Attention on the weather at Research Farm field day

CRAWFORDSVILLE — A trailer full of farmers and agricultural business owners toured the Southeast Iowa Research Farm last week for the Iowa State University facility’s fall field day.

A scattering of presentations around the grounds featured the greatest challenge Iowa farmers face this year: the weather. Experts at each stop detailed, in some form or another, the implications of a drought dating back to April, coupled with an unusually warm late summer.

“No surprise to anybody, we’re dry,” Research Farm Superintendent Cody Schneider said at the first stop of the day. “We track our moisture from March through October, and March through August, we’re 9.5 inches behind (the) 35-year average.”

Late rain hurt weed control: wheat helped

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An unseasonably dry spring put some fields in a difficult spot when it came to weed control. Schneider said pre-emerging herbicides usually activated by water had little effect when it didn’t fall from the sky. The result was more strain on post-emergence weed control.

One field fared better than others however. Schneider said a trial run for wheat double cropping and intercropping with soybeans proved effective at stopping unwanted plant growth.

“We did not spray any herbicide on the intercropped or double cropped acres,” Schneider said. “We were kind of wanting to see what we got for weed control just out of the wheat itself.”

The wheat on those fields was planted in October of last year. The intercropped beans were planted in mid-April, before the prior crop grew enough to be damaged by the planter. Double cropped beans were planted July 7, after the wheat harvest and luckily within days of the next rainfall.

The average wheat harvest came in around 89 bushels per acre, selling for $6 a bushel, according to Schneider. The farm superintendent said bean harvest projections looked promising for the test fields, adding that he hoped to repeat the project in future years.

“If you come to the annual meeting in March, I’ll be giving the full economic analysis of how it turned out,” he said. “This project definitely left us with a lot more questions than we got answered. What’s the appropriate nitrogen rate? Is there the right population of soybeans on the interplanting?”

Soil experts look at water absorption … one inch at a time

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Much of Southeast Iowa’s crops grow in clay-like soil, a geological reality with countless implications for producers in the area.

Washington County ISU Extension Agronomist Rebecca Vittetoe said the region’s dirt could hold onto water plants might otherwise use.

“If we have a really clingy soil where we’ve got smaller particles it’s going to hold onto that water more,” she said. “That loam, silt-loam soil type, that’s where the most plant-available water’s going to be. That’s that happy medium of, it’s holding that moisture but it’s not holding it so tight that our crops can’t extract it. On the clay side, yeah, it can hold more of that water, but there’s less of it that our plants can take up.”

Speaking from the bottom of a roughly six-foot deep pit in the middle of a cornfield. ISU Agronomy Graduate Student Clarabell Probasco showed that corn’s deep roots could still penetrate the soil, but that higher clay content generally meant less access to deeper water reserves.

“We do have roots coming pretty far down, past this tape measure, to about 60 inches,” she said. “So it’s got enough structure that roots are able to get pretty far down through the soil. So even in drier years like this you’re able to get water, you’re a little bit better off than in other parts of the state. And once we get down, it loses the structure. I’m just pulling out clumps of clay, there’s no natural breaks.”

For farmers with clay-like soil on their hands, ISU Agronomy Professor Bradley Miller said the best practice was to keep a rotation of crops with deep roots, which keep the deep soil broken up from one year to the next.

“When you get those cracks, that’s an opportunity for a root to exploit that opportunity and dig down deeper,” he said. “It’s not that roots can’t get deeper in this profile, we’re just not seeing that this year … it’s a question of if they have the opportunity, and what’s the growing conditions for that year.”

Field Agronomist Virgil Schmitt said those deep roots would come from corn with drought-resistant genetics, and on farms with attention to well-adjusted planting equipment to minimize trips through any given field.

“With corn we can take it down a ways, down to three inches, and it will come up pretty well,” he said. “With soy beans, you get down to about two inches and you won’t want to go much deeper than that … and we want to be thinking about soil compaction, what we can do to minimize that, because that’s going to limit roots here.”

Agronomist encourages more thoughtful planting practices

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Extension Cropping Systems Specialist Mark Licht gave a handful of consecutive presentations on the last stops of the field day. One of those focused on planting dates.

Recently developed practices break from conventional wisdom by putting soybeans into the ground before corn, since the former can better adapt to poor weather than the latter.

Licht said the better option, in reality was more nuanced, and depended not on when planting began, but when it ended.

“After about (May 20,) corn yield potential plummets,” Schmitt said. “Soybean yield potential, it declines, but not nearly as fast … if you can plant all your acres before May 15, honestly, it probably doesn’t matter if you plant soybeans first or corn first. If you have to plant 20,000 acres, (I’d) sure plant my corn first. It’s really important to get that corn planted, because if I start planting in later conditions, that’s a penalty on my corn side, it’s not as big of a penalty on my soybean side.”

Another part of Licht’s presentation focused on soybean seeding.

Speaking in front of a test plot for soy planted at rates of 20, 140 and 200 thousand seeds per acre, Licht said many farmers were spending more than they needed to on seed costs. Although some producers have rates exceeding 180,000, he said such a number was unnecessary.

“Our seeding great recommendation is basically 125,000-140,000, that’s where we’re at right now,” he said. “There’s other states that have some research that would suggest we can probably seed 100,000, have a final stand of 80,000, and still have our top yield potential … we’ll get some more data.”

Such a change would represent a massive paradigm shift in industrial agriculture.

Licht said the math worked out because soybean plants would naturally control their own population in fields.

“Soybeans self-thin, meaning you can start out with 200,000 seeds, and they’re going to have a higher plant mortality throughout the year,” he said. “That happens very easily as you go down from 200,000 to about 100,000 … we can lower our seeding rates and it’s not going to effect our yield potential, but it will save us on seed costs.”

Shooting too low is risky as well, however. Licht said beans in the 20,000-per-acre field had to compete with weeds, showing off one pulled plant wrapped in morning glories.

“When you plant this, it closes canopy about three weeks later, so your weed pressure is going to be a lot worse,” he said.

Comments: Kalen.McCain@southeastiowaunion.com