Assessment of Weed Interference on the Performance of Cowpea in Enugu State

Weed competition is among the most important biotic constraints to cowpea productivity in the humid and sub-humid zones of South East Nigeria, and quantifying the critical weed interference period is essential for designing economically rational weed management schedules. This study assessed weed interference effects on cowpea (Vigna unguiculata L. Walp.) growth and yield in Enugu North Local Government Area, Enugu State, South East Nigeria. A field experiment was conducted during the 2023 rainy season using a randomised complete block design with eight treatments representing weed-free and weedy periods of 2, 4, 6, and 8 weeks from crop emergence. IT97K-499-35 cowpea variety was used with three replications. Weed species composition, density, and dry weight were recorded weekly. Cowpea growth (plant height, leaf area index) and yield components (pods per plant, seeds per pod, seed weight, and grain yield) were measured. Results showed that maintaining weed-free conditions for the first 4 to 6 weeks after emergence was critical, with plots weeded for less than 4 weeks suffering up to 48.7 percent yield reduction compared to the season-long weed-free control. Grasses (notably Panicum maximum and Digitaria horizontalis) dominated the weed community and showed the highest competitive impact. The study recommends one to two hand weedings at 2 and 6 weeks after sowing as the minimum effective weed management schedule for cowpea production in Enugu State.

Keywords: weed interference, cowpea, critical weed period, Enugu State, weed management