Compost Teas: 24 hour, EM, IM, BD & fermented plant extracts

["Soil Foodweb, Inc." <info AT soilfoodweb.com>]

 Soil Foodweb Incorporated
 1128 NE 2nd Street
 Suite 120
 Corvallis, Oregon 97330

May 30, 2002

Dear members of the NOSB, Compost Task Force, NOP, AMS and other interested parties,

In opening, we’d like to acknowledge the progress made at the May NOSB meeting in regard to the compost standards in the national rule. The approved recommendations will expand the narrowly defined compost provisions to recognize a wider range of composting systems available to the organic grower and compost industry. These expanded definitions were extremely necessary and we applaud this improvement.
However, we feel the compost tea recommendations were not as well thought out. They were based on work with too few compost tea brewers, on prototype versions of the brewers and limited experimentation.  We would like to offer our support and expertise on improving the recommendation that has been made by the Compost Task Force concerning compost tea.
The recommendation presented by the Compost Task Force seems to be based on data described in the following statement found on the NOP website:  “However recent research at the USDA Agricultural Research Services Labs in Beltsville, MD and Corvallis, OR shows that certain approaches to compost tea or extract preparation are conducive to growth of enteric bacterial pathogenic organisms, such as enterotoxigenic E.coli and Salmonella."  We would like to make the important point that there are many factors influencing the quality of compost tea being produced and that these need to be considered before any rule is established.  The compost tea brewer, aeration, holding conditions, food resources and dose response are all important factors affecting the quality of the resulting compost tea and should be addressed before the rule on compost tea is finalized.
What models of tea making machines were used to conduct the research on which the recommendation is based?  Soil Foodweb, Inc. has tested dozens of tea making machines and results have shown that levels of bacterial, fungal, protozoan and nematode extraction differ widely, even when using the same batch of compost.  We should not base the decision to prohibit the use of sugar additives in tea on results from limited experiments using potentially less than adequate machinery.
Aeration is another key factor in proper brewing to prevent regrowth of human pathogens in tea. Human pathogens can only out-compete the diversity of beneficial bacterial and fungal species in tea if aeration drops below 5.5 to 6 ppm oxygen. Human pathogens can grow aerobically only when certain extremely restrictive lab conditions are provided.  E.coli may grow in normal atmospheres only if the selective conditions reduce the growth of competing organisms.  The colonies of E.coli growing in aerobic conditions are small due to the fact that lab media and aerobic conditions are not normal environments for these enteric organisms.  Consider that fecal coliforms only grow in the human colon, which is very anaerobic.  Fecal coliforms do not grow on your skin, in your lungs, or any other strongly aerobic environment.  E.coli, Salmonella and Shigella are considered bacteria that can only out-compete the normal microflora when these coliforms grow in reduced oxygen conditions.  Thus, by maintaining adequate oxygen levels in the tea machines, conditions are not appropriate for the growth of fecal coliforms.  This vital piece of information must be considered before we proceed with disallowing the use of sugars in compost tea preparation.
Yet another essential factor that needs to be considered is the holding condition that is provided for the tea after the brewing is completed.  Microbial teas must continue to be aerated after the brewing process is completed and should be used within 4 to 7 hours after aeration ends.  It is possible for tea to become anaerobic rapidly when aeration has been terminated, thus it is critical to maintain the growth of the competing aerobic organisms to prevent the pathogenic bacteria from growing.  In the USDA research, is it possible that testing took place after contamination by pathogenic organisms occurred due to oxygen-deprived conditions?
We’d also like you consider the implications of prohibiting the use of sugar as a food resource in compost tea brewing.  Suppression of plant disease after tea application results from high numbers of beneficial bacteria and fungi applied to leaf surfaces.  It is imperative that these organisms receive a carbon source to enable them to multiply during the tea making process.  However, if excessive sugar is added, tea can become anaerobic due to demands of high bacteria populations, thus selecting for fecal coliform growth.  Additionally, there are tea-making machines that produce anaerobic conditions in every run we have tested.  It’s true that these machines should be removed from the market, however, poor quality machines should not result in inhibitory rules for the entire industry. Testing by Soil Foodweb, Inc. has shown no contamination by fecal coliforms in teas made with numerous other tea making machines.
The final point we’d like you to consider is dose response.  Soil Foodweb, Inc and other companies working on compost teas maintain data showing the effectiveness of well-made teas.  Teas have been shown to be effective at preventing plant diseases in numerous organic and conventional systems, when applied at regular intervals throughout the growing season.  The proposed 120-day pre-harvest interval prohibits most certified organic growers from taking full advantage of the benefits of compost tea.  This will leave organic producers out of the loop in both on-going research and bona-fide practices and would be a real loss to the organic growers’ toolbox.
We are just beginning to understand the complexities involved in the relationships between plant and soil foodwebs.  After considering the points described above, and the tremendous benefits to organic growers from using properly made compost tea, it is clear that a ruling banning the use of sugar in making compost tea is a unfortunate reaction.  Please, do not allow the rule on sugar in compost tea to be approved.  It is inappropriate.  The lack of true scientific investigation into this matter should prevent any ruling at this time.

Sincerely,
 

Dr. Elaine Ingham                                                    HarryMcCormack 
Soil Foodweb, Inc.                                                    former Executive Director, Oregon Tilth
Corvallis, OR                                                            Certified Organic Grower, Sunbow Farm, OR