Agronomic constraints and unstable cropland limit climate change mitigation potential of cover crops in Europe

Agricultural soil carbon sequestration is promoted in European climate and agricultural policy. Yet, many estimates of “available land” for carbon sequestration practices assume all cropland is equally and durably suitable. Credible baselines should distinguish among areas where adoption is already in place, land that is not persistently cropped, and where implementation is limited by agronomic and environmental conditions.

Here, we report on these missing elements to improve area-based assessments of soil carbon sequestration for winter cover crops. First, we quantified adoption gaps using a farm survey in the Netherlands, Germany, and Spain (n = 321). While adoption was widespread among farmers in Germany (89%) and the Netherlands (98%), additional expansion was constrained by over-wintering main crops; the remaining available arable land was 11% in Germany and 25% in the Netherlands. In rainfed systems in Spain, cover cropping was not reported, consistent with concerns around water competition.

Second, we derived stable cropland estimates for Europe from multi-year Sentinel-based cropland layers (Copernicus land monitoring; 2017–2023), classifying pixels by temporal continuity of cropping. Stable cropland varied widely, ranging from 14% to 81% of regional cropland (EU average 56%). Large areas frequently transition to temporary grassland, suggesting these are better targeted by measures that maintain mixed systems or perennial grassland.

Adoption gaps and stable cropland alone may still overstate plausible expansion. We show that farmer-reported constraints beyond management control—short sowing windows and environmental conditions that prevent timely establishment—often hamper further uptake. This study shows these elements are needed to improve area-based mitigation estimates.