Glossary

ADAS Soil P index: A measure of the phosphorus (P) content of soil. This is determined using the Olsen's P method.

Diffuse pollution: comprises contamination and pollution arising from many dispersed sources. Pollution can enter a river or lake at a single point, such as an effluent discharge pipe. A discharge like this is called a point source. However, pollutants can enter a river at many different places in a catchment, which cannot be identified individually. Examples of diffuse pollution sources are sheet run off from fields or seepage of nutrients from soil into ground water. Diffuse pollution can come from many different sources and sources are often individually minor, but collectively significant. Information from DEFRA on diffuse pollution in agriculture can be found here.

Hydrological connectivity: the linkage of areas through different hydrological flow paths

Phosphorus: Phosphorus (P) is a non-renewable resource and biosolids have been used for many years as sources of P for agricultural crops.

Nutrient: Essential elements required for life. The addition of sewage sludge to land increases the nutrient content of the soil, however if application levels are based upon nitrogen concentration, this will result in excess phosphorus, as biosolids are enriched in the latter. Environmental concerns regarding nutrients arise when they become available to aquatic organisms and could, in severe cases, lead to freshwater eutrophication: algal blooms, excessive growth of aquatic weeds, reduced water transparency and local fish kills due to deoxygenation.

Sewage Sludge or Biosolids: Sewage sludge is a by-product of sewage treatment. Sewage sludge must be treated before it is used in agriculture in order to reduce odour, volume and pathogen levels

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