Chief agronomist William Lloyd at Cooma Rural Supplies said that a 40-kilogram bag of high analysis fertiliser used for grain and crop establishment used to cost farmers around $30 which now cost farmers around $70 a bag or close to $600 a ton.

"That's the most expensive stuff, there are cheaper ones around which are used for top-dressing but they've definitely increased," Mr Lloyd said.

An average farm could use anywhere from 50-300 tons of fertiliser a year Mr Lloyd said adding considerably to the cost of production for local farmers.

Mr Lloyd said the increase has been fuelled partly by increases in demand caused by population growth and the need to increase world food production.

The added expense to farmers in addition to freight and fuel increases means they will have to raise their prices to meet expenses.

Mr Lloyd said many farmers on the Monaro weren't in a position to do that anyway.

Another looming factor is rainfall if there isn't substantial fall before winter there is a very real chance the fertiliser will be ineffective.

"Farmers are faced with that extra burden, and run a real risk of the fertiliser not having any benefit," he said.

Mr Lloyd said farmers could reduce their fertiliser costs through better soil management and more accurate testing which would see fertiliser only being used where and when it was needed.