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Introduction
African nightshades can be found throughout Africa. There are
several wild species with black berries, but the most popular
cultivated species in West Africa have dark purple berries and
belong to Solanum scabrum. Common names of this species
include bitossa, jamajama, and zom. This
group of species is often erroneously referred to as Solanum
nigrum, a poisonous plant from Europe that is not usually
grown in Africa. African nightshades can grow on a wide range
of soil types but do not tolerate drought.
Seeds and
Sowing
The soil in the nursery should be loosened and enriched with
decomposed manure. Seeds should be mixed with sand and/or ash
for uniform sowing. Sow the mixture thinly, either by broadcasting
or in rows, 15-20 cm apart and cover with a fine layer of soil.
After sowing, the bed should be mulched with tall grass or a
similar material to retain moisture. This mulch can be removed
once the plants are 3 cm. Transplant when seedlings have 6 true
leaves and are 10-15 cm tall. Space plants 20x20 cm during the
dry season, and 20x50 cm during the rainy season to reduce diseases.
Spacing should be wider for large-leafed varieties like Foumbom.
Crop Management
Nightshades require large amounts of nutrients, and therefore
do well in soils that are rich in organic matter. They also grow
well on land covered with ash from recently burned vegetation.
Farmers generally use 20-10-10 NPK, urea, or sulphate of ammonia
when there is no manure available. Sidedressing is practiced
after every second harvest. However, excessive applications of
nitrogen can lead to foliar diseases as well as a build-up of
nitrites, which could become a human health risk.
Frequent irrigation is needed
for good yields. Aphids are a major pest, causing leaves to curl
and become unattractive to customers. Diseases are similar to
those of potatoes and tomatoes, thus rotating with other crops
such as amaranth is essential.
Harvesting
and Postharvest
The first harvest will be 5 weeks after transplanting. The stems
can be cut about 10 cm from the ground, so that new side shoots
develop. Pickings at weekly intervals will allow 6 harvests per
plant (more if plants are sidedressed). If complete harvesting
is practiced, spacing can be as close as 10x10 cm and plants
are uprooted. This method is mainly used when there is less than
2 months before the main staple-food crop will be planted. Roots
of these crops can be kept in water to keep the plants fresh.
Picking should be done early in the morning and the produce sold
the same day. Alternatively, the crop can be harvested late in
the afternoon and placed on plastic sheets or banana leaves.
The produce should be tied in small bundles and the flowers removed
before it is taken to market. Keep the bundles upright and water
them sparingly to retain freshness. The yield can be 40 tons
per hectare.
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