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) pr oduction were investigated in a loamy soil amended with pig slurry. Pi g 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 o r without acetylene (C2H2), which is assumed to inhibit the reduction of N2O to dinitrogen (N-2), and with or without dicyandiamide (DCD), w hich is thought to inhibit nitrification, Volatilization of ammonia (N H3). pH, carbon dioxide (CO2) and N2O production, and ammonium (NH4+) and nitrate NO3-;) concentrations were monitored. The pH of the pig sl urry amended soil increased from an Initial value of 7.1 to pH 8.3 wit hin 3 days: it then decreased slowly but was still at a value of 7.4 a fter 28 days. Twenty; percent of the NH4+ applied volatilized within 2 8 days. Sixty percent of the C applied in the pi:: slurry evolved as C O2, if no priming effect was assumed, but only 38% evolved when the so il was amended with DCD. Pig slurry significantly increased denitrific ation and the ratio between its gaseous products, N2O and N-2, was 0.2 1. No significant increases in NO3- concentration occurred, and N2O pr oduced through nitrification was 0.07 mg N2O-N kg(-1) day(-1) or 33% o f the total N2O produced, C2H2, was used as a C substrate by microorga nisms rind increased the production of N2O.