Grafted Apple Trees’ Density: A Study on the Impact of Differential Water and Nutrient Application in the Nursery

This study aims to evaluate the impact of irrigation and fertilization practices on the density of grafted apple trees in nursery settings. The primary hypothesis posits that a customized approach delivering water and nutrients aligned with the young tree's distinct growth phases and physiological requirements will yield superior planting material compared to conventional nursery methods. The study was conducted at a privately operated nursery located in northwestern Romania. The research investigated the impact of two apple cultivars (Gala and Jonagold), four irrigation levels (0 mm, 10 mm, 20 mm, and 30 mm), and four fertilization treatments (N0P0K0, N8P8K8, N16P16K16, and N24P24K24) on fruit tree density in the nursery. In comparison to the Gala cultivar (93.50% ± 6.195), the Jonagold cultivar displayed a marginally higher tree density percentage (95.63% ± 4.790). With a 30 mm watering norm, the tree density was at its highest value (99.38% ± 1.295), and it gradually declined with decreasing watering norms. There was no statistically significant difference in the percentage of trees with different fertilization levels. The cultivars Gala (99.25% ± 1.650) and Jonagold (99.50% ± 0.827) had the highest density percentages under the 30 mm watering norm. The highest trees’ density was consistently attained at the 30 mm watering norm across all fertilization levels, according to the interaction between fertilization and watering norm. A 100% tree density was achieved by the combination of the Gala cultivar, the 30 mm watering norm, and N16P16K16 or N24P24K24 fertilization. The Jonagold cultivar achieved a 100% tree density at the 20 mm watering norm with N0 P0 K0 fertilization and at the 30 mm watering norm with N0 P0 K0 or N16 P16 K16 fertilization. N24P24K24 fertilization at 0 mm watering norm (89.00% ± 6.944) for the Gala cultivar had the lowest densities. According to these findings, the most important element in reaching the highest fruit tree density in the nursery is the 30 mm watering norm; in a few combinations involving both cultivars, a 100% density was noted.