The seed contains 35–55% oil, and groundnuts are often classified as an oilseed
crop (like soybean) even though they belong to the Leguminosae family. In fact
groundnuts are mainly cultivated for their oil. The oil is high in oleic acid and fairly
high in linoleic acid, but low in other acids. It is “non-drying” ie it remains liquid,
without a surface film, when exposed to air.
N
With an annual global production of about 30 million MT, groundnuts rank in
the top 25 of the world’s food crops.
PLANTING
Soil: should be deep, well drained and sandy to encourage development of the long
tap root, up to 1.5 m long, and to allow the pegs to enter the soil surface. Soils should
be high in phosphate, calcium and sulphur.
Groundnuts tolerate a wide range of pH, though they have some preference for
slightly acidic soil—the optimum pH for light, very sandy soils is 5.5, and for sandy
loams is 6.0, up to about 6.5, root nodules often forming even in these acidic
conditions.
Fertiliser is very often not applied, although about 50–100 kg/ha of superphos-
phate is normally beneficial. Requirement for phosphate is high—see Rotation,
below.
The plants survive in high aluminium soils that would be toxic to other food
crops.
Seed rate: 50–80 kg/ha for Bunch types, 35–40 kg/ha for Spreading (Runner) types.
Minimum viable seeds to be planted per hectare: 80,000 on ridges, 110,000 on the
flat. Depth: 4–5 cm.
Seed spacing: 45–75 cm between rows, 10 cm between plants, either on the flat or
ridges. High plant populations, up to about 250,000 plants per hectare, are needed to
produce high yields.
Inoculation: this is advisable, unless it is known that well nodulated groundnuts,
cowpeas or velvet beans have been recently grown on that land.
Germination: the seed is very fragile and must always be handled carefully. The
seed should be left inside the shell for as long as possible before planting in order to
maintain its viability. Sometimes the whole pod is planted, but germination is then
slower and more uneven.
Viability is often good for 3–6 years if the seed is stored dry and cool. Medium
sized seed gives the best results. The seed of some varieties can remain dormant for
up to two years.
Rotation: often best to follow a well fertilised crop such as potatoes, maize or
cotton and apply no fertiliser to the groundnuts, which efficiently uses the residual
fertiliser.
They should not be planted after tobacco, soybeans or sweet potatoes, to reduce
nematode and stem rot damage. In parts of India groundnuts are rotated with rice.
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in Asia and Canada, where the summers are hot. The main producers are China
(10 12 million MT pa), India, Nigeria, Senegal, Sudan, America, Indonesia and Brazil.
Groundnuts are grown in almost all tropical and subtropical countries, up to 45