Optimizing soil amendments for food barley: biochar, wood ash, and lime synergies on acidic clay loam soil in Northeastern Ethiopia.

Soil acidity, characterized by aluminum toxicity and nutrient fixation, significantly limits food barley production in the Ethiopian highlands. This study evaluated the individual and combined effects of Biochar, wood ash, and lime on soil properties, barley yield, and economic returns in Legambo District. A field experiment was conducted using a 3 × 3 × 3 factorial arrangement in a randomized complete block design with three replications, testing Biochar (0, 5, 10 t ha⁻¹), wood ash (0, 0.2855, 0.571 t ha⁻¹), and lime (0, 5, 10 t ha⁻¹). The integrated application significantly improved soil fertility, raising pH from 5.2 to 6.8 and increasing available phosphorus by 204.6%. The highest gain yield (4.31244 t ha⁻¹) was achieved with the 10-0.571-10 treatment combination. However, partial budget analysis revealed that the 5-0.571-10 (t ha⁻¹) treatment provided the highest net benefit (368,668 ETB ha⁻¹). In contrast, the 0-0.571-10 (t ha- 1) interaction emerged as the most economically efficient option, boasting a remarkable marginal rate of return of 791.71%. Consequently, an integrated approach using Biochar levels with wood ash and lime is recommended as a sustainable strategy for regional food security and for soil fertility management.