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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
- 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.
- Cause:
- 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.
- Damage:
- 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,
- Black Leg
- Cause:
Fungus - Symptoms:
Brown to black spots on seedlings and dark canker on the stem. - Control:
crop rotation, destroy infected materials.
Harvesting
- 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
- 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.
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
- 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.