Effect of Nitrogen on Plant Growth and Leaf Chlorophyll Content of Cowpea (vigna Unguiculata)

Cowpea (Vigna unguiculata) is an important legume crop for food security, yet its productivity is often limited by soil nitrogen (N) deficiency. This study investigated the effects of nitrogen fertilizer concentrations (0, 1, 3, and 5 g) on the growth parameters of two cowpea varieties (IT99k-573-1-1 and Danila) over eight weeks. Key metrics evaluated included the number of leaves, plant height, stem girth, chlorophyll content, and leaf area. Results indicated that nitrogen application significantly influenced growth, with 5g generally yielding optimal outcomes. For instance, this concentration produced the highest number of leaves (8.125) and tallest plants (10 cm) by 8WAG, while 3g consistently underperformed across all parameters. The variety IT99k-573-1-1 demonstrated superior adaptability, outperforming Danila in leaf production, height, and leaf area. Notably, interactions between fertilizer concentration and variety were significant for plant height and leaf area but non-significant for stem girth and chlorophyll content, suggesting parameter-specific responses to nitrogen. The findings highlight the importance of balanced nitrogen application for maximizing cowpea growth, with 5g identified as the most effective dose. These results provide actionable insights for optimizing nitrogen use in cowpea cultivation, particularly for the IT99k-573-1-1 variety, and underscore the need for tailored fertilization strategies to enhance productivity