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Copyright by Jim Jensen, YELM Earthworm & Castings Farm, 1997  Permission granted to copy or post with complete attribution in whole, without addition, deletion, or substitution.


Earthworm castings provide many special benefits beyond what farmers or gardeners can expect from just manure or compost.  In fact, most specialists recommend that castings be used as a top dressing or supplement.  In this way, castings help make the most effective use of all your bulk soil amendments.  "A little goes a long way" because the benefits of castings are so concentrated.


In nature, composting worms tend to be highly localized, thriving in pockets of highly enriched, organic materials.  They will consume a great variety of organic wastes and excrete "worm castings" a highly valued soil conditioner.  Composting worms also tolerate a wide range of environmental conditions, which helps explain their adaptability.


Here are the results of research conducted by leading researchers around the world:


·               “Scientific studies show that worm-worked composts have better texture and soil-enhancing properties; hold typically higher percentages of nitrogen, potassium, and phosphorous; and may offer plants disease-fighting properties.”  [Edwards, 1988].


·               "Earthworm excreta (castings) are an excellent soil-conditioning material with a high water holding capacity and a natural time release' for releasing nitrogen into the soil."  [Harris, et. al., 1990].


·               “Vermicompost (castings) is a finely divided peat like material with excellent structure, porosity, aeration, drainage and moisture-holding capacity."  [Dominguez, et. al., 1997]


·               "Among the blessings of castings, vermiphiles count a smaller particle size than thermophilic compost, lower odor, enhanced microbial activity, and as a bonus, the vermicompost often contains worm cocoons, meaning a free work force for the future."  [Riggle and Holmes, 1994]


·               "Through vermicomposting the humic substances showed an increase of 40 to 60 percent which was higher than the value obtained for the composting process."  [Dominguez, 1997]


·               “An important feature is that during the processing of the wastes (manure) by earthworms, many of the nutrients they contain are changed to forms more readily taken up by plants, such as nitrate nitrogen, exchangeable phosphorus and soluble potassium, calcium, and magnesium.  The most surprising result [of our research] was that even 5% of worm-worked animal waste in the worm-worked waste/commercial mixture had a significant effect on the growth of plants."  [Edwards and Lofty, 1977]


·               In a study for the EPA, researchers reported, "Passage of organics through the earthworm's gut significantly alters the physical structure of the material.  Large particles are broken down into numerous smaller particles, with a resultant enormous increase in surface area.  As a result of the increase in surface area, any remaining odor-producing sulfides are completely oxidized, microbial respiration is accelerated by a factor of 3, and Salmonella bacteria are destroyed at a higher rate"  [Camp, Dresser and Mckee, 1980],


·               “The results obtained for the germination index showed a beneficial effect of earthworms and the highest values of this index were recorded at the final stages of the process.  The germination index was 65 to 70 percent higher in the treatments with earthworms than in the control (no earthworms)."  Regarding heavy metals:  "We found a decrease of between 35 percent and 55 percent of the bioavailable metals in two months."  [Dominguez, 1997]


·               "By shredding organic matter and contributing nitrogen, earthworms stimulate microbial decomposition.  Soil microorganisms live in the worm's gut as well as the surrounding soil and so the microbial content of casts is usually more concentrated than in surrounding soil.  Microbial activity in casts improves soil structure by encouraging aggregation of particles.  Microbial secretions (gums) and growth of fungal hyphae stabilize the worm cast.  Worm-worked soil is relatively water-stable and will resist soil compaction and run-off due to rains.”  [Edwards and Lofty, 1977]


·                  “In sum, earthworms must be seen not as a ‘miracle pill,’ a panacea for better soil and crop yields, but as an integral part of intelligent organic soil management practices.  As earthworms are dependent upon organic matter for food, and mulches for protection from heat cold, and drought, so do growing plants depend upon the earthworm, in combination with bacteria and other microorganisms, to maintain and improve soil structure and fertility.  When earthworms are seen as part of a living soil, existing in and contributing to a vital ecosystem, then the question of "whether earthworms create good soil, or good soil creates earthworms" becomes essentially meaningless.  Our aim is to improve our soils and grow higher yields of healthy crops, not to banter about academic questions.  In this pursuit, the earthworm has-beyond doubt-found a treasured place in the organic scheme of gardening and farming."  [Minnich, 1977]




Buchanan, M.A., et. al., "Chemical Characterization and Nitrogen Mineralization Potentials of Vermicomposts Derived from Differing Organic Wastes," Earthworms in Waste and Environmental Management, The Hague, Netherlands, SPB Academic Publishing, 1988.


Camp, Dresser, McKee, lnc~, Compendium on Soild Waste Management by Vermicomposting, Cincinnati, OH, Municipal Environmental Research Lab, EPA, 1980.


Dominguez, Jorge; '”esting the Impact of Vermicomposting," BioCycle, April 1997.


Dominguez, Jorge; Edwards, Clive; and Subler, Scott; "A Comparison of Vermicomposting and Composting," BioCycle, April 1997.


Edwards, Clive, "Historical Overview of Vermicomposting," Biocycle, June 1995.


Edwards, Clive, ed., "Breakdown of Animal, Vegetable and Industrial Organic Wastes by Earthworms" Earthworms in Waste and Environmental Management, The Hague, Netherlands, SPB Academic Publishing, 1988.


Edwards, Clive, and Lofty, J.R., Biology of Earthworms, Chapman and Hall, London, 1977.


Frank, Richard, et. al., "Metal Transfer in Vermicomposting of Sewage Sludge and Plant Wastes," Bull. Environ. Contam. Toxicol, 1983.


Haimi, J. and Huhta, V., "Capacity of Various Organic Residues to Support Adequate Earthworm Biomass for Vermicomposting," Biology and Fertility of Soils, Spring-Summer, 1986.


Harris, George, et al., "Vermicomposting in a Rural Community," Biocycle, Jan.1990.


Loehr, Raymond, et. al., Waste Management Using Earthworms: Engineering and Scientific Relationships (final project report), Washington, DC, National Science Foundation, 1984.


Minnich, Jerry, The Earthworm Book, Rodale Press, Emmaus, PA, 1977.


Riggle, David and Holmes, Hannah, "New Horizons for Commercial Vermiculture," BioCycle, October.


Scott, Margaret, "The Use of Worm-Digested Animal Waste as a Supplement to Peat in Loam less Com posts for Hardy Nursery Stock," Earthworms in Waste and Environmental Management, The Hague, Netherlands, SPO Academic Publishing, 1988.