Bambara groundnut deserves more attention as African food crop
While the bambara groundnut has many characteristics that make it an attractive food crop, very little research has been done to develop it commercially. This situation should be rectified, according to Gaebewe Ramolemana, who defended his PhD research on the nutrient requirements of bambara groundnuts in Botswana on March 30th. Ramolemana concluded that yields could be greatly improved through the addition of moisture, which enhances the availability of phosphorous, the nutrient most needed to stimulate the growth of this leguminous crop in Botswana
Bambara groundnuts immediately call to mind the image of the well-known groundnuts, or peanuts. However, the similarities stop at the fact that the edible bean-like seeds grow underground. They do not even belong to the same family, bambara groundnuts being related to cow peas. Bambara groundnuts have also received much less attention than ordinary groundnuts, a situation that Botswanan Gaebewe Ramolemana and other researchers have recently tried to change. His PhD comes at the end of a joint five-country research project funded by the EU, in which the potential of bambara groundnuts was investigated in Botswana, Tanzania and Sierra Leone
Valued in semi-arid Africa for their protein-rich contribution to diets, high drought-tolerance and low demands on the soil, bambara groundnuts are an important crop for home consumption and selling in the local markets. Their foliage also forms a useful fodder crop for livestock. Unlike normal groundnuts, the bambara groundnut can provide a reliable crop during unstable rains, at least yielding seeds for the next season. However, it has never attained value on the international market
This is not a complete coincidence, as the WAU's Dr Anita Linnemann, who first studied the bambara groundnut in the mid-1980s, explains: it is a women's crop and cultivated in less conspicuous corners of the bush. Also, it is daylight-sensitive, and difficult to grow on a large scale. Linnemann adds: There are many different varieties of bambara groundnuts grown in Africa to adapt to the local situation, but their favourable characteristics would be lost if developed for a wider market.
Ramolemana's research shows, nevertheless, that the potential for high yields can be greatly increased in Botswana by improving cultivation methods such as plant density, and through the addition of moisture. While farmers normally obtain yields of 500 kg of bambara groundnuts per hectare, Ramolemana's irrigated plots yielded 4.2 tonnes, with 2.8 tonnes under rainfed conditions. Because their root system is small compared with other important crops such as maize and pigeon pea, bambara groundnuts need more water to be able to take up enough nutrients to attain good yields
Ramolemana, who is a lecturer in soil fertility at the University of Botswana, advises against adding nitrogen fertiliser to bambara groundnuts, however. In his pot and field experiments, he found that adding nitrogen fertiliser had negative effects on the growth of this legume. For phosphorous, the most limiting nutrient in Botswanan soils, using P fertiliser only improved growth if added under specific conditions. His observations confirmed that adding phosphorous fertiliser only had an effect on the bambara groundnuts when it was added during the first two weeks after sowing, with moisture near field capacity. In fact, moisture was the most important factor for improving nutrient availability, Ramolemana concluded. He recommends fertiliser use only within a rotation, together with crops such as sorghum, maize and cow peas
In one of his thesis propositions, Ramolemana alludes to how his recommendation of a better moisture regime for crops such as bambara groundnuts can be financed: The future of Botswana agriculture lies below the topsoil. Diamonds account for 40% of the Botswanan national product. Amunda Salm