By Christina Dittmer
Hail and flooding this week decimated crops in many fields in the northern third of Iowa. However, soybeans and corn in the majority of the state that escaped severe weather are faring well, according to reports from agronomists and farmers.
Counties in northwest Iowa received 8 to 10 inches of rain and localized areas of hail causing crop damage in multiple counties. The Iowa Soybean Association reports that farmers in Palo Alto, Kossuth, Humboldt, Dickinson and Lyon counties were among those impacted by storms that swept through the state on Monday and again early Wednesday morning. Monday's storm dumped 3 to 6 inches of rain on several counties and included reports of tennis- to baseball-size hail.
"It's a blow to the gut," said Wyant Metzger, a farmer near West Bend. "Things were looking, as a whole, pretty good. But we're back to planting beans the last week of June like we were last year." Metzger's corn and soybean fields collected 2.5 inches of rain on Saturday and another 6.3 inches on Tuesday. "The fields are saturated so there is nowhere for the water to go, and as hard as it rained it just compounded the problem," he said.
Farmers will have to make replanting decisions on some fields
Jay Bargman, who farms near Rodman in Palo Alto County, watched as tennis ball sized hail fell on his crops, shattered lighting fixtures at his home and dented the roofs of out buildings. He kept several of the stones in his freezer as proof of the ordeal. "It was a long stretch of nasty weather," he said. "I have about 400 acres underwater right now and I'll lose about 100 acres. Some of the corn was sawed off, so it's gone."
Both farmers are in wait-and-see mode to see if they receive more rain this week before they can determine areas that will need to be replanted. "We'll replant beans until the 10th of July," Bargman said. "We should be replanted in a week-and-a-half but there are areas north of here that won't get it done."
Crops in the rest of Iowa looking good
Few problems with soybeans and corn were reported by Iowa State University Extension and Outreach field agronomists during their weekly conference call on Monday, June 16, says agronomist Mark Johnson who covers central Iowa. But that was before the flooding and hail in northern Iowa.
Crops in much of the state still look good as we are entering the last part of June, says Johnson. "Replanting is occurring in some parts of the state, but overall, things look good. In my area in central Iowa, corn and bean stands seem to be good with minimal replanting. Some fields are a little yellow, but if we get the rain and heat units predicted this week, plants will snap right out of it."
The June 16 USDA weekly Crops & Weather Report said 95% of the state's soybean acreage has emerged, 41 percentage points ahead of last year and 9 percentage points ahead of the five-year average. Almost the entire corn crop was out of the ground, up and growing and looking good.
Soybeans are mostly in the V1 to V2 stage, Johnson says. According to the June 16 USDA report, the crop was rated 2% very poor, 3% poor, 16% fair, 61% good and 18% excellent. Corn in the western part of Iowa was mostly in the V6 stage, while growth varies from V3 to V6 in the eastern half, agronomists said. The June 16 report said the corn crop on June 16 rated 1% very poor, 2% poor, 14% fair, 63% good and 20% excellent.
Johnson says there have been a "fair number" of calls from farmers about herbicide injury to corn. Herbicide that was sprayed on soybeans last year lingered in some fields longer than normal due to the dry fall in 2013. There are no major concerns about soybeans, he says. Waterhemp is starting to take off in fields. He recommends spraying as soon as possible. "Farmers need to get it before it gets out of control."
Assessing crop damage; is it too late to replant?
Aaron Saeugling, ISU field agronomist covering southwest Iowa, says tens of thousands of acres (primarily soybeans) have or will be replanted in areas of the state hit by this past week's bad weather. Large hail and torrential rain devastated crops recently in southwest Iowa and the far northwest parts of the state.
A limited amount of corn will be replanted due to the potential yield hit -- it's getting too late to replant corn. Planting late isn't as much of an issue, however, if you will harvest the crop for silage. Crop insurance considerations and previous herbicide applications will also play a role in deciding whether or not to replant, and whether to replant the field to corn or soybeans.
Soybeans replanted soon still have good yield potential, Saeugling says. According to Iowa State University research, soybean yields, on average, decline by .25 to .9 bushels per day that seed isn't in the ground after May 15.
Farmers replanting soybeans may want to consider changing the maturity group of the seed they use, which will compensate for a shorter growing season, Saeugling says. In southwest Iowa, farmers typically plant 2.9 to 3.5 maturity rating soybeans.
Information and resources after a flood
Brian Lang, ISU Extension field crop specialist on northeast Iowa, offers the following information and resources to farmers who've experienced flooding. He says the extent of flood damage on plants is related to the temperature of the water, the amount of water motion and the duration of the flood. Flooded plants have shorter survival windows with warmer temperatures, plants caught within water flow paths and plants completely submerged.
Corn observations: Young corn can survive flooded condition lasting four days under cooler temperatures (less than mid-60 degrees F), about two days under warm temperatures (mid-70 degrees F), and as little as 24-hours under hot weather. Flooded plants with leaves above the waterline are able to survive longer. Once water recedes, surviving plants will resume growth within three to five days. Plant survival could be confirmed by examining the color of the growing point, although by the time you could get back in the field with any equipment, it should be quite obvious what did not survive.
Silt deposited in corn plant whorls often gets pushed out with plant growth and doesn't cause any problems. However, it is possible for disease to be carried with the soil and infect the plants sometimes causing "Crazy Top". Information about "Crazy Top" can be found at the ISU Extension website. More information on the effects of flooding on young corn is available at the Purdue University Extension website.
Soybean observations: Soybean survival is similar to corn survival, but a bit more tolerant to flooding. Research from Minnesota shows that flooding for six days or more may result in plant loss. With warmer temperatures, soybean plants in flooded soils may only survive a few days. Yield losses are seldom noted in fields flooded for 48 hours or less. Four days or more of flooding stresses the crop, delays the plants' growth, and causes the plants to be shorter with fewer nodes. Flooding for six days or more can depress yields significantly, while flooding for a week or more may result in significant (or entire) losses of stand.
The rate of field drying after a flooding event also plays a large role in soybean survival. Also, researchers have found yield reductions to be much greater on flooded clay soils than on silt loam soils when flooded for the same period of time. At the V4 stage, these researchers reported yield losses of 1.8 bushels per acre per day of flooding on a clay soil and 0.8 bushels per acre per day on a silt loam soil.
Wet and flooded soils are especially favorable for the soilborne, moisture-loving pathogens Pythium and Phytophthora. Pythium appears to cause most damage to seedlings of soybean or corn, and Phytophthora can damage soybean seedlings or start infections in the early summer that may develop and kill soybean plants later in the summer.
Forage observations: Here is an Integrated Crop Management (ICM) Newsletter article from similar conditions back in 2007 covering the basic concerns with flooded hay and pasture stands. If flooded forage has noticeable silt deposits, it will not ensile or ferment well, and will be unpalatable. If possible, wait for another rain to wash off the silt, otherwise it might only be useful as bedding material.
Home cleanup: Visit the Extension "Recovering from Disasters" website at for resources after flooding and storm events.
Nitrogen losses in flooded soils: With flooding can come nitrogen losses. Here is an article that discusses research and estimating nitrogen losses.
Christina Dittmer is a Wallaces Farmer intern.