ISCF WAVE 1 AGRI TECH: Sphagnum Farming UK - A Sustainable Alternative to Peat in Growing Media

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.

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.

This consortium project will have an impact in the UK beyond the academic environment through close integration of University researchers (MMU and UEL) with the lead organisation Micropropagation Services Ltd (MPS) and commercial partners, Melcourt Industries (MI) and White Moss Horticulture (WMH), who sell plant growing media. The specific goals of this 18-month study are to investigate and develop the means of growing a Sphagnum crop, from genotype selection, tissue culture propagation, optimising conditions for initial establishment and early growth through to producing a field crop and understanding the environmental consequences of cultivation. In the short term, impacts for potential Sphagnum farmers will include identification of best genotypes for Sphagnum farming, protocols for conditions, planting and establishment methods, nutrients and water requirements and pest and pathogen control.

In the longer term, we anticipate specific impacts in the following areas:
* Companies producing growing media: The phasing out of peat in horticulture in the UK has serious implications for the users of quality growing media in the industry. Sphagnum as a growing medium will offer project partners WMH and MI access to a new income stream as an alternative to peat. Both companies are potential suppliers to the industry.
MI are closely involved in developing the Responsible Sourcing Scheme, an industry wide initiative supported by DEFRA to reduce the use of peat. WMH are one of the largest green waste composting processing facilities in UK. The potential to develop the supply chain within Europe will occur through the close contacts of MPS with key German growing media suppliers (Klasmann-Deilmann GmbH and others) and active membership of the IPS (International Peat Society).
* Plant growers: Horticulturalists will have access to an effective product with green credentials. Successful German commercial trials using ornamental plants such as Poinsettia have shown that the Sphagnum substrate supports plant growth and is a realistic alternative to peat.
* Farmers and Land owners: Sphagnum farming on wetland soils offers landowners a new, innovative high value crop. Typical UK farming sites proposed initially would include bare areas of harvested peat, areas of poor scrub grazing and later also peat soil agricultural areas subject to flood risk and inundation. For owners of peat extraction sites, Sphagnum farming offers the potential for economic and environmental sustainability from peatland areas beyond the current extractive, time-limited use.
* Public: Sphagnum Farming could affect the public in several ways to benefit their well-being. The success of Sphagnum Farming will increase rural employment in areas of wet, marginal land. It may also play a role in supporting regional nature conservation interests since peatbog vegetation has high conservation value and Sphagnum farms with rotational cropping could provide ecological corridors to link with designated conservation wetlands in line with proposals in the DEFRA 2010 report 'Making Space for Nature'.
* Government bodies: The project will inform policy in DEFRA, for example 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 an EU-LIFE Integrated Project bid focused on sustainable management of UK peatlands and peatland soils. 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. This research will explore changes in carbon dioxide and methane fluxes that follow the restoration of Sphagnum on degraded peat and thereby inform DEFRA policy on reduction of carbon emissions from peatlands for climate change mitigation.