Demonstrators rip up maize in farmer John Cottle's field
Approximately 40 protesters broke into the field and began ripping up the crop of GM fodder maize.
The protesters had ignored a large police presence and a force helicopter and jumped over barriers to get into the field in Sealand, Flintshire.
The injured man, who is not believed to have been seriously hurt, was taken by ambulance to the Countess of Chester Hospital.
Farmer John Cottle - who had refused requests by 150 anti-GM campaigners to scrap the fodder maize experiment - said he was disappointed the protesters had broken into his field.
The protesters had been holding an all-day rally in the latest bid to end Wales's only GM trial.
The rally followed a meeting of the GM Free Wales Campaign group at Connah's Quay Civic Hall, which was attended by anti-GM writer George Monbiot.
The event, part of a GM 'Action Day,' was chaired by Plaid Cymru's Euro MP Jill Evans.
Professor Howard Slater, a former professor of microbiology at the University of Wales and a campaigner for crop biotechnology, said attempts to halt the Sealand trials would undermine Wales's reputation as a world-class technology centre.
But even with the petition demonstrators are to hand to Mr Cottle, it is unlikely he will bow to the demands.
Mr Cottle refused a call from Rural Affairs Minister Carwyn Jones to abandon the trials on the English border after lobbying forced trials in Pembrokeshire to be scrapped in May.
Jill Evans said: "A strong alliance is developing in Wales of groups committed to a GM-free Wales."
Separate trials at Castle Cenlas Farm in Pembrokeshire were abandoned when farmer and former MP Tony Marlow accused the government of sending misleading messages over genetically-modified food.
The organic farmers are concerned about cross-contamination but Mr Cottle remains convinced about the benefits of the trials.