a field experiment was carried out with a split plot arrangement based on a randomized complete block design with three replications in 2014. triple super phosphate (0, 3.75, 7.5, 11.25 and 15 g m-2) was applied in main plots and phosphate bio-fertilizer (seed inoculation and topdressing) was allocated to sub plots. results indicated that application of plants with phosphorus (p) bio-fertilizer as topdressing increased plant height and the number of the lateral branches under low levels of chemical p fertilizer, while plants from seed inoculated with p bio-fertilizer had more of those traits under high levels of chemical p fertilizer. maximum leaf and flower dry weights were found under the lowest level of chemical p fertilizer. moldavian balm plant demonstrated highly responsiveness to biological fertilizers in terms of increase in essential oil (eo) percentage and yield. it can be concluded that the effects of bio-fertilizer as seed inoculation is more during the early vegetative growth of plants. thus, plants from seeds inoculated with p bio-fertilizer treatment had more biomass and eo percentage under high levels of chemical p fertilizer.