The NSW government has been urged to listen to the concerns of farmers after assertions from the premier and a senior minister that mining is more important to the state than farming.

NSW Primary Industries Minister Ian Macdonald on Friday supported Premier Nathan Rees' statement that mining was more economically valuable than farming.

Mr Rees' comments came after farmers demonstrated outside NSW Parliament House on Thursday to stress their concern that agricultural land was being "sacrificed" to mining.

The Mining Amendment Bill, which would ban any new mining on areas defined as prime agricultural land, was also defeated in parliament on Thursday.

"Ultimately mines generate many, many more jobs than agricultural production," Mr Rees said.

Mr Macdonald told reporters on Friday that while 100,000 NSW people were employed in farming, much of the work was part-time and seasonal.

He said the work created $5.6 billion in terms of exports.

But he said the mining sector, which employed about 75,000 people directly or indirectly, contributed $12.4 billion in exports last year.

"You have to remember the mining communities really contribute significantly to those localities where there is significant mining," he said.

The comments follow a long-running battle involving farmers in the Liverpool plains in northern NSW, who have been lobbying state and federal politicians to stop BHP Billiton from mining coal in the area.

Nationals leader Warren Truss criticised the NSW government's stance.

A spokesman for Mr Truss told AAP the statements "sound like they're coming from people more concerned about mining royalties than food security".

Mining had built the nation, however "you can't eat coal," the spokesman said.

"The NSW government would do well to listen to the concerns of people and try and work out a reasonable compromise rather than shooting the messenger," the spokesman said.

NSW Farmers Association president Jock Laurie said the issue had been put firmly on the agenda and it was clear the bill had a lot of support despite its defeat.

"We need to ensure that the voice of agriculture is heard," Mr Laurie said in a statement.

"Prime agricultural land and its water resources must be retained and the nation's agricultural resources safeguarded."