Greenhouse gas emissions after application of digestate: short-term effects of nitrification inhibitor and application technique effects

Nitrogen-use efficiency in arable agriculture after organic fertilization can be improved by the incorporation of digestate into soil and through the use of nitrification inhibitors. To test the efficiency and the interaction of these measures, a laboratory microcosm study was conducted with undisturbed samples from two arable soils – a Gleysol and a Plaggic Anthrosol. Treatments were digestate application by injection to 15 or 20 cm depths or by trailing hose with subsequent incorporation. Half of the replicates of each application treatment were treated with the nitrification inhibitor 3,4-dimethyl pyrazole phosphate (DMPP). Emissions of the greenhouse gases (GHGs) CO₂, N₂O and CH₄ were monitored during 51 days of incubation. Deeper injection (20 cm) did not lead to different GHG emissions compared with a shallow injection (15 cm). Application of DMPP decreased cumulative N₂O emissions significantly by 17–70%. DMPP inhibited N₂O fluxes and NO₃- production, suggesting a positive effect of DMPP on the mitigation of direct GHG emission and nitrate leaching at least during several weeks after digestate fertilization. The effect of DMPP is independent of the application technique.