Nitrous oxide emissions from a sandy-loam textured soil wetted to matric potentials of either-1.0 or-0.1 kPa were determined in laboratory experiments in which the soil was incubated in air (control), air plus 10 Pa C
2H
2 (to inhibit nitrification), 100 kPa O
2 (to suppress denitrification), 10 kPa C
2H
2 (to inhibit N
2O reduction to N
2 in denitrification) or following autoclaving. The total N
2O production, consumption and net N
2O emission from the soils together with the contributions to N
2O emission from different processes of N
2O production were estimated. The rate of N
2O production was significantly greater in the wetter soil (282 pmol N
2O g
-1 soil h
-1) than in the drier soil (192 pmol N
2O g
-1 soil h
-1), but because N
2O consumption by denitrifiers was also greater in the wetter soil, the net N
2O emissions from the wetter and the drier soils did not differ significantly. Non-biological sources made no significant contribution to N
2O emission under either moisture regime and biological processes other than denitrification and nitrification made only a small contribution (1% of the total N
2O production) in the wetter soil. Denitrifying nitrifiers were the predominant source of N
2O emitted from the drier soil and other (non-nitrifying) denitrifiers were the predominant source of N
2O emitted from the wetter soil.
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