Abstract:

To clarify the suitable maturity for one-time plucking of six upper tobacco leaves, ‘Yunyan 87’ was used as material, and three treatments of low maturity (M₁), medium maturity (M₂) and high maturity (M₃) were designed to carry out the harvesting and curing experiments of different maturity of upper tobacco leaves in Guiyang tobacco area of Hunan, and the fuzzy evaluation method was used to comprehensively evaluate the test results. The results showed that as the harvest maturity of middle tobacco leaves increased, the SPAD value of fresh tobacco and proportion of greenish tobacco leaves decreased, and the proportion of variegated tobacco increased; the maturity of tobacco leaves increased, the structure became loose, and the oil content increased; the single leaf weight of tobacco, thickness of leaf, weight unit leaf area and balance water ratio decreased; the contents of total sugar, reducing sugar, potassium and starch decreased, the contents of nicotine increased, and the availability of chemical components increased; tobacco yield and output value decreased. Compared with M₁ and M₃, index of appearance quality of M₂ treatment was 6.18% and -2.13% higher, physical properties index was 2.35% and 5.30% higher, availability index of chemical components was 30.88% and 4.55% higher, total score of smoking quality was 10.12% and 0.50% higher, the economic properties index was 8.96% and 12.97% higher, index of tobacco quality was 12.53% and 1.16% higher, and the comprehensive economic effect index was 10.11% and 6.98% higher. On the whole, M₂ was the most suitable ripeness for the 6 upper tobacco leaves; and the suitable harvest maturity of ‘Yunyan 87’ of upper leaves in Guiyang tobacco area of Hunan required that leaf surface turned yellow by 50%-80%, main vein became white by 50%-80%, branch vein became white by 30%-50%, part of the hair fell off, and there were more mature spots. When the SPAD value of fresh tobacco was 20.44-30.79, it could be used as a reference for guiding the appropriate harvest maturity of upper tobacco leaves of paddy- tobacco of ‘Yunyan 87’.

Key words: paddy-tobacco, upper flue-cured tobacco leaves, harvest maturity, quality of tobacco leaf, fuzzy comprehensive evaluation