Impacts of plant growth-promoting bacteria, compost and biodynamic compost preparations for alleviating the harmful effects of salinity on essential oil characteristics of lavender

Background Biodynamic agriculture and the use of plant growth-promoting bacteria (PGPBs) have been demonstrated to offer various benefits for achieving agricultural sustainability. The aim of this study was to evaluate the effects of PGPBs Azotobacter and Azospirillum, compost, and compost with biodynamic preparations (BD) on the essential oil (EO) characteristics of lavender under salinity stress.Research methods The experiment was carried out in a greenhouse for 2 years and involved three factors: four PGPBs, three types of compost, and three levels of salinity stress.Results The results indicated that the essential oil (EO) characteristics increased with 50 mM NaCl but decreased with 100 mM NaCl. Salt stress reduced the cell membrane stability (CMS) and auxin content, while increasing proline contents. However, the application of PGPBs, compost, and compost with biodynamic preparations had an opposite effect on CMS, auxin, and proline parameters compared to salt stress. Based on the results, the treatment that combined compost + BD with Azotobacter was found to be the most effective in enhancing the EO characteristics under both mild and severe salinity stress conditions.Conclusions The results of this study suggest that compost, biodynamic compost preparations, and PGPBs could be useful in enhancing the EO in medicinal plants and alleviating the adverse effects of salt stress on plants.