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110˚F. Weather to Take Toll on Late-Planted Corn, Soybeans

Rising temperatures likely to quickly sap moisture from soils and stress plants.

Hot and dry weather that’s moving into the Midwest likely will stress plants that have a shallow root system after being planted so late.

Much of the Midwest stretching from Nebraska into southern Michigan will see less than 50% of normal rain in the next 10 days, according to a report from Commodity Weather Group.

Temperatures are expected to top 100˚F. this week in southern Nebraska, Kansas, northern Missouri, and southern Iowa, the forecaster said. Crop stress is expected in about half of the southwestern Midwest with the main yield risk to early pollinating corn.

The weather hasn’t been overly hot thus far, but with temperatures rising and drier weather moving in, some plants that were planted late due to nonstop rain during what would normally be planting season are at risk to their shallow root systems.

“When crops grow under warmer-than-normal temperatures, which much of it has because it was planted so late, plants favor top growth over root growth a little bit,” said Emerson Nafziger, a professor emeritus in crop sciences at the University of Illinois, who also farms near Champaign, Illinois. “Hot, dry weather is always a concern.”

Excessive heat watches have been issued for much of the Midwest in a block stretching from southern South Dakota south through Nebraska into the eastern half of Kansas, according to the National Weather Service. The watches are in effect east into central Illinois and north into southwestern Wisconsin, the NWS said.  

Temperatures in northwestern Missouri are expected to be in the high 90s with heat indexes from 105˚F. to 110˚F..

In southern Missouri and Illinois, index values are forecast to be around 113˚F.

An already-shallow root system is worsened because the roots seeking water obviously have a harder time pushing trough dry soils, he said. They can go into dry soils if no moisture is present, but it leads to increased stress on the plant.

Still, he said, today’s hybrids are better at withstanding adverse weather and late planting conditions, which may mean the heat won’t affect yield and overall production as much as it would’ve in the past.

“Our hybrids are bred to put a root system out and test them under wide range of conditions, and those do relatively well under all conditions are best for release,” he said. “So we’ve moved to more resilient crops no matter if we planted in ideal conditions or not.”

Fields that were planted in the middle of May should be “fine,” Nafziger said, and from what he’s seen thus far, leaf health has been good in central Illinois. Most, however, were not planted in mid-May due to the nonstop rain almost the entirety of the Midwest faced during the normal planting window.

One thing he is worried about is the danger that farmers will “throw in the towel” on their crops before they need to.

“Humans will throw it in quicker than the crop will this year,” Nafziger said.

One field he recently assessed in Ohio had a pineapple quality that indicated it was suffering from stress. He drove by the field after a week of rainfall and it looked like it should, he said.

Producers need to keep an eye on their plants to make sure the leaves are keeping their color. Soils should have good moisture after all the rain the Midwest received the past two months, but with heat indexes well into the 100s, water can evaporate quickly.

The worst-case scenario is that in addition to the heat, the rain stays away.

“Temperatures in the 80s and 90s will take their toll eventually,” Nafziger said. “We’re losing, with a full canopy, about a quarter inch of water even though our soils tend to hold water really well. We can go two weeks (without rain) because the soil was fairly full to begin with. But it can’t go forever.”

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