Influence of nitrogen fertilisation on biometric features of two-year-old seedlings of pedunculate oak subjected for root pruning

Pruning is one of the important cultural treatments that have potential to influence hardwood seedling morphology. The aim of the study was to compare the growth of pedunculate oak seedlings, performed pruning roots, in the second growing season, fertilised full and reduced dose of nitrogen.

A total of 24 experimental plots, each with an the area of 0.04 ha, were designated. The roots pruning were made at the end of February 2014 using root pruning machine EGEDAL. The fertilisation, for all seedlings, was performed using ammonium nitrate in an amount of 25 kg ha⁻¹ of nitrogen. The second fertilisation was performed only for variants 2 and 4. For these variants, urea was used in an amount of 25 kg ha⁻¹. At the end of the growing season, the root collar diameter and the height of seedlings were measured.

A dose of nitrogen affects the height of pruned seedlings. The effect of the full dose of nitrogen on the height of the pruned seedlings was a statistically significant (p ≤ 0.05). There was no statistical difference in the height of the seedlings without pruning, fertilised with different dose of nitrogen.

Analysis of root collar diameter showed the significant differences between the variants. The Tukey test, at the significance level of p ≤ 0.05, showed a significant impact on the root collar diameter of pruned seedlings but no proven effect of nitrogen fertilisation. To conclude, we found that it is reasonable to reduce the doses of nitrogen fertilisation to half of recommended amount (25 kg ha⁻¹) if the root system is not pruned during the second growth year. Seedlings that has received pruning should be fertilised using the recommended doses of nitrogen.