Inoculation with mycorrhiza and Azotobacter chroococcum affects the quantitative and qualitative characteristics of Eryngium caeruleum at different planting densities

Eryngium caeruleum is a perennial native plant that grows under diverse climatic conditions of Iran. This study aimed to investigate the effect of mycorrhizal and Azotobacter inoculation on the quantitative and qualitative characteristics of E. caeruleum at various planting densities. Factors included three levels of plant density (10×30 cm, 20×30 cm, and 30×30 cm), two levels of seed inoculation with Vesicular-Arbuscular Mycorrhiza (VAM) fungi (inoculation with Glomus mosseae and without inoculation), and two levels of seed inoculation with Azotobacter chroococcum (with and without inoculation). The application of VAM fungi and A. chrooroccum significantly affected the measured traits. The interaction effect of plant density×mycorrhizal application and plant density×Azotobacter application on dry leaf weight was significant at a 1% level. The total leaf dry weight for the VAM treatments at a 30×30 cm plant density was 2.93 g. Also, the application of mycorrhizal fungus increased the essential oil percentage, the essential oil yield, and phosphorus concentration in the aerial organs by 132.68%, 100%, and 137.5%, respectively, compared to the control treatment. The simultaneous application of A. chroococcum and VAM improved the quantity and quality of the yield components of E. caeruleum by increasing the availability of mineral nutrients