Effects of sowing date on tobacco yield and quality

Six high quality varieties (lines) of tobacco were sown at different dates to explore suitable times for seeding and transplanting in Shaoguan tobacco fields. Chemical quality of the flue-cured tobacco was comprehensively determined using quality grading (grade C3F) assessment. Results showed that yield and quality of flue-cured tobacco were significantly influenced by sowing time. Tobacco economic value was determined from yield amount. Appropriate sowing date delay improved yield and economic value of flue-cured tobacco. However, yields heavily dropped due to too late sowing date, and the proportion of me-dium-high grade tobacco leaves after baking declined along with economic value. Chemical components such as nicotine, total nitrogen, starch and potassium were influenced by different sowing dates. Nicotine, total nitrogen (TN) and potassium (K₂O) of C3F leaves decreased under delayed sowing dates. However, starch increased significantly while flue-cured tobacco leaf quality deteriorated. Changes in the ratios of total nitrogen to nicotine (TN/nicotine), reducing sugar to nicotine (RS/nicotine) and potas-sium to chlorine (K₂O/Cl^?) under different sowing dates were mainly driven by differences in crop variety. Total scores of C3F leaves of “Yunyan 100”, “NX208” and “K326” tobacco varieties were relatively high for the three different sowing dates. This suggested that the qualities of three varieties of flue-cured tobacco were better than other varieties. Appropriate sowing dates en-hanced the chemical composition of tobacco leaves, which in turn benefited tobacco yield formation and quality grade. The results suggested that most suitable sowing date of tobacco in Shaoguan tobacco fields was Dec. 1 to Dec. 10. Similarly, the most suit-able transplanting period was Feb. 25 to Mar. 5.