App may diagnose N needs in corn leaves
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"Farmers may soon be able to use a digital camera or smart phone to diagnose nitrogen deficiency in corn plants, based on research by Larry Purcell, professor of crop, soil, and environmental sciences, and Doug Karcher, associate professor of horticulture, in the University of Arkansas Division of Agriculture and Dale Bumpers College of Agricultural, Food and Life Sciences."
A corn leaf was photographed under different light sources. Digital images were processed to determine the dark green color index (DGCI). The green and yellow disks serve as internal standards to correct for differences in lighting conditions.
Because nitrogen deficiency can reduce yields, farmers watch for symptoms and may submit plant samples for laboratory tests to determine if a supplemental nitrogen application is needed. The research by Purcell and Karcher could result in "an app for that" -- a smart phone application.
Purcell and his graduate students developed a method to measure the "greenness" of corn leaves using a digital camera and commercially-available software. Darker green leaves indicate a higher concentration of nitrogen because it is a key nutrient for plant development.
Leaves from plants that received a range of soil-nitrogen treatments were photographed under different light conditions with a dark green disk and a yellow disk. The disks provide reference points, regardless of the light conditions, for analyzing the leaf color based on a digital Dark Green Color Index (DGCI). Digital imaging software analyzes the variation from the DGCI level of greenness for a healthy nitrogen concentration to calculate the actual concentration in the plant tissue.
"Including color disks as internal standards opens up the possibility of taking digital images directly in the field and uploading the images to a server for immediate analysis of plant nitrogen status," Purcell said.
Continued research is focused on calibrating the amount of nitrogen to apply to corn to recover yield potential based on DGCI measurements, Purcell said. He is also developing DGCI measurements as a diagnostic tool for other non-leguminous crops.
The research appears in the September–October 2011 issue of the journal Crop Science and was featured on the front page of the Crop Science Society of America Web site: http://www.crops.org/.
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