The problem – why do we need this research?
Soil microbes are key to healthy soils: stabilising soil structure, enhancing plant growth, and delivering ecosystem services. Gardeners can optimise the way they improve soil health by working with these unseen subterranean allies. This helps people garden more in harmony with nature and climate.
However, we don’t know:
- How much soil health improvements can be expected in the garden
- How much and how fast soil improvers, biostimulants, plants, plant products, and gardening choices bring about measurable changes in the soil
- How soil management aims (like maximising plant growth, or carbon storage) are affected by the texture of soil in a garden (eg ‘loamy sand’ or ‘clay loam’)
The ‘Soil Health Platform’ at 911±¬ÁÏ Garden Wisley has been established to answer these questions. Once we understand how gardening choices and sustainability outcomes are affected by key characteristics of garden soil and gardening (such as starting texture and structure of soil), we can optimise our gardening and our advice to others, helping everyone improve their sustainability and plant quality. In this way we maximise our ‘handprint’ (positive impact) while minimising our ‘footprint’ (negative impact).
What are we doing?
The 911±¬ÁÏ Soil Health project began in 2025 at 911±¬ÁÏ Wisley and aims to equip gardeners and the horticultural industry with scientifically backed advice on how to improve soil sustainably through more informed gardening, planting choices, and use of inputs.
Led by Dr Marc Redmile-Gordon, the project includes experiments researching how to improve soil health and carbon storage.
The first is a laboratory experiment aiming to establish a benchmark on rapidly improving the physical health of 911±¬ÁÏ Wisley’s horticultural soils by applying ‘biostimulants’ (soluble sources of energy for soil microbes). These organic soil amendments are increasingly used by gardeners, and mimic the effects of the substances released by plant roots (exudates). They contain organic sources of nitrogen (in the form of amino acids) and carbon (in the form of sugars), empowering microbes to grow and produce substances that improve the soil.
The second experiment builds on this benchmark with outdoor trials at our new experimental site, the Soil Health Platform at 911±¬ÁÏ Wisley. These trials compare the sustainability and ability to improve soil health of two contrasting lawn seed mixes – one a ‘carbon saving’ mix, and one a ‘carbon pumping’ mix. The first seed mix grows slowly and so reduces the mowing requirement (reducing the release of embodied carbon in the form of fossil fuels), while the second maximises carbon inputs into the soil by plants (relatively short term carbon storage, but still important for climate mitigation). This investigation will help to clarify the extent to which gardening choices (seed choice, and use of grass clippings) can benefit soil health and help to mitigate climate change in the short, medium and long terms.
Measurements will include the responses of soil microbes, including the total amount of life in the soil (measured through soil microbial ATP), and the important substances they produce (‘extracellular polymers’ or ‘EPS’), which are used by microbes to modify soil structure for soil-wide benefits. We will also measure accumulation of carbon in the soil (in the form of MAOC; a relatively stable fraction of soil C), and the stability of soil aggregates (clusters of soil particles that create soil structure) as a practical measure of the extent to which soil health can be improved through microbe-assisted gardening.
What difference will this research make?
Most gardeners know that poor soil quality can be rapidly improved through bulky organic ‘soil improvers’. However, there are significant production and transport costs to this approach, and these raw materials are also needed to substitute peat in growing media as the UK transitions to peat-free horticulture.
By investigating ways to build soil health and fertility through living plants and concentrated organic products, we will empower gardeners to improve their soils, sustainably.
How will this project empower gardeners?
This research will empower gardeners to make more sustainable choices by enabling us to understand how much a) improvement of soil health, b) carbon storage, and c) sustainability gain can be expected from various approaches to managing soils, including the use of:
- Soluble soil improvers and microbial substrates: These give rapid and significant benefits to soil health and are an encouraging example of how much soil health can be improved in a short space of time, while reducing the need for fertilisers. These treatments can be used as a benchmark to which other approaches to improve soil health and carbon storage (such as mulches, fertilisers, plants) can be scientifically compared.
- Living plants: Plants improve soil health more slowly (often not measurable in the first few years of establishment). However, plants are a vital component of long-term soil health. We explore how plant cultivar selection can help gardeners improve their soil health. We also seek to demonstrate and quantify the long-term value of using plants to improve soils and help deliver climate mitigation targets. Differences between cultivars currently on offer will highlight opportunities for developing future cultivars that are optimised for improving soil health.
- Plant biomass: Plants don’t need to be living to improve soil health. Grass clippings, mulches, plant extracts, waste materials, biochar, homemade composts and more all contribute, empowering gardeners to improve soil health in a variety of ways.
A pressing need in the face of climate and biodiversity crises
Enhanced carbon storage in soils, and improving the soil health in gardens, could also displace significant national (and international) demand for shop-bought fruit and vegetables grown using conventional techniques. This can reduce the climate and biodiversity impacts of agriculture to grow food, including pesticides and carbon emissions.
Tailored advice
Gardens in the UK all have contrasting soil textures – sand, silt or clay. This determines how effective a gardener’s actions can be, and the best approach will differ between gardens and gardeners. This work will enable us to communicate the impacts of garden soil texture on climate mitigation and adaptation strategies, and give soil-specific advice to members, providing gardeners with bespoke information on how to garden most sustainably depending on their soil type.
Further information
Life under your feet – feeding plants and the planet
Our current advice
911±¬ÁÏ guide to soil types
Discover other ongoing projects in 911±¬ÁÏ Science here >
