CN110160967A - A kind of total nitrogen content evaluation method of crop canopies blade - Google Patents

A kind of total nitrogen content evaluation method of crop canopies blade Download PDF

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CN110160967A
CN110160967A CN201910305370.9A CN201910305370A CN110160967A CN 110160967 A CN110160967 A CN 110160967A CN 201910305370 A CN201910305370 A CN 201910305370A CN 110160967 A CN110160967 A CN 110160967A
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reflectivity
nitrogen content
wave band
total nitrogen
canopy
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赵晋陵
范玲玲
梁栋
徐超
黄林生
洪琪
张东彦
翁士状
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Anhui University
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Anhui University
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N2021/1793Remote sensing
    • G01N2021/1797Remote sensing in landscape, e.g. crops

Abstract

The invention belongs to crop biochemical component spectrum technical field of nondestructive testing, disclose a kind of total nitrogen content evaluation method of crop canopies blade: first, algorithm SPA, sensitivity spectrum characteristic data set, position feature data set and vegetation index characteristic data set are converted using successive projection;Then, the small the smallest sensitivity spectrum variables set of synteny is filtered out from sensitivity spectrum characteristic data set, position feature data set and vegetation index characteristic concentration;Finally, sensitivity spectrum variables set is carried out Partial Least Squares Regression PLS modeling, the appraising model of the total nitrogen content LNC of crop canopies blade is obtained.The model can accurately estimate crop canopies leaf total nitrogen content, be not much different with measured value.

Description

A kind of total nitrogen content evaluation method of crop canopies blade
Technical field
The invention belongs to crop biochemical component spectrum technical field of nondestructive testing, in particular to a kind of crop canopies blade Total nitrogen content evaluation method.
Background technique
Nitrogen is photosynthesis of plant and diagnosis crop nutrition condition necessary element, it and crop growth, length Gesture and quality is closely related and the emphasis of agronomy Experts ' Attention.Normally apply under nitrogen, plant amount of nitrogen sucking, fertilizer utilization efficiency, Crop yield and quality increase with the increase of amount of nitrogen.If but nitrogenous fertilizer crosses Sheng, will cause assessing index, rice produces The problems such as amount and quality decline, it also will cause land pollution when serious.Meanwhile the variation of crop leaf Different Nitrogen Concentration will affect plant The photosynthesis of object blade, so that certain variation occurs for leaf spectra.When crop leaf is compromised stress, leaf-nitrogen Concentration variation can spectrally generate response.Therefore, plant nitrogen situation can be monitored by the variation of leaf spectra.
High-spectral data spectral resolution with higher, can detect the minor change of plant leaf blade biochemical component, Detection has the characteristics that lossless, quick, has carried out quick, lossless monitoring to plant leaf blade biochemical component using EO-1 hyperion means Important content as vegetation growth of plant status evaluation.However, the high-spectral data with hundreds or even thousands wave band, is compared Although can provide more careful richer spectral information in multispectral, there is also high between mass data redundancy, neighbouring wave band The problems such as spending correlation.
Currently, the spectral variables extracted based on hyperspectral information can be generally divided into three classes: (1) reflected waveband feature: high Spectrum has more accurate wave band, can be good at the feature for reacting vegetation.Bai Limin et al. is mentioned using successive projection algorithm Take Wheat Leavess total nitrogen content canopy spectra 8 (1985nm, 2474nm, 1751nm, 1916nm, 2507nm, 1955nm, 2465nm, 344nm) sensitive band, wheat during jointing stage blade content appraising model is established, estimation precision is high, and stability is good;Zhang Xiao Flower bud et al. based on successive projection algorithm extract 12 characteristic wavelengths of Brassica campestris L seedling-flower-silique time of infertility blade (467nm, 557nm, 665nm, 686nm, 706nm, 752nm, 874nm, 879nm, 886nm, 900nm, 978nm, 995nm), inverting blade Nitrogen content estimation models, realize the visualization of nitrogen level;(2) sensitive position feature: Fu Yuanyuan et al. is to canopy of winter wheat Wave band depth analysis is carried out within the scope of spectrum 550nm-750nm, then to improve crop field winter wheat in conjunction with Partial Least Squares Regression The estimation precision of biomass;Wang Ping et al. extracts reflection to EO-1 hyperion visible light wave range (400nm~800nm) and absorbs position etc. Parameter, pick out ginseng higher to Chlorophyll from Maize correlation and relevant with corn pollution stress chlorophyll minor change Number, establishes BP neural network model, gradually enhances and extract the small change of Chlorophyll from Maize under farmland pollution stress state Change information;Du Huaqiang et al. analyzes 9 position features such as red side area, red paddy absorption depth in masson pine spectrum, establishes The Folium Pini chlorophyll content prediction model of Partial Least Squares Regression based on gaussian kernel function transformation, mean square error It is 0.0088, average absolute percentage error 0.7617%;(3) vegetation index feature: vegetation index is close red by visible light- The combination of the linearity and non-linearity of wave section, can quantitative response vegetation in any case upgrowth situation.Chen et al. is utilized Bimodal canopy nitrogen index (DCNI) is compared with some existing vegetation indexs, determines that the DCNI of wheat and corn is in research Optimal spectrum index, to assess the efficiency of crop nitrogen processing;Shu Meiyan et al. improves crop by constructing novel spectral index The precision of leaf area index EO-1 hyperion inverting;Tan Changwei et al. comprehensive analysis 10 common spectral vegetation indexes and summer corn The correlation and predictability of LAI.
Research shows that: current existing research uses EO-1 hyperion characteristics of variables, although monitoring and evaluation plant growth shape can be used for Condition parameter, but most researchs only use the spectral signature variable of single type, and different type spectral variables are all from difference Angle provides the useful information of plant growth parameter, therefore, if different types of spectral variables can be comprehensively utilized to monitor and make Object target component, which is one, may improve the approach of monitoring accuracy, and how to comprehensively utilize polymorphic type EO-1 hyperion variable and further dig The abundant information contained in pick EO-1 hyperion, the precision of crop nitrogen nutrition spectrum estimation is improved with this, is rarely reported.Another party Face, Partial Least Squares Regression PLS method are the extensions of multiple linear regression model, because it can reduce being total between data variable Linear problem and be widely used.
Summary of the invention
It is an object of the present invention to for existing using spectrum existing for EO-1 hyperion variable monitoring and evaluation crop nutrition aspect The excessively single problem of characteristic variable, the application provide a kind of total nitrogen content evaluation method of crop canopies blade.
To achieve the goals above, the technical solution that the application uses are as follows:
A kind of total nitrogen content evaluation method of crop canopies blade, comprising steps of
S1, algorithm SPA is converted using successive projection, from 400nm~1350nm, 1400nm~1790nm, 1990nm~ It is selected in the canopy leaves spectral region of 2350nm 6 the smallest with the total nitrogen content LNC1 synteny of known crop canopies blade Sensitive band constitutes sensitivity spectrum characteristic data set;
6 sensitive bands include for 4 canopy leaves reflectivity Ref wave bands and 2 first derivative FD wave bands;
4 canopy leaves reflectivity Ref wave bands are respectively 412nm, 724nm, 1084nm, 1343nm;
2 first derivative FD wave bands are 658nm and 937nm;
The total nitrogen content LNC1 of the known crop canopies blade detects to obtain by azotometer;
S2, algorithm SPA is converted using successive projection, in the position wave band used when being studied from crop EO-1 hyperion nitrogen, choosing The smallest two positions wave band SDb and Dr of synteny is taken, position feature data set is constituted;
The SDb is the sum of the canopy leaves spectral reflectivity first derivative FD of wave band at 490nm~530nm;
The Dr is the canopy leaves spectral reflectivity first derivative FD maximum value of wave band at 680nm~760nm;
S3, SPA algorithm is converted using successive projection, it is two the smallest that synteny is chosen from typical vegetation index VIs Vegetation index, i.e. normalized differential vegetation index NDVIg-b #With difference vegetation index DVI II#, constitute vegetation index characteristic data set;
The NDVIg-b #=(R573-R440)/(R573+R440);
Wherein, R573The canopy leaves spectral reflectivity for being wavelength at 573nm;
R440The canopy leaves spectral reflectivity for being wavelength at 440nm;
The DVI II#=RNIR-RR
Wherein, RNIRFor the mean value of the canopy leaves spectral reflectivity of wave band at 841nm~876nm;
RRFor the canopy leaves spectral reflectivity of wave band at 680nm~760nm;
S4, SPA algorithm is converted using successive projection, from sensitivity spectrum characteristic data set, position feature data set and vegetation The small the smallest sensitivity spectrum variables set of synteny is filtered out in index characteristic data set;
Wherein, the sensitivity spectrum variables set includes 2 canopy leaves reflectivity Ref wave bands, 1 first derivative FD wave band With normalized differential vegetation index NDVIg-b #
2 canopy leaves reflectivity Ref wave bands are respectively 724nm and 1343nm;
1 order derivative FD wave band is 658nm;
Sensitivity spectrum variables set is subjected to Partial Least Squares Regression PLS modeling again, the full nitrogen for obtaining crop canopies blade contains Measure the appraising model of LNC: Y=3.6344-5.7351X1-4.4275X2+1236.6X3+2.0886X4
Wherein, X1: wave band is the canopy leaves reflectivity Ref at 1343nm;
X2: normalized differential vegetation index NDVIg-b #
X3: wave band is the first derivative values of reflectivity at 658nm;
X4: wave band is the canopy leaves reflectivity Ref at 724nm.
Further, the 400nm~1350nm, 1400nm~1790nm, the canopy leaves light of 1990nm~2350nm Spectral limit is chosen obtain by the following method:
Reflectivity of the crop canopies blade in 350nm~2500nm wave-length coverage is measured, obtaining abscissa is wavelength, is indulged Coordinate is the spectrogram of reflectivity;Removing steam influences, and remaining wave band is 400nm~1350nm, 1400nm in spectrogram The canopy leaves spectrum of~1790nm and 1990nm~2350nm.
Further, the total nitrogen content LNC1 of the known crop canopies blade is obtained by the following method:
Crop canopies blade after progress spectral reflectivity measurement is put into 100 DEG C~110 DEG C of baking oven and dries 25min ~35min is dried to weight at then 75 DEG C~85 DEG C, obtains leaf samples;The leaf samples for weighing drying, then by sample leaf Piece crushes, then measures leaf samples nitrogen content with azotometer, obtains LNC 1.
Further, the formula of the first derivative FD is as follows:
Wherein, Rλ(j)It is the reflectivity of wave band j, Rλ(j+1)It is the reflectivity of wave band j+1, λ (j+1)-λ (j) is wave band j and j Wavelength difference between+1;
The first derivative of first derivative FD reflectivity of wavelength midpoint i between wave band j and j+1.
Further, the crop canopies blade is maize canopy blade or wheat canopy blade.
Compared with prior art, the beneficial effects of the present invention are:
The application converts SPA algorithm using successive projection, from sensitivity spectrum characteristic data set, position feature data set and plant The small the smallest sensitivity spectrum variables set of synteny is filtered out in index characteristic data set;Sensitivity spectrum variables set is carried out again inclined Least square regression PLS modeling, obtains the appraising model of the total nitrogen content LNC of crop canopies blade.Because establishing crop canopies EO-1 hyperion sensitive band, the spectral position that canopy leaves have been taken into account during the appraising model of the total nitrogen content LNC of blade are special It seeks peace typical vegetation index these three types spectral variables, compared to existing using single spectral variables monitoring and evaluation crop canopies Leaf total nitrogen content, stability is more preferable, more can accurately predict the total nitrogen content LNC of the crop canopies blade in sample to be tested.
Detailed description of the invention
Fig. 1 is the correlation spectrogram of training set reflectance spectrum (Ref) and first derivative spectrum (FD) and LNC 1 of the present invention;
Fig. 2 is the practical total nitrogen content LNC' of maize canopy blade of the present invention and the prediction total nitrogen content of maize canopy blade The precision evaluation figure of LNC.
Specific embodiment
Technological means of the invention, creation characteristic, achieving the goal is easy to understand with effect in order to make, below in conjunction with Specific embodiments of the present invention and attached drawing, are clearly and completely described technical solution of the present invention.
One, Preparatory work of experiment
(1) area is studied:
The crop used in the embodiment of the present invention is by taking maize leaves as an example, and experiment is in 2012 in national precision agriculture research Demonstration Base is carried out, and base is located at the Changping District, Beijing northeast little Tang Shan Zhen, and 40 ° 00 '~40 ° 21 ' of north latitude, 116 ° of east longitude 34 '~117 ° 00 ', height above sea level 36m.Soil types is moisture soil.Climate type is the continental monsoon climate in temperate zone, and winter is cold Cold, summer is hot, throughout the year drought.The corn of plantation is Nongda108 (osculant) and capital 8 (compact).3 nitrogens Nitrogen (N0), normal nitrogen (N1), 2 times of nitrogen (N2), 3 repetitions are not applied in horizontal processing respectively.Thickness of sowing is about 882m2。2012 Sowing on June 21, in, on October 15th, 2012 harvest.
(2) spectroscopic assay
Spectroscopic assay uses ASD FieldSpec FR2500 type field spectroradiometer (U.S. Analytical Spectral Device company), spectral region 350nm-2500nm is spaced 1.4nm, 1000nm- within the scope of 350nm-1000nm 1nm is spaced within the scope of 2500nm.Generally measured in Beijing time 10:00-14:00, when measurement fine, calm nothing Cloud, probe vertical is downward when observation, from the ground height 1.3m, and 25 ° of field angle, measurement front and back is corrected with reference to version every time.
(3) measurement of the total nitrogen content LNC1 of crop canopies blade known to
Cauline leaf is separated in time after carrying out spectral measurement, and blade is fitted into paper bag.Blade is put into 105 ° of baking 30min is dried in case, 48h or more is then dried under 80 ° of constant temperature, until weight.The leaf samples for weighing drying, then by blade powder It is broken, its nitrogen content is measured with kjeldahl apparatus (Buchi B-339, FOSS, Sweden).Totally 72 hillslope processes in this research, 48 cells are for training, and 24 cells are for verifying.
Two, principle and method
(1) high-spectral data pre-processes
To eliminate the partial noise in spectrum, spectrum denoising is carried out using Savitzky_Golay (SG) convolution exponential smoothing, By preliminary experiment, moving window width is 17, and when the degree of polynomial is 2, denoising effect is preferable.All kinds of spectral variables herein are such as First derivative, position feature and vegetation index etc., the spectral reflectivity after being all based on SG denoising are calculated, and wherein single order is led Number (FD) formula is as follows:
Wherein, Rλ(j)It is the reflectivity of wave band j, Rλ(j+1)It is the reflectivity of wave band j+1, λ (j+1)-λ (j) is wave band j and j Wavelength difference between+1;
The first derivative of first derivative FD reflectivity of wavelength midpoint i between wave band j and j+1.
(2) the position wave band used when crop EO-1 hyperion nitrogen is studied
The position wave band that 1 crop EO-1 hyperion nitrogen of table is used when studying
(3), typical vegetation index VIs
It has been reported that many different optical indexs in document, and verified they and vegetation parameter have well Correlation.This research has chosen 34 typical vegetation indexs (VIs) to estimate maize canopy leaf N content (being shown in Table 2).Wherein, Including 6 EO-1 hyperion vegetation indexs sensitive to nitrogen, such as best vegetation index (Viopt), normalized site attenuation (NDVIg-b #), ratio vegetation index (RVI I#)、RVI II#, association index (MCARI/MTVI2), bimodal canopy nitrogen index (DCNI#), there are also NDVI I#、RVI III#、DVI I#、SAVI I#, the normalization red side of difference (NDRE) etc.;And 23 typical cases Index, such as anti-atmosphere vegetation index (ARVI), difference vegetation index (DVI II#), enhance vegetation index (EVI), green normalizing Change vegetation index (GNDVI), improve non-linear vegetation index (MNLI), modified soil adjusts vegetation index 2 (MSAVI2), repairs Just simply than (MSR), NDVI II#, non-linear vegetation index (NLI), optimization SAVI (OSAVI), RDVI, ratio vegetation index (RVI IV), SAVI II#, TVI and improvement triangle vegetation index (MTVI2), index NDVI relevant to red sideRed-edge, CIRed-edgeAnd MTCI, and with the associated index of moisture (WI, NDWI), normalized difference infrared index (NDII), disease moisture It coerces index (DSWI) and standardization LAI determines index (sLAIDI*) etc., be related to the VIs of broadband information to above-mentioned, using pair The spectral response functions of inductive sensing device are calculated by EO-1 hyperion.
The typical vegetation index VIs of table 2 summarizes
(4) screening and modeling method
(1) successive projection converts algorithm SPA
In recent years, successive projection algorithm (successive projections algorithm, SPA) is being screened and is being extracted Increasingly extensive in the application of sensitive variable, it is a kind of forward variable choosing that can effectively eliminate synteny problem in spectral information Algorithm is selected, by reducing the redundancy between variable, representative characteristic parameter is selected for modeling, is greatly improved modeling The efficiency of analysis.With root-mean-square error (root mean square error, RMSE) for evaluation index, work as root-mean-square error Number when minimum is variable number.
(2) Partial Least Squares Regression
Partial Least Squares Regression (Partial Least Squares Regression, PLS) is one of statistics Method, it integrates principal component analysis, canonical correlation analysis and multiple linear regression analysis method, be a kind of research multivariate response or The modeling pattern of single dependent variable and more independents variable.It can be filtered out in the case where sample size is few synteny it is lesser at Point.
Consider m dependent variable y1,y2,…,ym, n independent variable x1,x2,…,xn。E0,E1,…,Er,F0,…,FrIt is two groups Data matrix is observed in the standardization of variables set, directly in E0,E1,…,Er-1Extract component t in matrix1,…,tr (r≤m),th(th It is independent variable collection X=(x1,…,xm)TLinear combination) it is as much as possible carry X in information, meanwhile, thTo dependent variable system F0There is maximum interpretability.If finally extracting r ingredient t to independent variable collection1,…,tr, Partial Least Squares Regression will be by building Vertical y1,y2,…,ymWith t1,…,trRegression equation, be then expressed as y again1,y2,…,ymWith the regression equation of former independent variable, i.e., Partial Least Squares Regression equation.
(3) statistical analysis technique
Phase is carried out with SPSS 24.0 to sensitive band, position feature, vegetation index and maize canopy leaf-nitrogen (LNC) The analysis of closing property.Verifying sample, coefficient of determination R are used as using 1/3 (24) sample for having neither part nor lot in modeling2, root-mean-square error RMSE With normalization relative error NRMSE (normalized rootmeanaquareerror) 3 indexs as index explanation, quantify Change the relationship between canopy leaves total nitrogen content.
Wherein xiIndicate the measured value of i-th of maize canopy leaf N content, i.e. LNC 1;yiIndicate i-th of maize canopy leaf The predicted value of nitrogen content;It is expressed as the measured value mean value of the maize canopy leaf N content of forecast set or actual measurement collection, whereinN indicates sample size.
Three, a kind of modeling process of the total nitrogen content evaluation method of crop canopies blade
A kind of modeling process of the total nitrogen content evaluation method of crop canopies blade, includes the following steps:
The selection of S1, sensitivity spectrum characteristic data set
(1) arbitrarily choose the canopy leaves of corn in 48 training centers, measurement maize canopy blade 350 nm~ Reflectivity in 2500nm wave-length coverage, obtaining abscissa is wavelength, and ordinate is the spectrogram of reflectivity;Remove steam shadow It rings, remaining wave band is 400nm~1350nm, 1400nm~1790nm, the canopy leaf of 1990nm~2350nm in spectrogram Piece spectrum, as a result as shown in Figure 1.
(2) the crop canopies blade after above-mentioned spectral reflectivity measurement will be carried out and is put into 105 DEG C of baking oven to dry Then 30min is dried to weight at 80 DEG C, obtains leaf samples;The leaf samples for weighing drying, then crush leaf samples, Leaf samples nitrogen content is measured with azotometer again, obtains the total nitrogen content LNC 1 of known crop canopies blade.
(3) algorithm SPA is converted using successive projection, from 400nm~1350nm, 1400nm~1790nm, 1990nm~ It is selected in the canopy leaves spectral region of 2350nm and the smallest 6 sensitive bands of LNC1 synteny, composition sensitivity spectrum feature Data set;
6 sensitive bands include for 4 canopy leaves reflectivity Ref wave bands and 2 first derivative FD wave bands;
4 canopy leaves reflectivity Ref wave bands are respectively 412nm, 724nm, 1084nm, 1343nm;2 first derivatives FD wave band is 658nm and 937nm;
The selection of S2, position feature data set
Algorithm SPA is converted using successive projection, the position wave band that the crop EO-1 hyperion nitrogen shown in the table 1 is used when studying In, the smallest two positions wave band SDb and Dr of synteny is chosen, position feature data set is constituted;
SDb is the sum of the canopy leaves spectral reflectivity first derivative FD of wave band at 490nm~530nm;
Dr is the canopy leaves spectral reflectivity first derivative FD maximum value of wave band at 680nm~760nm;
The selection of S3, vegetation index characteristic data set
SPA algorithm is converted using successive projection, it is minimum that synteny is chosen from typical vegetation index VIs shown in table 2 Two vegetation indexs, i.e. normalized differential vegetation index NDVIg-b #With difference vegetation index DVI II#, constitute vegetation index characteristic According to collection;
The NDVIg-b #=(R573-R440)/(R573+R440);
Wherein, R573The canopy leaves spectral reflectivity for being wavelength at 573nm;
R440The canopy leaves spectral reflectivity for being wavelength at 440nm;
DVI II#=RNIR-RR
Wherein, RNIRFor the mean value of the canopy leaves spectral reflectivity of wave band at 841nm~876nm;
RRFor the canopy leaves spectral reflectivity of wave band at 680nm~760nm;
The selection of S4, sensitivity spectrum variables set
SPA algorithm is converted using successive projection, from sensitivity spectrum characteristic data set, position feature data set and vegetation index Characteristic concentration filters out the small the smallest sensitivity spectrum variables set of synteny;
Wherein, sensitivity spectrum variables set include 2 canopy leaves reflectivity Ref wave bands, 1 first derivative FD wave band and Normalized differential vegetation index NDVIg-b #
2 canopy leaves reflectivity Ref wave bands are respectively 724nm and 1343nm;
1 first derivative FD wave band is 658nm;
Sensitivity spectrum variables set is subjected to Partial Least Squares Regression PLS modeling again, the full nitrogen for obtaining crop canopies blade contains Measure the appraising model of LNC: Y=3.6344-5.7351X1-4.4275X2+1236.6X3+2.0886X4
Wherein, X1: wave band is the canopy leaves reflectivity Ref at 1343nm;
X2: normalized differential vegetation index NDVIg-b #
X3: wave band is the first derivative values of reflectivity at 658nm;
X4: wave band is the canopy leaves reflectivity Ref at 724nm.
In order to further verify the application crop canopies blade total nitrogen content LNC appraising model stability and standard True property, has also done following test:
(1) it is tested by ASD FieldSpec FR2500 type field spectroradiometer in 48 training centers (modeling collection) and 24 It demonstrate,proves and arbitrarily takes one plant of plant in each area of area (test set), while measuring 48 training centers (modeling collection) and being tested with 24 The reflectivity of area (test set) is demonstrate,proved, each plant of plant measures 10 times, average, then remove the influence of steam part, use SPA algorithm filters out spectral reflectance of each plant of maize canopy blade at 440nm, 573nm, 658nm, 724nm and 1341nm Rate is denoted as R respectively440、R573、R658、R724And R1341
And then obtain NDVIg-b #=(R573-R440)/(R573+R440) specific value;In addition, passing throughR is calculated658First derivative FD658
By R1341、NDVIg-b #、FD658And R724It is brought into the estimation mould of the total nitrogen content LNC of crop canopies blade respectively Type: Y=3.6344-5.7351X1-4.4275X2+1236.6X3+2.0886X4In obtain modeling collection or test set maize canopy The prediction total nitrogen content LNCY of blade1~Y24
(2) the practical total nitrogen content of the maize canopy blade of modeling collection or test set is measured respectively with kjeldahl apparatus respectively LNC'Y'1~Y'24
(3) by the practical total nitrogen content LNC'Y' of the above-mentioned maize canopy blade for obtaining modeling collection1~Y'24With modeling collection The prediction total nitrogen content LNC Y of maize canopy blade1~Y24It substitutes intoIn Obtain coefficient of determination R2;It substitutes intoIn obtain root-mean-square error RMSE;It substitutes intoIn obtain normalization relative error NRMSE;Test set is obtained by above-mentioned Maize canopy blade practical total nitrogen content LNC'Y'1~Y'24With the prediction total nitrogen content of the maize canopy blade of test set LNC Y1~Y24It substitutes intoIn obtain coefficient of determination R2;It substitutes intoIn obtain root-mean-square error RMSE;It substitutes intoIn obtain normalization relative error NRMSE, concrete outcome such as table 3.
The practical total nitrogen content LNC''s and prediction total nitrogen content LNC of the maize canopy blade of the modeling of table 3 collection or test set Statistical analysis
, it can be seen that the canopy obtained using the total nitrogen content evaluation method of the crop canopies blade of the application from table 3 Leaf total nitrogen content is not much different compared to the practical total nitrogen content LNC' of maize canopy blade, illustrates the crop canopies of the application The total nitrogen content evaluation method of blade can accurately estimate canopy leaves total nitrogen content.
(4) in addition, with the practical total nitrogen content LNC'Y' of test set maize canopy blade1~Y'24For abscissa, with test Collect the prediction total nitrogen content LNC Y of maize canopy blade1~Y24It for ordinate, and is modeled, is obtained by Partial Least Squares Regression PLS To result such as Fig. 2, dotted line is the straight line of y=x in Fig. 2, and solid line is the practical total nitrogen content LNC' of test set maize canopy blade With test set maize canopy blade prediction total nitrogen content LNC simulation curve y=0.8422x+0.2868, from Fig. 2 more into One step illustrates that the total nitrogen content evaluation method of the crop canopies blade of the application can accurately estimate crop canopies leaf total nitrogen Content.
In conclusion SPA algorithm is converted using successive projection, from sensitivity spectrum characteristic data set, position feature data set The small the smallest sensitivity spectrum variables set of synteny is filtered out with vegetation index characteristic concentration;Again by sensitivity spectrum variables set into Row Partial Least Squares Regression PLS modeling, obtains the appraising model of the total nitrogen content LNC of crop canopies blade, which being capable of essence True estimation crop canopies leaf total nitrogen content, is not much different with measured value.
When embodiment provides numberical range, it should be appreciated that except non-present invention is otherwise noted, two ends of each numberical range Any one numerical value can be selected between point and two endpoints.Unless otherwise defined, the present invention used in all technologies and Scientific term is identical as the normally understood meaning of those skilled in the art of the present technique.Except specific method, equipment used in embodiment, Outside material, grasp and record of the invention according to those skilled in the art to the prior art can also be used and this Any method, equipment and the material of the similar or equivalent prior art of method described in inventive embodiments, equipment, material come real The existing present invention.
Disclosed above is only presently preferred embodiments of the present invention, and still, the embodiment of the present invention is not limited to this, Ren Heben What the technical staff in field can think variation should all fall into protection scope of the present invention.

Claims (6)

1. a kind of total nitrogen content evaluation method of crop canopies blade, which is characterized in that comprising steps of
S1, algorithm SPA is converted using successive projection, is selected from canopy leaves spectral region complete with known crop canopies blade The smallest 6 sensitive bands of nitrogen content LNC1 synteny constitute sensitivity spectrum characteristic data set;
6 sensitive bands are 4 canopy leaves reflectivity Ref wave bands and 2 first derivative FD wave bands;
4 canopy leaves reflectivity Ref wave bands are respectively 412nm, 724nm, 1084nm, 1343nm;
2 first derivative FD wave bands are 658nm and 937nm;
S2, algorithm SPA is converted using successive projection, in the position wave band used when being studied from crop EO-1 hyperion nitrogen, chosen altogether Linear the smallest two positions wave band SDb and Dr, constitute position feature data set;
SDb is the sum of the canopy leaves spectral reflectivity first derivative FD of wave band at 490nm~530nm;
Dr is the canopy leaves spectral reflectivity first derivative FD maximum value of wave band at 680nm~760nm;
S3, SPA algorithm is converted using successive projection, the smallest two vegetation of synteny is chosen from typical vegetation index VIs Index, i.e. normalized differential vegetation index NDVIg-b #With difference vegetation index DVI II#, constitute vegetation index characteristic data set;
NDVIg-b #=(R573-R440)/(R573+R440);
Wherein, R573The canopy leaves spectral reflectivity for being wavelength at 573nm;
R440The canopy leaves spectral reflectivity for being wavelength at 440nm;
DVI II#=RNIR-RR
Wherein, RNIRFor the mean value of the canopy leaves spectral reflectivity of wave band at 841nm~876nm;
RRFor the canopy leaves spectral reflectivity of wave band at 680nm~760nm;
S4, SPA algorithm is converted using successive projection, from sensitivity spectrum characteristic data set, position feature data set and vegetation index Characteristic concentration filters out the small the smallest sensitivity spectrum variables set of synteny;
Wherein, sensitivity spectrum variables set includes 2 canopy leaves reflectivity Ref wave bands, 1 first derivative FD wave band and normalization Vegetation index NDVIg-b #
2 canopy leaves reflectivity Ref wave bands are respectively 724nm and 1343nm;
1 order derivative FD wave band is 658nm;
Sensitivity spectrum variables set is subjected to Partial Least Squares Regression PLS modeling again, obtains the total nitrogen content LNC of crop canopies blade Appraising model: Y=3.6344-5.7351X1-4.4275X2+1236.6X3+2.0886X4
Wherein, X1: wave band is the canopy leaves reflectivity Ref at 1343nm;
X2: normalized differential vegetation index NDVIg-b #
X3: wave band is the first derivative values of canopy leaves reflectivity at 658nm;
X4: wave band is the canopy leaves reflectivity Ref at 724nm.
2. the total nitrogen content evaluation method of crop canopies blade as described in claim 1, which is characterized in that the canopy leaves Spectral region is 400nm~1350nm, 1400nm~1790nm, 1990nm~2350nm, and the canopy leaves spectral region It chooses and obtains by the following method:
Reflectivity of the crop canopies blade in 350nm~2500nm wave-length coverage is measured, obtaining abscissa is wavelength, ordinate For the spectrogram of reflectivity;Removing steam influences, in spectrogram remaining wave band be 400nm~1350nm, 1400nm~ The canopy leaves spectrum of 1790nm and 1990nm~2350nm.
3. the total nitrogen content evaluation method of crop canopies blade as described in claim 1, which is characterized in that the known crop The total nitrogen content LNC1 of canopy leaves detects to obtain by azotometer.
4. the total nitrogen content evaluation method of crop canopies blade as described in claim 1, which is characterized in that the known crop The total nitrogen content LNC1 of canopy leaves is obtained by the following method:
By carry out spectral reflectivity measurement after crop canopies blade be put into 100 DEG C~110 DEG C of baking oven dry 25min~ 35min is dried to weight at then 75 DEG C~85 DEG C, obtains leaf samples;The leaf samples for weighing drying, then by leaf samples It crushes, then measures leaf samples total nitrogen content with azotometer, obtain LNC1.
5. the total nitrogen content evaluation method of crop canopies blade as described in claim 1, which is characterized in that the first derivative The formula of FD is as follows:
Wherein, Rλ(j)It is the reflectivity of wave band j, Rλ(j+1)The reflectivity of wave band j+1, λ (j+1)-λ (j) be wave band j and j+1 it Between wavelength difference;
The first derivative of first derivative FD reflectivity of wavelength midpoint i between wave band j and j+1.
6. the total nitrogen content evaluation method of crop canopies blade as described in claim 1, which is characterized in that the crop canopies Blade is maize canopy blade or wheat canopy blade.
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