By Christine Stebbins
CHICAGO (Reuters) - Abnormally dry areas expanded in the U.S. western Corn Belt, including the top crop state of Iowa, over the past week to put much of the corn crop at risk, according to a weekly drought report.
The U.S. Drought Monitor, issued by state and federal climate experts, said dry conditions in the U.S. Midwest for the week ended Thursday, reached 18.94 percent, up from 7.16 percent a week earlier. Dry areas expanded in Minnesota and Iowa south to Missouri, Arkansas and Louisiana.
The spread of the dryness comes as most of the corn crop enters its critical yield determining phase, raising concerns about the region's corn reaching its full yield potential.
"The next seven to 10 days are going to be critical. If they don't get rain during pollination time then there's going to be some serious crop damage," Richard Heim with the National Climatic Data Center and author of this week's Drought Monitor told Reuters.
Currently, the U.S. government is forecasting a record corn harvest of nearly 14 billion bushels as most of the crop is in good shape and conditions are favorable - a big change from a year ago when two-thirds of the country was in drought.
The biggest increase in dry area was in Iowa where nearly 63 percent of the state was rated abnormally dry, compared to less than 20 percent last week.
"According to July 21 U.S. Department of Agriculture reports, 64 percent of the topsoil was rated short or very short of moisture in Arkansas with 24 percent of the pasture and rangeland in poor or very poor condition. Missouri had 60 percent of the topsoil short or very short of moisture and Iowa had 57 percent so rated, which was a jump of 22 percent since last week," the report said
East of the Mississippi River is drought free, while drought conditions remain entrenched in the southern Plains where 66.3 percent of region is in "moderate to exceptional" drought - nearly unchanged from a week ago at 67 percent.
Spotty heavy rains from southeastern Kansas to northeast Oklahoma, up to five inches in some places, helped ease drought stress there. But much of the northern Plains was drier than normal, according to the Drought Monitor.
Link to the monitor: http://droughtmonitor.unl.edu/monitor.html
(Editing by Bob Burgdorfer)