Potato is one of the most widely grown vegetable crops in Koga Irrigation Scheme. Conventional irrigation frequency determination method and blanket recommendation of fertilizers dominate the potato cropping system in the area. Thus, a field experiment was conducted with the objective to investigate the effects of NPS fertilizer rate and irrigation frequency determination method on the growth, yield and yield parameters of potato. The treatments consisted of six levels of NPS fertilizer (0, 90.8, 136.2, 181.6, 227.4, 272 kg ha-1) combined with two irrigation frequency determination methods (WFD and CWR) which were laid out in RCBD with three replications. NPS fertilizers and irrigation frequency determination methods in their main effects had significantly influenced almost all the tested parameters of potato. In addition their interaction effect influenced days to flowering and maturity, stem number per hill, leaf area index, plant height and average tuber weight of potato significantly. Significantly maximum marketable tuber yields of potato were obtained when potato plants were irrigated based on the WFD method as well as when the potato plants were supplied with 272 kg ha-1 NPS fertilizer. Moreover, irrigation of potato based on WFD produced the highest crop-water productivity (7.14 kg m-3) than irrigation based on CWR (6.55 kg m-3). Based on the partial budget analysis, 272 kg ha-1 NPS fertilizer with WFD method of irrigation frequency determination gave the maximum net benefit (107,588.00birr ha-1). However, application of 227.4 kg ha-1 NPS fertilizer irrigated with WFD method gave the highest marginal rate of return (1813.36%) which can be recommended for economical and agronomical feasible production of potato in Koga Irrigation Scheme. But the results are limited to one season and location, multi-seasonal and location studies are further recommended. Key Words: Crop-Water-Requirement (CWR), Plant height, Wetting Front Detector (WFD)