Corn fields shrivelled and soyabeans withered in the drought-hit US last summer. But the resulting rally in food commodities meant that 2012 was a good year for agribusinesses from trading houses to tractor makers.

Since the 2007-08 food crisis, when the price of potash, a key crop nutrient, jumped 10-fold to almost $1,000 a tonne on the spot market, fertiliser commodities have been seen as a way to ride the boom in agricultural markets. Miners such as BHP Billiton sought potash assets, while new entrants have piled into the potash market.

But investors in fertiliser groups suffered a disappointing 2012. The market, despite a tumble during the 2008-09 financial crisis, has stayed at historically high levels, spurring China and India, the main buyers of fertilisers, to seek alternatives to potash. They sat on the sidelines during the latter half of last year.