Winter wheat geometry identification by bidirectional canopy reflected spectrum

Abstract

Effect of crop leaf angle on canopy reflected spectrum cannot be ignored in the inversion of leaf area index (LAI) and the monitoring of the crop growth condition using remote sensing technology. In this study, experiments on winter wheat (Triticum aestivum L.) were conducted to identify crop leaf angle distribution (LAD) by bidirectional canopy reflected spectrum. Canopy reflected spectrum has significant differences among erectophile, planophile and horizontal geometry varieties at essentially the same LAI value. Canopy reflectance value at near infrared of the erectophile variety was lower than that of the horizontal variety. The effects of LAI and crop LAD on canopy reflectance were studied among erectophile, planophile and horizontal LAD varieties. The Standard Deviation (STDEV) of canopy reflectance at the near infrared bands (800 nm and 1100 nm) was more significant than those of visible bands (450 nm, 550 nm, 680 nm). It indicates that near infrared bands could be used for different LAD wheat varieties identification. The method for identification of crop geometry parameters was by the bidirectional canopy reflectance at different wave bands and view
angles. The bidirectional reflectance of visible and near infrared bands at 15°, 30°and 45°field of view for the main viewing plane could be used for identification of erectophile, planophile and horizontal LAD varieties based on bidirectional data. For erectophile varieties, the bidirectional canopy reflectance at near infrared was f45°＞f15°＞f30° (f45°, f15°and f30°mean the canopy reflectance at 45°, 15°, and 30°, respectively), in the visible band it was f45°＞f15° ≈ f30°. For planophile varieties, the bidirectional canopy reflectance in the near infrared and visible band was f15°＞ f45°＞f30°. For horizontal varieties, the bidirectional canopy reflectance in the near infrared and visible band was f45° ＞f30°＞f15°. So, it is feasible to identify erectophile, planophile and horizontal varieties of wheat by bidirectional canopy reflected spectrum.

Keywords: winter wheat, bidirectional canopy reflectance, crop geometry, leaf orientation value (LOV)
DOI: 10.3965/j.issn.1934-6344.2008.02.027-031
Citation: Huang Wenjiang, Wang Jihua, Wang Zhijie, Ma Zhihong, Zhao Chunjiang. Winter wheat geometry
identification by bidirectional canopy reflected spectrum. Int J Agric & Biol Eng. 2008; 1(2): 27－31.