VEGETABLE PRODUCTION
Vegetables
are crops grown for their edible leaves, roots, stems, bulbs, and fruits. They are rich in source of vitamins and
minerals. Some are also used to feed
livestock. Others are sold fresh in the
market to provide income. Vegetables are
also a source of raw materials for industries.
Benefits
of growing vegetables on the farm
• They are rich
sources of minerals and vitamins to human diet.
• They can be sold for
cash to generate income for the farmers.
• They provide
roughages in the diet important in the proper functioning of the stomach.
• Their residues can
also be used as fodder for livestock and poultry.
• Their residues can
also be used as mulches to provide organic matter in the soil.
• Growing vegetables
requires relatively less labour as compared to other crops.
• They take less time
to mature and this gives returns faster
• They can easily be
grown on small scale in home gardens
• Vegetables can be
eaten raw as salads or cooked as vegetables
• Legume vegetables
fix nitrogen in the soil
• They can easily be
inter planted with other crop to allow efficient utilization.
Disadvantages
of growing vegetables
• Their production
requires a lot of labour and time, they need to be raised in the nursery first,
then transplanting them to the main garden, irrigating them and spraying them
against pest and diseases
• They are highly
perishable thus need to be sold immediately after harvesting. This makes marketing of vegetables difficult.
• Their production
requires relatively more capital
• They have limited
market; their demand is restricted to urban and Peri-urban centers.
• They are highly
affected by pests and diseases requiring constant spraying with pesticides
which pollute the environment and make vegetable production expensive.
Classification
of vegetables
1.
Classification
of vegetables on the basis of the part used as food. Such parts include; leaves, stems, roots, fruits,
flowers, pods, and bulbs.
Vegetables
are grouped into the following categories:
1.
Leaf
vegetables for example kales and cabbages.
2.
Root
vegetables for example carrots, beets, radishes and turnip
3.
Fruit
vegetables for example French beans and okra.
4.
Stem
vegetables for example asparagus, leeks and spring onions.
5.
Bulb
vegetables for example bulbed onions and garlic.
Classification
of vegetables of vegetable according to their botanical family
1.
Solanaceae
family for example tomatoes, pepper, egg plants, Irish potatoes etc
2.
Brassicaceae
family for example cabbage, cauliflower, kale etc
3.
Cretaceously
family for example pumpkin, cucumber, and water melon.
4.
Alliaceae
family for example onions, leek and garlic
5.
Leguminosae
for example beans, peas etc.
Principles
of vegetable growing
• Always plant at the
right time
• Plant at the current
spacing
• Plant seeds at
recommended depth
• Maintain a soil
cover throughout the growing period e.g always mulch the soil.
• Control weeds in the
field
• Always rotate the
vegetables with legumes
• Harvest them at the
right stage of growth
• Always grade the
harvested crops according to size and quality, shape and colour.
• Always destroy crop
residues after harvesting to destroy pests and diseases
• Also apply
fertilizers if the soil fertility is low
• Always prepare land
in time
• Control pests by
sanitary measures and chemicals
• Carry out irrigation
in the dry season
• Grow key varieties
that are suitable for climate and farming system
Nursery
Practices
A
nursery bed is a piece of land of any convenient length prepared for raising
seedlings for the later transplanting. A
seedbed is a piece of land of any size that has been prepared for sowing seeds
or receiving planting materials. A
seedling bed is a special type of nursery bed used for raising seedlings that
have been removed from nursery bed due to overcrowding before they are ready
for transplanting.
Reasons
for raising vegetable seedlings in a nursery bed
• It economizes on the
amount of water and chemicals used since
seedlings are in small area
• Many seedlings are
raised in a small unit area
• It reduces crop
failure since it is possible adequate care to crops in a nursery bed.
• It reduces the time
taken by the crop in the field
• It enables a farmer
to select only healthy and vigorously- growing seedlings that establish faster
• It reduces the
amount of labour spent caring for the seedlings
• It makes it easier
to manage the seedlings in terms of watering, weeding, and controlling pests
and diseases.
• Some vegetable seeds
are very small to successfully plant at the correct spacing and depth.
Factors
to consider when selecting a site for a nursery bed
1.
Nearness
to the water source; the site should be established near a water source for
easy watering
2.
Type
of soil; the site should have well-drained, deep, and fertile soil, preferably
sandy loam.
3.
It
should be easily accessible by the farmer and machines.
4.
Topography;
it should be on a gentle sloping land to avoid flooding of the beds when it
rains.
5.
Security;
it should be well secured from thieves and damage by livestock.
6.
Well-sheltered;
the place should be free from strong winds
7.
Previous
cropping; areas where the same crop species had been planted should be avoided.
8.
Freedom
from pests and diseases; the site should be free from pests and diseases.
Establishing
a vegetable nursery
Preparation
of the nursery bed
• Select a suitable
site and mark it out.
• Clear vegetation and
remove the trash
• Dig or plough the
site deeply to remove all perennial weeds
• Harrow the bed to a
fine tilth and then level it
• Measure and divide
the nursery bed into sections of about 1m wide and any convenient length , with
60cm paths between individual beds
• Sterilize the soil
by burning trash on top of the bed or using soil sterilizers.
• Spread phosphatic
fertilizers or well rotten manure
• Mix the fertilizer
or manure well with the soil using a rake
• Make shallow drills,
1cm deep, and 10 to 20 cm apart.
• Drop the seeds
uniformly in the drills. Cover the seeds
lightly with soil.
• Spread a thin layer
of mulch on top of the bed
• Water the nursery
bed and erect a shade to minimize water loss through evaporation.
Nursery
management practices
The
routine nursery management practices include the following
• Mulching; it involves
spreading of mulch material such as plants leaves over the soil surface
immediately after sowing seeds. It is
done to insulate the soil against moisture.
After emergence of seedlings, all the mulch is removed to avoid
smothering the young seedlings
• Shading; this
involves the erection of a shade over the nursery bed. It is done to prevent scorching of seedlings
by direct sunshine. Shading also prevent
damage of seedlings by raindrops.
• Watering; this
involves the application of water to the nursery bed. It is done to maintain the right moisture
levels in the nursery. Watering is most
important when the conditions are dry.
• Thinning or pricking
out; this refers to the removal of excess seedlings from the nursery bed. The removed seedlings are taken to another
space within the same nursery bed or to a seedling bed. Thinning reduces overcrowding in the nursery
and enables seedlings to grow vigorously and healthily
• Pest and disease
control; this involves using appropriate methods such as spraying, to control
diseases and pests. Most caterpillars
are destructive to seedlings
• Weed control; it
involves controlling weeds to reduce their competition for growth factors with
the seedlings. It is done by uprooting
the weeds to minimize root disturbance
• Hardening off; this
refers to the gradual exposure of seedlings to conditions close to those found
in the field after transplanting. It is done
by reducing the amount of shade, and the frequency of watering the seedlings. Hardening off enables the seedling to
withstand harsh conditions in the field.
• Transplanting; is
done during the evening or during cloudy day or cool day. Transplant only healthy and vigorous
seedlings. During transplanting,
seedling should be lifted with the soil lump around the roots to minimize
disturbance to the roots. Before
transplanting, the nursery should first be watered to soften the soils so as to
reduce damage to the seedlings during lifting of seedlings.
Steps
in transplanting vegetable seedlings
• The stage of
transplanting vegetable seedlings from the nursery bed is 10 to 15 cm height,
or 4th to 6th
true leaf stage or 4 to 6 week of age.
• Transplant the
seedlings when it is cool
• Water the nursery
bed before lifting the seedlings to minimize root damage.
• Select healthy and
strong seedlings
• Lift the seedlings
with a lump of soil on their roots
• Use appropriate tool
for lifting, such as a garden trowel
• Avoid damaging the
roots when lifting seedlings. Dig holes
in the seedbed that are big enough.
• Put insecticides in
the planting holes to control soil-borne pests
• Plant the seedlings
at the same depth as they were in the nursery
• Mix phosphatic
fertilizer or well-rotten manure with top soil and fill in the planting holes
• Firm the soil around
the base of the seedlings.
Cultivation
some common vegetable crops
Cabbage
(Brassica
oleracea)
Ecological
requirements
Altitude;
cabbage
with large-round head prefers high altitude of 1800 to 2900m while cabbage with
small- conical head prefers low altitude of 900 to 1500m above the sea level.
Rainfall;
the
crop requires well distributed rainfall throughout the growing period. Where the rain is not sufficient. Irrigation of the crop should be done
Soil; the crop requires
deep, well drained and fertile soil of moderate pH
Varieties;
cabbage
has many types and varieties. Some are
quick maturing while others are slow maturing.
Early maturing varieties include; Copenhagen market, sugar loaf,
Brunswick, Chinese cabbage, celery, early jersey, and cafe spits Kool and early
offenham. Mid-season or late maturing
varieties include; drumhead, gold acre savoy, perfection, succession and
winning stadt
Nursery
practices
• Choose a site where
there has never been Solanaceae crop in the last three years
• Make seedbeds
depending on the soil moisture, the bed may be raised or sunken
• Apply fertilizers
such as phosphatic and nitrogenous fertilizers.
• Select good seeds
from a reliable supplier
• Sow the seeds in
shallow drills in rows and then cover the seeds with a thin layer of soil. Drills should be 1cm deep and 15-20 cm apart
• Provide shade or
mulch. Mulch should be removed as soon
as the seeds start to germinate this prevents etiolation of the seedlings due
to too much shading.
• Water the bed twice
a day. The frequency of watering however
depends on the weather
• Control weeds by
hand pulling of any weed
• Control pests and
diseases through spraying with appropriate insecticides and sanitation
• Acclimatize the
seedling before they are transferred to the field.
Land
Preparation
The
land should be deeply cultivated, the vegetation should be destroyed, and trees
and tree stumps should be removed. Dig
holes at the spacing of 60cm X 60cm. incorporate farm yard manure in the soil.
Transplanting
• Seedlings are ready
for transplant after one month, when they are 6-10cm in height
• Water the seedlings
before transplanting to soften the soil so to allow easy lifting of seedlings
• Select and
transplant healthy and vigorous seedlings and discard the weak and stunted ones
• Transplanting should
be done on cool or cloudy day or in the evening.
• During transplanting
seedlings should be lifted with a lump of soil to prevent root damage
• Plant the seedling
to the same depth as they were in the nursery.
Spacing; Spacing varies
with the climate or variety. The spacing
is 60cm X 60cm for most varieties
Fertilizer
application; manure
should be spread in the seed bed. Also
super phosphate should be applied per planting holes and later top dressed with
CAN or nitrogen sulphate.
Mulching;
mulches
should be applied in between the rows or around the crop. Mulches can be obtained from dry plant
tissues. Mulches help to conserve
moisture in the soil, prevent weed growth, and also prevent the soil from
slashing to the leaves which could spread soil pathogen to the crop.
Weed
control; this
is very important in cabbages which are not mulched. Cabbage field should be kept free from weeds
to reduce competition for growth factors and pests in the field. Weeding can be done by hand pulling, or using
herbicides.
Pests
and diseases control; cabbages
should be sprayed with fungicides and other pesticides to reduce attack by
pests and diseases. Common pests
include; diamond back moth and cut worms.
These can be controlled by applying pesticides. Some diseases include black rot and blackleg. These can be controlled by sanitary measures
and fungicides.
Harvesting;
the
best time to harvest cabbages is when the heads are heavy and hard. Harvest the head with at least 4 wrapping
leaves. Harvesting is done using knives.
Green
Pepper (Capsicum
annum)
Growth
requirements
Green
pepper prefers sandy loam soil that drains freely and contains plenty of
organic matter. Warm climate is ideal
with well distributed rainfall.
Husbandry
practices
Land
preparation
The
land should be deeply ploughed and tree canopies reduced to allow full sunlight
to reach the plants. Also work some
organic matter into the soil to enhance nutrient and moisture supply to crops.
Planting; seedlings from the
nursery bed are usually used for planting.
They are transplanted when they are 8-10 weeks old. Planting in the field is done at the
beginning of the rainy season to ensure ample moisture supply to the crops. Dig holes large enough to accommodate the
roots. Transplant the seedlings during
cool hours. Plant the seedlings in the
holes and refill them loosely with top soil.
Spacing; green peppers
should be planted approximately 12-18 inches apart to have room to grow without
competing with one another, and allow ample working space for the gardener.
Irrigation; peppers are thirsty
plants. They need a moderate supply of
water from the moment they sprout until the end of the season. Irrigation during dry weather helps to
maintain moisture supply to keep the plants in production. Drip or overhead irrigation can be used for
this purpose.
Weed
control; pepper
plant is less tolerant to weed infestation.
Weeds provide a refuge for most pests and can also spread fungi and
viruses to nearby healthy pepper plants.
Weed control can be achieved by mulching, hand hoeing and pulling of
growing weeds
Fertilizer
application; peppers
are light feeders. Too much application
of fertilizer tends to make the pepper plants develop lush foliage at the
expense of fruit production. Apply NPK
5-10-10 fertilizer into the soil prior to transplanting, also side- dress the
plants with a light sprinkling of NPK 5-10-10 when blossoming starts, just to
give the plants a boost if needed
Mulching;
cover
the prepared bed with organic mulch or use a dark coloured polythene mulch at
least a week before transplanting. This
will heat the soil beneath and provide a better growing condition for young
pepper plants. The generated heat also
helps to kill harmful bacteria and root nematodes. Mulch will also help the soil retain moisture
throughout the season as the plants grow.
Staking;
peppers
are easily damaged when laden with fruit.
For support, tie the plants to stakes using nylon strings, which have
some 'give' as the stems enlarge. The
support prevents logging of plans; keeping the plant and fruit away from the
ground to prevent infection with soil bacterial
Pests
and diseases control; regular
pest control is important. Destructive
pests like cut worms, horn worms, aphids and borers are controlled by using
pesticides and keeping the plats weed free.
Diseases
such as anthracnose mosaic, and bacterial spot can be controlled by planting
disease-resistant varieties, spraying with fungicides and bactericides and
ensuring proper sanitation.
Harvesting;
peppers
are usually harvested at an immature stage and also can be harvested at any
stage of growth, but their flavour doesn't fully develop until maturity. Frequent harvesting increases yields. If you continually pick the peppers before
they mature, the plants will continue to produce fruits in their quest to
develop viable seed. Use a sharp knife
or garden shears to cut the tough stem.
Tomatoes
(Solanum
lycopersicum)
Ecological
requirements
Altitude; 0 to 2100 m above
sea level
Temperature;
optimum
temperature of 21 to 27degrees, with a diurnal range of 5 to 6
Rainfall;
760mm
to 1300mm per annum that is well distributed.
Irrigation is carried out in dry areas or during the dry season
Soils; deep fertile and
well drained loamy soils
Soil
pH; 6
to 6.5
Nursery
establishment and management
Nursery
establishment
• Select a suitable
site where members of solanaceae family have not been grown for the last three
years. In high rainfall areas, the
nursery bed should be raised to facilitate drainage whereas in dry areas the
nursery beds should be sunken to conserve the available moisture.
• Dig the site deeply
to remove perennial weeds and stones
• Harrow the site to a
fine tilth. The nursery should be 1m
wide and of any length
• Level the nursery
using the rake
• Make shallow drills,
1cm deep and 10cm to 20cm apart across the bed using sticks or a finger
• Drop seeds singly
and uniformly and cover lightly with soil
• Spread a thin layer
of mulch on top of the bed
• Water the bed
Nursery
management
• Remove the mulch as
soon as the seedlings start to emerge
• Erect a shade above
the nursery
• Water the nursery
twice a day ; in the morning and late in the evening
• Control weeds
regularly
• Control pests and
diseases once symptoms of attack are noticed
• Prick out or thin
the seedlings to 7cm or 8cm apart to avoid overcrowding
• Harden off the
seedling before transplanting to increase their chances of survival in the
field
Land
preparation
This
should be done early before the onset of rains
• Clear all vegetation
and remove any tree stumps
• Plough the seedbed deeply
and remove all perennial weeds
• Harrow the land to a
medium tilth
• Prepare planting
holes, 15cm deep, and 15cm wide. The
spacing should be 0.9m X0.6m X0.5m depending on varieties
Transplanting
• Apply organic manure
or one teaspoonful of DSP in the planting holes
• Apply an appropriate
insecticide to control soil-borne pests
• Transplant the
seedlings when they attain a height of 10cm to 15cm 0r at 4th to 6th
true leaf base stage or 4 to 6 weeks of age
• Transplant on a cool
cloudy day or late in the afternoon
• Water the nursery
bed well before transplanting. Use a
garden trowel to lift the seedlings with ball of soil around the roots.
• Select only the
healthy and vigorously growing seedlings
• Water the seedbed
before it receives the seedlings
• Place each seedling
in the planting hole. Plant at the same
depth as they were in the nursery.
• Firm or compact the
soil around the seedlings. Mulch and
then water the seedlings.
Field
management practices
• Conduct timely
gapping of seedlings that might have died after transplanting.
• Water regularly,
especially during the dry spell
• Top dress by two
split applications of nitrogenous fertilizers
• Weed early and
regularly, Stake all tall varieties
• Prune to remove
excess suckers and prevent leaves from touching the ground
• Stake all plants;
this is not important in dwarf varieties
• Control pests such
as the American boll worms by spraying with appropriate pesticides
• Control diseases
such as tomato blight through spraying with appropriate chemicals.
Harvesting
Timely
harvesting helps to reduce damage of the fruits by pests and to enable
transportation of the fruits to the market.
Tomatoes are usually harvested using hands
Fresh
market fruits should be picked as soon as they start to ripen
Fruits
for canning need to ripen properly for processing
Onion
(Allium
cepa)
Varieties: early cape yellow
flat, Excel, Granex, Red Bermuda, Red creole, Texas grano, White creole, and
yellow Bermuda
Growth
requirements:
onion can be grown under a wide range of climatic conditions, but they succeed
best in mild climate without excessive rainfall or great extremes of heat and
cold. Cool conditions, with an adequate
moisture supply are most suitable for early growth, followed by warm, drier
conditions for maturation, harvesting and curing. They can be grown on variety of soils but
grow best on light fertile soil. Optimum
pH is about 6.0 – 7.0
Husbandry
practices
Seedbed
preparation
Land
should be thoroughly prepared, remove all trees and tree stumps, cultivate the
soil deeply, and then carry out secondary tillage to pulverize the soil
Planting;
planting
is carried out at the beginning of the rain season. For direct planting, seed are sown directly
in shallow drills of 1cm, in rows about 30cm apart at the rate of 4-5 kg/ha and
later thinned to about 7.5cm apart within the row.
For
transplanted seedlings, transplanting is done on a cloudy day or in the evening. Prior watering of the nursery bed is
important to soften the soil and to allow easy lifting
Weed
control;
onions are less competitive and growth is very much affected by weed
infestation. Weed control is achieved by
using herbicides and cultivation with a hoe however care must be taken not to
damage roots and developing bulbs
Fertilizer
Application;
onions give good response to organic manures.
Phosphates and potash may be applied at or before planting, with later
application of nitrogen as a top dress
Irrigation; onions require a
good supply of soil moisture. Most of
the required water is normally provided by rainfall as long as planting is done
at the beginning of the season. However,
if planting was done off season, or if the rainfall is scanty, irrigation of
the plants is necessary
Pests
and disease control; the
most serious pests of onions are thrips, the stem and bulb nematodes
These
are controlled by timely planting, crop rotation with non- host plant and
spraying with appropriate pesticides. The
most important diseases of onions are downy mildew, purple blotch, and pink rot. These can be controlled by field sanitation,
crop rotation and spraying with appropriate fungicides
Harvesting; this must be done
when onion is mature 90- 150 days after planting depending on the variety. At maturity the tops droop, fall over, and
begin to die back. As all plants do not
mature at the same time, harvesting is done when about 25% of the tops have
fallen. Bulbs are dug out using a hoe.
Carrots
(Daucus
carota)
Ecological
requirements
Altitude; 0 to 2900m above
sea level. Temperature; optimum 24
degrees
Rainfall; optimum 750mm to
1000mm that is well distributed
Soil;
deep,
loose and well drained soils with a reasonable amount of sand
Soil
pH;
6 to 6.5
Seedbed
preparation
• Dig the land early
before the onset of rains
• Clear vegetation and
remove all stumps
• Dig the seedbed to
about 20cm deep and remove all perennial weeds
• Harrow the land to a
fine tilth. Do not apply manure as it
induces forking
Planting
·
Carrot
seeds are sown directly into the main seedbeds
·
Make
continuous drills 30cm to 40cm apart. Apply
DSP in the drills at the rate of 90kg/ha.
·
Apply
potassium oxide for good root development and mix the fertilizer well with the
soil before planting
·
Place
the seeds in the drills at the rate of 5
to 6 kg/ha
·
Cover
the seeds lightly and then carry out rolling
Field
management practices
·
Thin
two weeks after germination to attain a distance of between 5cm and 8cm between
individual plants.
·
Keep
the field weed free
·
Earth
around the plants during weeding to encourage tuber expansion and to prevent
the tubers from getting a greenish colour due to exposure to the sun
·
Top
dress with CAN at the rate of 60kg/ha. Do
not exceed this rate to avoid vegetative growth
·
Carry
out irrigation during dry conditions
·
Control
pests such as aphids and moles using appropriate pesticides
Harvesting
Carrots
are ready for harvesting 3 to 5 months after sowing. Avoid over maturing as it may cause root
splitting. Harvest manually by uprooting
or lifting using a forked hoe. Remove
the leaves and wash the carrots. Store
at low temperature (0c) and high relative humidity
Bulb
onions (Allium
cepa)
Ecological
requirements
Altitude; 300m above sea
level, optimum 2100m. Temperature of 13
to 29 degrees
Rainfall; over 1000mm,
supplied throughout the growing period. Otherwise
irrigate
Soil; fertile and well
drained
Soil
pH; 5.6
to 6.8
Planting; onions can be sown
directly into the main field or started off in a nursery bed
Direct
seeding
• Make seed drills
spaced at 30cm to 38cm between rows and 10cm to 15 cm within the rows
• Place the seeds in
the drills at the rate of 7 to 11 kg/ha
Nursery
establishment
• Select a suitable
site which is well-drained
• Dig the site deeply
to remove all perennial weeds
• Harrow the site to a
fine tilth
• Mix the soil with
well rotten manure
• Add lime if the soil
is acidic
• Level the nursery
bed using a rake
• Sow the onion seeds
very thinly into drills, 13mm deep
• Cover the seeds with
light soil
• Water the nursery
bed gently
• Harden off the
seedlings by reducing shading and watering intervals
Transplanting
• Transplant the
seedlings at the age of 8 weeks or when they attain the thickness of a pencil.
• Spacing should be
30cm to 38cm X10cm to 15cm.
• Apply DSP fertilizer
in the drills at the rate of 250kg/ ha.
• Trim roots and some
leaves to regulate growth.
Field
management Practices
• Thin directly -sown
onions to a spacing of 8cm between two plants within rows
• Control weeds manually,
taking care not to damage the shallow roots or compact soil around the crop.
• Top dress using CAN
at the rate of 250kg/ha.
• Control pests such
as onion thrips and nematodes using appropriate methods and insecticides.
• Control diseases
such as purple blotch and downy mildew using appropriate methods.
Harvesting
and Marketing
Onions
can be harvested at green stage or as dry bulbs. Harvesting of dry bulbs is done when 25% of
the crop has fallen over. When leaves
start drying, the crops should be broken or bent at the neck to hasten
withering of the stem. Harvesting can be
done manually or mechanically. The
onions should be dried in the sun and the outer skin peeled off before storage.
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