Compost Tea and Hydroponics

hank_mili(Z11)January 16, 2006

I was wondering if anyone has tried using aerated compost tea as the nutrient solution for his or her hydroponic projects with any degree of success. This forum did have a couple of links related to compost tea but there has not been too much discussion on the subject.

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I have a worm farm and I feed them all kitchen waste and that makes very nice compost tea.

I tried using it by adding to my hydro reservoir and got some nasty pathogens and biota plugged up my pumping system.

I began to treat tea with H2O2 and the pathogens went away.

No noticeable difference in growth rate, plant taste, fruit mass......stopped using the tea in hydro and now put it on dirt garden where it is hugely successful.

    Bookmark   January 16, 2006 at 9:19AM
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Thanks for sharing your experience with CT (compost tea) Willard. I was speculating about what happens to the microbes after the CT is made.

The microbes either dies from lack of nutrients or lack of oxygen whichever comes first. The result as you have pointed out is a slimy mess.

I was thinking of ways to mitigate this problem.

1) The microbes can be killed (serialize the CT) and microbes removed or 2) maintain the microbes with food and oxygen to prevent them from dying.

Either way though the need for a protein skimmer to remove the DOC (dissolved organic compounds, including dead microbes) would be necessary.

Other questions related to CT, which I'll try to address in another thread.

1) What is the nutrient content of CT?

2) Can or should the CT be supplemented with inorganic nutrients and/or organic additives like humic/fulvic acids.

3) What about EC and pH?

Questions, Questions.

Here's a helpful site on how to make CT

    Bookmark   January 16, 2006 at 11:50PM
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1) What is the nutrient content of CT?

In the worm farm,

Spunky says hello, dry worm castings are 2-2-2 NPK ratio.

Tea is variable depending upon input, but is 3-1-1 when last measured. I send it to a lab who does the work.

    Bookmark   January 18, 2006 at 10:32AM
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Wow Willard that is very interesting information. Were they able to measure TDS concentration (PPM) or EC?

    Bookmark   January 20, 2006 at 12:02AM
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Hi Hank Mili

You have already heard that the tea is starved for oxygen, as it requires oxygen for the microbial population as well as the plant roots.

Passive hydro is still hydro, though.

Idea 1: Make your own soilless mix from peat and perlite at 1-1 ratio. Maybe add one cup of dolomite lime per cubic foot of mix. Put in well drained containers, and watch near hydro results as you water daily. As plants get larger, depending on container, you may wish to irrigate them automatically 2-3 times per day with the tea.

Concerned about food for the microbes, or about them eating all the plants' food? Go to you local feed store, buy some liquid molasses, and feed it to your plants with the tea, or alternate. The sugar feeds the microbes and it has lots of micronutrients.

Idea 2: watering coco coir daily should work as well. It looks like peat, but is more similar to rockwool. Organic feed methods work well in coco.

With either of these, you could opt for dry molasses and mix it with you medium. One teaspoon per gallon for the liquid. Don't know about the dry. Grocery store bought molasses is just as good, but it's cheaper at the feedstore!

Good Luck

    Bookmark   January 21, 2006 at 4:10PM
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Putting sugar of any kind in a mechanical pumping system will trash any bearing, impeller, orifice, emitter and etc.....

Not to mention crystallizing in the reservoir and on surfaces exposed to the sugar.

I'll add the nutrients and let the plant make the sugar.

Compost tea in a recirculating system does nothing once the biota are removed.

    Bookmark   January 24, 2006 at 9:55AM
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The sugar (molasses) is used to feed the microbes when making the tea. It should be depleted by the time the CT is ready for sterilization in say 2-3 days.

Once sterilized the dead microbes and other large organic compounds in the CT need to be removed (with a protein skimmer maybe?).

Hopefully what is left is "microbe excretions" in water or as we call it in hydro land "nutrient solution".

    Bookmark   January 25, 2006 at 12:30AM
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I'll measure TDS of next worm-farm tea and post results.

    Bookmark   January 25, 2006 at 7:45PM
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Worm farm tea is over 2000 ppm and off-scale for my meter.

I credit this to the fact that it is winter here and the throughput in the compost is much reduced in winter.

In summer, I add 20-50 lbs garden waste green stuff/week; in winter, it's lucky to be a pound or two. More oxidation, more water, more dilute tea......

    Bookmark   January 26, 2006 at 9:39AM
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2000+, that is much more than what I expected. That puts the EC around 2800+. I guess diluting the CT would be advisable. Great information thanks Willard.

Going to try to make some CT in the next few weeks myself to see if I can get similar results. Thanks again.

    Bookmark   January 27, 2006 at 3:26AM
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Hi Caveman what is the reasoning behind mixing peat with perlite since perlite is inert?

    Bookmark   January 27, 2006 at 3:38AM
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I don't know about granulated sugar, but I have used molasses in a reservoir with a mag-drive pump with no problems.

Hank Mili

The reason for the peat is that I am describing a passive hydro system that is hand or automatically watered at least once per day with compost tea. The perlite ensures plenty of oxygen. The peat holds moisture, and will allow the medium to act as soil where the microbes can continue to break down the organic stuff, obviating the protein skimmer.

What I am imagining is a large barrel or trash can where the CT is made. Drop a venturi powerhead in there to move and aerate the tea. You will be stunned at how long an organic mixture will stay fresh this way. (at least one week) When it is time to water, dunk a can in and water the pots of perlite/peat, or use a sump pump, hose, and watering wand. (the latter is my personal choice)


    Bookmark   January 27, 2006 at 6:18PM
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hank_mili(Z11) I understand. Somehow I was thinking you were using the perlite to make the tea. Sorry.

My goal in starting this tread was to see if it was possible to make a pure nutrient solution from CT. I this context "pure nutrient solution" = sterilized CT with no microbes or large organic compounds in the solution. The idea is to use this processed CT as a substitute/replacement for normal inorganic hydroponic solutions.

Here are the steps that I think needs to be done to get to this "processed" CT.

1. Start making CT in the normal manner. Here is a good link for making CT:

Notes: Aeration is critical and giving some supplemental food sound like a good idea. Need to measure and record the TDS/EC several times during the "cooking" process to see when the TDS/EC reading starts to level off. This indicates the "food" is running out and/or the microbes are starting to die off.

2. Sterilization. At this point it is time to kill everything. The idea is to prevent anaerobic activity and to stabilize the nutrient concentration. Sterilization can be accomplished by heating or chemical treatment. H2O2 is a good way but I was going to try an ozone generator in an airlift bucket. On a previous experiment using plain tap water and this setup an ORP reading of 650 was possible. At this level sterilization is achieved.

3. Removing microbes/organic compounds. Short of a centrifuge I think a protein skimmer can be effectively used to remove the dead microbes and larger organic compounds. I think. This is the only piece I have not tried.

At the end of all this work is hopefully something useable.

    Bookmark   January 28, 2006 at 2:20AM
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Have any of you tried running a simple aerated system with the compost tea not a flood and drain or submersible pump type system? I have tomatoes going right now with sea kelp, alfalfa, and molasses and so far so good. I'm going to try something a little more potent.
thanks for the ideas guys...
Oh, take a look at the doctor dirt site. They have some good info on there. I hope that the link works okay.

Here is a link that might be useful: doctor dirt fertilizer info

    Bookmark   April 30, 2006 at 7:27AM
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Here's something for the lighter side.

Here is a link that might be useful:

    Bookmark   April 30, 2006 at 6:10PM
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I can't find any references to using a frequent-flow worm tea as a hydroponic fertilizer. Just set up your worm bins in a row to be automatically watered several times per day and collect the resulting "leachate" or "worm tea" for use as your liquid fertilizer for the hydroponic system. You would need to add more or less worm beds depending on the size of your system. The worms can be fed shredded vegetable and fruit waste collected (probably free) from local grocery stores and restaurants. Or grow your own worm food in the form of Comfrey which worms love and is fast growing and highly nutritious AND Organic.

    Bookmark   June 21, 2012 at 1:30PM
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I am glad there is interest in this aspect of "worm tea" and hydroponics. I have been experimenting with hydroponics for over 20 years, originally in a very controlled manner, weighing each powdered nutrient on a jeweler's scale, etc. etc. Then I prostituted myself by using Miracle Grow, Scott's and whatever was available, all with similar and might I say very excellent results. However it was all very chemical and very un-organic.

So, for the last 12 months, I have been producing Worm Tea (just pour 10 gallons water over your worm bin daily and collect the results) and watering my containerized patio garden with that and nothing else, no fertilizer, no nothing, with incredible health, growth and productivity of all my plants.

Then about 4 months ago, I set up a small automated hydroponic system in 6" PVC pipes fed entirely with the "worm tea" I described above. No other fertilizer has been added, and the plants are growing as if they had the exact nutrients they require. Results are really good, could not ask for better. You just have to understand that this type of worm tea sometimes has "particulates" in it and is not suitable for "emitters", "sprayers" and so on. Just keep the orifices in your hydroponic system to about 1/8" or larger and filter the intake. I really think that this variation on "worm tea hydroponics" can successfully make the leap from chemical and petroleum based fertilizer hydroponics to truly "organic hydroponics". We all just need to document this journey and communicate via this wonderful blog.


    Bookmark   December 20, 2012 at 8:53PM
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I did a trial last year with CT alone on a bubbler. I grew some basil with very good result (big and healthy leaves and high grow rate). But the fresh CT must diluted (1:1, do not use tap water. The chorine in the tap water can kill the micros) before being used as liquid nutrient. Sometime, I just mix the old one with the pure fresh one (because the old one has been depleted).
I did it without dumping the old ones for more than 4 months. They still grow fine. I still suggest to replace it every 2 weeks.

I am currently experimenting on strawberry. They are still babies. To make the solution as weak as possible and organic, I am using the water from a planted fish tank. Will post update when their root establish.

    Bookmark   April 18, 2013 at 11:54PM
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