Effect of nitrogen fertilization rate on vegetative growth of an intensive apple orchard under optimal irrigation

Abstract

Nitrogen is one of the main nutrients determining the intensity of vegetative growth and canopy formation in apple orchards, particularly under conditions of optimal water supply. The aim of the present study was to evaluate the effect of different nitrogen fertilization rates on the vegetative growth of an apple orchard grown under optimal drip irrigation. The evaluation was based on data obtained from an experiment conducted during the period 2023–2025 in an intensive apple orchard with the cultivar ‘Florina’ grafted onto MM106 rootstock. Three fertilization treatments were investigated: unfertilized control (V0), ammonium nitrate – 5 kg.da-1 N (V1), and ammonium nitrate – 8 kg.da-1 N (V2). Vegetative growth was assessed annually through trunk cross-sectional area, tree height, and crown volume. Nitrogen fertilization had a statistically significant effect on all investigated parameters throughout the experimental period (p ≤ 0.05). Fertilized treatments showed higher values compared with the control, with the strongest effect observed at the highest nitrogen rate. The differences between treatments increased over time, confirming the effect of nitrogen nutrition on the development of the orchard.