Interactive Effects of Soil Texture and Sowing Depth on Seedling Emergence Dynamics of Bambara Groundnut (Vigna subterranea L. Verdc.)

Abstract

Aims: Bambara groundnut (Vigna subterranean L. Verdc.) is an underutilized African legume with high nutritional value and strong adaptation to marginal environments, yet its field establishment is often unreliable due to poor seedling emergence. This study aimed to evaluate the combined effects of soil texture and sowing depth on seedling emergence dynamics in order to identify optimal practical, soil-specific sowing recommendations that can enhance crop establishment and productivity for smallholder farmers. Study Design: A completely randomized factorial experiment combining three soil textures and six sowing depths Place and Duration of Study: The experiment was conducted under greenhouse conditions using soils representative of major Bambara groundnut production zones in West Africa. The trials were repeated three times at one-month intervals, between January and May 2025. Methodology: Three soil types (sandy, gravelly and clayey) were used. Seeds were sown at six depths (2, 3, 4, 5, 6 and 7 cm) in pots. Seedling emergence was monitored daily. Emergence parameters including First Day of Emergence, Last Day of Emergence, Time Spread of Emergence, Mean Emergence Time, Coefficient of Velocity of Emergence and Emergence Percentage were determined. Data were analyzed using two-way analysis of variance. Results: Sowing depth significantly affected all emergence parameters. Shallow sowing (2-4 cm) resulted in rapid, synchronized and high-percentage emergence, with values reaching up to 98%. Deeper sowing (>4 cm) significantly delayed emergence, extended emergence duration and reduced final emergence percentages. Soil texture had a secondary but significant effect, particularly at greater depths. Sandy soil consistently promoted faster and more uniform emergence, whereas gravelly and clayey soils limited emergence due to increased mechanical resistance and reduced aeration. Conclusion: Optimal emergence of Bambara groundnut occurs at shallow sowing depths, particularly in sandy soils. These results provide clear, agronomically relevant guidance for farmers, supporting soil-specific sowing depth recommendations that can improve stand establishment, reduce early crop failure and enhance yield reliability.