Making Better Compost Teas
 By Tad Hussey
 As time has gone by, we are constantly learning more and refining our knowledge regarding aerated compost teas, nutrient teas, and other forms of liquid applications for soil and plant health. I see a lot of misinformation out on the internet and answer a lot of the same questions time and again, so I thought I would take the opportunity to address some of the more important topics in another article for people.

 1. Compost tea (ACT) is not a fertilizer or nutrient application. The purpose of making ACT is to add a diversity of beneficial aerobic organisms with good active and total biomass. These sets of organisms are archaea/bacteria, fungal hyphae, amoebae, and flagellates (with some ciliates). There are some nutrients in ACT, but they are not the main purpose of brewing ACT . This leads me to my next point.

2. You want a "balanced" tea when making ACT. I see recipes all over the internet for a fungal tea or a bacterial tea or a vegetative tea or flower tea. The main benefit of ACT is nutrient cycling. It's a shotgun approach. That means you're putting out all the beneficial microbes you can and letting the plant determine what it wants in the rhizosphere basses on its exudates. The plant is in control. If the plant wants more bacteria in the root zone it will put out more bacterial exudates. People get confused when they see the plant succession table and see that annuals prefer a bacterial soil so they think they want a bacterial tea. I contend that having the fungal spores/hyphae in the tea will serve to improve the quality of the tea and overall soil health.

3. Are vortex brewers are better than other designs? I hear this argument a lot but it doesn't hold water from a scientific perspective or in my own experience with direct microscopy. Yes, they look cool and it is possible to make a good tea using a vortex design. What ultimately affects the quality of your tea is the ability of your brewer to maintain appropriate levels of dissolved oxygen throughout the entire brew cycle. An air lift, whether a vortex is formed or not, is the most efficient way of raising dissolved oxygen, however many other designs are possible. The important thing is that the microbes are extracted from the compost/soil particulate and that there are no "dead zones" in the brewer where dissolved oxygen levels can drop or material can settle.

 4. Is it possible to brew perpetually? This is one of the most damaging claims I've heard from other brewer makers. The short answer is "no" and I'll explain why. When ACT is brewed for 24-36 hours (approximate times based on multiple variables), you're creating an unsustainable amount of aerobic microbial activity and diversity. At some point your tea "peaks." There's no way to tell for sure without a microscope but hopefully if you bought a brewer the manufacturer can give you guidelines based on your ambient air temp, compost/food inputs, elevation, etc..). Regardless, after this "peak" point the microbes will have eaten most of the food sources you added at the beginning of the brew cycle (molasses, microbe catalyst, kelp meal, alfalfa meal, etc...). When this occurs you will start to see monocultures over time, meaning one morphology (shape) of bacteria will dominate the tea, which will then be consumed by one type of flagellate. Your tea will fluctuate back and forth between bacteria and flagellates. The flagellates will eat all the bacteria until there's not enough food left and then die off, only for the bacteria to bloom again and repeat the cycle. Think of it as a Darwinian experiment inside your brewer where "survival of the fittest" dominates. Remember that ACT is a "shotgun approach" to increase nutrient cycling. Well over time that diversity completely disappears and you lose much of the benefit of ACT. Of course, the first thought then is "why can't I just add more compost or food sources to the brew after a certain time period?" This sounds like a great idea but in reality it just doesn't work. I've tried brewing over the period of a week on multiple occasions where I took a brewer to trade shows and pulled samples every 10 minutes throughout the day. I found it very difficult to manage the tea and the quality of the brew would vary wildly from hour to hour. I'm not saying it can't be done but I found even with intense monitoring with the microscope it was very challenging and I would have been much better off just throwing out the tea and starting over. Of course, these brews were just for demonstration purposes and not for actual plant or soil applications.

5. How do I judge a compost tea or compost tea brewer or product? This is a tough question and frankly the answer isn't what you'll want to hear. The only way to evaluate ACT is with direct microscopy. I've seen some companies that will show you some great before and after pictures, but these are typically done without any controls to determine efficacy. If they can't show you any real data or microscope work, then I wouldn't waste my time with what they have to say. There is a lot of snake oil salesmen in the ACT and organic gardening industry who can make any product sound amazing. While I can't say what is worth your money, I can tell you what I wouldn't buy.
 - Any company that dismisses the importance of science or microscopy for evaluating ACT. I've heard some pretty mystical claims out there that sound amazing but when I tested the products under a microscope I found them to be severely lacking. It may not hurt your soil or plants but isn't worth the money.

 - Any "instant compost tea" product or microbial product unless you are looking for a specific microbe to deal with a specific problem. There are some species of b. subtilis that can be applied to combat certain fungal pathogens, or predatory nematodes that can be quite effective. If they just say there's a million of this bacteria and a million of another,'s probably a waste of money. You will have way more beneficial microbes in ACT and they will be active versus these dormant products where the microorganisms are dormant or have been “put to sleep.”
 - Any finished compost tea that has been brewing for more than 36 hours at a hydro shop or nursery. We charge $5/gal at our farm and sell it 1 day a week on Saturdays during the growing season. Customers know this is the day they can get the tea because it has to be fresh. We also recommend they get it right before they leave the store and go home and immediately apply it.

 6.  ACT isn't expensive. It should cost anywhere from pennies to $10 max to buy compost tea supplies for a 5 gallon brewer. As you use larger brewers it gets even cheaper per gallon. I've seen some companies charge up to $75 to brew 1 batch using their ingredients. There's no secret formula or recipe. Don't fall victim to the marketing hype and put that money toward better use.

Well, I hope this article will help you in making more informed choices regarding ACT. If you have any questions, you can email me at