Killing corn with nettle, growing it with rye

Corn benefits from cover crops like cereal rye. Henbit/dead nettle is attractive and helps the soil, but it can actually be harmful to corn.

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April 15, 2021 - 10:14 AM

Zach Louk, head salesman at Green Cover Seed, squats down to show the radical contrast between soil with henbit dead-nettle growing in it versus cereal rye. Photo by Trevor Hoag

What does your cornfield look like right now?

If it’s a beautiful sea of purple, that’s bad.

But if it’s coming up green, that’s good.

The first is henbit/dead-nettle with its attractive purple flowers.

The latter is cereal rye, a cover crop that increases corn yields.

Dale Strickler, agronomist at Green Cover Seed, explained how henbit not only is not a cover crop but a weed that “really, really suppresses corn yield.”

“Where it is, the corn is visibly worse.”

So although henbit is “good for the soil,” said Strickler. “It’s horrible for corn.”

Zach Louk of Green Cover Seed holds up a bouquet of cereal rye, a cover crop recommended for cornfields. “That’s all the tillage we have, right there, in those roots,” he said. Photo by Trevor Hoag / Iola Register

Yet despite its harmful effects, many local farmers continue allowing henbit to grow in their fields, believing it to ultimately be beneficial.

“As far as soil conservation goes, yes, … [henbit] prevents erosion, puts some root exudates into the soil.”

“… But it also appears to have an allelopathic effect. That is, when plants produce a natural toxin that affects other plants.”

It’s the same reason why you shouldn’t plant tomatoes near a walnut tree.

Toxification can not only stunt growth, Strickler added. “People see the effect of henbit on their corn crop and say, ‘Oh, this is what a cover crop does.’”

Zach Louk of Green Cover Seed holds up a bouquet of cereal rye, a cover crop recommended for cornfields. “That’s all the tillage we have, right there, in those roots,” he said. Photo by Trevor Hoag / Iola Register

This is completely contrary to the message Strickler wants to send, since by contrast, “a cover crop is one you select for the benefit of the next.”

“Corn receives a lot of nitrogen fertilizer, and doesn’t have a very efficient root system,” Strickler continued. “So there’s always nitrogen left over after you harvest the corn crop.”

“All that nitrogen that’s left over doesn’t help the soybeans [that will rotate into the field next], but it does help the weeds.”

By contrast, according to Strickler, “using a rye cover crop, it’ll sponge up all that excess nitrogen, and convert it into protein.” 

Moreover, “you can use that rye to create a condition where weeds simply don’t compete, which can save you a lot of herbicide costs.”

Henbit, especially, can’t withstand competition from other plants, and so putting in a cover crop like cereal rye typically makes it disappear.

Zach Louk, head salesman at Green Cover Seed, explains how no-till farming works in relation to plant roots and other factors.Photo by Trevor Hoag / Iola Register

Strickler also said that winter peas, crimson clover and hairy vetch are good cover crops for corn, though he added that “ordinarily, ahead of corn, we like a legume cover crop.”

Regardless, the key thing is coming around to the idea that following harvest in late fall, the space in-between cash crops can be supplemented with covers.

As mentioned above, one such cover crop is cereal rye, some of which is planted in a cornfield (just east of Moran), that Green Cover Seed salesman Zach Louk showed to this Register reporter.

He explained how “the rye breaks up the soil for us, and it feeds the bacteria over the wintertime, creates organic material and slowly decomposes.”

Imagine, after it dies, spreading out a bit like mulch.

Once that happens, Louk said, “it’s going to cool the soil, reduce evaporation and give us that weed control that we need for later in the season.”

“As it decomposes,” he elaborated, “the microbes transfer the nutrients over and they start to become available to the corn.”

Louk continued, saying, “if it’s 100 degrees out and the sun’s beating down, normal soil temperature is about 110 on top soil. This [cover crop ground] is going to be 85.”

Cooler soil means healthier plants.

There’s a larger picture worth considering as well, suggested Louk.

“After the 7-inch rain we had,” he said, “what most people don’t understand is the Neosho River, along it is primarily tillage. Well every time it rains, the sediment goes into the river. It goes downriver, sediments up at John Redmond [Reservoir], and it costs $20 million to dredge out eroded farmland.”

Hence, Louk contends that not only is no-till farming a viable option, financially and ecologically; in time, the government will require using such erosion-prevention measures in order for farmers to receive their subsidies.

“When it rained really hard,” Louk added, “all the people who had tilled fields, had miniature rivers running out their fields.”

Ariel, the cover crop princess, is a very good girl. Photo by Trevor Hoag / Iola Register

“Whereas with our [no-till fields],” he said, “you couldn’t have found a drop of dirty water.”

For Louk, then, it’s not simply a question of knowing which plants to prevent taking root and those to encourage.

The goal is creating environmentally-sustainable practices that can provide for the planet in the long-term.

“We’re building the future,” he said. “We’re not here to just hang out.”

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