The Effect of Macro Elements and Foliar Application of Micro Elements on the Yield and Quality of Damask Rose (Rosa damascena Mill)

Abstract

Rosa damascena Mill. is one of the oldest and most valuable medicinal plants, widely utilized across the pharmaceutical, food, and cosmetic industries worldwide. The essential oil derived from this species is considered an important commercial raw material due to its high economic value and unique aromatic constituents. This study was conducted at the Alborz Research Station to evaluate the effects of macroelement fertilization and foliar application of iron-based microelements on the quantitative and qualitative characteristics of damask rose grown under field conditions. The experiment was arranged in a split-plot layout within a randomized complete block design with three replications. The main plots comprised 14 different fertilization treatments, including chemical fertilizers, cow manure, and various combinations of both. The subplots consisted of foliar spraying with nano iron chelate at four levels (0, 1, 2, and 3 applications). The findings revealed that macro- and microelement treatments significantly affected the number of flowers per plant, petal yield, essential oil content, and essential oil yield (p ≤ 0.01). The highest essential oil yield (6711.6 g ha⁻¹) and essential oil content (0.078%) were obtained in treatments where N120P120K120 fertilization was combined with three foliar applications. This indicates that the combined supply of macro- and micro-nutrients substantially enhances essential oil biosynthesis by providing optimal nutritional conditions. Furthermore, the study demonstrated that fertilization regimes also caused notable alterations in essential oil composition. Key aromatic constituents such as citronellol, nonadecene, hexadecanol, and tricosene exhibited significant increases under high-input fertilization conditions. In particular, citronellol and nonadecene critical compounds determining fragrance quality reached their highest levels in treatments receiving both macro and microelement inputs. This highlights that nutrient management is not only a tool for improving yield but also a key factor influencing product quality through modulation of secondary metabolite profiles. Overall, the results of this research show that integrated nutrient management strategies are highly effective in enhancing both biomass production and the chemical quality of essential oil in damask rose cultivation. Nutrient optimization not only improves agricultural productivity but also enriches valuable constituents within the essential oil, thereby increasing the economic value of rose-based products.