Response of Cowpea Mutant Lines to Planting Distance and Seasonal Variation in the Semi Deciduous Ecozone

Abstract

Cowpea (Vigna unguiculata) is an important legume crop grown for its nutritional and economic benefits, particularly in the tropical and sub-tropical agro-ecological zones in Sub Saharan Africa. However, optimizing cowpea production remains a challenge due to an inadequate knowledge on the ideal spacing and cowpea varieties suited for specific climatic conditions. This study aimed to evaluate the growth and yield potential of three cowpea mutant lines (M1:HansM9 (12) (3), M2:HansM9 (12) (5), and M3:HansM9 (12) (25) in referenced to two standard varieties (Mi4: Asontem (An improved variety) and Mo5: Hansadua (improved variety) in a semi-deciduous agro-ecological zone. The study employed a 3x5 factorial experiment laid out in a split-plot design with three (3) spacing intervals (S1; 60 cm × 20 cm, S2:60 cm × 30 cm, and S3:60cm × 40cm) during both the major and minor rainy seasons. There were fifteen treatment combinations with four (4) replications resulting in a total of sixty (60) plots. The spacing interval treatments were employed at the main plots (Block) with the three mutant lines and the two varieties on the subplots. Various vegetative and reproductive parameters, including plant height, number of branching, plant girth, canopy size, number of pods, seeds per pod, and total seed weight per hectare were studied. Results showed that the closest spacing (60 cm × 20 cm) led to the highest grain yield, particularly for the mutant line HansM9 (12) (25), which outperformed other varieties in terms of total seed weight and overall yield. In contrast, the wider spacing (60 cm × 40 cm) promoted greater vegetative growth, making it suitable for practitioners aiming to maximize biomass production. The major rainy season was found to be the most conducive for growth and yield, while irrigation is recommended to enhance productivity during the minor season. In summary, HansM9 (12) (25) is recommended for high-density planting (60 cm × 20 cm) to maximize grain yield, especially during the major season. Asontem is more suited for biomass production, particularly at wider spacing (60 cm × 40 cm)