INFLUENCE OF FOLIAR NUTRITION WITH MACROELEMENTS ON APPLE TREE GENERATIVE ACTIVITY: PHYSIOLOGICAL ASPECTS

In orchards of southern horticultural zones of Russia (alluvial-meadow and chernozemic-alkaline soils) studies of foliar nutrition of apple trees with different macroelements (N, P, K) were carried out aimed at regulating their generative activity. It was observed that foliar nutrition with urea and nitroammophoska exerted a positive influence оn the photosynthetic activity of apple trees and increased the transfer of metabolites from leaves to absorption sinks (seeds and fruit tissues). Nitroammophoska influenced the generative activity of apple trees more effectively than urea. Treatment of trees with nitroammophoska at an early fruit stage (organogenesis stages X-XI) increased substantially seed viability and improved tree productivity in terms of both total yield and fruit size. Moreover, this mineral fertilizer applied at the stage of decreasing shoot growth (before organogenesis stages III and IV) provided varieties of different ripening periods with substantial improvement of flower bud formation. Thus, foliar application of nitroammophoska at defined organogenesis stages gives the possibility to specifically regulate the production process; it may increase annual fruit yield and quality of seeds .