The effect of lower leaf removal and nitrogen application to flue-cured tobacco yield, crop throw, and economic return
Research was conducted in North Carolina to quantify the impact of the number of lower stalk leaves removed at topping and the subsequent application of four rates of liquid nitrogen. At topping, either 0, 4, or 8 leaves were removed from the lower stalk positions of flue-cured tobacco. Immediately following leaf removal, nitrogen (28 % liquid Urea-Ammonium-Nitrate) was band applied adjacent to plants at one of four rates: 0, 5.6, 11.2, or 16.9 kg N/ha in a solution volume of 187 L/ha. Leaf density, SPAD measurements, and tissue samples were collected over a five week period following treatment application to quantify changes in leaf morphology and nitrogen content. Following the conclusion of the growing season, leaf yield, quality, value, crop throw, and economic value were determined. Preliminary results demonstrate reductions in crop yield of 448 and 896 kg/ha when four and eight leaves were removed, respectively. In addition, crop value declined by $1,697 to 2,989/ha in the same leaf removal scenarios. Nitrogen application did not improve leaf yield enough to offset the financial losses incurred by leaf removal, nor did it appear to have significantly influenced leaf morphology. Despite dramatic yield and economic losses, the goal of reducing priming and lug grades was achieved in both leaf removal number treatments, with the four and eight leaf removal systems producing 19 and 3 % X grades, respectively, compared to 33 % X grades where leaf removal did not occur. Despite such unfavorable results in 2016, it is hypothesized that poor growing conditions (excessive heat and low precipitation) experienced after leaf removal and nitrogen application prohibited plants from recovering at least a portion of yield and value. Research will continue in the 2017 growing season.