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The responses of two air-cured burley tobacco (Nicotiana tabacum L) cuItivars ro nitrogen fertilizer were evaluated in a field sxperiment, using
complelely randomized block design with factorial treatments in four replications, at Tirtash Tobacco Research Institute, Mazandaran. Burley 21
and burley 26 were the two air-cured cultivars used and zero, 60, 120 and 180 kg h-1 net nitrogen were the four levels of nitrogen applied. The results showed that each of the two cultivars used, was more efficient in either dry
matter production or improving the qualitative attributes. In burley 26 the higher leaf yield is associated with higher net assimilation rate and in burley 21
the higher price per unit of weight is associated with increased nicotine percentage. The income per hectar, as the resultant effects of these two
parameters. was significantly higher in burley 21. Application of nitrogen fertilizer at 60kgh-1 increased net assimilation rate, leaf yield and income per hectar, and at the rate of 180 kgh-1, increased nicotine percentage.