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Chapter 10 Salinisation
Salinisation is identified as a significant threat in Europe by the Soil Thematic and is also worldwide a very significant problem in arid areas of Australia, America and elsewhere. Salinisation is classically the processes where salts are mobilized in soil profiles by irrigation or capillary action and where evaporation causes the salts to accumulate. This only occurs where irrigation waters are salty and excesses of sodium can adversely impact soil physical structure undermining plant growth and the filtering capacity of the soil.
There is little evidence for the classical salinisation process occurring in Scotland and irrigation is not even widely practiced let alone with salty water. If climate change led to more irrigation this threat might need to be re-visited.
There are however a number of other pathways for salt to have an impact on soils in Scotland:
- Atmospheric deposition of sea salt has local impacts for example along maritime coasts of islands and small areas of the western seaboard of Scotland
- While salt cations and exchangeable salts are measured in Scottish soils there is no data on water soluble sodium chloride or sodium adsorption that would be required to measure parameters to assess salinity or sodicity.
- There are natural saline gley soils within saltmarshes, which provide important habitats in south-west Scotland and more locally in estuaries around the country.
- Salt in road grit has local impact on soils on road verges, for example Highland Council spread an average of 60000 tonnes of salt in an average winter ( http://www.highland.gov.uk/yourenvironment/roadsandtransport/wintermaintenance/). This salt was spread on 1388km of A roads and 977 km of B roads, and 4310km of C or unclassified roads. This computes to an average of 8.99 kilogram per metre of non-trunk roads. BEAR Scotland are responsible for Trunk roads and no figures were obtained for these.
In conclusion soils in Scotland are relatively unaffected by the classical salinisation process therefore and it is a negligible threat.
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