Soil health is one of the key factors, which decides the yield of crops. Organic manures are indispensable factor in vegetable production and monitoring soil health. The humus substances in the soil have multiple effects, in which the influence of humic acid on plant growth can be grouped into indirect effect on physical, chemical and biological properties of the soil and direct effect on physiological and biochemical processes of plants. The present study was undertaken to assess the effect of lignite humic acid and fertilizers on soil available nutrients and bulb yield of onion. A green house experiment was conducted in Coimbatore during kharif 2003 with Onion (Var.Co 4). Treatments consisted of control (T1), 75% recommended dose of NPK (T2), 100% recommended dose of NPK (T3), 100% NPK + 10 kg humic acid ha-1 as soil application (T4), 100% NPK + 20 kg humic acid ha-1 as soil application (T5), 100% NPK + 0.1% humic acid as foliar spray (T6), 100% NPK + 10 kg humic acid ha-1 as soil application + 0.1% humic acid as foliar spray (T7), 75% NPK + 10 kg humic acid ha-1 as soil application + 0.1 humic acid as foliar spray (T8), 100% NPK + 10 kg humic acid ha-1 as soil application +0.1% humic acid as seed bulb soaking + 0.1% humic acid as foliar spray (T9) and 75% NPK + 10 kg humic acid ha-1 as soil application + 0.1% humic acid as seed bulb soaking + 0.1% humic acid as foliar spray (T10) were replicated thrice and laid out in CRBD. The recommended package of practices were followed and the crop was harvested at maturity and bulb yield of onion was recorded. The soil samples were collected at post harvest stage of crop and were analysed for available nutrient status using standard procedures. The results on the bulb yield indicated that application of humic acid @ 20 kg ha-1 along with 100 per cent recommended dose of NPK recorded the highest bulb yield of 150.7 g pot-1 which was 12 per cent increase over the recommended dose of NPK. The lowest yield was noticed with the control (98.1 g pot-1). Application of humic acid @ 20 kg ha-1 along with 100 per cent recommended dose of NPK improved the organic carbon content of post harvest soil from 0.30 per cent in control to 0.35 per cent and it also enhanced the cation exchange capacity of soil by 18 per cent. The available N, P and K content were increased from 105 to119.3 mg kg-1, 7.9 to 12.63 mg kg-1 and 132 to 139 mg kg-1 respectively due to combined application of humic acid and fertilizers.