The bambara groundnut (Vigna subterranea (L.) Verdc.) is an annual, creeping legume with glabrous, trifoliate leaves. It has a deep taproot surrounded by lateral profuse roots bearing N-fixing nodules. Flowers are presented as papilionaceous racemes. Once fertilized, the flower is drawn below the soil through a tunnel. Fruits are 2 or 3-seeded pods, 1.5 to 3 cm long, wrinkled and at first indehiscent. Seeds are round, smooth and very hard when dry (Ecoport, 2009). Average yields are 300-800 kg/ha, but can range from 100 kg/ha up to 4 t/ha.
Vigna subterranea grows well where groundnut does not (Brink et al., 2006). It is cultivated primarily for its seeds, which are used as human food. In Africa, it is the third most commonly eaten legume after groundnut and cowpea (Omoikhoje, 2008). The seeds are used in many types of foods, some of which are an important part of human diets. Mature, dry seeds are boiled and eaten as a pulse. Seeds can be milled to make flour. Ripe seeds are very hard and must be cooked for longer than those of other legumes. Cream-coloured seeds are often preferred to red and black seeds, because they are less bitter and take less time to cook. Large seeds are preferred to smaller ones, especially for use as a snack. Smaller seeds are ground into flour for use in various recipes.
The processing of Vigna subterranea results in by-products (shells of offals) that can be fed to animals. Seeds can also be fed to animals if surplus to human requirements. The leafy shoots are used as fodder (Brink et al., 2006).