Biochar-based fertilizers increase crop yields in acidic tropical soils

Abstract

Depletion of soil organic carbon and nutrients creates mounting challenges for agricultural production in tropical regions, putting livelihoods and food security at risk. Biochar-based fertilizer (BBF) has been suggested as a tool to maintain yields while concurrently improving soil organic carbon content and related soil functions. This study aims to evaluate the effects of different BBF formulations (biochar–digestate and biochar–vermicompost) on the yield of wheat and soil properties in soils ranging from highly acidic to near neutral pH in the mid- and highlands of the Oromia and Sidama regions of Ethiopia. Our results showed that combining biochar with organic and/or inorganic fertilizers significantly increased above-ground biomass and dry grain yield in acidic soils. Application rates of 20 t ha⁻¹ yielded the highest improvements, outperforming inorganic fertilizers by enhancing grain yields by up to 94% and biomass by 58%. Soil analyses revealed that BBF can increase soil pH, nutrient availability and cation exchange capacity. Its effectiveness varied with soil conditions, showing limited impact in less acidic soils, which supports its specific role in mitigating soil acidity and related fertility deficiencies. Hence, BBF is a promising alternative soil amendment for smallholder farms. Adoption of BBF into integrated soil fertility management could reduce the dependency on imported inorganic fertilizers, promote a circular bioeconomy and contribute to carbon sequestration, making it a viable option for sustainable agriculture in tropical acidic soils.