The effect of calcium prohexadione on apple tree productivity in intensive orchards

Goal. To evaluate the effect of different application regimens of calcium prohexadione on the productivity of Fuji and Honey Crisp varieties of the apple in an intensive orchard, specifically on fruit set, fruit weight, and total yield. Methods. Field study — to examine the effect of the studied factors on the formation of crop productivity indicators; laboratory study — to determine qualitative yield indicators; quantitative-weight analysis — to determine the yield structure parameters; comparative-calculational analysis; and mathematical-statistical analysis — to substantiate the reliability of the obtained results. Results. The study was conducted in 2020 – 2023 at the orchard of Uman National University. The soil was podzolized chornozem. It was found that the application of calcium prohexadione (Pro-Ca) significantly increased the number of fruits in both varieties, leading to higher yields. The highest yields were obtained when using the calculated doses of Pro-Ca and applying it twice at a rate of 1.25 kg / ha. At the same time, as the number of fruits increased, their average weight decreased, indicating limited assimilation resources. Partial coverage of the canopy with the preparation proved to be ineffective. Varietal differences were observed: Honey Crisp produced a higher yield due to greater fruit weight, while Fuji produced a higher yield due to a greater number of fruits. Conclusions. Calcium prohexadione is an effective growth regulator for increasing apple tree productivity in intensive orchards. The optimal application schemes are those that take into account the physiological condition of the plants and involve two applications of the product at a dose of 1.25 kg/ha. To achieve the maximum effect, uniform coverage of the canopy with the product is necessary, and the varietal characteristics of the crop must be taken into account.