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I have read that you can get a tumbler type of composter and collect the "juices" from the composter. This is referred to as "compost tea".

Does anyone know what the real usage of this is? Some perusal of the Internet would suggest that holds some sort of magical qualities. How is it different from other organic fertilizers? Has anyone noticed significant differences when using it?

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I don't think that is what compost tea is. Compost tea is water you collect in a rain barrel or drum that you steep compost in. Wait, that's called manure tea. (I was going to answer this, but I turned it into a comment) –  Peter Turner Jun 10 '11 at 2:36
    
We have a compost barrel that sits on the lawn. The "juices" just drain on the grass. After a couple of years, I have not seen a significant increase in grass growth. Probably because it is still 'raw' (eg. Essentially black tea and coffee!). In other words I agree with Peter, If that is what compost tea is, then it doesn't seem very effective. –  winwaed Jun 10 '11 at 2:39
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Since there is some discussion on what "compost tea" is. Here is link on how to make it. dep.state.pa.us/dep/deputate/airwaste/wm/recycle/tea/tea1.htm –  wax eagle Jun 10 '11 at 11:48
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Wormeries have a sump underneath that collect liquid. There are claims that it's full of nutrients. I've used it mixed with water but not carried out any scientific tests of it's efficacy. I can say that where my wormery is stood the moss has grown very quickly where it has overflowed. –  StephenPaulger Jun 10 '11 at 14:46

4 Answers 4

It's less about any sort of "specialness" of the tea (which I've more often generated from a worm bin, such as this one from Amazon, that are designed to produce more liquid than solid compost), and more about the fact that you're taking kitchen and garden waste and producing something that can aid in the growth of your plants.

I'd expect that there would be quite a bit variation in the compost teas you would produce based on the differences in material that might be in your composter or worm bin from load to load.

There are a couple of things that are nice about the compost teas you produce on your own. The first is you know what's gone into it. There aren't always standards as to what exactly is an "organic" fertilizer and what can or can't go into the box. I've certainly heard certain brands being accused of using chemicals that are more questionable than what the labeling would lead you to believe.

The second this is that it's more convenient to use than the solids. Whenever I've produced it, quite a bit of it tends to end up on my indoor plants (my partner won't let me bring a shovel full of compost into the house, oddly enough). There's always places in my garden and yard where it's easier to pour some (diluted) tea than try to spread the solids. I've also read that application of the tea to the leaves gives some additional benefit to the plants, but I don't think I've noticed any effect or read anything scientifically verifying this claim.

I should also point out that, when you have a composter that sits directly on the ground, it's good to place this somewhere that the tea that leaches into the ground might be able to help any nearby plants. I've often tried to have a compost bin near the garden that I move from season to season in an attempt to build up soil nutrients in different places.

The bottom line is that it's not going to do any special magic. Its benefit comes from the fact that it's a wonderful byproduct of the composting process (something that every gardener should be doing as much as possible anyway) that's worth capturing if you can.

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The liquid that comes out of the bottom of your composter is more properly called "compost leachate". It may be nutrient rich, but may also be loaded with whatever pathogens were present in the feedstock. Use with care (probably not on edibles).

"Compost tea" is the product created by soaking finished compost in water for a period of time. There are various levels of sophistication that you can apply to achieve various levels of quality and benefits from your tea.

Teas contain nutrients, microbes, and fungi. The benefit of nutrient content is that it provides a liquid plant food with quickly soluble nutrients. The benefit of the microbes and fungi is that they may suppress some plant diseases when applied as a foliar feed (i.e. sprayed on the leaves).

Unfortunately "microbes" includes both beneficials and pathogens (like E. Coli). There is some controversy in the organic growing community about whether compost tea should be regulated like manure tea (which is regulated in the U.S. under the NOP). The science here is young and still trying to catch up.

The method and recipe used to brew the tea determine what it has in terms of nutrients microbes and fungi (aerated vs nonaerated, which "foods" were added to the brew -- sugars, seaweed, acids, salts, etc). Adding sugars will feed the microbes. Other ingredients will encourage fungi. Aeration will encourage certain microbes and fungi. Length of brew has an impact. Nonaerated compost that is brewed for a longer period will contain mostly anaerobic microbes since the aerobic microbes and fungi will have used up all the air in the liquid during the early part of the brew cycle.

The feedstock you use will have a huge impact on the effectiveness. If you start with weak compost you'll end up with weak tea. There's a lot of junk on the internet (especially where people are trying to sell you a system) that claims that compost tea has some kind of "magical" properties. But you basically get out what you put in.

If you're doing further research on compost tea, be careful which sources you choose to read. Most people selling "compost tea systems" seem to overstate the benefits (as expected). The scientific journals can be a little heavy to read. The University Extension services are pretty good sources, though they tend to oversimplify too often for my liking. This article at MOFGA is good, but is starting to be a bit dated. ATTRA tends to have accessible but comprehensive coverage of topics like compost tea.

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I haven't used it myself so I can't speak as to it's effectiveness, however I did find This page

By using compost tea to replace chemical-based fertilizers, pesticides, and fungicides, you can garden safer and be more protective of the environment. Compost tea:

Increases plant growth
Provides nutrients to plants and soil
Provides beneficial organisms
Helps to supress diseases
Replaces toxic garden chemicals

Evidently you spray it on?
Hope that helps!

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The below quote comes from this answer here on SE.

  • I make 5 gallons of compost tea each week (from late Spring to earlier Autumn "Fall") and apply the 5 gallon batch to the front garden one week, then the following week apply a new fresh 5 gallon batch to the back garden. I repeat that cycle for the period given previously. I have been doing this for 2 years now, and without question I have noticed a massive increase in worm activity eg lots of worm castings on the surface of the soil.

    • I spread the 5 gallons of Compost Tea via a watering-can over approx 1800ft² (170m²). Lawn area is about the same front & back for me. So one week the front lawn gets treated, then the following week the back lawn gets treated, repeat, repeat...

Additionally you may find this answer, to this question, How to make manure tea without e. coli, here on SE of some interest...

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