Slurry wizard

Our slurry wizard enables you to work out your slurry storage requirements and explore different storage scenarios to comply with regulations.

September 2024 update – important message for those with earth bank lagoons

A formula error has been identified in the October 2023 and March 2024 versions of Slurry Wizard. This will result in an underestimation of the working capacity of earth bank lagoons (due to the freeboard formula not accounting for the slope angle). The September update of Slurry Wizard fixes the issue.

If you used the previous versions of Slurry Wizard and your slurry storage system includes an earth bank lagoon, the tool has likely underestimated the working slurry storage capacity your system provides. The degree to which your working capacity was underestimated depends on the size of your lagoon and the slope angle.

You may wish to review your previous calculations using the updated tool. Apologies for any inconvenience caused.

Slurry wizard: A tool to calculate the volume of slurry produced on farm 

By entering basic farm information such as animal numbers, yard and roof areas that capture rainfall, and housing periods, the wizard calculates the volume of slurry that the farm will produce on a monthly basis.

This data, together with the farm’s current slurry storage capacity, is used to calculate how long it takes to fill the available storage and whether more capacity is needed.

Note that the wizard will only function correctly if you have Microsoft Excel installed on your device.

What does it do?

• Calculates the total amount of nitrogen produced to allow those farming within an NVZ to meet the obligation to stay beneath the required threshold
• Helps you explore the potential impact and cost from changes to infrastructure such as redirecting rainwater, roofing dirty yards, increasing storage capacity or installing a slurry separator
• Provides a cost/benefit analysis for fitting rainwater goods to redirect clean water and covering dirty yards 
• Helps you understand the impact of changes such as increases in herd size, moving from straw yards to cubicles, introducing outside loafing areas, changes to the housing period and dirty water management can be quantified

Recent changes to the wizard include more accurate rainfall data. The rainfall data that has been incorporated into this version of the Slurry Wizard tool uses the Centre for Ecology and Hydrology’s Gridded Estimates of Areal Rainfall (GEAR) 1 km dataset, which covers the whole of the UK. To access this data the farm location needs to be identified with a 10-figure grid reference.

Another enhancement makes it much easier for pig farmers to account for the slurry and wash water produced on their farms to be accounted for. A wider range of available bank slopes for earth-banked slurry stores and the ability to incorporate slurry bags has also been added. 

Our slurry wizard user guide can be read online or downloaded as a Word file.

Read online

Download the guide in Word

Slurry Infrastructure Grant

Defra offers a grant to help replace, build additional or expand existing slurry stores to provide six months of storage, helping farmers improve the use of organic nutrients on farms and reduce pollution. When applying, a copy of the farm's Slurry Wizard storage capacity calculation and rainfall data is required.

Round 2 of the grant is now closed to new applicants, and a new round is expected in the autumn of 2024.

More detail is available on GOV.UK: About the Slurry Infrastructure grant, who can apply and what it can pay for