Effect of liquid manure on the mole fraction of nitrous oxide evolved fromsoil containing nitrate

The same emission factor is applied to fertiliser N and manure N when calcu lating national N2O inventories. Manures and fertilisers are often applied together to meet the N needs of the crop, but little is known about potenti al interactions leading to an increase in denitrification rate or a change in the composition of the end-products of denitrification. We used the N-15 gas-flux method in a laboratory experiment to quantify the effect of liqui d manure (LM) application on the fluxes of N-2 and N2O when the soil contai ned fertiliser (NO3-)-N-15. LM increased the mole fraction of N2O from 0.5 to 0.85 in the first 12 h after application. More than 94% of the N2O was f rom the reduction of NO3-, probably due to aerobic nitrate respiration as w ell as respiratory denitrification. (C) 2000 Elsevier Science Ltd. All righ ts reserved.