Purpose: The current study evaluated the influence of different nitrogen (N) concentrations (0, 5, 10, and 14.6 mM) on plant growth, essential oil (EO) yield and compositions, some biochemical, and physiological traits of Salvia officinalis L. which grown in soilless conditions to explain any differences in the studied characteristics. Methods: This experiment was carried out based on a completely randomized design to assess the effects of different N levels (0, 5, 10, and 14.6 mM) on the nutrient content, growth, EO yield and compositions, and biochemical characteristics of sage under hydroponic condition. Results: The results showed that N concentrations affected plant growth traits, micro- and macronutrient uptake, EO yield and compositions, photosynthetic pigments, total soluble sugars, proline, and total phenolic content, as well as antioxidant activity. Based on the findings, 0 mM N level reduced all of the studied traits. The greatest accumulation for N, P, K, Mg, Mn, Fe, B, Cu, Zn, Ca, Mo, the highest chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid, total soluble sugar, proline, total phenolic contents, antioxidant activity and EO yield and the least S content were observed at the highest N concentration (14.6 mM). The highest oxygenated monoterpenes (80.92%), as the main group of compounds, was observed at 14.6 mM N level. The application of 10 mM N showed the highest α-thujone as the major compound. Conclusion: 14.6 mM was the suitable concentrations of N which can improve plant growth, nutrient content, and biochemical characteristics of sage as well as EO yield and composition by true nutrient management.

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