CASE STUDIES

“Using an alternative to synthetic fertilisers makes sense for both the soil and the wider environment. We’re already seeing stronger growth and healthier young trees across the woodland. I’m keen to continue working with Re-Genus on other sites, with the longer-term aim of phasing out synthetic fertilisers and reducing the need for second-stage applications and unnecessary weeding.”
– Phil Di-Duca, MICFor, Kelpie Woodlands

Background

In June 2024, the Mackay Family Forestry and Farming Partnership began establishing new native broadleaf woodland at Tanlawhill Farm as part of a habitat-focused creation scheme. The site, historically grazed by sheep and cattle and shaped by decades of agricultural management, presented challenges familiar across the Scottish Borders: compacted ground, browsing pressure, nutrient lock-up, and soils with variable microbial activity.

Alongside these physical challenges, the regulatory context for woodland creation continues to evolve. Woodland managers must now demonstrate stronger ecological performance under frameworks such as the Ecological Site Classification (ESC) and the National Vegetation Classification (NVC), alongside environmental assessments and biodiversity-led grant mechanisms. These pressures are placing greater emphasis on biodiversity, soil function and demonstrable ecological enhancement and prompting foresters to explore approaches that put soil function and long-term resilience at the center of woodland design.

Against this backdrop, Kelpie Woodlands’ Operations Director, Phil Di-Duca, was interested in trialing Re-Genus Woodland Grow as a more biology-aligned alternative to the standard woodland NPK fertiliser typically applied at planting. His objective was to support a more resilient establishment phase, reduce early losses, and explore a system more consistent with current environmental policy and future natural-capital reporting.

The Project

The trial took place at Graham’s Rig, part of the Tanlawhill landholding, where Kelpie Woodlands planted a diverse mix of native broadleaves including birch, aspen, oak, hazel, willow and alder. The woodland creation design was planted at a density of 1,800 trees per hectare, giving a total of approximately 27,000 trees across the 15-hectares site.

To understand whether a biological approach could improve early establishment, Phil Di-Duca set up a comparison between two adjacent areas on comparable ground. One section of 7.5 ha was treated with a standard woodland NPK fertiliser, while the other 7.5 ha received Re-Genus Woodland Grow pellets applied at planting.

Woodland Grow is a natural, fungi-rich pellet manufactured in the UK and designed to feed soil biology, providing nutrition through gradual, microbially mediated release rather than rapid solubility.

Phil was keen for the forestry sector to move away from highly soluble synthetic NPKs and move towards approaches that work with soil processes rather than bypass them. He wanted a product that aligned with peat-free systems, supported microbial diversity and fitted within modern environmental assurance schemes. The slow-release, microbiome-supporting design of Woodland Grow resonated strongly with what he described as “the direction the industry is moving towards: soil health, biodiversity uplift and long-term resilience.”

This trial created an opportunity to directly compare the two fertiliser approaches within the same landscape, soil type and establishment conditions, and to evaluate how improved soil biology might influence the performance of young native woodland.

Measurement Methodology

To evaluate early performance, Re-Genus Technical Lead Sam Brook conducted a structured assessment after the first growing season.

A random selection of birch and alder was taken across both the standard NPK area and the Woodland Grow area. Tree height was measured from the ground to the leading shoot, and girth was recorded 5 cm above the vole guard, following common early-establishment practice. Measurements were supported by observational notes covering leader vigour, canopy colour, stem form and browsing evidence.

This method provided a clear, consistent comparison of performance between the two fertiliser regimes under identical ground and climatic conditions.

Results After One Growing Season

Birch

Birch showed the strongest response to the biological approach offered by Woodland Grow.

• Woodland Grow average height: 139 cm
• Standard NPK average height: 76 cm
• Increase: +83%

The birch in the Re-Genus treatment area demonstrated more vigorous leader shoots, stronger stem form and better lateral bud development, all of which are indicators of reduced early stress and improved rooting.

Alder

Alder also responded positively.

• Woodland Grow average height: 121 cm
• Standard NPK average height: 81.6 cm
• Increase: +48%

Because alder is naturally associated with nitrogen-fixing bacteria, the uplift here could suggest that the microbial support provided by Woodland Grow contributed more than simple nutrient addition.

Across both species, the treated area displayed greener canopies, faster height gain and more even establishment – signs that soil biology was beginning to play a more prominent role in nutrient cycling and moisture availability.

Why Soil Biology Matters for Woodland Creation

Phil emphasised the increasing role of soil health in forestry decision-making. Modern woodland schemes must do more than plant trees – they must demonstrate biodiversity improvement, soil protection and long-term resilience.

He also noted that woodland managers are thinking more carefully about the environmental footprint of fertilisers. Traditional NPKs are often highly soluble, prone to leaching and offer limited support to the soil microbiome. In contrast, a biological approach helps unlock nutrients already present in the soil and provides a more stable growth trajectory.

The first year is the most vulnerable phase for newly planted native woodland, especially on ex-grazing land:

• Faster height gain reduces exposure to hare and deer browsing.
• Better early rooting improves drought resilience.
• Improved growth allows trees to compete with aggressive vegetation on old agricultural ground.
• Strong first-year performance reduces restocking costs and mortality.

Phil noted: “Anything that gets trees away quicker saves money, reduces losses and builds resilience. If biology-led fertilisers can give us that advantage, they fit perfectly with where forestry is going.”

Environmental Benefits

Woodland Grow contributes to several environmental priorities:

• Reduced reliance on synthetic NPK and their associated carbon footprint
• UK-manufactured, reducing transportation emissions
• Supports soil biology, consistent with the direction of ESG reporting, UKFS revisions and biodiversity-net-gain frameworks
• Aligns with industry movement toward peat-free, biology-positive inputs
• Potential to complement environmental management plans, NVC habitat targets and ESC suitability assessments

Phil also highlighted increasing regulatory scrutiny and the need for products that fit with modern policy and natural capital frameworks – an area where Woodland Grow’s biological approach offers clear advantages.

Conclusion

Based on the early results, the Tanlawhill trial demonstrates that supporting soil biology during the establishment phase can deliver measurable performance improvements, especially in restock areas where nutrient cycling and soil recovery can be more challenging.

By replacing the standard woodland NPK with Woodland Grow, the site achieved:

• 83% greater height growth in birch, and
• 48% greater height growth in alder

These outcomes support the wider environmental and regulatory direction of UK forestry, where soil function, biodiversity and long-term resilience increasingly sit at the centre of woodland management.

Re-Genus and Kelpie Woodlands will continue to monitor the site, gathering multi-year data on soil activity, survivability and broader ecosystem response.