In the new alluvial soil of Navsari (Gujarat), a field experiment was conducted in Rabi season to study the yield, quality and post harvest life of onion (Allium cepa L.) cv. ‘Gujarat Onion White-1’ as affected by weed management and fertilizer levels during two conjunctive years of 2008-09 and 2009-10. Weed population were decreased significantly with application of pendimethalin 1 kg/ha or oxyfluorfen 0.24 kg/ha supplement with one hand weeding at 40 DAT during both the season of investigation. Echinochloa spp., Trianthema portulacastrum, Digera arvensis. Physalis minima. and Cynodon dactylon. were found as major weeds in experiment field. Further, pendimethalin 1.0 kg/ha followed by one hand weeding  produced higher onion bulb yield of 39.3, 36.6 and 38.0 t/ha during both years as well as in pooled, respectively and found at par with oxyflourfen 0.24 kg/ha + one hand weeding at 40 DAT and weed free treatments. In pooled, increasing fertilizer rate from 75% to 125% of RDF was found effective and the higher level of fertilizer (125% RDF) gave the highest bulb yield, which was 10.52 and 19.43% more than of the F2 and F1 levels, respectively. Regarding post harvest life of bulbs, weight losses (%), black mould development (%) and sprouting (%) were remained unaffected by weed management and fertilizer levels except significantly higher weight losses (%) was observed under weed management treatment. On the basis of interaction, it is inferred that the treatment combination of (pendimethalin 1 kg/ha fb one hand weeding at 40 days after transplanting supplement with 100% RDF) found most appropriate (39.86 t/ha) and profitable not only to secure the net return of   2,69,422/ha with  7.85 BCR per unit cost of onion production but also save 25% of fertilizer.