Study On Monitoring Nitrogen And Soluble Sugar Of Winter Wheat Based On Spectral Remote Sensing Data

Nitrogen is essential mineral elements to the growth and development of winter wheat it is the main component of winter wheat protein,nucleic acid,phospholipid,many enzymes and coenzyme,hormone,chlorophyll which are closely related to photosynthesis.Soluble sugar is mainly acquired through the plant photosynthesis.Soluble sugar gives energy and metabolic intermediate to winter wheat growth and development,and it also plays an important role in the signal function.In addition,soluble sugar is important regulatory factor for the winter wheat growth and gene expression.In current years,unreasonable use of chemical fertilizers will lead to the disorder metabolism of plant nitrogen and sugar,and the negative effect on the quality of winter wheat will also commonly happeced.Moreover,it caused the pollution of the environment.With the development of remote sensing technology,it supports potential tools to to timely,accuratly and nondestructively monitor the physiological and biochemical indicators of winter wheat in order to provide the basis for guiding precise fertilization.In this paper,the winter wheat experiment conducted in Xialinghou village of Wenxi county was as the research object.The canopy spectral characteristics of winter wheat in irrigated land and dry land,and the achange rule of content of chlorophyll,carotenoid,leaf area index(LAI),plant nitrogen and soluble sugar were analyzed.We also contructed quantitative relationship between the content of chlorophyll,carotenoids,LAI,plant nitrogen,soluble sugar and vegetation indexes derived from the hyper spectral and satellite remote sensing data.Thus the spectral monitor models of plant nitrogen and soluble sugar were constructed based on the intermediate variables of chlorophyll content,carotenoids,leaf area index.Moreover,mathematical statistical methods have been applied to analyze the quantitative relationship between soil nitrogen and plant nitrogen and to build a spectral monitor model of soil nitrogen.The main results were as follows:1.At different growth stages,the change trend of chlorophyll,carotenoid content,LAI,nitrogen content,soluble sugar content of winter wheat were consistent in irrigated land and dry land.The chlorophyll and the carotenoid of winter wheat in dry land were higher than irrigated winter wheat.However,the LAI,nitrogen content and the soluble sugar content was higher in irrigated land.2.At different growth stages of winter wheat,the cnopy spectral changed consistently in irrigated land and dry land.There was a peak at 550 nm,and the reflectance of 650-750 was quickly changed,and reflectivity of 750-1350 was ups and downs.There was a spectral peak in red edge position of first derivative spectral reflectance.The original canopy spectral curve and first derivative spectra curve graduly smoothed from the jointing stage to the mature stage of winter wheat.3.Comparing the model performance of nitrogen,the best predictive models were based on the link of chlorophyll at the jointing stage for both irrigated and rainfed winter wheat with R2=0.9146,0.7708;RE=0.1847,0.1216;RMSE=0.0309,0.0317,repectively.The chlorophyll proved to be highly related to the nitrogen and the vegetation indexes as predictive model performed best for both irrigated and rainfed winter wheat at heading stage and filling stage.For the monitor models of soluble sugar,the intermediate variable was different in irrigated land and dry land at the different growth stage.However,all models performed reliable and robust after the validation.4.The nitrogen and soluble sugar models based on the satellite remote sensing data was feasible by analyzing the decision coefficient,relative error and root mean square error.However,compared the performance of hyperspectral models,the models based on the satellite remote sensing data was not good.5.The canopy spectral reflectance of the winter wheat at each growth stage and the soil nitrogen content were significantly different under different levels of nitrogen fertilizer.Soil nitrate nitrogen,available nitrogen and the nitrogen content of the winter wheat reached to significant levels,and their relation coefficient was ranged from 0.73 to 0.82.However,the soil total nitrogen content and the nitrogen content of the winter wheat plants are hardly relevant.The best spectra parameters of the remote monitoring model of the soil nitrate nitrogen and available nitrogen contents are SAVI(1040,680)and RVI(1040,680)respectively,which is consistent with the result of validating model.