Ammonia Emissions from Irrigation of Dilute Pig Slurries

Approximately 20% of pig slurry in the UK is applied to land as dilute slurry (<2% dry matter content) via irrigation systems, which may result in larger emissions of ammonia (NH3) to the atmosphere than conventional application techniques. This study aimed to quantify this source under UK conditions and to assess the possibilities for emission abatement using alternative application techniques. Methodology was developed to measure emissions during irrigation, from both raingun- and boom-mounted splashplate systems. Measurements were also made following irrigation at both field- and small-plot scales. Emissions during irrigation of pig slurry to land were small, representing <0·1–2·5% of the total ammoniacal N (TAN) applied. Emissions from the land surface following irrigation were also small, typically amounting to only 10% of the TAN applied. Application via trailing hoses (band spreading) gave some reductions in emission for applications to growing crops, but no reduction when used on cereal stubble. Irrigation of dilute pig slurries does not therefore represent a major source of NH3 emission in the UK and, based on the results of this study, replacement of raingun or splashplate irrigation systems with trailing hose booms cannot be recommended as a worthwhile mitigation option.