Research on hyperspectral reflectance characteristics for spring wheat in rainfed agriculture areas of Loess Plateau

Diagnosis of crop growth and nutrient status is critical for prediction of agriculture yield and quality at Growth stage. An experiment was conducted for find out spr-wheat canopy and leaf spectral characters non-destructively measurement. The experiment included four cultivars and seven levels of density (D) in 2006. Hyperspectral canopy and leaf reflectance (350-2500 nm) data recorded at various growth stages were measured by an ASD Field Spec Pro FR2500 in different stages, and the contents of Leaf area indices (LAI) of spr-wheat , measured by a LAI2000 plant canopy analyzer, ground dry biomass(ADM) and the plant height(PH) to the spectra were determined. The results revealed that the spectral differences were clear for the canopy and leaves of spr- wheat under different density levels at booting and ripening stage. The hyperspectral reflectance of the canopy and the leaf for four species spr-wheat in the same density were compared and it indicated that there is obviously difference in these four kinds spr-wheat leaf spectral reflectance in NIR region at booting stage. This indicates the possibility to identify the wheat type using the hyperspectral reflectance data. Furthermore, the red edge feature showed there were "double peak" for the spr-wheat at booting stage and the 'blue shift' phenomena for the position of red edge (lambdared)from booting to ripening, meanwhile, the results showed that the lambdared,Dlambdaredand Sredwere the sign of the wheat growing. And lambdaredmay indicate the grown period. The LAI, ADM were significantly correlative to the spectral variables, and the relationship among NDVI and LAI and ADM is the best at booming stage and that of the ratio of the NIR and green and LAI and ADM is the best at ripening stage. Dlambdaredand PH are good correlation. This indicated that some right spectral variables would be used to estimate the biophysical parameters for spr-wheat.