Soybean Association plot features cover crop options

DECATUR, Ill. — Examples of typical and not-so-common cover crops used in corn and soybean rotations were featured in a recent plot tour on the Farm Progress Show grounds.

The Illinois Soybean Association set up the plots last year when the show was in Illinois and continued the plots during the off-year.

Jim Isermann, Streator area farmer, agronomist and independent ag consultant for ISA, led the cover crop plot tour at the 4R Field Talk jointly hosted with the Illinois Fertilizer and Chemical Association. The plot features 16 individual species.

“Cover crops are broken down into two categories — cool season and warm season,” Isermann said. “A warm season species really likes the heat, really likes moisture, and is going to take off very good under those circumstances.

“Cool season species like cooler temperatures. They don’t generally like heat a lot. So, in our corn/soybean rotations, we’re going to use cool season species a lot more often because they like cool temperatures.

“A cool season species doesn’t necessarily mean it will overwinter, but it can handle some frost and will continue to grow for a while, whereas the warm season species can’t handle any frost whatsoever and immediately die off.

“Cool season grasses have played a very big role in cover crops for obvious reasons around here because they are very winter hardy, they’re relatively inexpensive and they can give us a lot of biomass.”

Here are the cereal cover crops in the plot Isermann highlighted.

Cereal Rye

Cereal rye is the most commonly used cover crop due to its ability to overwinter and spring regrowth. Its stand is extremely relative to planting date. Cereal rye can be very winter hardy if planted early enough.

Cereal rye ahead of soybeans seems to work very well, but there can be issues when it’s used ahead of corn. Because it is a grass, it has some allelopathic effects which can be a benefit for weed control, but doesn’t necessarily give any positives on corn.

Also, because of its high biomass, it can end up taking a lot of nitrogen out and causing some issues. So, alternative cover crops are considered ahead of corn.

Triticale

A cross between wheat and rye, triticale ahead of corn has been studied in trials. One of its advantages is it breaks dormancy later in the spring, so termination can be moved a bit later.

On the downside, if there isn’t a timely spring termination, its biomass is similar in size to cereal rye.

While it has been promoted as an alternative ahead of corn, it doesn’t quite have as much safety as Isermann said he’d like to see ahead of a corn crop.

Triticale can be a great cover crop. It needs to be planted a bit earlier. It can take off early and provide more fall growth. It’s frequently used on the forage side of things.

Barley

There has been some growth over the past few years in using barley as a cover crop. The reason it was very popular prior to that is due to cost that has since been reduced.

Barley isn’t as winter hardy and needs to be seeded earlier, compared to cereal rye that can seeded whenever and will grow. Barley should ideally be seeded in October.

Depending on the year, planting could go into November with the understanding that it will get riskier if planting is later in the year.

“Barley is slower to break dormancy in the spring, but even if it gets away from us, it doesn’t have that same overall growth compared to cereal rye that might be 6-foot tall at that point in the spring,” Isermann said.

Barley would only be in the 24- to 36-inch ranged depending on the variety and the conditions.

Oats

Oats are a winter kill, cool season species. The crop may be advertised as winter oats, meaning it can handle a lower temperature before it dies.

Isermann doesn’t believe it’s true winter oats in the same sense that there are winter cereal rye or winter wheat.

He cautioned against using oats if wheat is in the rotation. Cereal grains into wheat can result in contamination, and proper management needs to be applied.

Annual Ryegrass

In his opinion, annual ryegrass is “hands down, probably the best cover crop. If I had to pick one cover crop I could only use, it might be annual ryegrass if I could manage it,” Isermann said.

There are two problems with annual ryegrass — getting it to live and getting it to die.

“If you can figure out how to manage those two situations, it can be a spectacular cover crop,” Isermann said.

It’s a small seed and great as a forage. It has the advantage of having a low seeding rate that can be seeded with a drone.

Several cereals may have seeding rates of 30 to 50 pounds per acre, while annual ryegrass has 5, 10, 15 pounds per acre rate.

Annual ryegrass has done a lot of good for those soils in southern Illinois. Moving farther north, it has more issues. It has to be established earlier.

In Isermann’s area, it needs to be in by Sept. 1, and it’s also sensitive to some herbicides.

Tillage Radishes

Brassicas were the next stop in the plot tour. Part of the mustard family, tillage radishes have “kind of been the rock star of the brassica family,” Isermann said.

Rapeseed

This cover crop has been used extensively the past 10 to 12 years. It has some winter hardiness and is more winter hardy than some of the other brassicas.

It is essentially canola. It’s just a different term in order to be specific about the varieties selected for cover crops.

Some canola can be Roundup Ready. It can give a good tap root. It can get pretty large if it overwinters.

With the grasses, glyphosate is used for termination. For brassicas or legumes, a 2,4-D product should be used for termination because they can be problematic to kill with just with glyphosate.

Rapeseed is fairly small, so it’s easy to use as a throw-in. It’s pretty inexpensive.

“If we’re going to look at doing a mix of cover crops, oftentimes we start with that basic idea of a grass, a brassica and legume. Looking at something like cereal rye and rapeseed or barley and rapeseed can be a good mix,” Isermann said.

Turnips

Purple top turnips are small seeds, providing “a lot of bang for your buck” in terms of offering diversity in a cover crop mix with a seeding rate of 3 to 4 pounds per acre, Isermann said.

Barkant

This forage turnip does not grow large bulbs like purple tops.

“Turnips get overlooked a lot for radishes, but can provide a great mix. They’re especially beneficial if incorporated into a livestock grazing system,” Isermann said.

He advises not to use only a brassica species for cover crops, but instead include them in a mix with other covers.

Camelina

It’s a brassica that’s an oil seed. It’s not necessarily very impressive as a cover crop except it can be planted later and still provide good overwintering. In fact, if camelina is seeded too early, it can winter kill and not provide any benefits.

Camelina is small-seeded, easy to add into a mix, provides some tap root and a good option, Isermann said.

Forage Sorghum

Summer annuals were also included in the plots. Similar to sorghum sudan, forage sorghum is a forage.

For those using corn silage for feeding beef cattle, forage sorghum can be a good alternative at a lower cost.

It can give provide opportunity even for something like double-cropping because it has a shorter season, but has a lot lower nitrogen needs and a lot lower seeding costs.

Pearl Millet

The first frost on summer annuals, the leaves are going to get slimy because the freezing process is going to break all of their cells open.

“If we’re grazing, there’s a concern for that in terms of prussic acid, particularly on the sorghum. That’s something you need to be aware of,” Isermann said.

Pearl millet is not known for having that prussic acid concern.

“As a cover crop, you may not always be looking at pearl millet or forage sorghum — you may be looking at some cheaper alternatives if you’re not worried about grazing,” Isermann said.

“There are five different types of millets with about eight to 10 different names. There’s German millet, Japanese millet, you’ll have some different options out there in cover crop mixes. They can all be good as cover crop mixes.

“I’m not afraid of putting them in there, but if I’m going to look to create hay or forage, I’m going to look at something like a pearl millet instead those other millets.”

Buckwheat

Organic producers and conventional farmers who want to reduce fertilizer application can benefit from buckwheat’s characteristics that include the releasing of phosphorous into the soil.

“You’re not going to get a whole lot of phosphorous out it if it’s a small part of a mix, but there are some out there managing it pretty aggressively and seeing some response,” Isermann said.

Winter Peas

Legumes are third option among cover crop families. Overwintering can be difficult for winter peas on most situations.

The downside of winter peas is aerial seeding or other applications where seeds will lay on top of the ground will not work out very well.

They’re like a soybean seed in size. They need to get in the ground and need good moisture to get going.

Winter peas can play a role particularly in larger mixes, not so much on their own. In looking at summer annual mixes, winter peas are a cool season crop, but they’ll grow well in summer annual mixes. They’ll get viny and produce some nitrogen.

Hairy Vetch

Described as one of the most winter hardy cover crop, hairy vetch can produce quite a bit of nitrogen. Some have used it with cereal rye and incorporated with a roller crimp.

Hairy vetch can produce a lot of nitrogen, but it also produces a lot of hard seed. So, it is something that once we put out on the farm it’s going to be around for a while, especially if it goes to seed.

Hard seed means it’s not going to germinate in that first year. Your seed tag will have a percent amount of hard seed.

“That’s basically how much of that produce is not going to germinate that year and will come in later years,” Isermann said. “The seed that you purchase will have a process done to it to reduce that amount of hard seed.”

The concern is if you have, for example, a non-GMO soybean field, hairy vetch could emerge and there would be no chemical options to remove it.

A 2,4-D product can be used for spring termination of hairy vetch. Glyphosate does not work well on the cover crop.

It’s a higher management cover crop, but can have some pretty good rewards. It does a little better if it has something to vine-up and grow around. So, you’ll often see it in a mix with other species.

Crimson Clover

Clovers are the other legumes in the plot. It’s one of the more popular legume cover crops in Illinois because of its winter hardiness.

It isn’t as winter hardy moving farther north in corn/soybean systems, but it does produce some nitrogen early on. It can be used in a lot of mixes.

Medium Red Clover

There’s been an uptick in the use of red clover the past few years, partly because the seed costs have decreased. Medium red clover is a perennial.

Legumes produce the most nitrogen when they flower. Something like red clover is going to flower later.

“That’s one of the reasons we like crimson clover is it flowers earlier in the year,” Isermann said. “So, if you’re really looking at the nitrogen component, you want something that’s going to flower a little bit earlier.”

Balansa Clover

It’s not new, but it’s been promoted over the last 10 years as a little more winter hardy and as a replacement for crimson clover.

It’s seen as a good option as part of some mixes and can ultimately produce more nitrogen if it overwinters.

Berseem Clover

Berseem clover does not overwinter and is best used as a summer annual option. One of its claims to fame is it is a legume that has a low bloat potential to it for livestock grazing.

“All of these legumes could be used in the livestock side. Things like a hairy vetch probably really aren’t the best for grazing. Once it puts the seed out, I’m not sure that it’s really appealing for a cow,” Isermann said. “Legumes can be a part of a mix, but we always have to watch that bloat potential.

“All of these in these plots can end up in mixes. I’m not trying to promote the idea of a single species, but we wanted to walk through and look at those attributes. Always think through the different management aspects.”