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6 ways to seed cover crops6 ways to seed cover crops

Think DifferentJerry Ackermann doesn’t need convincing when it comes to the benefits of cover crops. The Lakefield, Minn., farmer has experimented with several cover crops and seeding methods. “I’m getting braver,” he says. This is especially because he’s noticed the weed control benefits of cereal rye in the spring.He’s interested in a still-experimental planting method that’s getting a lot of buzz these days: interseeding annual ryegrass into corn, when plants are at the six- to 10-leaf stage. The cover crop germinates, then goes dormant when the canopy closes. In late August, when the canopy opens, it resumes growing. Ackermann trialed it on six acres of his farm this year.

Liz Morrison 1

August 19, 2014

9 Min Read
<p>Indiana farmer Cameron Mills rigged his highboy sprayer to test early seeding of cover crops in 90-foot strips to determine yield and soil benefits. He also changed herbicide use in these strips so his cover crops of annual ryegrass, crimson clover and hairy vetch would flourish.</p>

Cameron Mills planted his first cover crop in 2006. “We started with a John Deere 750 no-till drill, because we didn’t know any other way,” says the Walton, Ind., no-till corn and soybean producer. Mills has also planted covers with an air seeder and harrow, a highboy and an airplane – the latter being his preferred method.

Midwest farmers are deploying many techniques for planting cover crops: broadcasting with fertilizer spreaders, flying on the cover crop and modifying high-clearance sprayers. Others are pairing cover crop seeding with another field operation, such as vertical tillage, manure application or even combining.

Farmers are demonstrating “amazing innovation” in cover crops today, says Joel Gruver, a soil scientist and cover crops expert at Western Illinois University. He suggests that beginners try more than one cover crop planting method to spread out their risk and see what works on their farm.

The best seeding practice for your operation depends on your climate, cropping system, equipment, available labor and expertise, says Sarah Carlson, Midwest cover crop research coordinator for Practical Farmers of Iowa. Here’s a look at some of the ways Midwest farmers are making cover crop seeding work.


Planting after harvest

If you wait until after harvest to plant cover crops, your seeding choices include drilling, using a precision planter or broadcasting with or without incorporation.

The main constraint on after-harvest seeding in the Midwest is the short establishment window, which limits plant growth and cover crop seed choices, Carlson says. If you farm north of the 41st Parallel, your best choices are cereal rye, winter wheat or triticale. South of I-80, there is enough growing season after harvest to establish annual ryegrass and some legumes.



Drilling, precision planting offer reliable establishment

Drilling offers uniform seed placement at lower seeding rates and excellent seed-to-soil contact for quick germination, which is why Mills still drills all his cover-crop test plots. “But the downside is that it’s very slow,” he says. Labor becomes an issue, and the short window for growth means “you may not get a good enough stand to survive winter.”

Like drilling, using your precision planter to seed a cover crop provides the best seed placement and establishment with the least amount of seed, says Gruver, the Illinois soil scientist. With today’s wide planters, you can seed more acres after harvest than with grain drills, which in the Midwest are typically smaller. Split-row planters and GPS let you precisely place different species of cover crops for strategic benefits, he adds.


Broadcasting is faster, cheaper

Seeding cover crops with a spinner spreader or airflow unit is fast and cheap, “and can be successful as long as there’s some moisture,” says Jill Sackett, a cover crops specialist with University of Minnesota Extension. As with drilling, though, seed choices are limited for this after-harvest method.

After spreading seed, a light pass with a cultivator, harrow, vertical tillage tool or culti-packer increases germination, provided the seed is not buried too deep, Sackett says. For a couple of years, Cameron Mills planted cereal rye and annual ryegrass with a Valmar airflow applicator mounted on a Phillips harrow. The 45-foot harrow, running at 12 miles per hour, scuffed up the soil a bit and improved seed-to-soil contact.

Pairing fertilizer application and cover crop seeding saves a field pass. Josh Simon, a corn and soybean grower from Preston, Minn., has his local ag retailer broadcast 80 lbs/acre of cereal rye during his fall P and K application. The company uses a Case IH airflow applicator. Cereal rye seed mixes well with the granular fertilizer, he says.

Using an airflow applicator results in more uniform seed distribution than a spinner, Simon observes. “They are already doing a pass, so there’s very little extra expense to add the cereal rye” — just $1/acre for the application service. Simon follows with a 31-foot Case IH Turbo-Till operated at eight miles per hour, covering about 60 acres/hour. “It’s efficient, fast and painless,” he says.

Cereal rye will germinate if not incorporated, but it takes longer, Simon notes. On Oct. 15, 2013, he broadcast and incorporated cereal rye on 220 acres of soybean stubble and got about 80% germination, even though it turned cold early. He also seeded 46 acres of cereal rye into corn stubble on Oct. 23 but ran out of time to till it. Only 15% of the unincorporated seed germinated last fall, but this spring it all came up and produced eight inches of growth before he burned it down, two weeks prior to drilling soybeans into the residue. 


Planting earlier into your cash crop

Some farmers are giving their cover crops a head start by planting into standing corn and soybeans around Labor Day, as the cash crop is drying down. This gives cover crops several weeks to grow before harvest, spreads out labor and allows for more seed choices, Carlson says. But it is important to get at least two weeks of good growth before harvest to pay for overseeding, Sackett notes, “or it’s not worth the investment.”

Successful establishment requires timely rainfall and cover crop species that can germinate on the soil surface and tolerate some canopy shade, Carlson says.


Smaller seeds do best, such as annual ryegrass, crimson clover or cereal rye. Shade is an issue for some popular covers such as radishes, she adds.

Gruver advises to plant into standing corn when leaves are browned up to the ear. In soybeans, plant when 50% of leaves are turning yellow but before leaves fall. “We have more success seeding cover crops into corn than soybeans. We are more likely to see failures in soybean fields,” he says.


Aerial seeding is best for covering many acres

For the past five seasons, Mills has used Townsend Aviation, Monticello, to plant cover crops on his entire 3,500-acre operation in north central Indiana. They can seed about 1,200 acres/day.

Mills seeds 25 lbs/acre of annual ryegrass into standing corn and soybeans, paying $12.50/acre for application. He is also experimenting with cover crop mixes. The Mills’s use trucks and an auger to supply the aviation company’s seed tender at the airport.

Mills flies the cover crop into corn at the end of August. Although the conventional wisdom is that the canopy needs to be open, “we’ve flown cover crops on when the corn was anywhere from all green to all yellow leaves,” he says. Timing aerial seeding into soybeans is trickier, though. They fly it on when plants turn from bright green to dark green, any time from the last 10 days of August to the first 10 days of September.

“The key to successful aerial seeding is rain,” Mills says, so their number one goal is to schedule the application around it. “We work very closely with the pilots. We’ll bump a flight up a few days if we see rain coming.”

Cover crop establishment is less reliable with aerial application than with ground equipment, Gruver says, so seeding rates should be higher. Uniform application is another challenge. Getting complete coverage in field corners is difficult, Towery says, and obstructions such as power lines, towers or woods can interfere.

 “There’s huge variability in the quality of aerial seeding,” Gruver acknowledges. “Many pilots are getting into it because of demand, but they don’t have much experience yet.” Try to work with an experienced cover crop pilot, he says. Ask how the pilot calibrates the spread pattern for wind speeds as well as for different seed sizes and weights.

Cereal rye is “probably the most reliable choice” for aerial seeding, Gruver says. “It can be planted late, has good ballistics, throws uniformly and establishes well with broadcasting.”


Highboy applicators offer excellent coverage

Some growers are modifying their high-clearance applicators to plant cover crops into standing corn or soybeans. The seed is dropped below the crop canopy, providing excellent distribution, Towery says.

Using ground equipment provides more uniform coverage at lower seeding rates than aerial broadcasting, says Rachel Halbach, an agronomist for Hagie, Clarion, Iowa. However, soil conditions must be right to avoid compaction, she says, and if you’re not running on the same width as the planter, there will be some crop damage.


On slopes greater than 10%, Charles adds, high-clearance equipment may not stay on the contours in fully mature soybeans.

Combine seeds cover crop

Ray McCormick’s combine is more than a harvester. It’s also a cover crop seeder.

The long-time “never-tiller” from Vincennes, Ind., used to drill cover crops after harvest. Although drilling produced excellent cover crop stands, the labor demands were a huge constraint, requiring a full-time worker.

McCormick considered why cover crop seeding couldn’t be combined with harvesting. In 2011 — in the middle of harvest — McCormick and his son Nate mounted a small Gandy orbital air seeder and 10-bushel seed box on their eight-row corn head and placed seed tubes under each corn head snout. It worked so well on the first 300 acres, he just kept going.


The rig blows cover crop seed through the Gandy air tubes, throwing it forward between the snapping rollers as the corn is picked. The chopped corn residue falls over the seed, forming a protective mulch. It works the same way during soybean harvest, except that the cover crop seed is distributed behind the grain platform.

The handily located seed box refills easily from the bulk seed tender in about two minutes. McCormick broadcasts 10 to 15 lbs/acre of cover crop seed mixes, mainly annual ryegrass plus crimson clover, rape, turnips or radishes, depending on the following crop.

Because of the limited seed box capacity, this planting method requires smaller cover crop seeds; cereal rye seed is too bulky and requires a higher seeding rate. That limits the practice to areas south of I-70, where the post-harvest growing season is long enough to allow good establishment of annual ryegrass, says agronomist and cover crop expert Dan Towery, Ag Conservation Solutions, Lafayette, Ind.

“I can keep my seed cost down (about $7/acre for annual ryegrass seed and about $1/acre to apply it) because I get good placement and stands,” he says. However, “The number one advantage is the tremendous time savings. When you leave the field after harvesting, you’re done planting the cover crop, too.”

As for harvesting efficiency, McCormick says that seeding covers while combining really adds no harvesting time. The technique has worked so well that he is “committed to doing it on every acre,” of his 2,400-acre operation. 


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