Optimizing Soil Amendments for Food Barley: Biochar, Wood Ash, and Lime Synergies on Acidic Clay Loam Soil in Northeastern Ethiopia

Soil acidity is a major constraint to food barley (Hordeum vulgare L.) production in the Ethiopian highlands, where aluminum toxicity and nutrient fixation significantly limit crop yields. While liming is a common solution, its high cost often makes it impractical for resource-poor smallholder farmers. This study explores Integrated Soil Fertility Management (ISFM) by combining traditional lime with organic amendments like Biochar and wood ash to create a more sustainable and cost-effective reclamation strategy. The study aimed to determine the optimal combination of Biochar, wood ash, and lime that maximizes food barley yields while improving the chemical and physical properties of acidic clay loam soils in the Legambo District of Northeastern Ethiopia. A field experiment was conducted using a 3 × 3 factorial arrangement in a Randomized Complete Block Design (RCBD) with three replications. The treatments included three rates of Biochar (0, 5, and 10 t ha-1), wood ash (0, 285.5, and 571 kg ha-1), and lime (0, 5, and 10 t ha ^-1 ). Soil chemical properties and various agronomic parameters, including phenological, growth, and yield data, were collected and analyzed using ANOVA. The application of amendments significantly improved soil fertility, raising the pH from 4.1 to 6.2 and doubling available phosphorus. Biochar emerged as the most effective individual amendment, increasing grain yield by 71%. However, the highest physical grain yield of 4,312.44kg ha ^-1, a 104% increase over the control, was achieved through the triple interaction of 10t ha ^-1 Biochar, 751kg ha ^-1 wood ash, and 10t ha ^-1 lime. The study concludes that integrating organic and inorganic amendments provides a powerful synergy for reclaiming acidic soils. While the 10-751-10 treatment maximized physical yield, the partial budget analysis revealed that it was economically dominated by the high cost of Biochar. Instead, the treatment combination of 5t ha ^-1 Biochar, 751kg ha ^-1 wood ash, and 10t ha ^-1 lime is recommended as the most efficient strategy, providing the highest net benefit (360,668 ETB/ha) and a marginal rate of return of 200.1%.