sealPurdue News

May 22, 2002

Further planting delay forces farmers to consider new strategies

WEST LAFAYETTE, Ind. – The delay in planting across Indiana and Ohio has producers rethinking their crop strategies this year and wondering if they need to switch to earlier maturing corn hybrids.

Bob Nielsen, Purdue University Extension corn specialist, said farmers can continue with their current, full-season maturing hybrids until almost the end of May. However, if producers don't think they'll be planting for another two weeks in their area, they need to talk with seed dealers about other options.

"If we could plant today, we would say don't switch," Nielsen said. "The realization for many producers is that they are looking at another week delay and possibly longer before they can get in the fields. Farmers ought to be visiting with their seed dealers to find out what kind of inventory they have on early maturing varieties that have a high yield potential. If they put their name on a list to receive the seed, they can get the delivery taken care of in a timely manner and get down to the business of planting corn."

In the early 1990s Nielsen and Peter Thomison, Ohio State Extension corn specialist, researched the effects of delayed planting and found that corn adjusts the way it grows in response to a shorter season. Their research examined the amount of thermal time between planting and physiological maturity, or growing degree days, that hybrids need. A growing degree day is calculated by taking the average daily air temperature and subtracting 50.

"The plant actually reduces the amount of growing degree days it requires to mature, and so that works in our favor with delayed planting," Nielsen said. "A hybrid may require 2,700 growing degree days when it is planted in early May, but may only require 2,500 heat units by late May or early June. We actually gain some thermal time because of this effect of delayed planting, and that's why we can hold on to plant some of these varieties longer in the season than we used to think."

Since planting is pushed back this year, late planted corn will be influenced by stress more than early planted corn. Because of the shorter season, corn goes through its different growth stages later in the summer and is more susceptible to pollination problems, insects and disease, Nielsen said.

Commonly grown corn hybrids across Indiana take anywhere from about 105-118 days to mature, while varieties across Ohio take about 105-114 days to mature. However, this year producers may need to choose a seed that works better with the shortened growing season.

"Days to maturity cannot be compared to calendar days to make the decision on when to switch hybrids," Nielsen said. "It is based simply on relative differences in grain moisture at harvest, not on the actual number of calendar days it takes to mature the corn crop."

In Indiana, producers who haven't planted in the northern third of the state and in east central Indiana by the end of May need to switch to earlier hybrids ranging from 105-108 days to maturity, Nielsen said. However, the rest of the state's producers can still plant the seed they have due to a longer growing season.

In Ohio, corn planting may be further along in northern counties, Thomison said. But there are exceptions.

"It's a real patchwork," Thomison said. "There are some areas of northwest Ohio planted and then there are other areas with heavy clay soils where nothing is planted. According to some reports, I've heard that in southwestern and south central Ohio as much as 30-40 percent of acres in river bottoms have been planted."

Thomison said it is safe in northern Ohio to plant hybrids that take 105-107 days to mature until the end of May. In central Ohio, varieties that take 107-110 days to mature can be planted until the end of the month, while southern Ohio can safely plant hybrids that take 114 days or longer to mature.

If seed is not in the ground by the beginning of June, farmers in other areas of Indiana and Ohio will need to make adjustments as well. Nielsen and Thomison's recommendations for switching hybrids can be found in the Purdue and Ohio State Web publication titled "Delayed Planting and Hybrid Maturity Decisions".

Another part of the equation farmers need to consider before getting back in the fields is the amount of nitrogen left on the ground. Despite Indiana's record wet spring, fields should still have a significant amount of anhydrous ammonia left for this year's crop, Nielsen said.

"We probably have not lost a significant amount of nitrogen," he said. "Even if we say we have lost 10-15 percent of the nitrogen material that has been applied, that may still be adequate for the lower yield potential of late planted corn this year."

Nielsen said corn planted the first week of June will be pollinating in late July or early August rather than early July, when pollination normally occurs. This is typically the warmer and drier part of the season, which may cause a higher risk for stress. Corn also will be in a younger stage when leaf blight diseases, such as gray leaf spot, may hit, causing a greater risk of yield loss, he said.

Late planted corn also is more attractive to adult Japanese and western corn rootworm beetles, Nielsen said. European corn borer and southwestern corn borer moths also will be looking for corn to lay their eggs on in late summer.

"What's uncertain this year is the effect of having so many acres of late planted corn," Nielsen said. "The large number of delayed planted acres may actually help dilute the population of these insects. On any given acre there may not be as much pressure as there typically is if there is a late planted field randomly here and there."

Historically, Indiana has had low incidences of the European corn borer and southwestern corn borer, and farmers have not seen the economic benefit of planting Bt corn. However, Nielsen said producers may want to consider this option as protection against a potential infestation of these insects as long as they can find a buyer for their Bt grain.

Farmers in northern Indiana may be back in the fields yet this week, while other parts of the state continue to wait for the ground to dry. Nielsen said from May 10 until the middle of June, yield decreases 1-2 bushels of grain per acre each day a field is not planted.

"It begins to add up very quickly," Nielsen said. "You can be out in early June looking at yield potentials that are around 70 percent of what producers would have expected from corn planted in late April. It begins to add up pretty severely, which is obviously at the heart of the anxiety farmers feel now as they aren't getting the crop in the ground."

Writer: Jennifer Doup, (765) 494-6682,

Sources: Bob Nielsen, (765) 494-4802,

Peter Thomison, (614) 292-2373,

Ag Communications: (765) 494-2722; Beth Forbes,;

Related Web sites:
Purdue Extension Delayed Planting Web site

Purdue News Service: (765) 494-2096;

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