Take a Crop's Temperature

January 25, 2013 08:05 PM
Take a Crop's Temperature

Thermal imaging provides an in-season checkup

Checkups with your doctor are designed to avert a major health issue. Thermal imaging does the same for your field.

To determine a field’s stress level, look at an aerial photo that shows the variance in crop temperature. A cooler crop is less stressed; the warmer the crop, the more it is stressed.

"We’ve been able to use color photos, NDVI maps and now thermal images as scouting aids and as tools to help define and refine management zones," says Isaac Ferrie, who led the effort of adopting this technology in the Farm Journal Test Plots.

Thermal imaging is just emerging as a tool for farmers because the high-tech camera equipment that’s required is now more feasible.

"There are expensive components of this technology, and some were restricted from commercial use because they were also used as the heat-sensing element in the Tomahawk missile," explains Brian Sutton, a farmer and pilot who started a thermal imaging service called Aerial Crop Reconnaissance Experts (ACRE). "With time, the technology has become more accessible and I’ve been able to assemble a camera system that is much less cost-prohibitive."

Sutton, who farms with his family in northern Indiana, realizes the value of evaluating a crop from above with just the naked eye. To take the benefits a step further, he started a thermal imaging business three years ago.

"One of my first flights with the camera was over one of our soybean fields. I could see variation in the image that wasn’t showing up in an NDVI map," he says. "There was a vibrant heat pattern in the center of the field. I asked my brother, who planted the field, if he had an explanation for what I was seeing. My brother remembered that he put temporary fencing around that section of the cornstalks the previous fall to graze cows. It stood out clearly, right up to the fence lines. That was three years ago now, and we can still see the compaction. What we thought was cheap feed at the time turned out to cost us about 7 bu. per acre in soybean production."

How it works. Thermal cameras measure the energy emitted by the plants to produce infrared images, which are then processed to apply the scaling to show the variation in the area. The cameras can work just as well in the darkness of night. NDVI maps show a measure of crop health with near-infrared images that rely primarily on reflected light from the sun and amplify changes in color.

The camera has the ability to decipher differences of up to three-hundredths of a degree Celsius. The thermal image is then scaled down to a narrow temperature spectrum and a color palate is applied to assess the variation.

The thermal image provides 1-meter resolution. When collecting the thermal image, the ACRE service takes a color aerial photograph with a 24-megapixel camera to check for interference from clouds. Pictures are taken 10 to 14 days apart, starting at planting and continuing throughout the growing season.

With timeliness in mind, Sutton strives to deliver images to farmers within 24 hours after the plane lands. The images can be viewed on computers, iPads or iPhones. From there, farmers can use Sutton’s custom app to align the thermal image on top of a Google Earth map and then walk through the field on foot.

This past year, Sutton coupled thermal images with in-field scouting to learn more about how disease infestations appear in the photos.

"What I don’t like about a yield monitor is that there is nothing you can do from the combine to manage that crop better," he says. "With these images, I can see the problem areas of the field midseason, and then go out and ground-truth these areas, and possibly be able to react in time to help."

The ACRE network of providers will soon include pilots across the Midwest with access to the camera system.

"We’ve tried to grow our business slowly with farmer customers interested in learning how this technology can be beneficial. This coming year, we hope to have 100,000 acres flown," Sutton says.

To learn more about thermal imaging and how it can enhance scouting efforts, visit www.FarmJournal.com/thermal_imaging

You can e-mail Margy Fischer at mfischer@farmjournal.com.

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