Slurry stores required capacity

Find out why you should have sufficient slurry storage for your farm system. It is a legal requirement under several regulations. These regulations differ between England, Scotland and Wales but their primary purpose is to protect the environment.

When calculating your slurry storage requirement, you must account for any additional rainwater or washings that will enter the store, either directly or from other areas of the site, such as the silage clamps. This will require you to know your anticipated rainfall, taking account of wetter than average years.

You must also allow for the minimum freeboard space. Freeboard is the vertical distance between the top of your tank or lagoon and the slurry surface. For a steel or concrete store, you must include a minimum of 300 mm of freeboard. For earth-banked stores, you will need a minimum of 750 mm. This freeboard must always be maintained.

Having the right amount of slurry storage for your specific farm operation will allow you to make the most of the valuable nutrient content of your slurry. It will give you the flexibility to spread slurries at times when these nutrients, especially nitrogen, will be best for the crop, resulting in less need for bagged fertiliser and reduced risk of diffuse pollution. 

Our Slurry Wizard is a helpful tool that can be used to calculate the amount of slurry storage required for a livestock farm system.

Slurry storage capacity requirements are set by law. The rules differ between England, Wales and Scotland, so it is important to understand which requirements apply to your farm.

Commonly known as SSAFO regulations, this legislation requires a minimum of four months of slurry storage.

The NVZ regulations are enforced only within designated NVZ areas. To comply, you must have enough slurry storage to do the following:

• Comply with the minimum storage period for livestock manure
  • 22 weeks for cattle slurry
  • 26 weeks for pig slurry
• Adhere to the NVZ closed periods for spreading
• Spread slurry only in the correct conditions
• Comply with the maximum stocking densities and application rates of nitrogen

Commonly known as the ‘farming rules for water’, this regulation was introduced in England in 2018. These rules do not state a minimum capacity for your store.

However, it does stipulate that you must plan your applications of manures and fertilisers so that you do not exceed the needs of the crop or soil. You can use our nutrient management guide RB209 to create a nutrient management plan which would be required to demonstrate this. Find out more about nutrient management plans.

With every slurry application, you must be able to show that the application was made to meet the nutrient needs of the crop and not to empty your slurry store. This means that you would also need to justify the timing of your slurry application.

This legislation requires a minimum of four months of slurry storage.

These regulations apply to all farms in Wales and were introduced in February 2021, replacing the previous NVZ regulations.  

Detailed guidance documents are published on the Welsh Government website providing a step-by-step approach to the implementation of the regulations.

This legislation requires a minimum of four months of slurry storage.

Control of Pollution (Silage, Slurry and Agricultural Fuel Oil) (Scotland) Regulations 2003 (commonly known as the Scottish SSAFO Regulations) are no longer in force on their own. Instead, their core rules have been consolidated into Scotland's broader environmental framework, which is currently governed by the Environmental Authorisation (Scotland) Regulations (EASR).

These regulations also apply in designated NVZ areas in Scotland. Refer to the England section above for further details.

From January 2026, all farms which produce slurry in Scotland must have sufficient capacity to store the total quantity of slurry likely to be produced, in 22 weeks by housed cattle or 26 weeks by housed pigs.