Ammonia emissions from farming are causing environmental problems on local and regional scales in Europe and elsewhere. These emissions also reduce the efficiency of manure as a fertilizer 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 fertilizers. The processes involved in the release of ammonia from slurry, the transport of ammonium and pH changes in surface layers of stored slurry, and slurry and fertilizers applied to the surface of bare soils are described. Techniques and management practices that reduce ammonia emission are presented and evaluated. The book provides a better understanding of 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 book 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. Thesis.