Cover cropping poses unique challenges to organic farmers

Organic farmers considering soil-preserving cover crops need to understand all ins-and-outs of the strategy and be prepared to manage challenges unique to their production system.

Why it matters: Tracking the financial costs of introducing cover crops may seem basic if you consider only the cost of seed, planting and termination, but adding in the cost of yield in the following crop makes it more complex.

When it all lines up, and weather conditions are right, it can work well, but in more challenging years there can be lower yields.

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This was the message from Jake Munroe, a soil specialist with the Ontario Ministry of Agriculture, Food and Agrifood (OMAFA) during the recent annual Organic Conference in Guelph, as he shared his experiences working with organic producers across the province.

Munroe told Organic Conference attendees that this became clear when he and several on-farm cooperators conducted a multi-year, multi-site trial on roller-crimping fall-planted cereal rye prior to planting organic soybeans in the spring. He reported that the average yield from those plots over three years was 40 per cent lower than that of organic soybeans planted into bare ground and scuffled for weed control.

Munroe began the session by classifying cover crops under organic management into three categories: proven, intermediate-level, and emerging/innovative. He offered that roller-crimping fall-planted cereal rye under southern Ontario’s climatic regime fits under “intermediate.”

The system works better in wet years because the rye absorbs a lot of moisture. This was reflected in the study, where the dry years had the poorest yields.

A thicker crop of rye provides a denser mat after crimping to discourage weeds as well as crimping more effectively than lighter stands. Lighter crops of rye lead to more competition with the soybeans – both from rye that’s not completely killed and weeds that follow daylight through the less dense mat of fallen rye.

Morris Van De Walle, a trial participant near St. Marys, pioneered the method in Ontario after learning about its use in the northeast United States. Using a roller-crimper that he modified, he has used this method successfully on a farm scale for several years.

Jason Brownridge, a Wellesley area producer, wasn’t a trial participant but began experimenting with the method in 2022 despite its limited applicability in southern Ontario. He applied hog manure before rye seeding on Sept. 7, 2022. On June 3 and 4, 2023, he planted organic soybeans in two passes using two 15-inch rows for weed suppression instead of the standard 30-inch and roller crimped twice, June 2 before planting and June 8 after planting.

Munroe reported the soybean crop achieved a respectable yield of 45 bushels per acre, and in 2024, the field’s following organic corn crop also achieved a good yield.

“Jason followed all the tips we found from our study, and he had the weather helping him,” explained Munroe.

His process included planting cereal rye early and thick, having a backup plan in case rye establishment was poor or the long-term forecast was for a dry May and June, using a seeder for soybeans able to handle high levels of residue, and seeding the soybeans at a high rate (250-000 to 300,000 seeds per acre).

Munroe cautioned, however, that several others who participated in the roller-crimping trial decided not to continue with the practice. That wasn’t necessarily a negative outcome, though at least one of those producers, the OMAFA specialist continued, built on the experience to try out a cover cropping practice he labels as “innovative/emerging.”

Brett Israel of 3Gen Organics near Drayton didn’t have good experiences with roller-crimping fall-planted crops. Instead, he moved to minimum-till organic soybeans after harvesting a fall-planted cereal rye cover crop for pig forage.

Israel harvested the rye for forage in May, made two passes of a high-speed disc and drilled solid-seeded soybeans at 325,000 seeds per acre.

“That’s quite a high rate, but he’s not going in and scuffling. He needs that solid cover to compete with the weeds,” said Munroe

A conference attendee cautioned that soybeans need moisture to germinate, and in most years, seeds should be planted below the point of tillage so they can access that moisture.

Munroe agreed. “With these practices, you’ll have to ask yourself: do they work every year or one year out of every three? Because they need to be able to work every year if you want to see them adopted more widely.”

So far, the “proven” cover crop practices in organic production in Ontario happen mainly following winter wheat and happen mainly with termination through fall tillage.

Phil Oegema, near St. Thomas, transitioned to organic about seven years ago and uses an air seeder in early April that simultaneously applies organic-approved Good ‘N Green fertilizer while planting red clover at 8 lbs per into standing winter wheat.

Munroe knows of other growers using a similar approach, but they plant in March on frozen ground. One audience member said they seed both the wheat and the clover in the fall.

“I don’t have an answer yet on why more farmers don’t do that,” Monroe responded, regarding the fall planting.

In all cases, though, fall tillage to terminate the clover is part of the process. Munroe noted that Oegema comes from a conventional background, and like other conventional, soil-conscious producers converting to organics, he was reluctant about the amount of tillage required. Oegema tried leaving the clover until spring, but there was too much residue—even with an equipment set-up that handles residue well.

Adding a cover crop, he said, “needs to optimize growth in that following crop and not be a detriment.” And in Oegema’s case, the clover was a detriment under organic production unless he disc ripped it in the fall.

Dean Martin of Harrow, session moderator and a crop-producing member of host organization the Organic Council of Ontario, learned from Oegema that there is a significant amount of clover still alive with roots and some green holding the soil through the winter, even after the disc ripping. Oegema, Martin reported, tries to hold off on the fall tillage as long as possible so there will be cold soil and limited clover decomposition.

Another organic crop farmer Munroe works with, Terry Good of Meaford, broadcasts 70 pounds per acre of red clover after wheat straw harvest and cultivates. This is either grazed by cattle or left to grow until later in the fall and plowed. Soybeans are next in the crop rotation.

“Broadcasting is often thought of as pretty risky but if you get out there as soon as possible and incorporate it with a cultivator and a packer, the results are pretty good,” Munroe said.

Good prefers the plow instead of the offset disc because it cuts the roots more completely. But still in the following crop, “he has been amazed by the weed suppression.”

Calvin Horst near New Hamburg, broadcasts his post-wheat cover crop as well, but has moved away from red clover towards a multi-species mix. It’s terminated in the fall.

Munroe says cover crops help carry forward the nutrients that are originally applied in manure – typically just before cover crop seeding or a few weeks later when the cover crop enters a growth stage and can readily take up those nutrients. Clover is good for this if corn is the following crop. Oilradish isn’t as effective, however, because it breaks down too early in the spring and releases the N before the corn can use it.

Cereal rye, meanwhile, can be an N sink and not release it quickly enough to benefit the following crop.

“Especially when fertilizer prices are high, whether organic or conventional, there’s a lot of thinking around the value of manure as a resource,” Munroe offered.