Hyperspectral Characteristics And Estimating Model Of Leaf Quality Content In Tobacco Based On Potassium And Maturity Treatments

Hyperspectral remote sensing can obtain vegetation canopy information quickly and nondestructively,which is an important technology for monitoring crop growth in real time.This technology was used to monitor the field growth of tobacco in this study.Different potassium and maturity treatments were used in the experiment which was conducted in Guiyang county,Chenzhou city,Hunan province.ASD FIEL DSPEC 2500 field portable spectrometer was used to obtain the hyperspectral data from single leaf and canopy scales.The spectral parameters of tobacco physiological and biochemical indicators were screened to establish the quality index estimation model and evaluate the model in order to provides theoretical basis and application basis for quantitative remote sensing of physiological and biochemical indicators of tobacco leaves.The results of this study were as follows:?1?The near infrared high reflection region of canopy spectrum can be used to monitor the potassium nutrient status of tobacco in field.The hyperspectral reflectance curves of different potassium treatments were different due to different varieties and different growth periods.In the near infrared plateau area?750-1350nm?,the general rule of spectral reflectance curves of three growth periods was that the spectral reflectance curves of tobacco treated with appropriate amount of potassium were larger than those of tobacco treated with high amount of potassium,and less than those of tobacco treated with low amount of potassium.However,there were no significant differences in tobacco spectral reflection curves between K3 and K4 treated with excessive potassium,and between K0 and K1treated with low potassium.The suitable,high and low potassium conditions of tobacco plants in field could be monitored by using near infrared plateau.?2?There was a strong correlation between the canopy spectral reflectance and the NPK contents of tobacco treated with different potassium,red shift of characteristic spectral band appeared in different growth periods with the increase of potassium application.The spectral reflection bands of the canopy original characteristic of tobacco NPK contents are mainly in the near ultraviolet region 350-364 nm,visible region 382-392 nm,green region 555 nm,red regions 623-740 nm,near infrared region 975-1350 nm,middle infrared region 1524-1800nm,2000-2399 nm.The first order differential characteristic spectrum reflection band mainly concentrated in the near ultraviolet region of 358-359 nm,visible region 408 nm,blue region 433-444 nm,blue-green region 460-483 nm,green region 517-557 nm,yellow region 570-584 nm,orange region 591 nm,red region 674-772 nm,near infrared region801-1493 nm,mid infrared regions 1503-1800 nm and 2000-2348 nm.?3?The precision sensitive growth stage of tobacco NPK content estimation model was the topping period,and the precision of sub-processing model was high,and the model established by the first order differential characteristic band showed the best estimation effect.The estimation models of tobacco NPK contents at topping period were as follows:The most sensitive models for N content:y=3.897-1.78*X_DVI+0.047*X_CRI2?R²=0.766?by K0,y=3.595-228.472*X_526nm?R²=0.856?by K1,y=3.418-110.868*X_698nm?R²=0.882?by K2,y=3.171-3.947*X_714nm?R²=0.628?by K3,y=1.512-610.118*X_964nm?R²=0.617?by K4.The most sensitive models for P contenty=0.34-11.657*X_707nm?R²=0.807?by K0,y=0.284-8.668*X_712nm?R²=0.708?by K1,y=0.267-80.312*X_1529nm?R²=0.810?by K2,y=0.269-0.221*X_978nm?R²=0.924?by K3,y=0.193-56.165*X_1503nm?R²=0.874?by K4.The most sensitive models of K content:y=0.644+3.077*X_998nm?R²=0.724?by K0,y=2.153+5.402*X_1526nm?R²=0.796?by K1,y=1.729+3.441*X_975nm?R²=0.898?by K2,y=2.708+2.802*X_1138nm?R²=0.877?by K3,y=2.368+173.539*X_711nmby K4.?4?Among the tobacco varieties,plant positions and maturity treatments,different maturity treatments had the largest effect on the spectral reflection curve of tobacco single leaf.The hyperspectral characteristics of tobacco leaf location were as follows:When the treatments were unripe and immature,middle leaves>upper leaves>lower leaves.When the treatments were ripe and overripe:upper leaves>middle leaves>lower leaves.In addition,480-670 nm and 750-1350 nm had better“differentiation effect”for tobacco leaves with different maturity.?5?Nicotine and potassium content were the sensitive indexes of different maturity treatments.About the first order differential spectrum bands of three varieties,the sensitive bands were 536 nm,736 nm and 1001 nm for variety Yunyan 87,Xiangyan 5 and K326respectively.Chlorophyll and carotenoid contents were the sensitive indexes for different maturity treatment effect among the three leaf positions.The characteristic variable is the location variable Dy,vegetation index NDNI and vegetation index Lic2.?6?The best color characteristic parameters to identify the maturity grade of the middle and upper leaves of flue-cured tobacco were NRI and NDIg,R²>0.95.