Abstract: A field experiment was conducted to determine the optimum doze of NPK fertilizers for the onion (Allium cepa L.), variety Phulkara on a loamy soil. The bed size was 4.5 x 4.0 m. Six fertilizer treatments were tested in RCBD for the height of plant (cm), number of leaves plant-1, single plant weight, bulb diameter (horizontal and vertical), bulb size (Volume) and yield ha-1. Compared to other fertilizer treatments, the application of 80 N + 60 P2O5 + 40 K2O (kg ha-1) produced more leaves and largest bulb size and gave the highest onion yield (kg ha-1).