Abstract
Background and Objective: Soil degradation remains a significant constraint to sustainable production of white yam (Dioscorea rotundata Poir) in tropical regions, largely due to continuous cultivation and progressive nutrient depletion. While organic amendments like biochar and poultry manure have been studied in cereal and vegetable systems, their combined effects on yam-based systems remain underexplored. This study evaluated the effects of cocoa pod husk biochar (CPHB) and poultry manure (PM) on soil properties, leaf nutrient concentrations, growth, and tuber yield of yam grown on a degraded Alfisol in Owo, southwestern Nigeria.Methodology: A two-year (2023–2024) field experiment was conducted at Owo using a factorial randomized complete block design (RCBD) comprising three CPHB rates (0, 15, and 30 t ha-1) and three PM rates (0, 10, and 20 t ha-1), replicated three times. Soil physical and chemical properties, leaf nutrient concentrations, growth parameters, and tuber yield were evaluated following standard procedures.Main Results: Results showed that CPHB and PM, applied singly or together, significantly (P < 0.05) improved soil properties compared with the control. The combined application of 30 t ha-1 CPHB and 20 t ha-1 PM resulted in the lowest bulk density (0.90 Mg m-3), highest total porosity (66.3%), moisture content (19.5%), organic matter (3.58%), total nitrogen (0.21%), available phosphorus (18.7 mg kg-1), and exchangeable K (0.33 cmol kg-1). Leaf N, P, K, Ca, and Mg concentrations, growth, and yield attributes also increased. Averaged over two years, the highest tuber yield (46.1 t ha-1) was recorded with 30 t ha-1 CPHB + 20 t ha-1 PM, representing 35–82% yield increases over other treatments.Conclusions: CPHB and PM produced significant interaction effects on soil fertility, nutrient uptake, and yam yield on degraded Alfisols. Their combined application offers a sustainable approach for restoring soil productivity and improving yam production in tropical agroecosystems.