Slurry Storage Required Calculator

At least 22 weeks for most farms. Pig enterprises (more than 10 breeding sow places or 150 finishing pig places) and poultry enterprises (more than 500 places) need at least 26 weeks for that enterprise’s manure. You must also allow for rainfall and washings, and have regard to extra capacity for wet weather.

Inside a Nitrate Vulnerable Zone, enough to hold slurry produced from 1 October to 1 April (6 months) for pigs and poultry, and from 1 October to 1 March (5 months) for other livestock — plus rainfall, washings and any other liquid entering the store over that period.

Yes. Rain falling on uncovered tanks and lagoons, unroofed yards and any roofs or clean areas draining to the store all add to the volume. DAERA uses 25 mm a week as the Northern Ireland winter average. In England, gov.uk guidance says to allow for a wetter than average (1 in 5) year for your area.

Sometimes. In Northern Ireland, manure from stock on bedding can be stored as farmyard manure, rented storage or a manure processing contract can count, and out-wintered stock at low stocking rates can reduce the requirement. In England, slurry exported or spread on suitable low run-off risk land during the period can reduce it. These need records — talk to us if you are relying on them.

This calculator converts the excreta from stock on straw into tonnes using Defra’s standard factors — the excreta volume × 1.3 for dairy cows and × 1.15 for other cattle, sheep and pigs — plus any straw you add for bedding. Northern Ireland has no published tonnage figure, so for NI it is an estimate. Poultry litter, horses, goats and deer aren’t covered.

In a midden with the run-off collected — run-off from a midden counts as slurry and must be stored as slurry. In Northern Ireland FYM can also go in a compact field heap where it will be spread, for up to 120 days, not in the same place each year, and at least 20 m from a waterway, 50 m from a lake and 50 m from a borehole, spring or well.

In Northern Ireland, tanks built, enlarged or reconstructed after 31 December 2019 must be covered, and new above-ground tanks must be at least 50 m from a waterway. In England, new or substantially altered stores must meet the SSAFO regulations and be notified to the Environment Agency before use.