Three-hundred bushel corn appears to have become a new standard of sorts in the Southern U.S., with many growers making that much and more in recent years. But since it’s such a recent phenomenon, little research has been conducted into the inputs necessary for achieving such yields.

“In 2012 in Arkansas, we had one individual with a confirmed 300 bushels of corn per acre. And then this past year, we had some growers who topped that,” said Jason Kelley, University of Arkansas Extension agronomist, at the Alabama Corn/Wheat Short Course in Shorter.

Typically, whenever presentations are made about 300-bushel corn, all of the inputs into these fields are not divulged, he says.

“There are a lot of presentations out there on how to make 300, even 400-bushel corn, and sometimes it can be confusing, especially when it comes to applying it to your operation.

"Growers really want to know what raises the bar, and what really impacts 300-bushel corn. We’ve made higher yields in the last couple of years, and we want to know how to keep making those,” says Kelley.

Corn yields in Arkansas have been increasing rapidly, he says, with a record-high average yield of 182 bushels per acre in 2013.

“We’re doing a lot of things right in Arkansas, and a key is that we have a lot of irrigation. Back in 1970, about 5 percent of our corn ground was irrigated, and we were averaging about 40 bushels per acre. Since then, we’re all the way up to about 95 percent irrigated, and yields have been following that. Irrigation helps to level out some of the ups and downs, but it doesn’t automatically give us 300-bushel corn,” he says.

In fact, several states set corn yield records this past year, says Kelley. Mississippi, Alabama and Georgia all set records in 2013, in addition to Arkansas.

A lot of factors contribute to high corn yields, he adds, including good weather with plenty of rainfall and cooler temperatures, all of which occurred this past year. “Of course, hybrid and planting date also are factors, in addition to plant population, row spacing, good uniform emergence, fertility, irrigation, pest management, timely harvest and everything else.”

Crunching the numbers for high-input production

In 2013, two trials were conducted in the Mississippi river delta of Arkansas to evaluate which factors impact corn yield, says Kelley. Factors evaluated included deep tillage, starter in-furrow fertilizer, higher seeding rates, additional fertilizer and foliar fungicides. 

All of these factors were evaluated separately and then combined together into a high-yield system. When combined together, the high-yield corn system increased yields by as much as 40 bushels per acre.

“In our high-yield system we had about 390 units of nitrogen versus about 240 units, which would be our standard. The difference was 13 bushels with all of that extra fertilizer. So fertility wasn’t that limiting," he said.

The average yield in the two systems was 293 and 297 bushels per acre, says Kelley.

“But the big picture to me is how much all of those extra inputs cost. Our numbers will be different from yours, but our costs were as follows: Deep tillage - $12; in-furrow starter fertilizer – $25; increased plant population - $30; seed insecticide - $27 per bag; and two fungicide applications with an airplane - $50.

“Altogether, we had almost $275 in extra costs. At $4.50-per bushel corn, we needed 60 bushels to break even, and we got almost 40," he said.

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Putting everything together

Researchers at Arkansas, says Kelley, are looking at production factors individually and then what happens when all of these factors are put together to try and grow higher corn yields.

In the past, planting date studies have been conducted that cover from as early as March 6, all the way up until the first part of July, he says.

“Typically, we want to get planted by the first of April. Some years we get delayed, but if it gets to be the first of May, most growers want to be moving on to something else. With irrigation, we had about a two-month window in there where we could maintain close to 90 percent of our yield potential. To get those high yields, you need to have a good stand and be on the front side of that window.”

One of the reasons for planting early is to avoid the heat, he says. “In our area, it gets really warm in June and into July, and we want the corn to be silking by then. The later we planted, the more likely we are to be in that window where it’s much warmer during grain-fill. This past year, we had cooler temperatures, allowing us to plant corn a lot later than normal.

“We had corn that was planted in mid-May in 2013. Wet conditions also prevented us from planting early. We had contracts with the corn already being sold, and we still made 200 bushels when it was planted that late. So the temperature at the time of planting and throughout the season really does impact our yields.”

As for plant populations, growers in Arkansas usually plan in the low 30s on irrigated, 32,000 to 34,000. “We’ve looked at this in our research in recent years, with most of it coming on single 38-inch rows. Yields increase up to a certain level and then it plateaus out. We typically maxed out with a final plant population of around 32,000 or 33,000, on average. But averages don’t always tell us the whole story.”

Over a six-year period in southeast Arkansas, the yields was maximized at 34,000 plants for two-thirds of the time, says Kelley.

“But in one year, 43,000 topped us out, and that was the year in which we had the greatest yield. In some cases, with certain hybrids and in certain situations, increasing the plant population may help you to increase those yields slightly. But at the cost of seed, it can hit your pocketbook pretty hard.”

About half of the corn crop in Arkansas is on 38-inch rows with the other half being on 30-inch rows, says Kelley.

“The guys on 38 inches are trying to figure out how to get to something narrower. For some, the solution is a twin-row planter. We’ve done some work on this, and our biggest problem is that we’re not seeing an advantage with twin rows. We’ve got raised beds and we’re furrow-irrigating, so we have to make the water get down the rows, and it creates a challenge. In our situation, the twin rows planted up on beds doesn’t give us that yield boost we’re looking for.”

Where there were single, 38-inch rows and plant populations up to 40,000 or better, lodging became an issue, he says. “We didn’t have root lodging in the twin rows adjacent to it. So we’re doing something there with the twin rows, but it didn’t give us a whole lot more yield.”

Disease pressure can be variable on corn, depending on planting dates and the growing season itself, says Kelley.

“Our two main diseases in Arkansas are Northern corn leaf blight and Southern rust, along with some minor ones. Sometimes, we hear that to get to 300 bushels, we have to put out a fungicide. But it depends on planting date, the growing season, and other factors. Several years ago we did quite a bit of fungicide work. We planted corn in March, early in the window, made numerous fungicide treatments, and got a yield response of about 2 ½ bushels. That probably won’t pay for itself.”

But it might be a different story on late-planted corn, he says.

“We’ve got some data where we planted late and Southern rust came in early during grain fill, and we got up to a 40-bushel difference from using fungicides. So a lot depends on when you plant. When we plant in March or April, oftentimes we don’t have any disease problems. If it’s into May when we plant, then we start thinking about the possibility of using fungicides," he said.

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