Effects of NO3- -N/NH4+ -N ratios on Chardonnay grape seedling growth and nitrogen nutrition.

A sand culture experiment was conducted to determine the effect of different nitrogen supply forms on growth and nitrogen nutrition of Chardonnay grape seedling.Five NO-3-N/NH+4-N ratios were set up as 100/0,70/30,50/50,30/70, and 0/100 with total nitrogen being equal amount.The results indicated that Chardonnay grape seedling fertilized with NO-3-N/NH+4-N ratios for 70/30 had the highest biomass and root nitrogen absorption(70.89%);While Chardonnay grape seedling had the lowest biomass when fertilized with ammonium as the sole nitrogen source.The Chardonnay grape seedling fertilized with NO-3-N/NH+4-N ratios for 100/0 had the highest amount of nitrogen concentration and total N in leaf,while Chardonnay grape seedling fertilized with NO-3-N/NH+4-N ratios for 0/100 had the lowest,which were 61.8% and 19.46% of fertilized with NO-3-N/NH+4-N ratios for 100/0,respectively.The concentration of NH+4-N in root significantly correlated to the nutrient solution(r=0.9805),and the concentration of NH+4-N in root increased significantly when the proportion of ammonium nitrogen was higher than 30%.Leaf nitrate reductase activity was the highest when fertilized with NO-3-N/NH+4-N ratios for 70/30.The leaf nitrate reductase activity was impaired significantly when the proportion of ammonium nitrogen was higher than 30%,but the root nitrate reductase activity was not influenced.The experiment proved that NO-3-N/NH+4-N ratios for 70/30 was appropriate for the Chardonnay grape seedling,and a lower proportion of the NO-3-N/NH+4-N ratios increased the concentration of NH+4 in Chardonnay grape seedling organs,consequently inhibited nitrogen absorption and the biomass accumulation.