Nitrogen transformations and ammonia loss following injection and surface application of pig slurry: a laboratory experiment using slurry labelled with N-15-ammonium

A laboratory experiment was designed to determine the fate of N-15-labelled slurry ammonium ((NH4)-N-15-N) and compare soil inorganic-N distribution f ollowing surface applied or injected pig slurry. A system of cylindrical vo latilization chambers equipped to allow continuous trapping of ammonia (NH3 ) was used. Undisturbed soil columns were placed in the chambers prior to t he application of slurry. A nitrogen balance including soil, air and plant analysis was established for both treatments, 8 days after application. Ave rage cumulative emissions of NH3, were 15% and 11% of the total ammoniacal- N added with the surface and injected treatments, respectively. After 8 day s 55% of the (NH4)-N-15-N applied through slurry injection was recovered in the soil inorganic-N pool: 37% as (NH4)-N-15-N and 18% as (NO4)-N-15-N. Th ese figures compare with only 25% N-15-NH4 recovered with the surface appli ed slurry treatment: 7% as (NH4)-N-15-N and 17% as (NO4)-N-15-N. Immobiliza tion into soil organic-N accounted for 8% of the (NH4)-N-15-N applied for t he injected treatment and 6% of the surface applied slurry-N-15. N-15 uptak e by the grass was 2% and 7% for the injected and surface applied treatment s, respectively. The percentage of added N-15 accounted for was 76% for the injected treatment and 53 % for the surface applied slurry treatment.