The first minister is under pressure to step in and help overturn a controversial tractor ban on the new Aberdeen bypass.
Last month, farmers demanded transport chiefs scrap plans which would mean they would be unable to use the AWPR.
Transport Scotland has given the new £750million scheme a special designation which limits the distance farm traffic can travel, which effectively prohibits the agrucultural vehicles from the road.
The National Farmers’ Union Scotland has demanded the organisation overturns its decision, claiming farmers have borne the brunt of the major disruption caused by the project and should be allowed to take advantage of the new route.
Nicola Sturgeon attended the Turriff Show yesterday, the second-largest summer agricultural event after the Royal Highland Show, amid calls for her to back the union.
North-east MSP Peter Chapman said it was an “ideal opportunity” for the first minister to show she backed the local farmers.
He said: “My view is that this road is not a motorway, it is a dual carriageway and therefore tractors should be permitted to travel along the route.
“If not, we will be forcing agricultural vehicles through the middle of Aberdeen, which does nothing for efficiency, congestion or our greenhouse gas emissions.
“I have written to Transport Scotland, but I have yet to receive a response.”
Union bosses have criticised the policy as it means farmers will be unable to transport livestock from Ellon to Portlethen using a tractor.
The NFUS also argued the decision flew in the face of Scottish Government targets for reducing carbon emissions.
A Transport Scotland spokesman said: “The consequences of a special road designation for AWPR were considered at a public local inquiry (PLI) in 2008. The road has been progressed on the basis of the Orders presented at the PLI.
“As strategic traffic will transfer from the existing road network to the AWPR, we expect to see significant journey time savings on local roads, generating significant benefits for agricultural use.”
A Transport Scotland spokesman said the organisation would endeavour to reply to Mr Chapman at the “earliest opportunity”.
He added: “The consequences of a special road designation for AWPR were considered at a public local inquiry (PLI) in 2008. The road has been progressed on the basis of the Orders presented at the PLI.
“As strategic traffic will transfer from the existing road network to the AWPR, we expect to see significant journey time savings on local roads, generating significant benefits for agricultural use.”