effects of biofertilizers on yield and essential oil of peppermint (mentha piperita l.)

background & aim: nowadays, tendency to agricultural biotic product sustainable agriculture instead of chemical ‎fertilizers has been going up in all over the world. so, most pharmaceutical industries prefer to ‎use raw material which is produced from organic and stable system. producing organic ‎medicinal plants, such as peppermint, seems important in economical, ecological and ‎bio environmental aspects. experimental: three biological fertilizers effect (nitroxyn, supernitroplus, biosulfore) and urea on qualitative ‎and quantitative character of peppermint is the aim of this project which was done in a farm of ‎jihad daneshgahi institute of iran during 2008-2009, as a complete randomized block design ‎with 9 treatment fertilizer and 3 replications. nine treatments were as follows: azospirillum/azotobacter (nitroxin 4 and 8 kg/ha), azospirillum / bacillus subtilis/pseudomonas ‎fluorescens (super nitro plus 4 and 8 kg/ha), (biosulfur 4 and 8 kg/ha, urea fertilizer (75 and ‎‎100 kg/ha), and control treatment with no fertilizer.‎. results & discussion: the results indicated that all fertilizer treatment (biologic & urea) had a significant increase in most ‎character comparing to control treatment and among biofertilizers, nitroxin and supernitroplus ‎‎ (8 kg/ha) on par with urea fertilizer had the most effect additive on most characters. based on ‎this results, the above mentioned biofertilizers increased qualitative and quantitative yield of ‎peppermint. industrial and practical recommendations: according to the findings of this experiment, biological fertilizers led to increasing the qualitative and quantitative functions of peppermint. using biofertelizer including nitroxin and supernitroplus the utilization of nitrogen chemical fertilizers originated from urea can be reduced which is an efficient step in achieving to a stable agriculture and decreasing biochemical pollution.