Study On Estimation Model Between Rapeseed's Red Edge Parameters And SPAD

Rapeseed is the object of study in this research.ASD FieldSpec3Hi-Res is applied to acquire the canopy spectral reflectance of oilseed rape in different growth stages,and First-derivative spectroscopy is used to calculate the red edge parameters of Rapeseed in different stages.Analyzing the hyperspectral red edge features,the red edge amplitude,red edge area and correlation of SPAD of the Rapeseed under different kinds of fertilization by mathematical modeling and mathematical analysis,based on the application of MATLAB and SPSS.The red edge parameters such as the red edge area and red edge amplitude are obtained and the linear correlation of SPAD achieves at 1%,by means of significance testing.The main work and research results of this paper:1,Rapeseed's canopy spectrum red edge of the basic features:(1)In the early stage of Rapeseed's growth,due to the smaller leaf area of Rapeseed,the three-peak phenomenon of canopy spectrum was not formed completely due to the influence of soil and other factors,but with the growth of Rapeseed,Rapeseed Leaf area gradually expanded,soil and other factors on the canopy spectrum generated by the interference reduced,so the "three peaks" phenomenon began to appear.The first-order derivative spectra of the red-edged region of Rapeseed reached the unique "three-peak" phenomenon between 680 nm and 750 nm,and the three-peak position appeared at 690,719 and 724 nm,especially at flowering stage.obvious.(2)from the seedling period with the growth period,the red edge position to the long wave direction,until reaching 760 nm,red edge position began to stabilize,forming a unique "red side platform" phenomenon.(3)The effect of different cultivation factors on spectral red edge characteristics was less in the same phenological period.Compared with the different cultivating factors,the seedling Rapeseed had different influence on the red edge characteristics."50 kg / acre +2 million / mu","32.5 kg / mu +1 million / mu","32.5 kg / mu+2 million per mu" and other characteristics of the red edge of the spectrum has a great relationship.(4)The red edge area and the red edge amplitude of the rape were redshift with the growth period,and the red edge area and the red edge amplitude increased from theseedling stage to the flowering stage.The red edge area was used as a single independent variable,and the SPAD value of Rapeseed was used as the dependent variable.The linear regression,robust analysis model,polynomial regression,random forest and support vector regression modeling were used to construct the red edge Parameter and SPAD value estimation model,and the correlation accuracy of five mathematical models is detected.By observing the correlation coefficient,the results of the random forest model were better in the Rapeseed seedling stage,and the linear regression equation was more stable and the total incidence was good.The linear regression equation and the polynomial regression equation were established for three periods of rapeseed.The red edge parameter estimation model of SPAD was SPAD=-63.593Sred2 + 87.954 Sred +23.592.The fitting result was highly significant and could be applied to the model To estimate Rapeseed SPAD values.