Kersting's Groundnut

Kersting's groundnut is a low, creeping annual legume that produces its pods underground, like the peanut, after the flowers have been pollinated and pushed into the soil. The pods are small, about 1.5 to 2 cm long, and contain one or two kidney-shaped seeds. The seeds vary in colour from cream and brown to black and mottled. They are small, about 5 to 6 mm, hard when dry, and have a pleasant flavour that has been compared to beans with a slightly nutty taste. The crop is usually grown on poor sandy soils by small farmers, and the seeds are sold dried in local markets in Benin, Togo, Ghana, Burkina Faso and northern Nigeria. Preparation requires long cooking times.

Macrotyloma geocarpum is native to West Africa, where it was domesticated, and it is most grown in the savanna zones of Ghana, Togo, Benin, Burkina Faso, Mali and northern Nigeria. It is considered a neglected and underutilised crop. The common name honours Kersting, a German botanist and colonial administrator in Togo who described it in the early twentieth century. The Latin name geocarpum means earth-fruited, referring to the habit of ripening pods underground. Local names include aboboi in parts of Ghana and okpa in Igbo-speaking areas, though okpa also refers to Bambara groundnut pudding, so care is needed.

Archaeological evidence for the crop is sparse, but it is believed to have been cultivated in West Africa for centuries, as part of mixed farming systems with yam, millet and sorghum. Farmers valued it for growing in poor, dry soils, for its good flavour and for its role in local ceremonies and traditional dishes. Colonial botanists documented it in the early twentieth century, though it received little attention. In the later twentieth century, Kersting's groundnut declined in many areas because it needs hard work to harvest and lower yields compared with peanut and cowpea. Seeds are also difficult to cook, and the crop is often grown by women on small plots. In recent years, researchers and agencies promoting underutilised crops have drawn attention to its potential for food and nutrition security, drought tolerance and soil improvement through nitrogen fixation. Projects in Benin, Ghana and elsewhere are working on genetic resources, better varieties, and ways to reduce cooking time. It remains a minor crop, but one of cultural and local importance.

The seeds are boiled until soft, often for a long time, and eaten as a porridge or stew, alone or with oil, pepper and other seasonings. They are also ground into flour for making cakes, steamed puddings or fritters, and mixed with cereals. In some areas, the seeds are sprouted or fermented to make them easier to digest. The plant's leaves and stems provide fodder for livestock after harvest, and the crop improves soil fertility as a legume. The seeds have special roles in some traditional ceremonies and foods.

Analyses report that the seeds are high in protein, often around 20 percent or more, with useful amounts of carbohydrate, fibre, iron and other minerals. Like other pulses, they contain antinutritional factors, such as tannins and trypsin inhibitors, that are reduced by soaking and long cooking. Human studies are scarce, so the nutritional potential is based mainly on compositional data.