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Vegetable Production - Agriculture Form 2

Suggested Practical Activities in Vegetable production

Activity 1
Visit a vegetable farm unit and observe any disease conditions on the following vegetables.

  • Cabbage
  • Tomato
  • Carrot
  • onions

Activity 2
Visit a vegetable farm unit and observe the following pests and record the observation.

  • Cabbage saw fly
  • Aphids
  • Thrips
  • American bollworm

Vegetable Production

Background Information

Vegetables provide essential nutrients in our diet. Different types of vegetables are grown depending on their specific ecological requirements. The common vegetables grown are tomatoes, onions, cabbages and carrots.

Vegetable Production

Any crop that is grown and eaten fresh.
2.Annual crops:
Crops that complete their life cycle within a period of one year.
3. Night blindness:
A deficiency disease caused by lack of vitamin A leading to vision impairment.
4. Scurvy:
Deficiency of vitamin C characterised by bleeding of gums.
Deficiency disease due to lack of vitamin D characterized by oedema, paralysis and muscle wasting 6. Amaranthus:
A wild vegetable that is edible by humans and also acts as a weed.
A leafy part of the cabbage that is solid and compact.
A. mixture of vegetables such as onions ,carrots and sweet paper
9.Physiological disease:
A disease that interferes with functioning of internal eg Blossom end rot.
A condition in carrots leading branching of roots.
selective uprooting and destruction of diseased or pests infected plants.

Crop Production (V) Vegetable Production

Topic Objectives

By the end of the topic, you should be able to:

  • define a vegetable crop and classify them.
  • establish the following crops -tomatoes, onions, cabbages and carrots.
  • keep records of crop production.
  • market vegetable crops.
  • demonstrate an appreciation of agriculture as an economically lucrative activity.


Olericulture has gained popularity in tropical agriculture. The changing eating habits in the society which emphasize proper nutrition coupled with increase in population, has precipitated to an increased demand of vegetables. This topic covers aspects of the vegetable production.

In this topic you will be expected classify vegetables, grow and market named examples of vegetable crops. You will be expected to appreciate the importance of keeping appropriate records to ensure economic viability of the enterprise.

Vegetable Production

Vegetable as part of the diet

Vegetable crops provide mainly mineral salts and vitamins. They also supply fibre that is required in digestion.

The main vegetables grown in Kenya include: Tomatoes




Importance of vegetables to humans

The changing eating habit in the society has led to increased interest in production. The abundance of fibre in vegetables enhances digestion. Apart from providing important body vitamins and mineral salts, vegetables also make food appetizing.
Vegetables can be processed into sauces, juices and jams for preservation. Vegetables are also fed to animals as supplementary feeds.

Tomato production

Ecological requirement for tomatoes.
-Require warm climate
- Grow well at altitude 0 - 2100 m above sea level
- Moderate rainfall 760 - 1300mm
- Require fertile , deep and well drained soil

Nursery establishment and management of tomatoes

Tomatoes require various management practices from nursery bed preparation to transplanting. These includes:

  • Prepare nursery beds to obtain a fine tilth
  • Make raised beds 15cm high on low grounds
  • Make drills 10 to 15cm apart and place seeds before covering in shallow soil.
  • Water twice daily
  • Put mulch
  • Erect a shade but avoid dump and dark conditions
  • Hardening off should be done 2- 3 weeks before transplanting
  • Seedlings should be ready when they are 10cm high or 4 - 6 weeks old.

Land preparation for tomatoes.

Tomatoes should be planted in a field where members of Solanacea family had not been previously grown. This is to avoid build up of pests and diseases.


When transplanting tomatoes, the following activities are carried out.

  • Water the nursery first before transplanting
  • Choose the healthy and vigorously growing seedling for transplanting
  • Lift the seedling with a lump of soil around the roots using a garden trowel.
  • Plant one seedling per hole
  • Mulch and water the seedlings after transplanting

Field management practices

For tomatoes to establish and grow properly in the field, various management practices need to be carried out. Watering should be done immediately after transplanting and continued on regular basis. The seedlings should also be mulch.

Some of the management practices of tomatoes include:

  • Top dressing- when they are 25 -30cm using nitrogenous fertilizer for example C.A.N or urea
  • Gapping - Where tomatoes have failed to grow, the farmer should replace in order to achieve accurate plant population
  • Weeding -Tomatoes should be kept weed free
  • Staking - Tall tomato varieties must be staked in order to avoid breakage, soil borne diseases and fruits getting soiled.


- Tomatoes should be pruned in order to make them less bushy and to avoid too much vegetation at the expense of fruits.

See the video below to appreciate prunning of tomato plant

Harvesting and marketing of tomatoes


Fresh market tomatoes should be picked as soon as red colour appears.
Harvested tomatoes are packed and transported in large wooden crates.
For fresh market should be slightly under-ripe to allow them to reach the market before perishing.

Care should be taken not to bruise the fruits as this would lower their quality. Tomatoes are graded according to their freshness and ripeness depending on the taste of consumers.

Tomato pests and their control

Tomatoes are attacked by many pests while in the field. Among them are
the American bollworm and cutworms.
The Larva stage of American Bollworm (Heliothis amigera) is the most destructive. It attacks fruits of tomatoes by boring holes.
American bollworms can be controlled by spraying them with appropriate
Cutworms attack young seedling immediately after transplanting. It hides
just beneath the tomato seedling and only comes out at night to feed by
cutting the seedling at the base

Cutworms are controlled through:

  • Crop rotation
  • Appropriate insecticide

Tomato diseases and their control

Tomato blight

is caused by a fungus and it is most serious during cold and wet weather. The disease can only be prevented by spraying using fungicides since there is no cure after the disease has set in.

Bacterial wilt

Tomato crops suffering from bacterial wilt, withers and dries up even when the weather wet

There is no chemical control of bacterial wilt. Cultural measures used to control this disease include:

  • Uproot and burn affected crops (Rogueing)
  • Use of certified seeds
  • Crop rotation

Blossom end rot

Blossom end rot is a physiological disease. The affected tomato fruits appear rotten, water-soaked and dry at the blossom ends.

  • Too much nitrogen
  • Irregular watering
  • Calcium deficiency in young fruits

Control of Blossom end rot

  • Regular watering
  • Top dressing with right amount of nitrogen
  • Application of calcium compounds in the soil.

See the video below to appreciate tomato diseases and pests

Cabbage production

Cabbages are members of the Brassica family. This family includes crops
like kales (sukuma wiki], cauliflowers, Chinese cabbage, brussel sprouts
e.t.c.. Cabbages may be eaten raw in salads, boiled or cooked. The shape
and size of the head will depend on the cabbage variety.
Cabbages can be categorized as:

Early maturing

for example Brunswick, sugarloaf, early jersey, mukuki among others

Late maturing 6

for example Early drum-head, sure-head, prize drum-head among others

Ecological requirements for cabbages.

  • High altitude of 1,800- 2,900 above sea level.
  • Well distributed rainfall 750mm -2000mm per year.
  • Deep, rich, well-drained soils
  • PH of 6.5

Nursery establishment and management of cabbages.

Land for cabbage production should be deeply ploughed and harrowed to attain a fine tilth.
Make holes 10cm deep at a spacing of 90 x60 cm or 60 x 60 cm depending on variety.
Add organic matter in the holes and thoroughly mix with top soil.

Harvesting and marketing of cabbages.

Cabbages are ready for harvesting after 3 -4 months. Solid and compact heads are cut ready for Market. Grading of cabbages is based on compactness and heaviness of cabbage heads.

See the video below to appreciate Cabbages harvesting

Vegetable Production

Cabbage pests

Cabbages are attacked by many pests in the field. They include:

- attack leaves especially when the weather is dry.


- attack cabbage seedlings after transplanting

Cabbage saw fly

- eats the leaves of cabbage, leaving only the mid rib.
Control of cabbage pests involve use of appropriate insecticide, crop rotation, and irrigation

Disease of Cabbage

Damping off

is a fungal disease and it is characterized by cobweb-like black mass of fungi on young cabbage seedlings in the nursery. It occurs in heavily watered and shaded nursery beds. Control of this disease involves removal of shade, thinning use of less water and use of copper fungicides.

Black rot disease

This is a bacterial disease of cabbages that attack the pith of the stem.

When the stem is cut a black ring is seen at the center of the stem.
It is controlled through crop rotation

Downy Mildew (Fungal)

This is a fungal disease that occurs in wet misty conditions. It is characterized by fluffy fungal growth on the underside of leaves. Leaves turn brown to black spots on the upper surface.

The disease in controlled through:

  • Uprooting and burning (Rogueing)
  • Crop rotation
  • Nursery hygiene
  • Use fungicides

Vegetable Production

Carrot Production

Carrots (Daucus carota
)are important for their carotene content which manufacture vitamin A which is important for vision. They may be eaten raw or cooked. There are many varieties of carrots.
The main varieties of carrots include:

Fresh market varieties for example Chantenary
Processing /caning varieties for example Nantes
Oxhart varieties are grown for livestock.

Ecological requirements of carrots

  • Altitude 0 - 2,900m above sea level
  • Cool-warm temperature (High temperatures produce pale and short roots)
  • Adequate moisture- 750- 1000mm per year.
  • Deep fine tilth and well drained soils


Land should be prepared to a fine tilth since carrots are planted directly in the field through drilling method.
Seeds are established in rows of 20 -30 cm apart. They are then covered lightly with soil to allow quick germination of seeds.

Phosphatic fertilizer should be applied in the drills and mixed well with the soil. Avoid application of manure in the soil as it causes forking of carrots which lowers quality of produce.

Field management and harvesting

Field management of carrots compares to that of other vegetables. However, during weeding, earthing up of the soil around the carrot plants should be done to encourage tuber expansion.

Carrots are ready for harvesting 3- 5 months after transplanting depending on variety. Harvest manually by uprooting or use a forked jembe to lift the plant. Sell fresh or canned.

See the video blow to appreciate management and harvesting of carrots

Onion Production

Onions are used both as vegetables and also for flavouring foods such as stews, soups and as pickles. There are three varieties of onions, red creole, Tropicana hybrid and white creole.

Ecological requirements of onions

  • Hot warm climate although some varieties prefer cool conditions.
  • Long dry periods for ripening are required.
  • Altitude 2,100m above sea level
  • Soils should be fertile, well drained with a pH 6.0 -7.0
  • Requires over 1000mm of rain per year.

Onions are sown directly in the field or can be started off in a nursery.
Seeds are drilled and seedlings are transplanted followed by covering with little soil.
Avoid deep planting of seedlings as this inhibits bulb expansion

Field management practices

Timely thinning and top dressing should be carried out to maximize production. Weeding should be done carefully to avoid destroying the bulbs.

Onions have few pests. However, onion thrips should be controlled by spraying with appropriate insecticide.
Onion diseases include purple blotch and downey mildew. These should be controlled using appropriate fungicides as well as crop rotation

Harvesting and marketing

Onions are ready for harvesting in 5 months.
Harvest when the leaves start drying.
Break or bend the tops to fasten withering of stems.
Bulbs are dug up and left to dry in the shade for few says as they are turned daily for uniform drying.
Store in slatted boxes avoid rotting and inspect regularly.

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