It's Tea Time! Part 2

By Tad Hussey

In the last article we discussed the many different types of teas that farmers and gardeners use in their garden. We then focused on AACT or Actively Aerated Compost Tea, which is an aerobic water solution that has extracted the microbe population from compost along with the nutrients. In simple terms, it is a concentrated liquid created by a process to increase the numbers of beneficial organisms as an organic approach to plant/soil care.

When building your own brewer, here are a few pointers:

  1. You can't have too much air! Most homemade brewers aren't pushing enough oxygen to maintain good levels during the brewing process. One or even two aquarium pumps, typically isn't sufficient. A good rule in determining air flow is .08 cfm/gal. Our extended life motor pushes 51 liters/min at 1.5 psi. I would consider this a minimum for the inputs that we use, as our original system provides even more aeration (though the motor has a shorter life span and is also noisier). If you decide to use aquarium pumps, I would send one or two directly into the bottom of the bucket, using glass bonded air stones or a coil system. Then, another aquarium pump should be pushing air directly into the mesh bag containing the compost. This is important because the microbes have formed glues and are attached to the soil particulate. You need to really agitate the material to both keep it aerobic and strip the microbes out of their happy homes and into the water.
  2. According to Dr. Ingham, nylon stockings or cheese cloth don't allow for all the fungi and protozoa to escape into the brewer, or may become trapped in the stocking if used for filtering. If it is possible to avoid filtering, you're less likely to damage or be removing any organisms, though sometimes clogging can be a problem. We've discovered through testing, the optimum size for filtering compost tea is 400 microns. This will trap a majority of the particulate, while still allowing the microbes to escape.
  3. Make sure there's no dead spots in your bucket. You'll want to avoid a square bucket for this very reason, unless you design an apparatus that will fit in to all 4 corners of your brewer. We use a coil method in our brewer, where the coil fits snugly in the bottom of the bucket and then spirals around towards the center of the bucket, with holes every 1.5" to aerate the entire bucket evenly.
  4. Avoid using small parts or pieces that will be difficult to clean. Airstones can be problematic for this reason, and you will need to be diligent in cleaning them if you use them in your brewer. Cheap airstones are very difficult to keep clean, and you will find the quality of your tea decline rapidly with each brew as bio-film builds up on the inside of the air stone. If you do decide you use air stones, invest in some higher quality glass bonded ones, and be sure to soak and clean them after brewing.
  5. Always clean your brewer right away. If you wait to clean it, it will grow anaerobic bacteria and begin to stink. I had a brew going in my garage, and ended up hurting my knee so I was unable to clean it out after stopping the motor. When I got back to it in a few weeks, I had to throw the whole thing away because it had so much bio-film built up that I could barely get within a few feet of it due to the odor! You can use hydrogen peroxide, bleach, or any other anti-microbial cleaner.

Recipes:

There are many recipes available for making AACT. All involve the use of high quality compost. I'll focus on the 5 gallon size, though recipes are available in larger quantities. However, ingredients do not increase in direct proportion to the size of the tank, so please contact me directly if interested in recipes for larger brewers. Recipes are directly related to the amounts of dissolved oxygen in your brewer. As you add more food sources for the microbes, you need to add more air to ensure the tea stays aerobic (above 6 mg/liter dissolved oxygen).

Tim Wilson of Microbe Organics (www.microbeorganics.com) recommends these ratios based on his testing:

2.38% by volume compost or vermicompost (EWC) per gallon = .38 cups or around half a cup max or about 2 cups in 5 gallons max.

0.5 to 0.75% molasses by volume per gallon = 1.28 to 1.92 tablespoons per gallon. 0.75% is the maximum I use. It is a good bacterial and fungal food.

0.063% fish hydrolysate by volume per gallon = 0.16 tablespoon = 0.479 teaspoons or half a teaspoon

0.25% (max) kelpmeal by volume per gallon = 0.64 tablespoon or half a tablespoon

In our brewer, we use:

  • 1 heaping cup of compost (approx. 1 1/4 cups)
  • 1/2 cup of our foods (proprietary blend comprised of sulfate of potashmagnesia, feather meal, soymeal, cottonseed meal, mycorrhizal, kelp, and alfalfa meal)
  • 1 T. of organic alfalfa meal

We use volume instead of weight as a measure for our compost, as weights will fluctuate based on moisture content of the compost. We also don't use molasses because it is difficult to package and ship and also creates bacterial blooms, rather than slow growth of organisms, which may rapidly lower the dissolved oxygen levels in your brewer. However, it is a perfectly acceptable food substrate that tends to feed the bacteria in your tea. With all these ingredients, it is much better to start using less foods rather than more. If not looking at your tea through a microscope, I would use a recipe that has been tested and err on the side of too little foods, rather than too much.

Another thing to consider is that you want to maximize your biological diversity in your finished compost tea. We use 3 types of compost in our food kits:

Alaska Humus (brought down from Alaska, contains excellent biological activity and diversity, see www.alaskahumus.com or www.denaligold.us for more information)

Vermicompost (Woody materials, vegetable food scraps, cardboard, and newspaper that has been composted by worms.) I recommend this material over thermal compost for people who like to make their own compost, as vermicompost tends to be the most consistent material since the worms take care of the composting process for you)

Fungal compost that is mostly comprised of woody materials. We add food resources for the fungi and strive for the highest active and total fungal content we can achieve.

Brewing Temperatures:

There are a couple of schools of thought regarding brewing temperatures. One is that since the microbes in the tea will grow and reproduce most efficiently at 68-70˚F., this is the temperature at which you should brew your tea, regardless of the current soil or air temperature where you'll be applying the tea. The theory is that since you are using the shotgun approach to growing microbes, whatever microbes are unable to adapt to the conditions will either die or go dormant, becoming food resources for the other microbes in the soil. Since soil and air temperatures will change throughout the seasons and even from day to night, these organisms are highly adaptable and you will get your best results with this approach.

Another theory, and one that Dr. Ingham subscribes to, is that you want to brew at the ambient temperature you will be applying the tea. Therefore, if you are applying your tea as a soil drench on 60 degree soil, you'll want to brew at 60 degrees. You may need to extend your brewing cycle a bit for the colder temperatures, but this method will select for the organisms that will be most successful at the current temperatures in your soil and you won't suffer as much organism loss.

I believe we need much more research to determine the most effective brewing temperatures for AACT. However, since I haven't seen conclusive data either way, I tend to lean towards brewing at ambient temperatures, though this requires a bit more knowledge about your brewer and brewing cycle, as you will need to adjust your brewing time based on the temperature.

Application:

AACT can be applied in a variety of ways. One benefit of AACT is that it can't be over-applied, as it is comprised of beneficial biology and any biology that cannot survive will just go dormant or die and become food for other microbes.

Typical application rates are 20 gallons/acre for soil drenches and 5 gallons/acre for foliar applications up to 5 feet in height. Water is merely a carrier, so the tea can be mixed at ratios up to 5:1, water to tea, in order to get an even application across your property.

Depending on the size of the area you're spraying, you can use anything from a watering can to a backpack sprayer or larger. Make sure to avoid any pumps with an impellor or pump where the tea is being sent through something that could shred the fungi. Many people use the handheld pump sprayers or a pump backpack sprayer. These have been tested to not damage the biology, provided you don't over pump and hold the nozzle too close to the surface of the plant.

Make sure there is not a 90 degree angle in your nozzle tip. You can only use a hose-end sprayer if you don't have chlorine in your water supply. Think about the passage that the organisms will take from the brewer to the leaf surface of your plant and be as gentle as possible.

Other resources for information on compost tea are:

  • Keep It Simple, Inc. – My company which produces compost tea brewers, composts, and other biological amendments (humic acids, seaweed, etc..) www.kisorganics.com
  • Soil Food Web, Inc. – Soil Testing labs established by Dr. Elaine Ingham. Check out the “About Us” section and click on “Sustainable Approach” for more information on compost teas and the soil food web. You can also purchase “The Compost Tea Brewing Manual” by Dr. Ingham through this site. www.soilfoodweb.com
  • Microbe Organics – Tim Wilson in Canada has a site that is more focused on the microscopic aspects of compost teas. You can view his microscope work and also purchase his DVD if you plan on looking at your tea under a microscope. www.microbeorganics.com
  • Teaming with Microbes – Excellent book by Jeff Lowenfels on organic gardening using beneficial microbes. I highly recommend this book to everyone, you won't be disappointed! We have it available at a very competitive price on our website, when ordering other products.

Since this is a relatively new technology, there is a constant stream of new research and information relating to aerated compost teas and biological gardening practices. It's also important to test your soil and evaluate your garden or pumpkin patch to determine what deficiencies may exist.