Nitrate is a naturally occurring compound which is essential to plant growth. Its presence in excessive concentrations in water can, however, pose a public health and environmental risk. Diffuse pollution from agriculture accounts for the majority of nitrate in drinking water sources, although sewage and industrial effluent and leaks also contribute. Against a background of growing public concern about increasing nitrate concentrations in water supplies during the 1980s legislation and other measures have been set in place. A precautionary limit of 50 mg of nitrate per litre of treated ground water was established in 1985 by the EC Drinking Water Directive (80/778/EEC). The EC Nitrate Directive (91/676/EC) has subsequently been negotiated, with the general aim of improving water quality while maintaining an efficient agriculture.
MAFF has operated a voluntary, compensated Scheme within NSAs since 1990 with the objective of reducing nitrate leaching by encouraging changes to farming practices. Initially, a Pilot NSA Scheme was launched in ten areas where nitrate concentrations in drinking water sources exceeded or were at risk of exceeding the agreed EC limit. In July 1994, an updated NSA Scheme consisting of 22 new areas was launched as part of the UK package of measures under EC Regulation 2078/92, the 'Agri-Environment Regulation'. The Scheme was extended a year later to include the former Pilot areas, thus creating an integrated Scheme covering 32 NSAs.