NVZ Compliance Calculator
Check if your farm is in a Nitrate Vulnerable Zone and calculate the organic nitrogen loading from your livestock against the 170 kg N/ha/year limit (or 250 kg/ha with grassland derogation).
1. Your farm location
Used to check automatically if your farm is in an NVZ.
Spreading closed periods (England)
Select your situation to see when you cannot spread, and whether spreading is allowed today.
Wales, Scotland and Northern Ireland set their own closed periods — check your jurisdiction’s guidance.
Slurry storage capacity
Check whether you have enough storage to cover the NVZ closed period: 22 weeks for cattle slurry, 26 weeks for pig slurry. Enter only animals housed on a slurry-based system.
Open surface that rain falls into and drains to the store.
Dirty water stored separately can be left out.
Total usable volume of your slurry stores.
Set a farm location above to estimate rainfall automatically.
Weekly excreta volumes are standard government NVZ values (Crown copyright / OGL v3.0). This is a planning estimate — for a formal calculation use the AHDB Slurry Wizard and keep a record as DEFRA requires.
About this calculator
Livestock nitrogen coefficients are taken verbatim from DEFRA NVZ guidance standard values tables (PB 14050). NVZ designation polygons for England are from DEFRA NVZ 2021 Designations. Regulatory framework: Nitrate Pollution Prevention Regulations 2018 (England). Contains public sector information licensed under the Open Government Licence v3.0.
What this tool does: detects whether your location is in an NVZ and calculates whole-farm organic nitrogen loading from livestock.
What this tool does not do: field-by-field nutrient planning, manufactured fertiliser N calculations, crop N max, or spreading records. For record-keeping required by DEFRA (5 years), use a dedicated farm management system.
Wales and Northern Ireland are entirely designated as NVZ under their own devolved regulations (Water Resources (Control of Agricultural Pollution) (Wales) Regulations 2021 and the DAERA Nitrates Action Programme). Closed periods and storage rules differ from England — check your jurisdiction.
For decisions about your farm, consult an agronomist or the Rural Payments Agency.
Keep learning
New to data-driven farming? Read our complete guide to precision agriculture in the UK, see what precision farming actually costs, or take the free interactive introduction course — story-driven, narrated, and cited to AHDB and gov.uk.