Nutrient Uptake of Eucalyptus urophylla×E. grandis Seedlings in Response to Different Nitrogen Exponential Regimes

An exponential fertilization trail was conducted with five dose levels(applying a total of 0,50,100,150,200 mg) of nitrogen to assess the effects on different nitrogen levels on the growth,quality and nutrient status of Eucalyptus urophylla×E.grandis seedlings.The objective of this study was to reveal the nitrogen demand and determine the optimal nitrogen amount for E.urophylla×E.grandis seedlings.It was indicated that the height,ground diameter,biomass,SPAD value and quality index of seedlings increased with the increase of N supply,up to 100 mg,after then the ground diameter,biomass and quality index were unchanged,but the height and SPAD value remarkably decreased.The biomass of seedling was found positively significant correlation with the height,ground diameter,QI and SPAD value.Critical level approach was used for identifying N,P and K deficiencies of E.urophylla×E.grandis seedlings,and the critical values of N,P and K was 26.6,3.8 and 16.5 g/kg,while their optimal concentrations was ranged from 26.6 to 38.5,3.8 to 5.3,16.5 to 21.4 g/kg,respectively.In conclusion,100 mg would be the optimal nitrogen amount for E.urophylla×E.grandis seedlings.