THE INFLUENCE OF DIFFERENT DOSES OF FERTILIZATION ON STORAGE OF APPLES, CV. CORTLAND

The storage experiment was conducted from 1991 to 1992 but the trees were planted in autumn 1979 on gray brown podzolic soil developed from post glacial clay which is counted to the III.b class according to the Polish soil evaluation system. The trees were spaced at 5 x 3 m (667 trees per ha).

In the experiment apples from nine treatments with different fertilization doses of N, P, K and Mg in eight randomised blocks were compared (Table 1). Fertilization treatments diversified from full double dose of fertilizers to single doses of each fertilizer separately. Fruits after harvest were stored in a cold storage plant at 2–3°C and normal atmosphere for 5 months.

Evaluations of the effectivity of differentiated doses were carried out on the basis of: a) chemical analysis of fruits, b) useful and physical properties of fruit (mass of fruit, diameter, dimensions of red blush, firmness, and contains of extract), c) occurrence of pathogen disease and physiological disorders.

After an eleven year period of differentiated fertilization, no essential influence on unit yield dimensions from one tree was ascertained. However essential influence on fruit quality was ascertained. Fertilization had its influence on fruit colour and firmness, changes after harvest as well as during the period of storage.

Paralysis of fruits caused by fungus diseases and physiological disorders were essentially higher when storing fertilized fruits cv. Cortland. The main physiological disorder was bitter pit (c. 85 % of all paralyzed). Fertilization influenced increased losses during the period of storage and applying magnesium in a dose of 120 kg/ha appeared to be the most profitable.