FRANKFURT -- K+S AG said late Wednesday that it bought U.S.-based Morton Salt from Dow Chemical Co. for $1.68 billion. The deal makes the German fertilizer company the world's biggest salt producer and caps months of speculation about its expansion strategy.

With Morton, famous for its logo showing a girl holding an umbrella, K+S plans to expand its salt business in North America and save on distribution costs between Brazil, Chile and North America. It expects the acquisition to add to earnings from 2010 onward.

The deal, subject to antitrust approval, is expected to close in mid-2009.

Dow sold Morton Salt to pay down a bridge loan used to acquire Morton's parent Rohm & Haas Co. (ROH)

Investors sent K+S shares up 11% in Frankfurt trading Thursday. Commerzbank said Morton offers a high-margin business that will increase K+S's salt capacity by 78% and more than double its salt sales.

The company doesn't plan any other major acquisitions in the salt business, Chief Executive Norbert Steiner told journalists Thursday. He added that K+S isn't planning any takeovers in the potash sector, and that it will continue examining greenfield projects instead.