Drought, frost among Iowa farmers' crop concerns

Delayed planting season could suffer more if cold comes early

Dean Hunter of Iowa City harvests his field near Iowa City on Friday, September 28, 2012. (Kyle Grillot/The Gazette)
Dean Hunter of Iowa City harvests his field near Iowa City on Friday, September 28, 2012. (Kyle Grillot/The Gazette)

The expanding drought has taken precedence over the “F” word, frost, as the leading threat to Iowa farmers’ crops.

“Farmers are talking about both drought and frost. An early frost absolutely matters in a year of late crop development, but it feels farther away when the weather turns hot,” Bill Northey, secretary of the Iowa Department of Agriculture and Land Stewardship, said Thursday.

“Heat will be the big difference maker now,” said Brian Fuchs, one of the authors of the U.S. Drought Monitor, which in its latest report Thursday showed dry soils expanding in Iowa.

Consistent with one of the state’s driest Augusts in 141 years of records, the portion of Iowa rated as abnormally dry or in moderate drought leapt almost 8 percent in the past week, from 74.5 percent on Aug. 13 to 82.43 percent on Thursday, according to the latest U.S. Drought Monitor report.

Drought-related crop stress has been minimized by cooler-than-normal temperatures throughout much of the Corn Belt, said Fuchs, a climatologist at the National Drought Mitigation Center in Lincoln, Neb.

More heat coming

But with high temperatures in the lower 90s, as has been predicted for Iowa this week, “stress will become apparent, especially for soybeans,” he said.

“If we get heat and no moisture, corn ears won’t fill out to their ends and soybeans will be smaller and lighter,” Northey said.

Cooler-than normal weather starting in mid-July has dampened the impact of rainfall shortages, enabling corn and soybeans to pollinate with minimal stress, “but we need rain and warmth to finish the crops,” Fuchs said.

Warmth but little if any rain is in the outlook for this week, State Climatologist Harry Hillaker said.

If no more rain falls this month, which appears likely, this will be the fifth driest August on record, with a statewide average of 1.4 inches, well below the normal average of 4.2 inches, he said.

Cedar Rapids has recorded a barely measurable 0.11 inches for the month so far, following a subnormal 2.78 inches in July, according to Hillaker.

Iowa City and Burlington have been even drier, with cumulative August totals of 0.08 inches and a trace, respectively, Hillaker said.

Despite the midsummer dry spell, Fuchs said he and his colleagues see no signs of a protracted Midwest drought.

Signals indicate fall could be wetter than normal, which would hamper harvest, he said.

Until recently, meteorologists had been talking since late July about the state’s “September-like weather.”

“We’d better not have October-like weather in September,” said Iowa State University corn authority Roger Elmore.\

Growing days

The number of growing degree days required for corn maturity depends, of course, on the seed variety. The range encompasses 2,100 growing degree days for short-season corn to as much as 3,200 GDDs for long-season corn.

In Iowa, hybrids requiring 2,700 growing degree days are fairly standard.

As of Aug. 21, Iowa had accumulated on a statewide basis about 2,046 GDD, which is about 120 growing degrees below normal — the equivalent of about five average summer days. In Cedar Rapids the deficit was 172 GDD; in Iowa City, 151. Across Iowa, growing degree day accumulations ranged from 1,810 in Mason City to 2,363 in Fort Madison.

Iowa State University’s Iowa Environmental Mesonet tracks growing degree days from May 1, when crops would normally be emerging from the ground, but this year hardly any of the state’s corn and soybeans was even planted until the middle of May.

In effect, the approximately 400 growing degree days accumulated in May were for all practical purposes wasted.

The third and fourth weeks of September in the Midwest “could be marked by an early frost or freeze for the corn and soybean growing area, about two or three weeks earlier than usual,” said Paul Pastelok, head of the Long-Range Forecasting Team for

With temperatures forecast to drop to the mid- to low 30s, the cold snap could shorten the growing season, which started late because of cold, wet weather, according to AccuWeather, a commercial forecaster based in State College, Pa.

“Any frost in September will do a lot of damage to crops in central Iowa,” said Grant Kimberley, who farms with his dad near Maxwell.

With crops in that region about a month behind normal, even a normal first frost in the first or second week of October would cause problems, said Kimberley, director of market development for the Iowa Soybean Association.

“About 50 percent of the state’s soybeans were planted in June, so a lot of things have to fall into place to harvest a good crop,” he said.

Kimberly said he hopes Iowa farmers do not experience another “40-40-40 harvest” like they did in the fall of 1993 following the state’s wettest year.

Those numbers, he said, stand for 40-pound test weight (well below the 56 pounds per bushel average), 40 percent moisture (more than double the harvest norm, entailing the need for expensive drying) and a 40-cent discount at the elevator.

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