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). Every check can be saved as a dated record in a free account, so you have your loading history in one place.
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 the 2025 to 2028 designations, read every week from the layer behind the Environment Agency's own NVZ map (“Nitrate Vulnerable Zones (NVZ) 2025 - 2028”). Appeals against these designations have closed, and the Environment Agency updated its map on 1 June 2026 to reflect the outcomes; the date shown with your result is when our copy was last refreshed from it. 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, calculates whole-farm organic nitrogen loading from livestock, and — with a free account — keeps each calculation as a dated record you can come back to.
Record keeping: every result can be saved to your account with its date, holding name, total organic N, area, loading, your limit and whether you are under derogation. They are listed on your account page and you can delete any of them. There is no charge and no subscription.
What this tool does not do: field-by-field nutrient planning, manufactured fertiliser N calculations, crop N max, or a spreading diary of what went on which field on which day. The DEFRA requirement to keep records for five years covers more than the loading figure, so this is a record of your loading checks, not your whole NVZ file.
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 Nutrients 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.
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