Cover Crops Shine in Dry Years

Cover Crops Shine in Dry Years

Not only do crop roots penetrate deeper but so does water.

Whether it’s too much or too little rain, cover crops can be the key to water management on cropland soils.

Several Midwest farmers say they first turned to cover crops because of too much water. No-till, terraces, contouring, grassed waterways and other practices -- even in combination -- haven’t controlled soil erosion well enough on their farms.

At the same time, Ron Althoff, an agronomist and cover crops seed rep for Saddle Butte Ag in Effingham, Ill., says the big payout for cover crops comes when there’s not enough water, in a drought year. Benefits pile up faster in years like last year, with too much water early, then little rain later in summer.

Farmers say cover crops not only retain moisture but also build soil organic matter.

“Cover crops shine in a dry year,” says Althoff, who has 10 years of experience both growing cover crops himself and working with farmers mostly in Illinois, Indiana, Ohio and Michigan. “After a few years of cover crops, you find your corn roots are penetrating so much deeper into the soil, especially in hardpan soils. They’re deep enough that they’re in moisture later in the year.”

A six-inch high annual ryegrass plant can grow roots five feet deep after several years of use, Althoff explains. “It’s a compounding effect. The first year, the roots might penetrate two feet deep. The corn roots will follow those roots. Then the next year, new ryegrass roots will follow the corn root channels, and go another foot deeper because they grew so easily in the top two feet,” Althoff says.

“In the third year you’re likely to get to more than four feet deep, and the fourth year you might get to six feet deep. And we know the corn roots will follow those channels.”

In 2012, a drought year across much of the Midwest, “we saw soybean yields typically eight bushels an acre higher, and corn yields 30 and even 50 bushels higher where cover crops had been established for several years,” Althoff says.

Better infiltration

In addition to getting the crop roots deeper into the profile to take advantage of that soil moisture, the practice gets more water into the profile overall.

“I’ve been involved in pipe tests for infiltration, and seen infiltration rates increased by ten times with cover crops,” Althoff says. “When we get those cloudbursts on tilled fields with no cover, it all runs off. But we can capture that water and get it into the ground with covers,” he says.

That’s what Kelly Tobin wants from cover crops. Tobin has seen first-hand that the roots of cover crops ease compaction and increase infiltration. The long-time conservationist thinks cover crops should be used on every acre of corn and soybeans in Iowa.

“The reality is that our cropland soils in Iowa can be uncovered for six months of the year, and our greatest nutrient losses can come outside the growing season,” the New Market, Iowa, farmer says.

Tobin is using cover crops to make full use of nutrients rather than let them leave the farm. He’s doubled his soil organic matter from 2.1 to 4.2 in five years of using cover crops, and increased corn yields an average of 11 bushels an acre. He’s doing that while dropping fertilizer rates.

“I used to use 150 pounds of N, but more recently dropped to 120 pounds and this year I’ll drop below 100 pounds,” he says. “What I want to do is improve infiltration and water holding capacity on the heavy soils in these hills to prevent erosion and runoff. The roots in a cover crop make so much difference in that.” Tobin uses cover crops on all 370 of his corn and soybean acres and more on rented ground.

Erosion by the pound, not ton

Where conservationists talk in terms of several tons per acre of soil loss per acre as “allowable” soil loss, Dave Brandt says his long-term no-till and cover crops system allows less than 100 pounds an acre in soil loss. “We have virtually no water coming off our land,” says the cover crops veteran from Carroll, Ohio. Brandt has built organic matter levels up in his soils, and gets higher yields with less fertilizer.

“My thought is that cover crops are part of your crop insurance program. Take $25 of that crop insurance premium to plant cover crops, to help you reduce your other inputs,” he says. “We don’t want a lot of N left in the soil from our corn crop, so we take it out with cover crops. That gives us higher bean yields -- we had 69 bushel beans last year,” Brandt says. The muck soils on his farm need to be dried out, he says, and he lets cereal rye grow long into the spring to accomplish that.

Steve Berger of Wellman, Iowa, has used cover crops for ten years and now uses them on all his cropland. “There are a lot of reasons to use cover crops, but our top reason is to control runoff and soil erosion. Berger uses no-till, contouring and terraces on his land, but wanted more control of runoff. He also wants to build organic matter.

“We’re getting organic matter increases from the roots of cover crops -- we’ve seen one-tenth of a percent increase each year over more than 10 years using cover crops and no-till,” Berger says. “I don’t think cover crops is something to jump in and out of -- it’s a long term decision for us. We’re trying to get more of the soil on our farm looking like fencerow soils, with high organic matter and great pore spaces for water infiltration.”

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