Özet:

Tree growth, productivity, fruit quality attributes, and antioxidant activity were tested in apple cultivar Idared under different fertilization treatments from the 22nd to the 23rd year after planting in a heavy acidic soil under western Serbian conditions. Treatments included the use of aged cattle manure, compound NPK (15:15:15) mineral fertilizer, a multinutrient fertilizer commercially named Italpolina (ITP) (NPK + organic carbon + humic acids), two types of N mineral fertilizers (calcium ammonium nitrate [CAN] and urea), and control (no fertilization). Results showed that Idared trees were more vigorous when fertilized with the two N fertilizers than when treated with another mineral, organic, or multinutrient fertilizer. Urea promoted the highest yield per tree and unit area, while yield efficiency was the highest in the control and those under treatment with urea, compound NPK, and manure. Fertilizer regimes had a significant effect on fruit weight and flesh firmness, but their effects on fruit size and dimension ratio were not significant. Compound NPK resulted in the greatest fruit weight, whereas firmness and soluble solids content were the highest in manure treatment. Titratable acidity (TA) was the highest in control trees and after CAN application, while urea induced the highest ripening index. Fertilizer treatments had no significant effect on the contents of invert sugars, sucrose, and total sugars (TS). The TS/TA ratio was highest under urea treatment and lowest in the control and under CAN application. ITP led to the highest values for total phenolics, total nonflavonoids, and total antioxidant capacity, while the highest total flavonoid content was obtained with compound NPK.

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