Compost Tea Demonstration
Betty Nethery
Llano Master Gardener
What is "Actively Aerated Compost Tea"? (AACT)
Brewing compost tea is a method of multiplying the beneficial organisms from selected compost or soil materials. All soils have some organisms. By using compost from the richest, most diverse sources, vast populations of beneficial organisms multiply at exponential rates, doubling and re-doubling.
A solution extremely rich in microbes such as fungi, bacteria, protozoa, nematodes and microarthropods (microscopic insects) is derived by actively aerating mature, microbial rich compost in water. The best and most active teas have a great diversity of organisms. Compost tea also contains soluble nutrients.
The gentle bubbling of the air generated by the aquarium pump breaks organisms loose from the compost in the bag. Some composts may produce excessive amounts of foam which can be reduced by adding 2 or 3 drops of vegetable oil, but not olive, coconut or canola oils. I ignore the rare occurrence of this. It has not been a problem.
Actively aerated compost tea differs from "Compost Leachate" in that an abundance of oxygen allows the exponential increase in organisms. Some microbes DOUBLE THEIR NUMBER every 8 minutes! Fungi are much slower in doubling their population, requiring from hours to days. Nematodes double at an even slower rate and protozoa even more slowly. To be present in the Compost Tea, a seed population of every microbe must be present in the compost bag in the brewing liquid.
"Compost Leachate" can actually produce an anaerobic fluid that may actually kill some plants and has been used in killing fire ants. (I have heard it is a component of ANTIFUEGO Fire Ant Killer.)
Materials/Supplies for AACT
CONTAINER---AQUARIUM AIR PUMP---AIRSTONES---TUBES---TEA BAG---COMPOST---MOLASSES---BIO-GRO, etc---WATER to fill container, having allowed chlorine to evaporate. From 5 to 55 gallons.
To Make Compost Tea
Compost Tea is made in a CONTAINER nearly full of WATER, which, if from a city’s treatment plant, must be allowed to stand for at least 10 to 15 minutes to allow the Chlorine to evaporate. (I would be over conservative in this timing and let it sit for a full day.) Any chemicals in the water are apt to kill the beneficial organisms.
An AQUARIUM PUMP with an AIRSTONE at the bottom of the container and, preferably, a second AIRSTONE in a bag of compost containing sources of diverse life. Begin running the air pump as soon as you begin measuring the compost for the bag or adding the molasses.
It is best to use a mature but fairly recent compost with as many diverse elements as possible or practical. It is best if the elements of the compost pile are of local origin, assuring that the compost and compost teas contain bacteria which thrive in your area.
Do not use a bad smelling compost. If the compost does not smell earthy or has an offensive odor, it may have become anaerobic. I have read (and should have noted where) that the "earthy smell" in good compost and good garden soil is the odor of the bacteria present. Without them, the soil is inert and merely a "not too sterile" growing medium. It is only when the soil bacteria break down the nutrients in the soil that the nutrients become available to the plant for fueling its growth.
The barrels that turn for quick compost actually break up the strands of developing fungi resulting in the best bacterial life, but no fungal life. A pile which has been built and left for nature to take its course makes the compost richest in fungal life. The mycelium developing under old woodpiles is particularly rich in fungal life. Single source composts, such as Cotton Gin Compost, have a limited diversity of bacterial life.
Dave Franks' adaptation of Compost Tea-making apparatus;
 Basket with airstones |
 Brewer with basket |
 Brewer with Bag |
Good Elements For Making Compost
Bat guano, turkey manure, cow manure, worm castings, garden waste, yard clippings, leaves, dry or green native wood particles, humus materials, vegetable peels, rotten fruit, weeds.
Use a minimal amount of compost in your recipe to avoid the brew becoming anaerobic: 2 pounds per 5 gallons, 5 to 7 pounds for a 25 gallon container and 10 pounds for the 55 gallon drums. This is placed in a netting bag to prevent the compost from having to be strained out of the tea. The bag of compost can be removed from the brewer after 6 to 8 hours and emptied on the garden or back in the compost pile. It still has a lot of good left in it.
A bought compost may be used or mixed with your own. Just remember that the more diverse sources plus your locally made compost will give you the widest spread of microbial life. John Dromgoole has LADY BUG Revitalizer Compost, considered one of the best "bought" composts. I have also used Oma’s and, of course, Malcolm Beck’s compost. Borrow some from your neighbor and pay back with a share of the compost tea.
The microorganisms which have been broken loose from the compost, and their resulting population explosion, must have a food source in addition to the small amount of supportive nutrients in the solution in order to insure a rapid increase in numbers. For a tea rich in fungi, use oatmeal, kelp or bran (also in a bag) or fish hydrolysate or water extracted humates.
Excellent food sources for the bacteria are molasses (I use Fain’s molasses and have never used the others.), sugar, simple sugars, carbohydrates and proteins. Do not use honey as it may kill some or all of the bacteria!
I usually add a small amount of BIO-GRO as a food source, but don’t know what good it does.
Elaine Ingham is the originator of this most useful, economic and easily applied garden additive. She says to use untreated molasses, not agricultural grade. I use a ½ cup measure of Fain’s Molasses in a 55-gallon drum of water.
Compost tea should be brewed at a water temperature of not less than 65 degrees and not more than 85 degrees and when the outside temperature is not too cool or hot. Certain specific temperatures promote specific populations of organisms. Microbial life will peak at about 24 to 30 hours, but may continue to increase another 12 hours. At this time the Compost Tea should be applied to the soil or plants, although the tea will "keep" for another day or two if the aeration is continued. Without aeration the tea will become anaerobic in 4 to 6 hours. This time limits carrying fresh tea to your neighbor, other property, or even to a microscope to see the creatures you have allowed to develop!
Applying Compost Tea
After the tea is brewed, just before applying it, you may want to add mycorrhizal fungus spores, liquid fertilizer (fish emulsion or seaweed extract) or Super Thrive.
The tea may be diluted to cover an area using 5 gallons to the acre. I use mine full strength out of the barrel, either in the irrigation system or sprayed with a sump pump emptying the barrel container in a large droplet spray on the tops and undersides of the leaves. (This sets powdery mildew back about 3 days on my climbing cantaloupes where I obtain good leaf coverage.) I carry it to the green house and apply it from a watering can to those plants. Anywhere in-between these concentrations is fine. I do like full strength on plants and, of course, it is diluted in the irrigation water.
I’m not sure about putting nutrient-rich Compost Tea in drip hoses. Could it fertilize the organisms causing a scum build-up to stop the water flow? My barrels have a faucet at the bottom and I walk along and apply the full-strength fluid along the side of the plants at this low pressure. I don’t ever want water hitting the soil with enough force to spatter up little disease-carrying droplets of water.
Your brewer MUST BE CLEANED to avoid the buildup of biofilm (scum in the corners and on the inside of the container) which produce the anaerobic organisms and E-coli. There are dozens of E-coli bacteria, with only one a danger for human consumption. Human consumption is the watchword. We use fertilizer from unappetizing sources but probably wash it off before eating garden produce.
I seem to speak of food production and not mention flowers. I don’t spray Compost Tea on my peppers, green bean pods, broccoli, cauliflower, cabbage or lettuce. It MAY BE ADDED to the irrigation water. I wash and peel tomatoes so a little tea on the fruit isn’t going to make it into my digestive system.
I think that spraying Compost Tea on and under leaf surfaces vastly reduces plant disease and pest problems. It may be that Red Spiders just don’t like the wet undersides of tomato leaves and 2007 was a wet year. I can’t remember assessing results of this in 2006. Anecdotal evidence is not very scientific.
High-pressure sprayers can damage the living organisms of Compost Tea so the sprinkler-can approach or the little hand sprayer are the least damaging.
What are the benefits of compost tea?
Suppress foliar diseases by covering upper and lower leaf surfaces with the tea so as to leave no space for damaging organisms.
Suppress root diseases by suppressing root rot and by encouraging mycorrhizal and other beneficial fungi.
Help with insect control by covering and thickening the leaf surfaces making them less susceptible to insect damage. The microorganisms in the soil protect the roots from soil dwelling pests (such as plant-attacking nematodes).
Help with weed control by eliminating compounds from the soil, loosening the soil and creating an environment not suitable for weed growth (Do you ever notice that certain parts of the yard or garden have different weed problems?).
Build soil structure adding beneficial microorganisms which help loosen and oxygenate the soil so the roots can expand and thrive, allowing the plants to stay vigorous and resistant to pests and diseases.
Reduce water usage 30% to 70% just by increasing the water-holding capacity of the soil.
Make nutrients more available to the root systems and retaining the nutrients in the soil. As the soil improves, leaching and run-off are eliminated thus protecting your rivers, lakes and streams.
Decompose toxins in soil with microorganisms breaking down ANY toxic compound, eliminating any toxic chemicals previously used in the landscape.
Help maintain a natural nutrient cycling in the soil by increasing the number of microbes in the soil thus making nutrients more available to the soil.
When to apply compost tea
As a foliar spray: 20 gallons (with water to carry it) per acre.
As a soil drench: 20 gallons (with water to carry it) per acre.
This figures to be 1 pint to 2 quarts per 1000 square feet.
Compost tea should be applied every one to two weeks to build up soil microbial life and the plants. Once the microbial life of the soil is sufficiently improved, the plants in good health and the fungal problems under control little as two to three applications a year is adequate.
Fine droplets should not be applied between 10:00 A.M. and 3:00 P.M. Large droplets can be applied any time of day.
Do not waste your compost tea on very dry soils. Apply sufficient water to the soil before spraying or pouring on tea.
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