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Thursday, Aug. 25, 2016

Cover crop crash course

Saturday, October 27, 2012

Aaron Andrews, of Iowa Learning Farms, uses a rainfall simulator to demonstrate how a field with cover crops holds water, compared to other surfaces, during a farm field day on Friday at Pete Crew's farm near Webb.
(Photos by Gabe Licht) [Order this photo]
Chilly temperatures and a persistent wind could not keep area farmers from attending a farm field day about cover crops at Pete Crew's farm near Webb.

"Last year was a bad year for cover crops," said Crew, who has been implementing the strategy for two years. "There was not much moisture, but it survived and provided some cover. We think it fits pretty well with strip tilling. Six months out of the year, we have nothing on the field otherwise."

Crew said cover crops protect "worn out hills" from erosion, increase nightcrawler activity and add organic matter.

Sarah Carlson, of Practical Farmers of Iowa, talks about rye grass as one of many cover crop options that add organic matter to soil and help control erosion. [Order this photo]
"You'll add organic matter, but conservation is the biggest thing," Crew said. "With corn-on-corn rotations, we're more concerned about nitrogen."

Legumes such as crimson clover, hairy vetch and winter peas can increase nitrogen to aid corn crops.

"We're pinched for time here because it gets so cold," Sarah Carlson, of Practical Farmers of Iowa, said. "I don't think you should put on fall anhydrous; I think you should side dress. You'll increase growth by adding nitrogen to it. When using rye before corn, make sure you're not nitrogen deficient. Legumes bring the carbon-to-nitrogen ratio down."

Carlson does not believe cover crops have a significant effect on moisture levels.

"Small grains are not water hogs like corn," she said. "You don't want it taller than your boots if moisture is short. It will mulch back to the ground."

Crew added that some individuals told him the cover crop would dry up the moisture, but he pointed out that it also provides cover from the sun.

"I think it's a wash," he said.

Crew's cover crop was aerially applied at a rate of 45 pounds of seed per acre on Aug. 24.

While Carlson said 70 pounds per acre is recommended, she applauded Crew on his timing.

"If you go too early, it will take moisture from your cash crop so you need to find times when crops are slowing down so the new rain goes to the cover crop," Carlson said.

Once a cover crop is established, it retains rainwater better than other surfaces, which Iowa Learning Farm's Aaron Andrews demonstrated with a rainfall simulator.

"Intense tillage starts to perform like concrete when it comes to retaining water, so we really promote no till and strip till," Andrews said. "We expect the runoff from the cover crop section to be clearer than the intense tillage section and maybe even the no till section."

Other benefits of cover crops include the potential for grazing cattle and harvesting up to 60 or 70 acres of small grains.

While cover crops may negatively affect yields, Carlson expects that impact to decline.

"Over time, we think we'll see a decrease in the effect on cash-crop yields," Carlson said. "State cost share is also available. You could be compensated up to $25 per acre for cover crops."

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