Barge rates for export grain from major U.S. interior origins are running 29% to 57% below the five-year average, the U.S. Department of Agriculture announced Thursday.

Barge operators attribute the decline to weakened demand for barge services dating back to October 2015. As of March 29, St. Louis export grain barge rates were 210% of tariff ($8.38 per ton), 44% lower than the five-year average of 302% of tariff ($12.05 per ton).

Barge rates rallied slightly over the past two weeks as barge supply adjusted to traffic increases when portions of the Upper Mississippi River that were closed during the winter reopened. Rain-induced high-water conditions on the Lower Mississippi restricted tow sizes and slowed logistics for river export facilities, also contributing to the rate rally, the USDA said.