Alarm bells are ringing among farm advisors on Overseer’s future and what a possible replacement could be if the nutrient management programme is ditched by the Government.
The recently published review on Overseer has challenged aspects of the software’s ability to model nitrogen flows, dismissing the 20-plus years old programme as providing nothing more than a “coarse” understanding of a farm’s nutrient losses.
But the review has farm consultants across the country concerned the model has been assessed for purposes it was never intended for and any rejection of it as a nutrient measuring tool leaves the door open for top-down regulatory controls.
Canterbury consultant Charlotte Glass says Overseer was never developed to give an absolute real-time number on nutrient losses, as the review panel suggests it should.
“Overseer is a beautiful scenario tool for comparing different farming systems’ effects on a property. It is an excellent effects-based process model that enables us to innovate with techniques, as we learn more on nutrient losses. However, it should never have been used is as an absolute number linked to compliance,” Glass says.
Now up to its seventh version, Overseer has over time incorporated more science, including most lately the effect of deeper-rooted grasses like plantain in absorbing nitrogen.
The panel lambasted Overseer for a lack of on-surface nitrogen movement, soil profile modelling and for using average climate data, versus real-time.
But Glass was optimistic over time better understanding of hydrology and nitrates would be incorporated into it, as other factors have in the past.
Rob Macnab, Waikato farm consultant and fellow board member with Glass on the NZ Institute of Primary Industry Management, says his concern was the Government picked up on the panel’s criticisms and the door opened to greater top-down regulatory rules.
He says the panel’s extensive criticisms have blindsided the industry on where it should head with nutrient modelling.
“We had expected there to be some flaws noted, but to come back and say ‘not fit for purpose’ and to only give it a year to find an alternative?” Macnab questioned.
So far water quality regulations have focused on outcomes, leaving the industry to develop and innovate with new methods to meet the required outcomes.
The one key exception to date is the 190kg of nitrogen a hectare a year limit imposed this year.
The Government has undertaken to continue funding Overseer in its current form for another year as alternatives are investigated.
“Going to absolute values shuts down the path to looking at innovative approaches to dealing with nutrients,” he asked.
He acknowledged Overseer had sometimes made things more difficult than needed to be in the past by delaying the incorporation of new science into its modelling algorithms.
“But that was probably down to a resource issue and it has responded better over time. Overseer could also have been more upfront in what was or was not included and it was affecting modelling,” he said.
Macnab says if Overseer was tossed out, it left questions over training courses and accreditation for the software unanswered.
“And then there are regional councils. They are left high and dry where it has been used as a tool for incorporating nitrogen limits. There have been challenges, including by Dr Doug Edmeades on its suitability for regulation, which were tossed out by courts,” he said.
He says the immediate impact on farmers was very real. He had clients in Western Lake Taupō district required to furnish their nitrogen discharge levels and had to rely on Overseer to do it.
“This is highly impactful upon their business. And virtually every irrigation company in the country has set their N limits on Overseer – are these to become null and void?” he asked.
Rotorua-based Perrin Ag director Lee Matheson says any uncertainty over Overseer’s future only provided farmers with less reason to comply, preferring to wait to see what alternative tools are presented.
His business covers Rotorua Lakes and Taupō catchments, two iconic natural regions where nutrient loss has been determined by Overseer for the past 10-15 years.
Lake Taupō includes a globally unique nitrogen trading programme, with allowances based on Overseer calculations in a scheme that has won OECD recognition for its success.
His company has been involved from an early stage advising NZ regional councils on how Overseer should be used and cautioned them about how they used it in regulation.
Matheson shares Glass and Macnab’s concerns about ‘where next’ for Overseer.
In its review response, the Government has outlined some options, including a next generation of Overseer to address issues, a new risk index tool using elements of Overseer, or a completely new approach using a new nutrient loss model.
“You have to be able to come up with a viable alternative,” Matheson said.
“A lot of alternatives I have seen still rely upon Overseer as the measurement tool, they are just using a different model to allocate the resource.”
He cautioned farmers criticising Overseer to be careful that if they pushed for Overseer to be dropped, whatever replaces it has to be better.
“Getting rid of it does not get anyone off the hook,” he said.
