Effects of N and K Fertilization on Internal and External Fruit Quality of Three Major Florida Orange Cultivars1

Abstract This is a report of a 4 × 4 NK factorial experiment over a 6-year period using ‘Hamlin’, ‘Pineapple,’ and ‘Valencia’ orange trees [ Citrus sinensis (L.) Osbeck] on rough lemon rootstock ( Citrus jambhiri Lush.) planted on Astatula f.s., formerly classified Lakeland f.s. Main effects of N and K were considered independently because interactions were not significant for most measurements. Increases in N rate increased the juice content and acid, whereas increases in K resulted in higher acid and lower soluble solids with an accompanying lower soluble solids/acid ratio. Smaller sized fruit, more green fruit, and a lower packout were a result of increased N rates. Increased K rates did not influence external characteristics of the fruit other than producing larger fruit. Rind blemishes occurred more often at the low N rate and diminished as the N rate increased. Incidence of decay in storage was greatest at the lowest N rate. Creasing was found to be significantly related to high N and low K rates.