The Effects of Biostimulants on the Physiological Processes of Yield Formation and Resistance of Apples to Spring Frosts

The present research aimed to evaluate the effectiveness of new organo-mineral biostimulants in an apple orchard, including their relevance to spring frosts and to enhancing yield. The study evaluated the effects of foliar sprays with organo-mineral fertilizers on apple yield, comparing three treatments: 1—control (no treatment); 2—foliar spray with a 1% blend of “WPU” Antifreeze and 1% “WP Drip Ca + Mg”; 3—foliar application using a 3% solution of both “WPU” Antifreeze and “WP Drip Ca + Mg”. The NPC “White Pearl” foliar sprays exhibited cryoprotective properties to spring frosts through multiple mechanisms, i.e., prevention of cellular dehydration via elevated bound water content and accumulation of osmoprotective compounds including proline and soluble sugars. This research shows that the applied treatments improved carbohydrate metabolism by enhancing the biosynthesis of glucose and starch, as well as changing the donor–acceptor relationships between the leaf apparatus and the fruit toward the forming apple, promoting a better outflow of assimilates into ripening fruits. The 1% solution treatment enhanced apple yield by 70% (1.7-fold) relative to the untreated control. These findings indicate that the “White Pearl” organo-mineral fertilizer NPC (especially at 1% concentration) could serve as an effective supplement to conventional apple farming practices, boosting overall productivity.