Ammonia volatilisation and crop yield following land application of solid–liquid separated, anaerobically digested, and soil injected animal slurry to winter wheat

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 (NH3). The NH3 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 NH3 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 NH3 emission from approximately 20% (surface band spreading) to approximately 5% of applied Total Ammoniacal Nitrogen (TAN). The NH3 emission from surface-applied anaerobically digested slurry was found to be almost twice that from surface-applied untreated slurry.