THE EFFECTS OF NITROGEN SOURCE AND CONCENTRATION ON THE GROWTH AND MINERAL COMPOSITION OF PRIVET

Nursery crops are fertilized with nitrogen (N) to enhance their growth and appearance, and crop responses to fertilization vary with form of N supplied and with plant species. This experiment, conducted in a greenhouse, examined privet (Ligustrum ibolium L.) growth and composition as affected by three N sources: 100% of the N as nitrate, 100% of the N as ammonium and a 50%–50% mixture of nitrate-N and ammonium-N. Nine different concentrations (in treatments incrementally ranging 0 to 300 mg N/L) of the three N regimes on privet growth and composition were studied in sand culture. After 240 days of treatment, total growth (mass or shoot extension) of privet did not differ among the three N sources. However, growth increased with increased N concentration with maximum growth occurring between 50 and 250 mg N/L. Although root mass did not vary among the N sources during the experiment, privet grown with ammonium nutrition had more blackened, discolored roots than plants grown with nitrate or mixed nutrition;...