Seeding cover crops from 30 feet above

Slideshow: When aerial-seeding cover crops compared to a applying a liquid product, a pilot must deal with a whole different set of considerations.

In Nebraska, seeding a cover crop can come with certain risks and unknowns. When this involves interseeding into a standing cash crop while flying 135 to 140 miles an hour, it brings a whole new set of challenges to the table.

Aerial interseeding of cover crops has been a hot topic at various meetings and field days, with the most recent boom in cover crop interest. But it's something Roth Aerial west of Milford has been doing for over 40 years.

"We actually started seeding in the late 1970s," says Jerrel Roth, owner and founder at Roth Aerial. "In the early years, it was either wheat or rye we'd spread for cattle to graze. It wasn't much, just a few cattlemen doing it for grazing in the fall. It's a little different now. There's still a lot of it being grazed, but it's more about getting cover crops out there to help with the soil, whether maintaining soil health or preventing erosion."

Over the last 10 years, interseeding cover crops aerially has taken off even more, especially as programs, such as the Environmental Quality Incentives Program, have offered cost-share funding for the practice. Meanwhile, seed corn producers have recognized an opportunity to establish cover crops early after male rows are destroyed, giving aerial seeding a solid niche to fill in Nebraska's seed corn country.

"Since the first years we went into cover crops, it has continued to increase," Roth says. "We thought maybe it would run its course, but our acres increase each year."

"That tells me that despite the challenges you can have with it, people are realizing the benefits," adds Ryan Krenk, agronomist at Roth Aerial, who has seeded cover crops on his own farm near Milford for nine years.

However, there's another reason it's getting more popular, especially in Nebraska where the growing season isn't quite as long as states to the South. "With an aircraft, we can seed into a standing crop; you can't do that with a drill," Krenk says. "The other advantage of airplanes is speed; you can fly it on a lot quicker if you're working with a tight window."

Seeding from above
In these situations, aerial seeding makes sense. However, from the pilot's point of view, seeding cover crops from the air takes a whole other set of considerations. In theory, the setup isn't all that different from a ground rig. Roth Aerial uses a liquid tank converted to a dry capsule, offering better use out of the aircraft. However, the act of seeding is far different from a high-clearance interseeder or drill.

The air enters through the front spreader mounted on the bottom of the aircraft and, similar to a Venturi effect, spreads the seed out to make a full swath before it falls to the ground.

When seeding covers, pilots typically fly around 30 feet off the ground – compared to 8 or 10 feet when applying liquid product. This means pilots need to compensate for wind and speed. When entering a field, for example, it's necessary to give the seed a certain amount of lead time, because it's coming out of the gate at the same initial speed as the aircraft. The same is true for leaving a field – a certain amount of lag time must be accounted for.

"When you're moving at 140 miles per hour, that seed is coming with you, so you have to know your wind conditions," says Ron Troyer, pilot at Roth Aerial. "The seed is still moving at 140 miles per hour, and when you drop it, it carries a bit before dropping. You have to allow for that."

When seeding with a drill or high-clearance machine, applicators know they are seeding with a consistent swath width. This isn't the case when seeding from the air. Here, swath width varies depending on seed density and shape, wind conditions, and the size and speed of the aircraft.

"You're basically dropping millions of little mini bombs. If you look at cereal rye seed, it's got a miniature torpedo look," Krenk says.

"Oats are very light. When they come out of the spreader, they don't have as much momentum," Troyer says. "So you have a different swath width. If we use turnips and radish, they're really bulky and dense, and you can chuck them out a ways. It's like throwing a baseball compared to a feather."

Seeding rate also makes a difference, and varies depending on the species being seeded. Some cover crops, like turnips and radishes, are bulkier, and suited to lower seeding rates of around 4 pounds per acre. The seeding rate for lighter-seeded crops like oats and rye is typically higher — anywhere from 30, 40, 50 or even up to 70 pounds per acre.

Roth Aerial uses technology to adjust the seed box gate automatically, opening or closing it a certain amount to compensate for different seed sizes and swath widths. These automatic adjustments are made by the GPS, keeping the gate box adjusted for a constant seeding rate.

"It's going to give me a constant rate whether flying at 100 or 150, that gate opening is going to adjust to get the rate we need. If I'm flying into the wind, I might use 140 for no wind conditions," Troyer explains. "If we have a little wind at 10 mph, and we're flying into the wind, my groundspeed is only 130. So the GPS and the gate automatically adjust that for me so I'm putting on the right rate."

Setting up for success
While it's true not all cover crops are created equal from an aerodynamic standpoint, it's also true not all cover crops are created equal for seed-to-soil contact. Krenk's preference is smaller-seeded cover crops like cereal rye, as well as higher-density seeds like turnips and radishes.

With higher-than-normal rainfall during the 2018 growing season, Krenk notes this year has been an ideal one for aerial interseeding.

"I like to seed as soon as leaves on the cash crop are turning yellow. The seeds will sprout; they'll get a little spindly. But once the sunlight hits them, they take off. That's usually within two weeks," Krenk says. "The biggest thing for me is getting it on before a prolonged rain event like we had in early September. If you've got a cover crop on before that, you're money. I put my own cover crop on my field when I saw the forecast for rain in September, and it turned out absolutely fantastic."

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