Crop Production V (Vegetables) - Agriculture Form 2 Notes

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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.


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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