MADISON, Wis. – Indications are there will be more soybeans going in the ground in Wisconsin and elsewhere this spring. Properly dealing with cover crops ahead of planting and being extra diligent in management of second-year soybeans are advised.

It’s a matter of weeks before soybeans are planted in some parts of the state. For farmers who have cover crops established, cover crops need to be terminated two weeks before planting, said Shawn Conley, University of Wisconsin-Madison soybean specialist. Once the crop emerges, options for using herbicides to terminate the cover crop are considerably more limited.

Multi-state-university recommendations developed by the Crop Protection Network say don’t reduce herbicide use because of cover crops. Always use pre-emerge residual herbicides with multiple sites of action. Apply at full rates because cover-crop residues can reduce the amount of herbicide that reaches the soil. And be aware that residual herbicides can later interfere with cover-crop establishment and may have restrictions such as grazing.

Although cereal rye can suppress 60 percent to 80 percent of some specific weeds, the ability of other crops to suppress weeds can be variable.

According to network specialists, waiting 10 to 14 days to plant after the cover crop has died is risk management for insect pests such as armyworm and black cutworm. Not planting immediately after cover-crop termination also reduces disease risk. Cover crops can be a “green bridge” that increases pathogen populations.

Trio of farmers provides tips

Three veteran Wisconsin cover-croppers shared cover-crop tips at a recent Wisconsin Cover Crops Conference in Stevens Point, Wisconsin.

Nick Miller of Miller Farms near Oconomowoc, plants 3,800 acres of corn, soybeans and wheat. After eight years of cover-cropping, the majority of acres are planted in cover crops. After corn and soybeans, winter rye is broadcast-seeded for a fairly thin stand of a couple plants per square foot. He said the rye helps pull moisture out of the soil, helping dry the soil in the spring.

Miller said he planted 400 acres of soybeans into green rye. He sprayed pre-emerge herbicide with a glyphosate burndown after planting.

“It worked very well,” he said.

There are several keys to success.

  • Ensure good seed-to-soil contact.
  • Treat cover crops like cash crops in terms of timeliness of operations.
  • Understand cover crops aren’t a quick fix.
  • Maintain good records of pesticides applied.

Vic Goettl of Goettl Grains and Twin Top Dairy near Chippewa Falls

  • aerially seeds — either a cover-crop mix that includes annual ryegrass, crimson clover and turnips; or straight cereal rye into corn in early September. Because crimson clover and annual ryegrass survive winter, he terminates with glyphosate in spring. He no-tills soybeans between corn rows.

Goettl said he likes biodiversity in cover crops. Cover crops have improved both physical and biological properties of his soil, he said, as evidenced by the “boot test.” Instead of his boots caked with mud in the spring or after a rain, his boots are somewhat clean.

Jay Aspenson of Ferryville operates 1,500 acres of corn, soybeans and wheat. He relies on cover crops to reduce erosion in the Driftless Area region of southwest Wisconsin. He has incorporated wheat into his rotation to allow for longer-season cover crops and good soil benefits.

Aspenson terminates a cover 10 days ahead of planting corn. But he’s terminated cover the same day or the day after planting soybeans. He said cover crops are good for positive public relations with landlords.

More soybean-on-soybean planting likely

With more Wisconsin growers likely planting more acres of soybeans in 2018, some of that ground will be second or even third-year beans. That’s a practice not recommended by Conley and other UW-Madison crop specialists.

Farmers need to balance short-term profitability – anticipated by planting more soybeans in 2018 – with long-term economic sustainability, Conley said. Results from a long-term crop-rotation study by the university shows soybeans clearly benefit from crop rotation. After five years of corn, it took only three years of continuous soybeans for yield to drop to within 7 percent of 20-plus years of continuous soybeans. Second-year soybeans yielded within 5 percent of soybeans grown in a corn-soybean rotation.

“Our data clearly shows that three or more years of continuous soybean gives ... a 7-plus-bushel-per-acre hit when compared to a corn-soy rotation and moves (yield) close to that of continuous soybean,” Conley said. “In short, (farmers) are setting ... long-term profitability up for a hit.

“If it were my land, I would stick to my rotations on my owned land and consider second-year soybeans on the rented ground.”

Farmers should be aware that soybean after soybean alters field-pest complexes and may take years to undo.

“Also don’t automatically think that simply adding a cover crop to this soybean-soybean rotation will ‘fix’ these issues,” Conley said.

Growers planting second- or third-year soybeans this year should plant a different variety than the one in the field in 2017. Ensure it has strong disease resistance to problems that surfaced in that field.

“I know growers are going to want to cut back on inputs, but 2017 brought us above-trend yield,” Conley said. “An 80-bushel soybean crop meant you removed about 98 pounds per acre of potash-equivalent fertilizer.”

Growers routinely rely on carryover fertilizer for soybean when rotated with well-fertilized corn, he said. Soybean after soybean may require additional fertilizer, especially potassium.

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Jane Fyksen writes about crops, dairy, livestock and many other agricultural topics; she is the crops editor for Agri-View based in Wisconsin. Email for more information.