Ammonia emission from field applied manure and its reduction—invited paper

Emissions of ammonia to the atmosphere are considered a threat to the environment and both United Nation treaty and European Union legislation increasingly limit emissions. Livestock farming is the major source of atmospheric NH3 in Europe and field applied manure contributes significantly to the emission of NH3 from agriculture. This paper presents a review of studies of NH3 emission from field-applied animal manure and of the methods available for its reduction. It is shown that there is a complex relationship between the NH3 emission rate from slurry and the slurry composition, soil conditions and climate. It is concluded that simple empirical models cannot be used to predict ammonia emission from the wide range of circumstances found in European agriculture and that a more mechanistic approach is required. NH3 emission from applied solid manure and poultry manure has been studied less intensively than slurry but appear to be controlled by similar mechanisms. The use of trail hoses, preor post-application cultivation, reduction in slurry viscosity, choice of application rate and timing and slurry injection were considered as reduction techniques. The most effective methods of reducing ammonia emissions were concluded to be incorporation of the animal slurry and farmyard manure or slurry injection. Incorporation should be as close to the application as possible, especially after slurry application, as loss rates are high in the 1st hours after application. Injection is a very efficient reduction technique, provided the slurry is applied at rates that can be contained in the furrows made by the injector tine. © 2001 Published by Elsevier Science B.V.