PEATLESS moves from testing to validation in La Rioja
The first demonstration activities of the PEATLESS project in La Rioja are already under way. At the Mushroom Technological Research Centre, CTICH, laboratory trials are testing sustainable, renewable and technically viable alternatives to peat for use as casing soil in the cultivation of Agaricus bisporus.
This work responds to one of the main challenges facing the mushroom sector. Peat offers excellent agronomic performance, but its extraction has a significant environmental impact, and its future availability may become increasingly limited as European peatlands receive greater protection.
PEATLESS therefore focuses on generating practical evidence that can support the development and future uptake of growing media with significantly reduced peat content. The project develops and tests locally sourced alternatives for mushroom cultivation, seedling production and ornamental horticulture.
Testing twelve alternative mixtures
The first laboratory trial evaluated a total of twelve alternative mixtures.
Each formulation was compared with a conventional casing soil made from 100% peat. The aim was to assess how the mixtures performed throughout the full mushroom cultivation cycle and identify their main strengths and limitations.
The research team monitored several key aspects:
- Water-retention capacity
- Irrigation requirements
- Mycelium development
- Fructification
- Mushroom production
This comparison is important because efforts to reduce peat use in horticulture must be supported by practical evidence. Alternative mixtures need to be tested under cultivation conditions and assessed against the technical performance expected from peat-based casing soils.
“Reducing peat requires alternatives that can be tested, compared and progressively adapted to real production needs.”
Moving from first results to a second trial
The results of the first trial provided the basis for a second laboratory-scale trial, which CTICH is currently carrying out.
The mixtures that showed the most promising performance have been selected for further evaluation. At the same time, other formulations have been modified using the knowledge gained during the first cultivation cycle.
This process of continuous improvement is one of the main pillars of PEATLESS. Rather than treating each trial as an isolated test, the project uses the results from every stage to refine the mixtures and move closer to a technically viable alternative to peat.
The aim is not only to identify promising materials, but also to determine how the different components should be combined and conditioned to obtain the physical and chemical properties required for mushroom cultivation.
Characterising each formulation before cultivation
Before a mixture can be included in a cultivation trial, its physical and chemical properties must be carefully characterised.
The structure of the casing soil influences water retention, aeration and the speed at which the mycelium colonises the material. Different raw materials behave in different ways, meaning that each formulation may require specific adjustments.
Parameters such as pH and electrical conductivity are also important.
A pH close to neutral or slightly alkaline favours crop development. By contrast, excessively high electrical conductivity can make mycelial growth more difficult and negatively affect production.
For this reason, all formulations are analysed and adjusted when necessary before cultivation begins.
Building confidence through practical evidence
PEATLESS does not only seek to identify materials with environmental potential. It also aims to determine how those materials should be combined and conditioned to create casing soils with physical and chemical properties comparable to those of peat.
This practical focus is especially relevant for growers and advisors. For peat-reduced alternatives to be adopted, they must be reliable, understandable and compatible with everyday production needs.
The project therefore addresses some of the main barriers affecting the adoption of alternative growing media, including technical uncertainty, economic considerations and growers’ confidence. PEATLESS responds to these barriers through locally sourced materials, real-world trials, training and practical evidence.
“Each trial brings PEATLESS closer to a casing soil that can combine lower peat use with the performance required by the mushroom sector.”
Preparing for semi-commercial validation
The results obtained so far are promising and confirm that several formulations have significant potential.
However, laboratory performance must still be validated under conditions that are increasingly close to commercial cultivation.
Once the planned laboratory trials have been completed, the five best-performing formulations will be selected. These mixtures will then move into a semi-commercial phase in the CTICH cultivation rooms.
This next stage will be essential for checking the stability and reproducibility of the results and for determining whether the selected formulations can respond to the practical requirements of the sector.
From research to locally relevant solutions
La Rioja plays a central role in the first PEATLESS demonstration campaign. It is where the project begins to turn its objectives into practical activity through substrate testing, early validation and engagement with growers and other regional stakeholders.
By moving from laboratory comparison to semi-commercial validation, PEATLESS is generating the evidence needed to make peat-reduced solutions more practical, credible and relevant for mushroom growers, advisors and substrate suppliers.
The work carried out by CTICH will help establish objective criteria for future casing-soil formulations and support a gradual and informed transition towards reduced peat dependence.
Further information, audiovisual materials and project publications are available in the PEATLESS resources section.
