Determining the efficacy of boron, NPK, and sheep manure applications on 'foşa' and 'yomrali̇' hazelnut cultivars grown in yomra district (Trabzon)

This study investigated the effects of various boron, sheep manure, and chemical (NPK) fertilizer combinations on phenological, morphological, husk, leaf, and kernel quality (moisture, crude fat, protein, vitamin E) parameters of 'Foşa' and 'Yomrali' hazelnut cultivars in Yomra (Trabzon). Fertilization strategies significantly influenced hazelnut quality and nutritional value, with cultivar-specific responses observed. Phenologically, 'Foşa' was an early cultivar, maturing on August 5, 2024, while 'Yomrali' was late-maturing, reaching harvest maturity on August 20, 2024. Highest fruit and kernel weights were recorded for 'Foşa' with Com. 17 (Boron 200 + Sheep Manure 20 + Chemical Fertilizer 1 dose) (4.14 g and 2.14 g), and for 'Yomrali' with Com. 14 (Boron 200 + Sheep Manure 20 + Chemical Fertilizer 0 dose) (3.83 g and 1.99 g). Kernel ratio was optimized in both 'Foşa' (51.99%) and 'Yomrali' (52.48%) with 1 dose chemical fertilizer. Shell thickness was thinnest in 'Foşa' with Com. 14 (0.85 mm) and 'Yomrali' with Com. 1/Com. 25 (0.81 mm). Kernel cavity was minimized in 'Foşa' with Com. 24 (3.82 mm) and 'Yomrali' with Com. 3 (0.77 mm). Blanching ratios increased with high boron and organic manure, while husk separability was high in 'Foşa' (Com. 25, 2.37) but weaker in 'Yomrali'. High boron doses suppressed leaf area. Kernel moisture content was optimized for storage in 'Foşa' (Com. 25, 4.22%) and 'Yomrali' (Com. 27, 4.10%). Protein content increased in 'Foşa' (Com. 17, 18.04%) and 'Yomrali' (Com. 20, 17.92%). Crude fat content reached its highest levels in 'Foşa' (Com. 16, 59.82%) and 'Yomrali' (Com. 18, 58.65%). Vitamin E (α-tocopherol) content significantly increased compared to controls, reaching its highest in 'Foşa' (Com. 17, 466.89 µg/g) and 'Yomrali' (Com. 14, 458.12 µg/g). In conclusion, a strong interaction exists between cultivar genetics and fertilization combinations on hazelnut quality and nutritional value. The study highlights that balanced use of boron, sheep manure, and chemical fertilizers is critical for enhancing hazelnut quality and nutritional value, underscoring the importance of integrated fertilization strategies.