This research was conducted on the grapevine "Red Roomy" cultivar seasonally in 2020 and 2021 to study the effect of both 100% potassium RDK as a soil application, which was the recommended dose, and 50% potassium RDK plus one of the foliar fertilizer sources, such as Hanfu humate (4000 ppm), Delta Sol standard (4000 ppm), nano-K₂SO₄ (750 ppm), potassium silicate (4000 ppm), and Novastroka (4000 ppm), on Red Roomy grapevine vegetative growth, fruit production, and berry characteristics. Data revealed the possibility of using foliar fertilizer sources to partially replace mineral potassium fertilizer. The data showed that the maximum values from vegetative growth traits, yield components, and juice chemical properties were measured on vines treated with 50% RDK + 4000 ppm Novastroka, followed by vines treated with 50% RDK + 4000 ppm Delta Sol standard. Moreover, the minimal amounts of these characteristics were scored on vines treated with 50% RDK + 4000 ppm Hanfu humate. It could be concluded that applying 50% RDK + 4000 ppm Novastroka to vines three times annually was necessary to ensure the optimal traits for vegetative growth, improving standards of fruit quality, harvest, and the nutrition condition of a vine, in addition to reducing the production costs and environmental pollution resulting from the increased use of mineral fertilizers on Red Roomy grapevines under Assiut conditions in Egypt.