N dynamics and sources of N2O production following pig slurry application to a loamy soil

Carbon (C) and Nitrogen dynamics and sources of nitrous oxide (N2O) production were investigated in a loamy soil amended with pig slurry. Pig slurry (40000 kg ha(-1)) or distilled H2O was applied to intact soil cores of the tipper 5 cm of a leanly soil which were intubated under aerobic conditions for 28 days at 25 degrees C. Treatments were with or without acetylene (C2H2), which is assumed to inhibit the reduction of N2O to dinitrogen (N-2), and with or without dicyandiamide (DCD), which is thought to inhibit nitrification, Volatilization of ammonia (NH3). pH, carbon dioxide (CO2) and N2O production, and ammonium (NH4+) and nitrate NO3-;) concentrations were monitored. The pH of the pig slurry amended soil increased from an Initial value of 7.1 to pH 8.3 within 3 days: it then decreased slowly but was still at a value of 7.4 after 28 days. Twenty; percent of the NH4+ applied volatilized within 28 days. Sixty percent of the C applied in the pi:: slurry evolved as CO2, if no priming effect was assumed, but only 38% evolved when the soil was amended with DCD. Pig slurry significantly increased denitrification and the ratio between its gaseous products, N2O and N-2, was 0.21. No significant increases in NO3- concentration occurred, and N2O produced through nitrification was 0.07 mg N2O-N kg(-1) day(-1) or 33% of the total N2O produced, C2H2, was used as a C substrate by microorganisms rind increased the production of N2O.