Response of cowpea (Vigna unguiculata, L., Walp) to inter-row spacing and weed competition

Weed infestation is one of the major factors attributed for the poor yield of cowpea in Nigeria and other parts of sub-Sahara Africa (SSA). Field trials were therefore conducted to evaluate the effect of row spacing and different weeding levels on weed control, growth and yield of cowpea during the early and late wet seasons of 2009. In both seasons, the use of 60 cm row spacing resulted in significant (P < 0.05) reduction in weed density by 18 – 39% and weed biomass by 17 – 27% with subsequent increase in cowpea growth and grain yield than 75 and 90 cm row spacing. Cowpea grain yield increased by 67 – 109% in the early season and 24 – 56% in the late season at 60 compared to 75 and 90 cm row spacing. Hoe weeding reduced weed growth significantly in both seasons with the lowest weed density and biomass recorded in plots weeded thrice. However, this was not significantly different from weed density and biomass recorded with two weedings in both seasons. Hoe weeding twice resulted in optimum growth and grain yield of cowpea. An additional weeding, however, did not improve cowpea growth and yield in both seasons. The results of this study showed that narrow (60 cm) inter-row spacing and two hoe weedings at 3 and 6 weeks after sowing (WAS) will improve weed control and productivity of cowpea. Additional weeding is considered superfluous.