Monitoring Wheat Growth By Using Spectral Feature Of Narrow Band And Wide Band

Remote sensing can rapidly determine the growth status and production of wheat in the field, which offers important technical support for implementation of precision farming.In this study, a series of field experiments with different wheat varieties and nitrogen levels were carried out in two years. Based on analysis of canopy spectral reflectance, albedo, growth index and yield index, with statistic analysis by Matlab, Oring, Spss in wheat plant, the characteristics of canopy hyperspectral reflectance under different conditions and their correlation to nitrogen status, growth characters, and yield in wheat were quantified computed in this paper. The sensitive spectrum parameters and quantitive regression models of nitrogen status, leaf area index, biomass, greenness features and production were established. Then, testing the different models by inter-annual independent experimentral data, which provided technical basis for non-destructive monitoring and precise diagnosis of wheat growth. The main conclusions of this study are as follows:(1)In this study, we compared the variation patter of canopy reflectance, albedo under different nitrogen supply, growing stage and cultivar in wheat. Results showed that the reflectance at near infrared reflected flatincreased with increasing nitrogen supply, whereas reflectance at visible band decreased. Canopy albedo of wheat was firstly raising then falling as it grows, albedo daily variation lessened with solar elevation angel in sunny day, and there was significant linear relationship between them(R2=0.79, P<0.01).(2) The equations based on PND1690, P_Area1690all had good fitting effects, which with the leaf thickness, and the determination coefficient were0.70,0.71. Water index WI, water stress index MSI and mid-infrared simple vegetation index one MSVI1, these parameters performance stability with leaf water, the correlation reach5%significant level.(3) The relationship of Lo, SDr/SDb and leaf nitrogen content reached a significant level, and the determination coefficient of cane nitrogen content and Depth980、Area980were high. The relationship of albedo and nitrogen content was stable. Albedo and leaf N content was significantly positively correlative(R2=0.61), and the stem N content passed0.05confidence test(R2=0.42).(4) Based on the change patterns of SPAD value under different nitrogen supply with growth stages, correlations of greenness features and reflectance and albode were investigated, and put forward quantitative equation forecasting SPAD and chlorophyll of leaf in wheat. The correlation between FD664、SDr/SDb and SPAD value had reached marked level, and the relationship of those parameters and chlorophyll had reached marked level as well. And, it was piecewise function, which was built by SPAD value and albode, and the two equations all meet significantly correlated level.(5)To analyze the correlation between canopy reflectance, albode and yield index, then we found that SDr/SDb, Lo and Area672were the good versatility parameters. Whereby, the prediction accuracy of Mu ear number and SDr/SDb was0.46in the flowering peri-od, and the correlation between theoretical yield and SDr/SDb, Area672, ND672meet si-gnificantly correlated level in jointing stage. The yield index had a remarkable correlation to albode, the determination coefficient of theoretical yield and albode was0.66.The experimental result showed that using the reflectance and albedo to diagnosis and monitor wheat growing change characteristics and yield index could be more feasible, and it provided a reference for plant growing change characteristics.