Wednesday, 17 November 2021

An update from Overseer


By Dr Caroline Read, chief executive of Overseer Limited

There has been significant interest in the government’s response to the peer review of Overseer and it’s fair to say the Overseer team has received a few enquiries from farmers, rural professionals and regional councils since the report’s release in August.

We’re certainly heartened by the support from the primary sector, in particular those farmers and growers who recognise the value of OverseerFM as a farm planning and management tool. They consistently tell us OverseerFM helps them make better decisions to improve their farm's environmental sustainability and productivity, including when it comes to nutrient budgeting.

One of the key tasks over the past few weeks has been reminding people what OverseerFM isn’t.

The tool does not measure nutrient loss in real-time and it was never designed for this purpose. The peer review saw this as a weakness, but our independent science advice is that Overseer’s approach of estimating cumulative annual nutrient losses is suitable to support the sort of scenario testing OverseerFM is most often used for, and which is of greatest value to our users.

Put simply, the peer review report saw OverseerFM fail at something it was never designed to do. It’s like an Olympian being judged as failing in the high jump when they were competing in the shot put.

What we and our users know is that OverseerFM is proven in its ability to support farmers and growers make more informed decisions about their nutrient management practices that help improve their environmental performance.

It’s a sophisticated indicator of risk that considers the reality of a farm situation. Feedback from fertiliser companies like Ravensdown, farmers, scientists, rural professionals, regional councils and levy groups such as Beef + Lamb New Zealand and DairyNZ all back this conclusion.

We do welcome scrutiny and feedback on the OverseerFM science model and Overseer Limited is always looking to develop and improve the utility and reliability of OverseerFM. We have never said the tool is perfect, no model can do everything.

The review report does raise some valid points on how to improve some of the sub-models used within the OverseerFM science model that we are keen to explore to further develop the tool.

In line with this, we are already working on reflecting N uptake of deep-rooted plants and after nearly three years of work, we have recently incorporated new crops into OverseerFM. There are now 71 crops that can be modelled in OverseerFM, including 15 new crops recently added. We've also updated the climate data in OverseerFM – moving the monthly average climate data from 1981-2010 to 1991-2020 and requiring farms to be located to ensure the best climate data is used in each analysis.

While we are continuing to improve the model in line with the government response to the review, we have concerns with the report’s conclusions about the reliability of OverseerFM’s results because they were not sufficiently supported by testing and are contrary to the results of previous scientific reviews and over 15 years of use by experts.

We do not agree that there is no role for OverseerFM in supporting effective freshwater management for New Zealand.

Overseer Limited is focused on what happens next as a result of this review and we aim to ensure that OverseerFM continues to be as useful in the regulatory space, as a tool that underpins the development and validation of farm plans.

In the meantime, Overseer Limited remains confident that the software does what it was designed to do.

Farmers and rural professionals can keep using it – consistent with our guidance – to help make more informed nutrient management decisions by modelling the impact of changes in farm practices.