Growth Promotion and Changing Chemical Composition of Tobacco by Potassium Levels and Application Timing under Rainfed Condition

Potassium (K) enhances plants’ resistance to drought by regulating the opening and closing of stomata and triggering enzymatic activity under water-limiting conditions. This study investigates the effects of foliar application of potassium nitrate (KNO3) on rainfed tobacco (Nicotiana tabacum L.) plants concerning yield, quality grade index, gross income, number of seed pods per plant, seed yield per plant, reducing sugar, nicotine, and ammonia. The experiment was conducted with two different application frequencies (single or two applications) and four different doses (0, 2, 4, and 8 g/L) in a randomized complete block design with three replications. The increase in KNO3 dose resulted in an increase in all investigated parameters. However, significant increases were observed in the treatment parameters where KNO3 was applied twice compared to the treatment where KNO3 was applied once. Gross income in the treatments with 4 and 8 g/L doses of KNO3 were 20.11 and 20.55% higher, respectively, compared to the control. Additionally, the treatments with two applications showed a 14.60% increase in gross income compared to the single-application treatments. Nicotine and ammonia values in plants obtained from the third harvest exhibited an increase of 91.8 and 31.05%, respectively, compared to the first harvest. It can be determined from the study that KNO3 foliar application has a positive effect on the quality parameters of tobacco plants grown, especially in rainfall-dependent regions, and it was also determined that two applications of 4 g/L dose has more positive effects.