Aerated compost tea for plant nursery productin

I read somewere that aerated compost tea is so much better than "normal" compost tea. I have a tiny backyard nursery and sell plants. I wonder how I can fertilize my plants in a sound way.
Compost tea would be a doable method. How is the setup for an aerated compost tea? What pumps are used (brand, something good sturdy preferably solar)? Which plants (we live in Australia)?
I have got nettle and Russian comfrey, yarrow unfortunately no horsetail. I could plant more borage. Any ideas suggestions?

Hi Angelika,

It's a bit discouraging that nobody's replied to your question in a month and a half. I have no hands-on experience with aerated compost teas yet, but the research and the claims I have read lead me to believe the topic deserves much more attention that it gets here on Permies.

I recommend you visit microbeorganics.com and just start reading. The site is full of useful information including compost tea recipes, building your own compost tea maker (sometimes referred to on the site as a bioreactor or a "microbulator"), or they'll sell you one if you prefer to buy. The author even has specific recommendations on pumps. There's a ton of info on the the whys and wherefores of aerated compost tea -- just about anything you might need to know.

As for what plants to use for you compost, I don't think they give specific recommendations, but they do say that you want your compost pile to be warm, but not hot. They goal is to have a highly diverse microbial population to start your tea with, and the heat of a hot pile will kill the many desirable bacteria that can't take the high temperature. They also recommend vermicompost as a great ingredient.

Powering your compost tea maker's pump with solar will probably be more expensive than you expect. You will have to plan on providing 50 watts continuously for at least 48 hours. That means a bank of batteries big enough to get you through interruptions in sunshine such as clouds and of course night! You can't just pause the batch and start up the next day either. Once the aerobic bacterial population has started to boom, their oxygen demand is constant and the population will crash very quickly if there's any interruption of the air supply. Brewing aerobic compost tea off grid is something I've thought about, but so far I don't have any idea how to make it practical.

Hope this helps.

Angelika: I've tried to do both. The aerated tea is definitely more difficult to make, and I did not see enough difference in results to warrant it for myself. I used a "waterfall" effect from a pond pump to get air, there's more than one way to skin that cat. Remember, cold water holds more O2 than warm/hot water, and there's a limit in any case, so aeration above a certain point is useless.

Here's my current method, which I bet will work for you: Get a 5 gallon bucket, and some 5 gallon paint strainer bags from Home Despot or your local DIY store. Put the strainer in the bucket, and pack with nettle clippings. Fill the bucket with water, let it ferment for 1-3 days, depending on the temp. You'll end up with a stinky solution with a Total Dissolved Solids (TDS) of around 2000 ppm, which is too strong for most plants. I pull the strainer bag, and dump the bucket into a 55 gallon drum, which I then fill up with water, and use this as my "tea". This is pretty dilute. For reference, if you go straight hydroponic (all nutrients in the water, none in the substrate) you aim for 1000-1200 ppm. So, consider how rich your potting mix is when planning your tea.

As far as horsetail goes, my understanding is that this is used to provide Si. If that's why you are using it, you can substitute composted or charred rice hulls in your mix, a much easier way to get it. You only need about 1 tbs per gallon, too much Si causes plant deformities and stunted growth.

I've also used kefir grains in my tea, since they thrive in anaerobic conditions, but here again, I did not see different results, so I don't do it anymore. I also stopped using compost, because my nettle plants are HUGE, and compost fines tend to block my drain for the tank.

My next step, which will have to wait till the nettles get big again, will be to brew the tea, dilute to 1000 ppm, and send a sample to the lab to see the levels of soluble nutrients. In a perfect world, you'd like to end up around 200N-30P-200K-180Ca-50Mg, but I'd be surprised if you get that kind of soluble Ca from tea.

One last thought: I'd bet the N form in tea is mostly ammonia. This means if you use it strong, you'll likely get ammonium toxicity (especially in cold weather), which shows up as downward-curled leaves. This is just conjecture until I get lab results, though. Too much urine does the same thing, FYI...

Don't rule out this tea as a revenue adder to your existing business. Sell it by the gallon.

Jim, it's good to hear from someone who's actually tried his hand at aerated compost tea. Sorry to hear that your results weren't encouraging. You are right that making a good aerated compost tea is more difficult. Still, I'd like to keep this thread on the topic of AERATED compost teas, since as I noted in my previous post, I feel the topic gets less attention at Permies than it warrants.

As I read your post, I see a very big difference in the thinking behind compost tea and aerated compost tea. You mentioned nutrients several times, which reflects the fact that most people think of compost tea (and compost for that matter) as an organic fertilizer -- a way to add nutrients to the soil. I.E., as a chemical amendment. In contrast, the primary purpose of applying AERATED compost tea is to modify the micro-ecologies of the soil and the root zones, leaves and stems of the plants.

Elaine Ingham, a huge advocate of aerated compost teas and one with serious research chops, contends that you won't find an actual shortage of silicon or nitrogen or any other plant nutrient anywhere you might want to grow food. The issue is not what is physically present but what is physiologically available to your plants. The key to understanding why aerated compost teas work is to realize that plants and microbes have co-evolved to achieve this physiological availability by extracting and modifying the minerals from the rocks and clay of the soil and from the air (N). After many eons, they are very, very good at it. The goal in using aerated compost tea is to reestablish those co-evolved microbe communities where they have been disrupted or destroyed by so many of the common practices of modern agriculture (particularly tilling, chemical fertilizers, fungicides and mono-cultures).

It's possible to fail utterly with aerated compost tea if your brewing doesn't create the right conditions for breeding the beneficial bacteria, protozoa and fungi which are the only measure of a successful aerated compost tea. Even if you get everything right and come out with a tea teeming with life, it can still take several applications over an extended period before the micro-ecology of your target site is noticeably improved.

Jim I would encourage you to try again. Persistence should pay off, not just in nutrient balance for you plants but in a better pH balance in the root zone and a lower incidence of disease organisms.

As for Wayne's comment, compost and compost tea may be a source of revenue if you have more than you can use yourself, but there are many logistic barriers to selling AERATED compost tea as a product. They stem from the fact that the life in the tea must remain viable until it is applied to the target site. You can't just store it on a shelf or load it into a truck like a bag of 20-20-20. It needs a constant supply of oxygen. I could see something like a lawn/garden/tree service though, where a truck with an aerating tank and sprayer is driven to the client's site and the tea applied on a fixed schedule (allowing the tea to be prepare in the days before it is needed).

you need to feed your microbes.

my recipe: 5 gallons finished compost. 1 lb raw sugar (or 2 cups of mollases). in 50 gal non-chlorinated water.

My setup: 1 55 gal plastic drum. 1 fish tank air pump with 2 airstones. 1 submersible pump connected to a ring of tubeing with holes

My process: dump all ingredients int the bucket, turn on the pumps, let it sit for 72 hours, strain and spray.

the compost process differs if i plan on spraying trees or the garden.

I appreciate Micky's astute comments on this thread, and agree fully with everything.

This is something I am very interested in as well.

As I read your post, I see a very big difference in the thinking behind compost tea and aerated compost tea. You mentioned nutrients several times, which reflects the fact that most people think of compost tea (and compost for that matter) as an organic fertilizer -- a way to add nutrients to the soil. I.E., as a chemical amendment. In contrast, the primary purpose of applying AERATED compost tea is to modify the micro-ecologies of the soil and the root zones, leaves and stems of the plants.

I agree. I read the book Teaming With Microbes, which details this method and why to use it, citing Elaine Ingham's work. I have not ordered my pump yet to do any of it myself, but it is an investment that I will make.

Hi Jim:

The aerated tea is definitely more difficult to make, and I did not see enough difference in results to warrant it for myself. I used a "waterfall" effect from a pond pump to get air, there's more than one way to skin that cat.

My guess, is that this was not enough oxygen, Jim. The one time I saw compost tea being made by people who really know what they are doing was at a Permablitz lead by Javan Bernakevitch and Gord Hiebert at the Darfield Earthship. The pump was strong enough that the water had a very 'active boil'. It was really, really moving a lot of air into the water. Getting this right is important.

It's possible to fail utterly with aerated compost tea if your brewing doesn't create the right conditions for breeding the beneficial bacteria, protozoa and fungi which are the only measure of a successful aerated compost tea.

This was stressed by the instructors and by the Teaming With Microbes book.

Excellent points being made here. However, I was answering in light of the poster's original question, i.e. how to fertilize nursery plants for sale.

I started in container production, one of the challenges is providing nutrients to a limited root mass. Fast-growing crops will use up what is stored in a one-gallon pot in as little as one month, hence the need for water-soluble nutrition. That's why, unless you get lucky and nail your ratios, you will frequently see deficiencies appear, or toxicity if you over-supply something. You can even get blockage, i.e. too much K blocks the absorption of Mg.

One approach is to make the potting soil richer, but once you get over an EC of about 4, most plants suffer salt stress, so you can't simply add more compost to the mix beyond a certain point.

There's a lot of baloney in the "organic" world (I hate that term, any compound with carbon is organic). I'll bet most of the people here know this, but plants cannot take up nutrients that are not in a water-soluble form. The reason we need the soil biota is to make the conversion from raw materials like manure into "chemical" form so the plant can use it. I wouldn't use CaNO3 in my garden, but for a potted plant with no way to send roots anywhere else, it provides nitrogen and calcium already in the form it needs to be for the plant to use it. Adding urea prills to your soil is chemically no different than peeing on it, except urine provides many more nutrients. This is also why nutrient-dense food can be grown with 3-part hydroponic formulas.

As for dissolved oxygen (DO2), unless you are injecting oxygen (from a tank), the most you can get at the temps we would consider normal is 8 ppm. More agitation will not get you more DO2, so the goal should be to get to 8 ppm and stay there, even as the micros reproduce. Unfortunately, I have not seen anyone measuring DO2 in their teas (yet). That's probably because a meter costs at least $400. If someone sends me a check, I'll be happy to run a series of experiments...

The other reason for agitation is to keep things suspended that would normally settle out. To really be scientific, we would brew the tea in a clear container, using known inputs (what bacteria and fungi are actually in that compost?) and known variables (what are my O2 levels?) Even using the same compost pile inputs, I've seen variability due to moisture content and time of year that radically changed the temperature profile, which we know changes the microflora.

I think we are still in the art phase with aerated compost teas, but I think container production will do just fine on non-aerated teas, based on my experience (which is still pretty limited).

Another issue is pH. When I start with my well water, the pH is 7.8. After brewing with molasses, the pH drops in 2-3 days to 3-5, depending on how much molasses I use. This is probably from lactic acid production, but without testing, I really don't know. I do know that watering container plants with water at a pH of 3 over time will give you Ca deficiency, which is ugly in tomato and pepper production.

Dang variables!

After doing some reading, it seems the method used to brew the tea is dependent on the end use, and there are some warnings.

Aerated (ACT) is about the same as non-aerated (NCT) when it comes to fungal pathogen suppression-

http://www.ncbi.nlm.nih.gov/pubmed/23456856

Neither tea should get "commercial nutrients" (what are those?) unless you like E. Coli and salmonella-

http://www.ncbi.nlm.nih.gov/pubmed/17477249

ACT is best for damping-off suppression-

http://www.ncbi.nlm.nih.gov/pubmed/18944450

Finally, there's this from Chalker-Scott:

http://puyallup.wsu.edu/wp-content/uploads/sites/403/2015/03/compost-tea-2.pdf

Unfortunately, the abstracts don't describe the brewing methods and materials...