Carbon storage in agricultural topsoils and subsoils is promoted by including temporary grasslands into the crop rotation

Summary

This study assessed how temporary grasslands incorporated into crop rotations affect soil carbon sequestration in Swiss agricultural soils. Using 54 permanent grassland and cropland sites with varying TG proportions, the authors developed a novel bulk density correction method and found linear increases in both topsoil and subsoil carbon stocks with increasing TG proportion. The findings demonstrate that subsoil carbon responses are substantial and must be included in carbon accounting for agricultural climate mitigation strategies.

UK applicability

The methodological approach and quantification of subsoil carbon responses are transferable to UK farming systems, particularly in regions with similar soil types and climate. However, UK-specific validation would be needed given differences in soil characteristics, rotation practices, and climate between Switzerland and the United Kingdom.

Key measures

Soil organic carbon (SOC) stocks (kg C m−2) at 0–20 cm (topsoil) and 20–50 cm (subsoil) depth; bulk density (BD) corrections; TG proportion in crop rotations; soil clay content and pH

Outcomes reported

The study quantified soil organic carbon (SOC) storage in croplands and measured how temporary grasslands (TG) in crop rotations affect SOC stocks down to 50 cm depth. It demonstrated that a 10% increase in TG proportion would induce an SOC gain of 0.40 ± 0.13 kg C m−2, with equivalent linear responses in topsoil and subsoil.

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