Horticulture New Zealand is backing the submission of new evidence to the Environment Court on the much debated Manawatu-Whanganui regional plan.
The horticulture body is one of a number of farmer and grower organisations that strongly oppose the court's ruling on the One Plan released earlier this year.
The court has backed the council's proposal to impose nutrient caps on intensive farming and vegetable-growing operations to protect waterways from nitrogen pollution.
Farmers and growers say it will threaten their livelihoods.
The Environmental Court will consider further evidence before making a final ruling.
Hort NZ, Federated Farmers, Fonterra and Ravensdown will support the submission of a Landcare Research Institute report which indicates the economic cost of of the One Plan would be far greater than the council has calculated.
One scenario indicates farm profits could fall by 22 - 43% as a result of land use changes needed to meet water quality targets in the plan.
Hort NZ chief executive Peter Silcock says it disagrees with the Regional Council view that the Landcare Report is irrelevant, as he says while it is not specific to the One Plan it is indicative of what might happen under the regional plan.
The Environment Court will hear further submissions in February-March next year, before releasing a final decision.