Manawatu-Rangitikei Regional Council says there's a misconception that all farmers will need to make changes to the way they operate, once the One Plan comes into effect.
The plan which the Environment Court endorsed last week, tackles everything from water quality, nutrient run off and hill country erosion.
Council chairman Bruce Gordon said at this stage nothing is set in concrete and the Environment Court decision is an interim one.
He said there could be some 'toing and froing' between the council and the Environment Court before anything is finalised.
The plan then has to go before the council to be adopted and Mr Gordon said that's not likely to happen before the end of November.
Based on the council's current consents for irrigation, he said only about half the 900 dairy farmers will be affected by new nutrient management rules, along with four sheep and beef farms, 36 horticultural businesses and 18 cropping farms.