Abstract
Summer cover crops can improve soil fertility and contribute to nitrogen (N) supply in temperate cropping systems, yet the effects of mixture composition and sowing timing remain insufficiently documented. This study evaluated biomass production and N accumulation of five multispecies cover crop mixtures grown in Estonia during 2024–2025 under two sowing dates per year. Aboveground biomass, botanical composition, and carbon (C) and nitrogen concentrations were measured to assess productivity, species contributions, and residue quality. Earlier sowing was generally associated with higher biomass and N accumulation, with first-sown mixtures producing, on average, 38.7% more biomass than later-sown mixtures. Mixture performance was strongly shaped by species composition and competitive hierarchies. Total N accumulation of the cover crop mixtures ranged from 42 to 275 kg N ha−1 depending on mixture composition and sowing time, with mixtures dominated by common vetch (Vicia sativa L.) achieving the highest values. Oat (Avena sativa) dominated and contributed substantially to biomass in mixtures lacking competitive legumes, whereas sunflower (Helianthus annuus) and maize (Zea mays) performed less well under delayed sowing. Low-growing species such as Persian clover (Trifolium resupinatum) produced little biomass when grown with highly competitive species. Legumes exhibited lower C:N ratios than non-legumes, while mixture-level values remained moderate, suggesting residue quality with potential for favourable decomposition and nutrient release in summer cover crop systems under temperate conditions.
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Claims 12
Claim · model-written summary
Earlier sowing was associated with greater cover crop biomass, averaging 38.7% more.
Verbatim
e0“Earlier sowing was generally associated with higher biomass and N accumulation, with first-sown mixtures producing, on average, 38.7% more biomass than later-sown mixtures.”
Claim · model-written summary
Earlier sowing was associated with higher nitrogen accumulation.
Verbatim
e0“Earlier sowing was generally associated with higher biomass and N accumulation, with first-sown mixtures producing, on average, 38.7% more biomass than later-sown mixtures.”
Claim · model-written summary
Species composition and competitive hierarchies strongly shaped mixture performance.
- Taxon
- Mixturee0
- Outcome
- Mixture performancee0
- Qualifier
- species composition and competitive hierarchiese0
Not reportedDirection
Verbatim
e0“Mixture performance was strongly shaped by species composition and competitive hierarchies.”
Claim · model-written summary
Total nitrogen accumulation ranged from 42 to 275 kg N ha−1 across composition and sowing time.
Verbatim
e0“Total N accumulation of the cover crop mixtures ranged from 42 to 275 kg N ha−1 depending on mixture composition and sowing time”
Claim · model-written summary
Common vetch dominated mixtures had the highest nitrogen accumulation.
Verbatim
e0“mixtures dominated by common vetch (Vicia sativa L.) achieving the highest values.”
Claim · model-written summary
Oat dominated and substantially contributed to biomass without competitive legumes.
- Taxon
- Oat (Avena sativa)
Avena sativae0 - Outcome
- biomasse0
- Direction
- dominatede0
- Qualifier
- mixtures lacking competitive legumese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Oat (Avena sativa) dominated and contributed substantially to biomass in mixtures lacking competitive legumes”
Claim · model-written summary
Sunflower performed less well under delayed sowing.
- Taxon
- sunflower (Helianthus annuus)
Helianthus annuuse0 - Outcome
- performed less welle0
- Direction
- less welle0
- Qualifier
- delayed sowinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“sunflower (Helianthus annuus) and maize (Zea mays) performed less well under delayed sowing.”
Claim · model-written summary
Maize performed less well under delayed sowing.
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“sunflower (Helianthus annuus) and maize (Zea mays) performed less well under delayed sowing.”
Claim · model-written summary
Persian clover produced little biomass with highly competitive species.
- Taxon
- Persian clover (Trifolium resupinatum)
Trifolium resupinatume0 - Outcome
- biomasse0
- Direction
- littlee0
- Qualifier
- when grown with highly competitive speciese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Persian clover (Trifolium resupinatum) produced little biomass when grown with highly competitive species.”
Claim · model-written summary
Legumes had lower carbon-to-nitrogen ratios than non-legumes.
Verbatim
e0“Legumes exhibited lower C:N ratios than non-legumes”
Claim · model-written summary
Mixture carbon-to-nitrogen ratios remained moderate.
Verbatim
e0“mixture-level values remained moderate, suggesting residue quality with potential for favourable decomposition and nutrient release in summer cover crop systems under temperate conditions.”
Claim · model-written summary
Moderate mixture carbon-to-nitrogen ratios suggested favorable decomposition and nutrient release potential.
Verbatim
e0“suggesting residue quality with potential for favourable decomposition and nutrient release in summer cover crop systems under temperate conditions.”