The Effect of the Organic Nutrient Disper Himifer GS and Spraying with Tryptophan on the Vegetative Growth Traits and Medicinal Active Compounds of the Plant Rosmary (Rosmarinus officinalis)

Abstract

. A field experiment was conducted in a plastic greenhouse covered with Saran at the College of Agriculture and Marshes, University of Dhi Qar, during the winter season of 2024–2025, using one-year-old rosemary plants (Salvia rosmarinus). The study aimed to investigate the effects of foliar application of Disper Humifer GS at 0, 2, and 4 g L⁻¹ and tryptophan at 0, 25, and 50 mg L⁻¹, individually and in combination, on vegetative growth, essential oil content, and some active compounds. The experiment was conducted as a factorial experiment using a Completely Randomized Design with three replicates. Treatments were applied as three foliar sprays at 15-day intervals, and means were compared using the Least Significant Difference test at P ≤ 0.05.The results showed that Disper Humifer GS at 4 g L⁻¹ significantly increased most vegetative growth characteristics, recording 64.67 cm plant height, 5.394 branches plant⁻¹, 240.78 leaves plant⁻¹, 48 g dry weight, 12.27 mg 100 g⁻¹ fresh weight chlorophyll, and 5.900 g 100 g⁻¹ fresh weight carbohydrates. It also produced the highest essential oil percentage (1.651%) and increased Cymene, Linalool, and Camphene concentrations.
Tryptophan at 50 mg L⁻¹ recorded the highest values for most growth characteristics, including plant height (76.78 cm), branches (6.46 plant⁻¹), leaves (253.442 plant⁻¹), dry weight (53.78 g), chlorophyll (13.30 mg 100 g⁻¹), and carbohydrates (30 mg 100 g⁻¹), with essential oil reaching 1.558%.The interaction treatment of 4 g L⁻¹ Disper Humifer GS + 50 mg L⁻¹ tryptophan (A2B2) significantly improved most traits, achieving 79 cm plant height, 7 branches plant⁻¹, 259 leaves plant⁻¹, 1.723% essential oil, and the highest Camphene and Linalool concentrations.