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June 17, 2003

Agronomist: Slow-growing corn playing tricks with farmers' eyes

WEST LAFAYETTE, Ind. – Indiana corn growers who look at their emerged crop in dismay could be seeing an optical illusion, said Bob Nielsen, Purdue University Cooperative Extension Service agronomist.

While corn planted as early as two months ago might seem hopelessly behind in development, it is not, he said.

"In much of the northern part of the state a lot of the corn went in mid- to late April, about a week or two earlier than normal," Nielsen said. "A lot of the mid- to late April corn is now around the six-leaf stage, or maybe the seven-leaf stage in spots. It's not as far along as you'd want it to be given such an early planting, but compared to the whole season we're maybe a week behind normal, which isn't all that bad.

"That means instead of this early corn pollinating in the early part of July it's probably going to be the middle part of July."

Any catch-up growth isn't likely to occur until September because the crop season is too far along for early summer "heat units" – an agronomic way of measuring temperature and its affect on a crop's growth potential – to make much difference, Nielsen said.

Farmers still might produce a good corn crop despite the slow growth, Nielsen said. Weather conditions and other factors could be key.

"In and of itself slow development doesn't necessarily have a direct impact on yield," Nielsen said. "But in the sense that a slowly developing crop is less vigorous, it is also less tolerant of other stresses. There are individual fields around the state where the corn's been developing very slowly and it's also been attacked by soil insects, soil diseases or soils that are excessively wet. In those fields we've seen some stand loss and uneven growth because of these stresses."

Planting got off to a fast start in April but stalled when May brought rain and cool temperatures. Southern Indiana counties were hit hardest by adverse weather conditions, making it nearly impossible for farmers to finish planting. Another series of storms rumbled through the state this past week (6/8-6/14), further postponing planting operations.

As of Sunday (6/15) just 72 percent of corn acreage was planted in southern Indiana, compared to nearly 100 percent in northern and central Indiana, according to the Purdue-based Indiana Agricultural Statistics Service.

Farmers in southern Indiana are nearing a crossroads, Nielsen said.

"Those who still have intended corn acres left to plant are going to have to make some decisions," he said.

"The rain events that have come through the state will delay planting even further and finally get us out to a point where, agronomically, it's necessary to start thinking about switching to soybeans. Those decisions need to be made now because with this rainfall it can easily put planting out another week, and suddenly we're into late June and things need to change."

Late-planted corn also is more susceptible to leaf blights and the destructive southwestern corn borer, Nielsen said. "Those are some of the red flags on the horizon farmers will need to be aware of," he said.

Farmers with emerged corn have other issues to contend with, Nielsen said.

"In the northern two-thirds of the state where the corn crop is pretty much completely in, the two major issues for the next several weeks are weed control and sidedress fertilizer application," he said. "The rains that have come through have interfered with both of those operations."

Whatever progress farmers are able to make in planting, spraying or fertilizing corn must happen quickly.

"Once you get to the latter part of June or early part of July, then we're getting very close to the pollination period," Nielsen said. "At that point, it's pretty much out of our hands, and there's not much else to be thinking of in terms of management."

Writer: Steve Leer, (765) 494-8415, sleer@purdue.edu

Source: Bob Nielsen, (765) 494-4802, rnielsen@purdue.edu

Ag Communications: (765) 494-2722; Beth Forbes, bforbes@aes.purdue.edu; http://www.agriculture.purdue.edu/AgComm/public/agnews/

Related Web sites:
Purdue University Corn Growers' Guidebook
Indiana Agricultural Statistics Service


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