A field experiment on olive (Olea europaea L.) saplings examined the influence of the Acadian seaweed extract and organic humic acid, carried out from March to November 2022 in an orchard located in Jazirah, Ramadi Region, Iraq. The study aimed to determine effects of foliar application of seaweed extract Acadian and organic fertilizer humic acid with concentrations of 0, 250, 500, 750, and 1000 mg L^-1 on olive saplings’ foliage. Results showed spraying coefficients with individual treatments of Acadian and Humic fertilizers at the concentration of 1000 mg L^-1 significantly outperformed most studied traits. These provided the highest averages for main stem height (92.93 and 98.67 cm), main stem diameter (6.193 and 6.060 mm), leaf number (479.2 and 397.7), leaf area (602.4 and 455.1 cm²), leaf chlorophyll content (73.60 and 75.73 SPAD), dry weight of vegetative parts (97.87 and 91.40 g), and root system (23.13 and 18.07 g), respectively. The interactions of both factors at 1000 mg L^-1 concentration were superior on olive saplings for the main stem height (131.00 cm), main stem diameter (7.067 mm), leaves seedling^-1 (670.3), leaf area (689.0 cm²), leaf chlorophyll content (83.67 SPAD), dry weight of vegetative parts (122.33 g), and root system (28.33 g). The study concluded, based on results, that foliar fertilization, whether with biological or organic fertilizer, contributes positively and effectively to improving olive seedlings’ growth.

Keywords: Olive (O. europaea L.), Acadian seaweed extract, organic Humic, nutrients, vegetative, root system

Key findings: The results revealed a greater improvement in growth and morphological traits of olive (O. europaea L.) saplings with foliar application of organic fertilizers at a concentration of 1000 mg L^-1.