FERTIGATION IN YOUNG APPLE ORCHARDS BY USING DIFFERENT FORMS OF NITROGEN

Nitrogen supply by both N-forms was carried out with the same fertilizers and timing during the 3rd and 4th season, providing 20 g N/tree/year in the 3rd year but 30 g N/tree/year in the 4th year after planting as follows:

1. Check (control): ammonium-nitrate was spread on the soil strip + drip irrigation.
2. Fertigation using special fertilizers of NH₄- and NO₃- forms of nitrogen and periodically divided during the season i.e. high rate of NH₄-N in the first, but high rate of NO₃-N in the second half of the season.
3. Fertigation by similar fertilizers providing nearly the same ratio between NH₄-and NO₃-N, during the whole season.

Trunk increment (TCSA, cm²) and specific amount of shoots were incereased by treatment 2 in trees of cultivars possessing relatively low vigour (like Jonathan, Idared), but were not affected in any other cases. The method of nitrogen supply, however, proved to be more important: trees fertigated (treatments 2 and 3, resp.) produced a higher crop than those in check plots. Nevertheless, the productivity of trees in plots of fertigation treatments was dependent on cultivars, too.

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