Water Framework Directive  - A link to the Defra website:
http://www.defra.gov.uk/environment/water/wfd/index.htm

Nitrogen revision of RB209 - A link to the Defra website:
http://www.defra.gov.uk/farm/environment/land-manage/nutrient/fert/rb209/index.htm

HGCA publications about RB209
Topic Sheet 68 : N management of strobilurin-treated winter wheat
Topic Sheet 63 : Managing arable crops in NVZs in England
Topic Sheet 63a :  Managing arable crops in NVZs in Scotland

Also, see relevant entries under soil fertility above