Dynamic kinetic characteristics of different forms of nitrogen absorbed by Larix olgensis seedling

Hydroponic experiments were carried out to study the kinetics of NH+4 and NO-3 uptake by root of Larix olgensis seedling. The results indicate that the uptake rates of NH+4 and NO-3 uptake are both decreased as the seedling growth, and NH+4 uptake is totally more efficient than NO-3. When both NH+4 and NO-3 are supplied, compatibility of seedling root with NH+4 and NO-3 in fast growing period would be influenced negatively, which leads to the decrease of uptake rates of both ions. However, when both NH+4 and NO-3 are supplied in early growth period, the uptake rates of the ions would be influenced negatively, or even NO-3 uptake would be promoted because of carriers of NO-3 stimulated by NH+4 input compared to single NO-3 as N source. It is concluded that NH+4 fertilization is recommended in Larix olgensis seedling cultivation throughout the whole growth period, which could improve the efficiency of N uptake, and both NH+4 and NO-3 as N source of fertilizers should be applied at the early growth period.