Not Your Grandma’s Tea: How to Make Compost Tea

Rebecca Flad    How To

When it comes to gardening, compost tea can truly be your best friend.

So what is compost tea?

Well in short, it is the utilization of water, compost and a food source to exponentially increase the amount of microbial activity. These microbes benefit the soil and in turn, benefit your plants. Additionally, it has been noted that compost tea can increase root growth and health. Even better, it can help ward off insects, bacteria and fungus that are not beneficial to your plants. This is done just as white blood cells overpower an infection or virus; the good bacteria in the tea out competes the harmful ones.

What goes into compost tea?

There are many different recipes floating around on the internet, most of which will work just fine. The most important thing to remember is that you are trying to multiply microorganisms like bacteria and fungi. These can be found in home compost, some bagged compost and vermicompost (compost using worms) or EWC (earth worm castings).

Now, to get the microbes to multiply they must have a food source. The most common food source is unsulphured blackstrap molasses but, you can also use fish hydrolysate, alfalfa meal and kelp meal to name a few.

Finally, the last component to ACT (aerated compost tea) is oxygen. This is where things can get expensive or relatively cheap based on how many gallons of tea you need.

Diluting Your Tea

Since water is merely a carrier of the microbes, diluting the tea is fine. I sometimes don’t dilute if I’m only going to need 5 gallons of water. However, if say I use 50 gallons of water I would dilute 10:1. That comes out to 5 gal of tea for 50 gallons of water.

Just remember, the more you dilute, the less microbes will get to each plant. While this is okay, you may want to use the tea more frequently if diluting heavily. Typically, I use diluted tea 1-2 times per week. Although, you can use it as much as you want just be careful that overwatering does not occur.

Choosing & Setting Up Your Air Pump

Now that you know how much tea you need to brew, you can decide on an air pump. Currently, I use an eco plus 3, which can be found at garden stores or online for about $40.

Once you’ve got an air pump to use, you will need the following to finish setting up your air pump to brew tea:

  • two 5 gallon buckets,
  • a few 5 gallon paint strainer bags,
  • some air stones or air diffusers
  • and tubing to attach the air stones to the pump.

*Please do not use standard aquarium pumps found at Walmart or Petco because they generally are not powerful enough to deliver the amount of oxygen needed.

Making Compost Tea

Now that we have everything setup and ready to go, we can start combining the ingredients and brewing our compost tea. For a 5 gallon brew, you will need the following ingredients:

  • 6 tbsp unsulphured blackstrap molasses
  • 1 cup Earth worm castings
  • ½ cup cow compost
  • ½ cup mushroom compost

Please note that the mushroom and cow compost are optional. These are not needed to create a nice brew. If you choose to leave those two ingredients out, use 2 cups of EWC rather than 1 cup.

adding water for compost tea

First, I like to add about 4 gallons of water to the 5 gallon bucket.

adding molasses to compost tea

This is followed by adding in the molasses. I mix that around by hand ensuring there isn’t any stuck to the bottom of the bucket.

aerating compost tea

Then, I drop in the air stones that are connected to the air pump and turn it on to begin aerating the mixture. After this, I add in the EWC and compost.

cover compost tea

Immediately after adding these, I put the paint strainer over the bucket to keep out any unwanted debris and bugs.

Now, you will let the tea brew for the next 12-48 hours. Usually, I brew mine about 20-24 hours. Additionally, I try to keep the temperature around 75 degrees Fahrenheit, so you may find brewing it indoors is best. Once you are done brewing, the tea should be used immediately. If you let it sit without any oxygen it may only last for a few hours.

Using Your Compost Tea

preparing to strain compost tea

Once the tea is finished brewing, I take off the paint strainer and put it inside the empty 5 gallon bucket.

straining compost tea

Then, I carefully pour the tea from the brewing bucket to the empty one to filter out any chunks of compost via the paint strainer.

After that, simply water into your garden or dilute and water into your garden.

top dressing from compost tea

BONUS: Use the leftover sludge as a top dressing for your plants.

Of course, we can’t forget the clean up either! After brewing, you should always thoroughly clean out the buckets, air stones and air lines. I usually use 3% hydrogen peroxide to do my cleaning.

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