RESPONSE OF YOUNG APPLE TREES TO NITROGEN FERTILIZATION, ON TWO DIFFERENT SOILS

In the spring 2000 'Jonagored' apple trees/M.9 rootstock were planted at 3.5 × 1.5 m in Warsaw-Wilanów, on a fertile silty loam alluvial soil, and at 4.0 × 1.2 m in Falenty Nowe near Warsaw, on a grey-brown podsolic loamy soil. From spring 2000, five or six fertilizer as ammonium nitrate treatments were applied: (1) N-0 (check); (2) N-50 (50 kg N ha^-1, over the whole orchard area in early spring); (3) N-100 (100 kg N ha^-1, over the whole area, in early spring); (4) N-100_delayed (100 kg N ha^-1, over the whole area, in early spring, starting from the fourth year after planting); (5) N-100sward (100 kg N ha^-1, in early spring, starting from the fourth year after planting, in _sward alleyways only); (6) N-50+50 (split dose – 50 kg N ha^-1 in early spring + 50 kg N ha^-1 ca. five weeks later, overall). Treatment (6) was applied in Falenty only. Leaf N levels in both orchards increased as a result of fertilization, although not significantly, reaching the highest values in N-100 treatments. The increment of TCSA for 2000-2001 and 2002-2003 was not affected by N fertilization. The first yield was harvested in the 2nd year after planting (2001) only in Falenty, and it did not depend on fertilization. Starting from the third year after planting (2002) trees bore fruit in both orchards, but neither dose nor mode of N application had any significant effect on yield. The cropping efficiency coefficient, calculated in relation to the TCSA in autumn 2003, did not depend on N fertilization. No significant effect of fertilization on mean fruit weight was noted. Leaf N content, growth and initial bearing depended on orchard location. A higher leaf N content was noted in Falenty, although the soil in Wilanów was richer in humus. Trees in Falenty showed less vigorous growth, and their early yields were higher than in Wilanów.