Farm fields have taken on a strong political bias in every corner of Scotland in the past two weeks of campaigning before the independence referendum on 18 September.

Hundreds of fields along the edges of motorways, major routes and even single-track roads now sport huge signs urging passing motorists to vote Yes or No, as both sides in the debate appeal to farmers to support their cause.

Stacks of straw bales bearing slogans have also been built up beside roadside fences and farmers have used combines to carve out their political allegiances in sloping crops of grain.

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In the fields, the “No thanks” signs predominate and give a strong indication of the overall allegiance of a Scottish farming industry that has become strongly engaged in the political debate.

NFU Scotland president Nigel Miller, who emphasised his political neutrality, said the huge turnout at the union’s series of regional meetings on independence proved the industry regarded the referendum as a big deal.

“More than 2,000 members turned up over the summer and filled marts. I can’t think of another issue that would have resulted in such a turnout,” he said.

“Farmers possibly feel there’s more at stake for their livelihoods than other sectors of society because of the European money that supports the industry and the significance of markets for produce south of the border. Many cereals and potato growers see their produce as UK commodities and use English research so they want to know all the facts before deciding.

“And there are quite a number of Conservative voters in the farming community so we probably shouldn’t be surprised to see so many No signs.”

Many farmers, including Better Together campaigner Peter Chapman, from Aberdeenshire, have had signs destroyed or defaced as soon as they have been erected. And rural affairs minister Richard Lochhead, who is MSP for Moray, said Yes farm signs were quickly ripped down in his constituency.

“It would appear there’s a team going round with that sole purpose,” he said.

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Support for the Yes campaign took an unusual form on Innes MacPherson’s farm at Mulben Mains near Keith. He hammered in two posts to support a giant No sign only to have it trampled a few hours later by his Simmental bull. “He was bred in Ireland. And clearly a Yes supporter,” he said. “It’s very annoying but it has certainly entertained the neighbours.”