Managing permanent grasslands for carbon sequestration in Scottish soils

Grasslands cover a large area of Scotland’s land and their management can influence whether grassland soils release or store carbon and by how much.

This project synthesises the best state of knowledge on the effect of management practices on soil carbon sequestration in permanent, managed Scottish grasslands and modelled potential application.

Main findings

• We found some good evidence for the effects of specific practices on carbon sequestration in managed grassland.
• However, we found little evidence on the interaction between factors and the efficacy of these measures under diverse environmental conditions.
• Our modelling simulations suggest increases of 1-2.5 tonnes of additional carbon stored per hectare where carbon inputs to soil can be increased by 10% for a 30-year period. If achievable, benefits would likely plateau as saturation in soil is reached. They also highlight the risk of negative effects of additional grazing.
• Factors affecting sequestration potential include grazing rates, grass species, application of fertiliser and tillage.
• Evidence supports the addition of non-synthetic substances (e.g., plant residue and manure) to soil and the selection of high yielding grass species mixes for increasing carbon sequestration where this is possible to apply. Some evidence exists for the use of synthetic fertiliser to increase soil carbon sequestration although the environmental costs of fertiliser production/ application make this less appealing.
• The application of biochar as a method for increasing soil carbon sequestration would require more research, especially on biomass for production and on its impact on yield and the environment. Evidence for the application of lime for increased productivity is inconclusive.
• The evidence for the effects of managing grassland for carbon sequestration in soil is mixed. We did find more conclusive evidence on the effects of altering inputs than on the effects of influencing carbon sequestration through the turnover (degradation) of existing soil carbon.
• Replacing synthetic fertiliser with carbon-containing fertiliser will lead to stronger increases in carbon sequestration when applied in the correct circumstances. However, this will not apply across the whole of Scotland due to limitations to supply. Sources of additional organic material hold the largest potential for increases as most manure produced on-site is currently also applied on-site.