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.

Land drainage is essential to maintaining the productivity of Scottish agriculture. It also has significant potential to mitigate greenhouse gas emissions.

Wet soils can produce large quantities of Nitrous Oxide, a powerful greenhouse gas. Much of these emissions may be avoided through adequate agricultural drainage.

The Scottish Government has historically provided funding for the drainage of wet agricultural land. However, there is evidence that the condition of Scotland’s drainage infrastructure has deteriorated in the past 50 years, with little investment currently taking place.

As such, improving agricultural drainage infrastructure could represent a cost effective greenhouse gas mitigation measure.

Through a review of existing data, this report identifies:

• the current state of Scotland’s agricultural drainage infrastructure;
• the potential magnitude of greenhouse gas abatement from installing or improving drainage; and
• the impacts that such activity may have on other climate change mitigation policies.