Aerial seeding explored in establishing cover crops

Gloria Hafemeister
Aerial seeding can help establish cover crops in a timely manner.

OCONOMOWOC - Aerial seeding is a popular method to help no-tillers get cover crops established in a timely manner. This method works particularly well for Wisconsin farms where the season for establishing cover crops after corn or soybean harvest is very short.

Damon Raebe is an experienced ag pilot and shared ideas with farmers attending a recent Ag Resource Conference in Oconomowoc.

He says, “Flying on covers in northern climates too early can starve the seeds for sunlight or leave them prey to slugs and earthworms.”

If results from aerial seeding are spotty, some farmers are quick to point the finger at the pilot. While pilot error is possible, there’s a whole lot more that goes into successful applications, Raebe says.

His long-time experience with aerial seeding cover crops has convinced him that those who establish their cover too early, while there is too much growth on the original crop, are losing the cover due to lack of sunlight to keep the sprouted plants growing.

Timing is key

He emphasized the importance of waiting until the corn or soybean crop begins to dry and leaves whither to provide light to the soil surface. In corn that will be harvested for silage, 10 days before harvest is ideal for the establishment of cover crops by air.

During an early fall where grain corn harvest might be ongoing in early October, there’s enough time for covers seeded in September to access enough heat units and daylight to grow up through post-harvest residue.

But if harvest happens in November, when there’s fewer heat units and daylight, leftover residue might smother the covers and kill them before farmers see any results.

Aerial seeding into grain corn should be done when the leaves are dried up to the ear and in soybeans, the seed should not be broadcast until the leaves have turned and start to shrivel.  Aerial seeding works good in seed corn because much of the top of the plant has been removed by detassling and allows more light through.

Monitoring results

Heidi Johnson, UW-Extension Dane County, and Raebe have worked together to establish cover crop test plots.

Working with farms in the Yahara Pride conservation group, Johnson said they found that cover crops, including rye, established early in September were much thicker and bigger at the time of killing frost than those established two weeks later. Those established at the end of September were even smaller.

Heidi Johnson, UW-Extension, and Damon Raebe, an aerial seeding specialist share ideas with growers at a recent soils meeting in Oconomowoc.

“So we would recommend that if you can’t get a cover in early, switch to a different type of cover like oats or barley.  Radishes, if planted late, don’t get big enough to help much if they are planted after September 1,” she said.

Monitoring soil, Johnson said their test plots revealed twice as much nitrate in the soil for late planted cover crops compared with those that were established early.

“These covers really soak up nutrients and hold them until spring,” she says.

Not all farmers will want to fly on their seed to establish a cover crop. Some have had success following the corn chopper with a grain drill. Raebe points to some myths about the establishment of cover crops. He says many farmers believe it will only work if it is a wet fall. In reality, cover crops only need a half-inch of rain to get established.

“Moisture is not the limiting factor, light is,” he said.


Regarding predators, he said he has seen earth worms carry the seeds into their channels.

“I saw this in the 2014-15 season. The seed germinated and was buried in an earthworm channel, then grew in the spring. Earthworms moved the seed around but they did not kill it.”

A bigger problem is slugs.They eat the germ end off of rye seed before it sprouts. He says slugs only appear on cloudy days so if it is sunny for several days after seed is established it will have more opportunity to sprout before they attack it.

Johnson points out that in their research plots they observed less bother by slugs in barley seed. Slugs ate the rye and triticale seed first and then the rye. She said more research is needed, however, to determine if this is always the case.

If slugs do prefer rye, she says a combination of rye and barley could be planted to lure the slugs to the rye and give the barley an opportunity to sprout before they reach it.

Pre-sprouting seed could help but Raebe says the logistics of handling pre-sprouted seed make it impractical to use this approach.

He suggests checking the field before establishing the cover by placing a board in the field to see if there are any slugs on it. He also suggests that slugs are more of a problem in wet years than dry years.

Working with the aerial applicator

Raebe said anyone interested in aerial seeding should provide a map of the fields, coordinate with the pilot on things like who will supply the seed.  Arrange a schedule ahead and schedule way ahead to get on pilot’s schedule.

While weather is a factor, Raebe says he has flown seed on in light rain. He cannot apply it in heavy rain or when it is extremely windy.

“If you decide to have your seeding done by airplane, contact your neighbors ahead so they will know what is happening,” he said. “People don’t like chemicals but they don’t mind seed. Make sure they understand.”

Aerial seeding can be done on fields ten acres or bigger. Seeding must be done 50 feet above the ground. Chemical spraying is done 8-10 feet above so treelines are less of a problem for seeding than for chemical application.

Pilots have legal flying restrictions, however, in areas where a farm field is surrounded by subdivisions.