Nitrous oxide emissions from manure and inorganic fertilizers applied to spring barley

Nitrous oxide emissions from soil amended with untreated liquid manure (slu rry), anaerobically digested slurry, or inorganic fertilizers (calcium ammo nium nitrate or urea) were quantified in a field study revering two growth seasons of spring barley (Hordeum vulgare L.), In the first year incorporat ion before seeding was compared with trail hose application 5 wk after seed ing, In the second year all fertilizers were applied before seeding, while soil moisture and initial NO3- availability was varied. Accumulated N2O los ses between the time of fertilization and ca. 1 July represented 0.14 to 0. 35%: of total N in 1996 and 0.34 to 0.64% in 1997, In both years the highes t N2O emissions were observed with untreated slurry, whereas digested slurr y and inorganic fertilizers Here at a similar level,Increasing the soil moi sture content or NO3-; availabiliiy had no significant effect on accumulate d N2O losses. Although metabolizable C may thus have stimulated N, emission s via denitrification from untreated slurry, the largest contribution to N2 O fluxes probably came from nitrification with all fertilizer types, Using the IPCC guidelines it was estimated that anaerobic digestion of slurry per se could potentially reduce N,O emissions from Danish agriculture hy 1.2 t o 2.5%.