Gardner's have been using actively aerated compost teas for decades. Even longer compost leachate's have been used for hundreds of years by farmers all over the world. The main difference in the two is that an AACT uses air to add oxygen to the water to help multiply microbes. Where as a leachate is typically just compost soaked in water. To be fair aerating compost teas hundreds of years ago would have proven to be difficult.
Since we live in times with air pumps, and electricity it makes sense to create actively aerated compost teas instead of leachates. I do see a lot of confusion when it comes to compost teas. Firstly a lot of people get a compost tea mixed up with a nutrient tea. A compost tea is designed to add microbes to your soil. That's it. It changes to a nutrient tea when you add in things that will bring in nutrients whether they be macro or micro. Lets say you are adding bat guano to your compost tea to add phosphorous to your plants. That changes how the tea will brew, and makes it a nutrient tea instead of a compost tea.
Nothing wrong with this train of thought, but there is a distinction that very few people acknowledge. Killing two birds with one stone isn't a bad things, but with the addition of nutrient inputs you are going to throw off the microbes ability to replicate properly. Without using a microscope for every brew, you will be just shooting in the dark.
This brings me to microscope use with compost teas. If you are making compost teas, and you don't use a microscope, then you really have zero idea how good or bad the tea is. I have seen over the years people try to hack the system by measuring dissolved oxygen, using the earthy smell as an indicator, or saying that a giant frothy head means its a good tea, but none of that is true like using a microscope. Once you have tuned your brewer and recipe to get replica-table results then there isn't a need to scope every brew. Until then, it's a crap shoot.
The most important thing to remember with compost teas is that if it doesn't smell earthy, but has a sour smell, then it is indeed bad and went anaerobic. Other than that you most likely won't make a “bad” tea, it just may not be as “good” as you think. I have personally used the above factors to measure the quality of compost teas, and by all means it showed that they were “good” compost teas. After scoping them I then saw that they were indeed “bad”. By “bad” I mean the microbial life in the tea was next to nothing. These teas would not do much for your soil, and you pretty much wasted your time.
What are you trying to achieve with a compost tea?
You need to figure out the reasoning of why you “feel” you need to add a compost tea to your garden. Is it to boost plant performance, and growth? Is it to diversify the microbial population in your soil? Is it to add nutrients to the soil? All of these are entirely different things, and your logic behind them will vary.
Personally I use to use compost teas once per week. Nothing wrong with that at all. They were brewed for microbial count, and scoped every time. I did add alfalfa meal, molasses, fish hydrolysate, and kelp to aid the production of microbes. I was not trying to add nutrients to the soil. I did this for many years, and scoped thousands of brews. Then I began working with Korean Natural farming inputs, and I relied less on compost teas.
Now over a decade later I only use 1 compost tea per cycle to help diversify my microbes. For me personally my plants have seen an overall improvement in the quality of the finished product, with less inputs by focusing on knf inputs more. The side benefit is brewing compost tea once per week gets old as fuck. When I was doing weekly brews I would brew a 55 gallon drum outdoor and multiple 5 gallon buckets indoors every week for years. I felt like I was a slave to the teas. My plants looked good, but they look even better now that I use both compost tea and knf inputs.
From my over a decade of experience I can see that both have their place in all organic gardens. As someone that is getting older, I tend to now want to gravitate toward the best results for the least amount of work. As you age your time becomes more precious, and you have acquired the knowledge to get max results the easiest way possible.
How often should I use compost teas?
Again, this is going to depend on what you are trying to achieve. From my personal experience plants will react favorably to a weekly dose of compost tea. That being said, I now only apply compost tea once per cycle, and rely way more on knf inputs to achieve optimum growth. I do believe it is important to diversify your microbial population so the addition of compost teas in any organic garden is a benefit when done properly. Experiment with your garden and log results to see what works best with your program. Then you can add compost tea directions to your home garden, or your commercial garden via a SOP.
What kind of compost tea brewer should I use?
I spent 2 years designing my own line of compost tea brewers to eventually stop producing and selling them. I learned a lot from all of those brews to get to that point. The major take away I got was if done properly a simple air stone brewer with plenty of air flow can brew a good tea. If you want to bump up the amount of know how to make a brewer, a pvc pipe inserted into the bucket with one or two pieces running horizontally on the bottom of your brewer with holes drilled into it can make the process of brewing tea even easier. The biggest thing is make sure to use enough air when brewing a tea. Don't skimp on the air pump. Then you will just have to buy a bigger air pump and have a tiny air pump sitting around doing nothing. You can always adjust the rate of air flow on a larger pump with a valve, where as you can't make a smaller pump more powerful.
vortex brewer designs seem to work for s lot of people, and there are plans and videos online to show you how to make those fairly easily. As always, experiment with any brewer you make, and try to get your brews down so well that you can replicate your results.
How long should I brew my compost tea for?
I can only speak form my experiences, but brewing a tea in 24 hours that is considered “high quality” doesn't happen very often. I have done a few, but they were brewed outside, in the summer when temps stayed warm all day and night. My go to for the average person in regards to a time frame is 36 to 48 hours. With the thousands of brews I have done this seems to be the sweet spot. If the air temps are cooler then a longer brew will be necessary.
How long is a compost tea good for?
This is a very misunderstood part of the compost tea story. I feel it stems from people selling tea at farmers markets, and hydro stores brewing up what they would want to call “compost tea”. Once your tea is brewed for 36 to 48 hours, and you have scoped it to verify that it is indeed the quality that you want, you need to use it in a couple of hours. After 6 to 8 hours I would consider it a “bad” tea and not use it.
Can't I just keep brewing it until I am ready to use it?
Hell to the no you can't. If you just brew longer because you timed it's application incorrectly you can easily make it go past the point of no return and end up being a “bad” tea, or even going anaerobic. After brewing and scoping a few teas you will know approximately the window when the tea will be finished, and you can plan accordingly. The microbes will eat up your food source, and then begin to die off if you brew to long.
What Kind of compost should I use in my tea?
This depends on if you want to go fungal dominant or bacterial dominant. For a balanced tea using multiple different sources of compost, including worm castings, is a good overall place to start. I would shy away from municipal waste compost personally. That's the free stuff that your city, or county gives away. It comes from yard waste in your area, and if you have ever seen what your neighbors spray on their lawns you would no it's a no go in an organic garden.
Should I be brewing for fungal dominance, or bacterial dominance?
As with everything it depends on the context of what you are wanting to Achieve. In my gardens I add wood chips, and use knf inputs that bring a fungal dominance to the soil. Our right out of the bag soil is made with compost that is mixed with forest waste to bring a fungal quality to the soil. So in these two instances I would brew for bacteria, amoebas, and flagalettes. You will most likely end up with some fungal activity in your compost teas, but for me I brew for the above microbial powerhouses.
The reason I brewed so many compost teas over the years was to increase nutrient cycling which would increase the amount of nutrients that are bioavailable to the plant. With knf inputs like lactic acid bacteria serum, and fermented fruit juices, they can do this same thing but amplified with very little effort. For diversification reason, and to keep a balanced soil microbial population, I do believe the use of some compost teas is beneficials to the long term performance of most any organic no-till living soil garden.
Can I just buy that ready made “tea” from my local hydro store?
You sure can if you like putting poop soup in your soil. Can the store verify all inputs that were used in the tea? Can the store show you a picture of the slide they took via their microscope to verify the tea was good? Do they continue to brew this tea for a day or two past the point of when it would be considered “finished” because not enough customers have come in to buy the tea? Do they thoroughly clean the brewer and all components between every brew? With a couple of hour window of when to harvest and use the tea, how can a hydro store verify that you are getting a tea worth anything? They can't, and it's only a sales gimmick meant to get you in the store, and take your money. I would not ever buy, or receive free, a tea from a hydro store that doesn't have the slightest fucking idea what they are doing. Just make it yourself.
Let's wrap up my rant with these nuggets
As with anything do your research, and experiment as much as possible. Try not to get stuck on YouTube for days at a time, and actually spend your time brewing teas first hand. If you only take away one thing from this entire compost tea rant let it be this; Buy a microscope so that you can learn how to properly brew a compost tea.
P.S. Stop buying ready made teas from hydro stores. Your plants don't like poop soup, I promise. I don't care what the store posts on Instagram, it's just a bad idea.
