Those in the industry are expecting dairy farmers will need to retire at least 20 per cent of their land to meet nitrogen leaching criteria.
And while Andrew Day, a Pahiatua sheep and beef farmer and supporter of the One Plan in its entirety, is optimistic that in time Horizons will have a workable plan that still protects the environment, he sees trouble ahead.
"In the short term, Horizons are in a hell of an ugly bind," he told the Dannevirke News.
"I know the council and environment groups have been putting their heads together for a workable solution, but not all farming businesses can survive a shift to being responsible for their pollution.
"Horizons got themselves into a real jam because they were so generous with the consents in the Mangatinoka catchment, in southern Tararua, and basically they've given a massive transference of wealth from farmers in the upper Manawatu catchment [Woodville north to Norsewood], because of the consents issued down south.
"Any wriggle room there may have been in the One Plan has been gifted to those Mangatinoka consents."
Mr Day said he was concerned for dairy farmers currently operating without a consent.
"They are farming under the goodwill of people not taking a legal challenge against them.
"Really, this is a legally challenging gun at regional councillors' heads."
Mr Day was waiting on the outcome of general election to see if National and New Zealand First could govern by themselves.
"There's a full range of solutions up in the air at the moment and, like Neil Filer, the president of Tararua Federated Farmers, I worry about the new-entry farmers who thought they'd done their due diligence when purchasing their properties.
"They've got no money to come and go on to meet tough One Plan requirements."