Field studies were conducted at the Central Crops Research Station, Clayton. NC. during 1977 and 1978 to determine whether prespecified leaf chemistries could be achieved through cultural manipulation. The flue-cured variety, NC 2326, was grown under five treatments, lrrigated (IRR), Rainfed (RAIN), Leached (LEACH), Stressed (STRESS), and in 1978 only, Irrigated plus 2X-Nitrogen (IRR 2X-N). The IRR treatment was fertilized and cultured normally; soil moisture was maintained above 15% available water by irrigation. The RAIN treatment received normal N fertility and the levels of nicotine and reducing sugars were allowed to be determined by the response to rainfall. The LEACH treatment was fertilized normally, soil moisture was maintained above 30% available water by irrigation, and residual N was leached from the root zone at about topping time to induce an early transition to starch accumulation. In the STRESS treatment, N fertility was increased by 25% and transparent plastic shelters were erected to impose an 18-day moisture stress beginning at Crop Day 42 (38-day moisture stress beginning at Crop Day 49 in 1978) In order to prolong N uptake and metabolism and delay starch accumulation. In 1978, a treatment (IRR 2X-N) was added in which N fertility was Increased two-fold (relative to IRR) and soil moisture was maintained above 15% available water by irrigation. These treatments were successful both years in moving nicotine levels in the desired directions relative to the IRR treatment. In 1976, the alkaloid concentrations in the IRR 2X-N and STRESS tobaccos were significantly higher, and that in the LEACH tobacco was lower, than in the IRR tobacco. However, judicious irrigation in 1977 did not overcome the deleterious effects of the hot, dry growing season. The nicotine levels of all treatments were higher than the projected levels but, again, the nicotine level in the STRESS treatment was increased and in the LEACH treatment was decreased significantly relative to the IRR treatment. Sugar levels were lower in all treatments than had been expected. The anticipated changes were, however, in the desired directions in all cases. Thus it appears that sugar levels are much less amenable to manipulation than are nicotine levels. Yields of the various treatments generally were not significantly different. Usability of the tobaccos was decreased in response to higher N fertility and/or low soil moisture. Smoke evaluation of the 1976 tobaccos by a trained panel indicated that only the IRR 2X-N tobacco was unacceptable. These results suggest that it is possible to manipulate leaf chemistries but only within limits that are relative to the IRR treatment whose actual chemistry levels will be determined by the season.

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