Fertigation and effluent injection

Fertigation or effluent injection can help growers reduce synthetic nitrogen use on farm, minimising the risk of nutrient loss, but these systems should be carefully managed to avoid risks to water bodies and public health.

Irrigation New Zealand has published an extensive guide to the use of fertigation on farms, and a list of certified irrigation system designers, to support the use of fertigation and effluent injection.

What is effluent injection?

Effluent injectionEffluent injection is when you directly inject filtered effluent into the base of your irrigator and apply it to land with your irrigation water through the same line.

This is common practice on many dairy farms in Canterbury.

This practice is different from under-slung systems where a secondary line connected to an effluent pond is often attached under centre pivot spans to allow raw ’slurry’ effluent to be distributed via separate sprinklers.

The added risk during effluent injection is that a loss of pressure could cause effluent to flow in reverse, contaminating your water source. If you wish to practice direct effluent injection, a backflow prevention device is required.

If you spread liquid effluent on farm you need a consent to discharge contaminants to land and an Effluent Management Plan (EMP), including correct effluent storage requirements.

What is fertigation?

Fertigation is a process in which your synthetic fertiliser is mixed with water and applied through your irrigator. Most fertiliser suppliers – including Ravensdown and Ballance – sell products designed to be used in fertigation. 

The two main environmental risks you need to manage with fertigation are fertiliser storage and backflow contamination.

If you are thinking about introducing fertigation on your property or would like to know more, industry professionals should be able to help. If you belong to an irrigation scheme, they should be your first contact. Irrigation New Zealand also has information and guidance on fertigation.

Effluent management and application

If you are applying effluent on your land, effluent management must be covered in your Farm Environment Plan.

If the irrigator you use for applying effluent or fertiliser crosses a watercourse such as an on-farm drain or stream, you will need to ensure that no pathogens or nutrient-enriched water is discharged where it can contaminate that water course, for example, by using a variable rate irrigation (VRI) system.

In addition, if you are injecting synthetic nitrogen or effluent through an irrigation system connected to a freshwater source, you need an effective backflow prevention device.

If you suspect a cross-contamination even may have occurred, you must notify us immediately on 0800 765 588.

Fertiliser storage

Fertiliser is considered a hazardous substance, and Worksafe guidelines for managing hazardous substances apply to both the storage of solid and liquid fertilisers.

For detailed information on working with solid fertilisers, see Worksafe's Safe working with ground-spread fertiliser page. 

Liquid fertilisers are stored ready to be injected into the irrigation system. They are a high-risk hazardous material and extra precaution must be taken to avoid nutrients entering groundwater due to leakage. 

Storing fertiliser on farm will require a resource consent for storage of hazardous material unless you can comply with Permitted Activity rules 5.65-5.67 in the Canterbury Land and Water Regional Plan.

These include:

  • The fertiliser is approved under the Hazardous Substances and New Organisms Act 1996 and storage and use is in accordance with all conditions of the approval.
  • The fertiliser is stored under cover in a facility that is appropriately designed, constructed and managed to fully contain a leak or spill.
  • The fertiliser will be stored more than 20m from a water body or bore.
  • Fertiliser storage will be inspected at least once per month and maintained or repaired if any defects are detected.
  • A current inventory of fertilisers is maintained and made available to Environment Canterbury or emergency services on request.

Even if these conditions can be met, we strongly suggest you discuss your situation with a consents planner to determine if a resource consent will be required. It is a user-pays system, but we offer a free hour’s advice at the outset. Contact us to set up an appointment with one of our consents planners or complete this online pre-application advice form. 

We expect national guidelines on fertiliser storage will be coming in the future. The following are our interim guidelines on the safe storage of liquid fertiliser.

Bulk storage safe distance

Fertiliser must be:

  • stored at least 10 metres from any hazardous materials, e.g., oxidizers, solid fertilizers, poisons and pesticides (agricultural chemicals)
  • stored at least 10 metres away from any combustible materials such as diesel, LPG
  • stored at least 30 metres away from any dwelling
  • located so that any spills cannot contaminate stock feed or stock watering sources
  • located so that spilt fluid fertilizer cannot come into contact with any areas where welders, grinders and other maintenance equipment are being used
  • located so as to avoid accidental collision by vehicles. If tanks placed in high traffic areas, consider the use of bollards
  • located so that any spills will not contaminate streams, lakes, or waterways (at least 50 metres away)
  • located 10 metres from overhead powerlines.
Safe storage and bunding
  • Ensure tanks, pipework and valves are fit for purpose and resistant to corrosion, and are inspected for damage at least annually by a suitably qualified technician.
  • Check tank has sufficient capacity before delivery, and avoid overfilling
  • The storage vessel (Bulk tank) must be constructed from an appropriate material and strength whereas to avoid accidental rupture due to weight differences between water and liquid fertiliser (water = 1kg/1ltr, UAN = 1.2kg/1ltr).
  • Secondary containment (Bunding) must be installed for storage installations (including mixing stations) designed to hold volumes of 1001 litres and greater but not including Intermediate Bulk Container’s (ICBs) as this would impact many products that have little to no environmental hazard.
  • Secondary containment (Bunding) must be designed:
    • to contain all contents from an immediate vertical tank seam failure
    • avoid soil surface/sub surface leaching
    • Provide adequate provision for spillage recovery.
  • Secondary containment cannot consist of a permeable bund.
  • Secondary containment must provide a minimum holding capacity of 110% of the total stored volume (30,000l = 33,000l).
Additional considerations
  • Entry to the farm from a public road must be safe and clearly defined.
  • Farm roads must be in good condition and capable of supporting a tanker weight and size with sufficient room for tanker to turn around without leaving the main farm road.
  • Farm bridges, creek and irrigation channel crossings must be fit for tanker crossings under full load.
  • There must be a clear area, free of rubbish and tripping hazards, between the delivery tanker and the tank filling point.
  • Bowsers and mobile tanks must be stable and carefully sited of before filling and dispensing.
  • Appropriate onsite PPE for personnel and contractors must be provided.
  • Fertiliser bulk storage must be clearly labelled with appropriate signage to avoid accidental use of storage or liquids.
  • You must document handling procedures for filling a mobile tanker or spray unit, from the main storage unit to minimise the loss of soluble fertiliser from filling hoses (e.g., valves on the end of the hose that attaches to the mobile tank or sprayer that can be turned off (as well as one on the main tank) and a bucket that the hose end can rest in to catch drips.
  • You must document procedures, staff training, and absorbent materials and equipment for dealing with spillages and emergencies.

Need help?

If you have any questions about fertigation or effluent injection, please contact your fertiliser specialist, farm consultant, Land Management Advisor or call Customer Services on 0800 324 636.

More information

What is liquid nitrogen fertiliser?

Liquid nitrogen fertiliser is a solution designed for use through irrigation systems which is a practice called fertigation. A benefit of fertigation is that the amount of nitrogen applied to pasture and crops can be accurately controlled and applied little and often.

  • Ravensdown manufactures a liquid nitrogen fertiliser called Flowfert N which is an 18% liquid nitrogen solution.
  • Ballance Agri nutrients manufacture a comparable product called Nrich Liquid Urea 19N. 

Does fertigation count towards the 190 kg/ha/year synthetic nitrogen cap?

Under the National Environmental Standards for Freshwater (NES-F), any substance applied to plants or soil for nutrition that contains more than 5 per cent nitrogen by weight is considered synthetic nitrogen.

If you are practicing fertigation, in almost all cases, the nitrogen you use to fertigate will be above the 5 per cent nitrogen by weight threshold and will count towards your N cap. 

For the purposes of fertigation, the nitrogen load should be calculated based on the concentration of the liquid N fertiliser that arrives at the farm gate (typically 18–19 per cent by weight), or if made up on-farm, the concentration injected into the irrigator – not the concentration that leaves the irrigator after dilution with irrigation water.

If you are practicing effluent injection, the organic nitrogen content of the effluent will not count towards the synthetic nitrogen cap.

For more information, see the synthetic nitrogen cap page on our farmers' hub.

Is liquid nitrogen fertiliser a hazardous substance?

Most liquid nitrogen fertilisers are classified as hazardous substances under the Hazardous Substance and New Organisms (HSNO) Act. The term hazardous substance refers to any product or chemical that has properties that are explosive, flammable, oxidising, toxic, corrosive, or toxic to the environment.  

The Environmental Protection Authority (EPA) is responsible for approving hazardous substances for use in New Zealand. This includes the rules for classification (conditions of approval), labelling, safety data sheets, packaging, and disposal, as well as protecting the environment and public health.

WorkSafe enforces the requirements for the use, storage, and handling of hazardous substances in the workplace.

What are the environmental risks with storing fertiliser?

Fertiliser is a hazardous material, and storing and handling any type of fertiliser brings risks. However, the risks of causing water pollution when storing and handling liquid fertiliser are much higher than for solid fertiliser. 

If a 30,000-litre tank containing liquid urea were to rupture, be punctured by machinery, or the valves and pipework damaged, the spilt urea would be hydrolysed to ammonia or ammonium. In the soil, this would be converted to nitrate, which would leach into the groundwater, and pose risks to human health. Any ammonia entering a stream or river would be toxic to aquatic life, resulting in the death of fish and other organisms. It would also contribute to excessive plant and algal growth (eutrophication).

Do I need secondary containment (bunding) for my liquid nitrogen fertiliser tank?

Accidents can happen. Secondary containment systems (bunding) ensure that hazardous substances like liquid fertiliser are contained if they escape from the primary storage tank or container. This reduces the risk of harm to your staff and the local water environment.

Whether you legally require secondary containment will depend on the specific substance and amount being stored.  

WorkSafe's Hazardous Substances Toolbox contains a workbook to help you complete an inventory of substances and a calculator to help you with the requirements for different substances you are planning to store.

In addition, LWRP rules require that hazardous substances stored within Community Drinking Water Protection Zones be stored undercover in a facility designed, constructed, and managed to contain a leak or spill and allow substances to be collected or safely disposed of.

Regardless of HSNO and current LWRP requirements, bunding liquid nitrogen fertiliser tanks is good practice. Bunding should be designed to capture 110% of the largest container or tanks in the secondary containment system. To be effective, bunded storage areas should be covered or actively managed to remove collected water after rainfall events. Double-skinned tanks are also an option.

Liquid fertiliser stores must also be located at least 20 metres from drains, ditches, and surface waters, and at least 50 metres from springs or bores. Separation distances should be greater if there is no secondary containment or bunding in place.

Is there a minimum storage volume for liquid fertiliser above which bunding is required?

The Hazardous Substances (Hazardous Property Controls) Notice 2017 specifies threshold quantities for secondary containment and emergency response plans depending on the specific hazard classification of the substance.  

Urea is a class 9.3C ecotoxic substance and does not require secondary containment, and we have no specific storage volume thresholds.  

Nevertheless, established good practice is to provide secondary containment for stored quantities more than 1000 litres and for bunding designed to capture at least 110 percent of the largest tanks in the secondary containment system.

It is also critical that tanks are designed for the type of product being stored. For example, urea is heavier than water, so storing liquid fertiliser in a water tank carries a risk that the tank will fail. 

If spilled, urea can be very damaging to the environment. Whether spillage is accidental, or the result of poor management or vandalism, this could result in groundwater, surface water and drinking water pollution with legal and financial consequences.

Do bowsers and mobile tanks need bunding?

There are no specific rules in the CLWRP on secondary containment for bowsers and mobile tanks. However, mobile and temporary storage tanks can also pose a significant hazard to watercourses and groundwater. 

To reduce the risk of pollution, consideration should be given to mobile tanks and bowsers with integral secondary containment. Suitable siting on level solid ground before filling or dispensing is crucial. Hatches and manholes need to form watertight seals. All hatches, lids and valves should be closed and locked before moving laden tanks and bowsers. Roadways, farm tracks and bridges must be able to withstand fully laden bowsers passing over or being parked on them.

Where can I get further advice on secondary containment (bunding)?

Do I need resource consent to apply liquid nitrogen fertiliser to land?

You can apply liquid (or granular) fertiliser to land using an irrigator without resource consent, provided you can demonstrably comply with the conditions of permitted activity Rule 5.65. This requires the following:

  • Fertiliser must not be applied when the soil moisture exceeds field capacity.
  • Where a permanently flowing river, lake, artificial watercourse or wetland has riparian planting, fertiliser must not be applied onto the planting (except to establish the planting)
  • Fertiliser must not be applied within 10 metres of the bed of a permanently flowing river, lake, artificial watercourse, wetland boundary or any significant indigenous biodiversity site.

An application for resource consent must be lodged if these requirements cannot be met. Assessment of your application will consider the actual or possible environmental effects and the quality and auditing of a Farm Environment Plan. 

Fertiliser use may also be restricted by the nutrient management rules (farming land use activities) that apply to your region, which can be found in the Canterbury Land and Water Regional Plan, rules 5.65 to 5.67.

It is important to be aware that the Ministry for the Environment is currently considering amendments to the National Environmental Standards for sources of human drinking water. The changes include delineating Source Water Risk Management Areas (SWRMAs) and may introduce new controls on activities within them. The activities and controls are yet to be determined but could potentially include fertiliser application.

Do I need resource consent to inject liquid nitrogen fertiliser with my irrigation water?

You do not need a resource consent to inject liquid N fertiliser with your irrigation water, provided you have an appropriate backflow prevention device installed to ensure there is no backflow of contaminants directly into the water source. 

If you do not currently have a backflow prevention device installed and you are injecting liquid nitrogen fertiliser with irrigation water, you may need to apply for a resource consent.

We strongly suggest you discuss the requirements with one of our consents planners to determine if a resource consent is required. It is a user-pays system, but we offer a free hour’s advice. Contact us to set up an appointment with one of our consents planners or complete our online pre-application advice form.

In most cases, where resource consents have been obtained to take and use water or to discharge effluent to land, consents will already include conditions, which will require:

  • that an effective backflow prevention device is installed and operated within the pump outlet plumbing or mainline to prevent the backflow of contaminants into the water source;
  • that the device is tested at the time of installation and annually thereafter by a suitably qualified or certified person;  
  • that a copy of the test certificate is displayed on the pump shed wall and the test report is sent to us within two weeks of each inspection.

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