"More than 150 protesters joined a rally and march to urge Michael Wilkin to abandon plans for the tests in Preston, near Hedon.
Some of the demonstrators hammered home their message by symbolically planting organic potatoes near the GM potato trial site.
Campaigners listened to anti-GM speakers at the rally in Preston Road Community Centre, east Hull.
Then marchers carried placards and banners amid a strong police presence to ensure the nationally publicised demonstration passed off peacefully.
Organic grower Dr Gwen Egginton, one of the speakers, said: "We are appealing to the farmer to ditch the trial because it is something nobody wants except the big biotech firms."
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