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Diverse Rotation Key to Feeding Microorganisms

You want diversity in your diet, says Shannon Osborne, research agronomist with USDA ARS. “You can’t eat just an apple every day. The organisms that live in the soil are no different. They need diversity.

“When you have a continuous corn or a corn-soybean rotation, the diversity of microorganisms is very small,” she continues. “When you add cover crops, you increase the plant diversity, increase the number of species of microorganisms, and all of those have a particular benefit. You want diversity below the ground like you want above it.”

Keith Berns has found this to be true on his farm in Bladen, Nebraska. “If soil health is the goal, crop diversity cannot be ignored,” he says. “Plants were created to grow in diverse eco-systems, and this creates a balanced diet for soil biology.” Berns started using cover crops on his farm seven years ago to keep the biological activity alive after wheat harvest.

Jamie Scott of Warsaw, Indiana, believes in the importance of diversity so passionately that he’s using a 16-way cocktail mix in rotation with corn, soybeans, and wheat.

“If it’s corn after corn or corn after soybeans, that just isn’t enough,” says Scott. “In a three-year rotation on my farm, I now have 20 plant species touching my soils.”

Incorporating cover crops into a crop rotation isn’t a quick fix for soil health. Instead, it’s part of a long-term solution, as Steve Groff has found on his Pennsylvania farm. Groff, founding partner of Cover Crop Solutions, has increased organic matter from 2% to 4.2% through cover crop use and no-till.

Capture nutrients
Groff also uses cover crops to scavenge available nutrients, store them over the fall and winter, and release them for the next growing season.

“Cover crops benefit the bottom line by keeping nutrients where you want them,” he says. In his research, he analyzes the uptake of nutrients by cover crops, particularly to see if this dollar amount can compensate for the cost of planting cover crops.

“If you start to assign values to the amount of nutrients the cover crops take up, it starts to be valuable,” says Groff.

In one study, the amounts of nitrogen and sulfur that were captured, pulled up, and made available to the cash crop added up to $60 an acre.

The ability of cover crops to tie up nutrients is also important when cash crops aren’t able to use nutrients that have already been applied. After a midseason hailstorm last summer, Berns planted a cover crop to capture nitrogen so it wouldn’t leach away.

Groff had a similar situation in which he planted tillage radish into a prevented-plant field to help capture nitrogen. The following season, he only needed to apply 50 pounds of N to achieve 230-bushel corn.

Manage increased rainfall
Ray Gaesser, chairman of the American Soybean Association and a southwest Iowa farmer, started using cover crops about five
years ago.

“My defining moment was in 2010 when I got 4 inches of rain in one hour,” he says. “My current practices, including no-till, weren’t built to handle that kind of event. That was a wake-up call to try something new.”

Gaesser now experiments with different cover crops, including legumes, radishes, turnips, and cereal rye, as well as different seeding methods to see what works best on his farm.

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