Farmers are considering taking legal action after a landmark water protection ruling in Palmerston North.
The Environment Court has approved Horizon Regional Council's plan to set limits on how much fertiliser and nutrients farmers can use on their land.
The limit is designed to stop nutrients leaching into waterways - killing plants and marine life.
However, farmers say the council has been given the power to tell them how to run their farms.
"I'm absolutely flabbergasted at it," said dry stock farmer Hew Dalrymple.
"If you can't grow those things because of a high nutrient requirement, you are going to have to look at other product."
Federated Farmers says lawyers are looking into whether legal action is possible.
"It raises questions about how those farmers will cope, how can they even monitor it, how can they form rules around it," said vice-chairperson Andrew Hoggard.
The decision could have far-reaching implications beyond the waterways in the Manawatu-Raingtikei region.
Horizon says other councils are watching their progress closely and they have already been approached by the Waikato District Council.
Chairman Bruce Gordonadmits it will cost more for farmers to upgrade their effluent systems but the council believes it will be affordable.
"We're also going to be working through the process so farmers and industry don't need to be scared at this stage and I like to think that if targets can't be met there'll be amendments in the future."
Gordon said the community has said the level of degradation in New Zealand waterways is not acceptable.