Voluntary code details how farmers can reduce ammonia emissions

A  guide published on Friday (27 July) sets out the steps farmers, advisers and contractors can take to reduce ammonia emissions and help improve air quality.

The Code of Good Agricultural Practice for Reducing Ammonia Emissions sets out simple steps all farmers can take to reduce ammonia emissions, such as using a nutrient management plan to calculate fertiliser application rates.

See also: Ways to reduce farm ammonia emissions

It also includes more significant recommendations for slurry storage, spreading equipment and infrastructure, alongside innovative techniques such as slurry and digestate acidification and separation.

Defra environment minister Thérèse Coffey said: “Air pollution is not just an urban issue and, with 88% of ammonia emissions coming from farming, the government is taking concerted action.

“With clear new guidance and financial support, we will help farmers across the country to take action, reduce emissions and help improve air quality.”

Financial help

Defra says it is investing £3m over the next three years to fund a specialist team of experts who will offer advice and guidance on the most effective ways to reduce emissions from ammonia on farmland.

It will also fund demonstrations of the latest low-emission spreading equipment and one-to-one advice, which will be available from catchment sensitive farming officers by the end of this year. 

The countryside productivity scheme under the Rural Development Programme for England is already offering 40% grants towards much of the manure management equipment recommended in the code.

This includes low-emission spreading equipment, slurry and digestate storage bags, digestate processing equipment and mild acidification equipment.

Farmers in priority catchments for reducing water pollution may also be eligible for grants towards covers for slurry stores and lagoons under the Countryside Stewardship scheme.


The voluntary code has been written by Defra in collaboration with the NFU, the Agriculture and Horticulture Development Board (AHDB) and the Agricultural Industries Confederation.

NFU environment forum chairman Mark Pope said the code would benefit the environment and resource efficiency.

“Farmers have recognised there is a need to reduce their ammonia emissions and the sector has made improvements, with levels dropping by 10% in the past 30 years.

“However, further reductions are required from the industry in order to meet targets set under the government’s Clean Air Strategy. We urge Defra to continue to offer farmers guidance on this issue, alongside targeted financial support where necessary.”

Key advice from the Code of Good Agricultural Practice

Storing organic manures

  • Ensure your farm has enough well-maintained storage to be able to spread slurry only when your crops will use the nutrients.
  • Cover slurry and digestate stores or allow your slurry to develop a natural crust.
  • Use slurry or digestate storage bags.
  • Cover field heaps of manure with plastic sheeting.

Spreading organic manures

  • Use a nutrient management plan and regularly test manure and soil to calculate suitable application rates and plan timing.
  • Spread only the right amount, in the right place, at the right time.
  • Spread in cool, windless and damp conditions.
  • Spread slurry and digestate using low emission spreading equipment (trailing hose, trailing shoe or injection) rather than surface broadcast (splash plate).
  • Incorporate solid manure, separated fibre, cake or compost into the soil by plough, disc or tine as soon as possible and at least within 12 hours
  • Consider processing slurry or digestate, such as by acidification (with professional equipment and advice) or separation.

Spreading manufactured fertilisers

  • Use a nutrient management plan to calculate suitable times and rates of application.
  • Switch from urea-based fertilisers to ammonium nitrate.
  • Use urease inhibitors with urea-based fertilisers.
  • If applying urea-based fertilisers, spread when rainfall is due, apply by injection to soil or incorporate into soil as soon as possible.
  • Apply ammonium nitrate in cool and moist conditions but avoid applying when rainfall is expected.

Livestock diets

  • Consider using a professionally formulated diet to match the nutrient content of the feed to the requirements of the animal at different production stages.

Livestock housing

  • Regularly clean housing and yards and remove manure. For example, use a belt system to remove layer manure twice a week and regularly wash and scrape cattle yards.
  • Minimise the amount of mixing between urine and faeces (as ammonia forms when these two mix). For example, use grooved floors in cattle housing to channel urine.
  • Minimise the surface area of exposed slurry pits. For example, use V-shaped gutters and reduce the surface area of the slatted area in pig housing.
  • Keep poultry litter and manure dry. For example, ventilate colony deep pit or channelled systems.

Ammonia emissions on the rise

The  Code of Good Agricultural Practice coincides with publication of a  report from the Environment Agency (EA), which shows, unlike other main air pollutants, emissions of ammonia have increased since 2013, with damaging consequences for soils, habitats and freshwaters.

The vast majority of UK ammonia emissions, 88%, come from the agricultural sector as a result of such activities as fertiliser use and slurry storage, says the EA.

“Higher concentrations and deposition levels are associated with areas of intensive livestock production, especially dairy and beef.”

EA chairwoman Emma Howard Boyd said: “Urgent action is needed if we are going to tackle the hidden blight of ammonia emissions. As custodians of the land, farmers must take the lead by changing their land management practices.”

The report shows  progress has been made in reducing many pollutants, such as nitrogen oxide, particulate matter and sulphur dioxide.

“However, while legal limits are being met for the majority of pollutants… under current projections, emission reduction targets for 2030 will not be met,” it adds.

As such, the government has moved to address these issues by publishing its Clean Air Strategy, which is out for consultation. Clean air is also the first of the 10 major goals set in the 25-year environment plan.