CN103868880B - Wheat leaf blade nitrogen content monitoring method based on the bimodal index of spectrum and the construction method of monitoring model thereof - Google Patents
Wheat leaf blade nitrogen content monitoring method based on the bimodal index of spectrum and the construction method of monitoring model thereof Download PDFInfo
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Abstract
The invention discloses a kind of wheat leaf blade nitrogen content monitoring method based on the bimodal index of spectrum and the construction method of monitoring model thereof, it is intended to solve existing wheat leaf blade nitrogen content monitoring model universality and the relatively low technical problem of accuracy.The construction method of present invention wheat leaf blade based on the bimodal index of spectrum nitrogen content monitoring model comprises the following steps: information gathering；Delimit band, red limit；Build the bimodal index in red limit；Determine optimum critical cutting wave band；Set up monitoring model；Testing model.The present invention constructs the wheat leaf blade nitrogen content monitoring model that precision is high, universality is good；Autgmentability and the stability of this monitoring model are strengthened, and the monitoring of wheat leaf blade nitrogen content is had higher precision and accuracy.Present invention wheat leaf blade based on the bimodal index of spectrum nitrogen content monitoring method, uses aforementioned monitoring model, estimates Semen Tritici aestivi Leaf nitrogen concentration in field to be measured, and accuracy is high, method is simple, easily operated.
Description
Technical field
The present invention relates to agricultural vegetation growth information non-destructive monitoring art field, be specifically related to a kind of wheat leaf blade nitrogen content monitoring method based on the bimodal index of spectrum and the construction method of monitoring model thereof.
Background technology
Semen Tritici aestivi is the cereal crops that China is important, during wheat planting, nitrogenous fertilizer uses the effective way being to improve its yield and quality, along with amount of nitrogen increases, though yield of wheat improves to some extent, but nitrogen utilization efficiency substantially reduces, environmental pollution effect increases the weight of, and more has that plant lodging, the ripest remaining green when it is due to become yellow and ripe, pest and disease damage increase the weight of and the danger such as quality deteriorates.According to statistics, the chemical nitrogen fertilizer in being manured into soil only has 35%～50% utilization absorbed by crops, the especially Semen Tritici aestivi utilization rate only 32% to nitrogenous fertilizer, and remaining major part leaching loss to lower soil, water body and evaporate in air.Excess uses chemical fertilizer, not only causes the environmental problems such as soil, water body, air, also can pollute agricultural product, affect health, add production cost simultaneously.Therefore, greatly develop wheat crop growth real time monitoring, wheat plant Nitrogen Status is carried out in real time, quickly and correctly detects, accurately management and regulation and control amount of application of nitrogen fertilizer, to guaranteeing crop yield and QT Quality Target, improving fertilizer utilization efficiency, reduce environmental pollution significant, this is also the key technology that modern agriculture fertilizing management is in the urgent need to address.
Traditional crop plant nitrogen content detection method depends on destructive sampling, lab analysis measures, although result is more reliable, but time and effort consuming cost is high, and has certain hysteresis quality.In recent years, fast development along with hyperspectral technique, application spectrum lossless detection technology can monitoring crop nitrogen nutritional status real-time, it has also become current and future field crops growing way and the important method of nutrient diagnosis, accurately manages the reliable technical support of offer for crop nitrogenous fertilizer.At present, numerous scholars propose sensitive wave length and the method for a lot of non-destructive monitoring green vegetation nitrogen contents, as directly used spectral reflectivity estimation plant nitrogen content, the different sensitive band of utilization builds ratio vegetation index monitoring nitrogen content, application spectral signature variable (such as curve of spectrum reflection peak or absorption paddy feature and derivative spectrum characteristic quantity etc.) direct inversion N content of crop tissue；Many researcheres are had to use polynary gradually linear regression technology to set up N content of crop tissue Forecast of Spectra equation further.Above method is mostly based on multispectral data and carries out, there are spectral resolution low, the shortcoming that wavelength band is little, and analysis of based on EO-1 hyperion only uses a few characteristic wave bands, the excavation application level causing vegetation EO-1 hyperion abundant information is inadequate so that the nitrogen spectrum evaluation method of structure exists the limitation that autgmentability is strong, stability lacks.In addition, there will be in spectrum monitoring technique study, single band model stability is poor, there is oversaturated defect in two waveband vegetation index model, especially in wheat increase yield process, colony is big, Dry-matter production is high so that the accurately instruction sensitivity of plant nitrogen nutrition is deteriorated by two waveband vegetation index.Meanwhile, forefathers choose the spectral signature variable of establishment and multiband model also slightly complicated in structure and algorithm, thus cause the temporal and spatial stability of monitoring model, universality and monitoring accuracy poor, have slackened its production application to a certain extent.Therefore, under the rigid demand that Unit Grain Production constantly refreshes, trying to explore new core sensitive band, developing algorithm is simple and the spectral index of reliable results will be the emphasis applied in modern agricultural production of non-destructive monitoring technology and difficult point.
Summary of the invention
For above-mentioned the deficiencies in the prior art, the technical problem to be solved in the present invention is to provide that a kind of universality is good, accuracy is high and mechanistic strong wheat leaf blade nitrogen content monitoring method based on the bimodal index of spectrum and the construction method of monitoring model thereof.
The construction method of present invention wheat leaf blade based on the bimodal index of spectrum nitrogen content monitoring model, comprises the following steps:
(1) information gathering: the hyperspectral information of the wheat canopy blade of the different growing stage in collection zones of different the most respectively, then use five step smoothing methods of routine that the curve of spectrum is smoothed；Tong Bu with spectral information collection, the corresponding wheat leaf blade actual measurement nitrogen content gathering wheat leaf blade sample and determining different growing stage in zones of different with conventional method of analysis；
(2) band, red limit delimited: select wavelength 680nm as red limit starting point, 755nm as red limit terminal, there is the feature of obvious double-peak feature in the first derivative spectra according to wheat canopy blade in the range of this red limit, determines that this critical cutting wave band of bimodal is k；
(3) the bimodal index in red limit is built: calculated the bimodal index in red limit by following formularaNVI:
,
Wherein, k is the wheat canopy spectrum critical cutting wave band in the range of red limit,R 755、R 680、R kIt is respectively the wheat canopy blade spectral reflectivity corresponding to 755nm, 680nm, k nm wave band；
(4) optimum critical cutting wave band is determined: by bimodal for red limit indexraCorresponding with step (1) gained for NVI wheat leaf blade actual measurement nitrogen content carries out correlation analysis, uses the fine sampling method of high-spectral data decrement, take dependency the highest time k value, be defined as the critical cutting wave band of optimum；
(5) monitoring model is set up: survey nitrogen content and the bimodal index in red limit according to the wheat leaf blade of different growing stageraThe direct quantitative relationship of NVI, construct following corresponding wheat leaf blade nitrogen content monitoring model: Y=a ×raNVI+b
, wherein, Y is wheat leaf blade nitrogen content,raNVI is the bimodal index in red limit, and a is coefficient, and b is constant term, and the value of a, b is tried to achieve via linear regression mode.
Also include after step (5): step (6) testing model:
Use accuracy and the universality of independent time Semen Tritici aestivi test data Test And Checkout step (5) described wheat leaf blade nitrogen content monitoring model, use multiple correlation coefficientR 2 , root-mean-square deviation RMSE and relative error RE it is carried out overall merit, wherein the computing formula of RMSE and RE is as follows:
WhereinO i Nitrogen content value is surveyed for wheat leaf blade in test,P i For the wheat leaf blade nitrogen content value of monitoring model estimation, n is model measurement test samples number.
In described step (1), the hyperspectral information of Semen Tritici aestivi canopy leaves is measured and is used field EO-1 hyperion radiometer, and band value is 350 ~ 1100
Nm, spectrum sample is spaced apart 1.4 nm, and spectral resolution is 3 nm.
The method measuring wheat leaf blade actual measurement nitrogen content in described step (1) is: Tong Bu with spectral information collection, every community takes Semen Tritici aestivi 20 strain, press organ to separate, each organ is dried at 80 DEG C, is weighed, use its total nitrogen content of Kjeldahl nitrogen determination after pulverizing, go out wheat leaf blade actual measurement nitrogen content by various position leaves leaf dry weight weighted calculation.
In described step (4), under critical cutting wave band k is spaced the step change of 1nm between red border area in 680nm～755nm, calculate the value of its corresponding red limit bimodal index raNVI, and the wheat leaf blade actual measurement nitrogen content corresponding with described step (1) gained carries out correlation analysis, draw as k=705nm, red limit bimodal index raNVI is the highest with the dependency of wheat leaf blade actual measurement nitrogen content, and then obtains:
。
Being applicable to the Semen Tritici aestivi in the Yellow River and Huai He River region from the jointing stage to the wheat leaf blade nitrogen content monitoring model in grouting later stage is: Y=3.7032 ×raNVI+0.6922。
Having the beneficial effects that of the construction method of present invention wheat leaf blade based on the bimodal index of spectrum nitrogen content monitoring model:
1. based on the bimodal index of spectrum, construct the wheat leaf blade nitrogen content monitoring model that precision is high, universality is good, significantly enhance and use the mechanistic of monitoring model estimation wheat leaf blade nitrogen content；
2. the abundant spectral information that in the method makes full use of characteristic wave bands, multiple wavelength are provided, simplifies comprehensive computing and the structure optimization of wheat canopy blade multiband light spectrum information so that autgmentability and the stability of the monitoring model that the method builds are strengthened；
3. overcome existing vegetation index in wheat increase yield process, tend to saturated and that Leaf nitrogen concentration sensitivity is declined defect, especially wheat leaf blade nitrogen content monitoring under different location, different cultivars, different Nitrogen Level is had higher precision and accuracy；
4. achieve the real-time acquisition of wheat nitrogen information, hardware product exploitation for the lossless tacheometer of portable nitrogen provides critical bands selection, promote crop nitrogenous fertilizer based on spectral analysis technique and accurately manage the extensive application with Efficient Techniques of Regulating, establish technical foundation for the remote sensing technology directly application in accurate agricultural.
Present invention wheat leaf blade based on the bimodal index of spectrum nitrogen content monitoring method comprises the following steps:
(a) information gathering: the hyperspectral information of the first wheat canopy blade gathered according to a conventional method in field to be measured, then with five conventional step smoothing methods, the curve of spectrum is smoothed；
B () calculates red limit bimodal index raNVI: according to the hyperspectral information of step (a) gained, calculates the red limit bimodal index raNVI of wheat canopy blade in field to be measured according to the described step (3) in the construction method of above-mentioned wheat leaf blade nitrogen content monitoring model, (4)；
(c) calculate wheat leaf blade nitrogen content: according to above-mentioned wheat leaf blade nitrogen content monitoring model calculate the wheat leaf blade nitrogen content Y:Y=a in field to be measured ×raNVI+b
, wherein, Y is wheat leaf blade nitrogen content,raNVI is the bimodal index in red limit, and a is coefficient, and b is constant term.
In described step (a), the hyperspectral information of Semen Tritici aestivi canopy leaves is measured and is used field EO-1 hyperion radiometer, and band value is 350 ~ 1100
Nm, spectrum sample is spaced apart 1.4 nm, and spectral resolution is 3 nm.
In described step (b), k=705nm,。
Being applicable to the Semen Tritici aestivi in the Yellow River and Huai He River region from the jointing stage to the wheat leaf blade nitrogen content in grouting later stage monitoring equation is: Y=3.7032 ×raNVI+0.6922。
Having the beneficial effects that of present invention wheat leaf blade nitrogen content monitoring method based on the bimodal index of spectrum:
1. using aforementioned wheat leaf blade nitrogen content monitoring model based on the bimodal index of spectrum, estimate Semen Tritici aestivi Leaf nitrogen concentration in field to be measured, method is simple, it is easy to operation；
2. simplify comprehensive computing and the structure optimization of wheat canopy blade multiband light spectrum information, overcome existing vegetation index in wheat increase yield process, tend to saturated and that Leaf nitrogen concentration sensitivity is declined defect, wheat leaf blade nitrogen content monitoring under different location, different cultivars, different Nitrogen Level is had higher precision and accuracy；
3. achieve the real-time acquisition of wheat nitrogen information, hardware product exploitation for the lossless tacheometer of portable nitrogen provides critical bands selection, promote crop nitrogenous fertilizer based on spectral analysis technique and accurately manage the extensive application with Efficient Techniques of Regulating, establish technical foundation for the remote sensing technology directly application in accurate agricultural.
For concrete operation step and the flow process of the present invention, make further details of explanation by combining accompanying drawing below.
Accompanying drawing explanation
Fig. 1 is the flow chart of the construction method of present invention wheat leaf blade based on the bimodal index of spectrum nitrogen content monitoring model.
Fig. 2 is raNVI and the dependency diagram of wheat leaf blade nitrogen content under different critical cutting wave band (k nm) of the present invention.
Fig. 3 is the modelling effect figure of raNVI of the present invention and wheat leaf blade nitrogen content monitoring model.
Fig. 4 is the test effect figure of raNVI of the present invention and wheat leaf blade nitrogen content monitoring model.
Detailed description of the invention
The flow chart of the construction method of present invention wheat leaf blade based on the bimodal index of spectrum nitrogen content monitoring model is as it is shown in figure 1, be embodied as step the following detailed description of the method.
(1) information gathering: utilize field EO-1 hyperion radiometer to use observation technology vertically downward to measure the hyperspectral information data that wheat canopy comprises 350-1100nm wavelength band, then use five step smoothing methods of routine that the curve of spectrum is smoothed；Tong Bu with spectral information collection (simultaneously, same to place), corresponding collection wheat plant sample, divides sample through plant, dries, pulverizes and weigh, use Kjeldahl nitrogen determination wheat leaf blade actual measurement nitrogen content (%).
(2) band, red limit delimited: select wavelength 680nm as red limit starting point, 755nm as red limit terminal, there is the feature of obvious double-peak feature in the first derivative spectra according to wheat canopy blade in the range of this red limit, determines that this critical cutting wave band of bimodal is k.
Red limit (rededge) is that the reflectance formed at the Multiple Scattering of blade interior at the strong absorption of red spectral band chlorophyll and near infrared band light due to vegetation steeply rises, and is formed steep and is bordering on the hypotenuse of straight line.This specific form in reflection spectrum curve is peculiar by plant, and Chinese scholars gives the concern of height to this always, and is called " red limit ", and its wavelength location is typically in 660～770nm.Red limit is that wheat leaf blade reflectance between 680nm～760nm increases the fastest region, belong to the zone of transition of red light region and near infrared region, also it is the first derivative spectra flex point in this interval, comprising ground object target quantity of information the abundantest, the description on red limit includes position and the slope on red limit on red limit.Red limit is closely related with the various physical and chemical parameters of vegetation, is to describe plant pigment state and the important instruction wave band of health status, and therefore, red limit is the ideal tools of remote sensing investigation vegetation state.
Under different nitrogenous fertilizer gradient growing ways in the red edge regions of wheat canopy blade (680～760
Nm) the first derivative spectra has obvious response feature, first differential data stabilization near 680 nm, can be red limit starting point, and absorbs by force paddy for oxygen and water near 760 nm, and its first derivative spectra is unstable, can be by 755
Nm is as red limit terminal.Plant nitrogen nutrition is the most sufficient, and leaf area index is the biggest, and red limit slope is the biggest, and corresponding vegetation growth state is the best, and Red edge position there will be " moving to right ", and red limit slope becomes big；Otherwise, then Red edge position can accordingly " blue shift ", and red limit slope diminishes.Based on this, whole red limit (680～755 nm) quadratures as an entirety and calculates to obtain red limit area (SDr), and it all changes in regularity with nutrition status of the plant, growing way feature and growthdevelopmental stage.Although red limit area SDr is affected relatively big by crop growing state and nitrogen nutrition, but it is not high enough to the sensitive of wheat leaf blade nitrogen content, it is difficult to directly utilizes this formal parameter and directly indicates wheat plant nitrogen nutritional status.There is obvious double-peak feature in the canopy leaves the first derivative spectra of different growing way Semen Tritici aestivis in the range of red limit, determines that a boundary positions or line are as critical cutting wave band k, two such unimodal area (A at bimodal680-k, Ak-755) relative size different with nitrogen level performance with wheat growth period.
(3) the bimodal index in red limit is built: calculated the bimodal index in red limit by following formularaNVI:
,
Wherein, k is the wheat canopy spectrum critical cutting wave band in the range of red limit,R 755、R 680、R kIt is respectively the wheat canopy blade spectral reflectivity corresponding to 755nm, 680nm, k nm wave band；
Normalized difference vegetation index (Normalized difference vegetation index is called for short NVI) also referred to as green color index, it is the optimal indicator of vegetation growth state and coverage, closely related with vegetation nitrogen nutritional status.It is the reflection light estimated by EES earth exploration satellite, its red and non-linear conversion of near infrared band, total amount obtain divided by red and near infrared channels gap.It is that one uses the most extensive, effect also a kind of vegetation index form in current remote sensing information is extracted.Be currently based on HONGGUANG and near infrared reflectivity NVI vegetation index exist the most saturated, correct the shortcomings such as limited, noise is more, being difficult in adapt to the practical situation that current China land for growing field crops cereal crops resource highly dense type produces, it is indicative not accurate enough to Semen Tritici aestivi growing way and nitrogen nutritional status.
The present invention uses the bimodal index in red limitraNVI builds wheat leaf blade nitrogen content monitoring model, both the advantage of NVI index framework can have been given full play to, the advantage that red marginal ray spectrum information is abundant and sensitive information forward is cumulative can be utilized again, it is achieved the accurately monitoring of resource-intensive High-yield Wheat Fields Semen Tritici aestivi growing way and Nitrogen Status diagnosis.
Two unimodal areas of red edge regions carry out computing based on first differential numerical value, many owing to relating to wave band number, calculate process loaded down with trivial details, use integral algorithm to simplify the calculating process of vegetation index, obtain:
。
(4) optimum critical cutting wave band is determined: by bimodal for red limit indexraCorresponding with step (1) gained for NVI wheat leaf blade actual measurement nitrogen content carries out correlation analysis, uses the fine sampling method of high-spectral data decrement, take dependency the highest time k value, be defined as the critical cutting wave band of optimum.
(5) monitoring model is set up: survey nitrogen content and the bimodal index in red limit according to the wheat leaf blade of different growing stageraThe direct quantitative relationship of NVI, constructs following corresponding wheat leaf blade nitrogen content monitoring model:
Y=a×raNVI+b；
Wherein, Y is wheat leaf blade nitrogen content,raNVI is the bimodal index in red limit, and a is coefficient, and b is constant term, and the value of a, b is tried to achieve via linear regression mode.
(6) testing model: use accuracy and the universality of independent time Semen Tritici aestivi test data Test And Checkout step (5) described wheat leaf blade nitrogen content monitoring model, uses multiple correlation coefficientR 2 , root-mean-square deviation RMSE and relative error RE it is carried out overall merit, wherein the computing formula of RMSE and RE is as follows:
WhereinO i Nitrogen content value is surveyed for wheat leaf blade in test,P i For the wheat leaf blade nitrogen content value of monitoring model estimation, n is model measurement test samples number.
The present invention is described in detail below with embodiment, but following example limit the scope of the present invention never in any form.
Embodiment 1: carry out 3 field tests altogether, relates to different year, different quality types and different N fertilization, and concrete EXPERIMENTAL DESIGN is described as follows.
Test 1:2009-2010 is carried out in Agricultural University Of He'nan's science and education Demonstration Garden (Zhengzhou).Experimental cultivar is Henan wheat 49-198 and Henan wheat 34.The soil texture is moisture soil, organic 1.06%, and full nitrogen 0.091%, rapid available phosphorus 25.6 mg kg-1, available potassium 124.5
mg·kg-1.Front stubble is Semen Maydis.Test sets 5 nitrogen amount applied, respectively 0,75,150,225 and 300 kg hm-2Purity nitrogen.Respectively process to join and execute 150
kg·hm-2 P2O5With 120 kg hm-2
K2O, phosphorus potash fertilizer is completely used as base manure, and each nitrogenous fertilizer 50% that processes is used as base manure, and 50% topdressed for the jointing stage.Test random alignment, repeats for 3 times, plot area 7 × 2.9=20.3 m2, Basic Seedling 2.25 × 106·hm-2, line-spacing 20 cm, sowed October 14.Other cultivation management measures are with general High-yield Wheat Fields.This testing data is for the structure of monitoring model.
Test 2:2010-2011 is carried out in auspicious cloud town, Jiaozuo City Wen County.Experimental cultivar is Henan wheat 49-198 and Zheng wheat 366.The soil texture is cinnamon soil, organic 1.57%, and full nitrogen 0.114%, rapid available phosphorus 28.3 mg kg-1, available potassium 121.6
mg·kg-1.Front stubble is Semen Maydis.Test sets 4 nitrogen amount applied, respectively 0,90,180 and 270 kg hm-2Purity nitrogen.Respectively process to join and execute 120 kg hm-2
P2O5With 150 kg hm-2 K2O, phosphorus potash fertilizer is completely used as base manure, and each nitrogenous fertilizer 50% that processes is used as base manure, and 50% topdressed for the jointing stage.Test random alignment, repeats for 4 times, plot area 6 × 4.2=25.2 m2, Basic Seedling 1.8 × 106·hm-2, line-spacing 20 cm, sowed October 12.Other cultivation management measures are with general High-yield Wheat Fields.This testing data is for the structure of monitoring model.
Test 3:2011-2012 is carried out in Kaifeng County, Kaifeng.Experimental cultivar is short anti-58, Henan wheat 49-198 and Zheng wheat 366.The soil texture is moisture soil, organic 1.18%, and full nitrogen 0.104%, rapid available phosphorus 45.9 mg kg-1, available potassium 90.3 mg kg-1.Front stubble is Semen Maydis.Test sets 5 nitrogen amount applied, respectively 0,75,150,225 and 300 kg hm-2Purity nitrogen.Respectively process to join and execute 120
kg·hm-2 P2O5With 120 kg hm-2
K2O, phosphorus potash fertilizer is completely used as base manure, and each nitrogenous fertilizer 50% that processes is used as base manure, and 50% topdressed for the jointing stage.Test random alignment, repeats for 3 times, plot area 7 × 2.9=20.3 m2, Basic Seedling 2.7 × 106·hm-2, line-spacing 20 cm, sowed October 15.Other cultivation management measures are with general High-yield Wheat Fields.This testing data is for the inspection of monitoring model.
Concrete modeling method is as follows, and wherein, involved instrument and equipment if no special instructions, is routine instrument device；The involved raw material of industry if no special instructions, is commercially available regular industrial raw material.
(1) information gathering: wheat canopy blade hyperspectral information is measured and used U.S. Analytical
Spectral Device(ASD) company produce FieldSpec Pro FR2500 type back hanging type field EO-1 hyperion radiometer.Band value is 350 ~ 1100 nm, and spectrum sample is spaced apart 1.4 nm, and spectral resolution is 3 nm.Information measurement selects fine, calm or carry out time wind speed is the least, and time range is 10:00-14:00.During measurement, sensor probe is vertically downward, and the instrument angle of visual field is 25 °, away from canopy top vertical height about 1.0 m, ground field range a diameter of 0.44
m.Being a sampling spectrum with 10 spectrum, each observation station record 10 sampling spectrum, using its meansigma methods as the spectral reflectance value of this observation station.Tong Bu with spectral information collection, every community takes Semen Tritici aestivi 20 strain, separates by organ, and each organ is dried at 80 DEG C, weighed, and uses its total nitrogen content of Kjeldahl nitrogen determination after pulverizing, goes out wheat leaf blade actual measurement nitrogen content by various position leaves leaf dry weight weighted calculation.
(2) band, red limit delimited: select wavelength 680nm as red limit starting point, 755nm as red limit terminal, there is the feature of obvious double-peak feature in the first derivative spectra according to wheat canopy blade in the range of this red limit, determines that this critical cutting wave band of bimodal is k；Under different critical cutting wave band (k nm), the dependency of raNVI and wheat leaf blade nitrogen content is as shown in Figure 2；
(3) the bimodal index in red limit is built: calculated the bimodal index in red limit by following formularaNVI:
,
Wherein, k is the wheat canopy spectrum critical cutting wave band in the range of red limit,R 755、R 680、R kIt is respectively the wheat canopy blade spectral reflectivity corresponding to 755nm, 680nm, k nm wave band.
(4) optimum critical cutting wave band is determined: by bimodal for red limit indexraCorresponding with step (1) gained for NVI wheat leaf blade actual measurement nitrogen content carries out correlation analysis, uses the fine sampling method of high-spectral data decrement, take dependency the highest time k value, be defined as the critical cutting wave band of optimum；Under critical cutting wave band k is spaced the step change of 1nm between red border area in 680nm～755nm, calculate the value of its corresponding red limit bimodal index raNVI, and the wheat leaf blade actual measurement nitrogen content corresponding with described step (1) gained carries out correlation analysis, draw as k=705nm, red limit bimodal index raNVI is the highest with the dependency of wheat leaf blade actual measurement nitrogen content, r=0.914***, n=190, and then obtain:
。
(5) monitoring model is set up: survey nitrogen content and the bimodal index in red limit according to the wheat leaf blade of different growing stageraThe direct quantitative relationship of NVI, constructs following corresponding wheat leaf blade nitrogen content monitoring model:
Y=a×raNVI+b；
Wherein, Y is wheat leaf blade nitrogen content,raNVI is the bimodal index in red limit, and a is coefficient, and b is constant term, and the value of a, b is tried to achieve via linear regression mode.
Arbitrarily choosing k nm band po sition in red side wave section (680nm ~ 755nm), random combine is set upraThe linear regression model (LRM) of NVI and wheat leaf blade nitrogen content, take higher multiple correlation coefficient (R 2 K-band corresponding to) is as optimizing R k , thus utilize optimumraNVI sets up wheat leaf blade nitrogen content monitoring model.Based on above-mentioned newly constructedraNVI, utilizes the test data in 2009-2012 Nian Ge field experiment district, builds and is applicable to the Yellow River and Huai He River wheat during jointing stage to the Leaf nitrogen concentration monitoring model in later stage of being in the milk.Multiple by test statisticsraNVI set up monitoring model Y=a ×raNVI+b, and use multiple correlation coefficient (R 2 ) and standard error (SE) goodness of fit of monitoring model is evaluated.Fig. 3 shows the present inventionraNVI and the simulation effect of wheat leaf blade nitrogen content monitoring model, wherein vertical coordinate represents wheat leaf blade nitrogen content, and abscissa represents corresponding red limit bimodal index raNVI.Result shows, the Yellow River and Huai He River Semen Tritici aestivi from the jointing stage to the nitrogen content in grouting later stage monitoring equation is: Y=3.7032 ×raNVI+0.6922, multiple correlation coefficientR 2 Being 0.847, standard error SE is 0.390, sample number n=464.
The result of above-mentioned testing data is contrasted with the performance in wheat leaf blade nitrogen content is estimated of the existing spectral vegetation indexes, these conventional spectral vegetation indexes include: VOG, CTR, GM2, SR705, ND705, mND705, RI-1dB, REP, CAI, NAOC, TVI and DCNI etc., as shown in table 1 below.
Comparing result shows, provided by the present invention based on the bimodal index in red limitraThe accuracy of the wheat leaf blade nitrogen content monitoring model of NVI is higher, is better than existing vegetation index.
(6) testing model: in order to check the dependable with function of wheat leaf blade nitrogen content monitoring model, utilizes 2011-2012 independent trials data test above-mentioned model and check, utilize simultaneously multiple correlation coefficient between predictive value and observation (R 2 ), root-mean-square deviation (RMSE) and average relative error (RE) carry out Comprehensive Assessment, and draw 1:1 graph of a relation between observed value and predictive value, intuitively show the predictive ability of model.
By the present invention establish based on the bimodal index in red limitraThe assay of the wheat leaf blade nitrogen content monitoring model of NVI and conventional optimization vegetation index (REPle andmND705) assay compares, REPle modelR 2 , RMSE and RE be respectively 0.78,0.414 and 13.7%；mND705 modelR 2 , RMSE and RE be respectively 0.80,0.391 and 14.1%；And the present inventionraThe precision of prediction of NVI model is the highest, estimation error is minimum: as shown in Figure 4, wheat leaf blade nitrogen content based on the bimodal index in red limit from the jointing stage to grouting the later stage testing model: y=0.9023x+
0.5326, multiple correlation coefficientR 2 Being 0.848, root-mean-square deviation RMSE is 0.338, and average relative error RE is 11.9%, sample number n=190.
In sum, the construction method of present invention wheat leaf blade based on the bimodal index in red limit nitrogen content monitoring model, construct the wheat leaf blade nitrogen content monitoring model that precision is high, universality is good；Autgmentability and the stability of this monitoring model are strengthened, and wheat leaf blade nitrogen content monitoring under different location, different cultivars, different Nitrogen Level is had higher precision and accuracy.Present invention wheat leaf blade based on the bimodal index in red limit nitrogen content monitoring method, use aforementioned monitoring model, estimate Semen Tritici aestivi Leaf nitrogen concentration in field to be measured, accuracy is high, method is simple, easily operated, promote crop nitrogenous fertilizer based on spectral analysis technique and accurately manage the extensive application with Efficient Techniques of Regulating, establish technical foundation for the remote sensing technology directly application in accurate agricultural.
Above in conjunction with drawings and Examples, the present invention is described in detail, but, person of ordinary skill in the field it will be appreciated that, on the premise of without departing from present inventive concept, each design parameter in above-described embodiment can also be changed, form multiple specific embodiment, be the common excursion of the present invention, describe in detail the most one by one at this.
Claims (8)
1. the construction method of a wheat leaf blade nitrogen content monitoring model based on the bimodal index of spectrum, it is characterised in that comprise the following steps:
(1) information gathering: the hyperspectral information of the wheat canopy blade of the different growing stage in collection zones of different the most respectively, then use five step smoothing methods of routine that the curve of spectrum is smoothed；Tong Bu with spectral information collection, the corresponding wheat leaf blade actual measurement nitrogen content gathering wheat leaf blade sample and determining different growing stage in zones of different with conventional method of analysis；
(2) band, red limit delimited: select wavelength 680nm as red limit starting point, 755nm as red limit terminal, there is the feature of obvious double-peak feature in the first derivative spectra according to wheat canopy blade in the range of this red limit, determines that this critical cutting wave band of bimodal is k；
(3) the bimodal index in red limit is built: calculated the bimodal index in red limit by following formularaNVI:
,
Wherein, k is the wheat canopy spectrum critical cutting wave band in the range of red limit,R 755、R 680、R kIt is respectively the wheat canopy blade spectral reflectivity corresponding to 755nm, 680nm, k nm wave band；
(4) optimum critical cutting wave band is determined: by bimodal for red limit indexraCorresponding with step (1) gained for NVI wheat leaf blade actual measurement nitrogen content carries out correlation analysis, uses the fine sampling method of high-spectral data decrement, take dependency the highest time k value, be defined as the critical cutting wave band of optimum；
Under critical cutting wave band k is spaced the step change of 1nm between red border area in 680nm～755nm, calculate the value of its corresponding red limit bimodal index raNVI, and the wheat leaf blade actual measurement nitrogen content corresponding with described step (1) gained carries out correlation analysis, draw as k=705nm, red limit bimodal index raNVI is the highest with the dependency of wheat leaf blade actual measurement nitrogen content, and then obtains:
；
(5) monitoring model is set up: survey nitrogen content and the bimodal index in red limit according to the wheat leaf blade of different growing stageraThe direct quantitative relationship of NVI, constructs following corresponding wheat leaf blade nitrogen content monitoring model:
Y=a×raNVI+b；
Wherein, Y is wheat leaf blade nitrogen content,raNVI is the bimodal index in red limit, and a is coefficient, and b is constant term, and the value of a, b is tried to achieve via linear regression mode；
(6) testing model: use accuracy and the universality of independent time Semen Tritici aestivi test data Test And Checkout step (5) described wheat leaf blade nitrogen content monitoring model, uses multiple correlation coefficientR 2 , root-mean-square deviation RMSE and relative error RE it is carried out overall merit, wherein the computing formula of RMSE and RE is as follows:
WhereinO i Nitrogen content value is surveyed for wheat leaf blade in test,P i For the wheat leaf blade nitrogen content value of monitoring model estimation, n is model measurement test samples number.
The construction method of wheat leaf blade nitrogen content monitoring model based on the bimodal index of spectrum the most according to claim 1, it is characterized in that, in described step (1), the hyperspectral information of Semen Tritici aestivi canopy leaves is measured and is used field EO-1 hyperion radiometer, band value is 350 ~ 1100 nm, spectrum sample is spaced apart 1.4 nm, and spectral resolution is 3 nm.
The construction method of wheat leaf blade nitrogen content monitoring model based on the bimodal index of spectrum the most according to claim 1, it is characterized in that, the method measuring wheat leaf blade actual measurement nitrogen content in described step (1) is: Tong Bu with spectral information collection, every community takes Semen Tritici aestivi 20 strain, press organ to separate, each organ is dried at 80 DEG C, is weighed, and uses its total nitrogen content of Kjeldahl nitrogen determination after pulverizing, goes out wheat leaf blade actual measurement nitrogen content by various position leaves leaf dry weight weighted calculation.
The construction method of wheat leaf blade nitrogen content monitoring model based on the bimodal index of spectrum the most according to claim 1, it is characterized in that, it is adaptable to the Semen Tritici aestivi in the Yellow River and Huai He River region from the jointing stage to the wheat leaf blade nitrogen content monitoring model in grouting later stage is: Y=3.7032 ×raNVI+0.6922。
5. a wheat leaf blade nitrogen content monitoring method based on the bimodal index of spectrum, it is characterised in that comprise the following steps:
(a) information gathering: the hyperspectral information of the first wheat canopy blade gathered according to a conventional method in field to be measured, then with five conventional step smoothing methods, the curve of spectrum is smoothed；
B () calculates red limit bimodal index raNVI: according to the hyperspectral information of step (a) gained, calculates the red limit bimodal index raNVI of wheat canopy blade in field to be measured according to the described step (3) in claim 1, (4)；
C () calculates wheat leaf blade nitrogen content: the wheat leaf blade nitrogen content monitoring model set up according to claim 1 calculates the wheat leaf blade nitrogen content Y in field to be measured:
Y=a×raNVI+b；
Wherein, Y is wheat leaf blade nitrogen content,raNVI is the bimodal index in red limit, and a is coefficient, and b is constant term.
Wheat leaf blade nitrogen content monitoring method based on the bimodal index of spectrum the most according to claim 5, it is characterized in that, in described step (a), the hyperspectral information of Semen Tritici aestivi canopy leaves is measured and is used field EO-1 hyperion radiometer, band value is 350 ~ 1100 nm, spectrum sample is spaced apart 1.4 nm, and spectral resolution is 3 nm.
A kind of wheat leaf blade nitrogen content monitoring method based on the bimodal index of spectrum the most according to claim 5, it is characterised in that in described step (b), k=705nm,。
Wheat leaf blade nitrogen content monitoring method based on the bimodal index of spectrum the most according to claim 5, it is characterised in that being applicable to the Semen Tritici aestivi in the Yellow River and Huai He River region monitoring equation from the jointing stage to the wheat leaf blade nitrogen content in grouting later stage is:
Y= 3.7032×raNVI+0.6922。
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