CN110596048A - Method for quickly measuring potassium content in tobacco leaves by spectrum - Google Patents
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Abstract
The invention relates to a method for quickly measuring potassium content in tobacco leaves by spectrum, belonging to the technology of potassium nutrition diagnosis of the tobacco leaves, and the method is characterized in that a tobacco leaf potassium content estimation model is established in a functional form to fit the potassium content in the tobacco leaves, and a fitting model with the highest fitting degree is an equation y which is 423.3x and is established by taking spectral reflectance as an input variable2-258.7x +41.43, and-8.551 x with the first derivative of spectral reflectance as an input variable2+25.20x-11.92 and-388.0 x equation y established with the area of the blue edge of the tobacco lamina spectrum as the input variable2+33.09x + 6.114. The method uses a spectral diagnostic analysis technology to carry out nutrition diagnosis on the tobacco leaves, is used for establishing a spectral nutrition diagnosis model of the tobacco leaves, predicting the nutrition condition of tobacco leaf crops and guiding accurate fertilization of the tobacco leaf crops.
Description
Technical Field
The invention relates to a method for quickly measuring potassium content in tobacco leaves by spectrum, belonging to the technical field of potassium nutrition diagnosis of the tobacco leaves.
Background
The application amount of the agricultural fertilizer in China is increased from 4084 ten thousand tons in 1998 to 5859.41 ten thousand tons in 2017 year one by one, the average application amount of the fertilizer per mu is increased from 17.49 kilograms in 1998 to 23.48 kilograms in 2017 year, the total application amount of the agricultural fertilizer is increased by 43.5 percent in twenty years, the application amount per mu is increased by 34.25 percent, the total agricultural sowing area is increased by only 6.82 percent, and the imbalance of the increase is mainly caused by excessive application of the fertilizer by farmers for pursuing yield and not according to the fertilizer requirement rule of crops. The traditional fertilizing method not only causes the increase of agricultural production cost and the waste of production data, but also brings a series of environmental problems of reduced cultivated land quality, aggravation of soil acidification and salinization, eutrophication of rivers and lakes caused by nutrients lost to the environment, and the like. The essential point for solving the problem lies in accurately mastering the fertilizer requirement time, the fertilizer requirement amount and the like of each growth period of crops to carry out accurate fertilization on the crops.
Tobacco is one of the important economic crops in China, is widely cultivated in the regions of the south and north of China, and the soil environment has important influence on the growth and development and the yield and quality of the tobacco in tobacco production. The organic matter content is moderate, the soil rich in phosphorus, potassium and trace elements is an important condition for producing high-quality tobacco, if the organic matter content and the fertility in the soil are too low, the tobacco is weak in growth due to lack of nutrition in the growth process, plants are short and small, tobacco leaves are small and thin, and the yield and the quality are poor; if the soil fertility is too high, the produced tobacco leaves are thick and thick, the content of nitrogen-containing compounds such as protein and nicotine is increased, and the quality is poor. Therefore, the tobacco plant nutrition can be coordinated by accurate fertilization according to the soil fertility and the tobacco nutrition rule in the tobacco planting process, the fertilizer cost input is directly reduced, the fertilizer utilization rate is indirectly improved, the income of tobacco growers is increased, and a series of environmental problems caused by the traditional fertilization method are solved.
Nutrient diagnosis of crops is an important technical support for accurate fertilization. The crop nutrition diagnosis is a method for reasonably judging the growth condition of crops and the abundance condition of nutrients in crops by scientifically detecting and analyzing the nutrition condition of the crops, is a basic condition for scientifically fertilizing the crops, and is an important means for regulating the exchange process of nutrient substances such as nitrogen, phosphorus, potassium and the like and energy between the crops and soil. The plant nutrition diagnosis technology mainly goes through three stages of an empirical diagnosis stage, a chemical examination diagnosis stage and a physical method diagnosis stage. The traditional empirical diagnosis method has the advantages of simple and quick operation, but has the disadvantages of non-reproducibility, enough practical experience and high misjudgment rate. The chemical diagnosis method has the advantages of high accuracy of diagnosis results, high detection cost, complex detection operation, lag detection results and the fact that most detection work needs to destroy and sample, which becomes the main disadvantage of the chemical diagnosis method. Compared with the traditional empirical diagnosis and chemical diagnosis, the physical diagnosis avoids the defects of the former two diagnosis methods, can quickly, accurately, nondestructively and real-timely monitor the growth condition of the plant, and can obtain a diagnosis conclusion with high accuracy. The spectral diagnostic analysis technology is one of the important methods for physical diagnosis, and is widely applied to the fields of monitoring the growth condition and the nutritional state of crops and the like due to the characteristics of high detection speed, high accuracy, strong reproducibility, no destructiveness and the like.
Disclosure of Invention
The invention provides a method for quickly measuring potassium content in tobacco leaves by spectrum, aiming at the technical problems in the background technology.
The invention provides a method for quickly measuring potassium content in tobacco leaves by spectrum, which is characterized in that a tobacco leaf potassium content estimation model is established in a unitary quadratic function form to fit the potassium content in the tobacco leaves, wherein the fitting model with the highest potassium content fitting degree in the tobacco leaves is an equation y which is 423.3x and is established by taking spectral reflectivity as an input variable2-258.7x +41.43, and-8.551 x with the first derivative of spectral reflectance as an input variable2+25.20x-11.92 and-388.0 x equation y established with the area of the blue edge of the tobacco lamina spectrum as the input variable2+33.09x+6.114。
Further, the estimation model of the potassium content of the tobacco lamina is a one-dimensional quadratic equation y of 423.3x with the spectral reflectance as an input variable2-258.7x+41.43。
Further, the spectral reflectance is R526Which represents the spectral reflectance at the 526nm wavelength band.
Further, the 526nm wave band is green light.
Further, the first derivative of the spectral reflectivity is 100R'721Representing the first derivative of the spectral reflectance at the 721nm band.
Further, the 721nm wavelength band is red light.
Further, the tobacco lamina spectral blue edge area is 100 SDb.
The method of the invention establishes a regression equation of the tobacco leaf potassium content and the sensitive band spectrum in the form of an exponential function, a unitary linear function, a logarithmic function, a unitary quadratic function and a power function, and the regression equation is used as a tobacco leaf potassium content estimation model, and the result shows that the fitting degree of the regression equation established in the form of the unitary quadratic function to the tobacco potassium is highest.
The degree of fitting of the regression equation, the standard error and the standard deviation of the estimated value and the chemical analysis value of the fitting equation are used as the evaluation indexes of the precision and the dispersion of the estimation result of the fitting equation, and the variance is used for analyzing the difference between the chemical analysis value and the model estimated value and is used as the evaluation index of the accuracy of the estimated value; and respectively carrying out comprehensive evaluation on the accuracy, precision and dispersion of the estimation results of the tobacco leaf potassium content spectrum estimation model, and screening out the optimal estimation model for the tobacco leaf potassium content spectrum nutrition diagnosis.
Drawings
FIG. 1 shows the coefficient of correlation between the NPK content of tobacco leaves and the spectral reflectivity of each band.
FIG. 2 is a graph showing the correlation coefficient between the NPK content of tobacco leaves and the first derivative of the spectral reflectance of each band.
FIG. 3 is a schematic diagram showing the comparison of the estimated phosphorus content of tobacco lamina with the chemical analysis value for each model.
FIG. 4 is a schematic diagram showing the comparison of the estimated value of potassium content in tobacco lamina with the chemical analysis value in each model.
Detailed Description
In the process of the invention, Ri: represents the spectral reflectance at the i nm band; r'i: represents the first derivative of the spectral reflectance at the i nm band; n: represents nitrogen; p: represents phosphorus element; k: represents potassium.
By controlling the supply concentration of a single element, the spectral characteristics of the tobacco leaves under the concentration are obtained, a spectral database of the tobacco leaves with different nutrient concentrations is constructed, and data support can be provided for establishing estimation models of different elements of the tobacco leaves by analyzing and sorting the database. To fully illustrate the process of the present invention, the following experimental design was made.
1 design of the experiment
The test site is carried out in a greenhouse of a farm of Yunnan agricultural university, the tobacco variety to be tested is Yunyan 87, the tobacco variety is cultivated in a water culture mode, the nutrient solution used in the water culture is the nutrient solution obtained by improving and preparing on the basis of Hoagland complete nutrient solution, and the nutrient components are shown in the table 1.
TABLE 1 nutrient solution contents of the elements
The four levels of the nitrogen in the nutrient solution used in the tobacco cultivation process are respectively N0Is 0mg/L, N0.5Is 65mg/L, N1Is 130mg/L, N1.5195 mg/L; the four levels of phosphorus are respectively P0Is 0mg/L, P0.5Is 20.5mg/L, P1Is 41mg/L, P1.561.5 mg/L; potassium is set at four levels respectively as K0Is 0mg/L, K0.5Is 110.5mg/L, K1Is 221mg/L, K1.5The concentration of the nutrients is 331.5mg/L, and the concentrations of the other nutrients except for the control of the concentration of the nutrients in each treatment are all-element levels. The experiment was set up for a total of 10 treatments, repeated 6 times for a total of 60 strains. The macronutrient concentrations for each treatment are shown in table 2. Transplanting the tobacco seedlings into a specific water culture device, and applying an oxygenation pump to supply oxygen all day long, wherein the replacement period of the nutrient solution is four days.
Table 2 test treatments
2 acquisition of spectral data
The instrument used for collecting the spectral data is a FieldSpec 3 spectrometer of American ASD (Analytical spectral devices), the sampling intervals are 1.4nm (350-. The measuring range is 350-2500 nm; the light source adopts a halogen lamp matched with the spectrometer. When the spectral data of the tobacco leaf is acquired by using an ASD-fieldspec-3 ground object spectrometer, firstly calibrating the spectrometer by using a standard white board, then measuring the spectral data of 3 parts of the tip part, the middle part and the base part of the tobacco leaf, and taking the mean value of the spectral data of the three parts as the spectral data of the leaf; marking is carried out after each blade is collected, the blades are taken back for indoor analysis, and white board calibration is carried out on the spectrometer once every six blades are collected in the collection process; the collected tobacco leaves are mainly tobacco leaves of all tobacco leaves cultivated to the agglomeration period and the vigorous growing period.
3 determination of nitrogen, phosphorus and potassium content of leaf
Taking back the leaves with collected spectral data by using marked kraft paper bags, deactivating enzymes in a 105 ℃ drying oven in a laboratory, drying to constant weight at 75 ℃, grinding, sieving and putting into marked quick-sealing bags for later use. Plant leaf H2SO4-H2O2Digestion, namely measuring the total nitrogen of the leaves of the digestion solution by using a Kaschinger azotometer, measuring the total phosphorus of the leaves by using a vanadium-molybdenum-yellow colorimetric method, and measuring the total potassium of the leaves by using a flame photometer.
4 data analysis
The reflection spectrum and the analysis software for calculating and drawing the first derivative of the reflection spectrum are ASD-ViewSpecPro; calculating a correlation coefficient between the reflection spectrum and the nitrogen, phosphorus and potassium contents by using Excel 2007 office software; the correlation analysis of the spectral parameters and the nitrogen, phosphorus and potassium uses a sps 19 data analysis software.
The spectrum of 310-1130nm can be divided into eight different spectral regions according to the optical classification method by using the spectral data of the tobacco leaf collected by the spectrometer, and the spectral band corresponding to each spectral region is shown in table 3.
TABLE 3 spectral wavelength range division
On a first derivative diagram of the spectrum obtained after the first derivative processing is carried out on the spectral reflectivity of the blade, the blue edge amplitude value which is the maximum value of the first derivative in the blue light wave band (380-525nm) is recorded as DbThe position of the band where the maximum value appears is the blue edge position and is recorded asThe maximum value of the first derivative in the yellow light wave band (605-655nm) is the yellow edge amplitude and is recorded as DyThe position of the band where the maximum value appears is yellow edge position and is recorded asThe maximum value of the first derivative in the red light band (655-725nm) is the red edge amplitude and is recorded as DrThe position of the band in which the maximum occurs is called the red edge position and is recorded as
5 results and analysis
975 samples are obtained through tests, and statistical description of total nitrogen content, total phosphorus content and total potassium content of the samples shows that the average value of the total nitrogen content of the samples is 2.382%, the average value of the total phosphorus content is 0.471% and the average value of the total potassium content is 4.263%, the deviation value range of each nutrient index is-0.981-0.165, the kurtosis value range is-0.698-0.981, which accords with normal distribution, the difference between the maximum value and the minimum value of each nutrient component content is 6.404-25.2 times, which shows that the nutrient content range is wide and has better representativeness. The standard error value range of each nutrient data is 0.013-0.094, which indicates that each index is a weak variation index. The nutrient grading statistics at each level are shown in Table 4.
TABLE 4 statistical analysis of the data
The classification statistics description result of the total nitrogen content, the total phosphorus content and the total potassium content of 975 samples according to the total tobacco content grade shows that the absolute values of the kurtosis value and the deviation value of the sample data in the nutrient content range of each grade are less than 1 and accord with normal distribution, except that the ratio of the maximum value to the minimum value of the very low nitrogen level is 6.192, the ratio of the maximum value to the minimum value of the other nutrient grades is 1.1-1.8, and the result shows that the nutrient content range of each grade is wide and is basically representative. The standard error of each nutrient grade is 0.004-0.085, wherein the standard error of each grade of the phosphorus is in the range of 0.004-0.011 at the lowest. The nutrient grading statistics at each level are described in table 5.
TABLE 5 statistical description of the nutrient classifications
Under different nitrogen, phosphorus and potassium nutrient levels, the change trends of the reflection spectrum of the tobacco leaves are basically the same, namely, in the ultraviolet light wave band at the position of 310-380nm, reflected waves which rapidly decline and are unstable appear due to head end noise and the like, and the spectrum curve gradually tends to be stable until a first inflection point appears near 400nm of the blue light wave band; a lower and stable reflection platform appears in a blue light wave band of 400nm-500nm, a slow climbing appears in a blue light region of 500nm-525nm, a first reflection peak appears in a green light wave band, a peak value appears in a wave band about 550nm, the reflectivity gradually decreases, the reflectivity in the whole yellow light wave band decreases along with the increase of the wavelength until a lower reflection valley is formed at 680nm of a red light wave band and then the reflectivity quickly climbs, a further inflection point appears in an infrared light wave band about 740nm, and a higher reflection platform is formed in a near infrared wave band of 750nm-1050 nm. The whole reflection spectrum of the tobacco leaf accords with the specific spectral characteristics of green plants.
It can be seen that the spectral reflectance of the tobacco leaf in the blue, green, yellow, red and infrared bands gradually decreases with increasing nitrogen levels, while the spectral reflectance in the near infrared band increases; comparing the influence of the nitrogen level on the spectral reflectivity of the tobacco leaves, different phosphorus levels are shown in the whole spectral band of 350-1050nm, and the reflectivity is increased along with the increase of the phosphorus level; the influence of the potassium level on the spectral reflectivity of the tobacco leaves is opposite to the influence of different nitrogen levels on the spectral reflectivity of the leaves, and the effects are shown in that the spectral reflectivity in a blue light wave band, a green light wave band, a yellow light wave band, a red light wave band and an infrared light wave band is increased along with the increase of the potassium level, and the spectral reflectivity in a near infrared wave band is reduced along with the increase of the potassium level.
By carrying out derivation processing on the spectrum reflectivity, the influence of the background of the reflection spectrum and some system factors can be eliminated, certain overlapped areas of the reflection spectrum can be distinguished, and the identification and analysis are facilitated. The first derivative spectrum trends of the tobacco leaf spectral reflectivity at different levels of nitrogen, phosphorus and potassium contents are basically consistent; as can be seen from the first derivative spectrogram of the spectral reflectivity of the tobacco leaves, the tobacco leaves have obvious peak values in a blue light wave band, a green light wave band, a yellow light wave band and a red light wave band; different nitrogen levels have significant effects on the blue edge position, blue edge amplitude, green change position, green edge amplitude, yellow edge position, yellow edge amplitude, red edge position and red edge amplitude of the tobacco leaf. It appears that the green peak position and the red edge position show a distinct "red shift" with increasing nitrogen levels, the green edge amplitude decreasing with increasing nitrogen levels, and the red edge amplitude increasing with increasing nitrogen levels. The influence of different phosphorus levels on the blue edge position, the green change position, the yellow edge position and the red edge position of the tobacco leaf is small, but the green peak amplitude and the red edge amplitude are increased along with the increase of the phosphorus levels. The influence of the potassium level on the trilateral indexes of the tobacco leaves is shown in that the green peak amplitude and the red edge amplitude are reduced along with the increase of the potassium level, and the influence of the blue edge position, the green changing position, the yellow edge position and the red edge position is less clear.
Due to the fact that large noise interference exists in the ultraviolet light wave band of 350nm-380nm, the reflection spectrum of the wave band has large fluctuation, as shown in fig. 1, the correlation coefficient of the wave band also has large fluctuation, and the correlation coefficient shows a smooth change trend from the vicinity of 380nm of the blue light wave band. FIG. 1 is a schematic diagram of the correlation coefficient between the nitrogen, phosphorus and potassium contents of tobacco leaves and the spectral reflectivity of each band, and is a correlation coefficient between the nitrogen, phosphorus and potassium contents of tobacco leaves and the spectral reflectivity of each band obtained by performing correlation analysis on the nitrogen, phosphorus and potassium contents of each tobacco leaf and the spectral reflectivity of each band.
The correlation coefficient of the whole wave band shows that the nitrogen content of the leaves is in negative correlation with the spectral reflectivity of blue light, green light, yellow light and red light wave bands, and is in positive correlation with the spectral reflectivity of infrared light and near infrared light wave bands; the phosphorus content of the leaves is positively correlated with the spectral reflectivity of the whole wave band; the potassium content of the leaves is in positive correlation with the spectral reflectivity of blue light, green light, yellow light and red light wave bands, and in negative correlation with the spectral reflectivity of infrared light and near infrared light wave bands. As can be seen from the correlation coefficient of the tobacco leaf nitrogen content and the leaf spectral reflectivity, the tobacco leaf nitrogen content and the spectral reflectivity are weakly positively correlated in the ultraviolet light wave band of 350-; the tobacco leaf nitrogen content and the spectral reflectivity form low negative correlation at 711-721nm red light wave band, weak negative correlation at 721-727 nm leaf nitrogen content and the reflection spectrum, weak positive correlation at 728-730 nm tobacco leaf nitrogen content and the spectral reflectivity, low positive correlation at 730-780 nm tobacco leaf nitrogen content and the spectral reflectivity, and obvious positive correlation at 780-997nm infrared light wave band. The absolute value of the correlation coefficient is highest at 624nm in the yellow band, and the correlation coefficient is-0.6942.
The correlation coefficient of the phosphorus content of the tobacco leaves and the spectral reflectivity shows that the phosphorus content of the tobacco leaves in the range of 350nm to 457nm is obviously and positively correlated with the spectral reflectivity, but the fluctuation is large and the spectrum is unstable. The phosphorus content of the tobacco leaves at 447nm-490nm is in low positive correlation with the reflection spectrum, the phosphorus content of the tobacco leaves at 490nm-618nm is in obvious positive correlation with the spectral reflectivity, the phosphorus content of the tobacco leaves at 618nm-690nm is in low positive correlation with the reflection spectrum, the phosphorus content of the tobacco leaves at 690nm-1050nm is in obvious positive correlation with the spectral reflectivity, wherein the highest correlation coefficient is at 729nm of an infrared band, and the highest correlation coefficient is 0.796.
As can be seen from the correlation coefficient of the potassium content and the spectral reflectivity of the tobacco leaves, the fluctuation of the correlation coefficient of the potassium content and the reflection spectrum of the tobacco leaves is large at 350nm-425nm, and the correlation coefficient area of the 425nm spectral reflectivity and the potassium content of blue light is smooth. In a 425nm-714nm wave band, the content of the potassium in the tobacco leaves is obviously positively correlated with a reflection spectrum, in a 714nm-723nm wave band, the content of the potassium in the tobacco leaves is slightly positively correlated with the spectral reflectivity, in a 723nm-737nm wave band, the content of the potassium in the tobacco leaves is slightly positively correlated with the spectral reflectivity, in a 737-1050nm wave band, the content of the potassium in the tobacco leaves is slightly negatively correlated with the spectral reflectivity, wherein the highest correlation coefficient appears at 514nm of a green light wave band, and the highest correlation coefficient is 0.720.
Screening the absolute value of the correlation coefficient of the spectral reflectivity of each band and the nitrogen-phosphorus-potassium content of the tobacco leaves, and screening out the sensitive band for the nitrogen-phosphorus-potassium spectral diagnosis of the tobacco leaves according to the absolute value of the correlation coefficient, wherein the result shows that the sensitive band for the nitrogen spectral diagnosis of the tobacco leaves is 508nm of a blue light band, 605nm of a green light band, 624nm of a yellow light band, 693nm of a red light band, 750nm of an infrared light band and 935nm of a near infrared light band; sensitive wave bands for tobacco leaf phosphorus spectral diagnosis are 391nm of a blue light wave band, 533nm of a green light wave band, 607nm of a yellow light wave band, 725nm of a red light wave band, 729nm of an infrared light wave band and 1004nm of a near infrared light wave band; the sensitive wave bands of the potassium spectral diagnosis of the tobacco leaves are 514nm of a blue light wave band, 526nm of a green light wave band, 655nm of a yellow light wave band, 687nm of a red light wave band, 726nm of an infrared light wave band and 779nm of a near infrared light wave band; the NPK spectrum diagnosis sensitive wave band and the related coefficient of the tobacco leaf are shown in the table 6.
TABLE 6 wave band position with highest absolute value of spectral reflectivity coefficient of each wave band
As shown in FIG. 2, the nitrogen content, the phosphorus content and the potassium content of each tobacco leaf are respectively correlated with the first derivative of the spectral reflectance of each band, and the correlation coefficients of the nitrogen content, the phosphorus content and the potassium content of each tobacco leaf and the spectral reflectance of each band are obtained. From the correlation coefficient of the whole wave band, the absolute value of the correlation coefficient of the first derivative of the spectral reflectivity of each wave band of the tobacco leaf and the nitrogen, phosphorus and potassium content of the leaf is between 0 and 0.6, and the variation range of the correlation coefficient of each wave band is large, so that the curve of the correlation coefficient is not stable. The correlation coefficient of the tobacco leaf nitrogen content and the first-order derivative of the spectral reflectivity of each wave band is generally expressed as negative correlation between blue light and green light wave bands, positive correlation is expressed at yellow light wave bands, the correlation coefficient at red light wave bands is expressed as negative correlation except 677-697nm, the other red light wave bands are positive correlation, weak correlation is expressed at infrared wave bands and near infrared wave bands, wherein the wave band with the highest absolute value of the correlation coefficient is expressed at 709nm of the red light wave band, and the correlation coefficient is 0.603; the correlation coefficient of the tobacco leaf phosphorus content and the first-order derivative of the spectral reflectivity of each waveband is slightly correlated with the phosphorus content of the tobacco leaf except for the fact that the blue waveband and the infrared waveband have individual wavebands, the first-order derivatives of the spectral reflectivity of other wavebands and the phosphorus content of the tobacco leaf are in weak correlation, wherein the waveband with the largest absolute value of the correlation coefficient is arranged at 976nm of the near-infrared waveband, and the correlation coefficient is-0.391; the correlation coefficient of the potassium content of the tobacco leaves and the first-order derivative of the spectral reflectivity of each waveband is weak in whole, but the first-order derivatives of the spectral reflectivity of individual wavebands exist in the blue light waveband, the green light waveband, the red light waveband and the infrared light waveband, and the potassium content of the tobacco leaves reaches low correlation, wherein the waveband with the highest absolute value of the correlation coefficient is present at 880nm of the near infrared light waveband, and the correlation coefficient is-0.402.
Screening absolute values of correlation coefficients of first-order derivatives of spectral reflectivity of all bands and nitrogen, phosphorus and potassium contents of tobacco leaves, and screening out sensitive bands for nitrogen, phosphorus and potassium spectral diagnosis of the tobacco leaves according to the absolute values of the correlation coefficients, wherein the results show that the sensitive bands for nitrogen spectral diagnosis of the tobacco leaves are 440nm of a blue light band, 557nm of a green light band, 649nm of a yellow light band, 709nm of a red light band, 726nm of an infrared light band and 1000nm of a near infrared light band; sensitive wave bands for tobacco leaf phosphorus spectral diagnosis are 458nm of a blue light wave band, 541nm of a green light wave band, 626nm of a yellow light wave band, 671nm of a red light wave band, 750nm of an infrared light wave band and 976nm of a near infrared light wave band; sensitive wave bands for potassium spectrum diagnosis of tobacco leaf are 404nm of a blue light wave band, 539nm of a green light wave band, 615nm of a yellow light wave band, 721nm of a red light wave band, 731nm of an infrared light wave band and 880nm of a near infrared light wave band; the NPK spectrum diagnosis sensitive wave band and the related coefficient of the tobacco leaf are shown in the table 7.
TABLE 7 band position with highest absolute value of first derivative correlation coefficient of spectral reflectivity of each band
The results of the correlation analysis of the three-side parameters and the nitrogen content, the phosphorus content and the potassium content of the tobacco leaves show that the total nitrogen content of the tobacco leaves and the green peak amplitude, the blue edge area, the red edge area, SDr/SDb and (SDr-SDb)/(SDr + SDb) are significant on the 0.01 level, and the correlation with the blue edge amplitude, the yellow edge amplitude, the red edge amplitude, the yellow edge area, SDr/SDy and (SDr-SDy)/(SDr + SDy) is not significant; the total phosphorus content of the tobacco leaves is significant at the level of 0.01 with yellow edge amplitude, red edge amplitude and green edge amplitude, significant at the level of 0.05 with blue edge amplitude, blue edge area, SDr/SDy and (SDr-SDb)/(SDr + SDb), and has insignificant correlation with yellow edge area, red edge area, SDr/SDb and (SDr-SDy)/(SDr + SDy); the total potassium content of tobacco lamina was significant at the 0.01 level with green peak amplitude, blue edge area, SDr/SDb and (SDr-SDb)/(SDr + SDb), significant at the 0.05 level with red edge area and vegetation index (SDr-SDy)/(SDr + SDy), and insignificant in relation to blue edge amplitude, yellow edge amplitude and yellow edge area, as shown in table 8, where a indicates significant correlation on both sides of the 0.01 level and a indicates significant correlation on both sides of the 0.05 level.
TABLE 8 analysis of correlation between trilateral parameters and NPK content of leaves
6 tobacco leaf phosphorus content spectrum estimation model establishment
(1) Estimation model based on spectral reflectivity phosphorus
According to the analysis result of the correlation between the phosphorus content of the tobacco leaves and the spectral reflectance of the tobacco leaves, the spectral reflectance of a wave band corresponding to a correlation coefficient with the largest absolute value is screened in a blue light wave band, a green light wave band, a yellow light wave band, a red light wave band, an infrared light wave band and a near infrared light wave band respectively to serve as input variables, and a regression equation is established with the phosphorus content of the leaves in the form of an exponential function, a unitary linear function, a logarithmic function, a unitary quadratic function and a power function, as shown in table 9. The result shows that the fitting degree of the regression equation of the phosphorus content of the tobacco leaves and the spectral reflectivity of each sensitive waveband is lower in blue light and near infrared light wavebands, and higher in green light, yellow light, red light and infrared light wavebands, wherein the fitting degree of the regression equation fitting by taking the spectral reflectivity of 725nm in the red light waveband as an input variable is highest, and the fitting degree is greater than 0.9.
The results of analyzing the fitting forms of the five regression equations show that the fitting degree of a unary quadratic fitting form in various fitting equations is higher than that of other fitting forms, and then the unary quadratic fitting form is used as a linear fitting form. In the fitting equation of the tobacco phosphorus, the fitting equation with the fitting degree of more than 0.95 takes 533nm of green light as an input variable, and adopts an exponential regression equation and a unitary linear and unitary quadratic regression equation which are fitted, wherein the fitting degrees are respectively 0.951, 0.960 and 0.961; and a fitted one-dimensional quadratic regression equation with 725nm of red light as an input variable, the degree of fit of which is 0.950.
TABLE 9 estimation model based on spectral reflectance phosphorus
(2) Estimation model based on spectral reflectivity first-order derivative phosphorus
According to the analysis result of the first derivative correlation between the phosphorus content of the tobacco leaves and the spectral reflectance of the tobacco leaves, the first derivative of the spectral reflectance of a band corresponding to the maximum correlation coefficient of the absolute value is screened in a blue light band, a green light band, a yellow light band, a red light band, an infrared light band and a near infrared light band respectively to serve as an input variable, and a regression equation is established with the phosphorus content of the leaves in the form of an exponential function, a unary linear function, a logarithmic function, a unary quadratic function and a power function, as shown in table 10.
The result shows that the fitting degree of the first-order derivatives of the spectral reflectivity of the sensitive wave bands of the green light and the infrared light is smaller, and the fitting degree of the first-order derivatives of the sensitive spectral reflectivity of the other wave bands to the phosphorus of the tobacco leaves is larger than 0.784; the analysis results of various fitting forms show that the highest fitting degree of the first-order derivative of the tobacco lamina spectral reflectivity to the tobacco lamina phosphorus is a first order second order linear fitting equation. Wherein the fitting equations with the fitting degree of more than 0.85 in each regression equation are respectively as follows: the method is characterized by comprising a first-order linear regression equation and a second-order linear regression equation which are established by taking the spectral reflectance first-order derivatives of 548nm of blue light, 626nm of yellow light, 671nm of red light wave band and 976nm of near-infrared light wave band as input variables, wherein the first-order linear regression equation and the second-order linear regression equation are established by taking 750nm of yellow light as input variables, and the highest fitting degree is 0.980.
TABLE 10 estimation model based on spectral reflectance first derivative phosphorus
(3) Trilateral parameter phosphorus-based estimation model
Through carrying out correlation analysis on the phosphorus content of the tobacco leaves and three-edge parameters of the spectrum of the tobacco leaves, yellow edge amplitude (Dy), red pass amplitude (Dr) and green peak value (Rg) which are extremely obviously related are screened as input variables, and a tobacco leaf phosphorus regression equation is established in the form of an exponential function, a unitary linear function, a logarithmic function, a unitary quadratic function and a power function, as shown in Table 11. The result shows that the fitting degree of the regression equation of the trilateral parameters to the phosphorus content of the tobacco is not high, the fitting degree of the equation fitting in the form of a unitary quadratic equation in the five fitting forms is high, wherein when the yellow edge amplitude (Dy) is taken as an input variable, the fitting degree to the phosphorus content of the tobacco is highest, and the fitting degree is 0.862; the log-form regression equation with the green peak (Rg) as the input variable had the lowest fitness of 0.234.
TABLE 11 regression equation based on trilateral parameter phosphorus
7 tobacco leaf potassium content spectrum estimation model establishment
(1) Estimation model based on spectral reflectivity potassium
According to the analysis result of the correlation between the potassium content of the tobacco lamina and the spectral reflectance of the tobacco lamina, the spectral reflectance of the waveband corresponding to the maximum correlation coefficient of the absolute value is respectively screened in the blue light waveband, the green light waveband, the yellow light waveband, the red light waveband, the infrared light waveband and the near infrared light waveband to be used as an input variable, and a regression equation is established with the potassium content of the lamina in the form of an exponential function, a unitary linear function, a logarithmic function, a unitary quadratic function and a power function, as shown in table 12. The result shows that the fitting degree of the established blade potassium regression estimation model is higher than that of other wave bands by taking the spectral reflectivity of the sensitive wave bands of the blue light wave band, the green light wave band and the yellow light wave band as input variables. Analysis of the regression equation established by taking each sensitive wave band as an input variable shows that the fitting degree of the regression equation established in the form of unitary and quadratic to the content of the potassium in the tobacco leaves is high. The regression equation with the highest fitting pair is a quadratic equation with a degree of fitting of 0.883 established by taking the spectral reflectance at 514nm as an input variable, and the regression equation with the lowest fitting pair is a logarithmic regression equation with a degree of fitting of 0.370 established by taking the spectral reflectance at 726nm as an input variable.
TABLE 12 estimation model based on spectral reflectance of potassium
(2) Estimation model based on spectral reflectivity first-order derivative potassium
According to the analysis result of the first derivative correlation between the potassium content in the tobacco lamina and the spectral reflectance of the tobacco lamina, the first derivative of the spectral reflectance of the waveband corresponding to the maximum correlation coefficient of the absolute value is screened in the blue light waveband, the green light waveband, the yellow light waveband, the red light waveband, the infrared light waveband and the near infrared light waveband respectively to serve as an input variable, and a regression equation is established with the potassium content in the lamina in the form of an exponential function, a unitary linear function, a logarithmic function, a unitary quadratic function and a power function, as shown in table 13. The result shows that the fitting degree of the first-order derivative of the spectral reflectivity of each sensitive waveband and the content of the potassium in the tobacco leaves is high, wherein the fitting degree of the regression equation of the potassium in the leaves established by the red waveband is the highest. The fitting equations with the fitting degree larger than 0.9 are a unary linear regression equation and a unary quadratic linear regression equation which are established by taking 615nm of yellow light and 880nm of spectral reflectance of near infrared light as input variables, and an exponential regression equation and a unary quadratic regression equation which are established by taking 721nm of spectral reflectance of green light as input variables. The degree of fitting of the unary quadratic regression equation established by taking the spectral reflectance first-order derivative at 721nm of red light as an input variable is highest and is 0.918, and the degree of fitting of the logarithmic regression equation established by taking the spectral reflectance first-order derivative at 404nm of blue light as an input variable is lowest and is 0.75.
TABLE 13 estimation model based on spectral reflectance first derivative potassium
(3) Estimation model based on trilateral parameter potassium
By carrying out correlation analysis on the potassium content of the tobacco leaves and three-edge parameters of the spectrum of the tobacco leaves, screening green peak values (Rg), blue edge areas (SDb) and vegetation indexes SDr/SDb which are extremely obviously related as input variables, and establishing a tobacco leaf potassium regression equation in the form of an exponential function, a unitary linear function, a logarithmic function, a unitary quadratic function and a power function, as shown in Table 14. The results show that the fitness of the regression equation of the trilateral parameters to tobacco potassium content is relatively high with the blue edge area (SDb) and relatively low with the vegetation index SDr/SDb. The analysis results of the regression equation for fitting the potassium in the tobacco lamina with trilateral parameters as input variables show that the degree of fitting of the unary quadratic linear regression equation to the green peak value (Rg) and the blue edge area (SDb) is the highest, and the fitting of the exponential regression model to the vegetation index SDr/SDb is the highest. Among all the potassium regression equations, the regression equation with the highest fitting degree is a one-dimensional quadratic regression equation established by taking a blue edge area (SDb) as an input variable, the fitting degree is 0.825, and the regression equation with the lowest fitting degree is a logarithmic regression equation established by taking a green peak value (Rg) as an input variable, and the fitting degree is 0.442.
TABLE 14 regression equation based on trilateral parameter potassium
8 tobacco leaf phosphorus and potassium content spectrum prediction model evaluation
Based on the analysis results of regression equations established for the spectral reflectance, the first derivative of the spectral reflectance and the trilateral parameters of the tobacco leaves as input variables and the phosphorus content and the potassium content of the tobacco leaves, the regression equation with the highest fitting degree is respectively selected as an estimation model of the nutrient content of the tobacco leaves, as shown in table 15. Model estimation is carried out on the phosphorus content and the potassium content of 54 tobacco leaves respectively by using the 6 tobacco leaf nutrient estimation models, and the accuracy of the nutrient estimation models is evaluated by carrying out statistical analysis between model estimation values and chemical analysis values.
TABLE 15 model for estimating major elements of tobacco leaves
(1) Statistically analyzing the model estimation value and the chemical analysis value
The phosphorus and potassium content model estimation was performed on 54 tobacco leaves using a tobacco phosphorus and potassium content estimation model, and the model estimation values and chemical analysis values were statistically analyzed to obtain the results shown in table 16. The result shows that each diagnosis model can well estimate the nutrient content of the tobacco leaves, and the tightness and the discrete degree of the measured value of each measuring method of the phosphorus content and the potassium content of the sample are evaluated through the standard error and the standard deviation. The precision of each detection method for detecting the phosphorus in the sample is MP1>Chemical analysis value>MP2>MP3The discrete degree of each detection method to the phosphorus detection result of the sample is MP1>Chemical analysis value>MP2>MP3(ii) a The precision of each detection method on the potassium detection result of the sample is MK1>Chemical analysis value>MK2>MK3And the discrete degree of each detection method for the potassium detection result of the sample is MK1>Chemical analysis value>MK2>MK3(ii) a For the peak value and the skewness of the statistical analysis of the nutrient values measured by the detection methods, the absolute values of the peak value and the skewness of the nutrient content values detected by the chemical analysis method are less than 1, and the positive-phase distribution is basically met.
TABLE 16 statistical analysis of model predicted values and chemical analysis values
(2) Error analysis of model estimated value and chemical analysis value
As shown in FIG. 3 and FIG. 4, the result of the phosphorus content measurement of each phosphorus measurement method on the sample indicates MP by performing one-way anova on the chemical measurement value 54 of each sample nutrient content and the model estimation value1And MP2The predicted result of (A) is not significantly different from the result determined by the chemical analysis method, while the MP is3The prediction result of the phosphorus content of the sample is obviously higher than the chemical analysis result, which shows that the prediction result of the phosphorus content of the tobacco lamina by using the unary quadratic equation established by taking the spectral reflectance at 533nm and the spectral reflectance first-order derivative at 750nm as input variables can replace the determination of the phosphorus content of the tobacco lamina by a chemical analysis method. The measurement result of each potassium measurement method on the potassium content of the sample shows MK1And MK2Has no significant difference from the result of chemical analysis, and MK3The prediction result of the potassium content of the sample is obviously higher than the chemical analysis result, which shows that the prediction result of the tobacco lamina potassium by the unitary quadratic equation established by taking the spectral reflectance at 526nm and the spectral reflectance first derivative at 721nm as input variables can replace the determination of the tobacco lamina potassium by a chemical analysis method.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions.
Claims (7)
1. A method for quickly measuring potassium content in tobacco leaves by a spectrum is characterized in that a tobacco leaf potassium content estimation model is established through a unitary quadratic function form to fit the potassium content in the tobacco leaves, wherein a fitting model with the highest potassium content fitting degree in the tobacco leaves is an equation y which is 423.3x and is established by taking the spectral reflectance as an input variable2-258.7x +41.43, established with the first derivative of the spectral reflectance as input variableEquation y-8.551 x2+25.20x-11.92 and-388.0 x equation y established with the area of the blue edge of the tobacco lamina spectrum as the input variable2+33.09x+6.114。
2. The method for rapid spectrum determination of potassium content in tobacco lamina according to claim 1, wherein the estimation model of potassium content in tobacco lamina is a one-dimensional quadratic equation with spectral reflectance as input variable, y-423.3 x2-258.7x+41.43。
3. Method for the rapid determination of the potassium content in tobacco lamina according to claim 1 or 2, characterized in that the spectral reflectance is R526Which represents the spectral reflectance at the 526nm wavelength band.
4. The method for rapid spectrum determination of potassium content in tobacco lamina according to claim 3, wherein the 526nm wavelength band is green light.
5. The method for spectrally rapid determination of potassium content in tobacco lamina of claim 1 wherein said spectral reflectance first derivative is 100R'721Representing the first derivative of the spectral reflectance at the 721nm band.
6. The method for rapid spectrum determination of potassium content in tobacco lamina according to claim 5, wherein the 721nm band is red light.
7. The method for rapid spectroscopic determination of potassium content in tobacco lamina of claim 1 wherein the tobacco lamina has a blue edge area of 100 SDb.
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