Plant growth promoting rhizobacteria in an ecological cropping system: A study on basil (Ocimum basilicum L.) essential oil production

The use of biofertilizers containing beneficial soil microorganisms as alternative for chemical fertilizers is an effective way to improve plant growth, environment health and soil productivity. According to the importance of the production of medicinal plants in sustainable agricultural systems, an experiment was conducted during growing seasons of 2013-2014 and 2014-2015 at the Agricultural Research Farm of Ferdowsi University of Mashhad, Iran. Trial was done in a randomized complete block design (RCBD) with three replications and four treatments. The treatments were seed inoculation with biofertilizers including: 1- Nitroxin® biofertilizer (containing Azotobacter sp. and Azospirillum sp. bacteria), 2- Biophosphorus® biofertilizer (containing Bacillus sp. and Pseudomonas sp. bacteria), 3- Mixture of Nitroxin® & Biophosphorus® and 4- The Control (no inoculation). The results showed the most amounts of plant height, number of branches, plant dry matter and leaf area index were obtained from the plants treated with Nitroxin®. The maximum number of branches (11.2) was obtained from the plants treated with mixture of Nitroxin® and Biophosphorus®. Seed production was at the most in plants under Biophosphorus® treatment. Biological fertilizers increased dry shoot yield compared with the control.The highest percentage of essential oil (0.83%) was observed in control. The traits associated with the yield were higher in the second cut compared with the first and the third cuts. There was a significant positive correlation (r = 0.60**) between the plant height and the leaf yield. In general, the results suggest that biofertilizers especially Nitroxin® could improve growth characteristics and the yield of basil promising possibility of ecological production of this valuable medicinal plant indicating biofertilizers may be feasible in places with few resources.