Optimising carbon storage by
land-management

Abstract

As the UK’s largest non-government land-owner, the National Trust is committed to
reducing its impact on climate change, recognising the importance of soil organic carbon
(SOC), and its need for preservation. To establish if land-management could be optimised
to increase carbon storage, ‘The Wallington Carbon Footprint Project’ was implemented.
This study aimed to measure the Wallington Estate’s carbon stock, establish what controls
SOC, identify carbon under-saturated soils, and make land-management change to increase
SOC.
To achieve these objectives a soil sampling campaign and land-use survey were
undertaken at Wallington, with further sampling at a verification site in Cambridgeshire.
Land-use intervention trials measuring carbon fluxes and SOC change were combined with
computer modelling and questionnaires, to assess the impacts of land-use and
management change on SOC.
A land carbon stock of 845 Kt (60 Kt within biomass, and 785 Kt within soils) was
estimated for Wallington, with the greatest control on SOC identified as grassland landmanagement.
Other controls on SOC were: land-use, soil series, altitude, soil pH and landuse
history, indicating that these should be used in all estimates of SOC distribution and
stock. A possible link between phosphate fertilisation and SOC accumulation under
grassland was identified; however this was not confirmed in a year long field trial.
Incorporation of charcoal into soils was identified as a method of carbon sequestration,
with a simultaneous reduction in nitrate loss from soil. Surface application to grasslands
revealed no detrimental effects on soils, grassland productivity or water quality. Further
trials investigated the impacts of arable conversion to short rotation coppice willow, and of
peatland afforestation, both indentifying losses of SOC following the land-use change.
Measurement of biomass carbon gains, full life cycle assessment of the each landuse,
and the impacts of varying types of biochar are required before firm conclusions
regarding land-use change and carbon sequestration can be made.