Vermicompost as a suitable fertilizer for rose-scented geranium ( Pelargonium graveolens L.) production and reduction of chemical nitrogen need

In order to the yield maintenance along with environmental protection, the replacement or combination of chemical fertilizers with organic ones has received increasing attention recently. However, the yield and quality of production in aromatic plants differ from other plants. The present experiment was conducted for 2 years with the aim of evaluating the potential of vermicompost instead of nitrogen fertilizer for the production of geraniums without reducing its perfume quality. Regarded to the macronutrients, essential oil, and shoot yield, geranium treated with 20 ton ha −1 vermicompost and 16 ton ha −1 vermicompost + 40 kg ha −1 nitrogen had the best condition compared to other fertilizer regimes. Geranium is a perennial plant; hence the traits related to plant growth and yield were higher in the second harvest. Besides that, compared to treatments with a high amount of chemical nitrogen, the effects of vermicompost on the quality and quantity of geranium in the second yield were more effective and sustainable. Moreover, these findings suggested that an appropriate proportion of organic substitution not only provides uptake nutrients but also improves the essential oil yield and chemical composition. In fact, increasing the level of vermicompost resulted in improved oxygenated monoterpene content in geranium essential oil. According to the results of this study, cow manure-derived vermicompost could be a suited and sustained replacement for nitrogen inorganic fertilizer without any significant reduction in the quality and quantity of geranium products. Thus, it can be a practical step to reduce production costs, and environmental issues own to chemical fertilizers, particularly in aromatic plant cultivation. Graphical abstract