| چکیده انگلیسی مقاله |
Background and Objectives: Lemongrass (Cymbopogon citratus (DC.) Stapf), a perennial plant from the Gramineae family, is renowned for its rich polyphenol compounds, having significant medicinal, cosmetic, and culinary applications. Enhancing the quantitative and qualitative yield of lemongrass is of considerable economic importance. Salicylic acid, a key regulator of physiological and biochemical processes, acts as an elicitor to enhance the accumulation of secondary metabolites in plants. Similarly, nitrogen plays a vital role in plant growth, improving yield quantity and quality. This study investigated the effects of nitrogen fertilizer and salicylic acid on various quantitative and qualitative traits of lemongrass.
Methodology: A factorial experiment based on a randomized complete block design was conducted in 2021 at the Agricultural Sciences and Natural Resources research farm of the University of Khuzestan, Ahvaz, Iran. The experiment evaluated the effects of different levels of salicylic acid (0, 10 µM, and 100 µM) and nitrogen fertilizer (0, 50, 100, 150, and 200 kg/ha from a urea source) on lemongrass. Each treatment was replicated three times. In each fertilizer treatment, 20% of the nitrogen was applied after plant establishment, with the remainder applied in four stages alongside irrigation water to minimize leaching losses based on soil nitrogen content. Salicylic acid was applied via foliar spraying using a backpack sprayer when 70% of each plot was covered by lemongrass, with a second application 15 days later. Each plot measured 3 meters in width with six planting lines, each 3 meters long, 60 cm apart, and plants within lines were spaced 40 cm apart. The soil had a silty clay texture, pH of 7.5, and electrical conductivity of 2.6 dS/m. The studied traits included chlorophyll a, b, and total chlorophyll, carotenoid content, total fresh and dry weight, antioxidant activity percentage, total phenol content, and essential oil percentage and yield.
Results: The interaction between salicylic acid and nitrogen fertilizer significantly influenced all studied traits except antioxidant activity percentage. Nitrogen fertilizer alone significantly affected antioxidant activity, with the highest percentage (89.8%) observed at 150 kg/ha of nitrogen. The highest levels of chlorophyll a, b, and total chlorophyll were achieved with no salicylic acid and 150 kg/ha of nitrogen, showing increases of 140%, 42%, and 116%, respectively, compared to the control (no salicylic acid or nitrogen). The highest total fresh and dry weight was obtained with 100 µM salicylic acid and 100 kg/ha of nitrogen, representing a 75% increase over the control. The highest essential oil percentage (0.87%) and yield (65.6 g/m²) were observed with 10 µM salicylic acid and 150 kg/ha of nitrogen. In contrast, the lowest essential oil yield (18.29 g/m²) and percentage (0.45%) were recorded in the absence of salicylic acid and nitrogen and with no salicylic acid but 150 kg/ha of nitrogen, respectively.
Conclusion: Applying nitrogen fertilizer and salicylic acid enhanced the yield and percentage of essential oil, total dry matter, and total phenol content in lemongrass leaves compared to the control. The highest essential oil yield was achieved with 10 µM salicylic acid and 150 kg/ha of nitrogen fertilizer, demonstrating the synergistic effects of these treatments on lemongrass productivity and quality. |