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:-
- Bunch type e.g. Red Valentia maturing within 90
– 100 days
- Runner
type e.g.
Varieties and Yields
The
present growers yield in Kenya
Improvement
of husbandry practices.
Variety
|
Mean Kernel yield
Kg/ha
|
Red
|
1500
|
manipinta
|
2450
|
Makulu
Red
|
2750
|
Bukene
|
1530
|
Asyria
Mwitunde
|
1300
|
1360
|
|
Severe
116 ( white)
|
1250
|
Atika
|
900
|
770
|
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:-
Stage attacked
|
Type of damage
|
Control measures
|
|
White grubs
|
All stages
|
Roots, pods, young nuts
|
Well decomposed manure
|
Termites
|
All stages
|
Roots, stem base, pods
|
Early planting, field
hygiene, timely harvesting.
|
millipedes
|
seedling & plant
|
Pods, flowers
|
Cover exposed pods, close
soil cracks
|
Aphids
|
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
|
leaves
|
Brown ring spots Shedding
leaves
|
Crop rotation, field
hygiene
|
Rust
|
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
|
