Abstract
Abstract Maintaining or even increasing crop yields while reducing nitrous oxide (N 2 O) emissions is necessary to reconcile food security and climate change, while the metric of yield‐scaled N 2 O emission (i.e., N 2 O emissions per unit of crop yield) is at present poorly understood. Here we conducted a global meta‐analysis with more than 6000 observations to explore the variation patterns and controlling factors of yield‐scaled N 2 O emissions for maize, wheat and rice and associated potential mitigation options. Our results showed that the average yield‐scaled N 2 O emissions across all available data followed the order wheat (322 g N Mg −1 , with the 95% confidence interval [CI]: 301–346) > maize (211 g N Mg −1 , CI: 198–225) > rice (153 g N Mg −1 , CI: 144–163). Yield‐scaled N 2 O emissions for individual crops were generally higher in tropical or subtropical zones than in temperate zones, and also showed a trend towards lower intensities from low to high latitudes. This global variation was better explained by climatic and edaphic factors than by N fertilizer management, while their combined effect predicted more than 70% of the variance. Furthermore, our analysis showed a significant decrease in yield‐scaled N 2 O emissions with increasing N use efficiency or in N 2 O emissions for production systems with cereal yields >10 Mg ha −1 (maize), 6.6 Mg ha −1 (wheat) or 6.8 Mg ha −1 (rice), respectively. This highlights that N use efficiency indicators can be used as valuable proxies for reconciling trade‐offs between crop production and N 2 O mitigation. For all three major staple crops, reducing N fertilization by up to 30%, optimizing the timing and placement of fertilizer application or using enhanced‐efficiency N fertilizers significantly reduced yield‐scaled N 2 O emissions at similar or even higher cereal yields. Our data‐driven assessment provides some key guidance for developing effective and targeted mitigation and adaptation strategies for the sustainable intensification of cereal production.
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Claims 14
Claim · model-written summary
Wheat had average yield-scaled N2O emissions of 322 g N Mg −1.
- Taxon
- wheat
Triticum aestivume0 - Outcome
- yield‐scaled N 2 O emissionse0
- Direction
- >e0
- Value
- 322 g N Mg −1e0
- Qualifier
- 301–346e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“average yield‐scaled N 2 O emissions across all available data followed the order wheat (322 g N Mg −1 , with the 95% confidence interval [CI]: 301–346) > maize (211 g N Mg −1 , CI: 198–225) > rice (153 g N Mg −1 , CI: 144–163)”
Claim · model-written summary
Maize had average yield-scaled N2O emissions of 211 g N Mg −1.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“average yield‐scaled N 2 O emissions across all available data followed the order wheat (322 g N Mg −1 , with the 95% confidence interval [CI]: 301–346) > maize (211 g N Mg −1 , CI: 198–225) > rice (153 g N Mg −1 , CI: 144–163)”
Claim · model-written summary
Rice had average yield-scaled N2O emissions of 153 g N Mg −1.
- Taxon
- rice
Oryza sativae0 - Outcome
- yield‐scaled N 2 O emissionse0
- Direction
- lowerinferrede0
- Value
- 153 g N Mg −1e0
- Qualifier
- 144–163e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“average yield‐scaled N 2 O emissions across all available data followed the order wheat (322 g N Mg −1 , with the 95% confidence interval [CI]: 301–346) > maize (211 g N Mg −1 , CI: 198–225) > rice (153 g N Mg −1 , CI: 144–163)”
Claim · model-written summary
Yield-scaled emissions were generally higher in tropical or subtropical zones than temperate zones.
- Taxon
- maize, wheat, and riceOryza sativaTriticum aestivum
Zea mayst0 - Outcome
- Yield‐scaled N 2 O emissionse0
- Direction
- highere0
- Comparator
- temperate zonese0
- Setting
- tropical or subtropical zonese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Yield‐scaled N 2 O emissions for individual crops were generally higher in tropical or subtropical zones than in temperate zones”
t0“maize, wheat, and rice”
Claim · model-written summary
Yield-scaled emissions trended lower from low to high latitudes.
- Taxon
- maize, wheat, and riceOryza sativaTriticum aestivumZea mayst0
- Outcome
- intensitiese0
- Direction
- lowere0
- Setting
- low to high latitudese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“showed a trend towards lower intensities from low to high latitudes.”
t0“maize, wheat, and rice”
Claim · model-written summary
Climatic and edaphic factors explained global variation better than N fertilizer management.
- Taxon
- maize, wheat, and riceOryza sativaTriticum aestivumZea mayst0
- Outcome
- global variatione0
- Comparator
- N fertilizer managemente0
- Setting
- climatic and edaphic factorse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This global variation was better explained by climatic and edaphic factors than by N fertilizer management, while their combined effect predicted more than 70% of the variance.”
t0“maize, wheat, and rice”
Claim · model-written summary
Combined climatic, edaphic and management factors predicted more than 70% of variance.
- Taxon
- maize, wheat, and riceOryza sativaTriticum aestivumZea mayst0
- Outcome
- variancee0
- Value
- more than 70%e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“their combined effect predicted more than 70% of the variance.”
t0“maize, wheat, and rice”
Claim · model-written summary
Higher nitrogen use efficiency was associated with significantly lower yield-scaled N2O emissions.
- Taxon
- maize, wheat, and riceOryza sativaTriticum aestivumZea mayst0
- Outcome
- yield‐scaled N 2 O emissionse0
- Direction
- decreasee0
- Qualifier
- increasing N use efficiencye0
Not reportedTreatment
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a significant decrease in yield‐scaled N 2 O emissions with increasing N use efficiency”
t0“maize, wheat, and rice”
Claim · model-written summary
The analysis identifies yield thresholds for maize, wheat and rice in systems with lower emissions.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in N 2 O emissions for production systems with cereal yields >10 Mg ha −1 (maize), 6.6 Mg ha −1 (wheat) or 6.8 Mg ha −1 (rice), respectively.”
Claim · model-written summary
Wheat systems above 6.6 Mg ha −1 were identified in the reduced emission relationship.
- Taxon
- wheatTriticum aestivume0
- Outcome
- N 2 O emissionse0
- Direction
- decreaseinferrede0
- Value
- 6.6 Mg ha −1e0
- Qualifier
- production systemse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in N 2 O emissions for production systems with cereal yields >10 Mg ha −1 (maize), 6.6 Mg ha −1 (wheat) or 6.8 Mg ha −1 (rice), respectively.”
Claim · model-written summary
Rice systems above 6.8 Mg ha −1 were identified in the reduced emission relationship.
- Taxon
- riceOryza sativae0
- Outcome
- N 2 O emissionse0
- Direction
- decreaseinferrede0
- Value
- 6.8 Mg ha −1e0
- Qualifier
- production systemse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in N 2 O emissions for production systems with cereal yields >10 Mg ha −1 (maize), 6.6 Mg ha −1 (wheat) or 6.8 Mg ha −1 (rice), respectively.”
Claim · model-written summary
Reducing N fertilization by up to 30% reduced yield-scaled emissions at similar or higher cereal yields.
- Taxon
- maize, wheat, and riceOryza sativaTriticum aestivumZea mayst0
- Treatment
- reducing N fertilization by up to 30%e0
- Outcome
- yield‐scaled N 2 O emissionse0
- Direction
- reducede0
- Qualifier
- similar or even higher cereal yieldse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“reducing N fertilization by up to 30%, optimizing the timing and placement of fertilizer application or using enhanced‐efficiency N fertilizers significantly reduced yield‐scaled N 2 O emissions at similar or even higher cereal yields.”
t0“maize, wheat, and rice”
Claim · model-written summary
Optimizing timing and placement of fertilizer reduced yield-scaled emissions at similar or higher cereal yields.
- Taxon
- maize, wheat, and riceOryza sativaTriticum aestivumZea mayst0
- Treatment
- optimizing the timing and placement of fertilizer applicatione0
- Outcome
- yield‐scaled N 2 O emissionse0
- Direction
- reducede0
- Qualifier
- similar or even higher cereal yieldse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“reducing N fertilization by up to 30%, optimizing the timing and placement of fertilizer application or using enhanced‐efficiency N fertilizers significantly reduced yield‐scaled N 2 O emissions at similar or even higher cereal yields.”
t0“maize, wheat, and rice”
Claim · model-written summary
Enhanced-efficiency N fertilizers reduced yield-scaled emissions at similar or higher cereal yields.
- Taxon
- maize, wheat, and riceOryza sativaTriticum aestivumZea mayst0
- Treatment
- using enhanced‐efficiency N fertilizerse0
- Outcome
- yield‐scaled N 2 O emissionse0
- Direction
- reducede0
- Qualifier
- similar or even higher cereal yieldse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“reducing N fertilization by up to 30%, optimizing the timing and placement of fertilizer application or using enhanced‐efficiency N fertilizers significantly reduced yield‐scaled N 2 O emissions at similar or even higher cereal yields.”
t0“maize, wheat, and rice”
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