Friday, March 29, 2024

Overseer defends tool’s ability

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The head of OverseerFM, the farm nutrient management tool, has been forced to defend the software’s validity after a government technical review panel criticised its ability to capture all nitrogen losses and its lack of real-time data. Since its inception over 15 years ago, Overseer has evolved from a fertiliser nutrient management programme to a regulatory tool to establish nutrient limits in regional council catchments.
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The head of OverseerFM, the farm nutrient management tool, has been forced to defend the software’s validity after a government technical review panel criticised its ability to capture all nitrogen losses and its lack of real-time data.

Since its inception over 15 years ago, Overseer has evolved from a fertiliser nutrient management programme to a regulatory tool to establish nutrient limits in regional council catchments.

It played an instrumental part in establishing nitrogen loss limits in the Lake Taupō catchment, through the Taupō nitrogen management programme established in the early 2000s.

But the review panel has concluded in its current form, it would not have confidence in Overseer’s estimates for nitrogen losses from farms as a standalone measuring tool.

Concerns extended to its treatment of soil as a single homogenous layer and an inability to adequately capture overland flow of nitrogen.

It also had concerns over the use of climate data averaged over 30 years, rather than actual climate data, meaning weather events with high nutrient loss risk were not adequately accounted for.

Acknowledging the programme was not perfect, Overseer chief executive Dr Caroline Read says its strength has been in providing a common platform for councils, farmers, growers and catchment groups to engage on nutrient management.

Read took issue with the panel’s concerns that it did not offer a measure of real-time nutrient losses.

“Overseer has always been clear it was never designed for this purpose. The technical review panel saw this as a weakness but to date, expert user feedback has been that Overseer’s approach of estimating cumulative annual nutrient losses is suitable to support the sort of scenario testing, which is of greatest value to users,” Read said.

She did not agree with the panel’s suggestion that only a precision measuring tool working in real-time would deliver effective freshwater management for New Zealand.

“We understand a tool with the precision preferred by the panel is only one of the options that will be considered by government in the future,” she said.

She was also concerned the panel’s findings on OverseerFM’s results were not sufficiently supported by testing.

“We are concerned the panel findings are contrary to the results of previous scientific reviews and over 15 years of use by experts,” she said.

Beef + Lamb NZ chief executive Sam McIvor acknowledged questions had been raised about Overseer’s suitability as a tool for regulatory purposes.

“However, there is no doubt OverseerFM has been and still is a valuable farm management tool. But with any tool, there is always room for improvement and we would be supportive of any further investment to strengthen OverseerFM,” McIvor said.

He noted the review had particularly identified the “nitrogen” aspects of Overseer’s modelling as a weakness.

“We should recognise the other uses of OverseerFM, such as one of the tools farmers can employ to estimate their greenhouse gas emissions from feed consumption, which is a useful contribution to farmers measuring and managing their GHG emissions as part of He Waka Eke Noa,” he said.

In a joint statement, the ministers for environment and agriculture said over the coming year, Overseer will be supported while the “next generation” of the tool is developed, or additional tools are made available.

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