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Introduction
• A vegetable is any crop that is grown and eaten fresh.
• Vegetables are important both for nutritional and commercial reasons.
• They are categorized on the basis of the part used as food.
• Such parts include;
- Leaves,
- Stems,
- Roots,
- Fruits,
- Flowers,
- Pods
- Bulbs.
Vegetables are grouped into the following categories:
• Leaf vegetables for example kales and cabbages.
• Root vegetables for example carrots, beets, radishes and turnips.
• Fruit vegetables for example French beans and okra.
• Stem vegetables for example asparagus, leeks and spring onions.
• Bulb vegetables for example bulbed onions and garlic.
Tomatoes (Lycopersicon esculentum)
• Tomatoes are fruit vegetables widely grown in Kenya.
• The ripe fruit may be eaten raw cooked or processed to make tomato sauces, juices and pastes.
Ecological Requirements
• Altitude: 0-2100m above sea level.
• Rainfall: 7S0-1300mm per annum.
• Soils: deep, fertile and well drained.
Varieties
• Fresh market varieties:
- Money maker,
- Marglobe, hundred fold,
- Beef eater,
- Hot set,
- Super marmande
- Ponderosa.
• Processing varieties:
- Kenya beauty,
- San -marzano,
- Roma,
- Heinz 13S0,
- Primabel,
- Rutgers hybrid
- Cal- J.
Nursery Practices
• Choose a site which has not been grown Solanaceae crop in the last three years.
• Nursery beds are raised about 15cm above the ground level.
• Make drills of 20cm apart and 1cm deep drill and cover the seeds.
• Provide shade or mulch material.
• Water twice a day.
• Apply phosphatic fertilizers during planting.
Seedbed Preparation
• The land should be dug deeply to control weeds.
Transplanting
• Seedlings are ready for transplanting when they are 10-15cmhigh after about one month.
• Holes are made at a spacing of 60cm x 90cm.
• Apply 20gm of DSP in the planting hole.
• Transplant with a ball of soil around the roots.
• Apply mulch around each seedling.
• Transplanting is normally in the evening or on a cloudy day.
Field Maintenance
• Early control of weeds is necessary.
• Top dressing is done after crop establishes.
• Pruning and staking are done to train the plants to grow vertically.
Pests Controls
• American Bollworm
- Nature of damage: boring holes on the fruits.
- Control: spraying insecticides.
• Tobacco White Fly
- Nature of damage: suck plant sap from the underside of the leaf, hence may transmit viral diseases.
- Control: Destroy infected plant and spray insecticides.
Disease Control
• Late Blight
- Cause: Fungus
- Symptoms: dry patches on the leaves and fruits.
- Control: use of fungicides, crop rotation and destruction of affected materials.
• Blossom-end Rot
Caused by;
- Too much nitrogen in early stages.
- Irregular or infrequent watering.
- Calcium deficiency.
- Control: Apply calcium ammonium nitrate and correction of the above problems.
Harvesting
• For canning, fruits should be fully ripe.
• For fresh market, fruits should be partially ripe and packed in crates to avoid damage.
• The fruits should be graded according to;
- Size,
- Colour,
- Ripeness
- Freedom from blemishes.
Cabbage
• It is a leaf vegetable related to other brassica crops such as kales, cauliflower, Chinese cabbage and Brussels sprouts.
• Cabbage leaves may be eaten raw in salads, steamed, boiled or cooked in a variety of ways.
• The leaves can also be fed to livestock.
Ecological Requirements
• Altitude:
- Those with small heads: 900-1500m above sea level
- Those with Large heads: 1800-2700m above sea level.
• Temperature: require cool condition.
• Rainfall:
- 750-2000mm per annum.
- Should be well distributed throughout the growing period.
• Soils:
- Deep,
- Fertile
- Well drained.
Varieties
• Early maturing:
- Brunswick,
- Sugar loaf,
- Early jersey,
- Copenhagen market,
- Chinese cabbage,
- Celery cabbage,
- Cafe splits kool
- Gloria, mukuki,
- Golden acre .
• Late maturing:
- Drumhead,
- Savoy,
- Perfection,
- Winningstadt.
Nursery Practices
• The beds should be raised, dimension 1 m wide and any convenient length (usually 2-3m in length).
• Make drills of 15-20cm apart.
• Sow seeds by drilling and cover to a depth of 1 cm.
• Provide shade or mulch material.
• Apply phosphatic fertilizers and mix thoroughly with soil during planting.
• Water twice a day.
Seedbed Preparation
• Cultivation should be done during the dry season so that all the weeds are killed.
• Dig holes at the spacing of 60cm x 60cm.
• Incorporate farm yard manure in the soil.
Transplanting
• Water the seedlings before uprooting.
• Seedlings are ready for transplanting after one month that is when they are 1O-15cm in height.
• Select healthy and vigorous seedlings.
• Transplant the seedlings with balls of soil to prevent root damage.
• Plant to the same depth as they were in the nursery.
Field Maintenance
• Apply fertilizers during planting and top dress later.
• Control weeds to reduce competition.
Pest Control
• Diamond Black Moth
- Damage: Eats the underside of the leaf making windows or holes in the leaf.
- Control: Spray recommended insecticides.
• Cutworms
- Damage: Attacks the stem at the ground level causing he plant to fall.
- Control: Spray recommended insecticides.
Disease Control
• Black Rot
- Cause: Bacteria
- Symptoms: Leaves turn yellow and rotting of the stem giving an offensive odour,
- Control: Closed season, crop rotation, use certified seeds and spray appropriate chemicals.
• Black Leg
- Cause: Fungus
- Symptoms: Brown to black spots on seedlings and dark canker on the stem.
- Control: crop rotation, destroy infected materials.
Harvesting
• Cabbages are ready for harvesting 3-4 months after transplanting.
• The heads are cut when they are solid and compact.
• Harvested cabbages are sold immediately.
Carrots (Daucus carota)
• It is a root vegetable grown in the cool areas of Kenya.
• It is commonly eaten raw in salads but can also be cooked.
Ecological Requirements
• Altitude: 0-2,900m above sea level.
• Rainfall:
- 750 - 1,000mm.
- Well distributed throughout the growing period.
• Soils:
- It requires deep,
- Fine tilth
- Well drained soils that are free from obstacles to allow for root expansion.
• Temperatures: it requires cool to warm temperatures as very high temperatures result in the production of pale and short roots.
Varieties
• Fresh market varieties for example Chantenay and Nantes.
• Canning varieties for example Nantes
• Fodder varieties for example Oxhast.
Land Preparation
• The field should be well dug to a depth of about 20cm.
• The soil clods should be broken to give a fine tilth before planting.
• Manure should not be applied as it induces forking which reduces the crop quality.
Planting
• Carrots are planted directly into the main seedbed.
• Seeds are drilled into rows made 20-30cm apart.
• The seeds are then covered lightly and the soil pressed down.
• 90kg/ha of DSP should be applied at planting time in the drills.
• It should be mixed well with the soils before placing the seeds.
Field Practice
• Thinning -- it is done 2 weeks after germination.
• Weed control- the field should be kept weed free.
• Earthing up should be done while weeding to encourage root expansion ..
• Topdressing: after weeding 60kg of nitrogen per hectare should be applied as top dress.
• Irrigation - this should be carried out where or when there is not enough rainfall.
Pest Control
• Carrots do not have many field pests except the green aphids.
• These can be controlled by use of the appropriate pesticides.
Disease Control
• Occasionally attached by the mildews especially in wet and humid environment.
• Thinning can be done to reduce humid conditions.
Harvesting and Marketing
• Carrots are ready for harvesting 3-5 months after planting depending on the variety.
• They are lifted from the soil and sold fresh or canned.
Onions (Allium cepa)
• Onions are bulb vegetables grown in the warm areas of Kenya.
• They are used as a vegetable in salads and for flavouring foods, soups and stews.
Ecological Requirements
• Altitude: 0-2, 100m above sea level.
• Rainfall:
- 1,000mm of rain per year
- Irrigation in dry areas .
• Soils:
- Requires well drained fertile soils
- pH of 6.0 - 7.0 .
• Temperatures:
- Onions are a warm climate crops.
- However, some varieties prefer cool conditions.
• They require a fairly long dry period for ripening.
Varieties
• Red creole,
• Tropicana hybrid
• White creole.
Land Preparation
• The land should be well prepared leaving a fine tilth.
• Farm yard manure at 40 - 50 tonnes per hectare should be applied and mixed well with the soil.
Planting
• Direct: Seeds are drilled in rows 30cm apart and 8cm within the rows. 20kg/ha of DSP fertilizer is used.
• Indirect: Seeds are established in the nurseries before transplanting them in rows 30cm apart and 8 cm within the rows.
• Shallow planting is recommended for bulb expansion.
Field Management Practices
Thinning
• It is carried out only in the crop that has been directly planted so as to achieve spacing of 8cm between two plants within the row.
• The thinned plants referred to as spring onions are used as vegetables in salads.
Topdressing
• Calcium ammonium nitrate at the rate of 250kg per hectare is recommended for topdressing onions.
• This is done 3 months after planting.
Pest Control
Onion Thrips:
• These cause silvering and withering of leaves from the tips downwards.
• They are controlled by spraying with appropriate insecticides such as Diazinon or fenthion.
Disease Control
Purple Blotch and Downey Mildew
• Purple blotch;
- Characterized by oval greyish lesions with purple centres on leaves.
- This causes leaf curling and die back.
• Downey mildew;
- Characterized by brown spores covering the leaves leading to death of the whole plant.
- The two diseases are effectively controlled by crop rotation and application of appropriate fungicides.
Harvesting and Marketing
• Onions are ready for harvesting 5 months after planting.
• When leaves start drying the tops are broken or bent at the neck.
• This hastens the withering of the stems.
• The bulbs are then dug out and left to dry in a shade for a few days.
• Onions are graded according to size and marketed in nets of about 14 -16kgs.