The fertiliser co-operative, Ravensdown, has lifted the price of superphosphate from $270 a tonne to $511 a tonne, while the other large co-operative, Ballance, has increased it from $270 to $480 a tonne.
But such is the volatility of prices, Ravensdown sales manager Ross Aimer said last night they were under review and could be lowered today in what was likely to be a short-term measure.
Both companies have warned prices were expected to rise again later in the year, with Ballance chief executive Larry Bilodeau saying the company is changing from six-monthly to quarterly price reviews so it can react to price changes more quickly.
"It ain't over. It's phenomenal. There's no sign of it holding up on anything now."
Mr Bilodeau said in an interview he had returned from an industry conference at which supply contracts and deals were arranged, and every part of the sector was talking of higher prices.
In part, that was being driven by international concerns over food supply forcing up input costs such as fertiliser.
But, equally, Mr Bilodeau said, there were signs of what he called "demand destruction", where input costs were so high it was undermining the viability of food production.
All fertiliser products were affected by the higher prices.
Urea was now selling for over $920 a tonne, DAP over $1400 and potash over $850.
Mr Bilodeau said the higher prices would affect all farmers, but particularly income-starved sheep and beef farmers.
Most farmers had anticipated rising prices and brought forward their fertiliser programmes.
Ravensdown had held their superphosphate prices from December through to May 31 to help them.
Mr Bilodeau said the price of sulphur had increased 400% in the past year, shipping costs had soared, while imported costs had doubled in a year and now represented 80% of total operating costs.
He has never seen the sector so volatile.
"The current global fertiliser environment is uncharted territory for all of us in that we have never seen the international market subjected to so much unpredictable change.
"Our raw material and shipping costs have risen significantly, far ahead of anticipated levels."
Companies now have to pay for ingredients in advance of selling them, which Mr Bilodeau said had a significant impact on cash flow and related interest costs.
