Environmental conditions and agricultural management events affect the availability of substrates and microbial
habitat required for the production and consumption of nitrous oxide (N2O), influencing the temporal and spatial variability of N2Ofluxes from soil. In this study, we monitored for diurnal and event-related patterns in N2O
emissions in thefield, evaluated how substrate availability influenced denitrification, and assessed N2Oreduction potential following major events in two tomato (Lycopersicon esculentum) management systems on clay
loam soils: 1) conventional (sidedress fertilizer injection, furrow irrigation, and standard tillage) and 2) integrated (fertigation, subsurface drip irrigation, and reduced tillage). Potential denitrification activity, substrate limitation, and reduction to N2were measured with an anaerobic slurry technique. In thefield, we found no consistent
diurnal patterns. This suggests that controlling factors that vary on an event-basis overrode effects of diurnally
variable controls on N2O emissions. The lack of consistent diurnal patterns also indicates that measuring N2O
emissions once per day following major events is sufficient to adequately assess annual N2O emissions in
those systems. Nitrous oxide emissions varied per event and across functional locations in both systems. This illustrates that mechanisms underlying N2O emissions vary at relatively small temporal and spatial scales and
demonstrates the importance of studying N2O emissions in the context of events and functional locations. In
the conventional system, N2Ofluxes were high [74.2 ± 43.9–390.5 ± 90.1μgN2O-N m
−2
h
−1
]andN2O reduction potential was significant. Both management systems exhibited carbon limitation on denitrification rates;
and rates were N limited in the third fertigation event in the integrated system. Ourfindings suggest that denitrification is strongly contributing to high N2O emissions in conventional tomato cropping systems in California.
Hence, management practices that reduce the conditions that favor denitrification, such as subsurface drip
irrigation, are promising strategies for N2O reduction.
Published by Elsevier B.V
Environmental conditions and agricultural management events affect the availability of substrates and microbial
habitat required for the production and consumption of nitrous oxide (N2O), influencing the temporal and spatial variability of N2Ofluxes from soil. In this study, we monitored for diurnal and event-related patterns in N2O
emissions in thefield, evaluated how substrate availability influenced denitrification, and assessed N2Oreduction potential following major events in two tomato (Lycopersicon esculentum) management systems on clay
loam soils: 1) conventional (sidedress fertilizer injection, furrow irrigation, and standard tillage) and 2) integrated (fertigation, subsurface drip irrigation, and reduced tillage). Potential denitrification activity, substrate limitation, and reduction to N2were measured with an anaerobic slurry technique. In thefield, we found no consistent
diurnal patterns. This suggests that controlling factors that vary on an event-basis overrode effects of diurnally
variable controls on N2O emissions. The lack of consistent diurnal patterns also indicates that measuring N2O
emissions once per day following major events is sufficient to adequately assess annual N2O emissions in
those systems. Nitrous oxide emissions varied per event and across functional locations in both systems. This illustrates that mechanisms underlying N2O emissions vary at relatively small temporal and spatial scales and
demonstrates the importance of studying N2O emissions in the context of events and functional locations. In
the conventional system, N2Ofluxes were high [74.2 ± 43.9–390.5 ± 90.1μgN2O-N m
−2
h
−1
]andN2O reduction potential was significant. Both management systems exhibited carbon limitation on denitrification rates;
and rates were N limited in the third fertigation event in the integrated system. Ourfindings suggest that denitrification is strongly contributing to high N2O emissions in conventional tomato cropping systems in California.
Hence, management practices that reduce the conditions that favor denitrification, such as subsurface drip
irrigation, are promising strategies for N2O reduction.
Published by Elsevier B.V
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