Adjusting Cover Crop Strategies to Adapt to Warming Climate


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Thor Oechsner arrives at one of his wheat fields about 9 miles west of Cornell University’s Ithaca campus with a laugh and a shrug.

“It’s not all turnip flowers,” Cornell Extension support specialist Kristen Loria responds in answer to the farmer’s good-natured, nonverbal admonishment.

She’s referring to the bright blooms of yellow rockets that are not supposed to be mixed in with the green wheat.

The difference is that the forage turnip was planted intentionally as a supposedly winter-killed cover crop.

The yellow rocket, a common weed in grain crops in this part of New York, found its own way in.

The turnips had overwintered, which was not part of the plan either.

Cover crops that traditionally died over the winter are more likely to survive as the climate warms, causing a new management problem for farmers.

“It definitely is widespread this year, which I think is a first,” Loria said. “Throughout the state, oats, brassicas, that’s what I’ve heard about mostly.”

“She promised me that this would winter kill,” Oechsner quipped as they tromped through his field.

Oechsner farms around 1,000 leased acres of food-grade organic grains at 20 locations in the Ithaca area.

He is working with Cornell’s Sustainable Cropping Systems Lab, with funding from a New York Soil Health state grant, to see if early spring tillage can be eliminated for spring wheat.

“This trial was inspired by Thor,” Loria said. “It was really his idea, so we’re kind of supporting —”

“Enabling?” Oechsner interjected.

True Grist

Along with hard red spring wheat, hard red winter wheat, einkorn (related to the wheat grown almost 12,000 years ago), rye, buckwheat, corn and sometimes soybeans, Oechsner Farms grows an abundance of red clover.

“Red clover is a big part of my rotation,” Oechsner said, adding that clover is typically in his fields around two years out of a seven-year rotation.

“We spend quite a bit of time letting the land sit with red clover in it to sort of help with weeds, help the soil recover from all the tillage,” he said.

Some tillage is pretty much a given with organic farming, Oechsner said.

“We’re trying to figure out how else can we do this, or can we till it at a better time of the year where we don’t hurt the soil as much, when it’s drier,” he said.

His typical practice has been to plow down red clover in the spring, at a time when wet weather combined with tillage isn’t great for the soil.

“Instead we plant fall cover crops in late August that winter kill and then no-till plant the spring wheat into the cover crop residue,” Loria said.

Last year’s field trials with an oat-and-pea mix checked most of the cover crop boxes (weed suppression, winter soil cover), but didn’t deliver enough nitrogen to the soil to give Oechsner’s grain the protein boost his artisan customers demand.

Those customers include a local mill and bakery he helped found.

The hope was that a brassica such as forage turnip would make more nitrogen available to the grain crop at the right time to improve protein content, Loria said.

And even though the plot of spring wheat — drilled through the ice and a blanket of oat and pea residue in February — looked much cleaner than the adjoining plot interspersed with flowering turnips and some weeds, the wheat at this stage of growth in the turnip plot was still noticeably more robust.

One upshot of the experiment was that the oats did, for the most part, winter kill as intended, which didn’t happen on some other regional farms.

“Oat survival was spotty,” said agroecologist Matt Ryan, who heads the Cornell lab where Loria works. “There were reports in Pennsylvania.”

Seeding depth, fall planting date, landscape features and the presence of a nurse or companion crop are all factors to consider, he said.

“We will overcome,” Oechsner said of his upcoming wheat harvest. “I mean, it’ll probably hurt us some.”

By harvest time, the forage turnips will be dead, he said, and any seeds will be too tiny to be captured by the combine screen.

Learning Curve

When Oechsner started farming, he didn’t think about tillage releasing carbon into the atmosphere.

Now, he said, he is acutely aware every time he breaks ground.

“We’re really trying to hone these systems where not only does it give us a timely planting, because the crop is in the ground already early in the spring, which can help yields, but if we can somehow do this with less passes or less damage to the soil structure, less compaction …” Oechsner said. “There’s all these different factors that you need to try to mitigate.”

Too much of a good thing can be another challenge.

“The problem with a lot of these small grains is you can get too much nitrogen and then the crop can fall over, what they call lodging,” Oechsner said. “But the variety of spring wheat that we use is very, very resistant to lodging. I was afraid to plow clover down, because you’re talking about 120 pounds of nitrogen is going to be released, but this variety seems to be able to absorb that, stay standing and put that nitrogen into the head.”

Plowing down red clover helped Oechsner Farms break 15% protein in its wheat for the first time.

“I don’t have any scientific data behind this, but just watching the plants, it seems like the breakdown of the clover crop matches up pretty well with when the spring wheat needs nitrogen,” he said.

Timing is everything.

“There’s this period in the early spring before the soil has warmed up that the crop really wants a shot of nitrogen at green-up,” he said.

That’s when he top dresses with Chilean nitrate (and some potassium, sulfur and boron), where conventional farmers would be applying urea.

“That tends to kick the crop along while the more tied-up sources of nitrogen in the cover crops start to break down and provide it,” Oechsner said. “Especially when the soil temperatures are cold, the microbes aren’t really active. So this is where that stuff’s really helpful, but it’s just preposterously expensive.”

The experiment represents around 2% of Oechsner’s land, and he sees the partnership with Cornell potentially yielding best practices for the future.

“I think it we have to be prepared to pivot in the spring, which is easier for some systems than others,” said Loria, who besides being a field researcher grows dry beans.

That, she said, may include looking at different species that are more susceptible to winter killing than current options.

Meanwhile, Oechsner, who knows all about pivoting (he studied ag at Cornell, worked on a dairy farm, owned a VW repair shop and taught diesel mechanics on his way to becoming a full-time organic grain farmer), is enjoying himself.

“It’s doing something, trying something, and not just planting the same thing in the same place each time,” he said. “I think we’ve got to take our chances. And the great thing about working with this grant is they supplement part of the cost of this.”

Oechsner, who didn’t grow up on a farm (his dad was a public school history teacher in the New York City suburbs) said he hopes the team effort will help both him and other farmers.

“We’ve got Kristin and all the smarty-pantses from Cornell out here doing actual data as opposed to just the farmer out there going, ‘It looks a little less weedy; that’s a little greener.’ You know, we actually get real data on it so it can inform my decisions in the future.”

And those of other farmers, too, he said.

“Somebody has got to go out there and make the mistakes,” Oechsner said. “And that’s really what universities do. That’s why the land-grant university system is so important.”

That is what makes the support and financial incentives so critical, he said.

“They give you a little stipend for the seed or whatever it is, then we can take 20 acres and have some fun with it, see what happens,” Oechsner said.

“And we’ll definitely get a good crop off of this.”

Source: Lancaster Farming