Influence of nitrogen fertilization rate and application frequency on physical and phytochemical quality of 'Owari' Satsuma Mandarin across fruit developmental stages in North Florida.

Citrus trees require substantial amounts of nitrogen (N), making it essential to balance N inputs with tree demand to optimize yield and fruit quality. Because N requirements vary considerably over the growing season, identifying the appropriate application rate and timing is critical to align N supply with tree physiological needs. 'Satsuma' mandarin (Citrus unshiu) is a promising cultivar for north Florida due to its tolerance to cold temperatures; however, guidelines on how N management affect fruit quality during the fruit developmental stages remain limited. The present study evaluated the effects of varying N rates and application timings on fruit quality parameters of 'Owari' Satsuma mandarins and tracked their changes at different stages of fruit development. Treatments consisted of four N rates (112-280 kg ha⁻¹) and three applications frequencies (3, 5, and 7 split applications) were arranged in a randomized complete block design (RCBD) with four replications. Fruit quality was monitored at different stages of fruit development from early September through mid-December. Results indicated that N rate had minimal influence on physical fruit quality parameters, whereas split frequency of N application significantly affected fruit weight, peel weight, and fruit diameter, with the highest values observed with 7 split applications. Conversely, N rate significantly affected the juice percentage, particularly during the peak fruit development period (mid-November), with the highest juice content observed at the highest N rate (280 kg ha