Effect of Blended NPS Fertilizer Rates on Growth, Yield and Quality of Potato Varieties at Mulo District, Oromia, Ethiopia

Potato production in Ethiopia is constrained by poor soil fertility and limited use of balanced fertilizers. This study evaluated the effects of varying rates of blended NPS (Nitrogen, Phosphorus, Sulfur) fertilizer on the growth, yield, and tuber quality of five potato varieties-Belete, Gudanie, Milki, Gera, and CIP 396004.337 (Dagem)-in Mulo District, Oromia. A factorial randomized complete block design with three replications was used to test four NPS rates (0, 100, 200, and 300 kg ha<sup>-1</sup>). Increasing NPS rates significantly improved aboveground biomass, with Belete reaching 6.5 t ha<sup>-1</sup> at 300 kg ha<sup>-1</sup>. Total and marketable tuber yields also increased, with Belete achieving the highest marketable yield of 30 t ha<sup>-1</sup>. Higher fertilizer rates enhanced average tuber weight, tubers per plant, and dry matter content, benefiting processing quality. Unmarketable tuber yield declined, while tuber firmness improved, particularly in Belete and Milki, enhancing storage potential. Reducing sugar content decreased with increasing NPS, producing lighter chips suitable for processing. Sprout length was reduced at higher NPS levels, indicating improved tuber dormancy. Among the varieties, Belete consistently outperformed the others, followed by Milki and Gera, while Gudanie and CIP (Dagem) showed moderate performance. These findings highlight the importance of integrating improved potato varieties with optimal NPS fertilization to enhance yield, tuber quality, and farmer income, contributing to sustainable potato production and food security in the region.