Using Overseer

Overseer is a tool to model nutrient losses from land. It's used in a variety of ways by regulators, auditors and farmers.

How we use Overseer

Our Land and Water Regional Plan, which became operative in 2015, set limits on the amount of nutrients, particularly nitrogen (N), that can be lost from a farming system into freshwater.

Under this plan, farms that require a farming land use consent have a consented Nitrogen Loss Limit (NLL). The principal tool used to set these limits and monitor compliance with them has been Overseer nutrient modelling.

Overseer can take complex environmental and farm system information and estimate the N loss from a particular farm to the environment and groundwater. It shows how different management practices may contribute to the farm's overall nitrogen losses, and may be useful in identifying effective mitigation opportunities.

Government review of Overseer

In 2018, the Parliamentary Commissioner for the Environment recommended a review of Overseer given its increasingly important role in freshwater regulation in New Zealand.

The review indicated that Overseer in its current form was not always reliable to measure nutrient loss from farms. In response, the Government recommended that councils consider supplementary information when trying to understand total nitrogen losses. 

We have since adapted how our consenting and auditing processes use Overseer.

How we've adapted our use of Overseer

In December 2021, with collaboration from mana whenua and industry groups, we produced an interim solution to the Overseer review.

Consent processing and Farm Environment Plan auditing is operating under the revised approach, and will continue to do so until a new framework is decided as part of a future Land and Water Regional Plan.

We have not resumed auditing north of the Hurunui River or consenting in the far south, where discussions with the local Rūnanga have not yet concluded. We will contact affected landowners at the appropriate time.

Overseer use in the FEP auditing process

As a result of the Overseer review, we've increased emphasis on using a range of evidence to identify potential impacts on nitrogen loss to water.

We now use Farm Descriptors to describe the basic farm system. The four farm descriptors are:

Where any of the four descriptors for the farm have substantially changed, more evidence may be required to evaluate the impact of those changes on nitrogen loss. Your auditor will assess whether an Overseer nutrient budget is required as part of the package of evidence to support their level of confidence grading.

Overseer nutrient budgets remain a valuable form of evidence during the auditing process and are likely to be required for auditing more complex consents with nitrogen loss reductions, multiple loss limits, or non-contiguous land holdings.

It is important that farmers talk to their auditor early and explain any on-farm changes that have been made since the last FEP audit or since gaining resource consent, so that the auditor can advise you if you need to provide additional information.

Farm System Categories

Category Systems Description
A Dairy Tonnes DM/ha (Calculate feed eaten per ha, as per defined process)
B Dairy support A mixture of crops and pasture grown for rearing of dairy replacements and/or wintering of milking cows
C Sheep & beef A mixture of pasture and crops grown for breeding sheep, beef and/or deer, and could include a mixture of breeding and finishing
D Stock finishing A mixture of pasture and crops grown for stock finishing
E Deer A mixture of pasture and crops grown for deer breeding and/or finishing
F Outdoor pigs Management of land for production of pigs
G Other livestock Horses, camelids and other livestock categories
H Cut and carry Production of a range of forage crops for use off-paddock
I Arable 1 A mixture of crops (small seed, cereals and/or vegetables) grown for harvest
J Arable 2 A mixture of crops (small seed, cereals, pasture and/or vegetables) grown for harvest and stock grazing
K Horticulture Fruit, nuts and/or vegetables grown for harvest
L Viticulture Production of grapes grown for wine production
M Other Describe:
N Research farm Provides for scientific research, development and demonstration of farming practices and technologies

More information on FEP audits

  • Allow sufficient time to arrange for your audit to be carried out.
  • Find Environment Canterbury certified auditors.
  • Make sure your FEP is up to date to reflect your consent conditions.
  • Talk to your industry body, farming consultant or FEP auditor if you need support.
  • Let us know if your FEP will be audited under an irrigation scheme or ISO programme, or if the audit has already been completed.

Contact us on 0800 324 636 or email

Overseer use in consenting

All farming land use consents granted since December 2021 have been assigned Farm Descriptors. 

Applications for new farming land use consents, as well as farming land use consent renewals, require a current and baseline Overseer nutrient budget as a key tool to determine the Farm Descriptors.

Changes in land use should only be considered if there is evidence to show that what is being proposed won’t lead to higher nitrogen loss risk. 

We’re obligated to consider each consent application, but with the need to notify a new land and water plan in future, any consent that is issued is likely to be short-term. 

Frequently asked questions for Overseer users

Should I use Overseer now? What for?

You must have an Overseer budget if you are applying for a consent. This is a requirement of the Land and Water Regional Plan.

You can also use a budget if you’re being audited. For both consents and audit, your Overseer budget will be just one line of evidence and will need to be supported with other evidence.

If you have changed your farm practices since the last time you were audited, an Overseer budget may be required as one line of evidence.

Talk to your auditor or consent planner to find out whether this applies to you.

In all cases, you can use an existing nutrient budget as a line of evidence. See also the next question.

Should I do a nutrient budget now? Why should I invest in one if it’s only one type of evidence?

You will need an Overseer budget to apply for a consent. An existing budget may be sufficient - talk to your consent planner to find out what applies to your situation.

You can prepare a new nutrient budget for your FEP audit if you wish, but an existing one may be sufficient as a line of evidence.

When you book an FEP audit, discuss your situation with your auditor. They will be able to decide whether in your situation an Overseer nutrient budget, or other sources of evidence, will be needed for the audit.

Note that nutrient budgets provide you, your rural professional and auditor with useful information about farming systems and how different management practices contribute to the farm’s overall nitrogen losses.

Overseer also provides information to develop effective nitrogen loss mitigations which will help you meet your nitrogen loss targets and any required reductions.


Can I use an equivalent model?

At present we are implementing the interim solution to determine a farm’s nitrogen loss limit.

This is based on a farm narrative (farm system category and descriptors – see table below) rather than using OverseerFM to calculate the nitrogen loss rate (50 kg N/ha/yr, for example). 

If you choose to use an equivalent model, we will assess the model against the policies, objectives and community aspirations we deliver on, and make a decision accordingly.

How do I know what farming category(ies) my farm falls into?

The system categories are broad and will usually be clear (see above table). There is a subdivision of dairy farms based on a calculation using easily identified inputs.

For more information on this methodology, discuss with your consultant, FEP auditor or dairy company.

How can the narrative system work, especially on a mixed farm?

The system categories are broad. We will therefore use a single system category if possible (for example, arable with stock compared with arable without stock), but where there are clear distinctions between systems on a single farm, these can be defined separately if required.

What should I do differently to prepare for my first audit?

Book in with your FEP auditor early to ensure all necessary information can be prepared for your FEP audit.

Discuss your situation with your auditor and explain any farm system changes that have been made since you received your consent or since your last FEP audit.

Your FEP auditor will advise you what additional information you may need to provide for your FEP audit if there have been significant changes to your farming system since consenting or your last audit.

Each situation is different. Therefore it is important to talk to your auditor so they understand the farm and any system changes.

What should I do differently to prepare for my subsequent audit?

Unless you use an Overseer nutrient budget for other farm management reasons, don’t create an Overseer budget before you have discussed your situation with your FEP auditor.

Access any existing nutrient budget. If you are changing your farm practices, an Overseer budget may be required as a line of evidence. Talk to your auditor about this.

What should I do differently if I want to lodge a consent application?

Access any existing nutrient budget. Note that new consents will focus on a mixture of inputs (such as irrigation area, winter grazing area, farm system category) and outputs (nitrogen loss risk, for example).

Will processing my consent be more expensive?

Generally not, unless you are seeking to intensify your land use and additional evidence is required to show you will not be increasing your farm's nitrogen loss risk.

How long will it take to process my consent application?

We are likely to receive more consent applications than in the past. However, we are currently experiencing delays in processing resource consents.

Am I likely to get a short-term consent only? Why?

We’re obliged to consider each application individually under our statutory direction, but with the need to notify a new plan, certainty may best be served by granting relatively short-term consents.

I want to change my farm practices – what should I do?

Talk to us, particularly if you believe that what you are proposing may lead or amount to change in land use or increase your farm’s nitrogen loss risk.

Why has consent processing and Farm Environment Plan auditing started again in some areas but not others?

In developing the interim solution, we undertook to engage with mana whenua. Conversations have concluded with two of the four Tangata Whenua Advisory Service agencies but are ongoing with the other two.

We have restarted consent processing and FEP auditing in most areas of Canterbury. We have now also resumed auditing in far southern parts of the region. We have not restarted auditing north of the Hurunui River or consenting in the far south. We will contact affected landowners at the appropriate time.