NITROUS-OXIDE FLUX FROM POULTRY-MANURED EROSION PLOTS AND GRASS FILTERS AFTER SIMULATED RAIN

Adding carbon-rich materials to fields, like manure, may enhance denitrification. Grass filters, which are used to trap surface runoff from these fields, may also provide a carbon-rich environment that favors water infiltration and denitrification. Nitrous oxide (N2O) may be evolved in these settings. It is a radiatively important trace gas and intermediate in the denitrification pathway and several other microbial processes. We measured N2O flux, after simulated rain, using a soil cover technique in poultry-manured plots and grass filters receiving their runoff. Intact soil cores were used to relate the N2O flux to the denitrification potential of the plots. Nitrous oxide fluxes were smaller in grass filters than in manured plots, even though more denitrifying bacteria were present. The average N2O flux in the three most dynamic erosion plots was 755 mug N2O-N m-2h-1, which was 39% of the maximal denitrification rate measured in acetylene-blocked, NO3--amended soil cores. Nitrous oxide flux immediately after rainfall was greater than N2O flux measurements reported for similar agricultural settings.