MINNEAPOLIS (AP) - Icy conditions have forced an early end to shipping on the Upper Mississippi River.

The season officially closed Thursday with the towboat Mary K. Cavarra and its load of four barges heading south through Lock & Dam No. 2 at Hastings.

It's the earliest closing in the past 45 years.

The season 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.

Executive director Bob Zelenka of the Minnesota Grain and Feed Association says it's been a challenging year.

Zelenka says the river is the cheapest way of moving crops.

But the river's early closure means finding alternative ways to get those crops to New Orleans and foreign export markets.