ISCF WAVE 1 AGRI TECH - Sphagnum Farming UK - a sustainable alternative to peat in growing media

Lead Research Organisation: University of East London
Department Name: Sustainability Research Institute

Abstract

The current commercial extraction of peat for use as a growing media in horticulture is widely acknowledged as unsustainable, is destroying increasingly rare and highly-valued ecosystems, is having an adverse effect on carbon emissions, and is becoming increasingly difficult to sustain within the constraints of the planning process. A high-quality alternative to peat as a growing medium is urgently needed if the growing media industry is to have a long-term future. Commercially farmed Sphagnum moss could provide this because the highest-quality horticultural peat consists largely of semi-decomposed Sphagnum leaf and stem fragments. Fresh Sphagnum provides the same characteristics and properties as high-quality peat but cannot currently be readily obtained from the wild because Sphagnum-rich areas have become increasingly rare and those which do remain are largely now protected under environmental legislation. Sphagnum farming, on the other hand, offers the potential to provide a sustainable supply of high-quality growing medium into the foreseeable future. Such farming requires a source of starting propagules at the outset, however, to generate the initial crop. This is currently a significant obstacle for the same reasons that make wild harvesting of fresh Sphagnum undesirable and difficult. Until now it has not been possible to propagate and grow Sphagnum in large quantities, a limitation which has prevented active consideration of the possibilities offered by fresh Sphagnum. Micropropagation Services Ltd (MPS), however, have researched a unique laboratory technique for the micropropagation of Sphagnum which now offers the potential to grow this moss on a commercial scale. This novel solution involves the mass production of Sphagnum from leaf fragments using sterile tissue culture - micropropagation. Since 2008 MMU has supplied research support to MPS to develop methods of planting propagated Sphagnum in the field for habitat restoration. The scale of restoration using these methods in northern England is significant, having increased to 1,000 ha of upland peatland in 2013-2015.

The current project proposal aims to establish the underpinning processes, the cultivation requirements and the production potential involved in growing Sphagnum on a scale sufficient to form source material in quantities which would make Sphagnum farming a viable proposition using cultivation techniques which are applicable at the farm-field scale. Our project will focus on an area of peatland which has previously been used for commercial peat extraction but which has now reached the end of its commercial life because there is little peat left to extract. MMU research within the consortium project will be strongly integrated with approaches at smaller and larger scales led by the other partners. MMU will field test the growth of selected Sphagnum genotypes in experimental small field plots; we will investigate the possibility of increasing production through nutrient addition. Drained peatlands are a source of respiratory CO2. Re-wetting and cultivation of Sphagnum has the potential to sequester carbon through raising CO2 assimilation in photosynthesis and cutting CO2 losses in respiration. However, the switch from a dry to a wet peatland may stimulate methane (CH4) emissions from the bog surface and surrounding irrigation ditches. The time-course and net benefits of wetting and Sphagnum cultivation on carbon exchange require evaluation. Nutrient demand and cycling by Sphagnum farming has not been assessed but requires investigation in order to provide optimal supply for production while minimizing losses such as emissions of the greenhouse gas nitrous oxide or release to water courses of dissolved inorganic nitrogen. Increased knowledge learned from MMU research will guide product development through improvement of Sphagnum production within an environmentally sustainable farming system.

Technical Summary

Commercial extraction of peat for growing media in horticulture is unsustainable, is destroying highly valued ecosystems and having an adverse effect on landscape greenhouse-gas (GHG) emissions. A sustainable alternative to commercially-valuable 'white peat' is needed to preserve peatland carbon stocks and to give the growing media industry a long-term future. This project aims to establish the principles and practicalities of growing Sphagnum moss as a commercial crop for use in horticulture and the consequences of this for GHG emissions and nutrient losses. Our partners Micropropagation Services Ltd (MPS) have developed tissue culture micropropagation of Sphagnum, which offers the potential to grow this moss on a commercial scale on re-wetted peatlands. Consortium research will use glasshouse growth trials, experimental field plots on a former peat-extraction site near Manchester, and larger field-trial plots established on agriculturalised peat near Loughborough. A detailed digital terrain model (DTM) of the various field plots will be obtained by University of East London (UEL) using terrestrial laser scanning (TLS) on the prepared ground, and a series of 'peat anchors' will provide fixed reference points to measure any subsequent swelling of the peat following re-wetting and Sphagnum crop growth and saleable volume over the project. GHG (CO2, CH4, N2O) flux rates and water chemistry will be monitored by Manchester Metropolitan University (MMU) to understand the effect of different treatments on carbon balance, nutrient use and global warming potential while UEL will monitor water relations of the various plots both in terms of the water table in the peat and the pore-water pressure in the Sphagnum. Increased knowledge learned from this project will guide product development and Sphagnum production within an environmentally sustainable farming system.

Planned Impact

This consortium project will have an impact in the UK beyond the academic environment through close integration of University researchers (UEL and MMU) with lead organisation Micropropagation Services Ltd (MPS) and commercial partners Melcourt Industries (MI). This 15-month study seeks to investigate and develop the means of growing a commercial-scale Sphagnum crop and understanding the environmental consequences of cultivation. We anticipate specific impacts from this work to be seen in the following areas:

Growing-media industry: The phasing-out of peat in UK horticulture has serious implications for the producers and users of quality growing media in the industry, particularly as UK demand for growing media is increasing. Sphagnum as a growing medium offers a potential new income stream in the form of a sustainable alternative to peat to project partner MI as well as to other UK companies currently engaged in peat extraction but increasingly faced with time-limited consents. In particular, MI are closely involved in developing the Responsible Sourcing Scheme, an industry-wide initiative supported by DEFRA to reduce the use of peat. The potential exists to develop the supply chain of growing media more widely within both the UK and continental Europe through close partner contacts with the growing-media industry - e.g. partner links to the industry through Defra, and MPS with key German growing-media suppliers (Klasmann-Deilmann GmbH).

Plant growers: Sphagnum farming offers the horticultural industry a long-term sustainable supply of growing media, providing an effective product with environmentally sustainable credentials which could qualify for an EU 'eco-label' (peat does not qualify). UEL links with, for example, Gardening Which? and RSPB also offer the potential to encourage retail take-up through schemes such as RSPB's 'Give Nature a Home'.

Farmers and Land owners: Sphagnum farming on wetland soils offers farmers and landowners a new innovative high value crop for areas of peat soil currently subject to agricultural drainage and use but which are therefore subsiding and thus increasingly at risk from flooding as well as releasing significant quantities of carbon. Sphagnum farming offers one novel means of maintaining productivity from such land even with increasing policy shifts towards re-wetting such farmed peat soils UEL links with Defra and the Soil Association can be used to develop and promote this new form of sustainable agriculture.

Construction and recycling industry: UEL's work with the construction and recycling industry offers the opportunity to develop novel, commercially attractive materials derived from mixing Sphagnum with industry waste.

Government bodies: The project will inform policy in DEFRA, for example through the Defra/HDC/horticultural industry funded programme of work to 'Progress the transition to responsibly sourced growing media use within UK horticulture' (SP1215, 2015-2019). DEFRA is also currently preparing a peatland strategy for England, seeking to establish the sustainable management of UK peatlands and peatland soils, assisted by UEL. Sphagnum farming could play an important part within this since it provides a means by which current unsustainable wetland use could be transformed into sustainable practice. The current project proposal will explore carbon fluxes associated with Sphagnum farming and thereby inform DEFRA policy on reduction of carbon emissions from peatlands for climate change mitigation. Meanwhile both carbon and climate change responses across society as a whole are being considered by the UK Committee for Climate Change, with whom UEL is actively involved. Novel ways of managing UK peat soils to reduce carbon emissions and reduce flood risk is a significant part of the UKCCC's deliberations.

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