Over the past three years, a curious turnaround has spread across Ontario. Some farm watchers explain it by pointing to lower commodity prices. Others attribute it to the increased attention on soil health and sustainability. Either way, interest in cover crops is growing stronger and stronger.
On some farms, the focus is on novel, multi-species blends and on inter-seeding into standing crops. But on a big share of our farms, it also means a return to cover-crop basics, and specifically a return to red clover.
Bill Deen has been researching the link between cover crops and soil health since joining the University of Guelph in 2000, where he inherited long-term data that now dates back more than 30 years. But it’s been in the past three to five years that Deen has witnessed a dramatic increase in interest in cover crops and what they can do for a cropping system.
Although he has also noticed an increased focus on multi-species cover crops (if growers can make such a system work on their farms, he says, that’s great), he also sees a role for the single-species approach.
“If you look at most of the data, in terms of cost, in terms of agronomic and soil-health benefits, in terms of nitrogen credit, red clover is still the one that’s hard to beat,” says Deen, an associate professor at the university.
The work conducted at the university’s Elora Research Station is detailed and it spans several decades, and most if not all of it points to cover-crop benefits including better soil health and improved yields.
But the recommendations have evolved, including recommended time of seeding. Deen’s experience indicates that the earlier red clover is broadcast into winter wheat, the better the emergence. That runs contrary to a more casual practice that says it’s fine to seed when you can get around to it.
Yet a failure to get a “good catch” of clover is often the reason farmers opt out of covers, Deen says. “Earlier is always better, and sometimes the nitrogen timing — if you’re going to do it at the same time — is too late,” he asserts.
Other recommendations are the same. “We’ve looked at broadcasting versus drilling into the stand,” says Deen. “There’s no difference, and we have some fairly good data sets on that, and Michigan State University has also looked at it and found no difference.”
But no till remains a concern. Deen and his colleagues have studied the impact of tillage on red clover, and some of that research indicates that red clover doesn’t perform well under a no-till management system. He also finds farmers have often said that establishing red clover was never such a difficult issue, and some have tied those challenges to higher-yielding wheat.
“It’s interesting that when the no-till drill was introduced, ever since then it seems our concerns regarding red clover stand have been increasing,” says Deen. “I’ve talked to dealers or retailers of red clover and they’ve said that as soon as a farmer gets a no-till drill, his complaints on red clover stands go up. Why that is is a bit unclear. We’re not going to get farmers to move away from no-till wheat, so that’s an issue. But it doesn’t seem as though red clover does as well under no till.”
Fertility another factor
Ask any crop adviser and they’ll agree that how a crop looks is often a gauge of how it’s performing. But that can be deceptive with clover. In other words, you might look at the field and say, “the wheat looks good but the clover looks poor,” even when the clover is actually doing its job.
“To build on that concept, our recommendations for N credits used to be worded that if you had red clover that was knee-high, you’d get a full nitrogen credit,” says Deen, adding that it had to be a thick and lush stand to qualify. “The reality is that yes, you seem to need a minimum amount of red clover but the relationship between red clover biomass and N credit above that minimum is not very strong. In other words, you can have a red clover stand that is 20 cm tall, and maybe not as thick as you’d like to see, but there’s a chance that you’re going to get a full nitrogen credit and a lot of soil-health benefits.”
Nitrogen application rates and their impact on emergence and uniformity have been studied as well, and while Deen has found higher N rates can put increased pressure on red clover, he’s also seen higher N rates resulting in high yields and no adverse impact on the red clover stand. But that leads to another reason why cover crops might have fallen out of favour: the focus on driving wheat yields in the past decade, something Adam Hayes has seen occurring.
“There’s been some work done to try to help improve the stands, seeding it earlier,” says Hayes, field crop soil specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA). “One of the challenges was our focus on wheat production and getting higher yields, so the canopies were denser and pulling more moisture out and providing more competition to the red clover.”
Two or three years ago, Hayes monitored long-term plots at the University of Guelph’s Ridgetown Campus, with red clover inter-seeded into the plots at different N rates. In the upper level nitrogen-rate plots that year, he confirms, it was tough for red clover to make it through.
In spite of those findings, red clover continues to be an easy way to get back into growing cover crops. It’s relatively inexpensive compared to the mixtures some growers are advocating, some of which can run upwards of $50 per acre. And research at Elora indicates that while oats might be an emerging favourite among cover crops, its N-credit impact on subsequent corn crops is not as significant or consistent as red clover.
Add one more factor — that red clover can be insured — and the crop seems to have nothing but advantages.
“If you consider the nitrogen credit from red clover, and the research work that Dr. Dave Hooker has done with and without it, he can show an eight-bushel corn yield advantage just to the red clover, not taking the nitrogen out of it,” says Hayes. “If you add to that the nitrogen credit, it’s a pretty significant payback, plus all of the soil health benefits you’re getting as well.”
Hayes says the biggest driver in the return to cover crops is soil health. He hears from a lot of growers who say their soils aren’t in very good shape, and are looking for ways to improve them. There’s also some increased interest from those who do a good job managing their soils and are looking for other methods to boost the biology and soil life that much more. And of course, there’s the ongoing concern about phosphorus levels in the Great Lakes, and that lends itself to growers doing more to reduce erosion and runoff of surface water.
“The more we can get cover crops into the cropping system and the longer we can have live roots in the ground, it does so much more to stimulate the soil life and help improve the soil structure and help slow water across the surface and get it into the soil,” says Hayes. “The more we can do to get water in the soil, the fewer issues we’re going to have from a phosphorus perspective.”
Farm experience — Tom Barrie
Tom Barrie is a huge advocate of red clover, incorporating it into his cropping plans for at least 40 years. Barrie is a dairy producer who manages Terwidlen Farms with his brothers Steve and Glenn, complete with 50 Jersey cows and 850 acres near Bowmanville, Ont. He’s in his 24th year in no till, and was the Ontario soybean yield champion in 2010 with 74 bu./ac. He follows two rotations, one that’s five years with soybeans, oats, clover haylage, winter wheat and corn. The clover haylage is under-seeded with his oats in Year 2 and the winter wheat is planted into the clover stubble, which is then fall-killed after the wheat harvest. That means he has red clover in the ground three years out of five, providing nitrogen for his corn and wheat.
His second rotation is a three-year plan, with corn, soybeans and winter wheat. (He dropped canola due to declining acres.) Barrie plants winter wheat and red clover together following soybeans to help him avoid any issues with establishing the clover in the spring. He also finds using an air drill for seeding gives him more accuracy than a spinner-spreader. After the winter wheat is harvested in Year 3, he fall-kills the clover cover crop. He can switch between the five- and three-year rotations, depending on distance from the home farm and his need for haylage.
It was Barrie’s father who opted for red clover over alfalfa because of alfalfa’s potential for winter kill (keeping in mind that alfalfa wasn’t as hardy then as it is now). Although he relies on red clover as a cover crop in some parts of his two rotations, Barrie emphasizes that it’s a valued source of forage for his dairy herd. He adds that it’s been a slow process in recognizing any benefits of having red clover in the rotation, instead noting that it’s more noticeable in soils without an under-seeded clover cover crop. He has a customer who grew wheat with red clover 10 years ago, but dropped it when wheat prices declined. Barrie planted his corn this past spring and noticed the soil structure was comparatively tougher.
“I would say that comparing our yield (to others), we’re adding 40 to 60 bu./ac. in corn,” says Barrie, who is also a Pioneer seed dealer. “We see it in other customers’ fields as well but you have to remember that our clover is part of a five-crop rotation that really works wonders. Most livestock guys run three or four years of alfalfa, then corn for two or three then reseed back to alfalfa. Oats and clover complement each other in their soil fungi improvements.”
As for his fertility needs, Barrie applies just 100 pounds of additional N, since his corn follows wheat which is two years post-clover. Half of his wheat is grown on clover sod and receives just 45 pounds of N, and he’s done it that way even though wheat will flourish without any added N. But a little bit early gets it off to a quicker start.
“If the year is a good one for wheat, then 100+ bu./ac. is normal,” he adds. “Our average up until the ice storm in 2013 was right around 105 but that year was pulled down to 75.”
Years ago, when OMAFRA’s Greg Stewart started his work on the pre-sidedress nitrogen program, Barrie’s N levels were as high as 265 lbs./ac., most of which is released when the corn can optimally use it. His highest overall field yield was after corn following wheat, and a 22-acre field ran 259 bu./ac. dry-weighed on his own scales. He acknowledges that he likely doesn’t spend as much on fertility as other growers might but the differences in his practices are obviously a big part of that equation.
Still, Barrie believes red clover is one of the easiest crops to establish, although he knows some growers who have had a tough time working with it. From a cost perspective, he’s saved money by growing his own clover seed, going with 10 to 12 pounds for a hay crop, and five to eight pounds per acre for under-seeding wheat.
But it also takes a shift in grower attitude, he says, with a focus on long-term net economics. In that scenario, clover is a winner, he says. “I think most growers want to maximize their gross dollars per acre,“ Barrie says. “To me, that’s the wrong way of looking at it.”