Wednesday, 28 November 2012

Growing Groundnuts in Kenya (arachis hypogaea)

The scientific name for groundnuts plant is arachis hypogaea while the local name is njugu Karanga. Groundnuts originated in South America. They are now grown from seed in most tropical, Subtropical and temperate countries between 40 N and 40 S latitudes, particularly in Africa, North America, South America and Asia. The seeds are rich in oil 38-50%, protein 25%, calcium, magnesium, phosphorus, potassium and vitamins. They are reported to have medicinal value particularly in the treatment of diarrhea and haemophilia. Most of the world groundnuts are processed into oil used for cooking. The cake that comes out of oil press is ground into flour and used in many human foods as its rich in protein. The seeds are eaten raw, as roasted snack, used in confectionary, used in soups and made into sauces to accompany meat and starchy dishes. In Africa the plant is grown by small scale farmers both for cash and subsistence.

Climate water and soil requirements
The crop grows well in warm tropics and subtropics below 1500 M above sea level. Optimum daily growing temperatures requirements are 30º C and growth stops at 15º C. The plant does not tolerate frost and cooler temperatures delay flowering and seed formation. Water requirements are 500 to 600 mm well distributed throughout the growing season for good growth. However the crop is drought resistant and can survive severe lack of water but yields are reduced. Pods grow underground crumbly free draining soils are required. But the plants also grow well in heavier clay soils. Harvesting in wet condition should be avoided, to prevent development of aflatoxin, a severe poison produced by Aspergillus spp of fungus, which releases chemicals dangerous to human health. The fungus causes both seeds and seedlings to rot. The infected seedlings are covered with black fungal spores. PH requirements range from 5.5 to 6.5.

Crop propagation
Plough the land and harrow to a good tilth. Prepare ridges which are 80cm apart with flattish tops. Seeds for sowing should be stored in their pods to be shelled a few days before planting. The seeds are planted in two rows on top of the ridge. Select clean well filled seeds for planting. Sowing seeds to a depth of 5-8 cm at a seed rate of 40-50 kg per ha is recommended depending on the seed size.
Groundnuts have two main types namely:-
  1. Bunch type e.g. Red Valentia maturing within 90 – 100 days
  2.  Runner type e.g. Homa Bay maturing in 120-150days

Varieties and Yields
The present growers yield in Kenya is 450-700kg/ha can be doubled though
Improvement of husbandry practices.

Mean  Kernel yield
Red Valencia
Makulu Red
Asyria Mwitunde
Texas peanut
Severe 116 ( white)
Homa Bay

Groundnuts compete poorly with weeds particularly during the early stages of growth. Earthing up should be done at the time of weeding to encourage pegging which refers the penetration of young nuts into the soil. Hand weeding is recommended after initiation of pegging to prevent disturbance to the growing nuts or damaging the flowers. Clean weeding should take place up to 6 weeks after which only hand weeding should be done.

Calcium is critically required during the pod formation stage and lack of it results in empty pods. Generally nitrogen fertilizers are not required as the plant is leguminous and fixes Nitrogen. In acidic soils lime can be applied to raise the ph and supply calcium. Moisture stress at flowering or pod formation stages reduces yields and therefore supplementary irrigation may be required for increased production and high quality seed. Rock phosphate at the rate of 200kg/ha is recommended in heavily eroded soils.

Maturity period is 90-130 days depending on the variety. Mature nuts should be firm and dry as well as brown on the outside. At maturity the inside of the pods is grey with a rattling sound when shaken. Dig up nuts with care to avoid breaking off and remaining in the ground. Dry for a period of 2-3 days, then remove the nuts from the plants and dry them on mats for 7-10 days, to a moisture content of 10%.Shelling should be done by hand followed by sorting to remove the  broken, dirty, damaged nuts which lower the quality and consequent selling price. Storage should be done in clean dry conditions to avoid growth of asperngillus  spp of fungi which relesases afflatoxin chemicals deadly to human health particularly the liver. Seed meant for planting the following year should not be shelled until a few days before planting.The major pests and disease challenging groundnut growing are shown below:-
Pest or disease
Stage attacked
Type of damage
Control measures
White grubs
All stages
Roots, pods, young nuts
Well decomposed manure
All stages
Roots, stem base, pods
Early planting, field hygiene, timely harvesting.
seedling & plant
Pods, flowers
Cover exposed pods, close soil cracks
Early growing stages
Vector of rosette virus
Early planting, conserve natural enemies e.g. ladybirds.
Damping off disease

Rotting of stems Seedling, petioles
Certified seed, crop rotation
Leaf spot
Brown ring spots Shedding leaves
Crop rotation, field hygiene
All aerial parts except flowers
Leaves, stems
Remove volunteer groundnut plants, crop rotation
Aspergillus crown rot
All growth stages
Wilting  of the plant
Rapid drying of nuts to 10% M.C
Bacterial wilt
All stages
Plant wilting
Rotation with cereals
Groundnut rosette Virus
All growth stages
Yellowing, mottling, stunting
Early planting, control of vector-Aphids