Abstract
Introduction In tropical agriculture, cover crops are increasingly adopted to improve soil health and system resilience. However, their influence on greenhouse gas (GHG) emissions, particularly nitrous oxide (N 2 O), remains underexplored in field conditions. Methods We evaluated how cover crop biomass affects N 2 O emissions and emission intensity (kg CO 2 eq t − ¹ grain) in tropical soybean systems across two field experiments (6 and 10 years) in the Brazilian savannah (Cerrado biome). GHG emissions were measured using static chambers on a weekly basis throughout the cropping seasons from 2022 to 2024. Results Soybeans followed by cover crops such as Mix CC [ruzigrass ( Urochloa ruziziensis ), millet ( Pennisetum glaucum ), and showy rattlebox ( Crotalaria sp ectabilis )] and ruzigrass contributed up to 202% more nitrogen and 51% more carbon inputs than soybeans followed by fallow and maize. The cover crop mix emitted ~6,000 kg C ha − ¹ as biogenic CO 2 in 2 years and 2,655 g N ha − ¹ as N 2 O, ~50%-fold more than the bare fallow. Nevertheless, although high-biomass systems increased N 2 O emissions during the offseason, they also enhanced soybean yield, leading to lower emission intensity. Discussion The structural equation model revealed that cover crop biomass not only had a direct positive effect on soybean yield (standardized coefficient = 0.67) and N 2 O emissions (standardized coefficient = 0.33) but also an indirect negative effect on emission intensity through yield compensation. These findings suggest that adopting cover cropping systems in tropical regions can efficiently contribute to increasing crop yields while improving nitrogen use efficiency, which is important for food security in these regions.
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Claims 10
Claim · model-written summary
Cover crops contributed up to 202% more nitrogen inputs than fallow and maize.
- Taxon
- Soybeans
Glycine maxe0 - Treatment
- cover cropse0
- Outcome
- nitrogene0
- Direction
- moree0
- Value
- 202%e0
- Comparator
- soybeans followed by fallow and maizee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Soybeans followed by cover crops such as Mix CC [ruzigrass ( Urochloa ruziziensis ), millet ( Pennisetum glaucum ), and showy rattlebox ( Crotalaria sp ectabilis )] and ruzigrass contributed up to 202% more nitrogen and 51% more carbon inputs than soybeans followed by fallow and maize”
Claim · model-written summary
Cover crops contributed 51% more carbon inputs than fallow and maize.
- Taxon
- SoybeansGlycine maxe0
- Treatment
- cover cropse0
- Outcome
- carbon inputse0
- Direction
- moree0
- Value
- 51%e0
- Comparator
- soybeans followed by fallow and maizee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Soybeans followed by cover crops such as Mix CC [ruzigrass ( Urochloa ruziziensis ), millet ( Pennisetum glaucum ), and showy rattlebox ( Crotalaria sp ectabilis )] and ruzigrass contributed up to 202% more nitrogen and 51% more carbon inputs than soybeans followed by fallow and maize”
Claim · model-written summary
The cover crop mix emitted about 6,000 kg C ha − ¹ biogenic CO2 over two years.
Verbatim
e0“The cover crop mix emitted ~6,000 kg C ha − ¹ as biogenic CO 2 in 2 years”
Claim · model-written summary
The cover crop mix emitted 2,655 g N ha − ¹ N2O.
- Taxon
- soybeanGlycine maxt0
- Outcome
- N 2 Oe0
- Direction
- moree0
- Value
- 2,655 g N ha − ¹e0
- Comparator
- bare fallowe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“soybean”
e0“2,655 g N ha − ¹ as N 2 O, ~50%-fold more than the bare fallow”
Claim · model-written summary
High biomass cover crops increased offseason N2O emissions.
- Taxon
- high-biomass systemse0
- Treatment
- high-biomass systemse0
- Outcome
- N 2 O emissionse0
- Direction
- increasede0
Not reportedComparator
Verbatim
e0“high-biomass systems increased N 2 O emissions during the offseason”
Claim · model-written summary
High biomass cover crops enhanced soybean yield.
- Taxon
- soybeanGlycine maxe0
- Outcome
- soybean yielde0
- Direction
- enhancede0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“they also enhanced soybean yield”
Claim · model-written summary
Higher soybean yield led to lower emission intensity.
- Taxon
- soybeanGlycine maxe0
- Outcome
- emission intensitye0
- Direction
- lowere0
- Qualifier
- enhanced soybean yielde0
Not reportedSetting
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“enhanced soybean yield, leading to lower emission intensity”
Claim · model-written summary
Cover crop biomass had a positive modeled effect on soybean yield, coefficient 0.67.
- Taxon
- soybeanGlycine maxe0
- Treatment
- cover crop biomasse0
- Outcome
- soybean yielde0
- Direction
- positivee0
- Value
- standardized coefficient = 0.67e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“cover crop biomass not only had a direct positive effect on soybean yield (standardized coefficient = 0.67)”
Claim · model-written summary
Cover crop biomass had a positive modeled effect on N2O emissions, coefficient 0.33.
- Taxon
- soybeanGlycine maxt0
- Outcome
- N 2 O emissionse0
- Direction
- increaseinferrede0
- Value
- standardized coefficient = 0.33e0
Not reportedTreatment
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“soybean”
e0“and N 2 O emissions (standardized coefficient = 0.33)”
Claim · model-written summary
Cover crop biomass had an indirect negative effect on emission intensity through yield compensation.
- Taxon
- soybeanGlycine maxt0
- Outcome
- emission intensitye0
- Direction
- negativee0
- Qualifier
- through yield compensatione0
Not reportedTreatment
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“soybean”
e0“but also an indirect negative effect on emission intensity through yield compensation”
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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.