Mar 30, 2012

Urban Garden Magazine | Breeding Microbes with Compost Tea

“We know more about the movement of celestial bodies than we do about the soil underfoot.”
~Leonardo da Vinci

Commercial grape growers in Sonoma and Napa pay big bucks for beneficial biology consultants to come to their vineyards. And for good reason—the right blend of microbiology in their soils can significantly increase the market value of their wine by promoting more sophisticated flavors and bouquets in their grapes. When it comes to actually selling the end product, it can be the difference between producing a bottle that sells for, say, ten bucks and one that sets you back fifty or more. Just think what an understanding of beneficial biology could do for the fruit and veggies in your garden?

Organic waste decomposing at a composting facility in sacramento, California.

So what exactly is this beneficial biology? How do we ‘capture it’ and put it to work in our gardens? It turns out that the answer’s been right beneath our noses all this time. Literally! Microbes form an integral component of all living systems. In fact, if microbes didn’t exist then you wouldn’t be worrying about them, because you wouldn’t be around either! While you ponder that fact, consider one more. There are more microbial cells in and on a human (or at least one not taking antibiotics) than there are human cells in your body!

We’re going to find out how to breed microbes (it’s easy!) and deploy them in our gardens. To this end we’ve pulled in beneficial biology expert, Evan Folds from Progress Earth, to give us a practical introduction to brewing your own compost tea–and using it to grow the most delicious, chi-filled produce imaginable!

Salivating? Then you’d best read on!

Give it up for microorganisms! They perform relatively Herculean acts for their size. Microbes are responsible for aiding limitless plant processes, including helping plants feed and protecting them from disease. They even help to create the very soil that serves to support the entirety of life on Earth. Meanwhile, many of us have become conditioned by modern marketing to foster a disdain and disrespect for microbial creatures (think hand sanitizers and antibiotics.) Healthy soil is alive with microbes. They form incredibly important mutualistic relationships with the plants we depend on for food. They break down organic matter (which is inaccessible to plants) into a form that plants can use. Think of them as little ‘compost conversion’ factories. Now start to imagine the potential for increasing the life force in your garden by learning how to breed these microbes at home! We’re talking about something called “actively aerated compost tea” or AACT for short. It’s “life juice” for your plants—a brown soup that’s full of beneficial microbiology, the essential components of any organic growing situation.

Compost Tea and Soil Food Web

Bubbling air through compost tea is essential to create a healthy, earthy-smelling brew

Brewing compost tea is easy and can be done in many different ways. You take some compost and other humus sources as a source for microorganisms and grow them to extremely high concentrations in an aerated water solution comprised of food sources and catalysts. The result? The soil food web unleashed in all its glory! Microbes and plants are natural teammates, so compost tea is simply the best way to replenish and enhance this wonderful relationship.

However, our current understanding of how to best take advantage of compost tea when growing plants can be called “rule of thumb,” at best. We know a lot about microbes, but relatively little about what they do or how to use them while growing plants.

Adding compost tea to rain water

There are potentially billions of microorganisms and thousands of feet of fungal hyphae in a mere teaspoon of quality compost. The fact is, microbes are so abundant, so pervasive in everything we do, that it’s no issue to promote astronomical numbers when discussing and marketing them in compost, or compost tea products. It’s easy to get bamboozled with all the hype surrounding compost and compost tea. Consider this: microbes are so small that up to 500,000 bacteria can fit in the period at the end of this sentence. When it comes to brewing your own microbes, high numbers are the easy part, but the number of microbes present in a biological sample is nowhere near as important as the diversity and strength of those organisms. Total numbers can be relevant when evaluating the balance of biological products or whether a humus product is stable, but it does not address the most important aspect of all—how well the product works in a real-life growing situation.
Biological Diversity and Microbe Strength

Many biological products available at your local grow store are created by microbes raised by humans in a laboratory. This biosynthetic approach is necessary for the cost effective distribution of certain microbes and has its merits, especially with mycorrhizae fungi, which cannot express their abilities without a plant and are not benefitted by brewing in compost teas. However, I believe that a biosynthetic approach cannot represent the full potential of an intact biological network. There’s no synergy amongst the different microbes as they didn’t grow up together. Remember, microbes aren’t robots, they’re unique dynamic living breathing life forms with varying abilities, even within a given species.

A key concept to grasp is that no living organism operates autonomously. In other words, there is a symbiosis, or “give and take,” found in the natural world that we humans take for granted, and therefore restrict. Think you grow your plants? Sorry but it’s far more likely that you merely get in the way and mess with the magic! All microbes operate by way of teammates. They play off of each other, with one teammate unlocking the ability of the next. The big man cannot dunk without the assistance from the point guard. When 52 different organisms (ones that were individually grown by a human in a Petri dish) are brought together as an end product intended for use in a gardening situation, the optimal result is surely compromised. Remaining with our basketball analogy for a moment longer, the team’s overall ability is hindered if all the players are not on the court and, even if they’re all present, what happens if the coach puts the players in the wrong positions?

Sure, microbes don’t play basketball (as far as we know) so you may be forgiven for thinking that it’s not feasible to identify ability in microbes. But first, check out some Bt products. Bt is a bacterium called Bacillus thuringiensis. It’s commonly used in gardening because it’s gentle with plants, but very capable of parasitizing the larval stage of common pest insects. The Bt organisms geared towards fighting larvae such as caterpillars are called the kurstaki strain and the Bt aimed at fighting mosquito larvae in water is named the israelensis strain. These organisms are of the same species and illustrate differing abilities depending on the application.

Microbes can react and adapt…by design. Did you hear about the “new” proteobacteria discovered by scientists in the wake of the recent oil spill? Look it up. BP must have been stoked!
Making and Using Actively Aerated Compost Tea

So, you want to brew your own compost tea. Where do you start? The answer is humus! Microorganisms are found dormant in quality humus sources like compost or worm castings, but can be awakened and stimulated to grow under the right conditions. There are several different methods for creating compost tea (AACT). It’s simply a matter of adding your humus source to water and using air pumps to increase the amount of air in the water solution in order to grow microbes. The final part of the jigsaw is to add some sort of food and catalysts for the microbes to grow, such as molasses, kelp, rock dust, fish, humate, sea minerals, etc.

Brewing your own AACT is similar to running an aquarium. You aerate water for fish the same way you do for microbes, or for roots in a deep-water-culture hydroponics system.

The porous bag allows microbes to escape and enter the solution while keeping the tea free from debris.
DIY Compost Tea Shopping List

You can purchase ready-to-go brewers if you want to make your life nice and easy. Alternatively you can make one yourself. To brew compost tea, you’ll need a pump, some air tubing, a gang valve, and three bubblers.
An aquarium pump large enough to run three bubblers or air stones
Several feet of tubing
A gang valve
Three bubblers
A porous bag for the compost, like a nylon stocking OR Something to strain the final tea, like an old pillowcase or tea towel.
A bucket

All the components of your own compost tea brewer can be obtained at your local garden store for around $60. Without sophisticated equipment it’s hard to determine technical aspects like dissolved oxygen, so it’s best to keep it simple. A small aquarium air pump is sufficient for up to 10 gallons. More air will not be harmful; it’s simply that water can only hold so much of it. If you want to use higher volumes of water, you may want to consider getting a larger air pump.

As your compost tea brews (it usually takes about 12––24 hours) you will notice a layer of foam forming on the surface. This is nothing to worry about and is actually a result of the proteins produced by biological growth. This foam is a good sign that your compost tea (or rather the microbial life within) is flourishing.

Deliberate overuse of bat guano.

Some foods sources such as bat guano create more of it, but a good fish oil (or the active ingredient in comfrey called allantoin) will keep things in motion and keep the foam down if need be. Foam is generally not a concern, especially when using suggested recipes from reputable compost tea companies.

When brewing AACT keep in mind that the higher the water temperature the greater the biological growth, but the lower the dissolved oxygen. It’s a matter of physics that the warmer the water temperature, the less oxygen can be dissolved. It is also true that the colder the water temperature the slower the biological growth. Dissolved oxygen levels above 6 parts per million (ppm) will provide sufficient biological growth, and levels around 8 ppm are attainable at room temperature. An accepted approach among compost tea enthusiasts is to brew AACT at a similar temperature to where it’s being used, for example; if your root zone temperature is 68°F (20°C), brew the AACT around this temperature.

The food source utilized when brewing compost tea can determine the microbe grown. This idea follows the concept of succession. An acre of land left fallow will begin to regenerate using annual plants (weeds), and then progress into more perennial species (grass, vegetables) until it culminates into a forest (perennial hardwoods). Over the course of this natural process, fungi become gradually more dominant than bacteria. This is not black and white, but is evident in the fungal dominance of old growth forests.

So what does this knowledge mean? Well, you can use it to brew compost teas that make more sense to what you are growing. For instance, a sugar source like molasses fed to a balanced stable compost inoculant will encourage more bacterial growth, whereas kelp or fish fed to the same inoculant will encourage more fungal growth. The same is true for other inputs, like Equisetum (horsetail), which encourages the growth of beneficial nematodes. To be clear, molasses does not discourage fungi from growing, it simply encourages bacteria more. Similarly, using a fungal dominant tea on an annual plant will not harm it in any way; it’s a better/best scenario. There is so much more to be discovered as da Vinci reminds us—we know more about the stars.
Using AACT

Microbes given a proper environment can grow to extraordinarily high concentrations. The book Secrets of the Soil states that a single microbe reaching maturity and dividing within less than half an hour can, in the course of a single day, grow into 300 million more, and in another day to more than the number of human beings that have ever lived. Further, according to the book Microcosmos, bacteria, in four days of unlimited growth, could outnumber all the protons and even all the quarks estimated to exist within the universe. This reality allows growers to use as little as five gallons on an entire acre of land, roughly equivalent to about a one cup per gallon dilution.

Compost tea can be used in unlimited ways and really cannot be used incorrectly unless you are overwatering your plants. Some growers choose to use compost tea on every watering, but weekly applications or on reservoir changes would be sufficient. It is even possible to experience benefits from compost tea with just one application. After all, you’re dealing with living organisms that can populate and reproduce by themselves if given proper conditions.

It is a common supposition that synthetic products (i.e. mineral based nutrients) kill microbes. While this is certainly true on some level, using compost tea with synthetic nutrient regiments can produce good results. The image inset illustrates the use of a leading compost tea brew used at one cup per gallon on weekly reservoir changes in a mineral-based hydroponic situation growing jalapenos.

Again, it’s a better/best scenario; you’re better off using compost tea and mitigating the potential harshness of your mineral-based nutrients than worrying about the microbes dying.

It is always advisable to check nutrient concentrations with a meter before using a tea on sensitive or special plants, but by keeping inputs at or near recommended amounts there should be no fear of burning. “Burning” a plant is actually a water stress based on total ion concentration. Having too many ions around a root system sucks water out of the plant via osmosis, causing the plant to respond by sending its available water into the middle of the leaf and leaving the edge to burn. Because compost tea is created at relatively low concentrations (600-800 ppm) burning is a non-issue when used at recommended levels.

As if to underline the previous point, compost tea can be used with seedlings and cuttings with great success. The sooner and more microbes used the better, even in hydroponics. Use a gallon of compost tea to 20-50 gallons of water in hydro reservoirs; some growers even use compost tea concentrate as their primary reservoir solutions. Consider using organic and organic-based nutrients as food sources for biological inoculants. It is not necessary to feed microbes after you have implemented them into a garden, but it can certainly have a positive influence. After all, natural farming is about feeding microbes, not the plant.
Compost Tea as a Foliar Application

You can even use compost tea as a foliar spray. Some growers spray their plants every day, but once a week will do the trick for measureable results. When using compost tea you are harnessing a synergy of living microbes for general benefit, however, this is one of the occasions when a targeted biological product can be effective. Many times the microbes used in human designed microbial products are found naturally in compost, but not in high enough concentrations to make them applicable once pests or disease have struck. In the end, a pest or disease is simply a biological imbalance of some sort, so when one trophic level gets out of whack a higher concentration of a certain microbe can work effectively.

The active ingredient in many biological fungicides is the bacterium Bacillus subtilis, which is found naturally in compost. This concentrated organism will work better on a disease outbreak, but if used consistently, compost tea can work preventatively to allow the disease to express itself in the first place. The more consistent you are in delivering microbes to the leaves and root zone of your plants, the more benefits you will receive.

Compost tea can even help control pests if used consistently, many bacteria found in compost seek protein, which is what comprises the exoskeleton of many target pest species. As with any new endeavor in the garden, isolate a test plot and experiment before implementing it into the entire growing situation.

There is no real precedent for using Actively Aerated Microbial Extracts (AAME) in compost tea brews, but it’s certainly a good idea for experimentation. Some grow stores set up multiple compost tea units for grow/bloom or bacterial/fungal purposes. I anticipate that we will start seeing them for pest and disease control too in the near future.
AACT Brewers

There are varied compost tea units available on the market, everything from a five gallon bucket to large commercial units. For the most part, the unit you choose will be based on volume size and convenience, not biological performance.

There is a healthy debate regarding the importance of the size of the air bubble produced by air diffusers and another on whether they need to be used at all. While it is certainly true that the smaller the bubble the more surface area exposed to the solution, it is unclear whether this really makes a difference based on maximum dissolved oxygen levels considering water holds a finite amount of oxygen relative to its temperature.

Filter bags to hold compost are also a point of difference between respective models. They are used strictly for convenience so that the compost tea brew does not clog up sprayers after creation. This can save time, but must be balanced with what is not extracted from the physical compost when brewing. As mentioned above, microbes hold on really tight. A quality humus is colloidal and most inputs used are soluble, so a filter bag is not absolutely necessary. You can always filter it after you are done brewing.

It is vital to use quality water when brewing compost tea, and in your garden in general. If you are unsure of your water source, use a filter. There are quality reverse osmosis (RO) filters and de-chlorinators on the market for reasonable prices. Most nutrient solutions are not designed to account for what comes through the tap, so if possible start from zero ppm. Remember, chlorine kills microbes and it’s added to just about every public water supply in some form for this very reason. Bubbling your water will remove chlorine in a couple of hours, but not chloramines, its more persistent cousins—also used in many municipal water supplies. At the very least, let your water sit out for 24 hours before using it to brew tea. Ideally, invest in a reverse osmosis water purification system.
Composts, Inoculants and Food Sources for Compost Tea

When brewing compost tea, starting with a quality microbial product is essential. This is a major problem with people who compost in their back yards. Organic matter doesn’t melt; it’s biologically digested. It’s not advisable to use manure to make compost tea because manure is not yet plant food. This is why black cow “compost” at the hardware store costs $1 a bag. It’s aged manure. It’s mulch, not plant food. Remember, trees in a forest don’t eat leaves; they eat what the microbes make of them.

Some growers use worm casings as the sole basis for their compost teas. While this is certainly a viable option to brew tea, worms are predominately a bacterial organism, and do not contain some of the trophic levels of beneficial organisms, such as fungi, nematodes, protozoa, ciliates, etc. that provide vital benefits to plants and gardens. Worms sequester bacteria in their gut in order to work their magic, like termites use fungi to digest the wood they eat. To brew a better tea, consider using worm castings along with a balanced humus product.

Food sources for compost tea include molasses, kelp, fish, bat guano, and generally anything that was once alive that is soluble enough to be put into solution, even fruit pulp. It is important to note that recipes and preferences vary widely, for instance, some may recommend up to 16 tablespoons of molasses per 5 gallons of water, others only 1 tablespoon. Be sure to experiment based on these general recommendations, but here are a couple of simple recipes:

Use the formulating company’s recommendations for humus and catalyst per gallon, then for a bacterial dominant tea, use 4-6 tablespoons of molasses and 2-4 tablespoons of kelp to five gallons of aerated water. Reverse the ratio for a more fungal dominant tea.
Three Simple AACT Recipes (All for 5 Gallon (19L) brewers)
Bacterial Dominant Tea

1.5 pounds (700g) bacterial compost or vermicompost
3-4 tablespoons (45-60ml) liquid black strap molasses
4 teaspoons (23g) dry soluble kelp or 2 tablespoons of liquid kelp
3-4 teaspoons (15-20ml) fish emulsion
Equal Ratio – Fungi : Bacteria Tea

1.5 pounds (700g) 1:1 fungi to bacteria compost
3-4 tablespoons (45-60ml) humic acids
4 teaspoons (23g) dry soluble kelp or 2 tablespoons of liquid kelp
3-4 teaspoons (15-20ml) fish hydrolysate
Fungal Dominant Tea

2 pounds (900g) fungal compost
3-4 tablespoons (50ml) humic acids
2 teaspoons (10ml) yucca extract
4 teaspoons (23g) dry soluble kelp or 2 tablespoons of liquid kelp
4-5 teaspoons (20-25ml) fish hydrolysate

Recipes from ‘The Compost Tea Brewing Manual’, 5th Edition by Dr Elaine Ingham.

Fish-based natural fertilizers are generally obtained in one of two forms, condensed fish solubles known as emulsions, or enzymatic digested fish known as hydrolysates. Fish hydrolysate is cold processed (minced, enzymatically digested and liquefied) to preserve proteins for quick turnover by microbes into nutrients for plants. Emulsions are created using extreme heat, and while they may be easier to work with because they are further refined, the processing removes valuable ingredients and denaturing nutrients. While both fertilizer forms can benefit a compost tea, hydrolysates retain the natural oils from the fish that are a very potent fungal food.
Mineral Catalysts

One thing that is not discussed enough in the compost tea community is the use of mineral catalysts. Catalysts, as we know, change the speed of a reaction. It’s important to understand that microbes work indirectly via chemical decomposition. In other words, bacteria don’t chew on a banana peel in a compost pile, they offer up an enzyme (biological catalyst) that works to chemically break it down. Enzymes are specialty proteins that work like keys to a lock for important biochemical reactions within living organisms, plants and people included. All enzymes incorporate a single molecule of a trace mineral—such as manganese, copper, iron or zinc—without which an enzyme cannot function. We all know the benefits of adding enzymes to our gardening systems, but not many growers know that you get free enzymes from microbes.

Microbes help plants eat and, in return, plants feed microbes. In fact, over half of the energy derived through photosynthesis by plants is fed to the soil as exudates. Think of an exudate as a meal for microbes. Plants actually know what they need, they just can’t tell us. This means that plants have the ability to attract specific trophic levels (imagine the balance of the big fish and the little fish in the ocean) of microbes by preparing food from its surrounding environment that attracts those capable of generating what is deficient in the plant. This biological/plant network, or intelligence, if you will, cannot be established overnight, but it can be tapped into if we are aware of it. This is especially true when growing indoors in artificial environments.

It’s important to provide everything for plants so they can be allowed to eat what they desire, but it’s even more important to allow microbes a complete tool kit. Not doing so is like hiring someone to build a house and only providing them half the tools. The pictures inset illustrates a side-by-side conducted with a broad-spectrum mineral product. The tea sample on the left was brewed in the presence of many more elements than the tea sample on the right. Note the enhanced foaming and darker color after only four hours.

Other catalysts to consider are rock dusts, yucca extract, or any broad-spectrum natural mineral. Remember, these materials are not “food” for microbes; they help microbes eat their food.
Buying AACT

Your grow store might be one of the many who offer up their own in-store brew from units operated inside the store. If you choose to purchase compost tea from a gardening store, be sure to use it as soon as possible. We have seen evidence of beneficial life for up to three days under a microscope with some systems, but it is always advisable to use it the day you get it from the shop. Make sure to ask your retailer about the components of the compost tea being brewed, including the biological source and whether mineral catalysts are being used. If they have a microscope set up, even better. Make a habit of reconciling the microbes you see under the scope before you take it home with the results you are getting in your garden.

Some models found in stores involve refrigerating brews and coordinating pickups on certain days, while others encourage running the units perpetually by adding food source, catalysts, and microbes daily based on the amount of water added to the unit.
Brew Times

The most commonly heard figure for brew times is 12-24 hours. If pressed for why, a common answer is because bacteria are most active in these stages. While bacteria are beneficial to plants, so are many other microorganisms. Take protozoa for example. It is well known that compost tea brewed for over 24 hours begins to develop protozoa and ciliate dominance. (The brew “matures.”) Protozoa are extremely efficient nitrogen (N) cyclers, so why would a grower looking for more nitrogen not brew their tea longer to populate more protozoa dominance? Further, they are also the shredders in the soil; they eat bacteria and fungi like a shark eats fish in the ocean. Humus is actually the guts of microbes. They have digested available organic matter to create stable dormant humus (plant food). The guts of microbes are actually fertilizer bags. Why wouldn’t we want protozoa in there creating nature’s plant food shredding up bacteria?

There is no “right” way to brew compost tea, only better and best. Before long we will have developed biological feeding schedules that direct growers on how long to brew their compost teas given humus, foods, and catalysts to accomplish the microbe spectrum that makes sense for the plant and stage of growth, like we do mineral products. If one wants bacteria to use as a foliar, use molasses and brew for 12 hours. For a higher fungal: bacteria ratio for hardwoods, brew 24 hours using fish hydrolosate and humates. Feed hay has shown promise in increasing protozoa counts, so brewers can use it and brew for 48 hours to sequester more for their gardens. The possibilities are endless.

Some growers are experimenting with aerating their microbes for a period of time before adding food sources. The idea is that some microbes wake up faster than others, so brewing without food lets all of them get their feet on the ground, so to speak. Makes sense, but much more research needs to be conducted. The new frontier in natural gardening will develop around these ideas. One thing is for sure, we’ve got a lot of work to do. But, hey, it could be worse, we could be sitting in a cubicle.

If we approach the biological situation of our soils and hydro systems humbly, we will be in a far greater position to benefit. We can get more out of our plants than we have come to expect. Growing plants is about much more than feeding a plant directly, it’s about taking stock of their total environment, including the biological (microbial) and energetic (biodynamic) aspects of the growing situation. Rather than listen to ourselves, let’s listen to our plants for a change.

If you’ve never used compost tea with your plants, you’re not maximizing the genetic potential of your garden. Consider this your clarion call. Stop by your local garden store and get started today.

“Nutrition as it is today does not supply the strength necessary for manifesting the spirit in physical life. A bridge can no longer be built from thinking to will and action. Food plants no longer contain the forces people need for this. So long as one feeds on food from unhealthy soil, the spirit will lack the stamina to free itself from the prison of the body.” — Rudolf Steiner • Creator of Biodynamics (1861-1925)

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