Effects of row spacing and weed infestation on yield of bambara groundnut, Vigna subterranea (L.) Verdc. in South Africa

Bambara groundnut, Vigna subterranea (L.) Verdc. is an important grain legume crop in Africa. The production of bambara is limited by farmers' poor cultural practices as well as weed interference. The effect of row spacing on yield of bambara and weed interaction has so far not been studied in detail. Therefore, this paper reports on the effects of row spacing on the performance of bambara and weed suppression. The trials were conducted in two seasons. A popularly grown bambara cultivar, SB 7-1, was planted under field conditions at the Agricultural Research Council-Grain Crops Institute (ARC-GCI) research station in Vaalharts, South Africa, in the 2009 and 2010 cropping seasons. The treatments consisted of four row spacings (45, 60, 75 and 90 cm apart), laid in a randomised complete block design for each year. The plots were weeded twice, at 1 and 2 months after planting. Weed incidence, abundance, biomass and dry matter were determined immediately after each weeding. Grain and fodder yields were taken at maturity. Results showed significant differences (P <= 0.05) among the row spacings for fodder and grain yields, and weed total biomass and dry matter. Row spacings of 45 and 60 cm exhibited lower weed biomass and dry matter than 75 and 90 cm, and consequently produced higher grain yield. Mean yield decreased with increasing row spacing during the two seasons from 2079 kg/ha-1 at row spacing of 45 cm to 1017 kg/ha-1 at row spacing of 90 cm. The study found that planting bambara at row spacings of 45 or 60 cm is optimum for maximum yield with minimum weed interference.