The effect of chloride application rate to the yield, quality, and chemical constituents of flue-cured tobacco
Chloride (Cl-) application rates that exceed 33.6 kg/ha are generally discouraged in the production of flue-cured tobacco due to the negative effects the micronutrient can impart to yield, quality, and smoke flavor/aroma. Despite the negative effects associated with Cl- application, unintentional applications of the nutrient sometimes occur. To quantify the season long effects of Cl- application, research was conducted in North Carolina. In 2016, four application rates of Cl- (0, 33.6, 67.3, and 100.9 kg Cl-/ha) were evaluated in flue-cured tobacco fertilized with liquid 28 % urea-ammonium-nitrate. Tissue samples were collected from the fourth leaf below the apical meristem at five growth stages: two weeks after fertilizer application, at layby, two weeks after layby, at topping, and after curing. Leaf Cl- concentration increased with Cl- application rate, with the 67.3 and 100.9 kg rates typically being greater than the one percent threshold established by industry. In addition, cured leaf Cl- concentration was greater than one percent in all treatments where Cl- was applied. Despite high Cl- concentration, toxicity symptoms were not observed in either growing environment, indicating that visual symptoms of excessive Cl- cannot be solely relied upon to determine if excessive application of Cl- has occurred. Leaf yield, quality, and value were not affected by Cl- application; although, it is probable that smoke flavor and aroma would be negatively impacted in treatments receiving >67.3 kg Cl-/ha. The concentration of other nutrients (N, P, K, Mg, S, and NO3-) was generally not affected by Cl- application rate within each sampling interval. Research will continue in three additional North Carolina environments in 2017.