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Compost Tea

Compost Tea has become a very popular topic. The following is a quote from Fine Gardening (ref 2):

Gardeners all know compost is terrific stuff. But there’s something even better than plain old compost, and that’s compost tea. As the name implies, compost tea is made by steeping compost in water. It’s used as either a foliar spray or a soil drench, depending on where your plant has problems.

Why go to the extra trouble of brewing, straining, and spraying a tea rather than just working compost into the soil? There are several reasons. First, compost tea makes the benefits of compost go farther. What’s more, when sprayed on the leaves, compost tea helps suppress foliar diseases, increases the amount of nutrients available to the plant, and speeds the breakdown of toxins. Using compost tea has even been shown to increase the nutritional quality and improve the flavor of vegetables. If you’ve been applying compost to your soil only in the traditional way, you’re missing out on a whole host of benefits.

Let’s look at the facts.

Compost Tea

Aerated Compost Tea

What is Compost Tea?

This seems like a simple question, but it’s not. There is no clear definition of compost. Compost can be made from a large variety of materials, and each compost is different. If you make tea from two different types of compost you will get two different types of tea.

The nutrient content of each type of compost tea will be different.

One of the reported benefits of compost tea are the ‘microbes’. If we assume this to be true then is it not important to know which microbes are in the tea? It certainly is. The problem is that unless you have a fairly sophisticated lab you won’t know this. Home gardeners have no way to know which microbes are in their tea.

The microbe content of each type of tea will be different.

Tea can be made in two very different ways; aerobically and anaerobically. The term aerobic means that the tea is made in the presence of oxygen; you usually bubble air through the tea as it is brewing (see picture above). When tea is made anaerobically, it is made without added oxygen. You simply let the smelly sludge sit in a pail. The method used to make the tea is very important because microbes tend to favor one or other of these living conditions. They either like living with oxygen present or they prefer less oxygen. So the method you use to create the tea is very important to determine the type of microbes in the tea.

Aerobic soil bacteria inhabit soils that contain a lot of air; the light fluffy type of soil we all know to be good for plants. Anaerobic soil bacteria tend to live in wet, compacted clay type soils where there is little oxygen present – not the kind of soils we want. So why is it that many recipes for compost tea use the anaerobic method? That makes no sense and I can’t explain it.

There is also something called manure tea which is the same as compost tea except it is made from manure.

Bokashi composting is something completely different and is described in detail in Bokashi Composting Myths.

What Are the Benefits of Compost Tea?

Proponents of compost tea ascribe a wide range of benefits – see the above quote from Fine Gardening.

One thing is clear to me. If a product or gardening technique does everything under the sun, it is always too good to be true. When it sounds like snake oil, it probably is snake oil! Run for the hills.

There are a few main benefits that would be worth discussing. Compost tea is claimed to provide:

  • An increase in nutrients
  • A decrease in diseases
  • Additional microbes for the soil

A recent study compared ACT compost tea to using just compost and is described in Compost Tea – Does it Work?

Does Compost Tea Increase Nutrients?

To clarify the question it should be stated more clearly as; Does compost tea add more nutrients than compost alone? There is no doubt that compost tea adds nutrients. But does the process of making tea increase the level of nutrients compared to just using compost without brewing? If they both add the same amount of nutrients–why bother making tea?

If you think about it for 2 seconds you will realize that this is a silly notion. Think about what you are doing in making tea. You take a handful of compost and you put it in a bucket of water. Microbes take over and start digesting the compost.

Your original handful of compost had a certain amount of nitrogen, phosphorus and potassium. No matter what process you use, you will never increase the amount of these nutrients in a plastic bucket (except for some minor organics falling in an uncovered bucket). The microbes might breed and grow and digest things, but the total amount of nutrients remains the same. In fact it might actually be less since some of the nitrogen might be converted to ammonia which evaporates into the air.

What about the quoted statement above “compost tea makes the benefits of compost go farther “. The nutrient content (NPK fertilizer numbers) of say 500 ml of compost is 2.6 – 0.9 – 2 (average value for composted cattle manure; source Alberta Agriculture Department). If I now add this to a 5 gal pale (about 20 L), I still have the same ratio of nutrients, namely 2.6 – 0.9 – 24, but it is now diluted 40 times (500 ml to 20 L). The nutrient value of the tea is now 0.07 – 0.02 – 0.05. That is an extremely dilute fertilizer. For comparison human urine has a nutrient value of 11 – 1 – 2.5, that’s 160 times as much nitrogen as compost tea. Sure you can probably spread the tea over a larger area than a handful of compost, but if you do that the amount of nutrients added to the soil is  negligible – so why bother??

The fact is that making tea from compost does not increase the amount of nutrients. It does not make the compost ‘go further’. If you want to add nutrients to the garden just add the compost directly.

In the post, Compost Tea NPK Values, I have a closer look at the NPK values and what manufacturers of the tea and kits for making tea have to say about their products.

Will Compost Tea Decrease Diseases?

This topic has been evaluated extensively by Linda Chalker-Scott, Ph.D in reference #3. There are limited studies about disease reduction by compost tea, and the results are inconclusive.

The concept here is that the tea has a high concentration of microbes. When these are sprayed onto leaves they populate the surface of the leaves to such an extent that invading pathogenic microbes can’t take a hold. The good tea microbes out compete the potentially bad ones.

For this to work, the sprayed on microbes would need to colonize the leaves (ie live and breed on the leaves). This requires that the new environment, ie the leaf surface, has enough food for them and the oxygen levels are right for them.

Clearly, the oxygen levels would be high and so you can expect that anaerobic microbes would die out quickly. Anaerobic tea just won’t work.

The native microbes on plant surfaces are not well understood. The picture below shows an electron microscope image of a leaf surface showing the microbes present. There are anywhere from 1 t0 10 million microbes on each 1 square centimeter of plant. Nobody knows what happens when more microbes are sprayed onto the leaf. I can’t help wondering why the large number of naturally occurring microbes can’t out compete the potentially bad ones and yet the ones sprayed on in the tea will do this??

In summary, there is little scientific evidence to support the idea that compost tea solves disease problems.

Compost tea and disease control

Microbes on the surface of a leaf

 Photo Source: Gerd Innerebner and Roger Wepf/ETH Zurich

Does Compost Tea Add Microbes to the Soil?

There is no doubt this is true. You have a pail full of slimy microbes and if you spread it around the garden you are certainly adding microbes to the garden.

There is a new gardening  trend of adding microbes to the soil under the assumption that the soil ‘needs microbes’. I’ve looked at this myth in more detail in the post Soil Microbes. In summary; the soil already has lots of microbes and adding a bit of tea is not going to make much of a difference.

If you are interested in identifying the microbes in tea you should read this before buying a microscope and taking Dr. Ingham’s course: Soil Bacteria – The Myth of Identification and Management.

The scientific study discussed in Compost Tea – Does it Work? clearly shows that adding microbes from ACT tea does not impact plant growth.

Can Compost Tea be Dangerous?

It is important to ask this question. Even if there are some minor benefits for using compost tea, they could be outweighed by risks.

Think about what you are doing when you make the tea. You are creating an incubator for microbes. You are providing the moisture, the food and the right oxygen levels to grow microbes. But which microbes are you growing? You have no idea know.

The reality is that along with the ‘good’ microbes you might also be growing ’harmful’ ones. You could be growing microbes that will make you or your plants sick. Tea that is aerated can contain Salmonella and E. coli both of which can prove to be deadly to humans. Remember the contaminated lettuce? That was E. coli contamination. You could also be growing microbes that are harmful to plants.

The process for making compost tea is not selective – you grow whatever is in the pot.

I am confident that the risk is low. But why take the risk when the benefits of compost tea are at best, minimal?


If you want to make some compost tea, go ahead. You will probably not harm anything and you just might have some fun doing it. But understand that there is currently no evidence that compost tea is any better than using just compost. Be a smart gardener and just spread the compost on the soil as a mulch. Nature will do the rest.


Further Comments:

This post now has quite a few comments. Many of them are from people with feelings about this topic but without any scientific evidence that their feelings are correct. If you have some references to discuss – please continue posting comments. If you have no valid references to support your position – don’t bother commenting, because I will not approve the comment.

For more information and explanations about the myths promoted by Dr. Ingham, have a look at these posts:

Teaming With Microbes – In Depth Book Review

Soil Bacteria – The Myth of Identification and Management

Teaming with Microbes – A Close Look, Part 1

Teaming with Microbes – A Close Look, Part 2

Compost Tea – Does it Work?



1) Application of Two Microbial Teas Did Not Affect Collard or Spinach Yield:

2) Brewing Compost Tea :

3) Compost Tea and Disease Reduction:

4) Photo source for Aerated Compost Tea: Lily Rhoads

Robert Pavlis
Editor of
I live in southern Ontario, Canada, zone 5 and have been gardening a long time. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

I hope you find Garden Myths an educational site that helps you understand your garden better.

154 Responses to 'Compost Tea'

  1. BigFriendlyGardener says:

    Admittedly my tests have only been on my own garden at home but the results were plain to see. I have several citrus trees, blood orange, lime, lemon, grapefruit, and have constant issues with iron deficiency. I have had success using liquid iron supplements applied to the soil and as a foliar spray. I have been able to achieve comparable results with repeated applications of compost tea to the soil using all store bought ingredients–no specific sources of iron included. For years I had spread compost as a mulch around the plants and never saw a discernible effect. But with compost tea I could clearly see the symptoms of iron deficiency decrease. Obviously the tea had made the iron in the soil more available to the plants.

    I have also done a fair amount of container gardening and in that context there is absolutely no substitute for compost tea. Typically when growing plants in containers there is a limited volume of space for watering and applying mulch. Personally I like to leave adequate space so I can give a large amount of water to the plant before it overflows the container–I loathe watering someone’s garden when they fill their pots right to the brim. With compost tea it is far easier to apply the beneficial microbes to containers than with solid compost.

    Many of the gardens I work in are completely mulched with some sort of bark or wood chips which make applying compost as a mulch very time consuming and irritating as you have to pull back the decorative mulch from every plant you want to give compost to. Again, compost tea makes application so much easier. Applying compost mulch to a lawn is a pain but tea is easy.

    I think their will always be variance in compost teas because that is the nature of life and that to request scientific data with broad implications will never give you the answers you seem to want. As there are no standards for compost tea you have many people doing many things differently. It is quite possible that some people know what they are doing while many do not. All my experiences with compost tea show that it is not something you can just apply once and expect to see amazing results–I have never seen this happen with compost as a mulch either. When I achieved my best results with organic gardening it was with compost tea applied every two to three weeks. Had I tried to apply compost mulch at the same rate I would have gone through quite a bit of compost, but with the tea I was able use a far smaller volume of physical material which I think is a win in terms of overall time and motion efficiency.

    While I have my brew routine streamlined from start to cleanup and storage, I unfortunately see many people brewing in a manner that makes me cringe. Some people just let the compost sit in water for days and don’t aerate. Few take the time to understand the importance of feeding the tea but also not over-feeding–I don’t brew “fertilizer teas” but I do brew to help unlock and make accessible the nutrients in the soil or applied as powder/pellets. I see tea brewing in dirty containers with loads of bio-slime from previous brews–equipment must be kept clean! Perhaps the most common mistake I see is people using a tiny air pump to aerate a huge container of tea for far too many hours. It is important to understand the oxygen retention capabilities of water, how temperature affects this, and how populations of microbes can boom and bust during the brew.

    Yes tea is more complicated but I enjoy the learning/experimenting process. I would argue that for the average gardener who just wants a nice garden that compost as a mulch is a better use of their time than futzing with tea. But for those who are interested in putting in the time and energy to see if they can give their plants an extra boost I think tea is great, and great fun.

    The way you categorically dismiss tea is unfortunate since it is impossible to prove or disprove the benefits as there are far too many variables to draw broad sweeping conclusions. One cannot prove the existence or non-existence of god, but it works for some people.

  2. Paul says:

    I make steeped compost tea to use in places where adding full compost is not possible. ie. to plants growing in pots

  3. Mike Byrne says:

    Robert, thank you for the very interesting read. Thank you for keeping it scientific. Why there is never love for inconclusive evidence is troubling…speculation and anecdotal accounts are not replacements for empirical evidence; not when you earnestly seek a truth beyond your bias, desires, and best guesses.
    My question is about bonemeal tea. I am wondering if you have any evidence or hypothesis on the effectiveness of hot brewed bonemeal tea? My hopes is to use it as an injected fertilizer for tomatoes. Typically, if added to the soil, bonemeal slow releases calcium (so I have read anyway). Tomato sometimes develops blossom end rot, which is said to be the cause of low calcium uptake by the plants (could mean low calcium in soil). This happened to me. In my case, I know that the calcium level in the soil is low (soil test). So, you see my interest in correcting the issue at once. The plants are under plastic mulch and are irrigated via drip tape lines. The irrigation system has an injector as well, which I intend to use to incorporate calcium via hot steeped bonemeal tea.

    • If you have low levels of calcium, use a soluble calcium source – not bonemeal. Calcium nitrate will dissolve easily and also add nitrogen. There are also liquid calcium fertilizers.

      Blossom End Rot is a result of not enough calcium getting to the fruit – not the same thing as “uptake by plants”. Inconsistent watering is the usual culprit, but low calcium levels in soil can also cause it. Blossom End Rot

      • Peg Young says:

        Very interesting stuff. Thank you. I had some zucchini which developed blossom end rot. They were near a Mugo Pine, which, I understand, creates acidic soil. I saved my washed egg-shells and blended them into a powder which I worked into the soil for the zucchini. No blossom end rot this year!

        • Consider getting my book – Garden Myths. all of the following myths are discussed in the book.

          Evergreens do not make the soil acidic. Their needles are barely acidic and much less acidic than rain. Besides a more acidic soil will make more calcium available to plants.

          Egg-shells do not compost, so they sit in the soil for ever, adding few nutrients.

          Blossom End Rot is rarely a soil calcium deficiency – it is usually caused by irregular watering. If you did not see it this year egg shells had nothing to do with it.

      • Peg Young says:

        I had a thought. I have a drum-style composter that I am trying. I’ve had to put a basin under it to collect the liquid that drips out of the seam. (It stains the patio bricks.) Can I dilute it and use it like compost tea? I’d rather not just dump it.

  4. Gaston says:

    More of a question than a comment. Granted tea may not actually do anything for the subsoil biome. Is it possible that brewing the tea and adding it back into the compost will speed up the breakdown of the material in the compost bin?

  5. Colin says:

    Hey Robert, interesting article, I’m an indoor container gardener. What’s the best way to feed the plants during seedling/grow/flower? What should I use and at what ratio?

    • At seeding don’t use anything. Once you have seedlings use any cheap soluble fertilizer – something with more nitrogen, and less phosphorus – like 10-2-4. Most of the fertilizer will be washed out of the pot when you water so NPK ratio is not that important.

  6. Karla Tipton says:

    I’m just trying to figure out how to make my grass grow better and to break down my extremely high clay based soil. I don’t want to raise the height of my yard by adding compost and I have around 6,000sq ft of grass. I’m assuming it would take a lot of compost to help. I thought the compost tea would help my situation. Now it seems I’ve wasted money on all the ingredients for the tea?? I feel like I like I just read that one bad review on Amazon that made me decide not to buy something even though there were so many good reviews! Please help!

    • Grass grows better with more nutrients, and more air. fertilize with either compost or synthetic fertilizer. Aerate at least once a year. Leave clippings on the lawn. The soil will slowly get better.

      Compost tea will not work any better than compost. You can’t take a handful of compost, make tea and expect it to condition a big area.

  7. Kevin says:

    I’m very new to the world of composting, and I’d prefer to keep things simple and cheap (don’t have the time or money to invest beyond that). I use simple plastic tubs with holes. I rotate them from time to time to encourage aeration (though not as often as I probably should, but I’m amazed at how quickly the process is nonetheless). Unless it’s really dry, I let the rain provide the moisture needed, and holes in the bottom to drain the excess moisture. But I realized I’m probably losing nutrients by not collecting that runoff. So I made myself a simple “compost tea” collection system, which collects nothing more fancy than the runoff. I was searching to find if there were any of my plants that should not be the recipients of that “tea” when I came across this article. Informative. Thank you. Surely, I would think, but maybe incorrectly, that there must be some benefit to using my simple “tea,” but now I’m wondering if it’s not enough of a benefit to make it worth my effort (again, I’m usually short inn time as it is). Thanks for any thoughts you might offer in response.

    • The run off from compost does contain nutrients and is good for plants.

      The point of the article is that it is not worth making tea as a separate process – just use the compost. some people are taking your “finished compost” and then making tea out of it. This last step is a waste of time.

  8. Ryan Ducharme says:

    This link has a number of links with research from Universities contradicting everything yoy say here. There are real benefits of using aerated compost teas

    • The links are all about worm castings and worm casting tea – I never discussed that topic in this post.

      No one doubts that worm castings provide nutrients to soil and plants. The important question is – is tea made from them better than using just the castings? Based on the titles of the links – none have looked at this question.

  9. Ryan Ducharme says:

    I may have missed it and this might be old but what about indoor container gardening. Would worm casting tea be beneficial to replace microbes that most likely die when soil dries in between waterings?

    • If the microbes die in the soil in the pot, then any you add will also die. That is one of the fundamental problems with the idea of adding microbes to soil. If the soil environment supports their growth – they are already there and you don’t need to add more. If it does not support them – adding them will not help.

      Potted plants have lots of microbes – maybe not as many as garden soil, but they are not all dead.

  10. may says:

    Thanks for enduring the zealotry of the tea advocates Robert. After several years in the gardening biz, plus growing up gardening with my grandparents I find it amazing how many people are so detached from just plain old composting. Too many people these days didn’t grow up with any experience growing plants and will believe anything they read about quick fixes and miracle products while reading from their screens. Plus the internet offers up plenty of snake oil to anyone wanting to believe on all manner of topics.
    I also find it amazing how many people will advocate for doing things the ‘natural way’ and then will go on to tell you how they’re brewing concoctions that are better than what nature does and sprinkling mined minerals (ie. Rock dust) that the plants just simply wouldn’t have if not for their intervention. This just doesn’t make sense to me. Even if your tea was adding huge amounts of microbes, minerals, fungi, this would only makes sense if you know you have an insufficiency of these. If you are constantly adding to soil that is already full of microbes, fungi, minerals, etc it is likely you are actually damaging nature and contributing to runoff just like the ‘green revolution’ of the past. Modern agriculture began with the exact same mentality that humans know better and if we only added these few nutrients in the form of fertilisers we could make nature better and produce more yields faster.
    My experience has shown me that plants and their fungal and microbial partners are much more sophisticated than we give them credit for and believing that you can improve them by simply adding water to compost or sprinkling some rock dust on them is oversimplifying, even if it is made to sound complicated or scientific. I have been impressed by how convincing some of these products sound at first but when you look deeper they usually have all the signs of being an easy sell to those already wanting to believe, a marketers dream. You will never convince the zealots, even with clear evidence. Plus as we have seen in this thread there are many variables in nature that make it difficult for the believer to weed out the anecdotal evidence from the repeatable science, making the selling of such easy fixes hard to combat. Plus science as you have mentioned also has its limitations, leaving much to be studied further.
    Keep up the questioning Robert, it is very valuable for gardeners to be able to see information from all angles so they can make their own informed decisions. There are many people whose experience has led them to similar conclusions to yours, they just aren’t as vocal as the zealots because they are out in the garden.

    • I like the statement “plants and their fungal and microbial partners are much more sophisticated than we give them credit for and believing that you can improve them by simply adding water to compost or sprinkling some rock dust on them is oversimplifying. ” so true.

      And for the most part we still understand so little of this world.

  11. Hi Robert, I am no great advocate for compost tea, and was genuinely interested by your article. However you ask for evidence of the benefits of compost tea. A simple search of google scholar generated this list:
    I haven’t time to read all 31,000 results but of the first eight peer reviewed articles, one (the oldest) requests more research and seven conclude compost tea has positive benefits, in a diverse range of areas. I also think you miss a crucial point in your ‘Does Compost Tea Increase Nutrients’ section; the locked up nutrients in the soil are almost always way more than the plant needs, the key question is which of those nutrients are actually accessible to the plant. A key argument for compost teas is that making the nutrients available in liquid soluble form makes them much more accessible, both as root and foliar feeds. Overall nutrients don’t increase, but accessible nutients do; that’s the theory anyway.

    • A lot of the articles found are not peer reviewed, test for very special cases, don’t do field studies etc. I used you search criteria and looked up this one:

      This one has at least two problems.
      1) It did not perform statistic analysis on the data. It looks as if there are some positive results, but without the stats we don’t know if the differences are significant. Given this fact, I doubt it was peer reviewed – no reviewer would allow this kind of reporting.
      2) It tested compost tea against water. This is not very useful since the test should be comparing compost to compost tea. Nobody doubts that compost tea has more nutrients than water.

      So this study, assuming the data is significant, only proves that the nutrients in compost, when applied as a tea benefit plants. It does not show that tea is better than compost alone.

      Re:”A key argument for compost teas is that making the nutrients available in liquid soluble form makes them much more accessible”. This is the type of claim made but where is the proof? It is quite possible that as soon as these nutrients hit the top surface of the soil, that they are absorbed by soil particles, which would mean that they never reach the roots. This is in fact what happens to phosphates even when applied by liquid fertilizers so it is quite reasonable to assume the same happens to phosphates in tea.

      How locked up are the soil nutrients? We are finding out that the availability of nutrients away from the roots is quite different from near the roots. The roots modify the pH of the soil around them, the rhizosphere, to make the nutrients more soluble.

      • Sorry Robert I can’t accept these articles are not peer reviewed. Of the eight I looked at, all are in peer reviewed journals, as far as i can make out.

        On your point about locked up nutrients, I didn’t make any claims about proof. Rather, my point is that you ask ‘Does Compost Tea Increase Nutrients?’ and then dismiss this possibility. But no-one is really claiming that; the claim, as I understand it, is that tea increases the availability of the nutrients to plants.

        I think your last para gets closest to the truth; we are only just beginning to understand the mysterious world of the soil, so should expect new discoveries all the time, and shouldn’t expect conclusive proof. I encourage everyone to look at the articles I cite and make their own minds up.

        • i did not say that “articles are not peer reviewed”. What I said is “A lot of the articles found are not peer reviewed, test for very special cases, don’t do field studies etc.”

          Lots of people claim that compost tea adds more nutrients than compost.

          You say “tea increases the availability of the nutrients to plants”. If the tea is not adding more nutrients, how exactly is it doing this? If this were true than a lab should be able to measure this – any reference that shows this increase of nutrients?

  12. Aaron says:

    You can contol the microbial content of the tea with products containing strains of beneficial microbes and fungi like subculture M and B. This is a generalised article and full of Overly argumentative repsonses from the author. Anecdotal trials and evidence in my own expreiments have taught me that you are totally incorrect. Sometimes soils need help to stay healthy and an idiotic article like this is clearly just designed for the attention

    • How will adding beneficial bacteria to the bacteria already in the compost ensure that only those in the added bacteria grow? Show me a single reference that has identified the bacteria is such tea.

      If you have conducted proper research – I’d love to see the references.

      • Thomas Brophy says:

        May I add a slightly different perspective? If a person put say 50 # of fish bones and guts into a 55 gal. drum, a shovel of garden soil, maybe some kelp, filled the rest of the drum with water, and allowed the mess to age from 6 months to a year, would this mixture applied as a tea be beneficial to lots of different plants?

        • Yes it would. But nobody doubts that. The question to ask is, would the tea work any better than composting the same material and using the compost. Or would the tea work any better than just laying the material on the ground. The current answer to this is no – the process of making the tea is not adding any value.

          • Thomas Brophy says:

            Thanks for your response, with which I certainly agree. However, making a solution of this gusty mess enables the nutrients to be spread more evenly among raised beds than plunking the solids on the surface. Additionally, there is far less attraction to destructive pests (e.g., raccoons, possums, cats, etc.)
            Do you suppose I will have created any pathogenic organisms that should not be applied to the soil?
            Again, thanks for your wise analysis.

          • Most animals do not go after compost. They do like some of the input ingredients going into compost making.

            One of the reported concerns with compost tea is that user never knows if they are brewing pathogens. I don’t know how serious of a problem this is, but it is one argument against using compost tea. Spreading the compost does not have this problem.

        • Tom Hughes says:

          Hi Thomas, if you leave that mixture in water for 6 months you are going to need to create a very hazardous foul-smelling poisonous substance. It will be very harmful to plants, humans, and other animals. Please do not try this.

          Robert I can’t believe you haven’t said so in your repsonse. It clearly shows that you have very limited understanding in this area.

          All of the microbes that usually exist in healthy un-waterlogged soil (I.E the sort of soil that most crop plants are adapted to grow in) will die within weeks. The drum will slowly be colonised by a much more limited selection of anaerobic microbes that float in as spores from nearby dead animals and other places like sewers. These microbes and the toxic substances (alcohols etc…) have no place in cropping environments, but you may find at the bottom of lakes where dead animals have been rotting for years, or in sewers.

          E.coli and numerous other dangerous microbes that grow in STAGNANT WATER will most likely be present in the drum.

          • Your statement ” going to need to create a very hazardous foul-smelling poisonous substance”. You will still get decomposition and that releases nutrients. this is really no different than making compost tea without air. Your “toxic substances like alcohol” will be used as a food source once they are applied to the soil.

            It is true that dangerous microbes might grow – but that is also true of compost tea.

  13. Graham Chiu says: Effect of Aerated Compost Tea on the Growth Promotion of Lettuce, Soybean, and Sweet Corn in Organic Cultivation

    “In the study, application of aerated compost tea from organic compost based using MOVR (the mixture of rice straw compost, vermicompost, and Hinoki cypress bark compost) to the root zone increased the plant shoot and root growths and yield of the red leaf lettuce, sweet corn, and soybean. Thus, compost tea could be used as an agent for promoting plant growth in organic cultivation of crops.”

    • Thank you for posting a reference.

      1) the study was done in the greenhouse, not in the field. Any results from it may not translate to the field – you certainly can’t assume they will.
      2) the plants were grown in “media based with coconut beat and peat moss”. This is about as far away from real soil as you can get.
      3) the application rate was “rate of 50 ml per plant” – that is huge compared to suggested field application rates.

      This study shows that compost tea will grow larger plants than plain water, in a soilless mix that has very little nutrients in it. No body doubts that. It proves nothing about what happens in the soil.

  14. Alexander Narath says:

    Hey Robert,
    I just wanted to say thanks for a counter argument against ACT, some of what you said I agree with and some of it I do not. I was a little confused with the topic because there are many types of compost teas and I think you are referencing the steeped bag of compost method which is the most basic one. For use in a garden I don’t think you gain much benefit from using compost tea and I agree with you that it is more beneficial to just add the compost to the soil. Top dressing is always optimal if you have bed space. As a foliar spray compost tea can be useful because the bacteria in the compost tea break down the nutrients to a bio available state where the leaves can absorb the nutrients. It is marginal but if you water a lot it can green up the growth. It won’t be like a full blown fertilizer. The area where ACT is useful is in potted plants. In a pot you may not have room to topdress anymore compost so by making a compost tea you can get some of the benefits of compost without increasing planter/pot volume. If you use concentrated fish emulsion and concentrated worm castings then you can get a tea that is viable for all fertilizer needs.

    • Re: “As a foliar spray compost tea can be useful because the bacteria in the compost tea break down the nutrients to a bio available state where the leaves can absorb the nutrients.”

      Foliar feeding is not an effective way to feed plants. Most of the nutrients just fall to the ground, and if absorbed, some of the nutrients, like calcium, stay in the leaves and are not transported around the plant.

      Since brewing is only done for a few days, most of the organic matter has not been converted to nutrients. This takes years once the organic matter is in the soil.

      The leaves are already covered with bacteria that would decompose any tea sprayed on them. I have seen no evidence that spraying bacteria on leaves add any benefits.

      • Aurelien B says:

        ACT, which promotes microbial or fungal activities is best for soil, that is, for root development. You measure the efficiency of compost teas by measuring the root growth in details, nothing else.

      • Alexander Narath says:

        Fair enough on the foliar feeding. I honestly don’t know much about foliar feeding I am just regurgitating what I have been told in that regard. I have been told foliar feeding can help with some critical nutrient deficiencies because the leaves will absorb select nutrients faster than a root zone feeding but I do not have a source for that or first hand experience. What I do know is that bacteria and other beneficials are important in living soils. If you have a healthy soil then it will naturally balance the bad bacteria. The idea behind compost tea (at least what I have been taught and practice to great effect) is that if you formulate it correctly you are feeding the bacteria already in the soil and reinforcing their populations. The compost tea will not have a high level of available nutrients but the boost in biological activity will boost nutrient levels in the soil. It does take years for organic material to be broken down naturally but if you create an environment that is perfect for the decomposers then it can happen much quicker. This is why hot composting works quicker than cold composting. I want to clarify though that my compost tea is made from bottled compost extracts and is not made in the traditional way with bags of compost being steeping and aerated. I know there are some purists that would probably consider my method more of a fertilizer application then a compost tea. As for the traditional methods I don’t think they have much benefit for the reasons you already outlined I.e. There is simply not enough nutrient potential to make a difference. It may boost biological decomposition if organic material is already in the soil but if you have poor soil to begin with compost tea will do nothing. Also if you are using soil that is inert and relies on synthetics amendments then compost tea will do nothing. The only exception to this is if you make a compost tea with very specific bacteria in it then it can be used to flush salts from inert mediums but this requires a specific inoculant and cannot be achieved with just plain compost tea. If you think of compost tea in terms of feeding the plant then you will run into contradictions because it doesn’t make sense from that point of view. But if you think of compost tea as feeding the soil which in turn feeds the plant then it makes more sense. That is how I have been taught at least and I could be completely wrong about all of it.

        • “that if you formulate it correctly” – that is what people say but since nobody knows what is in their compost tea I see no way to do this.
          “reinforcing their populations” – soil already has all the microbes it can handle. If it is low, the microbes there just multiply.
          “boost in biological activity ” – people say this, but there is no evidence that there is any biological boost.

          All of these kinds of statements sound good, but where is the proof? Where is the scientific research to show it actually works?

          • Aurelien B says:

            One other study more likely to be of interest for gardens, concerning strawberries:

            Fruit and Soil Quality of Organic and Conventional Strawberry Agroecosystems (Plos one, september 2010)

            “Our findings show that the organic strawberry farms produced higher quality fruit and that their higher quality soils may have greater microbial functional capability and resilience to stress. These findings justify additional investigations aimed at detecting and quantifying such effects and their interactions.”

      • Ken says:

        When you make any kind of compost tea it should be to increase the microbe and fungi population and activity in the soil which ultimately provides essential nutrients for the plants.

        • Making tea does not seem to increase fungi population – only bacterial, in the tea. Where is the evidence that adding tea to soil has any effect on the microbe population in soil?

  15. Aurelien B says:

    The Bokashi composting method allows to easily produce at home with simple kitchen wastes fresh organic matters as fertilizers for the soil, in situ.

    This may be unpleasant to the whole fertilizer industry (chemical and organic) but it is true. We all know that chemical, industrial fertilizers are nefast to the soil and so for the plants and the human beings (inducing the use of pesticides, fongicides and so on), but organic fertilizers are nothing but fermented organic matters in liquids or dried organic matters.

    Those organic supplements can at very low cost be created at home through one’s kitchen wastes with the help of the bokashi method. And the best they are if one’s own food is organic and diverse, encouraging one to a healthy diet too, in order to give to the plants that one cultivates a healthy diet too as a consequence.

    Thanks for listening

    • Not quite sure what you are saying here, but the comment “We all know that chemical, industrial fertilizers are nefast to the soil and so for the plants and the human beings”, assuming ‘nefast’ means wicked, is not true. I have discussed this in many posts.

  16. Will says:

    Searching several academic databases lead to a wealth of evidence that compost teas do in fact provide many benefits, mainly increased disease suppression, increased growth and yields. The disease suppressing ability of foliar CT is well established. I’m not going to take the time to cite the dozens upon dozens upon dozens of scholarly articles published in further dozens of scientific journals because anyone can read the abstracts on Google Scholar by taking a few moments. I found it difficult to find a study that didn’t show some positive benefit of compost tea use, especially in terms of disease suppression. The results are highly varied because of the number of substrates, techniques and plants used to conduct the studies but the evidence is mounting in favor of compost tea application. It is simple to make and apply and can be done very affordably and shows great benefits to organic production.

    In terms of toxicity by pathogenic microbes, it is universally recommended to not apply CT before harvest, usually one to two weeks before harvest date. The CT would have a minimal impact at this late stage and should be used as a preventative measure, not to treat symptoms.

    • I’ll be posting another paper in a couple of weeks that show not benefit from ACT on landscapes. In fact compose used directly produced better results.

      In the mean time can you post one link for a metadata study that shows compost tea suppresses disease?

      • Ken says:

        When you use tea it gets to the Rhizosphere faster. That way the microorganisms that exist around the roots can do what they do and leave nutrients immobilized where the plant can access them. Rather than waiting for top dressed compost to be mixed in the soil below by the biology within the soil already. (anthropods, earthworms,etc.)

        • Re: “When you use tea it gets to the Rhizosphere faster” – faster than what? What are you comparing it to? The Rhizosphere already hosts huge bacterial populations – they are there before you even start making the tea.

          Besides most of the tea will soak into soil as soon as it comes in contact with it. I have never seen any evidence or even claims of the tea moving bacteria to the roots.

  17. dakota says:

    I completely disagree with nearly every point you’ve made. ACT will fertilize your plants with readily available nutrients/minerals. It will save you money by utilizing microbes with a substantially smaller amount of material and aenoribic conditions promote a pathogen rich environment. I think you should be less stubborn and do research yourself. It seems you have a very skewed vision as to your resources and “COMMERCIAL FERTILIZERS” are horrible. They leach through soil into groundwater for one, and secondly they run off into rivers and streams causing algae blooms which kill fish. This article is bogus and proves absolutely nothing!

    • I am sorry to say you don’t even understand the basics of fertilizers. The nutrients in compost tea are exactly the same as the nutrients as in commercial fertilizers. This is basic chemistry and not disputable.

      ACCT can NOT provide more nutrients than what was in the compost used to make the tea. This is a basic law of physics that says you can’t create matter from nothing.

      • Jeff Tufts says:

        Commerical bottle nutes/ferts are just watered down garbage anyway why not use teA? Even if the effect is minimal its better to make tea on your own for way less than 20 a bottle of watered down shit. How were fertilizers developed? Industrial waste.

      • Jeremy Hunter says:

        Wow I can’t believe you have been arguing this for 2 years! So my question would be, during all this time, have you ever actually tried using compost tea? Or even better, you did a side by side?

        The thing is..
        Your right in a sense, there is only so much NPK in the stuff! But you are totally off when it comes to everything else, you are refrencing physics but you have aparently no knowledge of actual soil science, of which you are trying to represent with this article..

        So yeah the NPK is what it is, and the minerals, random particles and micro nutrients are what they are too. But where it gets complicated is how each of these elements interacts with the plant, or even if they are there for the plant at all.. Lots of nutrients are only available to the plant within a small window of pH, which may vary with temp.. And some stuff is to big particle size to break down.

        We are barely beginning to understand the soil food web, the symbiotic relationship of fungi, bacterias and other microbes, with the plant and its root system. It not only acts as a communication highway but as a nutrient factory, helping breakdown nutrient particles with acid they secrete, but not just blindly, in communication with the plant, the microbes will source what is needed and find it in the soil and “plasma stream” it to plant..

        So anyway, where your missing the point is that we are brewing microbes and life into to tea, that then make our plants more efficient at getting there nutrients. And yeah all the microbes are in the compost, but by making tea, we are waking them up and multiplying there numbers, and giving them there first boost of sugar so they can go to town!

        • I actually know a lot about soil chemistry.

          For example – your statement “Lots of nutrients are only available to the plant within a small window of pH” is completely false. first of all it is quite a wide window, and secondly at the limits of the window the nutrients become less available – they don’t stop being available.

          pH does not vary with temperature as you suggest.

          Re: “some stuff is to big particle size to break down” – what does that mean? size of particle has nothing to do with how easily it breaks down. Stuff – I assume you mean molecules break down based on their chemical structures.

          In your last paragraph – you are just putting words together that make things sound good. There is no scientific basis to what you are saying.

      • Seems to me like you have a personal vendetta against miss Ingham and her practices. Nothing about this article sounds very scientific or objective. Thanks for your Opinion on things. We are all entitled to viewing things differently. Do you have a chemistry degree? Organic Vs Synthetic nutrients are completely different molecular structures bonded differently with different charges. Nice nonformative article. Thanks for muddying everything up for those of us that seek true knowledge and social expansion.

        • I don’t have a personal vendetta against Dr. Ingham, in fact, I acknowledged in my writings that many of her ideas are correct, but others are not.

          I have degrees in chemistry and biochemistry. The statement “Organic Vs Synthetic nutrients are completely different molecular structures bonded differently with different charges.” is completely false. Neither plants nor any lab in the world can tell the difference between a nitrate ion from synthetic fertilizer or an organic source. Same for the other nutrients.

    • howe says:

      I’m not a fan of commericial fertilizers as I tend to burn my plants. But using very little of them is actually very safe. Anyway, they are all ions when watered, just like how compost tea is made up, just at higher doses. Then again, I find compost tea a waste of time. I just put the compost on the soil, and it do its works naturally. I’m “brewing my compost tea” on the soil. From an industrial point of view, compost tea is a waste of time and a non value added step.

      Keep pouring compost tea every to your plants, give lots of it. I’m sure the phosphates will eventually reach groundwater. In case you didn’t know, too much organic manure can cause groundwater pollution.

      • In fact some of the latest studies have concluded that organic farming with the use of manures are producing more runoff pollution than conventional farming – on a per pound of produce produced. More on that in a future post.

  18. scott says:

    Plenty of proof.

    Dr. Elaine Ingham has been proving it for 30+ years. In her course she provides she has a case study proving properly brewed compost tea can completely wipe out botrytis after the vines had been purposely infected with the disease.
    The unfortunate thing about these methods is a lot of enexperienced people are trying to mimic, giving this biological process a bad rap.
    No one should be playing with these methods unless they know what they are doing and can properly analyze what they are doing under a microscope.

    • So you say “No one should be playing with these methods unless they know what they are doing and can properly analyze what they are doing under a microscope”. That means no one except some microbiologists should be making compost tea. Farmers and gardeners will not be able to do this type of analysis even though Dr. Ingham makes such claims in her courses.

      Dr. Ingham has not published any research on compost tea to support her theories. What she does do is report on personal observations that have not been backed by scientifically published research. Until the work is published in peer reviewed journals it proves nothing.

      • Scott says:

        I’m not a microbiologist and am confident in analyzing soil the way Elaine has shown me.

        Personal observations from an experienced microbiologist is good enough for this farmer/gardener. Peer reviewed journals be damned if what I learnt through her courses works. There were more than enough case studies provided through her course that shows what she is doing works.

        Having no prior knowledge of Elaine or her work and having completed her courses, it seems everything you state about what she advocates is bass ackwards, and it seems I am not the only one who comes to your site and sees this.

        All I can really do is recommend you go straight to the source, take her course or the cheaper route pay for a consultation with her. Write all your concerns/questions down and speak with her about it, than make your conclusions. It is all to easy to misinterpret what someone is trying to say online or in books, this is why one on one is the best way to get clarity. If you have the funds, the course would be the most beneficial for you, she covers a wide range of topics.

        You know I’d almost be willing to even pay the hour rate for her consultation service, just so you can get this clarity. More critical thinkers like you who are well spoken, experienced with growing and can get a message out to the masses need to see the benefits to using these methods.

        The reason why I made the statement you quoted is because it is all to easy to make compost/tea and negatively effect your plants, or have no results at all, which does no good for getting this knowledge out to the masses.

        Funny thing is, generally speaking one rarely really hears of the success stories of anything, usually it is the failures….pissed off people or let down people seem to be more encouraged to share their results. This is why it is important to have those with experience practicing these methods, so not to detract from the work that is being done. Eventually enough people will be practicing these methods, with a portfolio filled full off success stories to back them up, and better yet offering their services to gardeners/farmers, and even better more people teaching others to do it themselves, but we are not there it.

        Best wish to you Robert

      • Chet Atkins says:

        “That means no one except some microbiologits should be making compost tea. Farmers and gardeners will not be able to do this type of analysis even though Dr. Ingham makes such claims in her courses.”

        I see your still on about this Robert and I know you don’t let my comments go through anymore. I’m still determined to banter you over this becauze you’re condesending to everone that disagrees with you and I don’t like it. Plus, I just feel like I’m having a one-way one-on-one with you and I do like that.

        That being said, what in the world are you talking about in the quoted section above? As a proficient writer and someone who seems to understand sciences pretty well, it’s an outrageous claim. I am not a microbiologist, but I do own a microscope, and I am able to count and ID the important microbes, bacteria, fungus, yeasts, and their respective ratios in a compost tea sample. I know plenty of non-microbiologists (farmers in fact) that can do this as well, if not much better than I can.

        Also you mentioned a “basic law of physics” that apparently states, “you can’t create matter from nothing. If you’re reffering to e=mc^2, that THEORY was disproven almost a decade ago now.

        Thank you for your time Robert, hope you’re well.

        • The quote you picked out is a clarification of something someone else said – I did not say the original sentence.

          If your comments were removed it was because either they added nothing to the conversation or your tone was unacceptable – like saying “you’re condesending to everone that disagrees with you and I don’t like it. ” If you don’t like it, please visit other blogs. This is my blog and you are a guest here.

          I believe that the basic laws of physics that says “you can’t create matter from nothing” is one of Newton’s laws.

  19. Someguy says:

    It was to my understanding that compost teas add more readily available nutrients to the root zone, rather then ‘adding more nutrients’. (Opposed to simply composting in the soil)
    When you add ingredients to the soil to be decomposed, it takes several months to years to break down. However, water and oxygen speed this process, and a byproduct of this is additional microbes (which further the decomposition rates) there for feeding your plant yummy nutrients within days opposed to …

    • It is the microbes that decompose organic matter in the tea. How much decomposition do you get in a couple of days? Nobody ever says.

      The tea might speed up decomposition and make nutrients available sooner. But if that is the requirement – just use fertilizer – it is even faster.

      • Fertiliser? Full of heavy metals? Are you crazy? When we use acids and other processes to extract fertilizer from rock we also extract a lot of stuff that has been proven to cause autoimmune disease. Also when I spay my plants bugs find them unapealing . clearly you have never used this. The microbes are pretty predictable if wormcast is used. I can’t believed this. compost tea has been my single most reliable go to when encountering disease or bugs. Those who use compost tea are mostly organic gardeners so why would you suggest fertilizer when compost tea is the perfect organic fertilizer. There is no myth to this I couldent garden organically without this seemingly magic microbe fertilizer. Try it on a small problem area it works.

        • Fertilizer is not full of heavy metals nor does it cause autoimmune disease. Now you are just making stuff up.

          How can the ‘microbes be predictable’ when you can’t ensure they are always the same type??

          Compost tea has not been proven to be anything but compost – which we know adds nutrients.

  20. Mikey S. says:

    Hey Robert

    Happy to see some healthy skepticism here.

    I was suspicious of claims that compost tea foliar sprays would have any effect at all, especially on disease resistance and increased nutrient uptake?! and stumbled on this article. Nice points!
    I think it’s important to temper much of the hype with this application method.

    I would like to add some thought though, to round out the discussion, lest we throw the baby out with the compost water:)

    It is my understanding that a compost tea merely operates like other liquid fertilizers, though much less controlled, effective, and focused seeing as one isn’t entirely sure what is in the tea (however we are certain that there is a bunch of stuff in there that plants do like, NPK etc. maybe something like 10 – 8 – 8 or higher if you make great compost, but still paling in comparison with any classic mineral fertilizer out there). That is, I assume that proper use of compost tea should follow the same regiment of liquid fertilizer application – short term boosts of available partially mineralized nutrient. This is in contrast to any other solid soil amendment which usually has a sliding scale of nutrient release time. Good soil management would/could make use of both of these types BTW.

    Although it may be less effective than straight Anhydrous Ammonia or Urea there is little to no worry that you will burn your plants and the soil PH will most likely not shift drastically one way or the other.
    Also you don’t need gloves or masks or coveralls for application – though you may want them 🙂 In that regard it is a very user friendly and forgiving tool in the gardeners/farmers repertoire. And if one is trying to convert a conventional operation, no matter the scale, into one using more sustainable methods, I think this is an interesting way to frame the issue/start the process.

    And let me be clear that I am only discussing nutrient here and not by any means attempting to show preference for soil management style or method…just discussing this one application method in isolation of the larger story. I am a huge advocate of soil amendments that promote good soil structure (colloids and cation exchange) and I don’t think compost tea is very effective in that regard (if at all).

    Just a few grains of salt added here so we don’t end up dismissing what is basically an application method.


    • You are correct it will add nutrients. The fertilizer numbers of compost are about 1-1-1, a tenth of your numbers. If we dilute this to make tea the resulting liquid is significantly lower.

      I agree you can use this to fertilize the garden. But why not just use the compost and do less work?

      • Mikey S says:

        Hey Robert
        You’re right, my mistake. My npk was waaaaaay off.

        Yeah my points are moot. Better off spreading your piss around if you’re looking for a liquid fertilizer. At least you’d still have some of that nitrogen.

        agree that less work is the way to be:)

      • Brendan says:

        compost tea for one is not about makeing more nutrients thats the authors bad its about taakei g a handfull of complost full of fungi protizoa and bateria and adding a food sourcer water and oxogen .then you brew for 12 to 48 hrs depending on what microbs yu are after durring the brewing process those bacteria and fungi protizoa erat the sugar source or protien source and they strat produceing more of the same bacteria fugi and protizoa in huge numbers .This is why you brew compost tea and this is why compost tea gos a hell of alot further than compost a cubic foot of compost will add signifigant biology to a very larg area of soil however 50 gallons of tea diluted at 10 gallons water to 1 gallon tea will repopulate a huge area of soil

        • Do you have scientific proof that fungi and protozoa are increased in the brewing process?

          A recent study I will write about soon showed that there was no increase in fungi during the brewing process. Bacteria do increase.

          But you are missing the point. No one is suggesting you don’t get more bacteria by brewing. The issue is that the soil already contains billions of times more bacteria than you have in the brewing pail. Soil already has lots of bacteria. Adding a few more, relative to what is already there is not going to make a difference.

  21. Connor says:


    I am curious if you feel this is the same if you are making a compost tea and adding specified soil innocculants, like glomus intraradices, trichoderma harzanium, streptomyces, etc. Do adding these to an earth worm casting tea make them more readily available and at a higher population? I like making AACT, but I always add different microbes with different recipes when I want a certain population in my soil. Is this effective? I also like to mix in the innocculants straight with the soil. Thanks for the info, great blog!


    • I am curious – how do you know “which population your soil needs”?

      This is a fundamental flay in this whole idea of adding microbes to soil. We (ie scientists) don’t know which microbes are in the soil – there are thousands of species that have not been identified. And we don’t know which will make the soil better for plants.

      And, there is no scientific evidence that adding microbes to soil actually makes any difference – except in some specific disease cases.

      • I think that all microbes improve nutrient buffering and compost tea merely puts a random variety which will be compete if their particular ecological niche has room. On the whole, compost tea is too much work and too much can go wrong.

      • Compostlady says:

        You keep saying that we (those who brew ACT) don’t know what is in the tea (microbes)…but this is discovered in a lab under a microscope…there is a surefire way to identify various organisms…soooo, yeah.

        • Actually there is NOT a sure fire way to identify all microbes. Certainly not under a microscope.

          Most soil microbes have not been identified – so why do you think a gardener could do this using a microscope? At best soil microbes are classified into large groups based on morphology – that is what Dr. Ingham promotes. DNA labs can get DNA profiles of microbes, but even this just puts them into classes of microbes.

          Spend some time on Google looking at scientific papers about soil bacteria identification and you will quickly see the problems.

  22. Nathaniel Johnson says:

    I often take issue with people that prescribe anything as a silver bullet and compost tea is no different. I think that you are correct in that compost tea for the once-in-a-while gardener is a bad idea, and anaerobic compost tea is always a bad idea. The biggest benefit of compost tea is that it allows a skilled gardener/farmer to push diverse microbes across large areas (say a lawn, orchard, row crops, etc). However it is not very useful if those same areas do not have the necessary soil composition and structure. I believe compost and mulch will provide typical gardeners with more than enough nutrients and will gradually help improve structure along with some carefully chosen amendments based on a soil study.

  23. Dan says:

    Couple things. I was watching one yard revolution on youtube. He said he is having “better results without tea” he does use controls as well. So that kind of proves your point. I like how you mention ignorance in the original post, then you get a bunch of debate over it lol.

    Something I noticed from one yard revolution is he said make compost tea from weeds when you don’t have Humphrey (this is before he discovered no results from compost tea). So even in your post you say that it does have nutrients but we’re arguing the increase in microbes. My question is, if I throw the leaves from my weeds in water and water my plants with the tea is it better than just watering from a hose? I’m trying to repurpose the weeds without having them in my compost pile.

    • Weeds added to water will decompose and add some nutrients to the water. They stink like hell in the process if you don’t aerate. This water will then be better than just tap water – but only marginally.

      A better way is to just drop the weeds in the garden and let them decompose there. Less work and you get the same nutrients.

  24. William says:

    I’m afraid this article is crudely inaccurate. Have you heard of the soil food web?? those microbes may consume resources but as you said with physics, the energy is only converted and not wasted. This process helps to balance PH and provide a much broader range of bio metabolism necessary for vibrant and more nutritional fruit. Chemical Fertilizers are well known to kill or inhibit these beneficial bacteria. These statements are supported by factual research and not opinion as far as i know.

    • I have. I have even written about Teaming with Microbes. A lot of the information in this book and the information promoted by Dr Ingham about the Soil Food Web is incorrect and is not supported by science.

      Microbes don’t adjust soil pH.

      Chemical fertilizers do NOT kill or inhibit bacteria in soil. That is the subject of my next post and it is one of the biggest mistakes in the Soil Food Web Theory.

      If you think the information in the blog post is wrong – then provide scientific evidence.

    • teehowe says:

      Chemical fertilizers could actually feed bacterias with more nitrogen to speed up decomposition of organic matter.

  25. Trimothy Leary says:

    Fantastic resource. Between this and Linda Chalker-Scott’s Horticulture myths, and the Professors blog. Man, it’s just so nice to see fact based analysis.

  26. TeeHowe says:

    I agree that compost tea and compost are no different in terms of total nutrients. I have never used it before. But could compost tea be a faster acting/faster release of nutrients since more of the organic matter area is covered by moisture and more of these can fill in the gaps in the soil? Since the compost on its own tend to have less exposed area, decomposition of organic matter is slower. In other words, compost tea is fast release and compost being slow release.

    • Compost in or out of water will have the same surface area. Moist compose will decompose faster than dry, but being in water will not speed up the decomposition. The brewing process will probably release a bit more nutrients in the short term if air is added, but keep in mind that compost takes at least 5 years to decompose. Speeding it up by a day or two is not making much difference.

  27. flgardener says:

    Just my thoughts: I know this is an old thread….
    1) Most people use compost tea in conjunction with compost, in a traditional garden setting, to gain whatever benefits they can from both.
    2) The argument that keeps getting raised is “use commercial fertilizer, if you want that result”. In my experience, gardeners using compost tea, generally try to stay away from chemicals… which is why the exploration of this option.
    3) Isn’t there room for new advances, and the mistakes and breakthroughs that come along with the research involved in getting there, in gardening?

    • You can’t use “most people” when talking about compost tea. Everyone suggests different practices. Most in fact believe in tea so strongly they don’t use compost. Quite honestly – there would be no point in using both. If you plan to use compost – why use tea?

      The nutrients in tea and in compost are no different from the chemicals in commercial fertilizer.

      There is nothing wrong with trying things. However, there is a big problem in making claims which can’t be substantiated.

    • samuel w adams says:

      I strongly disagree with this author. Can only compare the article to my own results though.

  28. Marc says:

    Blimey! Came across this as looking into worm composting on the balcony just for fun (I am a plant analphabet) and couldn’t understand the need of the tea step. Until clearly proven otherwise i will just pass on the tea. but your fencing and good responses to each point raised are priceless!! thanks.

  29. tim says:

    Well I didn’t read many of the replies but I had a few cents to add, sorry if this repeated. First as far as the beneficial microbes goes you have some great points, lack of control of what kinds of microbes you are growing is an issue. First you should always grow your tea in an aerobic environment, 99 % of what the tea is for is for the introduction of be beneficial “fungi” which for the most part prefer fresh air. what fungi do is digest nutrients in the soil and trade them to the plant for other nutrients in a symbiotic relationship much the same way we rely on the micro flora in our stomachs to digest our food some bacteria can be beneficial and some bacteria can be grown in an an aerobic environment and fungi can be grown in an anaerobic environment but for the most part an aerobic environments grow the best fungi and bacterial colonies for these purposes. So by growing in the aerobic environment you are setting up the environment to favor the microbes you desire. Your second point was different compost make different tea and that you would a full lab to really control the tea and this is on the nose accurate. Thankfully are a bunch of companies that supply these beneficial microbes such as “ancient forest” giving you known strains of these beneficial microbes. For $10 – $15 you can buy several of these packets and it’s enough to brew tea for two or three years. as a foliar spray I have no idea of its efficacy and that’s why I was looking this up in the first place.

    • Most discussion of brewing aerobic tea focus on the value of bacteria – not fungi. Bacteria or fungi – does not really matter. The soil has lots of both of these and does not need more to be inoculated. Feed the ones in the soil and they will grow.

      Amazon says that “Ancient Forest” contains “more than 35,000 species of bacteria and over 5000 species of fungi”. You say that Ancient Forest ‘knows’ the strains they are providing. Do you have any idea what it would take to identify this number of microbes?? What if ,in a new batch, a few were different from a previous batch – would they stop selling the product? If a strain is missing in a new batch would they add it back in? The claim that any company knows the strains in soil is ridiculous. Most soil microbes have not even been identified, so no company is doing this.

      But it is good to know that “Ancient Forest is a natural product consisting of 100-percent pure forest humus” – if anyone wants some all they need to do is go to a forest and scoop some up into a bag – costs nothing.

      By the way – the company does not even know what humus is. Pure forest humus would not contain any microbes!! They are using the term ‘humus’ incorrectly. See

      • Mike N Ike says:

        You can throw all the science you think you know at this but all I know is proof is in the results. You have no idea what species of bacteria /fungi are in there but guess what. ..they sure do work. I bring back plants from the dead with a simple tea so something good is going on. Don’t care about the rest. That’s for you to try to figure out. I go off of strictly results and they are solid as a rock. Funny thing is it works every single time too. Next day is like an explosion when off, truly amazing. So I’m gonna keep mixing this useless/toxic brew and hopefully some day someone wicked smart can tell me what’s in it!

        • A claim like “I bring back plants from the dead” is a sure sign that your results can’t be believed. Not physically possible.

          If your results are “solid as a rock” then report on them. Lets get the details. What controls did you use? How many replicates did you use? etc. I really doubt your results are solid as a rock. But if you believe – then continue doing what you are doing.

  30. Federic says:

    I was reading about this ultimate tea for bioponics, that solve all the problems related to micronutrients, I am not a specialist but I knwo that Fe is a limitant element in aquaponics systems, and hidroponics I think so ! Well this famous or infamous tea really resolve this problem ? including the others micronutrients that the plant needs ?

  31. farmer Brown says:

    What makes this entire post invalid is his claim that compost tea does the same as a growing in Compost. The nutrient value is actually increased exponentially in tea rather than the slow turnover process of natural composting but that’s not my argument at all. What he fails to mention is that people are not using compost tea instead of growing in dirt. They are using it to INCREASE the nutrient value of their soil. Many people who grow in containers often use compost tea because they lack the ability to add more soil and compost .

    …Your personal attacks on me have been removed – there is no place for them here!

    • Unfortunately you fail to understand basic chemistry and physics! For your statement “The nutrient value is actually increased exponentially in tea rather than the slow turnover process of natural composting but that’s not my argument at all” to be true, the most fundamental law of physics would need to be invalid – the conservation of mass. A handful of compost has a certain weight of carbon, nitrogen, phosphorus etc. No matter what you do to that compost, the weight will never change. So the ‘nutrient value’ can’t go up by brewing it.

      Re: “Many people who grow in containers often use compost tea because they lack the ability to add more soil and compost . ” They might use compost tea, but not because they can’t add soil or compost. Compost can be added as a mulch and there is no point in adding more soil – the container already has that. what the plants need are nutrients and most people add them using fertilizer.

  32. Erik says:

    I think you have gone out of your way to turn a blind eye to the research that has been done. There are many Universities that have done research on compost tea including Harvard and Ohio State University. These are not new studies and there are many more that that tend to be ignored by people that wright these types of articles. If your looking to prove or disprove something way not start with actual studies?

    • I did precisely what you have suggested – I started with the studies. I did not find a single one that showed, in field trials, that compost tea performed better than just compost. There are lab studies, and there are field studies that show compost tea might have an effect – most in fact show no effect. But I have not found a single one that compares compost to compost tea in the field. They only compare compost tea to nothing or to water. That only proves that compost has nutrients – we already know that.

      Since you know of such studies, please forward a couple of links for them. I would really like to see the evidence to prove compost tea works.

      • Federic says:

        Erick, I am get lost, if you said that harvard and ohio u, have been involve in those investigations, what other information will be provide by the author if both are suppose to see the same reports.

  33. Chet Atkins says:

    Are you arguing that compost itself is bad? The only thing compost tea really does is multiply what is already in the compost by giving the microbiology the proper conditions for feeding and breeding. This seems like a jealous rant from someone who has never tried compost tea. There are several holes in your argument.
    First, you spent much more time going over the improper ways to make compost tea. If you do a little research, you will find the most people recommend stirring your water as often as possible if you don’t have an air pump. Voila, oxygen!
    Second, OF COURSE there are going to be different compositions of nutrients and microbes. That doesn’t mean that it’s not beneficial still. Plus, microbes do two things that you did not account for in this article: they form a hierarchy and play by the population rules that they all realize are in place. Microbes also “fix” nutrients in the soil and the tea, making them more immediately available. So there goes your “compost tea doesn’t add any additional nutrients other than what was already in the compost” argument
    Third, When you say compost tea does “everything under the sun”. It makes me think that you don’t know how to garden at all. You obviously researched the topic enough to know exactly what compost tea is supposed to do and that plants need much more than microbial life and nitrogen to live and prosper.
    Fourth, By the way, you don’t need a “sophisticated lab” to do testing on compost tea. All you need is a microscope that goes to at least x1000, which you can buy for about $100 these days. If you don’t have a microscope, you can use a laser pointed through a drop of tea pointed at a blank wall in a dark room. Works great as a microscope.

    • I never said compost is bad. It is very good for soil. I also never said compost tea is bad for soil. What I said is that compost tea is not better than compost.

      Your statement “The only thing compost tea really does is multiply what is already in the compost” is not correct. Nutrients are not multiplied. The quantity of microbes in the tea may well be larger than the microbes in the compost – but nutrients are not increased.

      Re: ” you spent much more time going over the improper ways to make compost tea” – I spent very little time going over the methods used for making the tea and there are many recipes on the internet – who’s to say which is the “proper” way? The fact is that the basic arguments I made don’t change with the method used to brew the tea.

      Re: “Microbes also “fix” nutrients in the soil” – what does that mean? I Googled the expression and did not find one hit for it. If you are trying to say that microbes in soil make nutrients available in a form that plants can use – I agree. But this happens in soil anyways even if you don’t add compost tea. having more microbes in the tea will have limited effect once they are added to the soil. I have never seen a study that showed a marked increase in microbes in soil after adding compost tea.

      You have said nothing that contradicts my point that “compost tea doesn’t add any additional nutrients other than what was already in the compost”. This is really simple – if the compost contains 100g of phosphorus for example – the tea cannot contain more than 100g of phosphorus. Brewing tea does not create new molecules.

      A simple microscope is not going to allow you to identify the thousands of different bacteria species in tea or soil. Try and find a single reference where someone has identified all of the bacteria in a compost tea sample – you won’t find it because it is a huge undertaking. In fact most microbes existing in soil have not yet been identified – it is that big of a problem.

    • Chet Atkins says:

      The people with microscopes can positively determine an increase or decrease in aerobic vs aerobic life in a sample of water. Thus determining a proper way to make compost tea by experimentation. We can also determine fungal/bacterial ratios with a great degree of accuracy.

      The one source you found that seems to imply that compost tea didn’t effect collard or spinach yield doesn’t go over how they made the tea (except for the fact that they use manure – which, in my experience, is a terrible idea), gives one of the most general definitions of compost tea that I’ve ever read, and it’s vague as to if they gave the compost group any nutrients at all. The way it’s written, they may have planted the compost group in the “previously sandy loam” soil without amending it or adding nutrients, in which case their experiment would be invalid for use in this case.

      “Microbes don’t increase the nitrogen levels in the original compost. They just convert it from one type of compound to another.” Robert Pavlis, feb 19 2015
      Exactly, they change it from one compound to another, the second compound being similar, but more immediately available to the plants. When you multiply the microbes in a tea by aerating it for 36-44 hours, they are doing all the work (to transform nutrients) in a short period of time compared to the longer period of time that it would take the soil microbes to break it down. And it also leaves food for the soil microbes to break down so they can continue living happily.

      Your claim that your compost tea stunk, proves that it was not made correctly. My compost tea barely smells at all and if you get your nose right up to it, it smells like sweet tea.

      My sources are all books and hands on experience.
      “Teaming with Microbes: The Organic Gardener’s Guide to the Soil Food Web” by Jeff Lowenfels
      “Teaming with Nutrients: The Organic Gardener’s Guide to Optimizing Plant Nutrition” by Jeff Lowenfels
      “The Contrary Farmer” by Gene Logsdon

      Since you seem to like internet sources so much, give this one a read:

      • I agree with a microscope you can tell if you are increasing the number of microbes. But that has never been disputed. If you add water, and nutrients, and bacteria, you will grow more bacteria – everyone agrees on that point. Where I have a problem is that you don’t know which bacteria you are growing. Therefore you can’t say the ones you are growing are actually good for soil.

        No one disputes that the bacteria in tea are decomposing the compost faster. So what! That does not mean you will get bigger yields especially if you dilute the heck out of it when you apply it to the garden. Even if this were the case, you could just use some commercial fertilizer and get a fast feeding – you would not need the tea.

        “Teaming with Microbes” is a good read but not all of it is based on scientific fact. I would not use that as your source of information.

        Re: “”. Contains lots of information about compost tea. I did not see a reference to a published study that compared compost tea to compost, in a real field study. I admit I did not read the whole thing. If there is such a study I’d like a reference to it.

        Here is a review of the currently available scientific information about compost tea.…/403/2015/03/compost-tea-4.pdf Here are the references used for the review

  34. Vonwendelhaus says:

    All microbes are not the same. However, when a lab runs a biological assay on a compost product, all they do is look under a microscope with a gridded slide and count.

    They measure fungal hyphae and rely on their experience, but with all due respect, they don’t truly know what they are looking at. Arguably, they can’t.

    The true merit of biological products cannot be gleaned visually. It is unobservable. Think about it, can you see athletic or musical ability in people by looking at them?

    As much as we like to tell ourselves that we “understand” how Nature works…we really don’t.

  35. Sampson says:

    My understanding was that lacto fermented aerobic compost tea made the nutrients more easily accessible to the plants, perhaps in the same way that fermented foods are much easier for humans to digest? So for example a lacto fermented aerated comfrey tea would provide nutrients to the plant much faster then simply mulching with comfrey and waiting for the soil microbes to break it down. I haven’t researched this much yet so have no resources but am curious to hear your thoughts on this theory.

    • I think you are mixing up two types of composting. Bokashi is a lacto fermentation process. Compost tea is not usually.

      Does a fermented comfrey leaf feed plants faster than a fresh leaf? maybe, but only slightly. To be fair, you would need to put the leaf on the ground at the same time you start making the tea. By the time the tea is ready, the leaf on the ground is no longer fresh and has started to decompose. Both leafs are mostly intact. both leaves still need a lot of composting. The decomposition process is a long one – years. Finished compost continues to break down for about 5 years – see my blog posts on compost.

      Besides – why do you need faster composting? If you need fast nutrients for plants use commercial fertilizer. If you want a slow feed for plants compost.

      • Sam Hubert says:

        Yes, to really get an idea of how the lacto-ferments are effecting the soil you’d have to compare an equal amount of plant matter decomposing into the soil, and thankfully research into this area is finally being done.
        As for why you would need faster composting, and why not just use a commercial fertilizer…
        lacto-fermented plant teas are free, can be harvested from the same land I’m growing on, and don’t require an industrialized system to bring them to me. I’m not making the assumption that the lacto fermented teas do indeed provide fast nutrients for the plants, but if they did prove to be as effective, or nearly as effective, as commercial fertilizers then there’s no chance I’d ever purchase a commercially made product again.

        • So far there is no evidence that teas either from compost or from Bokashi are any better than using the material before making tea. If you like lacto-fermented compost – go ahead an use it. It is also free.

  36. brixguy says:

    You seem to be confusing terms here. Nobody talks NPK when they talk about tea. If you’re looking to feed your plants with what’s in your bucket……that is a nutrient drench. Apples and oranges.

    Tea is all about brewing a micro herd that will accelerate the release of nutrients in the soil. You personally may not believe it works, but it only points to your limited experience, and lack of tools for analysis.

    I make a tea with castings from my worm bin. The electrical conductivity of the solution shows almost no available nutrients. After watering with the tea, the EC of my soil rises as the microbes break down my amendments. I have concrete data that proves nutrient cycling. Maybe you should tool up, and revisit this topic. Microscopes are cheaper than brewers, so being ill equipped is no excuse for bad science.

    • The three claims I reported were found on various websites promoting compost tea – one of them is nutrients. I am reporting what others claim to be benefits.

      It is not my ‘personal’ believe that it does not work. Scientific testing has failed to show any benefits from compost tea. You are right – I have limited experience. But then the conclusions in my post are NOT based on my experience – they are based on solid peer reviewed scientific testing.

      Where have you published this ‘concrete data”? I’d like to see it.

      • Andrew says:

        Dr. Clive Edwards at Ohio State University soil ecology lab has been an initially reluctant advocate of compost teas. His research shows how aqueous extracts of vermicompost result in similar growth and plant health benefits as applications of compost and vermicompost itself, for less cost and easier use. His research is here;

        His paper on plant pathogens and vermicompost tea;

        More research if these links don’t work;

        • Thanks for the posts and the references.

          For the moment, lets assume that the conclusion “aqueous extracts of vermicompost result in similar growth and plant health benefits as applications of compost and vermicompost itself, for less cost and easier use” is true. What the reference says is that both compost and tea produced similar results. So making tea makes sense if it costs less and or it is easier to use.

          So we have a pile of compost. We can use it as is, or make tea and then spread the tea. Why would making the tea cost less? It won’t. In fact making tea would either cost the same if we ignore cost of labor and extra equipment needed, or it might cost more if we include these. the labor costs of application also need to be considered.

          Is it easier to use? The reference tests different mixtures of tea, but the average is a 1:10 ratio of compost to water. This means that the tea has 11 times the bulk and weight of the compost alone. Why would spreading 11 times as much be easier? It is certainly not easier for the home gardener who is doing this by hand. But the reference is clearly looking at farm operations. If you have tractors, and large container vehicles for holding all the tea – it is probably easier to spread a liquid than a solid.

          This is a fundamental problem with a lot of research – it is geared to farming. From the point of view of a gardener, the reader of this blog, spreading tea is not easier, nor is it more cost effective. I can spread 1 wheelbarrow of compost much faster than 11 of liquid tea. And I don’t have to make the tea!

          For gardening, these references do not support the call for using teas. If the benefits are the same, teas are certainly harder to use due to the extra weight and bulk. In addition the references have the following issues.

          1) All of the work was done in a lab or greenhouse setting. That is very different than in the field. There are no results in the references that show tea works in the field.

          2) None of the data compares using just compost vs tea made from the same compost. Most studies miss this important point. If the tea is not better than using just the compost – why should anyone bother making stinky tea?

          • Malcolm says:

            Hi Robert,
            Love your Blog and approach to an area that is full of idea’s without scientific rigor. I did want to point out one thing though. You state that one issue is that the tests in the lab or greenhouse are very different from field tests. This is true, but it shouldn’t be regarded as a weakness per se. Lab and greenhouse studies are surely necessary to help control for variables which may overwhelm the results. But they can be used to determine if an effect exists before moving to field trials.
            In this case I imagine that any effect in the lab or greenhouse would have to be large otherwise it would disappear in field trials with different soils and microbes.
            Before we could conclude a result we need to know if there are field trials with negative results or if field trials have not been done?

            Keep up the good work!

          • I agree lab work is critical to the process. If you can’t see an effect in the lab you might as well forget most field trials.

            But once an effect is confirmed in the lab, you need to move it to the real world. Thee have been lots of real world tests of compost tea. Some show results, and many do not. The problem with almost all field trials is that they compare compost tea to water, and then they may see improvements. What needs to be done is compare compost tea to adding the same amount of compost. I have not seen any such trial.

  37. iancunliffe says:

    Hi Robert,

    Thanks for this very thoughtful, logical post. I think this post attracted a lot of ‘haters’ simply because most people don’t use logic to determine what they should do, they use logic to justify what they already want to do. People tend to shop for the facts that best suit their wants.

    As a newer vegetable gardener, I got excited about the idea of compost tea (“Giant veggies? Wow!!”) but the more I looked for hard data to back up the hype, the more it appeared that the whole thing was just a bunch of self-perpetuating excitement that seemed to have miraculously transformed into fact. The many split tests (1 group with aerobic compost tea/1 group without) that independent gardeners have shared on line would indicate that there is no immediately perceivable benefit to adding compost tea (when other growing conditions are already optimal).

    I’m still going to have some fun experimenting with this, but I won’t hold my breath waiting to yank a 2 foot carrot out of my patch.

    All the best…


    • I agree with your comments. People look for evidence to support their beliefs instead of looking at evidence. I tried compost teas myself a while ago – stinks too much for me 🙂

      • kevin myers says:

        It most likely smelled because it went anaerobic. Ohio State University and North Carolina State University have information on the benefits of vermicompost tea showing the results they have come up with. I myself have used VC tea for over a year now and have seen great results, (having done test studies with non VC tea and VC tea plants) and have actually made a business out of it. The risks of things like salmonella and the like are very unlikely with vermicompost and what I produce I have had tested by Penn State University and is certified organic.

        • Lots of people have information – but has North Carolina State University published their results? Can you provide links.

          Instead of comparing “non VC tea and VC tea”, you need to compare VC tea with just using the VC. No one doubts that vermicompost ads value to plants. But there is no evidence that making the tea adds value.

      • Compost tea that stinks has gone anaerobic and shouldn’t be used.

  38. Tristan says:

    I am sorry to say this is a very lazy article. How can you use common sense and basic rhetoric to refute scientific knowledge? Compost tea is best for indoor or potted because it focuses on creating and sustaining the highest quality soil as opposed to blindly, and inanely, adding nutrients that your plants won’t be able to directly consume. The point of compost tea is to keep the microbes alive and healthy and feeding the plant. Yes beneficial bacteria and fungi(mycorrhizae) exist in nature but the more you have the better your plants will produce. You should go and read the book “Teeming with Microbes” and inform your opinions before you attempt to inform others…

    • Several references were given to back up the points I made – the comments are not just based on common sense.

      You say “Compost tea is best for indoor or potted” – not according to most of the people who advocate compost tea. Most use it in the garden. Please provide some references for using it in pots.

      You say “it focuses on creating and sustaining the highest quality soil as opposed to blindly, and inanely, adding nutrients that your plants won’t be able to directly consume”. So this must mean that you do a lab test on your compost tea? Otherwise you would have no way of knowing which nutrients your tea is providing, and in that case you are adding nutrients just as blindly as someone who uses fertilizer – no, that is not correct. The person using fertilizer actually knows what they are adding.

      You say “but the more you have (microbes) the better your plants will produce”. This is not necessarily true. Even if you add lots of microbes they will only live if you also provide organic matter for them to eat. Compost tea adds less organic matter than just adding the compost to the soil. Besides that – plants growing in pots don’t need microbes at all. Regular fertilization replaces them quite nicely. The ultimate potted plant is grown hydroponically – they grow just fine.

  39. Joerg says:

    We will make a scientific test of compost and compost tea here at the university. I can keep you updated in our results.

    • Please do. both topics are of great interest to me and the readers. Especially compost tea is a hot topic these days.

      I’ve looked at a lot of data about compost teas. What I find lacking is a good comparison between using the tea and the compost. Most work looks at benefits of the tea alone. What one really needs to demonstrate is that the effort of brewing tea is worth the effort ie it is better than just using the compost directly. In fact I would compare three things: the compost, the tea, and the sludge left over from the tea making process.

  40. Nick says:

    Incomplete understanding of soil biology. Also slimy anaerobic “compost tea” is just failed compost tea. To deny that providing the CORRECT soil microorganism increases the efficiency of the whole biological system is….well you fill in the gap. Compost tea is not meant to “add nutrients”. The whole gist of your article is plainly inaccurate.

    • I never said that it was not important to provide the CORRECT soil microorganisms–what I said is that nature does this for you. You just have to feed what is already there–straight compost does that. How do you know that the compost tea you are brewing contains the RIGHT soil microorgansims? Nobody is testing this stuff to see what is growing in it. In fact the FDA will soon release a cautionary statement that brewing compost tea can be a health risk due to the possible brewing of disease organisms.

      Just search the internet and you quickly find that there are two ways to make compost tea–anaerobic and aerobic. The one is NOT “failed compost tea”.

      You might not believe compost tea adds nutrients, but that is a benefit believed by many–just see the quote at the beginning of the post!

      • The right microbes are in Wormcast. If you start with the right culture and materials you will get a consistent product.

        • How do you know the right microbes are in wormcast? How do you which microbes are in your wormcasts?

          This is a basic problem with compost tea. Nobody knows what microbes you have. And they don’t know if they are good for the soil.

  41. David says:

    The point is that microbes in the tea die in the soil and feed the plants nitrogen. Also one should be using worm compost as a means for growing the bacteria. It has all the correct soil bacteria in it. I agree with you compost is one of the best ways to add organic mater but also bacteria to the soil. But compost tea when done right really spreads out that compost you have made. I would also like to say that mulching is my all time favorite.
    In regards to compost tea, it does not necessarily grow giant vegetables, only if you use seeds that have the genes to grow that big, but I have seen that crops really benefit from the extra boost in my own garden over the years. To compare it with compost I would say it does give you more than the same amount of compost would do. This is just my experience.

    • It is true that microbes die, and the nitrogen and other nutrients help to feed the plants. But where did the microbes get the nitrogen? They got it from the compost, manure or worm compost. No matter what kind of tea you brew, you don’t increase the amount of nitrogen, unless the bacteria in the tea use nitrogen from the air, and there is no indication that they do this.

      Microbes don’t increase the nitrogen levels in the original compost. They just convert it from one type of compound to another. The statement “compost tea when done right really spreads out that compost you have made” is a complete myth, that is unsubstantiated by any scientific evidence I have seen. However, if you have some scientific studies that support your opinion, I would love to see them.

      • I think your misunderstanding aact you add a source of culture and a nutrient material. The nutrient material should be close to sterile so the Wormcast microbes can dominate the medium. Never over brew and if sugar is added use as soon as it gets a foam head. I prefer to not use sugar as it accelerates the process to much and causes it to spoil. The nitrogen comes from the nutrient added to the pail broken down by the microbes added in the form of Wormcast.

        • I do understand ACCT. I don’t understand the point you are trying to make?

          If you are trying to convince me that ACCT compost tea works – provide a scientific reference that compares tea to the same amount of compost added in a field condition.

  42. Lee Reich says:

    You’ve got to be careful criticizing compost tea — for advocates, it’s more religion than fact. I weighed in on compost tea in my blog also ( which you might also want to check out. As a fellow iconoclast, you might also be interested in my past comments on permaculture ( Keep up the good work.

    • Robert Pavlis says:

      Thanks for visiting and your comments. A religion–that makes sense–people do a lot of things for religion. I now have more recent data that shows the number of microbes in compost tea is in fact extremely low. All the hype would have you believe that the brew was full of them and that they add benefits. Turns out there are very few microbes in the tea–I guess there is just not enough nutrients for them to grow 🙂 I’ll post more on this in the future.

      I have followed your writings for quite some time, both in books and magazines. They always made so much sense to me. I especially liked the series you did on soil in Fine Gardening. Thank you.

  43. Water says:

    You are dead wrong. I have personally witnessed the effects of compost tea on my wheat.
    It is a wonderful way of spreading compost. Microbes are the life of the soil. All around us is sterile soil because chemical fertilizers kill all microbes. You are dead wrong. Go do more research. All my Research that I have done is from books and experimentation. I did not just read some gardeners blog of the Internet. GO do 5 years of intensive study before you make the statements that you made above.

    • Robert Pavlis says:

      Chemical fertilizer, when used properly does not kill microbes. In most farm situation it is the cultivation and lack of organic matter that kills microbes.

      Microbes are important to the soil–that agrees with my statements. However, soil already has microbes and does not need more. What it needs is food for the existing microbes ie organics.

      Since you have performed experiments on compost tea, can you provide a link the the data you have collected? All of the research papers I have looked at where compost tea is tested in field conditions fail to show any benefits over and above that obtained from spreading just the compost. If you have such references I would very much like to see them.

  44. Kendra says:

    A lot of the things being said here make no sense to me…

    If compost tea could contain E.Coli or Salmonella, couldn’t the un-brewed compost contain this as well?

    Regular compost is going to differ, just as compost teas will. Why would I need to know the microbial content of a compost tea, but not of regular compost?

    If the nutrients in a tea would be overly diluted, couldn’t you just add less water? Like with frozen fruit juices.

    Lastly, while normal gardening soil might not need added microbes, indoor container gardens benefit from them, since the potting mixes used might not contain microbes. While normal compost would solve this issue, not everyone composts – commercially bought compost tea mixes can help.

    • Robert Pavlis says:

      Very good questions.

      Compost could also contain E.Coli or Salmonella. The process of making the tea tends to increase the population of these. People who feel that the tea has value feel that the more microbes they can add to soil the better–so they are trying to grow them. If the microbes in the tea are important, then you must also believe it is important to grow the right ones and to know which microbes are in the tea. People who promote compost tea don’t know which microbes they have, and each batch could be different.

      People who use compost directly are doing so because of the nutrients and organic matter in it. They don’t care which microbes are in it because they will all eventually die and turn into nutrients.

      The truth is that the microbes added to soil don’t matter. Microbes in soil are very important, but nature has already put the right ones in the soil. The ones we add will probably not grow well and just die.

      You could add less water to concentrate the nutrients, but the common recipes don’t suggest this. They add lots of water to a handful of compost and then expect it to contain a lot of nutrients. It does not work that way. People who believe in compost tea have been misinformed about the nutrients in tea.

      Potting soil, if new, will normally not contain microbes. Most people growing in pots will fertilize their plants and so the plants really do not need the microbes to provide the nutrients. In fact most people over fertilize and there are plenty of nutrients available to plant roots. If you are going to add fertilizer you can select from many types; synthetic, organic and even compost tea. In my post “What is organic Fertilizer” I discuss the fact that all of these are the same–from the plants point of view.

      Let’s say you decide to add your fertilizer as compost tea. You can buy it in two basic forms; compost and already made tea. Buying it as compost does not make sense. Why not buy a finished fertilizer and save yourself the trouble of making the tea? Besides when you buy the compost as special “compost tea’ compost it is ridiculously expensive. See my post here about manure tea which is the same thing.

      Few companies sell ready made compost tea. I have not been able to find one source ( I have not looked real hard) that gives the nutrient value of the compost tea ie the NPK values. Without this you have no idea what you are buying. You are probably paying a lot for colored water because if the nutrient value was high enough to qualify as fertilizer it would be mentioned on the bottle–it would help sell the product.

      Potted plants are growing in a very artificial environment. Most of the cultural practices that are good for your garden, especially those for soil building, do not apply to potted plants.

  45. Robert Pavlis says:

    The added quote should end with phosphorus as per original reference. Unfortunately that advice is incorrect. It is true that you should not add phosphorus unless you know you have a known deficiency. But adding compost tea is no better since it adds no real nutrients and if it does add very low levels you don’t know what you are adding. Adding either makes no sense unless you know you are solving a specific deficiency problem.

  1. […] unless tests done on the soil show a deficiency. You're better off introducing your plant to the wonders of compost tea than popping out the […]

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