Soil acidity constraints crop production in tropical regions due to increases in aluminum toxicity and reductions in nutrient availability. Acidic soils are widespread in the highlands of Southwestern Oromia, Ethiopia, where maize is a major crop. This study evaluated the effects of soil amendments and phosphorus (P) fertilization on post-harvest soil properties, maize physiology, and grain yield during the 2023 and 2024 growing seasons across 14 farmers’ fields in Kersa, Bedele, and Mettu districts. A split-plot design was used with farms as replicates, testing three soil amendment (calcitic lime, biochar, vermicompost) relative to a non-amended control and four P fertilizer rates (0, 15, 30, and 45 kg P ha⁻ 1 ). Calcitic lime and vermicompost markedly improved soil fertility, enhanced maize physiological performance, and increased yields, whereas biochar was less effective. Lime was most effective in raising soil pH (0.58 units), lowering acidity saturation (73%), and increasing P availability, resulting in 38–78% yield gains over the control. Vermicompost also achieved substantial gains (41–66%) over the control. Although P fertilization increased productivity, its efficiency declined with increasing acidity saturation. Findings indicate that yield response to P fertilizer is constrained by soil acidity and that P management in clay-rich acidic soils requires prior or concurrent soil acidity correction. Integrated strategies combining lime or vermicompost with P fertilization significantly enhanced nutrient availability, maize growth, and productivity. These results highlight the importance of site-specific soil fertility management tailored to acid soil constraints for improving maize yields in tropical soils.
Dereje et al. (Sat,) studied this question.