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Expert: ‘Cover crops should be a normal, agronomic practice’

By Staff | Sep 29, 2017

Alan Lange, resource consesrvationist for the USDA, put on a demonstration during the field day with the rainfall simulator. The rainfall simulator, he said, shows the ability of soils to stand up against the rain.



EAGLE GROVE – The Boone River Watershed project, in partnership with The Nature Conservancy of Clarion, hosted a field day last Friday near Eagle Grove.

The field day was split into two sections, starting at a restored oxbow and ending the morning at the Gray Farm, where cover crops took over most of the discussion for the day.

Todd Nielsen, farmer of the Gray Farm, said they have been using cover crops on the farm for eight years along with no-till for 12 years.

Nielsen said their cover crops are blown on the crop ground each fall and this year, due to some termination issues of cereal rye last spring, Nielsen said they are experimenting with oats as a cover crop option this fall.

“We are using some oats this year to see about easier termination in the spring,” he said. “Typically we will terminate the day we plant, so many years we had trouble for the rye to terminate. It delays our planting.”

The issue this year, Nielsen said, was they wanted to wait for it to warm up to give the herbicide a chance to kill the cover crop.

“We didn’t have one of those warm days until the first of May this year,” he said. “That’s why we went to oats. We were pulling our hair out trying to wait to terminate the cover crops to be able to go plant corn.”

Nielsen said they had 72 pounds of oats aerial applied in one field. He doesn’t anticipate any issues combining his beans over the new growth of oats coming up.

“I did it last year with the rye. It just makes the cutter bar a little green is all,” Nielsen said.

He added they have definitely seen benefits of cover crops – especially when it comes to keeping nitrates in the field and out of the tile and river. Improved soil health and microbial action, he said, has also improved.

“We know by water monitoring this dredge ditch out here, there’s been less nitrates going through the tile with the cover crops out there – that’s been a proven fact,” he said.

They have stopped using anhydrous ammonia for their nitrogen source and have seen, he said, an increase in earthworm activity by going with 32 percent over the top.

Nielsen said his nitrogen program consists of 50 pounds down along with the burndown for the cover crops in the spring. Then, with the help of a watchful eye and soil nitrate tests and tissue sampling, they know when it is time to go back in with a sidedress application of more nitrogen.

Affect on yields

Nielsen was asked if he thinks his cover crops have had an affect on yields.

“We possibly have lost yields. I don’t know that for sure yet,” he said. “I look back over 10 years at what this farm normally does. I look back at 2014. We had cover crops and that was the best year we had on this farm – it was a 200-plus bushel year, but I need to go back to not planting cover crops and see if we can see a difference again.”

Nielsen he is planning on the possibility of going one year without cover crops if they have further issues with termination in the spring.

“We will see how the oats work first,” he said. “If they let us get into the field earlier, that’s a big difference. I think we’re losing some yield because of our planting date. We can’t get the stuff in the ground in April, we’ve lost a week’s worth of potential and I have a little concern about that.”

Nielsen said cover crops have been helpful with weed pressure.

Although they haven’t reduced their herbicide inputs yet, they have been able to hold off their post-emergent herbicide applications longer.

“We have a longer wait, so we have seen better weed control,” said Nielsen.

This, he said, is due in part to the mat the cover crop leaves on the ground.

“That mat helps control the seeds for awhile longer,” he said. “Sooner or later, those weeds will pop through.”

Sarah Carlson, Midwest cover crop director for Practical Farmers of Iowa, said they are available to help farmers investigate medium-size plot scales and share that information with neighbors, this, she said, helps to save everybody time and money on what cover crop system works the best.

Cover crops, Carlson said, should be considered a part of every farm.

“I would say cover crops, in general, in this state, we’ve thought about it as a water quality practice first, as an erosion reduction practice maybe second – more for conservation, but I feel like we should be way over that by now,” she said. “Cover crops should be an agronomic decision tool, just like you decide on nitrogen, fertilizer and fungicides. It’s really way beyond conservation and is an agronomic tool at this point and we need to think about cover crops as a normal, standard practice.”

Carlson also believes that, by not taking advantage of cover crops, a producer could be missing out on yields.

“If we’re not using cover crops, we’re leaving yield on a table in some cases – especially on a soybean year,” she said. “I am not just saying that because I love cover crops. I am saying that because that is what data tells us from on farm research trials. Specifically in a soybean year, we see yield increases and herbicide reduction costs.”

Corn, she said, is sometimes a different scenario.

“In a corn year, it’s a little tougher, we don’t see the quick responses, but we do in the eight- to 10-year mark of using cover crops,” she said.

Cover crops applications

Carlson said a common system for planting cover crops is by aerial application in the early fall.

“It’s the typical system that you all are using – flying rye in fall into standing corn or soybeans in that Labor Day window,” she said.

Grasses, she said, are some of the first cover crops. Options producers should choose, with maybe a mix of brassicas – such as turnips and radishes – especially if a producer needs to meet NRCS cover crop mix goals.

Carlson advises to try to avoid using legumes in cover crop mixes.

“I am just not too excited about legumes,” she said. “They are just too small. There’s no way they are going to pay for themselves with nitrogen fixation and they are too expensive.”

When choosing a cover crop to plant in the fall, looking to the spring for termination should be key in helping to make those decisions.

“For termination, a number one defense could be winterkill,” Carlson said. “Winterkill is a big option for termination of the cover crops.”

Oats, Carlson said, should winterkill as well as those brassicas.

“Turnips and radishes will winterkill, small grains will winterkill, rapeseed sometimes won’t – like canola, it is a brassica that can over winter and survive,” she said.

The second option for terminating cover crops is through spray management in the spring. Carlson said winter wheat could be an option versus rye because of its slow growth.

“If we have trouble killing rye in the spring ahead of corn, we could switch to winter wheat,” she said. “We’ll still need to terminate winter wheat in the spring ahead of corn, but it will be much shorter in the spring.”

Winter wheat, according to Carlson, grows much, much slower in than rye in the spring.

“It’s two to two-and-a- half weeds behind rye in the spring,” she said. “But it has still overwintered and protected your soil, it has still overwintered and took up a bunch of nitrogen to keep it out of the tile line. It still can be giving you some winter weed control and will have less trouble dealing with it in the spring because it will be shorter.”

Carlson said winter wheat requires heat, and that is why it doesn’t get growing as much as rye. Winter wheat, she added, also features a similar root system as rye. It just doesn’t go as deep.


“To me rye is the best,” she said. “I love rye, but in all reality it is tough to manage it in the spring, and so many people are going to switch to oats because of what happened this spring,” she said. “I think we might want to switch to a small grain cover crop ahead of corn and if rye was a trouble this spring, I think oats is a good option, but I think winter wheat is a good option because it will overwinter.”

Winter wheat also allows for a later planting date.

“Wheat can be planted well into October,” she said. “This allows for a late planting date post-harvest. It can winterkill, like usually in March, when it warms up and then gets cold and we don’t have any cover. That is when you will lose winter wheat, but, by then, we have protected the soil for a long time.”

If termination of a cover crop requires a herbicide, Carlson said to plan for warm weather.

“You will need a full rate of herbicide, warm weather and be spraying in the middle of the day and hopefully it is the start of a three day warm-up, but that is rare that time of year,” she said.

Carlson recommends to begin scouting those fields in March. If the rye is already several inches tall in mid-March, she said to be ready to spray on that first warm day.

“We need to pay attention ahead of corn – we need to be mindful,” she said.

Be careful of tank mixes of herbicide and nitrogen, she advised.

“If you’re going to be putting nitrogen down with the herbicide, if using a tank mix, you want to make sure you have enough warm weather for the herbicide to work,” she said. “If you have too much (nitrogen) in the tank, it can reduce the effectiveness of the herbicide.”

Cover crops in soybeans

The world is the limit, Carlson believes, when it comes to cover crops and soybeans.

“It’s like a free-for-all,” she said. “Don’t be scared. All of your corn stalk acres should be covered in cereal rye going in to soybeans. That should be normal practice. Just no-till plant soybeans right into that residue the day after you spray it and don’t look back.”

If tillage is still a part of your operation, Carlson said that is fine.

“Work those corn stalks in, in the fall; establish cereal rye when you work corn stalks in and try to no-till plant in the spring. Rye can be put out late. It will still grow,” she said.

Carlson advises producers shouldn’t kill rye ahead of soybeans until right ahead of planting.

“Just do it a couple of days ahead or day after soybean planting,” she said. “I would say that is the best way to get the weed control from the cereal rye.”

Rolling the rye is another option for rye termination, she said.

“Use a land roller – roll that rye down,” she said. “There’s a better weed control mat of the rye and better sunlight for the soybeans.”

Cover crop injury

Residual post-emergent herbicides, Carlson said, could cause some cover crop injury.

“Whatever residual you put down in the corn and soybeans year, in a dry year, with heave soils, those herbicides are going to reduce your cover crop’s growth and you’re going to have cover crop injury.”

Carlson suggest planting cover crop seeds into soils from a field in August and compare those to seeds planting in potting soil.

“Do a comparison to know what you can put down, you might waste thousands of dollars in radishes that aren’t gong to grow,” she said.

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