Effect Of Different Nitrogen Levels On Hyperspectral Characteristic And Physiological-biochemical Indices For Tobacco

Nitrogen plays an important role in the growth, yield and quality of tobacco, andtobacco is very sensitive to nitrogen nutrition. Therefore, reasonable nitrogen fertilizer isnecessary during the growth stage,and nitrogen fertilizer reasonably correct application has apivotal role on tobacco. It is necessary to adopt a non-destructive, quick, convenient technique tomonitor crop water status by employing hyperspectral remote sensing. In this work, terrestrialremote sensing platform was employed to research canopy physiological-biochemical indices andhyperspectral reflectance characteristics under different soil nitrogen levels, spectral reflectioncharacteristic of flue-cured tobacco crown height, flue-cured tobacco physiological andbiochemical indexes were analyzed with the crown layer of the corresponding spectral parameters,using stepwise regression method to estimate model is established for a variety of physiologicaland biochemical indicators, and Samples were randomly selected in order to evaluate the predictvalue and the test value, results showed that the model has a good estimation and prediction ability.Main research conclusion is as follows:1.The hyperspectral reflectance curves of tobacco canopy and leaf both have the commonreflection characteristics of plants, further, the reflectivity of tobacco canopy under different watertreatments has significant difference; In the visible light area, the height of canopy spectralreflectance is mainly influenced by the change of chlorophyll content,and in the near-infrared lightarea the height of canopy spectral reflectance is mainly affected by canopy structure and biomass.During the whole growth period, within the scope of visible light canopy reflectance of the canopyreflectance change rule expression is increased with the increase of nitrogen content, canopyspectral reflectance are: N4> N3> N2> N1. In each growth period the rule expression is:vigorous growth stage> lower leaf of mature device stage> middle leaf of mature device stage>upper leaf of mature device stage> root elongation stage. Canopy of red edge of first orderdifferential spectrum has a "twin peaks" phenomenon, the canopy red edge of flue-cured tobaccounder different nitrogen has a "twin peaks" phenomenon, and the most obvious "double peak"phenomenon is in the vigorous growth stage; With the stage of Flue-cured tobacco under differentnitrogen levels growth, red edge parameters are decrease gradually, and the blue edge can be seenobviously shift phenomenon.2. The influence of different nitrogen levels on flue-cured tobacco physiological and biochemicalindexes are obvious. During the reproductive period, contents of chlorophyll a, chlorophyll b, totalchlorophyll and carotenoid content, leaf fresh weight, leaf dry weight, leaf water content, roundfresh weight, ground dry weight and plant water content all become higher with the increase of nitrogen level. Reducing sugar, total sugar and other carbohydrates are mainly characterizedincreased with the increase of nitrogen level, and each nitrogen treatment during the reproductiveperiod all showed increasing trend. The variations of total nitrogen content under differentnitrogen levels are increased with the increase of nitrogen level, but in each growth period thechange trend of total nitrogen content and the change trend of reducing sugar and total sugar,performance are different and it shows for vigorous growth stage> root elongation stage> matureperiod. Along with the advancement of growth period, the content of nicotine have been graduallyincreased, which showed that the nitrogen can effectively regulate the nicotine content of tobacco;nicotine content in tobacco of different nitrogen levels shows for N4> N3> N2> N1, differentnitrogen treatment zero nicotine content is significantly higher than the N1nitrogen treatment.3. Through the observation of the canopy reflectance during the tobacco grown in open fieldobservation, it was found that the most relevant characteristic variables of the contents ofchlorophyll a, chlorophyll b, total carotenoid content, chlorophyll, leaf fresh weight and leaf dryweight, leaf water content, round fresh weight, ground dry weight and plant water content are theyellow edge amplitude and the yellow-edge position; the most relevant characteristic variables ofChlorophyll a, Chlorophyll b, total Chlorophyll content, carotenoid are the ratio of red edge areaand blue edge area and the normalized ratio of red edge area and blue edge area. The most relevantcharacteristic variables of leaf fresh weight and leaf dry weight, leaf water content, round freshweight, ground dry weight and plant water content are the ratio of green peak and red vale and thenormalized ratio of green peak and red vale. The most relevant characteristic variables of reducingsugar, total sugar and total nitrogen are red edge amplitude and the blue edge position; the mostrelevant characteristic variables of reducing sugar, total nitrogen and nicotine are the yellow edgeposition and yellow edge amplitude; the most relevant characteristic variables of reducing sugar,total sugar, total nitrogen are the red edge area.4. Use physiological and biochemical indices of tobacco canopy as the dependent variable,spectral parameters of19species of leaf as the independent variables, the stepwise regressionprediction model were established. The significance test results of the model’s complexdetermination coefficient and independent variable regression coefficient via the random samplesshowed that the the data reached significant. The results further proved that spectral parameterscan be used to estimate the physiological and biochemical indices of tobacco. A new method willbe supplied to the nitrogen management for the tobacco farmland, which can predict the tobaccogrowth condition and quality under different nitrogen levels, soil water contention easily andfastly.