Abstract:Exponential nutrient delivery can bring about a steady state of nutrition in the plant and improve nutrient uptake，and hence accelerate seedling growth. An exponential fertilization trial was conducted with six N dose levels (applying a total of 0, 1000, 2000, 3000, 4000, 5000 mg/seedling in this experiment) of nitrogen to assess the effects on different nitrogen levels on growth and foliar nutrient status of Aquilaria malaccensis and Aquilaria sinensis seedlings with the different nitrogen levels. The objective of this study was to reveal the nitrogen demand and determine the optimal nitrogen amount for A. malaccensis and sinensis seedlings. It was indicated that ground diameter，height and biomass seedlings increased with the increase of nitrogen supply，up to 3000 mg/seedling，after then growth performance and biomass were unchanged and leaf area remarkable decreased. Critical level approach was used for identifying N，P and K deficiencies by means of foliar analysis in A. malaccensis seedlings，and the critical values of N，P，and K ?were 35.55, 1.75 and 17.99 g/kg，while their optimal concentrations ranged from 35.55 to 53.11, 1.75 to 2.73, 17.99 to 26.63 g/kg，respectively. And the critical values of N, P and K of A. sinensis were 37.78, 3.08 and 18.89 g/kg，while their optimal concentrations ranged from 37.78 to 58.56, 3.08 to 4.44, 18.89 to 29.28g/kg. Based on these data, it could be inferred that 3000 mg/seedling would be the optimal nitrogen amount for A. malaccensis and sinensis seedlings.