ABERDEEN, S.D. — Cover crops are a relatively new thing in the region's agriculture, and they carry special challenges for organic producers who don't have chemical solutions to fall back on to control weeds.
One panel at the Northern Plains Sustainable Agriculture Society annual meeting and convention in Aberdeen, S.D., in late January addressed how cover crops work for organic farmers in different settings in the Dakotas. Here's some of what they said:
Mittleider has been planting cover crops for a dozen years — radishes, oats, sorghum or clover. It's different mixes for different soil types, he said. He doesn't grow row crops. He uses alfalfa and clover in rotation.
Kidder County has annual precipitation of about 14 inches. Cover crops have to be more drought tolerant there.
They have dropped some crops in their blend. "Is it cost-prohibitive? If you use the right blends you might have $40 to $50 per acre in the seed, and was it worth that? Soil health — what it's doing to your ground — is the most important thing, but it's also a financial aspect," he said.
Mittleider often uses inventories of seed they have on the farm. That might be a pound of turnips and a pound of radishes. "If we have some seed leftover — some oat seed, or this or that — we use that also as part of our cover crops," he said.
Mittleider said weed problems can be prominent one area, but not in an area 200 miles away.
"Who knows the farm better than the man who has walked it and farmed it for a lifetime," he said.
Brakke started experimenting with cover crops about 20 years ago, starting with planting sweet clover or other clovers as a companion crop with corn. They also dedicated a year of cover crops, "plowing in a stand of buckwheat followed by plowing in a stand of clover, and then putting on a winter cover."
"We find as many failures with cover crops as successes," he said. "Maybe that's just our failures, but I think it's a little different situation in the Valley."
Brakke said he hears about farmers using multi-species cover crops — maybe 12 to 15 species — but he finds that to be "unpredictable on our farm, how that's going to turn out." He said he is more of the camp of one or two species in a cover crop mix.
"When we get so many species in a cover crop mix, one species — for one reason or another, perhaps temperature, could be rainfall — will grow much faster than the others. We have to terminate it before it makes seed. We have another crop that's just emerging, or really hasn't done its work (in the mix) yet."
He said it's frustrating and expensive to buy organic cover crop seed and have to "terminate two-thirds of them that haven't done anything yet," he said. He said conventional farmers have chemicals to terminate cover crops, while organic producers must rely on frost or tillage, which isn't always feasible.
Some of the companies that formerly made "Lightning Weeder," tools that use electricity to kill weeds, are coming back into the picture for organic producers and conventional producers needing to handle herbicide-resistant weeds.
SD row crops
"Typically, some version of a cover crop will correct any or all of those issues," Johnson said. "It's the right amount of cover crops, the right kind of cover crops, when it's placed and how it's used, as well as incorporating a grazing system of sheep, cattle or goats."
Johnson and his relatives think of alfalfa as a cover crop, as it stays in the ground for more than a year.
"That typically results in a better crop stand in the following year," he said.
The Johnsons have a six-year rotation, including three years of solid-seeded crops — with oats and two years of alfalfa — and then other years for row crops. The Johnsons use winter rye as an unharvested, "green manure" cover crop in the row crop scenario.
Organic producers have no problem with weed resistance to chemicals.
"It's a question of why are those weeds there?" Johnson said. "It's Mother Nature's way of correcting a problem. If I have mustard, for example, I have to figure out why that mustard is there. That mustard is trying to fix a problem in that ground — crop rotation or lack of nutrients that may be allowing that mustard to grow when I want to raise soybeans."
He said the ultimate goal might be no-till organic.
"It's a whole realm I'm trying to wrap my head around," he said. He said he needs a tillage cycle to interrupt weeds.