(Compares results with estimates; adds forecast, merger details, share move and background)
Jan 26 (Reuters) - Potash Corp of Saskatchewan Inc POT.TO POT.N reported a lower-than-expected quarterly profit, hurt by weak prices, but said it expected potash sales volumes to rise in 2017.
U.S.-listed shares of the company, which reported a 21.9 percent drop in fourth-quarter sales, were down 6 percent in premarket trading on Thursday.
The company forecast 2017 potash sales volumes to rise to 8.7 million-9.4 million tonnes from 8.6 million in 2016.
Potash prices are hovering around their lowest in nearly a decade, under pressure from bloated capacity and weakening farm incomes, but they have edged higher since summer.
Potash Corp and rival Agrium Inc AGU.TO announced in September a plan to merge, combining Potash Corp's fertilizer capacity, the world's largest, and Agrium's farm retail network, North America's biggest.
Agrium's chief executive said on Wednesday that the merger had received regulatory approval from Russia and Brazil but was awaiting approval from the United States, Canada, China and India. regulatory review and integration processes are advancing, and we expect the transaction will close mid-2017," Potash Corp CEO Jochen Tilk said in a statement on Thursday.
The fertilizer company said it expected earnings of 35 cents to 55 cents per share in 2017, including merger-related costs of 5 cents per share.
Potash Corp also said that it determined in the quarter that the carrying value of certain assets should be assessed for potential impairment.
The assessment is ongoing, with a particular focus on phosphate, Potash Corp said, adding that the company expected to complete the process no later than late February.
The company's net earnings plunged to $59 million, or 7 cents per share, in the fourth quarter ended Dec. 31, from $201 million, or 24 cents per share, a year earlier. on average had expected earnings of 9 cents per share, according to Thomson Reuters I/B/E/S.
The company's sales fell to $1.06 billion from $1.35 billion.