GENOTYPIC VARIATION AND YIELD OPTIMIZATION IN BAMBARA GROUNDNUT (VIGNA SUBTERRANEA L. VERDC.) UNDER VARYING PLANT POPULATION DENSITIES IN THE SUDAN SAVANNAH

Abstract

Bambara groundnut (Vigna subterranea L. Verdc.) is an underutilized African legume valued for its resilience to drought and poor soils, yet the genotypic variation in its response to plant population density remains underexplored. This study investigated the growth and yield performance of three Bambara groundnut genotypes (Cream Brown Eye, Cream Black Eye, and Mottled Brown Eye) under three population densities (160 × 20 cm, 160 × 30 cm, and 160 × 40 cm) in the Sudan savannah of Nigeria using a split-plot design. Significant effects of genotype, density, and their interaction were observed for plant height, petiole length, and yield components. Wider spacing enhanced vegetative growth, while intermediate density (8 plants m⁻²) maximized grain yield (1.85 t ha⁻¹), reflecting a parabolic density–yield relationship. Among genotypes, Mottled Brown Eye exhibited superior shelling efficiency (82.4%) and productivity index, indicating greater assimilate partitioning and competitive balance under moderate population pressure. The differential density responses among genotypes highlight the presence of exploitable genetic variation for density tolerance and yield stability. These findings suggest that moderate plant density optimizes canopy development, photosynthetic efficiency, and yield per unit area under semi-arid conditions, providing a framework for genotype-specific planting density recommendations to enhance Bambara groundnut productivity and sustainability in dryland cropping systems.