Effects of different N sources on growth, nutrient uptake and ionic balance of Larlix gmelini seedlings

The effect of different sources and levels of N on dry matter production, nutrient uptake and ionic balance of Larlix gmelini was studied. The results showed that the growth of the plants fertilized with ammonium was not as good as the control treatment. The growth of the plants fertilized with ammonium nitrate did not differ significantly from that in control or nitrate treatment, but was better than that in the ammonium treatment. Total cation concentrations in shoots varied little with N level in the ammonium and ammonium nitrate treatments, while those in the shoot increased with N level in the nitrate treatment. The treatments had little effect on the anion concentrations in the shoot. In the roots, the concentrations of both cations and anions changed little except for SO42- and Ca2+. There existed a higher carboxylate production in the plants fertilized with nitrate. The ratio between the production of carboxylate and the production of organic N D(C-A)/DNorg was constant with N supply in the plants receiving nitrate, but obviously declined with N supply for ammonium-fed plants. D (C-A)/DNorg values were intermediate between those of the nitrate and the ammonium-fed plants as for the mixed N source.