Monitoring Growth Characteristics Based On Canopy Transmission Spectrum In Winter Wheat

Real-time and accurate monitoring of wheat growth is an urgent need for the development of modern precision agriculture,providing technical reference for timely adoption of appropriate field management measures.The distribution and reduction of light in the canopy are closely related to the canopy structure of crop.The study of growth monitoring based on canopy transmission spectrum is conducive to the rapid monitoring of wheat growth and the optimization of field management.Therefore,based on field experiments in different years,varieties,water and nitrogen gradients and growth periods,this study analyzed the transmission spectra and the quantitative relationship between plant water content and LAI,explored the spatial distribution of the amount of the canopy within the pervious to light and the quantitative relationship between wheat growth parameters.The expected results provide theoretical basis and technical support for winter wheat growth monitoring.Firstly,based on the different spzuizhongectral characteristics of canopy transmittance and first-order differential under different nitrogen and irrigation treatments,the quantitative relationship between transmission spectrum and first-order differential and plant water content in different growth stages was systematically analyzed and compared.In the difference of light quality,the sensitive water content and parameters of plant water content were selected,and the monitoring parameters of wheat plant water content based on sensitive parameters were established.The results show that the first-order differential transmission spectral parameters sensitive to the water content of wheat plants mainly include red edge amplitude(Dr),red and blue amplitude normalization index(Dr-Db)/(Dr+Db),and red edge area(SDr).right peak area(RSDR),bimodal area ratio(RIDA),and bimodal area normalization index(NDDA),based on the quantitative relationship between the red-edge double-peak area ratio(RIDA)and the normalized index(NDDA)The equation predicts the water content of wheat plants with high accuracy and stability.Secondly,based on the clear changes of wheat canopy leaf area index(LAI)and PAR transmittance with nitrogen application rate and growth process,the vertical variation of other light transmittance and its correlation with corresponding LAI were further analyzed.The results showed that LAI showed a single peak dynamic change with the promotion of growth period,the highest value appeared in the heading stage,and increased with the increase of nitrogen application rate;PAR transmittance decreased first and then increased with the growth period,and with the application Nitrogen levels increase and decrease.The correlation between the light transmittance of different light qualities and the corresponding LAI showed a significant negative exponential correlation.The different levels of light quality were from strong to weak: red edge,blue light,PAR,green light,near infrared and red light.Regression analysis was carried out between the light transmittance and the LAI.The red edge transmittance,blue light transmittance and PAR transmittance were better(R2 > 0.740),especially the red edge transmittance-LAI model was reliable.The wheat leaf area index was monitored with the highest accuracy(R2=0.752).At last,based on the clarification of the correlation between the light quality interception of the canopy spatial site and the main agronomic indicators,the feasibility of monitoring the growth of wheat based on the high-quality spectrum of canopy site combination was established.The results showed that the leaf area index and plant nitrogen content were fitted to R/FR1-9 and GR1-9(1: the near-positional point of the planting level;9: the 40 cm height of the inter-row level).It has strong consistency during different growth periods,and a unified model can be established,and the fitting equation has higher precision;a single-time fitting equation needs to be established between plant water content and biomass and R/FR1-9 and BL1-9.Overall,the use of R/FR1-9 can better indicate the dynamic changes of leaf area index,plant nitrogen content,plant water content and plant biomass,and has broad application prospects in crop growth monitoring.To sum up,the transmission light information in the canopy of wheat is related to the growth accounts of wheat closely.Based on the canopy transmission spectrum information,the wheat growth status can be monitored in real time and accurately,which can promote the development of information agriculture and provide a solid theoretical basis for agricultural standardized production.