DIRECT AND INDIRECT EFFECTS OF N-PHENYL-PHTHALAMIC ACID AND FERTILIZATION ON FRUIT SETTING AND FRUIT QUALITY PARAMETERS OF APPLE (MALUS DOMESTICA BORKH.)

On seven apple cultivars (‘Gala Must’, ‘Gloster’, ‘Granny Smith’, ‘Idared’, ‘Jonagold’, ‘Jonathan Csány 1’, ‘Mutsu’), the authors studied the influence of N-phenyl-phthalamic (PPA) acid and fertilization on flowering, fruit set and fruit quality in the years 2003-2004. The research results showed that PPA application extended the flowering time of most of the cultivars. Fruit set of apple cultivars increased in many cases when the regulator was applied. Additional nutrient supply may increase the fruit set also. The increase of fruit set also increased the number of fruit harvested per tree. Quality parameters were influenced by fertilization and fruit number per tree. For example, when N-phenyl-phthalamic acid was applied without fertilization the fruit number per tree increased considerably but this was not reflected in improved yields. The reason for this is that fruit set was high and fruit received insufficient nutrition to sustain their growth. The skin colour of fruits was decreased in several cases by the treatments. In one respect, the enlarged fruit number caused shading of others and the fertilization increased the vegetative shading by leaves.