|Sudduth, Kenneth - Ken|
Submitted to: American Society of Agricultural Engineers Meetings Papers
Publication Type: Other
Publication Acceptance Date: 3/31/2001
Publication Date: N/A
Technical Abstract: Previous research has shown that reflectance of visible and near-infrared light can be used to predict the amount of N fertilizer needed by a corn crop. Past studies used data collected around solar noon with clear skies. However, for practical application, the system must work under cloudy skies or away from solar noon. The reflectance characteristics of canopies/plants sunder these conditions are not well known. Our objective for this project is to improve spectral radiometer reflectance corrections for variations in incoming sunlight so that reflectance readings can be used in making fertilizer recommendations regardless of time of day or cloud conditions. Spectral radiometers will be mounted in a stationary position about 25 cm above the canopy. Readings will be taken from morning until night over several days with a range of sky conditions (sunny, overcast, partly cloudy). Experiments will be done on corn ranging from knee-high to just before tasseling. Mathematical functions will be developed to compensate for the effects of changing sun angle and cloud conditions and incorporated into programs for converting radiometer readings into variable-rate N recommendations. These programs will ultimately be used for real-time control of variable-rate N applicators based on corn plant reflectance measured with a spectral radiometer.