Improvement of production and quality of essential oils in multi-cut peppermint (Mentha x piperita L.) through eco-friendly fertilizers in the semi-arid highlands

The semi-arid highlands offer favorable temperature and radiation conditions for cultivating medicinal plants organically. This practice not only supports the sustainability of the ecosystems in these regions but also presents a valuable opportunity for the production of medicinal plants. Peppermint, a highly sought-after medicinal plant, presents a favorable choice for farmers residing in semi-arid regions due to its versatile applications across various industries. To assess the biomass and essential oil (EO) of peppermint, the utilization of diverse fertilizer sources across different cuttings has been examined. The experimental treatments consisted of four fertilizer sources including poultry manure (POM), sheep manure (SHM), cattle manure (CAM), and chemical fertilizers (CHF), and different cuttings, namely first cutting (CUT1), second cutting (CUT2) and third cutting (CUT3). Plants treated with POM and SHM gave the highest biomass in CUT1 and CUT2, respectively. The nutrient content (macro- and micro-) raised with the application of POM and SHM. The highest EO content was recorded in POM treatment and CUT2. Plants amended with POM had the greatest EO yield in three cuttings. The major EO constituents were menthol (35.2%-58.3%), menthone (3.1%–33.6%), menthyl acetate (1.1%-9.4%), iso- menthone (0.41%-8.8%), with the highest percentages of these compounds reached in treatments with organic manures in various cuttings. High-quality EOs (high menthol and low menthoufuran content) were obtained with organic manure treatments in three cuttings. Plants amended with POM, CHF and CHF showed the highest antioxidant capacity of EO in CUT1, CUT2 and CUT3, respectively. Overall, the usage of POM and SHM can be recommended for increasing biomass and improving the quality of peppermint EO during the growth season, while maintaining ecosystem sustainability by replacing chemical fertilizers in the semi-arid highlands.