OVERSEER® is an agricultural management tool which assists farmers and their advisers to examine nutrient use and movements within a farm to optimise production and environmental outcomes. The computer model calculates and estimates the nutrient flows in a productive farming system and identifies risk for environmental impacts through nutrient loss, including run off and leaching, and greenhouse gas emissions.


OVERSEER® is a nutrient budgeting model that is widely used in New Zealand and is required to be used under some regional council policies. It can assist farmers and regulators with the following:

  • Calculating on-farm budgets for a wide range of nutrients and farming systems (pastoral, arable/vegetable and fruit crops) based on data inputs readily available from the farm.
  • Understanding the fate of these nutrients is an important precursor to developing a Nutrient Management Plan.
  • Calculating and reports farm-level emissions (greenhouse gases) for farms based on the farm-specific methods that are related to the National Inventory methodology.
  • Emissions are reported on a per hectare and per product basis. This allows users to identify major sources on farms and to test management strategies for decreasing emissions.
  • Calculating maintenance nutrient applications for pastoral farms, i.e. the levels of nutrients required to maintain the current soil test values.

Is a useful fertiliser planning tool on its own, additional software is used by fertiliser companies to provide farm specific econometric information for further developing fertiliser recommendations. This information can support farmers and their advisors in planning nutrient use and assessing the potential environmental losses. OVERSEER® modelling can also support environmental policy development, most notably around Lake Taupo and as a part of Horizons One Plan. OVERSEER® does not include economic analysis, so outputs needs to be combined with other economic models to assess impacts of options on the farm business.

The OVERSEER® model has its own website which provides a full explanation of the model, how to use it, benefits of use, and it provides a range of publications and science papers. https://www.overseer.org.nz/

Latest Version 6.3.0 (2018)
State of Development Released and updated
Current Development Activity Overseer Farm Modelling (FM) software - a new online application of Overseer is due for release in May 2018

Development Contact

Antony Williams - Product Manager
Overseer Ltd

Main Developers

  • AgResearch
  • FertResearch
  • Rezare Systems


Outcome Areas Environmental
Management Domains Land, Freshwater
Subdomains Contaminant Losses, Crop/Farm Systems
Intended End Users Fertiliser representatives, farmers, scientists, policy researchers
Spatial Resolutions Unknown
Spatial Extents Land or Business Unit
Spatial Dimensions 1D
Temporal Resolutions Years
Temporal Extents Unknown
Steady State or Dynamic Steady State
Level of Integration Environmental

Input & Output Data

Key Input Data Land Use, Rainfall
Input Data Formats XLS(X)
Key Output Data Drainage nutrient loss


Open/Closed Source Closed Source
Licence Type No Licence

User Information

Operating Systems MS Windows
Software Needed Unknown
User Interface Graphical desktop
Ease of Use Easy
Use in Policy Process Plan (Policy Formulation), Do (Policy Implementation), Check (Policy Evaluation)

For Manuals, release notes, guides and technical manuals see:



Support Training courses available

Technical Considerations

Methods included for managing uncertainty https://www.overseer.org.nz/uncertainty-in-model-results
Analytical Techniques Input/output
Model Structure

Overseer Model

Keywords fertiliser, nutrient budgeting, nutrient management planning, greenhouse gas
Linkages to other Models
Key References

See:  https://www.overseer.org.nz/  for general information

or https://www.overseer.org.nz/publications for range of publications

Technical Description of OVERSEER - 2015 (PDF)


Associated Case Studies

Overseer - South Canterbury Hill Country

Environment Canterbury (ECan) and the Lower Waitaki Zone Committee (ZC) have been running a collaborative community process to help decide on water quality and quantity limits for the proposed South Canterbury Coastal Streams (SCCS) area.


Other Key Case Studies

For examples of OVERSEER use see: https://www.overseer.org.nz/publications

Using OVERSEER in Regulation - 2016 (PDF)

Using OVERSEER within the Rules for the Lake Rotorua Catchment - 2014 (PDF)

South Canterbury:  Fietjie 2014 Estimating nitrogen loss from land uses in the hill country of the South Canterbury Coastal (SCCS) area  Environment Canterbury report no.  R14/129