BHP Billiton's $39 billion hostile bid for Canada's Potash Corp has shone a spotlight on the mineral, a key ingredient in fertilizers.

Below is an overview of the current market for potash:

• Although there are a number of producers, international potash sales negotiations are handled by two main entities, one in Canada, the other serving Former Soviet Union (FSU) producers, which set annual contracts with main buyers India and China.

• In Canada sales are led by Canpotex, the world's largest exporter, owned by Saskatchewan producers, Agrium, Mosaic and Potash

• The other sales entity handles FSU exports, and is known as Belarussian Potash (BPC). It is the export agent of Uralkali and Belaruskali.

• The two marketing companies typically settle annual deals with big buyers in India and China. Other consumers, such as Brazil, tend to buy on a more ad-hoc basis.

• Analysts said moves are afoot to go to a quarterly system and eventually market clearing pricing, as has been the case in iron ore and coal. BHP was a big advocate of that.

• Annual demand for potash runs at around 50 million tons. In 2008-2009 demand fell towards 40 million tons in response to the collapse in world markets. Miners cut output, but stocks built up and the industry is still running below capacity, using up stockpiled material.

• Potash prices soared above $1,000 a ton during the commodity boom in 2007-08. It has since crashed to about $350 to $375 a ton levels, but is still well above its historical average.

• The last big greenfield expansion phase took place in the 1970s and it has taken since then for demand to catch up with capacity.

• Based on supply and demand forecasts, analysts said the market will remain well-balanced to 2014-2015 as brownfield expansions meet rising demand. After that conditions may tighten.