Abstract: Field experiments in southeast Tibet were conducted to study the effect of nitrogenous fertilizer supply and its forms on tobacco. The result indicateds that the yield, production value, and the contents of nicotine, potassium oxide and total nitrogen of the cured leaves were positively correlated to the amount of Napplication, and significantly and negatively correlated to the percentage of superior-medium class leaves of tobacco and contents of deoxidize sugar. The highest yield and best quality of tobacco were obtained by applying75kg Nper hectare. Inorganic nitrogenous fertilizer could significantly improve the yield and quality of tobacco, compared with organic nitrogenous fertilizer . Although there was no significant difference among ammonium N, nitrate Nand nitrate-ammonium Napplication,the effects of ammoniun N,nitrate N,and nitrate-ammoniun Napplication were significantly higher than that of urea application.The effect of ammoniun Napplication on tobacco yield and quality was better than that of nitrate Napplication,and the important reason was the great difference in the process of absorption and assimilation of ammoniun Nand nitrate N.

Key words: Tobacco, Nitrogen supply, Nitrogen forms, Yield, Quality, Tibet, nitrogen application level, litter decomposition, water treatment, desert grassland