NEW YORK (Reuters) - Potash miner Prospect Global Resources Inc (>> Prospect Global Resources Inc) won't open its first mine until at least 2015, but the American upstart is already upsetting the multibillion-dollar fertilizer industry where a few players control a crucial ingredient in the global food chain.

China, with an insatiable appetite for fertilizer to help feed its growing population, has long been dependent on Canpotex, the Canadian sales agency that supplies a third of the world's potash.

But in December, Canpotex reluctantly agreed to a six-month supply contract with China at $400 per tonne, a $70 per tonne discount from its last contract price and a steeper cut than expected.

China got the cheaper price partly because it used as leverage a separate 10-year agreement inked last October with Prospect.

While macroeconomic and local factors - from economic growth to weather and production issues - do influence the contracts, Prospect's arrival is chipping away at Canpotex's near-monopoly. The stakes are high in a business that typically has profit margins of around 50 percent.

"We think Prospect Global is the best potash investment opportunity in North America," said Steven Sugarman of COR Capital, a private equity firm that is the company's fifth-largest shareholder. "We like the geology, we like the location and the team they've put together."

With demand for corn and other commodities booming around the world - and potash prices up roughly 150 percent in the past decade - food and fertilizer are hot commodities. Prices have cooled recently, but are still at decade-highs.

BlackRock Inc (>> BlackRock, Inc.), Apollo Global Management LLC, and Ted Waitt, the co-founder of computer company Gateway, have taken note. They invested in Prospect - which went public last year - largely as a bet on a shake-up of the fertilizer industry.

Prospect is also helmed by some big names in the fertilizer industry. James Dietz, a Prospect board member, was Potash Corp's chief operating officer for more than 10 years, and Patrick Avery, Prospect's chief executive, previously ran Intrepid Potash Inc (>> Intrepid Potash, Inc.), which has mines in New Mexico.

Prospect finds itself an unwelcome new kid on the block, with rivals quick to cast doubt on its ability to hang tough amid the fertilizer industry's highs and lows.

"I don't take it seriously whatsoever," said Jim Prokopanko, chief executive of much-larger rival Mosaic Co (>> Mosaic Co), which owns Canada's Esterhazy, the world's largest potash mine.

"It'll be a small producer if it ever sees the light of day," he said in an interview.

That view is being tested as Canpotex, which is controlled by Mosaic, Potash Corp (>> Potash Corp./Saskatchewan Inc.) and Agrium Inc (>> Agrium Inc.), negotiates a supply deal with India. Most analysts expect that contract price to be lower than its predecessor.

SCRATCHING THE SURFACE

Prospect is the largest of three companies developing a potash reserve in Holbrook, Arizona, an arid, flat scruff of land in the state's northeast corner.

Passport Potash Inc (>> Passport Potash Inc) and privately held Hunt Consolidated Inc are exploring other parts of the reserve, though Prospect is farthest along in terms of development and funding.

Despite a BNSF train depot and several large tourist attractions - a meteorite exploded over Holbrook 100 years ago, attracting rock collectors - the town's unemployment rate is 13.5 percent. Mining promises to change that.

Arizona's potash deposit was quietly forgotten after a small geological expedition uncovered it in the 1960s. The deposit started to get more attention in 2008, as potash prices started to climb high enough to justify the more than $1 billion needed to develop a mine.

To exploit the land, Avery and other executives initially drew in BlackRock and other high-profile debt and equity investors. The group bought a publicly listed shell company to allow them to quickly become a listed company in June 2012 without going through the normal process of an initial public offering.

Several stock offerings since the firm became listed have diluted shares and pushed Prospect's stock down 40 percent in the past six months. More capital may be needed, a step that could further dent the share price.

"We are talking to other groups about more equity stakes to help us get started on drilling," Avery said.

Apollo is finalizing a $100 million debt financing deal, and BlackRock is the company's third-largest stockholder, with more than 5 million shares.

Top shareholders, many of whom invested before the firm went public, have said they believe the company is a long-term investment that will radically alter the fertilizer market.

If fully developed, Holbrook's fertilizer deposit would nearly double annual U.S. production of potash, one of the most-important nutrients that farmers apply to boost harvests.

Russia and Canada have the world's largest potash reserves, each with more than 3 billion tonnes compared with 130 million tonnes in the United States. The grade of Holbrook's potash deposit, at 11 percent to 13 percent, is roughly half the industry average.

But Prospect's production costs will be lower than those of its rivals because of milder weather and less digging required to reach the deposits, boosting margins.

Canpotex and Russian rivals operate primarily in colder climates and have potash reserves about 3,700 feet deep. Mosaic had to freeze an underground lake just to reach Saskatchewan's Esterhazy mine.

Prospect's Arizona potash deposit, by contrast, is roughly 1,000 feet deep in a year-round warm climate and closer to key West Coast ports than Canpotex facilities in Canada.

"A lot of these positive issues offset the lower grade reports," said Steven Rauzi of the Arizona Oil & Gas Conservation Commission, which oversees potash drilling in the state.

Prospect expects it will only cost about $112 per tonne to produce potash at its Arizona mine. The industry average is roughly $135 per tonne. That makes profit margins especially high, with market prices for potash above $400 per tonne.

China is taking 25 percent of Prospect's forecast 2 million tonnes of annual potash production, or 500,000 tonnes a year, an amount that will still make China the largest importer of American potash. The rest, if sold abroad, will only further roil Prospect's rivals when it hits the global market as competition intensifies to feed a growing population.

Canpotex will supply 1 million tonnes to China under a six-month supply contract that expires in June. But the fact that China was able to cut part of its dependence on Canadian potash showed that the world's second-largest economy is getting creative to feed its people.

For every $10 per tonne drop in the price of potash, Potash Corp's earnings slip by 7 cents per share, according to Credit Agricole.

That's not lost on Potash Corp analysts and investors, who peppered CEO Bill Doyle about Prospect in an earnings call last fall. Doyle played down the threat.

"If you look at the economics of the business today, there is no return on that investment," Doyle said of Prospect Global. "We don't pay much attention to it."

Prospect CEO Avery, however, points to the world's growing need for food, and adds that he is bullish on his company's potential - if for no other reason than the land on which it sits. "It is amazing," he said, "how well situated our plot of land is."

(Reporting By Ernest Scheyder; Editing by Patricia Kranz and Claudia Parsons)

By Ernest Scheyder