Advancing understanding of sustainable production on livestock farms: The importance of accurately assessing upland soil carbon stocks

Whilst it is generally understood that grasslands are able to store significant amounts of carbon and that much of our degraded agricultural soil has capacity to build carbon stocks and potentially mitigate on-farm emissions, to date, the greater focus of studies has been on the response of lowland grassland soil carbon to management practices. In contrast, comprehension of current and potential soil carbon stocks in heterogeneric ‘upland’ or marginal farmed environments is currently lacking, and the potential for sustainable livestock production to deliver increased soil carbon sequestration unsubstantiated. With upland farming systems producing 29% and 44% of breeding cows and sheep respectively, understanding the impact of changes in upland livestock management on soil carbon is critical to ensure future land management scenarios are environmentally positive and can sustain food production.

We aim to address this knowledge gap by combining field surveys of soil carbon concentrations and stocks with modelling of potential soil carbon change under nutrient, land use and climate change scenarios using the process-based N14CP model. In this contribution we will present the empirical data and carbon modelling results.

Three 'upland' livestock farms in Cumbria, UK were chosen as representative of diversity of parent material, climate, topography and livestock farming practices. Pedogenic-stratified random sampling of the top 0 – 30cm soil at a rate of 1 sample per 2 hectares; ≥5 metres apart was conducted July-September 2024. Samples were assessed for bulk density (corrected for coarse fragments ≥2mm) and carbon concentration (by dry combustion).

Preliminary analyses suggest high spatial variation in bulk density, soil carbon concentration and stocks within and between farms, reflecting the heterogeneity of ‘upland’ environments. Our sampling approach demonstrates that detecting change in soil carbon empirically, with confidence, is unlikely to be possible in these diverse landscapes, with implications for predicting carbon sequestration potential as climate mitigation.