A new slurry inoculant containing specialised strains of bacteria and fungi has been found to reduce crust formation on slurry stores by almost a third.

It aims to help farmers to improve slurry management and reduce the need for bought-in fertilisers.

Bedding and inoculants specialist EnviroSystems has redeveloped SlurryBugs with the help of findings from a two-year study.

The study, which was 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.

The results of the study 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).

EnviroSystems said this is because organic materials are released into the slurry when the crust is broken down.

The company also ran specialist trials at Myerscough College’s dairy farm to ensure the study could be completed with reliable outcomes.

Head of research at EnviroSystems, Dr. David Townsend, said: “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 20L 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.

Crust formation

EnviroSystems said 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,” Townsend said.

“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.”