Icy conditions on the Upper Mississippi River have put an end to the 2014 shipping season, the earliest closing in the past 45 years.

With the towboat Mary K. Cavarra and its load of four barges heading south through Lock & Dam No. 2 at Hastings on Thursday, the season officially came to a close, putting a bookend on a choppy year that began last spring with the second-latest opening and came to a 26-day halt in midsummer so crews could clear flood-borne silt from the navigation channel.

"It's been a real challenging year for us," said Bob Zelenka, executive director of the Minnesota Grain and Feed Association, which represents about 550 grain elevators and feed mills across the state.

Minnesota's corn harvest, forecast at 1.29 billion bushels, has been completed, and all but a small percentage of the state's estimated 305 million bushels of soybeans have been picked, Zelenka said. But the river's early closure means finding alternative ways to get those crops to New Orleans and foreign export markets. Half the state's agricultural exports are shipped on the Mississippi River.

"The river is the cheapest way of moving our products," he said. "Obviously, if we lose that option it puts a lot of pressure on our other modes of transportation."

For shippers, it's been a full seven months of trying to play catch up, and now it's over too soon, said Lee Nelson, president of Upper River Services Inc. in St. Paul, which moves barges between river terminals. Besides grain, the river is a key conduit for commodities such as cement, road salt and fertilizer.

"With the year we've had, everyone was hoping for as much time as possible," Nelson said.

Ice measured at nearly 3 feet thick on Lake Pepin delayed the start of the season until April 16. That was followed by late floods that deposited millions of tons of silt around Wabasha and Winona, halting river traffic until the silt could be dredged.

With the onset of winter, Nelson's crews were scrambling over the past week to get towboats and barges — some that had yet to be loaded and some that couldn't be unloaded — out of St. Paul to avoid being locked in by ice. And none too soon: About two dozen towboats with about 200 barges have been stranded by an ice gorge — a mass of ice clogging the shipping lane — above Lock & Dam No. 10 near Guttenberg, Iowa, which is still part of the St. Paul District of the U.S. Army Corps of Engineers.

Bryan Peterson, navigation manager for the Corps, said ice is now at a thickness not usually seen until December, and the towboats are working their way through, but it's a slow process. A coming thaw could bring relief.

"Mother Nature is dictating everything," Peterson said.

Despite the late start this spring, the midseason disruption and the early closure, cargo tonnage on the Upper Mississippi was up more 10 percent this year, Peterson said.

It's not clear, however, what effect the early closing of the river will have on farmers, Zelenka said. For now, rail shipping — pressured by demands of transporting oil and related goods to and from North Dakota — has been adequate. Along with railroads putting money into infrastructure and equipment, he said, low grain prices are prompting farmers to hold onto their grain rather than ship it immediately in hopes of getting a better payday.

The early river closure also means the seasonal layoffs at Upper River Services will start a few weeks early.

"We've been working feverishly all year," said Nelson. "It's early for them to be stopping, but they're also very tired."