Low soil fertility is one of the most important constraints limiting onion production in Ethiopia. Optimize the production of onion by applying the appropriate blended fertilizer rate is important in the study area of Raya Azebo. The experiment was conducted on Mehoni Agricultural Research Center at Fachagama site in 2018and 2019 cropping season under irrigation to determine optimum blended fertilizer rate and to assess it’s economic feasibility for onion yield and yield components. The treatments were laid out in randomized complete block design with three replications. Four rates of NPSFeZn blend fertilizer (150, 200, 250 and 300 kg/ha), three rates of N (69, 92 and 115 kg/ha), one blanket recommended rate and a control having a totally of 14 treatments. Result revealed that application of blended fertilizer did not significantly affect on Bulb length, Bulb diameter, Bulb Weight and un market bulb yield. There was significance difference on plant height , marketable and total bulb yield .The highest Bulb height, Bulb diameter and bulb weight was recorded from the combination of 200 kg/ha NPSFeZn blended and 69 kg/ha N . The highest marketable bulb yield (32.44 t ha -1) and highest Total bulb yield (34.79 t ha -1) was recorded at the combination of 200 kg /ha blended fertilizer and 150kg /ha urea. Regards to net benefit, the maximum (154,490 ETB ha-1) net benefit was obtained from the combination 200 kg/ha blended fertilizer and 69 kg/ha N and this can be recommended for the study area.