Soil carbon and farm productivity implications of Regenerative Agriculture
Soil carbon sequestration on farmland has the dual potential to help mitigate anthropogenic greenhouse gas emissions and reverse soil degradation, through building soil organic matter. This compelling narrative is receiving increasing attention from policy makers and corporates interested in emissions offsets through carbon markets, in addition to NGOs, farmers and land managers focused on improving soil health through adoption of regenerative agriculture practices. However, the soil carbon and agricultural productivity implications of changes in farmland management need to be quantified in a context-specific manner to determine their utility and appeal for climate change mitigation. Previous work has demonstrated soil carbon and/or productivity benefits from adopting individual practices on a global scale, and there is a broad consensus that increased soil carbon correlates with higher yields, but to date there has been little working considering how the relationship between soil carbon and yield changes across different regenerative practices.
My DPhil research uses systematic review methods to assemble a comprehensive and robust evidence base of the soil carbon and farm productivity implications of adopting regenerative agriculture practices in temperate oceanic regions, including reduced tillage, use of cover crops and integrating leys in arable systems, and rotational grazing, use of herbal leys and silvopasture in livestock systems. I use Bayesian hierarchical models to meta-analyse data from these studies to identify trade-offs and synergies between soil carbon sequestration and yield when implementing these practices, and to gain insights into how the soil carbon-yield relationship changes between practices. I also use this evidence base to parametrise spatially-explicit implementations of the RothC soil carbon model, to estimate the total soil carbon change achievable if regenerative agriculture practices were adopted UK-wide as part of a climate change mitigation strategy. Finally, I am conducting a programme of interviews with industry experts and farmers in two case study regions (mid Northumberland and west Devon) to caveat these theoretical estimates with the relative appeal of regenerative practices to land managers, and the drivers, barriers and legitimate reasons for non-adoption.