Abstract
Abstract Increasing levels of atmospheric CO 2 are expected to enhance crop yields and alter soil greenhouse gas fluxes from rice paddies. While elevated CO 2 ( ) effects on CH 4 emissions from rice paddies have been studied in some detail, little is known how might affect N 2 O fluxes or yield‐scaled emissions. Here, we report on a multi‐site, multi‐year in‐situ FACE (free‐air CO 2 enrichment) study, aiming to determine N 2 O fluxes and crop yields from Chinese subtropical rice systems as affected by . In this study, we tested various N fertilization and residue addition treatments, with rice being grown under either (+200 μmol/mol) or ambient control. Across the six site‐years, rice straw and grain yields under were increased by 9%–40% for treatments fertilized with ≥150 kg N/ha, while seasonal N 2 O emissions were decreased by 23%–73%. Consequently, yield‐scaled N 2 O emissions were significantly lower under . For treatments receiving insufficient fertilization (≤125 kg N/ha), however, no significant effects on N 2 O emissions were observed. The mitigating effect of upon N 2 O emissions is closely associated with plant N uptake and a reduction of soil N availability. Nevertheless, increases in yield‐scaled N 2 O emissions with increasing N surplus suggests that N surplus is a useful indicator for assessing N 2 O emissions from rice paddies. Our findings indicate that with rising atmospheric CO 2 soil N 2 O emissions from rice paddies will decrease, given that the farmers’ N fertilization is usually sufficient for crop growth. The expected decrease in N 2 O emissions was calculated to compensate 24% of the simultaneously observed increase in CH 4 emissions under . This shows that for an agronomic and environmental assessment of effects on rice systems, not only CH 4 emissions, but also N 2 O fluxes and yield‐scaled emissions need to be considered for identifying most climate‐friendly and economically viable options for future rice production.
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Claims 11
Claim · model-written summary
Rice straw yield increased 9%–40% under elevated CO2 with at least 150 kg N/ha.
- Taxon
- rice
Oryza sativae2 - Treatment
- elevated CO 2e1
- Outcome
- rice strawe0
- Direction
- increasede0
- Value
- 9%–40%e0
- Qualifier
- ≥150 kg N/hae0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Across the six site‐years, rice straw and grain yields under were increased by 9%–40% for treatments fertilized with ≥150 kg N/ha”
e1“elevated CO 2”
e2“Chinese subtropical rice systems”
Claim · model-written summary
Rice grain yield increased 9%–40% under elevated CO2 with at least 150 kg N/ha.
- Taxon
- riceOryza sativae2
- Treatment
- elevated CO 2e1
- Outcome
- grain yieldse0
- Direction
- increasede0
- Value
- 9%–40%e0
- Qualifier
- ≥150 kg N/hae0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Across the six site‐years, rice straw and grain yields under were increased by 9%–40% for treatments fertilized with ≥150 kg N/ha”
e1“elevated CO 2”
e2“Chinese subtropical rice systems”
Claim · model-written summary
Seasonal N2O emissions decreased 23%–73% under elevated CO2 across six site-years.
- Taxon
- riceOryza sativae2
- Treatment
- elevated CO 2e1
- Outcome
- seasonal N 2 O emissionse0
- Direction
- decreasede0
- Value
- 23%–73%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“seasonal N 2 O emissions were decreased by 23%–73%”
e1“elevated CO 2”
e2“Chinese subtropical rice systems”
Claim · model-written summary
Yield-scaled N2O emissions were significantly lower under elevated CO2.
- Taxon
- riceOryza sativae2
- Treatment
- elevated CO 2e1
- Outcome
- yield‐scaled N 2 O emissionse0
- Direction
- lowere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“yield‐scaled N 2 O emissions were significantly lower under”
e1“elevated CO 2”
e2“Chinese subtropical rice systems”
Claim · model-written summary
At 125 kg N/ha or less, elevated CO2 had no significant effect on N2O emissions.
- Taxon
- riceOryza sativae2
- Treatment
- elevated CO 2e1
- Outcome
- N 2 O emissionse0
- Qualifier
- ≤125 kg N/hae0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For treatments receiving insufficient fertilization (≤125 kg N/ha), however, no significant effects on N 2 O emissions were observed.”
e1“elevated CO 2”
e2“Chinese subtropical rice systems”
Claim · model-written summary
The mitigation of N2O emissions under elevated CO2 was associated with plant N uptake.
- Taxon
- riceOryza sativae2
- Treatment
- elevated CO 2e1
- Outcome
- N 2 O emissionse0
- Qualifier
- plant N uptakee0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The mitigating effect of upon N 2 O emissions is closely associated with plant N uptake”
e1“elevated CO 2”
e2“Chinese subtropical rice systems”
Claim · model-written summary
The mitigation of N2O emissions under elevated CO2 was associated with reduced soil N availability.
- Taxon
- riceOryza sativae2
- Treatment
- elevated CO 2e1
- Outcome
- N 2 O emissionse0
- Qualifier
- a reduction of soil N availabilitye0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The mitigating effect of upon N 2 O emissions is closely associated with plant N uptake and a reduction of soil N availability.”
e1“elevated CO 2”
e2“Chinese subtropical rice systems”
Claim · model-written summary
Yield-scaled N2O emissions increased as N surplus increased.
- Taxon
- riceOryza sativae1
- Outcome
- yield‐scaled N 2 O emissionse0
- Direction
- increasese0
- Qualifier
- increasing N surpluse0
- Setting
- rice systemse1
Not reportedTreatment
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increases in yield‐scaled N 2 O emissions with increasing N surplus”
e1“Chinese subtropical rice systems”
Claim · model-written summary
The authors propose N surplus as an indicator of paddy N2O emissions.
- Taxon
- riceOryza sativae0
- Outcome
- N surplus is a useful indicator for assessing N 2 O emissionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“N surplus is a useful indicator for assessing N 2 O emissions from rice paddies”
Claim · model-written summary
The decrease in N2O emissions was calculated to offset 24% of the concurrent increase in CH4 emissions.
- Taxon
- riceOryza sativae1
- Outcome
- N 2 O emissionse0
- Direction
- decreasee0
- Value
- 24%e0
- Qualifier
- increase in CH 4 emissionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The expected decrease in N 2 O emissions was calculated to compensate 24% of the simultaneously observed increase in CH 4 emissions”
e1“Chinese subtropical rice systems”
Claim · model-written summary
The authors recommend considering CH4, N2O and yield-scaled fluxes when assessing future rice production.
- Taxon
- riceOryza sativae0
- Outcome
- N 2 O fluxes and yield‐scaled emissions need to be considerede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“not only CH 4 emissions, but also N 2 O fluxes and yield‐scaled emissions need to be considered for identifying most climate‐friendly and economically viable options for future rice production.”
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See all 159 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.