Designing peat free blends

Peat as a growing medium has been sold in garden centres and used in glasshouses since the 1960s. It has the ability to improve soil structure and retain water while allowing air circulation. The extraction of peat for compost in horticulture has led to the degradation of peatlands which are vital carbon stores. If the UK is to reach net zero in the horticulture sector, the industry must move to peat free products.

Alternatives to peat do exist but supplies are either expensive or not available in enough quantities. For some applications, peat can be replaced with a single sustainable growing medium. However, a blend of raw materials is often necessary to meet production cost and product quality criteria.

ADAS Horticulture is the only laboratory offering a growing media analysis and design service. Our goal is to speed up the development of new, reliable, and high performing peat alternative growing media.

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Physical property analysis

A combination of materials can be used to replace peat in growing media blends. Understanding how the properties of these new materials can best match crop needs is critical to finding suitable replacements.

Growing media graph physical property analysis 2d

2D plot of physical property data. Parameters: Available water (AW), Air filled porosity (AFP), Dry bulk density (Db). Point colours: Peat (black), coir (blue), wood fibre (cyan), bark (pink), green compost (green).

We asses three physical properties as indicators of growing media performance:

  1. Available water (AW) or water holding capacity.
  2. Bulk density (Db) which affects the cost and logistics of transport.
  3. Air-filled porosity (AFP) so there is sufficient pore space for plant roots to remain aerated, but not to the extent that the plant is drought stressed.

Using our model and our reference library of materials, we can accurately assess new materials and design substrates that will provide a rooting environment similar to peat.

Please note, we need a minimum of 10 litres of each material for testing.


Chemical analysis

Alongside physical properties, we work with trusted testing laboratories to analyse:

  • pH
  • electrical conductivity (EC)
  • nutrients
  • cation exchange capacity
  • microbial stability
  • herbicide residue testing (growth test or chemical test)
  • biological stability testing
  • pathogen testing

Other lab tests are available on request.

Additional analysis options available

Mechanical handling

Most prototype blends will flow through potting machines and tray fillers, but some set ups need a slower flow. We are able to test the suitability of new materials to mechanisation.

Blocking testing

Some sectors need peat based growing media to form free-standing blocks for propagation. Let us know if you require this as part of testing.

Reporting results

Our clients will receive all the raw data, along with analysis and a report detailing the suitability of test materials for use in growing media.

This can be accompanied with a follow up meeting with a consultant to discuss further product development where required.

Blend performance trials

Experimental and commercial testing of new growing media blends

As experts in on-site large-scale commercial trials, we are able to host multi-option irrigation and nutrient delivery system trials. These can be modified to accommodate any plant type, from bedding through to young trees.

Fine-tuning growing media mixes to work with a certain growing system type (e.g. drip, overhead sprinkler, subsurface irrigation, CRF / liquid feeding nutrition, etc.) may require live crop testing.

Experimental testing

These are small scale, controlled experiments with a test species of your choice or with species recommended by us to reflect the desired end use of your product.

An example set up for an experimental trial for ornamental pot plant production:

  1. To the blend, we place up to three species which are easy/moderate/difficult to grow.
  2. We also test four replicates against an industry standard potting mix in a polytunnel or on hardstanding.
  3. We assess plant height, vigour and root establishment.
  4. We analyse the data and produce a summary report.

Commercial testing

Take your trial blend to the next level and scale up to test in a commercial setting. Trial details tailored to suit your requirements and budget.

Make an enquiry

Please contact to enquire about our growing media services.

Any of the above services can be chosen in any combination. Price will be given on application as experimental or commercial trial work pricing will depend on location, duration and complexity.


Our consultants can offer industry workshop delivery or training to share our specialist growing media and crop system knowledge. Contact us if you’d like to know more.