UPDATE 4-Potash Corp sees opportunities amid the crisis

* Potash Corp CEO sees acquisitions as market slumps

* Boosts stake in Israel Chemicals to 12 percent

* Beats quarterly estimates; shares up 3 pct (Adds details from CEO interview; in U.S. dollars unless note)

By Roberta Rampton and Scott Anderson

WINNIPEG, Manitoba, Oct 23 (Reuters) - Potash Corp of Saskatchewan (POT.TO) (POT.N) feels the sting of the global financial crisis but believes growing world food demand should keep it "sheltered" from the worst of the economic storm.

Potash Corp, the world's largest fertilizer maker, wants to use the downturn to "buy cheap" and expand, Chief Executive Bill Doyle said.

"Certain competitors of ours may find themselves to be in a leveraged position unexpectedly, and there may be opportunity for us to take advantage of that," Doyle told analysts.

"When you have these type of times, and people get themselves in trouble, it's Darwin's theory, proved," he said.

Potash Corp spent about $115 million overnight to boost its stake in Israel Chemicals (ICL.TA) to 12 percent from 10.3 percent, after being approached by an investor looking to cash out, Doyle said in an interview, declining to name the seller.

"To be able to buy it at a 60 percent discount to what we think the value is, we think that's good work," he said.

Potash shares rose 3 percent to $85.99 on the Toronto Stock Exchange on Thursday after the company said it earned more in the third quarter than it did in all of 2007, its record year.

Profits climbed five-fold to $1.24 billion, or $3.93 per share, up from $243.1 million, or 75 cents, a year earlier.

Analysts had expected a profit of $3.52 a share, according to Reuters Estimates.

Potash shares peaked in June as concerns about shrinking world grain stocks boosted demand for fertilizer, and prices for nutrients soared because of supply shortages.

But the shares have since dropped 65 percent as hedge funds and other investors soured on commodities and became concerned farmers would cut back on fertilizer use.

Doyle said the stock is undervalued because of fear, not fundamentals. He admitted the plunge has made Potash Corp itself look like an attractive takeover target.