Type: Master Composter
Name: William M. Kruidenier
City: Charlottte, NC
Launch: February 6 - May 4, 2002
Location: Nature Museaum-Charlotte, North Carolina
Project: Making and Using Compost Tea
Funding: Mecklenburg Solid Waste Management

II. ACKNOWLEDGEMENTS
Since I am not a scientist, I have had to rely on the work of others for learning about the science of compost tea. Primarily, I have relied on the work of Dr. Elaine R. Ingham, a leading expert in the burgeoning field of compost tea production and application. Her book, The Compost Tea Brewing Manual (3rd edition, March 2002), is the most up-to-date resource on the science of compost tea brewing (see RESOURCES at the end of this paper for more information).

 

My inspiration for the home compost tea brewer comes from an article written by Dr. Ingham in the October/November 2000 issue of Kitchen Gardener--The Vegetable and Herb Gardening Journal (no longer being published).

These were the two primary resources consulted in the preparation of this paper. Because much of the information below has been gleaned from general reading on the subject, I will not footnote every fact but will give credit here to Dr. Ingham s works as being the best and primary sources in my research.

 

Overview:

 

I. PURPOSE
The purpose of this brief paper is two-fold:

 

A. To give a general overview of the benefits of compost tea.
B. To describe how to assemble and use a simple compost tea brewer.

 

Description: III. COMPOST TEA

A. Definition

 

Simply put, compost tea is a liquid soil and plant amendment which makes the microbial life found in compost available as a liquid foliar spray or soil drench. By extracting the beneficial microorganisms from compost, they can be put to use as a defensive barrier against disease pathogens and as a participant in the nutrition producing soil food web.

The simplest way to picture compost tea is to think of a making tea from a tea bag. A cup of steaming water is used to extract the flavor from crushed tea leaves inside a flow-through tea bag. The contents of the tea bag changes the water into tea. In the same general sense, we will be submerging a bag of compost into a bucket of water and allowing the compost to change the water into compost tea. That tea is then used to benefit plant growth in a number of ways. (The analogy stops there--compost tea doesn t use hot water, etc.--but the big idea is suitable as an illustration.)

B. Benefits of Compost Tea

1. Its liquid form means it can be sprayed and poured, thereby adding new delivery systems to compost.

2. Compost tea is concentrated compost; the benefits of the living microorganisms go farther with tea than with regular compost.

3. As a liquid spray, compost tea can be used to coat the leaves of plants and thereby help prevent and/or suppress foliar diseases in plants. It also speeds the breakdown of toxins which may be on or in the plant.

4. As a liquid spray, compost tea provides nutritional uptake to the plant through a leaf s stomata (tiny openings in the epidermis of a leaf; like pores in human skin). Spraying compost tea on plants has been compared to feeding someone through an I.V. (intravenously) as opposed to eating solid food. The nutrition enters the bloodstream of the plant immediately.

5. As a liquid, compost tea can be used to drench the soil around the root pack of a plant providing immediate microbial stimulation to the soil food web from which the plant draws its nutrition.

6. The use of compost tea has even been shown to increase the nutritional quality and flavor of vegetables, to extend root systems deeper into clay and hardpan soil, to restore percolation to non-draining soils, and other benefits as well.

 

C. The Science of Compost Tea

Four primary categories of microbes can be transferred from compost to compost tea, and then to soil and/or leaf: Bacteria, fungi, protozoa, and nematodes. The most important for foliar spray are the bacteria. When leaves are covered with compost tea, the bacteria in the tea accomplish several roles: The take up space on the leaf surface making it difficult for airborne bacterial pathogens to become established; they may suppress existing pathogens; they consume available food supplies on the leaf surface which pathogens might otherwise survive on; and they make nutrients available to the plant through the leaf stomata (openings). Tea should be sprayed on both sides of plant leaves, covering at least 70% of the plant.

Compost tea is best used as a preventative, not a cure-all. Transplants can be sprayed as soon as they get their first true sets of leaves, and periodically afterwards as new leaves appear. However, if existing leaf diseases are noticed, spraying with compost tea regularly can help control their spread and may cause them to be arrested.

 

D. Compost

The key to good compost tea is good compost. Since the abundance and health of the microbial life in compost tea has its origins in the compost from which the tea is made, it stands to reason that high quality compost is required to produce high quality tea.

MCPLANT students have been taught how to make good compost, but the following guidelines should be recalled--along with a couple of factors specific to compost being prepared for compost tea:

[NOTE: The following information draws on Dr. Ingham's scientific background and represents the best-case scenario. Measuring ratios of raw ingredients is not easy for the beginning composter. Compost tea can be made and used even if the ratios of raw materials are not perfect to begin with. As Dr. Ingham says, Make the tea, use it, and let the plant sort out what it can use best. Other factors, such as aeration during the brewing process, are more critical than exact ratios--but the ratios should be followed as much as possible as experience in composting is gained. The average home composter is not going to have a regular pile and a pile for making tea. Therefore, I would encourage you to make the hottest, best pile you can and use the resulting compost for making tea.]

1. Carbon to Nitrogen Ratio. The standard figure for creating good compost is a C:N ration of 30:1. That is a chemical ratio, not a volume ratio. In other words, you don t need 30 parts of carbon by volume to each part of nitrogen. According to most sources, the 30:1 (C:N) chemical ratio will happen when layering approximately equal layers of brown (carbon) and green (nitrogen) materials in the compost bin. That changes when preparing compost to make tea. Compost can be prepared differently depending on whether a high fungi count (soil drench) or high bacterial count (foliar spray) is desired in the tea. High-fungi compost is best for mulching around many plants, but research has shown that the most effective compost tea for foliar spray has a high bacterial count rather than a high fungal count.

 

To prepare compost for making high-bacterial compost tea you should use a mix of:

 

 

 

25 percent high-nitrogen ingredients (manure and legumes such as alfalfa, pea, clover, or bean plant residues). Grass clippings from the first two or three spring cuttings qualify as high-nitrogen; the rest of the season s grass cuttings are simply green material (next category).

 

45 percent green ingredients (any green plant residue, kitchen scraps [never meat or oils], coffee grounds, egg shells, mid-to-late summer grass clippings, etc.

 

30 percent woody material (sawdust, wood chips, non-glossy, non-color paper products, newsprint, fallen leaves, straw, dry/dead plant residue, etc).

 

The MCPLANT compost model calls for 50 pounds of rabbit food (alfalfa pellets) mixed with leaves to fill up the round wire compost bin. The alfalfa pellets qualify as high-nitrogen, but to achieve the high-bacterial mix you could cut down on the leaves by half and replace with green materials in the pile. It would be good to collect these materials to start with (e.g., gather food scraps from the neighbors over several days) and have all the material ready to build the pile at once rather than adding to the pile slowly. Creating the pile at once is the only way to get the temperature high enough to achieve the goal of destroying disease pathogens and bad bugs that you don t want in the tea.

 

2. Compost temperature. The compost pile must stay between 130°F and 160°F for three days. This guideline is not just for compost that is going to be used for tea but for all compost. Disease pathogens and root-eating nematodes (microscopic worm-like critters) will be killed at that temperature; temperatures above 160°F will begin to kill beneficial organisms in the compost.

 

Because the material on the outside of the pile must reach the target temperature range, it will need to be turned into the inside of the pile. Therefore, it may take 1-2 weeks for the entire pile to maintain the target temperature. Check the temperatures with your compost thermometer and keep the pile adequately moist (as wet as a damp sponge ). The pile may need to be turned every 1-2 days for the first week to keep air in the pile. Shutting off air to microorganisms has the same effect as closing a damper on a wood-burning stove--the fire will soon go out. After the pile has achieved the target temperature range the temperature can be allowed to drop below 135°F, turning the pile every 1-2 weeks until it is finished. The high temperature plays a specific role for only a few days--it is not a permanent requirement in the compost pile.

Here s a key statement from Dr. Ingham: The more you turn the pile, the more the compost tends to become bacterial. That's because any kind of disturbance destroys fungi by breaking up their mycelia and helps the bacteria beat the fungi by bringing the foods bacteria need into range for the tiny individual bacteria. So don't neglect turning the pile after the target temperature range has been accomplished.

After the pile becomes just warm, even cool, it is ready to use (perhaps 6-8 weeks if the pile has been turned consistently).

 

3. Worm compost. Composted worm castings can be used to make compost tea. They do not need to be heated as does normal compost since the digestive process of the worm destroys disease pathogens. If you have enough worm castings available simply use them as you would regular compost in the brewing process.

Implementation:

 

IV. COMPOST TEA BREWER

 

The brewer you will make is a very simple, but effective, system which will produce 2-3 gallons of tea at a time. It combines the basic elements of compost, water, air, microbial food sources, and time to produce compost tea. Larger commercial tea brewers have come on the market in the last few years which make up to 500 gallons of compost tea at a time for commercial agriculture applications.

 

A. Brewer components

 

 

 

5-gallon bucket (a second bucket [can be smaller] will come in handy when the tea is done)

 

small burlap bag (or other porous bag; see notes below)

 

standard electric aquarium pump (rated for aquariums of at least 5 gallons in size)

 

standard aquarium plastic air tubing (six feet total in three, two-foot pieces)

 

standard aquarium two-port gang valve

 

standard aquarium air stones or bubblers (two)

 

1 ounce of blackstrap molasses (about 1 1/2 Tablespoons)

 

other supplements (see below)

 

3+ gallons of pure (non-chlorinated) water

 

2 gallons of 95% completed compost

 

In addition, a large funnel with a mouth 5-6 wide, and a two foot square piece of tulle fabric (fine nylon mesh, a.k.a. bridal veil ) will help in the filtering and pouring process when the tea is finished.

 

B. Alternate brewing method

 

Compost tea may be brewed by simply mixing the compost directly with water in the 5-gallon bucket rather than putting the compost in a porous bag. This obviously allows for greater aeration of the compost since it is free-floating in the water. The disadvantage of this method is much greater difficulty in filtering the tea when it is ready since there will be lots of debris from the compost in the tea when it is done (depending on whether or not the compost was screened to get rid of uncomposted debris before putting it in the bucket).

 

For using tea as a root drench, this is not an issue since you can just dip in the bucket and get tea to pour around the base of a plant. Just let the tea sit for 15-20 minutes after turning the pump off and let the debris settle to the bottom of the bucket, then dip the tea out by hand.

 

However, if you are going to spray the tea (its most beneficial use in the garden) it must be fine-filtered to keep tiny pieces of debris from clogging up the sprayer tip. This will require several filterings using the free-floating method.

 

For purposes of beginning with compost tea, this paper recommends the use of the bag method to make filtering easier when the tea is ready. Raising and lowering of the bag in the bucket several times a day during brewing will aid the free flow of water through the compost in the bag (see details below).

 

 

The following diagram pictures the assembly of the brewer components:

 

Here are the simple steps:

1. Attach one 24 length of air tubing to the aquarium pump.
2. Attach the other end of that tube to the in port on the gang valve.
3. Attach the other two 24 pieces of tubing to the two out ports on the gang valve (make sure both ports are open all the way if there are adjustment screws or valves for each out port).
4. Hang the gang valve on the side of the 5-gallon bucket.
5. Attach an air stone to the free end of each of the two air tubes and lay them on the bottom of the bucket.
6. Fill the bucket half full with pure water.
7. Plug in the air pump and make sure both bubblers are releasing bubbles into the water.
8. Add 1-2 Tablespoons of blackstrap molasses to the water; stir until thoroughly dissolved.
9. Place the burlap bag of compost in the bucket of water.
10. Add enough additional pure water to come within an inch or so of the top of the bucket.

Those are the basic steps. However, DO NOT BEGIN BREWING TEA WITHOUT READING THE ADDITIONAL COMMENTS REGARDING EACH COMPONENT BELOW. There are a number of additional insights which will increase the likelihood of brewing a successful batch of tea.

 

D. Brewing compost tea

Step 1: Compost As stated above, good compost is the secret to good compost tea. To fill the small burlap bag that came with your kit, you ll need approximately two gallons (by volume) of compost. Just fill the bag until it is about 3/4 full, then use string or a twist-tie to close the top of the bag.

 

Step 2: The Bag Method You don t have to use a burlap bag to hold the compost; any porous bag will do (nylon, plastic, cloth). Two things are important: Porosity and purity. The larger the openings the more water will circulate through the compost (an old pillow case, for example, depending on thread count, will not allow as much water to flow through as a nylon mesh bag or burlap bag). The burlap bag which came with your kit is non-treated burlap. If you buy additional burlap bags make sure you get non-treated. Some burlap is treated with a chemical preservative to make the bags last longer, and the chemical will kill microorganisms. Same for any other material; make sure it has not been treated with chemicals. The air bubblers should sit on the bottom of the bucket; the bag will usually hold them in place. Swish the bag up and down in the tea several times a day to facilitate water flow through the compost.

 

Step 3: The Non-Bag Method If you put the compost directly into the bucket, fill it about half full of compost, then add water. When the brew cycle is finished, you can do the first filtering by using a wide, large-mesh kitchen strainer with handle to scoop out the compost and dump it in another bucket, allowing the tea to drain through the strainer before dumping. You should be left with 2-3 gallons of tea in the bucket, though it will still be too gritty to use in a sprayer. (See Straining below.) Also, stir the compost and water mixture with a stick several times per day to keep it well-mixed. The bubblers should sit on the bottom of the bucket under the compost.

 

Step 4: Water It is very important to use pure water with NO CHLORINE. Well or spring water is fine. To get the chlorine out of household tap water fill the bucket with three gallons of water and put the air bubblers in the bottom of the bucket. Turn the pump on and let the water aerate for an hour. The chlorine gas will be bubbled out of the water in that time and the resulting water will be safe to use. Allowing water to stand for a day without aeration will also allow the chlorine to evaporate. CHLORINE WILL KILL THE MICROORGANISMS IN COMPOST TEA.

 

Step 5: The Air Pump[Note: All the aquarium supplies are available at Wal-Mart, pet stores, etc. if you need replacements.] The air pump stays on during the entire 2-3 day brewing cycle. Mine stays on my back porch, plugged into an outdoor electric socket, even in the rain. It sits under an eave so is somewhat protected from heavy rains, but I haven t had a problem with it running all the time. Or you can brew your tea in the garage or a basement. Filtering the tea usually results in some spills, so if you brew indoors you may want to take it outdoors when finished.

Step 6: Air Stones or Bubblers Whether using the bag or non-bag method, the air stones will absorb dirt and grime from the water. They are made of very soft material (rock?) and can be gently cleaned with a soft brush to prolong their life. Be careful as it is easy to break the plastic nibs off where they connect to the air tube. If they get particularly dirty, soak them in vinegar -- or buy new ones (about a dollar for two stones). You can attach weights to the bubblers (thread the tube through a couple of washers before attaching the bubbler; or fasten rocks to the tube with rubber bands) if needed to keep them on the bottom of the bucket.

Step 7: Gang Valve Dr. Ingham suggests using a 3-port gang valve (and thus three tubes and bubblers in the bucket). Four would probably be better. That is, the more air the better, especially in the first 24 hours of the brew when the microbes are feeding and multiplying rapidly. We included 2-port valves with the kit to save money, but 3-4 bubblers would be ideal for a 5-gallon brewer.

Step 8: Air Tubing Make sure the air tubes stay connected. There are six places where the air flow can be disrupted by connections coming loose--and lack of air in the tea is the main thing that will make the tea go anaerobic. When that happens the microbes in the tea begin to die, the tea begins to smell, and its basically over. If you discover a connection has come loose, just reconnect it and keep going and see what happens. As long as the tea doesn t begin to smell it will probably get aerated again and be okay.

Step 9: Adding Molasses The purpose of adding molasses (and other additives) is to provide a food source for the microbes in the tea. An excellent additional additive is Icelandic (cold water) kelp, which adds minerals and protein to the tea. The kelp needs to be water-soluble (i.e., powder form) so if you buy kelp meal you will need to grind it in your coffee grinder or food grinder to get the particles down to as small a size as possible. Add 2-3 ounces for a 5-gallon brew. You can also add small amounts of additional sugar sources such as cane syrup, sugar beet syrup, spoiled carrot juice, pure squeezed apple juice. Other additives such as comfrey, nettle or dandelion soups can be made a day ahead and have been shown to add benefit to the tea (cut them up and soak/thrash them in a bucket of water for a day, then add that water to the brewing water before you begin brewing; not validated by scientific testing--anecdotal evidence only). Everything except the molasses is optional/extra. The molasses must be added in order to provide a basic food source for the microbes.

Step 10: Brewing The tea should brew continuously for 2-3 days. There is no definite stopping point short of doing hourly scientific analysis of the microbial activity of the tea. With good compost, plenty of air and food, and occasional stirring of the tea, a high-bacterial tea will result in 48-72 hours of brewing. A good plan is to start a batch on Wed or Thursday so it will be ready for use on the weekend. The tea should be used as soon as it is brewed. If aeration is continued it will remain viable for up to eight hours--but when it is done, it should be used. If the tea foams as a result of the quality of the compost, that is not a problem. A spoonful of vegetable oil (not olive or canola unless pure organic) will help keep foaming under control.

Step 11: Filtering With your compost tea brewer kit, you received a two-foot square piece of nylon netting and a wide-mouth funnel. When the tea is finished, to filter the compost tea from the brewing bucket to your garden sprayer. . . 1. Remove the burlap bag and place in a second bucket so it can drain additional tea.2. Wad the nylon netting up and stuff it in the neck of the funnel which is in the top of the garden sprayer.3. Stir the tea gently so as to mix it well.4. Pour the tea from the bucket, over the nylon netting, and into the garden sprayer. The netting will catch particles of compost and grit which could clog the spray tip. The netting can be rinsed out, dried, and used many times.

Step 12: Clean-up You can return the used compost to the compost pile or spread it in the garden as a mulch or soil amendment. There is plenty of microbial life left in the compost to contribute positively to the compost pile or the garden.

 

Recommendations:

 

V. USING COMPOST TEA

 

A. As a foliar spray

 

When the brewing cycle is finished, compost tea can be partially diluted (up to half) with pure water to extend coverage. But it can also be applied full strength which is preferable.

Spray in the cool parts of the day--before 9:00 a.m., after 4:00 p.m. Ultraviolet rays from the sun can kill bacteria in the tea.

When spraying, set your sprayer as close to mist as possible so you don t spray so heavily as to create run-off. Spray both sides of the leaves on at least 70% of the plant.

Chemical pesticide sprays in the air (even from a neighbor s yard) can kill the good bacteria in compost tea. You may need to re-spray if you have reason to believe pesticide spray has covered your plants (try rinsing the plants and waiting a day or so to give the pesticide time to wash off or become inert).

 

B. As a soil drench

When using compost tea as a soil drench, apply a pint or more to each plant. The point is to soak the root pack of the plant the size of which will vary depending on the plant. Apply whatever is necessary to ensure adequate coverage of the roots.

When using indoors to water houseplants, you can put compost tea in a small mister and spray the leaves (be careful of overspray on furniture and walls--compost tea can stain permanently). Or simply use it to water the soil, either full-strength or diluted by half with pure water.

 

C. Lawn spray

 

More and more reports are showing the powerful impact of compost tea on lawns. The problem is obviously having enough tea at one time to soak a significant portion of your grass at one time (consider doing sections at a time).

 

Once you get comfortable with brewing compost tea in a 5-gallon bucket, there is no reason not to make larger quantities. Using a 30 gallon trash can as a brewer, for instance, would simply mean multiplying the 5-gallon brewer ingredients by six to get proper quantities.

 

A key factor will be aeration. An aquarium pump adequate for a 5-15 gallon aquarium, running a two-port gang valve, will not provide adequate aeration for a 30 gallon brewer. Shop for a stronger air pump (they are rated by the size aquarium they will service, so look for one with a 30 gallon minimum), longer plastic tubes, a minimum four-port gang valve (or two gang valves--larger air pumps have dual outlets for running multiple sets of air accessories in an aquarium, so you could run multiple gang valves), and more air stones. Get a larger, untreated burlap bag, and your in business. Brewing 15-20 gallons of compost tea a week in a 30 gallon trash can could cover a lot of lawn!

 

Compost tea is being used extensively on athletic fields, golf courses, lawns, and other grass settings to increase soil tilth, root extension, nutrition, and disease suppression.

 

Additional:

 

VI. Resources

1. Ingham, Elaine R. The Compost Tea Brewing Manual (3rd edition, 2002). Soil Foodweb Inc., 1128 NW 2nd Avenue, Suite 120, Corvallis, Oregon 97330. (541)-752-5066 (http://www.soilfoodweb.com)

This is the best source in print on compost tea and can be ordered directly from Soil Foodweb Inc. Cost is $25 plus s/h.

2. Ingham, Elaine R., Edwards, Clive A., and Moldenke, Andrew R. Soil Biology Primer (rev. ed., 2000). Published by the Soil and Water Conservation Society in cooperation with the USDA Natural Resources Conservation Service.

This is an excellent introduction to the soil food web. There is more information in this book for the price ($7.00) than anything else available on soil. Anyone who wants to understand compost and compost tea should read this brief book. It can be ordered from Soil Foodweb Inc. (phone, web address in the previous citation).

3. Ingham, Elaine R. Brewing Compost Tea. Kitchen Gardener--The Vegetable and Herb Gardening Journal (October/November 2000), pp. 16-19.

Sadly, this magazine is no longer being published; it was an excellent resource for (primarily) organic vegetable gardeners. Back issues of the magazine are available at http://www.taunton.com/store/pages/backissue_kg.asp , including the issue containing this article.

4. The Soil Foodweb Inc. web site.

 

http://www.soilfoodweb.com This is Dr. Ingham's company's web site and is filled with information on compost and compost tea. You can also subscribe to her monthly free email report on her studies, activities, answers to questions regarding compost and compost tea, etc. The archives of her past monthly e-zines are available to read as well.

5. The Woods End Research Laboratory.

This lab in Mt. Vernon, Maine, is a leading scientific research site for compost and compost tea. Dr. William Brinton is head of the lab and a recognized authority. There are some resources on compost tea available on their web site http://www.woodsend.org .

 

6. A.T.T.R.A. (Appropriate Technology Transfer for Rural Areas) web site

ATTRA is the national sustainable farming information center operated by the private, nonprofit National Center for Appropriate Technology (NCAT) (a good site for all sorts of sustainable and eco-friendly lifestyle and technology information -- http://www.ncat.org ). ATTRA has tons of publications available for download on all sorts of sustainable and organic agriculture topics. Go to the web site and click on Publications, or enter tea in the search window for materials on compost tea. ,a href="http://www.attra.org">http://www.attra.org

7. A good article on making a compost tea brewer similar to the one described in this paper is at the Worm Digest web site (using vermicompost) (http://www.wormdigest.org/articles/index.cgi?read=66)

 

8. An email discussion list, based at YahooGroups.com, is available (http://groups.yahoo.com/group/compost_tea/) . To subscribe to the list send a blank email to compost_tea-subscribe@yahoogroups.com . You should be automatically subscribed to the group. Unsubscribe instructions are available on each posting. Dr. Elaine Ingham is not the moderator of the group, but is an active participant and offers lots of insights. The participants include some professional landscapers and growers who use compost tea in large quantities, and the discussions can get pretty scientific at times. But that is a good indication of the way compost tea is spreading as an organic growing amendment for plants and soil.

Best wishes for great success in brewing compost tea for your home, garden, and agricultural applications!

[NOTE: Please feel free to contact me with questions, suggestions, or ideas on the brewing or use of compost tea: (704) 821-2528 or williamk@carolina.rr.com .]