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Scottish Environment LINK - The voice of Scotland's environment movement



Soil chemical and biological changes

A national-scale threat to soil quality in Scotland is enhanced acidification. The land areas of Scotland are classified as:

  • Strongly acidified 24.6%
  • Vulnerable 36.1%
  • No immediate risk 35.7%
  • No data 3.6%

The vast majority of organic waste applied to land in Scotland is agricultural waste, comprising manures, slurries and silage effluent. In 1996-1997, 185,000t of sewage sludge or 19% of the total produced was recycled to just over 4,000 ha of agricultural land at 597 sites; in 2002 it was 40% of the total. This is expected to rise to over 858,000 wet tonnes by 2005-2006, as a result of additional sewage treatment. Most sludge is likely to be applied to agricultural land.

The use of inorganic fertilisers and pesticides can impact on soil quality through changes in nutrient turnover rates, organic matter decomposition rates and the build up of pesticide residues in the soil. However, the long term impacts are as yet unclear. Inorganic fertiliser application to arable land has averaged 122kg/ha/y for N and 49 kg/ha/y for P in recent years. In addition, 7,767 t (active ingredients) of pesticides were applied to arable land in 1998.

Afforestation can have a range of effects on soil quality . The presence of a tree canopy alters the microclimate experienced by the soil. Temperatures are generally lower in a forest and transpiration and interception of rainfall by the canopy result in drying of the forest floor. Both temperature and moisture content strongly influence soil microbial processes. Planting and felling operations can damage physical, chemical and biological components of soils if not properly managed. The disturbance caused can result in the oxidation and loss of soil organic matter, resulting in the emission of CO 2 (SEPA, 2001)

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