New Directions in Cover Crops

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New Directions in Cover Crops

In the midst of a renaissance in soil health, researchers, agronomists and extension personnel have been pushing the message that everything a grower does in a field is connected to everything else. Fertility is linked to planting depth, just as mycorrhizal fungi are connected to weed management. Nothing happens on its own without some effect above or below ground.

That same message is beginning to influence the use of cover crops. Gone are the days when growers would default to underseeding winter wheat with red clover. Now they have dozens of options, and they can pick an approach that is as unique as the soil on their farms.

It all means a lot more questions are getting asked about the connections that cover crops can make, and what you can expect to achieve.

The topic of cover crops is certainly nothing new. Presentations on the benefits and challenges of cover crops have dotted agendas of conferences and annual meetings for the past 10 years. What’s changed is the open-mindedness of growers and the growing body of data and perspectives accumulated from years of using different species, as well as the increased understanding of how soils are interacting.

Is it one single factor that’s been driving the uptake of cover crops? Not according to Todd Woodhouse, who cites a number of industry partners who are generating greater awareness of cover crops, including the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) and the Ontario Soil and Crop Improvement Association (OSCIA). Together with support from industry agronomists and advisors, it creates a “strength in numbers” approach.

“Then you have some groups out there — like the Innovative Farmers Association of Ontario (IFAO) —that have brought trends from other parts of North America,” says Woodhouse, market development agronomist with Bayer. “They’ve done a good job of advocating for cover crops.”

More growers are even conducting trials inter-seeding a grass cover into standing corn.photo: Courtesy Anne Verhallen, OMAFRA

Growers have also recognized the impacts of soil management, especially growers who have adopted more of a cash crop operation and are less involved in livestock production. Woodhouse believes they may be noticing the effects of tillage-related erosion, whether that’s seeing more brown snow from wind erosion in the winter or brown water that comes with water erosion in the spring.

He also agrees that farmers can be pushed to the limits when considering cover crops because for many, it’s one more layer on an already stretched workload. The addition of precision agriculture, demands for sustainability, and tougher quality requirements from processors are already taking so much more focus.

Yet the benefits of cover crops — and the wealth of opportunities that come from them — are being measured with greater frequency among growers. There’s more interest in the “why” of cover crops, as well as the “how” behind their management and use. Growers are expanding their options too, for instance by considering using a late-season cover as a forage source or for weed suppression.

“Glyphosate resistance brings a little more attention to that because those weeds are lot more difficult to control, especially post-emergent,” says Woodhouse. “With some of the latest weed species that have come along, like waterhemp — which can emerge through the year and be a problem — anything we can do to stop these weeds from having a chance to grow is a good thing. That’s one of the untold stories of cover crops — its ability to control weeds that we don’t want from establishing on our farms.”

Always room for more

Using cover crops has almost become a matter of necessity for Odette Ménard. She has monitored the practice’s evolution for nearly 30 years, realizing that different uses or expectations produce different results and interpretations.

Ménard has been a regular speaker at IFAO annual conferences, becoming both advocate and expert on soil management and the use of cover crops. She’s witnessed their expanded uses, from keeping the soil growing after a cereal crop to adapting corn row widths to generate greater plant biomass. However, much of that evolutionary process is based on the idea of “seeing something growing” with a cover crop. If there is no growth, it’s often deemed a failure.

In the early 1990s, Ménard was working with green manures in the hope that those plants would provide some N, P and K value to subsequent crops. At the time, she remembers the first trials working with ryegrass planted into corn, when the cover crop didn’t grow. That was an epiphany for her and she told the farmer that if the cover crop didn’t grow, it had actually worked.

“That’s probably the first time I understood that feeling of wanting to see a result,” says Ménard, soil and water conservation advisor with the Quebec Ministry of Agriculture, Fisheries and Food (MAPAQ). “I was always saying that the inter-crop or the green manure was giving us something, that it was living or growing on leftovers. If there was some sun left or if there was nutrient left or if there was water left, it would pick it up. If there were no leftovers, it wouldn’t grow, and that meant that the commercial crop was taking it, and it didn’t pick up something that the corn needed.”

Oilseed radish, seen here as single cover crop into winter wheat, is also a frequent species in multi-blends.photo: Courtesy Anne Verhallen, OMAFRA

It’s a subtle, yet important twist on the value of cover crops, where something visible is perceived as worthwhile. Ménard suggests it’s that same visibility factor that influences adoption of cover crops versus no-till farming. Cover crops require seed, fertility, equipment and even advisory services. No till is perceived as “doing nothing,” which is why there are fewer no-till advocates in industry and more are addressing the benefits of cover crops.

Three and one

When farmers talk about using cover crops, the same basic question comes up: “Why?” or “What is your goal?” Ménard believes the answer reveals much about the farmer and hopefully, the practices they have in mind to optimize everything in the field — the commercial crop, the fertility, the cover crop and ultimately the soil.

In her work, Ménard often deals with farmers whose first interest is the soil, which changes the way they approach their farming operations. Looking at the soil first, it’s not a cover crop, nor is it an attempt to “fill a hole” during the latter part of a growing season. It’s recognizing the commercial crop rotation that a farmer plants, harvests and sells, and the fertility rotation that’s feeding the soil. They’re part of a whole system, a complementary approach, not something that’s compartmentalized.

That same thought process also looks beyond the three essential properties of all cover crops: they cover the soil, they feed the microbes in the soil and they recycle nutrients. After that, the true goals come out of a fourth property, whether that’s protecting against erosion, scavenging nutrients or adding nitrogen to the soil profile.

“It’s a very important one because this one is going to tell you about the choice of cover crop you’re using and the strategy you’re going to be using and what you’re looking at,” says Ménard. “It’s the most difficult step in cover cropping, that we don’t give the cover crop its three benefits. If you wanted to do something else, this will tell you what to choose, how to do it and what to look at.”

Say it again

Of all the lessons learned about various practices in agriculture, Anne Verhallen believes repetition may be the one that works best. Like Woodhouse and Ménard, Verhallen acknowledges that the use of cover crops isn’t a new subject, but sharing the message repeatedly seems to be generating greater interest. And that’s inspiring a willingness to try new approaches, accept new uses for cover crops and consider their impact on soil health.

But there are many challenges associated with expanding cover crop practices beyond a red-clover-after-winter-wheat standard. Verhallen notes growers can be overwhelmed by “what to change, how to change, when to change and by what degree to change.” It’s similar to the confusion and stress growers might experience from the precision ag sphere, i.e. that sense of being overloaded by the need to have every new system or unit. Instead, it’s best to choose one approach, familiarize yourself and enhance what you have before incorporating another component.

“Once you see the value, it’s easier to accept the layer of management that’s required,” says Verhallen, soil management specialist with OMAFRA. “It comes back to seeing the value of a cover crop. My first question is always, ‘What’s your goal?’ or ‘What are you trying to achieve?’ Depending on your goal, that will determine whether you see value.”

It is easy to see the value for a livestock producer who’s looking for extra feed. A grower with herbicide-resistant Canada fleabane will see the value of a thick, lush cover crop of cereal rye. It’s not as clear a story around nutrients but it’s a very clear story around erosion, whether it’s wind or water erosion.

“It’s not always a dollar value, not always something you can put in your pocket and say ‘This made me money,’” adds Verhallen. “It goes back to the goals: Are you trying to improve soil health? Are you trying to improve the overall soil resource that you’re handing on to the next generation? They want it to be as good or better than when they got it.”