Nitrogen, in the form of ammonia, is lost from organic manures (such as slurry, solid manure and litter, digestate, sludge and compost) when they come into contact with air, particularly on warm or windy days. Nitrogen is also lost from manufactured fertilisers during spreading. The more that this occurs, the more nitrogen is lost as ammonia, meaning the material is a less effective fertiliser and loses value. Therefore, measures to reduce ammonia emissions and improve overall nutrient management practices could reduce the amount of manufactured fertiliser that farmers need.
A summary of the relevant key points for compost and digestate is provided below. Further information, rationale and sources of support are provided in each chapter.
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.
- keep poultry manure and litter dry.
- 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.
Full details can be found here.