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How To Make Compost Tea Step-by-Step Instructions

Once you learn how to make compost tea, you’ll create more lively soils, and as a result, grow much healthier plants. Using the instructions on this page, we’re confident that a well-brewed compost tea will soon become one of your greatest gardening assets.

Before we teach you how to make compost tea, we wanted to re-state one important thing. In our professional opinion, compost tea should only mean one thing: Actively Aerated Compost Tea or AACT. In order to make sense of this term, it’s easiest to describe what it is not. Please refer to our making compost tea page for the best explanation of what compost tea is not.

Okay, it’s time to start teaching you how to make compost tea.

The following brewing instructions will teach you how to brew a very basic compost tea. We will be using “The Basic, Starting-point, Bacterial Tea” recipe from Dr. Elaine Ingham’s The Compost Tea Brewing Manual. If you would like to learn how to make compost tea that is tailored to specific types of plants (e.g. lawns, annuals, perennials, trees), please see our page on compost tea recipes.

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Step 1 – Gather Your Goods

The first step in learning how to make compost tea is to gather all of your supplies and equipment. You will need the following:

  • 5-gallon bucket or pail
  • air pump
  • aeration tubing*
  • heater (optional)
  • compost tea bag (optional)
  • high-quality compost
  • microbe food (e.g. 1.6 oz. liquid black-strap molasses, 0.8 oz. soluble kelp, and 0.3 oz. fish emulsion)
  • 5 gallons of dechlorinated water

*Avoid using a basic aquarium aerator/bubbler, since they are usually not strong enough, and don’t provide enough oxygen to keep your brew aerobic.

If you don’t want to purchase a bunch of separate ingredients, we suggest you try a pre-made compost tea kit. These kits are great when you are first learning how to make compost tea, because they contain a balanced compost as well as all of the microbe foods.

Note – Please do not use any compost tea ingredients that contain preservatives or antibiotics. They will destroy your microbes, and defeat the purpose of making compost tea. If you are just learning how to make compost tea, we recommend that you read all of the labels on your ingredients very carefully.

Step 2 – Dechlorinate Water

We prefer to use distilled water in our brews, but when you are first learning how to make compost tea, just use tap water. Tap water is usually loaded with chlorine, which will kill some of your microbes, so we need to dechlorinate the water. This is quite simple. Just add the water to your 5-gallon brewer, and use the aerator to bubble water through it for a minimum of 20 minutes. This will cause the chlorine to be released as a gas.

There is also some concern about the chloromines in tap water. Unlike chlorine, chloromines don’t evaporate as easily. We recommend running your water through a carbon filter, or using distilled or reverse osmosis water. You can also add a small amount of humic acids (0.25 oz.) to your tea. Humic acids help to bind up the chloromines. Another way to neutralize the chloromines in your water is to add a small amount of powdered ascorbic acid (vitamin C).

Step 3 – Bag Compost

The third step in learning how to make compost tea, starts by placing your compost inside your compost tea bag. Tie the bag nice and tight, and place it into your dechlorinated water (turn your aerator off temporarily). Some people like to use a piece of a pantyhose for their compost tea bag, however, we find these to be too tightly knit, and tend to restrict some of the microbial movement. Thankfully, when you buy a compost tea kit, you’ll also get a compost tea bag.

If you are using a heater, now is the time to add it to the water and allow the temperature of the water to reach ideal levels. The microbes we are trying to grow are much happier with slightly warmer temperatures, so we like to use a heater to bring our water temperatures up to about 75 degrees Fahrenheit (approximately room temperature) prior to making compost tea. During the brewing process, temperatures should never exceed 100-110 degree Fahrenheit. Please know that the heater is not critical when you are first learning how to make compost tea.

Be sure to position your compost tea brewer in a location that is away from direct sunlight. Also, you may want to make sure its in a place where it can overflow. This tends to happen from time to time, especially if you are experimenting with new ingredients.

Update – April 2012 – We’re now brewing most of our tea without a bag. We simply place the compost, along with the microbes foods, in the water and allow them to move about freely.

Step 4 – Add Microbe Food

Now is the time to add your microbial food, and turn on the aerator again. You’ll notice that most of the foods stay on the surface of the water, but don’t fret, this is only temporary. Once the microbes start to move into the solution, these foods will start to be digested.

If you are just learning how to make compost tea, please don’t forget to check the time when you start your brewer. You’ll want to record it on a piece of paper, so you don’t forget. It will also help to calculate when to turn your brewer off.

Step 5 – Wait

Depending on the size of your brewer, you will have to wait 12-48 hours for your compost tea to be complete. In our case, we will wait 12 hours. If we were to wait much more than 12-14 hours, we would need to add more food for the microbes, and probably a little more compost. With the specific brewer we are using, the microbial population tends to peak between 11-13 hours of brewing, so to maximize the microbes in our finished tea, we want to stop the brewing during that window of time.

Don’t forget to check your tea every couple hours (assuming you’re not brewing throughout the night – which we often do). When we were initially learning how to make compost tea, we checked our
brews almost every hour because we were
so excited.

You’ll want to check on your tea for a couple reasons. The first, is to check that the brew isn’t bubbling over the sides of your container, and making a mess of your brewing area. We’ve had this happen far too often and it’s not pretty. The second reason, is to check that your tea hasn’t gone anaerobic. Your tea should always have an “earthy” odor. If you find that your tea has an offensive odor, please stop your brew and discard the tea. Avoid throwing this tea on your garden soil or compost pile.

The presence of foam on the surface of your tea usually indicates that there are free proteins, amino acids or carbohydrates present. If the foaming gets too excessive, you can suppress it using organic surfactants, such as vegetable oil (not olive or canola oil!). Flaxseed oil works well.

Step 6 – Turn Off and Strain

How to Make Compost Tea - Step 5 After waiting the desired amount of time (12-48 hours), please turn off your brewer.

You now have to make a decision – How will you use your new batch of compost tea? Will you use it as a soil drench or a foliar application?

If using it as a soil drench, you can choose to dilute the tea or apply it full strength. Please note – It is very very hard to over apply compost tea (assuming it is brewed correctly). If you’re going to apply it as a soil drench, there is no need to strain your tea prior to applying it. However, if you are going to using it in a foliar application, we highly recommend straining your tea prior to putting it through your sprayer. Try to use a strainer with a 400 micrometer mesh or screen (e.g. paint strainer). This size mesh is big enough to allow the fungi and nematodes to flow through it, while trapping larger particulate matter that will eventually clog your sprayer. Avoid using socks or pillowcases, since their fibers are too tight.

Did you know that 5 gallons of compost tea can be diluted to cover approximately one acre of land, while still producing benefits? So if you’d like to cover more area with your one brew, please dilute it as needed. Just remember to use decholrinated water for your dilution as well.

Step 7 – Wash Equipment Immediately

Bioslime in compost tea brewer Step 7 in learning how to make compost tea is very important: wash your equipment! We like to do it right before we apply our tea, just to make sure we don’t forget.

During the brewing process, a variety of bio-slimes will build up inside your brewer. These will appear on your brewer walls, tubes, and especially, in any small crevices at the bottom of your brewer.

The image to the right shows a small amount of bio-slime on the side of the compost tea brewer; the pressure of the hose water isn’t even strong enough to remove it.

To clean these slimes while they are still wet, we recommend rinsing off all of the parts of your brewer (except the electric pump) with your garden hose. You may also need to use some elbow grease. If these slimes have been allowed to dry (shame on you!), you can use 3% hydrogen peroxide in water or a solution of 5% baking soda to remove them.

Step 8 – Apply Compost Tea

compost tea sprayer nozzle After learning how to make compost tea, now comes the fun part, applying it!

It is best to apply your compost tea immediately; however, it can still produce benefits if applied within 4-6 hours of removing the oxygen source. Some people wait up to 24 hours, but we don’t recommend that practice. It’s worth making the extra effort to ensure you’re able to apply it immediately.

If using a foliar application for your compost tea, please read the following

If you are using your compost tea as a foliar spray, you’ll want to make sure you avoid applying it in direct sunlight. Ultraviolet (UV) rays kill microbes, and you’re dealing with a huge population of them. If you can, you should apply your tea before 10 a.m. or after 3 p.m., when UV rays are weakest. If you are applying your tea as a soil drench, you don’t have to be as concerned with the affects of the sun.

If you are going to be foliar spraying your tea, you will want to make sure that the sprayer you are using is designed for compost tea. Many of the sprayers on the market, create too much pressure, and kill the microbes before they even make it to the plant surface. Sprayers should not exceed 70 pounds psi. There can also be an issue if the nozzle of the sprayer has a 90 degree bend in it. If so, the microbes hit this bend with so much force, that they can be damaged during application. Ideally, the nozzle will allow for a smooth, slightly-curved application (see example of an ideal nozzle in image).

It is also very important that you do not point the sprayer nozzle directly at the plant surfaces. This will cause the microbes to “splat” against the surfaces and possibly die. Instead, try to arch, or parachute, your application of tea onto the plant surfaces.

Step 9 – Relax and Enjoy

Finally, you’ve now learned how to brew compost tea, and it’s time to relax and enjoy all of its benefits.

To gain optimal benefits, we suggest you apply compost tea at least four times per year (e.g. 1x spring, 2x summer, 1x fall). However, if you are trying to overcome disease, you may need to apply compost tea every five to seven days. If your soils have ever been sprayed with pesticides, we recommend applying it more often.

If you have any further questions or comments, please write to us using our contact page.

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compost tea brewer

This is the only 12-hour Soil Food Web approved brewer in the world. It’s very easy to use and comes recommended by Dr. Elaine Ingham.

This is the same model that we started with 6 years ago for our backyard oasis.

To learn more, please visit our store.