It has fine narrow, green sepals 5cm long, and fine linear petals which are 1cm long which is reflexed in an open flower pale greenish-to cream with red stripes, later turning red with 10 stamens.

Hermaphrodite flowers per inflorescence are about 60 in number and the ratio of male to hermaphrodite flowers is about 6:1. Most flowers open between 6.00am and 6.00pm with peak opening period between 11.am and 12.30pm. The flowers are visited by flies and other insects; these transfer the sticky pollen to the stigma. Not all flowers pollinated produce mature fruits as there is uneven fruit fall due to physiological causes. About 10 percent of the hermaphrodite flowers produce mature fruits with an average of 5-6 fruits per inflorescence.

Cashew nut is a native plant of American tropics extending from Mexico to Peru, Brazil and West Indies, Mozambique, Tanzania, Benin, Kenya, Malagasy, Malawi, Nigeria, and Senegal. Cashew nut as a tropical crop can tolerate a wide range of soils except poorly draining swampy or water logged soils, with excessive salinity or alkalinity. It prefers loam and sandy loam to very sandy soils. In Uganda it does better in well-draining high soils of the eastern and northern regions. The trees are unusual crop in that they flower, set fruits, and maintain a full leaf cover during the driest part of the year.

Cashew nut is a drought resistant tree which is explained by the great horizontal growth of roots enabling it to thrive well in areas with marginal rainfall. It can resist drought if spacing is wide enough to avoid overcrowding of the trees.

Cashew nut can be planted from both seeds and vegetative in a nursery bed or directly in the field using seeds or cuttings. Seeds are soaked overnight in water and only those that sink and are of higher than average size are selected for planting. Plant cashew nut seedlings at the spacing of 12mx12m or 18mx18m.

Seedlings are raised in the nursery bed early in the season; a shade should be constructed to protect the seedlings from direct sun rays. Select seeds which are uniform in size and shape plant in polythene with the scar on the seed pointing downwards to allow radical to push out from the scar. The nursery is watered regularly if in dry season between November and February. The seedling will be ready for planting in the field within 6 weeks.  While planting remove the polythene by cutting the bottom of the polythene pot. The advantage of planting seedlings from a nursery bed is the uniformity of the plants.

USES

The most important products of cashew nut are the kernels which are used for dessert or confectionary purposes. The cashew nut shell can be used in a number of industrial products such as medicines, paint plastics, food preservatives, brake linings and ink.  Cashew nut apple has 45-50 percent non-drying apple which is used in beverages, jam; Fein. The sap from the bark is mixed with tree wax for making shoe polish.

NUTRITION VALUES

Cashew nut apple is said to contain 88 percent water, 0.2 percent protein, 0.2 percent fat, 11.6 percent carbohydrate and is rich in vitamin C. The nut contains 5 percent water, 20 percent protein, 45 percent fats, 26 percent carbohydrates, 1.5 percent fiber, and 2.5 percent mineral matter. The shell (pericarp) contains almost 50 percent cashew-vesicant oils. Cashew-shell liquid oil is composed of 70 percent anacardic acid, 5 percent cardanol, and 18 percent cardol.

PESTS AND DISEASES

Like any other plant, cashew nut can be attacked by two species of Helopeltis bug that do considerable damage by sucking the leaves, young fruits and flower which cause fruits to fall off. The Helopeltis schoutedeni do the same damage to the plant and these two species cause black lesions on the plants and plants get die back of the new shoots. The shoots grow into witch broom, e.g. growth of the twig at one point on branches. The pests can be controlled by spraying with summithion, dimecron, thiodan etc.

The most serious diseases appear to be anthracnose which is considered to be responsible for heavy crop loss, powdery mildew, and die back or pink-disease.