[USCC] FW: Recommendations for Safer Compost Tea

[Jim McNelly]

>_______________________________________
>
>ARS News Service
>Agricultural Research Service, USDA
>Sharon Durham, (301) 504-1611, sharon.durham at ars.usda.gov September 21,
>2006 --View this report online, plus any included photos or other
>images, at www.ars.usda.gov/is/pr
>__________________________________________________
>
>Compost tea is a brew favored by many organic growers. It's made by
>adding small amounts of mature compost to unheated water and leaving it
>to sit, or steep. The finished "tea" is then applied as a foliar spray
>or soil drench to promote plant growth and suppress microbes.
>
>Now new recommendations for making compost tea are being offered,
>thanks, in part, to research conducted by Agricultural Research Service
>(ARS) microbiologists David Ingram and Patricia Millner. Their studies
>had shown that additives sold for making compost tea--such as soluble
>kelp, fish hydrolysates, humic acid, rock dust and proprietary nutrient
>solutions--can spur the growth of bacteria.
>
>Generally, composting generates enough heat to reduce potentially
>harmful bacteria. But Ingram and Millner, with the ARS Environmental
>Microbial Safety Laboratory in Beltsville, Md., found that ingredients
>commonly added to compost tea may promote growth of a variety of
>microbes, including pathogens that can cause illness in humans.
>
>Experiments showed that when compost with very low numbers of Salmonella
>and Escherichia coli was used to make compost tea (fewer than two cells
>per milliliter of tea), the pathogens multiplied when additives were
>included in the initial water mixture. However, they remained
>undetectable in all the compost teas made without commercial additives.
>
>According to Ingram, this work counters the view among some compost
>tea-producers that the aerobic bacteria in compost will inhibit growth
>of human pathogenic bacteria when aerobic conditions and nutrient
>additives are present. Compost tea supplements can give even a few
>pathogenic bacteria a boost, so testing of the final tea before
>application may be necessary to ensure the absence of human pathogens.
>
>Recommendations and guidelines for safe production and use of compost
>tea have been developed by the Compost Tea Task Force, formed by the
>National Organic Standards Board.
>
>Read more about the research in the September 2006 issue of Agricultural
>Research magazine, available online at:
>http://www.ars.usda.gov/is/AR/archive/sep06/tea0906.htm
>
>ARS is the U.S. Department of Agriculture's chief scientific research
>agency.
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