EFFECT OF 25 YEARS OF DIFFERENTIATED FERTILIZATION WITH NPK AND MAGNESIUM ON GROWTH AND FRUIT YIELD OF APPLE 'CORTLAND' AND ON THE CONTENT OF MINERALS IN SOIL AND LEAVES

摘要

The studies were carried out during 1982-2007 in the experimental orchard of Pomology Department, University of Life Sciences in Poznan on the area of the Orchard and Experimental Farm in Przybroda. Trees of 'Cortland' apple on M.26 rootstock were planted in autumn of 1979 on proper grey-brown podsolic soil at 5 x 3m spacing (667 trees per 1 ha). The experiment consisted of 15 combinations grouped in 8 blocks. The first differentiated fertilization was applied in 1982, i.e. in the third year after planting and it was continued without any changes until 2007. Fertilization was done with nitrogen (in the form of 34% ammonium nitrate), potassium (60% of potash salt), phosphorus (46% triple superphosphate) and magnesium (24% magnesium sulphate) in the spring, 4-5 weeks before tree blooming. The differentiated fertilization had a significant effect on the content of available nutrients in soil, both in the arable and in the subarable layers. Fertilization with phosphorus, potassium and magnesium increased the content of these elements in both soil layers. No interdependence was found between the content of mineral elements in soil and in leaves. Independently of fertilization, leaf nutrient content was at the optimal level, 25 years of differentiated fertilization did not exert any effect on growth and yield of 'Cortland' apple, which depended more on the tree age and the course of weather conditions.