Soil Health Scouting: Drones, Satellites, Airplanes and Boots on the Ground – DTN

    ©Debra L Ferguson Stock Photography

    A mysterious deep-green rectangle convinced Randy Jax that aerial imaging had the potential to improve his farm.

    His family had grid-mapped its fields near Adams, Minnesota, for 15-plus years, and Jax thought he knew almost all there was to know about the farm’s soils. But, he was surprised this spring when he stared at an aerial image of a field near his farm buildings. The NDVI (Normalized Difference Vegetation Index) image, which was taken by a UAV (aka drone, UAS), contained a large rectangular shape that was greener than the area surrounding it. That indicated the corn plants within the square were thriving better than those outside it. 

    After digging into his family memory banks, Jax realized the rectangle was the outline of a pasture his father had used for dairy cows, a pasture that had been converted to cropland almost 20 years ago.

    His soil samples had detected high nutrient levels in that area but did not clearly “see” the rectangular shape.

    But the drone saw it. “NDVI shows the good or bad in smaller areas, and gives you information going forward,” Jax said.

    A simple thing, perhaps, but Jax’s discovery is indicative of what farmers are seeing with new eyes in the sky. Growers now can get overhead perspectives on their fields, which can help with variable-rate prescriptions for seed, chemical and fertilizer. Aerial imaging also can make replant decisions easier and more informed; they can shape the way a farm grows.


    Keys to the boom in agricultural aerial imaging are technologies that can capture valuable forms of digital photos. For example, near-infrared (NIR) images plus software can create NDVI maps, which make crop-health evaluation possible. Thermal imaging can detect variations in heat from a subject, which has potential when working with livestock. And three-dimensional aerial imaging can help see elevations in fields that are useful in designing contour systems and drainage tile layouts.

    UAVs have been collecting much of the imaging buzz lately. However, farmers and the consultants who serve them can choose from two other aerial photography platforms: airplane and satellite. Together, the three platforms are like trifocal glasses. Drones are for the closest work, airplanes give a medium view and satellites take the longest view possible. Farmers might use one, two or all three, depending on their circumstances and how fine they need imaging to be.


    Herb Dowse flew the UAV that found the mystery rectangle at Randy Jax’s place. Dowse is a precision agriculture specialist for Northern Country Co-op, which serves large swaths of northern Iowa and southern Minnesota. He flies both an AgEagle RX60 fixed-wing craft and a Phantom III rotorcraft. He also can reference satellite images “as a check” either before or after sending up a drone. He doesn’t use airplanes, in part, because not many pilots do that work in his coverage area.

    An AgEagle can cover 220 acres in less than 20 minutes, so Dowse uses it for broad acre work. That usually means evaluating in-season crops, but he also has used the AgEagle for mapping existing tile lines. If a customer isn’t sure where tile lines lie, Dowse can fly after a rain event and spot them based on NDVI images. Tile lines show up as red or yellow because there’s less vegetation immediately on top of them. If there is a break in a line, “They [his customers] don’t have to tear up 20 rows. Instead, they might only have to tear up three rows because they know exactly where the problem is,” Dowse said.

    He uses the Phantom III to focus on problem areas where it can hover for close-up work. Last year, for instance, he used the Phantom III to assess crop damage for an insurance claim after cattle got loose in a field.

    When used to evaluate the health of a crop, Dowse said, drone imaging is a first step. If he finds a problem, he always follows up with a personal inspection.

    John McNamara, an agronomist for Wiles Bros. Inc., a farm-supply company and farm in Plattsmouth, Nebraska, agreed that UAV flights should lead to boots on the ground. “A drone might tell me, ‘Hey, there is something different here.’ But, I am a firm believer in ground-truthing, walking an area to see exactly what is going on.”

    McNamara also has satellite imaging available to him through the company’s subscriptions to Climate FieldView and EncircaSM View. (Editor’s note: Encirca and DTN/The Progressive Farmer have a business partnership.) But, McNamara said, “Drones are better than satellites for pointing out problem areas,” because the resolution of the image is so much better.


    Drones typically produce images with resolutions as fine a 2 inches per pixel [the building blocks of an image]. Images from airplanes range from 10 inches to 3 feet resolution. Satellite images are the coarsest, at about 9 to 15 feet per pixel.

    UAVs can fly under the clouds, so weather is less of a factor than for airplanes or satellites. But, UAVs and winds don’t get along well, and by law, they have to fly under 400 feet. Also, you must have a permit from the Federal Aviation Administration to fly a UAS for commercial purposes, including farming. You also must fly only in line of sight, and you must have a spotter.

    Shadows from the sun early in the morning or late in the day can lessen the usefulness of UAV images. That limits flight times to mid-morning to mid-afternoon on sunny days. Some new imaging processing technologies can partially overcome this time/sunshine limit.


    Two years ago, Tim Tyson, of Parker, Kansas, founded his company—TNT Solutions—based on images taken from airplanes. “As far as getting information to farmers so they can get things done, we think airplanes are the way to go,” he said.

    Tyson is a dealer for AgPixel, a remote-sensing and geospatial analytics company, based in Johnston, Iowa. His customers are agronomists and consultants. He contracts with a pilot, and AgPixel processes the raw aerial imaging to import directly into SST and SMS software for writing prescriptions. He guarantees to deliver processed images within 24 hours after a flight. Tyson charges about $2 per acre.

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    Tyson recently added access to satellite images to his business portfolio, and he will fly a UAV when asked. “If you have a small project [under 80 acres], or you want to get down below 1-inch resolution, we can do that with a UAS,” Tyson said.

    “But if you are looking at a lot of acres [for most work], you don’t want a UAS, you want an airplane,” Tyson said.

    His pricing for drone work starts at $200. For satellites, he charges $.15 per acre per image with a minimum of 1,000 acres and 60 days subscription.


    Peter Scharf has used all three imaging platforms in working with farmers. He is a University of Missouri plant sciences professor who, in 2015, started a business named NVision AG. Motto: “Turn Yellow Back to Green … But Leave Green Enough Alone.” The idea is to provide crop consultants and their grower customers rate-control files for variable-rate application of in-season nitrogen in corn.

    Scharf does this by analyzing aerial images to determine which areas of a field might benefit from an extra shot of N. The rate-control files he writes can save a poor crop or turn a good crop into a great crop. The more yellow an area of corn is, the more it responds to added nitrogen, he said. Scharf recommends the most nitrogen where the corn leaves are the most yellow: “I have not found corn yet that is so yellow it is not worth saving.”


    When examining aerial images, Scharf tries to estimate yield loss if the grower takes no action. That gives farmers and consultants a cost/benefit approach to nitrogen application.

    When he started his business, airplanes were Scharf’s preferred platform for imaging. “The thing about a plane is one guy with a Cessna can do 10,000 acres in a day, and one guy with a drone can only do 1,000,” he said.

    Airplanes do have drawbacks. For example, it isn’t always possible to find a pilot who can fly on short notice or when the weather is right.

    “A lot of times when we are pulling the trigger, we want answers right now. We don’t want to schedule a plane to fly a few days from now,” said Thad Becker, precision ag director for MFA Inc. The farm-supply and marketing cooperative has more than 45,000 farmer/owners in Missouri and adjacent states. “Variable-rate fertilizer is kind of our bread and butter,” Becker said.

    Variable rate is where Scharf fits in. MFA has been a customer for two years, and he understands the urgency of its business. If he catches a nitrogen deficiency early, he said, he can recommend an application with a tractor-mounted toolbar. But later in the season, a highboy sprayer or even an aerial application might be necessary. “With ag, you probably have only four key decision points in a year. You have this little window in which to work,” he said.


    Scharf switched much of his imaging work from airplane to satellite this year. He was able to do so because some satellite image suppliers, especially Planet, have launched more satellites to make their product timelier.

    In the recent past, satellites only overflew most locations once or twice a month. If there was a cloud cover during the flyover, images were not useful. Now, Planet offers much more frequency because at least one of its satellites is overhead most days. Planet has a goal of photographing every part of Earth everyday.

    When Scharf tried satellites this spring, “I was just blown away to find images [for a client’s fields] from four days in a row,” he said. “That tipped the balance for me” from airplanes to satellites.

    Despite their lower resolution compared to images from airplanes or UAVs, satellite photos work well for writing the rate-control files that Scharf offers. “It’s a pretty coarse image, but it’s really quite adequate as long as the soil is covered [by vegetation],” he said. “The crop has to be hip to waist high to get a pretty good prescription out of it.”

    Satellite images are much less expensive than either airplane or drone images. A particular advantage is that, “Satellite images let you look backward in time,” Scharf said. Because of extensive archives of images, he can compare today’s views with those taken years earlier.


    Mark Thomeczek, of Marshall, Missouri, is owner of JBM Agronomics, part of the MFA network and a client of Scharf. He appreciates the three aerial imaging platforms and said they are all useful, but he is not afraid they will put him out of work. He visits clients’ fields nearly weekly in-season to make his own on-the-ground evaluations.

    “I don’t count on satellite or plane imaging to tell me there is a problem,” Thomeczek said. “I know that before I ever call in a request [for aerial imaging]. But I can’t georeference a problem from the ground. Peter’s [analytics] program can give us a good estimate of yield loss and profitability. [Without that] sometimes, I can’t do anything but a SWAG [scientific wild ass guess].”


    Scharf uses his experience with all three imaging platforms to make comparisons.

    — “What drones can do that nothing else can is get very high-resolution images that potentially have some very important application,” Scharf said. Example: Drones work well for replant decisions because images are higher resolution and even can see individual small plants.

    — “The promise with planes is to do it [collect imaging] earlier than with satellites. I have done it as early as knee-high corn,” Scharf said. That means earlier diagnosis and application.

    — “Speed is so important, I would love to see satellite be my meat-and-potatoes source of imaging for most of my fields,” Scharf said. Rather than set up a UAV or airplane, and hope for good weather, he can download a satellite image and immediately start analysis.


    Here’s a quick look at the advantages and disadvantages of the three aerial imaging platforms:

    UAVs (aka drones, UASs):

    — easy to deploy on short notice

    — highest image resolution

    — shortest flight time and least amount of area covered per flight


    — ability to go when the customer needs it, depending on weather

    — images on an as-needed basis

    — resolution good enough to allow writing prescriptions


    — bigger picture about what is going on; general overview

    — cheaper in the long run

    — lowest resolution

    — frequency of imaging questionable

    Jim Patrico can be reached at

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