Defra-backed trials aim to halve synthetic nitrogen use on dairy farms
Dairy farms could soon cut their reliance on synthetic nitrogen fertiliser without sacrificing yields, as scientists begin testing biological alternatives designed to slash emissions and boost efficiency.
The work is being carried out under Defra’s Farming Innovation Programme and will examine whether around 50% of synthetic nitrogen fertiliser used in dairy forage systems can be replaced with biological inputs.
The University of Nottingham is a research partner in Bio-Phage UK, a Defra-funded Low Emissions Farming project led by Terrafarmer and delivered through Innovate UK.
Trials will focus on practical performance on working farms, at a time when fertiliser costs, climate pressures and emissions targets are placing increasing strain on dairy businesses.
Bio-Phage UK is one of 15 innovation projects across England sharing £21.5 million in funding to help farms cut greenhouse gas emissions, improve resilience and maintain productivity.
Agriculture remains a significant source of nitrous oxide emissions, a greenhouse gas around 300 times more powerful than carbon dioxide over a 100-year period.
Dairy systems are intensive users of synthetic nitrogen fertilisers, making them a key focus for efforts to reduce emissions at source.
Researchers say improving nitrogen use efficiency through biologically mediated soil processes could offer a sustainable alternative, but adoption depends on strong, independent evidence from commercial conditions.
The University of Nottingham team will lead in-field greenhouse gas monitoring and the optimisation of biofertiliser strategies, alongside full life-cycle assessment of emissions.
Work will span key dairy forage crops including ryegrass, herbal leys and whole-crop systems, with field trials underway on three commercial dairy farms in England.
These trials are being supported by controlled glasshouse experiments to better understand soil chemistry and microbial responses.
Alongside biological fertilisers, the project will also test BIOCAT, a phage-based soil treatment that targets bacteria responsible for nitrous oxide production, offering a novel route to emissions reduction.
Dr Nick Girkin, associate professor in environmental science and director of the Centre for Sustainable Agricultural Systems at the University of Nottingham, is leading the university’s contribution.
He said the project is designed to deliver practical, system-wide evidence. “By combining direct measurements of greenhouse gas emissions, soil chemistry, microbial community responses, and whole-system life-cycle assessment alongside impacts on yield, the project generates robust evidence on a vital sustainability challenge for UK and global agriculture,” he said.
Dr Girkin said the findings could help guide future decision-making across the sector. “If successful, Bio-Phage UK could demonstrate a credible route to lower-emissions dairy forage production, delivering reduced reliance on synthetic nitrogen, improved nitrogen efficiency, and more resilient soil systems,” he said.
He added that the results will help farmers and policymakers distinguish between biological solutions that deliver genuine benefits and those that do not, supporting evidence-based decisions as UK agriculture moves towards a more sustainable future.
