Irish author JP Donleavy posted a sign declaring his cattle farm in Mullingar to be Ireland's first GM-free zone yesterday.
Similar announcements from other farmers are expected to follow as a precautionary step against the contamination of their produce with genetically-modified animal feed, seeds, crops and livestock.
Mr Donleavy's interest in genetically-modified food developed after he discovered that a new grass he believed was not native to Ireland was taking over his fields and contaminating the grass which his organic herd was eating.
He told The Irish Times yesterday that while GM food had improved farming in the US, resulting in increased food production, it was more serious than people realised.
GM Free Ireland, the organisation which is campaigning against genetically-modified foods in this country, claims that "Ireland's GM policy was formulated without the due public consultation process required by EU Directive 2001/18/EC".
GM farming had been legalised in the UK and if farmers in Northern Ireland adopted genetically-modified crops this might lead to irreversible contamination of organic crops in the Republic, they say.
Yesterday's announcement will be followed on Monday by a GM-free workshop in Temple Bar, Dublin. Speakers will include Mr Adrian Bebb, a leading European expert on designating areas to be GM-free, Pavitra Chalam from the GM-free movement in India and people connected with the Irish food industry. The benefits of keeping Ireland free of genetically-modified foods will be discussed..
EU laws on the labelling of GM produce came into effect across Europe on Sunday and have been welcomed by environmental and consumer groups.