Substantial moisture needed soon to save corn crop

With corn demand booming, there’s little margin for error in the 2007 crop. But, recent abnormally dry conditions in the central and eastern Corn Belt may be filling that margin already.

According to the U.S. Drought Monitor, much of Illinois, Indiana and Ohio south of Interstate 80 are either abnormally dry or in moderate drought. In some parts of the region, rainfall totals for the month of May were around half of normal—University of Illinois Extension agronomist Emerson Nafziger says since April 1, central Illinois has received half of the typical 10 inches of rain. Western Illinois has fared slightly better, but the dry conditions increase in severity from Champaign eastward.

“We really need some rain. I haven’t seen it this dry since 1988,” writes Agriculture Online Marketing discussion group poster Case IH farmer. “From the looks of it, I think this year the drought is pretty widespread and there are going to be pockets where they have good crops instead of, like last year, there were pockets of bad crops.”

At this point in the year, drier-than-normal conditions don’t “spell disaster yet” in Illinois, according to Nafziger. “We would rather have it moderately dry than very wet,” he says. “I think if we got two inches of rain over every inch of Illinois today, I don’t think the dryness up to now would have any effect.”

The more serious concern for the Illinois crop, Nafziger says, is further along in July, when the corn will need around one-third of its total water uptake. In order to maintain optimal yield potential, the agronomist says surplus moisture must fall.

“To have their crop turn out outstanding, it may take higher-than-average amounts in the next six weeks just to have enough,” Nafziger says. “It’s always a problem to say we need higher-than-average rainfall especially when there’s nothing to suggest that will happen.”

Nafziger’s latter point is true in the immediate future, at least according to Cropcast Weather Service. In a Dow Jones Newswires report Friday morning, the forecast called for a few rain chances early next week, but predominantly dry conditions are expected to persist through the rest of June. Some areas could see a light to moderate band of showers next week as a front moves through, but rainfall totals will likely be less than an inch.

This week’s U.S. Drought Monitor shows the abnormally dry and moderate drought conditions throughout Illinois, Indiana and Ohio (data courtesy U.S. Drought Monitor).

Indiana

In Indiana, where some of the highest producing corn counties are under severe stress, the eight-day outlook for rain is poor. The last significant rain Indiana producers received was on the Memorial Day weekend, ranging between one-half inch to three inches.

Tony Vyn, Purdue University agronomist says the rain that is expected to come in the next week is for the already wet areas of northern Indiana. The rain is needed in the southern and eastern parts of the state.

Agronomically, the drought is occurring at a time when the plant’s ears are determining kernel row numbers, and the number of kernals per row, Vyn says.

“Every one of those factors limits ear-fill. All of those factors limit yield potential,” Vyn says. “The plant has time to recover with better conditions later on during the grain-fill stage. So, it’s hard to say how much yield has been lost at this stage.”

Meanwhile, Vyn is surprised that droughty symptoms are even showing up on some of Indiana’s best soils. “Plus, we are seeing more drought stress on corn-on-corn acres than corn after soybeans,” he says. “So, the higher price pushing the producer to plant more corn is not helping.”

Ohio

Spotty localized rains like those forecast for next week in some areas have fallen recently in the eastern third of Ohio, but the major corn growing areas of the western third of the state remain under severe stress.

What’s this doing to the corn crop there? When the corn plant is at the three- or four-leaf stage, the high temperatures stunt growth, more so than lack of moisture. But, the moisture demands ramp up quickly, as the plant gets older.

Peter Thomison, Ohio State University Extension agronomist says some fields are past that tipping point. The uncertainty of rain until the end of next week is adding to the crop development.

“We are at the point where we will start to lose stand on some of this corn,” Thomison says. “That is unusual for us. Some of the corn leafs are rolling. Plus, in 10 days, the ears will start to form. If there is no rain coming, smaller ears will reduce yield potential.”

Other sure signs of a lack of moisture is the varied height of the corn plants. “We have some corn that is two inches high and some that is 20 inches high in the same field,” Thomison says. “The impact of uneven corn gets more severe with dry weather.”

Illinois

In Illinois, the dryness to date has had a less profound effect on the corn crop, Nafziger says. With heavier soils, the corn plants have been able to continue drawing from adequate subsoil moisture supplies. Those stocks are dwindling, but even with no rain, Nafziger says the crop could sustain itself through pollination despite reports that corn leaves are also starting to curl in Illinois just as they are in Ohio.

“This crop would be under a lot more stress without soils that can provide moisture,” he says. “Worst-case scenario, if it didn’t rain in three weeks, we would go into pollination and not do terrible at it.

“An inch of rainfall would be very helpful—it would provide enough for much of this crop to get through pollination okay, then we’d worry from then on.”

Moving eastward, however, as soils lighten, Nafziger acknowledges the crop is “suffering considerably more than ours.”

In terms of just how much rain is needed, the Illinois agronomist says the answer is contingent on “a game of subtleties.

“The corn planted earlier might do better. Any rain we get in the next week is going to be very helpful, but how each field responds to the lack of rainfall, we’ll have to just wait and see,” he says. “Today’s corn crop tends to be more resilient. We don’t have an indication that it’s more water-efficient than it was 20 years ago, but it’s more robust and gets more moisture out of the soil.

“But, we’re just pretending if we think it can not rain and we can still raise a crop.”

According to Friday’s Freese-Notis Weather, Inc., Weather Market Commentary, Monday’s USDA Crop Progress report, among other things, will give a good indication of just how much damage the Corn Belt has incurred from the dry conditions.

“Crop ratings will be down on Monday, considering the lack of rain and above normal temperatures seen this week and in the weekend,” according to Friday’s Freese-Notis commentary. “The Drought Monitor next Thursday will show a further expansion of drought concerns in the eastern Corn Belt, as that map is valid as of Tuesday…and there should not be rain before that time.”

Source: Mike McGinnis and Jeff Caldwell, Agriculture Online Editors

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