Crop Production V (Vegetables) - Agriculture Form 2 Notes

• Introduction
• Vegetable Crops
  • Tomatoes (Lycopersicon esculentum)
  • Cabbage
  • Carrots (Daucus carota)
  • Onions (Allium cepa)

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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
• 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.

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Vegetable Crops

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: 750 - 1300mm per annum.
• Soils: deep, fertile and well drained.

Varieties

• Fresh market varieties:
  • Money maker,
  • Marglobe, hundred fold,
  • Beef eater,
  • Hot set,
  • Super marmande
• 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
  • Cause
    - 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,

 

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;
  • 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.

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