Any experience with 'Soil Soup'?

JillH(z5 seMI)November 3, 2003

I attended a soil seminar this past weekend (hosted by our county extension/master gardener program) and heard a very intriguing endorsement of a new method of making compost tea. According to the speaker, a self-described "former composting addict," researchers have discovered that the microbial benefits of compost tea are heightened considerably--as much as 1000x--by aerating the tea for 24 hours. Thus treated, the tea can be applied to the ground before planting or as a foliar feed on the growing plants, and you won't need to use any other compost or fertilizer--just some fall & winter mulch. This means no more making and scrounging tons of compost. (Incidentally, our speaker was not a salesperson--just a soil guy giving us general overview of recent findings in soil science).

The catch is, you can't just use a fish tank bubbler or even multiple fish tank bubblers to aerate this tea, which I guess some people are doing. Researchers have found that you need an industrial pump to aerate the liquid sufficiently and encourage all the good stuff to grow in quantity. Currently, there is at least one company producing these pumps, the Soil Soup folks. (They have a website. I don't know the address but you can just google Soil Soup and you'll get it). Their cheapest package is somewhere around $330--not outrageous, but I'm certainly not going to plunk any money down until I hear lots more positive buzz on this.

I did a quick search and didn't find any threads on this stuff over on the soil forum, perhaps because the price puts it a bit out of the reach of the casual experimenter. And it's a new thing. So, I'm wondering if any market gardeners on this forum have used this product or heard anything about its efficacy?


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Some of the claims made don't seem to be scientifically sound to me. I believe there is some merit in aerating compost tea. I believe that in a controled and regulated situation it may have billions of times more benefits than regular old compost tea. I believe that if I were to do this in my backyard it wouldn't be under lab conditions. If making compost is hard work for you than making compost tea isn't gonna be any easier. There is the easy way to compost (toss it in the corner or bury it where you need it) but it just isn't the pretty way. Making compost tea can be quite messy. About the method of aeration. If an aquarium air pump can put enough oxygen into water to supply a school of fish it darn sure can supply a colony of bacteria and protozoans. Oxygen is oxygen - water will only hold so much before it becomes foam or vapor - it doesn't matter how the oxygen gets into the tea, you could sit there with a soda straw and blow bubbles all day if you wanted, you can only put so much oxygen into the liquid and you would only need an idustrial pump if you were doing industrial loads of tea.

Keep in mind that there is plenty of scientific literature stating the foliar feeding doesn't work - now, I myself have seen plants turn around after spraying fertilizer on their leaves but this was in my garden with no controls or measuring apparatus so I have no idea if the foliar feeding did the trick. I question how spraying aerated compost tea on the surface promotes deep root growth? But I would make home brew oxygenated compost tea and use it when I had time - but in my case just plain ol compost works wonders.

    Bookmark   November 4, 2003 at 4:10PM
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JillH(z5 seMI)

Yep, it makes sense to me that oxygen is oxygen, no matter how you get it in. I understood from the seminar that it wasn't that fish bubblers don't work at all--just that they don't seem to work as well as these commercially marketed pumps do by keeping the good critters multiplying rapidly. (This measurement, I understand, is based upon lab analysis of the numbers of beneficial lifeforms in the tea). I'd love to hear firsthand about positive results from fish bubblers or jacuzzi tub pumps--something I could get cheap.

Hope it doesn't sound like I am looking to replace compost. I've spent this month collecting/chopping/piling up greens and browns for mulch & compost, & negotiating with my local city gov't to have them drop off many, many loads of chopped leaves for making leaf mold. I love the stuff. I'm just wondering if I am relying too much on compost alone & perhaps ought to incorporate the application of compost tea into my farming. I don't mind the mess of making it--I just don't think of doing it.

Obviously, I don't know much about compost tea and I could be very wrong here, but it sounds to me as if compost tea may work differently than compost; compost improves soil fertility & tilth through the addition of humus & nutrients to the soil, while compost tea encourages plant health by introducing live biota to the soil & plant which help to suppress disease. Of course, they both encourage healthy plant growth. Does that sound right?

I do get powdery mildew and other fungal diseases, especially in our humid late July & August, & it sounds like compost tea could help me out there. As far as I understand, directly applying the tea to the soil or foliar feeding the "soil soup" (or homemade aerated compost tea) doesn't act as a fertilizer--rather, it contains "good" biota which act to suppress disease, both fungal and bacterial (depending upon the composition of the compost used) on the plant.

    Bookmark   November 4, 2003 at 9:39PM
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Odd that no one else wants a part of this conversation.

I think the claims about introducing beneficial live biota to the soil and plants would be true but maybe a bit exaggerated. I don't see how the soup could cure a fungal infection with one application since the live biota would die within a few hours (the soup would dry out) and the fungal infection outlasts wind and rain and watering with or without fertilizers. I don't have a huge powdery mildew problem so I have no way to test this out. I do have a soil fertility problem so I will consider any method to improve on that front.

I just think that the average gardener would only use a limited amount of soup and that could be satisfied with a large bucket and a fish tank airpump and bubblestone. Remember you dillute this stuff quite a bit. Also remember that it only "lives" for about 12 hours after you mix it up. If you're like me you don't have hours each day to spend fertilizing. I'm lucky if I get 4 hours on one weekend day to work in the garden - so I need things in smaller supplies. Now my yard could stand to have a full time gardener and lots of compost tea to drink all day but that will never happen.

    Bookmark   November 5, 2003 at 10:16AM
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annebert(6b/7a MD)

I believe the claims are valid. What you're doing with aerated compost tea is growing a concentrated population of beneficial bacteria from compost in a way very similar to how microbiologists grow bacteria in the lab (and I should know, because I did that for years). If you douse fungus-infected plants with this stuff, the beneficial bacteria will out-compete them or kill them, whatever their mechanism of action is.

I also think the soil soup pump is a scam, and a fishtank pump will work just fine. If you could also add agitation, that would help - but doing a smaller volume that can be well-aerated by your pump should work well.

There is tons of discussion on this issue in other fora - try soil and compost.

    Bookmark   November 7, 2003 at 8:59PM
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Those of you with powdery mildew--I have success with pouring (but ideally you could spray) diluted milk on the leaves of your plants. Yes, it does come back some when conditions are rainy (but then your milk spray will wash off anyway) so you have to reapply. It keeps plants producing.

I just use whatever milk has not been finished at dinner and dilute, or milk that has gone bad. If nothing has powdery mildew and the cats and chickens have had enough, I throw it on the compost for the microbial goodies that it is supposed to provide.

    Bookmark   November 8, 2003 at 7:57PM
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david52 Zone 6

Just browsing by, but can add 2 ¢ worth on airation, my background is in fish farming so we had to deal with it. You guys are right, this is creating a bacterial soup that is more concentrated than normal by the addition of oxygen and, probably, the release of metabolic wastes (eg ammonia) through physical agitation and introduction of excaping air bubbles.
Any thing that blows air will work, you would want something with an electric motor designed to run continuously for 12-24 hours, like aquarium pumps or an industrial fan, or perhaps something like a shop vac with the hoses reversed, with the nozzle at the bottom of the container.
Anyway, I'm sure that a growth curve of the bacteria population would be exponental for a while, then start to taper off as some other limiting factor other than oxygen enters the equation. that would only be an issue if this was done on a large scale. Trying it out with a bucket and an aquarium pump would be easy.

    Bookmark   November 10, 2003 at 12:15PM
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Demeter(z6 NJ)

There has been lots of discussion about aerated compost teas over on the Soil, Compost and Mulch forum, ranging from people with the buckets and aquarium airstones to commercial scale setups. Perhaps you might want to check in over there?

    Bookmark   November 10, 2003 at 5:42PM
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robbins(z5/6 MO)

Check with the compost tea digest forum on I think yahoo - there is a lot of info - also do a Google search on Elaine Ingham or Soil Web. The Soil Soup tea makers make a lot of bacteria, but no fungi - ok for some things, but .... There are quite a lot of tea makers out there - we are using Alaska Giant and making 100 gallon batches at a time. Not bad mess wise. There is a ton of info and research reportings if you get looking. Good luck.

    Bookmark   November 12, 2003 at 10:09AM
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juniorballoon(Z8a WA)

There are bacteria, or was it a fungus, can't remember which, that is in compost that will kill fungus' that do attack garden plants. It is called something like Actinomides. I'll try to get the right name and more info.

I read about it because my compost pile was steaming one daya nd I cut into it and saw a whitish powdery substance that I thought was ash. Turns out it was these little buggers.


    Bookmark   November 12, 2003 at 3:09PM
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spartangardener(z4 MN)

Looking at the soil soup website, it's not that it's just an aeration pump. Their "bioblender" both stirs and aerates the mixture. They are definitely not the only company making suitable equipment, but they're probably right that a fish tank bubbler is not as effective. Oxygen transfer to water is all about how much surface area exists between the water and the air relative to the total volume of water. If you're able to produce twice as many bubbles of the same size with pump a v. pump b, you get a higher dissolved oxygen concentration with pump a. (There is an upper limit to this enhancement, but you likely won't reach it with a fish tank bubbler.) If you include stirring in addition to just aeration, you likely increase the number of bubbles and foam (and dissolved oxygen) compared to what you get with aeration alone because there are chemicals dissolved from the compost and released by the bacteria that act to stabilize the foam. If you think of the tank with just a bubbler, most of the liquid in the tank is not in contact with a bubble surface at any given instant in time. The mixing improves that.

You have several options:
1) Add a mixer to David's idea.
2) Pump the soup continuously from the bucket with the compost "tea bag" over a nearly vertical flat surface so that it flows down the flat surface in a thin film and back into the bucket like those "zen mood fountains." If the film is thin enough and if it covers a sufficiently large surface area, you'll get good aeration of the water. Evaporation will be a concern, though, so you'll need to either have it in an enclosed space to control the humidity or watch the water level.
3) Pump the soup continuously through a piece of window screen so that the soup is in droplets. Now at any given instand in time, the distance between the water molecules furthest away from the air-water interface will be much shorter than it is in the bubbler-aerated system, so the oxygen has a shorter distance to travel. Same idea as thin film above, with same concerns about evaporation.

    Bookmark   November 23, 2003 at 9:04PM
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Ok, I get it,, but my question is just how big is your garden? My time is limited, my yard is small, you only need about a gallon of this soup anyway (remember you dilute it quite a bit) - so why would I need an industrial sized machine to crank out vats of soilsoup? I can rig up a 5 gallon bucket with a wand type aquarium bubbler so that the whole area is agitated for next to nothing. I need to spend the few hours I've got gardening not messing with a machine to make soilsoup.

    Bookmark   November 24, 2003 at 12:24PM
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flowermanoat(Z9, Central.CA)

It's not reasonable that a pint or a gallon or a hundred gallons of compost tea, containing by weight, perhaps, one or two or three percent of microorganisms would replace tons of organic matter. A clear violation of the law "Conservation of Matter", usually discussed in the first lesson of Chemistry 101. Where's the N the P and the K going to come from?

I practice no-till and keep my acre garden under permanent mulch supplied by a full-time maintenance gardener at at least a rate of a ton every couple of weeks. I'm sure that a lot of fine compost tea gets leached out of that. And it is a continuous process, easy to maintain because all I need to do is keep adding mulch. No tanks, pumps, stirring, spraying, etc., required and I can give my time and attention to planting, harvesting and selling--things that really need to be done.

    Bookmark   December 25, 2003 at 2:41PM
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mycarbumps(Zone 6b E.TN)

my background is in hydroponics and i am mostly self taught but there are lots of things you could do to increase the # of microbes in your tea. as for airating the tea- you would be doing something important to hydroponics, increasing the D/O (disolved oxygen) all you need to do this is break the surface tension with a bubbler or a water-fall or anything that disturbs the water especally on the top. if you want more info look up "disolved oxygen hydroponics" on google. good luck ~Ryan

Here is a link that might be useful: some of my hydroponic systems

    Bookmark   January 6, 2004 at 10:26PM
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wasabi_(Z6a WesternNC)

IÂm having a little trouble visualizing whirled peas doing calisthenics, but hope this topic continues to get attention...I find it interesting and compelling.

Obviously tea will not take the place of building good soil, but used to enrich and inoculate micro-herd growth and to help deter disease (through vitality) it makes sense. It seems an especially good fit with vermicomposting, as the worm castings are naturally rich in microbes.

As I understand it the oxygenation, however achieved, encourages aerobic bio-growth of the good guys which is used to inoculate the plants via foliar feeding and/or root soak. (as opposed to the anaerobic stuff that can actually be toxic or detrimental to the plants)

Has anyone investigated the venturi approach using a water pump?
Anyone have any suggestions for good recipes of easy to obtain ingredients?


(visualize whirrled peas doing calesthentics)

    Bookmark   January 28, 2004 at 5:28PM
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larry_c(z6 Stl. Mo.)

"Search Just the Soil Forum
Search results for: compost tea
There were 47 matches."

We have had many discussions about this project over in the " Soil,Compost and Mulch" forum.

I tried it last year (for the first time) and I was very pleased with the additional nutriments that it provided.That is all that I view it addition..not a replacement for the compost or fertilizer. This liquid is merely a faster way to get the nutriments into the soil for me. I use a 35 gallon Wally World trash can ( $ 3.50) and two 20 gallon fish tank bubblers. I had more tomatoes than any other year. The plants grew so fast that I am going to plant fewer starts and clone from them very two weeks.
The above link is a basic tutorial on making compost tea.
This link contains extensive information on compost tea.

"Compost tea is used for two reasons: To inoculate microbial life into the soil or onto the foliage of plants, and to add soluble nutrients to the foliage or to the soil to feed the organisms and the plants present." Crazy Larry

    Bookmark   February 15, 2004 at 2:00PM
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kissyfur(zone 9b)

Hello everyone, I just found this thread. I have a little experience with a home made aerated compost tea maker too.
I have a rectangular rubbermaid bucket,a large aquarium pump with 2 tube hook ups, and some 96 cent tubing to run 2 cheap bubble tubes that run all the way accross the tub twice so all area is covered.(The tubes are sold as bubble wall)and I poked more holes in them, used a T connector so I could hook tubing on both sides of the bubble tubes.
I run it an hour with water more than 3/4 full to let any chlorine bubble off.add GOOD black compost-fresh with lots of bacteria in it loose-ly about 8 cups or so.a couple handfuls of alfalfa pellets for nitrogen,and about 1 oz mollasses,i'm using the sulphered kind, i don't know which works better.Then stir carefully a few times a day to get the bacteria active.It's ready after about 3 days,If I can't use it then I feed it a bit more mollasses and stir.
I cup it out into a 2 gallon watering can,watering it down about half.I put the used compost around the roses and tomatoes and they really respond. It never stinks like regular compost tea, it actually smells yummy- ok,I haven't tasted it or anything. I REALLY WANT to experiment with worm castings,and wonder if blood meal or fish meal will make it better.Those of you that use the Evan's Alaskan Giant, I want to know what's in his starter! maybe the ingredients are on the back of the bag.He has some other ingredients too.Come on...What's in it? I've heard he uses something else to feed the brew instead of mollasses. Fess up.

    Bookmark   November 10, 2004 at 5:46PM
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FYI has anyone tried a product called Enki Super-oxygenating Watering Device? The product uses electrolysis to oxygenate water and sells for $100. This amounts to a watering can that is plugged into 110v. I stumbled into this while experimenting with something unrelated (a hydrogen generator). I use 8 blank stainless steel electric wall plate covers (99 cents each) to build anode and cathodes for electrolysis (alterneting positive and negitive plates). These are connected to a auto battery and produce H which bubbles off and O2 which clouds the water. I assume the O2 is - for the most part absorbed into the water until it reaches capacity. The interesting part is that after my well water is filtered by both an iron filter and water softener the plates connected to 12 volts turn the water red after just a few minutes. I believe this is due to the large amount of absorbed O2 and the small amout of remaining iron. This could be of interest to go a step further than the aquarium pump as the manufacture of the Enki system claims that their device will oxygenate water to 150% of capacity in 30 minutes. I would oxygenate the water with this method first before adding compost etc.

    Bookmark   April 2, 2008 at 4:59PM
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Belgianpup(Wa/Zone 7b)

Here's some info from ATTRA (National Sustainable Agriculture Information Service) on this subject.


Here is a link that might be useful: Notes on Compost Teas

    Bookmark   April 20, 2008 at 4:09PM
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