Agricultural Science


Agricultural Science


  • 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 vegetablesfor example kales and cabbages.
  • Root vegetablesfor example carrots, beets, radishes and turnips.
  • Fruit vegetablesfor example French beans and okra.
  • Stem vegetablesfor example asparagus, leeks and spring onions.
  • Bulb vegetablesfor 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: 0-2100 m above sea level.
  • Rainfall: 750-1300 mm per annum.
  • Soils: deep, fertile and well drained.


Fresh market varieties:

  • Money maker,
  • Marglobe, hundred fold,
  • Beef eater,
  • Hot set,
  • Super marmande

Processing varieties:

  • Kenya beauty,
  • San -marzano,
  • Roma,
  • Heinz 1350,
  • 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.


  • Seedlings are ready for transplanting when they are 10-15cm high 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.


  • 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.

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