Abstract
Assessments of the efficacy of mitigation of greenhouse gas (GHG) emissions from paddy rice systems have typically been analyzed based on field studies. Extrapolation of the mitigation potential of alternative management practices from field studies to a national scale may be enhanced by spatially explicit process models, like the DeNitrification and DeComposition (DNDC) model. Our objective was to analyze the impacts of mitigation alternatives, management of water, fertilizer, and rice straw, on net GHG emissions (carbon dioxide, methane, and nitrous oxide fluxes), yields, and water use. After constructing a GIS database of soil, climate, rice cropping area and systems, and management practices, we ran DNDC with 21-yr alternative management schemes for each of the approximately 2500 counties in China. Results indicate that, despite large-scale adoption of midseason drainage, there is still large potential for additional methane reductions from Chinese rice paddies of 20 to 60% over 2000-2020. However, changes in management for reducing CH4 emissions simultaneously affect soil carbon dynamics as well as N2O emissions and can thereby reorder the ranking of technical mitigation effectiveness. The order of net GHG emissions reduction effectiveness found here is upland rice > shallow flooding > ammonium sulfate > midseason drainage > off-season straw > slow-release fertilizer > continuous flooding. Most of the management alternatives produced yields comparable to the baseline; however, continuous flooding and upland rice significantly reduced yields. Water management strategies appear to be the most technically promising GHG mitigation alternatives, with shallow flooding providing additional benefits of both water conservation and increased yields.
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Claims 7
Claim · model-written summary
Additional methane reductions of 20 to 60% were projected for Chinese rice paddies during 2000–2020.
- Taxon
- rice
Oryza sativae0 - Outcome
- methane reductionse0
- Direction
- reductionse0
- Value
- 20 to 60%e0
- Setting
- Chinesee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice”
e0“there is still large potential for additional methane reductions from Chinese rice paddies of 20 to 60% over 2000-2020.”
Claim · model-written summary
Changes that reduce CH4 also affect soil carbon dynamics and N2O emissions, changing mitigation rankings.
- Taxon
- RiceOryza sativat0
- Outcome
- soil carbon dynamics as well as N2O emissionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice”
e0“changes in management for reducing CH4 emissions simultaneously affect soil carbon dynamics as well as N2O emissions and can thereby reorder the ranking of technical mitigation effectiveness.”
Claim · model-written summary
Net greenhouse gas reduction effectiveness ranked upland rice highest and continuous flooding lowest.
- Taxon
- riceOryza sativae0
- Outcome
- net GHG emissions reduction effectivenesse0
- Qualifier
- upland rice > shallow flooding > ammonium sulfate > midseason drainage > off-season straw > slow-release fertilizer > continuous floodinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The order of net GHG emissions reduction effectiveness found here is upland rice > shallow flooding > ammonium sulfate > midseason drainage > off-season straw > slow-release fertilizer > continuous flooding.”
Claim · model-written summary
Most management alternatives produced yields comparable to baseline.
- Taxon
- RiceOryza sativat0
- Treatment
- management alternativese0
- Outcome
- yieldse0
- Direction
- comparablee0
- Comparator
- baselinee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice”
e0“Most of the management alternatives produced yields comparable to the baseline”
Claim · model-written summary
continuous flooding significantly reduced rice yields.
- Taxon
- RiceOryza sativat0
- Treatment
- continuous floodinge0
- Outcome
- yieldse0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice”
e0“continuous flooding and upland rice significantly reduced yields”
Claim · model-written summary
upland rice significantly reduced rice yields.
- Taxon
- RiceOryza sativat0
- Treatment
- upland ricee0
- Outcome
- yieldse0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice”
e0“continuous flooding and upland rice significantly reduced yields”
Claim · model-written summary
Shallow flooding was judged promising for greenhouse gas mitigation, water conservation, and yield gains.
- Taxon
- RiceOryza sativat0
- Outcome
- shallow flooding providing additional benefits of both water conservation and increased yieldse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice”
e0“Water management strategies appear to be the most technically promising GHG mitigation alternatives, with shallow flooding providing additional benefits of both water conservation and increased yields.”
The same questions in other papers
flooding · yield · Oryza sativa (rice)Positive and negative results
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