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Optical Reflectance and Fluorescence for Detecting Nitrogen Needs in Zea mays L.Nitrogen (N) status in field grown corn (Zea mays L.) was assessed using spectral techniques. Passive reflectance remote sensing and, both passive and active fluorescence sensing methods were investigated. Reflectance and fluorescence methods are reported to detect changes in the primary plant pigments (chlorophylls a and b; carotenoids) in higher plant species. As a general rule, foliar chlorophyll a (Chl a) and chlorophyll b (Chl b) usually exist in approx.3:l ratio. In plants under stress, Chl b content is affected before Chl a reductions occur. For reflectance, a version of the chlorophyll absorption in reflectance index (CARI) method was tested with narrow bands from the Airborne Imaging Spectroradiometer for Applications (ASIA). CARI minimizes the effects of soil background on the signal from green canopies. A modified CARI (MCARI) was used to track total Chl a levels in the red dip of the spectrum from the corn canopy. A second MCARI was used to track the auxiliary plant pigments (Chl b and the carotenoids) in the yellow/orange/red edge part of the reflectance spectrum. The difference between these two MCARI indices detected variations in N levels across the field plot canopies using ASIA data. At the leaf level, ratios of fluorescence emissions in the blue, green, red and far-red wavelengths sensed responses that were associated with the plant pigments, and were indicative of energy transfer in the photosynthetic process. N stressed corn stands could be distinguish from those with optimally applied N with fluorescence emission spectra obtained from individual corn leaves. Both reflectance and fluorescence methods are sensitive in detecting corn N needs and may be especially powerful in monitoring crop conditions if both types of information can be combined.
Document ID
20030093742
Document Type
Preprint (Draft being sent to journal)
Authors
McMurtrey, J. E. (Department of Agriculture Beltsville, MD, United States)
Middleton, E. M. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Corp. L. A. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Campbell, P. K. Entcheva (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Butcher, L. M. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Daughtry, C. S. T. (Department of Agriculture Beltsville, MD, United States)
Date Acquired
August 21, 2013
Publication Date
January 1, 2003
Subject Category
Earth Resources and Remote Sensing
Meeting Information
IGARSS 2003 (International Geoscience and RemoteSensing Symposium)(Toulouse)
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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