Tef (Eragrostis tef) is one of most important food crops grown in Benishangul Gumuz region of Ethiopia and is produced in different agro-ecologies in the region. However, its productivity is constrained by a number of problems, of which soil nutrient is the most important one. Information on the response of tef to Nitrogen (N) and Phosphorus (P) fertilizers in Assosa Zone is inadequate. Field experiments were conducted at two locations for two years (2012-2013) to investigate the response of tef to N and P fertilization. Five levels of nitrogen (0, 23, 46, 69 and 92 N kg ha–1) and four levels of phosphorus (0, 10, 20 and 30 kg P ha–1) were studied in factorial combinations in a randomized complete block design (RCBD) with three replications. The results revealed substantial responses of tef to the main effect of N and P on days to heading and panicle length, the main effect of N on days to emergency, and the main effect of P on days to 90% physiological maturity. Nitrogen by P interaction effect was significant on plant height, straw and grain yield. Grain yield increased significantly from 708.6 to 1681.1 kg ha-1 with increase in the level of N and P from the control (0/0 N/P) to 46 kg N and 10 P kg ha-1. The magnitude of increase in grain yield due to application of 46 kg N along and 10 kg P ha -1 was 137 % higher as compared to the control. The partial budget analysis also indicates that applications of 46 kg N ha-1 and 10 kg P ha-1 are the most economical fertilizer rates to tef growers compared to the other levels in the study area.
