Optimizing phosphorus and potassium fertilization enhances potato (Solanum tuberosum L.) yield and nutrient status in northwestern Ethiopia

Potato (Solanum tuberosum L.) productivity in northwestern Ethiopia is limited by poor soil fertility and nutrient imbalances, particularly deficiencies of phosphorus and potassium in Nitisols, resulting in suboptimal yield and tuber quality. This study aimed to evaluate the combined effects of different phosphorus and potassium fertilizer rates on potato yield, yield components, and nutrient accumulation under Nitisol conditions. A field experiment was conducted using three phosphorus rates (0, 34.5, and 69 kg P₂O₅ ha⁻¹) and four potassium rates (0, 100, 200, and 300 kg K₂O ha⁻¹) arranged in a factorial randomized complete block design with three replications. Yield components, total and marketable yields, and plant tissue phosphorus and potassium contents were measured and analyzed using analysis of variance. The interaction between phosphorus and potassium significantly affected major yield components, including marketable tuber number per hill, marketable tuber weight, marketable yield, and total tuber yield. The highest marketable tuber number (11.80) was obtained from 69 kg P₂O₅ ha⁻¹ combined with 300 kg K₂O ha⁻¹, whereas the maximum marketable yield (48.32 t ha⁻¹) and total tuber yield (49.14 t ha⁻¹) were achieved with 34.5 kg P₂O₅ ha⁻¹ combined with 200 kg K₂O ha⁻¹. Fertilizer application also enhanced phosphorus and potassium concentrations in both shoot and tuber tissues. The combined application of 34.5 kg P₂O₅ ha⁻¹ and 200 kg K₂O ha⁻¹ is recommended to improve potato productivity in Nitisols. Future studies should focus on multi-season validation, and integrated nutrient management strategies.