The Response of Canopy Direction Reflectance Spectrum for the Wheat Vertical Leaf Distributing

The accurate information access and analysis of crop canopy are the basis of quantitative research on crop information. This experiment was conducted using two winter-wheat (Triticum aestivum)cultivars P7(leaf erect) and ZY9844(leaf horizontal). The wheat canopy direction spectral reflectance over 350–2 500nm with view angles of 0°, 30°, 60°, 90°, 120°, 150° and 180° to the vertical line to wheat row were measured, using delamination slice method from underlayer of the wheat canopy to upside at milking stage, and compared the direction spectral characteristic of removing difference leaf layer. The contributions of different layers to Canopy Direction Spectra (CDS) were preliminarily defined, which are obviously different at 300–700 nm, 800–1300 nm and 1400–1800 nm. Compared the traditional 90° observational angle, the spectral information observed at the 0° angle mainly revealed the information of upper canopy and the lower layer had little impact on their spectra. However, the spectral information observed at 30° and 60° angles reflected the whole canopy information and the status of the lower layer of canopy had great effect on their spectra. Variance analysis indicated that ear layer of canopy and the first top leaf blade made greater contributions to CDS. The reflectance spectra of upper leaves for ZY9844 had less impact than that of P7. The canopy spectral information was effected by the observation angles. It is a method to improve crop canopy spectral estimation precision that changed the measured angle for different canopy structure.