BHP Billiton chief executive Marius Kloppers has unveiled long-term plans to spend up to $US10 billion ($10.4 billion) moving into fertilisers in an attempt to benefit from growing global food demand amid limited farming land.

Mr Kloppers, speaking in London last week, said BHP believed agricultural commodities were set to experience the same growth in prices as metals have and that the miner planned to capitalise on this by becoming a major player in Canadian potash, used to make fertiliser.

"We've got an absolutely world-class resource in potash in Canada, which was based on a view taken that the agricultural commodities would go in the same direction as the more metals-orientated minerals," Mr Kloppers told a London meeting of the Melbourne Mining Club.

"We bought the assets for not a lot of money and they have the real opportunity that, perhaps with upside, we could invest billions, perhaps $US10 billion over the next decades, and take them into a very, very significant producer of potash," he said, adding the asset had the potential to produce for several decades.

BHP last month agreed to spend $US282 million buying out its 25 per cent partner in potash ground in Saskatchewan.

The ground and development plans are at an early stage, with BHP releases and presentations not yet giving the project a name.

According to plans laid out early last year, the miner is carrying out a concept plan that it intends to follow later this year with a prefeasibility study that will not be finished until 2010.

BHP chief commercial officer Alberto Calderon summarised the company's interest in fertiliser products last year in a Sydney presentation.

"The acreage available in terms of (farming) land per person is going down, the world's population is going up," Mr Calderon said.

Potash is one of three main fertilisers in the word, along with phosphate and ammonium nitrate, and BHP said it was used by more developed countries, with potash use increasing as median incomes went up.

This puts demand from China and India in the same field as metals growth, with BHP and Rio Tinto both tending to highlight demand expected as middle classes grow in those countries.

Mr Calderon said BHP had no regrets about selling its phosphate business to Incitec Pivot in 2006 because potash had a better industry structure than phosphate.

"It is high-capital, it's high-technology and it's limited basins," he said. "That in turn leads to good industry structure and high margins" of between 40 per cent and 60 per cent.

Mr Calderon said about six players controlled three-quarters of the world's production out of two basins, in Canada and Russia, and barriers to entry were high.

"You are talking about $US1.5 billion and eight years to construct 2 million tonnes of capacity, which is not a big" operation, he said.

"You're talking about a complex, expensive endeavour which in the end has a high probability of high margins and that's exactly what we like."