Agronomic biofortification in tomato: balancing micronutrient enrichment, yield, and fruit quality

Introduction: Micronutrient fertilisation is a promising strategy for agronomic biofortification of tomatoes. Yet, its effects on yield formation and fruit quality remain insufficiently clarified, particularly when multiple nutrients and application methods are considered simultaneously. Methods: This study evaluated a range of fertilisation treatments differing in application method (soil, foliar, and combined) and dose, assessing their effects on fruit mineral composition (Fe, Zn, Mn, Cu), yield components, and quality traits, including physicochemical properties, antioxidant capacity, and an integrated quality score (IQS). Results: Fertilisation significantly affected fruit mineral composition, with the strongest enrichment observed for Fe, Zn, Mn, and Cu. The highest micronutrient concentrations were recorded at the highest soil application rate (5%), but this treatment caused a substantial yield reduction. In contrast, moderate treatments, particularly 1% soil and 0.1% foliar + 0.5% soil application, achieved significant mineral enrichment while maintaining stable productivity. Yield variation was primarily driven by changes in fruit number rather than fruit weight. Fruit quality traits responded strongly to fertilisation, with higher doses enhancing antioxidant capacity and moderate treatments improving taste balance. The highest IQS was obtained under a combined moderate treatment (0.5% foliar + 1% soil). Principal component analysis revealed a partial trade-off between mineral enrichment and yield, while identifying treatments with balanced performance across mineral composition, productivity, and quality. Conclusions: The results demonstrate that effective agronomic biofortification of tomato fruits can be achieved through moderate, well-optimised fertilisation strategies. Such approaches enhance micronutrient content without compromising yield or overall fruit quality, providing a practical framework for sustainable improvement of the nutritional value of horticultural crops.