Effect of foliar feeding with AgroPell calcium-containing fertilizer on plant productivity and fruit quality of apple trees in the Prikubanskaya horticultural zone of Krasnodar Krai

This paper studies the biological effectiveness of foliar feeding with AgroPell fertilizer on apple trees cultivated on leached chernozems in the Prikubanskaya horticultural zone, Krasnodar Krai (Russia). The experimental design was adjusted according to the specific objectives of each research year. In 2021, the study focused on the AgroPell solution, involving a gradual increase in fertilizer doses during fruit growth and ripening, along with varied application frequencies. In 2022–2023, the objectives were to investigate the impact and identify the most effective doses and application frequencies of the solution for trees. It was found that treatments with a dose of 7.0 kg/ha (solution concentration 7.0 g/l) caused leaf edge scorch in apples. Treatments with doses of 2.5 kg/ha and 5.0 kg/ha showed no phytotoxic effects. Under the weather conditions of 2021–2023, AgroPell application contributed to an increase in the average fruit weight and improved fruit retention on Prikubanskoe apple cultivar, resulting in a yield increase of 2.9–10.7 t/ha. The study revealed that the number of applications had a greater influence on the yield increase than the preparation dose. The difference in yield increase between variants with doses of 2.5 and 5.0 kg/ha was 0.7–1.0 t/ha, while the difference between variants with three and four applications at the same dose was 1.2–1.5 t/ha. Foliar feeding with the AgroPell agrochemical increased the calcium content in apples and maintained their commercial quality during storage. By the end of the storage period, the proportion of premium fruit had been 13.1–47.2% higher than in the control. The research identified the most effective dose of AgroPell fertilizer and the optimal application frequency as 5.0 kg/ha and 6 treatments per season, respectively.