The flue-cured variety NC 2326 was grown under 36 management systems comprised of all combinations of two soil types, subsoiled or not-subsoiled, three rates of nitrogen fertilization, and three moisture regimes. Coupled with the dry season of 1980, the cured tobaccos differed widely in quality. Biochemical observations during the growth of these plants support the conclusion that the key to flue-cured quality is the timing of the metabolic transition from nitrate reduction to starch accumulation. When fertilization has been precise and soil moisture adequate for the timely uptake and reduction of nitrogen, this transition occurs about simultaneously with flowering; leaves fill out, ripen properly, and cure easily. The cured tobaccos have good physical characteristics and are compositionally balanced with respect to sugars and nicotine (ratio, S/N = 6-8). Over-fertilization or/and drought delays the transition allowing for more nicotine to be synthesized and, because of rapid shortening daylengths, less starch accumulates subsequently; such tobaccos are chemically imbalanced (S/N < 5). Conversely, underfertilization (or/and leaching) triggers this metabolic shift prematurely thereby restricting nicotine production and permitting much starch to accumulate; these tobaccos too are imbalanced chemically (S/N < 9).

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