For the best part of a decade the potash market struggled with overcapacity and low prices. But as sanctions throttle supplies of the fertiliser from Russia and Belarus, which account for almost 40 per cent of global supply, buyers are scrambling for cargoes and warnings are growing of a global food crisis.

In Brazil, an agricultural powerhouse, prices have surged 185 per cent over the past year hitting records above $1,100 a tonne, according to commodities consultancy CRU. In Europe they are up 240 per cent to €875 a tonne.

Mined from underground deposits formed during the evaporation of ancient seabeds, potash is a mineral rich in water-soluble potassium, one of the three essential nutrients required for crop growth. Crucial to the production of food staples such as corn, soy, rice and wheat, a sudden plunge in supply threatens to devastate global crop yields.