Groundnut, Goober, earthnut
Arachis hypogaea is a globally important legume crop originating in South America. A low-growing, annual plant, depending on variety A. hypogaea can reach lengths of 70 cm. Leaves are opposite, pinnately compound, and leaflets are borne in opposing pairs (4 leaflets per leaf). A. hypogaea leaves are also nyctinastic, meaning they close at night. Flowers are 1-1.5 cm in width and range from yellow to orange in color, forming in clusters above the ground on plant stems. When fertilized, the flowers give way to “pegs” (fruit stalks) that elongate and penetrate the soil to form 3-7 cm long pods.
A. hypogaea seeds are an important food staple globally. The seed, itself, is high in protein, and can also be pressed for valuable cooking or industrial oil. Pod casings and seed castings can be incorporated into animal fodder. The green foliage, seeds, and dry crop residue are valuable fodder sources for livestock. A nitrogen-fixing plant, A. hypogaea enriches the soil when plowed under or used as green mulch.
- Rainfall – 400-4000 mm
- Soil Types – well-drained, loose, medium textured; pH 4.5-8.5
- Temperature Range – 10-45°C
- Day Length Sensitivity – none
- Light – prefers full sun
Seedbeds for A. hypogaea should be prepared flat or with a wide ridge to accommodate pegging. Similarly, seeds are best sown before heavy rains begin as pegging requires the soil to be light, sandy and level. Seeds should be planted 4-7 cm deep, at rates of 60-80 kg/ha.
Harvesting and Seed Production
A. hypogaea are ready for harvest when the insides of the peanut hulls turn dark, before nuts begin to sprout, or when the plants turn brown (usually 80-150 days after planting, depending on variety). Plants may be dug up (by hand, hoe or plow) and left in the field to dry, with pods exposed to the sun and air. Depending on relative humidity, pods will need to be dried further by hanging in a dry place in burlap sacks until moisture content is 10% and seeds rattle when shaken. Seeds matured during rainy season can become toxic due to fungal inundation.
Pests and Diseases
The potato leafhopper and mites feeding on the underside of the leaf both cause yellowing of the leaf. Irrigation may help to dislodge both pests. During harvest and post-harvest activities, keep seeds dry with adequate air circulation, as high moisture/humidity is conducive to the development of a liver-damaging mold called aflatoxin.
Cooking and Nutrition
The ripe seeds are used primarily as a high-protein food crop for humans and unripe pods can be eaten as a vegetable. Seeds can be eaten fresh, roasted, boiled, ground for nut butter or pressed for oil. Peanuts contain various vitamins and minerals necessary for human and animal health. In sensitive individuals, an allergy to A. hypogaea can be quite severe.
Duke, J.A. 1983. Handbook of Energy Crops. unpublished. . Accessed 17 July 2019.
Ecocrop. 1993-2007. Secale cereale. Food and Agriculture Organization, Rome, Italy. ecocrop.fao.org/ecocrop/srv/en/dataSheet?id=2199. Accessed 17 July 2019.
Ntare, B.R., 2007. Arachis hypogaea L. [Internet] Record from PROTA4U. van der Vossen, H.A.M. & Mkamilo, G.S. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. . Accessed 17 July 2019