Synergistic Effects of Biofertilization and Foliar Boron Application on Reproductive Performance, Yield, and Fruit Quality of Olive (Olea europaea L.) Trees

• Lanja Hussen Mohammedamin1 Mohammed Abdul Aziz Lateef 2 Ali A. Zainel 3

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Olive trees (Olea europaea L.) are among the most important fruit crops in semi-arid regions; however, their productivity is often limited by inadequate nutrient management during the flowering period. This study was conducted during the 2025 growing season in Dibis District, Kirkuk Governorate, Iraq, to evaluate the effects of biofertilizer and foliar boron application, individually and in combination, on flowering characteristics, yield, and fruit quality of olive trees. A field experiment was arranged in a randomized complete block design (RCBD) using three levels of biofertilizer (0, 10, and 20 mL L⁻¹) and three levels of foliar boron (0, 50, and 100 mg L⁻¹). The results revealed significant effects of both factors and their interaction on all studied parameters. The application of 20 mL L⁻¹ biofertilizer significantly improved flowering traits, yield components, fruit physical characteristics, oil content, and total soluble solids compared with the control treatment. Likewise, foliar spraying with 100 mg L⁻¹ boron enhanced reproductive efficiency, fruit set, and overall fruit quality. The combined application of 20 mL L⁻¹ biofertilizer and 100 mg L⁻¹ boron produced the highest values for most measured traits, indicating a strong synergistic effect. This response was attributed to enhanced microbial activity in the rhizosphere, improved nutrient availability and uptake, better carbohydrate translocation, and the positive role of boron in reproductive and metabolic processes. Consequently, the combined treatment reduced flower and fruit abscission and improved source–sink relationships. The findings suggest that integrating biofertilizer with foliar boron application is an effective and environmentally sustainable strategy for improving olive yield and fruit quality under semi-arid conditions

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