Summary:
- 94 % reduction in ammonia volatilisation when treated slurry is spread on
grassland - 28 % lower ammonia release during onfarm storage of treated slurry.
- Fresh grass yield increase from 13t to 20t
- Typical cost: £3.62 per cow per year
An initial trial, conducted by the University of South Wales, found that the slurry inoculant, SlurryForSoil, reduced ammonia emissions by up to 94%
at application.
SlurryForSoil was one of five innovations selected by SBRI for the research project, funded by the Welsh Government. The project aimed to find and
develop cost-effective solutions that reduce harmful pollutants entering the atmosphere as a result of agricultural practices.
“This independent trial provides further evidence that our cost-effective slurry inoculant delivers both for the environment and for dairy farms,”
says Romney Jackson, Director of SylgenBio, manufacturer of SlurryForSoil.
“Capturing nitrogen that would otherwise be lost to the atmosphere as ammonia and putting it into the soil where plants can use it, benefits
everyone – farmers, supply chain partners and wider society.”
Professor Sandra Esteves, University of South Wales, adds: “Reduction of ammonia emissions are critical at improving air quality and reducing
climate change. Microbes are known to deliver numerous functions in soil health, crop growth and emission modulation. The potential high
reduction of ammonia emission is promising and at USW we are progressing experimental studies to further knowledge and findings in
this field.”
Additional work is planned to evaluate replication of the results in a variety of farms and slurry types, and to further study the reasons behind this
reduction.
Supply chain collaboration
Governments across the UK have committed to reducing ammonia emissions by 80% by 2030. Achieving this ambitious target requires
collaboration. Leprino – the world’s largest manufacturer of mozzarella cheese – is proactively encouraging its dairy farmers to use SlurryForSoil
and has supported the manufacturer, SylgenBio, to apply for research initiatives such as the SBRI grant.
“This work is important in showing farmers the effectiveness of solutions such as SlurryForSoil, building trust that the solution adds value to their
business as well as demonstrating to policy makers that agriculture can continue its social license to produce,” says Ben Williams, Sustainability
Manager at Leprino.
“The significant reduction in emissions shown in this trial as well as the boost to forage yields and quality, shows that more regenerative ways of
farming, using modern technological solutions, is a key tool for more profitable and more sustainable dairy production.”
SlurryForSoil in the lab and the field
A comprehensive suite of trials was designed to explore the effects of SlurryForSoil across two Welsh dairy farms, and in the laboratory.
On farm, the slurry inoculant was added to one of two tanks storing cattle slurry. Researchers measured the polluting gases emitted from stores
before applying the treated and untreated slurries to grassland, where tents captured emissions which were measured.
The first farm trial, at Trefynys Farm in Carmarthenshire, took place between May and September 2024 and used slurry from its fully housed
herd of 350 Holstein cows. It proved to be a worthwhile pilot.
“Through this trial we got some very valuable and interesting results. Being the first trial of its kind, it was also a learning experience for all involved. In comparison with a laboratory, a cattle shed is a challenging environment for sensitive equipment,” notes Romney.
SlurryForSoil reduces stored slurry emissions
The host of the second farm trial – Drysgolgoch Farm in Pembrokeshire – was chosen because it is more typical of a Welsh dairy farm. The herd of
approximately 750, mainly shorthorn milking cows, is housed over the winter with block calving in spring and autumn. The trial was conducted
between October 2024 and March 2025.
“The tank which was inoculated with SlurryForSoil collected slurry from approximately 400 cattle fed a diet of grass silage and mixed ration,”
explains Romney.
Slurry which had been treated with SlurryForSoil saw a 28% decrease in overall ammonia emissions during storage.
“SlurryForSoil is a complex blend of microbes and many have been chosen because they are known to consume the organic material found in slurry,” says Romney. “The bacteria and fungi use these nutrients in their life processes – growing, reproducing etc. In doing so, the nutrients are held
within the cells of the micro-organisms, rather than being lost to the atmosphere.
“By breaking down the complex organic compounds into simpler ones, this process also homogenises slurry, reducing the need to stir and
lowering the risk of blockages at application.
“When applied to the soil, these microbes support plant growth either by releasing the nutrients into the soil when they expire or through the
symbiotic relationships they form with plants,” explains Romney.
SlurryForSoil lowers emissions at application
The final element of the trial saw the slurries mixed and applied to two halves of the same field. Tents captured the release of any gases and
showed that SlurryForSoil reduced average ammonia emissions by up to 94%.
“Too often lowering the emissions on-farm is expensive, either in time or money. SlurryForSoil on the other hand, typically costs just £3.62 per cow,
and is proving to lower emissions while increasing grass quality and yields. It makes storing and handling slurry quicker, easier and cheaper too,” says Romney.
SlurryForSoil grows more grass than urea
Following the SBRI trial, SylgenBio continued to monitor the effects of SlurryForSoil at Drysgolgoch Farm.
“The side of the field that received untreated slurry yielded 13.2t/ha while the treated side yielded 20.56t/ha. Dry matter grass yields increased
significantly too,” says Romney.
The farmer then tested the effects of increasing urea applications from 120kg to 170kg/ha across both the treated and untreated halves. The area
of the field which received SlurryForSoil-treated slurry yielded 23.28t/ha. While the untreated yielded just 18.4t/ha.
The highest dry matter yields came from the quarter which had received average nitrogen rates as well as treated slurry. It outperformed both
quarters with higher nitrogen rates.
“The bacteria and fungi in SlurryForSoil are scientifically proven to have other plant growth promoting benefits such as mobilising and
transporting nutrients in soils, improving root growth and access to water, and contributing to soil aggregation,” explains Romney.
“With yields exceeding the likely effects of the additional nitrogen captured by the microbes, the gains are likely to be a result of these
longer-term benefits.”
Romney recognises that abundant nutrients can inhibit the symbiotic relationships between plants and soil microbes, and suggests that this is
the reason why additional nitrogen together with treated slurry didn’t result in the highest dry matter yields.
Trial impacts
Reflecting on the impacts of the finding, Romney said: “Biological products often suffer from a lack of scientific evidence to support their claims and,
understandably, stakeholders can be skeptical about them. We want to change that.
“SlurryForSoil has been the subject of many lab and field trials and there’s a significant body of evidence proving that by increasing grass quality and
yield, reducing the need for fertiliser, and lowering the fuel requirements to stir slurry in store, SlurryForSoil enhances the sustainability and
resilience of farming.”
Those benefits extend beyond the farm gate. In April 2024, Leprino calculated that the slurry inoculant could reduce its suppliers’ carbon
footprints by 4,000t.
“Being able to add ammonia reduction to the list of benefits is a milestone both for this product and for the wider industry. Our government is
committed to reducing ammonia emissions by 80% by 2030. 87% of which come from agriculture. SlurryForSoil has been proven to be a cost-
effective solution which can help our industry, and the government achieve this ambitious target.”
