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Climate and Soil
Requirements
African nightshades, also called mnavu, can be found throughout
East Africa. There are several species with black berries, but
the most popular are those with orange berries belonging to Solanum
villosum. 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 require regular rains or frequent
irrigation. It does not tolerate drought.
Seeds and Sowing
Young plants have a fragile root system. 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. It is
advisable to add dry, dust-like chicken manure to this mixture.
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 converted with a layer of tall grass to retain
soil moisture during the dry season. This grass can be removed
once the plants are about 3 cm.
Transplant when seedlings have 6 true leaves and are 10-15 cm
tall. The spacing should be 20 m in the row by 40 cm between
the rows. Direct sowing during the rainy season results in taller
plants with larger leaves and branches, but this system requires
an additional month of precious rainy season time.
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 mainly use 20-10-10 NPK, urea, or sulphate of ammonia
when there is no poultry or farmyard manure available. Sidedressing
is practiced after every second harvest. However, application
of large quantities of nitrogen make the crop vulnerable to disease
unless there is a proper balance with potassium and can be a
health risk as it will have an impact on the level of nitrites
in the leaves and stems.
Frequent irrigation is needed
for a good leaf yield. Weeding is only needed during the early
stages. Aphids are one of the main pests; these insects cause
leaves to curl and become unattractive to customers. Diseases
of nightshades are similar to those of potatoes, tomatoes, and
peppers. Therefore crop rotation with non-Solanaceous crops like
amaranth is essential. In areas with a high humidity, wider plant
spacing should be used.
Harvesting
and Postharvest
The crop will be ready for the first harvest about 5 weeks after
transplanting. The stems can be cut about 10 cm from the ground,
so that new side shoots develop. Pickings at roughly 7-14 day
intervals will allow 3-4 harvests per plant if there is no additional
manure or fertilizers, and more harvests if there is. Complete
harvesting is practiced when the spacing is as close as 10 x
10 cm and plants are uprooted. This method is sometimes used
when there is suitable land available, but less than 2 months
before the main staple-food crop will need to be planted. Roots
of these crops can be kept in water to keep the plants fresh.
The yield can be up to 20-25 t/ha.
Picking should be done very 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. These should be tied in small
bundles. The flowers should be removed before the crop is taken
to market. Water these bundles sparingly to retain freshness. |
