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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