Field experiments (IMAGE) Aarhus University Caption The atmospheric concentration of nitrous oxide primarily increases due to the agricultural use of commercial fertilizers and livestock manure. A recent study has determined the emission levels of nitrous oxide from various sources such as commercial fertilizers, slurry, and biogas slurry under Danish conditions. Credit Jens Bonderup Kjeldsen Usage Restrictions Only to be used with this article License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.