Vegetable crops consist of a diverse range of plants that are suitable for eating raw or
uncooked. This group includes lettuce, baby leaf, celery, watercress,
radish, and salad onion. These vegetables are grown for their
economic importance to man and are very familiar in every Nigerian home. Apart
from these other vegetables, some other tropical crops have also been
successfully cultivated in different parts of Nigeria.
These
include lettuce, cabbage, cucumber and carrot. These four vegetables are very
popular with people from temperate countries who live in Nigeria. The plants
are a common feature of vegetable salad often served at cocktail parties, and
other menu in big hotels.
You
will definitely see that they are a crucial part of the menu of the people.
Read On: Common Food Crops in Nigeria
Vegetable Crops in Nigeria
1. Cabbage (Brassca
oleraccal)
Cabbage
grows well in high latitude areas of Nigeria such as the Jos, Plateau State
where the annual mean temperature is low. However, cabbages may successfully be
cultivated in wet, hotter areas if suitable seeds are available and the
seedlings and transplants are carefully managed. The time of planting must be
carefully selected, while the plants must be adequately supplied with the right
nutrients to ensure success. In addition to mean low temperature, the soil must
be well manure and fertilized. Adequate shade is also necessary to prevent
excessive loss of water.
Cultivation
It
is possible to grow cabbages all year round. However, the best results are
achieved when the sowing time is carefully selected. It is best when the heads
of young plants are forming, at the coldest time of the year
[December/January].
This
timing enables the young plant to withstand harsh harmattan conditions. The
seeds are sown in nursery beds individually, leaving about 46cm between
adjacent plants. Seeds should be sown at a depth of 0.6cm.
Germination
takes place in about five days. Thinning of the seedlings should take place
three days after germination. About four weeks after germination, the seedlings
may be transplanted into well-fertilized and prepared beds.
Each
seedling should be lifted carefully with a ball of soil, around the roots to minimize
the disturbance to the roots. Each cabbage plant is planted at 50cm intervals,
under adequate shade.
Fertilizer Application
During
the process of growth, a nitrogen-containing fertilizer such as ammonium
sulphate or N.P.K. should be sprinkled on to the soil around the plant every
2-3 weeks. Cabbages are gross feeders, which require a lot of nitrogen,
potassium and phosphorus.
Harvesting
Cabbages are usually ready for harvesting two to three months after planting.
During harvesting, the stalks are usually cut and thrown away. If however the
stalks are left in the ground, they may develop into new cabbages, which could
eventually be harvested.
Importance
Cabbages
are cultivated for their abundant leaf growth. The leaves are either cooked or
used as a major ingredient in the preparation of vegetable salad. The leaves
also supply vitamins and minerals needed for maintaining good health. Cabbages
are also of value as roughage, which facilitates digestion of food.
2. Carrot (Daucus carota)
Carrot
is yet another foreign vegetable that has been successful1y cultivated in
several parts of Nigeria. Two main varieties of carrot are commonly grown in
Nigeria. These are the stump-rooted type and the point-rooted variety.
Cultivation
Unlike
cabbages, the seeds are sown straight into the permanent beds where they
germinate, grow, develop, bear fruit and become ready for harvest. Carrots
prefer lightly, sandy soil with good supply of plant nutrients. Compacted clay
soil may lead to poor formation of roots.
The
seeds are usually planted in drills (shal1ow depressions in the soil) in
December or January, about 1.2cm to 2.5cm deep. The drills are usually 10-15cm
apart. The drills are located in rows, which are about 30cm apart. The
germination of the seeds can be increased by soaking them in water or mixing
them with moist sand.
Seed Treatment
The
worst pest of carrot seeds should be treated with chemicals such as Dieldrin,
Aldrin or Lindare as a precaution against carrot fly. The optimum temperature
for high yield is 60° -
70°F.
3.2.3 Seed Bed Preparation Before sowing, a surface dressing of super phosphate
fertilizer, ammonium sulphate and potassium sulphate should be done on the soil
to speed up growth. The use of farm yard manure must be avoided as it causes
the forking of roots. Similarly, application of excess nitrogen based
fertilizer must be avoided as it causes the splitting of roots.
Seed-Bed Maintenance
Germination
of seeds is slow as it occurs many days after sowing. The soil around young
plants should be covered with dry grasses (mulching) to retain water in the
soil and reduce the growth of weeds. When the plants are 2-3cm high, they are
thinned to leave 5-8cm between plants. The young carrot plant bears a few
fern-like compound leaves, which arise from the crown of the root. Availability
of water in the soil is an important factor which affects root formation;
therefore, the plants must be well watered during the processes of growth and
development.
Harvesting
The
harvesting of mature carrots is done 60 to 90 days after planting. During
harvesting, the roots are pulled out of the soil. The shoots may and may not be
removed before they are marketed. Harvesting of carrots must be timely as the
roots can go woody if left too long.
Carrot
fly usually attacks carrots; also of great threat are fungi diseases such as
leaf blight, bacteria and nematode diseases such as soft rot and root rot,
respectively. To control the spread of bacteria and fungi diseases, infected
plants should be burnt. Fumigating the soil with nonagon several weeks before
the commencement of planting can control nematode disease.
Importance
Carrots
are grown, primarily, as food crop because of their fleshy roots. The roots of
the most suitable variety for eating have a milk flavour; and are reasonably
sweet, crisp and tender. Carrots have a considerable good nutritional value.
They contain an orange coloured matter called carotene, which is particularly
valuable in human and animal diets.
Carotene
is an important source of vitamin A, which is required for the normal
functioning of the human eye. In addition, the roots contain sugar and calcium
salts needed for the development of strong bones and teeth. The roots can
either be eaten raw, used along with other vegetables for preparing salads;
they can be cooked in different ways. The roots are rarely dried. However, when
carefully roasted and ground into powder, they could also acts as a substitute
for coffee. They can also be used as flavour in soups and stews. Extract from
carrots are also used for colouring butter.
In
addition, several very large coarse and no tasty varieties of carrot are
cultivated abroad. These varieties are used as food for livestock, most
especially, horses and rabbits.
Read On: Identification of Crops According to Life Cycle and Nature
3. Cucumber (Cucumis
sativus)
The
cucumber family of plants is climbing vegetables, which are very useful to man
in both the tropical and temperate regions of the world. They are spreading or
climbing plants. Many varieties exist such as cucumber, melons and pumpkins,
which have been successfully cultivated in different parts of Nigeria. We shall
limit our discussion to the cultivation of cucumber.
Cultivation
Cucumber
grows well in outdoor ridges where there is sufficient warmth, moisture and a
good supply of plant nutrient. It prefers a fairly loose soil enriched with
organic manure. Cucumber may not do well in highly compacted waterlogged clay
soil. Like carrots, the seeds are grown straight into permanent beds or ridges.
They germinate, grow, and produce fruits, which are harvested. The sowing of
the seeds should begin at the end of the rainy season (about October).
This
may continue throughout the dry season, if adequate watering is maintained. The
seeds are sown on previously prepared sandy beds, which have been adequately
manured and fertilized. Two rows of seeds are sown per bed. A spacing of l0cm
should be maintained between the rows and 60cm between the seeds. The seeds
should be sown in little soil depressions not more than 2cm deep.
When
sowing is completed, the ridges are covered with dead grasses (mulching). This
prevents excessive loss of water, which could lead to the germinating seeds
becoming dry. Have you noted the similarities between the cultivation of
carrots and cucumber?
You
remember that:
i.
The seeds are planted directed into the soil.
ii.
They prefer fertilized, loose, sandy soil.
iii.
Mulching is necessary for success. Other similarities, and of course, some
differences will be made known to you as you read on.
Germination
Germination
of cucumber seeds occurs 3 - 4 days after sowing. As they are climbing
vegetables, they soon develop climbing aids called tendrils, and then, start to
climb. Hence, it is important that adequate support is provided for the
seedlings, in advance. Shrub branches or sticks, which are approximately 1
meter in length, will provide an adequate support for cucumber. Have you noted
some differences between the cultivation of carrot and cucumber?
If
you do not, remember that:
i.
Carrot seeds germinate very slowly, while cucumber seeds germinate in 3 - 4
days.
ii.
Carrot does not require any support, but cucumbers do. Note too that provision
of support is necessary in both the cultivation of tomatoes and cucumber, but
for different reasons. Write down the reasons. If you have difficulty
remembering the reasons go back and revise the relevant sections of previous
units.
Disease Control
Mildew
fungi readily attack the leaves of cucumber plants, causing a lot of damage.
This decreases performance of the plant.
To
control this disease, the leaves of cucumber plants should never be sprayed
directly with water. Watering should be restricted to the soil around the stem.
Badly infected plants should be pulled up and burnt, to avoid the spread of the
infection. A chemical used for, controlling fungal diseases (fungicide) such as
dithane can be used to treat infected plants. To ensure success, weeds must be
closely controlled by hoeing. However, hoeing must be carefully done to avoid
damage to stem roots, which are located around the surface of the soil.
Harvesting
Cucumber
fruits mature in about two months, after the seeds are sown. The fruits are
harvested manually, by plucking. Unless diseases destroy the plants, harvesting
of fresh fruits may continue for another one month.
Importance
Cucumber
plant is cultivated for its juicy and crisp fruit, which can be eaten raw. It
can be used as an important ingredient in the preparation of vegetable salads.
It is rich in vitamin C and mineral salts. The vegetable is sold in local
markets to generate revenue for farmers.
Read On: Types of Soil: Characteristics and Importance
4. Lettuce
Lettuce
is not really a tropical crop. It is usually grown in temperate regions of the
world. However, certain varieties have been successfully grown in the tropics
with proper care. For example, webb's wonder has been successfully grown in the
cold parts of Nigeria (for example, Jos Plateau). This variety has crisp
curling, and glossy but fleshy leaves. Lettuce grows well in well-drained soil
with adequate supply of organic matter.
Cultivation
Viable
seeds are sown in nursery beds or boxes, which have been previously fertilized.
Old seeds should not be planted. It is important to sterilize the soil in the
nursery boxes to destroy harmful soil organisms such as bacteria, fungi,
viruses and nematodes, which may attack the lettuce plant. Weeds are also
destroyed through the process of sterilization. This prevents such weeds from
competing with lettuce plant for valuable plant nutrients.
Nursery
Recall
that tomato and cabbage seedlings have to be given special nursery care to
ensure success. If you do not remember this similarity in the cultivation of
these vegetables, note it now. The seeds of lettuce are grown in drills of a
depth of about 1.2cm to 25cm. After dropping the seeds into the drills, they
are lightly covered with soil. The soil is subsequently pressed down with a
planting shovel.
Germination
Germination
takes place within a few days. The young seedlings should be well watered and
provided with adequate nutrients through regular fertilization. The seedlings
should be transplanted in 3-4 weeks when they have 4-5 leaves. Each seedling
should be transplanted with a ball of soil around the roots. Recall the reasons
for this practice? It is to ensure minimum disturbance and damage to the roots.
Seedlings should be spaced at 20cm intervals. There should be no more than four
rows of plants per bed or ridge. Mulching should be done to prevent young
seedling from drying out. During the dry season, plants should be watered
frequently and possibly with light shading.
Disease
Control
Bacterial leaf spot, mosaic virus and root knot nematode disease may attack
lettuce plants. Sterilizing the soil of the nursery bed can control these
diseases. Badly infected plants should be pulled out and burned.
Harvesting
Lettuce
is ready for harvesting six to twelve weeks after planting. The plants are
pulled out of the ground and washed thoroughly and disinfected before
consumption.
Importance
Like
carrot, cabbage and cucumber, lettuce can be eaten raw. Lettuce is cultivated
for its leaves, which are rich in vitamin C and mineral salts. The leaves are
also used for preparing salad.
Conclusion
You
have noticed that these vegetables are common features of vegetable salads and
they also perform better in some locations in Nigeria than even some temperate
countries. They supply vitamins and minerals needed for maintaining good
health.
This
article has really enumerated the importance of cultivating the four
vegetables- cabbage, carrot, cucumber and lettuce. They are all cultivated from
seeds while adequate fertilization and watering of seeds will improve their
performance. Cabbage, carrot, cucumber and lettuce can be eaten raw as salad.
They also serve as important sources of vitamin C and mineral salts.
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