Two field experiments were carried out during the 2010/2011 and 2011/2012 dry cropping seasons of October–March to investigate the effects of 0, 40, 80 and 120 kg/ha NPK 15:15:15 and crop spacings on the growth and yield of onion plant ( Allium cepa
L.). The experiment was a factorial combination of three spacings 15 x 20 cm, 20 cm x 20 cm and 25 cm x 25 cm; and four levels of NPK 15:15:15 inorganic fertilizer at 0, 40, 80 and 120 kg/ha NPK laid out as a randomized complete block design (RCBD) with three replications. Each replicate had 12 plots for a total of 36 plots. Data was collected on growth and yield characters and analysed. Results of this study indicated that the spacings of 25 cm x 25 cm and 20 cm x 20 cm were statistically similar and enhanced the growth and yield of onion in terms of leaf length, individual bulb and shoot weight of onion better than 15 cm x 20 cm. However, bulb and shoot yield were significantly higher with closer spacing of 15 cm x 20 cm and 20 cm x 20 cm. Application of 80 kg/ha of NPK 15:15:15 fertilizer significantly increased the leaf length, bulb, and shoot yield above the other treatments. Therefore, for optimum yield of onion production in Edo ecology and convenience in planting application of 80 kg/ha of NPK 15:15:15 with 20 cm x 20 cm spacing is recommended.