Acetylene and N-serve effects upon N2O emissions from NH4+ and NO3− treated soils under aerobic and anaerobic conditions

Abstract N 2 O emissions from soils treated with NH 4 + -N under aerobic conditions in the laboratory were 3- to 4-fold higher than those from controls (no extra N added) or when NO 3 − -N was added. Although the emission of N 2 O-N in these field and laboratory experiments represented only 0.1–0.8% of the applied fertilizer NH 4 + -N and are therefore not significant from an agronomic standpoint, these studies have conclusively demonstrated that the oxidation of applied ammoniacal fertilizers (nitrification) could contribute significantly to the stratospheric N 2 O pool. Like N-serve, acetylene was shown to be a potent inhibitor of nitrification as it stopped the oxidation of NH 4 + -N to (NO 3 + -N + NO 2 − )-N and hence reduced the evolution of N 2 O from nitrification within 60 min after its addition. Although high amounts of NO 3 − -N were present, the rate of denitrification was very low from soils with moisture up to 60% saturation. The further increase in the degree of saturation resulted in several-fold increase of denitrification which eventually became the predominant mechanism of gaseous N losses under anaerobic conditions.