Field experiments have been conducted with the objective of identifying optimum rate of the newly introduced NPS fertilizer for profitable production of potato at Koga Irrigation Scheme, Northwestern Ethiopia. Six NPS fertilizer rates and three potato varieties which were factorial combined and laid down in Randomized Complete Block Design in three replicates were tested on two different farmlands. Most growth, yield, and yield components of potato were increased with increasing rates of NPS fertilizer which differed with varieties and locations. Highest marketable tuber yields of Belete (55.37 t ha(-1)) and Gudene (46.83 t ha(-1)) varieties were recorded with the of 283.75 kg ha(-1) NPS fertilizer in location I (soil with low phosphorous content). The yields of Gudene variety recorded at the range of 181.6 to 283.75 kg ha(-1) NPS fertilizer were however statistically similar. Farmer's local potato variety on the other hand recorded the highest marketable tuber yield (28.98 t ha(-1)) in location II (soil with high phosphorous content) supplied with 227.0 kg ha(-1) NPS which was similar with yields at the range of 102.12 to 283.75 kg ha(-1) NPS fertilizer. On soils with low phosphorous content, production of Belete, and Gudene varieties with application of 283.75 and 181.60 kg ha(-1) NPS fertilizer rates, respectively, are recommended while on soils with high phosphorous content production of local, and Gudene varieties supplied with 136.20 and 181.60 kg ha(-1) NPS, respectively, are recommended for higher profitability of potato production at Koga Irrigation Scheme.
