Optimization of mineral nutrition for the Florina apple tree variety on the leached chernozems in the foothill zone of the Kabardino-Balkaria

Introduction. Intensive orchards on the leached chernozems in the foothill zone of the Kabardino-Balkaria require refinement of mineral nutrition systems for apple trees, taking into account varietal characteristics and fruit quality. The goal of the research was to investigate the effect of different doses and ratios of mineral fertilizers on the growth processes, yield, and biochemical composition of the Florina apple tree fruits in order to develop an effective fertilization system for intensive plantings. The objects and methods of the research. Field experiments were conducted in the orchard planted in 2016 with the Florina apple tree variety (SK-2 rootstock, 5x2 m layout) on slightly leached heavy loamy chernozem (pH 7.3; humus 2.5 %; P₂O₅ – 44.8; K₂O – 234.0 mg/kg). The scheme included 15 variants: control, nitroammophoska 16-16-16 (60, 90, 120 kg active ingredient/ha) and 8-24-24 (30, 40, 50 kg active ingredient in nitrogen) against the background of calcium nitrate (25 kg Ca/ha), as well as variants with Izagri foliar feeding. The replication was fourfold. The results and discussion. A dose of 120 kg N/ha enhanced vegetative growth (shoot increment 63.5-64.3 cm), but reduced the content of dry matter, sugars, and vitamin C. The best results were obtained with nitroammophoska 8-24-24 (50 kg N/ha) + Ca + foliar feeding: yield 28.9 t/ha (+15.1 %), fruit weight 182 g (+8.9 %), sugars 13.1 %, vitamin C 10.5 mg %, sugar-acid index 43.7 (1.6 times higher than the control). With a smaller leaf area, these variants ensured higher productivity due to the redistribution of assimilates into the fruits. Conclusion. The optimal system is the following: 8-24-24 nitroammophoska (50 kg N/ha) + calcium nitrate + Izagri foliar fertilizer, providing balanced nutrition and high fruit quality. Nitrogen rates above 90 kg/ha are not recommended due to excessive vegetative growth and deterioration of biochemical parameters.

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