In a letter sent to the U.S. Army Corps of Engineers, the National Corn Growers Association urged the Army Corps to delay its planned mat-laying work along the Mississippi River.

“This comes at a terrible time for U.S. corn farmers,” said NCGA President Chip Bowling. “We produced a record crop in 2014, much of which will be transported along the Mississippi River. It is imperative that barge traffic not be impeded, and as much grain as possible is transported before winter.”

In the letter, NCGA notes that the closure is being done with little notice, and it will result in significant delays of grain shipments.

Read the full letter here.