Irrigation and Effluent

Irrigation is utilised by a range of land uses, in areas of Aotearoa New Zealand that have restricted rainfall, impacting production (i.e. pasture and/or crop growth). The main irrigation areas in Aotearoa New Zealand include the eastern parts of Hawkes Bay, Wairarapa, Marlborough, Canterbury, and Otago. About 65% of irrigation in Aotearoa New Zealand takes place in Canterbury.

Irrigation types

Pivot Irrigator

Pivot irrigation

  • Part circles to full circles (fixed point)
  • Corner arms to get more area.
  • 5-25ml applications depth, short rotation length.
Lateral Irrigator

Lateral Irrigation

  • Not a fixed structure; moves up and down.
  • Needs hose moved often.
  • 10-25 ml application depths depending on rotation.
Fixed Grid irrigation

Fixed grid

  • Used on hill and in corners.
  • On timers, and radio systems (dependent on system).
  • Lighter application depths, switching on for 20-30 min more frequently.

K-Line irrigation

K-line Irrigation

  • Higher application depths.
  • Moved either once a day or twice a day (twice a day is recommended)
  • Easy to maintain.
  • Rotation can be long.
  • Multiple along one line of hose.
Roto-Rainer Irrigator

Roto-Rainer irrigation

  • Higher application depths.
  • Some switch off at the end of their runs.
  • Travel along wire rope, with a drag hose.
Gun irrigation

Gun Irrigation

  • Higher application depths.
  • Switch off at the end of their runs.
Longline irrigation

Long-line Sprinklers

  • High application depth (30-65mm)
  • One sprinkler on a line of hose.
  • Longer rotations.
  • Dry spots are common.
Dripline Irrigation


  • Typically found in vineyards and orchards.
  • Very light applications generally run on timers.

Good management for irrigation

Good management practices were developed in partnership by industry groups, crown research institutes and Environment Canterbury. These include:

  • Ensure any new development, upgrade or redevelopment is consistent with irrigation industry codes of practice.
  • Evaluate your irrigation system annually to demonstrate optimal performance using irrigation industry guidance.
  • Measure irrigation water take with a water meter. Track soil moisture levels throughout the season to justify irrigation events (e.g. using soil moisture balance calculations or soil moisture probes or tapes).
  • Evaluate annual irrigation use for consistency with estimated agronomic needs for the season based on climatic data and pasture/crop requirements.
  • When conducting dairy shed washdown and milk cooling, ensure dairy sheds use no more water than necessary to produce hygienic and safe milk. Measure dairy shed water use with a water meter.
  • Apply water to maintain soil between stress point and field capacity. Knowledge of evapotranspiration, field capacity and use of soil probes can assist in achieving this.
  • Apply a water volume informed by all relevant factors (e.g. crop type, plant growth stage, soil type and field capacity).

Make sure there is a demonstrable reason why irrigation is to be applied:

  • to replace soil moisture deficit; through the use of a soil moisture meter or soil water budget.
  • for the purpose of herbicide activation
  • to prepare soil for cultivation
  • frost protection
  • for fertigation.

Soil moisture monitoring is based on the soils Profile Available Water (PAW) and is generally shown through a soil moisture trace.

It is good management for irrigation decisions to be made through soil moisture monitoring, rainfall and weather forecast.

Source: ECan

Benefits of good irrigation management

  • Protects water quality and quantity.
  • Save on pumping costs.
  • Protects soil structure and retains valuable nutrients.
  • Compliance with conditions of water supply.
  • A well-managed system will save on labour and maintenance costs.

Source: DairyNZ

As a manager or advisor for irrigation there is responsibilities to have strategies in place including:

  • Understand and work within the conditions or rules that are set by the irrigation scheme or regional council, and govern the supply of water for irrigation;
    • A limit on the flow (rate of take) such as litres/second, cubic metres/day or week
    • A limit on the total volume that can be taken in a month, a season or a year.
    • Other consent conditions may include defining the area that can be irrigated and the land uses, plus requirements not to water roads, tracks or other non-productive areas.
  • Protect water quality,
  • Be as efficient as possible with water and energy use, while maintaining or improving production.
  • Ensure any new irrigation is designed with efficient use of water, energy, labour and capital.

Source: DairyNZ

Ensuring the irrigation system is efficient:

  • Any new development, upgrade or redevelopment is consistent with the Irrigation Design and Installation Codes of Practice and Standards. Using an Accredited Irrigation Design company is the best way to achieve this.
  • Any new development, upgrade or redevelopment is commissioned to demonstrate it has achieved its design performance parameters.
  • Irrigation is scheduled i.e. soil moisture monitors and soil water budgets.
    • When scheduling irrigation, water use must be compliant with your consent conditions - this is a legal requirement.
  • Operators are trained.
    • Training is key for everyone involved in irrigation and must include health and safety considerations.
    • IrrigationNZ runs practical irrigation manager and irrigation development training days and workshops that provide a great way for irrigators to upskill and be safe.
  • The Irrigation System is efficient including all irrigation systems having an annual performance assessment (a Bucket Test) to demonstrate they are performing efficiently.
    • IrrigationNZ has developed a number of resources for irrigators including guides, templates and checklists, these are available free to all IrrigationNZ members, or provided free as part of the training.
    • DairyNZ has developed a number of resources as well for irrigators including guides, templates and checklists.
    • CropX Bucket Test is an easily downloadable, free app that assists with Bucket testing.
  • Auditable records are kept.

Variable rate irrigation

Variable rate irrigation (VRI), where the application rate of irrigation water across an area changes depending on soil type and other factors, can decrease leaching losses of nitrogen (N) and phosphorus (P).

At a farm scale

  • Variable rate irrigation (VRI) technology can decrease farm leaching losses and nutrient concentrations in groundwater and surface waterways. In a 2017 study, nitrogen (N) and phosphorus (P) at the downstream site under VRI were about 80–85% less than that lost under uniform rate irrigation (URI).
  • Nutrient applications also need to be matched to crop requirements and soil type.

At a broader scale

  • Wider adoption of VRI technology could maintain or decrease farm leaching losses and nutrient concentrations in receiving waterbodies compared to areas with widespread URI or flood irrigation.
  • In future, if more precise application of irrigation water and nutrients over space and time is achieved, even greater gains in nutrient loss reduction could be possible.
Soil water movement
Figure 2. Soil water movement
Soil water movement
Figure 3. Soil moisture trace


Effluent is a combination of manure, urine and washdown water. Effluent is a valuable resource which, when managed well, increases pasture production and reduces fertiliser costs. There are generally two components to an effluent system; storage and application. By designing effective collection, storage, treatment and dispersal systems, we can use them to maximum effect - whether that's to increase pasture production, or protect the quality of our rivers, streams, oceans and groundwater.

The nutrients, and other contaminants within effluent can cause environmental damage, especially in fresh and ground water.

On-farm benefits of good effluent management

Good effluent management is a combination of having a well-designed effluent system and processes for people that make sure the effluent the system collects is applied to pasture in the right amount at the right time. Benefits include:

  • Fertiliser savings
  • Improved soil condition
  • Prevention of animal-health issues
  • Compliance with council rules or resource consent.
  • Making good effluent irrigation decisions

Source DairyNZ

Effluent storage

Having well-designed and constructed storage facility will save you time and money. The key is good planning and working with the right people.

The benefits of a well-designed storage system:

  • Peace of mind
  • Increased flexibility around irrigating
  • Effective utilisation of nutrients and water
  • Reduced risk of effluent non-compliance
  • Environmental protection

Build the perfect effluent storage pond for you:

Storage ponds need to have the correct amount of cubic metres to ensure compliance and enable appropriate spreading, and be lined appropriately to stop leakages.

Storage options include lined ponds and above ground tanks are the two options available when choosing an effluent storage system for your farm.

A well-designed storage pond is:

  • sealed to avoid leakage to groundwater.
  • allows for ongoing operation and maintenance, and is appropriately sized for the volume of effluent produced now and in the foreseeable future.
  • compliant with regional and district council and Building Act requirements.

How much storage do you need?

DairyNZ has developed the Dairy Effluent Storage Calculator (DESC), with herd size, climate information, yard size and daily water usage can determine the required cubic metres. A Dairy Effluent Warrant of Fitness (EWOF) certified consultant is able to assist with this calculation.

Dairy Effluent Storage Calculator

Farm Dairy Effluent (FDE) systems should:

  • Capture all FDE.
  • Spread the FDE at a time that allows uptake by plants.
  • Uniformly spread the FDE to the desired depth, and at the desired intensity.
  • Control FDE application to within the boundaries of the application area.
  • Ensure that FDE systems can be operated safely.
  • Comply with all regulatory requirements, including consent conditions.
  • All new effluent systems should be designed to Farm Dairy Effluent (FDE) design code of practice.

How you can do this with a Farm Dairy Effluent (FDE) system:

  • Calculate suitable storage using the Dairy Effluent Storage Calculator. This enables FDE to be stored when soil and management conditions are unsuitable for FDE land application.
  • Seal all areas where FDE is collected (including feed pads). All new effluent systems should be designed to FDE Design Code of Practice standard.
  • Seal and maintain all storage facilities to ensure effluent is contained. Actively manage storage to ensure capacity is available when required.

How you can do this with a deer enclosure system:

  • Store effluent for later dispersal to land where appropriate.
  • Ensure effluent and run-off water does not enter natural waterways untreated.
  • Keep solid waste away from waterways.
  • Clear faecal/urine surface material annually.
  • Ensure paddock enclosure systems do not result in significant or irreparable soil loss or erosion.

Effluent spreading

Spreading is important to ensure effluent is appropriately utilised, and does not contaminate surface or ground water.

The key to good effluent spreading decision making is understanding the soil water deficit. It is essential to prevent ponding and run-off and to avoid applying effluent to saturated soils. Soil water deficit is the amount of water (ie effluent) which can be applied to the soil before it reaches field capacity (which refers to the amount of water held in the soil after excess water has drained away). If effluent is added at field capacity it will likely result in ponding, runoff or leaching.

To get good value out of effluent and reduce environmental risk consider:

  • Timing of application - The best way to ensure that plants can take up nutrients from effluent is to only spread it when there is sufficient soil moisture deficit / capacity available in the soil. If the soil is too wet there will be leaching or run off.
  • Rate of application/depth of application - Good practice involves ensuring the effluent is applied at a rate that can infiltrate the soil and not pond or run off, drainage beyond the plant roots is avoided and it is spread evenly.
  • Where possible, leave a buffer strip next to waterways and farm boundaries and know your consent conditions and/or regional rules.

Application of farm dairy effluent should be avoided on shallow, stony free-draining soils with low capacity to retain P. Soils of this type are common in the Canterbury region. Current regulations and good practice for dairy farms are not enough to mitigate phosphorus (P) losses from FDE applications on these soils.

Source: Our Land & Water

The DairyNZ Farm Dairy Effluent Spreading Calculator (app or Excel spreadsheet) allows farmers to easily calculate nutrient loadings and application rates for dairy effluent based on a number of customisable inputs. OverseerFM can also assist with determining nutrient loading. This means that farmers can manage the application of their effluent nutrients with greater precision.

There are two calculators in this app, the Quick Calculator which is for spray irrigation systems such as travelling irrigators and sprinklers, and an Advanced Calculator which is for slurry tankers and muck spreaders.

Spreading sludges and separated solids

Effluent is commonly grouped into three broad categories based on dry matter (DM) content: liquids (0-5%), slurries (5-15%) and solids (>15%).

Spreading effluent solids requires specialist machinery which is suited to the type of effluent being spread:

  • Effluent high in sand or long feed fibre content is easier to load with a tractor.
  • Slurry tankers can generally pump and spread effluent less than 15% solids.
  • Muck spreaders are best at handling effluent above 20% solids.
  • The effluent between 15-20% solids is generally the most difficult to handle with loading equipment and requires a sealed muck spreader.


How you can do this:

  • Apply effluent to pasture and crops at depth, rates and times that best prevent loss and to increase utilisation. Ensure your distribution area complies with your consent conditions (use OverseerFM® to calculate).
  • Take account of nutrients supplied by effluent or manure when calculating fertiliser requirements. (You can use the DairyNZ FDE calculator.)
  • Ensure no effluent is spread on an area pigs are grazed.

How you can do this:

  • Calibrate spreading equipment according to its design specifications specific to the product being spread.
  • Apply effluent efficiently. Record effluent applications, including product, rate, date and location.
  • Evaluate your effluent system annually to demonstrate optimal performance, e.g. through an application efficiency test (bucket test).

Irrigation application systems

Keeping on top of maintenance tasks for irrigation application equipment is essential for good performance and many farmers like to keep a regular check on their application depths and rates.

Travelling irrigator

Travelling irrigator


  • Ability to move behind cows (follow grazing round).
  • Cheaper option.
  • Needs a timer or fail-safe system to ensure do not over apply in case of issue/emergency.


  • High application rates.
  • Difficult to move (depending on length of pipe).
  • Needs to be moved frequently.
  • Nozzles and pipes need to be checked regularly for blocks and damage


Injected irrigator


  • Low application rates
  • Easy to get large volumes out and cover a large area quickly.
  • Dilutes effluent with water


  • Can erode the metal work on irrigator.
  • Can block sprinkler nozzles.
  • Requires solid separation.
  • Have to put through pure if unable to irrigate.


Underslung irrigator


  • Low application rates.
  • Easy to get large volumes out and cover a large area quickly.
  • Can run without water running through pivot.


  • Block nozzles can be an issue.
  • Wear and tear on infrastructure due to extra weight of pipe.


K-Line irrigator


  • Cheaper option.
  • Low risk as does not move (unable to tip over).
  • Lower application rates.
  • Works off timers.


  • Need to move frequently (more than once a day).
  • Nozzles and pipes need to be checked regularly for blocks and damage.