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Notes on Compost Teas |
| By Steve
Diver NCAT Agriculture Specialist © NCAT 2002 ATTRA Publication #IP118/103 |
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AbstractThe ATTRA publication Compost Teas for Plant Disease Control, published in 1998, will be updated. In the meantime, here are a few supplemental notes and resource listings. Two additional items are enclosed as well:
Table of Contents
Compost Teas vs. Compost ExtractsFirst, it may be helpful to share some common terminology and practices associated with compost teas. How do compost teas differ from compost extracts or compost leachates? Compost LeachateCompost windrow leachate—the dark-colored solution that leaches out of the bottom of the compost pile—most likely will be rich in soluble nutrients; but, in the early stage of composting it may also contain pathogens. It would be viewed as a pollution source if allowed to run off-site. Compost leachate needs further bioremediation and is not suitable or recommended as a foliar spray. Compost ExtractCompost watery extract—made from compost suspended in a barrel of water for 7 to 14 days, usually soaking in a burlap sack—a centuries-old technique. The primary benefit of the extract will be a supply of soluble nutrients, which can be used as a liquid fertilizer. Compost TeaCompost tea, in modern terminology, is a compost extract brewed with a microbial food source—molasses, kelp, rock dust, humic-fulvic acids. The compost-tea brewing technique, an aerobic process, extracts and grows populations of beneficial microorganisms. SummaryCompost teas are distinguished from compost extracts both in method of production and in the way they are used. Teas are actively brewed with microbial food and catalyst sources added to the solution, and a sump pump bubbles and aerates the solution, supplying plenty of much-needed oxygen. The aim of the brewing process is to extract beneficial microbes from the compost itself, followed by growing these populations of microbes during the 24- to 36-hour brew period. The compost provides the source of microbes, and the microbial food and catalyst amendments promote the growth and multiplication of microbes in the tea. Some examples of microbial food sources: molasses, kelp powder, and fish powder. Some examples of microbial catalysts: humic acid, yucca extract, and rock dust. Liquid Organic Extracts vs. Compost TeasBuilding on the concept of compost teas as a liquid organic extract, what are some other common organic extracts used as a liquid drench or foliar spray? Manure TeaManure-based extracts—a soluble nutrient source made from raw animal manure soaked in water. For all practical purposes, manure tea is prepared in the same way as the compost extracts described in the preceding section. The manure is placed in a burlap sack and suspended in a barrel of water for 7 to 14 days. The primary benefit of the tea will be a supply of soluble nutrients, which can be used as a liquid fertilizer. Herbal TeaPlant-based extracts—stinging nettle, horse tail, comfrey, clover. A common method is to stuff a barrel about three-quarters full of fresh green plant material, then top off the barrel with tepid water. The tea is allowed to ferment at ambient temperatures for 3 to 10 days. The finished product is strained, then diluted in portions of 1:10 or 1:5 and used as a foliar spray or soil drench. Herbal teas provide a supply of soluble nutrients as well as bioactive plant compounds. Liquid ManuresMixtures of plant and animal byproducts steeped as an extract—stinging nettle, comfrey, seaweed, fish wastes, fish meal. Liquid manures are a blend of marine products (local fish wastes, seaweed extract, kelp meal) and locally harvested herbs, soaked and fermented at ambient temperatures for 3 to 10 days. Liquid manures are prepared similarly to herbal tea—the material is fully immersed in the barrel during the fermenting period, then strained and diluted and used as a foliar spray or soil drench. Liquid manures supply soluble nutrients and bioactive compounds. SummaryCompost teas and herbal teas are tools that can be made on the farm to enhance crop fertility and to inoculate the phyllosphere and rhizosphere with soluble nutrients, beneficial microbes, and the beneficial metabolites of microbes. CautionWheareas raw animal manures are used as a compost windrow feedstock, the composting process—thermophyllic heating to 135-160° F for 10-15 days—assures pathogen reduction. The raw organic matter initially present in the compost windrow undergoes a complete transformation, with humus as an end product. Any pathogens associated with raw manures will be gone. So caution is extended: Manure teas are NOT the same thing as compost teas or compost extracts. Because of concerns over new pathogenic strains of E. coli, the author advises growers to reconsider manure teas and/or to work with a microbial lab to ensure a safe, worthwhile product. Methods of Compost Tea ProductionBucket-Fermentation Method"Passive" compost tea is prepared by immersing a burlap sack filled with compost into a bucket or tank, stirring occassionally. Usually the brew time is longer, from 7 to 10 days. This is the method that dates back hundreds of years in Europe, and is more akin to a compost watery extract than a "brewed" and aerated compost tea. Bucket-Bubbler MethodThe equipment setup and scale of production are similar to the bucket method, except that an aquarium-size pump and air bubbler are used in association with microbial food and catalyst sources added to the solution as an amendment. Since aeration is critical, as many as three sump pumps may be used in a bucket simultaneously. With homemade compost tea brewing, a compost "sock" is commonly used as a filter-strainer. Ideally, the mesh size will strain compost particulate matter but still allow beneficial microbes—including fungal hyphae and nematodes—to migrate into solution. Single-strand mesh materials such as nylon stockings, laundry bags, and paint bags are some of the materials being used; fungal hyphae tend to get caught in polywoven fabrics. If burlap is used, it should be "aged" burlap. Trough MethodLarge-scale production of compost teas employs homemade tanks and pumps. An 8- or 12-inch-diameter PVC pipe is cut in half, drilled full of holes, and lined with burlap. Compost is placed in this makeshift trough. The PVC trough is supported above the tank, several feet in the air. The tank is filled with water, and microbial food sources are added as an amendment. A sump pump sucks the solution from the bottom of the tank and distributes the solution to a trickle line running horizontally along the top of the PVC trough filled with compost. As the solution runs through the burlap bags containing the compost, a leachate is created which then drops several feet through the air back into the open tank below. A sump pump in the bottom of the tank collects this "tea" and distributes it back through the water line at the top of the trough, and so on. Through this process, which lasts about seven days, the compost tea is recirculated, bubbled, and aerated. The purpose of the microbial food source is to grow a large population of beneficial microorganisms. Commercial Tea BrewersCommercial equipment is available for the production of brewed compost teas (see a list of suppliers below). Usually there is a compost sack or a compost leachate basket with drainage holes, either of which are used to hold a certain volume of compost. The compost-filled container is placed in a specially designed tank filled with chlorine-free water. Microbial food sources are added to the solution. A pump supplies oxygen to a specially-designed aeration device which bubbles and aerates the compost tea brewing in the tank. SummaryDepending on your scale of production and the level of financial resources available to purchase commercial brewing equipment vs. making some kind of homemade brewer, there are several methods to choose from. Research at Soil Foodweb, Inc. in Corvallis, Oregon has shown that differences exist in the beneficial attributes of compost teas, with commercial tea brewers producing the greatest numbers and diversity of beneficial microorganisms. Compost Tea Brewing EquipmentGrowing Solutions, Inc.
Soil Soup, Inc.
Microb Brewer
EPM Inc.—Earth Tea Brewer
Compara—Xtractor
Soil Foodweb: Concepts, Microbial Analysis, ApplicationHumus—and organic matter in its many forms—provides both food and shelter for soil organisms. Soils and composts contain a rich diversity of life. The soil foodweb is the community of micro- and macro-organisms that live in these environments. Essentially, compost tea production is a brewing process that extracts microorganisms from compost followed by microbial growth and multiplication. This includes beneficial bacteria, fungi, protozoa, and nematodes. When compost teas are sprayed onto the leaf surface, these beneficial organisms occupy spatial niches on the leaf surface and gobble up leaf exudates that pathogenic organisms would otherwise feed on to prosper; other microbes directly interfere with pathogenic organisms through antagonism. Ideally, compost teas contain both an Abundance (immense total number) and a Diversity (vast mixture) of beneficial microorganisms which perform different functions. Pathogenic organisms that land on the leaf surface simply cannot compete with the beneficial organisms and therefore have a greatly reduced chance to initiate disease in the first place. Dr. Elaine Ingham, a microbial ecologist in Corvallis, Oregon, has elevated our collective knowledge of the soil foodweb. In her graduate studies, as well as in her work as Associate Professor at Oregon State University, Ingham pioneered research into microbial analysis of soils, composts, and compost teas. Using the "direct look" method, she views and counts microorganisms with high-performance light microscopy enhanced with epifluorescent staining and illumination. In the late 1990s, she established a commercial lab known as Soil Foodweb, Inc. (SFI), thus providing a service that allows farmers and land managers to gain insight into the soil foodweb condition of their soils and composts. Foliar-applied plant extracts, liquid manures, and compost teas can be further understood in the context of their influence on the rhizosphere and phyllosphere. These terms refer to those biologically-active regions surrounding the root surface and leaf surface where microbial communities exist. The slide show—Compost Teas: A Tool for Rhizosphere+Phyllosphere Agriculture—provides a complementary introduction to this topic. In collaboration with the people who have on-the-ground experience with compost teas—namely the organic farmers using compost teas and the manufacturers of compost tea brewing equipment—Dr. Ingham and Soil Foodweb, Inc. have pioneered advancements in aerobic compost tea brewing on the West Coast. The following characteristics of a healthy soil foodweb, good-quality compost, and good-quality compost tea are based on her work. Characteristics of a Healthy Soil Foodweb, per Gram of Soil600 million bacterial individuals Minimum Standards for Compost (for Row Crop Plants), per Gram of Compost50-70% — moisture Minimum Standards for Compost Tea, per Milli-Liter of Compost Tea10-150 µg — active bacteria The Soil Biology Primer is a landmark publication from the USDA on the living components of the soil. It provides a graphics-rich summary of the soil foodweb and relates foodweb health to soil health. It features individual chapters on soil bacteria, fungi, protozoa, nematodes, arthropods, and earthworms. Printed copies can be ordered through: Soil and Water Conservation Service at 1-800-THE-SOIL, or by email. Laboratories that Specialize in Microbial Analysis for Compost TeasSoil Foodweb, Inc. BBC Laboratories, Inc. Key LiteratureCompost Tea Brewing Manual. 2000. By Elaine R. Ingham. Soil Foodweb, Inc., Corvallis, OR. 60 pages. $25 through SFI. www.soilfoodweb.com/02_resources/c_tea_manual.html
Organic Farming Research Foundation. Information Bulletin No. 9, Winter 2001. www.ofrf.org/publications/news/ib9.pdf
Organic Teas from Composts and Manures. Richard Merrill, OFRF Grant Report 97–40. www.ofrf.org/publications/Grant%20reports/97.40.10.Merrill.Fall97.IB9.pdf
Effectiveness of Compost Extracts as Disease Suppressants in Fresh Market Crops in British Columbia. Sylvia Welke, OFRF Grant Report 99–31. www.ofrf.org/publications/Grant%20reports/99.31.10.Welke.Spr99.IB9.pdf
Compost Tea for Organic Farming and Gardening. 2001. By William Quarles. The IPM Practitioner. Vol. 23, No. 9 (September). p. 1–8.
Investigations into Liquid Compost Extracts ("Teas") for the Control of Plant Pathogenic Fungi. William F. Brinton and Andreas Trankner; a BioCycle conference paper. www.woodsend.org/compost_tea.pdf
Compost Practices for Control of Grape Powdery Mildew (Uncinula necator). Andreas Trankner and William F. Brinton; a Biodynamic journal reprint. www.woodsend.org/will2.pdf
Further Web ResourcesBioCycle Reprints: Compost Teas and Compost MicrobiologyUnderstanding Compost Tea Time for (Compost) Tea in the Northwest Brewing Up Solutions To Pest Problems Evaluating Microbiology of Compost Using Compost To Control Plant Diseases Compost MicrobiologyCompost Microbiology and the Soil Food Web
Microbial Diversity Guide for Compost and Soil Dr. Elaine Ingham: The Soil Foodweb & Compost TeasThe Soil Foodweb Soil Foodweb Information The Soil Foodweb Structure Foodweb "Funtions" in a Living Soil: The Benefits to Plants and Soils The Soil Foodweb: Its Importance in Ecosystem Health Dr. Ingham's Monthly E-Zine
Anaerobic Bacteria and Compost Tea Brewing Compost Tea Web Resource Collections on Soil BiologySoil Biology Information Resources For Land Managers, Resource Professionals, and Educators Compost Specialists: David Granatstein & Harry HoitinkSuppressing Plant Diseases with Compost Foliar Disease Control Using Compost Tea Compost Teas and Liquid Humus Controlling the Compost Process: Compost-Amended Potting Mixes Compost and Disease SuppressionSustainable Management of Soil-borne Plant Diseases Suppressing Plant Diseases with Compost On-Farm Composting: Plant Disease Control/ Composts for Disease Suppression Microbial Ecology of Compost-induced Disease Suppression Disease Suppressive Compost as an Alternative to Methyl Bromide Compost Teas: Regional ReportsCompost Tea Trials Final Report
Alternatives for Use & Management of "Compost Tea"
Evaluation and Prioritization of Compost Facility Runoff Management Methods
Evaluation of Compost "Tea" for Reuse Opportunities (1997 & 1998)
Evaluation of Compost Facility Runoff for Beneficial Reuse, Phase 2
Compost Teas: Popular PressBrewing Compost Tea Bainbridge Island: Healing the Earth 'Compost Tea' Allows Gardeners to Brew Greener Pastures Wake Up Your Garden With Compost Tea Making Fermented Compost Tea From The Garden: Oxygen-Rich Compost Tea Can Help Ward Off Summer's Water Blues Feed Your Foodweb: Compost Tea Strengthens Plants, Defends Against Disease Compost Teas: Research ReportsResponse of Alternaria spp. Blight and Septoria spp. Leaf Spot to Biological Disease Compost Cures All Peach Brown Rot Study at Woodleaf Farm, Oroville, CA North Coast Apple Scab Trials 1993/1994, Organic and Conventional Materials Comparison University Research Compost Tea and Blossom Brown Rot Compost Teas: The Worm Digest QuarterlyA Homemade Compost Tea Brewer Compost Teas: Brewing a Sweet Blend Compost Teas: Complementary ATTRA ResourcesCompost Teas for Plant Disease Control Compost Teas: A Tool for Rhizosphere+ Phyllosphere Agriculture
By Steve Diver
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