TOMATO FRUIT QUALITY BETWEEN CLUSTERS IS DIFFERENTIALLY AFFECTED BY NITROGEN AND POTASSIUM SUPPLY

Abstract

Fruit quality is significantly affected by the nutrient status of plants; nonetheless, it has not yet been deeply explored how nitrogen (N) and potassium (K) supply affects tomato fruit quality between clusters during the vegetative and reproductive stages of the crop. The aim of this study was to evaluate the effects of N and K on fruit quality parameters of three clusters of hydroponically grown tomato (Solanum lycopersicum L.). Nitrogen (10, 12, 14 and 16 mol_c N m^-3) was evaluated at the vegetative stage, and potassium (5, 7, 9, 11 and 13 mol_c K m^-3) at the reproductive stage. The evaluated N and K concentrations showed significant main effects on the quality attributes total soluble solids, citric acid percentage, reducing sugars, color and lycopene concentration; yield was affected only by K, while the effects of N × K interaction were not significant. Increasing N concentrations from 10 to 16 mol_c m^-3 enhanced hue angle, brightness, reducing sugars and citric acid percentage, but decreased total soluble solids and lycopene. As K increased from 5 to 13 mol_c m^-3 in the nutrient solution, total soluble solids, citric acid, reducing sugars, lycopene, yield and fruit brightness increased, but hue decreased. Total soluble solids, reducing sugars and lycopene gradually increased from the first to the fifth cluster, while yield, color attributes of hue and brightness tended to decrease as the crop cycle progressed. Titratable acidity percentage showed no clear trends between clusters. It is concluded that N and K differentially affect tomato quality between clusters.