* TSX ends down 0.62 percent at 11,274.20
* Potash Corp tumbles as much as 8 percent (Adds details)
TORONTO, Jan 28 (Reuters) - Toronto's main stock index ended lower on Thursday, weighed down by disappointing results and forecasts from market heavyweight Potash Corp (POT.TO).
The world's largest fertilizer producer led the index's decline all session, ending down 4.55 percent after C$111.26, after it reported earnings and a profit outlook well below market expectations. [ID:nN28196679]
Potash shares fell as much as 8 percent during the day, and despite the company's optimism that fertilizer demand would improve this year, it triggered a selloff in other fertilizer stocks.
Also dragging the index down was Canada's largest oil and gas company, Suncor Energy (SU.TO), off 1.04 percent at C$34.35, as the price of oil was fairly flat near $74 a barrel.
The Toronto Stock Exchange's S&P/TSX composite index .GSPTSE ended down 69.91 points, or 0.62 percent, at 11,274.20, though it managed to pare some losses after hitting its lowest level in more than two months earlier in the day.
Nine of the index's 10 main groups declined.
"Very rarely does it go one direction solidly, but we're still seeing some weakness. There's uncertainty," said Steve Ibel, institutional equities trader at Beacon Securities in Halifax, Nova Scotia.
"People are just reluctant to take on large positions. Right now, they're playing out month-end."
Soft quarterly results from big U.S. companies, ongoing concern about the uneven U.S. economic recovery, and fiscal worries in Greece have all contributed to negative investor sentiment. (Reporting by Ka Yan Ng; editing by Rob Wilson)