Low soil fertility is a major constraint to potato production in Ethiopia. A field experiment was conducted at rare research farm, main campus of HU in Ethiopia, during the main growing season of 2011 under supplementary irrigation to evaluate the effects of J. curcas L. press-cake and inorganic NP fertilizers on the productivity of potato (S. tuberosum L.) and soil properties. The treatments consisted of four rates of J. press-cake (0, 2, 4 and 6 t ha-1) and 5 rates of combined mineral NP (0 + 0; 0 + 46; 50 + 0; 50 + 46; 100 + 92 kg N + P, respectively, ha-1) fertilizers. The experiment was laid out as a RCBD in a factorial arrangement and replicated three times. The plot sizes were 3.75 m x 3.9 m. The distance between plots and blocks was maintained at 1 and 2 m, respectively. All agronomic and soil data were collected and analysis of variance was done. The results indicated that J. Press-cake along with mineral fertilizer significantly enhanced potato tuber yields and soil OM. From the results of the study, it could be deduced that 2 t J. press.-cake ha-1 resulted in an optimum total tuber yield.