LOCALLY SOURCED RHIZOBIA INOCULANT CARRIERS SUBSTITUTE COALBASED INOCULANT PREPARATIONS TO ENHANCE LEGUME CROP PRODUCTION IN SOUTHERN ETHIOPIA

Abstract

This study investigates the potential of locally sourced carrier materials for formulating rhizobia inoculants to enhance legume productivity and promote sustainable agriculture in southern Ethiopia. Inoculating legume seeds with effective rhizobia strains has been proven to significantly enhance nitrogen fixation, plant growth, and agricultural productivity. However, effective carrier materials are critical for maintaining rhizobia viability and functionality, yet suitable options are scarce in Ethiopia. Thus, we evaluated five locally available materials; coal, charcoal, silkworm feces (SWF), compost and water hyacinth biochar (WHBC), for their suitability as carriers. The physiochemical properties of the carrier materials, their storage conditions (4°C and room temperature), and effectiveness in promoting nodulation at intervales of 60 days for five times were evaluated. Physicochemical analysis revealed that WHBC and SWF exhibiting superior water holding capacity (647% and 230.46%, respectively), high nutrient and mineral contents, sustaining rhizobia counts above the commercial threshold (>108 CFU/g) for 300 days at both temperatures. Greenhouse experiments demonstrated that inoculants formulated with these carriers significantly enhanced nodulation and shoot biomass, exceeding the coal-based formulation used as standard in Ethiopia. The study advocated for their adoption to improve soil fertility, reduce fertilizer dependency, and enhance food security in Ethiopia.