How Long Before Compost Tea Goes Bad?

by Annette
(Tacoma, Wa)

How long is compost tea good for before it should not be used on plants?

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Mar 16, 2012
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Use Compost Tea Within 24 Hours
by: Dave

Hi Annette,

I recommend using your compost tea within 24 hours of ending your brewing cycle. After that, it can go anaerobic quite quickly. If you're ever in doubt, try the following...

First, smell the tea. Does it smell bad? If so, don't use it on your award-winning plants. Dump it in your compost pile, mulch pile, or un-planted garden soil. Does it still smell sweet or non-odorous? Then it's probably okay to use, but the benefits may be reduced compared to if you had used it immediately upon brewing.

When you're brewing actively aerating compost tea (AACT), you're forcing a lot of oxygen into the system. This allows microbes to flourish beyond what they would normally do in conditions without the added oxygen. But then you remove the oxygen source and guess what has to happen? There is a significant microbial die-off because they simply can't sustain those levels without your aerator. So the sooner you can apply the tea to your soils/plants, the better chance you have of more microbes surviving. The goal is to get as diverse a brew as possible out onto your gardens and then let Nature select what She needs.

Second, run a little experiment. Brew your tea with your specific type of compost and your specific ingredients and then test it on a single plant. Wait 24 hours, observe the results. Then apply it to another plant and observe the results. Wait 24 hours and do it again. Continue to observe and learn how long a tea brewed with that specific compost and those ingredients lasts. There is such a wide variety of compost and microbe foods to use in your teas that there really isn't a black and white answer to this question. It's all about experimenting, observing, and adjusting your ingredients until you get the results you're after.

To help remove some of the guess work, I always advise using a lab-tested brewer, microbial foods, and high-quality compost. Check out our store for a variety of well proven products.

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Mar 17, 2012
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How long before compost tea goes bad?
by: Haydn (Perth - Australia)

Hi Guys,

As a big fan of AACT I found this article interesting, thank you.

When I first started using compost tea I was told that tea should be used within 6 hours. However, when I graphed (see below) the drop in oxygen levels I was horrified to see that it took less than 2 ½ minutes to move into the anaerobic zone (ie less than 6 ppm 02) from a starting point of 7.3 ppm O2. The drop in O2 to 5.7 ppm was linear. On reinstating the air supply the recovery in O2 levels was rapid, taking 2 ½mins to get back to 7.3 ppm but was plotted as a reverse exponential curve.

The brew size was 20 lts with a bacterial bias and was made with 50 ml molasses, 25 ml liquid kelp, 25 ml fish emulsion and 750 gms of worm castings. The sample was taken 14 hrs. into a 24 hr brew. Temperature was 23.7, pH 8.4, elevation 60 m above sea level and air supply rate at 24,000 lts per hour.

I’ve since stopped using AACT as foliar feed because of the time it spends in the back pack sprayer. As a soil drench I can get it on the ground within the 2 ½ mins and that certainly works!

compost tea oxygen levels



Mar 20, 2012
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2.5 Minutes!!!
by: Dave

Haydn,

I love your willingness to dive into this topic and experiment. It's incredible to learn about this drop-off in oxygen levels, however, I think it's going to be a hard sell trying to get people to apply their compost tea within 2.5 minutes of brewing.

Any takers?

I don't think I can even move that fast.

It would be interesting to determine how much oxygen is present in your soil and just how many microbes survive this initial transition from brew to soil. That's got to be a huge shock with a significant die-off, don't you agree? However, I do see your point in that the more living microbes you can get into your soils, the more likely (we hope) that your rates of survival will increase as well.

Ideally, you have a sprayer that has a built-in aerator so you have the option for foliar spraying without the worry of your brew going anaerobic. I think all of the systems that Peter from Compostwerks builds are of this style.

Thanks again for sharing this with us. Don't stop.

d

Mar 03, 2013
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how long before yor compost tea goes bad
by: 3''tea

i run my foliar feed for 1 week,then toss.i keep my bubbler going until its gone.
but smelling your tea if you think its going bad is a great idea, the smell should be like clean dirt. keep it organic!

Sep 24, 2013
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This is really good to know.
by: Anonymous

Now I do not need to waste my hard-earned vermicompost tea. It makes sense based on the reactions of my various soils and plants perspective to the distance where the brewer sits.

Jun 20, 2015
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Humtea
by: P Moon

I've done a lot of research on AACT and almost all say they need to be used within 4-6 hrs of removing aeration. It seems like in most cases you can keep it aerated and a long as it stays above 6mg/L it's still safe to use, and effective (of course the higher the dissolved oxygen it stays at the better, i.e. stronger and/or more effective). So how does Humtea get away with a 72 hr brew and then 2 weeks longevity with their tea's?

Aug 03, 2015
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compost tea PH of 3.5
by: Mark allen

Hi we have herd that when you make compost tea you can lower the PH to 3.5 /then you can bottle it and store it for a while is this true--getback to me mwallen@telus.net

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