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When I first married my wife, I was very disappointed by her great love for tea. And we’re even not talking about Green Tea or oolong. We’re not even talking about compost tea yet. We’re talking about herbal teas. Weedy-plant-water meant for humans. It didn’t sit well with me.
If I drank something, I wanted it to either taste great or be ultra-caffeinated. Herbal tea was neither of those things. It wasn’t until I matured a little bit that I realized how many useful things my body can get from tea. There are teas that will lower blood pressure, increase energy, stimulate your bowels, and so much more!
Herbal teas are one of the healthiest drinks for humans. It’s like drinking water with a nice little addition of flavor and health benefits. That’s exactly what compost tea is for plants: nutritional tea with added probiotics.
The preferred method of most gardeners seems to be making an aerated compost tea by using an air pump. However, since I’m about as cheap as possible, I decided to go the much cheaper (free) route and brew some anaerobic compost tea.
What Is Compost Tea?
Compost tea is pretty much exactly what it sounds like. It’s a “brewing” of finished compost in water for a day or two. Proponents of anaerobic compost teas claim that, during that time, the most valuable part of the compost, the beneficial microbes, are pulled into the water. These microbes, along with the nutrients in the water should, in theory, maximize the growth potential of your plants.
Compost tea has been shown to have several great attributes for your garden (and dozens more than gardeners claim to see).
Most notable benefits of compost tea:
- Disease Prevention for Plants and Soils
- Promotion of Microbial Diversity
- Reduction of Toxic Run-off From Commercial Fertilizers
- Increased Plant Production Due to Added Nutrients
- Balance of Acidic Soils
The 4 Types of Compost Tea
There are three different types of compost tea that people make. Each one of these is made by putting the main ingredient (compost of some sort) in water and letting it sit. However, there are differences:
Aerobic Compost Tea
Aerobic compost tea (properly called AACT or Actively Aerated Compost Tea) is the most commonly used and typically the most recommended type of compost tea. Aerobic here means “in the presence of oxygen” and refers to the fact that this tea is oxygenated throughout the steeping process. The most common way to accomplish this is by placing an aquarium pump in a bucket so as to circulate oxygen into the water. That way, when the compost is added to the water (inside a mesh or burlap bag), aerobic microbial life will be favored.
Anaerobic Compost Tea
Brewed without oxygen, Anaerobic compost tea has a lot in common with homemade bokashi bran and is a very viable option for those who want a simple (or lazy) way of making compost tea. However, you can’t have your cake and eat it too. Anaerobic compost tea has several distinct disadvantages which we’ll discuss later.
Anaerobic teas are typically split into two types based on the medium that was used to brew them: bacterial teas or bloom teas (a more fungal tea). Both have similar benefits. The type you choose to brew will affect the steps required and is usually dictated by what you have on hand. I typically make a bacterial compost tea, as it is easier to make and more in line with the compost I have available.
Manure tea is very similar to the above teas except that it is a bag of manure (instead of compost) that you steep in water. My opinion (and the opinion of most experts) is: don’t brew manure tea. The same magic that will cause all the beneficial components to mix with the water will also draw out all the pathogens in the manure.
The most common (and concerning) one is e.coli.E.coli is commonly found in manure and can lead to extreme sickness and/or death. So while I don’t recommend any compost tea be used on food plants, I would not recommend manure tea for anything at all.
Bokashi tea is the liquid that is drained from a bokashi bucket during the fermenting and composting process. It is incredibly rich in microbes and nutrients and can be added to plants and soil (provided that it is properly diluted first).
The Pro/Cons of Anaerobic Compost Tea
The main advantage of compost tea is the massive amount of microbes that you are able to add to the soil when you use it to water plants. Common sense tells us that the more microbes we can get (and the better than strain), the better the tea will be.
In this area, aerobic compost tea knocks the socks off of anaerobic tea. Aerating your compost tea gives beneficial microbes all the air they need to reproduce like crazy. Without adequate oxygen, your tea will go anaerobic. The microbes produced will be less beneficial and have more in common with fermentation bacteria (like those found in bokashi composting) than traditional composting microbes.
An additional advantage of vigorous aeration is that the churning of the water will literally knock the microbes off/out of the compost, into the water. As long as an adequate temperature is maintained (mildly warm), your tea will be chock full of the right little guys.
While you’ll find tons of people on the net who are willing to vilify anaerobic tea, the truth is that there is a minimal number of scientific studies that have been published on either aerobic or anaerobic tea. In most cases, the results are dictated more by what the compost medium was than by how it was brewed.
For example, brewing compost tea from items such as bark or spent mushrooms seems to be the most beneficial. For a more thorough (although dated) review of the subject, check out this paper.
The summation of the research seems to be along the lines of, “Compost tea has some mild benefits. Properly aerated compost tea is slightly more beneficial than the anaerobic variety.”
How to Make Anaerobic Compost Tea: 6 Steps
I hesitate to call this an anaerobic compost tea recipe, but I guess that’s what it is. Luckily, compost tea is about the simplest thing you can make. If you have been successful at creating compost, you’ll have no problem here.
Step 1. Fill a container with warm water
Don’t get too hung up on temperature. I typically use a 5-gallon bucket (or several if I want to make a large batch). I typically don’t use something larger than a 5-gallon bucket for two reasons: compost tea is heavy and big containers are obnoxious to move, and it’s better to use up your tea quickly to avoid it turning really nasty.
One thing to be aware of is that you need to be using dechlorinated water for maximum effect. If you collect rainwater or have a well, this will be a non-issue for you. Otherwise, you’ll need to remove chlorination to encourage maximal microbial growth.
Step 2. Mix in an easily-microbe-accessible food source
This is as easy as mixing in a simple carbohydrate such as sugar or molasses. I typically add a couple tablespoons to my bucket and mix it thoroughly.
Step 3. Add compost to a porous container
You’ll want something that water can flow in and out of. Common items you can use include things like a burlap sack, a pillowcase, or pantyhose. I typically use a burlap sack as it is durable and reusable indefinitely (as long as you rinse it out/dry it out). It doesn’t really matter if your item is very porous and some of the compost gets into your tea.
Step 4. Let your bucket sit for 24-48 hours
Anaerobic compost teas don’t smell great, so don’t be put off by the unique poopy-vomit smell (unless it gets really bad). The water will darken as time goes on, but longer isn’t always better. Within the first day or two, your tea will get as saturated as it is going to get. If you let it go too long, your microbes will run out of food and it will start to rot.
Step 5. Remove your sack of compost from the water
If you want to wring it out, wear rubber gloves. Your compost tea is now done and you can apply it directly to plant foliage (some people use a sprayer, but this is more common with aerobic teas) or to the ground. To get the maximum advantage for my soil I make sure all the microbes and nutrients go straight into the ground.
Step 6. Add your finished compost tea to non-food plants
I prefer to add anaerobic compost tea to plants that I won’t be eating. I add a small amount to shrubs, potted plants, etc.
Compost Tea FAQs
What should I use compost tea for and how often?
Compost Tea can be applied to your yard or garden every 2-4 weeks. During times of plant stress or disease, you may want to apply it more frequently.
If I am going to be applying compost tea to my garden (or plants that will be consumed by humans), I steer clear of anaerobic teas. If you want to give your food garden a boost, get an aerator and make some proper AACT.
Can I make compost tea with store bought compost?
In theory, yes. Bagged compost would make something that resembles compost tea. However, store-bought compost is hit or miss (quality-wise) and is notoriously low in microbial activity. You’ll have far better results if you use freshly finished or active compost, especially one that you have made on your own so you are aware of the ingredients.
What types compost should not be used for compost tea?
Fully decomposed hot compost is the compost of choice for creating compost tea. Don’t use compost that contains manure, meat products, etc. One of your main goals is microbial growth, and you don’t want an explosion of pathogenic growth as well.
This is less of an issue if you are adding the compost tea to the flowers in your front yard, but you’ll still want to be careful when handling the tea or keeping it around.
What should you do with the “used up” compost?
In a perfect world, your compost tea would contain all of the microbes and beneficial nutrients of the compost, leaving behind only a fibrous husk. The truth is, however, is actually much better. Your “spent” compost will have the same microbial concentration as the finished compost tea.
Because you have encouraged such an explosion of growth, it’s very probable that your compost is actually richer in beneficial microbes than when it when into the water. I typically reintroduce my compost to my pile with some added scraps to feed all the new microbes. Just be aware that you will need to work hard to keep your pile balances and aerobic if you’re introducing too many anaerobic bacteria.
At the end of the day, you better have some tea brewing! I can’t say that I have developed another green thumb or anything, but since I employed compost teas my garden plants seem more robust and healthy.
Be sure not to rely on compost tea exclusively, but use it as part of a whole soil/improvement plan for your garden. So get composting, get tilling, get brewing, and maximize your garden’s potential!
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