Iowa’s crop damage minimal from storms, ISU agronomist says

Agriculture-related storm damage was minimal last week, according to Brian Lang, the Iowa State University Extension agronomist for northeast Iowa.

The first 3 inches of rain, which fell June 16, was mostly absorbed by thirsty soil, causing little crop damage or erosion, Lang said.

The heavy rains that fell later in the week caused some flooding of crop fields, especially in river valley bottomlands, but the overall percentage of affected crops was low, he said.

'It was not something that will affect prices on the Chicago Board of Trade,” Lang said.

So far this month, the statewide average rainfall has been 7.36 inches, nearly twice the 3.86 average for the entire month of June, according to State Climatologist Harry Hillaker.

Last week the statewide average precipitation was 3.66 inches - more than three times the weekly normal of 1.17 inches, Hillaker said.

Many parts of northeast Iowa had considerably more than the average.

Bob Hemesath, who farms between Calmar and Ossian, where about 10 inches of rain fell last week, reported some corn under water and some 'green snap” of cornstalks caused by strong winds.

Runoff from 6.5 inches of rain last week caused soil erosion that will need to be repaired this fall, said Mark Recker, who farms between Oelwein and Arlington.

'We had some erosion, but to be honest with you the ground took it pretty well,” Hemesath said.

Residue left on crop fields, conservation practices such as grass waterways and the timing of the storms when the corn was big enough to absorb the force of falling rain all helped to limit erosion, he said

Recker said it has been too wet to get into the fields to fully assess the extent of erosion, but he said he expects the gullies have 'cut a little deeper than normal.”

Hemesath and Recker said they had some crops under water last week.

'When the ground is saturated for extended periods, you lose some of the nitrates applied to fertilize the corn, and it shortens the effective life span of your herbicide,” Recker said.

Hail and strong winds, the chief crop threats during summer storms, were quite isolated, according to Lang.

Lang said the extent of flood damage on plants is related to the temperature and movement of the water and the depth and duration of the coverage.

Young corn can survive four days' flooding under cooler conditions but only half as long under warmer conditions, he said.

Likewise, plants with leaves above the water line will survive longer than completely submerged plants, and plants immersed in still water will survive longer than plants exposed to running water, he said.

Once water recedes, surviving plants will resume growth within three to five days, Lang said.

'We need four or five straight days of sunshine” to dry out soggy fields and speed the recovery of swamped crops, Hemesath said.

Recker said farmers also need dry weather to resume spraying of herbicide and nitrogen.

'Hopefully, some of these predicted rain events will start missing us,” he said.

Hemesath said he's beginning to wonder if extreme rain events similar to the ones in the past week are really that much out of the ordinary.

'The last few years it seems like they are becoming all too common,” he said.

Hillaker said his recent analysis of Iowa rainfall records indicates about a 20 percent increase in annual rainfall since the 1950s.

'We are seeing more heavy rainfall events but also more light and medium rainfall events,” he said.

Because additional rainfall is more likely to fall on saturated soils, a 20 percent increase in rainfall translates into a much higher percentage of destructive runoff, according to Hillaker..

The ratio is about 1 to 4; a 10 percent increase in rainfall will result in a 40 percent increase in runoff, he said.