Effects of Exponential Nitrogen Nutrition on Growth and Quality of Eucalyptus Seedlings

An exponential fertilization trail was conducted with five levels(0,50,100,150,200 mg·seedling-1) of nitrogen fertilizer to assess the effects of different levels on growth,leaf chlorophyll content and quality index of Eucalyptus urophylla×E.grandis clone DH32-29 nursery plants.The results showed that the mean height,ground diameter,biomass,chlorophyll content and quality index of these nitrogen fertilizer levels were 260.7%,128.7%,554.8%,129.9%,471.2% more than those with no fertilizer respectively.Height,ground diameter,biomass,chlorophyll content and quality index of E.urophylla×E.grandis plants increased at first with the increase of nitrogen supply,but then decreased markedly.The tallest plants were obtained with 50 mg·seedling-1 of nitrogen and the maximum chlorophyll content with 150 mg·seedling-1 of nitrogen.When the nitrogen level reached 100 mg·seedling-1,the ground diameter,biomass and quality index were maximum.The treatment with no fertilizer had the biggest root-shoot ratio,but other indexes were all at their minimum values.It was concluded that 100 mg·seedling-1 nitrogen would be the optimal level for production of quality nursery plants of the clone E.urophylla×E.grandis DH32-29.