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Corn-on-corn yield boost is goal for many researchers

<b>By ANN HINCH<br>
Assistant Editor</b></p><p>

NASHVILLE, Tenn. — With corn turning such a profit, Midwestern growers wanting to take advantage of every season to cash in face a tough decision: do they plant corn after soybeans, or can they get away with double-cropping corn?<br>
As part of a production research presentation focusing on corn, soybeans and wheat at last week’s Commodity Classic conference in Nashville, Dr. Roger Elmore, Iowa State University extension corn specialist – on behalf of himself and extension agronomy specialist Lori Abendroth – briefly presented some findings regarding corn after soybeans (CS) compared to continuous corn.<br>
For the last few years, continuous corn has been a big issue in Iowa. On average, there’s significant improvement in corn yield if it’s been planted after soybeans, as opposed to after corn. <br>However, he noted a study in which corn was planted after five years of soybeans, then planted again in a row a few times with no more soybeans, in which the biggest single drop in yield came after the corn was planted a second time; after that, he said, yield seemed to stay about the same for subsequent plantings.<br>
With high-yield corn, Elmore said the rules seem to change, citing three separate observations from Kentucky, Minnesota and Nebraska. Yes, there’s still a differential between CS and continuous corn, but it seems a narrower margin than at the lower-yield levels, even though growers still need to worry about continuous corn’s increased susceptibility to diseases such as Gray Leaf Spot, Northern Corn Leaf Blight and corn nematode.<br>
Another concern is Western Corn Rootworm (RW), but Elmore said by planting RW-resistant varieties, growers may see better yields on corn after corn. Dr. Fred Below, professor of plant physiology for the University of Illinois, agreed about the transgenic corn.
“That rootworm trait’s going to go a long way toward improving your yield,” he said.<br>
Tilling<br>

Elmore could not advocate for or against tillage in terms of yield, explaining each field is different and farmers need to make individual decisions based on soil type, drainage and the like. Below compared the old stalks to corpses, explaining corn does not like to grow well in the middle of previous corn residue – “And I can’t say I blame it,” he added.<br>
In every corn-after-corn test field he studied, Below said there was a yield reduction in early plant growth when old corn residue was present. Mike Missman, who grows continuous corn in Woden, Iowa, agreed his biggest challenge is residue management and said he chops the stalks in the fall to allow the soil to warm more quickly and, when he does plant later, it facilitates seed-to-soil contact for better early-growth emergence.<br>Missman also said he uses urea when tilling those fields, which breaks down old corn stalks chemically, and applies 32 percent nitrogen during spring planting. He also plants some CS corn, for which his only preparation is applying nitrogen in the fall on soybean stubble.
To growers who use no-till, Below joked, “The data shows it’s fun to till; (but) it’s expensive.” He said in his research, tillage was actually low on the list of factors influencing continuous corn’s success – that is, it wasn’t as important as choosing the right hybrid, good weather and the right nitrogen application.<br>
Elmore said an ISU study showed continuous corn yield may be boosted to CS levels by applying more nitrogen. For anyone who believes Iowa growers may already be on increased nitrogen application, Elmore pointed out its per-acre usage in Iowa has, in fact, not increased since the early 1980s.<br>
“Which tells you, we either super-overapplied in the early 80s, or we’re using nitrogen even better than we were,” he said.
Of course, most corn growers dream of ever-higher yields to get the most value from their land and their trips to the elevator.
From the Civil War until about 1930, yields remained roughly the same; that was when seed hybrids were introduced into fields, and Elmore said yield increased at the rate of approximately one bushel/acre per year for a few decades, then rose sharper to 1.87 bu./acre annually.<br>
At that rate, he said by 2030, the national average could be just under 200 bu./acre.<br>
He’s heard projections of 300, but said for that to happen between now and 2030, the yearly rate of increase would have to triple and stay there.<br>
The biological limit for corn yields is thought to be as high as 470 bu./acre, but so far, Elmore said even the highest National Corn Growers Assoc. annual yield contest winners have remained at roughly the same level for the past 20 years – far below 470 – and that extreme possible highs seem to be plateauing between 340-390.<br>
“There’s a yield ceiling,” he said. “We’ve got to break through it.”
He did point out not every grower should expect such yields even if they were to someday become the national average, since individual fields vary in water, sunlight and the like.<br>
“I don’t want you to think I’m telling you to go home and grow 300-bushel corn,” Elmore deadpanned.<br>
It’s safe to presume most, if not all, corn growers attending the talk would enjoy such yields.<br>
John Tomasek, a semi-retired demolition worker who lives in Grinnell, Iowa, owns 2,700+ acres in Iowa and Illinois, farmed entirely by five separate sharecroppers.<br>
Each splits their profits 50/50 with him. “(Higher) yields become leases,” he pointed out.<br>
He has never been a farmer, and though he discusses what his growers plant each year with them, he said what they choose – right now, it’s a 2-to-1 overall ratio of corn to soybeans (no wheat) – is ultimately their decision.<br>
“If you have a car, you have one driver,” Tomasek said.
“You don’t have a front-seat and a backseat driver. I believe in listening to them; these guys are good.”

3/5/2008