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ARS Home » Plains Area » Lincoln, Nebraska » Agroecosystem Management Research » Research » Publications at this Location » Publication #138041
Title: USE OF A CROP CANOPY REFLECTANCE SENSOR TO ASSESS CORN LEAF CHLOROPHYLL CONTENT

Author
item Shanahan, John
item Schepers, James
item CALDWELL, R - UNIV OF NE/LINCOLN
item LUCHIARI, ARIOVALDO - EMBRAPA/BRAZIL
item Francis, Dennis
item Schlemmer, Michael
item HOLLAND, K - HOLLAND SCIENTIFIC

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 6/23/2002
Publication Date: 8/30/2002
Citation: Shanahan, J.F., Schepers, J.S., Caldwell, R.M., Luchiari, A., Francis, D.D., Schlemmer, M.R., Holland, K. 2002. Use of a crop canopy reflectance sensor to assess corn leaf chlorophyll content. American Society of Agronomy Abstracts. #135324. CDROM.

Interpretive Summary: The goal of this work was to evaluate the ability of passive and active multi-spectral reflectance sensors for estimating leaf chlorophyll content and serve as a trigger for N applications based on in-season readings. Reflectance for the passive sensor system is determined by measuring percent-reflected light from the canopy relative to incoming in four spectral bands (blue, green, red, and NIR). The active sensor system measures canopy reflectance by irradiating the canopy in two spectral bands (green and NIR) with modulated light emitting diodes (LED) and then demodulating the reflected light collected by the detector optics in the sensor. Variation in canopy vigor was generated in small plots in 2001 and 2002 using different N fertilizer rates, corn hybrids, and plant densities. Canopy reflectance readings were collected with both sensors along with simultaneous chlorophyll meter readings (Minolta SPAD-502) throughout the season. Sensor output was converted into green normalized difference vegetation index (GNDVI) values. Sensor-generated GNDVI values along with chlorophyll meter reading will be presented to compare and evaluate the performance of the crop canopy sensors.

Technical Abstract: The goal of this work was to evaluate the ability of passive and active multi-spectral reflectance sensors for estimating leaf chlorophyll content and serve as a trigger for N applications based on in-season readings. Reflectance for the passive sensor system is determined by measuring percent-reflected light from the canopy relative to incoming in four spectral bands (blue, green, red, and NIR). The active sensor system measures canopy reflectance by irradiating the canopy in two spectral bands (green and NIR) with modulated light emitting diodes (LED) and then demodulating the reflected light collected by the detector optics in the sensor. Variation in canopy vigor was generated in small plots in 2001 and 2002 using different N fertilizer rates, corn hybrids, and plant densities. Canopy reflectance readings were collected with both sensors along with simultaneous chlorophyll meter readings (Minolta SPAD-502) throughout the season. Sensor output was converted into green normalized difference vegetation index (GNDVI) values. Sensor-generated GNDVI values along with chlorophyll meter reading will be presented to compare and evaluate the performance of the crop canopy sensors.