NPK Fertilization Modulates Morphophysiological Responses, Yield, Fruit Quality, and Mineral Composition of Solanum lycopersicum L.

NPK fertilization can modify crop yield and contribute to the production of foods with greater nutritional value. However, further studies are needed to understand how different NPK rates modulate the responses of Solanum lycopersicum, particularly regarding fruit quality. Therefore, this study evaluated the effects of different NPK fertilization rates on the morphophysiological traits and yield of S. lycopersicum L. plants, as well as fruit quality based on physicochemical attributes, antioxidant activity, and mineral composition. The experiment was conducted under a completely randomized design with five treatments: T1 (700 kg ha−1), T2 (1000 kg ha−1), T3 (1500 kg ha−1), T4 (2000 kg ha−1), and T5 (2500 kg ha−1). The results showed that T3 exhibited the most favorable performance in morphological variables, with a plant height of 154.61 cm, a leaf area of 20.1 cm2, and 3.86 inflorescences per plant. This treatment also achieved the highest yield, with a total tomato production of 1.58 kg per plant and an estimated productivity of 52,666.7 kg ha−1 (52.67 t ha−1). Regarding stomatal characteristics, T3 presented 23.33 stomata and a stomatal density of 106.1, according to the corresponding measurement units. Concerning fruit physicochemical quality, T3 exhibited a balanced profile of physicochemical attributes and antioxidant activity, with intermediate values for total soluble solids (6.13 °Brix), total soluble sugars (4.32%), and antioxidant capacity assessed using the ferric reducing antioxidant power (FRAP) assay (23.6%). Regarding mineral composition, fruits from plants subjected to T3 showed greater accumulation of calcium, potassium, and magnesium, with concentrations approximately 70–100 times higher than those in the control treatment. These results suggest that the NPK rate of 1500 kg ha−1 simultaneously favored plant growth, yield, and several attributes associated with fruit nutritional quality. In contrast, lower or higher rates were associated with less favorable responses in several evaluated variables. Overall, NPK rates differentially modulated plant growth, yield, and fruit nutritional quality, with T3 (1500 kg ha−1) showing the most favorable overall performance.