WHAT IS COMPOST TEA?
Aerated compost tea looks like a murky brown liquid (sometimes foamy on top) that has a rich, earthy, somewhat sweet smell. This liquid is alive, teeming with trillions of micro-organisms, with a rich diversity of thousands of kinds of bacteria and fungi. The secret to all this life is the brewing process: air is forced through a mixture of high-quality compost and complex microbial foods suspended in water. The oxygen and nutrients produce an extraordinary explosive growth of bacteria and fungi.
Consider that a teaspoon of good compost contains a billion or more bacteria. Given the right environment, those bacteria can double in population every 20 minutes. In the normal brewing period of 12??48 hours, those microbes turn into countless numbers of beneficial organisms. Added to soil or a hydroponic solution, the microbes quickly go to work, converting everything around them into food for plants.
COMPOST TEA INGREDIENTS
Compost Starter
The quality of compost tea depends on its basic ingredient ?? the compost or source of microbial life. Like the ??starter? used in yogurt, everything depends on the micro-organisms it contains. The USDA has warned compost tea makers of the possibility of contamination by Salmonella and E-coli found in some commercial manures and composts. It is essential to use only the highest-quality organic non-manure, unpasteurized compost to make tea. Experienced growers build their own compost piles that heat up from biological activity. The resulting dark brown substance is a nursery for beneficial organisms and is good for compost tea.
Most compost tea makers reach for vermicompost or worm castings. These are easily available and have high levels of bacteria. Obtain them from a reputable organic supplier, because their effectiveness depends on the species of worm and the kind of food they have been fed. One drawback is that worm castings may not have the necessary diversity of fungal spores.84 MAXIMUM YIELD USA November / December 2007
Gaining popularity with compost tea makers is a fine-grained humus that comes from Alaska. This is marketed under a number of different names: Alaska Humisoil, Alaska Humus, or Alaskan Magic. Extensively tested by independent laboratories, this humus has been found to harbor an extraordinary diversity of both bacteria and fungi, and it is naturally free of pollutants and pathogens.
Aerated Water
To make tea, the starter compost is added to pure, aerated water. High levels of chlorine in the water may kill off the microbes, so it is important to aerate the water for a couple of hours to allow chlorine to off-gas. The dissolved oxygen level must be kept high to nourish the aerobic microbes. Many efficient aeration or brewing systems are now available. You can make your own using an air pump and a bubbling system. A double-outlet aquarium pump with a bubbler, to produce tiny micro-bubbles and gently agitate the tea, is sufficient air to brew a 5-gal. bucket.
Brewing the tea is as much an art as a science; treat the tea like a living organism. Insufficiently aerated compost tea may go anaerobic, which is poisonous to plant roots. This is easy to determine because the tea gives off a sour smell. Leave the tea for more than six hours without aeration and it dies from lack of food and air.
Microbial Foods
Microbes are hungry. Like every living thing, they need to be fed. The art of compost tea brewing is knowing how much and what nutrients to add to make the kind of tea you need. Bacteria feed on simple sugars, easily available in the form of non-sulfured molasses. Nutrients such as fish protein support both bacteria and fungi. Kelp, humic acid, and fibrous materials such as oat bran are good fungal foods. Brewing at shorter, higher temperatures of 75ºF??85ºF, tends to produce a quick bloom of bacteria. Brewing longer at lower temperatures of 60ºF??75ºF gives the fungi a chance to flourish.
Why the concern for bacteria and fungi? Fast-growing leafy plants prefer a more bacterially dominated environment for their roots, while woody-stemmed plants like it more fungal. If you want to grow greens or annuals, then brew for bacteria. If tomatoes, shrubs, or trees are what you are looking for, go more fungal. In general, a balanced bacterial/fungal tea will produce great results across the board. If you are unsure whether your tea has the optimum diversity of microbes, send it to a reputable lab for testing (see Soil Foodweb, Inc.).
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WHY USE COMPOST TEA?
Making compost tea may sound a bit complicated, but the results can be extraordinary and the ideas behind it make intuitive sense. Plants and soil life have grown up together, co-evolved over millions of years. The countless organisms in healthy soil ?? bacteria, fungi, protozoa, nematodes, arthropods, earthworms, and plant roots ?? form a living ecology called the ??soil food web.? Prey and predator, catalyst and symbiote are interlocking parts of the great web of life.
The underpinnings of this ecology are the microbes and their relationship with roots. Many microbes are drawn to plant roots, which feed them tiny drops of sap. In exchange these cri􀄴ers break down minerals into easily digestible forms and fix nitrogen from the air. Not only are microbes food for other important members of the soil-food web, but their dead bodies are super plant nutrition. Plants prefer their food biologically pre-digested, just as we prefer our food cooked. On this diet they naturally grow stronger and healthier.
COMPOST TEA AND SOIL
Organic growers have been using aerated compost teas for about 20 years. The positive stories are many and the scientific evidence is growing steadily. Research results, while somewhat confusing, suggest that aerated compost tea enhances soil fertility, growing bigger, stronger plants with larger yields. Just as important, foliar spraying with tea can help control a number of plant diseases (see ??The Secrets of Foliar Spraying,? Maximum Yield, July/August 2007).
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Tomato plants treated with compost tea are stronger and resist blight be􀄴er; turf roots grow more vigorously; grape, banana, and avocado have higher production and less disease; seedlings show less damping off; le􀄴uce and greens produce faster growth. An important two-year research program by the Rodale Institute and Penn State University conclusively showed that aerated compost tea reduced powdery mildew on grapes by 50 percent and increased potato yields by 19 percent. Those potatoes had an extremely high mineral content.
More anecdotally, commi􀄴ed tea users say that the microbes in compost tea help break up impacted soils, clean up toxic chemicals, and greatly cut down on the need for added fertilizers. Some results are remarkable: John Evans, winner of numerous Guinness World Records for giant vegetables, used only compost tea to grow his 19-lb. carrot and 75-lb. Swiss chard.
COMPOST TEA IN HYDROPONICS
Many organic hydroponics growers use extracts of compost or worm castings in their solutions. If they add organic nutrients to these extracts and aerate, they are essentially brewing compost tea. Using the microbes to convert nutrients into superlative plant foods makes obvious good sense ?? and it is more ??natural.? Compost tea contains the most important active ingredients of soil. It creates a ??soil-like? environment around hydroponically grown root systems. Because plants and microbes
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naturally live together, roots do not get burned in compost tea solutions.
There are, however, some technical issues. A solution filled with microbial life must be handled with care. If it is not continually and fully aerated, anerobic bacteria will take over, creating a smelly, toxic mess. Systems using aerated compost tea should be flushed regularly to prevent clogging of pumps and nozzles by dead microorganisms. These show up as foam or scum and can o􀄞en be taken care of with appropriate filters and skimmers. It is also important to use only organic nutrients and microbial foods ?? chemical nitrogen and phosphorous kill off microbes.
Some users, to avoid problems, purposely kill the microbes in their tea with H2O2. The resulting sterile solution is high in organic nutrients but loses the benefit of the biological relationship between microbe and root. With a li􀄴le care and a􀄴ention, compost tea can help re-create the most natural, complete, and productive growing environment for plants.
CONCLUSION
So, should you consider compost tea as part of your growing program? The answer depends as much on your personality as on the benefits of the product. If you like to get your hands dirty messing around with compost, if organics and micro-organisms are a passion for you, and if you enjoy brewing your own beer or making your own wine, then compost tea is definitely for you. If, on the other hand, you prefer a clean, controlled growing environment, then you might want to give it a miss.
Before you decide it??s compost tea time, research thoroughly. There are a number of brewers and compost tea systems on the web and in gardening and hydroponics stores. Brewers should be simple and easily cleaned; their main function is to adequately oxygenate and agitate the brewing solution. The compost starter needs to be of the highest quality and the microbial nutrients need to create a rich, balanced brew of bacteria and fungi. Once you start brewing and see the amazing results, it is unlikely you will ever go back to growing without aerated compost tea.
RESOURCES
Lowenfels, J. and W. Lewis (2006) Teaming with Microbes.
Soil Foodweb, Inc.
texas grass Reviewed by texas grass on . good maximum yield article on compost teas WHAT IS COMPOST TEA? Aerated compost tea looks like a murky brown liquid (sometimes foamy on top) that has a rich, earthy, somewhat sweet smell. This liquid is alive, teeming with trillions of micro-organisms, with a rich diversity of thousands of kinds of bacteria and fungi. The secret to all this life is the brewing process: air is forced through a mixture of high-quality compost and complex microbial foods suspended in water. The oxygen and nutrients produce an extraordinary explosive Rating: 5