So what is the market to make of the assertion by BHP managing director Marius Kloppers that the group's Jansen potash project in Canada is "very exciting". Potash? Is BHP out to excite the market by becoming the world's biggest miner and farm-product group?

Apparently so, judging by comments in London by Mr Kloppers. In the London interview, which followed BHP's recent annual meeting, he made clear that an expansion into potash - the common name for fertiliser forms of the element potassium - was an aim of the group.

"Our focus is on our Jansen [potash] project [in Canada]. We spent $US100 million on it last year, and we will spend more this year," Mr Kloppers said. "And that is really the project we would like to get into production as soon as possible. We think it is very exciting."

The presence of potash in BHP' s portfolio of development opportunities harks back to the reign of former managing director Chip Goodyear. The financial crisis has since intervened, but the original rationale of Mr Goodyear, and now Mr Kloppers, in backing the potash push is the same. It's all about feeding the world. And when you are talking about a bulk commodity with (projected) high-growth consumption rates, a high cost of entry and where underground mining expertise is an advantage, potash just might fit the bill.

Since the financial crisis, much of the world's potash production has been shut down. The price, nevertheless, is doing OK thanks to concentrated ownership, which allows for shifts in demand to be quickly matched by production. The price is down since last year when it approached $US1000 a tonne. But at $US450-$US500, it is still well above long-term averages.

The shutdown in production and lower prices reflect the global farmers' choice to cut expenditure on the crop nutrient when times are tough. But with rising living standards in China, India and Brazil - all of which have potassium-deficient soils - the world can afford to "under-fertilise" for only so long.