Agronomic Performance and Nitrogen Fixation Potential of Promiscuous Soybean (Glycine max L. Merrill) Varieties in Northern Ghana

African Journal of Agriculture | Vol. 13, No. 8, August 2026 | pp. 058–065

DOI: 10.46882/2026/AJA/000741

Article Type: Original Research Article

Title: Agronomic Performance and Nitrogen Fixation Potential of Promiscuous Soybean (Glycine max L. Merrill) Varieties in Northern Ghana

Names of Authors: Kwaku O. Asante¹, Abdulai M. Fuseini¹, Grace E. Mensah²

Authors’ Affiliations: ¹Council for Scientific and Industrial Research (CSIR)-Savanna Agricultural Research Institute, Tamale, Ghana; ²Department of Agronomy, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana

Abstract: Soil nitrogen depletion is a major barrier to smallholder crop productivity in the savanna zones of northern Ghana. Cultivating promiscuous soybean (Glycine max L. Merrill) varieties—which form symbiotic relationships with indigenous Bradyrhizobium strains without requiring chemical inoculants—presents a cost-effective strategy to improve soil fertility and raise family incomes. This multi-locational field experiment evaluated the nodulation efficiency, nitrogen fixation capacity, and grain yield of four advanced promiscuous soybean varieties (Jenguma, Quarshie, Songda, and Suvita) against a non-promiscuous check (Anidaso). Biological nitrogen fixation (BNF) was quantified using the nitrogen-15 (¹⁵N) natural abundance technique. The promiscuous variety Songda recorded the highest nodule dry weight (184.6 ± 12.5 mg/plant) and numerical nodule count at 50% flowering. Songda derived 72.4% of its total nitrogen requirements from atmosphere-based fixation, equating to an estimated mean of 84.6 kg N/ha returned to the soil profile. The grain yields differed significantly among varieties (p < 0.01), with Songda producing the highest clean grain yield at 2.45 t/ha, followed by Jenguma at 2.12 t/ha, compared to only 1.24 t/ha for the non-promiscuous control. Songda also maintained a high harvest index (0.46). This study demonstrates that using the Songda variety provides dual benefits, delivering high grain outputs while substantially improving nitrogen balance in savanna cropping systems.

Keywords: Biological nitrogen fixation, Glycine max, Promiscuous varieties, Nodulation, Grain yield, Savanna ecology

Manuscript Timeline: Received: April 20, 2026; Revised: May 29, 2026; Accepted: June 22, 2026; Published: August 16, 2026

Citation: Asante, K. O., Fuseini, A. M., & Mensah, G. E. (2026). Agronomic Performance and Nitrogen Fixation Potential of Promiscuous Soybean (Glycine max L. Merrill) Varieties in Northern Ghana. African Journal of Agriculture, 13(8), 058–065. DOI: 10.46882/2026/AJA/000741

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