To provide better advice to farmers and authorities on the most efficient way to reduce ammonia volatilisation from slurry applied to fields with standing crops, various treatments and injection methods were tested in field trials. In six separate experiments conducted at Research Centre Foulum, Denmark from 2007 to 2009, pig slurry was applied to winter wheat ( Triticum aestivum L.) to determine how anaerobically digestion, solid-liquid separation of slurry and different soil injection techniques influence crop yield and ammonia emissions (NH 3). The NH 3 emission was measured by either a wind-tunnel method or by a micro-meteorological mass balance method. Both injection and solid-liquid separation were found to reduce NH 3 emission. The emission from the separated slurry did not include the emission from the solid fraction. Most effective injection techniques were found to be a winged tine or a combination of discs and a tine, which reduced NH 3 emission from approximately 20% (surface band spreading) to approximately 5% of applied Total Ammoniacal Nitrogen (TAN). The NH 3 emission from surface-applied anaerobically digested slurry was found to be almost twice that from surface-applied untreated slurry. Injection did not affect yields significantly compared with surface application in any of the experiments, but did result in a significantly increased protein content in grains compared to band application, which increased the nitrogen utilisation of slurry nitrogen. Of the techniques tested, soil injection and solid-liquid separation reduced NH 3 emissions most effectively.
