Bio-inoculants and phosphorus application improved faba bean productivity and nodulation in acidic soil conditions in Ethiopia

Abstract

Phosphorus (P) is less available in acidic soils because of its interaction with iron and aluminium, which results in lower crop yields. To address this issue, a field experiment was conducted using a split-split plot design with three replications to evaluate the effect of Rhizobium inoculation and P rates on the agronomic attributes and economic returns of faba beans. The main plots were assigned to Rhizobium, with subplots for varieties and sub-subplots for P rates. Rhizobium inoculation increased the number of nodules per plant and seeds per pod by 23.6% and 11.1%, respectively. P application resulted in an 88.8% increase in nodule count. The interactions among Rhizobium, P, and variety significantly influenced plant height, branch and pod count, above-ground biomass, shoot biomass, and grain yield. Inoculated Dosha at 30 kg P ha⁻¹ produced taller and higher pods, with increases of 24.4% and 66.2% compared to uninoculated and unfertilized Numan. Grain yields increased by 214% in inoculated Numan, while biomass yield increased by 79.4% in inoculated Dosha, compared to uninoculated and zero P-supplied Gebelcho. Economic analysis revealed the highest net benefit of 317,842.9 ETB ha⁻¹ and a marginal rate of return of 1972.6% from applying 20 kg P ha⁻¹ with Rhizobium inoculation. Based on the current findings, the application of Rhizobium in combination with P at 20 kg ha⁻¹ enhances the productivity and profitability. Therefore, these treatment combinations are recommended for farmers aiming to boost productivity and economic returns in the study areas and other agroecological systems.