The Australian fertiliser supplier has been subject to grower criticism recently following its record profits at a time when farmers are paying record prices to fertilise the crops.

But a spokesman for Incitec Pivot says that urea, an internationally traded fertiliser, is subject to global supply and demand pressures.

"The recent spike followed the imposition of an additional 100pc export tax on fertilisers imposed by the Chinese Government, taking the total export tax to 135pc," the spokesman said.

"This has the immediate effect of virtually stopping urea exports from China, which represents 15pc of the amount of urea traded in the world.

"Taking this amount of product out of the market forced up global prices at a time of increasing fertiliser demand to meet the world food shortage."

Last year China exported almost six million tonnes of urea.