This study was carried out during the two successive seasons (2021and 2022) on the first and second ratoon of healthy uniform banana var. Grand Nain (Musa spp.), to study the effect of different slow-release potassium fertilizers (15% K₂O) on vegetative growth, productivity and fruit quality. Plants grown in silty clay soil under flood irrigation system in a private orchard at Al-Badari, Assiut, Egypt. The rates were (2, 4 and 8 kg slow-release potassium) + 400 g potassium sulphate / plant /year were added as soil drench during mid-March, mid-June and mid- September while, (1,6 kg) potassium sulphate dose used in control treatment was added at monthly intervals as soil application from mid-March until mid-October. The obtained results showed that, all treatments had a significant effect on enhancing the vegetative growth parameters, i.e. number of green leaves /plant and plant total leaf area (m² /plant). Also, improving yield, bunch weight (kg), number of hands /bunch, hand weight (kg), number of fingers /hand, finger weight (g), finger length (cm), finger circumference (cm), finger pulp weight (g) and finger peel weight (g). Treatment of slow-release potassium at 8 kg + 400 g potassium sulphate gave the highest values of physical properties of banana plants (cv. Grand Nain) in both seasons compared to control treatment (1.6 kg potassium sulphate). On the light of previous results, it could be concluded that fertilizing the banana by K fertilization via slow-release form to get high yield with good fruit quality.