Pictured Above: HIRING THE BEST PILOT. Damon Reabe recommends no-tillers ask their aerial applicator if they do dry pattern testing, if they’ve handled the species of cover crops they want seeded and if they can ensure the seed will be flown on uniformly to help them determine the best pilot for the job.

One of the biggest concerns and complaints no-tillers have about flying on cover crops is that it doesn’t result in a good stand.

It’s an issue Damon Reabe is very familiar with. A pilot and owner of the aerial application companies Dairyland Aviation and Reabe Spraying Service in Waupun, Wis., Reabe understands the challenges in achieving good seed-to-soil contact from an airplane. But in the last 6 years of studying stand failures, he’s come to identify the key factors that can greatly increase the odds of a uniform stand.

At the 2018 National No-Tillage Conference, Reabe explained why your cover crop species, location, seeding rate and timing all play an important role in the success of your aerial-seeded cover crops, and how to troubleshoot failures.

1 Hire the Right Applicator

Online Extra

Click here to learn more about Damon Reabe’s aerial seeding equipment setups. And click here to hear his podcast about flying on cover crops successfully.

At the conference, Reabe showed the audience a photo of spring barley that had been flown into a field of sweet corn to prove that a good, uniform stand is possible with an aircraft when it’s done correctly.

But it’s only possible if the applicator takes the time to verify their uniformity. 

For Reabe’s operations, they do this through a lot of testing. Using seed collectors perpendicular to the plane’s flight path, they release the cover crop seed as they fly over. At the bottom of the collectors is a vial that weighs the amount of seed caught to the gram.

The results are then put into pattern-testing aerial application software, which gives them an output of the best spread pattern.

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“If we have adjustments to make after we’ve done the testing, all we do is simply move the veins on the spreader,” Reabe says. “It’s a real simple process. By widening one compartment, you put more seed in the light spot and less seed in a heavy spot.” (For details and photos of the application equipment, visit our Online Extras.)

No-tillers should know whether their aerial applicator has done this level of fine-tuning before hiring them. Reabe recommends asking your applicator the following questions: 

  • Do you do dry pattern testing?
  • Have you handled this seed species?
  • Are you sure it’s going to be uniform?

2 Choose From Shallow-Seeded Species

The second factor that plays a role in the success of flying on cover crops is the cover crop species. Unfortunately, some species will not achieve a good stand when they’ve been aerial seeded.

Reabe has found that if a species has a minimum planting depth greater than ¾ of an inch, it’s not going to work.

“You’re dealing with a seed species that just isn’t going to grow lying on top of the soil,” he says.

He recommends growers find the minimum planting depths for their cover crops in the Sustainable Agriculture Research & Education’s (SARE) book, “Managing Cover Crops Profitably.”

Reabe has found most grass species, brassicas and clovers work well with aerial seeding. He’s never had any success with any kind of pea, as they require deeper planting depths.

“Basically a large-seeded legume needs incorporation into the soil,” he says. “So if you’re going to go broadcasting, whether it’s aerial or otherwise, that’s not likely going to work because it needs to be planted.”

3 Consider Location, Shade, Drought

The good news is there are plenty of species that do well with aerial application. So the next thing a no-tiller needs to think about is whether that species will do well in their location.

The first thing to consider is your winter hardiness zone and whether a species will overwinter in your zone, Reabe says. He also recommends checking the shade and drought tolerance of a species. In his experience, the greater those are the better luck you’ll have with aerial seeding it.

Example of successful aerial seeding of cover crops

STRONG STANDS POSSIBLE. This photo of spring barley that was flown into sweet corn proves that no-tillers can have good success with aerial seeding. Choosing an aerial applicator that has worked with and pattern tested the uniformity of the cover crop species being seeded is key.

“You’re going to be broadcasting these seeds into the shade and you don’t know exactly when it’s going to rain,” he explains. “So those are other things you need to consider when you’re picking these seeds.”

He notes that all of this information can be found in the SARE book.

4 Determine Your Seeding Rate

Once a no-tiller has decided on his cover crop species, he needs to determine his seeding rate.

The SARE book provides a recommended rate range for drilling a species, which Reabe has found works well with aerial application. He suggests going in the middle of the rate range. For example, SARE recommends drilling barley at a rate of 50-100 pounds per acre, so 75 pounds per acre would be a good rate for aerial seeding.

“These broadcast rates, when you get a catch, are going to be far more cover crop than you’re interested in,” he says. “Those are rates that when it grows, it’s not a cover crop. It’s a crop.”

The exception to this is annual ryegrass, because of how light the seed is. He recommends flying on annual ryegrass at 25 pounds per acre. He notes it’s “the most stressful seed species to fly on,” adding that if wind speeds exceed 7 mph they have to quit because the seed the will float off target.

5 Will it Reach the Soil?

Another reason annual ryegrass can be a challenge to fly on is because it may not reach the soil, especially in no-till fields that have heavy amounts of residue.

Reabe recalls flying on a mix of 15 pounds annual ryegrass, 4 pounds crimson clover and 4 pounds radish per acre into a soybean field. The previous crop had been corn.

One side of the field’s stand was almost nonexistent, while the other side was strong. What happened?

It turned out that where the cover crop did well had previously been a fence line that the farmer took out and tilled prior to the soybean crop. Where the cover crop stand was poor they found the annual ryegrass seed sitting on top of the previous year’s corn residue. 

“It never made it to the ground,” Reabe says. “So this is a real issue. It’s less of an issue with your larger seeded grasses — your small grains, cereal rye, wheat, triticale, oats and barley. They can stand being on top of residue.”

He explains that even if those seeds don’t touch the soil, they’ll germinate and have enough starch in them for the root to reach the soil before it dies. “Annual ryegrass is a smaller seed and just doesn’t have that same amount of starch within it in order to survive that process.”

6 Time it Right

The last step — and in Reabe’s experience, the most important — is to fly on cover crop seed at the right time.

“We’re all thinking that the earlier we put the seed out, the better, but what I’ve found is this seed needs to be placed in the field at a point where within 2 weeks after it germinates, it can get some access to some sunlight,” he says. 

He compares it to weeds. Once a crop like corn fully canopies, it will shade out the ground, effectively killing any weeds that have germinated. 

“Well, the same fate will happen to your cover crop,” he explains. “These plants need access to sunlight in order to grow.”

Reabe saw this first-hand with a field where he flew on 2 bushels of spring barley per acre into a field of silage corn in the fall of 2013.

The grower had planned to harvest the corn on Sept. 18, so Reabe flew the covers on Sept. 6. The silage was too wet on the 18th, so the farmer only ended up harvesting part of the field.

When Reabe went to check on the covers on Sept. 25, he discovered that where the corn hadn’t been harvested, the barley was competing with it for sunlight. The corn was 14 feet tall and on 20-inch rows, so the canopy was dense. The barley had 8- to 10-inch-long leaves growing straight up, while its roots were only ¼ to ½ inch deep. 

But where the corn had been harvested, the barley was only about 4 inches tall and the roots went down about 6 inches.

Reabe checked on that barley again 2 days later and discovered the plants in the unharvested corn were dying. He believes this was due to drought stress. Even though there was moisture in the soil, at the shallow depth the roots were at it was “bone dry,” because it hadn’t rained in 4 or 5 days.

The rest of the silage was harvested 10 days later on Sept. 28, and the impact that had on the cover crop was still visible a month later. By Oct. 29, the barley that had access to sunlight had a much thicker stand than the barley that had to compete for it.

When flying into grain corn, Reabe recommends waiting until the corn has senescenced up to the ear, because the lower leaves on the corn plant will start to bend down, and within a few weeks the upper leaves will start to die back, allowing more sunlight to reach the cover crop.

 

How Much Rain Do You Need for Aerial Seeding?

While some no-tillers may assume that you need a lot of rain in the fall to succeed with aerial seeding, Damon Reabe says that’s not the case.

A pilot and owner of Dairyland Aviation and Reabe Spraying Service, Reabe says that while rain is necessary for cover crop seeds to germinate, a grower doesn’t need consistent rainfall to have success with aerial seeded covers.

At the 2018 National No-Tillage Conference, Reabe showed the audience several photos of strong cover crop stands that had been seeded in a year where there was a dry summer and fall.

He explains that in a drought year it’s not going to work, but his point is that the cover crops don’t need “monsoon rains” for it to work.

“You need a half inch or a nice soaker to get the seed germinated and get it started. Then it will take care of itself,” he says.

On soybeans, he recommends waiting until they are turning or have mostly turned for the same reason. 

“You can apply this concept to whatever crop it is that you’re trying to interseed into,” he says. “You’ve got to keep in mind that these things are going to need access to sunlight.”

He adds that if the barley had received a little rain, it probably would have been OK.

“But you’re going to need some pretty reliable rain showers in order to keep this going, in my opinion.”

Troubleshooting Failures 

Even when a farmer and applicator do everything correctly, failures can still happen. When a failure occurs, Reabe tries to go out to those fields to determine what went wrong and how it can be avoided in the future.

In doing so, Reabe has identified three factors that can result in an aerial seeding failure.

slug can cause problems with aerially seeded cover crops

STEALING SEED. Slugs can also be a problem for aerial seeding, as they’ll eat the seed. Damon Reabe has found they seem to prefer winter annual seeds that don’t have a husk.

1 Heavy Residue and Shrinking Day Length 

Just as too much residue can prevent a cover crop from reaching the soil, residue that falls on a growing cover crop can also impact its growth.

Reabe recalls one field where spring barley was growing in grain corn. At harvest, the farmer used chopping heads, which placed all of the residue on top of the cover crop. This happened in the middle of November, so the cover crop no longer had enough daylength or heat units to grow back through the residue.

“It’s like laying a blanket on your lawn,” he says. “My experience has been it’s over. No more cover crop. It’s dead.”

It’s a critical factor for growers to consider when they’re deciding whether to aerial seed, he adds.

“How early do you think you’re going to harvest this crop and what are the temperatures going to be? What are your daylengths?”

Being located in Wisconsin where daylength is much shorter, Reabe has researched the issue and found that it’s a critical component to the growth of cereal grains.

“They need heat units,” he says. “It’s the length of the night that has a big impact on cereal grain growth. So a big consideration is, ‘What’s the residue going to be after harvest and what are the growing conditions at that point?’”

2 Earthworms Stealing Seed

Earthworms may be a no-tiller’s friend, but they can also be trouble for broadcasted cover crops.

Reabe was investigating a field where they did everything right — the soybeans had turned, they received rain — and nothing was growing. So he got a shovel out and dug up one of the earthworm middens. Inside the earthworm channel was the cover crop seed, 3½-inches deep, with the plant trying to find its way to the surface.

By the spring, the farmer told Reabe the field had greened up.

“What happened was the earthworms took some of the seed down and the plants simply hadn’t emerged yet,” Reabe says.

It’s also evidence of earthworms when the cover emerges in clumps.

 

Sandy Soils Work Well

Damon Reabe has had good success flying cover crops onto several different soil types, including clays, muck soils with high organic matter and prairie loam soils. But perhaps the best soil type the Wisconsin pilot has seeded is sand.

“My experience is I have not found slugs on sand,” he says. “So when I do aerial seeding into sandier soils, it’s awesome. It works really, really well. I’m really happy with the results.”

“I can’t possibly put them in little 3-inch circles,” he says. “It doesn’t work that way. The earthworms really did move them.”

Reabe notes there’s nothing to be done about this, just that growers need to be aware it’s happening. While it may not be the kind of distribution a no-tiller is hoping for, it doesn’t mean it was a failure.

3 Hungry Slugs

Unfortunately, earthworms aren’t the only creatures getting ahold of cover crop seed.

While scouting a field one day, Reabe found a cereal rye seed with its hull missing. Worried that the hopper on his airplane was knocking the germ off the seed, he started investigating further. That’s when he discovered a slug eating the germ end of a seed.

He immediately reached out to the NRCS and University of Wisconsin to correlate whether a lack of cover crop stand was due to the presence of slugs. They confirmed this is an issue on Wisconsin farms, which resulted in the NRCS publication “Slug Damage to Cereal Rye Seed.”

Because of this issue, whenever Reabe receives a call from someone who would like to aerial seed, he asks the farmer to scout for slugs and describes how to scout for them, noting there are some options for dealing with slugs once they know they’re there.

The first option is to pick a seed species the slugs won’t eat. Reabe has tried oats, barley, wheat and triticale where there is a lot of slug pressure. While slugs will eat them all, he says, they’ll start with the winter annual seeds that don’t have a husk.

“They seem to like the rye, the wheat and triticale,” Reabe says. “They eat those first, then they go to the oats and barley,” which have husks that protect the germ end more.

He’s also noticed that where he’s seeded mixes with vetch and radish, the slugs don’t seem to bother with those species. He’s not sure about clover, because he hasn’t scouted it for slugs yet.

The slugs also seem to leave annual ryegrass alone. 

“I’m not saying they wouldn’t eat annual ryegrass, the leafy part of the grass, but they don’t seem to eat the germ end before it even germinates,” he explains. 

Reabe notes that they aren’t using these seed species as much in Wisconsin due to the short growing conditions for cover crops. In Indiana, Illinois or southern states, he thinks they may be viable options because of the longer growing season.

But if a no-tiller knows he has slugs and he wants to use cover crops, Reabe says the best solution is to drill them.

“If you have the option of drilling your cover crop, drill your cover crop,” he says. “Don’t get an airplane out there. If you’ve got the manpower, time and equipment and you want to for sure have this thing come up, you’re going to need a drill.

“We’re broadcasting seeds with airplanes. You’re laying them on top. There’s risk associated with that.”

Alternative Solution: Spring Seeding 

One option to aerial seeding covers while avoiding both slugs and earthworms is to frost seed them in the spring.

It’s a practice Reabe has done a lot of with clover into wheat. So he wondered: Why not try frost seeding cereal rye or spring barley in the spring?

So in March 2017, he frost-seeded cereal rye into soybean stubble. A month later the stand was thick and uniform, with no clumps from earthworms moving the seeds around.

“When you do a frost seeding, the slugs and earthworms are dormant,” Reabe explains. “So we lost the fall growth, which is a big problem, I realize. But if it didn’t grow at all or you don’t have time to plant it in some other method, or the ground’s frozen by the time you get done harvesting, this is an actual viable option.”

He notes that the nice thing about using cereal rye late enough in the spring is that it will germinate and grow, but it will remain vegetative.

“If cereal rye doesn’t go reproductive, the carbon-to-nitrogen ratio stays very low,” Reabe says. “When you kill this, whatever nitrogen that this has trapped in its organic matter is pretty likely to be given back to your field.”

He tried frost-seeding again this year, and while he says it was a poor year with the late spring, they still got a very good stand. It’s too early to tell what works and what doesn’t, but after 2 years he’s happy with the results.

If a no-tiller decides to try this, Reabe points out that it’s important to spread the residue evenly during harvest, because if it’s not, it’ll likely result in an uneven cover crop stand.