Results of Investigation of Mineral Nutrition and Weather Conditions Influence on Biochemical Composition of the <i>Veniyaminovskoe</i> Variety Apple Tree

The results of a seven-year study (2017–2023) of the influence of hydrothermal conditions of the growing season and of mineral fertilizers on the chemical composition of apple fruits are presented. The object of the study was the Venyaminovskoe apple cultivar grown in a field experiment to study the effectiveness of mineral fertilizers in a medium-sized apple orchard. The experimental orchard was planted in 2013 with a space of 6 × 3 m. Annual spring application of increasing doses of nitrogen (in the form of ammonium nitrate – 33% of active substance) and potash fertilizers (in the form of potassium chloride – 40% of active substance) has been carried out since 2015. Foliar top dressing was carried out three times during the growing season with 1% urea solution and 0.3% potassium sulfate solution. The content of soluble solids, the sum of sugars, ascorbic acid, phenolic compounds (catechins) and the sugar acid index were determined in the fruits. It is shown that the use of soil and foliar application of nitrogen and potash fertilizers did not have a significant effect on the content of the studied components. It has been established that the most significant factor affecting the chemical composition of fruits is the weather conditions of the growing season and of the last month before fruit harvesting. At the same time, the content of ascorbic acid on average over the seven years of the experiment was significantly higher compared to the control in the variant with the application of maximum doses of nitrogen and potash fertilizers (N90K120) into the soil and also in conjunction with non-root top dressing in doses: N30K40 и N60K80. The application of fertilizers in maximum doses of N90K120 had a negative effect on a significant increase in the content of titrated acids in fruits.