Slurry is a valuable product, and you must make it work for you

A two-year study, funded by Innovate UK and conducted in collaboration with Myerscough College, Preston, shortlisted almost 30 strains of bacteria and fungi and narrowed it down to a final five, which were tested under laboratory-controlled conditions.

These micro organisms were found to work most effectively on maximising the complex lignocellulosic biochemical pathways within slurry stores.

Slurry bugs by EnviroSystems

The results showed:

29% reduction in crust formation by using SlurryBugs and 23% reduction when using SlurryBugs Maintenance 10-15% increase in each of the following nutrients in the treated slurry (nitrogen, phosphorus, potassium, sulphur). This is because organic materials are released into the slurry when the crust is broken down. New studies are currently in progress to look at this further.

To help validate the work, the company ran specialist trials at Myerscough College’s dairy farm to ensure the study could be completed with reliable and accurate outcomes.

Dr David Townsend, head of research at EnviroSystems, explained: “Trialling slurry additives on full-scale farm systems presents difficulties due to the huge volumes of slurry involved and the inability to run controls or duplicates within a controlled setting.

“As a result, we mimicked a slurry lagoon using 20litre drums, which allowed us to increase our scrutiny over the experiments and the accuracy of the data we collected.”

The control and treated drums were dosed with the relevant additives and maintained under closely monitored conditions for three months. Each treatment was repeated four times to ensure the results were reliable.

After treatment, the slurry in the drums was weighed, with the crust removed and weighed separately.

Slurry storage

Preventing crust formation

Reducing crust formation is becoming more critical as the 2027 date for mandatory slurry store covers nears.

“Crust mitigation is directly linked to Defra’s good agricultural practice guide, which recommends covering slurry and digestate stores to reduce ammonia emissions and to ensure farms have enough storage to be able to spread slurry only when crops will use the nutrients,” explained Dr Townsend.

“Without farmers managing the crust, they will have no idea what is happening underneath the cover, and by the time a crust becomes noticeable, it might be too late to intervene.

“By using the SlurryBugs and SlurryBugs Maintenance, we can confidently offer farmers peace of mind that the crust formation will be minimised and slurry storage maximised.

“In addition, by improving the nutrient value of slurry by releasing trapped nitrogen, carbon, phosphate, and potassium materials into the slurry, farmers have the potential to reduce the use of synthetic fertiliser,” he said.

Using the products

The inoculants should be applied in a two-step process. New customers and those with a crusting issue are advised to use SlurryBugs to break down any existing crust and prevent any fibrous material added to the store from accumulating. Each sachet (1.5kg) will treat 500m3 of slurry for the duration of its storage. Customers are advised to treat for the duration of the storage at the beginning following spreading.

Once a homogeneous slurry has been achieved and the crust is under control, SlurryBugs Maintenance is a lower-concentration product that can help prevent further problems. It can also be used over the summer to top up the bacteria content and prevent dry crusts from forming ahead of the next storage season.

Dr Townsend added: “Slurry is a valuable product, and you must make it work for you. Not only have we refined our products through this rigorous testing and utilising specialist strains of bacteria, but we have also made it easier for farmers to treat their slurry and prevent any unforeseen crust crisis from occurring.”