ADAS, part of the RSK Group, has joined forces with growers and growing-media manufacturers to accelerate the development of new growing-media mixes to support the transition to peat-free horticulture.
Peatlands, formed over thousands of years, are under threat from human activity such as drainage for agriculture, burning, overgrazing and peat extraction for use as a fuel and in growing media.
In 2020 alone, the UK used 2.3 million cubic metres of peat in growing media, of which 68% was used by amateur gardeners and 32% by professional growers.
Using peat in this way is unsustainable, and extracting from peat bogs to provide growing media for gardeners destroys rare habitats and contributes to climate change.
This is why ADAS is working with the horticulture industry to eliminate the use of peat and has made significant progress on the development of growing-media blends that are made up of alternative materials from more sustainable sources.
It is possible to design peat-free growing media mixes that have similar characteristics to peat-based products.
However, it has not been a straightforward process. Although sustainable raw materials exist, a blend is often necessary to produce a high-quality growing medium that is a suitable alternative to peat.
ADAS experts have been conducting intensive research on peat-free growing media and have now developed an innovative new approach to designing peat-free growing media mixes.
Between 2015 and 2019, the Agriculture and Horticulture Development Board and Defra provided funding for ADAS to carry out a large programme of peat-free growing media trials with commercial growers on a range of crops including bedding and pot plants, hardy nursery stock, protected edibles, soft and top fruit, and salad crops.
“These trials showed us and the growers than we can produce peat-free mixes that perform as well as peat,” explained Dr Jill England, ADAS Head of Horticulture.
“Most peat-free growing media mixes are produced by blending a mix of materials, predominately wood fibre, bark, coir and green compost.
“It is important to get the ratio of materials used right as this will impact on the quality and characteristics of the growing media. ADAS has developed a new rapid-screening and blending programme to help do just that,” she added.
Dr Andrew Watson, Quantitative Horticultural Consultant at ADAS, said, “Our research has identified three key physical properties as indicators of growing media performance: available water holding capacity, bulk density and air-filled porosity.
“We can analyse the individual raw materials for these physical properties and use this information to recommend a suitable mix of material to produce a high-quality growing media mix.”
Meanwhile, Chris Forster-Brown, Ecologist at ADAS, emphasised the need for action to be taken to be taken as soon as possible to stop peat use in horticulture.
“Peatlands are one of our most valuable ecosystems,” he said. “They are home to many species of rare plants, insects and birds.
“They are also our largest terrestrial carbon store, containing more than twice as much carbon as is stored in all the world’s forests. That’s why it is vital that we act now to eliminate our use of peat in horticulture.”