Organic nutrient input enhances legume performance and subsequent impact on maize yield and profitability in a smallholder farming system of Ethiopia

Abstract Proper management of soil is crucial for supporting long-term crop production and addressing multiple sustainability challenges in smallholder cropping systems. Integration of legumes offers a promising means to support soil health and reverse degradation; however, key questions remain as to how nutrient management influences legume performance and their potential to restore soils. We conducted a field experiment in Ethiopia, based on legume-maize rotations, in order to: i) evaluate how nutrient management strategies influence legume performance for different legume species, ii) quantify impacts of nutrient management and legume species on key soil health indicators and subsequent impacts on maize yield, and iii) calculate the relative economic benefits of different nutrient management strategies for each legume species and maize in a smallholder farming context. In the first phase, three nutrient management strategies [1) inorganic fertilizer, 2) manure, and 3) control (no nutrient input)] were combined with two legume species (common bean and soybean), in a full factorial design with four replicate blocks. Maize was planted in all plots in the following season. Manure application to beans increased grain yield across both legume species by 129% relative to the control. Both manure and fertilizer greatly improved nodulation across legume species, especially for common bean. Manure improved key soil health parameters as seen by reduced bulk density and increased pH, soil organic matter fractions, and available P. Manure also improved maize yield by 41 and 161% relative to fertilizer and the control, respectively. The manure application in common bean-maize and soybean-maize rotations increased net profit by 166% and 111% compared to the control, respectively, while fertilizer increased profit by 117% and 36%. Our findings suggest that integrating legumes with manure application can improve soil health, crop yields and enhance profitability, highlighting its potential as a practical strategy for sustainable intensification in smallholder farming system