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

Abstract

A laboratory experiment was designed to determine the fate of 15N-labelled slurry ammonium (15NH4-N) and compare soil inorganic-N distribution following surface applied or injected pig slurry. A system of cylindrical volatilization chambers equipped to allow continuous trapping of ammonia (NH3) was used. Undisturbed soil columns were placed in the chambers prior to the application of slurry. A nitrogen balance including soil, air and plant analysis was established for both treatments, 8 days after application. Average cumulative emissions of NH3 were 15% and 11% of the total ammoniacal-N added with the surface and injected treatments, respectively. After 8 days 55% of the 15NH4-N applied through slurry injection was recovered in the soil inorganic-N pool: 37% as 15NH4-N and 18% as 15NO3-N. These figures compare with only 25% 15NH4-N recovered with the surface applied slurry treatment: 7% as 15NH-N and 17% as 15NO3-N. Immobilization into soil organic-N accounted for 8% of the 15NH4-N applied for the injected treatment and 6% of the surface applied slurry-15N. 15N uptake by the grass was 2% and 7% for the injected and surface applied treatments, respectively. The percentage of added 15N accounted for was 76% for the injected treatment and 53% for the surface applied slurry treatment.