Abstract
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.
Highlights
Groundnut (Arachis hypogea L.) is a major grain legume in the world, cultivated for both human and animal consumption (Dapaah et al, 2014)
The P fertilizer rates (PR) x inoculant rates (IR) interaction was not significant on plant height at 8 weeks after sowing (WAS), the effects of PR and IR did influence plant height significantly, such that plant height at 30 kg P2O5/ha and inoculant at 6 g/kg seed increased significantly compared with their respective control (Table 1)
Effective nodule number was influenced by the effects of PR and IR with P rate at 60 kg P2O5/ha and inoculant rate at 6 g/kg seed recording the highest number than their respective controls (Table 1)
Summary
Groundnut (Arachis hypogea L.) is a major grain legume in the world, cultivated for both human and animal consumption (Dapaah et al, 2014). Low and declining soil fertility, especially phosphorus (P) deficiency, in smallholder groundnut farms has been described as the fundamental biophysical factor responsible for the declining yield in Sub-Saharan Africa (Naab et al, 2009). Some authors (Naab et al 2005; Kamanga 2010) have reported a significant yield response of groundnut to P application Despite, these benefits, results from various studies on the optimum application rate of P to enhance groundnut yield proves to be inconsistent. Studies by Mouri et al (2018) reported higher yields with P rate at 60 kg P2O5/ha whiles Taruvinga (2014) found no significant effect when P rate was increased beyond 45 kg P2O5/ha.
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