Blowing it? Consultant urges winter rye cover crops as a moisture and weed management tool
Farmers in the southern Red River Valley who experienced drought conditions a month ago, along with 50 mph winds, now have gotten a shot of rain. Soils that moved also moved weed seed, which can contaminate neighboring fields with tough-to-control waterhemp. A return to hot, dry conditions makes those weeds even harder to control.
SOUTHERN RED RIVER VALLEY — Early dry conditions in 2021 combined with high winds have caused a movement of soil that spread weed seeds and soil-borne diseases to neighboring farms.
“We had a lot of ‘open’ fields last winter, so soil blew soil off those fields this spring” and winter, said Greg LaPlante, president and owner of GL Crop Consulting, which operates primarily in the southern Red River Valley. He’s been scouting crops and giving advice since 1981.
LaPlante said this spreads both weeds and soil-borne diseases.
It can spread pathogens such as soybean cyst nematode, a microscopic roundworm that attacks roots of soybean and other host plants. The eggs carry with the soil in the wind, he says. Wind also can move “sudden death syndrome,” a fungus that attacks soybeans in-season which causes an early death to the soybean crop.
Once either problem gets into the field, it can take lots of money to correct.
“It almost gets to be like a leukemia” in human health terms, LaPlante said. “You can keep it from killing you, but it requires a lot of treatment so that you can have some type of quality of life.”
LaPlante notes that spray drift issues often wind up in court. He thinks if the economic consequences rise, weed and pathogen issues will be there, too.
Bowed, not killed
LaPlante gave a tour of one of his client’s Enlist-tolerant soybean fields in a location he wanted identified only as the southern Red River Valley. The soybeans were direct-seeded into a rye cover crop, which was planted last August and terminated with glyphosate about 10 days before spring soybean planting.
A neighbor’s field had been planted to sugar beets in 2020 and harvested in October. The field suffered from excess rain and an inability to control waterhemp, and it got too late to establish a protective cover crop.
The neighbor’s field was followed by soybeans in 2021.
Winds howled 50 mph in April and May, sending soil, weed seeds and pathogens onto his client’s field. A few shots of rain totaling about an inch in June have germinated the weeds.
LaPlante’s client was able to spray when the weeds were 1 inch to 3 inches.
The neighbor sprayed when the weeds were 6 inches to 8 inches.
“We may have sprayed on a Monday, and he may have sprayed on a Friday,” LaPlante explained. “That’s how fast waterhemp grows.”
He figured the weed seed populations were about the same between the two fields. The dirt blew in a finger-shaped intrusion, similar to how snow drifts.
“If the rye hadn’t been here, growing, the dirt would have intruded probably a fourth of the field — 1,000 feet, rather than 150 feet,” he said. The rye operated as a kind of “catch crop” for the blowing soil.
On June 15, the client’s smaller weeds were dying, wrapped close to the surface.
The neighbor’s taller weeds were taller “bent over” from the “phenoxy response,” but clearly not dead. Phenoxy is a plant growth regulator — the effective ingredient in herbicides like 2, 4-D, dicambas and others. The chemistry mimics natural hormones and induces rapid, uncontrolled growth. The weed effectively “grows itself to death,” as they say.
In the “Fargo clay” soil in this area, farmers say they have about five days for planting “between it being too wet for planting, to being bone dry and not being able to get it planted,” LaPlante said.
This client has used rye cover crops for about four years. Other clients have been doing it for up to nine years, with information North Dakota State University’s Soil Health Initiative, led by soil health specialist Abbey Wick .
Wick said "not enough" farmers are trying out winter rye.
"Given the erosion we've seen this spring, not enough are using this practice. It's a good place to start," she said.
She's heard of farmers having residual herbicide blown into their field, killing a non-compatible crop.
LaPlante noted that university researchers in North Dakota, Minnesota and Iowa have shown no negative effect on yields from using rye cover crops when managed properly.
He estimates fall-seeded rye protects only about 5% of sugar beets and soybeans in the area. He thinks about half of 2021 sugar beets, however, were planted in the spring with cereal crops as a cover crop. That practice was very effective against high winds in May, especially when planted edge-to-edge in the fields.
Farmers manage the rye cover crop for the desired moisture effect.
The idea is to let it grow to use excess moisture or kill it before it removes too much.
“It requires management to make sure we’re not drying it out too much," he said. “Tillage requires management, too. It’s just different.”
This client field had been planted to corn in 2019 and harvest was delayed to December due to snow and cold. Because of the lack of tillage in 2019, and wet soil, the field was in a prevented-planting situation in 2020. The client had the rye planted by airplane in August 2020.
The soybeans were planted in mid-May 2021. On the east side of the field, they used a corn planter with 30-inch spacing because they were dry. On the west side of the field they used a no-till drill and 15-inch spacing.
“A lot of people think they need specialized equipment (to direct-seed) but a lot of growers have invested in these planters with the electronic down-force, and we’ve found in this field that actually works very well,” he said. “Farmers don’t have to gear up and buy a whole line of equipment."
Fingers of weed seed
In the spring of 2021, with the moisture removed, the field warmed up more quickly than if it had been tilled black.
“You don’t have the 6 million tons of cold, wet soil in the top couple of feet. It’s kind of a fallacy that it won’t warm up with the cover crop on it,” LaPlante explained.
LaPlante has heard reports from northern North Dakota where no-till fields were more susceptible to late freezes, ostensibly because the lighter-colored residue did not warm up as much as dark-colored tilled soils.
He said he hasn’t seen that phenomenon in central North Dakota, where conventional- and no-till fields froze out equally.
“We actually had more mortality on the black soil than on the rye cover crop,” he said.
Farmers are understandably fearful of changing crop practices.
“We’ve just been through two really wet seasons,” he said. "But the fact is that farmers are running out of chemistry to control herbicide-resistant weeds like waterhemp and — of course — Palmer amaranth.”
Killing weeds when they are small is critical.
He picked up a 2-inch tall waterhemp plant, noting it might have six or seven growing points. To compare, LaPlante pulled a 14-inch waterhemp plant that was sprayed five days later. It was alive at the top and had over 60 growing points, including several viable points at the base to recover from.
He adds that it’s a numbers game.
“If I’m trying to control, with the chemistry, 1,000 plants per acre and 1% is resistant, I can manage that. We can remove those weeds … by hand, because we can identify them early. They may never go to seed," he said. "But if you have 1 million plants per acre, because of this situation, now a 1% failure rate is quite significant. It requires another spray, which then puts a little more pressure on that herbicide, as far as resistance building up.”
If waterhemp develops resistance to the 2.4-D — the Enlist trait — there isn’t much to fall back on anymore. It’s strictly Liberty (herbicide).
“The clock is ticking. We have to do a better job of management,” he said.