Effects of biochar and vermicompost application on the physicochemical properties of acidic soils in Sidama Region, Ethiopia

Soil acidity is a major constraint on crop productivity in tropical agriculture, particularly in regions like Ethiopia, where smallholder farmers often lack access to conventional amendments such as lime. While biochar (BC) and vermicompost (VC) have been studied individually, their combined potential for remediating acidic soils under local conditions remains insufficiently explored. This incubation study evaluated the effects of BC (0, 3, and 6 t ha -1 ) and VC (0, 2.5, and 5 t ha -1 ) application on the physicochemical properties of acidic soils from the Hula and Gorche districts in Sidama, Ethiopia. The treatments followed a completely randomized design (CRD) with three replications. Statistical analyses were performed using SAS 9.4. The findings indicated that the amendments significantly (p < 0.05) enhanced key soil indicators. The combined application of 6 t ha -1 BC and 5 t ha -1 VC increased soil pH by 18.4% (from 4.9 to 5.8) in Hula soil. While 3 t ha -1 BC and 5 t ha -1 VC in combination increased pH by 15.7% (from 5.1 to 5.9) in Gorche soil. Both individual and combined treatments improved soil organic carbon (OC), total nitrogen (TN), available phosphorus (AP), exchangeable bases (Ex. bases), cation exchange capacity (CEC), and percent base saturation (PBS), while reducing exchangeable acidity (EA) and extractable micronutrients. These results demonstrate that BC and VC can be effectively integrated to ameliorate soil acidity and enhance fertility, offering a sustainable alternative and a potentially useful amendment strategy for acidic soils. While these findings are encouraging, further field studies are recommended to assess their long-term effects on soil properties, crop agronomic performances and economic viability under real farming conditions.