High heat and little rain during the past week led to an unusual, quick expansion of drought conditions in Iowa and Illinois, damaging crops in the biggest U.S. corn- and soybean-growing states.
About 25 percent of Iowa had a moderate drought on Aug. 27, up from 7.9 percent a week earlier, while Illinois jumped to 20 percent from none, the U.S. Drought Monitor said yesterday in a report. Parts of Iowa received less than 25 percent of normal rain during the past 60 days, and much of Illinois got less than half of normal since June 30, data from the High Plains Regional Climate Center show.
After a wet May and June delayed planting, the U.S. Department of Agriculture cut its soybean-crop forecast by 4.8 percent on Aug. 12 and reduced its corn estimate for a third straight month. July was the 20th coldest in 119 years in Minnesota, Wisconsin, Michigan and Iowa, National Weather Service data show. Soybean futures are up 17 percent from an 18- month low on Aug. 7 on forecasts for dry weather, and corn rose 7.5 percent from a 35-month low on Aug. 13.
"The heat and drought are speeding crop development and reducing yield potential daily," Roger Elmore, an agronomist at Iowa State University in Ames, said in a telephone interview. "We are skipping over critical stages of development that probably can’t recover even if temperatures cool and a little rain falls."
While the crops need hot weather to develop, temperatures that approached 100 degrees Fahrenheit from Nebraska to Indiana in the past five days can cut corn yields at least 3 percent a day while reducing the number of seeds and seed weight in soybeans, Elmore said.
Cool weather during the first 19 days of August masked the stress that the dry spell was causing to crops over most of the Midwest, Planalytics Inc. said in a report yesterday. The epicenter of the crop damage is in Iowa, based on the vegetative growth index that the forecaster constructs biweekly from satellite images.
Corn yields in Iowa probably are down to about 150 bushels an acre, compared with an estimate of 165 bushels a week ago, said Kent Jessen, the director of merchandising for West Des Moines, Iowa-based Heartland Cooperative, which has 52 grain terminals across 17 counties. Soybean yields will be 35 bushels an acre at best in his area, compared with 48 a year ago. The average yield in the region where drought is most severe in Iowa was 52 bushels from 2007 to 2011, he said.
"The flash drought has caused severe and irreversible damage very quickly," Jessen said. "The beans are going downhill much quicker than the more mature corn. There are some soybean fields that have received only 2 inches of rain since they were planted in June."