On-farm bio-stimulants and closed-loop soil health at Pollybell Farm
Our recent On-Farm Bio-Stimulants and Closed-Loop Soil Health event at Pollybell Farm, brought together a diverse audience of farmers, growers, researchers and advisers for a day of practical learning and discussion. Funded by Ocado through the Farm to Fork partnership, the event focused on how farms can improve soil health, build resilience and reduce reliance on external inputs by making better use of biological processes and resources already available on-farm.
Managing on farm diversification at scale
Hosted by James Brown and the Pollybell team, the day provided an opportunity to see how a large, highly diversified farming business is integrating regenerative principles across its operations. Pollybell manages a wide-ranging farming system including organic vegetables, organic and conventional cereals, dairy, environmental schemes and wildlife habitats. This diversity provides opportunities to test innovative approaches and investigate how nutrients and carbon can be retained and recycled within the farm system.
A central theme was the importance of understanding soil as a complex interaction between physical, chemical and biological processes. Craig Bargery, farm manager, stressed that biological interventions are most effective when supported by good soil structure, appropriate nutrition and careful management. Their approach is underpinned by detailed soil analysis, including Terramap data, tissue testing and agronomic monitoring, which helps guide decisions around cultivations, amendments and nutrient management.
Johnson-Su compost system
Particular interest centred on Pollybell's work with Johnson-Su compost bioreactors, a method of producing biologically rich compost designed to act as an inoculant for soil and crops. Unlike conventional composting systems, the Johnson-Su process focuses on creating diverse fungal and microbial communities using on-farm materials. Pollybell's compost mixes included combinations of chicken manure, willow bark chips, vegetable waste, grass clippings and leaf litter, composted in static aerobic systems designed to maintain airflow throughout the pile. After an initial thermophilic phase, the compost is matured with the aid of earthworms, creating a product rich in fungi, bacteria and protozoa.
Monitoring results presented on the day demonstrated the significant biological activity that can be achieved through this process. Data comparing Johnson-Su compost with typical farm soils showed substantial increases in microbial biomass, protozoa and fungal populations, including mycorrhizal fungi. The aim is not simply to add nutrients, but to support the soil food web and improve nutrient cycling, root development and overall soil function.
Tom Hopkins, farm agronomist from Farmacy, discussed different methods of applying the Johnson-Su product. As well as using the mature compost as a seed treatment or soil amendment, they are producing liquid extracts, often referred to as compost 'tea'. The extraction process involves placing approximately 20 kg of Johnson-Su compost in a compost bag within an IBC tank and brewing it in water for several hours, sometimes with additional biological food sources. This creates a liquid inoculant that can be applied directly to crops, modules or soils, helping distribute microbial communities more efficiently across larger areas.
Exploring the benefits of biochar
Alongside the biological work, Pollybell is also exploring the potential of biochar as part of a closed-loop soil health strategy. The farm operates a pyrolysis system that converts willow biomass into biochar, creating a stable form of carbon that can be incorporated into soils while also contributing to carbon sequestration. Craig and Tom explained how biochar can act as a habitat for soil microorganisms and a carrier for biological inoculants such as Johnson-Su compost extracts. They are also investigating 'cluck char', produced through the use of biochar within poultry housing systems, where it absorbs nutrients and organic materials before being applied to land.
Several ongoing trials are assessing the interaction between Johnson-Su biology, biochar and cluck char. Nursery experiments involving broccoli production are comparing different combinations of char and biological treatments, while field-scale cabbage trials are testing whether biochar and cluck char applications, combined with Johnson-Su treatments, can improve crop performance. Early observations suggested some nutrient-locking effects in the nursery, highlighting the importance of robust trials and long-term monitoring to understand how these systems function under commercial growing conditions.
Farm walk
The afternoon farm walk provided an opportunity to view some of these trials first-hand. While the work remains at an early stage, it was valuable to see the practical application of the concepts discussed during the presentations and to hear the team's thinking around trial design, monitoring and future evaluation.
Key takeaways
One of the key takeaways from the day was that, although Pollybell has significant resources and multiple business enterprises that enable it to invest in innovation, the underlying principles are relevant for growers of all scales. The audience ranged from market gardeners and small-scale growers to larger farming businesses and researchers, yet there were practical lessons for everyone around building soil biology, recycling nutrients, retaining carbon and reducing dependence on imported inputs.
The openness and generosity of James, Craig and Tom made the event particularly valuable. They shared not only their successes but also the challenges, uncertainties and questions that remain. This willingness to share learning created an environment of genuine knowledge exchange and demonstrated the value of collaborative approaches to tackling some of agriculture's most important challenges.
The Soil Association is extremely grateful to the Pollybell team for hosting the event, and to Ocado for funding the day through the Farm to Fork partnership and supporting opportunities for farmer-to-farmer learning across the sector.