Effect of Bio Fertilizer on Growth, Yield Attribute and Yield of Groundnut (Arachis Hypogaea L.) Varieties at Lowland Areas of South Omo Zone, South Ethiopia

Groundnut (Arachis hypogaea L.) is an important oilseed and protein crop, yet its productivity in Ethiopia is constrained by poor soil fertility and limited access to improved varieties. Bio-fertilizers, particularly Rhizobium inoculants, offer an environmentally friendly option to enhance nitrogen fixation and crop yields. This study evaluated the effect of Rhizobium inoculation on the growth, yield attributes, and yield of five groundnut varieties (Shilmith, Bulki, Babile-4, Werer 961, and Roba) under lowland conditions of South Omo Zone during the 2024 main cropping season. Treatments consisted of two inoculants (GND Moderate-2 and GNA 10) and a non-inoculated control, arranged in a 5 × 3 factorial within a randomized complete block design (RCBD) with three replications. Results revealed significant (p < 0.05) effects of variety, inoculation, and their interaction on phenology, growth, and yield traits. Inoculated plants generally outperformed the control, with Shilmith inoculated with GND Moderate-2 achieving the highest grain yield (16.72 q ha⁻¹), followed by Bulki with the same inoculant (16.33 q ha⁻¹). Partial budget analysis indicated that Shilmith × GND Moderate-2 generated the highest net benefit (188,148 ETB ha⁻¹), confirming both agronomic and economic advantages. Overall, the study demonstrates that adopting the Shilmith variety with GND Moderate-2 inoculation could substantially enhance groundnut productivity and profitability in the lowland agro-ecologies of South Omo Zone.