CHICAGO, Aug 19 (Reuters) - A clearer picture of damage to crops in the path of last week's derecho storm emerged on Wednesday, as crop scouts on an annual tour scrambled across blown over corn stalks and wind-battered soybean fields in Illinois and Iowa.
Iowa officials on Tuesday warned much of the crop in the path of the Aug. 10 storm would not be harvested. Some 14 million acres, or 57% of Iowa's area planted, were impacted.
Iowa corn is key for both commodity markets and global food supply chains. A big loss in the top growing state could eat into a record-large national corn forecast at a time when China is buying more of the grain.
About 52% of all the corn produced in Iowa was growing on farmland affected by the derecho, according to a Gro Intelligence analysis of satellite, environmental, and government data. In an unlikely, but worst-case, scenario where none of the corn is salvaged, it would mean the loss of about 1.38 billion bushels of corn, according to Gro, an agricultural data and AI company.
That would cut the U.S. Agriculture Department's current forecast of U.S. farmers harvesting a record 15.278 billion bushels of corn this fall.
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Iowa crops devastated by weather phenomenon
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Iowa crops devastated by weather phenomenon
MALCOM, IA - AUGUST 11: In this aerial view from a drone, two destroyed grain bins lie on the ground near railroad tracks at the Heartland Co-Op grain elevator on August 11, 2020 in Malcom, Iowa. Iowa Gov. Kim Reynolds said early estimates indicate 10 million acres, nearly a 1/3 of the states land used for crops, were damaged when a powerful storm battered the region a day earlier. (Photo by Daniel Acker/Getty Images)
CEDAR RAPIDS, IA - AUGUST 16: A downed power line leans over a street in Cedar Rapids, Iowa on Sunday, August 16, 2020. A rare Derecho storm battered large sections of Cedar Rapids leaving people homeless and without power. (Photo by KC McGinnis/For The Washington Post via Getty Images)
MALCOM, IA - AUGUST 11: In this aerial image from a drone, damaged grain bins are shown at the Heartland Co-Op grain elevator on August 11, 2020 in Malcom, Iowa. Iowa Gov. Kim Reynolds said early estimates indicate 10 million acres, nearly a 1/3 of the states land used for crops, were damaged when a powerful storm battered the region a day earlier. (Photo by Daniel Acker/Getty Images)
LUTHER, IA - AUGUST 11: In this aerial image from a drone, damaged grain bins are shown at the Heartland Co-Op grain elevator on August 11, 2020 in Luther, Iowa. Iowa Gov. Kim Reynolds said early estimates indicate 10 million acres, nearly a 1/3 of the states land used for crops, were damaged when a powerful storm battered the region a day earlier. (Photo by Daniel Acker/Getty Images)
LUTHER, IA - AUGUST 11: In this aerial image from a drone, damaged grain bins are shown at the Heartland Co-Op grain elevator on August 11, 2020 in Luther, Iowa. Iowa Gov. Kim Reynolds said early estimates indicate 10 million acres, nearly a 1/3 of the states land used for crops, were damaged when a powerful storm battered the region a day earlier. (Photo by Daniel Acker/Getty Images)
LUTHER, IA - AUGUST 11: A damaged grain bin sits on top of a pile of soybeans at the Heartland Co-Op grain elevator on August 11, 2020 in Luther, Iowa. Iowa Gov. Kim Reynolds said early estimates indicate 10 million acres, nearly a 1/3 of the states land used for crops, were damaged when a powerful storm battered the region a day earlier. (Photo by Daniel Acker/Getty Images)
TAMA, IA - AUGUST 11: Corn plants are shown pushed over in a storm-damaged field on August 11, 2020 in Tama, Iowa. Iowa Gov. Kim Reynolds said early estimates indicate 10 million acres, nearly a 1/3 of the states land used for crops, were damaged when a powerful storm battered the region a day earlier. (Photo by Daniel Acker/Getty Images)
MARSHALLTOWN, IA - AUGUST 11: In this aerial image from a drone, damaged grain bins stand at the Key Cooperative grain elevator on August 11, 2020 in Marshalltown, Iowa. Iowa Gov. Kim Reynolds said that early estimates indicate that 10 million acres, or nearly a third of the state's crop land was damaged in a powerful storm that battered the region a day earlier. (Photo by Daniel Acker/Getty Images)
TAMA, IA - AUGUST 11: In this aerial view from a drone, corn plants are shown pushed over in a storm-damaged field on August 11, 2020 in Tama, Iowa. Iowa Gov. Kim Reynolds said that early estimates indicate that 10 million acres, or nearly a third of the state's crop land was damaged in a powerful storm that battered the region a day earlier. (Photo by Daniel Acker/Getty Images)
TAMA, IA - AUGUST 11: In this aerial view from a drone, corn plants are shown pushed over in a storm-damaged field on August 11, 2020 in Tama, Iowa. Iowa Gov. Kim Reynolds said that early estimates indicate that 10 million acres, or nearly a third of the state's crop land was damaged in a powerful storm that battered the region a day earlier. (Photo by Daniel Acker/Getty Images)
TAMA, IA - AUGUST 11: Corn plants are shown pushed over in a storm-damaged field on August 11, 2020 in Tama, Iowa. Iowa Gov. Kim Reynolds said that early estimates indicate that 10 million acres, or nearly a third of the state's crop land was damaged in a powerful storm that battered the region a day earlier. (Photo by Daniel Acker/Getty Images)
MALCOM, IA - AUGUST 11: Workers clean up the remains of a destroyed 350,000-bushel grain bin at the Heartland Co-Op grain elevator on August 11, 2020 in Malcom, Iowa. Iowa Gov. Kim Reynolds said that early estimates indicate that 10 million acres, or nearly a third of the state's crop land was damaged in a powerful storm that battered the region a day earlier. (Photo by Daniel Acker/Getty Images)
TAMA, IA - AUGUST 11: In this aerial view from a drone, corn plants are shown pushed over in a storm-damaged field on August 11, 2020 in Tama, Iowa. Iowa Gov. Kim Reynolds said that early estimates indicate that 10 million acres, or nearly a third of the state's crop land was damaged in a powerful storm that battered the region a day earlier. (Photo by Daniel Acker/Getty Images)
MALCOM, IA - AUGUST 11: Workers clean up the remains of a destroyed 350,000-bushel grain bin at the Heartland Co-Op grain elevator on August 11, 2020 in Malcom, Iowa. Iowa Gov. Kim Reynolds said that early estimates indicate that 10 million acres, or nearly a third of the state's crop land was damaged in a powerful storm that battered the region a day earlier. (Photo by Daniel Acker/Getty Images)
MALCOM, IA - AUGUST 11: Damaged grain bins at the Heartland Co-Op grain elevator are shown on August 11, 2020 in Malcom, Iowa. Iowa Gov. Kim Reynolds said early estimates indicate 10 million acres, nearly a 1/3 of the state's land used for crops, were damaged when a powerful storm battered the region a day earlier. (Photo by Daniel Acker/Getty Images)
FRANKLIN GROVE, IL - AUGUST 10: A John Deere agricultural tractor sits under a collapsed building following a derecho storm, a widespread wind storm associated with a band of rapidly moving showers or thunderstorms, on August 10, 2020 near Franklin Grove, Illinois. The storm moved across the Midwest with winds recorded near 100 mph in Iowa and Illinois. (Photo by Daniel Acker/Getty Images)
POLO, IL - AUGUST 10: Broken off corn plants lie in a field following a derecho storm, a widespread wind storm associated with a band of rapidly moving showers or thunderstorms, on August 10, 2020 near Polo, Illinois. The storm moved across the Midwest with winds recorded near 100 mph in Iowa and Illinois. (Photo by Daniel Acker/Getty Images)
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Furthermore, drought conditions are also stressing crops in Iowa this growing season, according to scouts surveying western and north-central Iowa on the Pro Farmer Midwest Crop Tour's third day.
The latest U.S. Drought Monitor, prepared by a consortium of climatologists, showed nearly 80% of Iowa was abnormally dry as of Aug. 11 and nearly 19% was in a "severe drought."
While parts of western Iowa showed robust corn and soybean crops, some scouts saw a drop in corn yield potentials in the west-central and central counties hit by both drought and high winds.
Corn yield potential averaged 162.4 bushels per acre (bpa) at 8 stops in west-central Iowa counties - below last year's crop tour average in those areas of 192.71 bpa and the three-year tour average of 186.28 bpa.
A second leg averaged corn yield potential at 167.7 bpa in five stops in central Iowa - also below last year's and the three-year averages.
"Some of this, you can harvest," said Sherman Newlin, a crop scout and Illinois farmer. "Some of this, you won't be able to."
Exactly how much of Iowa's corn crop is lost won't be known until combines start to roll in next month, said agronomists. But corn yields in the affected areas would be down about 50% from their pre-storm expectations, according to an estimate from Iowa State University Extension field specialist Virgil Schmitt.
"We have got everything from corn that is laying completely flat - that is basically a total loss - to corn that has not been affected at all, to everything in between," Schmitt said. (Reporting By P.J. Huffstutter and Mark Weinraub in Chicago, additional reporting from Julie Ingwersen in Chicago, editing by Richard Pullin)