Effect of Potassium Source and Rate on Yield, Quality, and Tobacco-Specific Nitrosamines in Dark and Burley Tobacco

Field trials were conducted in Princeton, Murray, and Lexington, KY in 2016–2018 to determine response of dark and burley tobacco to potassium source (potassium sulfate or potassium chloride) and potassium rate (0, 93, 186, or 279 kg K ha−1). Field sites that showed higher potential for potassium yield response were selected based on low soil test potassium levels from soil samples collected in early spring each year. All potassium applications were made between 1 and 10 days before transplanting. Significant yield responses to potassium were seen in 5 of 12 trials at sites that had initial soil test potassium levels of ≤150 kg K ha−1. Although cured leaf chloride levels were >1% on average where potassium chloride was used, negative effects on cured leaf moisture were only seen in 1 of 12 trials, and negative effects on quality grade index were not seen in any trial. The most consistent effect of potassium chloride application seen in this research was a 28% reduction in average total tobacco-specific nitrosamines (TSNA) compared to potassium sulfate application. These results showing lower TSNA from potassium chloride applications, along with minimal effects on moisture and quality grade index, may cause the tobacco industry to reconsider the long-standing preference for potassium sulfate as the potassium source for tobacco production.