iarjasfrIARJASFRIARJASFR2789-598Xhttps://doi.org/10.47310/iarjasfr.2021.v01i01.014Response of Medium Maturing Maize (Zea mays L.) Hybrids to Different Rates of Nitrogen Fertilizer under Irrigated Condition at Melko, Jimma ZoneRidaAbarashadAbagisaOda Bultum University, College of Agriculture, Department of HorticultureCrop yield is a function of genotypes, environments, and crop managements. Nitrogen is one the most yield-restraining crop nutrient in crop production globally. Blanket recommendation of Nitrogen fertilizer for all location by taking research result of specific area without recognizing the inherent soil properties of specific areas and genotype used under particular conditions could not be replicated to some other area expecting similar output. Hence, the current field experiment was conducted in 2016/17 to investigate the Response of Medium Maturing Maize (Zea mays L.) Hybrids to Different Rates of Nitrogen Fertilizer under Irrigated condition at Melko, Jimma Zone. A factorial experiment involving three maize hybrid two of which were quality protein maize hybrids (BHQPY545, MH138Q) and one conventional hybrid (Shone)widely used in study area;and  four rates of nitrogen fertilizer (0, 50, 100, and 150 kg ha-1) were tested in Randomized Complete Block Design (RCBD) with three  replications. The result indicates that as both main effect of maize hybrids and N - rate was significant (p<0.05) on, plant height, ear length, number of kernel per ear and only main effect of N-rate was highly significant (p<0.01) on number of ear per plant. However, both main effect of N-rate and maize hybrids was not significant (p<0.05) on hundred kernel weight. Similarly, the result depicted that the main effect of N- rate and maize hybrids was also highly significant (p<0.01) on grain yield and above ground dry biomass yield. Grain yield increase from 4094.7 to 7950.5 kg ha-1 as N-rate increase from zero to 150 kg ha-1. Significantly lowest (5778) and highest (7100.9) kg ha-1 grain yield was obtained from hybrid, MH138Q and BHQPY545, respectively. However, there was no statistically significant difference between hybrids, BHQPY545 and Shone on grain yield performance. On other hand significantly lowest (8732) and highest (14084) kg ha-1above ground dry biomass yield were obtained from 0 and 150 kg N ha-1, respectively. However, there were no statistically significant difference between nitrogen fertilizer rate of 50,100 and 150 kg ha-1 on above ground dry biomass yield. Significantly lowest (10546) and highest (13344) kg ha-1above ground dry biomass yield was obtained from hybrid, MH138Q and BHQPY545, respectively. Main effect of nitrogen rate was also significant (p<0.05) on harvest index. The lowest (0.48) the highest (0.57) harvest index, was obtained from 0 and 150 kg N ha-1, respectively. The interaction effect was not significant (p<0.05) for all parameter under study.