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Diurnal pattern of nitrous oxide emissions from soils under different vertical moisture distribution conditions
Xu, Junzeng; Wei, Qi; Yang, Shihong; Wang, Yanhua & Lv, Yuping
Abstract
The diurnal pattern of nitrous oxide (N2O) emissions is
essential in understanding how weather and soil conditions
influence the daily mean estimate of N2O fluxes.
Incubation experiments were conducted to investigate the
effects of vertical soil moisture distribution patterns on
diurnal variation of N2O emissions. Clear diurnal patterns
of N2O emissions on both surface watering (SW) and
subsurface watering (SUW) treatments (SUW12, SUW15,
and SUW18) were detected from soil sample (I), silty clay,
and soil sample (II), sandy loam, where peak N2O fluxes
usually occurred between 12:00 and 18:00 h. Different
vertical watering patterns resulted in changes in the daily
range of N2O fluxes and peak time. Mean fluxes from the
SUW12, SUW15, and SUW18 treatments were 37.4%,
32.7%, and 43.3% lower than those from SW treatments
from soil sample I, and 32.0%, 40.3%, and 41.1% from
soil sample II. Moisture distribution patterns under SUW
soils could be effective to mitigate N2O emissions. The
N2O emissions from soil sample I ranged from178.3 to
2741.0 μg N2O m-2 h-1, which was more than in soil sample
II with 7.0 to 83.7 μg N2O m-2 h-1. The different soil texture
and N content level might account for the differences in
magnitude of N2O fluxes from soils. The optimal soil
moisture condition for peak N2O fluxes in the SW treatment
had relatively narrower ranges than the SUW treatments
with 46% to 60% water-filled pore space (WFPS) for soil
sample I and 26% to 34% WFPS for soil sample II even
though surface soil moisture for peak N2O fluxes were
somewhat different from the previously reported optimal
soil moisture range of 45% to 75% WFPS.
Keywords
Diurnal pattern; nitrous oxide; non-uniform vertical distribution; soil moisture; water-filled pore space
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