Nitrogen and potassium requirements of tomato plants for the optimization of fruit quality and antioxidative capacity during storage.

While nitrogen (N) and potassium (K) fertilizers are commonly used in tomato fields for increasing plant growth and productivity, concepts regarding the interactive effects of these elements on tomato fruit quality during storage are ambiguous. The interactive effects of potassium (0, 250 and 500 mg kg soil^− 1) and nitrogen (0, 150 and 300 mg kg soil^− 1) fertilizers were tested on tomato fruit size at harvest, and their quality was evaluated after 30 days of storage at 4 °C. Fruit mass, firmness, taste-related parameters, inorganic nutrients, bioactive compounds, and antioxidative capacity of the fruits were investigated after the storage period. Application of 250-500 mg K in combination with 150 mg N per kg soil improved fruit mass at harvest and reduced loss of mass during storage. By increasing the soil’s K supply, the fruits exhibited significant increases in their amount of potassium, TSS and TA contents, antioxidative capacity, concentrations of lycopene, phenolics and ascorbic acid. Nonetheless, increasing the soil’s K concentration reduced Ca concentration and firmness of the fruits. By increasing the N concentration in the soil, a trend of decline was observed in the fruits’ TSS, soluble phenolics, lycopene and ascorbic acid contents. However, higher amounts of N and TA contents were detected in fruits treated with 300 mg N kg soil^− 1. N treatments did not affect the antioxidative capacity of the fruits. Accordingly, application of 250 mg K + 150 mg N kg soil^− 1 was suggested as the optimum treatment that could yield tomato fruits with high quality and that would also have improved storage capability. [ABSTRACT FROM AUTHOR]