Yield response and economic benefits of groundnut to phosphorus fertilization and inoculant rates in Northern Ghana

Groundnut (Arachis hypogea L.) is a major source of dietary protein, cultivated for both human and animal consumption. However, in West Africa, the yields are low, renewing the interest to evaluate groundnut response to P fertilizer (P) and rhizobium inoculant (IR) application. A study was conducted on the experimental field of the University for Development Studies, Nyankpala in the Northern region of Ghana to evaluate the interactive effect of three P rates (0, 30 and 60 kg P2O5/ha) and three IR rates (0, 3 and 6 g/kg seed) on groundnut yield and to assess the economic viability of these technologies to farmers. The study was conducted using a 3 × 3 factorial laid out in a randomized complete block design with three replications. Nodule count and pod number per plant were significantly affected by P fertilizer rates (PR) and rhizobium inoculant rates (IR) interaction. The effects of PR and IR significantly increased grain yield of groundnut, with 60 kg P2O5/ha and 6g inoculant/kg seed recording the highest grain yield of 2708.3 and 2376.6 kg/ha respectively. Correlation analysis suggested that major determinants of groundnut grain yield were nodule count, effective nodule count, pod number and pod weight. Gross benefits were higher in treatment with P fertilizer and/or inoculant application. Estimated B/C ratios also indicated that, compared to the control, all the treatments are attractive. Therefore, cultivating groundnut by using P fertilizer and/or inoculant may provide the most economically viable and low-risk options for increasing groundnut yield in northern Ghana. Key words: Phosphorus, rhizobium inoculant, gross benefit, groundnut, grain yield.