N2O AND NO EMISSIONS FROM GRASSLAND SOILS AFTER THE APPLICATION OF CATTLE AND SWINE EXCRETA

N2O and NO fluxes from grassland soil after the application of cattle and swine excreta were measured by a closed chamber method in the autu mn and winter of 1994 to 1995. Fresh excrement and urine were spread o n the grassland experimental plots and these gas fluxes were measured one or two times a week. In the autumn experiment, N2O and NO fluxes b egan to increase several days after the application, the NO flux reach ing a maximum after 16 days. In the winter experiment, N2O and NO flux es began to increase 45 days after the application and reached a maxim um after 80 days. Nitrous oxide flux was influenced by soil water cont ent, high water content leading to high N2O flux. The ratio of NO-N/N2 O-N in the flux was in the range of 1.1 to 13.7, and negatively correl ated to the soil water content. In the winter experiment, the total em ission rate of NO was 0.48% and 0.45% of total nitrogen in the applied cattle and swine excreta, respectively. The total emission rate of N2 O was 0.085% and 0.098% in the applied cattle and swine excreta, respe ctively.