Abstract:

To clarify the suitable harvest maturity of upper tobacco leaves in Ningxiang, ‘Yunyan 87’ was used to design three treatments of low maturity (M1), medium maturity (M2) and high maturity (M3), the effects of different harvest maturity on the physical characteristics of tobacco leaves were studied, the fuzzy evaluation method was used to comprehensively evaluate the test results, and the effects of harvest maturity, leaf position and their interaction on physical characteristics of tobacco leaves were studied by η² value analysis. The results showed that with the delay of the harvest time of upper leaves, the stem ratio of upper leaves decreased, while the leaf thickness increased. Compared with those of M1 and M3, the single leaf weight of M2 was 7.64% and 12.79% higher, the leaf thickness was 11.70% and -14.37% higher, the stem ratio was -4.54 and 1.33 percentage points higher, the equilibrium moisture content was 0.14 and 2.86 percentage points higher, the leaf specific weight was 14.59% and 39.81% higher, and the physical characteristic index was 7.31% and 7.01% higher, respectively. The effect of harvest time on the physical characteristics of upper tobacco leaves was 35.04%, and the effect of leaf position was 29.98%. The interaction effect of harvest time and leaf position was 34.98%. The effect of harvest maturity on physical characteristics was leaf specific weight> leaf thickness> stem ratio> equilibrium moisture content> single leaf weight. The leaf appearance characteristics on the 13th leaf position for suitable harvest maturity were as follows, the leaf surface turned yellow by 70%-80%, most of the midrib fell off, the leaf surface was shiny, wrinkled, and little sticky feeling. The main vein turned white by 4/5, and the branch vein turned white by 1/2. The leaf margin was curled and wrinkled, the leaf tip showed a downward hook, and the mature spots appeared on leaves.

Key words: upper tobacco leaves, harvest maturity, physical characteristics, fuzzy evaluation, effect analysis