Nutritional value of bambara groundnut (Vigna subterranea (L.) Verdc.) : a human and animal perspective.

Abstract

Bambara groundnut (Vigna subterranea (L) Verdc.) is an indigenous African legume that is reported to have wide adaptation to a range of environments. It is popular among subsistence farmers in sub-Saharan African. However, research on the crop still lags behind that of other established legumes and in most places the crop is still cultivated from landraces, with no locally improved varieties available. The objective of the study was to evaluate the nutritional and agronomic potential of bambara groundnut. Three separate experiments were undertaken, (i) seed quality determination during germination, (ii) controlled environment study to determine yield and nutritional quality under water stress and (iii) field trials to determine the effect of seasons and location on nutrient composition. The results showed that the darker coloured seeds had a faster germination rate. Black speckled seeds had the highest (crude protein) CP after 8 (20.67%), 16 (22.11%), 24 (20.68 %), and 48 hours (20.77%), on the other hand cream seeds had the lowest CP after 16 (19.30%), 24 (18.71%), and 72 hours (19.16 %). The results showed that nutrient composition varied during early imbibition and the variations could be associated with seed colour and duration of imbibition. Under controlled environments, statistically significant differences were observed for plants under 100% ETc when compared with plants under 30% ETc with regards to stomatal conductance. Bambara groundnut landrace selections were able to adapt to the limited water under 30% ETc by closing their stomata. The lower stomatal conductance at 30% ETc relative to 100% ETc demonstrated a regulation of transpirational losses, through effective stomatal control. Under field conditions, the interactions between seasons, location, irrigation systems, sequential harvesting and crop varieties is one that needs sufficient planning so as to maximise nutrient quality and overall crop production. The nutritive value and mineral contents of bambara groundnut landrace selections varied considerably in response to water regimes, sequential harvesting, locations and seasons. These findings suggested that bambara groundnut is a drought resistant crop and can aid as an affordable all year round forage supplement for ruminants during the dry seasons.