A group of land owners says its sceptical about whether the Overseer computer programme is the best tool to manage the clean-up of Lake Rotorua.
Bay of Plenty regional council is using Overseer software to measure and regulate nitrogen leaching from farms as part of the Rotorua Te Arawa Lakes programme.
The programme is still under consultation, but the group Protect Rotorua says the council has shifted the nitrogen loss goal posts by updating its version of Overseer.
The group's spokesperson, Rotorua deer farmer Sharon Love, said the original benchmarks were done in Overseer 5 but the current version is 6.2 although that may have changed again.
"So with the version of Overseer changing, it's a moving target for everybody, so nobody's actually sure what their benchmark is or what the current leeching is. Overseer isn't a tool that was designed to measure pollutants, it was a tool to work out how much fertiliser you needed. So it's a pretty hard ask for it to turn into a measurement tool for allocating nitrogen to farms.
"As a farmer who doesn't use a consultant and who doesn't use Overseer and doesn't use a fertiliser rep, you know you're forced to go to a consultant to let them tell you whether you are doing the right or wrong thing on your farm regarding nitrogen into the lake.
"Farmers, in general, want to look after their land. With the right education and goals in mind, there's no reason why everybody can't do a little bit less on their land to end up with a better lake, but it's got to be fair and in an environment that's fair," she said.
The owners of Overseer assured Parliament last month they have a plan to address problems with the software to make it a more effective regulatory tool.