What is driving the focus on nutrient management?
The National Policy Statement for Freshwater Management, issued by central government in 2011, requires all regional councils to set quality limits on all ground and surface water bodies within their region by December 2030.
Under the Sustainable Dairying: Water Accord, milk companies have signed up to collect and model nitrogen (N) loss and nitrogen conversion efficiency (NCE) from all dairy farms. This means farmers will need to provide N loss and NCE performance information and benchmarks to their suppliers.
Hotspots for nitrogen losses on a dairy farm
Click on the hotspots below for information or scroll down the page to read them all.
Pathway to water: Leaching due to stock urine in a concentrated spot; minerals stirred up during tillage; poor fertiliser application or winter fallow leaching.
Practices to reduce N leaching:
- Urine N leaching can be reduced through appropriate paddock selection, grazing time and grazing regime.
- Fertiliser N leaching can be reduced through the use of crop calculators to gauge need and precision application to ensure appropriate application and timing.
- Winter fallow N leaching can be reduced through the use of a cover crop or late harvests.
- Mineral N leaching can be reduced through the use of minimal tillage.
Pathway to water: Leaching if fertiliser is applied in inappropriate amounts, times or locations
Practices to reduce N leaching:
- Avoid direct leaching by not applying in winter or to water logged soils.
- Soil test to ensure other nutrients are not limiting.
- Optimise your response rate and pasture utilisation.
Pathway to water: direct runoff or leaching due to application at inappropriate amounts, times and locations.
Practices to reduce N leaching:
- Measure effluent application rates to ensure they are suitable for your soil type
- Ensure storage is sufficient so you don’t have to irrigate during wet periods and busy times
- Have an effluent block that is a suitable size for your application and makes efficient use of your nutrients.
Pathway to water: Runoff due to poorly maintained infrastructure, leaching due to unsealed storage
Practices to reduce N leaching:
- Ensure storage ponds and tanks are lined to prevent leaching and big enough to avoid irrigation onto wet soils and during busy times
- Maintain your infrastructure regularly to avoid leakage, burst pipes, blocked nozzles and pump failure.
Generally irrigation water is not a source of nutrient loss. Like rain, irrigation water decreases the available water holding capacity of soil which increases the risk of N leaching. Oversaturation of soils can also lead to pooling and runoff.
Pathway to water: Most N leached in dairy systems comes from urine patches. The rate of N applied per ha in a urine patch can be equivalent to 500-1000 kg N/ha /yr. Plants cannot use all the N before it drains down the soil profile and leaches.
Practices to reduce N leaching:
- Use off-paddock facilities strategically to capture the N from dung and urine - for more information on stand-off facilities click here.
- Grazing cows off-paddock in the autumn months before winter rains flush N downwards reduces N leaching the most.
Before you make changes to the farm system or invest in off-paddock facilities, analyse your situation thoroughly to ensure it solves your problem, and your system remains profitable YES add here.
Pathway to water: Most N leached in dairy systems comes from urine patches. The rate of N applied per ha in a urine spot can be equivalent to 500-1000 kg N/ha /yr. Plants cannot use all the N before it drains down the soil profile and leaches. Grazing cows off in winter will reduce the N leached on the milking platform and can have positive effects on soils and pasture grown.
Practices to reduce N leaching
- Grazing cows off farm in winter may help reduce N leached on your milking platform, but just transfer the leaching to another area. Wintering off farm also has large system effects which you need to review carefully. To review your wintering system and determine options click here. Or visit the Southern Wintering Systems page for more information.
Before you make changes to the farm system or invest in off-paddock facilities, analyse your situation thoroughly to ensure it solves your problem, and your system remains profitable.
Frequently asked questions
What do all the N figures mean? N loss? N surplus? N conversion efficiency?
N loss is how much of your nitrogen inputs are lost or leached to waterways. The diagram below shows the N cycle including where N is leached out the bottom.
N conversion efficiency (NCE) describes the proportion of nitrogen going into a farm (inputs) that is converted to saleable products (outputs). NCE is expressed as a percentage. 60% NCE means that 60% of your Nitrogen inputs are being converted into saleable outputs.
N surplus is the difference between N inputs (fertiliser, clover, supplementary feed) and N outputs in product (milk, meat, exported feed) It is calculated using a nutrient budget.
What is P loss?
P loss refers to how much of your phosphorous (P) inputs are lost or leached to waterways. P tends to bind to soil particles (sediment). Dung and farm dairy effluent contain high levels of P. Therefore losses of P on dairy farms are closely linked to losses of sediment and faecal matter.
The majority of P is lost to waterways in two ways:
Overland flow - when dung, fertiliser or farm dairy effluent are applied on land with a slope, it it increases the risk runoff into water, particularly if in rains shortly after.
Erosion - P is sticky and binds to soil particles. Any activities that disturb the soil, such as pugging, cultivation or erosion, cause losses of soil particles and therefore losses of P.
The diagram below shows the P cycle including where P runs off into water.
How can I reduce P loss?
You can reduce P loss by carefully managing P in fertiliser and effluent as well as managing sediment and faecal matter losses.
Some practical practices are:
- Use riparian planting as a buffer between paddocks, races and the water. The plants act as a filter, slowing down runoff and catching sediment and P.
- Carefully select your paddocks, grazing routines and crops to minimise disrupting the soil and runoff to waterways, particularly during winter months.
- Maintain races and direct water running off them away from waterways and into paddocks through the use of cut-offs.
- Test soil regularly to ensure Olsen P levels are within the optimum range; this minimises the amount of P leaving your farm in loss events.
- Control slips and hillside erosion to prevent losing valuable topsoil and P to waterways.
- Direct any effluent that collects on hard surfaces such as concreted races, bridges or culverts into your effluent system.
- Use good management practices to apply your P fertiliser and effluent to ensure they do not run off to waterways.
What part does science play in the nutrient limit setting process?
- Improved scientific understanding and increased research around the relationship between nitrogen leaching and water quality is the main driving force behind environmental rule changes.
- There are many scientific projects looking at options for farmers to reduce their nutrient loss. Pastoral 21, Forages for reduced N loss, are examples of such projects. Their scope ranges from component aspects of feed, urine patch, and rumen plot research through to farmlet and whole farm scale monitoring.
- DairyNZ is involved with industry partners AgResearch, Plant & Food, FAR, Massey University, and Lincoln University to better understand the environmental and economic aspects of the farm system.
Why do the rules keep changing?
- As knowledge around the relationship between water quality and land use has evolved and as land use (e.g. urban growth, agriculture, and industry) has intensified, national government and regional councils have adjusted their rules accordingly.
- In many regions the rules have not actually changed, however the interpretation or enforcement has become stricter as the impact of not enforcing them becomes clearer.
A good example of this is Variation 6 in the Waikato Region; a requirement for water take consents had always existed but had not been effectively enforced until Variation 6 allowed it to.
- It's not only about dairy farming - all industries (e.g. factories, mills, horticulture, sheep and beef and dairy, etc.) will need to contribute to improving water quality relative to their impact. It is good practice to speak with your young stock or winter graziers (if you have them) to ensure your animals are not allowed to enter waterways while on their property.
- Central government has made it clear they want to actively engage local communities to determine which water quality values to protect and what level or protection is needed.
Collaborative stakeholder groups are being formed from the different stakeholders in the catchment to work out the values and recommend limits. They will all then have to stick to the rules, not just dairy farmers.
What can I do now?
The best thing you can do is to improve your understanding of how your farm is performing environmentally, and what the risks of this may be. There are two ways to do that: through education and training and through a system of measure/monitor/record.
- Education or training could be about attended formal courses such as the ASL Nutrient Management courses, IrrigationNZ Managers Training etc. It could also be informal such as reading DairyNZ resources or scientific articles.
- Measuring, monitoring and recording are important to ensure you have accurate data for inputs and outputs of the system. It also ensures you have accurate data around the performance of effluent irrigators, irrigation systems, timing and placement of nutrients etc. These records help you identify risks and make good business decisions. The DairyNZ Farm EnviroWalk is a great tool to identify risks on your farm.
- There are many changes you can put into action that do not cost anything to implement. Farming by using best management practices will have benefits to your system and the environment. Overseer already assumes that you are farming this way, so it will not influence future impacts of policy change but will show how you are being responsible on your farm.
- Accurately define what your farm situation (nutrient budget, risks, etc.) was before you started making changes. Then document what changes were made and when they occurred, with documented proof (GPS maps, receipts, contracts, photos, etc). This could be used to show how you are being responsible on your farm.
- There is a risk if we don’t make improvements now that water quality will continue to decline in some areas, and consequently rules and regulations may be tougher on us, as we have not shown responsibility by improving.
What is DairyNZ doing to help?
- DairyNZ is working at the policy development stage and also at the implementation stage of regional plans to ensure dairy farmers are well represented. For more information see the Advocacy and Policy section of this website.
- We are also working with other primary sector groups, including Federated Farmers, to respond to the regulatory processes regional councils are implementing including catchment limit setting.
- We have support from our water quality scientists who work to ensure regulations have a sound basis in science. Our economists help quantify the impact of changes on the region.
- Together with industry partners AgResearch, Plant & Food, FAR, Massey University, Lincoln University we research the environmental aspects of the farm system.. This helps us inform regulators and farmers to reach targets or limits.
What is Overseer and how does it work?
Overseer is the software programme used to model nutrient cycling on-farm and one of the outputs is an estimate of nitrogen losses to water, reported as kg Nitrogen/hectare/year.
A variety of farm information is collected from the farmer and then, along with accurate soil and climatic information, the farm system is modelled in the Overseer programme following a consistent process guided by the ‘Best Practice Data Input Standards’. These standards outline a standardised method of modelling farm systems, to ensure the process is as robust as possible.
What's happening in my region?
Check out the In Your Region section of the website for updates on what is going on in your region. Or click on your region below: