Plan Ahead for Covers

Fall Cover Crops Require Springtime Decisions

Emily Unglesbee
By  Emily Unglesbee , DTN Staff Reporter
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A cover crop peaks through the remains of the corn crop it followed. Make sure the herbicides you use on crops like corn and soybeans won't harm your fall cover crops. (DTN photo by Pamela Smith)

ROCKVILLE, Md. (DTN) -- AJ Blair won't plant cover crops on his corn, soybean, cattle and hog operation in central Iowa until early fall. Yet the details of how and what he will plant are already running through his mind as he slogs through chores in snowy barnyards this winter.

Cover crops require planning, just like a cash crop. Decisions made this spring on corn and soybean fields will affect what covers you can plant and how they will fare this fall, experts told DTN.

Among the most important things to consider are the maturity groups you will grow, the herbicides you will use, what benefits you're seeking from cover crops and how you hope to plant them.

GET TIME ON YOUR SIDE

As Blair has discovered in his eight years of cover crop experimenting, planning ahead doesn't guarantee success. The weather has occasionally hijacked his plans for planting and sabotaged a cover stand or two.

Selecting shorter-season corn and soybean varieties will help get time on your side, often without sacrificing yield, said Keith Berns, co-owner of Green Cover Seed, based in Nebraska.

"For example, we've gone from mid-group IIIs to mid-group IIs in beans and haven't seen any yield penalties," he told DTN. "That can be the difference between harvesting in mid-September instead of into October."

If you're hoping to graze livestock, plan to put the shortest-season varieties on the earliest-planted fields to maximize the growth of the cover crop, he added.

The planting method will also affect the cover crop's growing season. For Blair, grazing his 45 mama cows is the best way to get a short-term return from the cereal rye mixes he plants after his cash crops. So he aims to broadcast cover crop seed within his standing crops with an airplane or a high-clearance sprayer around Labor Day to get a good stand before the first freeze.

The weather will determine which method is better -- wet years may require an airplane and dry ones will benefit more from the sprayer -- but it would be wise to research your local options now, Berns said. Sometimes co-ops will reserve a high-clearance sprayer for just that purpose, but they need to know that there is local interest, Blair said.

Following the combine with a no-till drill produces the best cover crop stand, but this method is best suited for growers with long, mild falls and spare hands at harvest.

"I think drilling after harvest is the best way to do it, but to come in with a drill and follow the combine in the fall is kind of difficult logistically," Blair said. "We haven't gotten there yet."

Keep in mind that the seeding rate will vary according to planting method. "Normally we say if you're broadcasting seed, you'll need 25% to 33% more seed than what you would drill," Berns said. You can use Iowa State Extension's cover crop calculator (http://bit.ly/…) to find an appropriate seeding rate.

PICK THE RIGHT COVERS -- AND PROTECT THEM

Most growers don't put in cover crop orders until the summer, so selecting seed now might seem premature. However, the herbicides you apply to your corn and soybean crop could have repercussions for certain fall-planted covers.

"Check your herbicide line-up and figure out which ones have really long residuals and may affect the cover crop growth down the road," Berns advised.

Weed scientists from the University of Missouri have compiled three years of data on which corn and soybean herbicides are likely to harm the most common cover crops. See their research here: http://bit.ly/….

Keep in mind that if you plan to harvest your cover crop or graze livestock on it, planting it after an herbicide that wasn't labeled for that cover crop species is technically illegal. See a list of the plant back restrictions of common corn and soybean herbicides from the University of Wisconsin here: http://bit.ly/….

Blair recommends prioritizing your corn and soybean crop when it comes to herbicide carryover concerns. "Let's get the right herbicide for our cash crop first," he said.

THE RIGHT COVER FOR YOUR FARM

So which cover crops do you want? The answer depends on many factors, Berns said. Do you want to graze livestock or just improve your soils? Prevent erosion? Add nitrogen? Are you prepared to terminate the crop in the spring, or do you want it to die over the winter? How early do you get into your fields -- do you cut corn for silage or do seed production, which often allow for August planting?

Cereal rye remains one of the most popular choices and is the primary cover in Blair's mixes. It can grow in cool soils, it overwinters well and its deep roots keep soils in place, Berns noted. This year, Blair added triticale alongside his cereal rye mix and left some acres un-grazed going into the winter for springtime forage and baling.

Annual ryegrass is another good, deep-rooted forage crop, but it requires more establishment time than cereal rye. If you're looking for a cereal option that doesn't require spring management, oats are a good bet because they don't overwinter, Berns added.

Tillage radishes are a popular choice among farmers but need a longer growing period in the fall. For colder climates, rapeseed might be a better bet, Berns said. Blair's cattle prefer the taste of turnips, another option for breaking up compaction and adding soil organic matter.

For growers looking to add nitrogen for a spring corn crop, hairy vetch is a legume that overwinters well, Berns said. For growers who have milder winters, crimson clover is also a good option, he added.

Once you have a sense of which species you need, alerting seed dealers early in the year will help ensure they have a good inventory prepared, Berns said.

Is your head spinning yet? Take the plunge, and don't get too overwhelmed with the decisions ahead, Blair advised. "The biggest thing is just to start somewhere," he said. "Put something out there and five years from now, maybe you'll have a program figured out. But it will take five years from the first year to figure it out, so start now and plan on some mistakes along the way."

Emily Unglesbee can be reached at emily.unglesbee@dtn.com

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Emily Unglesbee