Optimizing Nursery Production of Apple Trees: Assessing the Dose-Response to Water and Fertilizer in Two Cultivars

This study examined the effects of two apple cultivars (Gala and Jonagold), four irrigation levels (0, 10, 20, and 30 mm), and four fertilization treatments (N0P0K0, N8P8K8, N16P16K16, N24P24K24) on nursery tree density. Jonagold exhibited a slightly higher mean density (95.63% ± 4.790) compared to Gala (93.50% ± 6.195). Tree density peaked at 99.38% ± 1.295 under the 30 mm watering norm and declined with reduced irrigation, while fertilization levels showed no significant independent effect. Both cultivars achieved their highest densities under the 30 mm watering norm (Gala: 99.25% ± 1.650; Jonagold: 99.50% ± 0.827), and several cultivar–fertilizer–irrigation combinations reached 100% density. The lowest density (89.00% ± 6.944) occurred in Gala under the N24P24K24 treatment without irrigation. Overall, results indicate that irrigation, particularly the 30 mm norm, is the key determinant of maximizing nursery tree density, with select combinations enabling complete survival.