Estimating leaf area index considering the crop geometry effection

The quantitative effect of crop canopy reflected spectrum by leaf area index (LAI) and average leaf angle (ALA) was studied. Effect of ALA on canopy reflected spectrum can not be ignored with inversion of LAI and monitoring of crop growth condition by remote sensing technology. It indicated that canopy reflected spectrum has significant difference between erective and horizontal cultivars by radiative transfer model and measured experiment data. Investigations have been made on identification of erective and horizontal cultivars by bidirectional canopy reflected spectrum. The bidirectional reflectance of visible and near infrared bands at 15 degrees, 30 degrees and 45 degrees field of view for the main viewing plane could be used for identification of plant structural types based on bidirectional data. For erective varieties, the bidirectional canopy reflectance at near infrared was f45 degrees>f15 degrees> f30 degrees, at visible band was f45 degrees>f15 degrees approximate to f30 degrees; For middle varieties, the bidirectional canopy reflectance at near infrared and visible band was f15 degrees>f45 degrees> f30 degrees; For loose varieties, the bidirectional canopy reflectance at near infrared and visible band was f45 degrees>f30 degrees> f15 degrees. So, it is feasible to identify loose, middle and erective varieties of wheat by bidirectional canopy reflected spectrum. The result indicates that the application of EVI is affected by LAD, so LAD should be considered when retrieve LAI using enhanced vegetation index (EVI).