Mining giant BHP Billiton (NYSE:BHP) has constructed a solid foundation that spans a core group of natural resources: iron ore, petroleum, copper, and coal. Each of these "pillars" provides a means for meeting the diverse needs of a developed and developing world. It is now adding a fifth pillar -- potash.

BHP has long been interested in harnessing this important soil nutrient, and even attempted to jump-start its entrance into the industry by trying to buy PotashCorp (NYSE:POT) in 2010, though it was ultimately thwarted by the Canadian government. Instead it bought the Jansen deposit in Saskatchewan, which, when finally operational, could become one of the world's largest potash mines.

Jansen mine shaft. Source: BHP Billiton.

So far BHP has spent more than $1 billion on the project and this past summer approved the expenditure of $2.6 billion over the next few years, further developing it with mine shafts expected to be completed by 2016 and surface facilities coming online in 2017. Even as the miner's capital and exploration budget declines elsewhere, BHP is pouring more resources into potash generally and Jansen specifically, though at 5% of its capital budget it is still a modest outlay, which recognizes the upheaval the industry is going through.

The potash market was thrown into tumult this year with the breakup of the Belarusian potash cartel that promised to pressure pricing on the commodity. Because potash isn't traded on public markets like other commodities, prices are set by producers negotiating with their customers. The prospects for a price war to break out as each producer negotiated for greater market share caused the shares of all producers to tumble. They're only just now getting their sea legs again.

Investors may have been worried about BHP's decision to go headlong into this project at such a sensitive time, but no doubt looking at the global growth of population, income, and agricultural needs, expecting demand for the fertilizer component to grow is not unreasonable. BHP says demand could widen at an annual rate of as much as 3% for the next 17 years, creating "compelling long-term fundamentals of the potash industry."

I agree, and though I find PotashCorp to be a particularly attractive major player at the moment, BHP's Jansen mine will be a force to be reckoned with, perhaps as soon as 2020, when the miner anticipates it will begin full-scale operations.

BHP holds exploration rights to more than 14,500 square kilometers in the Saskatchewan potash basin of Canada, which is home to half the world's potash deposits. Although still in the feasibility stage, Jansen has an expected output of 8 million tonnes a year for the estimated 70-year life of the mine. The miner's made rumblings about seeking out a partner for the project, which could prove an interesting and timely investment for PotashCorp, or the other two big North American players, Agrium and Mosaic.

When BHP made its bid for PotashCorp several years ago, it set itself up for failure by saying it would withdraw from the Canpotex marketing consortium and market the nutrient on its own, just as it does with its other commodities (which is why the Canadian government shot the deal down). One of the three members might be willing to finance further development of the project in exchange for BHP's agreeing to become part of the marketing group and help keep pricing from collapsing further.

With a thaw under way overseas in the Belarusian drama, an argument can be made that a floor has been reached for potash prices. With a new greenfield site coming online within the next decade, it could prove a special asset for all involved.

BHP Billiton is in the process of constructing a fifth pillar that could one day rival or even exceed in value the other pillars holding up its vast natural resources portfolio.