Investigations have assessed the environmental benefits of soil organic matter (SOM) storage at two long-term European experimental research sites: (i) SOM data from a soil conservation (set-aside) site in the UK and (ii) SOM data from a carbon sequestration benchmarking site in Lithuania. The first case study (Hilton, UK) illustrates the environmental benefits of changes in SOM content before and after the adoption of set-aside, a recognized soil conservation technique. Ten run-off plots (7–15° gradients) were put to ley in 1991. Run-off and erosion rates decreased to tolerable levels once ~30% vegetation cover had established and remained low (mean of 69 plot years 0.21 t ha–1 year–1, SD 0.14). Meanwhile, SOM content increased consistently and significantly on the set-aside plots (mean of 2.22% by weight in 14 years) and soil erodibility significantly decreased. Results suggest using grass-leys for set-aside is a viable soil conservation technique, which may also contribute to carbon sequestration. The second case study (Kaltinenai, Lithuania) addresses the issue of comparing international SOM databases to assist carbon modelling and carbon sequestration estimates. Five analytical approaches have been used to calculate SOM. Linear correlation and paired regression equations were used to calculate the various techniques. Correlation coefficients varied between r = 0.83–0.98 (n = 92, P<0.001). Based on the strength and significance of these relationships, it is proposed that simple linear or more complex paired regression equations can be confidently employed to recalculate SOM data between various analytical methodologies. However, it also demonstrates the potential difficulty of international carbon benchmarking, as part of the global policy to ameliorate climate change.