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What cover crops mean for hypoxia

What’s the first thing that pops into your mind when someone says “cover crops”? Stopping soil erosion, right? It took Barry Fisher nearly an hour during a tour of cover crop plots at Roger Wenning’s farm to mention soil savings.

“We’re taking another look at cover crops, and we’re excited about how they could help capture nutrients not used by the crop,” said Fisher, state agronomist with the Natural Resources Conservation Service. “It’s not only an opportunity to save on fertilizer bills, but it’s environmentally friendly.”

Annual ryegrass leads the pack of the newest class of cover crops.

“It’s an outstanding nitrogen scavenger,” Fisher said. “It can literally stop nitrate from exiting a field in tile lines if the crop didn’t use all the N. It could reduce contributions toward hypoxia in the Gulf.”

Key Points

• Renewed interest in cover crops is linked to capturing nutrients.

• Cover crops could cut fertilizer bill if managed correctly.

• Plots help farmers learn more about cover crop options.

Capture power

Eileen Kladivko, earthworm and water-quality specialist at Purdue University, quantified the ability of cover crops to keep N and other nutrients in the field. “A good cover crop of cereal rye sequesters 20 to 40 pounds of N per acre, keeping it out of tile lines,” she said.

Instead, it’s available for crop use or for building soil organic matter. However, rye can keep nitrogen temporarily tied up in the spring. You may want to supply N through starter fertilizer. Some N will be released later in the season, and the rest will be used to slowly build up organic matter as cover crops decay.

After N is captured by a cover crop in the fall, it’s possible to lose some the next spring, depending upon how early the cover crop is killed, Kladivko noted. It’s an issue with cover crops that die naturally of freezing, such as oats.

Why mess around with small plots?

Roger Wenning doesn’t hesitate when asked why he’s in his third year of cover crop plots and field days on his own farm.

“What could be better than seeing how various cover crops work on my own farm, on my soils in my system?” Wenning asks.

The Decatur County Soil and Water Conservation District supervisor seeded 80 small plots last fall, trying various combinations and planting at different times. He hosted a field day in late fall and intends to hold another in early spring 2010.

“I also learn from listening to the experts from the Natural Resources Conservation Service, Purdue and other places who talk at field days,” he says.

Eileen Kladivko, a Purdue agronomist, is collecting detailed data on a portion of the current plot, hoping to verify how many nutrients are captured by various cover crops.

A no-tiller, Wenning utilizes cover crops in his operation. He aerially seeded ryegrass into cornstalks. With plenty of early fall moisture, he achieved good stands of annual ryegrass on most fields where it was sown last fall.

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ON THE STUMP: Barry Fisher likes nothing better than talking about how cover crops help farmers better manage crop nutrients. Here he examines annual ryegrass and the fibrous roots it produces in a plot on Roger Wenning’s farm.

This article published in the January, 2010 edition of INDIANA PRAIRIE FARMER.

All rights reserved. Copyright Farm Progress Cos. 2010.