Processes controlling ammonia emission from livestock slurry in the field

The processes of NH3 emission from field-applied slurry are reviewed and their relative importance assessed. In achieving this objective, the study served to focus on a number of features that have not previously been highlighted. These include the effect of the size of the area to which slurry is applied, the interaction between solar radiation input and wind speed, the role of the solid chemistry and the interaction between slurry NH4+ and the slurry/soil cation exchange capacity (CEC). The most important processes controlling NH3 volatilisation were considered to be turbulent and molecular diffusion in the atmosphere, meteorological processes controlling evaporation and surface temperature, the ion production and buffering processes controlling the pH of the slurry/soil liquid, the solid chemistry that determines precipitation of NH4+ to slurry dry matter, the physical processes controlling the movement of slurry liquid into and within the soil, and the interaction of slurry liquid with soil CEC. (C) 2003 Elsevier B.V. All rights reserved.