Growth and yield performance of Bambara groundnut (Vigna subterranea) genotypes under varying periods of weed interference in Nigeria

Abstract

Bambara groundnut (Vigna subterranea) is a climate-resilient, underutilized legume with high nutritional value. However, weed interference during critical growth stages remains a major limitation to its productivity. This study assessed the critical period of weed interference in two Bambara groundnut genotypes (cream round and brown round) under Sudan Savanna conditions during the 2020 wet season. The experiment, conducted at two locations (BUK and Guringawa), used a randomized complete block design with three replications. Treatments involved maintaining plots either weed-free or weed-infested for 3, 6, 9, and 12 weeks after sowing (WAS), followed by the opposite condition until harvest. Weed interference had significant effects on multiple agronomic traits. At BUK, plots kept weed-infested for 12 WAS recorded the highest weed cover score (4.83) and weed dry biomass (61.3 g/m²), while weed-free plots for 12 WAS had the lowest weed cover (1.00) and biomass (14.5 g/m²), and the highest weed control index (52.0%). Similarly, leaf area index peaked at 5.6 under 12 WAS weed-free conditions but dropped sharply to 0.5 when infested for the same duration. Stand count at harvest rose to 25,9 plants ha⁻¹ under 12 WAS weed-free but declined to 5,6 plants ha⁻¹ under prolonged infestation. Yield traits followed the same pattern: total dry matter, number of pods, and kernel yield per plant were highest in 12 WAS weed-free plots (19.4 g, 33.8 pods, 25.7 g, respectively) and lowest when weed-infested for 12 WAS (3.36 g, 11.6 pods, 12.7 g, respectively). Genotypic effects were largely non-significant, though cream and brown types differed slightly in vigor and leaf number at BUK. Maintaining a weed-free period of at least 12 WAS significantly enhanced Bambara groundnut growth, physiological traits, and yield components, underscoring the need for early and sustained weed control in semi-arid farming systems.

Key words: Bambara groundnut, genotypes, critical period, weed interference, susceptibility