Growth and yield response of cowpea [ <i>Vigna unguiculata</i> (L.) Walp.] to nitrogen fertilizer and inoculant application

Abstract Cowpea ( Vigna unguiculata (L.) Walp.), is an important crop for addressing food security in Africa, especially Ghana. However, its production is limited by soil nutrient deficiencies, particularly nitrogen (N). This study aimed to assess the impact of N fertilizer application and inoculation on the growth and yield of cowpea. A factorial experiment was conducted with two inoculant strains (WB74and BR 3262) and four N fertilizer levels (0, 15, 30, and 45 kg N/ha) laid out in a randomized complete block design with four replications. Plant height, branching, leaf number, yield components, N fixation, and N derived from the atmosphere were measured. At 25 and 35 days after planting (DAP), the 45 kg N/ha treatment produced the tallest plants, which was significantly higher than those from other treatments. Both inoculant strains improved growth compared to the control. The 45 kg N/ha treatment had the most branches, while the 30 kg N/ha treatment had the most nodules per plant. At 40 DAP, the WB74 had the most effective nodules. The 45 kg N/ha treatment produced the highest grain yield, and the BR 3262 strain outperformed the control and WB74. N fixation and N derived from the atmosphere were highest with the 45 kg N/ha treatment, and the BR 3262 inoculant had greater N fixation than the other treatments. For optimal cowpea growth, N fixation, and yield, a combination of N fertilizer application and inoculation should not be overlooked.