Impact of Planting Date and Spacing on the Growth and Yield of Two Cowpea Varieties (SLIPEA 4 and Tented Beans) in the Lowland of Njala University, Kori Chiefdom, Southern Region

Abstract

A field experiment was conducted in 2024 at the School of Agriculture and Food Sciences, Njala University, Moyamba District, Southern Sierra Leone, to evaluate the effects of planting date and spacing on the growth and yield performance of two cowpea (Vigna unguiculata L.) varieties. The experiment was laid out in a Randomized Complete Block Design (RCBD) with three replications. Each gross plot measured 15 m² (5 m × 3 m), and the total experimental area covered 532.5 m² (35.5 m × 15 m). Treatments consisted of three planting dates (early August, mid-August, and late August) and three spacing regimes (90 cm × 20 cm, 60 cm × 20 cm, and 30 cm × 20 cm). Results showed significant differences (p < 0.05) in growth and yield parameters in response to planting date and spacing. Early August planting recorded superior vegetative growth, including plant height (123.3 cm and 139.3 cm), number of branches per plant (7.8 and 12.31), stem girth (10.03 cm and 13.28 cm), number of leaves per plant (145.2 and 141.21), and leaf area (45.67 cm² and 49.90 cm²) at maturity and harvest. Among spacing, 90 cm × 20 cm produced the tallest plants (138.3 cm and 148.0 cm), highest number of branches (8.11 and 10.2), thickest stems (15.6 cm and 15.66 cm), highest leaf count (143.40 and 141.21), and largest leaf area (66.60 cm² and 49.90 cm²). Early August planting also produced the highest yield attributes: pods per plant (13.30), seeds per pod (6.17), 100-seed weight (20.33 g), dry pod weight per plot (499.67 g), dry seed weight per plot (387.00 g), plants harvested per plot (78.83), and seed yield (448.17 kg/ha). Similarly, 90 cm × 20 cm spacing recorded the highest pods per plant (10.89), seeds per pod (6.17), 100-seed weight (19.67 g), dry pod weight per plot (447.67 g), dry seed weight per plot (339.11 g), plants harvested per plot (88.11), and seed yield (439.67 kg/ha). Although both varieties adapted well, SLIEPA 4 consistently outperformed Tented Beans. Early August planting combined with 90 cm × 20 cm spacing was identified as the optimum practice under Njala conditions.