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Proceedings Paper

Use Of Reflectivity Ratios To Measure Light Interception By Crops
Author(s): Mahendra Kumar
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Paper Abstract

A leaf typically has a small reflectance (about 0.1) in the visible spectral region and a larger reflectance (about 0.6) in the near infra-red region. Spectral differences are due to selective absorption by the chlorophyll in the red and internal leaf scattering in the near infra-red. The reflectance of a crop canopy is similar to leaf reflectance but other factors such as the orientation of leaves, shadows, background reflectivities, solar zenith angles and the physiological status of the plants modify the process. The ratio of light reflected in the near infra-red and red spectral bands is well correlated with the amount of vegetation cover. Normally, light intercepted by vegetation is determined from a knowledge of the leaf area index. It is proposed that the ratio far red/ red (or visible) can give a direct measure of the amount of light intercepted by a crop, thus bypassing destructive leaf area determinations.

Paper Details

Date Published: 18 November 1980
PDF: 7 pages
Proc. SPIE 0234, New Developments and Applications in Optical Radiation Measurement, (18 November 1980); doi: 10.1117/12.958950
Show Author Affiliations
Mahendra Kumar, University of Nottingham (United Kingdom)


Published in SPIE Proceedings Vol. 0234:
New Developments and Applications in Optical Radiation Measurement
A. J. Allnutt, Editor(s)

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