History and ownership of Overseer
Overseer was first developed in the 1980s to determine fertiliser application rates on pasture and has supported farmers to learn more about nutrient losses from their farms.
The Ministry for Primary Industries, the Fertiliser Association of New Zealand, and AgResearch each hold a one-third stake in the Overseer intellectual property. In 2016, they established Overseer Limited to manage, develop, and license Overseer for use.
Overseer Limited released OverseerFM in June 2018. This paid software service is part of an agreed business plan.
Reviews of Overseer
In the context of the Government’s 2020 freshwater reform and water quality goals, it is important for farmers to have confidence in the tools they use to meet regulatory requirements.
Overseer has undergone several rigorous reviews.
The Parliamentary Commissioner for the Environment (PCE) released a report in 2018 called Overseer and regulatory oversight: Models, uncertainty and cleaning up our waterways. That report made several recommendations.
Overseer and regulatory oversight: Models, uncertainty and cleaning up our waterways
Review of the Overseer model in 2019 and 2020 found shortcomings
In 2019 and 2020, a scientific advisory panel reviewed the Overseer model in line with international best practice methods.
At the time, the panel concluded that, in its current form, it would not have confidence in Overseer's estimates of total nitrogen lost from farms.
It identified a general concern with the model structure, as well as some specific areas of concern.
The panel found that the use of average climate data, homogeneous soil profiles, and the assessment of only one species of nitrogen meant that Overseer estimates did not comprehensively account for nitrogen losses in some catchments and for some land uses.
Find out more about the Overseer technical review, its findings, and the Government's response
Overseer's redevelopment programme
A redevelopment programme of Overseer began in December 2021 to address the concerns raised as part of the independent review of the decision support tool.
Overseer released new versions of its software in December 2022 and April 2023, which incorporated work from the redevelopment programme.
The redevelopment programme has addressed some concerns raised by the independent review and has alleviated concerns related to model assumptions.
Validation of modelled nitrogen-loss results against observations shows that Overseer is rated "very good" for grazed pastures and "satisfactory" and "good" for crop systems against internationally peer-reviewed metrics for environmental models.
The Technical Advisory Group (TAG) set up to establish and review the Overseer redevelopment programme, noted that the work was carried out to a high standard and that it improved confidence in the use of the model.
The TAG has been wound up and the Overseer redevelopment programme has been completed.
Overseer redevelopment programme report – Technical paper [PDF, 962 KB]
Who to contact
If you have questions about Overseer, email info@mpi.govt.nz
