Effects of harvesting time on yield and quality of 6 upper leaves of flue-cured tobacco in southern Hunan tobacco-growing area.

To investigate the optimal harvest time for 6 upper leaves of flue-cured tobacco in southern Hunan tobacco-growing area, the effects of different times (conventional harvest time and 4, S, 12, 16 days after the conventional harvest time) for harvesting the 6 leaves at a time on the economic traits and sensory quality of tobacco leaves were studied. The results showed that the SPAD value, sugar-nicotine ratio and nitrogen-nicotine ratio of tobacco leaves decreased as the harvest time of upper tobacco leaves was delayed. Compared with tobacco leaves harvested at conventional harvest time, the maturity as well as the maturity characteristics and appearance quality could be improved by delaying harvest time properly. The output value and sensory quality of tobacco leaves increased first and then decreased when harvest time was delayed. When harvest time was delayed for 4 days, the output value of the harvested leaves was the highest; while the sensory quality was the highest when delayed for 6-8 days. In consideration of tobacco leaf quality, economic benefits and requirements for cigarette raw material, regression analysis indicated that it was appropriate to harvest 6 upper leaves at a time on the 7th day after the conventional harvest time. [ABSTRACT FROM AUTHOR]