Effects of nitrogen fertilisation on apple trees grown in three different locations

The experiments were established in autumn 1993 or in spring 1994 in three locations: (a) Warsaw-Wilanow, Central Poland, on alluvial loamy soil; (b) Przybroda near Poznan, Western Poland, on grey-brown podsolic sandy clay and (c) Babtai near Kaunas, Central Lithuania, on grey-brown podsolic loamy clay. 'Sampion' on M.9 (Wilanow and Przybroda) and 'Sawa' on M.9 (Babtai) one-yearold unfeathered trees were spaced in Wilanow and Babtai at 3 x I in and in Przybroda at 3.5 x I in. Herbicide strips (I in wide) were maintained along tree rows and sward in alleyways. In Wilanow and Przybroda five N fertiliser treatments were applied: (1) N-0, check, without N; (2) N-50, 50 kg N/ha, applied in early spring on the whole soil surface; (3) N-100, 100 kg N/ha, in early spring on the whole surface; (4) N-50+50, 50 kg/ha in early spring + 50 kg N/ha 5 weeks later, on the whole surface; (5) N-50(herb), 50 kg N/ha of the herbicides strips only, in early spring. In Babtai only the first four treatments were compared. Ammonium nitrate was used as N fertiliser. Leaf N content increased as a result of fertilisation, reaching the highest values in N-100 and N-50+50 treatments, though in Babtai the differences were not significant and leaf N values were unusually low. A significant effect of N fertilisation on tree size expressed as TCSA after 6 years (in autumn 1999) was found in Babtai only. 'gampion' trees in Wilanow and Przybroda started to bear fruit in the 2(nd) year (1995) while 'Sawa' in Babtai gave the first fruit in 3(rd) year (1996). Significant yield increase resulting from fertilisation was noted in Babtai in the years 1996-1998, in Przybroda in 1997 and in Wilanow in the last year (1999) only. Cumulative yield was higher from fertilised trees only in Przybroda and Babtai. Increase in fruit size as a result of fertilisation was noted only in Przybroda in 1995 and 1998 and in Babtai in 1996 and 1997.