For a new view of crop production, try rising above it all.
Aerial images of fields are useful tools for detecting crop variations and equipment problems that are hard to see from the ground, says Tom Oswald, a Cleghorn, IA, farmer who’s used aerial imagery for several years.
From a bird’s eye view, you can spot nitrogen (N) deficiencies, poor irrigation-water distribution, drainage problems and uneven seeding or fertilizer application. Geo-referenced aerial photos can show storm damage, soil compaction, disease infestations, even marauding wildlife. Aerial images are also helpful for finding old tile lines or soil variations.
The view from 1,000 ft. up offers “a different perspective,” Oswald says, one that can have an important influence on how growers manage their farms. “I doubt if I have ever seen an aerial photo that hasn’t stimulated me to think deeper about my crop-management strategy. It adds a dimension you likely would not see otherwise. Think of the old saying about how you can’t see the forest for the trees.”
Rosalind Leeck, formerly with the Indiana Agriculture Department, now with the Indiana Soybean Alliance, has worked with a group of Jasper County farmers who are using aerial imagery to evaluate N management. For growers, the sky view often provokes “Aha! moments,” she says. “You can identify things right away that you can’t see with scouting.” Equipment goofs are a good example. Planter row skips, plugged nozzles, center irrigation-pivot stops or slips, herbicide overlaps – “these are things you wouldn’t necessarily see from the roadside or on the yield monitor.”
For instance, uneven N application sticks out like a sore thumb from the air.
Jason Abbring, Wheatfield, IN, had no idea that three knives on his anhydrous ammonia applicator were partially plugged until he saw the evidence on an aerial photo taken in late August. “It was a big surprise. I wouldn’t have known about this without the image. I couldn’t see it on the yield monitor because I applied the anhydrous at an angle to the rows.”
The aerial image of Abbring’s cornfield, taken as part of a pilot program sponsored by the Indiana Department of Agriculture and the Indiana On-Farm Network, showed a distinct pattern light and dark green striping. The lighter green stripes were N-stressed plants, says Dan Perkins, a conservation specialist with the Jasper County Soil and Water Conservation DistrictinRensselaer. Perkinsused GIS tools to zoom in on the photo and measure the distance between the stripes, which correlated to the spacing of Abbring’s anhydrous knives.
Perkins also used the aerial image to collect samples for late-season stalk-nitrate tests, a measure of N sufficiency. “We call it guided stalk-nitrate sampling,” Perkins says. Instead of sampling at random, the geo-referenced photos lead you to a field’s problem areas.
Samples taken from Abbring’s field in 2010 revealed N stress in the partly plugged rows. In addition, the stalk-nitrate tests showed that the entire field “had not had enough N to accommodate a reasonable yield,” Abbring says, due to heavy rains.
As a result of this information, Abbring cleaned and double-checked all the anhydrous knives and added an N stabilizer to his spring preplant N application. “If you don’t know a problem exists, it’s pretty hard to cure it.”
A top-down view of nutrient placement
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.
Free aerial images available on the Web
Free digital aerial imagery is available for many states through the National Agriculture Imagery Program, or NAIP, administered through the USDA’s Farm Service Agency. The geo-referenced photos are taken in late summer and available for downloading from the Internet in November.
Because of the timing, NAIP images can’t be used for in-season management,” says Rosalind Leeck of the Indiana Soybean Alliance, “but you can see things that are helpful” for future management, such as stand issues, drainage problems, compaction and areas that could benefit from conservation structures. For more information, go to http://datagateway.nrcs.usda.gov/.
For more timely images, you can contract with a local pilot to fly your fields and take digital photos. That’s what Hertz Farm Management does in late July and August, says Farm Manager Chad Hertz, Waterloo, IA. “We target where we need investments to improve a farm,” such as drainage tile, eroded hilltops, wet areas, non-uniform fertilizer applications or erosion control.
“The images aren’t geo-referenced, but you can definitely see what’s going on,” Hertz says. If a group of neighbors go together to hire a pilot to take photos of their fields, the cost is usually quite reasonable, he says.
Photos to learn from
The Iowa Soybean Association On-Farm Network’s website is loaded with in-depth analysis of images (www.isafarmnet.com/RemoteSensing/RemoteSensing.html) and a gallery of fascinating aerial photos with explanations of what they reveal. There are examples of nitrogen and moisture stress, insect and storm damage, field variations and equipment errors. You can even see an image of a cornfield studded with mysterious round circles caused by – believe it or not – wallowing bears.