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

Adding carbon-rich materials to fields, like manure, may enhance denit rification. Grass filters, which are used to trap surface runoff from these fields, may also provide a carbon-rich environment that favors w ater infiltration and denitrification. Nitrous oxide (N2O) may be evol ved in these settings. It is a radiatively important trace gas and int ermediate in the denitrification pathway and several other microbial p rocesses. We measured N2O flux, after simulated rain, using a soil cov er technique in poultry-manured plots and grass filters receiving thei r runoff. Intact soil cores were used to relate the N2O flux to the de nitrification potential of the plots. Nitrous oxide fluxes were smalle r in grass filters than in manured plots, even though more denitrifyin g bacteria were present. The average N2O flux in the three most dynami c 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.