Three tobacco varieties were grown over a three-year period under three nitrogen fertilization treatments in order to establish any relationships among fertilizer levels, nicotine, and nitrosonornicotine (NNN) levels of the cured tobacco leaves. Generally, we found that higher levels of nitrogen fertilization led to higher levels of alkaloids and NNN. Attempts at blocking the nitrosation of alkaloids in a pre-harvest, field-study were not successful. Based on a converter tobacco study, nornicotine was a more efficient precursor of NNN than nicotine. Compared to normal flue-cured tobacco, air-dried bright tobacco had highly reduced NNN levels.

(Full article published with kind permission from "Tobacco International")