UK Slurry, Silage and SSAFO Regulations 2026

Last updated: May 2026. This guide pulls together the SSAFO Regulations 2010, the Farming Rules for Water 2018, the NVZ Action Programme, the spreading closed periods and the Capital Grants 2026 items for storage upgrades. I do not run livestock myself, so this is written as an observer looking at the framework that lands on every dairy, beef, pig and mixed unit in the country, and on every neighbour and tenant who shares a parish boundary with one. It is general information, not legal or environmental advice. See the action checklist for what to do this week.

I farm salad and veg in Suffolk, and in the last two seasons I’ve added a block of arable on rented ground. I don’t keep a single cow. I have, though, spent enough mornings at the edge of a neighbour’s slurry lagoon, or watched the tanker go past at dusk in October, to know that the rules around silage, slurry and farm fuel are the most expensive piece of regulation in British farming that nobody outside the industry has heard of. They affect every mixed farm, every tenant taking on a converted dairy yard, and anyone whose ditch runs downstream of a clamp.

This is my best attempt to set out what the law actually says in 2026, what the Environment Agency is doing about it, and where the grant money is. I’ve leaned on the underlying statutory instruments and the published Defra and EA guidance. The Sources section at the end gives chapter and verse.

The legal architecture, in one piece

The headline regulation is the Water Resources (Control of Pollution) (Silage, Slurry and Agricultural Fuel Oil) (England) Regulations 2010, universally called SSAFO.[1] Wales has its own Water Resources (Control of Agricultural Pollution) (Wales) Regulations 2021 in force across the whole country.[2] Scotland’s regime sits in the SSAFO (Scotland) Regulations 2003 with the Water Environment (Diffuse Pollution) (Scotland) Regulations 2008.[3] Northern Ireland has its own 2003 equivalent.[4]

Sitting on top, two further bodies of law do the day-to-day work. The Nitrate Pollution Prevention Regulations 2015 set out the NVZ Action Programme: storage capacity, closed periods, application limits.[5] The Reduction and Prevention of Agricultural Diffuse Pollution (England) Regulations 2018, normally called the Farming Rules for Water, apply everywhere in England, NVZ or not.[6] The Defra Codes of Good Agricultural Practice for ammonia and for water sit alongside as the statutory codes the inspector will quote.[7]

The bones of it: SSAFO governs how you store the stuff, NVZ rules govern when and how much you spread, Farming Rules for Water govern where.

What SSAFO actually requires

The standards in SSAFO are statutory, not good practice.

For a silage clamp: impermeable base, effluent tank of at least 20 cubic metres or two days’ production at peak (whichever is larger), perimeter channels to collect run-off, adequate walls, and a site at least 10 metres from any watercourse.[8] Bag and bale silage is exempt from the construction standard but caught by the 10-metre rule.

For a slurry store: a structure with adequate strength and a 20-year design life, capacity of at least four months’ production, walls and base impermeable to slurry, the same 10-metre watercourse setback.[9] New or substantially altered stores require 14 days’ written notice to the Environment Agency before first use. Missing that notice is one of the most commonly prosecuted SSAFO failures.

For agricultural fuel oil: secondary containment of at least 110 per cent of tank capacity (or 25 per cent of the combined total for multiple tanks), bund integrity, and sensible siting from drains and watercourses. Smaller farm tanks are caught by the Oil Storage (England) Regulations 2001 when used for non-farming purposes, which sweeps in a great many domestic heating oil tanks on farmhouses.[10]

The four-month figure is the absolute statutory floor. In practice, very few livestock farms can plan to it, because the NVZ rules and the Farming Rules for Water both push the working figure much higher.

The 6-month figure everyone talks about

In an NVZ, which now covers around 55 per cent of England’s land area, the Action Programme requires storage of at least six months’ worth of slurry for pig and poultry units, and five months for cattle.[11] On a wet site, on heavy land, or where the closed period bites, even five months is rarely enough.

The Farming Rules for Water do not state a storage figure, but they prohibit spreading where there is a “significant risk of pollution”.[12] In an EA inspection, that prohibition translates into a question: did the farm have enough storage to wait for ground conditions that did not pose a risk? If the answer is no, the rule has been broken, NVZ or not.

So the working planning figure across most of England in 2026 is six months. Most dairy advisers I’ve talked to plan to seven on heavy ground. The figure matters because every store built or extended to a smaller capacity is, in effect, a store that will be at capacity in a winter where the closed period runs long and the soil stays saturated. That is exactly the situation in which slurry ends up in the ditch and the EA ends up in the yard.

The closed periods, in plain numbers

The NVZ closed periods for slurry, poultry manure and other high readily-available-nitrogen organic manures are:[13]

Tillage land, sandy or shallow soils: 1 August to 31 December. Tillage land, all other soils: 1 October to 31 January. Grassland, sandy or shallow soils: 1 September to 31 December. Grassland, all other soils: 15 October to 31 January.

For manufactured nitrogen fertiliser the periods run shorter, finishing in mid-January or early February depending on land type. Solid farmyard manure with low readily-available N has its own narrower closed period of 1 November to 31 January for tillage on sandy soils only.

The closed periods are not a Defra suggestion. They are the operative law within an NVZ, and the EA’s view, supported by case-law on the Farming Rules for Water, is that spreading outside the closed period but onto saturated ground is itself a breach of the diffuse-pollution rules.[14] In other words, the closed period is the minimum, not the planning target.

The bovine spreading windows in practice are shorter than the published dates suggest. A wet October can shut a farm down a fortnight early. A late spring can keep tankers off the field through the first half of March. Build the store to ride it out, or pay the contractor for emergency removal at £4 a cubic metre and an unhappy phone call.

Run-off, slopes, watercourses: the Farming Rules for Water

The Farming Rules for Water apply in England whether you are in an NVZ or not. The eight rules cover three families of duty.[15]

Planning: every farm must match organic manure and fertiliser applications to crop and soil need, and take account of weather and soil conditions. Soil testing every five years is the benchmark.

Application: no spreading within 10 metres of a watercourse (5 metres with verified precision equipment), 50 metres of a spring, well or borehole, or on land waterlogged, flooded, snow-covered or frozen for more than 12 hours in the preceding 24. Slopes greater than 12 degrees are restricted; greater than 15 degrees prohibited where there is a runoff risk.

Storage and yards: stores must not leak, run-off from yards must be contained, and soil compaction that causes runoff must be remedied.

These are the rules the EA uses when a clamp seeps, a yard washes into a ditch, or a tanker leaks at a field gate. The maximum fine on indictment is unlimited; the Civil Sanction regime can attach a Variable Monetary Penalty up to £250,000 without a court appearance.[16]

The inspections, and the prosecution trend

The Environment Agency has been more active on agricultural pollution since 2023 than at any point I can remember. EA data shows 4,191 farm inspections in England in 2023/24 against 2,891 in 2022/23, weighted heavily to dairy and intensive livestock units.[17] The Agriculture Regulatory Performance Report 2023 found around half of inspected farms non-compliant in at least one respect, with slurry storage capacity and application timing the two leading categories of breach.[18]

The prosecutions have followed. A Cumbrian dairy was fined £30,000 in 2023 for a slurry lagoon overflow; a Devon mixed farm £14,000 in 2024 after a silage effluent discharge killed an estimated 1,800 fish in a chalk stream.[19] The pattern is consistent: storage at or below capacity in October, a wet autumn, a decision to spread on saturated ground or to overfill the store, and a downstream watercourse with a fish kill that brings the EA in.

A farmer two parishes over from us took an £8,000 hit and a 12-month compliance plan last year for a yard run-off into a drain that fed a trout stream. He’d been farming it the same way for fifteen years. The drain had moved. The rules had moved. He hadn’t. He’s mid-way through a slurry separator install and a yard re-grade, and reckons the total cost will be the wrong side of £45,000 by the time the grant catches up.

If I’m honest, the EA’s posture has changed and the numbers prove it. A clamp or a store that was tolerated through the 2010s is being looked at hard in 2026.

Capital Grants 2026: the storage money on offer

The Slurry Infrastructure Grant has been the major Defra programme for storage upgrades, with three rounds between 2023 and 2025.[20] As of May 2026 the SIG sits inside the wider Capital Grants offer launched in February 2026, with funding bands for new or expanded slurry stores of £25,000 to £250,000 covering up to 50 per cent of the eligible cost, conditional on the store taking the farm to a minimum of six months’ capacity and being fitted with a cover that meets the ammonia code.[21]

Capital Grants 2026 also funds slurry separators, slurry acidification kit, low-trajectory spreading equipment (trailing shoe, dribble bar, shallow injector) under the FETF stream, and concrete yard re-laying with clean and dirty water separation.[22] Application sits inside the Rural Payments service.

The grant does not pay for itself in feeling-good terms. A typical 1,500-cubic-metre slurry store with cover is in the £180,000 to £240,000 bracket before grant, so even a 50 per cent contribution leaves £90,000 of cost to find. The case for taking it is not the headline saving; it is the avoided cost of an EA prosecution, an insurance claim refusal, and a forced winter slurry export.

What I’d actually do, if I ran cattle, is apply in the first eligible window every time the scheme opens. The grants are not generous enough to make uneconomic storage economic. They are exactly generous enough to bring forward a build that will have to happen anyway.

Silage in 2026: the part everyone underrates

Silage clamps are the lower-profile cousin of slurry stores, and the prosecutions on silage effluent are sharper than the slurry ones because the effluent concentration is roughly two hundred times that of raw sewage at the point of release.[23]

The AHDB Silage Manual gives the figures: BOD of fresh silage effluent of 30,000 to 80,000 mg per litre against a treated sewage discharge consent of around 20 mg per litre.[24] A modest leak into a watercourse is, in oxygen-demand terms, the equivalent of a small market town’s untreated sewage going straight in.

The SSAFO standards are the floor. The working standards in 2026 are higher: kerbed perimeter channels, sumped effluent tanks at twice the SSAFO minimum where rainfall exceeds 1,000 mm a year, and impermeable covers replaced before the third cut. The pinch point is the first 48 hours after closing the clamp, when effluent production peaks.[25]

What this means for non-livestock neighbours

I’m an arable and salad-and-veg grower. I don’t have a slurry store or a clamp. Two things still land on me.

The first is the Farming Rules for Water themselves. They apply to all organic manures, including digestate from a local AD plant or imported FYM. If I take in digestate, I am as caught as the dairyman who produced it.

The second is the parish-level reality. A clamp leaking into a ditch upstream of my salad block is a contamination problem for my crop and a notifiable food-safety issue for my customer. The right response is not to grumble at the gate but to ring the neighbour first, then ring the EA on 0800 80 70 60 if there’s an active pollution incident, and to keep a dated record.[26] A grower who treats the rules as the dairy farmer’s problem will be the grower who finds a customer refusing a load because of an upstream incident.

The action checklist for this week

If you run livestock, take a tape measure to the slurry store and work out the days of storage you actually have at typical December throughput. If it is less than six months, get the Capital Grants 2026 application in.

If you run a clamp, walk the perimeter channel and the effluent tank in the next week. A blocked channel or a half-full tank in May is a prosecution waiting for September.

If you take in digestate or imported manure, file the supplier paperwork, the analysis and your application records together. The EA’s first ask in an inspection is the paperwork on third-party manures.

If you are an arable or horticultural neighbour to a livestock farm, walk your ditches at the parish boundary once a quarter and photograph the state. The dated picture is worth more than a memory if you need it later.

If you operate a domestic heating oil tank on a farmhouse, check the bund. The most prosecuted SSAFO breaches at the smaller end are unbunded or failed-bund fuel tanks on farms.

Further reading

The Environment Agency’s Rules for Farmers and Land Managers to Prevent Water Pollution is the working briefing on Farming Rules for Water. AHDB’s Silage Manual and Slurry Management guides are the best free practical handbooks. Defra’s NVZ guidance pages on gov.uk carry the current closed-period maps and the Action Programme rules. The Code of Good Agricultural Practice for Farmers, Growers and Land Managers is the document the inspector will quote.

For BritFarmers readers, this guide sits alongside the UK Farming Grants Guide, the UK Farm Safety Guide and the Farm Inheritance Tax 2026 Guide.