From local resources to practical low-peat casing soils
As part of #PEATLESSSpain, La Rioja is becoming the first demonstration territory where the PEATLESS project is turning peat reduction into practical activity.
At the Mushroom Technological Research Centre, CTICH, researchers are evaluating renewable materials and by-products that could be incorporated into new casing-soil formulations for the cultivation of Agaricus bisporus.
The objective is not only to identify materials with environmental potential. The work also aims to understand whether they can provide the physical and chemical properties required by mushroom growers in real production conditions.
This practical approach reflects one of the central messages of the PEATLESS project: reducing peat use should not mean increasing uncertainty or making cultivation more difficult.
Local materials with potential
The materials currently being evaluated include:
- Spent mushroom substrate
- Different plant fibres
- Composted bark
- Vermicompost
- Sheep wool
- Other renewable resources and by-products
Many of these materials come from local resources or side streams generated by other sectors.
Their use could help reduce dependence on peat while creating new value for materials that currently have limited applications. This makes them particularly relevant to the PEATLESS approach, which seeks to combine peat reduction with local availability, circularity and practical adoption.
“Local materials can support peat reduction, but their properties must first respond to the practical needs of cultivation.”
Why every material behaves differently
Alternative materials cannot be treated as direct replacements for peat.
Each raw material has its own characteristics. Some retain more water, while others provide greater aeration. Their structure may also influence how quickly the mycelium colonises the casing soil.
These differences are important for growers because they can affect irrigation management, crop development and production.
For this reason, PEATLESS is examining not only which materials are available, but also how they behave and what role each one could play within a formulation.
This work supports the campaign’s aim to communicate early evidence in a way that is practical, credible and easy to understand, helping growers and advisors assess the real potential of low-peat solutions.
A closer look at the materials
The video below introduces some of the materials being evaluated at CTICH and shows why properties such as water retention, aeration and structure must be considered when developing low-peat casing soils.
Combining and conditioning the materials
A promising raw material may still require adjustments before it can be used effectively.
Small amounts of auxiliary materials can be added to:
- Improve the structure of the mixture
- Optimise water retention
- Support adequate aeration
- Create suitable conditions for mycelial development
This means that the performance of a casing soil does not depend only on the materials selected. It also depends on how those materials are combined and conditioned.
The aim is to develop formulations that are more sustainable while remaining compatible with the technical requirements of mushroom production.
This is especially important for #PEATLESSSpain, which seeks to build confidence through real demonstration work rather than presenting peat reduction only as an environmental objective.
“A viable low-peat formulation depends on the right combination of materials, properties and cultivation requirements.”
The importance of pH and electrical conductivity
The chemical properties of each mixture must also be controlled.
Two important parameters are pH and electrical conductivity.
A pH close to neutral or slightly alkaline favours crop development. By contrast, excessively high electrical conductivity can hinder mycelial growth and negatively affect production.
For this reason, all formulations are carefully characterised before cultivation trials begin. When necessary, adjustments are made to bring these values within an appropriate range.
This type of technical knowledge is essential for growers and advisors, who need reliable criteria before considering the adoption of new casing-soil formulations.
More information about the technical and adoption challenges addressed by PEATLESS is available in the project’s key insights.
Technical and regulatory challenges
Some materials also present specific limitations.
For example, the agricultural use of sheep wool requires compliance with specific legislation.
Other materials may be promising from an environmental point of view but still need improvements before they can provide physical properties comparable to peat.
These challenges show why experimental assessment is necessary before any material can be considered for wider use.
The PEATLESS work plan combines technical validation with environmental, economic, social and regulatory analysis to support the development of more viable growing media.
Turning local resources into practical knowledge
The role of CTICH within #PEATLESSSpain is not limited to testing individual materials.
The centre is developing practical knowledge about:
- Which materials have the greatest potential
- How they should be combined
- Which adjustments they require
- Which parameters must be controlled
- What barriers need to be addressed before wider adoption
This information can help growers, advisors and substrate suppliers better understand how local resources may contribute to peat reduction.
By making the properties, limitations and possible uses of these materials more visible, PEATLESS is helping create the conditions for local uptake, greater confidence and more informed growing decisions.
La Rioja therefore serves not only as a testing location, but as the starting point for a demonstration approach that can later be adapted and replicated in other regions.
More information about CTICH and the organisations involved in the project is available on the PEATLESS consortium page.
Further publications and communication materials can be found in the PEATLESS resources section!
