field experiment was conducted to study the effects of liming and NPS fertilizer rates on yield and yield components of onion (Allium cepa. L) During the 2017 irrigation season in Koga Irrigation Scheme. The availability of soil nutrients depends on various factors including the pH values of the soil and the amount of fertilizers applied . The aim of the present study was to evaluate the effects of liming and NPS fertilizer in order to contribute to production and productivity of onion in the study area. The treatments consisted of two levels of lime rate (0 and 2 t ha-1) and five levels of N: P2O5: S fertilizer (0:0:0; 17.17:34.35:6.32; 34.35:68.7:12.65; 51.52:103:18.97 and 68.7:137.4:25.5 kg/ha) laid down in a Randomized Complete Block Design (RCBD) with three replications in a factorial arrangement. Yield and yield components of onion were collected timely as per their respective standard procedures and analysis of variance for the collected data was done using SAS version 9.3. The results of the study revealed that most of the phenological, growth and yield related parameters of onion were significantly affected by lime and NPS fertilizer rates. The highest leaf length (37.3 cm), plant height (42.5 cm), bulb weight (78.9 g),bulb diameter (5.8 cm), marketable bulb yield (27.31 t ha- 1) and total bulb yield (28.4 t ha-1) were recorded from 271.12 kg ha-1 NPS rate and application of 2 t ha-1 lime. However, onion plants without lime and NPS fertilizer application were inferior in all growth and yield parameters. The highest net profit (38,189 ETB ha-1) with highest MRR (1771.7 %.) was recorded from the combination of 2 t lime ha-1 and 271.12 kg ha-1 NPS. Thus, it can be concluded that application of 2 t ha-1 lime and 271.12 kg ha-1 NPS proved to be superior with respect to marketable yield as well as economic advantage for the study area and areas with similar agroecologies. Nevertheless, it is recommended to repeat the experiment on wider scale in different agroecologies for wider utilization. Key words: Bombay red onion Variety, Liming, marketable yield, plant height, bulb yield