Interest surges in cover crops

U.S. farmers use ‘catch crops’ to minimize nitrogen and phosphorus loss

It’s become difficult to avoid cover crops.

The crops, which improve soil health, help boost the yields of subsequent cash crops or provide forage for livestock, are constantly in the agricultural media, and many farm conferences have them on the agenda.

Many farmers remain skeptical of the hype, but the innovation has become a normal farming practice in the United States, says a University of Manitoba expert.

“We’re talking about cover crops this morning because cover crops are now … part of conventional agriculture in North America … because of the widespread adoption of leading farmers and the response from … policy (makers), mostly in the U.S., to promote cover crops as a practice,” said Yvonne Lawley, a U of M plant scientist who spoke at the Manitoba Agronomists Conference in December.

Describing cover crops as conventional might be a stretch, but they are an extremely hot topic right now, particularly south of the border.

“We’ve never seen anything taken up as rapidly as using cover crops,” Barry Fisher of the U.S. Department of Agriculture’s Natural Resources Conservation Service told the New York Times.

U.S. data verifies Fisher’s comment:

  • A survey by the USDA’s Sustainable Agriculture Research and Education (SARE) division shows that producers who use cover crops doubled acres on their farms from 2011-15.
  • The typical adopter in the U.S. last year was expected to seed 339 acres of cover crops.
  • Iowa farmers seeded cover crops on 472,000 acres last year, which was a 35 percent increase from 2015, according to the Iowa Farm Bureau.
  • U.S. Census of Agriculture figures show that American farmers seeded 10 million acres of cover crops in 2012. SARE has set a goal of 20 million acres by 2020.

Cover crops in Canada and the northern U.S. Plains, mainly vetches, radishes and peas, are mostly used for soil remediation or extending the livestock grazing season.

However, they serve a different purpose in the U.S. Midwest, where many producers are seeding “catch crops” to minimize nitrogen and phosphorus loss.

“I use the term catch crop because the purpose of that cover crop is really to manage nutrients that might be leaching through the soil,” Lawley said.

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“These catch crops are for areas that might not be frozen all winter long…. This is really what’s driving changes in the landscape … policies promoting cover crops.”

Nutrient leaching is not normally a concern during a prairie winter, but there are numerous uses for cover crops in Western Canada.

Lawley said rehabilitating wet areas in a field is a good place to start.

“I think the biggest window (of opportunity) is where things go wrong,” said Lawley, who is from the U.S. and has been researching cover crops for several years.

“We’ve had a lot of areas, in a lot of years, with wet soils. (We’re) taking those wet soils and doing something with them, using (cover) crops to manage and bring them back into production.”

Another opportunity is planting a cover crop following the harvest of winter wheat or fall rye to im-prove soil fertility for subsequent crops.

Many presentations and discussions focus on the ideal cover crop cocktail, or combination of five, 10 or 20 plant species in a mixture.

Lawley said the emphasis on cocktails is probably unnecessary.

“I think, starting out, picking two, three or four species and putting them together … is very practical … and I think you’re going to see the same kind of impacts (benefits),” she said.

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“If we’ve got some leftover soybean seed around, that can be as useful as some of these more exotic (species), like cowpeas.”

Instead of focusing on what they are seeding, growers should understand why they are using a cover crop.

Lawley said the reasons include fixing nitrogen, providing food for soil micro-organisms and alleviating soil compaction or soil salinity.

Ducks Unlimited Canada has been promoting cover crops, and several organization representatives listened to Lawley’s presentation in Winnipeg.

Michael Thiele, a Ducks Unlimited grazing club co-ordinator, said a small number of Manitoba producers have adopted the practice, but momentum is building.

“It’s growing quickly,” he said.

“Mainly the cattle guys. They’ve sort of caught on to it quicker.”

Lawley hopes the trend continues, but one critical piece is missing in Western Canada. The Prairies may need a new organization that supports research and promotes cover crop use.

“We have a fairly well established network of funding research for commodity specific (crops),” Lawley said.

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“What we’re struggling with here is who funds soil management research.”