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| Titel |
Simulating N2O emissions from irrigated cotton wheat rotations in Australia using DAYCENT: Mitigation options by optimized fertilizer and irrigation management |
| VerfasserIn |
Clemens Scheer, Stephen DelGrosso, William Parton, David Rowlings, Peter Grace |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250088991
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| Publikation (Nr.) |
 EGU/EGU2014-3172.pdf |
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| Zusammenfassung |
| Irrigation and fertilization do not only stimulate plant growth, but also accelerate microbial
C- and N-turnover in the soil and thus can lead to enhanced emissions of nitrous oxide (N2O)
from soils. In Australia there are more than 2 million hectares of agricultural land under
irrigation and research has now focused on a combination of nitrogen fertilizer and irrigation
management to maintain crop yields, maximize nitrogen use efficiency and reduce N2O
emissions. Process-based models are now being used to estimate N2O emissions and
assess mitigation options of N2O fluxes by improving management at field, regional
and national scales. To insure that model predictions are reliable it is important to
rigorously test the model so that uncertainty bounds for N2O emissions can be
reduced and the impacts of different management practices on emissions can be better
quantified.
We used high temporal frequency dataset of N2O emissions to validate the performance
of the agroecosystem model DayCent to simulate daily N2O emissions from sub-tropical
vertisols under different irrigation intensities. Furthermore, we evaluated potential N2O
mitigation strategies in irrigated cotton-wheat rotations in Australia by simulating different
fertilizer and irrigation management scenarios over a climatically variable 25 year time
span.
DayCent accurately predicted soil moisture dynamics and the timing and magnitude of
high fluxes associated with fertilizer additions and irrigation events. At the daily scale we
found a good correlation of predicted vs. measured N2O fluxes (r2 = 0.52), confirming that
DayCent can be used to test agricultural practices for mitigating N2O emission from
irrigated cropping systems. The simulations of different fertilization and irrigation
practices in cotton-wheat rotations over a 25 year time frame clearly showed that
there is scope for reducing N2O emissions by modified fertilizer and irrigation
management. For wheat and for cotton the model predicted that a reduced fertilizer rate can
sustain high yields but substantially reduce N2O losses. These results emphasize
the need for site and crop specific N management practices with increased N use
efficiency to minimise N2O emissions and maximise the economic benefits at the same
time. Irrigation intensity had only a minor effect on N2O fluxes, but a significant
effect on yield with highest yields under the optimized irrigation scenario, which
was in good accordance with the field data. Our simulations clearly show that the
N2O intensity (N2O emitted per ton of yield) can be significantly reduced while
maintaining high yields by an optimized irrigation and fertilization strategy. Regular
irrigation when the available water content is depleted will help to optimize yield, while
avoiding excessive applications of N fertilizer will significantly reduce N2O losses. |
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