Lemongrass (Cymbopogon citratus (DC.) Stapf): Effects of saline irrigation, fertilization, and climate conditions on physiology, biochemistry, and essential oil components

• Lemongrass shows resilience to saline stress, with fertilizers boosting growth and oil. • Study assesses lemongrass responses to varied fertilizers under different salinity levels. • Salinity decreased yield, yet all fertilizers improved it with no major differences. • Salinity increased antioxidant enzymes, anthocyanins, flavonoids, and oxidative stress. • Correlations found between traits and oil components, showing lemongrass’s adaptability. Lemongrass cultivation is resilient to saline stress across various regions, and the application of different fertilizers enhances both growth and essential oil production. This study investigated the physiological, biochemical, and essential oil component responses of lemongrass to several fertilizer sources, including non-application; nitrogen, phosphorus, and potassium (NPK) chemical fertilizer; nitroxin; arbuscular mycorrhizal fungi (AMFs); and biosulfur. These treatments were evaluated under varying levels of salinity stress in irrigation water (≤10, 100 ± 5, and 200 ± 5 mM) across two climatic regions in Iran: Firuzabad and Varamin. The experimental design utilized a split-plot arrangement within a completely randomized block design with three replications, conducted from 2021 to 2022. High salinity stress resulted in a reduction in plant yield by 12.5 % in Firuzabad and 15.3 % in Varamin. However, the application of various fertilizers mitigated these negative effects, with no significant differences observed among the fertilizer treatments. The highest recorded plant yields were 4183.1 kg.ha⁻¹ in Firuzabad and 4331.9 kg.ha⁻¹ in Varamin. Salinity stress significantly increased the activities of antioxidant enzymes, including peroxidase (3.28-fold), catalase (6.5-fold), superoxide dismutase (1.6-fold), and ascorbate peroxidase (1.82-fold) in Firuzabad, with specific enzyme responses varying depending on the fertilizer treatment applied. Salinity also raised sodium ion concentrations while decreasing potassium ion content and the potassium-to-sodium ratio. The application of AMFs, Nitroxin, and Biosulfur in Firuzabad, along with all fertilizer levels in Varamin, resulted in elevated sodium and potassium ion levels. Essential oil content increased with salinity, particularly in Varamin, where AMFs led to levels 2.48 times higher than the control treatment. Neral and Geranial were the predominant essential oil components, influenced by salinity and the different fertilizers used. In Firuzabad, NPK chemicals produced the highest Neral content (38 %), whereas AMFs yielded the highest Geranial content (40.3 %). In Varamin, nitroxin exhibited the highest Neral (35.11 %), and AMFs again showed the highest Geranial (33.66 %). Overall, AMFs resulted in the highest average Geranial in both regions. This study highlights the complex correlations between various plant traits and essential oil components, demonstrating that lemongrass cultivation can effectively withstand saline stress. The application of nitroxin and AMFs fertilizers enhances growth, essential oil production, and antioxidant activity, while alleviating the adverse effects of salinity on yield and ion balance.