Compost Tea Task Force releases long-awaited recommendations

By Dan Sullivan

April 19, 2004: On April 6, the National Organic Standards Board (NOSB) Compost Tea Task Force laid out its much anticipated recommendations for the handling of compost tea. Now National Organic Program (NOP) administrators must decide which of these recommendations to insert into the Federal Register as amendments to the NOP Final Rule.
The NOP is now taking public comment, which may be sent to Katherine.Benham@USDA.GOV. (Benham is advisory board specialist to the NOP.) If you would like your comments read at the NOP’s next meeting please note this at the beginning of your letter. Those who wish to make their comments in person may do so at the NOP’s April meeting in the Buckingham Meeting Room at the Best Western Inn of Chicago, 162 East Ohio Street. Comments will be heard from 8:30-10 a.m., Wednesday, April 28; and from 8-10 a.m., Friday, April 30. Or, mail comments to Benham’s attention at: USDA-AMS-TMP-NOP; Room 4008-South Building; 1400 Independence Avenue, SW; Washington, DC 20250-0020.

The challenge facing the task force was to adequately address the potential for microbial hazards—including the possibility of contaminating crops with human pathogens—while not going overboard with unnecessary precautions and thereby regulating the usefulness right out of compost tea as a nutrient source and disease suppressant.

The debate that has been brewing in the compost tea world centers on whether the introduction of simple sugars (such as molasses) in order to rapidly increase the microbial population of compost tea creates a too-hospitable environment for harmful pathogens, such as strains of E. coli and Salmonella.

One camp, spearheaded by task force member and Soil Foodweb, Inc. founder Elaine Ingham, Ph.D., has argued that such pathogens would only multiply if they had been present in the compost in the first place. On the other side of the argument are those scientists who warn that these spiking agents change the original compost product and set up too many unknown variables, such as rapid fermentation.

Erring on the side of caution, the Compost Tea Task Force has set up separate, more restrictive guidelines for those who use “compost tea additives” in their brews than for those who do not. (In its most basic form, compost tea is made simply by steeping well-aged compost in water for a number of days and using the resulting liquid as a foliar spray and to water plants at their roots.) An interesting footnote to all of this is that mineral- and plant-based catalysts—which came on the compost tea scene largely as an answer to concerns about the detriments of simple sugars—also now fall under the more restricted use category. In other words, and indeed in the specific language of the recommendations, any “materials other than water and compost added at the start of the compost tea making process to increase microbial biomass/populations” is subject to the more stringent guidelines. Needless to say in a debate that has raised the hackles of more than one scientist, regulator, and farmer, not everyone is fully satisfied.

Compost Tea Task Force recommendations include:

  • Potable (drinkable) water must be used to make compost tea and for any dilution before application.
  • Equipment used to prepare compost tea must be sanitized before use with an approved sanitizing agent.
  • Compost tea should be made with compliant compost or vermicompost—as spelled out by earlier guidelines of the Compost Task Force, or as prescribed in section 205.203 (c) (2) of the NOP rule. For compost tea, this applies to 100-percent plant feedstock materials in addition to manure feedstocks because of the recognition that non-manure compost feedstocks may still harbor high levels of fecal bacteria.
  • Compost tea made without compost tea additives can be used without restriction.
  • Compost tea made with compost tea additives can be applied without restriction if the compost tea production system (same compost batch, additives, and equipment) has been pre-tested to produce compost tea that meets the EPA-recommended recreational water quality guidelines for a bacterial indicator of fecal contamination. This includes monitoring for significant levels of E. Coli and enterococci (another antibiotic-resistant pathogenic bacteria).
    At least two compost tea batches must be tested. The average population of indicator bacteria across both batches is the yardstick for a passing or failing grade. (The quality assurance pretest will have to be repeated for each new batch.) Once it passes again, compost tea from the specific system may be used without restriction (provided none of the potential variables, such as brew times or boosting agent formulas, is altered).
    If compost tea made with compost tea additives has not been pre-tested for indicator bacteria, its use on food crops is restricted to the 90/120-day pre-harvest interval (it may not be applied within 90 days of harvest for produce not in direct contact with the soil, and not within 120 days of harvest of produce that touches the soil). Crops not intended for human consumption, ornamental plants, and grain crops intended for human consumption are exempt from pre-testing as well as the 90/120-day pre-harvest rule.
  • Compost extracts—any mixture of compost, water, additives, and adjuvants not held for more than one hour before use—may be applied without restriction.
  • Raw manure extracts or teas may be applied to the soil with 90/120 day pre-harvest restrictions; foliar applications are prohibited.
  • Compost leachate may be applied to the soil with a 90/120 day pre-harvest restriction; foliar applications are prohibited.
  • Compost tea is not allowed for the production of edible seed sprouts.

The task force wrapped up its report by stating that the growing acceptance of compost tea as a biologically based production tool for both organic and conventional farmers pointed to the need to further investigate its efficacy and safety. The task force urged the USDA to forward these efforts and specifically to address “critical data gaps, uncertainties, and variability in existing data that limit the evaluation of potential crop contamination by the current task force.” More data is needed, the task force concluded, in order to fully evaluate potential contamination factors while preserving the highest possible efficacy of compost tea as a nutrient source and disease suppressant.

Critics of the recommendations say that they are too restrictive and too broad-spectrum, that they favor large producers who can afford expensive and frequent testing over small farmers who cannot, and that they offer yet another example of organic producers hands being tied from using a tool that they developed while conventional farmers are free to use the same tool with impunity.

Find the full Compost Tea Task Force Report at

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