Ammonia emissions from cattle slurries applied to grassland: Should application techniques be reconsidered?

Ammonia is easily lost after land spreading of livestock slurries. Low-emission techniques entailing injection and trailing shoes have therefore become compulsory in the Netherlands on grassland. There is an argument that the emission of ammonia after surface application is overestimated and that the emission of various other nitrogen (N) compounds, following the prescribed low-emission techniques, is underestimated. Opponents also claim that injection in particular decreases grassland yields due to its negative effect on soil quality and biodiversity. They state that a similar reduction in ammonia emissions could be realized via low-protein dairy cow diets and slurry spreading under favourable weather conditions. This study evaluates these claims and concludes that low-emission techniques reduce the loss of ammonia effectively and increase the availability of N to grassland. There are no indications that low-emission techniques per se have negative effects on soil quality, the productivity of crops and biodiversity. It has also been demonstrated that the efficacy of proposed alternatives is limited.