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Unique weather a factor in record 2004 Midwest crop yields
Eva Kingston,
State Water Survey
217-244-7270; eva@sws.uiuc.edu
Jim Barlow, Life Sciences Editor
217-333-5802; jebarlow@illinois.edu
|
3/11/05
CHAMPAIGN, Ill. —
If farmers talk big about 2004 crops as they get ready to head out into
the fields this spring, let them talk. Believe them. Last year’s
crop season saw record yields in every major crop amid the closest-to-perfect
weather conditions of the last century, scientists say.
“Never before have corn, soybeans, sorghum, and alfalfa hay all
achieved record yields in the same year,” said Stanley A. Changnon,
chief emeritus of the Illinois State
Water Survey (ISWS) and an adjunct professor of geography at the University of Illinois at Urbana-Champaign.
In Illinois, the average corn yield in 2004 was 180 bushels per acre
– 16 bushels an acre higher than the record set in 2003. Soybean
yields was 50.5 bushels per acre, beating a record set in 1994 by five
bushels per acre. Record high corn yields also were reported in Iowa,
Indiana, Missouri, Nebraska and Ohio. Nationally, the corn yield was
160 bushels per acre – 18 bushels an acre above the 2003 record.
“Planting during the 2004 growing season was early,” Changnon
said. “Summer temperatures were below normal with no hot days.
Rainfall was adequate. Crop-yield predictions issued during the growing
season and up through August 2004 did not anticipate the high magnitude
of the corn and soybean yields that actually occurred.”
Sophisticated crop-weather models relying on daily temperature and rainfall
values of 2004 also did not calculate yields as high as the actual yields.
Predictions and
model-generated yields were 7 percent to 15 percent lower than final
corn yields for the 11 Corn Belt states, and 15 percent to 33 percent
lower than final soybean yields of the Midwest.
Those outcomes, Changnon said, help to reveal that weather conditions
critical to generating extremely high yields of all Midwest crops were
not detected. He and his son David Changnon, a geography professor at
Northern Illinois University in DeKalb, decided to take a closer look
at the weather conditions during 2004.
“A climatological evaluation revealed that summer 2004 conditions
were unlike any experienced during the past 117 years,” Stanley
Changnon said.
They found that an unusually high number of sunny days had occurred,
aiding photosynthesis. The frequency of summer days with clear skies
was a critical, beneficial factor for all the crops grown in the Midwest.
“When a large number of clear days occurred in most previous summers,
conditions were hot and dry with much above average temperatures and
below average rainfall. Temperatures in 18 of the 33 summers between
1888 and 2003 with frequent clear skies averaged between 1.2 degrees
Farenheit and 4.5 degrees Farenheit above the long-term average,”
Stanley Changnon said.
Summers with frequent clear skies, well below average temperatures,
and above average rainfall occurred in just two years in the past 117
years: 1927 and 2004. Skies were clear on many more days in 2004 than
in 1927, and June and August rainfall in both years had different magnitudes.
Thus, the 2004 weather conditions were anomalous.
Summers with below average temperatures in all three months (June, July
and August), as in 2004, occurred in 18 previous summers between 1888
and 2003. Sky conditions during those cool summers were mostly cloudy,
quite different than in 2004.
Sunny, cool conditions in 2004 were a result of 20 cold Canadian fronts
that crossed the Midwest, followed by strong high-pressure systems for
several days. Each such intrusion dropped temperatures 5-15 degrees,
followed by several clear days. High-pressure centers dominated the
atmospheric circulation and kept warm, stationary fronts with their
attendant penetrations of warm, moist air masses away from the Midwest.
“The atmospheric circulation pattern during summer 2004 was unusual,
but these conditions and their crop impacts are not considered indicative
of those expected with a change in climate due to global warming,”
Stanley Changnon said.
The report detailing the study is available from the ISWS
Web site. The research was conducted as part of the weather-climate
impacts program of the Midwestern
Regional Climate Center and the ISWS climate program. The climate
center is funded by the National Oceanic and Atmospheric Administration
and the state of Illinois.
