Prices have already been quoted at about $800 a tonne and rumours were rife that some merchants might even start rationing what is fast-becoming a precious resource. For farmers who got in early and bought fertiliser at a lesser cost before Christmas the prices were not so difficult to bear but this strategy was cold comfort for those yet to shell out on this year's cropping inputs.

NSW Farmers' Association, grains committee chairman, Mark Hoskinson said the price had gone up by at least $200 a tonne in the last month or so.

"Not only has the price gone up but the supply is tight," he said.

"Supply is so tight in fact that I have heard of some rationing going on."

Mr Hoskinson said both MAP and DAP, essential inputs for many cropping farmers, would be difficult to source until April.

And he said there was concern about the fickleness of prices for grain and poor returns.