Rapid Monitoring Maturity of Flue-cured Tobacco with Spectrum Vegetation Index of Fresh Leaves

In order to rapidly and quantitatively monitor the maturity of flue-cured tobacco,the spectral analysis of middle and upper tobacco leaves under two fertilizer application modes was conducted,and the relationships of chlorophyll content,carotene content and the ratio of carotene to chlorophyll in fresh leaves at different maturity stages with first derivative spectra and vegetation index were investigated. The results showed that with the increase of maturity,the spectral reflectance of fresh leaves increased gradually in visible bands, while decreased gradually in near-infrared bands. The wavelengths of 560,660,710 and 1100 nm could be used as the sensitive bands for monitoring the maturity of fresh leaves. There existed the highest correlation coefficient (r=0.984) between ratio vegetation index (RVI)(1100,660) and chlorophyll content,and the developed model could well monitor the maturity of fresh leaves(R²=0.9029). When the value of RVI(1100, 660) ranged from 2.81 to 3.47,middle leaves were mature;when it was lower than 2.72,middle leaves became over mature;when it was higher than 3.75,middle leaves were unripe.