On this page:
Fertiliser value of effluent
Farm dairy effluent is a natural, dilute liquid fertiliser. It contains nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), sulphur (S) and trace elements that you’d normally pay for to have applied to pasture.
Think of dairy effluent as a resource, not waste. The average dairy herd (244 cows) produces the same amount of effluent as a town with about 3,400 people, such as Otorohanga.
When spread over land, the effluent of 100 cows can save farmers up to $1,500 in fertiliser a year. This saving could be significantly higher for high input farms (for example, farms feeding supplements).
Applying the maximum amount of nitrogen from effluent allowed per year (150 kg per hectare), also provides the following approximate amounts of nutrients:
- 17 kg of phosphate per hectare
- 135 kg of potassium per hectare
- 20 kg of sulphur per hectare
- smaller amounts of magnesium and calcium.
Applying effluent
Effluent can be irrigated ‘fresh’ from a small sump or a tanker. However, irrigating from ponds or other storage facilities may give you better flexibility:
- when soil is waterlogged (too wet to absorb the effluent)
- if there is an equipment breakdown.
Remember to cover water troughs when irrigating effluent. Protect waterways on your farm by:
- not irrigating within 50 metres of a water supply
- leaving a strip of non-irrigated land next to all watercourses – at least 20 metres wide
- ensuring that spray drift isn’t getting into nearby streams or rivers.
Soil – a living filter
Soil acts as a ‘living filter’. It treats the applied effluent by changing it:
- physically – filtering out effluent particles, breaking them down and incorporating them into the soil structure
- chemically – absorbing nutrients and making them available to plants
- biologically – harmful micro-organisms (such as bacteria) present in the effluent are retained by the soil, or are killed when the effluent dries or when they become exposed to sunlight.
Don’t apply too much
Soil can only filter so much effluent at a time. It’s important not to irrigate to a depth of more than 25 millimetres during each application. This is because too much effluent can:
- kill pasture – especially where effluent has ‘ponded’ on the soil surface
- pollute nearby streams and rivers – where it runs off paddocks into waterways
- pollute ground water – by seeping too deep into the soil
- reduce pasture growth – by seeping too deep into the soil, past the root zone (see diagram below).
Working out how much effluent to irrigate
Although effluent contains many nutrients, it is the environmental effects of nitrogen that determine how much you can irrigate onto land. Too much nitrogen can reduce pasture performance and reduce water quality in neighbouring waterways.
In the Waikato region, no more than 150 kilograms of nitrogen in effluent can be applied per hectare per year. You’ll need to get effluent tested to work out how much nitrogen is going onto your land during irrigation.
Special! Test for less
Environment Waikato is giving a limited number of dairy farmers the opportunity to test their effluent at the discounted rate of $75 + GST - normally $90 + GST. Register now, only 500 samples will be tested at this discounted rate.
It's as simple as...
- Register for this offer and receive a Hill Laboratories sample kit.
- Before irrigating, put four ice cream containers in the path of your irrigator.
- After irrigating, measure and record the depth of effluent in each container.
- Tip the effluent from the ice cream containers into a bucket and then pour it into a sampling bottle.
- Send your sample bottle to the lab.
Register now, call Environment Waikato's Freephone 0800 800 401.
The Overseer nutrient budget can be used to help determine how much land is needed for effluent irrigation.
Find out more about managing farm nitrogen.
Nitrogen levels in effluent
If you know exactly how much nitrogen is in effluent, you can work out the most effective application rates for your land.
Recent studies of farm dairy effluent in the Waikato show the average nitrogen content is around 0.04 percent, and 0.165 percent for pond slurry. However, nitrogen content will vary between farms and even within a farm, so it’s best to get effluent tested for exact nitrogen concentrations. Most registered analytical laboratories will be able to analyse the nitrogen content of effluent for you.
How deep does each application have to be?
Each effluent application must not be more than 25 millimetres deep. How deep you irrigate effluent over an area will depend on how much nitrogen you want to apply. Use our online calculation sheet to work out application depth, given that you know:
- the nitrogen content of the effluent
- how much nitrogen (kilograms) you want to spread per hectare.
Working out application rates
Once you’ve worked out the application depth, you’ll need to work out the application rate for your irrigator.
Spray irrigators
- Using the same principal as a rain gauge, mark a scale on the sides of several containers.
- Place the containers within the area being irrigated.
- Stop irrigating when the desired depth (maximum of 25 mm) has been applied.
Other irrigators
To ensure you don’t over-irrigate, use our online calculation sheet to work out effluent application rates for:
- travelling irrigators – the distance an irrigator needs to travel (in metres) per hour
- stationary spray ‘cannons’ – the length of time a spray head can stay in one place
- tanker systems - the distance an irrigator needs to travel (in metres) per hour.
Ongoing irrigation management
When irrigating check for ‘ponding’, particularly in areas where there has been pugging damage. Stop ‘ponding’ by avoiding irrigation in these areas, or improve the drainage by:
- loosening the soil in small ponding areas with a spade
- breaking up the soil surface – for example, by shallow ripping.
Because effluent contains a range of nutrients, irrigated areas will need less fertiliser. Talk to your fertiliser consultant about the reduced fertiliser needs of irrigated blocks.
Regulations for applying effluent
In the Waikato region, applying effluent to land is a permitted activity. This means farmers can apply effluent without having to get a resource consent, as long as you follow these conditions:
- No more than 150 kilograms of nitrogen can be applied per hectare, per year (1.5 applications at 25 mm deep and 0.04 percent nitrogen).
- The farmer/contractor must have contingency measures in place in case there is prolonged wet weather or a pump breaks down.
- Any ponds or effluent holding facilities must be sealed to reduce leakage.
- The farmer/contractor must spread effluent and sludge in a way that reduces odour and spray drift.
- Each effluent application must not be more than 25 mm deep.
- Effluent must not run off the land into waterways.
- Effluent must not pond on the land surface after application.
If asked by Environment Waikato, the person applying the effluent must be able to show that they have met the above conditions.
Find out more
Find out more about nutrient management and use our online calculation sheets for:
For more information on Environment Waikato’s policy on discharges to land, check out section 3.5.5 of our proposed Waikato Regional Plan. View this map to see the locations of permitted effluent discharge sites and consented volumes discharged to land in our region.
Find out more about treating nutrient runoff in wet areas.
Environment Waikato monitors stock density to find out where livestock farming is likely to have the most effect on soil and water quality in the region.
Check out the Livestock Improvement Advisory for more information on effluent management.
Dairying and the Environment Committee Managing Farm Dairy Effluent
revised and updated edition 2006
Preface
(97 kb, 13 seconds to download, 56k modem)
Chapter 1: Managing Farm Dairy Effluent
(3372 kb, 481 seconds to download, 56k modem)
Chapter 2: Land Application
(4741 kb, 677 seconds to download, 56k modem)
Chapter 3: Pond Systems
(5450 kb, 778 seconds to download, 56k modem)
Chapter 4: Effluent From Feed Pads, Stand Off Areas and Other Sources
(955 kb, 136 seconds to download, 56k modem)
Chapter 5: Regional Council Perspectives
(589 kb, 84 seconds to download, 56k modem)