How Much Slurry Storage Do I Need?
Getting slurry storage right is a legal requirement in NVZs — and a practical necessity everywhere. Too little capacity forces winter spreading when ground conditions are poor and spreading is restricted. Here's how to calculate what you need.
Quick answer
A dairy cow produces around 15 litres of slurry per day. For NVZ compliance you typically need 6 months' storage — approximately 2.7 m³ per cow. For 100 cows that is around 270 m³. Use the calculator below for your exact requirement.
Quick Storage Requirement Calculator
NVZ minimum: 26 weeks
Total litres
263k L
Storage needed
263 m³
With freeboard
289 m³
Freeboard figure includes an approximate 10% allowance for the 300 mm regulatory freeboard requirement. Use the detailed calculator for a full compliance check including dirty water and rainfall.
Slurry Output & Storage Requirements by Livestock Type
| Livestock type | L / day | 16 wk (L) | 25 wk (L) | 26 wk (L) |
|---|---|---|---|---|
| Dairy cows | 15 L | 1,680 | 2,625 | 2,730 |
| Beef — fully housed | 10 L | 1,120 | 1,750 | 1,820 |
| Beef — part housed | 7 L | 784 | 1,225 | 1,274 |
| Finishing pigs | 6 L | 672 | 1,050 | 1,092 |
| Sows (incl. piglets) | 12 L | 1,344 | 2,100 | 2,184 |
| Housed ewes | 2 L | 224 | 350 | 364 |
Litres per head per storage period. Divide by 1,000 for m³. Does not include rainfall or dirty water run-off — add these for a compliant assessment. Source: AHDB / DEFRA guidance.
NVZ rules: what the regulations actually require
In Nitrate Vulnerable Zones in England, you must have sufficient slurry storage to avoid spreading during the closed spreading period (1 October – 31 January for cattle slurry). That is 17 weeks of closed period, but in practice you need at least 22–26 weeks' capacity to allow for weather limitations on either side of the window. The regulations do not specify an exact store size — they require you to demonstrate you can comply with the closed period rules.
Don't forget rainfall and dirty water
The figures in the table above are slurry output only. Any store with an open roof or exposed reception pit also collects rainfall — which can add 10–25% to required capacity depending on your location and store design. Dirty water from yard wash and dairy parlour must also be accounted for if it enters the slurry system. Always use total inflow — not just animal output — when sizing a store.