Abstract
Abstract Cover crops (CC) have the potential to reduce the dependency of rice ( Oryza sativa L.) production on chemical N fertilizers and the associated environmental and economic risks. While extensively studied in tropical and subtropical systems, their potential in Mediterranean lowlands remains underexplored. This study evaluated whether CC could reduce chemical N fertilization in a Mediterranean rice system (Ebro Delta, Spain). Rice was grown during three seasons (2020–2023) preceded by a bare fallow, hairy vetch ( Vicia villosa Roth), or ryegrass ( Lolium multiflorum Lam.) during the winter period, and with 4 different fertilizer N rates (0, 120, 180, and 240 kg N ha −1 ) under a split-plot design. Besides testing rice productivity, we developed a simple but effective indicator to assess the economic impact of cover crops by adapting the marginal net return of grain production to include cover cropping costs. Differences in biomass accumulation between the CC species were variable across years, with ryegrass being more dependent on precipitation, but also negatively affected by the N fertilization for the rice from the previous season. Due to its sole reliance on soil N uptake, ryegrass never produced more biomass N than hairy vetch. Rice yields were 13% lower and N use efficiency 16% lower after ryegrass than after bare fallow across fertilization levels. Hairy vetch tended to improve rice development (i.e., NDVI and panicle density) but did not translate into higher yields or N use efficiency compared to bare fallowing, potentially due to inhibited N mineralization under anaerobic conditions in flooded environments. Consequently, CC implementation significantly reduced profitability, showing how economic incentives are needed to encourage adoption. Implementing hairy vetch as CC increased the soil total N by 10%, potentially benefiting long-term rice production. These findings offer practical insights for agronomists and policymakers focused on enhancing the sustainability of Mediterranean rice systems.
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Claims 10
Claim · model-written summary
Ryegrass biomass depended more on precipitation and was negatively affected by prior rice nitrogen fertilizer.
LoliumOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ryegrass being more dependent on precipitation, but also negatively affected by the N fertilization for the rice from the previous season.”
t0“rice”
Claim · model-written summary
Ryegrass produced no more biomass nitrogen than hairy vetch.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ryegrass never produced more biomass N than hairy vetch.”
t0“rice”
Claim · model-written summary
Rice yield was 13% lower after ryegrass than bare fallow.
- Taxon
- Rice
Oryza sativae0 - Treatment
- ryegrasse0
- Outcome
- Rice yieldse0
- Direction
- lowere0
- Value
- 13%e0
- Comparator
- bare fallowe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Rice yields were 13% lower and N use efficiency 16% lower after ryegrass than after bare fallow across fertilization levels.”
t0“rice”
Claim · model-written summary
Rice nitrogen use efficiency was 16% lower after ryegrass than bare fallow.
- Taxon
- RiceOryza sativae0
- Treatment
- ryegrasse0
- Outcome
- N use efficiencye0
- Direction
- lowere0
- Value
- 16%e0
- Comparator
- bare fallowe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Rice yields were 13% lower and N use efficiency 16% lower after ryegrass than after bare fallow across fertilization levels.”
t0“rice”
Claim · model-written summary
Hairy vetch tended to improve rice NDVI and panicle density.
- Taxon
- riceOryza sativae0
- Treatment
- Hairy vetche0
- Outcome
- NDVI and panicle densitye0
- Direction
- improvee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Hairy vetch tended to improve rice development (i.e., NDVI and panicle density)”
t0“rice”
Claim · model-written summary
Hairy vetch did not increase rice yields compared with bare fallow.
- Taxon
- riceOryza sativat0
- Treatment
- Hairy vetche1
- Outcome
- yieldse0
- Direction
- did not translate into highere0
- Comparator
- bare fallowinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“did not translate into higher yields or N use efficiency compared to bare fallowing”
t0“rice”
e1“Hairy vetch tended to improve rice development (i.e., NDVI and panicle density)”
Claim · model-written summary
Hairy vetch did not increase rice nitrogen use efficiency compared with bare fallow.
- Taxon
- riceOryza sativat0
- Treatment
- Hairy vetche1
- Outcome
- N use efficiencye0
- Direction
- did not translate into highere0
- Comparator
- bare fallowinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“did not translate into higher yields or N use efficiency compared to bare fallowing”
t0“rice”
e1“Hairy vetch tended to improve rice development (i.e., NDVI and panicle density)”
Claim · model-written summary
Cover crop implementation significantly reduced profitability.
- Taxon
- riceOryza sativat0
- Treatment
- CC implementatione0
- Outcome
- profitabilitye0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CC implementation significantly reduced profitability”
t0“rice”
Claim · model-written summary
Hairy vetch cover cropping increased soil total nitrogen by 10%.
- Taxon
- riceOryza sativat0
- Treatment
- hairy vetch as CCe0
- Outcome
- soil total Ne0
- Direction
- increasede0
- Value
- 10%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Implementing hairy vetch as CC increased the soil total N by 10%”
t0“rice”
Claim · model-written summary
Authors concluded economic incentives are needed for cover crop adoption.
- Taxon
- riceOryza sativat0
- Outcome
- economic incentives are needed to encourage adoptione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“economic incentives are needed to encourage adoption”
t0“rice”
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