Flame seedless grapevines received 40 unite (N) of real nitrogen per feed over the 2020 and 2021 growing seasons. Approximately 57.1 g/N/vine of nitrogen was applied as 100% mineral fast release fertilizers (Ammonium nitrate) or as 25–50% quick release N fertilizers, specifically urea formaldehyde, urea with a phosphate coating, and urea with a sulfur coating. The purpose was to choose the optimal slow-release Nitrogen fertilizers and ratio among various Nitrogen sources. In terms of growth and yield, besides the physical and chemical traits of the berries, using nitrogen as 25% fast-release mineral nitrogen (ammonium nitrate) in addition to 75% slow-release nitrogen fertilizer (urea formaldehyde, phosphorus-loaded urea, and sulfur-loaded urea) produced the best results. With the application of nitrogen as a 100% fast-release mineral, ammonium nitrate, these features were reduced. Urea with a sulfur coating was the most effective slow-release Nitrogen fertilizer in this respect, followed shortly thereafter by urea alongside a phosphorus coating and urea-formaldehyde.  It is advised to use 25% fast release nitrogen (ammonium nitrate plus 75% slow-release nitrogen fertilizer) for Flame seedless grapevines to increase yield and berry quality (sulfur-coated urea).