The influence of foliar fertilisation on the biometric indicators of apple trees

The objects of the study were trees of the Veteran and Orel striped apple varieties and the biostimulator organomineral fertilizer “Biostim Universal”, containing N (total) 6.0%, K2O 1.3%, SO3 5.0% and free amino acids of plant origin 10.0%. Leaf top dressing was carried out 4 times per season with an interval of 14 days, starting from the second decade of May. The experimental scheme included 4 options: 1st — control (without treatment); 2 nd –4 th — spraying of trees with agrochemicals with consumption rates of 3, 5 and 7 l/ha. The repetition of the experiment is threefold, with 5 trees each. The increase in the diameter of the Orlovskoye striped strain by the end of the growing seasons of 2024 and 2025 was the maximum for the “Biostim” variant of 5 l/ha — 49.3% and 34.9%, respectively. According to the Veteran variety, 53.5% in 2024 for the “Biostim” variant of 5 liters/ha and 41.9% in 2025 for the “Biostim” variant of 7 l/ha. The winter variety Veteran revealed more stable values of biometric indicators for the variants, regardless of the formative pruning, weather conditions during the research years and the consumption rate of the drug. In the autumn variety Orlovskoye striped, an increase in the dosage of the drug to 7 l/ha in the arid conditions of 2024 with elevated temperatures in the summer months had a negative impact on crown formation. In 2025, in conditions of sufficient moisture supply in this variant, the trees recovered, the increase in crown diameter relative to 2024 was the maximum — 102.9%. According to a set of biometric indicators, higher and more stable values were obtained with leaf top dressing with “Biostim Universal” agrochemicals of 5 l/ha.