Odour and ammonia emissions following the spreading of anaerobically-digested pig slurry on grassland

Anaerobically digested and untreated pig slurries were spread on grassland plots and measurements of odour and ammonia emissions made using a systems of small wind tunnels. Digestion reduced total solids (TS), total nitrogen (TN) and volatile fatty acid (VFA) content of pig slurry and increased pH value. Odour emission during the first 6 h following application was reducd by between 70–80%. Odour intensity was also reduced, but odour offensiveness when measured at the same intensity was unchanged. Digestion had no significant effect on the ammonia volatilization from pig slurry following application to grassland.