Ammonia emissions from farming are causing environmental problems on local and regional scale in Europe and elsewhere. These emissions also reduce the efficiency of manure as a fertiliser in crop production. This thesis presents a body of research and development on technologies to reduce ammonia emissions from stored animal slurry, field-applied slurry and mineral fertilisers. The processes involved in the release of ammonia from slurry, transport of ammonium and pH changes in surface layers of stored slurry and slurry and fertilisers applied to the surface of bare soils are described. Techniques and management practices that reduce ammonia emission are presented and evaluated. With continued research, we will better understand the relationships between ammonia emissions and the most important underlying processes. This information can be used to develop technologies, models and decision support for better management of animal manure, leading to a minimal negative impact on the environment and a strong positive impact on plant production. The thesis makes a contribution to research using basic science to develop applied technological solutions. It also proposes areas for future research that can enable efficient use of manure and reduce environmental pollution.