What types of microbes are naturally found in sphagnum peat? How do they react to heat? At what temperature do they die? What is the temperature range for peat production?
A.M. VirginiaAnswer: It is first important to define the types of peats available in the commercial trade. Peat moss is a general term that includes several grades of peat. The Web site of the Canadian Sphagnum Peat Moss Association (CSPMA) provides a resource room with “Terms and Definitions of Peat and Peat Moss.” There can be important distinctions between these different grades and types of peat and peat moss in terms of microbial characteristics.Terms and Definitions of Peat and Peat Moss In: Resource Room: Horticultural Teaching Plan, Canadian Sphagnum Peat Moss Association www.peatmoss.com/hortprog1.html
peat moss or moss peat
Characteristics & Qualities of Peat Characteristics of sphagnum peat and other horticultural peats Degree of Decomposition Using Peat
Sphagnum peat moss is a common ingredient in potting mixes and is widely used in horticulture. It is highly valued as an organic media component because it provides porosity and holds moisture. However, it is considered inert and does not contribute mineral elements. Sphagnum peat can support microbial populations introduced by blending with composts and pine bark. In fact, potting mixes containing peat moss, compost, and pine bark are valued for their disease-suppressive characteristics.The following excerpt from Premier Horticulture describes the microbial characteristics of sphagnum peat moss.
Various reports have confirmed that Sphagnum peat moss has disease suppressive qualities against certain root-rot pathogens. This is due to the presence of beneficial microorganisms. Contrary to popular belief, most peat moss producers do not sterilize or pasteurize their peat-based products for three reasons. First, Sphagnum peat moss is essentially free of pathogens and pests (Tahvonen, 1993). Second, it kills disease suppressive microorganisms found in Sphagnum peat moss (Tahvonen, 1993). Third sterilization is expensive.Sphagnum peat moss bogs contain many microorganisms including Bacillus, Arthrobacter, Actinomyces, Streptomyces, Penicillium, Cladosporum, Trichoderma, Mucor, etc (Belanger, 1988 and Tahvonen, 1993). Of these, Trichoderma and Streptomyces are quite effective at suppressing certain root disease organisms (Tahvonen, 1993) due to their synthesis of antibiotics. Their presence in Sphagnum moss has been found to suppress Fusarium, Rhizoctonia solani, Phythium, (Tahvonen, 1993 and Chen, 1986) and Alternaria brassicicola (Tahvonen, 1993). The remaining microorganisms suppress root rot pathogens through competition. Simply stated, there is a limited amount of space and resources therefore, if a lot of beneficial organisms are present it is difficult for root rot organisms to establish themselves.Sources of Sphagnum peat moss vary in microbial populations and composition. Therefore, disease suppression is not always predictable (Tahvonen, 1993). Blonde, fibrous peat from the surface of the bog has higher microbial populations versus darker, decomposed peat from deeper layers in the bog (Hoitink, 1991). Only blonde, fibrous peat, classified as H2 to H3 on the von Post decomposition scale (e.g. PRO-MOSS ‘TBK’) provides enough beneficial microorganisms to promote disease suppression. Disease suppression lasts about 6-10 weeks (Hoitink, 1997). However, when a plant is planted into a Sphagnum peat-growing medium, populations of disease suppressive microorganisms sometimes increase (Tahvonen, 1993). Literature Cited
Belanger, A., et.al. 1988. Peat A Resource of the Future. Centre Quebecois de Valorisation de la Biomasse, Sainte-Foy, Quebec.Chen, Y. and Y. Avnimelech. 1986. The Role of Organic Matter in Modern Agriculture. Martinus Nijhoff Publishers, Netherlands. Hoitink, H.A.J., Y. Inbar and M.J. Boehm. 1991. Status of Compost-Amended Potting Mixes Naturally Suppressive to Soilborne Diseases of Floriculture Crops. Plant Disease 75(9): 869-873. Hoitink, H.A.J., A.G. Stone and D.Y. Han. 1997. Suppression of Plant Diseases by Composts. HortScience 32(2): 184-187. Tahvonen, R. 1993. The Disease Suppressiveness of Light Coloured Sphagnum Peat and Biocontrol of Plant Diseases with Streptomyces sp. Acta Horticulturae 342: 37-42.
Source:Disease Suppression Associated With Sphagnum Peat Moss Premier Press, Summer 2000, Vol. 7/No. 2 www.premierhort.com/website/profweb/aprofweb/premierpress/archives/summer00vol7-2/apress7-2b.html The following excerpt from the inactive ATTRA publication Disease Suppressive Potting Mixes addresses the use of peat moss in disease suppressive potting mixes.
Disease-supressive potting mixes are developed by (a) incorporating suppressive organic amendments such as certain types of peat moss and good quality composts, (b) inoculating composts and/or potting media with microbial biocontrols such as Trichoderma, Gliocladium, Bacillus, and Pseudomonas, or (c) inoculating potting media with plant-health promoting microorganisms such as mycorrhizae. Dr. Harry Hoitink (2), a plant pathologist at Ohio State University , has pioneered much of the work with disease suppressive composts. Dr. Hoitink started working with composted bark as a disease-suppressive ingredient in nursery mixes in the early 1970s. The research program at Ohio State University has been so successful that methyl bromide has not been used in the Ohio nursery industry in two decades (1).Through research, Hoitink and others have determined that pathogens such as Pythium are suppressed by general competition, while others such as Rhizoctonia require specific microbial antagonists. Light peat moss, or sphagnum peat, is known to be suppressive against Pythium for about six to seven weeks. However, dark peat moss that comes from deeper layers in the bog does not exhibit suppressiveness and may in fact be conducive to pathogens. Apparently, sphagnum peat contains naturally occuring microflora. As long as a plethora of microflora are present, they compete for nutrients with pathogens such as Pythium and Phytophthora through a process known as “general suppression”. Thus, when sphagnum peat is used in potting mixes to start plugs and transplants, it often doubles as a natural disease suppressant for the lifetime of the seedling. Likewise, microflora-rich composts are generally suppressive to Pythium and Phytophthora.However, to provide reliable control of Rhizoctonia, inoculation of compost piles after the thermophyllic stage with known antagonists such as Trichoderma and Flavobacterium is required. Earthgro, a Lebanon, Connecticut, compost company that manufactures potting mixes, specializes in microbial inoculation for control of Rhizoctonia.
There is a peat humus product brand-named Alaska Humus that is sold as a substrate for the production of “compost teas” in farming and gardening. The company claims that Alaska Humus contains an estimated 35,000 species of bacteria and 5000 species of fungi; apparently this estimate is based on molecular analysis.The Web site of the Canadian Sphagnum Peat Moss Association (CSPMA) contains resources you may find helpful. In particular, see the list of peat moss association members, which provides Web address contacts for prominent horticultural suppliers of peat moss-based potting mixes, such as ASB Greenworld Ltd., Conrad Fafard, Inc., Premier Horticulture, The Scotts Company, and Sun Gro Horticulture. These companies may be a source of technical information.Most of the scientific literature on microbial ecology of peat moss and peat bogs deals with methanogenic microbes. Some research concludes that 70% of the methane released into the atmosphere is of biogenic origin, and Northern peatlands are the source of 40 to 60% of the global methane budget. Several papers are cited below. ResourcesCanadian Sphagnum Peat Moss Association — CSPMA 7 Oasis Court St. Albert Alberta , Canada T8N 6X2 780-459-0939 FAX email@example.com www.peatmoss.comAlaska Humus Company 711 M Street , Suite 102 Anchorage , AK 99501 907-258-1504907-258-1525 FAX [Contact: Jeff Lowenfels] E-mail: Jeff@gardener.comwww.alaskahumus.comUpton M., B. Hill, C. Edwards, J.R. Saunders, D.A. Ritchie, and D. Lloyd. 2000. Combined molecular ecological and confocal laser scanning microscopic analysis of peat bog methanogen populations. FEMS Microbiol Lett. Vol. 193, No. 2 (Dec. 15). p. 275-81.Basiliko, N., J.B. Yavitt, P.M. Dees, and S.M. Merkel. 2003. Methane biogeochemistry and methanogen communities in two Northern peatland ecosystems, New York State. Geomicrobiology Journal. Vol. 20, No. 6 (November-December). p. 563-577.Krumholz, L.R., J.L. Hollenback, S.J Roskes, and D.B. Ringelberg. 1995. Methanogenesis and methanotrophy within a Sphagnum peatland. FEMS Microbiol Ecol. Vol. 18. p. 215-224.Lloyd D., K.L Thomas, A. Hayes, B. Hill, B.A. Hales, C. Edwards J.R. Saunders, D.A Ritchie, and M. Upton. 1998. Micro-ecology of peat: Minimally invasive analysis using confocal laser scanning microscopy, membrane inlet mass spectrometry and PCR amplification of methanogen-specific gene sequences. FEMS Microbiol Ecol. Vol. 25. p. 179-188.McDonald, R., M. Upton, G. Hall, R.W. Pickup, C. Edwards, J.R. Saunders, D.A Ritchie, and J.C. Murrell. 1999. Molecular ecological analysis of methanogens and methanotrophs in blanket bog peat. Microbial Ecol. Vol. 38. p. 225-233.