The winter grain crop in southern Queensland has been all but destroyed by flooding, costing the industry about $A400 million.
Agforce grains president Wayne Newton says any winter crops of wheat and chick peas that are not harvested, will most likely be ruined.
He told the ABC it was also likely to have a devastating impact on summer crops of sorghum and cotton.
"It's certainly going to be reduced yield from some of the crops," he said.
"Some crops are totally drowned and some have just been inundated.