Abstract: To investigate the growth response of broad-leaved trees to amino acid organic nitrogen fertilization, the effects of different N rates(12, 24 and 48 mg·seedling^-1) and different forms of nitrogen(organic nitrogen and inorganic nitrogen) fertilization on the growth of Populus simonii×P. nigra seedings were studied using the sowing seedlings. The regardless of inorganic nitrogen(ammonium nitrate) or organic nitrogen(arginine), the seedling height, diameter and total biomass of P. simonii×P. nigra seedling increased with the increase of nitrogen application rate, but the nitrogen use efficiency of seedlings treated with medium N fertilizer was the highest. The growth performance of seedlings treated with inorganic nitrogen(ammonium nitrate) and organic nitrogen(arginine) showed no significant difference under the same nitrogen application rates. The application of organic nitrogen could achieve the same effect of promoting seedling growth as the application of inorganic nitrogen. Different amino acids and their combination fertilizers have significant effects on the growth of P. simonii×P. nigra seedlings. Under the condition of single amino acid fertilization, arginine was the best one to promote seedling growth, followed by glutamic acid and glycine. Under the combination of amino acid fertilizers, the combination of arginine fertilization seedlings grow well, the combination of glycine fertilization seedlings grow poor. Different amino acid fertilization treatments had no significant effect on the nitrogen content of different organs of P. simonii×P. nigra seedlings.

Key words: Populus simonii×, Populus nigra, seeding morphology, amino acid-N, biomass, nitrogen concentration