Nitrous oxide losses from untreated and digested slurry as influenced by soil moisture and application method

• Successful validation of soil packaging and gas sampling methods.
• Increasing water filled pores space stimulated N2O emissions.
• Limited effects of soil injection of animal slurry on N2O emission.
• Tendency for increased N2O emission following injection of fermented slurry.

Effects of injection depth, slurry composition and soil moisture content on N2O emissions were investigated at laboratory scale. A loamy sand soil was moistened to 61, 64 or 71% of water-filled pore space (WFPS) and packed to the field bulk density. Using a mechanical device, untreated (UN) or anaerobically digested (AD) pig slurry (122 kg N ha−1) was injected to 30 or 60 mm below the soil surface to simulate closed slot injection. Soil with no slurry applied was included as reference. Incubations were carried out at 20 °C for 30 days; emissions of N2O and CO2 were determined several times by a photo-acoustic analyser. Pre-trials were conducted to validate soil packing and gas analysis methods. The experimental setup was found suitable for studying the regulation of N2O emissions from soil. In some cases, increasing WFPS stimulated N2O emissions while in other cases the increase in emission was not statistically significant with increasing WFPS. There were no effects of injection depth and slurry treatment, except that at 71% WFPS N2O emissions were lower from UN compared to AD slurry and the untreated control.