The experiment was carried out during Robi season of 2018-2019 in the research field of Soil Science Division, BARI, Joydebpur, Gazipur. Seedlings of onion (BARI piaj-4) were raised on the net house of Soil Science Division, BARI, Joydebpur, Gazipur. The silted (sandy clay loam) soils were collected from the bank of Turag river at Kodda, Gazipur was used in the seedbed. Cowdung was used at 1 kg m-2 in the seed bed. The pH of cowdung was 6.7 and the nutrient contents were: organic matter 14.1%, N 0.8%, P 1.26%, K 0.88%, Ca 1.55%, Mg 0.82%, S 0.62%, Fe 0.25% and Mn 0.112%. The soil contained 42 AM (100-1 g soil) spores of indigenous mixed AM fungal species and each gram of soil contain a population of rhizobium, azotobacter and phosphate solubilizing bacteria (PSB) was 5.0 x 104, 5.5 x 104 and 4.5 x 104, respectively. The experiment was conducted under unsterilized soil conditions. Soil pH was measured by a combined glass calomel electrode (Jackson, 1958). Organic carbon was determined by the Wet Oxidation Method (Walkley and Black, 1934). Total N was determined by modified Kjeldahl method (Jackson, 1962). Calcium, K and Mg were determined by NH4OAc extraction method (Black, 1965). Copper, Fe, Mn and Zn were determined by DTPA extraction followed by AAS reading. Boron was determined by the CaCl2 extraction method. Phosphorus was determined by the Modified Olsen method (Neutral + Calcareous soils) according to Olsen et al. (1954). Sulphur was determined by CaH4(PO4)2.H2O extraction followed by turbidimetric turbidity method with BaCl2. Chemical fertilizers @ 100 kg N ha-1 from urea, 55 kg P ha-1 from TSP, 75 kg K ha-1 from MoP, 22 kg S ha-1 from gypsum, 5 kg Zn ha-1 from ZnSO4 for onion were applied (BARC, 2012). All other fertilizers except urea-N and 2/3rd of MoP were applied as basal during final land preparation and urea-N was applied at three equal splits and 2/3rd of MoP were applied as two equal splits. The experiment was designed in RCBD with 6 treatments and 4 replications. There were six treatments viz. T1: 100% N of Recommended Dose, T2: 90% N + Azotobacter inoculum, T3: 80% N + Azotobacter inoculum, T4: 70% N + Azotobacter inoculum, T5: Azotobacter inoculum and T6: Control. A blanket dose of PKSZn was applied for each treatment. Healthy seedlings of onion (BARI piaj-4) were collected from the seedbed, net house of soil science division, BARI, Joydebpur, Gazipur. Six square meters (2m × 3m) plot was prepared in the experimental field of soil science division, BARI, Joydebpur, Gazipur. After preparing the experimental plot, seedlings were transplanted at a spacing of 20 cm × 10 cm. Onion seedlings were transplanted on 5th December 2018. Intercultural operations like watering, weeding, insect pests management etc, were done when necessary. Topdressing of urea and MoP fertilizer were done as per schedule. Five plants of onion from each plot were collected after 45 days after transplanting for recording some growth parameters like plant height, a number of leaf plant-1, shoot weight and root weight. The onion was harvested on 27th March 2019. Some parameters like plant height, individual bulb weight, bulb length, bulb diameter and bulb yield plot-1 were recorded. Data were statistically analyzed using Analysis of Variance (ANOVA) following the CropStat package while all pair comparisons were done by Statistix 10.