Evaluation of nitrogen sources and rates on yield and quality of modern flue -cured tobacco cultivars.

摘要

Nitrogen has a more pronounced effect on the growth and quality of tobacco than any other essential element even though it is not taken up in the highest quantity. Soil nitrogen regime affects plant development more than any other nutrient from seedling stage through the time of final harvest. The role of nitrogen in the development and quality of tobacco is of major importance with respect to time of absorption, form of nitrogen absorbed, rate of application, concentration in the leaf and numerous other aspects. Soil nitrogen must be sufficient during early and mid-season growth stages to ensure vigorous, but not excessive growth, and it should be nearly depleted by flowering for the plant to mature and ripen properly insuring a quality leaf. In general, as total N in the plant increases, above the amount required for maximum growth, quality of flue-cured tobacco tends to decrease.;Field studies were conducted at two locations in 2004, 2005, and 2006 to evaluate sources and rates of nitrogen for the production of flue-cured tobacco. Calcium nitrate, ammonium nitrate, and urea ammonium nitrate (UAN) were evaluated. Sources were chosen based on previous research that provided inconsistent results when using ammonium nitrate and UAN for flue-cured production. The rates of nitrogen evaluated were 0, 22, 45, 67, and 90 kg N/ha in all years with 112 and 134 kg N/ha rates added in 2005 and 2006. All treatments received 134 kg of potassium per hectare within seven days of transplanting. Nitrogen application was applied twice with one-half of the total applied within the first week after transplanting and the balance applied approximately 14 days later. Nitrogen source did not affect yield, grade index, value, total alkaloids, total reducing sugars, or leaf color. Yield increased at all locations as nitrogen rate increased up to 67 kg/ha. Yield decreased at nitrogen rate above 90 kg/ha. Dollars per hectare followed the same trends as yield since grade index was not affected by nitrogen rate. Total alkaloids increased as nitrogen rate increased up to 112 kg N/ha. Inversely, total reducing sugars decreased as nitrogen rate increased. Leaf color in the field increased as nitrogen rate increased. Soil nitrate levels increased at the highest level of nitrogen tested at both topping and final harvest sampling times.