Effect of nitrogen fertilization on the content of mineral components in soil, leaves and fruits of ’Šampion’ apple trees

The experiment was carried out in the Experimental Orchard Przybroda of the Department of Pomology, Pozna Agricultural University in the years 2001–2003. Trees of ‘Šampion’ on M.9 rootstock were planted in the spring 1994 on virus-free rootstock EMLA 9 at spacing of 3.5 × 1 m (2 857 trees per ha) on grey-brown sandy loam podsolic soil. The experiment included the following 5 treatments of nitrogen fertilization: 1. N0 – control; 2. N5 – 5 g N·m-2, applied once in early spring; 3. N10 – 10 g N·m-2 applied once in early spring; 4. N5+5 – 5 g N·m-2 in spring + 5 g N·m-2 at the end of May; 5. N5herb –5 g N·m-2 in early spring, within the herbicide strip only. Nitrogen fertilization had a significant effect on changes in the assimilable elements in soil. It exerted an effect on the decrease of assimilable potassium in the arable and subarable layer and an increase of assimilable magnesium improving the K : Mg ratio. A smaller effect was found in the changes of assimilable phosphorus content and in soil reaction. Nitrogen fertilization had an effect on the increase of total nitrogen content in leaves and it decreased the content of phosphorus. The content of assimilable components in soil was not correlated with the content of general components in leaves. The content of mineral components in fruits was closely correlated with the component content in leaves. Climatic conditions, and particularly the absence of atmospheric precipitations and the increase of temperature, as well as the aging of trees contributed to the decrease of the content of nitrogen, phosphorus, potassium and magnesium and to the increase of calcium content.