Chin J Plant Ecol ›› 2009, Vol. 33 ›› Issue (4): 791-801.DOI: 10.3773/j.issn.1005-264x.2009.04.018

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TIAN Yong-Chao, YANG Jie, YAO Xia, ZHU Yan, CAO Wei-Xing*()   

  1. Jiangsu Key Laboratory for Information Agriculture, Nanjing Agricultural University, Nanjing 210095, China
  • Received:2008-12-04 Revised:2009-03-15 Online:2009-12-04 Published:2009-07-30
  • Contact: CAO Wei-Xing


Aims Quantifying the relationship between red edge area parameter and canopy leaf nitrogen status is the foundation for real-time and non-destructive monitoring of crop growth status and precision nitrogen fertilization in rice (Oryza sativa). Our objectives were to analyze 1) characteristics of the first-derivative reflectance spectra in red edge area and 2) the quantitative relationship of red edge area shape parameters to canopy leaf nitrogen concentrations, using different nitrogen levels and rice varieties and based on canopy hyper-spectral reflectance of field-grown rice in different years.
Methods Spectrum in the red edge area was significantly affected by different nitrogen levels and different rice varieties, and a “three-peak” feature could be observed with the first derivative spectrum at about 700, 720 and 730 nm. The maximum heights of the three peak bands changed with different nitrogen levels, so sub-areas surrounded by the first derivative spectra curve and x coordinate were formed by dividing the red edge area with the “three-peak band line”. Two random sub-areas were selected to calculate ratio (double peak symmetry, DPS) and normalization (normalized double peak symmetry, NDPS), which were related to canopy leaf nitrogen concentrations.
Important findings DPS based on the ratio of two different red edge sub-areas, and NDPS with normalization of the two different red edge sub-areas were significantly related to leaf canopy nitrogen concentrations in rice. Results of model calibration and validation indicated that DPS (A675-700, A675-755) and NDPS (A675-700, A675-755), ratio and normalized difference of areas in 675-700 to 675-755 nm red edge region, respectively, performed the best in estimating leaf canopy nitrogen concentration. Thus, these two spectral indices were suitable red edge area shape parameters for monitoring leaf canopy nitrogen concentrations in rice.

Key words: Oryza sativa, leaf canopy, red edge area, double peak symmetry, normalized double peak symmetry, nitrogen concentration