Soil erosion and compaction in Scottish soils: adapting to a changing climate

Sustainable soil management is a particular challenge as Scotland adapts to a changing climate, and has been highlighted by the Adaptation Sub-Committee, in its UK Climate Change Risk Assessment 2017. Soil compaction and erosion have been identified as being important, particularly in exacerbating flooding impacts and decreasing soil carbon storage.

This report collates the current state of confident knowledge for Scotland – what we know, what we don’t know and what is under active debate.

Key findings

Much of what we know about erosion rates on agricultural land in Scotland comes from a few, individual studies of erosion events, but there is a growing body of evidence that can be used to examine the role of land use (both current and historic), soil type and slope on erosion susceptibility. Other factors such as antecedent moisture content, ground cover and presence of tramlines also play a role, making it difficult to be certain when, or if, erosion will occur.
Soil erosion models with sediment yield as an output seem to exaggerate the amount of soil loss and are difficult to validate, although they do offer a way to examine the relative changes in erosion rate under different land uses and changing climates.
There is a link between soil compaction and erosion; soils that become compacted have a restricted capacity to store rainfall and generate overland flow more quickly than soils that are not compacted. This overland flow can then cause erosion.
The greatest driver of soil compaction is machinery weight, which has been increasing over the past few decades, although using wide tyres, dual wheels and low pressure tyres can reduce the impact.
We have a better understanding of field level effects with evidence gathered in Aberdeenshire following storm Frank (December 2015) suggesting erosion seemed more prevalent in areas that were more intensively managed.

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