Yield of potato (Solanum tuberosum L.) increased by more than two-folds through nitrogen and phosphorus fertilizers in the highlands of North-Western Ethiopia

Ethiopia has a huge potential to increase the production and productivity of potato (Solanum tuberosum L.) mainly in north-western regions where current potato yields are less than 10 t ha−1. Soil fertility and disease are the major yield-limiting factors of potato in this part of the country. Three-year’s on-farm research was conducted to get the optimum economic levels of nitrogen (N) and phosphorus (P) nutrients for the major potato-growing areas of north-western Ethiopia. A factorial experiment with four levels of N (46, 92, 138, and 194 kg ha−1), three levels of P2O5 (46, 69, and 92 kg ha−1), and one pilot treatment with no NP nutrient inputs was used. A randomised complete block design with three replications was used. The findings of the research showed that more than 40 t ha−1of potato could be attained (about four times the current productivity) in the study areas through NP nutrient management. The yield was increased significantly with an increased rate of N at all sites (p < 0.01). The yield difference was nonsignificant (p > 0.05) between P levels for most of the sites and years. The financial analysis of the findings for Yilmana Densa district indicated that applying 138 N and 46 P2O5 kg ha−1, together, gave a marginal return of (Birr/Birr) 70.9, whereas 138 N and 69 P2O5 kg ha−1 resulted in 10.7. For the South Gondar, 138 N and 46 P2O5 kg ha−1 gave a marginal return of 24.3 (Birr/Birr). Therefore, based on the farm gate price of potato and the cost of fertilizer, 138 N, combined with 69 P2O5 kg ha−1, is recommended for the Yilmana Densa. For the South Gondar, 138 N, combined with 46 P2O5 kg ha−1, is recommended. Potato; Soil fertility; Tuber yield; Partial budget; South Gondar; Yilmana Densa; Nitrogen, Phosphorus.