Yet another interesting project involves the possibility of eventually developing a smart phone app that provides a reading of “corn leaf nitrogen concentration just by taking a photograph.

“It isn’t available yet, but it’s possible with current technology. You’d run the photo through a software package — maybe also on a smart phone — that would analyze it and then tell you whether your leaf nitrogen is sufficient or deficient.”

The researchers have taken it “a step further and done calibrations looking at color analysis of corn at the six leaf to eight leaf stage. From the photos, the software calculates how much nitrogen is lacking in order to recover 90 percent to 95 percent of yield potential.

“We’d like to extend that technology,” Purcell says. “We’ve looked at using this a bit in wheat, rice and cotton. We’ve looked at the method in these crops — establishing the relationship of the color from the photo to see if it correlates with leaf nitrogen. In every case, it does. But we haven’t done the calibration part like we have in corn.

“In corn, we can actually take a picture of vegetative leaves at V-6 and, from that, tell you how much nitrogen to apply to recover yield potential.”

The technology actually began in turfgrass research. Purcell and Doug Karcher, University of Arkansas turfgrass scientist, have collaborated on this for about four or five years.

“After I saw his work in turfgrass I said, ‘Doug, we should try this in some agronomic crops. Let’s give corn a try.’

“Things really fell into place, and we’re very excited about it. There is actually a patent pending on some of the technology. Perhaps it will be commercialized and be put in farmers’ hands.”

Does the photograph have to be a closeup of a leaf? A wider shot of the field?

“Up until now, most of our work has involved separating the topmost collared leaf from the corn plant,” Purcell says. “Those leaves are put on a pink background — that’s because, on the color spectrum, pink is as far away as you can get from green.

“Then, within each picture, there is a yellow disc and a dark green disc, which serve as color standards. This allows us to use different cameras, or to take the picture in different lighting conditions, under a shade tree or back at the shed under a fluorescent light. Because of the colored discs, we can adjust for those conditions.”

A special camera isn’t needed for the process — just some type of digital camera.

“The things you need for color standards can be picked up at most hardware or paint stores,” Purcell says. “Just tell them which color paint to mix, paint a board, and then you’re ready to go.

“Another possibility we’ve played with is to take the photos from an airplane. At one time, we shot photos from a plane using big plywood boards painted pink with large yellow and green circles to serve as color standards.”

But, he says, “That gets away from the idea that this should be something a farmer can utilize quickly and carry in his truck. If he feels his corn looks a bit yellow or his pre-plant N was lost due to an extended wet period, he can just take out the camera and shoot.

“We want him to be able to answer questions quickly without someone having to fly overhead snapping pictures.”