New growing media blends to reduce reliance on coir

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Coir-free growing media has the potential to work as well as coir for strawberry crops, if irrigation and nutrition are optimised, delegates at a recent workshop have heard.

As part of a project to develop responsibly sourced growing media blends as alternatives to peat, a model is being developed to predict the performance of any given blend of growing media for containerised production. Extensive trialling is then undertaken to validate and refine model predictions. This will help to ensure that growers can have confidence in the growing media’s commercial performance in order to facilitate the rapid uptake of new blends.

While strawberry growers have already replaced peat with coir to a large extent, there is still concern about the industry’s reliance on a single raw material, so coir-reduced and coir-free blends are being tested as part of the research.

Growers were invited to view the strawberry trials, which are being hosted at New Farm Produce in Lichfield, at an event facilitated by the project team and promoted by AHDB Horticulture in April.

Stephen McGuffie from New Farm Produce said, “Currently we rely totally on coir and while it is a good product it does have limitations. Structure is the most important element of the trial for me over the longer term of two to three years, if this fails and the product slumps it will not be suitable for soft fruit crops. Both coir-free and coir-reduced show some promising results as we look at the plant growth, however we will be more informed on performance when we have the harvest results for this season.”

Barry Mulholland, ADAS UK, who is leading the research said, “We have been using irrigation and nutrition regimes designed for standard coir media. Despite this, the trials show these coir-free and coir-reduced media do have the potential to perform as well as or better than coir, with improved understanding of blend performance and appropriate adjustments to irrigation and nutrition.”

Delegates at the event heard how there was no significant difference in total yield or percentage class 1 fruit for bare root strawberry plants in the coir-reduced or coir-free product blends.

There was a slight reduction in yield in the trial blends compared with the coir control sample, however the research team at ADAS who are running the trials believe that with optimised irrigation and nutrition, there is the potential for coir-free products to work just as well as coir.

The strawberry trials are taking place using the variety Malling Centenary, planted into troughs in nine commercially available growing media treatments: one nursery coir control, four coir-reduced products and four coir-free products.

Coir has been widely adopted for substrate strawberry production but growers at the open day were interested in alternative growing media products should coir become more expensive or difficult to obtain,” added Dr Mulholland.

Growers attending the NIAB Leafy Salads Open Day on 22 June will be able to hear more about the research into responsibly sourced growing media for blocking. The latest annual grower summary from the project will soon be available on


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