Farming groups have concerns about incoming freshwater farm plans - as new regulation seeks to reduce the impact farming has on the country's waterways.
The government released the long awaited freshwater farm plan timeframes earlier this month.
Farmers and growers will need a freshwater farm plan if they have 20 hectares or more in arable or pastoral use, five hectares or more in horticultural use, or 20 hectares in combined use.
Waikato and Southland farmers will be first in line - and have 18 months from 1 August to submit their freshwater farm plans.
But Beef and Lamb, Federated Farmers, DairyNZ and Deer Industry have sent a letter to the government calling for greater clarity on the timeframes and how existing regional or sector plans will be integrated with the new ones.
DairyNZ chair Jim van der Poel said many farmers already have good practices on farm for protecting waterways.
"The sector needs more detail on how existing regional, industry and sector-led plans will transition to regulated freshwater farm plans over reasonable timeframes," he said.
Federated Farmers president Wayne Langford said farmers need certainty on the rules so they were fair and practical as they were rolled out.
"We don't want to see excessive costs heaped onto farmers who are already under significant financial pressure, or unnecessary duplication of the work that's gone into existing industry or regional plans," Langford said.
"This needs to be a carefully managed process with a sensible transition."
The rollout period for the remaining regions will be outlined before the end of the year - and they will also have 18 months to comply.
The government has invested $22.5 million from the Essential Freshwater fund to help the industry develop the plans.