The effects of foliar potassium and zinc sprays on growth, production, and fruit quality in Olea europaea L. cv. "Sorani" were tested in a field experiment conducted at Bakrajo, Sulaimanyia, Kurdistan - Iraq, during the 2024 growing season. Fifteen-year-old olive trees were spaced 3 × 2 meters apart in a factorial randomized complete block design with three replications. Twenty-seven trees of uniform size, health, and vitality were selected and assigned to nine treatment combinations of potassium (0, 1.5, and 3 ml.l-1) and zinc (0, 1.5, and 3 g.l-1). Foliar sprays were applied three times, starting on July 3, 2024. The results showed that foliar applications of potassium and zinc, whether alone or combined, significantly enhanced vegetative growth parameters (leaf area, leaf dry weight, and leaf mineral content), yield components (fruit fresh and dry weight, fruit length, diameter, and tree yield), and fruit chemical properties (oil percentage, total soluble solids, and fruit potassium and zinc contents). The treatment with 3 ml.l-1 potassium and 1.5 g.l-1 zinc produced the highest values for most measurements, including fruit oil percentage (38.60%), total soluble solids (17.10%), and tree yield (9.57 kg per tree). These benefits may be due to potassium's role in assimilating transport, enzyme activation, improve physiological functions and osmotic regulation, along with zinc's function in chlorophyll synthesis, auxin metabolism, and enzymatic activation. The study suggests that a balanced foliar application of potassium and zinc is an effective and practical method for enhancing olive tree growth, productivity, and fruit quality in Kurdistan’s semi-arid climate.
Mama et al. (Sun,) studied this question.