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Alternatives to peat

Dermot Callaghan, Head of the Horticultural Development Department, explains why Teagasc is renewing research emphasis on finding alternatives to peat-based growing media in horticulture.

TResearch Autumn Winter 2021Peat is a universal ingredient used for most plant species in almost all production systems in Ireland and around the world. Its physical and biological attributes, combined with its low nutrient status and predictable interaction with chemical fertilisers, is what sets it apart for professional production. The batch-to-batch consistency it offers is the key factor contributing to successful large-scale plant, crop and mushroom production.

The design of plant production systems, production protocols – including nutrition regiments – and integrated pest management approaches are developed with peat-based media at their centre. Due to its excellent biological, chemical and physical properties, peat is a main component of substrates. It maintains a stable physical structure and is comparatively lightweight, allowing it – and the products grown in it – to be transported. It also interacts well with existing nursery equipment and machinery.   

Moving from soil to soil-less culture systems has had very significant advantages in the modern era of horticultural production in Ireland. Some of this upside has been in environmental terms. The opportunity to combine growing media technology and greenhouse growing has led to input reduction and output recovery with significantly improved yield and quality.

This has improved the opportunity for import substitution of key horticulture food and plants.

Environmental concerns about peat

The extraction of peat for any purpose, however, even as a highly valued ingredient in a plant and food-producing sector like horticulture, has come under increasing scrutiny.  Extraction is currently challenging from a legal, environmental and regulatory point of view: the dual consent system needs compliance with planning permission and Integrated Pollution Control (IPC) license requirements. Additionally, consumers are increasingly interested in the sustainability credentials of products.

There is a renewed emphasis on finding alternatives to peat-based growing media in Teagasc. This research area has attracted significant attention nationally and internationally in recent decades, but it is destined to become a central pillar of horticultural research across Europe and further afield in the coming decade.

Designing a peat-free approach

Alternatives to growing media will need to achieve equitable yields and product quality compared to standard peat products. The batch-to-batch consistency required by large-scale professional producers will pose a significant research challenge and require very detailed risk assessment and performance evaluation in crop specific production systems.

In the future, there will be a requirement to develop manufacturing processes and novel technologies to design new growing media using new approaches. There will also be a requirement to optimise material processing through composting and refinement of pyrolysis and hydrothermal-carbonisation technologies.