Drones provide new perspective on crops' needs

In a data-driven world, an eye in the sky can yield a clearer picture of where a farmer's crop is going.

Teams of students and instructors from the University of California, Merced, and California State University, Fresno, have been working with the Merced office of UC Cooperative Extension on a multiyear project to understand what drones can do on the farm. Their latest refinements and discoveries were on display during a UCCE field day at Bowles Farming in Los Banos.

Justin Metz, a technology integration specialist at Bowles who's also an FAA-certified drone pilot, said the farm's drone program allows it to check crops for stress from pests, weeds or water. He and the college teams demonstrated their drones' capabilities over a field planted in processing tomatoes to the 80-plus in attendance.

"That allows us to recognize different situations as they are evolving with the different sensors that we have," such as communicating wirelessly with motion sensors or weather stations, Metz said. "You take all those different layers of information, and you can kind of really focus in and narrow on what the issue actually is."

Flying over fields two to three times a week, he said, allows the farm to build datasets of images taken by the drone that can be compared with satellite imagery, soil maps, yield maps and the history of the field.

Working in areas of spotty cellphone service has been the objective of the Fresno State team, led by professor Gregory Kriehn. His team placed sensors in the tomato field, then sent the drone up to collect data from them.

"We've been developing some ground sensors we can deploy out in the field and detect temperature and humidity," Kriehn said. "We're now also able to detect infrared, and we've stabilized the network communication protocol between the drone and the nodes, so it's very robust in terms of always pulling up all of the data from the ground sensor nodes as well."

The sensors, Kriehn said, "sleep" when they're not taking readings and can be left in the field for months at a time.

"The point here is to get an aggregate picture of what's happening on the ground in addition to the aerial imagery that we're taking at the same time, so we can do some additional ground-truthing, with the end goal being to detect localized stress over time," he said.

Fresno State's drone research has been expanding, he added.

"We're beginning to do image stitching and image analysis," Kriehn said, noting that his team has also been working with a private company on imaging of almond orchards.

Imagery has been the focus of the UC Merced team, which sent up a demo drone to take photos of the tomato field using both color and infrared cameras.

Doctoral student Haoyu Niu showed how the drone connected to a laptop after being programmed in advance for altitude and flight pattern.

"After it comes back, we can collect hundreds of images," Niu said.

Software stitches the images together, helping a farmer detect signs of water stress and make decisions as to when and where crop-protection materials may be needed, he added.

Metz said such imagery has been a big help.

"We're only putting on the material that we absolutely need to do, and then only in the amount that we need," Metz said. "So instead of spraying the entire field at this rate, we're spraying portions of the field, and then saving and not utilizing the pesticide or herbicide that we don't need to."

David Doll, a UCCE scientist in Merced who's leading the drone project, said an early objective was to come up with an inexpensive drone carrying a modified point-and-shoot camera that someone who's not necessarily a tech expert can use.

"We didn't really know how (drones) were going to fit into the agricultural scenario, especially when we get to perennial crops," Doll said. "A lot of that had to do with trying to figure out if this is going to be something that people are going to do on the individual level, or if companies or businesses will essentially take charge and find a way to deploy drones to help do a variety of imaging services on farmers' properties."

Early imagery work focused on NDVI, or Normalized Difference Vegetation Index, to help look for signs of water stress. The problem, Doll said, is by the time such stress is visible in NDVI, the damage is done, so the team has been looking at different ways to calculate water stress.

"We feel that we're getting some level of confidence that we can use the point-and-shoot camera and, through a variety of fractional calculus equations, we're able to get a relatively strong correlation between plant water stress from the crown of the tree in comparison to stem water potential," Doll said.

"Thermal imaging has been shown to be very effective at determining even mild levels of stress on trees," he added, noting that a couple of services have been providing this.

While the research has focused on tree crops, Doll said he sees no reason it wouldn't be useful for tomatoes, and added that drones equipped to read sensors might even be able to read animals' ear tags to help ranchers and dairy farmers keep track of their herds.

It was the aerial-photo aspect that brought Doug Thiel, owner of Thiel Air Care in Chowchilla, to the field day.

"California ag aviation needs imaging," Thiel said. "That's what we've been lacking."

As the owner of aerial-application planes and helicopters, Thiel said his overriding concern is preventing a midair collision between a low-flying aerial applicator and a drone.

Communication with aerial applicators as to who's going to be flying where and when, Thiel said, is key—a point emphasized by the National Agricultural Aviation Association, which launched its own drone safety campaign at www.agaviation.org/uavsafety.

People seeking to become commercial drone pilots, including farmers, will have to do as Metz did and become certified under Federal Aviation Administration Part 107 regulations. Particulars can be found at www.faa.gov/uas/getting_started/part_107/.

(Kevin Hecteman is an assistant editor of Ag Alert. He may be reached at khecteman@cfbf.com.)