Fertiliser prices have soared on the back of a softening Australian dollar and increasing demand.
The price for phosphate fertiliser in the United States fell $100 in the second half of last year, leading to a drop in prices in Australia.
But a $40 a tonne increase in the US in December has led Australian farmers paying up to $200 a tonne more for DAP.
Victorian Farmers Federation grains president Brett Hosking says it's unclear why prices have increased so dramatically.
"We need to make sure that any input prices that come into our country, or into our industry, are competitive and are adjusted fairly and according to what's realistic and fair for them to be charging," he said.
"You know, it's pretty tough for growers out there and we need to make sure that our input prices aren't driving people out of business."
Incitec-Pivot is a fertiliser manufacturer and marketer.
The company's chief operating officer James Whiteside says Australian prices are subject to global factors.
"The first thing farmers need to realise is that the price they pay for fertiliser in Australia is absolutely reflective of what's happening in international markets," he said.
"The majority of fertiliser is imported... so whatever happens overseas, given that the market is intensively competitive, flows through to prices that farmers see pretty much straight away."
Mr Whiteside says freight costs have increased since harvest.
He says he expects most farmers' fertiliser bills will increase $100 to $150 a tonne.
Rabobank senior analyst Michael Harvey says he's expecting prices to level out in the months ahead
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