The “top-down” view gave Ogden, IA, farmer Craig Heineman a deeper insight into N placement.

“I was seeing ‘waves’ in the field,” he says — a mysterious pattern of taller corn plants that didn’t follow the rows. Heineman was stumped until he looked at an aerial photo, provided by the Iowa On-Farm Network. From above, the taller plants showed up as a line of dark green spots crossing the rows on a diagonal.

That spring, Heineman had injected anhydrous ammonia at an angle to the rows. “Every place the injection site intersected a row, the corn was greener,” he says. The advantage of planting closer to the N band was clear.

Aerial imagery also showed Heineman a potentially expensive problem with his anhydrous tool bar, which has dual shutoffs. “One side wasn’t opening up correctly,” so half the bar wasn’t putting out the full amount of N, even though his controller showed that the total amount being injected was okay. The misapplication showed up on an aerial photo of the field taken last August. So this fall, “we had the bar tested first.”

 

On irrigated cropland, aerial imagery has really opened growers’ eyes to water-distribution problems, especially on center pivot irrigation, says Dave Varner, a University of Nebraska Extension educator in Dodge County.

“We see lots of nozzle issues, under-watered corners, leaks where crops flooded. These are hard to see from the ground,” he says. Aerial photos capture “concentric rings where nozzles are not spaced correctly, or where nozzles are plugged or incorrectly calibrated, so water is distributed unevenly. And the farther out on the pivot the problem is, the more acres it affects,” he adds. “Walking through the field, you wouldn’t notice these things, except maybe by chance. But from the air, they’re very noticeable.”

 

Although aerial imagery is an under-used technology, Varner says, more farmers are starting to adopt it for mid-season N management, especially growers who “fertigate.”

Jerry Mulliken, a Nickerson, NE, agronomist and pilot, has been shooting aerial images of corn and soybean fields for 25 years. He shoots 200-300 fields each season from his Cessna 172, equipped with true-color and near-infrared digital cameras. Mulliken processes the two types of photos to create images that show degrees of N stress.

Mulliken’s clients make a color-reference strip in cornfields by applying a non-limiting rate of N — usually about 40 lbs./acre more than the rest of the field. Mulliken then photographs the field weekly, from the 10-leaf stage until just after silking. If the check strip is darker green than the rest of the field in the calibrated photo, more N can be applied through the irrigation system or with high-clearance equipment. “The advantage is, it’s easy for farmers to implement,” Mulliken says, and “the extra bushels can be fairly significant.”

Jason Webster says aerial photos are “the best and simplest way” to monitor in-season N status. Webster is the director of Beck’s Hybrids Practical Farm Research in Downs, IL.

Beck’s offers its customers high resolution, geo-referenced aerial images to help them evaluate their crops. These images, which cost about $2/acre, reveal a lot about N status, field variability and overall crop health, Webster says, and also “predict areas of both high and low yield with a very high level of accuracy.”

Aerial photos are helpful for assessing drainage needs, too, he says. “It’s an excellent tool for communication between tenants and landowners.”

Aerial imagery doesn’t eliminate the need for crop scouting, Webster says, “but it fits in very well with a traditional scouting program.” Beck’s has developed a mobile application that downloads aerial images to a smartphone or iPad, then uses the device’s GPS function to go right to the trouble spot in the field.

 

The bird’s eye view has an uncanny way of sticking in your mind’s eye, observes Tom Oswald, the Cleghorn, IA, grower. In the fall of 2011, for example, he was trying out a new style of anhydrous knife. After he’d applied three tanks, he realized that two of the 12 knives were badly plugged. “With my strip-till system, I knew that 75 acres were going to look like a pin-striped suit from the air!”

He fixed the problem, then turned off 10 of the knives and ran over the field again, applying N to the two missed rows. “That’s the kind of thing you become aware of by looking at imagery,” he says.