Yield and fruit quality of Malus domestica Borkh. as influenced by novel organomineral fertilizers

One of the most promising methods of increasing the yield and quality of agricultural products is the application of environmentally friendly compounds, such as natural biostimulants. The use of organomineral nutrient complexes contributes to a significant increase in the adaptive properties of plants and, as a result, increases productivity and improves yield quality. This paper shows for the first time the effectiveness of using new organomineral fertilizers as additional elements in cultivation of apple trees under the soil and climatic conditions of the Orel region. The aim of the work was to study the effect of new organomineral fertilizers on the yield and quality of apple fruits before and after long-term storage. Tests of the natural plant complex White Pearl (NPC WP) (OOO AgroPlus Group of Companies, Russia) were carried out at the experimental plot of Russian Research Institute of Fruit Crop Breeding in 2021-2022. Phytomodulator NPC WP Universal (WPU) Antifreeze was a suspension of a group of minerals of natural origin containing a concentrate of extracts of spruce, pine and Siberian fir needles. Phytocorrector NPC WP Drip Ca + Mg is an extract of vegetative mass of oceanic bioflora with an organomineral basis. The study was performed with a triploid apple ( Malus domestica Borkh.) cultivar Sinap Orlovsky of late winter ripening the fruits of which are predisposed to scald and bitter pitiness. The apple trees were grafted on a medium-sized rootstock 54-118. The scheme of the tree layout in the orchard was 6½3 m. The experiment was laid on the 2013 planting site with the agro-gray forest soils, humus content of 3-4 % and humus horizon capacity of 30-35 cm. The rows were naturally overgrown with grass. Herbicides were applied into the pre-trunk strips. The agronomic practice was as generally accepted for the crop. In the early spring period, the plants were two-fold non-root treated with 1.0 % NPC WPU Antifreeze solution. Subsequent treatment was carried out in spring during the “closed inflorescence” phenophase with a tank mixture of 1.0 % of NPC WPU Antifreeze + 1.0 % NPC WP Drip Ca + Mg. In summer, the leaves were treated four times with the drugs. In the control, the plants were untreated. The fruit yield (in kg) harvested during the period of removable fruit maturity was assessed individually from each pant by weighing. The commercial qualities, chemical composition and keeping quality of the fruits under storage were evaluated. The fruits were stored in the CV114-S refrigerator (Polair, Russia) for 211 days at +2 °C. The content of calcium and magnesium was determined by the trilometric method on a flame photometer M 410 (Sherwood Scientific, Ltd., UK); potassium and phosphorus were measured after dry calcination and dissolution of ash in 20 % hydrochloric acid according to the guidelines. In the research, it was revealed that the complex application of organomineral fertilizer of the NPC WP line significantly increased the yield (by 72.5 %) and the average fruit weight (by 20.3 g) of the cultivar by optimizing the nutritional regime of plants. In addition, non-root treatments favorably affected the consumer and commodity qualities of fruits both at harvest and after long-term storage. Treatments with a tank organomineral mixture improved the taste qualities of Sinap Orlovsky fruits by increasing the amount of sucrose (by 25.6 %) and ascorbic acid (by 20.5 %) compared to control. The treatment of plants contributed to a close-to-optimal ratio (K+Mg)/Ca = 11.2. Under treatments, there was a higher yield of commercial fruits (by 14.8 %) compared to control. Moreover, the wastes were 3 times less. The use of natural plant complexes ensured a reduced incidence of bitter pitines, i.e., with prolonged storage, fruits with this disease were 2 times fewer. The degree of fruit lesion with scald was 2.5 times less. The number of microbiological damages decreased. The tasting score of the treated fruits was 4.7 points for a