The organisation would need to "contract in expertise not available in-house to develop the planning, science and economic aspects of our alternative plan", according to its website.
That figure has now been doubled, to $100,000.
Former Rotorua/Taupo Federated Farmers president Neil Heather said the organisation was still waiting for a date for a pre-hearing conference, which was likely to be scheduled for the next couple of weeks.
"We hope to then have an idea of the likely timeframes for evidence exchange and hearing.
"We have been very impressed with the community support and the generosity from farmers. We still require donations as participating in this process is extremely expensive.
"As a result of the positions the various parties are taking, we have had to double our funding target."
Heather said Federated Farmers was concerned that if it did not participate, "Plan Change 10 may be changed in a way that is even more disastrous for farmers".
"It is very frustrating that farmers are effectively being asked to pay for this hearing three times over – through their regional rates, district rates and funding our participation."
The Bay of Plenty Regional Council declined to confirm if the case was heading to court.
A spokeswoman said 140 landowners had engaged with the Land Use Advice and Support Service, which assists landowners affected by Plan Change 10 to understand their obligations and, where necessary, work with an independent Land Use Advisor to develop a Nutrient Management Plan.
"Regional Council encourages rural landowners in the Lake Rotorua Catchment who have not yet engaged with the Advice and Support service to call (07) 921 3377 to find out how Plan Change 10 affects them."