Abstract: Experiment was conducted to study the effect of FYM only and different combinations of nitrogen and potassium on the onion bulbs (var. Swat-I) production. Phosphorous at 100 kg ha–1 was used as a constant dose. Treatments included control, FYM only, 0-100-90, 60-100-90, 90-100-90, 120-100-90, 90-100-0, 90-100-60 and 90100-120 kg NPK ha–1. Control plots and those treated with FYM produced maximum number of culls (un-marketable bulbs) i.e. 29,25 and 27.75 per plot, respectively. Application of fertilizers reduced the number of culls per plot. No significant differences were found among the treatments for bulbs obtained with thick neck. However, increasing rate of N resulted in greater number of thick neck bulbs. Number of double bulbs counted were also increased with the increase of nitrogen. High nitrogen dose improved the bulb size significantly. Greater number of small-sized bulbs were produced from the plots received no fertilizer or FYM only. Significantly highest yield (14.04 t ha–1) was obtained from the plots treated with maximum amount of N (120-100-90). All treatments did not show any significant effect on the percent moisture content, dry weight and TSS.